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Development of a Reed Valve Model for Engine Simulations for Two-Stroke Engines
Technical Paper
2004-01-1455
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
Engine manufacturers and product designers are currently under significant pressure to reduce fuel consumption, emissions, and noise from two-stroke engines. Improved engine breathing goes a long way toward overcoming these challenges by providing better charge delivery, complete exhaust gas scavenging, and minimal fuel short-circuiting.
Reed valve motion and the resulting gas flow are highly coupled phenomena. Understanding and controlling these dynamics and their interactions is critical to effective intake breathing. A comprehensive effort to model reed valves at a level sufficient for engine design using engine simulations is still incomplete. This work is focused on the assessment, development and validation of a reed valve model suitable for engine simulations.
In this work, a representative two-stroke engine reed valve is modeled in a detailed fluid/structures, multi-physics CFD code which fully resolves both the flow-field and the details of the deflecting reed plate.
This same reed valve geometry is modeled in a 1D engine simulations code. In lieu of detailed experimental measurements, the CFD simulation results are used to provide the flow and lift data for various differential pressures. These are input into the 1D model as flow coefficients vs. lift.
A comparison of results, between the 1D engine simulation and the original fluid/structure CFD, shows excellent agreement for the maximum lift, the lift vs. time profile, and for the overall flow predictions.
In the 1D simulation code, the standard component model representation of a reed valve is as a spring-mass-damper physical model. It was found that this model, while not an exact representation of the bending reed, did provide adequate agreement.
Additionally, the predicted lifts were compared with uniformly loaded deflecting beam theory assuming the up-stream and down-steam pressures are uniformly applied on either side of the reed valve. It was found that the while this assumption is an adequate first level approximation for low lift conditions and suitable for preliminary design analysis, the CFD results indicate that it does not hold for high lift conditions.
In this work, a method was demonstrated which allows design engineers to investigate reed valve design options from the detailed CFD perspective and from the 1D engine simulations perspective, and thus to develop a good reed valve model for analysis prior to testing. This allows the engineer to screen potential designs with simulation before the more expensive task of building and testing prototypes. The validated reed valve model can be incorporated directly into a full engine simulation with confidence.
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Dave, A., Siddiqui, A., Probst, D., and Hampson, G., "Development of a Reed Valve Model for Engine Simulations for Two-Stroke Engines," SAE Technical Paper 2004-01-1455, 2004, https://doi.org/10.4271/2004-01-1455.Also In
References
- Nuti, Marco Emissions from Two-Stroke Engines SAE Publications 0-7680-0215-X 1998
- Hinds E. T. Blair Belfast G. P. SAE Technical Paper 780766 Unsteady Gas Flow through Reed Valve Induction Systems 1978
- Blair G. P. Hinds E. T. Fleck R. SAE Technical Paper 790842 Predicting the Performance Characteristics of Two-Cycle Engines Fitted With Reed Induction Valves 1979
- Myers, Mark A Study of Reed Valves University of Wisconsin Madison 1984
- Miller, Daniel A Study of Reed Valve Performance on an Engine Simulator using Dimensional Analysis University of Wisconsin Madison 1987
- Fleck R. Blair G. P. Houston R. A. R. SAE Technical Paper 871654 An Improved Model for Predicting Reed Valve Behavior in Two-Stroke Cycle Engines 1987
- Fleck Robert McGregor Alan Harrington Paul A. SAE Technical Paper 942528 Evaluation of Reed Valves in High-Performance, Two-Stroke Engines 1994
- Mitianiec Wladyslaw Badawcze Pro-Mo SAE Technical Paper 961802 Theoretical and Experimental Study of Gas Flow through Reed Valve in a Two-Stroke Engine 1996
- Fleck Robert Dr Cartwright Anthony Dr Thornhill David SAE Technical Paper 972738 Mathematical Modeling of Reed Valve Behavior in High-Speed, Two-Stroke Engines 1997
- Cunningham, G. Kee, R.J. Kenny, R.G. Reed Valve Modelling in a CFD Simulation of the Two-Stroke Engine Proceedings of the Institution of Mechanical Engineers, Part D, Journal of Automobile Engineering 1999 213 D1 37 45 0954-4070 1999