Research Journal of Applied Sciences 2 (11): 1135-1142, 2007 ISSN: 1815-932X © Medwell Journals, 2007 Corresponding Author: Semin, Automotive Excellent Center, Faculty of Mechanical Engineering, University Malaysia Pahang, Locked Bag 12, 25000 Kuantan, Pahang, Malaysia 1135 Air Flow Analysis of Four Stroke Direct Injection Diesel Engines Based on Air Pressure Input and L/D Ratio Semin, Rosli Abu Bakar and Abdul Rahim Ismail Automotive Excellent Center, Faculty of Mechanical Engineering, University Malaysia Pahang, Locked Bag 12, 25000 Kuantan, Pahang, Malaysia Abstract: The air flow through engines is equally important to have accurate values for coefficients of discharge through the combinations of valves, ports and ducts of engines. In this air flow analysis is investigated of air flow is desirable for intake flow through the exhaust flow port using SuperFlow Flowbench. The air flow of the diesel engines can be quite measured under steady flow conditions for a range of pressures and valve Lift per Diameter (L/D). This syudy presents experimental results for air flow investigating in the intake and exhaust flow port of four stroke direct injection diesel engines. The airflow measurements and calculation are shown for various pressures, valve Lift per Diameters (L/D) ratio conditions at the intake port pipe to cylinder and cylinder to exhaust port pipe geometries. The result shown that, the increasing pressure input in port flow on fixed valve L/D can increase the air flow through engine cylinder. Key words: Coefficient of discharge, correction test flow, test pressure, valve lift, diesel engines INTRODUCTION This gives an exhaust port pressure that changes with The importance of the diesel engine performance through an intake valve whose are changes with time, the parameters are geometrical properties, the term of intake port pressure alters because the cylinder pressure efficiency and other related engine performance is affected by the piston motion causing volumetric parameters. A wide variety of inlet port geometries change within that space. patterns used to accomplish this over the diesel size range This study presents the experimental results for air (Heywood, 1998; Bakar et al., 2007; Kowalewicz, 1984; flow of four-stroke direct-injection diesel engines using Stone, 1997; Ganesan, 1999; Ismail et al., 2008; Blair, 1999). SuperFlow Flowbench. The SuperFlow Flowbench is The diesel engines port flow coefficient of discharge for designed to measure air-flow resistance of engine cylinder a particular flow discontinuity is defined as the ratio of heads, intake manifolds, velocity stacks and restrictor actual discharge to ideal discharge. In an engine plates (Superflow Technologies Group, 2004). In the environment, ideal discharge considers an ideal gas and SuperFlow Flowbench, for four-cycle engine testing, air is the process to be free from friction, surface tension, etc. drawn in through the cylinder head into the machine, Air flow coefficients discharge are widely used to monitor through the air pump and exits through the vents at each the flow efficiency through various engine components side of the flowbench. The amount of flow is displayed in and are quite useful in improving the performance of these cubic feet per minute (cfm), liters per second (lps) or cubic components (Fleck et al., 1996; Superflow Technologies meter per hour (cmh). The flow meter measures the Group, 2004; Blair et al., 1995, 1998; Danov, 1997; pressure difference across an adjustable flow orifice in the Ismail et al., 2008; Blair and Gorden, 1999). flowbench. By selecting different ranges, the flow meter The air flow process into, through and out of the can be used to obtain high accuracy over reads 5-100% of engines are unsteady (Ismail et al., 2008). Unsteady air any flow range selected in either intake or exhaust flow flow is defined as that in which the pressure, temperature direction. The full scale flow measurement range of and gas particle velocity in a duct are variable with time. SuperFlow SF-1020 can be varied from 25+1000 cfm or In the exhaust air flow of engine, the unsteady air flow 12 -470 lps. behavior is produced because the cylinder pressure falls In this experiment of air flow test in SuperFlow with the rapid opening of the exhaust valve or valves. Flowbench, flow is tested consists of blowing or sucking time. In the induction or intake flow into the cylinder