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  • 1985-1989  (7)
  • 1
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    Hydrogen scramjet with sidewall injection - Shock tunnel simulations (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A free-piston shock tunnel has been used to obtain test data on a scramjet combustion chamber with sidewall injection. The results obtained indicate that combustion was strongly influenced by a region of fuel whose temperature was held below its ignition temperature by wall-cooling effects; this increased the fraction of unburned fuel and resulted in a significant loss of specific impulse. Aerodynamic heating would keep the walls above hydrogen ignition temperature in an actual scramjet powerplant, however. Maximum specific impulse was obtained with a combination of parallel and transverse injection in a long combustion chamber, followed by a dual stage expansion.
    Keywords: AIRCRAFT PROPULSION AND POWER
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    NASA TECHNICAL REPORTS
  • 2
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    Scramjet sidewall burning: Preliminary shock tunnel results (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Experiments performed with a two dimensional model scramjet with particular emphasis on the effect of fuel injection from a wall are reported. Air low with a nominal Mach number of 3.5 and varied enthalpies was produced. It was found that neither hydrogen injection angle nor combustor divergence angle had any appreciable effect on thrust values while increased combustor length appeared to increase thrust levels. Specific impulse was observed to peak when hydrogen was injected at an equivalence ratio of about 2. Lowering the Mach number of the injected hydrogen at low equivalence ratios, less than 4, appeared to benefit specific impulse while hydrogen Mach number had little effect at higher equivalence ratios. When a 1:1 mixture by volume of nitrogen and oxygen is used instead of air as a test gas, it is found that hydrogen combustion is enhanced but only at high enthalpies.
    Keywords: SPACECRAFT PROPULSION AND POWER
    Type: NASA-CR-176420 , NAS 1.26:176420 , REPT-12/85
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    NASA TECHNICAL REPORTS
  • 3
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    Further shock tunnel studies of scramjet phenomena (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Scramjet phenomena were studied using the shock tunnel T3 at the Australian National University. Simple two dimensional models were used with a combination of wall and central injectors. Silane as an additive to hydrogen fuel was studied over a range of temperatures and pressures to evaluate its effect as an ignition aid. The film cooling effect of surface injected hydrogen was measured over a wide range of equivalence. Heat transfer measurements without injection were repeated to confirm previous indications of heating rates lower than simple flat plate predictions for laminar boundary layers in equilibrium flow. The previous results were reproduced and the discrepancies are discussed in terms of the model geometry and departures of the flow from equilibrium. In the thrust producing mode, attempts were made to increase specific impulse with wall injection. Some preliminary tests were also performed on shock induced ignition, to investigate the possibility in flight of injecting fuel upstream of the combustion chamber, where it could mix but not burn.
    Keywords: AERODYNAMICS
    Type: NASA-CR-179937 , NAS 1.26:179937 , RR-10-86
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  • 4
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    Shock tunnel studies of scramjet phenomena (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Commissioning of the new T4 shock tunnel at the University of Queensland implied that it was no longer necessary to focus the work of the research group about an annual test series conducted in the T3 shock tunnel in Canberra. Therefore, it has been possible to organize a group for work to proceed along lines such that particular personnel are associated with particular project areas. The format of this report consists of a series of reports on specific project areas, with a brief general introduction commenting on each report. The introduction is structured by project areas, with the title of the relevant report stated under the project area heading. The reports themselves follow in the order of the project area headings.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-181721 , NAS 1.26:181721
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  • 5
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    Silane as an ignition aid in scramjets (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: This paper presents the results of experiments on silane/hydrogen combustion in a scramjet model configured as a constant area duct with a central injector. Intake flow conditions were created by free piston shock tunnels with simulated flight speeds ranging between 1.4 and 4.2 km/s. Intake conditions were restricted to three nominal Mach numbers. Boundary layer heating appeared to be responsible for ignition at low temperature, high Mach number conditions. Concentration of silane in hydrogen was varied, as well as intake temperature and pressure. Results indicated that silane in concentrations as low as 2.5 percent in hydrogen, was effective as a fuel additive for scramjets at conditions where hydrogen alone could not support combustion. An unsteady effect was observed as the intake temperature approached the lower limit for combustion. The combustion temperature limit rose significantly as the intake pressure was reduced to low levels. Computer simulations using a one dimensional premixed analysis suggested that although silane enhanced the combustion process, it was strongly dependent on the initial concentration of free radical oxygen. Results from the simulations were comparable to experimental results for some conditions.
    Keywords: PROPELLANTS AND FUELS
    Type: AIAA PAPER 87-1636
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  • 6
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    Hydrogen scramjet with side wall injection (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Preliminary results are presented from an experimental evaluation of a hydrogen-burning wall-injection scramjet engine, performed in the free-piston shock tunnel at the Australian National University. The advantages of scramjet propulsion for high-Mach-number high-altitude flight are reviewed, and the need for an alternative to injection struts is indicated. Pressure profiles and heat-transfer measurements for constant-area and diverging ducts are presented graphically and characterized in detail. The ability of the injected flow to shield the chamber wall from the heat of the freestream flow is demonstrated. The extrapolation of the shock-tunnel results to flight conditions, however, is made difficult by the fact that a significant amount of fuel passes through a quenched zone without burning, seriously degrading overall performance.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: National Space Engineering Symposium; Mar 25, 1986 - Mar 27, 1986; Sydney; Australia
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  • 7
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    High Reynolds number heat transfer to the cold walls of a model scramjet (1987)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The results of simultaneous heat transfer and pressure measurements at the walls of three different configurations of a model scramjet are presented. The heat transfer results are compared with results empirically predicted from the pressure measurements. It is shown that the measured heat transfer rate is comparable with, or lower than, that predicted for a laminar boundary layer. A mathematical model is proposed for the film-cooling effect observed when a hydrogen fuel is injected along a wall of the scramjet. In this mathematical model, the heat transfer rate is shown to be insensitive to the velocity profile in the insulating layer of fuel. The model suggests that the cooling layer is turbulent and that 90 percent of the fuel is mixed with the air.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Australasian Fluid Mechanics Conference; Dec 08, 1986 - Dec 12, 1986; Auckland; New Zealand
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