Comparative studies on fly ash coated low heat rejection diesel engine on performance and emission characteristics fueled by rice bran and pongamia methyl ester and their blend with diesel M. MohamedMusthafa * , S.P. Sivapirakasam, M. Udayakumar Mechanical Engineering Department, National Institute of Technology, Trichy-Thanjavur High way, Thuvagudi, Tiruchirappalli 620015, Tamil nadu, India article info Article history: Received 12 May 2010 Received in revised form 16 December 2010 Accepted 18 December 2010 Available online 25 February 2011 Keywords: Low heat rejection engine Fly ash coating Biodiesel Rice bran methyl ester Pongamia methyl ester Diesel Emission abstract In this study, for the first time, fly ash was used as a thermal barrier coating material in a diesel engine. The study consists of three phases. In first phase, biodiesel was prepared in a laboratory scale setup by single step base catalyzed transesterification method. In the second phase, engine combustion chamber elements such as cylinder head, cylinder liner, valves and piston crown face were coated with fly ash, which is a thermal power plant waste, to a thickness of 200 mm by using plasma spray coating method. In third phase, experiments were carried out on fly ash coated single cylinder diesel engine fueled by methyl ester of rice bran, pongamia oil and its blend (20% by volume) with diesel. The test run was repeated on uncoated engine under the same running conditions and the results were compared. An increase in engine power and decrease in specific fuel consumption, as well as significant improvements in exhaust gas emissions (except NOx) were observed for all test fuels used in the fly ash coated engine compared with that of the uncoated engine. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Energy conservation and efficiency have always been the quest of engineers concerned with internal combustion engines. The diesel engine rejects about two thirds of the heat energy of the fuel as a waste, (one-third to the coolant and one-third to the exhaust) remaining one-third as a useful power output. Theoretically if the heat rejected could be reduced, then the thermal efficiency would be improved, at least up to the limit set by the second law of thermodynamics [1]. Low Heat Rejection engines aim to do this by reducing the heat lost to the coolant. The diesel engine with its combustion chamber elements insulated by thermal barrier coating is referred to as Low Heat Rejection (LHR) engine. Average in- cylinder gas temperature increases due to insulation in LHR engines. In compression stroke around TDC in-cylinder gas temperature increases by 250 K in LHR engine in comparison to standard engine. This will reduce ignition delay period of fuel injected to cylinder. So, combustion starts before sufficiently mix- ing of air and fuel. Combustion characteristics of LHR diesel engines are different from standard diesel engines in four ways [2]. (a) Ignition delay period shortens; (b) Diffusion burning period increases while premixed burning period decreases; (c) Total combustion duration increases; (d) Heat release rate in diffusion burning period decreases. A large number of studies on performance, structure and dura- bility of the LHR engine have been carried out since 1978 [3] pre- sented a new concept of the LHR engine combined with the turbo compound system. Although the use of LHR engine concept is found to be promising, the reported studies showed contradictory results. Most of the researchers have resulted in fact; insulation reduces heat transfer, improves thermal efficiency and increases energy avail- ability in the exhaust. However, contrary to the above expectations some experimental studies indicated that almost there was no improvement in thermal efficiency [4] and [5]. Different materials such as silicon carbide, silicon nitride, aluminum, magnesium sili- cate and other ceramic materials have been used in LHR engine concept. In this study, for the first time, fly ash material has been used for engine combustion chamber elements coating due to its excellent insulating characteristics, strength and thermal expansion characteristics [6,7]. The literature [8e16] showed that researchers have tried LHR engine concept with diesel, neat biodiesel and blends of biodiesel with pure diesel. However, limited studies are available * Corresponding author. Tel.: þ914312503408; fax: þ91431250133. E-mail address: mdm_712003@yahoo.co.in (M. MohamedMusthafa). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy 0360-5442/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.energy.2010.12.047 Energy 36 (2011) 2343e2351