A test on DI diesel engine fueled with methyl esters of used palm oil

Abstract

Used palm oil collected from different restaurants in Tirunelveli region of south India was converted into methyl esters (biodiesel) by transesterification. Biodiesel produced from used palm oil was blended with diesel by different volume proportions (25%, 50% and 75%). Biodiesel and its blends were tested in a DI diesel engine at constant speed by varying loads (between 20% and 100%) to analyze its performance, emission and combustion profile. The results obtained were compared with diesel fuel. B25 and B50 showed performances similar to diesel fuel. Smoke density of B100 and B75 were lower than diesel by 19% and 10% at full load. At full load measured CO emission for B100 and B75 were 52.9% and 35.2% lower than diesel HC emission for B100 and B75 were 38.09% and 19.05% lower than diesel. NO_X emission was higher for all biodiesel blends. B75 showed lower amount of emissions throughout the test. Ignition delay for B100, B75, B50 and B25 were 2.1°, 1.9°, 1.7° and 1° lower than diesel. Combustion profile was smoother and no knocking was experienced while operating with biodiesel blends. B50 produced peak cylinder pressure.

Introduction

In India diesel engines are widely used for transport and agricultural machinery due to its superior fuel efficiency. The increasing cost of petrol has made people to depend largely on diesel based engines. Due to depletion and higher cost of petroleum based fuels researchers around the world look for alternate fuels. Biodiesel which is mainly mono alkyl esters of long chain fatty acids has been accepted as a suitable alternate to diesel fuel [1]. Moreover, the emission is very much reduced by utilizing biodiesel. Biodiesel blended with diesel fuel showed better performance. Vegetable oils because of their higher viscosity and huge carbon deposits can be used only as a short term fuel in diesel engines [2]. Viscosity of vegetable oils can be reduced and made equivalent to diesel fuel by transesterification [3]. Large number of feedstocks including non-edible oils and wastes from hotels, beef tallow and chicken feather meals are utilized for biodiesel production. In developed countries used cooking oils are available in plenty and are used as cheap feedstocks for biodiesel production. Phan and Phan [4] carried out transesterification of waste cooking oils with methanol and KOH as catalyst. They obtained a maximum yield of 90% for a molar ratio of 8:1 at a temperature of 50 °C with 0.75 wt% KOH. Cayli and Kusefoglu [5] reported best yield for two step base catalyzed transesterification of used soybean oil at room temperature compared to one step process. Rafiqul Islam et al. [6] carried out transesterification of waste canola oil with different concentration of NaOH. They found a better yield of 94% for 0.8 wt% of NaOH. Enciar et al. [7] utilized different base catalysts with ethanol for transesterification of waste frying oils they noticed that potassium hydroxide of 1 wt% gave better yield at a molar ration of 12:1 at 78 °C. Yu et al. [8] reported an increase in emission and deposition of coke like substances during utilization of waste cooking oil from noodle industry in diesel engines. Bari et al. [9] found that waste cooking oil heated upto 55 °C prevented clogging, they also noticed an increase in head loss across for waste cooking oil compared to diesel fuel. Pugalvadivu and Jeyachandran [10] reported that viscosity of waste frying oil could be made equivalent to diesel fuel by heating it to a temperature of 135 °C. They suggested the use of preheated oil for short term operation in diesel engine. Nanthagopal and Subbarao [11] utilized waste cooking oil-diesel mixture in emulsion with water they noticed reduced NO_X emission and CO emission while operating for 20% water content in the emulsion. They reported higher smoke and particulate emissions. Agarwal et al. [12] experienced operational and durability problems while running CI engines with linseed oil, mahua oil and rice bran oil. The same problems were not reported by them while running with esterified linseed oil. Ramadhas et al. [13] tested diesel engine with different blends of rubber seed oil ester with diesel. They noticed an increase in fuel consumption and reduction in emissions. Al-Widyan et al. [14] utilized ethyl esters of waste vegetable oils in diesel engine. They reported better performance and reduced emissions for biodiesel blends. Agarwal et al. [15] investigated the effect of exhaust gas recirculation (EGR) on engine emission; they experienced a reduction in NO_X emission with an increase in HC and CO emission. They found declination in lubricating oil quality and durability with EGR. Sahoo and Das [16] analyzed combustion of jatropha, karanja and polanga based biodiesel in diesel engine. They reported a decrease in ignition delay and an increase in cylinder pressure for all biodiesel compared to diesel. Gumus [17] reported better combustion for hazelnut kernel methyl ester with increasing injection timing, compression ratio and injection pressure. Buyukkaya [18] has tested different blends of rapeseed oil with diesel fuel. He reported combustion characteristics similar to diesel, decreased engine emission, and ignition delay.

In India because of huge population and availability of large number of restaurants a huge amount of edible oil is consumed for food preparation. The used oil thus produced is dumped outside resulting in environmental degradation. This could be avoided if these used oils are collected and converted into biodiesel. In this study used palm oil was collected from different restaurants in Tirunelveli region of south India and was converted into biodiesel. The biodiesel thus produced is blended with diesel at different volume proportions and tested in a DI diesel engine to evaluate its performance, emission and combustion profile.