Design and Simulation of Hybrid Double Solenoid Valve Actuator

Transcription

1 2016 International Conference on Mechanics Design, Manufacturing and Automation (MDM 2016) ISBN: Design and Simulation of Hybrid Double Solenoid Valve Actuator Jawad ASLAM 1,2,a,*, Xing-Hu LI 1,b,*, Yan WANG 1,c, Hai SUN 1,d 1 School of Transportation Science and Engineering, Beihang University, 37 Xueyuan Lu, Haidain Qu, Beijing, , China 2 School of Mechanical and Manufacturing Engineering, National University of Science and Technology, NUST, H-12, Islamabad, 44000, Pakistan a jawad_mtsa@yahoo.com, b lxh@buaa.edu.cn, c wybuaa@buaa.edu.cn, d @163.com *Corresponding author Keywords: Permanent magnet, Magnetomotive force, Camless engine, Finite element modeling. Abstract. This paper proposes a novel hybrid valve actuator (HVA) with permanent magnet (PM) and electromagnet (EM) magnetomotive force (MMF) for variable valve timing camless engine. Traditional double solenoid valve actuator (DSVA) has inherent problem of high power consumption, as armature is at equilibrium position away from electromagnet therefore to move armature to open/close position and for keeping armature latched to EM. Hybrid PM/EM valve actuator is proposed in this study. The finite element analysis is performed with Ansys Maxwell on static characteristics of traditional DSVA and HVA on bases of actuator holding force. The equivalent model of static analysis is introduced into Ansys Simplorer for dynamic analysis. The simulation results depict reduce power consumption and transition time of proposed HDSVA over DSVA. Introduction The traditional engine utilizes camshaft for valve timing (intake and exhaust). The camshaft lifts poppet valve to fixed displacement and time for limited operating range. The optimization of camshaft does not guarantee optimum behavior on wide range of engine operations [1]. This results in compromise between engine torque, low fuel efficiency and exhaust emissions. Therefore OEMs developed and employed variable valve actuation system. The variable valve timing (VVT) changes camshaft phase of intake valve with respect to exhaust valve while variable valve lift (VVL) provides different valve displacements. The VVT controls valve independent of crank angle thus results in reduction in CO2 emission by 20%, an improvement of 15% in fuel economy, an improved torque output of 10% and HC (Hydrocarbon) emission at cold start is reduced by 50% [1-9]. Variable valve timing actuators pioneered over years by OEMs include mechanical, hydraulic, motorized and electromechanical/electromagnetic actuators. The main streaming actuators commercialized are Toyota VVT-i, Honda VTEC, Hitachi VEL, Nissan Neo VVL, Mitsubishi MIVEC and Mazda S-VT. 2 The present VVT systems lack continuous timing change, added the complexity to the engine and foremost engine torque output improvement is less [3]. In recent year fully flexible double solenoid valve actuator (DSVA) is prototyped but

2 not yet commercialized due to inherent problem of acoustic noise, high power consumption, complexity, control and mechanical wear. The DSVA is shown in Fig.1. Figure 1. Double solenoid valve actuator. The problem of high power consumption is partly due to high coil current input to overcome spring force and keep armature latched. The other contributing factor is power requirement at start-up to fully open/close valve when armature is at equilibrium position, between two solenoids [4]. Power consumption problem can be solved by hybrid permanent magnet (PM) and electromagnet (EM) valve actuator. The hybrid valve actuator (HVA) reduces power consumption by using the PM reluctance to hold valve open/close [5]. Therefore at start-up the armature is latched to solenoid and is not at equilibrium position. The HVA with rectangular core, PM, and non-asymmetric armature is studied [3-8]. Rectangular core HVA requires precise motion of armature stem to prevent failure of operation. The mechanical wear prevails due to absence of cylindrical motion and presence of torsional vibration. The PM is placed in series with EM coil flux causing demagnetization of PM by excessive inverse current. Mechanical wear is limited by employing symmetric armature [10]. In axis symmetric reluctance HVA the PM is placed in parallel with EM coil flux incorporating parasitic air gaps to avoid demagnetization of PM [11-13]. In this study a novel axis symmetric, low-inductance, cylindrical, hybrid MMF with PM/ EM actuator is proposed. Comparative study of static and dynamic characteristics of DSVA and HVA are studied in Ansys Maxwell and Simplorer. Proposed Hybrid Valve Actuator HVA is composed of two pre-stressed springs keeping armature at equilibrium position, between two solenoids. The spring constant defines transient time of spring-mass system of HVA. The iron yoke is divided into three parts yoke, yoke cover plate and yoke base plate separated by air gaps. The secondary air gaps provide detour to EM coil flux without circulating through PM and causing demagnetization.

3 The diametric polarized cylindrical PM provides reluctance to latch armature at seating position in absence of coil current. The coil inductance is reduced by introducing two circular parallel coils thus reducing transient time by assisting swift rise of current [14]. The coils have similar number of turns and wire diameter therefore low coil resistance for proposed coil configuration. The schematic of HVA is shown in Fig. 2. Figure 2. Structure of proposed MHVA. The operation control of HVA is depicted in Fig. 3. Yellow and red lines define flux generated by PM and EM respectively. At beginning of cycle armature is latched to lower solenoid seat thus keeping valve open as shown in Fig. 3a. Reluctance from PM generates holding force (FH) larger then spring force (FS) to open valve. The coils are recharged with inverse current to generate release flux that weaken PM flux thus assisting spring force (FS) to release armature from lower solenoid seat as seen in Fig. 3b and run towards valve closing position. Coils are discharged as armature is released and crosses equilibrium position as depicted in Figure 3c. Catching of armature at upper solenoid is assisted by charging coils at upper solenoid thus strengthening reluctance to overcome FS as shown in Fig. 3d. Once armature is latched at upper solenoid seat coils are discharged and PM reluctance hold valve closed as seen in Fig. 3e. The process is repeated to open valve as shown in Fig. 3f to 3a. Simulation and Analysis The proposed design has vertical symmetry therefore solenoids (upper/lower) can be modeled separately to reduce complexity and computational time. In Maxwell materials for core, coil and PM are selected as Iron, copper and Nd35Fe respectively. Triangular mesh division is utilized with adaptive subdivision and convergence accuracy of 1%. The excitation in terms of ampere turns (Aturns) is applied to coil area; the simulations get FH, inductance and other physical parameters.

4 Static Analysis The analysis performed for FH at different current and armature position. The FH for DSVA and HVA with varying armature position and coil current can be seen Fig. 4a and 4b. The HVA show increase in FH by 43.04%, 50.94% and 65.38% at seating position at 500 Aturns, 400Aturns and 300Aturns respectively. Similar trend is observed at equilibrium position with growth of 46.90%, 52.12% and 61.50% at 500Aturns, 400Aturns and 300Aturns respectively. FH strengthening is due reluctance amplification of PM by coil current. Power dissipation is increased for DSVA to achieve similar magnitude of force as HVA. The presence of PM provides reluctance to hold armature at former seat in the absence of coil current. Figure 3. Working process of MHVA.

5 Figure 4. (a) Sensitivity of HVA FH at different current (b) Sensitivity of DSVA FH at different current. Thus power needed in DSVA to hold armature diminishes and also at startup as armature is kept at seat not at equilibrium position. Therefore need to attract armature to seat position is not required at engine startup. HVA requires inverse current to de-latch armature from former seat. The inverse coil current nullifies PM reluctance thus armature is detached from former seat under influence of spring force. The inverse current effect on PM FH is shown in Fig. 5a. The inverse current decreases PM FH force on armature at 1mm by 63.72%. The inverse current requirement is directly dependent on size of PM. Therefore optimum size should be selected for optimum power dissipation. The similar decrease in trend is observed for armature at 2mm and 3mm by 63.25% and 68.69%. FH at 0mm depicts PM FH. The decrease in FH further extends due increase in distance from PM magnet. The FH for DSVA is not affected by inverse current due to absence of PM. FH is amplified similarly in both direction of current as depicted by Fig. 5b. Figure 5. (a) Sensitivity of HVA FH for different coil current orientation (b) Sensitivity of HVA FH for different coil current orientation. Dynamic Analysis Dynamic analysis is performed in Simplorer platform which assists in interdisciplinary mechanical and electrical system design. Simplorer and Maxwell can work collaboratively for electromagnetic valve multi physics field coupling simulation. Equivalent circuit of HVA is

6 imported from Maxwell with current as input and force as the output of HVA. Simplorer model is shown in Fig. 6. The HVA input voltage, armature mass and spring stiffness is selected as 24V, 0.3Kg and 18kN/m respectively. E1 R1 R2 L1 I1_N1 I2_N1 I1_N2 I2_N2 Force1_N1 Force1_N2 F m Ideal 0 L2 0 k Figure 6. Simplorer simplified mechanical and electrical circuit. The transient period of coil current for DSVA and HVA is shown in Fig.7a. Current rise is quicker for HVA there are two parallel coils. The coil resistance decreases for this configuration as resistance of two coils are in parallel. The peak current of HVA is 6 A and transient period last for 7.5ms. For DSVA the peak current is 4A but transient period ends after 14.5ms. The slower rise in current is due to single coil. The rise in current last after induce voltage becomes equal to applied voltage after which current decreases. The rise after 7.5ms and 14.5ms occurs due to stalling of armature at former seat. The position of armature with time is depicted in Fig. 7b. HVA shows improved transient response as armature reach equilibrium position from former seat in 7.6ms whereas DSVA reach equilibrium position in 14.4ms. The power dissipation HVA for 24V input and transient time of 7.6ms is reduced by 22.2% in comparison to DSVA. Figure 7. (a) Current transient response of HVA and DSVA (b) Position versus time of HVA and DSVA. Conclusion In this study, the proposed HVA and DSVA model are analyzed for varying armature position from equilibrium to open/close position. HVA for same coil current and armature

7 position depicted increase in FH in comparison to DSVA. The cylindrical configuration of core provides larger volume to FH ratio. The transition time HVA is reduced approximately half of DSVA. Power consumption of proposed HVA is attenuated by 22.2%. At lower engine speed DSVA depicts larger power requirement as armature latching period increases but for HVA does not consume power for holding armature at former seat. Acknowledgement Project ( ) supported by the National Natural Science Foundation of China. References [1] Seinosuke Hara, Seiji Suga, Satoru Wanatabe and Makoto Nakamura,Variable valve actuation system for environmental friendly engines, Hitachi Review. 58,7(2009), [2] Sellnau, M. and Rask, E., Two-Step variable valve actuation for fuel economy, emissions, and performance, SAE Technical Paper (2003) doi: / [3] Jinho Kim and Dennis K. Lieu, Designs for a new, quick-response, latching electromagnetic valve, IEEE International Conference on Electric Machines and Drives, San Antonio, TX, (2005) [4] Jinho Kim and Dennis K. Lieu, A new electromagentic valve actuator with less energy consumption for variable valve timing, Journal of Mechanical Science and Engineering. 21, 4, (2007), [5] Jen Rens, Richard E. Clark and Geraint W. Jewel, Static performance of a polarized permanent-magnet reluctance actuator for internal combustion engine valve actuation, IEEE Transaction on Magnetics. 42, 8 (2006), [6] Richard E. Clark, Geraint W. Jewell, Stephen J. Forrest, Jan Rens and Christophe Maerky, Design features for enhancing the performance of electromagnetic valve actuation systems, IEEE Transaction on Magnetics. 41, 3 (2005), [7] Ryan R. Chladny, Charles Robert Koch and Alan F. Lynch, Modeling automotive gas-exchange solenoid valve actuators, IEEE Transaction on Magnetics. 41, 3 (2005), [8] Jinho Kim and Junghwan Chang, A new electromagnetic linear actuator for quick latching, IEEE Transaction on Magnetics. 43, 4 (2007), [9] Jin-Ho Kim, Joung-Hwan Chang, Se-Myung Park, Ki-Il Hwang and Jae-Yong Lee, A novel electromagnetic latching device for variable valve timing in automotive engine, 14th Biennial IEEE Conference on Electromagnetics Field Computation. Chicago, IL (2010), 1. [10] Jan Albert, Remus Banucu, Wolfgang Hafla and Wolfgang M. Rucker, Simulation based development of a valve actuator for alternative drives using BEM-FEM code, IEEE Transaction on Magnetics. 45, 3 (2009),

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