K. Anand

Experimental investigations on combustion of jatropha methyl ester in a turbocharged direct-injection diesel engine

Suitability of vegetable oil as an alternative to diesel fuel in compression ignition engines has become attractive, and research in this area has gained momentum because of concerns on energy security, high oil prices, and increased emphasis on clean environment. The experimental work reported here has been carried out on a turbocharged direct-injection multicylinder truck diesel engine using diesel fuel and jatropha methyl ester (JME)-diesel blends. The results of the experimental investigation indicate that an increase in JME quantity in the blend slightly advances the dynamic fuel injection timing and lowers the ignition delay compared with the diesel fuel. A maximum rise in peak pressure limited to 6.5 per cent is observed for fuel blends up to 40 per cent JME for part-load (up to about 50 per cent load) operations. However, for a higher-JME blend, the peak pressures decrease at higher loads remained within 4.5 per cent. With increasing proportion of JME in the blend, the peak pressure occurrence slightly advances and the maximum rate of pressure rise, combustion duration, and exhaust gas temperature decrease by 9 per cent, 15 per cent and 17 per cent respectively. Although the changes in brake thermal efficiencies for 20 per cent and 40 per cent JME blends compared with diesel fuel remain insignificant, the 60 per cent JME blend showed about 2.7 per cent improvement in the brake thermal efficiency. In general, it is observed that the overall performance and combustion characteristics of the engine do not alter significantly for 20 per cent and 40 per cent JME blends but show an improvement over diesel performance when fuelled with 60 per cent JME blend.

Predicting surface tension for vegetable oil and biodiesel fuels

Vegetable oil and biodiesel are considered as alternatives to diesel fuel due to their favorable engine characteristics and renewable nature. Estimates of their surface tension values are essential in understanding fuel spray behavior. This study proposes an approach for predicting the surface tension of vegetable oil and biodiesel based on their composition. In the proposed methodology, the surface tension of fatty acids and methyl esters are first estimated using suitable property correlations available in the literature. The suitability of correlations is adjudged based on validation with the measured data. Further, the correlations are also modified to improve the predictions. A weighted average mixing rule is then employed to determine the surface tension of the vegetable oil and biodiesel from their measured composition. The predicted and measured surface tension values of karanja, palmolein and coconut are compared and found to agree within 7 percent over a useful temperature range of up to 353 K. The effects of transesterification and compositional variations on the surface tension of biodiesel fuels are also discussed in this paper.

Surrogates for Biodiesel: Review and Challenges

Biodiesel is being considered as a renewable fuel candidate to completely or partially replace fossil diesel. Understanding its combustion is key to assess its applicability in practical compression ignition engines. Significant progress has been made in understanding biodiesel combustion through experimental studies, development of reaction kinetics to describe its oxidation, and simulations in typical engine environments. The use of surrogates in place of the real biodiesels plays a crucial role in this endeavour. This chapter reviews the existing studies revolving around surrogate fuels for biodiesels. Thereafter, the challenges ahead in this context to further enhance our knowledge of biodiesel combustion are presented, and possible options to address these are discussed where appropriate.

Effect of Long Storage Stability of Karanja (Pongamia) Derived Biodiesel Fuel on the Performance, Combustion and Emission Characteristics of a Multi-Cylinder Turbo-Charged Direct Injection Diesel Engine

Due to its renewable nature, emission advantage and easy adaptation, biodiesel is emerging as an alternative to fossil diesel. There are however concerns on biodiesel storage stability aspect due to the presence of unsaturated content in its composition. This paper discusses on studying the effect of long term storage stability of Karanja derived biodiesel (KME) on the performance, combustion and emission characteristics of a turbo-charged, multicylinder, direct injection diesel engine. For aged karanja derived biodiesel (A-KME) stored in a mild steel container for 500 days, both the fuel properties and the engine performance are found to change. It is observed that the aged fuel as compared to the fresh karanja derived biodiesel (F-KME) showed i) an increase in the acid value and kinematic viscosity from 0.374 mg KOH/g to 0.89 mg KOH/g and 5.6 to 5.7 cSt respectively, ii) a slight decrease in ignition delay and maximum rate of pressure rise, iii) a maximum increase in peak cylinder pressure of about 10% and duration of combustion of 8 deg. CA, iv) a decrease in brake thermal efficiency to an extent of over 4%, v) an increase in un burnt hydrocarbon emissions particularly at low loads, and, vi) a significant increase in exhaust nitric oxide (∼30%) and the smoke emissions (∼78%) at higher loads.Copyright