Changchun, China. 1 State Key Laboratory of Automotive Simulation and Control, Jilin University, 5988 Renmin Street

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1 Applied Mechanics and Materials Online: ISSN: , Vols , pp doi: / Trans Tech Publications, Switzerland The Design of an Electromagnetic Valve Actuator (EMVA) Suitable for Scavenging Two-stroke Engine Yinuo Hu 1, a, Jiayi Ma 2, b, Shuo Jia 3, c*, Bin Yang 4, d, Qingfang Hou 5, e 1 State Key Laboratory of Automotive Simulation and Control, Jilin University, 5988 Renmin Street Changchun, China a huyn1511@mails.jlu.edu.cn, b majiayi@jlu.edu.cn, c jiashuo1511@mails.jlu.edu.cn, d yangbin1511@mails.jlu.edu.cn, e houqf1511@mails.jlu.edu.cn Keywords: Electromagnetic Valve Actuator (EMVA), Scavenging Two-stroke Engine, Seating Velocity, Magnetic Flux, Current, Control Strategy. Abstract. This research is aimed at designing a suitable electromagnetic valve actuator (EMVA) which could efficiently improve energy saving performance of engine for scavenging two-stroke engine. Our Group simplified the GM s EMVA and made it suitable for the engine used in experiment. CFD and mathematical modeling software were used to help our designing. According to the result of CFD, the design meets the intake requirements of the engine. Introduction With the rapid change of energy situations and increasing aggravation of environmental pollution problems, the international community has become more stringent for economic efficiency of automobile engine fuel and limits on harmful emissions. The variable valve technology, especially the one with application of the electromagnetic valve actuator (EMVA), is able to significantly improve the energy saving performance of the engine, and has become one of the key directions in engine research. [1] The valve parameters of the EMVA have been changed flexibly and thence the performances of the engine under different conditions have been improved. Many domestic and foreign research institutes are committed to the development and research of EMVA. Currently, a large number of institutions in the world have accepted double-spring-based and double-electromagnet-based EMVA schemes. The EMVA has many advantages, including individually and flexibly controlling the inlet valve and the exhaust valve for any valve timing; simplified structure of the engine; lower energy consumption; enabling to turn off some of the cylinders, etc. But at the same time, the EMVA also has some obvious drawbacks. When the valve is seated, the noise is difficult to control; the electromagnetic response speed is not high enough; energy consumption is large and the size is too big. The aim of our study group is to research and develop an EMVA suitable for scavenging two- stroke engines. As the revolving speed of the scavenging two-stroke engine is low and the mechanical structure is relatively simple, it can effectively circumvent the shortcomings of traditional electromagnetic valve actuators: insufficient layout space and low electromagnetic response. In the course of the study, to effectively control the seating impact is the focus of the research. The Structure of the EMVA Currently, the electromagnetic valve actuator schemes of FEV and GM are much representative in the market. FEV's EMVA (shown in Fig.1) is characterized by separately placing the two springs above and below the upper and the lower static iron core; the static iron core is approximately rectangular; the armature is in rectangular shape. The EMVA is also equipped with a hydraulic lash adjuster. The open and close of the valve is achieved by the connecting and the cutting of the current in the upper and lower electromagnetic coils. The working principle and composition of GM's EMVA (shown in Fig.2) device are different from those of FEV's EMVA. In GM s EMVA, the permanent magnet is located in the middle of two electromagnets. When the valve is located at the two extreme positions (fully close and fully open), coil A and coil B are not energized; the magnetic All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-18/02/16,08:33:57)

2 1442 Mechatronics Engineering, Computing and Information Technology flux direction of the magnetic field generated by the electromagnet is opposite to that of the permanent magnet, weakening the magnetic field generated by the permanent and making the magnetic force smaller than the spring force. The armature moves downward with the spring force. When the armature has moved across the midpoint, the magnetic force is greater than the spring force, and the magnetic armature continues to move downward driven by the magnetic force until the valve is closed. Then, the current in coil A is cut off. Upper spring Upper electromagnet Armature Lower electromagnet Lower spring Valve Spring A Electromagnet coil A Magnet Electromagnet coil B Spring B Valve Fig.1 EMVA scheme of FEV Fig.2 EMVA scheme of GM In the design process, our group thinks that both above schemes have adopted double electromagnetic coils. This method increases the electrical control difficulty and is not conducive to reduce the size of the electromagnetic valve actuator. After comprehensive comparison of advantages and disadvantages of the two schemes, our group has taken the GM electromagnetic valve actuator as the base and simplified the overall structure (shown in Fig.3). Electromagnet Magnet Valve Fig.3 Design Scheme of EMVA In the work course of the electromagnetic valve actuator, the magnetic flux in space is changed by adjusting the current size to carry out control of the valve. During the opening of the valve, a current I 1 flows in the electromagnet and generates the magnetic flux, of which the direction is opposite to that of the permanent magnet; a repulsive force is generated between the electromagnet and the permanent magnet, and thus the valve is opened. For closing the valve, a current I 2, of which the direction is opposite to that of the I 1, flows through the electromagnet and a suction force is generated between the electromagnet and the permanent magnet to close the valve. In this scheme, only one electromagnet is used, and thus the control circuit is simplified; it can effectively reduce the difficulty of single-chip programming; the electromagnet is independent of the movement of the valve, eliminating the possibility that the electromagnet pulls off the wire in high-speed movement; the control mechanism is located away from the inlet valve, enabling to reduce the interference of temperature change on the magnetic field in the intake process. In order to minimize disturbance to the magnetic field during operation, the valve, inlet and other parts are all made of aluminum alloy and engineering plastics.

3 Applied Mechanics and Materials Vols Numerical Simulation of Inlet Flow Field In the process of design, the single-cylinder scavenging two-stroke engine that the research team has used for the test is an engine with a revolving speed of 1200r/min, a piston diameter of 105mm, a piston stroke of 158mm, and a displacement of 1.36L. At the start of the intake, the atmospheric pressure of the gas storage warehouse is 0.03MPa; at the end of the intake, the atmospheric pressure is 0.09MPa, with the valve diameter of 40mm and the valve stroke of 5mm. In accordance with the intake requirement of this two-stroke engine, the electromagnetic valve actuator needs to finish the intake within 25ms. Our group has used the ICEM CFD and Fluent in the Ansys13.0 for CFD simulation of inlet flow field. Using the k-omega SST turbulence model can conduct the complex intake turbulence simulation effectively [2, 3]. In the simulation, the gas storage warehouse is taken as the computational domain; two pressure inlets are set; the inlet pressure is the standard atmospheric pressure; the vacuum of the computational domain is set to 0.07MPa. The simulation results show that when the diameter of the intake pipe is 22mm, this intake system can complete intake within 10ms (shown in Fig.4 and Fig.5). This is in full compliance with the intake requirement of the engine. Fig.4 Mesh of the intake flow field Fig.5 Pressure distribution 10ms after the intake starts Current Computation of the Control Circuit The seating speed of the valve should be less than 0.1m/s to control the impact of seating the electromagnetic valve actuator and reduce the noise when the valve works. When the valve works, the control circuit changes the magnetic flux in space by changing the current size and the status of the current in the electromagnet, and thus the forces acting on the valve are changed to control the acceleration and speed of movement of the valve. To ensure the speed meet the requirement when the valve is seated, the valve should be moved in uniformly accelerated motion. The forces on the valve are computed according to Newton's second law, and the current size is computed with the electromagnetic empirical formula. F= 2 (NI) (F is the electromagnetic force on the valve; µ is the constant of electromagnetic induction; S is the cross-sectional area of the magnetic path; Kf is a constant, taken 1.5 in the design; σ is the magnetic gap; N is the turns of the electromagnetic coil; I is current size in the electromagnetic coil.) The current versus time curve (shown in Fig.6) is drawn using the mathematical modeling software, which will be used in the programming process of electronic control unit.

4 1444 Mechatronics Engineering, Computing and Information Technology I/ t/s Fig. 6 I-t curve Strategy on Electrical Control Electrical control system mainly consists of the MC9S12XS128MAA single-chip microcomputer (SCM) and the peripheral amplification circuit. The program is shown in Fig.7. The system controls the open and close of the EMVA according to the real time pressure of the gas storage warehouse measured by the pressure sensor. When the atmospheric pressure is less than 0.03MPa, the microcomputer will first determine whether the valve is open; if the valve is closed, the program of opening valve will be executed immediately. The SCM will output PWM signals according to the parameter values given at different time points and replenish current into the electromagnet through the opt coupler amplifier circuit to open the valve. The sensor will detect the seating impact of the valve limit while the valve is open. If the pressure is too large, it will change the corresponding parameters so that the impact force is reduced until the pressure reaches the safety value. When the atmospheric pressure is greater than 0.09MPa and the valve is open, the program of closing valve will be executed immediately. At the same time, the sensor will detect the impact of valve seating and conduct the feedback regulation. Summary Fig.7 Portion of electric control program In our study, by simplifying the inlet structure of the original electromagnetic valve actuator, applying the optimized CFD simulation inlet design and using mathematical modeling software to write electronic control procedures, we design an electromagnetic valve actuator applicable to the scavenging two-stroke engine. The design meets the intake requirements of the engine. In the next study, the engine bench test will be conducted. I n the test, the air pressure sensor and the pressure sensor will be applied to measure the intake efficiency of the valve and the seating impact force, which will be used to help improve the design of electromagnetic valve actuator and verify the accuracy of the CFD simulation.

5 Applied Mechanics and Materials Vols Acknowledgements This work was financially supported by Jilin University State Key Laboratory of Automotive Dynamic Simulation and Innovative Program of Automotive Engineering College of Jilin University. References [1] Lulu Li, Finite element analysis of electromagnetic valve actuator(in Chinese) [2] F. R. Menter, M. Kuntz and R. Langtry, Ten Years of Industrial Experience with the SST Turbulence Model, Turbulence, Heat and Mass Transfer 4. Begell House, Inc [3] F. R. Menter. Zonal Two Equation k-omega Turbulence Models for Aerodynamic Flows, AIAA 24th Fluid Dynamics Conference, July 6-9, 1993, Orlando, Florida, AIAA [4] Zhi en Liu, Yankun Jiang, Guohua Chen, Hongling Zhang, Hongtao Chen, Research on the method of CFD aided design of engine inlet(in Chinese), Chinese Internal Combustion Engine Engineering Vol. 27 No. 6 Dec [5] Goldste R J, Variables of electromagnetic valve actuator performance, Engine Technology International, 1997, (11): [6] Alessandro di Gaeta, Umberto Montanaro, Silvio Massimino, Carlos Ildefonso Hoyos Velasco, Experimental Investigation of a Double Magnet EMVA at Key-On Engine: A Mechanical Resonance Based Control Strategy, 2010 SAE International October 25,2010.

6 Mechatronics Engineering, Computing and Information Technology / The Design of an Electromagnetic Valve Actuator (EMVA) Suitable for Scavenging Two-Stroke Engine /