Variable capacity operation of a vapor ejector equipped with an adjustable needle

摘要

Vapor ejector technology compresses gas using thermal rather than mechanical or electrical energy.For a given motive pressure, ejector capacity is constant; it is a direct function of the motive nozzlethroat area. When the available thermal motive power is changed, an adjustable needle could movewithin the motive nozzle, varying the throat area. A steam activated vapor ejector test bench was usedto investigate this design strategy. First, tests were completed with two constant area motive nozzleshaving throat areas of 12.8 mm~2 and 20.3 mm~2. Then, a needle-equipped motive nozzle, having amaximum throat area of 20.1 mm~2, was evaluated over approximately the same throat area range.Experimentally evaluated ejector performance was similar for both the needle-equipped and theconstant area nozzles, for moderate throat area reduction. However, for throat area reductions greaterthan 24%, the needle-equipped ejector showed a performance penalty compared to the constant areaejector.