No abstract

No abstract

In this paper, a novel type of Annular Connecting Straight Cylinder Engine (ACSCE) is proposed, and an innovative dynamic position gas distribution system based on airway reuse is designed. Combined with the characteristics of the differential rotation of the rotor cylinder, the thermodynamic model of the air-powered working process for ACSCE is established. The mathematical structure model of the gas distribution system is also described, and the influence of different parameters of the gas distribution port, including the position angle, size and shape, on in-cylinder working pressure of ACSCE are analysed. The simulation and experimental results show that the position angle of the intake and exhaust ports of the Central Valve Shaft (CVS) has a greater impact on incylinder working pressure, while the port size of CVS has a relatively small effect, and the port size of the Rotary Valve (RV) also has a great impact on in-cylinder working pressure, while the port shape has less effect. When the intake port position angle φ z 0 = 78°, the exhaust port position angleφ z 0 ' = 30 o , the intake port size d 1 =10 mm , the exhaust port size d 1 ' =14 mm of CVS and the port size d 2 = 6 mm of RV, the ACSCE can be in correct gas distribution state and work stably.

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.

Abstract. In order to reduce the resistance and increase speed for a high-speed wheeled amphibious vehicle, a wheel-retracting mechanism was applied to a walking mechanism and the influence was researched. Firstly, to obtain a reliable numerical method, a realizable shear stress transport (SST) k-ω turbulence model and computational fluid dynamic (CFD) model built by an overset mesh technique was used and compared with the corresponding model tests. Secondly, the effect of the wheels' flip angle on resistance, heave and pitch was investigated. Then, the wheel well was optimized by numerical simulation. Finally, the results showed that the influence of the wheels on resistance was more significant, and the larger the wheels' flip angle was, the more significant the resistance reduction would be. An optimized wheel well was beneficial to resistance reduction. Furthermore, the running attitude became steadier, thereby decreasing the heave and pitch.