Numerical Simulation and Experimental Investigation of Different Cooling Structures on Cooling Performance and Fuel Consumption of a Two-Cylinder Motorcycle Engine

The reasonable engine cooling system design can give a better cooling of engine, the coolant flow direction and different cooling structure designs have great impact on the cooling performance and fuel consumption of engine. Therefore, to gain a deeper understanding of the impact of different cooling system designs on engine cooling performance, three different split cooling structures and two oil–water heat exchanger (OWHE) layouts are designed for a two-cylinder motorcycle engine. Three-dimensional CFD analysis method is used for analyzing the coolant velocity distributions and one-dimensional systematic analysis method is used for analyzing the system flow rate at those cooling structure designs and OWHE designs. Meanwhile, experimental investigation of different cooling structures and OWHE layouts on fuel consumption is conducted by the bench test of worldwide motorcycle test cycle. Results indicated that the difference of coolant flow velocity distribution for four cooling structures are small and the flow resistance of Case D is lowest at fully opened thermostat condition. The fuel consumption of Case D is 4.78 L/100 km, 1.4% lower than that of Case A with the fuel consumption 4.85 L/100 km. The combined split cooling structure Case D and OWHE layout one is proven as the optimal cooling design with 4% fuel consumption reduction compared with that of original cooling structure Case A. The research results can provide theoretical reference for engine cooling performance evaluation and give valuable data to motorcycle designers for quick evaluation of design and quick solutions of improved design.