US20110277447A1 - Engine, Particularly CROR Engine, for an Aircraft - Google Patents

Engine, Particularly CROR Engine, for an Aircraft Download PDF

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Publication number
US20110277447A1
US20110277447A1 US13/190,990 US201113190990A US2011277447A1 US 20110277447 A1 US20110277447 A1 US 20110277447A1 US 201113190990 A US201113190990 A US 201113190990A US 2011277447 A1 US2011277447 A1 US 2011277447A1
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United States
Prior art keywords
rotor
engine
blades
geometric parameter
frequency
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Abandoned
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US13/190,990
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English (en)
Inventor
Arne Stürmer
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Deutsches Zentrum fuer Luft und Raumfahrt eV
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Deutsches Zentrum fuer Luft und Raumfahrt eV
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Assigned to DEUTSCHES ZENTRUM FUR LUFT- UND RAUMFAHRT E.V. reassignment DEUTSCHES ZENTRUM FUR LUFT- UND RAUMFAHRT E.V. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: STUERMER, ARNE
Publication of US20110277447A1 publication Critical patent/US20110277447A1/en
Abandoned legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C11/00—Propellers, e.g. of ducted type; Features common to propellers and rotors for rotorcraft
    • B64C11/46—Arrangements of, or constructional features peculiar to, multiple propellers
    • B64C11/48—Units of two or more coaxial propellers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64C—AEROPLANES; HELICOPTERS
    • B64C11/00—Propellers, e.g. of ducted type; Features common to propellers and rotors for rotorcraft
    • B64C11/30—Blade pitch-changing mechanisms
    • B64C11/306—Blade pitch-changing mechanisms specially adapted for contrarotating propellers
    • B64C11/308—Blade pitch-changing mechanisms specially adapted for contrarotating propellers automatic
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02K—JET-PROPULSION PLANTS
    • F02K3/00—Plants including a gas turbine driving a compressor or a ducted fan
    • F02K3/02—Plants including a gas turbine driving a compressor or a ducted fan in which part of the working fluid by-passes the turbine and combustion chamber
    • F02K3/04—Plants including a gas turbine driving a compressor or a ducted fan in which part of the working fluid by-passes the turbine and combustion chamber the plant including ducted fans, i.e. fans with high volume, low pressure outputs, for augmenting the jet thrust, e.g. of double-flow type
    • F02K3/072—Plants including a gas turbine driving a compressor or a ducted fan in which part of the working fluid by-passes the turbine and combustion chamber the plant including ducted fans, i.e. fans with high volume, low pressure outputs, for augmenting the jet thrust, e.g. of double-flow type with counter-rotating, e.g. fan rotors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
    • B64D27/00—Arrangement or mounting of power plants in aircraft; Aircraft characterised by the type or position of power plants
    • B64D2027/005—Aircraft with an unducted turbofan comprising contra-rotating rotors, e.g. contra-rotating open rotors [CROR]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T50/00—Aeronautics or air transport
    • Y02T50/60—Efficient propulsion technologies, e.g. for aircraft

Definitions

  • the invention relates to an engine for an aircraft flying in a cruise flight direction.
  • the invention relates to an engine for an aircraft flying in a cruise flight direction, which comprises at least one rotor driven about a rotor axis oriented in the cruise flight direction and having a plurality of rotor blades, wherein at least one geometric parameter of the rotor blades that influences the propulsion characteristics of the rotor is variable.
  • the invention relates to such an engine for an aircraft which is designated as a CROR (Contra Rotating Open Rotor) drive or engine, and in which two open rotors are driven in opposite directions about a common rotor axis oriented in the cruise flight direction of the aircraft.
  • CROR Contra Rotating Open Rotor
  • the formulation “rotor axis oriented in the cruise flight direction” used here is not intended to mean that the rotor axis has to be exactly parallel to the cruise flight direction of the aircraft. Instead there may be a pitch angle or pitch between the rotor axis and the cruise flight direction. Further, there will typically be a variation of the pitch of the rotor axis over different flight configurations of the aircraft. In the present invention, however, the pitch of the rotor axis remains comparatively small and is always smaller than 45° . As a rule, it remains below 15° . In the present invention, it is also possible, but by no means mandatory, to track the cruise flight direction with the rotor axis of the engine. Usually, the rotor axis will be fixed with regard to the structure of the aircraft to which the engine is mounted.
  • Aircraft with engines comprising at least one rotor driven about a rotor axis oriented in the cruise flight direction of the aircraft, which are generally designated as propeller-driven aircraft, display basic advantages in short-haul flight operation as compared to jet-driven aircraft. This particularly applies to aircraft with CROR engines.
  • Propeller-driven aircraft are also connected with general disadvantages.
  • the excitation of vibrations in the structure of a propeller-driven aircraft, i.e. of structure-borne noise, and of air-borne noise at a frequency which is a product of the number of blades of the rotors and their rotational frequency as well as higher harmonics thereof belongs to these disadvantages.
  • interaction tones provide a further source of noise.
  • Interaction tones are generated by the interaction of different flows of both rotors, like for example of blade tip vortices and blade wakes.
  • the frequencies of the interaction tones results from arbitrary sums of the products of the blade numbers and the rotational frequency of the rotors and of higher harmonics thereof.
  • blades of propellers and open rotors are directly subject to any variations of the incident flow resulting from pitch or stall effects, which may result in azimuthally variable blade loads and thus also in generation of noise.
  • a variability of a geometric parameter which influences the propulsion of the rotor serves for having a further variable for adjusting the thrust of the engine besides the rotational frequency of the rotor.
  • the geometric parameter influencing the propulsion of the rotor is simultaneously adjusted for all rotor blades of the rotor, and this is done at a very low frequency as compared to the rotational frequency of the rotor.
  • the geometric parameter influencing the propulsion of the rotor is the pitch angle of the profile of the rotor blades with regard to their plane of rotation about the rotor axis.
  • a periodic variation of the pitch angle of the individual rotor blades of a rotor is known from helicopters and is a precondition for a lateral movement of helicopters having a rotor axis which is oriented essentially vertically.
  • US 2006/0097103 A1 discloses an integrated propulsion and guiding system for an aircraft in which the blade pitch variation principle of a helicopter is used for an engine having a rotor axis which is not oriented vertically but which is strongly inclined with regard to the cruise flight direction of the aircraft.
  • a dynamic pitch control for wind power plants is known from DE 202 20 134 U1.
  • the energy take-up of the individual rotor blades is determined.
  • the pitch angle, i.e. the angle of incidence, of the individual rotor blades is adjusted for homogenizing the energy take-up of all rotor blades. In this way, the torque transmitted to the drive train of the wind power plant is more uniformly distributed over the entire flow area covered by the rotor blades.
  • a engine for an aircraft which comprises at least one rotor driven about a rotor axis oriented in the cruise flight direction of the aircraft, and in which a generation of noise which increases with the performance or efficiency of the engine or which is due to stall effects is reduced or even avoided.
  • the present invention relates to a engine for an aircraft flying in a cruise flight direction.
  • the engine comprises at least one rotor having a plurality of rotor blades.
  • the at least one rotor is driven about a rotor axis at a rotational frequency; the rotor axis is oriented in the cruise flight direction of the aircraft; and at least one geometric parameter of the rotor blades that influences the propulsion characteristics of the rotor is variable.
  • the engine of the present invention comprises a controller which periodically varies the geometric parameter of the rotor blades at at least one frequency. This frequency is at least as high as the rotational frequency of the rotor.
  • the present invention relates to a Contra Rotating Open Rotor (CROR) engine for an aircraft flying in a cruise flight direction.
  • the CROR engine comprises a first open rotor having a first number of rotor blades, and a second open rotor having a second number of rotor blades.
  • the first number and the second number of rotor blades are equal; the first and the second rotors are driven about a common rotor axis in opposite rotational directions at same rotational frequencies; the rotor axis is oriented in the cruise flight direction of the aircraft; the first rotor is arranged in front of the second rotor with regard to the cruise flight direction; and at least one geometric parameter of the rotor blades of the second rotor that influences the blade loading of the second rotor is variable.
  • the CROR engine of the present invention further comprises a controller which periodically varies the geometric parameter of all blades of the second rotor at the same time and at at least one frequency depending on a relative angle position of the first rotor and the second rotor. This frequency is at least 2 n times as high as the rotational frequencies of the first and second rotors, n being the equal number of blades of the first and the second rotors.
  • FIG. 1 is a perspective view on a CROR engine with two rotors each having eight rotor blades.
  • FIG. 2 is a side view on the CROR engine according to FIG. 1 ;
  • FIG. 3 shows a front view on a CROR according to FIGS. 1 and 2 , and a plot of the unsteady blade loads over the rotation angle of the two rotors of the CROR engine.
  • the geometric parameter of the rotor blades which is variable, and which influences the propulsive force of the rotor is periodically varied by a controller at at least one frequency which is at least as high as the rotational frequency of the rotor.
  • the geometric parameter of each rotor blade which influences the propulsion characteristics of the rotor, is at least once changed and returned to its starting value over each rotation of the rotor blade about the rotor axis.
  • the general intention of the present invention is to avoid unsteady loads on the rotor blades by which vibrations, particularly noise, may be excited. In principle, this is achieved in that different incident flows on each individual rotor blade over its various rotational positions about the rotor axis are compensated for by varying its geometric parameter in such a way that the load on the rotor blade is kept constant to an as far extent as possible.
  • the frequency at which the controller has to vary the geometric parameter for keeping the load constant depends on the particularities of the engine. As a rule, it is as high as the rotational frequency of the rotor or it is a plurality thereof.
  • the controller may vary the geometric parameter of the individual rotor blades depending on their angle position with regard to an engine mount of the engine.
  • the location of the engine mount by which the engine is mounted to the structure of its aircraft influences the flow incident on the rotor and particularly the distribution of different incident flows over the flow area covered by the rotor. These influences are due to the engine mount itself or due to a resulting location of the engine with regard to, for example, a wing of the aircraft.
  • a known phenomenon in this regard is the wing box humming in propeller-driven aircraft, which is caused by the individual rotor blades passing through the flow areas in front of the high pressure side and in front of the low pressure side of the wing. By means of the present invention, this wing box humming may be reduced if not avoided completely.
  • the controller preferably varies the geometric parameter in such a way that any unsteady forces to which the rotor blades are subjected are minimized.
  • force sensors may be provided at the rotor blades whose signals are supplied to the controller as a value to be kept constant.
  • the controller is a closed loop controller for keeping the force signals constant.
  • the controller may also be designed in such a way that it minimizes a secondary effect of the instationary incident flow on the rotor blades in that it varies the geometric parameter in such a way that excitations of air-borne or solid-borne noise by the rotor are minimized.
  • corresponding vibration sensors for monitoring the respective noise are to be provided whose signals are supplied to the controller.
  • the controller is a closed loop controller which minimizes the supplied vibration signals.
  • the present invention is particularly intended for use with engines comprising open rotors.
  • the engine according to the present invention is a CROR engine having two open rotors driven in opposite directions about a common rotor axis.
  • the controller at least varies the geometric parameter of the rotor blades of the back rotor, i.e. of the rotor located in a more downstream position with regard to the incident flow. Additionally, the controller may also vary the same or another geometric parameter of the blades of the front rotor.
  • the controller may vary the geometric parameter with all rotor blades of the back rotor always at the same time to compensate for a varying incident flow on the rotor blades of the back rotor.
  • the controller may generally vary the geometric parameter of the rotor blades of the back rotor depending on the relative angle position of both rotors, as this relative angle position determines the variation of the flow incident on the rotor blades of the back rotor by the rotor blades of the front rotor.
  • the frequency at which the controller varies the geometric parameter influencing the propulsion characteristics in a CROR engine is preferably at least 2 n times as high as the rotational frequency of its two rotors.
  • n is the blade number of the front rotor.
  • the absolute frequency at which the controller varies the geometric parameter of the Blades is in a typical range from 10 to 250 Hz.
  • the geometric parameter influencing the propulsion characteristics of the rotor may particularly be the angle of incidence of the respective rotor blade which is also designated as the pitch of the rotor blade. It may, however, also be a torsion of the respective rotor blade or the airfoil shape distribution of the respective rotor blade should this deometry of the rotor blades be dynamically variable.
  • the CROR engine is designed to be mounted in a pusher configuration to the aircraft.
  • variations of the flow incident on the rotor blades of both rotors due to, for example, a pylon to which the engine is attached may also be compensated for by the variation of the geometric parameter influencing the propulsion characteristics of the rotor blades according to the present invention to such an extent that no vibration, particularly no noise is induced by them.
  • FIGS. 1 and 2 depict an engine 1 which is a so-called CROR engine 2 .
  • a CROR engine has two rotors 3 and 4 one arranged behind the other which are rotating in opposite directions about a common rotor axis 5 .
  • Both rotors 3 and 4 are open rotors in which the incident flow is not limited in radial direction with regard to the rotor axis 5 .
  • both rotors 3 and 4 comprise a same number of eight rotor blades 6 and 7 , respectively.
  • the pitch 12 of the individual rotor blades 6 and 7 with regard to the rotational planes of the rotors 3 and 4 is variable by means of a controller 13 as indicated with rotor blade 7 ′.
  • the pitch of each rotor blade 6 and 7 may be varied for a plurality of times over each rotation of the rotors 3 and 4 about the rotor axis 5 depending on their absolute rotation angle about the rotor axis 5 and on the relative rotation angle of the two rotors 3 and 4 . In this way, unsteady loads on the rotor blades 6 and 7 and resulting excitations of air-borne and solid-borne noise are reduced or even completely removed.
  • the CROR engine 2 depicted in FIGS. 1 and 2 is intended to be mounted to an aircraft in a pusher configuration, and is attached to the structure of the aircraft via an upstream located pylon not depicted here.
  • unsteady loads on the rotor blades 6 and 7 occur at a frequency which is a product of the rotational frequency and the number of blades 6 and 7 of the rotors 3 and 4 .
  • Such unsteady loads are also known from engines having one rotor only. Due to the interaction of the flow variations generated by the two rotors 3 and 4 there are additional unsteady loads at a frequency which is 2 n -times the rotational speed of the rotors 3 and 4 . These additional unsteady loads particularly occur at the rotor blades 7 of the back rotor 4 but also at the rotor blades 6 of the front rotor 3 .
  • these unsteady loads are plotted for one rotor blade of each rotor over the rotation angle 4 ) about the rotation axis 5 .
  • the curve 8 indicates the load on one rotor blade 6 of the front rotor 3
  • the curve 9 indicates the load on one rotor blade 7 of the back rotor 4 .
  • the curves 10 and 11 show the development of the average values of the curves 8 and 9 .
  • the variation of the curves 8 and 9 indicate that the unsteady loads on the blades of the back rotor 4 are higher but generally of the same frequency as the unsteady loads on the blades of the front rotor 3 which is attributable to the same number of blades of the rotors 3 and 4 here.
  • the realization of the present invention may be based on an adjustment of the incident angle (pitch) of the rotor blades which is anyway provided with most engines.
  • the adjustment of the pitch may be varied at a higher frequency than usual. It may also be necessary that the adjustment is possible for the individual rotor blades at different points in time.
  • the geometric parameter of all rotor blades of a rotor may be synchronously changed (see above). Then, the individual rotor blades do not have to be controllable with regard to their parameter varying the thrust individually.

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  • Engineering & Computer Science (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)
US13/190,990 2009-01-31 2011-07-26 Engine, Particularly CROR Engine, for an Aircraft Abandoned US20110277447A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE102009007013.3 2009-01-31
DE102009007013A DE102009007013A1 (de) 2009-01-31 2009-01-31 Triebwerk, insbesondere CROR-Antrieb, für ein Flugzeug
PCT/EP2010/050950 WO2010086338A2 (de) 2009-01-31 2010-01-27 Triebwerk, insbesondere cror-antrieb, für ein flugzeug

Related Parent Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2010/050950 Continuation WO2010086338A2 (de) 2009-01-31 2010-01-27 Triebwerk, insbesondere cror-antrieb, für ein flugzeug

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US (1) US20110277447A1 (de)
EP (1) EP2391536B1 (de)
DE (1) DE102009007013A1 (de)
WO (1) WO2010086338A2 (de)

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US20120137765A1 (en) * 2010-12-01 2012-06-07 Hannes Wagner Sensor Device for Measuring a Direction of Incident Flow and Evaluation Device Therefor
JP2013137020A (ja) * 2011-12-20 2013-07-11 General Electric Co <Ge> 騒音を低減するための先端形状を含むエーロフォイルおよびそのエーロフォイルを作製するための方法
FR2990718A1 (fr) * 2012-05-16 2013-11-22 Airbus Operations Sas Helice pour moteur d'aeronef comprenant des moyens de reduction du bruit a moyennes et hautes frequences et amelioration de la perception acoustique.
JP2016500603A (ja) * 2012-10-18 2016-01-14 スネクマ ブレードのピッチを制御するための装置および方法
US9279338B2 (en) 2011-06-22 2016-03-08 Airbus Operations (Sas) Method for balancing a propulsive system having non-hull contra-rotating propellers
FR3029576A1 (fr) * 2014-12-04 2016-06-10 Snecma Procede pour reduire le niveau de bruit d'une soufflante de turbomachine
US9701395B2 (en) 2014-01-06 2017-07-11 United Technologies Corporation Contra-rotating open rotor distributed propulsion system
US20170313405A1 (en) * 2016-05-02 2017-11-02 Ratier-Figeac Sas Blade pitch control
US20190225318A1 (en) * 2018-01-25 2019-07-25 General Electric Company Aircraft systems and methods
US10414486B2 (en) 2015-11-30 2019-09-17 General Electric Company Airfoil for a rotary machine including a propellor assembly
US10738694B1 (en) * 2018-08-23 2020-08-11 United Technologies Corporation Turbofan with motorized rotating inlet guide vane

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CA2751805A1 (fr) * 2009-02-27 2010-09-02 Snecma Aubes de soufflante a calage cyclique
FR2967131A1 (fr) * 2010-11-10 2012-05-11 Gfic Sarl Propulseur a rotors contrarotatif silencieux au decollage
DE102011011489A1 (de) 2011-02-17 2012-08-23 Eads Deutschland Gmbh Propellerblatt sowie damit versehenes Triebwerk für ein Luftfahrzeug
DE102019134692B4 (de) 2019-12-17 2023-09-14 Deutsches Zentrum für Luft- und Raumfahrt e.V. Verfahren und elektrisch angetriebener Propeller oder Rotor mit Einrichtungen zur Minderung tonaler Schallabstrahlungen

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US9540094B2 (en) 2012-05-16 2017-01-10 Aibus Operations (Sas) Propeller for an aircraft engine comprising means for reducing noise at middle and high frequencies and improving the acoustic perception
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DE102009007013A1 (de) 2010-08-12
WO2010086338A2 (de) 2010-08-05

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