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The world is facing a twin crisis of environmental degradation and fossil fuel depletion. Alternative fuels are seems to be a promising solution for low exhaust emissions. Liquefied Petroleum Gas (LPG) is a prominent alternative fuel with well developed distributed infrastructure and increasing number of Gasoline engines are now being converted to run on LPG considering the fuel economy and low exhaust emissions. This paper describes the bi-fuel (LPG/Gasoline) concept on a single cylinder engine. Air cooled Direct Injection (DI) diesel engine converted to operate on gasoline engine with electronic ignition system and it is having feature to change the spark ignition timing w.r.t. speed. The compression ratio was also reduced suitable to SI operation. CFD analysis was performed to review and subsequently to increase the cooling capacity of the engine.

The rising demand for cleaner vehicles considering the upcoming stringent emission norms like Euro-IV has promoted development of CNG vehicles. The need for expensive after treatment technologies has imposed constraints on Euro-IV Gasoline and Diesel engine development. On the contrary CNG engines have easily met Euro-III norms with Carburetion technology and Euro-IV and beyond norms with Injection technology. CNG has proved to be a clean and environmentally friendly fuel, significantly improving the ambient air quality of cities. The addition of Hydrogen to CNG has potential to even lower the CNG emissions and is considered to be the first step towards promotion of a Hydrogen economy. Worldwide experts have described Hydrogen as the cleanliest fuel for IC Engines [1, 2 and 3]. Hythane is the patented blend of 15% of Hydrogen in CNG by Energy content. HCNG is the blend of Hydrogen and CNG in varying proportions.

Environmental degradation is on the rise due to the increased motor vehicle population. One of the strategies adopted to curb deteriorating environmental quality is the use of alternative fuels like Ethanol, Compressed natural gas and Liquefied Petroleum Gas. Natural gas is the world's most plentiful combustible fuel, abundantly available in all the continents. This naturally occurring fuel requires little or no treatment prior to use as compared to liquid petroleum products. Natural gas is also the lowest costing fuel. The use of CNG as an automotive-fuel results in significant reduction in the level of vehicular pollutants CO, HC, NOx, SOx, Pb and PM [1, 2, 3 and 4]. Additionally, the use of CNG results in reduction in the emissions of greenhouse gases (CO2), owing to the lower Carbon-to-Hydrogen ratio of the methane (CH4), as compared to other hydrocarbon fuels [5, 6 and 7].

In this paper, the results obtained during the optimization of the dedicated CNG 6-Cylinder naturally aspirated engine are described with the optimization strategy. Most of the diesel engines after conversion to CNG engines are having high valve overlap leading to high HC emission along with less fuel economy and high swirl leads to reduced volumetric efficiency. These issues were examined in detail and experimentation was carried out to assess the effect of low swirl thereby resulting in high flow leading to increase in volumetric efficiency and reduced emissions. The engine variables optimized for CNG operation were the engine compression ratio, ignition timing, spark plug selection, catalytic converter loading, design of first stage regulator with improved heating circuit and second stage pressure regulators, mixer venturi size, power screw setting, and intake/ exhaust system geometry.

In recent years the Government of India has supported the use of Liquified Petrolium Gas (LPG) in public and private vehicles. One of the ways to reduce emission is use of alternative fuels. Among alternative fuels, LPG is one of the most promising mainly because of its low exhaust emissions. The papers about LPG used in three wheeler, cars for SI or CI converted to SI engines had been published extensively in the last two decades. The applications of LPG to bi-fuel or single fuel engines are tried widely at this time. But the extensive study of LPG for small SI single cylinder two stroke engine of three wheeler two stroke engine is not reported in depth. This paper describes development of bi-fuel (LPG/Gasoline) concept of a single air cooled 200 CC single cylinder two stroke engine for three wheeler application.

Present day technology is continuously being upgraded in order to meet demand for cleaner vehicles by meeting stringent emission norms. The other driving force is vehicle performance in terms of drivability, fuel economy and comfort. Gasoline engine meets all the requirements except fuel economy, where in diesel engine has an advantage. The need of the hour is to achieve drivability, comfort and fuel economy of diesel engine. Apart from development of direct injection common rail and hybrid electric vehicle, this need has also caused development of gaseous fuels like LPG. The gaseous fuel could be CNG, LPG or Hydrogen depending upon the availability. This will also help in delay of depletion of fossil fuel reserves. Main features of this technology are its cost effective operation, modular nature and adaptation on old generation of vehicles.