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The thermal management system of the water medium retarder using engine coolant (water and ethylene glycol) as transmission medium, omits oil-water heat exchanger in the structure. When the hydraulic retarder is operated, the valve is connected with the retarder and water pump, and then the engine coolant enters the working chamber. The kinetic energy of the vehicle is converted into internal energy of the coolant, and the heat is discharged to the external environment through the engine thermal management system. The braking torque of the water medium hydraulic retarder is determined by the water medium flow rate in the working chamber. The smaller the valve opening degree, the greater the braking torque and the faster the heating transmission fluid. Small valve opening is not conducive to the loss of heat. It will affect the normal working of the engine and hydraulic retarder.

Hydraulic retarder, as an auxiliary braking device, is widely used in commercial vehicles. Nowadays, the hydraulic retarder’s internal oil is mainly cooled by the coolant circuit directly. It not only aggravates the load of engine cooling system, but also makes the abundant heat energy not be recycled properly. In this study, an independent energy supply device with organic Rankine cycles is applied to solve the problems above. In the structure of this energy supply device, the evaporator’s inlet and outlet is connected in parallel with the oil outlet and inlet of the retarder respectively. A part of oil enters the evaporator to transfer heat with the organic fluid, and the rest of oil enters the oil-water heat exchanger to be cooled by the coolant circuit. According to the different braking conditions of the retarder, the oil temperature in the inlet of the hydraulic retarder can be kept within the proper range through adjusting the oil flow rate into the evaporator properly.

In this work, a XD132 Road Roller from XCMG in China was employed as a research basis to study the heat exchange performance of the heat dissipation module under varied working conditions. The module in the XD132 consists of a cooling fan and three radiators. At first, the numerical investigation on the elementary units of radiators was performed to obtain Colburn j factor and Fanning friction f factor, which were used for the ε-NTU method to predict the radiator performance. The fan was numerically tested in a wind test tunnel to acquire the performance curve. The performance data from both investigations were transformed into the boundary conditions of the numerical vehicle model in a virtual tunnel. A field experiment was carried out to validate the simulation accuracy, and an entrance coefficient was proposed to discuss the performance regularity under four working conditions.

The incomplete combustion and misfire of diesel engine during starting result in unwanted white smoke. The histories of combustion and emission in different phases under different start conditions were studied in this paper. The optimization of the fuel injection control strategy under start conditions was performed. When the diesel engine is started under low temperature, the control strategy adapted to start the engine with a certain constant fuel mass injected per cycle, there may be misfire cycles in the initial period or in the transitional process, which is mainly caused by the mismatch between the fuel mass injected per cycle and the instantaneous engine speed. Therefore, an optimized control strategy was put forward, namely, the engine starts with high fuel mass injection in the first several cycles and then decreases step by step during the transitional period until it operates at idle condition. This strategy was validated to decrease significantly the misfire cycles.