Journal of Material Science and Mechanical Engineering (JMSME) Print ISSN: 2393-9095; Online ISSN: 2393-9109; Volume 2, Number 7; April-June, 2015 pp. 20-23 © Krishi Sanskriti Publications http://www.krishisanskriti.org/jmsme.html An Experimental Measurement of Ignition Delay for Diesel Fuel Blends at Different Cylinder Pressures Md Nazeem Khan 1 , Inayat Hussain 2 1 Department of Mechanical Engineering, Al-Falah University, Faridabad, Haryana, India nazeem.gla@gmail.com 2 Department of Mechanical Engineering, Invertis University, Bareilly, (U.P), India inayat.hussain786@gmail.com * corresponding author Abstract: The key to efficient operation of a diesel engine is in the controlled ignition and combustion of the fuel. The ignition delay, can impact on power output, combustion efficiency, and engine maintenance. Measurement of ignition delay is an important aspect for the design of engines. An experimental study was done for the measurement of ignition delay characteristics for pure diesel oil and coconut oil-diesel fuel blends (50%:50%) at various ambient pressures (cylinder pressures) at a given hot surface temperature and injection pressure. An experimental set up fabricated for this purpose based on optical method for measurement of ignition delay. The ignition delay of fuel spray was measured by recording the time delay between the event of injection and the event of appearance of flame inside the combustion chamber by using digital storage Scope-Meter. Keywords: Digital Storage Scope-Meter, Fuel Blends, Hot Surface Temperature, Ignition Delay, 1. INTRODUCTION The study of possible alternative liquid fuels derived from biomass is not a new topic. Although, during the last decade ethanol and biodiesel became the best-known liquid bio fuels, numerous studies examine different chemical structures as possible bio fuels and record their pros and cons. [1] The ignition delay time can be defined as the period between the creation of a combustible mixture, as by injection of fuel into an oxidizing environment, and sustain and onset of the rapid reaction phase leading to the rise of temperature and pressure. The ignition delay times can also be indicated by either a fixed temperature increase or an evolution of certain species. Masjuki et al (2001) performed dynamometer tests to evaluate the performance, emission and ignition delay characteristics of an indirect-diesel engine fuelled by blends of coconut oil and diesel fuel. Results showed that 10–30% coconut oil blends produced a slightly higher performance in terms of brake power than that of diesel. All the coconut oil blends produced lower exhaust emissions including polycyclic aromatic HC and particulate matter. [2] Auto- ignition is the spontaneous combustion of a mixture of fuel and oxidizer in the absence of any ignition source. The ignition occurs after some period of mixing between the fuel and oxidizer occurs. It is the initiation of overall chemical reaction. Geyeret et al (1984) conducted trials on a certified diesel fuel, cottonseed oil, sunflower seed oil, methyl ester of cotton seed oil, and methyl ester of sunflower seed oil. They compared the engine performance and emission characteristics and reported slight improvements in thermal efficiency and higher exhaust gas temperatures when operating on vegetable oils; equal or higher gas-phase emissions with vegetable oils; and significantly higher aldehyde emissions, including an increased percentage of formaldehyde. [3] Wang et al (2006) evaluated the performance and gaseous emission characteristics of a diesel engine when fuelled with vegetable oil and its blends of 25%, 50%, and 75% of vegetable oil with ordinary diesel fuel separately. The engine was operated at a fixed speed of 1500 rpm, but at different loads .They reported that the basic engine performance, power output and fuel consumption are comparable to diesel when fuelled with vegetable oil and its blends. The emission of NOx from vegetable oil and its blends were lower than that of pure diesel fuel. [4] 1.1 Necessity to Reduce Ignition Delay: Too short an ignition delay period does not normally create operational problems, but there is likely to be a loss of fuel efficiency. An extended ignition delay however can lead to poor running of the engine and, in the extreme, to damage of engine components. This is because with long ignition delay a relatively large amount of fuel droplets will have been injected