A Comparative Study on Map Based and Closed Loop Simulation Model of Coolant Circuit for a Two Wheeler Liquid Cooled Engine

The basic requirement of a vehicle cooling system is to ensure that the components of the engine are adequately cooled under vehicle operating conditions. Engine life and effectiveness can be improved with effective cooling. In designing process, simulation plays a vital role. A clear understanding of the coolant flow and pressure developed within the cooling system is important in designing the coolant circuit. The efficiency of the cooling system depends on the flow delivered by the impeller. The work aims at the study of performance characteristics of a backward curved impeller in a two wheeler cooling system. The objective is to compare the operating points such as pressure drop, flow delivered and power consumed from mapped Computational Fluid Dynamics (CFD) simulation and closed loop CFD simulation. Moving Reference Frame (MRF) model was used to simulate the rotary motion of the impeller. RANS K-Epsilon two equation turbulence steady state model was used to solve the 3-D numerical model. Coolant system consists of coolant jacket, thermostat, radiator and a pump. The individual system restriction developed against flow rate by coolant jacket, thermostat and radiator is found from steady state CFD simulation. The coolant circuit CFD simulation of the impeller is done for one speed and the values for other pump speeds were found using fan laws. P-Q curve for different pump speeds is plotted and the cumulative system restriction of coolant jacket, thermostat and radiator is mapped on pump P-Q curve to get the impeller operating points. In closed loop system the whole coolant circuit is solved for flow, flow happens based on the impeller motion. The operating points of the impeller are obtained directly, values for different impeller speeds are calculated using fan laws, the errors associated with mapping the results can be avoided with closed loop simulation. An experimental validation is done for flow delivered, power consumed and pressure drop. A comparative study is done to validate the errors associated with the mapped results. A numerical methodology has been devised for simulating a closed loop coolant flow circuit.