Study Of Multi-cylinder Cooling Water Jacket Flowing Non-uniformity

Cooling system is one of the most important systems of a diesel engine. The cooling system provides a suitable temperature for engine working parts. But due to the flow resistance and nonuniformity of heat transfer, different cylinder has different working conditions. The three-dimensional fluid field and pressure field and temperature field is studied based on multi-cylinders cooling water jacket.The three dimensional model of cooling water jacket are built by SolidWorks, including waterway of cylinder head, cylinder liner and return pipe. The grid models are built by ICEM.The fluid field simulation calculation of different cylinders quantities are conducted by software Fluent. The results show that, under the same intake mass flow, the engine cooling water jacket intake pressure decreases with the cylinder quantities grows. The intake pressure declines from 157.9kPa of three cylinders to 77.44 kPa of six cylinders. The nonuniformity of mass flow distribution increase with the increases of cylinder quantity. The nonuniformity of three, four, five and six cylinders mass flow distribution respectively are 8.62%, 18.11%, 32.18%, 47.88%. Also the lager the quantity is the more the nonuniformity grows.The research decreases the nonuniformity and flow resistance by two steps structural modification, such as one of the cylinder liner connecting hole modification and both sides of cylinder liner connecting holes modification. Compared with the original cooling water jacket, the intake pressure of cooling water jacket decreases from 79.91 kPa to 70.92 kPa, 8.99 kPa in total, the decrease range is 8.4%. The nonuniformity decrease from 43.52% at the beginning to 20.84 by the end of modification, the decrease range is 22.68%, which is a great improvement.The research conducts two different ways of to study the influence of temperature boundarys on the cooling water jacket temperature filed, one is different combustor surface temperature and the other is different intake water temperature. The simulation calculation results show that, as the combustor surface temperature increase, the intake and outlet temperature of cylinder heads show a linear increase. Also the temperature difference between intake and outlet shows a linear increase. The temperature difference between intake and outlet increases 0.7K, when the tempareture of combustor surface increases 10 K. With the increase of intake water teamperature, the intake and outlet temperature of cylinder heads shows a linear increase. The outlet water temperature also increases. But the temperature difference between intake and outlet shows a linear decrease, which will decrease 2.3K when the intake water temperature increase 5K.