STUDY ON VIBRATION CONTROL METHODS OF DIESEL ENGINE FUEL INJECTION SYSTEM

Transcription

1 The st International Congress on Sound and Vibration -7 July,, Beijing/China STUDY ON VIBRATION CONTROL METHODS OF DIESEL ENGINE FUEL INJECTION SYSTEM Cao Yipeng, Zheng Dayuan, Ge Huijun, Ma Xiuzhen. College of Power and Energy Engineering,Harbin Engineering University, Harbin, China 5. 75th Research Institute of China Shipbuilding Industry Corp., Luoyang, China 79 Fuel injection system noise is an important part of diesel engine mechanical noise. According to each component of fuel injection system working process, each exciting force can be sorted to fluid or mechanical exciting forces and the characteristic of each force is studied. In this paper, BG diesel engine is used as calculating model. The effects of structure parameters on exciting forces are analyzed. Furthermore, the vibration responses of fuel injection system excited by fluid and mechanical forces are calculated. In addition, the function cam and the constant pressure valve are adopted to control the vibration amplitude of structure. The comparison of vibration intensity shows that the control method can decrease the exciting force and vibration of fuel injection system effectively.. Introduction The fuel injection system is one of the most important parts of diesel. The power, economy, emissions performance of diesel are all influenced by diesel fuel injection system property. Therefore, the fuel injection system working process, simulation method, the contribution and the separation method [], factors [] are received more interests. With the requirement of diesel power higher, the high pressure fuel pump was designed, which caused high vibration of fuel pump at the same time. The fuel injection system noise control methods were studied by experimental method in the beginning. With the development of simulation method and hardware, the effects of installation style and install location selection on bump structure vibration amplitude are studied []. In addition, the structural optimization design, damp material selection and other methods [, 5] are used to structure vibration control. System excitation Mechanical Excitation Fluid Excitation Contact force of cam and roller Impact of needle and seat The oil pressure Figure.The fuel injection system excitation composition. ICSV, Beijing, China, -7 July

2 st International Congress on Sound and Vibration (ICSV), Beijing, China, -7 July In this paper, the numerical method is adopted to calculate the vibration and noise of fuel injection system and the engine [, 7]. According to the structural relationship of each component, the all exciting forces of fuel injection system are divided into mechanical excitation and fluid excitation, shown in Fig.. The fuel pressure within the pump is treated as the fluid excitation source. The contact force between cam and roller, bearing force are defined as mechanical excitation. The dynamic model of the pump structure is built and the mechanical excitation and fluid excitation forces are calculated. The engine vibration and noise responses are calculated by finite element method in time domain. The functional cam and constant pressure delivery valve are used to structural vibration and noise control.. Analysis of fuel injection system exciting force. Model description The BG diesel fuel injection system is selected as analysis model built by AVL software in this paper, which is shown in Fig.. Nozzle Holder Leak Pressure Nozzle Leakage Needle 9 8 Nozzle Chamber Sac Orifice Injector Nozzle 7 Nozzle Holder Bore Cylinder Pressure P Injection Line In-Line Pump Injector 5 Valve Chamber 5 Delivery Valve In-line Pump Pump Chamber Spill Port Plunger Feed Pressure P Cam Profile Figure.The BG diesel fuel injection system AVL model. The pump structure is made of aluminum alloy, which cam lift profile style is the tangents. The base circle radius of cam is mm. The radius of roller is 8.5mm. The mass and diameter of plunger is.g and 9.5mm respectively. The plunger cave initial cavity is 85.59mm. The length of high pressure tubing is 5mm and the inner radius is mm. The mass of needle is 8.95g and the maximum lift range is.mm.. Results and discussion.. Original model On the base of fuel injection system HYDSIM model, the oil pressure in pump, high pressure tubing, nozzle and the mechanical forces of cam, roller are calculated in the same time. The exciting forces in time domain and frequency domain are shown in Figure, Figure. ICSV, Beijing, China, -7 July

3 st International Congress on Sound and Vibration (ICSV), Beijing, China, -7 July 7 x 7 pump x.5 pump fuel pressure (pa) 5 amplitude angle ( ) (a)time domain (b)frequency domain Figure.The pressure in fuel pump chamber 8 x 7 7 line.5 x line fuel pressure (pa) 5 amplitude angle ( ) (a)time domain (b)frequency domain Figure.The pressure in high pressure tubing The time domain curve in Figure shows that the oil pressure in fuel pump chamber reaches the peak value at fuel injector moment. Other moment, the oil pressure is very small. The spectrum curve shows that the energy of oil pressure in fuel pump chamber is focused below 7Hz. The trend of pressure in high pressure tubing is different. After fuel injector moment, the oil pressure oscillates during the whole period, which will excite the pump structure. The pressure acts on structure below Hz will be higher. On the base of fuel injection system design rule, the function cam and constant pressure delivery valve are adopted to change the original structure in this chapter. The effects of new structure on exciting force are analyzed in the following... Function cam The original tangent cam is modified to the function cam and the lift, velocity and acceleration of two types of cam are shown in figure 5. The mechanical excitation and fluid excitation are calculated and the results are shown in figure, in which the red curve represents the result of original cam and the green curve is that of modified cam. 8 8 lift(mm) lift(mm) x 5 x.5 velocity(mm/s) acceleration(mm/s) velocity(mm/s) 5 5 acceleration(mm/s) (a)tangent cam (b)functional cam Figure 5.The lift, velocity and acceleration of two types of cam ICSV, Beijing, China, -7 July

4 st International Congress on Sound and Vibration (ICSV), Beijing, China, -7 July Hertz stress [N/mm^] Original Model [N/mm^] Modified Model [N/mm^] ref. angle[deg] (a)mechanical excitation Injection Line [bar] Original Model [bar] Modified Model [bar] ref. angle[deg] (b)fluid excitation Figure.The comparison of mechanical excitation and fluid excitation between two cams Figure shows that the function cam can reduce the mechanical and fluid excitation. On the basis of injection pressure designed, the cam contact stress decreased significantly. In addition, the fluid excitation in the high pressure tubing and nozzle is reduced a little. The movement of needle is smoother than the original one. The vibration of engine might reduce... Constant pressure delivery valve Another method is use the constant pressure delivery valve to replace the original constant volume valve. The AVL model is shown in figure 7. The CPV which is consisted with opposite direction oil delivery valve and ball non-return valve is used in this chapter. The mass of ball valve is.8g and diameter is mm. The ball valve maximum lift is mm and the opening pressure is 5Mpa. The ball valve spring stiffness, damping is N/mm and.ns/mm respectively. The results are shown in figure 8. Injection Line Constant Pressure Valve Valve Chamber Check Valve 5 Delivery Valve Pump Chamber Figure 7.The AVL model of constant pressure delivery valve. Hertz stress [N/mm^] Constant Volume [N/mm^] Constant Pressure [N/mm^] ref. angle[deg] (a)mechanical excitation Injection Line [bar] Constant Volume [bar] Constant Pressure [bar] ref. angle[deg] (b)fluid excitation Figure 8.The comparison of mechanical excitation and fluid excitation between two valves Figure 8 (a) shows that two curves are nearly same which means the adoption of CPV can t decrease the mechanical excitation effectively. However, the fluid excitation in high pressure tubing and nozzle is decreased greatly which can be seen in figure 8 (b). It can be predicted that the noise and vibration of engine will decrease. ICSV, Beijing, China, -7 July

5 st International Congress on Sound and Vibration (ICSV), Beijing, China, -7 July. Analysis of structure acoustic characteristic. Original model The fuel injection system is installed on the engine and the engine vibration is calculated by finite element method in time domain. The nodes velocities on the engine surface are read out to calculate the acoustic characteristic. The field point location is shown in figure 9. Figure 9.The field point location of engine. The radiated noise from diesel engines at m is calculated by boundary element method. The pressure distribution at 9Hz Hz Hz and 5Hz are shown in figure. Figure.The pressure distribution at 9Hz Hz Hz and 5Hz. The figure shows that the highest sound level, 77dB can be seen above the engine because it is the nearest place to the high pressure tubing and the nozzle. The second highest one is in front of the engine; the place that oil pump is installed. Because of the boundary condition, sound pressure at the other location of engine is smaller. Sound pressure level is calculated as, pe SPL = log ( db) () p Where the p e is RMS sound pressure, p ref = -5 Pa; the reference sound pressure. Total SPL can use the law of superposition of energy, n ref L / L ( OA) = lg( ) () i= ICSV, Beijing, China, -7 July 5

6 st International Congress on Sound and Vibration (ICSV), Beijing, China, -7 July In order to calculate the sound pressure level, the 9 reference points are selected, which location can be seen in figure 9. The total sound pressure calculated by boundary element method and the result is shown in table. Table. The total sound pressure level. Point Number result SPL(dB) Acoustic pressure control.. Function cam According to the result got in chapter.., the original tangent cam is changed to the function cam to achieve the low mechanical excitation. The optimized sound pressure at reference point and is shown in figure original system modified system 75 7 original system modified system sound pressure level (db) sound pressure level (db) (a)referent point (b)referent point Figure.The sound pressure level comparison The figure shows that the sound pressure is decreased in almost all frequency bands. That is to say the function cam can reduce the engine noise caused by fuel injection system. The trend of sound pressure distribution around the engine is not nearly same with figure. The sound pressure of engine with adoption of improved cam profile is shown in table. The sound level reduces.85db. Table. The total sound pressure level of system with function cam. Point Number result SPL(dB) Constant pressure delivery valve The original valve is changed to constant pressure delivery valve. The effect on engine radiated noise is shown in figure. sound pressure level (db) original system modified system sound pressure level (db) original system modified system (a)referent point (b)referent point Figure.The sound pressure level comparison ICSV, Beijing, China, -7 July

7 st International Congress on Sound and Vibration (ICSV), Beijing, China, -7 July In figure, the sound pressure is decreased greatly in nearly all frequency bands except some low frequencies. Because the adoption of constant pressure delivery valve can control the fluid excitation of fuel injection system, the sound level above the engine is reduced effectively. The sound pressure of engine with constant pressure delivery valve is shown in table. The sound level reduces 5.dB. Table. The total sound pressure level of system with CPV. Point Number result SPL(dB) In summary, the constant pressure delivery valve can reduce the fluid excitation in fuel injection system. The use of function cam can reduce the mechanical excitation. The results show that the former method can decrease the sound level more effectively. Two method can be combined together to achieve the better control effect in design process.. Conclusion The fuel injection system excitation source model and finite element model of BG diesel is built in this paper. The fluid and mechanical excitation characteristic of system is analyzed. The vibration and radiated noise of engine is calculated. The main excitations of fuel system can be divided into two parts, which are fluid and mechanical excitation. The mechanical excitation is mainly concentrated below 5Hz. The fluid excitation spectrum is wide. The two kinds of excitation reach the peak value in injection time. The function cam and the constant pressure delivery valve are used to reduce the force of system. The results show that two methods can reduce mechanical and fluid excitation. The engine vibration response caused by fuel injection system is calculated by finite element method. The radiated sound pressure distribution of engine is calculated by boundary element method. The highest sound level can be seen on the surface of engine which it is the nearest place to the high pressure tubing and the nozzle. The function cam and the constant pressure delivery valve are used to reduce the vibration and radiated noise of engine. The results show that the sound pressure level can be decreased about.9-5.7db. Acknowledgement The research is supported by the Fundamental Research Funds for the Central Universities (HEUCF). This paper is funded by the International Exchange Program of Harbin Engineering University for Innovation-oriented Talents Cultivation REFERENCES L. Pruvost, Q. Lecle`re. Diesel Engine Combustion and Mechanical Noise Separation Using an Improved Spectrofilter, Mechanical Systems and Signal Processing, (7), 7 87, (). Avinash Kumar Agarwal, Dhananjay Kumar Srivastava. Effect of Fuel Injection Timing and Pressure on Combustion, Emissions and Performance Characteristics of a Single Cylinder Diesel Engine, Fuel,, 7-8, (). Ryouta Minamino. Fuel Injection Concept for the Future Clean Diesel Engines, CIMAC Congress, Shanghai, China, May, (). ICSV, Beijing, China, -7 July 7

8 st International Congress on Sound and Vibration (ICSV), Beijing, China, -7 July 5 7 A. Albarbar, F. Gu, A.D. Ball, A. Starr. Acoustic Monitoring of Engine Fuel Injection Based on Adaptive Filtering Techniques. Applied Acoustics, 7(), -, (). Shigehiro Usuda, Masaya Otsuka, Masahisa Nagata. Noise and Vibration Reduction of Newly Developed. l Direct Injection Diesel Engine, JSAE Review, (), 85-89, (). H. Zheng, G.R. Liu, J.S. Tao, K.Y. Lam. FEM/BEM Analysis of Diesel Piston Slap Induced Ship Hull Vibration and Underwater Noise, Applied Acoustics, (), -58, (). Rune Nordrik. Vibration Characteristics of a V Medium Speed Gas Engine, CIMAC Congress,Bergen, Norway, 7 June, (). ICSV, Beijing, China, -7 July 8