Tamanu oil - an alternative fuel for variable compression ratio engine

Raj and Kandasamy International Journal of Energy and Environmental Engineering 2012, 3:18 http://www.journal-ijeee.com/content/3/1/18 ORIGINAL RESEARCH Open Access Tamanu oil - an alternative fuel for variable compression ratio engine Mohan T Raj1* and Murugumohan Kumar K Kandasamy2 Abstract Biodiesel can be produced from vegetable oils and also from waste fats. Biodiesel is a mono-alkyl-ester of long chain fatty acids derived from renewable feedstock such as vegetable oils by transesterification process. The esterified cotton seed oil, pungam oil, rice bran oil, and tamanu oil are chosen as the alternative fuels. Among these oils, tamanu oil is considered for the first time as an alternative fuel. An experiment is conducted to obtain the operating characteristics of the variable compression ratio (VCR) engine run by chosen esterified oils, and the results are compared with esterified tamanu oil. From the comparison of results, it is inferred that the engine performance is improved with significant reduction in emissions for the chosen oils without any engine modification. The effective compression ratio can be fixed based on the experimental results obtained in the engine since the findings of the present research work infer that the biodiesel obtained from tamanu oil is a promising alternative fuel for direct-injection four-stroke VCR engine. Keywords: Biodiesel, Esterified tamanu oil, Compression ratio, VCR engine, Transesterification Background Vegetable oils have good ignition quality since they are not branched and have very long molecular chains. Certain functional groups and the poor volatility could be responsible for their low cetane numbers. The heating value of vegetable oils is somewhat lower due to oxygen content, and viscosity and carbon residue are higher than diesel due to their larger molecular mass and chemical structure [1]. The flash point of these oils is much higher than that of diesel, indicating that they are much safer to store than diesel oil. They are about 10% denser than diesel [2]. Their cold point is higher, indicating problems of thickening or even freezing at low ambient temperatures. It is evident that vegetable oils are much less volatile than diesel. This makes their slow evaporation when injected into the engine. Vegetable oils have cetane numbers of about 35 to 50 depending on their composition [3]. It is seen that the value is very close to diesel. The compression process effectively starts only after the intake valve closes and also depends on the momentum of the flow into the cylinder, and thus, the actual realized amount of compression ratio * Correspondence: 1 Department of Mechanical Engineering, SASTRA University, Thanjavur, Tamilnadu, India Full list of author information is available at the end of the article is known as the effective compression ratio (ECR). ECR is a more suitable indicator of the compression process, and it also influences the engine operation. One of the very promising and interesting fields of study involves the use of alternative fuels including biodiesel and diesel fuels to provide effective solutions [4]. The development of treatment devices has also mitigated the emission problem to a large extent while allowing the combustion process to be optimized for maximum fuel efficiency [5]. Lehman et al. [6] obtained high ester conversion with a 6:1 M ratio of methanol to vegetable oil. In the process of peanut oil esterification, the 6:1 M ratio liberated significantly more glycerol than the 3:1 M ratio. These investigators also found that glycerol yields increased from 77% to 95% as the sodium hydroxide catalyst increased from 0.2% to 0.8% at the 6:1 M ratio. Fatty ester is the major product, and glycerol is the by-product. Barsic and Humke [7] have found that transesterification is one of the methods by which viscosity could be drastically reduced and the fuel could be adopted for use in diesel engine. The transesterification process involves reacting vegetable oils with alcohols such as methanol or ethanol in the presence of a catalyst (usually sodium hydroxide) at about 70°C to give the ester and the by-product glycerin. This esterified vegetable oil is popularly known as biodiesel which is commercially © 2012 raj and kandasamy; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Raj and Kandasamy International Journal of Energy and Environmental Engineering 2012, 3:18 http://www.journal-ijeee.com/content/3/1/18 available in developed countries due to its distinct advantage over the conventional diesel. Free fatty acids (FFAs) present in the pongamia oil have got the greater influence in the process of converting it into biodiesel. This has been observed during the biodiesel preparation process in the laboratory level. However, their high viscosity and poor volatility lead to reduced thermal efficiency and increased hydrocarbon, carbon monoxide, and smoke emissions. Vellguth [8] studied the performance of a direct-injection single-cylinder diesel engine on vegetable oil. He conducted a variable load test on the engine with rapeseed oil, peanut oil, and soybean oil. He found that vegetable oils which are results of performance are comparable to diesel values with slightly reduced thermal efficiency. He concluded that vegetable oils could be directly used as fuel in diesel engines on a short-term basis. Ramesh et al. [9] investigated the performance of a glow plug-assisted hot surface ignition engine using methyl ester of rice bran oil as fuel. Normal and mnemonic crown pistons were used for their tests. They reported an improvement in brake thermal efficiency of about 1% when the glow plug is on. The percentage improvement in brake thermal efficiency was higher in the case of normal piston compared with that in the case of mnemonic piston. Larry Wagner et al. [10] studied the effect of soybean oil esters on the performance and emissions of a four-cylinder direct-injection turbocharged diesel engine. They found that the engine performance with soybean oil esters is the same with diesel. Clark et al. [11] studied the effect of methyl and ethyl esters of soybean oil on engine performance and durability in a direct-injection John Deere four-cylinder diesel engine. They observed that the engine fuelled with soybean esters produced less power output with an increase in fuel consumption. Emissions results were found to be similar to diesel. Panwar et al. [12] conducted an experiment in single-cylinder variable compression ratio diesel engine at different loads. The engine performance for castor methyl ester was investigated. The lower blends of biodiesel increased break thermal efficiency and reduced fuel consumption. The work done by Gumus et al. [13] deals w (...truncated)