Electronically Variable Pressure Regulator (EVPR)

A new programmable electronically variable pressure regulator (EVPR) concept accurately controls the local outlet or remote system pressure. It uses an integral pulse width modulated rare earth permanent magnet motor operating in response to redundant pressure transducer feedback signals. The EVPR is a simple single stage device that does not use dynamic seals or pilot valving. Conversion of partial revolution motor torque to poppet lifting force is accomplished by pure flexure action to avoid using bearings. The flexure drive (called the ROTAX) has a variable lead to minimize motor weight and power consumption. Breadboard tests were completed successfully on two critical design elements of the EVPR: the ROTAX and the motor. The ROTAX cable system was tested for 250,000 cycles without failure. The breadboard motor met the basic design requirements including the design torque and power consumption. Prototype parts were fabricated, and testing of the prototype EVPR has started. It is PC computer controlled to facilitate programming, data acquisition and analysis. A lightweight dedicated microprocessor is planned for the flightweight EVPR

A computational fluid dynamics evaluation of a pneumatic safety relief valve

Safety relief valves are well established components preventing catastrophic failure of pressurised systems when non-normal operating conditions occur. However, it is only recently with developments in CFD techniques that the capability to predict the complex flow conditions occurring in the valves has been possible resulting in only limited studies being found in the literature. This paper presents experimental and theoretical investigations applied to a safety relief valve designed for the refrigeration industry but extended here to consider pneumatic systems since air is the compressible fluid. The discharge flow rate and valve forces are determined both theoretically and experimentally for different valve lift conditions and related to the detailed flow conditions (pressure, temperature and Mach number) in the valve predicted by CFD techniques. The CFD code FLUENT has been used with a two dimensional axisymmetric RANS approach using the k-İ turbulent model to predict the highly compressible flow through the valve. The model has been validated by comparison with experimental measurements and the predicted results show good agreement, providing confidence in the use of CFD techniques for valve design and improvement

Research study of the vortex valve for medium-temperature solid propellants

Fluid state control system with vortex valves for solid propellant gas generator flow throttlin

Pressure control and analysis report: Hydrogen Thermal Test Article (HTTA)

Tasks accomplished during the HTTA Program study period included: (1) performance of a literature review to provide system guidelines; (2) development of analytical procedures needed to predict system performance; (3) design and analysis of the HTTA pressurization system considering (a) future utilization of results in the design of a spacecraft maneuvering system propellant package, (b) ease of control and operation, (c) system safety, and (d) hardware cost; and (4) making conclusions and recommendations for systems design

Pilot operated cartridge valve - Dynamic characteristics measurements for energy efficient operation and application

The two-stage on/off valve scheme is studied in this thesis which is able to rapidly actuate within the fraction of a second for directional flow control applications. And also, it was able to replicate characteristics of direct operated solenoid on/off valves in the same category, with the addition of higher flow rate capacity up to 200 l/min and above with pressure drop under 5 bar. The valves utilized for piloting of the hydraulic operated cartridge valve are the normally closed and normally open direct solenoid operated on/off valve. In the experiments, the internal piloting structure is adopted to avoid external pressure source and keeping valve operation dependencies minimum to the electric power. The switching time was found to be lowest at 100 bar, that is approximately 12 ms for opening and 30 ms for closing from the point of activation signal. It is also observed that the flow rate has negligible effect on the switching duration and changing the poppet area ratio to 50% of Ax from 96% can reduce down the closing time. Further, it was observed that the internal piloting has its drawbacks which creates a closed loop between main valve metering edge and pilot chamber. This resulted in oscillations in form of poppet movement near the dead end on either side of the stroke, and also if the system is not stiff or due to pressure waves traversing in the long hoses. Another positive outcome from the measurements showed that different switching methods such as, intermittent, continuous and pulse switching can be performed in a controlled manner, but the study was limited to the capability of the valve scheme. Moreover, the simulation model is also built in the Matlab/Simscape environment to refine the valve model based on the experiment results for further measurements that were limited by the physical system. Additional simulations are conducted to reduce the marginal difference between the opening and closing duration by restricting the stroke length to 5 mm, contrary to the original 8.5 mm, at 200 l/min and the switching duration was considerably reduced by half of the original duration. The experiments were conducted for flow in one direction only, whereas in simulation also the bi-direction flow capability is also carried out to displace an actuator with constant velocity, while lifting and lowering and holding of the load to certain position

Redundant actuator development study

Current and past supersonic transport configurations are reviewed to assess redundancy requirements for future airplane control systems. Secondary actuators used in stability augmentation systems will probably be the most critical actuator application and require the highest level of redundancy. Two methods of actuator redundancy mechanization have been recommended for further study. Math models of the recommended systems have been developed for use in future computer simulations. A long range plan has been formulated for actuator hardware development and testing in conjunction with the NASA Flight Simulator for Advanced Aircraft

The Total In-Flight Simulator (TIFS) aerodynamics and systems: Description and analysis

The aerodynamics, control system, instrumentation complement and recording system of the USAF Total In/Flight Simulator (TIFS) airplane are described. A control system that would allow the ailerons to be operated collectively, as well as, differentially to entrance the ability of the vehicle to perform the dual function of maneuver load control and gust alleviation is emphasized. Mathematical prediction of the rigid body and the flexible equations of longitudinal motion using the level 2.01 FLEXSTAB program are included along with a definition of the vehicle geometry, the mass and stiffness distribution, the calculated mode frequencies and mode shapes, and the resulting aerodynamic equations of motion of the flexible vehicle. A complete description of the control and instrumentation system of the aircraft is presented, including analysis, ground test and flight data comparisons of the performance and bandwidth of the aerodynamic surface servos. Proposed modification for improved performance of the servos are also presented

Space shuttle OMS helium regulator design and development

Analysis, design, fabrication and design verification testing was conducted on the technological feasiblity of the helium pressurization regulator for the space shuttle orbital maneuvering system application. A prototype regulator was fabricated which was a single-stage design featuring the most reliable and lowest cost concept. A tradeoff study on regulator concepts indicated that a single-stage regulator with a lever arm between the valve and the actuator section would offer significant weight savings. Damping concepts were tested to determine the amount of damping required to restrict actuator travel during vibration. Component design parameters such as spring rates, effective area, contamination cutting, and damping were determined by test prior to regulator final assembly. The unit was subjected to performance testing at widely ranging flow rates, temperatures, inlet pressures, and random vibration levels. A test plan for propellant compatibility and extended life tests is included

STS-39 Space Shuttle mission report

The STS-39 Space Shuttle Program Mission Report contains a summary of the vehicle subsystem operations during the fortieth flight of the Space Shuttle and the twelfth flight of the Orbiter Vehicle Discovery (OV-103). In addition to the Discovery vehicle, the flight vehicle consisted of the following: an External Tank (ET) (designated as ET-46 (LWT-39); three Space Shuttle main engines (SSME's) (serial numbers 2026, 2030, and 2029 in positions 1, 2, and 3, respectively); and two Solid Rocket Boosters (SRB's) designated as BI-043. The primary objective of this flight was to successfully perform the planned operations of the Infrared Background Signature Survey (IBSS), Air Force Payload (AFP)-675, Space Test Payload (STP)-1, and the Multipurpose Experiment Canister (MPEC) payloads