EXPERIMENTAL INVESTIGATIONS ON PERFORMANCE OF DUAL FUEL DIESEL ENGINE USING CNG AND BIODIESEL

Abstract

The power generation and transportation sectors are heavily dependent on fossil fuels, whose combustion results in high level of air pollution. However, uncertainties about the long-term availability coupled with price perturbation of fossil fuels are a key challenge due to which alternative fuels are getting more attention. Gaseous fuels such as Compressed Natural Gas (CNG) or hydrogen are very promising for use in Spark Ignition (SI) or Compression Ignition (CI) Engines. The research on the use of gaseous fuels in CI engines is still underway unlike SI engines, where it has even been commercialized. The utilization CNG with environmental friendly liquid biofuels is one of the most promising combustion techniques in dual fuel CI engine without a reduction in power. Also, application of exhaust gas recirculation (EGR) will improve the performance of dual fuel engine. The objective of the present research work is to evaluate dual fuel combustion technique using a different combination of fuels. The effect of the use of CNG as primary fuel and, diesel, Jatropha oil methyl ester (JOME), Orange peel oil methyl ester (OPOME) and their blends as pilot fuel in CI engine, on combustion, performance and emissions characteristics of the engine was studied and compared with baseline data of diesel engine operation. A Kirloskar diesel engine (Model-CAF 8) was modified in such a way that it can operate in both conventional diesel mode as well as dual fuel mode. The engine was run at the rated speed of 1500 rpm for six loading conditions (i.e. no load, 20%, 40%, 60%, 80% and full load) for both the modes. During dual fuel combustion mode, the mass flow rate of pilot fuel was kept constant and mass flow rate of CNG varied with the load. The engine was connected to a

Experimental Investigations on Performance of Dual Fuel Diesel Engine using CNG and Biodiesel P a g e | viii computer to analyze the in-cylinder pressure data which would further help to calculate the mass burn fraction, heat release rate, and cumulative heat release. A combustion chamber was also developed to measure the ignition delay of liquid fuels. An exhaust gas recirculation (EGR) set up was also developed for the present work. Response surface methodology (RSM) was used as an optimization tool for biodiesel production. The evaluation of physicochemical properties (such as density, kinematic viscosity, cetane number, flash point etc.) of all pilot fuels was carried and found suitable for use. The auto-ignition temperature of all pilot fuels was also evaluated. The engine trial was conducted by taking different fuel combinations (i.e. CNG+diesel, CNG+JOME, CNG+J50D50, CNG+OPOME, CNG+OP50D50) with and without application of EGR and the combustion, performance and emissions characteristics of dual fuel engine were studied. It was found that JOME, OPOME and their blends show better results compared to diesel as pilot fuel in dual fuel engine especially up to higher load. The use of biodiesel shows better BTE and lower CO emissions than diesel as pilot fuel. However, at full load, diesel as pilot fuel has highest BTE compared to all another mode of operations. The highest BTE of the conventional diesel engine was found 28.58%, where the highest BTE for dual fuel mode was found 30.65%, 30.35%, 30.51%, 30.44% and 30.58% for diesel, JOME, J50D50, OPOME and OP50D50 as pilot fuel respectively. It was clearly observed that the blending of biodiesel in diesel improves the BTE of the engine. The utilization of EGR was found to improve the emissions characteristics of dual fuel engine. At low load and with EGR, NOX emissions reduced by 18.4%. The application of EGR also reduced the CO and UHC emissions by 3.2% and 6.3% respectively. Also, at low load, the application of EGR increases the BTE of the engine by 3%.

Experimental Investigations on Performance of Dual Fuel Diesel Engine using CNG and Biodiesel P a g e | ix It is concluded that dual fuel engines are capable of reducing exhaust emissions without reducing the power and CO and unburned HC can be reduced with the application of EGR in dual fuel engine. Further investigations on advancing injection timing of pilot fuel are recommended in order to meet with emission regulations.