Experimental Investigations on Lubricity and Cold Flow Properties of Biodiesel

Abstract

The desirability of developing biodiesel from different tree born oil seeds and decreasing the dependency on petroleum based fuels has been discussed by many over the last few decades. However some of the important issues of biodiesel like lubricity, low temperature flow characteristic, material compatibility have not been sufficiently investigated. In this paper, an attempt has been made to explore the lubricity and cold flow properties of biodiesel separately based on the experimental results. These two properties though may not be related with each other but plays significant role towards the long term acceptability of biodiesel in an existing CI engine. For biodiesel, the lubricity parameter is important to evaluate in the context of recent advent of ultra low sulfur diesel fuel (<10 ppm sulfur in Europe) which has raised the concern over the ability of these fuels to sufficiently lubricate diesel engine components in fuel injection system. In the very specific case of biodiesel, the lubricity could be defined as its ability to minimize or completely prevent wear in fuel pumps and injectors. Also, the biodiesel fuels derived from fats or oils with significant amounts of saturated fatty compounds will display higher cloud points and pour points which questions the pumping and injecting of these biodiesel in CI engines under cold climates. The lubricity of Jatropha Oil Methyl Ester, one of the potential specie for India is explored by evaluating the wear characteristics of plunger and barrel of CI engine fuel pump using bench test. Fuel pump plunger test specimen was made of mild steel pin and the rotating disc indicative of barrel in fuel pump was made from EN-31. Several tests were conducted on pin on disc machine using biodiesel for specific wear rate and friction characteristic to establish its lubricity. Results indicated that biodiesel from Jatropha has better lubricity over diesel fuel and has lower specific wear rate over diesel. The cold flow properties of biodiesel were evaluated with and without pour point depressant towards the objective of identifying the pumping and injecting of these biodiesel in CI engines under cold climates. Four different biodiesel were tested to identify the effect of cold flow improver on cloud and pour points. Ethanol has been considered as a cold flow improver in the present investigations. Effect of ethanol on cold flow behavior of this biodiesel was studied. A considerable reduction in pour point has been noticed.