| Both advantages of rocket engine and air-breathing engine are integrated into one kind of propulsion system,called Rocket-Based-Combined-Cycle (RBCC),which has multiple operating woke modes,including ejecting,subsonic combustion,supersonic combustion and rocket mode,with each mode operating at varying flying stage. RBCC has prominent potential of high efficiency and low cost,and so it is recognized as an advanced propulsion system of future single-stage-to-orbit reusable spacecraft and hipper-sonic missile. It has been broadly investigated in foreign countries and has been progressed into small and full-scale flying stage. The domestic research plan has been proposed and undertaken in nowadays. The progress in subsonic and supersonic combustions has been attained,but the ejecting mode and mode match of RBCC has just been begun. As one of key technologies to acquire the adequate thrust to start the RBCC propulsion system,whether the ejecting technology can produce thrust augmentation in ejecting mode of RBCC is greatly related to whether the potential advantages of RBCC 's high efficiency and low cost can be realized. It is of great significance to investigate performance characteristics and thrust augmentation mechanism in RBCC engine. This dissertation just deals with the mixing and combustion flow in a experimental Strutjet RBCC in ejecting mode to investigate its performance characteristics and thrust augmentation mechanism by applying numerical simulation technique. The detail is as follows:1. In consideration of computation exactness and cost,the unstructured grid,RNG K - e turbulence model,Renold-averaged N-S equations and second order upwind scheme were used to solve 3D turbulence flows with and without secondary combustion of a experimental Strutjet RBCC in ejecting mode. According to the jet theory and the characteristics of the flow,the flow can be divided into 6 zones:supersonic core zone,supersonic mixing zone,subsonic mixing zone,secondary flow zone and expanding zone. The rules to distinguish these zones were established.2. The mixing degree model was established to study the mixing progress of primary and secondary flow. The loss elements of all zones were deeply analyzed and thus the quantitative loss models based on total pressure loss and entropy increase respectively were constructed. The results show that the performance loss magnitude and distribution in ejecting mode of RBCC can be better described by the quantitative loss model expressed by entropy increase.3. The effects of such elements as primary flow total pressure,flow rate,degree of fuel rich,nozzle structure,flying speed and secondary combustion on ejecting mode performance were researched. It was found that thrust augmentation can be achieved on the condition that the flying mach number is above 0.7. To deeply analyze thrust augmentation mechanism in low speed range,the research was further continued by changing secondary combustion organization and aft-body configuration. Four conclusions were obtained:1) The ideal maximum performance of RBCC engine is basically determined by the match of RBCC 's basic operating parameters such as the ratios of primary/secondary mass flow rate,total pressure,total temperature and the ratio of overall oxidant/fuel mass flow rate,etc. But the real performance can be obtained is mainly determined by the ejected secondary mass flowrate,the mixing degree,the mixing efficiency,and the secondary combustion efficiency can be obtained. 2) The ejected secondary mass flow rate,the mixing degree and the mixing efficiency are synthetically affected by the configuration of RBCC engine,especially the mixer and the primary nozzle,in which the primary nozzle,including shape,number and distribution mainly determines the mixing degree;while the mixer configuration primarily determines the mixing efficiency. 3) The secondary combustion can't affect the mixing degree and mixing efficiency between primary flow and secondary flow apparently,but the heat it's released can increase pressure,temp...
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