Browse Publications Technical Papers 2019-26-0286
2019-01-19

Optimization of EGR Mixer to Minimize Thermal Hot Spot on Plastic Duct & Soot Deposition on Throttle Valve Using CFD Simulation 2019-26-0286

In recent time, with inception of BS VI emission regulation with more focus on fuel economy and emission, many engine parts which were conventionally made from metal are getting replaced with plastic components to attain better fuel economy. EGR is commonly used technique to reduce the emission in diesel engine along with after treatment devices. EGR reduces the temperature inside the combustion chamber there by reducing the NOx. With compact engine layout EGR mixer are often located very close to throttle valve there by increasing the possibility of soot deposition on the throttle valve. Once these soot & unburnt hydrocarbons present in EGR cool down they may transform into a sticky tar kind of substance, which obstructs the functioning of throttle valve over the time. We investigate the hot spot on plastic EGR mixing duct during the mixing process of exhaust gases with fresh air, for turbocharged & intercooled diesel engine. The exhaust gas for EGR is bypassed from the exhaust manifold, cooled down in intercooler and mixed with the intake air at upstream of the intake manifold. Mixer module is provided to create turbulence in the flow for better mixing of EGR & fresh air. The current work is focused on design optimization of the EGR Mixer, for lesser surface temperature on plastic intake duct, equal cylinder-to-cylinder distribution & reduced soot deposition on throttle valve. The boundary conditions for the highly pulsating flow are taken from transient one-dimensional simulation. Computational Fluid Dynamics (CFD) simulations are performed, for different EGR mixers, to evaluate & reduce temperature on the plastic duct, soot deposition and increase EGR mixing quality. For the final model, surface temperature, soot deposition and cylinder-to-cylinder distribution are found well within the limit. Hot spot location on the mixing duct & soot deposition on the throttle are well matched with the test results. The simulation is performed for few critical engine operating conditions. The process for predicting surface temperature on EGR mixing duct, probability of soot deposition & cylinder to cylinder variation due to dynamically varying flow, pressure & temperature are developed and validated.

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