Linear Engine / L2V4bGlicmlzL2R0bC9kM18xL2FwYWNoZV9tZWRpYS80Nzg0

Acknowledgements

I first thank Dr. Nigel Clark for providing me with an opportunity to work with him, and for being my advisor and friend. His guidance and comments have aided me in my college career. Next, I thank Dr. Victor Mucino for providing support for me during the first part of my graduate work. I thank all of my committee members, Dr. Christopher Atkinson, Dr. Scott Wayne, Mr. Ralph Nine, for their support in my thesis work.

I give great thanks to Richard Atkinson and Tom McDaniel for their help in the design and construction of the test engine. Without the support and guidance of these two individuals the engine would not have progressed to the extent that it has. Justin Kern, John Anderson, Dustin McIntyre, Dave McKain, Ron Jarrett, and Marcus Gilbert all deserve thanks for helping, supporting, and encouraging me.

I give my family a thanks for their support of me during this busy time. Last but not least I thank my fiancé Rayna for her, help, love and support through the duration of my masters work. Rayna’s support made it much easier to carry on through any discouraging moments.

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List of Tables

3.1.In-cylinder pressures and pressure force as a function of the slider displacement.

3.2.Simulation constants.

3.3.Test trials mass and bore values.

4.1.Prototype component description.

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List of Figures

3.1.The ideal engine model at the beginning of a left to right compression stroke ( x = −xs ).

3.2.The ideal engine model with the pistons at the midpoint position ( x = 0 ).

3.3.Pressure volume diagram of limited-pressure cycle.

3.4.Four regions can be seen for the pressure balance due to the limited-pressure cycle of operation.

3.5.Obtained half stroke can be seen to be a function of the amount of heat input and the percentage of heat input at constant volume.

3.6.The constant pressure expansion coordinate defines how much heat is input at constant pressure. It can be seen to be a function of the heat input and φ.

The compression ratio is defined by the geometry of the engine and the achieved half stroke.

The period of the operating cycle is seen to be the smallest for a Diesel cycle of operation. The cycle period increases as the amount of heat input at constant

3.9.The average frequency is related directly to the operational period.

Slider mid-stroke velocity is seen to increase with an increase to the specific heat input.

Slider position versus time shows near constant velocity over the majority of the

the end of the stroke due to the heat input at constant volume. This can also be

seen in Figure 3.12.

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3.12.Slider Velocity versus time shows the velocity is near constant for most of the stroke.

3.13.Work output versus time shows positive work being performed during the expansion stroke and negative work during the compression stroke. During the gas exchange operation when the exhaust port is open, work output can be seen to have offsetting positive and negative work regions.

3.14.In-cylinder pressure versus time.

3.15.In-cylinder pressure versus in-cylinder volume shows a pressure trace of the idealized model.

4.1.Diesel prototype.

4.2.Dimensional sketch of cylinder assembly.

4.3.Diesel prototype engine control module block diagram.

4.4.Overhead view of engine setup.

4.5.Front view of engine.

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1. Introduction

The present day internal combustion engine has proven to be successful as a means of producing power. In its current form, the internal combustion engine converts the linear energy of the pistons to rotational energy by means of a slider-crank mechanism. Components such as the crankshaft are the cause of much of the friction in the current internal combustion engine. The use of a linear engine would eliminate this friction by eliminating the crankshaft and other rotational components and also the friction on the piston due to side thrust caused by the slider-crank mechanism. This reduction in friction would greatly improve the efficiency of the engine.

Past studies of free piston engines have shown that they would be useful in situations where linear power delivery could be used. Researchers have been studying methods to use linear power delivery. One such method has been for fluid power delivery either in the form of a hydraulic pump mechanism or an air compressor. Free piston engines have also seen use as gas generators where a mix of the exhaust gas and compressed air from the engine was sent to a gas turbine. Also, linear engines could see use in the production of electrical power through the use of a linear alternator. Past studies conduced at West Virginia University have concentrated on the use of a small bore, two-stroke cycle, linear gasoline engine in conjunction with a linear alternator for the generation of electrical power [1-4]. One conclusion from the study was that a large bore and high compression ratio was desirable to reverse the piston motion at the end of its stroke. Finally, it was also concluded that unthrottled operation would be desirable, because throttled operation made the engine difficult to control.

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