Investigation On Combustion Organization In Turbocharged Solid Propellant Ramjet

With increasing requirements for tactical missile, such as high-speed, high mobility and long-range strike, propulsion system is required to have a wide envelope and high specific impulse. In view of this context, Turbocharged Solid Propellant Ramjet(TSPR) is proposed as one of the most ideal propulsion for the tactical missiles, which combines Solid Propellant Ramjet(SPR) and Air Turbo Rocket(ATR). It has the advantages of wide envelope and high performance. Stable and efficient combustion is one of the most critical requirements for high-performance engine. Compared with SPR and ATR, there are lots of difficulties in TSPR’s combustion organization, such as multiple-streams combustion, unfavourable mixing due to the inlet mode, the lack of relevant technology, and so on.Therefore, study on combustion organization is exigent and significant to improve the overall performance and promote the engineering process of TSPR.In the present thesis, considering the characteristics and difficulties of combustion organization in TSPR, the scheme design, combustion characteristics experiments, combustion enhancement technology and experimental verification were carried out by theoretic analysis, numerical simulation and experiment. The main study works and conclusions are as follows:(1) The TSPR scheme has been designed and it provides a studying object for combustion organization. TSPR performance model is improved, and provided a theoretical approach to engine design. The selecting principle of solid propellant is proposed. The comparing results show that solid hydrocarbon fuel-rich propellant suits driving turbine, and boron-based propellant is good for afterburning. The turbocharged system uses a single-stage centrifugal compressor and a single-stage impulse turbine based on the TSPR principle experiments, and finally the TSPR scheme is designed. The main design parameters are as follows: the engine thrust is 1500 N, the airflow mass is 1.55kg/s, the pressure ratio of the compressor is 3.2 and the rotation speed is 80000 rpm.(2) TSPR combustion experiments have been performed, and the primary and secondary combustion characters have been obtained, and it provides the foundation work for further research of combustion enhancement technology. The experimental combustion system with multiple-throat-nozzle that can simulate turbocharged system is established. In order to solve the ignition problem of ATR mode under normal temperature air condition, the upper limit of excess air coefficient for solid hydrocarbon propellant is obtained, and is about 2.3, and the operating mode can be switched from TSPR to ATR, which can significantly improve the ignition characteristics.(3) Combustion enhancement technology of TSPR has been investigated, and the high efficient combustion scheme has been proposed, and the combustion efficiency has increased significantly. A combustion numerical simulation method is established, and intake mode at the front the afterburner, diffuser scheme, and the intake mode of the afterburning gas is analyzed. The driving-turbo gas and pressurized air enter the afterburner in coaxial way, which makes it difficult to achieve efficient combustion. The intake scheme, which combined pressurized air jet in an oblique way and driving-turbo gas at high speed rotation, is proposed, and the mixing degree is increased significantly. The afterburner flow field distribution in ATR mode is characterized by fuel-rich region in the center and oxygen-rich region in the outside. Therefore, afterburning gas entering into the afterburner in transverse jet way is benefits for engine performance and injecting the gas into oxygen-rich region by the speed control that is the key to accomplish efficient combustion. Additionally, multi-stage diffuser scheme is designed to improve useable total pressure and the inlet air quality of afterburner. The optimum value of combustion enhancement scheme is obtained and its applicability during wide operations is verified by simulated calculation results.(4) The TSPR ground principle experiment has been performed, and the results have validated the feasibility of combustion organization. The TSPR principle engine and the ground experimental system are investigated based on efficient combustion scheme. TSPR ground principle experiment has been performed successfully for the first time. The average thrust is 1516 N, and the specific impulse is 4010m/s, and the combustion efficiency in TSPR mode is 84.81% which increases by 38.71% than that of base configuration.