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Diedrich, J. H.

Publications and source records attributed to Diedrich, J. H..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Analytical and physical modeling program for the NASA Lewis Research Center's Altitude Wind Tunnel (AWT)

An effort is currently underway at the NASA Lewis Research Center to rehabilitate and extend the capabilities of the Altitude Wind Tunnel (AWT). This extended capability will include a maximum test section Mach number of about 0.9 at an altitude of 55,000 ft and a -20 F stagnation temperature (octagonal test section, 20 ft across the flats). In addition, the AWT will include an icing and acoustic research capability. In order to insure a technically sound design, an AWT modeling program (both analytical and physical) was initiated to provide essential input to the AWT final design process. This paper describes the modeling program, including the rationale and criteria used in program definition, and presents some early program results.

Abbott, J. M.↗
NASA NTRS1983

Turbofan blade stresses induced by the flow distortion of a VTOL inlet at high angles of attack

A 51-cm-diameter turbofan with a tilt-nacelle VTOL inlet was tested in the Lewis Research Center's 9- by 15-Ft Low Speed Wind Tunnel at velocities up to 72 m/s and angles of attack up to 120 deg. Fan-blade vibratory stress levels were investigated over a full aircraft operating range. These stresses were due to inlet air flow distortion resulting from (1) internal flow separation in the inlet, and (2) ingestion of the exterior nacelle wake. Stress levels are presented, along with an estimated safe operating envelope, based on infinite blade fatigue life.

Williams, R. C.↗
NASA NTRS1981

A summary of V/STOL inlet analysis methods

Methods to analyze the aerodynamic performance of V/STOL inlets at the NASA Lewis Research Center are discussed with emphasis on recent extensions and applications. Methods include the specification of the Kutta condition for a slotted inlet, the calculation of suction and tangential blowing for boundary layer control, and the analysis of auxiliary inlet geometries at angles of attack. An optimum diffuser velocity distribution is also developed, which can result in the shortest no-boundary layer control inlet and the lowest loss for the required amount of diffusion.

Hwang, D. P.↗
NASA NTRS1980

Optimum subsonic, high-angle-of-attack nacelles

Many proposed advanced aircraft - but especially tilt-nacelle, subsonic-cruise, V/STOL aircraft - require nacelles that operate over a wide range of aerodynamic conditions. The optimum design of such nacelles and their inlets is described, including how the inlet low-speed design conditions are selected, the conditions for which the various regions of the inlet are designed, and appropriate criteria of merit. For low-speed operation the optimum internal surface velocity distributions and skin friction distributions are described for three categories of inlets: those without boundary-layer control (BLC), those with BLC, and those with blow-in door slots and retractable slats. Experimental results are presented that show the performance of the various types of inlets. At cruise speed the effect of factors that reduce the nacelle external surface area and the local skin friction is illustrated. These factors are cruise Mach number, inlet throat size, fan-face Mach number, and nacelle contour. The interrelation of these cruise-speed factors with the design requirements for good low-speed performance is discussed. Finally an inlet design without BLC and an optimized inlet design with slots and slats are compared to illustrate the possible reductions in nacelle size.

Luidens, R. W.↗
NASA NTRS1979

Some techniques for reducing the tower shadow of the DOE/NASA mod-0 wind turbine tower

Wind speed profile measurements to measure the effect of a wind turbine tower on the wind velocity are presented. Measurements were made in the wake of scale models of the tower and in the wake of certain full scale components to determine the magnitude of the speed reduction (tower shadow). Shadow abatement techniques tested on the towers included the removal of diagonals, replacement of diagonals and horizontals with round cross section members, installation of elliptical shapes on horizontal members, installation of airfoils on vertical members, and application of surface roughness to vertical members.

Burley, R. R.↗
NASA NTRS1979

An approach to optimum subsonic inlet design

The approach consists of comparing inlet operating requirements with estimated inlet separation characteristics to identify the most critical inlet operating condition. This critical condition is taken to be the design point and is defined by the values of inlet mass flow, free stream velocity, and inlet angle of attack. Optimum flow distributions on the inlet surface are determined to be a high, flat top Mach number distribution on the inlet lip to turn the flow quickly into the inlet and a low, flat bottom skin friction distribution on the diffuser wall to diffuse the flow rapidly and efficiently to the velocity required at the fan face. These optimum distributions are then modified to achieve other desirable flow characteristics. Example applications are given. Extension of the method is suggested.

Luidens, R. W.↗
NASA NTRS1979

Optimum subsonic, high-angle-of-attack nacelles

The optimum design of nacelles that operate over a wide range of aerodynamic conditions and their inlets is described. For low speed operation the optimum internal surface velocity distributions and skin friction distributions are described for three categories of inlets: those with BLC, and those with blow in door slots and retractable slats. At cruise speed the effect of factors that reduce the nacelle external surface area and the local skin friction is illustrated. These factors are cruise Mach number, inlet throat size, fan-face Mach number, and nacelle contour. The interrelation of these cruise speed factors with the design requirements for good low speed performance is discussed.

Luidens, R. W.↗
NASA NTRS1978

Low-speed aerodynamic performance of 50.8-centimeter-diameter noise-suppressing inlets for the Quiet, Clean, Short-haul Experimental Engine (QCSEE)

Two basic inlet concepts, a high throat Mach number (0.79) design and a low throat Mach number (0.60) design, were tested with four diffuser acoustical treatment designs that had face sheet porosity ranging from 0 to 24 percent for the high Mach number inlet and 0 to 28 percent for the low Mach number inlet. The tests were conducted in a low speed wind tunnel at free stream velocities of 0, 41, and 62 m/sec and angles of attack to 50 deg. Inlet throat Mach number was varied about the design value. Increasing the inlet diffuser face sheet porosity resulted in an increase in total pressure loss in the boundary layer for both the high and low Mach number inlet designs, however, the overall effect on inlet total pressure recovery of 0.991 at the design throat Mach number, a free stream velocity of 41 m/sec, and an angle of attack of 50 deg; Inlet flow separation at an angle of attack of 50 deg was encountered with only one inlet configuration the high Mach number design with the highest diffuser face sheet porosity (24 percent).

Abbott, J. M.↗
NASA NTRS1978

An approach to optimum subsonic inlet design

Inlet operating requirements are compared with estimated inlet separation characteristics to identify the most critical inlet operating condition. This critical condition is taken to be the design point and is defined by the values of inlet mass flow, free-stream velocity and inlet angle of attack. Optimum flow distributions on the inlet surface were determined to be a high, flat top Mach number distribution on the inlet lip to turn the flow quickly into the inlet and a flat bottom skin-friction distribution on the diffuser wall to diffuse the flow rapidly and efficiently to the velocity required at the fan face. These optimum distributions are then modified to achieve other desirable flow characteristics. Example applications are given.

Luidens, R. W.↗
NASA NTRS1976

Measurement of model propulsion system noise in a low-speed wind tunnel

Methods are presented for making overall and directional acoustic measurements with forward velocity in the Lewis 9 x 15 V/STOL wind tunnel. Overall acoustic measurements are discussed; the acoustic calibration methods, instrumentation features, and types of experiments are presented. Selected data are presented as examples of the various types of overall measurements that are possible. The method of making directional acoustic measurements is presented, and the necessary alterations to the tunnel, specialized acoustic instrumentation, and calibration details are described. The results indicate that relative overall acoustic measurements can be made successfully and that directional acoustic measurements are feasible.

Diedrich, J. H.↗
NASA NTRS1976

Measurement of model propulsion system noise in a low-speed wind tunnel

Methods are presented for making overall and directional acoustic measurements with forward velocity in the Lewis 9 x 15 V/STOL Wind Tunnel. Overall acoustic measurements are discussed first. The acoustic calibration methods, instrumentation features, and types of experiments are presented. Selected data are presented as examples of the various types of overall measurements that are possible. The method of making directional acoustic measurements is then presented. The necessary alterations to the tunnel, specialized acoustic instrumentation, and calibration details are described. The results indicate that relative overall acoustic measurements can be made successfully and that directional acoustic measurements are feasible.

Diedrich, J. H.↗
NASA NTRS1975

Summary of model VTOL lift fan tests conducted at NASA Lewis Research Center

Early in this decade three model VTOL lift fan studies were conducted in the NASA Lewis Research Center's 9- by 15-foot V/STOL wind tunnel. The first experiment consisted of crossflow tests of a 15-inch diameter fan installed in a two-dimensional wing. The wing was then used for a study of installation effects on lift fan performance. The model tested consisted of three 5.5-inch diameter tip-turbine driven model VTOL lift fans mounted chord-wise in the two-dimensional wing to simulate a pod-type array. For the third program, a pod was attached to the wing, and an investigation was conducted of the effect of design tip speed on the aerodynamic performance and noise of a 15-inch diameter lift fan-in-pod under static and crossflow conditions.

Diedrich, J. H.↗
NASA NTRS1975

Summary of model VTOL lift fan tests conducted at NASA Lewis Research Center

The purpose of the tests was to obtain overall performance and influencing factors as well as detailed measurements of the internal flow characteristics. The first experiment consisted of crossflow tests of a 15-inch diameter fan installed in a two-dimensional wing. Tests were run with and without exit louvers over a range of tunnel speeds, fan speeds, and wing angle of attack. The wing was used for a study of installation effects on lift fan performance. The model tested consisted of three 5.5-inch diameter tip-turbine driven model VTOL lift fans mounted chord-wise in the two-dimensional wing to simulate a pod-type array. Several inlet and exit cover door configurations and an adjacent fuselage panel were tested. For the third program, a pod was attached to the wing, and an investigation was conducted of the effect of design tip speed on the aerodynamic performance and noise of a 15-inch diameter lift fan-in-pod under static and crossflow conditions. Three single VTOL lift fan stages were designed for the same overall total pressure ratio but at three different rotor tip speeds.

Diedrich, J. H.↗
NASA NTRS1973

Performance characteristics of a model VTOL lift fan in crossflow.

This paper presents a summary of principal results obtained from crossflow tests of a model 15-in.-diam lift fan installed in a wing in the NASA Lewis Research Center, 9 by 15 ft V/STOL Propulsion Wind Tunnel. Tests were run with and without exit louvers over a range of tunnel air speeds, fan speeds, and wing angle of attack. Fan thrust in crossflow was influenced by two principal factors: the effects of inflow distortion on blade-row performance, and changes in fan stage operating point brought about by changes in back pressure ratio. In this particular fan, flow separation on the inlet bellmouth did not appear to be a serious problem for crossflow operation.

Lieblein, S.↗
NASA NTRS1972

Installation effects on performance of multiple model V/STOL lift fans.

The location and appendages of a lift fan on a V/STOL aircraft are expected to have a measurable effect on fan performance. To study such installation effects, an experimental program was performed in which the individual performance of multiple VTOL model lift fans was measured. The model tested consisted of three 13.97-cm diameter tip-turbine driven model VTOL lift fans mounted chordwise in a two-dimensional wing to simulate a pod-type array. The performance data provided significant insight into possible thrust variations and losses caused by the presence of cover doors, adjacent fuselage panels, and adjacent fans. The effect of a partial loss of drive air supply on fan performance was also investigated.

Diedrich, J. H.↗
NASA NTRS1972

Fan and wing force data from wind tunnel investigation of a 0.38 meter (15 inch) diameter VTOL model lift fan installed in a two dimensional wing

Test data are presented for a 38-cm (15-in.) diameter, 1.28 pressure ratio model VTOL lift fan installed in a two-dimensional wing and tested in a 2.74-by 4.58-meter (9-by 15-ft)V/STOL wind tunnel. Tests were run with and without exit louvers over a wide range of crossflow velocities and wing angle of attack. Tests were also performed with annular-inlet vanes, inlet bell-mouth surface disconuities, and fences to induce fan windmilling. Data are presented on the axial force of the fan assembly and overall wing forces and moments as measured on force balances for various static and crossflow test conditions. Midspan wing surface pressure coefficient data are also given.

Yuska, J. A.↗
NASA NTRS1972

Installation effects on performance of multiple model V/STOL lift fans

An experimental program was performed in which the individual performance of multiple VTOL model lift fans was measured. The model tested consisted of three 5.5 in. diameter tip-turbine driven model VTOL lift fans mounted chordwise in a two-dimensional wing to simulate a pod-type array. The performance data provided significant insight into possible thrust variations and losses caused by the presence of cover doors, adjacent fuselage panels, and adjacent fans. The effect of a partial loss of drive air supply (simulated gas generator failure) on fan performance was also investigated. The results of the tests demonstrated that lift fan installation variables and hardware can have a significant effect on the thrust of the individual fans.

Diedrich, J. H.↗