Numerical Study and Experimental Investigation on the Effect of Valve Angle of EGR on Exhaust Gas Flow 2017-28-1950
The automotive industry in world is facing the problem of reduction of emissions coming out of the engine. Also, the stringent emission norms imposed by the regulating body for transition from BS IV to BS VI urges the auto makers to concentrate on new technologies to reduce the emissions. One of the major emissions coming out of the diesel engine is oxides of nitrogen (NOx) which is detrimental to human health. This NOx emission is formed when the combustion temperature of engine exceeds the threshold limit. There are several methods available to reduce these NOx emissions formed in-cylinder. Exhaust Gas Recirculation (EGR) is one such system, which reduces the NOx emission formed inside the engine by supplying a portion of the exhaust gases. By re-circulating exhaust gases, the air admitted to the engine is diluted. Further, due to the high latent heat of vaporization of water, water vapor tends to absorb more amount of heat that is generated during combustion. This in turn reduces the peak combustion temperature, which helps in reduction of NOx emissions from the engine.
This study emphasizes the effect of critical flow parameter on performance of EGR. Though several design variables contribute to the functionality and performance of the EGR, valve angle is one such critical parameter taken for this study. Valve performs two major functions viz., leak proof closing of valve with valve seat and metering the designed flow rate into the engine. For this study, three dimensional model was developed using commercially available software. Flow path was extracted for doing the numerical analysis.
Numerical analysis has been carried out in three cases to predict the flow rate of exhaust gases using computational fluid dynamic (CFD) commercial software. This enables the designer to understand the flow characteristics such as pressure and velocity in detail and helps to modify the design based on the flow phenomenon. The valves with three different valve angles have been developed to understand the effect of valve angle on EGR flow performance. The flow rate was measured experimentally for these three proposals. The simulation results when compared with the experimental results show a good agreement with variation of approximately 5%. The results show that higher the valve angle, higher the flow rate with lesser leakage through the system.