Research On Kev Technology Of Cartridge Starting For Missile Turbojet Engine

Cartridge starting technology is a key technology of gas turbine engines for missiles,which has its own uniqueness and development difficulties.The mastery of advanced cartridge starting design methods and test methods is of great significance for improving the overall research and development level of our country’s missile gas turbine engines.However,the current domestic research on cartridge starting technology is not extensive enough,and there are few researches on cartridge starting of turbojet engines that use both low-pressure atomizing nozzles and evaporative nozzles.This paper takes a certain type of turbojet engine based on the low-pressure fuel pump system as the research object.Through theoretical analysis,scientific calculations and experimental methods,relevant researches have been carried out on the ground cartridge starting characteristics and high-altitude cartridge starting characteristics of this type of engine,and the fuel supply matching rules and design methods of cartridge starting have been obtained.The main research contents are as follows:(1)Research on ground characteristics of cartridge starting.Aiming at the features of cartridge starting,a ground cartridge starting scheme was designed.Based on the analysis of the engine cartridge starting characteristics and influencing factors,the matching method of fuel supply law was obtained.The cartridge starting simulation test system was used to test and verify the fuel supply matching method.The results showed that shortening the fuel supply time before ignition can effectively reduce the adverse effect on starting acceleration caused by accumulated fuel combustion.The acceleration rate at the early stage of starting was positively correlated with the initial throttle amount,but the optimal fuel air ratio for ignition should be considered at this stage.When the switching point of the pressure atomizing nozzles and the evaporative nozzles was selected at low speed,the starting performance of the engine was less affected.The simple step-mode fuel increase method can meet the requirements of rotor acceleration in the late stage of cartridge starting,and the throttle step point should match when the engine enters the high-speed stage.The starting characteristics can be further optimized by using the appropriate second-order throttle at the late stage of starting.(2)Research on the steady-state performance of the engine when using high energy density fuel.Literature research and experimental evaluation were carried out on the necessity and feasibility of using high energy density fuel for a certain type of missile turbojet engine.The effect of the use of high energy density fuel on the steady-state conversion performance of the engine was studied.The results showed that high energy density fuel had little effect on the steady-state conversion performance of the engine as a whole,but the corrected fuel consumption rate of the engine at each steady-state corrected speed was slightly increased.Compared with the use of ordinary fuel,when the engine used high energy density fuel,the corrected fuel volume flow was reduced by about 16.5%on average.The high energy density fuel alone did not have a good bearing lubrication function,so the engine should choose a suitable blendable lubricant in actual use.(3)Research on high-altitude characteristics of cartridge starting.Based on the high-altitude simulation test system,the cartridge starting characteristics of the engine under high-altitude flight conditions were studied,and the cartridge starting envelope and the windmill starting envelope of the engine were obtained.The results showed that high-altitude oxygen supplementation can not only improve the high-altitude ignition performance and starting acceleration performance of the cartridge starting engine,but also greatly broaden the engine’s starting airspace and starting speed range under the premise of ensuring high starting reliability.The cartridge starting characteristics of the engine equipped with ten-head pressure atomizing nozzles were generally better than those of the engine equipped with five-head pressure atomizing nozzles.When the ten-head atomizing nozzle was used,the engine had a wider main fuel supply boundary.The fuel exit mode of the atomized nozzle had an important influence on the starting characteristics of the engine.Under the condition that the amount of atomized fuel accounted for a large proportion of the total fuel volume,the engine was prone to unstable starting phenomenon that the engine speed dropped when it exited directly during the high-speed stage of the starting process.When the atomized nozzle fuel was withdrawn according to the improved scheme,the engine’s starting characteristics were better.(4)Mathematical modeling and scientific calculation of the oxygen supplement process during high-altitude starting.Oxygen supplementation or not and the oxygen supplementation method had an important influence on the ignition and starting characteristics of the engine during high-altitude cartridge starting.In order to study the rules of oxygen supplementation during the high-altitude cartridge starting of the engine,a mathematical model of oxygen supply from the oxygen cylinder was established and scientific calculations were carried out.The calculation results showed that when starting at high altitude,the oxygen supplementary throttle nozzle with d=0.7 mm throat diameter was preferred to take into account the oxygen mass flow rate and oxygen supplementation time during the oxygen supplement process.Under the same initial conditions,the instantaneous mass flow of oxygen supplementation was related to the initial volume of the oxygen cylinder.The mass flow rate of double-cylinder oxygen supplementation was greater than the mass flow rate of single-cylinder oxygen supplementation,and the oxygen supplementation time of the former was twice that of the latter.