Effect of Injection Pressure on Exhaust Emissions of Diesel Engine Fuelled with Biogas and Biodiesel

Abstract

In the context of exhaustion of fossil fuels day by day due to heavy demand with the use of agriculture sector and transport sector, escalation of fuel prices in International Oil Market causing huge economic burden on developing countries like India and rise of pollution levels with fossil fuel, the exploration of alternative fuels has become pertinent. Gaseous fuels have many merits over liquid fuels, as the pollutants emitted by gaseous fuels are low due to clean combustion, high calorific value in comparison with liquid fuels. Vegetable oils are good substitutes for diesel, as they are renewable, comparable calorific value and cetane (meausre of combustion quality) number when compared with neat diesel operation. However, the disadvantages associated with vegetable oils such as high viscosity and low volatility cause combustion problems in diesel engines. They can be rectified to some extent by converting them into biodiesel. They are many methods to induct gaseous fuels such as port injection, carburetion technique, injection of gaseous fuel at the near end of compression stroke etc,. Investigations were carried out with biogas gas as primary fuel inducted by port injection and cottonseed biodiesel was injected into the engine in conventional manner. Particulate matter (PM), oxides of nitrogen (NOx), carbon mono oxide (CO) levels and un-burnt hydro carbons (UBHC) are the exhaust emissions from a diesel engine. They cause health hazards, once they are inhaled in. They also cause environmental effects like Green-house effect and Global Warming. Hence control of these emissions is an immediate effect and an urgent step. The pollutants of PM, NOx, CO and UBHC were determined at full load operation of the engine with varied injection pressure and compared with diesel operation on conventional engine. The maximum induction of biogas was 35% of total mass of biodiesel as full load operation. Particulate emissions were determined by AVL Smoke meter, while other emissions were measured by Netel Chromatograph multi-gas analyzer at full load operation. These pollutants were drastically reduced with induction of biogas and further reduced with an increase of injection pressure.