Optimization of heat transfer and efficiency of engine via air bubble injection inside engine cooling system

The advanced thermal management in the internal combustion engines has a key role in the overall performance, which directly effect on the total fuel consumption and engine exhaust emissions. Recently, a number of valuable studies have been carried out to evaluate and improve cooling system performance by using various technologies such as sliding vane rotary pump, ultimate cooling, double temperature circuits, integration, electrically-controlled valves and advanced algorithms for flexible control of the cooling system components, but, in this study an innovative strategy is presented to achieve this purpose. With a novel point of view, air-water mixture is employed to use in the cooling circuit. For this reason, at the point of coolant inlet to the engine, a constant pressure air injection mechanism was established, which can be adjusted at the desired flow rate by computer. The air injection strategy has two significant advantages. In the warm-up stage more air injection into the coolant fluid cause to a rapid heating of engine components by creating air layers around the cylinder. In the after warm-up state, however, air injection is decreased to a specified level for producing turbulence flow only in order to heat transfer enhancement and cooling purposes. Obtained results revealed that the periodic air injection by using special strategy can improve fuel economy and also decrease engine pollutant emissions. (C) 2017 Elsevier Ltd. All rights reserved.