Study On The High Speed Motorized Centrifugal Air Compressor With Water Lubticated Journal Bearings

In the crisis of energy resourse and environment,hydrogen fuel cell vehicle(FCV)has drawn attentions of government,enterprise and institutions due to their advantages of high efficiency and environmentally friendly.The development of the FCV relies on some key components and technologies,and the air compressor is one of them because the fuel cell requires an air compressor to supply pressured air to the stack.However,few effots have been made on investigation of the key technologies of the fuel cell compressor in China,which seriously restricted the development of domestic fuel cell vehicle industry.Thus,a study on the fuel cell compressor and its key technologies is taken here.A centrifugal air compressor in which water lubricated bearing and permanent magnet synchronous motor are used is proposed,theoretical and experimental researches were taken on the key technologies of the compressor structure.Taking full advantage of large gap between the motor and rotor,the seal problem of the motor can be solved by introducing a socket.After a dynamic optimization design on the compressor structure,the critical speed of the system was improved.The power consumption of rotor churning was decreased by taking some loss reducing measures on the sructure.The compressor prototype achieved the objective of 100000rpm and 10 kW,and stable operation was observed at the rated speed.The static characteristics of the water lubricated journal and thrust bearings applied in the compressor were studied in turbulence condition.The influences of bearing configuration parameters(clearance,pocket axial and circumferential widths)and opration parameters(supply pressure,eccentricity and rotation speed)are numerically analyzed.Some valuable results were obtained for the design of high speed water lubricated bearings.The stability of water lubricated bearing is one of the key issues for its application in the high speed compressor.Hence the influences of the station and rotation pockets,water supply structure,pocket number and configuration on the bearing stability were theoretically and experimentally analyzed.The bearing with orifice restrictors and Achimedean spiral pockets was proposed fot its excellent stability.In addition,the influence of turbulence on the bearing stability was studied under the condition of large Sommerfeld number.Since shock and vibration are inevitable for the bearing in the vehicle application,the anti-shock and anti-vibration characteristics of the propsed bearing are numerically studied by using a model in which the rough contact,partial lubrication and full film turbulence lubrication are considerd.It was found that the anti-shock and anti-vibration characteristics of the bearing both show anisotropy,and the upstream of the pocket is the weak postion to shock and vibration.Nevertheless,the critical shock and vibration amplituds of the proposed bearing under which rough contact between the shaft and sleeve occurs are 160 G and 100 G respectively,which satisfy the requirement of vehicle application.In addition,it was found that the anti-shock and anti-vibration characteristics are contradictory to the stability of the water film,the improvement of the transient performance will reduce its stability,vice versa.