Research On The Performance Of The Main And Sub Axial Airflow Ultra Compact Combustor

The main and sub axial ultra compact combustor realized axial second flow inlet,which has a great potential to be used in practical situations.To solve the problems that the axial velocity component of second flow has negative effects on combustion performance and increases cooling pressure of cavity's back wall,three new structures have been proposed to solve the problems,including backward-forward cavity,upward second flow and front-back second flow inlet cavity.The combustion and flow properties have been analyzed by using CFD method.The cavity width and sloping cavity's effects on the flow and combustion properties were first investigated.(1)The efficiency increases first and decreases then as width increases,a proper width could improve the combustion performance;(2)The forward cavity could enhance the mixture of high temperature gas and core flow air,which improves the distribution property of velocity and temperature in outlet;(3)The upper backward wall of backward-forward cavity increases the volume and the lower forward wall increases pressure gradient between cavity and passage,which boosts effiency and temperature distribustion in outlet;(4)The effiency of backward-forward cavity is higher than rectangle cavity in same volume.The effects of second flow's direction on combustion were studied then.(1)The upward second flow enhances radial migration of gas,which increases g-loading;(2)The upward second flow push high temperature area towards the front of cavity,which reduce the high temperature area near back wall;(3)The larger axial angle increases g-loading,but cuts down vortex combustion at same time,proper axial angle could improve combustion performance.Finally,the effect of front-top and front-back second flow inlet cavity on second flow rate and combustion performance were studied.(1)Front-top and front-back airflow second flow inlet cavity are efficient ways to increase the mass flow rate of second flow;(2)The back flow of front-back type cavity could push the reaction area towards the middle of cavity,which reduces the temperature of cavity's back wall;(3)The low pressure area created by restriction plate enhances the mixture of high temperature gas and core flow air,which improves the distribution of temperature in outlet.The comprehensive performance of backward-forward,upward second flow inlet and front-back inlet cavity is higher than based cavity,which provides a technical scheme for structure modification.