In order to reduce the resistance and increasing speed for a caterpillar track amphibious vehicle (CTAV), the stern flaps were applied and the influence was researched. Numerical simulations performed by STAR-CCM+ and model towing test reveal that stern flaps have greatly reduced the resistance, trim, and sinkage of the CTAV when the length Froude number is between 0.63 and 1.05. The length and flap angle were optimized by numerical simulation. In addition, the residual resistance plays a dominant role in resistance reduction, which contributes to more than 90% of the total resistance reduction. Installing stern flaps increase the vehicle waterline by 7% and enhance the virtual-length effect. Furthermore, the running attitude becomes steadier, thereby decreasing the trim and sinkage. Therefore the resistance performance of the CTAV can be enhanced by installing stern flaps with a proper length at an optimal flap angle. INDEX TERMS Caterpillar track amphibious vehicle, CFD, resistance performance, running attitude, STAR-CCM+.
A variable-configuration wheeled driving system is proposed to improve the obstacle-crossing abilities of unmanned vehicles. The effects of the wheel load on the wheels’ obstacle-crossing abilities are analysed using statics theory. Similarly, the effects of the suspension’s stiffness and the adhesion coefficient on the vehicle’s obstacle-crossing ability are analysed. Numerical calculation results show that a higher wheel lift height leads to improved obstacle-crossing abilities. A strategy to adjust the system configuration during obstacle crossing is designed with the wheel lift height acting as the optimisation target. The variable-configuration strategy is verified and the optimal adjustment of the middle axle is determined through simulations. An obstacle-crossing experiment shows that a vehicle can cross a 1-m step obstacle when the proposed variable-configuration strategy is applied. The obstacle-crossing ability of the unmanned vehicle can thus be greatly enhanced.
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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