Analysis Of The Internal Flow Mechanism And Leakage Flow Characteristic Of A Scroll Refrigeration Compressor

Scroll compressors have been widely used in the fields of industry,agriculture,medical equipment,transportation,etc.Their characteristics such as low noise,high efficiency and compact structure have also been approved by the industry.How to further develop high performance scroll compressors with more compact structure has always been the focus of researchers.The study of its internal flow mechanism and gap leakage characteristics is the key to achieve optimal design of scroll compressors.This paper established a three-dimensional unsteady numerical calculation model of a scroll refrigeration compressor.The internal flow and leakage flow field were calculated out with the model in detail,and then the model is verified by the experiment.The main work is shown as follows:(1)Based on structured dynamic mesh technology,a high-precision three-dimensional unsteady numerical calculation model of a scroll refrigeration compressor was established.Both tangential and axial clearance were included in the model.The numerical model was validated with experimental data.The results show that the volumetric efficiency,COP and adiabatic efficiency decreased by 5.11%,8%,and 6.32%,respectively,when the axial clearance model was included in the model,which is closer to the experimental value.The accuracy of the numerical model was greatly improved.When the pressure ratio is 3(theoretical pressure ratio is 2.63),the adiabatic efficiency reaches a maximum of 69.25%.(2)The pressure distribution is asymmetry in a pair of working chambers due to the asymmetry of the suction channel.The movement of orbiting scroll has opposite influence on the formation of leakage vortexes in one working chamber to another one,which results in uneven velocity and temperature distribution.The suction mass flow of the compressor is limited because of the special flow phenomena such as "cut off" and "source" existing in the suction flow passage.(3)Since the circumferential leakage path is first narrowed and then expanded,the pressure and temperature of the leakage fluid through the path first drop and then increase.Under low rotational speed or high pressure ratio operating conditions,the circumferential leakage flow has an important influence on the flow field at downstream of working chamber.A supersonic flow phenomenon occurs in the circumferential leakage channel,and the Mach number reaches a maximum value at the downstream of the radial gap.Radial leakage flow does not exhibit supersonic flow due to larger flow resistance.Comparing the three leakage models,the results show that the model of isentropic nozzles has a large deviation in the calculation of leakage due to neglecting the viscosity of the fluid,while the Bell leakage model is not suitable for the calculation of leakage at high Reynolds number and large gap.