Modification Design And Study On Loss Analysis Method Of Low-Pressure Compressor For Marine Gas Turbine

Gas turbine is an advanced ship power system.The development level of it directly determines a country’s ability to guarantee marine resources and maritime safety.To a certain extent,it also reflects the development level of national industry and manufacturing industry.For a marine gas turbine,the low-pressure compressor is the main component in the front end,it is particularly important for the low-pressure compressor to have good aerodynamic performance and work stably over a wide range.Ulike an aeroengines,marine gas turbine compressors have obvious characteristics such as attack angel matching and aspect ratio selection due to their operating environment,working characteristics and strict requirements of low operating conditions,which need to be further studied.In this paper,the influence of aspect ratio on the performance of transonic and subsonic rotor of an 8-stage marine gas turbine low-pressure compressor is studied based on the numerical simulation method.The influence law of aspect ratio and other parameters on blade profile loss is analyzed,and the analysis method of internal loss in multistage compressor is discussed.The modified design of the 8-stage compressor is completed,which not only improves the design point efficiency of the compressor,but also broadens the stable working range of the modified compressor at 60% speed.Firstly,the first and fourth stage rotors of a low-pressure compressor of an 8-stage marine gas turbine are chosen as the research objects.By changing the blade chord length,5kinds of aspect ratio schemes are determined.The numerical simulation of transonic rotor and subsonic rotor with different aspect ratio is carried out,and the reasons of the influence of aspect ratio on the performance of transonic rotor and subsonic rotor are analyzed.The results show that the change of aspect ratio will lead to the changes of blade boundary layer thickness and the intensity of shock wave at the tip of transonic rotor,and then affect the performance of compressor.Then,the middle section profile of different aspect ratio rotors are selected as the research object,The characteristics of variable attack angle and variable Mach number of plane cascades with different aspect ratio are calculated,and analyze the influence of aspect ratio on subsonic cascade profile loss.The method of extracting endwall loss of multistage compressor is discussed by using slip boundary condition on the upper and lower endwall,the loss distributions at design point and low operating points are compared.The results show that the profile loss of high-aspect-ratio cascade is higher than that of low-aspect-ratio cascade.The blade profile loss increased with the increase of Mach number.In the multi-stage compressor,the endwall loss increases stage by stage.Under different working conditions,the proportion of all kinds of compressor losses is different.In low operating conditions,both leakage loss and endwall loss are higher than the design point.Finally,the modification scheme of aspect ratio of the prototype is determined.Through numerical simulation,the design point efficiency of the modified machine is increased by0.4%,and the angle of the first four rows of guide vanes is adjusted to make the surge margin reach the level of the prototype under low working conditions,which meets the requirements of the modification.