Abstract— In the present paper, we report the single pulse detonation study using natural gas as the fuel. The detonation tube used was measured to be 1500 mm in length with 100 mm of internal diameter. The target of this research is to study the effect variable percentage of oxygen used as oxidizer and nitrogen as the diluents gas to the pulse detonation combustion of natural gas. The effects of different level of ignition energy used to initiate the pulse combustion and variable length of obstacle arrangement also being reported. The result shows that, from the experimental investigations natural gas is less sensitive to form detonation combustion for any percentage of nitrogen dilution. It is observed that the flame is propagating at high speed turbulent flame combustion except for longer length of obstacle it shows detonation propagations. Keywords— Detonation, natural gas, single pulse combustion, diluents gas. I. INTRODUCTION ulse detonation engine (PDE) recently has attracted several attention of researcher around the world today. As the operation of PDE involve shock wave generation by the compression of burnt mixture in a long tube that is closed at one end and open at the other end[1]. This phenomena also being proved by Schauer et al.[2] that PDE can deliver higher thrust with higher efficiency compare to an ordinary propulsion engine such as ramjet, pulsejet and any other type of propulsion engine. With this specialty, PDE is capable to be used in a wide range of application as the detonation waves created can travel with high Mach number [3]. The design of this kind of engine is much simpler than conventional propulsion engine as PDE will not required the use of compressor and turbine for compression and expansion stage. The mechanism to do this stage has been replaced by the shock wave itself that propagate inside the detonation tube and compressed the burnt mixture. Due to this, it is more efficient Manuscript received April 15, 2010. This work was supported by Ministry of Higher Education Malaysia. Grant VOT 78046. A.F. Mat Zin is with High-Speed Reacting Flow Laboratory(HiREF), Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Skudai, MALAYSIA (corresponding author: +60179305549; e-mail: faiz_krr@ yahoo.com). M.A. Wahid is with High-Speed Reacting Flow Laboratory(HiREF), Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Skudai, MALAYSIA (e-mail: mazlan@fkm.utm.my). K.M. Saqr is with is with High-Speed Reacting Flow Laboratory(HiREF), Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Skudai, MALAYSIA (e-mail: khaledsaqr@gmail.com). H.Ujir is with is with High-Speed Reacting Flow Laboratory(HiREF), Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Skudai, MALAYSIA compare to the conventional propulsion engine [4] as the weight is greatly reduced. It is claimed by NASA that by applying that constant volume combustion process (PDE cycle), this type of propulsion system could save up to seven percent of fuel consumption compare to conventional gas turbine engine and it is a huge fuel saving for airlines. II. LITERATURE REVIEW Several studies have been done by many researchers for past few decades regarding to single pulse detonation engine study. For example He Liming et al [5] study on single detonation wave in 1997. The objective of their study is to observe the conditions, mechanisms and regularities of the detonation wave formation. From their experimental investigations, one of the most important observations is that the fuel and oxidizer mixture must mix in the detonation tubes to form a stable detonation wave. Zhang et al [6] study the characteristics of detonation using propane as the fuel. In their investigations, series of experiment were run using several oxidizer configurations. They use air, oxygen and oxygen/air as an oxidizer in a square detonation tube. The objectives of their research is to study the propane detonation performance, the characteristic of deflagration to detonation (DDT), spread rule of wave and flame with the variations of equivalence ratio and degree of nitrogen dilution. Copper et al [7] have study the effect of environment on a single-cycle impulse of pulse detonation engine. The detonation tube is being hanged in a ballistic pendulum arrangement and then the air-pressured is decreased to below 100Kpa. The initial pressure of stoichiometric ethylene- oxygen mixture inside the tube varied between 100Kpa to 30Kpa. Their target is to predict the increase in impulse and blow down times as the pressure decrease below than 1 atm. This present article is concern on the detonation characteristic of natural gas for single detonation III. EXPERIMENTAL FACILITY HiREF experimental facilities for single pulse experiment include a detonation tube which is 1500 mm in length and 100 mm for it inner diameter with an obstacle set to be 44% of blockage ratio (see Figure 1). The configuration of the tube is closed at one end and open at another which is being damped into the damping tank. The ignition point is at the thrust wall using automotive spark plug. The ignition system is by using fix voltage with variable capacitance method to produce Single Pulse Detonation Study of Natural Gas Ahmad Faiz M.Z., Mazlan A.Wahid, Khalid M. Saqr and Haffis U. P Latest Trends on Theoretical and Applied Mechanics, Fluid Mechanics and Heat & Mass Transfer ISSN: 1792-4359 78 ISBN: 978-960-474-211-0