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At least 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Single stage, low noise advanced technology fan. Volume 3: Acoustic design

The acoustic design for a half-scale fan vehicle, which would have application on an advanced transport aircraft, is described. The single stage advanced technology fan was designed to a pressure ratio of 1.8 at a tip speed of 503 m/sec (1,650 ft/sec). The two basic approaches taken in the acoustic design were: (1) minimization of noise at the source, and (2) suppression of the generated noise in the inlet and bypass exhaust duct. Suppression of the generated noise is accomplished in the inlet through use of the hybrid concept (wall acoustic treatment plus airflow acceleration suppression) and in the exhaust duct with extensive acoustic treatment including a splitter. The goal of the design was attainment of twenty effective perceived noise decibels (20 EPNdB) below current Federal Air Regulation noise standards for a full-scale fan at the takeoff, cutback, and approach conditions. Predicted unsuppressed and suppressed fore and aft maximum perceived noise levels indicate that the cutback condition is the most critical with respect to the goal, which is probably unattainable for that condition. This is also true for aft radiated noise in the approach condition.

Kazin, S. B.↗
NASA NTRS1975

Two-stage, low noise advanced technology fan. 4: Aerodynamic final report

A two-stage research fan was tested to provide technology for designing a turbofan engine for an advanced, long range commercial transport having a cruise Mach number of 0.85 -0.9 and a noise level 20 EPNdB below current requirements. The fan design tip speed was 365.8m/sec (1200ft/sec);the hub/tip ratio was 0.4; the design pressure ratio was 1.9; and the design specific flow was 209.2 kg/sec/sq m(42.85lbm/sec/sq ft). Two fan-versions were tested: a baseline configuration, and an acoustically treated configuration with a sonic inlet device. The baseline version was tested with uniform inlet flow and with tip-radial and hub-radial inlet flow distortions. The baseline fan with uniform inlet flow attained an efficiency of 86.4% at design speed, but the stall margin was low. Tip-radial distortion increased stall margin 4 percentage points at design speed and reduced peak efficiency one percentage point. Hub-radial distortion decreased stall margin 4 percentage points at all speeds and reduced peak efficiency at design speed 8 percentage points. At design speed, the sonic inlet in the cruise position reduced stall margin one percentage point and efficiency 1.5 to 4.5 percentage points. The sonic inlet in the approach position reduced stall margin 2 percentage points.

Harley, K. G.↗
NASA NTRS1976

A rapid method for optimization of the rocket propulsion system for single-stage-to-orbit vehicles

A rapid analytical method for the optimization of rocket propulsion systems is presented for a vertical take-off, horizontal landing, single-stage-to-orbit launch vehicle. This method utilizes trade-offs between propulsion characteristics affecting flight performance and engine system mass. The performance results from a point-mass trajectory optimization program are combined with a linearized sizing program to establish vehicle sizing trends caused by propulsion system variations. The linearized sizing technique was developed for the class of vehicle systems studied herein. The specific examples treated are the optimization of nozzle expansion ratio and lift-off thrust-to-weight ratio to achieve either minimum gross mass or minimum dry mass. Assumed propulsion system characteristics are high chamber pressure, liquid oxygen and liquid hydrogen propellants, conventional bell nozzles, and the same fixed nozzle expansion ratio for all engines on a vehicle.

Eldred, C. H.↗
NASA NTRS1975

Spinning solid perigee stage

If the Space Transportation System is to serve in the 1980's for launching geostationary satellites that presently use the Delta and Centaur boosters, the cost of STS launches must be competitive. This can be accomplished through the provision of a multiple-launch capability in the orbiter, combined with the design of a low cost, spinning solid perigee kick motor (PKM). The PKM will be attached to the spacecraft and function essentially as the Delta third stage does today.

Rose, H. A.↗
NASA NTRS1975

Reduction of noise from a fan stage for a turbofan engine by use of long-chord acoustically-treated stator vanes

A set of acoustically-treated long-chord vanes was designed to replace the vanes in an existing fan stage to investigate the noise reduction possibilities of both increased stator chord length and this method of incorporating acoustic damping material. The vanes were tested with both active and inactive acoustic surfaces. The inactive tests showed significant broadband noise effects with noise reductions in the middle to high frequencies and an increase at low frequencies. No reduction in blade passage tone was observed, but decreases in the overtones were observed. The tests with the active acoustic treatment showed large noise reductions over a wide frequency range.

Dittmar, J. H.↗
NASA NTRS1975

Use of multiple-stage remote sensing techniques to develop forest stocking equations

Portions of a forest supporting density levels that affect natural resource yields must be quantified to estimate the operational feasibility of a proposed management system. Estimates of average parameters do not necessarily provide complete knowledge, particularly with frequently skewed forest parameters. Instead, another statistic, the portion of a forest supporting minimum density levels would be useful to set realistic limits to the implementation of management systems and to establish priorities for operational programs. Such a statistic can be obtained from solutions of forest stocking equations generated by applications of multiple-stage remote sensing techniques.

Bisson, H. R.↗
NASA NTRS1976

Stage separation study of Nike-Black Brant V Sounding Rocket System

A new Sounding Rocket System has been developed. It consists of a Nike Booster and a Black Brant V Sustainer with slanted fins which extend beyond its nozzle exit plane. A cursory look was taken at different factors which must be considered when studying a passive separation system. That is, one separation system without mechanical constraints in the axial direction and which will allow separation due to drag differential accelerations between the Booster and the Sustainer. The equations of motion were derived for rigid body motions and exact solutions were obtained. The analysis developed could be applied to any other staging problem of a Sounding Rocket System.

Ferragut, N. J.↗
NASA NTRS1976

Noise reduction from the redesign of a fan stage to minimize stator lift fluctuations

An existing fan stage, redesigned to reduce stator lift fluctuations, was acoustically tested for reduced noise generation. The lift fluctuations on the stator were reduced by increasing the stator chord, adjusting incidence angles, and by adjusting the rotor velocity diagrams. The experiments showed significantly reduced broadband noise levels in the middle to high frequencies. Blade passage tone power was not reduced, but decreases in the harmonics were observed. Aerodynamic improvements in both performance and efficiency were obtained.

Dittmar, J. H.↗
NASA NTRS1976

Nozzle selection for optimized single-stage shuttles

A computerized preliminary design procedure has been used to determine rocket-engine bell-nozzle configurations which achieve either minimum gross mass or minimum dry mass on an advanced technology winged single-stage-to-orbit launch vehicle. This procedure evaluates the trade offs between the optimized ascent flight trajectory performance and the flight vehicle sizing driven by the engine mass and propellant requirements. Numerous mission, flight, and vehicle related requirements and constraints are satisfied in this process. Propulsion system configurations which incorporate dual-position nozzles are evaluated and compared to configurations using all fixed nozzles.

Eldred, C. H.↗
NASA NTRS1976

The staging system: Display and edit module

The Display and Edit (D and E) Module described is one of six major modules being developed for the STAGING (STructural Analysis through Generalized INteractive Graphics) System. Several remarks are included concerning the computer environment and the architecture of the data base. The utility of this module is emphasized.

Edwards, E.↗
NASA NTRS1976

Performance of 1.15-pressure-ratio fan stage at several rotor blade setting angles with reverse flow

A 51 cm diameter low pressure ratio fan stage was tested in reverse flow. Survey flow data were taken over the range of rotative speed from 50 percent to 100 percent design speed at several rotor blade setting angles through both flat and feather pitch. Normal flow design values of pressure ratio and weight flow were 1.15 and 29.9 kg/sec with a rotor tip speed of 243.8 m/sec. The maximum thrust in reverse flow was 52.5 percent of design thrust in normal flow.

Kovich, G.↗
NASA NTRS1977

Effect of casing treatment of overall performance of axial-flow transonic fan stage with pressure ratio of 1.75 and tip solidity of 1.5

The effect of a number of casing treatments on the overall performance of a 1.75-pressure-ratio, 423-m/sec-tip-speed fan stage was evaluated. The skewed slot configuration with short-open slots over the midportion of the rotor had a stall margin of 23.5 percent, while the solid casing had a stall margin of 15.0 percent. The skewed slot configuration with long open slots extending ahead of and over portion of rotor displaced the stall line to the lowest flow at all speeds tested. At design speed, the peak efficiency for the long, forward open slots was 1 point less than that for the short midopen slots and 3 points less than that for the solid casing.

Osborn, W. M.↗
NASA NTRS1977

Cold air investigation of 4 1/2-stage turbine with stage loading factor of 4.66 and high specific work output. 1: Overall performance

The turbine developed design specific work output at design speed at a total pressure ratio of 6.745 with a corresponding efficiency of 0.855. The efficiency (0.855)was 3.1 points lower than the estimated efficiency quoted by the contractor in the design report and 0.7 of a point lower than that determined by a reference prediction method. The performance of the turbine, which was a forced vortex design, agreed with the performance determined by the prediction method to about the same extent as did the performance of three reference high stage loading factor turbines, which were free vortex designs.

Whitney, W. J.↗
NASA NTRS1977

Performance of low-pressure-ratio fan stage at two off-design blade setting angles

The overall and blade-element performance of a low pressure ratio, low tip speed fan stage at design speed is presented for tow off-design rotor blade angle settings. The rotor design tip speed is 243.8 m/sec and weight flow per unit annulus area is 175.8 kg/sec. Design weight flow and pressure ratio are 29.9 kg/sec and 1.151, respectively.

Kovich, G.↗
NASA NTRS1977

Stalled and stall-free performance of axial-flow compressor stage with three inlet-guide-vane and stator-blade settings

The performance of the first stage of a transonic, multistage compressor was mapped over a range of inlet-guide-vane and stator-blade settings. Both stall-free and deep-stall performance data were obtained. For the settings tested, as stall was encountered and flow was further reduced, a relatively sharp drop in pressure ratio occurred and was followed by a continuing but more gradual reduction in pressure ratio with reduced flow. The position of the stall line on the map of pressure ratio against equivalent weight flow was essentially unaffected over the range of inlet-guide-vane and stator-blade settings.

Urasek, D. C.↗
NASA NTRS1977

Aerodynamic performance of 0.4066-scale model of JT8D refan stage with S-duct inlet

A scale model of the JT8D refan stage was tested with a scale model of the S-duct inlet design for the refanned Boeing 727 center engine. Detailed survey data of pressures, temperatures, and flow angles were obtained over a range of flows at speeds from 70 to 97 percent of design speed. Two S-duct configurations were tested; one with a bellmouth inlet and the other with a flight lip inlet. The results indicated that the overall performance was essentially unaffected by the distortion generated by the S-duct inlet. The stall weight flow increased by less than 0.5 kg/sec (approximately 1.5% of design flow) with the S-duct inlet compared with that obtained with uniform flow. The detailed measurements indicated that the inlet guide vane (IGV) significantly reduced circumferential variations. For example, the flow angles ahead of the IGV were positive in the right half of the inlet and negative in the left half. Behind the IGV, the flow angles tended to be more uniform circumferentially.

Moore, R. D.↗