In this paper, a novel type of twin-rotor piston engine (TRPE) is proposed, and the circumferential oil film thickness for the piston ring in TRPE is analysed. Different from the integrated cylinder of a typical engine, the combined annular cylinder (CAC) of TRPE has unique structural composition and differential velocity motion characteristic, making the tribological performance more complicated. The main purpose of this paper is to reveal and explain the special tribological performance of TRPE, which has never been studied. Firstly, the special structural composition of CAC is introduced and the relative velocity between the piston ring and CAC wall at different circumferential positions of the piston ring is analysed. Then, based on the Greenwood-Trip asperity contact theory, radial and axial quasi-static equilibrium equations of the piston ring are both derived. The circumferential oil film thickness is calculated by solving the equilibrium equations and the two-dimensional average Reynolds equation within a cycle. Results indicate that there are significant differences in circumferential oil film thickness of the piston ring due to the special structure and motion of CAC, and the differences become greater as the output shaft speed increases. A long-time engine reverse towing experiment shows an obvious uneven wear phenomenon of the piston ring and CAC wall, which well validates the simulation results of the circumferential oil film thickness. The research work can be used as the basis of equal-wear design for the piston ring in TRPE with the help of surface texture technology, thereby greatly reducing the wear loss.
Amphibious wheel-track vehicle (AWTV) can change the vertical load of the wheels and the tracks through the active hydro-pneumatic suspension system, which shows significant advantages in terms of maneuverability and road passing ability. However, AWTV is a strong nonlinear system. The irregularity of the road, and coupling characteristics between the vertical load of the wheel-tracks and the terrain will greatly affect the tractive efficiency of the whole vehicle. Therefore, how to effectively distribute the vertical load between the wheel and the track to improve the tractive efficiency of the whole vehicle is still a huge challenge. To address the above problems, based on the neural network (NN) and particle swarm optimization (PSO) algorithm, vertical load distribution strategy of the AWTV is proposed to improve its traction efficiency under different driving road in this paper. Firstly, the coupling dynamics model of AWTV with road and hydraulic system dynamics model of active suspension is established; Secondly, the wheel-track terrain model is built in EDEM-Recurdyn to collect data of vertical load and traction efficiency under the different soils and speeds, and the coupling function is obtained through NN; Then, the optimal vertical load of each axle is optimized through PSO; Finally, the feasibility and effectiveness of the strategy are verified by the simulation analysis under different road conditions and distribution strategies. The simulation and test results demonstrate that the proposed vertical load distribution strategy based on NN-PSO can effectively improve the traction performance of the AWTV in complex terrain environment, and have relatively superior control characteristics.
Combining the structural features of cam engines and opposed engines, a kind of opposed cam piston engine is designed, in which a kind of variable sine curves family applied to the cam working surface. Based on the structure of this engine, a thermodynamic zero-dimensional model of the working cycle was established, and the accuracy of it was verified by the numerical simulation model utilizing the engine simulation software AVL BOOST. Based on the zero-dimensional model, the changes in the pressure, temperature, and quality of the working fluid in the cylinder under different cam profiles were calculated, and on this basis, the engine’s thermal efficiency, mechanical efficiency, overall machine efficiency, and power per liter were solved. Compared with common civil vehicle engines, OCPE has higher power per liter and has better economic performance and power performance.
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