Design and Analysis of Thermal Management System of Power Matching Transmission in Energy Machinery

With the technical development of energy conservation and emission reduction technology, the internal structure of engineering machinery has become denser. The rising full-machine heat load that ensues challenges the effect of the cooling system. In the traditional thermal management system for the transmission in energy machinery, the cooling capacity does not fully match the load of each subsystem, and the thermal management components cannot adapt to the dynamic cooling demand of engineering machinery. To solve these problems, this paper designs and analyzes the thermal management system of power matching transmission in energy machinery. Firstly, the energy distribution among different components of engineering machinery, including, hydraulic system, transmission system, and cooling system, was described in each work section, and the dynamic matching method was detailed for hydraulic torque converter. Then, heat source engine, hydraulic torque converter, and hydraulic retarder were selected as the targets of thermal management for the power transmission system of loader. Next, the thermal management cycle was framed as a scheme in which the engine transmission system is independent with the cooling circulation system, and a heat transfer calculation model was constructed for loader transmission system. The proposed model was proved effective through experiments. The research results provide a reference for the thermal management of other subsystems of engineering machinery.

Multi-objective optimization design for the blade angles of hydraulic torque converter with adjustable pump

To improve the efficiency of a hydraulic torque converter with adjustable pump at low load and thus increase the operation scope of high efficiency, multi-objective optimization design is carried out for the blade angles by incorporating three-dimensional steady computational fluid dynamics numerical simulation, design of experiments, Kriging surrogate model and multi-objective genetic algorithm. The results show that the angle of blade trailing edge in first-stage stator is the main influencing factor of the efficiency of hydraulic torque converter with adjustable pump. All the peak efficiencies of hydraulic torque converter with adjustable pump at three openings of the pump are improved after optimization, and the increased extent increases with decreasing opening of the pump. The operation scope of high efficiency consequently increases from 2.46 to 2.67. Besides, the improvement for the efficiency of hydraulic torque converter with adjustable pump is achieved by increasing the efficiency of the pump. The increase of angle of blade trailing edge in first-stage stator and the decrease of angle of blade leading edge in second-stage turbine after optimization induce the positive angle of attack at the inlet of second-stage turbine, thus realizing the performance optimization of hydraulic torque converter with adjustable pump. This also explains the increased proportion of the torque of second-stage turbine at larger speed ratios after optimization and the fact that the angle of blade trailing edge in first-stage stator is the main influencing factor of the efficiency of hydraulic torque converter with adjustable pump. The established multi-objective optimization method provides a reference solution for the optimization design of blade angles and for the improvement of integrated efficiency of hydraulic torque converter.

Performance improvement and flow field investigation in hydraulic torque converter based on a new design of segmented blades

Hydraulic torque converter is of lower efficiency in the powertrain, particularly at low speed ratio, which is crucial for vehicles due to its ability of torque multiplication. Therefore, torque converters should be taken into account with both higher start-up acceleration and transmission efficiency. Inspired by the fact that the multi-airfoils of the aircraft can improve the lift, a new design of segmented turbine blade in torque converter is presented to improve the transmission efficiency and start-up acceleration. To ensure reproducibility and popularization, the camber line and shape of blades are extracted to obtain the expression in the Cartesian coordinate system. A scale-resolving simulation setting, large eddy simulation with kinetic energy transport, and refined hexahedron meshes, which were verified by our studies, are applied to simulate the three-dimensional transient flow numerically. According to the results of computational fluid dynamics analysis, the new design eliminated the ultra-high vorticity of the near-wall boundary layer to reduce the flow loss, which further improves fuel economy. The pressure difference in the segmented turbine blade is significantly higher than that of the original model, causing the improvement of powertrain performance. As a result, the torque ratio and nominal torque increase by 6.7% and 7.7%, respectively, at stalling speed ratio; meanwhile, the maximum efficiency increases by 1.1%. This research, using a new design of segmented blades, has many advantages, such as high starting torque ratio, large adjusting range, and greater fuel economy, and shows great potential to apply in the manufacturing process.

Research on the Shift Strategy for the Traction Vehicle with Automatic Transmission

Firstly, according to the working characteristic diagram of engine and hydraulic torque converter, the matching working point is found. On this basis, the theoretical model of gear shifting law is derived when the engine and the hydraulic torque converter work together by taking the acceleration of adjacent two gears equal as the shift point. Finally, the theoretical model is simulated, the shift pattern diagram of tractor automatic transmission is obtained and the shift pattern diagram is analyzed, and the results are of important reference value for further study of shift delay and other characteristics.

External characteristic analysis and stator parameter optimization for a torque converter

The performance of a flattened hydraulic torque converter is optimized with orthogonal experiment and response surface method, considering parameters of its stator blade, defined with nonuniform rotational B-splines. The optimization model, with maximum of the stalling torque ratio as an objective, is determined through an external characteristic statistical analysis under the new European Driving Cycle condition. The optimization results show that the stall torque ratio is increased by 10.83%, while the highest efficiency is above 84%.