| Faced with the increasingly severe energy and environmental problems,cleaning pollution-free energy has become a hot issue for people to study.In the field of automobile,proton exchange membrane fuel cell with low pollution and high efficiency has become the main power source of new energy vehicles in the future.Due to the special requirements of vehicle environment,centrifugal compressor has become the most potential air compressor for fuel cell,and its performance has an important impact on the power density of the whole fuel cell system.Therefore,the research and development of special centrifugal compressor for fuel cell is of great significance to promote the progress of new energy vehicle technology in China.In this paper,the research on centrifugal compressor of vehicle fuel cell based on air suspension bearing is carried out.The main research contents and results are as follows:(1)In this paper,the centrifugal compressor used in 100 k W fuel cell stack is designed.The rated speed of the compressor is 95000 rpm,the design flow rate is 0.125kg/s,the total pressure ratio is 2.5,and the efficiency requirement is not less than 70%.The overall structure scheme adopts two-stage series connection,and the impellers are arranged at both ends of the journal of the air bearing in a back-to-back manner.Through numerical simulation,the performance curve of the impeller is obtained,and the internal flow field is analyzed.On this basis,the diffuser and volute are designed,and a two-stage compressor model is constructed.The numerical results show that the total pressure ratio of the compressor is 2.54 and the isentropic efficiency is 73.375%,which meets the initial design requirements.(2)Set up an experimental platform for performance test of centrifugal compressor,and conduct performance experiments on the designed compressor prototype to verify whether it meets the requirements.The experimental results show that the prototype conforms to the operation characteristics of the traditional centrifugal compressor.Due to the limitation of experimental conditions,there are some errors between the measured data and the numerical simulation results,among which the maximum error of pressure ratio is 6.65%,and the maximum error of efficiency is 5.8%,all of which are within the acceptable error range.Therefore,it is considered that the experimental data have certain credibility,and the reliability of CFD simulation method is also verified.(3)The two-stage impeller of the compressor is optimized.Taking the isentropic efficiency as the goal and the pressure ratio as the constraint condition,through parametric modeling,combined with neural network model and genetic algorithm,the optimization scheme of impeller was obtained.By comparing the performance of the impeller before and after optimization,it is found that the pressure ratio and efficiency of the first stage impeller increase by 4.35% and 4.22% at the design operating point.The pressure ratio of the second stage impeller increased by 2.78% and the efficiency increased by 1.96%.The calculation results of the designed speed show that the overall performance of the two-stage impellers has been improved,and the lifting effect is more obvious in the working range of large flow rate,the flow loss in the impeller is reduced,and the flow field is improved.The calculation of the whole impeller after optimization shows that the pressure ratio of the whole impeller is increased by 5.5% and the isentropic efficiency is increased by 2.34% at the design point.After optimization,the compressor performance is improved and the optimization goal is achieved.In this paper,through the design calculation and performance experiment of the compressor,a high-speed centrifugal compressor meeting the requirements of vehicle-mounted fuel cells is obtained,and the initial impeller is optimized to improve the performance of the impeller,which provides a reference for the follow-up research of the centrifugal compressor for vehicle-mounted fuel cells. |
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