Search Results

Continuously variable transmissions (CVTs) are usually used in small vehicles due to power limitations on the variable elements. Continuously variable power-split transmissions (CVPST) were developed in order to reduce the fraction of power passing through the variable elements [1,2]. The configuration presented in this paper includes a planetary gear train (PGT), which in combination with the CVT allows the power to be split and therefore increase the power envelope of the system. The PGT also provides a branch that can be used in a hybrid electric vehicle (HEV) operation through an electric motor. A conceptual design of a CVPST for a HEV is presented in this paper. The objectives are to show the different operational modes, with diagrams, perform a power analysis, develop the velocity and force equations and finally show the performance of the system with an example application.

The downwash of the prop-rotor blades of the Bell/Boeing V-22 “Osprey” in hover mode creates an undesirable negative lift on the wing of the aircraft. This downforce can be reduced through a number of methods. Neglecting all other effects, such as power requirements, this research investigated the feasibility of using circulation control, through blowing slots on the leading and trailing edge of the airfoil to reduce the wake profile under the wing. A model was built at West Virginia University (WVU) and tested in a Closed Loop Wind Tunnel. The airfoil was placed normal to the airflow using the tunnel air to simulate the vertical component of the downwash experienced in hover mode. The standard hover mode flap angle of 67 degrees was used throughout the testing covered in this paper. All of these tests were conducted at a free stream velocity of 59 fps, and the baseline downforce on the model was measured to be 5.45 lbs.

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.

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.

This paper describes the strategy for engineering design, modeling, and analysis of a planetary - CVT (Continuously Variable Transmission) system. The uniqueness of this mechanism arrangement resides in the combination of features associated to two conventional systems, namely a planetary gear train and a CVT pulley system, acting as a power circulation control unit. The pulley system features a manually activated control over the variable pitch ratios of the CVT, by means of which the overall system input/output velocity and power ratios can be controlled according the operational requirements. By using the belt drive as a feedback control unit (as opposed to the main driveline), one of the major problems or limitations of conventional CVT arrangements is overcome, namely the belt capacity of the system. Specifically, the output torque obtained through the planetary output shaft is greater than the torque circulating through the pulleys.

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.

The mechanism considered here, combines the functions of a planetary gear train and a continuously variable transmission (CVT) system, through a circulating power control unit, which results by connecting the sun-gear shaft and the ring-gear rotation through a variable pitch pulley system. The mechanism is simple and does not require clutches for its operation. Three basic configurations are presented, two of them produce a power feedback effect and a third one produces a power split forward, without a “geared neutral” condition. Parametric analysis is carried out in relation to the circulating power split feature in order to to assist in the design of an optimum configuration for light-weight applications. A parametric approach is used to generate a model that can be used to perform parametric sensitivity analysis.

A family of transmission systems based on a “Planetary Gear - CVT” mechanism is presented here. The systems considered consist of two compound planetary gear trains connected through a CVT pulley system to provide the power/torque split and recirculation function, without the use of additional clutches and/or chain drives. A two degree of freedom system results in which one of the degrees of freedom is directly related to the CVT ratio. The mechanisms considered here combine the gear reduction function of compound planetary gear trains with the continuously variable trans- used as a circulating power control unit. The kinematics and dynamics of this family of systems is presented with emphasis on the belt forces, torques on the various shafts and the overall input/output velocity ratios through the CVT ratio span. Then a parametric analysis is conducted to characterize the effect of the various functional ratios and parameters of the system in terms of the overall performance.

Continuously variable transmissions, commonly known as CVT's, have been shown to be feasible alternatives to the conventional multi-step gear transmissions (standard or automatic) typically used in automotive applications. Most CVT applications, however, rely on a shaft-to-shaft transmission arrangement, in which the belt-sheave action limits the load capacity of the transmission, particularly at the high power ranges (low speed, high torque). In this paper, a system based on a combined planetary gear train and a continuously variable pulley system is presented. The uniqueness of this arrangement is that the variable pulleys provide a power/torque split and recirculation function, which, when combined with the planetary gear train function, produces a continuously variable power split transmission system.

Enhancing the capabilities of established airframes to meet expanded mission requirements is preferential to the design of specialized aircraft. The high cost associated with the research and development of a specialized aircraft platform has shifted the concentration towards the modification of existing aircraft to support multiple C4ISR missions. The recently developed Oculus sensor deployment system is one such example of this trend, providing a fully integrated aerial visual enhancement platform with multi-mission capabilities. This paper provides a short survey of the Oculus sensor pallet system and overviews some of the multiple guidelines used which ensure that various remote sensing technologies may be securely and simultaneously deployed.

The development of a standardized roll-on, roll-off (RoRo) sensor pallet system for a C-130 aircraft was conceived by the National Guard and the Counter Narco-Terrorism Technology Development Office to assist in counterdrug reconnaissance activities within the United States and surveillance and reconnaissance missions worldwide. West Virginia University was contracted to perform the design and development of this system because of their innovative design ideas. Before development, the design parameters were established by these two DoD agencies, their mission requirements and by the limitations of the C-130 aircraft. These limitations include using Commercial off the Shelf (COTS) and Government off the Shelf (GOTS) items when developing the system that must be universal on all C-130 aircrafts variants B thru H. Further design criteria are by the limitations of the C-130 aircraft and its existing mission requirements.

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.

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.

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.

Continuously variable transmissions promise to improve the performance and drivability of vehicles. The design and implementation of continuously variable transmissions for medium or large displacement (power) engines have been hampered by the power limitations of the belts. A continuously variable transmission with a power split design (CVPST) has been developed to minimize the loading on the belt while providing for increased power transfer compared to existing designs. To aid in the design and development of this CVPST, a simulator program has been developed. The simulator can be used to optimize the CVPST and to compare with other transmissions. Finally, an optimized CVPST design is presented.

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.