Three-Dimensional Aerodynamic Desigin And Back Cavity Structure Research Of Centrifugal Compressor For Fuel Cell

In order to achieve the strategic goals of carbon peaking and carbon neutrality,it is necessary to vigorously develop new energy vehicles.Fuel cell vehicles,with their high efficiency,long driving range,and zero carbon emissions,have broad application prospects in heavy-duty and longdistance transportation industries,and are potential substitutes for traditional fuel-powered vehicles.As the key component of the air supply system for fuel cell vehicles,the centrifugal compressor plays a vital role in determining the performance and cost of the fuel cell system.In this study,a high-performance,wide operating range dual-stage centrifugal compressor is designed based on the requirements of a 130 k W high-power heavy-duty truck fuel cell system.The main tasks and objectives of this work are as follows:(1)This article presents the design of a dual-stage centrifugal compressor for a 130 KW fuel cell system.The design specifications include a rotational speed of 91000 r/min,a flow rate of 0.21 kg/s,a total pressure ratio of 2.3,and an efficiency of not less than 65%.The pressure ratio is achieved through pressure ratio allocation.The dual-stage compressor is arranged in a back-to-back configuration with air bearings at both ends and a high-speed motor in the middle.The design of the centrifugal compressor impellers,diffusers,and volutes is performed using Concepts NREC design software,and the design theories and methods are introduced in this study.(2)In order to improve the prediction of the aerodynamic performance of the centrifugal compressor,a quasi-one-dimensional mathematical model based on the Euler equations is established.This model incorporates source terms to represent the effects of blade forces,viscosity,and changes in flow area within the compressor.Empirical loss models are selected to account for various loss sources in the compressor,enabling the characterization of losses within the two-stage compressor under different operating conditions.The variation of loss coefficients with flow coefficients is obtained,and the magnitudes of losses in different components of the compressor are analyzed.(3)The one-dimensional model from COMPAL is imported into Axcent for three-dimensional geometric design,and a detailed analysis of the design process is conducted.NUMECA software is used to perform numerical simulations on both the low-pressure and high-pressure stages of the compressor.This allows for the assessment of the compressor’s performance at the design rotational speed,as well as an analysis of internal flow phenomena such as flow separation,blade tip clearance leakage,and jet wakes.A comparison is made between the simulation results and the one-dimensional predictions to validate the reliability of the onedimensional approach.Finally,the two-stage compressor and the ducting are matched to obtain a complete two-stage compressor assembly model.Simulation results are used to obtain the design curve at the specified rotational speed and to perform flow field analysis.(4)This study focuses on the axial force balance issue of a two-stage centrifugal compressor for fuel cell applications.It investigates the influence of the installation position of the labyrinth seal on the compressor’s performance and axial thrust magnitude,while revealing the typical flow mechanisms of the labyrinth seal.Numerical simulations are employed to analyze the effects of various geometric parameters of the labyrinth seal(such as the depth-to-width ratio H/B,tooth width t,gap width c,and number of teeth z)on its leakage characteristics and the magnitude of the compressor’s axial thrust.The optimal geometric parameters of the labyrinth seal are determined based on these analyses.This paper utilizes aerodynamic design and simulation calculations of the compressor,along with performance predictions under variable operating conditions,to obtain a centrifugal compressor that meets the design requirements for fuel cell applications.Additionally,it investigates the impact of the rim-side labyrinth seal structure on the compressor’s axial thrust and sealing performance.The findings of this study provide theoretical references for the subsequent development of fuel cell compressors.