Search Results

There are 30 million people in remote, rural communities in China without access to electricity. The government of China has initiated an ongoing effort to provide constant, reliable power to these citizens. Renewable energy is being utilized to solve this problem, which necessitates the use of a storage medium for energy, because renewable energies (i.e. wind and/or solar power) are inherently intermittent, variable, and largely unpredictable. By storing excess energy when it is plentiful (for a maximum feasible time of two days) and distributing it to the community in times of scarcity, the intermittent power is effectively leveled and auxiliary power is provided. A high-inertia flywheel was designed for this application because of its simplicity, ease of maintenance, low cost, and reliability. This design addresses many problems including bearing losses, aerodynamic losses, and distribution losses. The proposed design consists of a six spoke layout with a large outer ring.

Significant environmental and economic benefit could be obtained if spark ignited (SI) engines could be made more efficient. Engine operation using leaner fuel air mixtures at higher power densities and pressures promise higher thermal efficiencies. Mixtures required for such operation are often difficult to ignite with traditional spark plugs. In pursuit of better ignition sources, this paper presents a high-level model of an alternative microwave plasma ignition source under development. In this publication, atmospheric measurements of a pulsed microwave ignitor are used to derive an empirical model that will allow for control and increased energy delivery to the device. The model accounts for a simplistic plasma formation delay, a drop in resonance frequency as a result of plasma formation, and a subsequent change in associated microwave reflection coefficient.

Current research has involved manipulating the ignition inside of the combustion chamber. It has been demonstrated that an RF plasma flame can be generated from microwaves in a Quarter Wave Coaxial Cavity Resonator (QWCCR). By using this method, it may become possible for researchers to improve combustion and ignition characteristics of a modern internal combustion engine. Filling a plasma cavity with an appropriate dielectric medium can both alter electromagnetic properties and provide a suitable protective barrier to the harsh condition inside of a combustion cylinder. It is the purpose of this paper is to investigate both the operating frequency and quality factor of dielectric-filled cavities, as well as to suggest dielectrics that would be suitable for such an application.

In this analysis the structural integrity of the rotational system of a standardized roll-on, roll-off sensor pallet system was authenticated. The driving force behind this analysis was to ensure the structural integrity of the system and to locate the areas with optimization potential. This process will ideally lead to the weight reduction of individual components thereby allowing for the transportation of greater cargo during flight. Scaling down of these excessive areas will also allow for a reduced production cost and an increase in efficiency of the system. The study was comprised of the failure susceptibility of the individual components of the system. The major results include the optimization potential of individual components, as well as strategically rating and categorizing the failure capability of the components.

The Quarter Wave Coaxial Cavity Resonator (QWCCR) plasma igniter is designed, from previous theoretical work, as an ignition source for an internal combustion engine. The present research has explored the implementation of the QWCCR into an internal combustion (IC) engine. The QWCCR design parameters of inner conductor length, loop geometry, and loop position were varied for two igniters of differing operating frequency. Variations of the QWCCR radio frequency (RF) parameters, as a function of engine geometry, were studied by placing the igniter in a combustion chamber and manually varying the crank position. Three identical igniters were fitted with dielectric inserts and the parameters were studied before and after ignition was sustained in a twin-cylinder engine. Optimal resonator geometries were determined. Radio frequency parameter invariance was found with respect to crank angle and piston distance. The first successful IC engine ignition using a QWCCR was achieved.

A quarter-wave radio frequency coaxial cavity plasma ignitor can be used to generate a combustion-initiating energy source in an internal combustion engine. This paper outlines research results on the development of such an ignitor. The system, which operates in the 820 - 900 MHz frequency range, uses a high Q quarter-wave cavity that generates plasma when resonating. Pressure testing has shown that the device can generate plasmas at spark ignition compression pressures. A resonator operating at these frequencies has been attached to a static combustion chamber and modeled numerically in order to determine the operational characteristics of the device in a combustion chamber.

Crashworthiness is a measure of a vehicle's structural integrity during mechanical impact and of its ability to absorb energy and provide occupant protection in crash situations. Finite element modeling has been successfully used to simulate collision events; the present work uses these techniques to simulate the side impact of a mid-size car in order to investigate the crash characteristics of a 45 km/hr impact. Five different analyses were conducted on orthogonal and oblique impacts under varying conditions. The numerical results from the first analysis were compared with published experimental crash results, showing favorable comparisons for this numerical model prediction.

A finite-difference gas adsorption computer model for CO2, H2O, and N2 on zeolite 5A is discussed. It is part of an effort to predict results, via simulation, of changing a spacecraft CO2 removal system's operational configuration. The mathematical and numerical modeling approach, with emphasis on identification and independent verification of important adsorption physics, is described. The apparatus used to obtain single and multicomponent isotherms, and the subscale packed column bench test used to derive transfer coefficients and verify the model are described. The favorable comparison of simulation and test results show the potential for predictive capability with this modeling approach.

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.

In this paper an approach is presented for the system parameterization and synthesis of a Rand-Cam® Engine configuration based on an axial-cylindrical cam driven mechanism. This engine consists of a stationary axial-cylindrical cam on which axially moving pistons (vanes) sweep around the cam as they are driven by the rotor, providing the volume displacement as the rotor delivers the rotary output torque directly to the shaft. It has been documented that this engine configuration has some unique features that make it particularly suitable for high power to weight ratio applications. The modeling strategy makes use of higher order curve and surface modeling techniques and object modeling approaches based on profile extruding, blending operations and constructive solid geometry. Some of the resulting models are further used for finite element engineering analysis through a programmatic logic built into the parameterized general model.

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.

The unique shape of cruciform engines provides an alternative to the typical in-line or “V-shaped” engines. The planar nature of the mechanism provides either a low profile or thin engine with the ability to stack many 4 cylinder banks into a compact large engine. The sinusoidal motion inherent in this mechanism provides unique balancing aspects which ultimately further reduce the size of the power plant. The compact cruciform shape lends itself to applications in portable hydraulic pumps, compressors, hydraulic motors, internal combustion engines, etc.

Balancing to date, of the Stiller-Smith Mechanism, has been for a symmetric configuration. If two pistons are moved closer to the center of the engine to minimize spatial requirements and also reduce weight, then the mass center of the inner mechanism no longer travels in a circle about the center of the engine. It is shown how the overall balancing of the engine is not compromised using the example of a small 8-cylinder engine. The effects of the non-symmetry on the performance of the linear bearing is presented and the resulting additional engineering concerns are discussed.

The development of a mathematical model of StillerSmith Mechanism for the application of a 4-cylinder plunger pump system is presented. The magnitude and direction of the internal dynamic load are obtained by solving a set of equations using the overall geometric parameters, prescribed motions, inertia distribution, and applied torques on the system. The simulation presented here yields the history of the internal loads, which are then normalized with respect to the required peak output load on the plungers, through an entire rotary cycle. The approach allows for the development of further design criteria through parametric sensitivity studies.

In a recent study the present authors showed that piston motion in a compression ignition engine can have a small yet significant effect on ignition delay of diesel fuel. In particular, sinusoidal piston motion, or a motion with high dwell near top-dead-center, promotes reduced delay and improved cold starting relative to conventional slider-crank piston motion. This paper extends the analysis to the case of coal-diesel and coal-methanol blends, using experimental data from the thesis available in the literature. Ignition delay was shown again to be reduced with sinusoidal motion. In addition, the effect of piston motion on mass loss was considered. As expected, higher dwell near top-dead-center caused more mass loss, but there is still benefit to ignition delay of unusual piston motions unless the coefficient of leakage past the rings is very large.

The potential benefits of using advanced fiber-reinforced composites as an alternative to metallic alloys has been investigated for the design and fabrication of connecting rods in motion conversion mechanisms for internal combustion engines. Two types of mechanisms have been selected for this analysis: the common slider-crank mechanism and the new. Stiller-Smith Mechanism, in which the crankshaft is replaced by a floating gear system. An improved finite-element elastodynamic model, which includes the effects of longitudinal, bending and shear deformations, has been developed in order to quantify the relationships between the levels of bearing loads and vibrations of such mechanisms and the material design of their connecting-rods. An extensive parametric study has been conducted on the material system, the lay-up and the cross-sectional dimensions of elastic connecting rods, made of helically wound composite materials.

With few exceptions most internal combustion engines use a slider-crank mechanism to convert reciprocating piston motion into a usable rotational output. One such exception is the Stiller-Smith Mechanism which utilizes a kinematic inversion of a Scotch yoke called an elliptic trammel. The device uses rigid connecting rods and a floating/eccentric gear train for motion conversion and force transmission. The mechanism exhibits advantages over the slider-crank for application in internal combustion engines in areas such as balancing, size, thermal efficiency, and low heat rejection. An overview of potential advantages of an engine utilizing the Stiller-Smith Mechanism is presented.

A new technique of translating linear to rotary motion, using the Stiller- Smith mechanism, can be applied to the design of internal combustion engines and compressors. This new mechanism produces purely sinusoidal motion of the pistons relative to crank angle, which is a different motion from that produced by a conventional slider-crank mechanism, Influence of this sinusoidal motion on thermodynamic performance of engines and compressors was investigated theoretically and experimentally. Data are presented from a numerical analysis of compression and of spark-ignited combustion. Also, pressure-time curves for a standard and a modified (long connecting rod) spark ignition engine are compared. All data confirm that there is little thermodynamic difference between the Stiller-Smith and slider-crank devices.