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NASA NTRS1980

Energy efficient engine: Fan test hardware detailed design report

A single stage fan and quarter stage booster were designed for the energy efficient engine. The fan has an inlet radius ratio of 0.342 and a specific flow rate of 208.9 Kg/S sq m (42.8 lbm/sec sq ft). The fan rotor has 32 medium aspect ratio (2.597) titanium blades with a partspan shroud at 55% blade height. The design corrected fan tip speed is 411.5 M/S (1350 ft/sec). The quarter stage island splits the total fan flow with approximately 22% of the flow being supercharged by the quarter stage rotor. The fan bypass ratio is 6.8. The core flow total pressure ratio is 1.67 and the fan bypass pressure ratio is 1.65. The design details of the fan and booster blading, and the fan frame and static structure for the fan configuration are presented.

Sullivan, T. J.↗

NASA NTRS1987

Supersonic throughflow fans for high-speed aircraft

Increased need for more efficient long-range supersonic flight has revived interest in the supersonic throughflow fan as a possible component for advanced high-speed propulsion systems. A fan that can operate with supersonic inlet axial Mach numbers would reduce the inlet losses incurred in diffusing the flow from supersonic Mach numbers to a subsonic one at the fan face. In addition, the size and weight of an all-supersonic inlet will be substantially lower than those of a conventional inlet. However, the data base for components of this type is practically nonexistent. Therefore, in order to furnish the required information for assessing the potential for this type of fan, the NASA Lewis Research Center has begun a program to design, analyze, build, and test a fan stage that is capable of operating with supersonic axial velocities from inlet to exit. The objectives are to demonstrate the feasibility and potential of supersonic throughflow fans, to gain a fundamental understanding of the flow physics associated with such systems, and to develop an experimental data base for design and analysis code validation. A brief overview of past supersonic throughflow fan activities are provided; the technology needs discussed; the design of a supersonic throughflow fan stage, a facility inlet, and a downstream diffuser described; and the results from the analysis codes used in executing the design are presented. Also presented is an engine concept intended to permit establishing supersonic throughflow within the fan on the runway and maintaining the supersonic throughflow condition within the fan throughout the flight envelope.

Ball, Calvin L.↗

NASA NTRS1993

Summary of Lift and Lift/Cruise Fan Powered Lift Concept Technology

A summary is presented of some of the lift and lift/cruise fan technology including fan performance, fan stall, ground effects, ingestion and thrust loss, design tradeoffs and integration, control effectiveness and several other areas related to vertical short takeoff and landing (V/STOL) aircraft conceptual design. The various subjects addressed, while not necessarily pertinent to specific short takeoff/vertical landing (STOVL) supersonic designs being considered, are of interest to the general field of lift and lift/cruise fan aircraft designs and may be of importance in the future. The various wind tunnel and static tests reviewed are: (1) the Doak VZ-4 ducted fan, (2) the 0.57 scale model of the Bell X-22 ducted fan aircraft, (3) the Avrocar, (4) the General Electric lift/cruise fan, (5) the vertical short takeoff and landing (V/STOL) lift engine configurations related to ingestion and consequent thrust loss, (6) the XV-5 and other fan-in-wing stall consideration, (7) hybrid configurations such as lift fan and lift/cruise fan or engines, and (8) the various conceptual design studies by air-frame contractors. Other design integration problems related to small and large V/STOL transport aircraft are summarized including lessons learned during more recent conceptual design studies related to a small executive V/STOL transport aircraft.

Cook, Woodrow L.↗

NASA NTRS1997

Advanced Low-Noise Research Fan Stage Design

This report describes the design of the Advanced Low-Noise Research Fan stage. The fan is a variable pitch design, which is designed at the cruise pitch condition. Relative to the cruise setting, the blade is closed at takeoff and opened for reverse thrust operation. The fan stage is a split flow design with fan exit guide vanes (FEGVs) and core stators. The fan stage design is combined with a nacelle and engine core duct to form a powered fan/nacelle subscale model. This model is intended for use in combined aerodynamic, acoustic, and structural testing in a wind tunnel. The fan has an outer diameter of 22 in. and a hub-to-tip of 0.426 in., which allows the use of existing NASA fan and cowl force balance and rig drive systems. The design parameters were selected to permit valid acoustic and aerodynamic comparisons with the Pratt & Whitney (P&W) 17- and 22-in. rigs previously tested under NASA contract. The fan stage design is described in detail. The results of the design axisymmetric and Navier-Stokes aerodynamic analysis are presented at the critical design conditions. The structural analysis of the fan rotor and attachment is included. The blade and attachment are predicted to have adequate low-cycle fatigue life and an acceptable operating range without resonant stress or flutter. The stage was acoustically designed with airfoil counts in the FEGV and core stator to minimize noise. A fan/FEGV tone analysis developed separately under NASA contract was used to determine the optimum airfoil counts. The fan stage was matched to the existing nacelle, designed under the previous P&W low-noise contract, to form a fan/nacelle model for wind tunnel testing. It is an axisymmetric nacelle for convenience in testing and analysis. Previous testing confirmed that the nacelle performed as required at various aircraft operating conditions.

Neubert, Robert↗

NASA NTRS1998

Boeing 18-Inch Fan Rig Broadband Noise Test

The purposes of the subject test were to identify and quantify the mechanisms by which fan broadband noise is produced, and to assess the validity of such theoretical models of those mechanisms as may be available. The test was conducted with the Boeing 18-inch fan rig in the Boeing Low-Speed Aeroacoustic Facility (LSAF). The rig was designed to be particularly clean and geometrically simple to facilitate theoretical modeling and to minimize sources of interfering noise. The inlet is cylindrical and is equipped with a boundary layer suction system. The fan is typical of modern high-by-pass ratio designs but is capable of operating with or without fan exit guide vanes (stators), and there is only a single flow stream. Fan loading and tip clearance are adjustable. Instrumentation included measurements of fan performance, the unsteady flow field incident on the fan and stators, and far-field and in-duct acoustic fields. The acoustic results were manipulated to estimate the noise generated by different sources. Significant fan broadband noise was found to come from the rotor self-noise as measured with clean inflow and no boundary layer. The rotor tip clearance affected rotor self-noise somewhat. The interaction of the rotor with inlet boundary layer turbulence is also a significant source, and is strongly affected by rotor tip clearance. High level noise can be generated by a high-order nonuniform rotating at a fraction of the fan speed, at least when tip clearance and loading are both large. Stator-generated noise is the loudest of the significant sources, by a small margin, at least on this rig. Stator noise is significantly affected by propagation through the fan.

Ganz, Ulrich W.↗

NASA NTRS2000

A Method to Further Reduce the Perceived Noise of Low Tip Speed Fans

The use of low tip speed, high bypass ratio fans is a method for reducing the noise of turbofan jet engines. These fans typically have a low number of rotor blades and a number of stator vanes sufficient to achieve cut-off of the blade passing tone. Their perceived noise levels are typically dominated by broadband noise caused by the rotor wake turbulence - stator interaction mechanism. A 106 bladed, 1100 ft/sec takeoff tip speed fan, the Alternative Low Noise Fan, has been tested and shown to have reduced broadband noise. This reduced noise is believed to be the result of the high rotor blade number. Although this fan with 106 blades would not be practical with materials as they exist today, a fan with 50 or so blades could be practically realized. A noise estimate has indicated that such a 50 bladed, low tip speed fan could be 2 to 3 EPNdB quieter than an 18 bladed fan. If achieved, this level of noise reduction would be significant and points to the use of a high blade number, low tip speed fan as a possible configuration for reduced fan noise.

Dittmar, James H.↗

NASA NTRS2004

Large Well-exposed Alluvial Fans in Deep Late-Noachian Craters

Large, fresh-appearing alluvial fans (typically greater than 10 km long) have been identified during a systematic search of 100 m/pixel low-sun daylight THEMIS IR imaging in deep late-Noachian or early- Hesperian craters. Our study of these fans was augmented with MOLA-derived topography and high-resolution MOC and THEMIS VIS images where available. The influence of alluvial fan deposition on the topography of crater floors has been recognized in previous topographic studies. Recent Mars Odyssey-era studies have also identified and described in detail a fluvial delta or fan of approximately the same age as the alluvial fans of this study. Our results, at the time of this writing, indicate that these fans are only found in less than 5% of all craters = 70 km in diameter within a large study region. In every case the fan-containing craters were restricted to a latitude belt between 20 deg S and 30 deg S. All of which had significant topographic relief and appeared morphologically younger than typical mid-Noachian craters in the size range. However, large fans were not found in the most pristine (and presumably youngest) craters in this size range. Most Martian fans have morphologies consistent with terrestrial debris-flow-dominated fans.

Moore, J. M.↗

NASA NTRS2004

Large Well-Exposed Alluvial Fans in Deep Late-Noachian Craters

Large, fresh-appearing alluvial fans (typically greater than 10 km long) have been identified during a systematic search of 100 m/pixel low-sun daylight THEMIS IR imaging in deep late-Noachian or early-Hesperian craters. Our study of these fans was augmented with MOLA-derived topography and high-resolution MOC and THEMIS VIS images where available. The influence of alluvial fan deposition on the topography of crater floors has been recognized in previous topographic studies. Recent Mars Odyssey-era studies have also identified and described in detail a fluvial delta or fan of approximately the same age as the alluvial fans of this study. Our results, at the time of this writing, indicate that these fans are only found in less than 5% of all craters greater than or equal to 70 kilometers in diameter within a large study region. In every case the fan-containing craters were restricted to a latitude belt between 20 degrees S and 30 degrees S. All of which had significant topographic relief and appeared morphologically younger than typical mid-Noachian craters in the size range. However, large fans were not found in the most pristine (and presumably youngest) craters in this size range. Most Martian fans have morphologies consistent with terrestrial debris-flow-dominated fans.

Moore, J. M.↗

NASA NTRS2008

Low Frequency Noise Contamination in Fan Model Testing

Aircraft engine noise research and development depends on the ability to study and predict the noise created by each engine component in isolation. The presence of a downstream pylon for a model fan test, however, may result in noise contamination through pylon interactions with the free stream and model exhaust airflows. Additionally, there is the problem of separating the fan and jet noise components generated by the model fan. A methodology was therefore developed to improve the data quality for the 9 15 Low Speed Wind Tunnel (LSWT) at the NASA Glenn Research Center that identifies three noise sources: fan noise, jet noise, and rig noise. The jet noise and rig noise were then measured by mounting a scale model of the 9 15 LSWT model fan installation in a jet rig to simulate everything except the rotating machinery and in duct components of fan noise. The data showed that the spectra measured in the LSWT has a strong rig noise component at frequencies as high as 3 kHz depending on the fan and airflow fan exit velocity. The jet noise was determined to be significantly lower than the rig noise (i.e., noise generated by flow interaction with the downstream support pylon). A mathematical model for the rig noise was then developed using a multi-dimensional least squares fit to the rig noise data. This allows the rig noise to be subtracted or removed, depending on the amplitude of the rig noise relative to the fan noise, at any given frequency, observer angle, or nozzle pressure ratio. The impact of isolating the fan noise with this method on spectra, overall power level (OAPWL), and Effective Perceived Noise Level (EPNL) is studied.

Brown, Clifford A.↗

NASA NTRS2009

Channel Networks on Large Fans: Refining Analogs for the Ridge-forming Unit, Sinus Meridiani

Stream channels are generally thought of as forming within confined valley settings, separated by interfluves. Sinuous ridges on Mars and Earth are often interpreted as stream channels inverted by subsequent erosion of valley sides. In the case of the ridge-forming unit (RFU), this interpretation fails to explain the (i) close spacing of the ridges, which are (ii) organized in networks, and which (iii) cover large areas (approximately 175,000 km (exp 2)). Channel networks on terrestrial fans develop unconfined by valley slopes. Large fans (100s km long) are low-angle, fluvial features, documented worldwide, with characteristics that address these aspects of the RFU. Ridge patterns Channels on large fans provide an analog for the sinuous and elongated morphology of RFU ridges, but more especially for other patterns such as subparallel, branching and crossing networks. Branches are related to splays (delta-like distributaries are rare), whose channels can rejoin the main channel. Crossing patterns can be caused by even slight sinuosity splay-related side channels often intersect. An avulsion node distant from the fan apex, gives rise to channels with slightly different, and hence intersecting, orientations. Channels on neighboring fans intersect along the common fan margin. 2. Network density Channels are the dominant feature on large terrestrial fans (lakes and dune fields are minor). Inverted landscapes on subsequently eroded fans thus display indurated channels as networks of significantly close-spaced ridges. 3. Channel networks covering large areas Areas of individual large terrestrial fans can reach >200,000 km 2 (105-6 km 2 with nested fans), providing an analog for the wide area distribution of the RFU.

Wilkinson, Justin↗

NASA NTRS2010

Development of a Fan for Future Space Suit Applications

NASA's next generation space suit system will place new demands on the fan used to circulate breathing gas through the ventilation loop of the portable life support system. Long duration missions with frequent extravehicular activities (EVAs), the requirement for significant increases in reliability and durability, and a mission profile that imposes strict limits on weight, volume and power create the basis for a set of requirements that demand more performance than is available from existing fan designs. This paper describes the development of a new fan to meet these needs. A centrifugal fan was designed with a normal operating speed of approximately 39,400 rpm to meet the ventilation flow requirements while also meeting the aggressive minimal packaging, weight and power requirements. The prototype fan also operates at 56,000 rpm to satisfy a second operating condition associated with a single fan providing ventilation flow to two spacesuits connected in series. This fan incorporates a novel nonmetallic "can" to keep the oxygen flow separate from the motor electronics, thus eliminating ignition potential. The nonmetallic can enables a small package size and low power consumption. To keep cost and schedule within project bounds a commercial motor controller was used. The fan design has been detailed and implemented using materials and approaches selected to address anticipated mission needs. Test data is presented to show how this fan performs relative to anticipated ventilation requirements for the EVA portable life support system. Additionally, data is presented to show tolerance to anticipated environmental factors such as acoustics, shock, and vibration. Recommendations for forward work to progress the technology readiness level and prepare the fan for the next EVA space suit system are also discussed.

Paul. Heather L.↗

NASA NTRS2010

Quiet, Efficient Fans for Spaceflight: An Overview of NASA's Technology Development Plan

A Technology Development Plan to improve the aerodynamic and acoustic performance of spaceflight fans has been submitted to NASA s Exploration Technology Development Program. The plan describes a research program intended to make broader use of the technology developed at NASA Glenn to increase the efficiency and reduce the noise of aircraft engine fans. The goal is to develop a set of well-characterized government-owned fans nominally suited for spacecraft ventilation and cooling systems. NASA s Exploration Life Support community will identify design point conditions for the fans in this study. Computational Fluid Dynamics codes will be used in the design and analysis process. The fans will be built and used in a series of tests. Data from aerodynamic and acoustic performance tests will be used to validate performance predictions. These performance maps will also be entered into a database to help spaceflight fan system developers make informed design choices. Velocity measurements downstream of fan rotor blades and stator vanes will also be collected and used for code validation. Details of the fan design, analysis, and testing will be publicly reported. With access to fan geometry and test data, the small fan industry can independently evaluate design and analysis methods and work towards improvement.

Koch, L. Danielle↗

NASA NTRS2010

Broadband Fan Noise Prediction System for Turbofan Engines: Validation and Test Cases - Volume 3

Pratt & Whitney has developed a Broadband Fan Noise Prediction System (BFaNS) for turbofan engines. This system computes the noise generated by turbulence impinging on the leading edges of the fan and fan exit guide vane, and noise generated by boundary-layer turbulence passing over the fan trailing edge. BFaNS has been validated on three fan rigs that were tested during the NASA Advanced Subsonic Technology Program (AST). The predicted noise spectra agreed well with measured data. The predicted effects of fan speed, vane count, and vane sweep also agreed well with measurements. The noise prediction system consists of two computer programs: Setup_BFaNS and BFaNS. Setup_BFaNS converts user-specified geometry and flow-field information into a BFaNS input file. From this input file, BFaNS computes the inlet and aft broadband sound power spectra generated by the fan and FEGV. The output file from BFaNS contains the inlet, aft and total sound power spectra from each noise source. This report is the third volume of a three-volume set documenting the Broadband Fan Noise Prediction System: Volume 1: Setup_BFaNS User s Manual and Developer s Guide; Volume 2: BFaNS User s Manual and Developer s Guide; and Volume 3: Validation and Test Cases. The present volume begins with an overview of the Broadband Fan Noise Prediction System, followed by validation studies that were done on three fan rigs. It concludes with recommended improvements and additional studies for BFaNS.

Morin, Bruce L.↗

NASA NTRS2019

Conceptual Design of a Counter-Rotating Fan System for Distributed Boundary Layer Ingesting Propulsion

The present paper details the design of the counter rotating fans for a Turboelectric Distributed Propulsion (TeDP) system. Sixteen propulsors installed in mail-slot-shape nacelles are embedded on an aerodynamically optimized hybrid wing-body configuration. The hybrid-wing/body (HWB) configuration which was previously designed to satisfy the conditions of trim, longitudinally static stability and specific cargo space is employed as the baseline configuration in pursuing an optimal distributed propulsion system. A set of distributed propulsors is conceptually designed and the collective performance is evaluated against the target thrust mandated by the mission requirements. The concept of the distributed propulsion allows the fan pressure ratio to be around 1.27~1.32 for the target thrust. In addition, further splitting of the fan pressure ratio by using the counter-rotating fans for each slot realizes the target pressure ratio with low tip speed. In the distributed propulsion system, the nature of the flow conditions and/or the thickness of the ingested boundary layer may differ and result in different propulsive reaction of each individual propulsor. The optimization is, thus, approached from both the propulsion system and individual propulsor perspectives. An optimal distribution of the thrust and power output is determined by how the system utilizes each passage's propulsive characteristics and its interaction with the airframe. These system level analysis and optimization are conducted using an actuator disk model to account for the propulsion-airframe integration numerically. With respect to the propulsor level, aerodynamic shape optimizations of the fan blades are performed in a sequential multi-objective optimization process for various design objectives, such as mass flow rate condition, fan pressure ratio, efficiency and the exit flow angle of the fan stage by using a genetic algorithm, NSGA-II. The radial chord distribution, and meanline distribution of the rotors are designed on the circumferentially averaged axi-symmetric inlet profiles and tested on the six inlet profiles from six divided sectors to reckon flow distortion. The performances of the counter rotating fans are, thus, evaluated accordingly for obtaining distortion tolerant fan. The performance of the distributed propulsion system is evaluated by two CFD tools, i.e., a multi-stage turbo-machinery CFD code and one propulsion-airframe integration flow solver coupled with a body-force model. The optimized boundary layer ingestion propulsion system of 16 distributed slots not only reaches the system target thrust, but also delivers a close to 20% fuel saving benefit against its counterpart 12 distributed clean inlet propulsion system.

Boundary-Layer-Ingestion Propulsion↗

NASA NTRS2023

Quiet Spacecraft Cabin Ventilation Fan: Vibration Measurements Results

Quiet, efficient fans with minimal vibrations are needed to maximize the mechanical life of atmospheric revitalization system fans used for human life support systems for long duration space exploration missions. Several metal spacecraft cabin ventilation fan prototypes have been designed, built, and tested at the NASA Glenn Research Center Acoustical Testing Laboratory. Tests performed in 2021 of the first prototype of the metal fan measured vibrations greater than desired at design point speed and backpressure conditions. To try to reduce those vibrations, a second prototype of the fan design was developed which included a new lighter rotor with a tighter balance tolerance, a new collet to attach the rotor to the motor shaft more securely and repeatably, and a new bracket to center and hold the motor in the fan centerbody more precisely. The second prototype of the fan was tested in 2023 and the vibrations were measured with the fan operating at design point speeds in isolation but not throttled to design point back pressure conditions since it was not installed with inlet and exhaust ducting. Peak vibration was reduced from 4 mm/s to 1 mm/s. This paper is part of a series of reports documenting the performance of the prototype fan.

Fan↗

NASA NTRSDate not supplied

Spacecraft Cabin Ventilation Fan Research at NASA

NASA has recently made the geometry and solid model for a spacecraft cabin ventilation fan prototype available to the public via electronic file downloads from the NASA Technical Reports Server. This fan can be used for research and development by many organizations. The NASA Quiet Space Fan is 8.89 cm (3.50 in) in diameter, 22.9 cm (9.00 in) long, and the metal fan weighs 1.63 kg (3.6 lbm). The fan was designed to generate a system total pressure rise of 906 Pa (3.64 inches of water) at 0.709 m3/s (150.3 cfm) of airflow at 12,000 rpm (at 21.1ºC (70ºF) and 14.7 psia). Performance measured using standardized techniques showed good agreement with design and predicted values. A low-noise blade-vane count was chosen to reduce tonal noise generated by rotor-stator interaction for the first three blade passing frequency harmonics. In-duct microphone array measurements indicated that the most evident tones occur at frequencies of 1,800 Hz (1 BPF) and 7,200 Hz (4 BPF). Using reverberant room standard testing methods, the A-weighted sound power level for the fan operating at design point conditions was measured to be 71 dBA. This report describes the current set of publicly available information for this fan. The fan was designed, optimized, and tested with tools and techniques that NASA has traditionally used for turbofan engine research. This demonstrates that technology developed for aerospace applications can be used more broadly, since quiet and efficient fans are needed for many ventilation systems in spacecraft, aircraft, watercraft, land vehicles, and buildings.

fan↗

NASA NTRS1976

Acoustic and aerodynamic performance of a 1.83-meter (6-ft) diameter 1.25-pressure-ratio fan (QF-8)

A 1.25-pressure-ratio 1.83-meter (6-ft) tip diameter experimental fan stage with characteristics suitable for engine application on STOL aircraft was tested for acoustic and aerodynamic performance. The design incorporated proven features for low noise, including absence of inlet guide vanes, low rotor blade tip speed, low aerodynamic blade loading, and long axial spacing between the rotor and stator blade rows. The fan was operated with five exhaust nozzle areas. The stage noise levels generally increased with a decrease in nozzle area. Separation of the acoustic one-third octave results into broadband and pure-tone components showed the broadband noise to be greater than the corresponding pure-tone components. The sideline perceived noise was highest in the rear quadrants. The acoustic results of QF-8 were compared with those of two similar STOL application fans in the test series. The QF-8 had somewhat higher relative noise levels than those of the other two fans. The aerodynamic results of QF-8 and the other two fans were compared with corresponding results from 50.8-cm (20-in.) diam scale models of these fans and design values. Although the results for the full-scale and scale models of the other two fans were in reasonable agreement for each design, the full-scale fan QF-8 results showed poor performance compared with corresponding model results and design expectations. Facility effects of the full-scale fan QF-8 installation were considered in analyzing this discrepancy.

Woodward, R. P.↗

NASA NTRS1980

Application of coherence in fan noise studies

A study of fan noise was made by using the coherence function to obtain far field spectra that were coherent with the fan rotational rate. Choosing fan rotational rate as one of the two variables yielded new information about the far field noise generated during static fan testing. As a result of this coherent data processing, the inlet fan-tone noise present in static testing was determined to be mostly random when the rotor-alone and rotor-stator interaction tones were cut off. After the rotor-alone sound field was cut on, the sound pressure became coherent, and the angular extent of high coherence increased as fan speed was increased. In addition, the sound field was organized as a pattern of lobes whose amplitude varied slowly with time. Additional fan test results indicate that operating the fan with an inflow control device can partially reduce the fan-tone noise levels to those produced by coherent processing.

Balombin, J. R.↗