Research On Combustion Characteristics Of Afterburner Of Small Turbo-jet Engine And Validation Of Overall Engine Test

With the continuous development of the aviation industry,the requirements for engine power of various types of military and civilian aircraft have been continuously increased,putting forward new requirements for the design of aero-engines.However,due to the aircraft’s demand for high thrust is often only in the temporary state of start,climb,emergency maneuver,etc.,in order to solve this situation,the concept of"afterburning" was proposed for military engines.Currently,the afterburner that widely used in various types of engines is a reburning afterburner.It is located between the turbine outlet and the tailpipe nozzle.It injects fuel into the residual oxygen of the combustion chamber’s exhaust gas to reburning.A stable ignition core is formed by using the airflow at a low-speed recirculation zone formed after the V-shaped stabilizer.The fuel is stably burned in the afterburner,which can greatly increase the gas temperature in a very short time and increase the engine thrust.Since the difference of position and function between the afterburner and the main combustion chamber,there is a great difference in the working conditions between them.Because the afterburner occurs behind the turbine,the air velocity and temperature in the afterburner are much higher than in the main combustion chamber.Moreover,since the inlet gas in the afterburner is the exhaust gas flowing out of the main combustion chamber,which causes the oxygen content in the afterburner is lower than that of the main combustion chamber.This puts a severe test on the combustion organization in the afterburner.To solve this problem,various researches have been focusing on the balance between the ability of stablizing fire core of the V-shaped stabilizer and the pressure loss caused by the increase of the recirculation zone.The content includes changing the structural parameters of the stabilizer,designing integrated stabilizers,etc..Those researches obtained a more comprehensive and complete research results.However,most of the above studies are based on the structural parameters of large-scale vortex injection and turbofan engines,and the research on the micro-scale development of small turbojet engines is relatively small.To address this issue,this article has conducted related research.This paper discusses the effect of different intake parameters and stabilizers’structures on the performance parameters of an afterburner.(1)Numerical simulation method was used to simulate steady-state parameters for different stabilizer angles,different stabilizer widths,different inlet airflow temperatures,and different fuel jet velocities.A high-temperature hot wind tunnel test rig was set up.By changing the intake air temperature and the amount of fuel injected in the main combustion chamber,and supplemented with nitrogen,the intake air temperature in the afterburner chamber was changed to perform a transient ignition boundary test.(2)By using a combination of numerical simulation and experiments,a more comprehensive understanding of afterburner is obtained.By analyzing the different parameters,the afterburner numerical simulation results show that:the temperature field in the afterburner chamber is mainly affected by the stabilizer angle,width and fuel jet velocity;the turbulence intensity field is mainly affected by the stabilizer angle,width,inlet air temperature and fuel jet velocity;velocity field is mainly affected by stabilizer width and fuel jet velocity;fuel evaporation rate is only affected by inlet air temperature.From the transient test,it can be known that the higher the inlet air temperature,the less oil is required to successfully ignite and produce a stable flame.(3)In addition,a new ignition method of high-temperature heat jet for igniting an afterburner in a small-thrust engine is developed by means of numerical simulation and whole-machine test.Also for small thrust engines due to size limitations,the effect of afterburner length on combustion efficiency was explored.Through the combination of numerical simulation and whole engine test,it is known that under the same conditions in the main combustion chamber,the additional injection of the hot-jet ignition method in the main combustion chamber can effectively ignite the afterburner chamber to make it work normally,but the disadvantages is the turbine that needs to withstand transient high temperatures;increasing the length of the afterburner can effectively increase the combustion efficiency of the afterburner and increase engine thrust.