Research On Compressor Surge Based On One-Dimensional-Three-Dimensional Coupling Approach

Aero egnies,gas turbine engines and turbocharged engines are important to our country.Compressors are core components in engines.Compressor surge heavily affects performance and reliability of engines.A feature of surge is streamwise ossilation of flow through the whole compression system.It is greatly influenced by compressor and components in the system including pipe,plenum and throttle.The thesis will combine numerical simulation,theoretical analysis and dynamic experiments to develop a one-dimensional-threedimensional approach which considers compressible flow in pipe,plenum and throttle and the approach will be applied to investigate compressor surge.Primary content and innoviations include:(1)It is the first time to establish a one-dimensional-three-dimensional coupling approach for simulating surge.Method of characteristic is adopted to solve compressible flows in pipes.It is combined with three-dimensional simulation of compressors to establish the approach.The thesis proposes methods to tackle interfaces between one-dimensional and three-dimensional domains and methods for handling boundary condition.Equations in the approach are proved making the solution closed.The approach is applied to simulation flows in a shock tube.The results turn out to almost overlap analytical solution.The approach manages to simulate compressor surge.Phases of pressure rise,reverse flow,operating with negative mass flow,and flow recovery are captured.Period of surge cyle from simulation is slilimar ti experiments in magnitude.The history of pressure is close to experiments.(2)Influence of characiterisitcs of compressor components to surge is explored.The thesis changes characiterisitcs of compressor components via adjusting inlet prewhirl and diffuser vanes angle.It has been found that positive prewhirl and closing diffuser vanes improve flow stabilities of compressor components and manage to reduce surge flow.Results from one-dimensionalthree-dimensional coupling approach show that: for a compressor involving deep surge,inlet prewhirl of 30 degrees reduces compressor surge flow and period of surge cycle increases and closing diffuser vanes by 5 degrees makes it free from surge.The compressor becomes operating stably.(3)Influence of compressor characterisitc parameters to surge is explored.Mild surge,deep surge incorporating mild surge and deep surge are captured by one-dimensional-three-dimensional coupling approach.The three phenomena correspond to different throttles ranging from an open throttle to a closed throttle.Through appending time-varying function into throttle coefficient in one-dimensional-three-dimensional coupling approach,the thesis simulates processes of swiftly closing throttle and slowly closing throttle.It is found that surge pattern of compressor changes from mild surge to deep surge if the duration of closing throttle is fast;on the other hand,closing the throttle slowly makes the compressor become operating stably,which indicates that the speed of closing throttle has a significant impact on surge.