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Towards the effort of reducing pollutant emissions, especially soot and nitrogen oxides, from direct injection Diesel engines, engineers have proposed various solutions, one of which is the use of a gaseous fuel as a partial supplement for liquid Diesel fuel. These engines are known as dual fuel combustion engines. A dual fuel (Diesel-CNG) engine is a base diesel engine fitted with a dual fuel conversion kit to enable use of clean burning alternative fuel like compressed natural gas. In this engine diesel and natural gas are burned simultaneously. Natural gas is fed into the cylinder along with intake air; the amount of diesel injection is reduced accordingly. Dual fuel engines have number of potential advantages like fuel flexibility, higher compression ratio, and better efficiency and less modifications on existing diesel engines. It is an ecological friendly technology due to lower PM and smoke emissions and retains the efficiency of diesel combustion.

Single cylinder and two cylinder diesel engines are widely used as a source of power generation, three wheelers, agricultural machines and in small house-hold applications in India as well as other Asian countries. Use of high end technologies in such engines are very expensive and also becoming complex. Therefore simple mechanically controlled components are used for these engines which make them simple in operation and maintenance. In order to meet stringent emission norms, there is a need for the development of these engines. In the present work, an existing two cylinder naturally aspirated DI diesel engine is upgraded with Turbocharged & Intercooled (TCIC) version to meet the revised stringent stage-II emission limits. The two cylinder diesel engine has been upgraded with optimum selection of turbocharger, intercooler and EGR valve to control the EGR mass flow rate.

Single cylinder and two cylinder diesel engines are having prevalent applications for as a source of power generation, three wheelers, agricultural machines, small house-hold applications as well as in mobile towers in India and other south Asian countries. As emission limits for these segment of engines are becoming stricter than the existing limits, it is necessary to upgrade these engines to meet the various emission limits applicable. The design features & technical characteristics of these engines are very simple and primitive, hence, it is extremely difficult and challenging to make these engines emission compliant. By using the relevant simulation tools, the task of emissionising these engines can be made simple to a greater extent. It gives a greater flexibility and ease in analyzing, designing, and operating complex engine systems.

Vehicles with direct injection engines employ various methods for mixing fuel and air in an engine cylinder. Efficient mixing increases combustion burn rate, improving combustion stability and knock suppression. Spark ignition engines may use tumble flow motion to generate turbulence, which includes rotational motion generally perpendicular to the cylinder axis to improve air and fuel mixing. Depending on operating conditions, more or less tumble may be advantageous. In this paper the tumble motion of the charge air is studied and simulated only in the suction stroke. A direct injected turbocharged combustion system employing central-mounted multihole injector. This paper presents the comparative study of effect of intake port design with various levels of tumble motion for fuels used in SIDI engines on the engine performance characteristics.