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Construction vehicles own some inherent characteristics, such as low velocity, high power and following heavy heat flux et al. Aiming at decreasing flow resistance and managing airflow, a 39 ton single drum road roller from one of the biggest manufactures in China was employed as a research target to seek out the effect of air flow resistance on the performance of its heat dissipation system. For a start, a simplified 3D model of the road roller in a virtual wind tunnel was established with a commercial software, which was pre-processed in Gambit later. The radiators were set with heat exchanger boundary condition based on the analysis on the air-side elementary unit, as for the cooling fan, the experimental results in the wind tunnel were transformed into the corresponding boundary condition.

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.

Problems such as higher heat load in the diesel engine and the occurrence of crazes within the valve bridge of heavy-duty vehicle diesel engine should be solved, with the increase of the power density of heavy-duty vehicle diesel engine. In this paper, the heat load experiment of complete machine, temperature-measuring of bottom part of cylinder head and the three-dimension numerical simulation on coolant flow and heat transfer in the water jacket have been performed. The result shows that the main reasons of higher heat load of the engine are insufficiency of heat-sinking capability of the water-radiator and shortage of coolant flux; and the unsuitable flow field in water jacket in cylinder head, where only a little of the coolant can cool the bottom of cylinder head, is the main cause of cylinder head bottom over-heated and thermal crack in the valve-bridge region.

The paper reports an experimental and simulating exploration over a series of problems such as overheat of the complete machine and thermal cracks in the valve bridge region of cylinder head. The studies involve heat load test of complete machine, measuring the temperature of the bottom part of cylinder head, analyzing coolant-flow distribution of upper nozzles in the bottom side of cylinder head, and three-dimensional numerical simulation on the coolant flow in the sixth cylinder water jacket which lies on the most wicked heat transfer condition. The test and simulation results show that overheat of engine results largely from insufficiency of the heat-sinking capacity of water-radiator and shortage of the coolant flux. The unsuitable flow field in cylinder head water jacket, where only 12.22% coolant can cool the bottom of cylinder head, is the main reason causing cylinder head overheat on the bottom side and thermal cracks in the valve bridge region.

Transient heat transfer computer program of the coupling 3-D moving piston assembly-lubricant film-liner system is successfully developed for predicting the distribution of temperatures in the component system, in which the finite element technology has been employed. The heat transfer relation of the moving piston assembly-lubricant film-liner has been established and 3-D discrete model of the system is obtained with the hypothesis of thinking the lubricant film as 1-D heat resistance. The discrete models of single component are assembled into the whole coupling model with the coupling theory. Some appropriate ways have been employed to deal with the moving arrays in the stiffness matrix because of the moving boundary conditions. The software has been employed to analyze a gasoline engine.