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Dynamic simulation of an electrohydraulic open center gas-exchange valve actuator system for camless internal combustion engines / by Joshua M. Donaldson

by Donaldson, Joshua M.

Internal combustion engines -- Testing

Hydraulic control

Computer simulation

137 leaves : ill. ; 29 cm.

Advisors: Dr. John Lumkes, Jr., Dr. John Brauer, Dr. John Pakkala.

Introduction and background -- Review of literature -- Methodology -- Actuator system design overview and strategies -- Specifications and design -- Simulation model -- Simulation results -- Conclusions and recommendations -- References -- Bibliography -- Appendix I) Schematic of EHOCVA system configuration II) Detailed module design drawings III) AMESim model documentation IV) Fluid properties lookup table V) Constant-pressure (metering) system comparison model.

Camless engines require independent gas-valve actuators which can provide accurate control, sufficient force, and require only a small percentage of engine output power. A valve actuation system concept with apparent advantages in these areas over existing systems is proposed. A potential design of required system components is presented and dynamic simulation included which make feasibility conclusions from the standpoint of performance, packaging, and power efficiency. Trends toward downsized gas and diesel engines with high fuel efficiency and high specific power output fully warrant this research.

Based on consideration of valve actuation cycles and hydraulic power efficiency, an open-center hydraulic system schematic with series valves is the baseline of this project. Compact valve actuation and hydraulic spool-valve components were designed which would be suitable for typical engine layouts. With this potential design, hydraulic system simulation models were developed to predict the dynamic performance, power consumption, and tolerance to the temperature range of the application. Operating conditions and performance specifications were determined from technical paper references and consultations with Motorola engineers.

The modeling results presented in this report conclude that the proposed system is feasible from an engineering standpoint. Further development and testing would be required to determine this completely. It was confirmed that it may require as little as 1-2% of engine output power to operate this considered system. Technical journals estimated the power input for comparable prior systems at 4-7% of engine output. This input power affects the overall fuel efficiency and net gain of camless engines. Additionally fluid temperature variation was found to have a reduced impact on this system compared to a dynamic model the author created representative of prior-art metering systems.

Simulation results indicate the system may lend itself well to open-loop control, which would improve cost and reliability significantly by eliminating position sensors on each valve. Building on the results of this project, development of microprocessor control algorithms and laboratory testing of a prototype would be significant next steps.

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