R. Siva Kumar et al. Int. Journal of Engineering Research and Application www.ijera.com ISSN : 2248-9622, Vol. 6, Issue 6, ( Part -3) June 2016, pp.17-22 www.ijera.com 17 | Page Soot Formation in Diesel Engines By Using Cfd R. Siva Kumar 1 , Dr. K. Tirupathi Reddy 2 , P. Madhu Raghava 3 , P.Nagaraju 4 *( Mechanical Engineering, Santhiram Engineering College , Nandyal-518501, India.) **( School Of Mechanical Engineering, Rgmcet , Nandyal-518501, India.) *** ( Mechanical Engineering, Santhiram Engineering College , Nandyal-518501, India.) **** ( Mechanical Engineering, Santhiram Engineering College , Nandyal-518501, India.) ABSTRACT In order to meet the stringent emission standards significant efforts have been imparted to the research and development of cleaner IC engines. Diesel combustion and the formation of pollutants are directly influenced by spatial and temporal distribution of the fuel injected. The development and validation of computational fluid dynamics (CFD) models for diesel engine combustion and emissions is described. The complexity of diesel combustion requires simulations with many complex interacting sub models in order to have a success in improving the performance and to reduce the emissions. In the present work an attempt has been made to develop a multidimensional axe-symmetric model for CI engine combustion and emissions. Later simulations have been carried out. Commercial validation tool FLUENT was used for simulation. The tool solves basic governing equations of fluid flow that is continuity, momentum, species transport and energy equation. Using finite volume method turbulence was modeled by using RNG K-ɛ model. Injection was modeled using La Grangian approach and reaction was modeled using non premixed combustion which considers the effects of turbulence and detailed chemical mechanism into account to model the reaction rates. The specific heats were approximated using piecewise polynomials. Subsequently the simulated results have been validated with the existing experimental values. Keywords: IC engines, CFD, FLUENT, RNG K-ɛ model, La Grangian approach. I. INTRODUCTION The diesel engine, because of its highest thermal efficiency among currently available engines, has been a main power source for over a hundred years. It’s advantage in thermal efficiency is due to its combustion characteristics. Diesel fuel is injected with a high pressure environment (compression ratio as high as 24:1). The higher the compression ratio, the more efficient the cycle [Hey Wood, 1998]. However, for some of the reasons that the diesel engine is highly efficient, its power density and exhaust emissions have traditionally been less desirable than spark ignition (SI) combustion engines. In a diesel engine, the combustion rate is controlled by the fuel injection rate and mixing and diffusion rates, which are usually slower than the premixed combustion rate in typical gasoline engines. Diesel engines usually emit more particulate and NOx than their gasoline court parts the high temperature and pressure environment in the diesel engine cylinder because of its high compression ratio and high combustion temperatures makes it impossible to completely prevent NOx form forming. The soot formed in the fuel – rich regions, although partially oxidized in the expansion stroke, also remains in considerable amounts at exhaust valve opening (EVO). The problem of diesel engine emissions is exacerbated because of the trade - off feature between NOx and soot emissions. It is usually impossible to reduce both kinds of emissions simultaneously, since factors that tend to decrease one usually increase the other. For example, retarding the fuel injection timing is effective to reduce NOx formation by reducing the peak cylinder temperature and pressure. However, this method results in an increase of soot production because more soot formed due to the lower in - cylinder gas temperature has shorter time to be oxidized [Lee, 2002]. Increasing the EGR rate can decrease the NOx emission level, however less oxygen is available to oxidize soot. Eventually, any change in these engine parameters will unavoidably affect other important engine performance measures, like retarding injection timing causes lower thermal efficiency and higher Brake Specific fuel consumption (BSFC) [Hey Wood, 1998]. Increasing environmental concerns and legislated emission standards have led to the necessity of considering both conventional and unconventional means for reducing soot and NOx emissions in diesel engines which is also the motivation of the present study. For example, diesel engine manufacturers are facing the challenges of the extremely low diesel engine – out soot emission mandates to be implemented in the near future. Engine simulation, compared to RESEARCH ARTICLE OPEN ACCESS