A Study On The Method For Afterburner Combustion Without Stabilizers

In order to achieve high thrust-to-weight-ratio,vector thrust and high-efficiency afterburner,the new generation aeroengine has improved the pressure ratio,turbine inlet gas temperature,and afterburner inlet pressure.The development of afterburner parameters towards higher inlet gas temperature,lower inlet oxygen concentration,higher inlet gas velocity,lower resistance and smaller size and weight brings severe challenges to afterburner combustion.In order to achieve efficient and stable combustion in afterburner,an afterburner combustion method based on without stabilizers is proposed in the paper.Afterburner fuel is injected into the flow passage from the inlet of turbine or between turbine stages,and mixers are arranged at the outlet of turbine.The fuel atomizes,evaporates and mixes when passing through turbine and mixer,and then happens pyrolysis entering the chemical reaction stage.Finally,the fuel combusts spontaneously in afterburner and forms a stable combustion zone to complete the combustion process.Through theoretical analysis,numerical simulation and experiment,the organization mechanism of afterburner without stabilizer is explored in the paper,and the feasibility of the organization method of afterburner without stabilizer is proved.The main work is as follows.(1)According to the working conditions of afterburner,by analyzing the autoignition mechanism of liquid kerosene,the relationship between the physical and chemical processes of liquid fuel combustion and the autoignition delay time is clarified in detail,which provides theoretical support for the organization method of afterburner combustion without stabilizer.(2)Aiming at the physical and chemical process of liquid fuel of afterburner without stabilizer,atomization experiments in high-temperature and high-speed air,mixing experiments of fuel and gas downstream of mixer and combustion experiments of afterburner without stabilizers were carried out respectively.And three sets of experimental devices were designed to carry out atomization,evaporation,mixing and combustion organization verification experiments under atmospheric pressure.In the process of experimental verification,the jet atomization test device includes a high temperature hot wind tunnel to simulate the temperature and velocity of the turbine inlet air flow;In the afterburner experiment,the O2 content at the turbine inlet,the temperature drop of the gas flow in the turbine and the temperature and velocity distribution in the afterburner were simulated.(3)Aiming at the atomization and evaporation process of liquid jet in high-temperature and high-speed air flow,the atomization characteristics and influencing factors of forward injection and side injection into turbine stage were studied by numerical simulation.The trajectories and particle size distributions of fuel spray locating in different direction,circumferential and axial positions were analyzed at different turbine inlet temperatures,and the distribution laws of gaseous fuel concentration in the downstream of the turbine were obtained.On this basis,the transverse jet experiment was carried out to study the effects of different air temperature and velocity on the trajectory and spatial distribution of fuel.The results show that only changing the temperature and velocity of the airflow can not effectively change the spatial distribution of fuel in the downstream of the jet spray,and other measures need to be taken to obtain a uniform distribution of the afterburner fuel.(4)In view of the mixing process of fuel evaporated fuel and gas,semicircular mixer,rectangular mixer,triangular mixer and chevron mixer were designed.The influence of the vortex system produced by the mixer on the fuel distribution was studied in numerical simulation,and the mixing characteristics were further investigated by changing the location of fuel spray.The spatial distribution of gaseous fuel downstream of the mixer was analyzed through the experiments of different combined fuel Spray bars.The results show that the mixing uniformity of fuel can be improved by using the four mixers,which is about 80%higher than that without mixers.Multi point fuel supply can improve the fuel distribution.The uniformity of fuel distribution downstream of the mixer can be improved by increasing the temperature and velocity of air.The rectangular mixer can get the best mixing effect in a short distance,and the comprehensive performance is better.(5)Aiming at the combustion without stabilizers organization process,the afterburner organization experiments without stabilizers were carried out under different gas temperature,velocity and oxygen content.The fuel autoignition phenomenon and combustion process were obtained,and the afterburner performance was investigated.The experimental results show that kerosene can auto ignite and stably combust with the combustion organization method and structure mentioned in the paper.The combustion process mainly goes through four stages:random fire nucleus generation,fire nucleus expansion,unstable combustion and stable combustion.When combustion is stable,the combustion efficiency in the core flow can reach 99%.The flow field structure of parallel flow-vortex system-parallel flow is obtained by numerical simulation.The vortex structures downstream of mixer and in expansion section are conducive to fuel mixing with gas and autoignition,and the parallel flow in afterburner section is conducive to flame stability.The research results of the paper provide certain support for further organizing the spatial distribution of afterburner fuel and the combustion process of afterburner without stabilizers.