Effect of Multiple Injection Strategy on Combustion of Cotton Seed Oil Biodiesel in CRDI Diesel Engine

Owing to their higher thermal efficiency, fuel economy and power, diesel engines are found to be a successful option in commercial vehicles, either on road or off road. But in diesel engines NOx and smoke emissions are high due to heterogeneous combustion. There is immediate need to exert effort in reducing these harmful emissions and to comply with the stringent emission regulations imposed. It is observed that the requirements in order to reduce NOx and smoke are contradicting. Adaptation of better injection strategy helps in having better tradeoff between NO and smoke. For smoke reduction advancing injection is favorable, and for reducing NOx emission, retardation of injection timing is required. Biodiesel which is eco-friendly is a good renewable alternative fuel to petro-diesel. Various methods are tried for reducing NOx, like retardation of injection, water injection, EGR and so on. In this work multiple injection strategy is used for improving combustion process in CRDI diesel engine for having better compromise in the requirements for the reduction of NOx and smoke emission. Biodiesel blend B20 is prepared from nonedible cotton seed oil using transesterification process. Combustion characteristics are analyzed with a selected multiple injection strategy while retarding injection timings. The strategy consists of three fuel pulses: pilot, main and post. The fuel quantity in pilot is fixed at 10% and that in post is fixed as 0.5 mg per cycle. The pilot pulse is at 10° crank angle before main injection pulse and post is closely coupled with CAD of 3 from main injection. The timing of the main injection along with pilot and post was retarded from the recommended 23° bTDC in intervals of 3°. The parameters related to combustion, like temperature, in-cylinder pressure, rate of pressure rise, cumulative heat release, net heat release and mass fraction of fuel burned, are compared with the baseline data obtained with diesel single injection at 23° bTDC.