Development Of A Ultra High-speed Centrifugal Compressor For Hydrogen Fuel-cell

Developing fuel cell vehicles(FCVs)has been seen as one of the most valuable research fields for future vehicles under the background of building a global environment-friendly living condition.The FVCs rely on power source from the stack system,and air compressor serves as the necessary part of the proton exchange membrane fuel cell system(PEMFC),whose performance will directly determine the energy conversion efficiency of the stack sys tem,and ultimately influence the comprehensive performance of the FCVs.Centrifugal air compressor is regarded as the most potential candidate for PEMFC owing to its outstanding advantages of oil-free,small volume and high energy efficiency.The development and re search of centrifugal air compressor for fuel cell-based passenger vehicles is of great signifi cance to the advancement of FVCs related technology and the industry development in China.Based on these challenges,this paper designs and fabricates a centrifugal air compressor for fuel cell-based passenger car,which is driven by permanent magnet synchronous motor and supported by gas foil bea rings.The rated power of the air compressor is 5k W,the rated speed is 150 krpm,the flow is 50 g/s,and the pressure ratio is 2.1.Concrete research content including following several aspects:According to the overall performance parameters of the air c ompressor,the whole technical solution is firstly designed,and the specific parameters,materials and matching drive inverter are obtained through analysis.In order to ensure the performance and efficiency of the air compressor,the semi-open impeller and the independent labyrinth gas seal ring is selected as the required impeller and seal,respectively,constructing the compressing and sealing system.The vibration measurement platform of the compressor rotor is designed from the as pects of both hardware and software.The rotor-bearing system of the compressor is designed in detail based on the "Four-Step Method" proposed by Heshmat.Firstly,the specific size of the radial and thrust gas foil bearings of the system are defined according to the overall r equirements of the compressor and related empirical formula.Secondly,the static and dynamic stiffness and damping coefficient of the radial foil bearing are obtained based on the calculation model of Link-Spring foil bearing;Thirdly,the finite element analysis model of rotor dynamics is established to analyze the rotor dynamics of the designed rotor bearing system,which verifies the critical speed and the bearing stiffness margin of the rotor bearing system;Finally,the shaft centrifugal stress of rot ation is calculated according to the structure size of the rotor,and the strength and rational material selection are further confirmed based on the finite element analysis.The thermal characteristics of the compressor are analyzed by finite element method,and the cooling system of the compressor is further designed.The loss of the compressor motor is calculated and analyzed,and the temperature distribution of the compressor is obtained by magneto-thermal analysis.Aiming at the problem of severe heating for the compressor,the spiral groove water-cooling and air-cooling channels are designed,and the structural parameters of the spiral groove are obtained after detailed consideration.Finally,the motor thermal analysis finite element model coupled with cooling water channel is established to calculate the temperature distribution of the compressor after adding the water-cooling system.The simulation results show that the maximum temperature of the compressor is 155 ℃,which is located in the stator core of the motor.The air compressor prototype is constructed,and overall performance is further tested.The components of compressor are firstly manufactured and the corresp onding compressor prototype and rotor vibratio n test system are constructed.Two kinds of radial foil bearings,including the first-generation of full-circle type bearings and the second-generation of three-lobed type bearings are fabricated.The stability experiment of the air compressor system is carried out based on these two bearings,analyzing the influence of different bearing nominal-clearance on the vibration characteristics of air compressor rotor system.According to the analysis results,the stab le operation speed of the air compressor is in creased by adjustment of the bearing clearance and strengthening the structural rigidity of the bearing.Finally,the as-fabricated air compressor achieves a stable operation at 145 krpm,which further confirms the rational design scheme and the feasibilit y of the bearing rotor system technology.