ALBERT

Description: Oligochaete wormen komen vooral in zoet water voor. Maar in brak water en zelfs in de volle zee komen enkele soorten voor. Bij onderzoek naar marien benthos werden deze dieren traditioneel niet tot op soort gedetermineerd, omdat ze klein en lastig te determineren zijn. Ze zijn echter niet veel lastiger dan de nauw verwante Polychaeta, die ook hele kleine vertegenwoordigers kennen. In dit artikel wordt een overzicht gegeven van de 32 soorten die nu uit het zoute water in ons land bekend zijn, waarvan er hier zes als nieuw voor de Nederlandse fauna gepresenteerd worden. De vondst van Heterodrilus subtilis in de Noordzee is zeer bijzonder, omdat deze soort verder alleen bekend is van het typemateriaal, dat ongeveer honderd jaar geleden in de Golf van Napels werd verzameld.

Description: Het laatste overzicht van de wantsen van de Nederlandse waddeneilanden dateert van 2012. Een opsomming wordt gegeven van 43 nieuwe eilandrecords, waaronder vijf soorten die voor het eerst op de waddeneilanden zijn waargenomen. In totaal zijn er nu 380 soorten wantsen van de Nederlandse waddeneilanden bekend.

Description: Een overzicht wordt gegeven van waarnemingen van 33 soorten nieuwe of anderszins interessante soorten wantsen. Psallus aethiops (Miridae), Empicoris rubromaculatus (Reduviidae), Arocatus melanocephalus, Lygaeus simulans, Eremocoris fenestratus (Lygaeidae) en Nezara viridula (Pentatomidae) zijn nieuw voor de Nederlandse lijst, die daarmee nu 640 soorten telt. Naast nieuwe waarnemingen van zeldzame soorten wordt de recente uitbreiding van Cymatia rogenhoferi (Corixidae), Cardiastethus fasciiventris (Anthocoridae), Arocatus longiceps en Rhyparochromus vulgaris (Lygaeidae), Leptoglossus occidentalis (Coreidae), en Peribalus strictus en Rhaphigaster nebulosa (Pentatomidae) in kaart gebracht.

Description: In Nederland komen tien soorten ruighaarkevers (genera Dryops en Pomatinus) voor. Ze leven langs oevers van stilstaande en stromende wateren. Het was een verrassing toen in 2014 een vrouwtje van de zeer zeldzame Dryops striatellus gevonden werd bij Bakkeveen (provincie Friesland). De soort was sinds 1960 niet meer in Nederland gevonden. In 2016 werd D. striatellus op een tweede locatie nabij Bakkeveen gevonden. In dit artikel geven wij informatie over de soort en presenteren bijzonderheden over de Friese populatie en haar habitat.

Description: Op 14 oktober 2015 werd een halmvlieg met fraaie zwarte vlekken op de vleugels gefotografeerd in Hoogerheide (Noord-Brabant). Na vergelijking van foto’s werd geconcludeerd dat het moest gaan om Gampsocera numerata, welke determinatie later werd bevestigd. Reeds in 2009 bleek in België een mannetje van de soort gefotografeerd te zijn in een tuin in Evere. Ook in 2010 en 2015 is de soort in België gevonden. Dit zijn de eerste meldingen van G. numerata voor Nederland en België.

Description: Recently two exotic tubeworms new to the fauna of the Netherlands have been recorded in inshore waters in the delta area: Desdemona ornata and Pseudopolydora paucibranchiata. Within the Polychaeta these worms belong to the group of the Sedentaria. These construct a tube, in which the body of the worm is hidden. The head and feeding appendages protrude from the opening. Most probably these tubes are a major factor in the transport of these animals around the world, as they provide excellent shelters when they are attached to the hull of a ship or commercially traded shellfish.

Description: De boszandbij Andrena coitana leek verdwenen uit Nederland. Veertig jaar na de laatste waarneming in 1975 is weer een populatie van deze soort gevonden, bij Epe in Gelderland. De boszandbij is een kleine soort, die mogelijk nog op sommige plaatsen over het hoofd gezien is. In dit artikel wordt de kennis over deze bijzondere bij samengevat en gespeculeerd over de oorzaken van de achteruitgang in Nederland.

Description: In 2015 werd Kelisia monoceros voor het eerst in ons land verzameld bij Kamperland in Zeeland. Deze spoorcicade leeft op de algemeen voorkomende valse voszegge. De vondst wijst op een recente areaaluitbreiding. Een andere spoorcicade, Ditropsis flavipes, werd al eerder uit ons land gemeld, maar verspreidingsgegevens worden nu voor de eerste maal gepubliceerd. Ditropsis flavipes leeft monofaag op bergdravik, een in Nederland zeldzaam gras.

Description: Alle spinnen hebben gif in hun kaken om hun prooien te doden. Verreweg de meeste soorten kunnen de menselijke huid niet doorboren met hun kaken en zijn dus volkomen ongevaarlijk. Kogelspinnen uit het genus Latrodectus, oftewel weduwen, vormen een uitzondering. Deze exotische spinnen worden af en toe geïmporteerd in Nederland. In 2013 is het aantal vondsten van geïmporteerde Latrodectus-spinnen op een rij gezet in een risicobeoordeling, met als resultaat een lijst van tien records met bewijsmateriaal. Hier kunnen nu vier records aan toegevoegd worden. Hieronder bevindt zich een vondst van de bruine weduwe L. geometricus, die recent voor het eerst in ons land werd vastgesteld, en een eerste geval van uitgekomen eitjes van een Latrodectus in ons land, van de roodrugspin L. hasselti.

Description: In 2015 werd tijdens een monitoringsproject van mariene bodemfauna op het Friese front de vulkaanworm Maxmuelleria lankesteri aangetroffen. Dit is de eerste vondst in Nederlandse wateren. De vulkaanworm dankt zijn naam aan de vorm van de opening van zijn leefgang, een vulkaanachtige slibheuvel. Het is opmerkelijk dat deze grote, opvallende worm (12-18 cm lang) niet eerder is aangetroffen. Mogelijk ligt dit aan de ongebruikelijke bemonsteringsmethode. Anderzijds kan de vulkaanworm daadwerkelijk zeldzaam zijn.

Description: De kleine bleekvlekwespbij Nomada baccata behoort tot een complex van taxa rond de bleekvlekwespbij Nomada alboguttata. De kleine bleekvlekwespbij is vroeger verspreid over het land aangetroffen, maar de laatste waarneming dateerde alweer van 1992. In de afgelopen jaren werd de soort op twee plekken in ons land teruggevonden, in de Schoorlse duinen in Noord-Holland in 2012 en op de Tongerense hei bij Epe in Gelderland in 2015.

Description: De familie der sluipvliegen is één van de soortenrijkste vliegenfamilies in ons land. De larven ontwikkelen zich inwendig in ongewervelden, veelal vlinderrupsen. De groep is in ons land relatief goed bestudeerd en de afgelopen jaren zijn diverse aanvullingen op de checklist uit 2002 gepubliceerd. In dit artikel worden wederom twee soorten voor het eerst uit ons land vermeld. Hiermee komt het totaal aantal soorten dat in Nederland is vastgesteld op 336. Daarnaast wordt de herontdekking van een soort beschreven die al meer dan een eeuw niet meer waargenomen was.

Description: Canacidae zijn gebonden aan de kust en zou je daarmee typisch Nederlandse vliegjes kunnen noemen. In dit artikel melden wij een nieuwe soort van deze familie: Canace nasica en presenteren we een nieuwe Nederlandse checklist voor de familie. Naar de nieuwste taxonomische inzichten wordt daarbij de familie Tethinidae als subfamilie onder de Canacidae toegevoegd. Hiermee is de Nederlandse fauna een vliegenfamilie armer.

Description: De kassprinkhaan is een buitenbeentje onder de Nederlandse sprinkhanen en krekels. Ze komt van oorsprong waarschijnlijk voor in grotten in Oost-Azië en is door transport van eieren met plantenmateriaal over de hele wereld verspreid geraakt. Ze kan tijdelijk overleven in het kunstmatig grotmilieu van bijvoorbeeld kruipruimtes van woonhuizen, in kassen en tuincentra. Recentelijk werd een opmerkelijk grote populatie van de kassprinkhaan gevonden in het uitgebreide stelsel aan kruipruimtes onder een verpleeghuis in Friesland. De kassprinkhaan blijkt hier al ruim 40 jaar voor te komen. Het is waarschijnlijk de grootste Europese populatie van deze soort.

Description: In het kader van het project ‘Duik de Noordzee Schoon’ worden scheepswrakken onderzocht, beschreven en van afval ontdaan. Scheepswrakken vormen een bijzonder leefgebied in het mariene milieu, met een hoge biodiversiteit. Dit bleek weer tijdens onderzoek van visnetten die van ver weg gelegen wrakken waren verwijderd. Hierbij werden maar liefst vier nieuwe mosdiertjes voor de Nederlandse fauna aangetroffen.

Description: Pauropoda of weinigpoten zijn nauw verwant aan de miljoenpoten en duizendpoten. Het is een weinig bestudeerde diergroep, die bestaat uit kleine, witte en blinde bodemdieren die nauwelijks opvallen. Het meest kenmerkende zijn de gevorkte antennen, die wat bouw betreft uniek zijn ten opzichte van andere ongewervelden. Er zijn slechts acht soorten gemeld uit Nederland, alle behorend tot het genus Allopauropus. Recentelijk is een nieuwe soort, uit het genus Pauropus, in het westen van het land aangetroffen. Het betreft dus ook een nieuw genus voor de Nederlandse fauna. In dit artikel wordt de nieuwe soort voorgesteld, beschrijven we de habitat en geven we informatie over de verspreiding.

Description: In Nederland zijn natuurlijke en semi-natuurlijke graslanden relatief slecht onderzocht op de aanwezigheid van springstaarten. In de ons omringende landen zijn deze biotopen vaak rijk aan specifieke soorten die alleen daar voorkomen. Naar verwachting kunnen in dit milieu veel nieuwe soorten voor onze fauna gevonden worden, vooral op nutriëntarme, zandige en droge ondergrond. Recentelijk zijn twee soorten uit het genus Folsomides in graslanden in het zuiden van ons land aangetroffen. Het betreft hier een nieuw genus voor de Nederlandse fauna. In dit artikel worden het genus en de twee soorten voorgesteld, beschrijven we de habitat en geven we informatie over de verspreiding en begeleidende soorten van deze springstaarten.

Description: Psilota is een genus van kleine, zwarte zweefvliegen, waarvan de larven leven achter boomschors. In 1988 werd Psilota anthracina voor het eerst in Nederland waargenomen en lange tijd is het een zeldzame soort geweest. De laatste jaren wordt ze steeds algemener, vermoedelijk door een veranderd bosbeheer. Gaandeweg is gebleken dat er een tweede soort onder schuilging; P. atra. Toen in België een derde soort opdook was het wachten tot deze ook in Nederland aangetroffen zou worden. In 2012 was het zover. Als Nederlandse naam stellen we voor spichtige spitsbek.

Description: Het voorkomen van Badonnelia titei in ons land wordt in enkele publicaties genoemd. Deze exoot blijkt niet zeldzaam in archiefdepots overal in Nederland. In deze publicaties werd echter geen aandacht besteed aan het feit dat de soort nog niet als nieuw voor Nederland was gemeld, waar bewijsexemplaren zijn ondergebracht en hoe B. titei te herkennen is. De soort is daarom dan ook nooit doorgedrongen tot de diverse faunaoverzichten van Nederlandse stofluizen. Reden genoeg om deze zaken te behandelen in dit artikel, waarbij tevens een vindplaatsenkaartje wordt gegeven en de eerste vondsten uit woonhuizen worden gemeld.

Description: De omgeving van Ommen en Hardenberg is het enige gebied in Nederland waar alle vier de soorten rode bosmieren voorkomen, waaronder de in Noordwest-Europa zeer zeldzame stronkmier. Recent is aan de alarmbel getrokken omdat het niet goed gaat met deze soort. Aanleiding voor een nieuw onderzoek bij Ommen, waarbij alle bosmieren onder de loep zijn genomen.

Description: Firm coupling of genitalia is critical for copulation in most groups of insects. To counter female resistance that usually breaks off genital connection, male scorpionflies (Mecoptera: Panorpidae) usually provide nuptial gifts for the female and seize their mates with grasping devices. The notal organ, a modified clamp on tergum III of male scorpionflies, plays a significant role in seizing the female wings and helping maintain mating position during copulation. The mating behaviour remains unknown for the scorpionfly Furcatopanorpa longihypovalva (Hua and Cai, 2009) whose male lacks a notal organ. In this paper, we first attempt to study the mating behaviour of F. longihypovalva. The results show that the male provides liquid salivary secretion through a mouth-to-mouth mode for the female, and maintains copulation mainly by continuous provision of salivary secretion rather than by seizing the female with grasping devices. Thus the male copulates with the female in an atypical O-shaped position, with only their mouthparts and genitalia connected to each other. The salivary glands exhibit remarkable sexual dimorphism: short and bifurcated in the female, but well-developed and multi-furcated in the male. The extremely developed salivary glands of the male lay a structural foundation for the male to continuously provide liquid salivary secretion, and to help the male to mediate female resistance, being likely to serve as a compensation to his absence of the notal organ. We also investigated the functional morphology and copulatory mechanism of the male and female genitalia. The evolution of the atypical mating pattern of F. longihypovalva is putatively discussed as an adaptation in the context of sexual conflict.

Description: Female genitalia are widely underrepresented in taxonomic studies. Here we investigate the morphological variation among female copulation organs for a group of scarab beetles (Sericini) with similar ecology, external morphology and copulation mechanics. We examined traits qualitatively and quantitatively based on 80 and 18 species (genus Pleophylla), respectively. Additionally we explored whether female genitalia are affected by asymmetry. The vast diversity of slerotised structures including their shapes illustrated the high taxonomic and phylogenetic utility of female genitalia in this group. The morphometric analysis of Pleophylla, confirmed that sclerotisations in the ductus bursae are very suitable for species-level taxonomic purposes. Stable interspecific variation is more hardly discernable in other parts such as the vaginal palps (shape and size) or the other membranous structures such as the shape of the bursa copulatrix. Asymmetric genitalia that arose multiple times independently among insects are found in most of the examined Sericini species. Asymmetries regarded either the bursa copulatrix, or both the bursa copulatrix and ductus bursae and comprised sclerotised and non-sclerotised structures being most common in modern Sericini. Here, highly asymmetric sclerotised structures are linked with strong asymmetry of the male copulation organs. Widespread asymmetry among megadiverse Sericini with a complex male-female genital asymmetry suggests that the shift to asymmetry is phylogenetically rather conserved. From the range of hypotheses, sexual selection seems to be the most reasonable to explain the evolution and stability of asymmetry in chafer genitalia.

Description: Slakkendodende vliegen (familie Sciomyzidae) zijn al niet zo opvallend in het veld, maar de soorten uit de genera Pherbellia en Ditaeniella worden nog minder gevonden, mede doordat ze vrij klein zijn. De 14 Nederlandse soorten lijken sterk op elkaar. Dit artikel biedt een tabel om ze te kunnen herkennen en geeft informatie over ecologie en verspreiding.

Description: Platwormen komen in Nederland vooral voor in zoet water, maar er zijn twee soorten van landbiotoop bekend. De laatste jaren duiken steeds vaker exotische landplatwormen op in Europa, vooral in kassen en tuincentra, maar sommige kunnen ook buitenshuis overleven. Uit Nederland zijn Bipalium kewense, Caenoplana bicolor en Marionfyfea adventor gemeld. Omdat ze regenwormen en slakken eten, kunnen ze een grote invloed hebben op het bodemleven, met gevolgen voor natuurlijke ecosystemen en landbouwgebieden. In het buitenland is de aandacht voor exotische landplatwormen al groeiende. Zo wordt de Nieuw-Guineese landplatworm Platydemus manokwari door de IUCN tot de 100 ergste invasieve soorten aangemerkt. In Nederland is er nog nauwelijks aandacht voor landplatwormen. Daarom wordt in dit artikel de kennis over deze groep samengevat.

Description: Blaaskopvliegen zijn een van de groepen uit het atlasproject Leuke vliegen, dat in 2015 werd afgesloten. Het zijn over het algemeen opvallend gekleurde vliegen, die parasiteren bij bijen en wespen. In een overzichtsartikel uit 2014 werd de komst van Leopoldius calceatus al voorspeld en in 2015 werd soort inderdaad aangetroffen in Groeve Craubeek in de provincie Limburg en een jaar later op de Stratumse heide bij Eindhoven.

Description: Astigmatic mites probably form the most diverse cohort of mites. At present the former order of Astigmatina is ranked within the suborder Oribatida or moss mites. However astigmatic mites occupy a much wider range of habitats than other oribatid mites: from marine coasts to stored food, plant bulbs and houses. The vast majority live as commensals or parasites on a variety of hosts, ranging from insects to birds and mammals, inhabiting the fur, feathers, skin and even lungs and stomach. This first checklist for the Netherlands contains 262 species, but many more are to be expected. Brief data on occurrence and nomenclature are provided for each species.

Description: Eikelwormen zijn mariene wormen die een eigen klasse vormen, de Enteropneusta. In Nederland zijn het ook de enige vertegenwoordigers van de kraagdragers (fylum Hemichordata). Het zijn bijzondere dieren, die nauwer verwant zijn aan stekelhuidigen en gewervelde dieren dan aan gelede wormen. Het lichaam is ongeleed, met een gesteelde slurf, met daarachter een kraag en een langwerpig lichaam met tientallen kieuwspleten. De wormen leven in een U-vormige buis in zachte bodems. In de loop van de tijd zijn wel eikelwormen langs de Nederlandse kust verzameld, maar deze zijn nooit op naam gebracht. In dit artikel wordt ingegaan op de eerste vondsten van eikelwormen in de Oosterschelde.

Description: The gall midges are one of the most important groups of gall makers. Emerging larvae produce stimuli and the host plant responds by producing galls, fascinating structures which provide food and shelter for the developing larvae. Most gall inducing midges are host specific: they are only able to induce galls in a few, often related, plant species. A few species have different feeding modes: among them are saprophagous, fungivorous and predaceous species and some are used in biocontrol. We recorded 416 species in the whole area; 366 species are recorded from the Netherlands, 270 species from Belgium and 96 species from Luxembourg.

Description: Het gebeurt met enige regelmaat dat er boorvliegen versleept worden met plantaardige producten. De meeste schadelijke soorten komen uit de tropen en kunnen zich niet handhaven in Nederland. Noord-Amerikaanse soorten van het genus Rhagoletis kunnen in het klimatologisch vergelijkbare Europa wel voet aan de grond krijgen. Eerder bleek dit al met de Oost-Amerikaanse kersenboorvlieg en nu staat hetzelfde te gebeuren met de walnootboorvlieg.

Description: Door gebruik te maken van observatiekunstnestjes is het mogelijk om regelmatig een kijkje te nemen in de nesten van bijvoorbeeld graafwespen. Zij gebruiken de nesten om zich voort te planten. Zo kunnen we meer te weten komen over hun gedrag in het nest tijdens de voortplanting. In dit artikel worden de ervaringen met de graafwesp Psenulus fuscipennis beschreven. De verschillen in levenswijze met de kleine zeefwesp en bijenwolf worden toegelicht.

Description: De gele tubebij Stelis signata was sinds 1977 niet meer in ons land aangetroffen. Men dacht daarom dat deze bij uit ons land verdwenen was. In 2013 werd de soort echter op Waarneming.nl gemeld van de Strabrechtse hei en in 2014 van Afferden. In 2015 werd een vrouwtje gevangen op de Sprengenberg op de Sallandse heuvelrug. In 2011 heeft Natuurmonumenten hier kleinschalige maatregelen uitgevoerd voor specifieke heidesoorten, waaronder de aanleg van een flink aantal steilranden. Het microreliëf dat daarbij ontstaat vormt een belangrijke nestelplaats voor bijen en wespen. De vondst van de zeldzame gele tubebij op een van deze steilranden vormt de kroon op het werk.

Description: In 2007 werd Diplocoelus fagi bij Wageningen gevonden. De larven van deze kever leven in dood hout. Na de eerste vondst zijn diverse andere waarnemingen gedaan en D. fagi is nu bekend uit vier provincies. Omdat de soort in de omringende landen al lang bekend was, is deze late ontdekking opmerkelijk. Mogelijk hangt dit samen met het verbeterde bosbeheer, waarbij minder dood hout uit de bossen wordt verwijderd.

Description: The snail-killing fly Salticella fasciata was discovered in Belgium in 2010. Since then, several new localities on the Belgian coast were discovered and in 2014, the first record for the Netherlands was found. This is the first representative of the genus and also of the subfamily Salticellinae in the Netherlands. In this paper, records from Belgium and the Netherlands are reviewed and information on biology and habitats is summarised.

Description: Twaalf jaar geleden waren er nog geen Nelima-soorten bekend uit ons land. In 2004 en 2006 werden respectievelijk N. sempronii en N. doriae ontdekt. Beide soorten komen ten zuidoosten van ons land voor, en hebben naar alle waarschijnlijkheid Nederland recent bereikt. In 2012 werd op de Maasvlakte een derde vertegenwoordiger van dit genus gevonden: Nelima gothica. De vindplaats lijkt te wijzen op introductie door de mens. Gezien het voorkomen in de ons omringende landen is echter niet uit te sluiten dat hij van oudsher tot onze fauna behoort of recent op eigen kracht Nederland heeft bereikt. Hij zou op meer plaatsen langs de kust kunnen voorkomen. We presenteren de nieuwe soort en geven een overzicht van de vier Noordwest-Europese Nelima-soorten.

Description: Goudwespen zijn fraaie insecten, met felle metaalkleuren in de tinten rood, groen en blauw. Ze parasiteren vaak bij bijen en angeldragende wespen. In dit artikel wordt de eerste vondst van Chrysis equestris voor Nederland beschreven, waarmee het aantal in Nederland gevonden soorten nu op 57 komt. Deze goudwesp parasiteert bij de plooivleugelwesp Discoelius zonalis. Ze wordt in haar hele areaal weinig gevangen.

Description: Wing shape variation was investigated between the sexes and among four populations of the scorpionfly Dicerapanorpa magna (Chou, 1981) endemic to the Qin-Ba Mountains area, China through the landmark-based geometric morphometric approach. The results show that sexual dimorphism exists both in wing size and shape in D. magna. Significant differences exist in female wing size and shape among D. magna populations. The possible reasons of the wing variation are discussed based on the divergence time of D. magna in combination with the tectonic and climatic events in the Qin-Ba Mountains during the late Miocene-Pleistocene period. Whether reproductive isolation exists between different populations needs further research.

Description: The Flevopark is one of the most special green areas of Amsterdam with a rich nature. Twelve oribatid mite species were collected here in 2014 from bark and mosses on trees. Liacarus acutus and Perlohmannia dissimilis are reported for the first time from the Netherlands. It is not clear if the newly recorded species have always been overlooked or are recent immigrants.

Description: Watermijten zijn kleine spinachtige diertjes, die in zoet water leven. De aandacht voor deze diergroep is groot, omdat ze een rol spelen in de waterkwaliteitsbeoordeling. In de verspreidingsatlas uit 2000 worden 234 Nederlandse watermijten gemeld. Sinds die tijd worden regelmatig aanvullingen gerapporteerd. In dit artikel worden weer acht nieuwe soorten gemeld, wat het totaal nu op 266 brengt. Dit is een opmerkelijke toename van 13 % in 15 jaar.

Description: De publicatie van de naamlijst van de Nederlandse kieuwpootkreeften in 2002 was een grote stimulans voor nieuw onderzoek. Na de publicatie met aanvullingen in 2009 zijn er weer negen soorten bijgekomen, waarmee het totaal aantal soorten kieuwpootkreeften in Nederland nu op 124 komt. In dit artikel worden de nieuwe soorten besproken en wordt ingegaan op de redenen voor deze opmerkelijke uitbreiding.

Description: Prachtvliegen zijn vrij kleine vliegen die vaak een vleugeltekening hebben waardoor ze aan boorvliegen doen denken. De meeste soorten zijn weinig opvallend in het veld aanwezig en zitten vooral op hun waardplanten. Alleen de soorten waarvan de larven leven onder schors van boomstammen zijn opvallender aanwezig door hun balts of territoriaal gedrag. Ze proberen hun stukje boomstam te claimen door snel op en neer te lopen en tegelijkertijd driftig met hun vleugels te bewegen. Tot nog toe was de zeer fraaie Myennis octopunctata (Coquebert, 1798) de enige houtbewonende prachtvlieg in Nederland. In dit artikel wordt daar Homalocephala biumbrata aan toegevoegd.

Description: Integrative taxonomy tests the validity of taxa using methods additional to traditional morphology. The existence of two different morphotypes in specimens identified as Chrysotoxum vernale Loew (Diptera: Syrphidae) prompted their taxonomic study using an integrative approach that included morphology, wing and male-surstylus geometric morphometrics, genetic and ecological analyses. As a result, a new species is recognised, Chrysotoxum montanum Nedeljković & Vujić sp. nov., and C. vernale is re-defined. A lectotype and paralectotypes are designated for C. vernale to stabilize this concept. An additional species, Chrysotoxum orthostylum Vujić sp. nov., with distinctive male genitalia is also described. The three species share an antenna with the basoflagellomere shorter than the scape plus pedicel and terga with yellow fasciae not reaching the lateral margins. This study confirms the value of integrative approach for resolving species boundaries.

Description: Afterburners for turbojet engines have, within the past decade, found increasing application in service aircraft. Practically all engines manufactured today are equipped with some form of afterburner, and its use has increased from what was originally a short-period thrust-augmentation application to an essential feature of the turbojet propulsion system for flight at supersonic speeds. The design of these afterburners has been based on extensive research and development effort in expanded laboratory facilities by both the NACA and the American engine industry. Most of the work of the engine industry, however, has either not been published or is not generally available owing to its proprietary nature. Consequently, the main bulk of research information available for summary and discussion is of NACA origin. However, because industrial afterburner development has closely followed NACA research, the omission is more one of technical detail than method or concept. One principal difficulty encountered in summarizing the work in this field is that sufficient knowledge does not yet exist to rationally or directly integrate the available background of basic combustion principles into combustor design. A further difficulty is that most of the experimental investigations that have been conducted were directed chiefly toward the development of specific afterburners for various engines rather than to the accumulation of systematic data. This work has, nonetheless, provided not only substantial improvements in the performance of afterburners but also a large fund of experimental data and an extensive background of experience in the field. Consequently, it is the purpose of the present chapter to summarize the many, and frequently unrelated, experimental investigations that have been conducted rather than to formulate a set of design rules. In the treatment of this material an effort has been made, however, to convey to the reader the "know how" acquired by research engineers in the course of afterburner studies.

Description: In the early development of jet engines, it was occasionally found that excessive amounts of coke or other carbonaceous deposits were formed in the combustion chamber. Sometimes a considerable amount of smoke was noted in the-exhaust gases. Excessive coke deposits may adversely affect jet-engine performance in several ways. The formation of excessive amounts of coke on or just downstream of a fuel nozzle (figs. 116(a) and (b)) changes the fuel-spray pattern and possibly affects combustor life and performance. Similar effects on performance can result from the deposition of coke on primary-air entry ports (fig. 116(c)). Sea-level or altitude starting may be impaired by the deposition of coke on spark-plug electrodes (fig. 116(b)), deposits either grounding the electrodes completely or causing the spark to occur at positions other than the intended gap. For some time it was thought that large deposits of coke in turbojet combustion chambers (fig. 116(a)) might break away and damage turbine blades; however, experience has indicated that for metal blades this problem is insignificant. (Cermet turbine blades may be damaged by loose coke deposits.) Finally, the deposition of coke may cause high-temperature areas, which promote liner warping and cracking (fig. 116(d)) from excessive temperature gradients and variations in thermal-expansion rates. Smoke in the exhaust gases does not generally impair engine performance but may be undesirable from a tactical or a nuisance standpoint. Appendix B of reference 1 and references 2 to 4 present data obtained from full-scale engines operated on test stands and from flight tests that indicate some effects on performance caused by coke deposits and smoke. Some information about the mechanism of coke formation is given in reference 5 and chapter IX. The data indicate that (1) high-boiling fuel residuals and partly polymerized products may be mixed with a large amount of smoke formed in the gas phase to account for the consistency, structure, and chemical composition of the soft coke in the dome and (2) the hard deposits on the liner are similar to petroleum coke and may result from the liquid-phase thermal cracking of the fuel. During the early development period of jet engines, it was noted that the excessive coke deposits and exhaust smoke were generally obtained when fuel-oil-type fuels were used. Engines using gasoline-type fuels were relatively free from the deposits and smoke. These results indicated that some type of quality control would be needed in fuel specifications. Also noted was the effect of engine operating conditions on coke deposition. It is possible that, even with a clean-burning fuel, an excessive amount of coke could be formed at some operating conditions. In this case, combustor redesign could possibly reduce the coke to a tolerable level. This chapter is a summary of the various coke-deposition and exhaust-smoke problems connected- with the turbojet combustor. Included are (1) the effect of coke deposition on combustor life or durability and performance; (2) the effect of combustor design, operating conditions, inlet variables, and fuel characteristics on coke deposition; (3) elimination of coke deposits; (4) the effect of operating conditions and fuel characteristics on formation of exhaust smoke; and (5) various bench test methods proposed for determining and controlling fuel quality.

Description: Combustion must be maintained in the turbojet-engine combustor over a wide range of operating conditions resulting from variations in required engine thrust, flight altitude, and flight speed. Furthermore, combustion must be efficient in order to provide the maximum aircraft range. Thus, two major performance criteria of the turbojet-engine combustor are (1) operatable range, or combustion limits, and (2) combustion efficiency. Several fundamental requirements for efficient, high-speed combustion are evident from the discussions presented in chapters III to V. The fuel-air ratio and pressure in the burning zone must lie within specific limits of flammability (fig. 111-16(b)) in order to have the mixture ignite and burn satisfactorily. Increases in mixture temperature will favor the flammability characteristics (ch. III). A second requirement in maintaining a stable flame -is that low local flow velocities exist in the combustion zone (ch. VI). Finally, even with these requirements satisfied, a flame needs a certain minimum space in which to release a desired amount of heat, the necessary space increasing with a decrease in pressure (ref. 1). It is apparent, then, that combustor design and operation must provide for (1) proper control of vapor fuel-air ratios in the combustion zone at or near stoichiometric, (2) mixture pressures above the minimum flammability pressures, (3) low flow velocities in the combustion zone, and (4) adequate space for the flame.

Description: From considerations of safety and reliability in performance of gas-turbine aircraft, it is clear that engine starting and acceleration are of utmost importance. For this reason extensive efforts have been devoted to the investigation of the factors involved in the starting and acceleration of engines. In chapter III it is shown that certain basic combustion requirements must be met before ignition can occur; consequently, the design and operation of an engine must be tailored to provide these basic requirements in the combustion zone of the engine, particularly in the vicinity of the ignition source. It is pointed out in chapter III that ignition by electrical discharges is aided by high pressure, high temperature, low gas velocity and turbulence, gaseous fuel-air mixture, proper mixture strength, and-an optimum spark. duration. The simultaneous achievement of all these requirements in an actual turbojet-engine combustor is obviously impossible, yet any attempt to satisfy as many requirements as possible will result in lower ignition energies, lower-weight ignition systems, and greater reliability. These factors together with size and cost considerations determine the acceptability of the final ignition system. It is further shown in chapter III that the problem of wall quenching affects engine starting. For example, the dimensions of the volume to be burned must be larger than the quenching distance at the lowest pressure and the most adverse fuel-air ratio encountered. This fact affects the design of cross-fire tubes between adjacent combustion chambers in a tubular-combustor turbojet engine. Only two chambers in these engines contain spark plugs; therefore, the flame must propagate through small connecting tubes between the chambers. The quenching studies indicate that if the cross-fire tubes are too narrow the flame will not propagate from one chamber to another. In order to better understand the role of the basic factors in actual engine operation, many investigations have been conducted in single combustors from gas-turbine engines and in full-scale engines in altitude tanks and in flight. The purpose of the present chapter is to discuss the results of such studies and, where possible, to interpret these results qualitatively in terms of the basic requirements reported in chapter III. The discussion parallels the three phases of turbojet engine starting: (1) Ignition of the fuel-air mixture (2) Propagation of flame throughout the combustion zone (3) Acceleration of the engine to operating speed.

Description: Studies of the fundamental processes of combustion are usually concerned with wide ranges of investigation of individual processes. In general, each fundamental combustion process may be studied in an environment that is most suited to its evaluation and possibly unrelated basically to any practical application. The majority of the data presented in volume I of this series concern the fundamental aspects of combustion as functions of the individual occurrence of various contributing processes. In a jet engine, however, the various fundamental combustion processes may occur simultaneously and may interact. Furthermore, the engine environment usually does not permit independent variation of single combustion parameters, since specified operating conditions impose specific values on the parameters. In volume II, data are presented to show the effect of operating conditions on the over-all combustion process in different combustion components. To show the effect of operating conditions, it is necessary to specify the range of these conditions within which combustion components may operate. Therefore, this chapter presents only the operating conditions that might be required in the primary combustors and afterburners of typical current turbojet engines. (Corresponding information on ram-jet engines is presented in ch. xisi.) This chapter is not intended to serve as an explanation of engine operation. The operating conditions of the combustion components are presented in terms of total pressures and temperatures at the primary-combustor and afterburner inlets, reference velocities and outlet total temperatures of the primary combustors, and velocities at the plane of the flameholder in the afterburners. The data are presented to relate the operating regions of typical current turbojet combustion components to flight altitudes, Mach numbers, and modes of engine operation. Specifically, data are presented for the combustion parameters of the primary combustor and afterburner of three turbojet engines having rated compressor total-pressure ratios of 5, 8, and 12 under full-throttle conditions. Operational data for the primary combustor also include part-throttle operation at 70, 80, and 90 percent of rated engine speed and windmifling operation. The range of flight conditions includes altitudes from sea level to 65,000 feet and flight Mach numbers from zero to 1.6.

Description: The occurrence of ice accretion within commercial high bypass aircraft turbine engines has been reported by airlines under certain atmospheric conditions. Engine anomalies have taken place at high altitudes that have been attributed to ice crystal ingestion by the engine. The ice crystals can result in degraded engine performance, loss of thrust control, compressor surge or stall, and flameout of the combustor. The Aviation Safety Program at NASA has taken on the technical challenge of a turbofan engine icing caused by ice crystals which can exist in high altitude convective clouds. The NASA engine icing project consists of an integrated approach with four concurrent and ongoing research elements, each of which feeds critical information to the next element. The project objective is to gain understanding of high altitude ice crystals by developing knowledge bases and test facilities for testing full engines and engine components. The first element is to utilize a highly instrumented aircraft to characterize the high altitude convective cloud environment. The second element is the enhancement of the Propulsion Systems Laboratory altitude test facility for gas turbine engines to include the addition of an ice crystal cloud. The third element is basic research of the fundamental physics associated with ice crystal ice accretion. The fourth and final element is the development of computational tools with the goal of simulating the effects of ice crystal ingestion on compressor and gas turbine engine performance. The NASA goal is to provide knowledge to the engine and aircraft manufacturing communities to help mitigate, or eliminate turbofan engine interruptions, engine damage, and failures due to ice crystal ingestion.

Description: A fundamental exploratory experiment is conducted assessing the performance of a one-sided ejector with the eventual goal of noise reduction for jet engines. The hardware is comprised of an 8:1 rectangular nozzle together with an ejector box whose lower surface is flush with the lower lip of the nozzle. Secondary flow is allowed through a gap between the upper lip of the nozzle and a flap that constitutes the upper surface of the ejector. Wall static pressures and Pitot probe surveys are conducted to evaluate the performance of the ejector with variation of geometric parameters. It is found that addition of vortex generating tabs at the upper lip of the nozzle significantly increases secondary flow entrainment. The entrainment is further enhanced by a divergence of the ejector upper surface. Limited noise measurements are done. The baseline ejector (without tabs) often encounters flow resonance with accompanying tones. The tabs have the additional benefit of eliminating those tones in all cases. However, for the tabbed case, addition of the ejector produces insignificant further noise reduction. This is due to the fact that the flow remains unmixed on the lower half of the ejector. The focus of ongoing and future efforts is to achieve sufficient mixing of the flow so that the exhaust velocities are uniformly low, while keeping the ejector hardware short and lightweight.

Description: Three highly polished 15- included- angle cone- cylinders with hemispherical tips of several diameters ( 2, 3, and 4 in.) have been flown in order to obtain boundary- layer transition data at very low wall to local stream temperature ratios, and heat- transfer data. All surfaces had a 2-microinch average roughness height. Laminar flow existed over the entire hemispherical nose of the 2- and 3-inch-tip- diameter models throughout the complete flight history. Extreme cooling to wall to local stream temperature ratios at the sonic point as low as 0.20 did not cause transition on the nose for diameters as large as 3 inches. However, extreme cooling did cause early transition on the 4-inch model where it appears probable that transition occurred forward of the 45 station at a wall to local stream temperature ratio of about 0.26. Variations in tip diameter influenced transition downstream of the nose under conditions of extreme cooling. The 2-inch- tip model was laminar at all cone- cylinder stations at temperature ratios as low as 0.32 whereas the 3- and 4-inch-tip models were turbulent at the same local flow conditions but at higher wall to local temperature ratios. Transition on the cone and cylinder of the 3- and 4-inch- tip bodies appeared to be sensitive to local Mach number, and occurred at higher local temperature ratios when values of local Mach number were higher. Increasing the nose diameter from 2 to 3 inches significantly changed the local flow conditions for which laminar flow existed on the cone- cylinder afterbody. However, a further increase in tip size t o a 4-inch diameter had no discernable effect on the local flow conditions at transition. The transition results of the 3- and 4-inch-nose-diameter smooth bodies are similar to those observed on a 7/8-inch-nose-diameter body with roughened surfaces. Turbulent boundary layers resulted in both cases at very low wall to local stream temperature ratios. Both laminar and turbulent heat-transfer data were in good agreement with theoretical Stanton numbers when heat-transfer reduction due to tip blunting was considered.

Description: This presentation is on Electric and Hybrid Electric Propulsion: NASA's Approach, expectations, design and project requirements, and the motivation behind it.

Description: The development of new cowlings, applicable to a short-nose radial engine, is described. These cowlings, designated the NACA cowlings D(sub s) and D(sub sf), employ a larger spinner and a higher inlet-velocity ratio than does the conventional NACA cowling C. The pressures available for cooling and the estimated critical Mach number were found to be higher with the new cowlings than are usually encountered with the conventional NACA cowling C. Large-chord propeller cuffs were found to have a stabilizing effect on the flow entering the cowling and resulted in increased front pressures. Fan blades mounted on the spinner in the inlet opening had a similar effect.

Description: A comparison of the operating characteristics of 75-millimeter-bore (size 215) cylindrical-roller one-piece inner-race-riding cage-type bearings was made using a laboratory test rig and a turbojet engine. Cooling correlation parameters were determined by means of dimensional analysis, and the generalized results for both the inner- and outer-race bearing operating temperatures are compared for the laboratory test rig and the turbojet engine. Inner- and outer-race cooling-correlation curves were obtained for the turbojet-engine turbine-roller bearing with the same inner- and outer-race correlation parameters and exponents as those determined for the laboratory test-rig bearing. The inner- and outer-race turbine roller-bearing temperatures may be predicted from a single curve, regardless of variations in speed, load, oil flow, oil inlet temperature, oil inlet viscosity, oil-jet diameter or any combination of these parameters. The turbojet-engine turbine-roller-bearing inner-race temperatures were 30 to 60 F greater than the outer-race-maximum temperatures, the exact values depending on the operating condition and oil viscosity; these results are in contrast to the laboratory test-rig results where the inner-race temperatures were less than the outer-race-maximum temperatures. The turbojet-engine turbine-roller bearing, maximum outer-race circumferential temperature variation was approximately 30 F for each of the oils used. The effect of oil viscosity on inner- and outer-race turbojet-engine turbine-roller-bearing temperatures was found to be significant. With the lower viscosity oil (6x10(exp -7) reyns (4.9 centistokes) at 100 F; viscosity index, 83), the inner-race temperature was approximately 30 to 35 F less than with the higher viscosity oil (53x10(exp -7) reyns (42.8 centistokes) at 100 F; viscosity index, 150); whereas the outer-race-maximum temperatures were 12 to 28 F lower with the lower viscosity oil over the DN range investigated.

Description: Following a brief history of the NACA investigation of jet-propulsion, a discussion is given of the general investigation and analyses leading to the construction of the jet-propulsion ground-test mock-up. The results of burning experiments and of test measurements designed to allow quantitative flight-performance predictions of the system are presented and correlated with calculations. These calculations are then used to determine the performance of the system on the ground and in the air at various speeds and altitudes under various burning conditions. The application of the system to an experimental airplane is described and some performance predictions for this airplane are made. It was found that the main fire could be restricted to an intense, small, and short annular blue flame burning steadily and under control in the intended combustion space. With these readily obtainable combustion conditions, the combustion chamber the nozzle walls and the surrounding structure could be maintained at normal temperatures. The system investigated was found to be capable of burning one-half the intake air up the fuel rates of 3 pounds per second. Calculations were shown to agree well with experiment. It was concluded that the basic features of the jet-propulsion system investigation in the ground-test mock-up were sufficiently developed to be considered applicable to flight installation. Calculations indicated that an airplane utilizing this jet-propulsion system would have unusual capabilities in the high-speed range above the speeds of conventional aircraft and would, in addition, have moderately long cruising ranges if only the engine were used.

Description: Engine tests, together with estimates made at Langley Memorial Aeronautical Laboratory, indicate that a 25-percent increase in take-off power can be obtained with present-day aircraft engines without increasing either the knock limit of the fuel or the external cooling requirements of the engine. This increase in power with present fuels and present external cooling is made possible through the use of an internal coolant inducted through the inlet manifold. Estimates on aircraft indicate that this 25-percent increase in power will permit an approximate usable increase of 8.5 percent in the take-off load of existing military airplanes. This increase in load is equivalent to an increase in the weight of gasoline normally carried of between 30 and 65 percent.

Description: Average spanwise blade temperatures and cooling-air pressure losses through a small (1.4-in, span, 0.7-in, chord) air-cooled turbine blade were calculated and are compared with experimental nonrotating cascade data. Two methods of calculating the blade spanwise metal temperature distributions are presented. The method which considered the effect of the length-to-diameter ratio of the coolant passage on the blade-to-coolant heat-transfer coefficient and assumed constant coolant properties based on the coolant bulk temperature gave the best agreement with experimental data. The agreement obtained was within 3 percent at the midspan and tip regions of the blade. At the root region of the blade, the agreement was within 3 percent for coolant flows within the turbulent flow regime and within 10 percent for coolant flows in the laminar regime. The calculated and measured cooling-air pressure losses through the blade agreed within 5 percent. Calculated spanwise blade temperatures for assumed turboprop engine operating conditions of 2000 F turbine-inlet gas temperature and flight conditions of 300 knots at a 30,000-foot altitude agreed well with those obtained by the extrapolation of correlated experimental data of a static cascade investigation of these blades.

Description: Some of the considerations involved in the design of aircraft fuel tanks for liquid hydrogen are discussed herein. Several of the physical properties of metals and thermal insulators in the temperature range from ambient to liquid-hydrogen temperatures are assembled. Calculations based on these properties indicate that it is possible to build a large-size liquid-hydrogen fuel tank which (1) will weigh less then 15 percent of the fuel weight, (2) will have a hydrogen vaporization rate less than 30 percent of the cruise fuel-flow rate, and (3) can be held in a stand-by condition and readied for flight in a short time.

Description: The report summarizes source material on combustion for flight-propulsion engineers. First, several chapters review fundamental processes such as fuel-air mixture preparation, gas flow and mixing, flammability and ignition, flame propagation in both homogenous and heterogenous media, flame stabilization, combustion oscillations, and smoke and carbon formation. The practical significance and the relation of these processes to theory are presented. A second series of chapters describes the observed performance and design problems of engine combustors of the principal types. An attempt is made to interpret performance in terms of the fundamental processes and theories previously reviewed. Third, the design of high-speed combustion systems is discussed. Combustor design principles that can be established from basic considerations and from experience with actual combustors are described. Finally, future requirements for aircraft engine combustion systems are examined.

Description: A literature survey was conducted to determine the relation between aircraft ignition sources and inflammables. Available literature applicable to the problem of aircraft fire hazards is analyzed and, discussed herein. Data pertaining to the effect of many variables on ignition temperatures, minimum ignition pressures, and minimum spark-ignition energies of inflammables, quenching distances of electrode configurations, and size of openings incapable of flame propagation are presented and discussed. The ignition temperatures and the limits of inflammability of gasoline in air in different test environments, and the minimum ignition pressure and the minimum size of openings for flame propagation of gasoline - air mixtures are included. Inerting of gasoline - air mixtures is discussed.

Description: Tests of two propellers having two blades and differing only in the inboard pitch distribution were made in the Langley 8-foot highspeed tunnel to determine the effect of inboard pitch distribution on propeller performance. propeller was designed for operation in the reduced velocity region ahead of an NACA cowling; the inboard pitch distribution of the modified propeller was increased for operation at or near free-stream velocities, such as would be obtained in a pusher installation. conditions covering climb, cruise, and high-speed operation. Wake surveys were taken behind the propellers in order to determine the distribution of thrust along the blades and to aid in the analysis of the results. Test results showed that the modified propeller was about 2.5 percent less efficient for a typical climb condition at all altitudes, 2 percent more efficient for one cruise condition, and 5 percent more efficient for high-speed operation. speed condition, the modified propeller showed a 6-percent loss in efficiency due to compressibility; whereas the original propeller showed an 11-percent efficiency loss due to compressiblity. The lower compressibility loss for the modified propeller resulted from the fact that the inboard sections of this propeller could operate at increased thrust loading after compressibility losses had occurred at the outboard sections.

Description: Tests of four 10-foot propellers were made in the propeller-research tunnel for the Army Air Corps to check flight and static thrust test results made on several propellers embodying Clark Y and modified NACA 16-series sections. These propellers were identical as to diameter and activity factor and very closely identical in thickness ratio and pitch distribution. The blades embodied sections with both single- and double-cambered Clark Y, modified NACA 16-series, and a combination of Clark Y and modified NACA-16 airfoils. Tests covered a range of blade angles from 20 deg. to 70 deg., and were all made at tip speeds below 280 feet per second. Although these tests were not conclusive in themselves, owing to the conditions under which they were made, the results seem to check the flight and static tests as closely as would be expected.

Description: A thermocouple was installed in the crown of a sodium-cooled exhaust valve. The valve was then tested in an air-cooled engine cylinder and valve temperatures under various engine operating conditions were determined. A temperature of 1337 F was observed at a fuel-air ratio of 0.064, a brake mean effective pressure of 179 pounds per square inch, and an engine speed of 2000 rpm. Fuel-air ratio was found to have a large influence on valve temperature, but cooling-air pressure and variation in spark advance had little effect. An increase in engine power by change of speed or mean effective pressure increased the valve temperature. It was found that the temperature of the rear spark-plug bushing was not a satisfactory indication of the temperature of the exhaust valve.

Description: An investigation was made to determine a method of measuring fuel-air ratio that could be used for test purposes in flight and for checking conventional equipment in the laboratory. Two single-cylinder test engines equipped with typical commercial engine cylinders were used. The fuel-air ratio of the mixture delivered to the engines was determined by direct measurement of the quantity of air and of fuel supplied and also by analysis of the oxidized exhaust gas and of the normal exhaust gas. Five fuels were used: gasoline that complied with Army-Navy fuel Specification No. AN-VV-F-781 and four mixtures of this gasoline with toluene, benzene, and xylene. The method of determining the fuel-air ratio described in this report involves the measurement of the carbon-dioxide content of the oxidized exhaust gas and the use of graphs for the presented equation. This method is considered useful in aircraft, in the field, or in the laboratory for a range of fuel-air ratios from 0.047 to 0.124.

Description: As part of a general investigation of propellers at high forward speeds, tests of two 2-blade propellers having the NACA 4-(3)(8)-03 and NACA 4-(3)(8)-45 blade designs have been made in the Langley 8-foot high-speed tunnel through a range of blade angle from 20 degrees to 60 degrees for forward Mach numbers from 0.165 to 0.725 to establish in detail the changes in propeller characteristics due to compressibility effects. These propellers differed primarily only in blade solidity, one propeller having 50 percent and more solidity than the other. Serious losses in propeller efficiency were found as the propeller tip Mach number exceeded 0.91, irrespective of forward speed or blade angle. The magnitude of the efficiency losses varied from 9 percent to 22 percent per 0.1 increase in tip Mach number above the critical value. The range of advance ratio for peak efficiency decreased markedly with increase of forward speed. The general form of the changes in thrust and power coefficients was found to be similar to the changes in airfoil lift coefficient with changes in Mach number. Efficiency losses due to compressibility effects decreased with increase of blade width. The results indicated that the high level of propeller efficiency obtained at low speeds could be maintained to forward sea-level speeds exceeding 500 miles per hour.

Description: An investigation has been made to explore the possibilities of axial-flow compressors operating with supersonic velocities into the blade rows. Preliminary calculations showed that very high pressure ratios across a stage, together with somewhat increased mass flows, were apparently possible with compressors which decelerated air through the speed of sound in their blading. The first phase of the investigation was the development of efficient supersonic diffusers to decelerate air through the speed of sound. The present report is largely a general discussion of some of the essential aerodynamics of single-stage supersonic axial-flow compressors. As an approach to the study of supersonic compressors, three possible velocity diagrams are discussed briefly. Because of the encouraging results of this study, an experimental single-stage supersonic compressor has been constructed and tested in Freon-12. In this compressor, air decelerates through the speed of sound in the rotor blading and enters the stators at subsonic speeds. A pressure ratio of about 1.8 at an efficiency of about 80 percent has been obtained.

Description: Sound pressure levels, frequency spectrum, and jet velocity profiles are presented for an engine-afterburner combination at various values of afterburner fuel - air ratio. At the high fuel-air ratios, severe low-frequency resonance was encountered which represented more than half the total energy in the sound spectrum. At similar thrust conditions, lower sound pressure levels were obtained from a current fighter air craft with a different afterburner configuration. The lower sound pressure levels are attributed to resonance-free afterburner operation and thereby indicate the importance of acoustic considerations in afterburner design.

Description: The present paper examines potential propulsive and aerodynamic benefits of integrating a Boundary-Layer Ingestion (BLI) propulsion system into the Common Research Model (CRM) geometry and the NASA Tetrahedral Unstructured Software System (TetrUSS). The Numerical Propulsion System Simulation (NPSS) environment is used to generate engine conditions for Computational Fluid Dynamics (CFD) analyses. Improvements to the BLI geometry are made using the Constrained Direct Iterative Surface Curvature (CDISC) design method. Potential benefits of the BLI system relating to cruise propulsive power are quantified using a power balance method, and a comparison to the baseline case is made. Iterations of the BLI geometric design are shown, and improvements between subsequent BLI designs are presented. Simulations are conducted for a cruise flight condition of Mach 0.85 at an altitude of 38,500 feet, with Reynolds number of 40 million based on mean aerodynamic chord and an angle of attack of 2 for all geometries. Results indicate an 8% reduction in engine power requirements at cruise for the BLI configuration compared to the baseline geometry. Small geometric alterations of the aft portion of the fuselage using CDISC has been shown to marginally increase the benefit from boundary-layer ingestion further, resulting in an 8.7% reduction in power requirements for cruise, as well as a drag reduction of approximately twelve counts over the baseline geometry.

Description: Outline - Introduction: X-57 CFD task overview; Motivation. Part I, Computational simulations without propulsion: Establishing CFD (Computational Fluid Dynamics) Best Practices - Grid generation - Mesh refinement study - Numerical methods - Wind tunnel validation study; Power-Off Aerodynamic Database Results. Part II, Computational simulations with propulsion: Cruise Power-On Database; High-Lift Power-On Database. Summary.

Description: A rotor blade comprises an airfoil extending radially from a root section to a tip section and axially from a leading edge to a trailing edge, the leading and trailing edges defining a curvature therebetween. The curvature determines a relative exit angle at a relative span height between the root section and the tip section, based on an incident flow velocity at the leading edge of the airfoil and a rotational velocity at the relative span height. In operation of the rotor blade, the relative exit angle determines a substantially flat exit pressure ratio profile for relative span heights from 75% to 95%, wherein the exit pressure ratio profile is constant within a tolerance of 10% of a maximum value of the exit pressure ratio profile.

Description: Two short turbojet combustors designed for use with vaporized hydrocarbon fuels were tested in a one-quarter annular duct. The experimental combustors consisted of many small "swirl-can" combustor elements manifolded together. This design approach allowed the secondary mixing zone to be considerably reduced over that of conventional combustors. The over-all combustion lengths, for the two configurations were 13.5 and 11.0 inches, approximately one-half the length of the shortest conventional combustors. These short combustors did not provide combustion efficiencies as high as those for conventional combustors at low pressures. However, over the range of combustor-inlet total-pressures expected in aircraft capable of flight at Mach numbers of 2.5 and above, these short combustors gave very high efficiencies. A combustion efficiency of 97 percent was obtained at a combustor-inlet total-pressure of 25.0 inches of mercury absolute, reference velocity of 120 feet per second, and inlet-air total temperature of 1160 deg R. By proportioning the fuel flow between the manifold rows of can combustor elements, control of the combustor-outlet radial total-temperature profile was demonstrated. Combustor totalpressure loss varied from 0.75 percent of the inlet total pressure at isothermal conditions and a reference velocity of 75 feet per second to 5.5 percent at a total-temperature ratio of 1.8 and a reference velocity of 180 feet per second.

Description: A simulator to artificially generate turbofan broadband signatures using the ANCF (Advanced Noise Control Fan) test article is presented. [Development of a Broadband Acoustic Emulator to Mature Propulsion Noise Reduction (CFANS-BB: Configurable Fan Artificial Noise Source- Broadband)]

Description: Hot-air engines with dynamic compressors and turbines offer new prospects of success through utilization of units of high efficiencies and through the employment of modern materials of great strength at high temperature. Particular consideration is given to an aerodynamic prime mover operating on a closed circuit and heated externally. Increase of the pressure level of the circulating air permits a great increase of limit load of the unit. This also affords a possibility of regulation for which the internal efficiency of the unit changes but slightly. The effect of pressure and temperature losses is investigated. A general discussion is given of the experimental installation operating at the Escher Wyss plant in Zurich for a considerable time at high temperatures.

Description: The National Aeronautics and Space Administration (NASA) has developed independent airframe and engine models that have been integrated into a single real-time aircraft simulation for piloted evaluation of propulsion control algorithms. In order to have confidence in the results of these evaluations, the integrated simulation must be validated to demonstrate that its behavior is realistic and that it meets the appropriate Federal Aviation Administration (FAA) certification requirements for aircraft. The paper describes the test procedures and results, demonstrating that the integrated simulation generally meets the FAA requirements and is thus a valid testbed for evaluation of propulsion control modes.

Description: This paper presents a model-based architecture for performance trend monitoring and gas path fault diagnostics designed for analyzing streaming transient aircraft engine measurement data. The technique analyzes residuals between sensed engine outputs and model predicted outputs for fault detection and isolation purposes. Diagnostic results from the application of the approach to test data acquired from an aircraft turbofan engine are presented. The approach is found to avoid false alarms when presented nominal fault-free data. Additionally, the approach is found to successfully detect and isolate gas path seeded-faults under steady-state operating scenarios although some fault misclassifications are noted during engine transients. Recommendations for follow-on maturation and evaluation of the technique are also presented.

Description: The purpose of this article is to explain why the extension of the previously published C = (S/Ho)sqrt(J) scaling for opposed rows of staggered jets wasn't directly successful in the study by Choi et al. (2016). It is not surprising that staggered jets from opposite sides do not pass each other at the expected C value, because Ho/D and sqrt(J) are much larger than the maximum in previous studies. These, and large x/D's, tend to suggest development of 2-dimensional flow. Although there are distinct optima for opposed rows of in-line jets, single-side injection, and opposed rows of staggered jets based on C, opposed rows of staggered jets provide as good or better mixing performance, at any C value, than opposed rows of in-line jets or jets from single-side injection.

Description: Acoustic treatment designers have long been able to target specific noise sources inside turbofan engines. Facesheet porosity and cavity depth are key design variables of perforate-over-honeycomb liners that determine levels of noise suppression as well as the frequencies at which suppression occurs. Layers of these structures can be combined to create a robust attenuation spectrum that covers a wide range of frequencies. Looking to the future, rapidly-emerging additive manufacturing technologies are enabling new liners with multiple degrees of freedom, and new adaptive liners with variable impedance are showing promise. More than ever, there is greater flexibility and freedom in liner design. Subject to practical considerations, liner design variables may be manipulated to achieve a target attenuation spectrum. But characteristics of the ideal attenuation spectrum can be difficult to know. Many multidisciplinary system effects govern how engine noise sources contribute to community noise. Given a hardwall fan noise source to be suppressed, and using an analytical certification noise model to compute a community noise measure of merit, the optimal attenuation spectrum can be derived using multidisciplinary systems analysis methods. The subject of this paper is an analytical method that derives the ideal target attenuation spectrum that minimizes noise perceived by observers on the ground.

Description: A computational fluid dynamic (CFD) model of a rotating detonation engine (RDE) is used to examine the impact of an exhaust throat (i.e. a constriction) on performance. The model simulates an RDE which is premixed, adiabatic, inviscid, and which contains an inlet valve that prevents backflow from the high pressure region directly behind the rotating detonation. Performance is assessed in terms of ideal net specific impulse which is computed on the assumption of lossless expansion of the working fluid to the ambient pressure through a notional diverging nozzle section downstream of the throat. Such a semi-idealized analysis, while not real-world, allows the effect of the throat to be examined in isolation from, rather than coupled to (as it actually is) various loss mechanisms. For the single Mach 1.4 flight condition considered, it is found that the addition of a throat can yield a 9.4 percent increase in specific impulse. However, it is also found that when the exit throat restriction gets too small, an unstable type of operation ensues which eventually leads to the detonation failing. This behavior is found to be somewhat mitigated by the addition of an RDE inlet restriction across which there is an aerodynamic loss. Remarkably, this loss is overcome by the benefits of the further exhaust restrictions allowed. The end result is a configuration with a 10.3 percent improvement in ideal net specific thrust.

Description: The purpose of this paper is to propose specific power and efficiency as the key performance parameters for a turboelectric aircraft power system and investigate their impact on the overall aircraft. Key functional requirements are identified that impact the power system design. Breguet range equations for a base aircraft and a turboelectric aircraft are found. The benefits and costs that may result from the turboelectric system are enumerated. A break-even analysis is conducted to find the minimum allowable electric drive specific power and efficiency that can preserve the range, initial weight, operating empty weight, and payload weight of the base aircraft.

Description: A large-eddy simulation / Reynolds-averaged Navier-Stokes (LES/RANS) methodology is used to simulate premixed ethylene-air combustion in a model scramjet designed for dual mode operation and equipped with a cavity for flameholding. A 22-species reduced mechanism for ethylene-air combustion is employed, and the calculations are performed on a mesh containing 93 million cells. Fuel plumes injected at the isolator entrance are processed by the isolator shock train, yielding a premixed fuel-air mixture at an equivalence ratio of 0.42 at the cavity entrance plane. A premixed flame is anchored within the cavity and propagates toward the opposite wall. Near complete combustion of ethylene is obtained. The combustor is highly dynamic, exhibiting a large-scale oscillation in global heat release and mass flow rate with a period of about 2.8 ms. Maximum heat release occurs when the flame front reaches its most downstream extent, as the flame surface area is larger. Minimum heat release is associated with flame propagation toward the cavity and occurs through a reduction in core flow velocity that is correlated with an upstream movement of the shock train. Reasonable agreement between simulation results and available wall pressure, particle image velocimetry, and OH-PLIF data is obtained, but it is not yet clear whether the system-level oscillations seen in the calculations are actually present in the experiment.

Description: Hypersonic air-breathing engines rely on scramjet combustion processes, which involve high speed, compressible, and highly turbulent flows. The combustion environment and the turbulent flames at the heart of these engines are difficult to simulate and study in the laboratory under well controlled conditions. Typically, wind-tunnel testing is performed that more closely approximates engine testing rather than a careful investigation of the underlying physics that drives the combustion process. The experiments described in this paper, along with companion data sets being developed separately, aim to isolate the chemical kinetic effects from the fuel-air mixing process in a dual-mode scramjet combustion environment. A unique fuel injection approach is taken that produces a nearly uniform fuel-air mixture at the entrance to the combustor. This approach relies on the precombustion shock train upstream of the dual-mode scramjet combustor. A stable ethylene flame anchored on a cavity flameholder with a uniformly mixed combustor inflow has been achieved in these experiments allowing numerous companion studies involving coherent anti-Stokes Raman scattering (CARS), particle image velocimetry (PIV), and planar laser induced fluorescence (PLIF) to be performed.

Description: This presentation will be used to develop a level of partnership that is not within the current NASA program for N+3 engine operations.

Description: This paper presents analytical techniques for aiding system designers in making aircraft engine health management sensor selection decisions. The presented techniques, which are based on linear estimation and probability theory, are tailored for gas turbine engine performance estimation and gas path fault diagnostics applications. They enable quantification of the performance estimation and diagnostic accuracy offered by different candidate sensor suites. For performance estimation, sensor selection metrics are presented for two types of estimators including a Kalman filter and a maximum a posteriori estimator. For each type of performance estimator, sensor selection is based on minimizing the theoretical sum of squared estimation errors in health parameters representing performance deterioration in the major rotating modules of the engine. For gas path fault diagnostics, the sensor selection metric is set up to maximize correct classification rate for a diagnostic strategy that performs fault classification by identifying the fault type that most closely matches the observed measurement signature in a weighted least squares sense. Results from the application of the sensor selection metrics to a linear engine model are presented and discussed. Given a baseline sensor suite and a candidate list of optional sensors, an exhaustive search is performed to determine the optimal sensor suites for performance estimation and fault diagnostics. For any given sensor suite, Monte Carlo simulation results are found to exhibit good agreement with theoretical predictions of estimation and diagnostic accuracies.

Description: The NASA Environmentally Responsible Aviation (ERA) program is maturing technologies to enable simultaneous reduction of fuel burn, noise and emissions from an aircraft engine system. Three engine related Integrated Technology Demonstrations (ITDs) have been completed at Glenn Research Center in collaboration with Pratt Whitney, General Electric and the Federal Aviation Administration. The engine technologies being matured are: a low NOx, fuel flexible combustor in partnership with Pratt Whitney; an ultra-high bypass, ducted propulsor system in partnership with Pratt Whitney and FAA; and high pressure ratio, front-stage core compressor technology in partnership with General Electric. The technical rationale, test configurations and overall results from the test series in each ITD are described. ERA is using system analysis to project the benefits of the ITD technologies on potential aircraft systems in the 2025 timeframe. Data from the ITD experiments were used to guide the system analysis assumptions. Results from the current assessments for fuel burn, noise and oxides of nitrogen emissions are presented.

Description: NASA Glenn Research Center is investigating hybrid electric and turboelectric propulsion concepts for future aircraft to reduce fuel burn, emissions, and noise. Systems studies show that the weight and efficiency of the electric system components need to be improved for this concept to be feasible. However, advances in motor component materials such as soft magnetic materials, hard magnetic materials, conductors, thermal insulation, and structural materials are expected in the coming years, and should improve motor performance. This study investigates several motor types for a one megawatt application, and projects the motor performance benefits of new component materials that might be available in the coming decades.

Description: The purpose of this effort is to develop, demonstrate, and evaluate three asymmetric thrust detection approaches to aid in the reduction of asymmetric thrust-induced aviation accidents. This paper presents the results from that effort and their evaluation in simulation studies, including those from a real-time flight simulation testbed. Asymmetric thrust is recognized as a contributing factor in several Propulsion System Malfunction plus Inappropriate Crew Response (PSM+ICR) aviation accidents. As an improvement over the state-of-the-art, providing annunciation of asymmetric thrust to alert the crew may hold safety benefits. For this, the reliable detection and confirmation of asymmetric thrust conditions is required. For this work, three asymmetric thrust detection methods are presented along with their results obtained through simulation studies. Representative asymmetric thrust conditions are modeled in simulation based on failure scenarios similar to those reported in aviation incident and accident descriptions. These simulated asymmetric thrust scenarios, combined with actual aircraft operational flight data, are then used to conduct a sensitivity study regarding the detection capabilities of the three methods. Additional evaluation results are presented based on pilot-in-the-loop simulation studies conducted in the NASA Glenn Research Center (GRC) flight simulation testbed. Data obtained from this flight simulation facility are used to further evaluate the effectiveness and accuracy of the asymmetric thrust detection approaches. Generally, the asymmetric thrust conditions are correctly detected and confirmed.

Description: This paper covers the development of stage-by-stage and parallel flow path compressor modeling approaches for a Variable Cycle Engine. The stage-by-stage compressor modeling approach is an extension of a technique for lumped volume dynamics and performance characteristic modeling. It was developed to improve the accuracy of axial compressor dynamics over lumped volume dynamics modeling. The stage-by-stage compressor model presented here is formulated into a parallel flow path model that includes both axial and rotational dynamics. This is done to enable the study of compressor and propulsion system dynamic performance under flow distortion conditions. The approaches utilized here are generic and should be applicable for the modeling of any axial flow compressor design accurate time domain simulations. The objective of this work is as follows. Given the parameters describing the conditions of atmospheric disturbances, and utilizing the derived formulations, directly compute the transfer function poles and zeros describing these disturbances for acoustic velocity, temperature, pressure, and density. Time domain simulations of representative atmospheric turbulence can then be developed by utilizing these computed transfer functions together with the disturbance frequencies of interest.

Description: Air transportation is critical to U.S. and Global economic vitality. However, energy and climate issues challenge aviations ability to be sustainable in the long term. Aviation must dramatically reduce fuel use and related emissions. Energy costs to U.S. airlines nearly tripled between 1995 and 2011, and continue to be the highest percentage of operating costs. The NASA Advanced Air Transports Technology Project addresses the comprehensive challenge of enabling revolutionary energy efficiency improvements in subsonic transport aircraft combined with dramatic reductions in harmful emissions and perceived noise to facilitate sustained growth of the air transportation system. Advanced technologies and the development of unconventional aircraft systems offer the potential to achieve these improvements. The presentation will highlight the NASA vision of revolutionary systems and propulsion technologies needed to achieve these challenging goals. Specifically, the primary focus is on the N+3 generation; that is, vehicles that are three generations beyond the current state of the art, requiring mature technology solutions in the 2025-30 timeframe, which are envisioned as being powered by Hybrid Electric Propulsion Systems.

Description: A gas turbine engine includes a spool, a turbine coupled to drive the spool, and a propulsor that is coupled to be driven by the turbine through the spool. A gear assembly is coupled between the propulsor and the spool such that rotation of the turbine drives the propulsor at a different speed than the spool. The propulsor includes a hub and a row of propulsor blades that extends from the hub. The row includes no more than 20 of the propulsor blades.

Description: The cost and risk associated with the design and operation of gas turbine engine systems has led to an increasing dependence on mathematical models. In this paper, the fundamentals of engine simulation will be reviewed, an example performance analysis will be performed, and relationships useful for engine control system development will be highlighted. The focus will be on thermodynamic modeling utilizing techniques common in industry, such as: the Brayton cycle, component performance maps, map scaling, and design point criteria generation. In general, these topics will be viewed from the standpoint of an example turbojet engine model; however, demonstrated concepts may be adapted to other gas turbine systems, such as gas generators, marine engines, or high bypass aircraft engines. The purpose of this paper is to provide an example of gas turbine model generation and system performance analysis for educational uses, such as curriculum creation or student reference.

Description: The Intelligent Control and Autonomy Branch (ICA) at NASA (National Aeronautics and Space Administration) Glenn Research Center (GRC) in Cleveland, Ohio, is leading and participating in various projects in partnership with other organizations within GRC and across NASA, the U.S. aerospace industry, and academia to develop advanced controls and health management technologies that will help meet the goals of the NASA Aeronautics Research Mission Directorate (ARMD) Programs. These efforts are primarily under the various projects under the Advanced Air Vehicles Program (AAVP), Airspace Operations and Safety Program (AOSP) and Transformative Aeronautics Concepts Program (TAC). The ICA Branch is focused on advancing the state-of-the-art of aero-engine control and diagnostics technologies to help improve aviation safety, increase efficiency, and enable operation with reduced emissions. This paper describes the various ICA research efforts under the NASA Aeronautics Research Mission Programs with a summary of motivation, background, technical approach, and recent accomplishments for each of the research tasks.

Description: An injector for a multipoint combustor system includes an inner air swirler which defines an interior flow passage and a plurality of swirler inlet ports in an upstream portion thereof. The inlet ports are configured and adapted to impart swirl on flow in the interior flow passage. An outer air cap is mounted outboard of the inner swirler. A fuel passage is defined between the inner air swirler and the outer air cap, and includes a discharge outlet between downstream portions of the inner air swirler and the outer air cap for issuing fuel for combustion. The outer air cap defines an outer air circuit configured for substantially unswirled injection of compressor discharge air outboard of the interior flow passage.

Description: The purpose of this effort was to advance the selection, characterization, and modeling of a propulsion electric grid for a Turboelectric Distributed Propulsion (TeDP) system for transport aircraft. The TeDP aircraft would constitute a miniature electric grid with 50 MW or more of total power, two or more generators, redundant transmission lines, and multiple electric motors driving propulsion fans. The study proposed power system architectures, investigated electromechanical and solid state circuit breakers, estimated the impact of the system voltage on system mass, and recommended DC bus voltage range. The study assumed an all cryogenic power system. Detailed assumptions within the study include hybrid circuit breakers, a two cryogen system, and supercritical cyrogens. A dynamic model was developed to investigate control and parameter selection.

Description: NASA is developing a suite of hybrid-electric propulsion technologies for aircraft. These technologies have the benefit of lower emissions, diminished noise, increased efficiency, and reduced fuel burn. These will provide lower operating costs for aircraft operators. Replacing internal combustion engines with distributed electric propulsion is a keystone of this technology suite, but presents many new problems to aircraft system designers. One of the problems is how to cool these electric motors without adding significant aerodynamic drag, cooling system weight or fan power. This paper discusses the options evaluated for cooling the motors on SCEPTOR (Scalable Convergent Electric Propulsion Technology and Operations Research): a project that will demonstrate Distributed Electric Propulsion technology in flight. Options for external and internal cooling, inlet and exhaust locations, ducting and adjustable cowling, and axial and centrifugal fans were evaluated. The final design was based on a trade between effectiveness, simplicity, robustness, mass and performance over a range of ground and flight operation environments.

Description: The Integrated Technology Demonstration (ITD) 40A Low NOx Fuel Flexible Combustor Integration development is being conducted as part of the NASA Environmentally Responsible Aviation (ERA) Project. Phase 2 of this effort began in 2012 and will end in 2015. This document describes the ERA goals, how the fuel flexible combustor integration development fulfills the ERA combustor goals, and outlines the work to be conducted during project execution.

Description: A feasibility study was performed for an advanced commercial short-haul aircraft to evaluate the potential for increased service for short-haul flights that operate out of regional and community airports. An analysis of potential origin-destination markets and trip distances resulted in a seat capacity selection of 48 passengers and a design range of 600 NM. A down-select of advanced technologies resulted in a hybrid-electric propulsion system being chosen as the primary enabling technology. A conceptual design of the advanced aircraft was developed, and a mission and sizing analysis was performed, comparing variants of the advanced aircraft with different levels of electrification. Fairly aggressive levels of electrification and battery specific energy are needed for the hybridelectric architecture to realize any benefit in terms of total energy cost for the 600 NM design mission. The development and operational costs were estimated for the advanced aircraft and compared to the baseline. This analysis demonstrated the negative effect of the cost to develop the hybrid-electric technology on the eventual operating cost. A market analysis was performed to determine possible passenger demand for the advanced shorthaul aircraft. According to the market analysis, there is potential demand for such an aircraft, but not necessarily in many of the smaller regional and community airports that were the intended beneficiaries of this new aircraft concept.

Description: A fuel injector component includes a body, an elongate void and a plurality of bores. The body has a first surface and a second surface. The elongate void is enclosed by the body and is integrally formed between portions of the body defining the first surface and the second surface. The plurality of bores extends into the second surface to intersect the elongate void. A process for making a fuel injector component includes building an injector component body having a void and a plurality of ports connected to the void using an additive manufacturing process that utilizes a powdered building material, and removing residual powdered building material from void through the plurality of ports.

Description: A gas turbine engine includes a core flow passage, a bypass flow passage, and a propulsor arranged at an inlet of the bypass flow passage and the core flow passage. The propulsor includes a row of propulsor blades. The row includes no more than 20 of the propulsor blades. The propulsor has a pressure ratio between about 1.2 and about 1.7 across the propulsor blades.

Description: A fan section for an engine has a fan which rotates about an axis, the fan has an inlet for ingesting ambient air, and a non-axisymmetric nozzle for providing the fan with non-uniform back pressure.

Description: A centrifugal compressor research effort conducted by United Technologies Research Center under NASA Research Announcement NNC08CB03C is documented. The objectives were to identify key technical barriers to advancing the aerodynamic performance of high-efficiency, high work factor, compact centrifugal compressor aft-stages for turboshaft engines; to acquire measurements needed to overcome the technical barriers and inform future designs; to design, fabricate, and test a new research compressor in which to acquire the requisite flow field data. A new High-Efficiency Centrifugal Compressor stage -- splittered impeller, splittered diffuser, 90 degree bend, and exit guide vanes -- with aerodynamically aggressive performance and configuration (compactness) goals were designed, fabricated, and subquently tested at the NASA Glenn Research Center.

Description: The report "High Efficiency Centrifugal Compressor for Rotorcraft Applications" documents the work conducted at UTRC under the NRA Contract NNC08CB03C, with cost share 2/3 NASA, and 1/3 UTRC, that has been extended to 4.5 years. The purpose of this effort was to identify key technical barriers to advancing the state-of-the-art of small centrifugal compressor stages; to delineate the measurements required to provide insight into the flow physics of the technical barriers; to design, fabricate, install, and test a state-of-the-art research compressor that is representative of the rear stage of an axial-centrifugal aero-engine; and to acquire detailed aerodynamic performance and research quality data to clarify flow physics and to establish detailed data sets for future application. The design activity centered on meeting the goal set outlined in the NASA solicitation-the design target was to increase efficiency at higher work factor, while also reducing the maximum diameter of the stage. To fit within the existing Small Engine Components Test Facility at NASA Glenn Research Center (GRC) and to facilitate component re-use, certain key design parameters were fixed by UTRC, including impeller tip diameter, impeller rotational speed, and impeller inlet hub and shroud radii. This report describes the design effort of the High Efficiency Centrifugal Compressor stage (HECC) and delineation of measurements, fabrication of the compressor, and the initial tests that were performed. A new High-Efficiency Centrifugal Compressor stage with a very challenging reduction in radius ratio was successfully designed, fabricated and installed at GRC. The testing was successful, with no mechanical problems and the running clearances were achieved without impeller rubs. Overall, measured pressure ratio of 4.68, work factor of 0.81, and at design exit corrected flow rate of 3 lbm/s met the target requirements. Polytropic efficiency of 85.5 percent and stall margin of 7.5 percent were measured at design flow rate and speed. The measured efficiency and stall margin were lower than pre-test CFD predictions by 2.4 percentage points (pt) and 4.5 pt, respectively. Initial impressions from the experimental data indicated that the loss in the efficiency and stall margin can be attributed to a design shortfall in the impeller. However, detailed investigation of experimental data and post-test CFD simulations of higher fidelity than pre-test CFD, and in particular the unsteady CFD simulations and the assessment with a wider range of turbulence models, have indicated that the loss in efficiency is most likely due to the impact of unfavorable unsteady impeller/diffuser interactions induced by diffuser vanes, an impeller/diffuser corrected flow-rate mismatch (and associated incidence levels), and, potentially, flow separation in the radial-to-axial bend. An experimental program with a vaneless diffuser is recommended to evaluate this observation. A subsequent redesign of the diffuser (and the radial-to-axial bend) is also recommended. The diffuser needs to be redesigned to eliminate the mismatching of the impeller and the diffuser, targeting a slightly higher flow capacity. Furthermore, diffuser vanes need to be adjusted to align the incidence angles, to optimize the splitter vane location (both radially and circumferentially), and to minimize the unsteady interactions with the impeller. The radial-to-axial bend needs to be redesigned to eliminate, or at least minimize, the flow separation at the inner wall, and its impact on the flow in the diffuser upstream. Lessons were also learned in terms of CFD methodology and the importance of unsteady CFD simulations for centrifugal compressors was highlighted. Inconsistencies in the implementation of a widely used two-equation turbulence model were identified and corrections are recommended. It was also observed that unsteady simulations for centrifugal compressors require significantly longer integration times than what is current practice in industry.