Thrust 1 - Efficiency
Title
1E.2: High Speed On/Off Valves to Enable Efficient and Effective Fluid Power Systems
Project Leader
Prof. John Lumkes (Purdue)
Statement of Project Goals
The goals of the project are to research and develop advanced multi-domain models and increase the theoretical understanding of high speed digital hydraulic valves, experimentally validate the models, and apply the results to design valves in support of CCEFP projects and related digital fluid power applications. Digital valves will be implemented into several CCEFP projects and test beds to facilitate and validate the use of high speed on/off valves as enablers of efficient and effective fluid power systems.
The fundamental problem is the highly non-linear coupling between the electrical actuator, mechanical system friction in moving components, and fluid dynamics (flow forces and viscous friction). Project metrics will be achieved if, using the tools developed and dissemination during the course of this project, high speed digital valves are successfully modeled, simulated, tested, and implemented in related center projects and test beds.
Project's Role in Support of the Strategic Plan
This project supports the efficiency thrust and the compactness thrust of the strategic plan. The efficiency thrust is supported through the use of on/off valves to reduce metering losses in typical fluid power systems, increase the bandwidth and control of existing components, and to enable new, more efficient, fluid power components and systems. Compactness is achieved by the development of high speed positive sealing digital valves capable of operating at higher than standard pressures. Also, as hydraulic systems are made more efficient, they inherently become more compact due to reduction in size of the prime mover, cooling systems, hoses, and fittings. An understanding of the interaction between the electrical, mechanical, and hydraulic systems has enabled accurate models to be developed and combined with larger system models for the optimization of system efficiency, operating pressure, and dynamic response. Successful completion of this project will have a significant impact on the ability to develop and implement the control strategies proposed in project 1E.3 as well as the feasibility of that project. Project 1E.2 will benefit test beds 1 and 3 though high bandwidth control actuators, digital pump/motors, and virtual variable displacement pumps (VVDP similar to project 1E.1).
Description and Explanation of Research Approach
Understanding and analytically describing the non-linear coupling and impact of fluid dynamics (flow forces), electromagnetic transients, leakage flows, and mechanical deformations and friction in high speed switching valves enables fluid power systems with improved efficiency and effectiveness (meterless switching control, digitally controlled pump/motors, virtually variable displacement pumps, new system topologies, and improved control bandwidth for existing components). This work is an important and complementary component to the other ongoing work in the center. By providing fundamental understanding about the operation and implementation of high speed on/off valves, other researchers can study how the use of such valves impact their efficiency (component and system) and effectiveness (compactness, noise, reliability, etc.).
The valves considered in this project are axisymmetric positive contact sealing. In most conventional systems, as working pressure is increased, efficiency tends to decrease due to increased leakage and compressibility losses. It becomes increasingly difficult to seal using sliding surfaces (i.e. spool overlap and kidney/valve plates) and positive contact sealing surfaces are preferred at higher pressures to minimize leakage losses. One example high pressure application, pumps, usually rely on check valves in place of kidney valve plates and in doing so become fixed displacement unidirectional machines. High pressure, high speed on/off valves can enable a high pressure pump/motor to become variable displacement and bidirectional if the actively controlled valves replace the check valves such as in project 1E.3. This has benefits in the compactness thrust and urban vehicle test bed since high pressure and high efficiency hydrostatic transmissions become possible. Although positive contact seat type valves are preferred for minimizing leakage and tolerance requirements, the geometry of the seat leads to potentially large flow forces that make them difficult to actuate directly using electromagnetics, which saturate at a much lower equivalent pressure. New and innovate valves designs are needed that minimize the effects of the flow forces while retaining (or improving) the dynamic capabilities of switching type valves. Some work is addressing this issue through pressure balancing ports within the moving poppet (Lauttamas, et al. 2006).
There are four basic areas where fundamental science is being applied in this project. Past research has shown that numerical calculations do not accurately predict the magnitude and effects of steady state and dynamic flow forces (Johnston, et al., 1991). Because of this, CFD analysis is used to allow a more accurate description of these forces (Vaughan, et al., 1992) and the results will be used to construct a reduced order analytical model accurate enough for and capable of being embedded into a systems level model. Electromagnetic transients, as seen in high frequency eddy currents, affects the transient force of the actuator (Brauer and Mayergoyz, 2004; Piron, et al., 1998). Effects of eddy currents can be reduced with novel driving methods (peak & hold shaping, momentary reversed currents, and minimization of magnetic diffusion time constants). Area three includes the mechanical dynamics, impact forces, and contact sealing models. The combination of high pressures coupled with high switching speeds has the potential to negatively affect the reliability and lifespan of high speed valves. Finally, the behavior of the fluid is also important at the higher pressures and high switching speeds. This aspect of the project will be supported by other work within the center and is necessary to complete the system model of switching valves.
To address, study, and find solutions to these issues, a simulation model and the underlying theoretical models have been developed and utilized to generate new design concepts for optimized switching valves. The theoretical models include improved modeling of flow forces through CFD analysis and enhanced understanding of how flow forces affect the high pressure performance of the valve, especially at high switching speeds and the addition of new accurate lumped parameter electromagnet modeling techniques describing eddy current effects, magnetic fringing and leakage, and effects of nonlinear material properties captured using a nonlinear material data. The capabilities are not specific to one particular valve configuration and the simulation toolbox resulting from this work can be used to quickly design and simulate the flow characteristics and dynamic response characteristics for nearly any axisymmetric seat type valve actuated by electromagnetic actuators.
Figure 1: 2.0 valve main stage prototype assembly
Figure 2: 2.0 valve main stage prototype section view
References
Andruch, J. and Lumkes, J. (2009). Regenerative hydraulic topographies using high speed valves. SAE Commercial Vehicle Engineering Congress & Exhibition, October 2009, SAE Paper 2009-01-2846
Batdorff, M., and Lumkes, J. (2009). High fidelity magnetic equivalent circuit in an axisymmetric electromagnetic actuator. IEEE Transactions on Magnetics, 45(8):3064-3072.
Batdorff, M., and Lumkes, J., "Virtually Variable Displacement Hydraulic Pump Including Compressibility and Switching Losses", Proceedings of IMCE2006, IMECE2006-14838, 2006.
Birch, S. 2009. Delphi's new GDi components meet Euro6 with lower cost. Automotive Engineering International. December, p16.
Brauer, J. R. and Mayergoyz, I. D. "Finite-element computation of nonlinear magnetic diffusion and its effects when coupled to electrical, mechanical, and hydraulic systems," IEEE Trans. on Magnetics, vol. 40, pp. 537-540, 2004.
Feuser, A., "New Developments in the Field of Electrohydraulic Drive Technology", The Tenth Scandinavian International Conference on Fluid Power, SICFP, May 21-23, 2007.
Fronczak, F. J., Ma, J. S., and Beachley, N. H. Design of a High Speed, High-Flow, Three-Way Poppet Valve, National Conference on Fluid Power 105-7.3, 223-231, 2005.
Johnston, D., Edge, K., and Vaughan, N., "Experimental investigation of flow and force characteristics of hydraulic poppet and disc valves", Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, Vol. 205, March 1991.
Kim, J., and Chang, J., "A New Electromagnetic Linear Actuator for Quick Latching", IEEE Transactions on Magnetics, Vol. 43, No. 4, April 2007.
Lauttamas, T., Linjama, M., Nurmia, M., and Vilenius, M. 2006. A Novel Seat Valve with Reduced Axial Forces. Power Transmission and Motion Control 2006. pp 415-427.
Linjama, M., and Vilenius, M., "Digital Hydraulics - Towards Perfect Valve Technology", The Tenth Scandinavian International Conference on Fluid Power, SICFP, May 21-23, 2007.
Linjama, M., 2009. Energy Saving Digital Hydraulics. Proceedings of the Second Workshop on Digital Fluid Power, 2009, Linz, Austria.
Long, G. and Lumkes, J. (2010). Comparison of using 2/2 and 3/2 high speed on/off valves and different control strategies for cylinder position control. International Journal of Fluid Power, (2010) No. 1 pp 21-32.
Mahrenholz, J. and Lumkes, J., (2009). Coupled Dynamic Model for a High Speed Pressure Balanced 3-way On/Off Hydraulic Valve. J. Dyn. Sys., Meas., Control, 132, 10p.
Merrill, K., Holland, M., Batdorff, M., and Lumkes, J. 2010. Comparative Study of Digital Hydraulics and Digital Electronics. International Journal of Fluid Power, 11(3) pp. 45-51.
Merrill, K. and Lumkes, J. (2010). Operating Strategies and Valve Requirements for Digital Pump/Motors. Proc. of 6th FPNI-PhD Symp. West Lafayette 2010, pp. 249-258
Mikkola, J., Ahola, V., Lauttamus, T., Luomaranta, M., and Linjama, M., "Improving Characteristics of On/Off Solenoid Valves", The Tenth Scandinavian International Conference on Fluid Power, SICFP, May 21-23, 2007.
Plockinger, A., Schedl, R., and Winkler, B. 2009. Performance, Durability and Applications of a Fast Switching Valve. Proceedings of the Second Workshop on Digital Fluid Power, 2009, Linz, Austria.
Rannow, M., Ut, H., Li, P., and Chase, T., "Software Enabled Variable Displacement Pumps-Experimental Studies", IMECE2006, IMECE2006-14973, 2006.
Reichert, M., "Development of a piezo-driven pilot stage for highly dynamic hydraulic valves", Institute for Fluid Power Drives and Controls, RWTH, Aachen, Germany.
Sosnowski, T., Lucier, P., Lumkes, J., Fronczak, F., and Beachley, N., Pump/Motor Displacement Control Using High-Speed On/Off Valves, SAE Paper 981968, September, 1998
Vaughan, N., Johnston, D., and Edge, K., "Numerical simulation of fluid flow in poppet valves", Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, Vol. 206, March 1992.
Wilfong, G., Batdorff, M. and Lumkes, J. (2010). Design and Dynamic Analysis of High Speed on/off Poppet Valves for Digital Pump/Motors. Proc. of 6th FPNI-PhD Symp. West Lafayette 2010, pp. 259-269.
Winkler, B., Scheidl, R., "Development of a Fast Seat Type Switching Valve for Big Flow Rates", The Tenth Scandinavian International Conference on Fluid Power, SICFP, May 21-23, 2007.