An experimental investigation of supersonic rectangular over-expanded nozzle of single and two-phase flows.

摘要

This dissertation presents the results of an experimental investigation of the supersonic rectangular over-expanded flow of single and two-phase flows. Recent interest in rectangular supersonic jets is motivated by the need to reduce plume length and acoustically excited structural loads in the exhaust system of high performance aircrafts. Semi-periodic shock structures form in the jet plumes of these vehicles during low speed flight at off design conditions. These shock cells affect the jet velocity and temperature decay as well as the jet spread rate and its acoustic field. The flow regimes and shock structure in the plume was characterized for jets in quiescent atmosphere at overexpanded conditions. Instantaneous and phase average schlieren/shadowgraph images of the internal flow and the jets are presented to show the over-expanded shock structure and jet spread rate at different nozzle pressure ratios ranged from 1.6 to 9.5.; A high-pressure particle feeders have been constructed to steady feed the dispersed large particles and the seeding particle for LDA measurements at different particle loading rates. Schlieren pictures of the jets are presented to show the shock structure and jet spread rate. LDV measurements are presented for the jet flow field and the centerline velocity decay. The results indicate that the rectangular supersonic jet spread rate is greater along the minor axis and increases with the nozzle pressure ratio. The individual shock cell length, as well as the total number of shock cells within the jet plume were found to increase with nozzle pressure ratio. In two-phase rectangular jets of gas and dispersed solid particles the shock strength was found to attenuate with increased particle loading. The design, construction and initial shakedown of the facility has been accomplished. The effort required to reach this stage has been greater than initially expected. Further more detailed data acquisitions and measurements will be accomplished in future studies.