Analysis Of Influence Of Propeller And Inlet Aerodynamic Coupling On The Performance And Stability Of Engine

The normal and stable operation of the propulsion system is very important for the aircraft.When the turboprop aircraft is flying,the operating conditions of propeller/inlet/engine are highly coupled.The propeller slipstream and the inlet profile will affect the performance and stability of the engine.The aerodynamic interference of the propeller and inlet aerodynamic coupling on the engine is an important research direction of turboprop engines.Aiming at the phenomenon of aerodynamic interference of the propeller and inlet aerodynamic coupling on the engine,this paper established a propeller/inlet/engine aerodynamic interference test-bed with/without the effects of slipstream.Experimental research was performed under different working conditions,and the mixed dimensional simulation combining three-dimensional numerical simulation of the propeller and one-dimensional overall performance simulation of the engine was carried out.And the aerodynamic interference characteristics of the propeller and inlet aerodynamic coupling on the engine are explored through a combination of experiments and numerical simulations.On this basis,a preliminary exploration of the propeller slipstream suppression was carried out to provide useful theoretical support and method foundation for the design and optimization of turboprop engines.The main work of this paper is as follows:(1)In view of the increase in pressure and the inhomogeneous pressure distribution at the engine inlet interface caused by the propeller slipstream,a combination research of experiments and numerical simulations was done to study the effect of slipstream on the engine performance and stability.When the propeller speed remains unchanged,the slipstream effect caused by the increase of the propeller pitch angle is enhanced,which exacerbates the inhomogeneous distribution of the flow field at the engine inlet and leads to the gradual increases of the distortion index as well as the decrease of the surge margin.When the propeller pitch angle remains unchanged,with the increase of the core engine speed,the increase of the propeller speed increases the slipstream effect,which is not conducive to the uniform distribution of airflow,however,the large increase in the velocity head caused by the increase in engine mass flow helps reduce the distortion index,and the inlet exit distortion index comprehensively shows a gradual downward trend.(2)A single scoop inlet was designed,and the influence of the inlet profile on the performance and stability of the turboprop engine "was studied through numerical simulation and experimental methods.At the same propeller speed,small changes in engine mass flow caused by changes in the inlet profile have little effect on the total mass flow,which is mainly affected by the propeller,so changes in the inlet profile have little effect on the propeller characteristics.The changes of the inlet profile mainly affect the total pressure recovery coefficient and the distortion index of the engine inlet,the changes of which further affect the output power and the stability of the engine,leading to the impact on the propeller characteristics through the propeller speed.Therefore,the dynamic balance between the propeller/inlet/engine is achieved through power matching and mass flow matching.(3)Aiming at the inhomogeneous distribution of the pressure at the engine inlet caused by the propeller slipstream as well as the offset of the inlet,the influence of the guide vane and the aerodynamic grid on the parameters of the engine inlet was studied.The results show:the proper use of "#" shaped guide vanes suppresses the distortion of the inlet exit and leads to a relatively small total pressure loss;the aerodynamic grid effectively reduces the total pressure distortion of the engine inlet,but leads to a relatively high total pressure loss.And the balance between the increase in total pressure loss and the decrease in distortion index needs to be comprehensively considered when using guide vanes or aerodynamic grids for the propeller slipstream suppression.