An assessment of calophyllum inophyllum biodiesel fuelled diesel engine characteristics using novel antioxidant additives B. Ashok, K. Nanthagopal ⇑ , A.K. Jeevanantham, Pathikrit Bhowmick, Dhruv Malhotra, Pranjal Agarwal School of Mechanical Engineering, VIT University, Vellore 632014, Tamil Nadu, India article info Article history: Received 24 March 2017 Received in revised form 9 June 2017 Accepted 16 June 2017 Keywords: Calophyllum inophyllum Antioxidant Combustion Emission 2,6-Di-tert-butylphenol (Ethanox) 2,6-Di-tert-butyl-4-methylphenol (BHT) abstract In this present study, the effect of antioxidant additives with pure Calophyllum inophyllum methyl ester on the performance, combustion and emission characteristics has been investigated. New antioxidant additive namely Ethanox was added to the Calophyllum inophyllum biodiesel at concentrations of 200 ppm, 500 ppm and 1000 ppm for oxides of nitrogen reductions and the experimental results were compared to Butylated hydroxytoluene antioxidant at same concentrations. An experimental study was done on a twin cylinder, four stroke diesel engine at a constant speed of 1500 rpm with two different antioxidants, Ethanox and Butylated hydroxytoluene individually mixed with pure Calophyllum inophyl- lum at concentrations of 200 ppm, 500 ppm and 1000 ppm by weight. The experimental results showed that the addition of antioxidants with Calophyllum inophyllum biodiesel produced higher brake specific fuel consumption and higher brake thermal efficiency compared to pure biodiesel. Significant reductions in oxides of nitrogen emissions were observed with Ethanox and Butylated hydroxytoluene addition with biodiesel at all concentrations compared to neat biodiesel. The reduction oxides of nitrogen emission was 12.6% for Ethanox 1000 ppm and 21% for Butylated hydroxytoluene 500 ppm compared to neat biodiesel. Comparable combustion characteristics were obtained by addition of Ethanox with biodiesel than Butylated hydroxytoluene antioxidant. Moreover, the addition of Ethanox and Butylated hydroxytoluene antioxidants with neat biodiesel increase the carbon monoxide, unburned hydrocarbons and smoke emission at all concentrations than biodiesel. Ethanox addition with biodiesel has shown better results compared to Butylated hydroxytoluene antioxidant. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction Evolution of alternative fuels is instigated by the alarming rate of energy consumption across the globe in the field of transporta- tion [1]. Worldwide energy demand for the past five decades is increasing abnormally and it has become an important issue for the researchers to ensure energy security and environmental pro- tection. Due to the uncertainty in future availability of fossil fuels, people are showing appreciable interest in alternative fuels [2]. Alternate fuels have the potential to meet the present energy demand in a sustainable manner. Biodiesel is basically a fatty acid methyl ester derived from vegetable oils or animal fats which along with bio-ethanol is widely used as alternate fuels [3]. Pro- duction of biodiesel can be achieved with the help of triglycerids from many different feedstocks like rapeseed oil, sunflower oil, palm oil, soybean oil, animal fat and used cooking oil [4]. Due to their feasible existence and eco-friendly characteristics, biodiesel have become the first choice of replacing the conventional diesel fuel. Biodiesels can be extracted from nature and animal fats and have an upper hand over conventional petro-diesel by offering bet- ter cetane number, improved tribological properties, and suffi- ciently less CO and UBHC emissions [5]. Moreover, due to their biodegradability, renewability and non-toxicity in nature, the bio- diesel fuels are steadily gaining attention worldwide as a direct replacement of diesel fuel in internal combustion engines [6]. Bio- diesels are environmental friendly fuels produced from renewable sources which offer cleaner combustion over conventional petro- diesel fuel [7]. But several researchers indicated that for all biodie- sels, there is an increase in oxides of nitrogen emissions (about 13%) compared with conventional petro-diesel fuel. Other disad- vantages of biodiesel are that unlike mineral diesel, they are decay- able and oxidize as soon as they are produced and also have a lower heating value, higher viscosity and density compared to fos- sil fuels [8]. Biodiesels reacts with oxygen in the atmosphere to produce vaporizable compounds and caustic carboxylic acids which may damage the engine components [9]. To forbid the pre- mature oxidation of unsaturated biodiesel esters, anti-oxidant http://dx.doi.org/10.1016/j.enconman.2017.06.049 0196-8904/Ó 2017 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: nanthagopalk@yahoo.com (K. Nanthagopal). Energy Conversion and Management 148 (2017) 935–943 Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman