An Experimental Investigation of a Diesel Engine Ignition Delay using Biodiesel and Diesel Fuels

In the present study, the use of biodiesel collected from waste vegetable oil in a CFR diesel and a direct injection M 8.1 diesel engine is studied. Experiments were carried out in wide ranges of engine load conditions to evaluate the engine ignition delay with waste vegetable oil and its blends on volume basis with ordinary No.2 diesel fuel. The engine under investigation operates at a fixed speed of 730 rpm, but at different loads, i.e. 25%, 50%, 75% and 100% of full loads. First, the cetane number for blended fuels was measured in a CFR diesel engine based on ASTM-D613 standard method, and ignition delay of blended fuels was calculated based on the cetane number using the relationship between the two. Experimental results revealed that by increasing the biodiesel percentage in the blend, the cetane number of the blended fuels increases, which then causes reduction of the ignition delay. Then, M 8.1 diesel engine was tested at 4 loads and constant engine speed conditions based on the ECE R-49 standard. Engine cylinder pressure data was measured, and the first and second derivatives of pressure curves were drawn to obtain the ignition delay on the basis of these curves. The results indicated that by increasing the biodiesel percentage, ignition delay of blended fuels decreases. Comparison of the results for both methods for ignition delay of the diesel engine confirmed that incresing biodiesel percentage in biodiesel/diesel blended fuels reduces the ignition delay. The decreasing trend of ignition delay for the complete range of engine load though increase in the biodiesel percentage in the fuel blend is an important advantage in diesel knock, NOx emission, engine parts wear reduction, and lengthening the effective life span of the engine.