Search Results

A zero dimensional combustion model of an axial vane rotary engine has been developed. The engine is a positive displacement mechanism that permits the four “stroke” action to occur in one revolution of the shaft with a minimum number of moving components. Current modeling efforts for this engine require improved estimations of engine parameters such as chamber pressure, chamber wall temperature, gas temperature, and heat loss. The purpose of this investigation was to develop a zero dimensional combustion model that predicts the above-mentioned parameters in a quick and accurate manner for a spark ignition or compression ignition version of the engine. For this effort, NASA's ZMOTTO code was modified. Piston engine data and the results from the modified ZMOTTO code are in good agreement.

This paper outlines the development process of a radio frequency (RF) plasma ignitor and its application to internal combustion engines. The system features a high Q quarter-wave coaxial cavity resonator that serves as an electric field magnifier and as a discharge device. The preliminary characteristics of the cavity have been studied by the construction and operation of larger scaled devices. Testing has been performed using these devices in a testing apparatus operating under ambient conditions. Once an analysis of the large-scale device is complete, a smaller device, more inclined to interfacing with a standard engine, will be constructed and tested on a full scale engine. The final device is intended to operate in the 800-1500 MHz range.

In this paper, a new method for the hydro-dynamic analysis of a sliding cylinder in a fully lubricated parallel track is presented. The method is an extension of Booker's “Mobility Method” (developed for cylindrical journal bearings) to the case of sliding cylinders, in which the clearance between the track and the cylinder, the viscosity of the lubricant, the radius and length of the pin, the sliding velocity and the applied transverse load determine the hydrodynamic behavior of the cylinder. In the Rand Cam™ Engine [1]*, the axicycloidal motion of vanes is driven by a rotor and a cylindrical cam, and one of the alternative designs to provide this function is based on a cylindrical pin sliding within a track which follows the profile of the motion of the main cams of the engine. This function is very important for the engine, since it separates the load bearing function from the sealing function left to the apex-like seals.

The Rand-Cam engine is a positive displacement machine, operating on a four stroke cycle, which consists of a rotor with multiple axial vanes forming combustion chambers as the rotor and vanes rotate in a cam shaped housing. The cam housing, consisting of two “half-housings” or stators, contains a toroidal trough of varying depth machined into each stator. The two stators are phased so that the shallowest point on one trough corresponds to the deepest on the other. A set of six vanes, able to move axially through machined holes in the rotor, traverses the troughs creating six captured zones per side. These zones vary in volume with rotor rotation. Since each trough has two deep sections and two shallow sections with ramps in between, full four stroke operation is obtained between each pair of vanes in each trough, corresponding to twelve power “strokes” per revolution.

The Rand Cam engine is a novel design which avoids the use of pistons in favor of a cavity of varying size and shape. A set of vanes protrudes from a rotor into a circular trough in a stator. The vanes seal to the walls and base of the trough, which is of varying depth, and progress around the trough with rotation of the rotor. These vanes therefore pass through the rotor and are constrained to move parallel to the rotational axis. Intake and exhaust processes occur through ports in the stator wall which are revealed by the passing vanes. Advantages of the basic design include an absence of valves, reduction in reciprocating masses, presence of an integral flywheel in the rotor and strong fluid movement akin a swirl induced by the relative velocity between the rotor and stator.

This paper describes a Radio Frequency (RF) plasma ignitor concept intended for application to internal combustion engines. This system features a high Q quarter-wave coaxial cavity resonator, of simple construction, serving as a tuning element in the RF power supply, a voltage magnifier, and a discharge device attached to the combustion chamber. The resonator is filled with a dielectric and open at the discharge end. The center conductor is terminated with a revolute solid capacitive electrode which concentrates the associated electric field. This non-uniform electric field within the air/fuel mixture creates a corona discharge plasma which is excited at the RF operating frequency and the resulting ionic species recombine to initiate combustion. The RF excitation, relative to DC, reduces breakdown voltage and electrode degradation.

Corona discharge from a RF quarter wave coaxial cavity resonator is considered as a plasma ignition source for spark ignited (SI) internal combustion (IC) engines. The gaseous discharge processes associated with this device are analyzed using principles of gas kinetics and gaseous electronics, with assumed values for the electric field strength. Corona discharge occurs when the electric field shaped and concentrated by a single electrode exceeds the breakdown potential of the surrounding gas. Ambient electrons, naturally present due to ionizing radiation, drift in the direction of the externally applied field, gaining energy while undergoing elastic collisions with neutral molecules. After gaining sufficient energy they dissociate, excite, or ionize the neutral particles through inelastic collision, creating additional electrons. This process leads to avalanche electrical breakdown of the gas within about 10-8 sec.

The recent oil crisis has once again emphasized the need to develop both fuel efficient engines and alternately fueled engines, particularly for automotive applications. Engines which burn coal or coal pyrolysis products are attractive, but ignition delay and metal erosion problems continue to limit high speed operation of such engines. Further, the throttled spark ignition engine often used with methanol and natural gas does not prove an efficient or tolerant device for the combustion of a wide range of fuel. Therefore, an novel approach must be taken in order to achieve the efficient and flexible operation of such an engine. A novel design of a fuel tolerant engine suitable for burning coal fuels separates the combustion from the piston in order to have more careful flame control and to exclude the particulate matter from the engine's piston rings.

The Stiller-Smith Engine employs a non-standard gear train and as such requires a closer examination of the design and sizing of the gears. To accomplish this the motion of the Stiller-Smith gear train -will be compared to more familiar arrangements. The results of a kinematic and dynamic analysis will introduce the irregular forces that the gears are subjected to. The “floating” or “trammel” gear will be examined more closely, first stochastically and then with finite element analysis. This will pinpoint high stress concentrations on the gear and where they occur during the engine cycle, The configuration considered will be one with: an output shaft, negligible idler gear forces, and floating gear pins that are part of the connecting rods rather than the floating gear. Various loading techniques will be discussed with possible ramifications of each.

The Stiller-Smith mechanism is a new mechanism for the translation of linear motion into rotary motion, and has been considered as an alternative to the conventional slider-crank mechanism in the design of internal combustion engines and piston compressors. Piston motion differs between the two mechanisms, being perfectly sinusoidal for the Stiller-Smith case. Plots of dimensionless volume and volume rate-change are presented for one engine cycle. It is argued that the different motion is important when considering rate-based processes such as heat transfer to a cylinder wall and chemical kinetics during combustion. This paper also addresses the fact that a Stiller-Smith engine will be easier to configure for adiabatic operation, with many attendant benefits.

The Stiller-Smith Engine employs a double cross-slider that has several advantageous dynamic characteristics. These characteristics are described and developed analytically. This paper also develops and presents the force equations that describe the two-dimensional model of this engine. The necessary requirements to produce a balanced engine are derived and evaluated analytically.

New high-tech materials which are anticipated to revolutionize the internal combustion engine are being created everyday. However, their actual utilization in existing engines has encountered numerous stumbling blocks. High piston sidewall forces and thermal stresses are some of the problems of primary concern. The Stiller-Smith Engine should provide an environment more conducive to the use of some of these materials. Absent from the Stiller-Smith Engine is a crankshaft, and thus a very different motion is observed. Since all parts in the Stiller-Smith Engine move in either linear or rotary fashion it is simple to balance. Additionally the use of linear connecting rod bearings changes the location of the sidewall forces thus providing an isolated combustion chamber more tolerant to brittle materials and potential adiabatic designs. Presented herein is the development of this new engine environment, from conceptualization to an outline of present and future research.