Experimental investigation of the effects of pulse pressure distortions imposed on the inlet of a turbofan engine

Pulse pressure distortion effects imposed on inlet of turbofan engin

A method to account for variation of average compressor inlet pressure during instantaneous distortion analyses

A method is presented to calculate the available surge margin as a function of time and incorporate it into an instantaneous distortion analysis. Results show that inlet pressure variations which cause only a small change at the compressor exit can cause a significant variation in the available surge margin

Influence of structural disorder and large-scale geometric fluctuations on the Coherent Transport of Metallic Junctions and Molecular Wires

Structural disorder is present in almost all experimental measurements of electronic transport through single molecules or molecular wires. To assess its influence on the conductance is computationally demanding, because a large number of conformations must be considered. Here we analyze an approximate recursive layer Green function approach for the ballistic transport through quasi one-dimensional nano-junctions. We find a rapid convergence of the method with its control parameter, the layer thickness, and good agreement with existing experimental and theoretical data. Because the computational effort rises only linearly with system size, this method permits treatment of very large systems. We investigate the conductance of gold- and silver wires of different sizes and conformations. For weak electrode disorder and imperfect coupling between electrode and wire we find conductance variations of approximately 20%. Overall we find the conductance of silver junctions well described by the immediate vicinity of narrowest point in the junction, a result that may explain the observation of well-conserved conductance plateaus in recent experiments on silver junctions. In an application to flexible oligophene wires, we find that strongly distorted conformations that are sterically forbidden at zero temperature, contribute significantly to the observed average zero-bias conductance of the molecular wire

Interactive Simplifier Tracing and Debugging in Isabelle

The Isabelle proof assistant comes equipped with a very powerful tactic for term simplification. While tremendously useful, the results of simplifying a term do not always match the user's expectation: sometimes, the resulting term is not in the form the user expected, or the simplifier fails to apply a rule. We describe a new, interactive tracing facility which offers insight into the hierarchical structure of the simplification with user-defined filtering, memoization and search. The new simplifier trace is integrated into the Isabelle/jEdit Prover IDE.Comment: Conferences on Intelligent Computer Mathematics, 201

Analysis of dynamic inlet distortion applied to a parallel compressor model

An investigation of surge was conducted by using a parallel compressor model of the J85-13 compressor implement on an analog computer. Surges were initiated by various types of dynamic disturbances in inlet pressure. The compressor model was less sensitive to disturbances of short duration, high frequency, and long duration where the compressor discharge pressure could react. Adding steady distortion to dynamic disturbances reduced the amount of dynamic disturbance required to effect surge. Steady and unsteady distortions combined linearly to reduce surge margin

Performance of a J85-13 compressor with clean and distorted inlet flow

The results presented are of a series of experimental tests in which a J85-13 turbojet engine was subjected to both distorted and undistorted inlet total pressure conditions. A distinctive feature of the data base obtained is that it includes compressor interstage information not previously recorded for a J85-13 engine. Each of the eight compressor stages was instrumented to obtain the characteristics of the individual stages for undistorted inlet conditions, and these data are documented in the report along with the undistorted compressor overall performance. Also included in the report is the overall performance of the compressor exposed to 14 different distorted-inlet conditions - 10 circumferential patterns and 4 radial patterns. The distortion patterns were introduced using screens that spoiled from 8 to 50 percent of the compressor face area; the distortion screen density, or the area blocked by the screen wire per unit area of screen, varied from 26 to 69 percent

Experimental program for the evaluation of turbofan/turboshaft c conversion technology

A TF34 turbofan engine is being modified to produce shaft power from an output coupling on the fan disk when variable inlet guide vanes are closed to reduce fan airflow. The engine, called a convertible engine, could be used on advanced rotorcraft such as X-wing, ABC (Advanced Blade Concept), and Folding Tilt Rotor, and on V/STOL craft in which two engines are cross-coupled. The engine will be tested on an outdoor static test stand at NASA Lewis Research Center. Steady-state tests will be made to measure performance in turbofan, turboshaft, and combined power output modes. Transient tests will be made to determine the response to the engine and a new digital engine control system for several types of rapid changes in thrust and shaft loads. The paper describes the engine modifications, the test facility equipment, proposed testing techniques for several types of tests, and typical test results predicted from engine performance computer programs

Analytical investigation of nonrecoverable stall

A lumped parameter model of the TF34 engine is formulated to study nonrecoverable stall. Features of the model include forward and reverse flow, radial flow in the fan, and variable corrected speed. The purpose of the study is to point out those parameters to which recoverability is highly sensitive but are not well known. Experimental research may then be directed toward identification of the parameters in that category. Compressor performance in the positive flow region and radial flow in the fan are shown to be important but unknown parameters determining recoverability. Other parameters such as compressor performance during reverse flow and in-stall efficiency have relatively small impact on recoverability

Weight and Isometric Training in Relation to Certain Aspects of Golf Performance

The purpose of this study was to determine whether a weight lifting and isometric exercise program could be developed, which would enable a golfer to increase his distance off the tee without adversely affecting the accuracy of various golf shots. One group of ten subjects was used in this study. This group was tested in the fall of 1966 to determine the distance and accuracy with which they could hit the ball off the tee. The golfers were also tested for the degree of accuracy which they possessed in hitting the chip shot both for distance and angle deviation. They were then put on a training program, of weight lifting and isometric exercises, for an eight week period after Christmas. Comparisons were made between the mean differences for each item on the Initial and final tests. The null hypothesis was assumed in making the comparisons with rejection at the .01 level. This hypothesis was tested with the t technique for the significance of the difference between means derived from correlated scores from small samples. The results of the comparison shewed significant improvement in all of the items tested except driving deviation

Sipping Fuel and Saving Lives: Increasing Fuel Economy without Sacrificing Safety

Demonstrates how new fuel-efficiency technologies make it possible, and advisable, to significantly increase the fuel economy of motor vehicles without compromising their safety