Investigation of three lobes roots blower with special ejector

A volumetric Roots type blower with spur three or two lobes rotors has a high performance at a small unit size and is used mainly at the pressure ratio in the range of 1,4 - 1,6. A significant limitation of this parameter is due to the nature of the compressor working process, in particular a rapid, almost instantaneous increase in the pressure in the working chamber because of back flow. This leads to a decrease in performance and efficiency, and increase of the compressor noise level. One of the ways to overcome this drawback is the use of bypassing of part of compressed and cooled gas at injection through the ejector into the working chamber that is simultaneously disconnected from both discharge and suction. Due to this, the pressure increase process becomes more gradual as related to the rotor angle of rotation, and additional suction of portions of gas from the suction line by ejection effect becomes possible, which increases the efficiency and performance of the compressor. Experimental data confirm the efficacy of this method. Research of the Roots blower combined action with an ejector attachments based on the developed mathematical model has been presented.