Randall Tucker

Shaft-less energy storage flywheel

Embodiments of the present invention include a shaft-less energy storage flywheel system. The shaft-less energy storage flywheel system includes a solid cylindrical flywheel having permanent motor magnets mounted about the flywheel. The shaft-less energy storage flywheel system also includes a motor stator having motor windings carrying electrical currents. The motor windings of the motor stator are aligned with the permanent motor magnets of the flywheel such that rotation of the flywheel is induced through interaction of the motor winding currents and the magnetic field of the permanent motor magnets. The flywheel provides a magnetic flux path for the permanent motor magnets. In certain embodiments, the shaft-less energy storage flywheel system includes a magnetic bearing assembly disposed directly adjacent an axial face of the flywheel. The magnetic bearing assembly controls positioning and alignment of the flywheel without physically contacting the flywheel during normal operation.

A Modal Approach for Chaotic Vibrations of a Drillstring

The purpose of this paper is to present a methodology to predict vibrations of drilllstrings for oil recovery service. The paper extends a previous model in the literature to include drill collar flexibility utilizing a modal coordinate condensed, finite element approach. The nonlinear effects of drillstring / borehole contact, friction and quadratic damping are included. Bifurcation diagrams are presented to illustrate the effects of speed, friction, stabilizer gap and drill collar length on chaotic vibration response. A study is conducted on factors for improving the accuracy of Lyapunov Exponents to predict the presence of chaos. This study considers the length of time to steady state, the number and duration of linearization sub-intervals, the presence of rigid body modes and the number of finite elements and modal coordinates. The results may be helpful for computing Lyapunov exponents of other types of nonlinear vibrating systems with many degrees of freedom.Copyright

Direct Fuel Injector Power Drive System Optimization

Abstract : The objective of this study is to optimize the injector power drive system for improved fuel injection quantity and timing control. The power drive system was optimized for improved injection repeatability under different operating conditions such as fuel supply pressures. A coupled simulation of injector electromagnetic, pintle (needle) rigid body motion and computational fluid dynamics (CFD) model was employed to generate the optimal values of the 1st stage current, the 1st stage on-time and the 2nd stage current. The simulation results were validated against the experimental data measured with a photo detector measurement system.

Flywheel magnetic suspension developments

The authors provide an overview of many areas of the flywheel magnetic suspension (MS) R&D being performed at the Texas A&M Vibration Control and Electromechanics Lab (TAMU-VCEL). This includes system response prediction, actuator optimization and redundancy, controller realizations and stages, sensor enhancements and backup bearing reliability.

Fail Safe, High Temperature Magnetic Bearing for High Efficiency Gas Turbine Engine Applications

This paper contributes to the magnetic bearing literature in two distinct areas: high temperature and redundant actuation. Design considerations test results are given for the first published combined 538°C (1000°F)-high speed rotating test performance of a magnetic bearing. Secondly, a significant extension of the flux isolation based, redundant actuator control algorithm is proposed to eliminate the prior deficiency of changing position stiffness after failure.Copyright

Flash vapor fuel injector development

Following the single-fuel initiative, the US Army is transitioning its power plants from running on various fuels to a single fuel—JP-8. Due to its low vapor pressure, JP-8 could not be used to cold start or run gasoline engines without extensive retrofit. The feasibility of running a low compression ratio, spark ignition engine with direct injection of heated JP-8 was investigated. A preliminary study found that a small piston-type spark ignition engine would not start or run on JP-8 unless JP-8 was heated to certain temperature. JP-8’s thermal decomposition, or coking, was found to be a serious issue that must be addressed if fuel heating method would be used. A flash heater concept was proposed to solve problems of JP-8’s low vapor pressure on running low compression ratio spark ignition engines, as well as JP-8’s coking issue at high temperature. A flash vapor fuel injector was designed and tested to be capable of heating up JP-8 from 26.7 °C to its vaporization temperature of >154.4 °C under one-tenth of a second at the required flow rate. The longest duration heating test (>1 million injections) did not show any coking sign with flash heating. Ignition test results show equivalent or superior ignition characteristics of pre-heated JP-8 (with heater temperature at 260.0 °C or above) provided by the developed flash vapor fuel injector, compared with non-heated aviation gasoline.

High Temperature, Permanent Magnet Biased, Fault Tolerant, Homopolar Magnetic Bearing Development

This paper summarizes the development of a magnetic bearing designed to operate at 1,000F. A novel feature of this high temperature magnetic bearing is its homopolar construction which incorporates state of the art high temperature, 1,000F, permanent magnets. A second feature is its fault tolerance capability which provides the desired control forces with over one-half of the coils failed. The construction and design methodology of the bearing is outlined and test results are shown. The agreement between a 3D finite element, magnetic field based prediction for force is shown to be in good agreement with predictions at room and high temperature. A 5 axis test rig will be complete soon to provide a means to test the magnetic bearings at high temperature and speed.

Direct Fuel Injector Temporal Measurements

Abstract : The objective of this study is to measure high-frequency, short-duration, actual liquid fuel spray events using a simple photo detector and validate the results with high-speed camera measurements. This report presents an optical approach for detecting bulk fuel injections temporal characteristics, i.e. opening delay and duration times. A key component in the measurement system is a commercially available low-cost photo detector which is shown to be highly effective for detecting high frequency, short duration spray events. The paper provides an in-depth discussion of a photo detector based measurement system, a test fixture, and its validation. Test results with a two-stage pulse-width-modulation (PWM) current controlled approach are provided for various operation parameter settings. Its effectiveness is validated by comparing with the results obtained with a high-speed camera.