Abstract
The negative pressure valve EGR bears thermal load for a long period, thus its heat transfer characteristics have an important impact on the stability of the engine. The fluid solid coupling method was employed to analyze the contact heat transfer between the inner cavity of the valve and the cooling water as well as the high temperature gas based on CFD. As a result, the characteristics of the internal fluid velocity field, pressure field and temperature field were obtained. Besides, the heat transfer capability of the valve was also improved by adding the annular cooling water channel. The test results showed that the calculation method has a high calculation accuracy providing an important basis for the optimization design of valves.
Highlights
The EGR valve is an essential exhaust re-circulation device installed on both gasoline and diesel engines
The flow and heat transfer process of the cooling water and high temperature gas respectively in the upper and the lower part of EGR valve body could be classified in three physical problems: (1) the turbulent flow of incompressible viscous fluid in the valve body; (2) the convection heat transfer between the incompressible viscous fluid and the wall; (3) the heat conduction among the upper valve body, the lower valve body and the graphite pad machine body
According to the heat conduction theorem of Fourier, the control equation for boundary conditions of the fluid solid coupling conjugate heat transfer of the EGR valve is obtained as follows [6]: λ
Summary
The EGR valve is an essential exhaust re-circulation device installed on both gasoline and diesel engines. Only the flow law of fluid flow inside the valve was studied and the influence of fluid solid coupling heat transfer on the valve structure design of EGR system has not yet been involved. In the end of simulation, two cases that with and without cooling water were studied and the temperature field of the valve body and stem were obtained. After comparing and analyzing results obtained in two cases, proposed to increase adding cooling water gallery in upper valve body was proposed In this case, the results in experiment and simulation further showed this proposal could greatly improve the heat transfer condition for the valve body meeting the temperature requirements of the sealing ring and other attachments in the upper valve body.
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