SCI-PUBLICATIONS American Journal of Applied Sciences 5 (3): 197-202, 2008 ISSN 1546-9239 © 2008 Science Publications Fuel Injection Pressure Effect on Performance of Direct Injection Diesel Engines Based on Experiment 1Rosli Abu Bakar, 1Semin and 1Abdul Rahim Ismail 1 Author Manuscrip Automotive Focus Group, Faculty of Mechanical Engineering, University Malaysia Pahang, Locked Bag 12, 25000 Kuantan, Pahang, Malaysia Abstract: Fuel injection pressures in diesel engine plays an important role for engine performance obtaining treatment of combustion. The present diesel engines such as fuel direct injection, the pressures can be increased about 100 – 200 Mpa bar in fuel pump injection system. The experimental investigated effects of fuel injection pressure on engine performance. Experiments have been performed on a diesel engine with four-cylinder, two-stroke, direct injection. Engine performance values such as indicated pressure, indicated horse power, shaft horse power, brake horse power, break t mean effective pressure and fuel consumption have been investigated both of variation engine speeds - fixed load and fixed engine speed – variation loads by changing the fuel injection pressure from 180 to 220 bar. According to the results, the best performance of the pressure injection has been obtained at 220 bar, specific fuel consumption has been obtained at 200 bar for fixed load – variation speeds and at 180 bar for variation loads – fixed speed. The results of the experiment have given as graphics in this paper. Keywords: Diesel engines, performance, fuel injection pressure INTRODUCTION pressure is too higher, ignition delay period becomes shorter. Possibilities of homogeneous mixing decrease The diesel engine is a type of internal combustion and combustion efficiency falls down [2, 9]. engine; more specifically, it is a compression ignition The fuel injection system in a direct injection engine, in which the fuel ignited solely by the high diesel engine is to achieve a high degree of atomization temperature created by compression of the air-fuel in order to enable sufficient evaporation in a very short mixture[1, 14, 15]. The engine operates using the diesel time and to achieve sufficient spray penetration in order cycle. The diesel engine is more efficient than the petrol to utilize the full air charge. The fuel injection system engine, since the spark-ignition engine consumes more must be able to meter the desired amount of fuel, fuel than the compression-ignition engine[1, 10, 14]. The depending on engine speed and load, and to inject that used of diesel engines have extended in the last years to fuel at the correct time and with the desired rate. vehicles area due to their high efficiency also by Further on, depending on the particular combustion economic fuel cost [2, 3]. In present diesel engines, fuel chamber, the appropriate spray shape and structure injection systems have designed to obtain higher must be produced. Usually, a supply pump draws the injection pressure. So, it is aimed to decrease the fuel from the fuel tank and carries its through a filter to exhaust emissions by increasing efficiency of diesel the high-pressure injection pump, see Fig. 1. engines. When fuel injection pressure is low, fuel Dependent on the area of application and engine particle diameters will enlarge and ignition delay period size, pressures between 100 and 200 MPa generated. during the combustion will increase[2 - 9]. This situation The high pressures injection pump carries the fuel leads to increase pressure. Engine performance will be through high-pressure pipes to the injection nozzles in decrease since combustion process goes to a bad the cylinder head [12]. Excess fuel transported back into condition. When injection pressure increased of fuel the fuel tank. The functionality of the so-called unit particle diameters will become small. Since formation pump system is practically identical to that of the unit of mixing of fuel to air becomes better during ignition injector system and offers the same advantages and period, engine performance will be increase. If injection disadvantages. However, the pump and nozzle not Corresponding Author: Semin, Automotive Focus Group, Faculty of Mechanical Engineering, University Malaysia Pahang, Locked Bag 12, MEC City Gambang, 25000 Kuantan, Pahang, Malaysia, Tel: +609- 5492217, Fax: +609-5492244 197 Am. J. Applied Sci., 5 (3): 197-202, 2008 SCI-PUBLICATION combined into one unit. The camshaft driven a high- in Fig. 2, there are different thermocouples and pressure pump and thus directly coupled with the electrical units on the dynamometer and the engine. engine speed. The injection nozzle is located inside a Engine was tested in range of 600 - 1600 rpm with the so-called nozzle holder in the cylinder head and interval of 200 rpm and the fuel injection pressure connected via a high-pressure pipe with the pump. An setting from 180 – 220 bar with the interval of 10 bar. advantage of this system is that the pump and nozzle In the second experiment the diesel engine loads were not installed at the same place. This reduces the size of tested in 55% - 80% in interval of 5%, engine speed is Author Manuscrip the components that have integrated into the cylinder fixed on 1600 rpm and the fuel injection pressure head and simplifies the assembly of the injection setting from 180 – 220 bar with the interval of 10 bar. system[12]. Table 1: Specification of the engine Engine Parameters Value Bore (mm) 108.0 Stroke (mm) 127.0 Number of cylinder 4 t Max. cont. net power (HP) 112 Fuel nozzle injection pressure (bar) 200 Max. engine speed (rpm) 1800 Fig.2: Schematics of engine test bed Fig. 1: Unit pump system [12] In this research, no maximum speed and no maximum Effects of injection pressure on engine load reached. In the experiments, shaft horse power, performance have investigated on a unit pump system brake horse power, indicated pressure and fuel direct injection diesel engine. The diesel engine consumption were recorded by computer. In addition, performance and fuel consumption have been measured indicated horse power, break mean effective pressure both of variation engine speeds - fixed load and fixed and specific fuel consumption calculated from the engine speed – variation loads by changing the fuel experiments data. injection pressure. In the investigation is the effect of injection pressure in fixed load – variation engine RESULTS AND DISCUSSION speeds and fixed engine speed – variation engine loads in the fuel injection pressures are setting from 180 - 220 The experiment result on fixed load of 67 kW, in bar. interval engine speeds 600 until 1600 rpm and the fuel injection pressure setting from 180 – 220 bar. The MATERIALS AND METHODS variations for engine performance have given in Fig. 3 – Fig. 8. Then, the experiment result on fixed engine The specification of the selected diesel engine speed on 1600 rpm, in interval engine loads were tested shows in Table 1. An electrical dynamometer in 55% - 80% in interval of 5% and the fuel injection assembled on four-cylinder and two-stroke direct pressure setting from 180 – 220 bar. The variations for injection diesel engine used in the research. As shows engine performance have given in Fig.9 – Fig.14. 198 SCI-PUBLICATION Am. J. Applied Sci., 5 (3): 197-202, 2008 75 180 bar 50 70 190 bar Current 65 40 210 bar ) ) 60 220 bar W k m 30 ( t a 55 P ( H Author Manuscrip P I 50 B 20 45 10 40 35 0 400 600 800 1000 1200 1400 1600 1800 400 600 800 1000 1200 1400 1600 1800 Engine speed (rpm) Engine speed (rpm) Fig. 3: Injection pressures effect for IP Fig. 6: Injection pressures effect for BHP t 70 50 45 60 40 ) ) 50 m W t k 35 a ( ( P 40 P E H 30 I M 30 B 25 20 20 10 15 400 600 800 1000 1200 1400 1600 1800 400 600 800 1000 1200 1400 1600 1800 Engine speed (rpm) Engine speed (rpm) Fig. 4: Injection pressures effect for IHP Fig. 7: Injection pressures effect for BMEP 40 0.36 35 0.35 30 0.34 ) h 0.33 . ) 25 W W k 0.32 k / ( 20 g k P ( 0.31 H C S 15 F 0.3 S 10 0.29 5 0.28 0 0.27 400 600 800 1000 1200 1400 1600 1800 400 600 800 1000 1200 1400 1600 1800 Engine speed (rpm) Engine speed (rpm) Fig. 5: Injection pressures effect for SHP Fig. 8: Injection pressures effect for SFC 199 Am. J. Applied Sci., 5 (3): 197-202, 2008 SCI-PUBLICATION 73 65 71 60 69 55 ) ) W W k ( k ( 67 50 P P H I B Author Manuscrip 65 45 63 40 61 35 42 46 50 54 58 62 66 70 42 46 50 54 58 62 66 70 Engine loads (kW) Engine loads (kW) Fig.9: Injection pressures effect for IP Fig.12: Injection pressures effect for BHP t 71 50 48 69 46 ) 44 67 ) m t 42 W a ( k ( 40 65 P P E 38 H M I 63 B 36 34 61 32 59 30 42 46 50 54 58 62 66 70 42 46 50 54 58 62 66 70 Engine loads (kW) Engine loads (kW) Fig.10: Injection pressures effect for IHP Fig.13: Injection pressures effect for BMEP 43 0.29 41 39 0.27 ) h 37 . ) W 0.25 W k 35 / k ( g k P 0.23 33 ( H C S 31 F 0.21 29 S 27 0.19 25 0.17 42 46 50 54 58 62 66 70 42 46 50 54 58 62 66 70 Engine loads (kW) Engine loads (kW) Fig.11: Injection pressures effect for SHP Fig.14: Injection pressures effect for SFC 200 Am.