Journal of Mechanical Science and Technology 26 (4) (2012) 1241~1250 www.springerlink.com/content/1738-494x DOI 10.1007/s12206-012-0206-0 Performance and emission characteristics of a low heat rejection spark ignited engine fuelled with E20 † C. Ramesh Kumar 1,* and G. Nagarajan 2 1 CEAR, School of Mechanical and Building Sciences, VIT University, Vellore, 632014, India 2 CEG, Anna University, Chennai, India (Manuscript Received March 4, 2011; Revised August 30, 2011; Accepted December r 1, 2011) ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Abstract In internal combustion engines, the concept of low heat rejection (LHR) using thermal barrier coating on the surface of combustion chamber is gaining attention. Thermal barrier coating reduces the heat transfer to the cooling system, protects engine components from peak heat flux and fluctuating temperature produced during combustion and improves the performance of the engine. Information in the literature is plentiful for LHR diesel engine and only few studies exist on LHR spark ignited engine. The application of thermal barrier coating in spark ignited engine is limited by pre-ignition and knocking due to elevated combustion chamber temperature. A spark ignited engine with moderate insulation on the combustion chamber and higher octane fuel can overcome this difficulty. The objective of the present experimental study is to quantify the changes in performance and emission characteristics brought by partial thermal insulation on the combustion chamber of a four stroke spark ignited engine fueled with E20 blend. Partial thermal insulation was created by coating 0.3 mm thick Alumina (Al 2 O 3 ) on the cylinder head, inlet and exhaust valves. The changes are quantified with respect to unmodified engine fueled with gasoline. The combustion parameters such as flame development and rapid burn duration are also estimated and com- pared. The results indicate that partially insulated SI engine when fueled with E20 improves performance and reduces emission. A max- imum of 48% reduction in THC and 50% reduction in CO emission at part load was achieved. Keywords: Combustion; Emission; E20; LHR; SI engine ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- 1. Introduction Among different alternate fuels available, ethanol has been recognized as a renewable alternate transportation fuel for SI engine. As it has properties similar to gasoline it can be used in SI engines with some or no modifications. Information in the literature is abundant for automotive use of ethanol. Pres- ently ethanol is primarily used as blending fuel with gasoline in many countries. Ethanol provides additional oxygen for air fuel charge and improves combustion. When ethanol is blended with gasoline (< 30% by volume) it reduces carbon monoxide, net carbon dioxide, and hydrocarbon emissions [1- 4]. Ethanol reduces the cyclic variation of the MEP and im- proves the power and torque output [2]. Addition of ethanol increases the cylinder pressure and temperature and also de- creases the combustion duration [5]. Ethanol also improves the octane value of the fuel blend. A fuel with a higher octane number can endure higher compression ratio without knock- ing and improve the thermal efficiency of the engine [6]. Etha- nol’s higher latent heat of evaporation increases the evapora- tive cooling effect of air-fuel charge which increases the volumetric efficiency and also decreases the compressed charge temperature during the compression stroke. Ethanol has higher hydrogen to carbon ratio because of which it pro- duces more volume of gases per unit of energy compared to gasoline (i.e. ethanol yields higher volume of total exhaust gas than gasoline). This leads to higher mean cylinder gas pressure which performs additional work during expansion. Unfortu- nately some of the physical properties of the ethanol present problems when it is adapted in higher volume or as a sole fuel in SI engines. The major engine operation issues with higher levels of ethanol in blended fuels are higher latent heat, cold start, cold start emissions and aldehyde emission. Ethanol’s higher latent heat of evaporation can also be disadvantageous in cold start situations. A blend containing 10% ethanol re- quires about 15.2% more manifold heating in order to attain proper degree (homogeneous mixture) of air fuel mixture. Higher levels of ethanol (greater than 30%) reduce the vapor pressure of blend and adversely affect the cold starts, engine warm-up and heating (light off) of the three way catalytic * Corresponding author. Tel.: +91 9894189439 E-mail address: crameshkumar@vit.ac.in † Recommended by Associate Editor Kyoung Dong Min © KSME & Springer 2012