Research On Multi-variable Control Schedules And Variable Cycle Performance For Air Turbo Rockets

In order to improve the overall performance of ATR engine at both sea level static and cruise conditions,this paper focuses on the steady and dynamic state control laws with multivariable.To improve the adaptability of ATR to different flight missions,the performance of a variable cycle ATR(ATR-GE)which is combined of ATR-GG(Gas Generator)and ATR-Ex(Expander)is studied.The main work is as follows:First,an ATR off-design performance model is established,and at sea level static and cruise conditions,the influence of oxygen-fuel ratio on engine components matching and overall performance are detailedly analyzed while the compressor corrected rotation speed and fuel-air ratio keeping constant.The results show that,at the sea level static condition,the compressor operating point moves from surge line to choking region along the constant corrected rotation speed line with the decreasing of the oxygen-fuel ratio,and the thrust decreases with the decreasing of the compressor pressure ratio,but the specific impulse increases;the thrust is maximum while the rotating speed,the combustion chamber temperature and the turbine inlet temperature are maximum.At the cruise condition,the compressor operating point moves from the surge line to choking region along the constant corrected rotation speed line with the decreasing of the oxygen-fuel ratio,and the thrust increases with the increasing of air mass flow rate,during this process the specific impulse increases;the thrust is maximum while the engine rotation speed and chamber temperature are maximum,and the compressor operating point is located at the minmum pressure ratio on the constant rotation speed line.And then,an ATR overall performance optimization model is built based on the off-design model,and at sea level static and cruise conditions,the engine specific impulse is optimized at a given thrust while the fuel mass flow rate,oxygen mass flow rate and nozzle throat area are adjustable.The results show,at the sea level static condition,when the given thrust reaches design value,the engine maximum specific impulse is obtained while the rotation speed is maximum.The compressor operating point moves from surge line to choking region on the constant rotation speed line with the decreasing of the given thrust.When the compressor operate at the minmum pressure ratio point on the constant rotation speed line,the maximum specific impulse is obtained while the combustion temperature is maximum.At the cruising condition,the maximum specific impulse is obtained while the combustion temperature is maximum,and the compressor operate at the bottom of the characteristics map.Second,an ATR dynamic model considering the volume effect is established based on the volume chambers which are connected after the compressor,the gas generator and the turbine.The influence of different fuel flow and nozzle throat area control law on the ATR accelerating process is analyzed.Increasing the nozzle area can reduce the acceleration time and the fuel consumption,and also help to keep ATR working line away from the compressor surge line,because the compressor power decreases and the turbine power increases at this condition.Increasing the fuel flow can increase the turbine power and reduce the acceleration time and the fuel consumption,but the compressor working line is closed to the compressor surge line,and the combustion chamber exit temperature will increase.Finally,a temperature ratio parameter is defined to characterize the cycle state of ATR-GE,and the effects of the temperature ratio and combustor excess oil coefficient on ATR-GE overall performance are analyzed.The cycle of ATR-GE can be transited between the ATR-GG model and the ATR-Ex model smoothly by adjusting the temperature ratio.At the low flight Mach number conditions,the higher engine specific thrust can be obtained with a lower temperature ratio and a higher combustor excess oil coefficient.At high flight Mach number conditions,the higher engine specific impulse can be obtained with a higher temperature ratio and a lower combustor excess oil coefficient.