Abstract
The author reported the results examined about the effects of the shape on the performance of the multiple nozzle supersonic air ejectors in the previous paper. In the present paper, the experimental investigations of the effects of the expansion ratios of nozzles on the performances of the ejectors for small flow ratio and for medium flow ratio are described. The main conclusions are as follows. (1) The best performance can be gained in case that the driving jet through nozzle expands normally (or nearly normally). The values of the expansion ratios of nozzles for the multiple nozzle ejectors are same for the single nozzle ejectors, and they are as follows; for ejectors of type A with throat area ratio m=11.8: α=1.44 when P_0'=3atg, α=2.01 when P_0'=5atg, α=3.18 when P_0'=7atg, where α is the expansion ratio of nozzle, i.e. the area ratio of nozzle outlet to its throat and P_0' is the pressure of driving air before nozzle; for ejectors of type B with throat area ratio m=47.3: α=1.25 when P_0'=3atg, α=1.56 when P_0'=5atg, α=1.84 when P_0'=7atg. (2) In the range of large flow ratios, the multiple nozzle ejectors have better performances than the single nozzle ejectors. This fact can be accepted for all the expansion ratios of nozzles. (3) The jet noise is larger for the larger expansion ratios of nozzles. The effects of the expansion ratios of nozzles on the noise are much smaller than those of the employment of multiple nozzles. That is, the employment of multiple nozzles is greatly useful for reduction of noise.
