A New Multistage Swash Plate Piston Gas Pump

With the problem of energy crisis and environmental pollution being more and more serious, the technology of regenerative braking for vehicles is studied more and more thoroughly. The pneumatic regenerative braking system is a regenerative braking system which converts the braking-energy of vehicles to the pressure-energy of compressed gas by a gas pump in order to store and reuse them. The gas pump is one of the key components of the pneumatic regenerative braking system and its’ performance determines the efficiency of the regenerative braking. Therefore, the study on the high pressure gas pump used in the pneumatic regenerative braking system is meaningful and valuable. The paper aims to do an exploratory study and design about the gas pump which is used for the pneumatic regenerative braking.The principle of the pneumatic regenerative braking and hydraulic regenerative braking is basically the same and the characteristics of the gas pump/hydraulic pump used for regenerative braking are quite similar. Therefore, the author reads a large number of related domestic and foreign literature and expounds the developments of the pneumatic/hydraulic regenerative braking technology, in addition, the paper introduces the structures, working principles and application features of the gas/hydraulic pumps in particular which are used in the regenerative braking system. Then, on this basis, the paper’s main research contents are confirmed.Thorough comparative analysis of the characteristics and applications of many kinds of gas pumps and referring the key parameters of the gas/hydraulic pumps which are used in the regenerative braking system, a new multistage swash plate piston gas pump is proposed. According to the structural characteristics of the two-side swash plate gas pump and the law of relative motion of its’ pistons, it can achieve four-stage compression and apply the multistage compression to the swash plate axial piston pump by dividing the cylinders into several levels and connecting the cylinders at the same level in parallel and the cylinders at the adjacent level in series with check valve rectifying in the front and back cylinder cover. The advantages of the swash plate piston gas pump are small volume, light weight, high pressure ratio, excellent balance performance, small vibration noise and easier to achieve a high speed.The paper expounds the structural design and working principles of the gas pump and particularly explains the design of the piston components, rectification method, cooling system and lubrication system. Furthermore, the kinematic characteristics of pistons and the stress state of the key components such as pistons and swash plate during their working process are calculated and analyzed in detail.Firstly, mathematical model of gas compression and expansion process for one single cylinder of the swash plate piston gas pump with gas leakage and unsteady heat transfer is established based on the variable mass thermodynamic theory. The fourth order Runge-Kutta numerical method is used to solve the mathematical model. The variation curve of the gas mass, pressure and temperature of the single cylinder along with the main shaft angle in the work process of the gas pump are obtained. The effects of the gas leakage and unsteady heat transfer are also discussed respectively. Secondly, on this basis, the thermodynamic characteristics of the gas pressure and temperature of the complete gas pump in the multistage compression process are calculated and analyzed and the p-V diagram and T-s diagram for the working process of the swash plate piston gas pump are obtained. Moreover, the advantages of the multistage compression with respect to the single-stage compression are comparatively analyzed from two aspects of saving the indicated work of the compressed gas and reducing exhaust temperature.Finally, a prototype of the multistage swash plate piston gas pump is produced and the experimental programs for the gas pump are designed. What’s more, an experimental platform is built to make some preparations for the following working performance bench test of the gas pump and the experiment of pneumatic regenerative braking which will be simulated on a vehicle inertia test bench.