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Simulation research of the hydraulic drive for valves of internal combustion engine

Szydłowski T., Smoczyński M.

Journal of KONES

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2013

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Vol. 20, No. 2

385--391

EN

This paper describes simulation research of single-acting hydraulic drive for valves of internal combustion engines. The proposed drive was composed of commercial servovalve and typical hydraulic single-acting actuator. Research was performed for the prepared and verified model of this drive. In the paper mainly analysed was the impact of control signals on course of valve lift and its characteristic parameters like: delay of start of valve movement in opposition to the start of the control signal, the time of opening and closing of the valve, the valve lifting time, the course of valve lift, fill factor of the area under the valve lift curve and velocity of the valve subsidence. Special attention was given to the closing movement of the valve. Drive control was limited to step control signal. In the final phase of closing the valve, the control method had to slow down and stop the valve, but without a significant influence on the valve closing phase. During research the fill factor of the area under the valve lift curve was calculated and compared with values obtained for the classic drive with cam. A number of simulations allowed to determine the optimal control signal for the course with deceleration of the valve. Based on simulation studies it was found that comparable fill factors of the area under the valve lift curve for cam drive and analyzed electrohydraulic drive were obtained up to over 4000 rpm speed. Above this speed the factor was significantly smaller for hydraulic drive. For low engine speeds the values of factor were acceptable and amounted to about 0.7. Unfortunately for the valve opening times for engine speed 6000 rpm, tested drive did not provide the full opening of the valve and the fill factor of the area under the valve lift curve was unsatisfactory. In this research, the frequency characteristics of the servovalve published by their manufacturers were used. It demonstrated that because of the delay and response speed of the valve is necessary to use units generating a control signal ahead in relation to the desired moment of opening the valve.

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Experimental research of properties of hydraulic drive for valves of internal combustion engines

Szydłowski T., Smoczyński M.

Journal of KONES

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2013

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Vol. 20, No. 1

351--358

EN

This paper describes a research stand and results of experimental research of single-acting hydraulic drive for valves of internal combustion engines. The research stand of the hydraulic valve drive was consisted of: typical valve drive for high-speed internal combustion engine, commercial hydraulic actuator, commercial hydraulic accumulator and electrically controlled hydraulic distributor, which controlled the flow of oil supply to the hydraulic actuator. Rexroth commercial servovalve was used as hydraulic distributor for this valve drive. Components of hydraulic valve drive were mounted to specially designed research sleeve. On this sleeve complete drive, which consisted of a hydraulic cylinder and servovalve, was mounted. Drive control was performed in an open loop with a use of rectangular control signal. Displacement of the valve was measured by an optical displacement sensor. Tests were performed for constant lift of the valve, supply pressure set in the range of 6 to 10 MPa and at fixed temperature of the working medium and different initial deflections of valve spring. The behaviour of the drive was researched for bipolar and a rectangular control signals. Such range of measurements was to determine inter alia: the impact of the supply pressure and the control signals values on the drive work. Obtained results were used to verify the simulation model in a wide range of variation of the characteristic parameters of the electro-hydraulic actuator. The results of experimental measurements like valve movement and pressures in the drive were shown and analysed in this paper. With a reference to the valve movement, a detailed calculations of the valve kinematics were performed. Special attention was given to the opening and closing velocities of the valve, depending on the servo control signal. Subsidence valve velocity during its return movement was calculated. This subsidence valve velocity is an important parameter in terms of the applicability of this drive for the internal combustion engines. Valve opening time delay in opposition to the current control signal was also specified and discussed. Obtained results allowed to conclude that the proposed drive provides acceptable kinematic parameters for high-speed engines at supply pressures of at least 8 to 10 MPa. During the measurements acceptable valve subsidence speeds were obtained. It was found that there is a possibility of adjustment of this parameter by setting the slider servovalve negative overlap. Results became the basis of development of the model of this type of the drive. Further simulation studies will allow to evaluate the applicability of such valve drive for internal combustion engines. Further simulation studies allow to compare the proposed solution with known literature hydraulic valve drives.

3

Experimental verification of the model of electrohydraulic drive for internal combustion engine valves

Szydłowski T.

Journal of KONES

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2009

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Vol. 16, No. 3

401-408

EN

The paper presents experimental electrohydraulic valve drive for internal combustion engine. The design is asingle-acting hydraulic actuator with spring return controlled by servovalve. Such solution shouldgive free control of valve lift, valve open and valve close time. In the article the principles of the operation of the drive are described. The paper focuses on exploring the dynamic of experimental electrohydraulic engine valve actuation system working in open-loop. For investigations the mathematical and simulation models were elaborated. The values of unknown coefficients of the models were intercepted on two test stands. First of them served to servovalve research. Second was built on the basis of the prototype drive and let on the research of the dynamics of the all drive. Chosen results of these investigations are placed in the article. The drive was explored for different oil supply pressures, control signals and spring mounting lifts. Experimental dates let to verified dynamic mathematical model. Comparisons of valve lift proceedings obtained from experiments and simulations are presented in the article. Verified model let to execute the analysis of the features of such drive and point necessary modifications for the correct realization of the process of the gas exchange in internal combustion engine.

4

Model of hydraulic double-acting drive for valves of internal combustion engine

Szydłowski T., Smoczyński M.

Journal of KONES

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2009

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Vol. 16, No. 1

487-494

EN

The article presents the idea and the model of electrohydraulic double-acting valve drive for internal combustion engine. In this solution to control the position of the engine valve used Rexroth's servovalve and the double-acting actuator. This drive should give free control of valve lift, valve open andvalve close time. In the article the principles of the operation and the mathematical model of the drive are described. Submitted model gives bases to the initial value definition of the main parameters of the hydraulic drive. It lets execute the analysis of the features of such drive and point necessary modifications for the correct realization of the process of the gas exchange in internal combustion engine. The first results from the simulation showed that proposed solution allows obtaining desirable run of lift of valve in the wide range of engine speed. Comparisons of valve lift proceedings driven hydraulically and mechanically by the use of harmonic cam, for two engine speeds, obtained from simulations are presented in the article. These comparisons show that at greatest engine speeds it is indispensable the use of pressures of the working liquid exceeding 10 MPa to obtain nearing results to the classical mechanical timing gear. Preliminary simulation test results indicate that it may ensure desired run of lift of valve in the wide range of engine speed