Study on using acetylene in dual fuel mode with exhaust gas recirculation T. Lakshmanan * , G. Nagarajan Internal Combustion Engineering Division, College of Engineering, Anna University, Chennai, Tamilnadu 600025, India article info Article history: Received 15 June 2010 Received in revised form 17 March 2011 Accepted 22 March 2011 Available online 22 April 2011 Keywords: Dual fuel Timed manifold injection Exhaust gas recirculation Dilution effect Ignition delay Carburetion abstract Interest in employing gaseous fuels to internal combustion (IC) engines whether for stationary or mobile automotive applications has gained importance because of the economical, sustainable and environ- mental technical features associated with their usage. However, the incidence of preignition and knock remains a significant barrier in achieving their optimum performance potential. With the advent of latest technologies, the above barriers are eliminated. One such technique is timed manifold injection (TMI) of the gaseous fuel, which is controlled electronically to precisely monitor the induction of fuel to overcome the preignition problem in the intake. In the present investigation, acetylene was injected in the intake manifold in a single cylinder diesel engine, with a gas flow rate of 240 g/h, start of injection time is 10  aTDC and 90  CA (9.9 ms) duration, operated in dual fuel mode. In order to decrease the NOx emissions from acetyleneediesel engine, cooled EGR was employed. The cylinder pressure, brake thermal efficiency and emissions such as NOx, smoke, CO, HC, CO 2 and exhaust gas temperature were studied. Dual fuel operation with acetylene induction coupled with cooled EGR results in lowered NOx emissions and improved part load performance. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction National interest in generating alternating fuels for IC engines continues to be alive due to environmental concerns and the uncertainties associated with the future availability of fossil fuels. Gaseous fuels are getting more positive response from researchers and end-users compared to the past because of the current unfolding developments. When burnt, it produces virtually insig- nificant SOx, the main constituents of acid rain and substantially less CO 2 a key culprit in the greenhouse gas than most oil products. Therefore, gaseous fuels promise to be a suitable fuel for passenger cars, trucks, and stationary engines that can provide both good environmental effect and energy security. Use of gaseous fuel in diesel engines that use dual fuel concept is more economical with environmental advantage. In dual fuel engines, usually gaseous fuels are mixed with the air either in the intake manifold or through direct injection into the cylinder. The resulting mixture after compression is then ignited through the injection of a small amount of diesel fuel (pilot) in the usual way. This pilot liquid fuel auto-ignites to provide ignition source for subsequent flame propagation within the surrounding gaseous fuel mixture. In dual fuel engine, both spark ignited (SI) engine and compression ignited (CI) engine combustion co-exist together. Accordingly a dual fuel engine tends to retain most of the positive features of diesel operation even it surpasses occasionally those of the diesel engines, producing higher power outputs and lower emissions. The work of Karim [1e3] on utilization of gaseous fuel such as methane, propane, acetylene, ethylene and hydrogen in diesel engine reveals that the maximum amount of gas consumption is limited due to the onset of knock. He also reported that in dual fuel engines at low load, when gaseous fuel concentration is low, igni- tion delay period of the pilot fuel increases and some of the homogeneously dispersed gaseous fuel remains unburned and results in poor performance. Pilot fuel quality, injection timing, and intake temperature are important variables affecting the perfor- mance of dual fuel engine. Liu and Karim [4] studied the effect of admission of gaseous fuels and diluent in the dual fuel diesel engine. They reported that gaseous fuels and diluent would change the physical and chemical processes of the ignition delay period. The ignition delay period strongly depends on the type of gaseous fuel used and its concentration. As reported by Poonia et al. [5], most of the primary gaseous fuel remains unburnt leading to high HC and CO emissions at part loads, which is mainly due to lower in- cylinder temperature and extremely lean mixture available inside the combustion chamber. The performance of the dual fuel engine at part loads can be improved by preheating the intake air, thermal insulation of the engine cylinder (LHR), exhaust gas recirculation (EGR) and advancement of the injection timing. * Corresponding author. Tel.: þ91 9840154392. E-mail address: lux.bharani@gmail.com (T. Lakshmanan). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy 0360-5442/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.energy.2011.03.061 Energy 36 (2011) 3547e3553