COMBUSTION AND EMISSION STUDIES ON A SMALL DI DIESEL ENGINE USING JATROPHA BASED BIODIESEL

Abstract

Biodiesel plays a promising role among the various alternative fuel technology options for compression ignition engines, commonly known as diesel engines. Non edible feed stocks are economically feasible raw materials for biodiesel production in developing nations. Although neem, rubber, rice bran, castor, pongamia pinnata, and Jatropha curcas have been studied experimentally, the last one has been reported to be better choice for making biodiesel in India. The detailed literature survey indicates that although Jatropha biodiesel performs comparable to diesel there are some problems with the use of higher blends and hundred percent Jatropha biodiesel in the context of combustion and emission characteristics. Inefficient and incomplete combustion of Jatropha biodiesel due to the existing engine injection system design and operating conditions (which are optimized for diesel operation) are main causes for this. Thus there is a need to study the influence of injection system parameters along with engine operating parameters, in order to optimize the combustion and emission characteristics of diesel engine using Jatropha biodiesel as fuel. The scope of this research work is to study the influence of injection system parameters and engine operating conditions along with exhaust gas recirculation on the performance parameters of Jatropha biodiesel fuelled diesel engine. The experiments were performed on a small single-cylinder, four-stroke, air cooled, vertical, direct injection diesel engine which is widely used in small automotive vehicle applications. The engine control parameters varied during the experiments are static injection timing, injector opening pressure, nozzle configuration (nozzle hole diameter with number of holes), nozzle tip protrusion, percentage of exhaust gas recirculation (EGR), load and speed. The various output parameters measured and computed for analysis are brake specific fuel consumption (BSFC), brake thermal efficiency (BTE), cylinder pressure, peak cylinder pressure (Pmax), net heat release rate, maximum rate of heat release (HRRmax), maximum pressure rise rate (PRR.), CO, HC, NO emissions and smoke density. The present investigation has been carried out in three phases. In the first phase, the influences of injection timing, load and speed on performance, combustion and emission characteristics of diesel engine using Jatropha biodiesel as fuel are evaluated experimentally using full factorial design consisting of (33) with 27 runs. iii Statistical modeling technique (Response surface methodology (RSM)) is then employed to determine the relationship between the response and the input variables. An analysis of variance (ANOVA) is also carried out for each response variable separately, in order to test the significance of the relationship obtained between the response and input variables. After obtaining the validated output — input parameters relationships, these model equations are used to optimize the input parameter levels for the required objective of the output i.e. minimizing the fuel consumption and emissions and maximizing the thermal efficiency etc. For this, multi-objective optimization using method of objective weighting has been employed in the present work. The optimal solution is obtained using real coded Genetic Algorithms. In the second phase, the influence of fuel type, injection timing, injector opening pressure, nozzle configuration (nozzle hole diameter with number of holes), nozzle tip protrusion, EGR, load and speed were studied through statistically designed experiments using Taguchi's standard orthogonal arrays L18 (21X37) OA with 18 runs. Taguchi's signal-to-noise ratio method of analysis has been employed. The control parameter's significance test has been performed with ANOVA for the individual response variable. The significant parameters with their contributing percentages on the output parameters have been computed. Finally the optimal control factor levels were arrived for better performance and combustion and lower emissions for Jatropha biodiesel engine. A methodology has been established for optimal settings of engine operating, injection system and EGR parameters for optimum performance, combustion and emission characteristics of diesel engine using Jatropha biodiesel. Optimal injection timing, load torque and speed for the use of Jatropha biodiesel in diesel engine have been obtained with different objective functions for maximization of performance and combustion parameters while minimizing the emissions. In addition to injection timing, load and speed, the optimal control factor settings of the injector opening pressure, nozzle configuration, nozzle tip protrusion, (EGR) and fuel type have also been obtained for minimum fuel consumption and emissions and maximum thermal efficiency and peak cylinder pressure using Taguchi method. The proposed methodology can be extended to obtain the optimal engine operating conditions for a given biodiesel under research for optimization of engine performance, combustion and emissions. iv