Performance, emission and combustion evaluation of soapnut oil–diesel blends in a compression ignition engine R.D. Misra a,⇑ , M.S. Murthy b,1 a Mechanical Engineering Department, National Institute of Technology, Silchar, Assam, India b S.S.B.T. College of Engineering and Technology, Jalgaon, Maharashtra, India article info Article history: Received 19 December 2010 Received in revised form 27 February 2011 Accepted 2 March 2011 Available online 16 March 2011 Keywords: Soapnut vegetable oil Performance Emissions Diesel engine abstract Soapnut (Sapindus mukorossi) oil, a nonedible straight vegetable oil was blended with petroleum diesel in various proportions to evaluate the performance and emission characteristics of a single cylinder direct injection constant speed diesel engine. Diesel and soapnut oil (10%, 20%, 30% and 40%) fuel blends were used to conduct short-term engine performance and emission tests at varying loads in terms of 25% load increments from no load to full loads. Tests were carried out for engine operation and engine perfor- mance parameters such as fuel consumption, brake thermal efficiency, and exhaust emissions (smoke, CO, UBHC, NO x , and O 2 ) were recorded. Among the blends SNO 10 has shown a better performance with respect to BTE and BSEC. All blends have shown higher HC emissions after about 75% load. SNO 10 and SNO 20 showed lower CO emissions at full load. NO x emission for all blends was lower and SNO 40 blend achieved a 35% reduction in NO x emission. SNO 10% has an overall better performance with regards to both engine performance and emission characteristics. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Depleting petroleum reserves and increasing cost of the petroleum products demands an intensive search for new alterna- tive fuels. The scarcity of known petroleum reserves will make renewable energy sources more attractive. Biofuels are proved to be very good substitutes for the existing petro fuels. The essential minimum requirements for biofuels to be a more sustainable alter- native for fossil fuels are that they should be produced from renewable raw material and that their use has a lower negative environmental impact. Plant oils are renewable and have low sulfur in nature. As biofuels are more expensive than fossil fuels, the wide spread use of biofuel was restrained from its use in C.I. Engines [1,2]. In recent years, systematic efforts were undertaken by many researchers to determine the suitability of vegetable oil and its derivatives as fuel or additives to the diesel [3–7]. More than 350 oil-bearing crops have been identified [8]. Various oils such as soybean oil [9], jatropha oil [10–12], rapeseed oil [13,14], palm oil [15,16], sunflower oil [17], tobacco seed oil [18] Karanja oil [19], poon oil [20], orange oil [21], and waste cooking oils [22] have been tried successfully to run a diesel engine. The main advantages of vegetable oils as diesel engine fuel are ready avail- ability, renewability, lower sulfur and aromatic content, and biode- gradability. They also provide sustainability, reduction of green house gas emissions, regional development, and improvement in agriculture. The chemical composition of vegetable oil helps in reducing the harmful emissions [19,20]. Devan and Mahalakshmi [20], cited the work of De Almeida et al. [23] and Babu and Devarajane [24] to state that many researchers have shown that the diesel engine would run successfully without any modification on different blends of vegetable oil with diesel fuel. It has also been reported in the literature that the use of vegetable oil and their derivatives is economical and competitive compared to mineral diesel [25,26]. But the problems associated with vegetable oil are the high viscos- ity and low volatility. All vegetable oils are extremely viscous, with viscosities ranging from 10 to 17 times greater than No. 2 diesel fuel [27,28]. These properties have an adverse effect on fuel injec- tion system and may lead to heavy carbon deposits in the engine combustion chamber carbon deposition on the injector and the valve seats causing serious engine fouling [18,29]. But there is still a lot of work that has to be done to make vegetable oil really 0016-2361/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2011.03.003 Abbreviations: CO, carbonmonoxide; UBHC, unburnt hydrocarbon; NO x , nitro- genoxide; O 2 , oxygen; SNO, soapnut oil; SNO 10, etc., blend of soapnutoil10% +diesel 90% etc.; BTE, brake thermal efficiency; BSEC, brake specific energy consumption; IMEP, indicated mean effective pressure; A/F ratio, air fuel ratio; kW, kilo Watt; RPM, revolutions/minute; WC, water column; Deg, degree; TDC, top dead center; BSFC, brake specific fuel consumption; BMEP, brake mean effective pressure. ⇑ Corresponding author. Tel.: +91 9435072301; fax: +91 3842 224797. E-mail address: rdmisranit@gmail.com (R.D. Misra). 1 Research Scholar, Mechanical Engineering Department, National Institute of Technology, Silchar, Assam, India. Fuel 90 (2011) 2514–2518 Contents lists available at ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel