| Water source heat pump is widely used in the field of refrigeration and air conditioning for its outstanding environmental protection benefits,high efficiency and high reliability.As the core component of the heat pump system,the compressor has a great influence on the performance of the entire system.Single screw compressor stands out in volumetric compressor due to the advantages of balanced force,high volumetric efficiency,low noise and high reliability.Single slide valve mechanism is used in traditional single screw refrigeration compressor to achieve capacity adjustment.However,with the change of external working conditions,for a single slide valve capacity adjustment mechanism with a fixed internal volume ratio,the isentropic efficiency declines due to unmatching of internal and external pressure ratios,which seriously affects the performance of compressor.In this dissertation,the main geometric parameters of single screw refrigeration compressor for water source heat pump developed by the laboratory are calculated,the basic parameters of compressor,including the screw and the star wheel,were determined,and the maximum element volume and displacement of the compressor were calculated.The common capacity adjustment methods of single screw compressor are compared and introduced,and the slide valve action mechanism is described.The basic mathematic model for the design calculation of slide valve is established.The compound slide valve capacity adjustment was designed to adapt the changing of conditions,which overcomes the disadvantage of the lack of internal volume ratio adjustment.The adjustment characteristics and geometric characteristics of compound slide valve capacity adjustment mechanism,the adjustment characteristics of single slide valve were investigated.It is found that the closer to the intake port the starting position of the bypass port is,the smaller the volume ratio of internal volume and the amount of volume jump are.The full load performance experiment of single screw refrigeration compressor was analysed.A series of stability performance tests were conducted by changing the evaporation temperature,whether using spray cooling measure,internal volume ratio,refrigeration and heating conditions and the mechanical structure,materials,lubricants of the compressor.Exploring the influence of these factors on the performance of the compressor under full load.It was found that spray cooling can effectively reduce the compressor's exhaust temperature.With the increase of evaporation temperature,the compressor performance can be greatly improved.The use of 14701 star wheels to 1472192 star wheels can effectively improve the performance of the compressor.and making preparations for further improving compressor performance.The part-load working process model of single screw compressor was established,mathematical model was solving adopting Runge-Kutta method,and the change relationship between screw angle with the pressure,temperature,specific volume and mass of the gas in the elementary volume,the performance parameters of compressor including isentropic efficiency,shaft power,cooling capacity and COP were calculated.At the same time,a partial load performance test of single screw compressor was performed,the simulation results were compared with the experimental results,It is found that the mathematical model is more accurate.The validated model was used to simulate the process of single screw refrigeration compressor with compound slide valve,and the corresponding compressor performance parameters were calculated.It is found that the internal and external pressure ratios of compound slide valve compressors are well matched at full load,and the power consumption of by-pass port accounts for a small proportion of compressor power consumption under partial load.Under the same conditions,the performance of single slide valve and compound slide valve were compared to verify the advantages of compound slide valve to single slide valve. |
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