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Publication numberWO2005040559 A1
Publication typeApplication
Application numberPCT/EP2004/011546
Publication date6 May 2005
Filing date14 Oct 2004
Priority date17 Oct 2003
Also published asEP1687511A1
Publication numberPCT/2004/11546, PCT/EP/2004/011546, PCT/EP/2004/11546, PCT/EP/4/011546, PCT/EP/4/11546, PCT/EP2004/011546, PCT/EP2004/11546, PCT/EP2004011546, PCT/EP200411546, PCT/EP4/011546, PCT/EP4/11546, PCT/EP4011546, PCT/EP411546, WO 2005/040559 A1, WO 2005040559 A1, WO 2005040559A1, WO-A1-2005040559, WO2005/040559A1, WO2005040559 A1, WO2005040559A1
InventorsPaolo Pietricola
ApplicantPaolo Pietricola
Export CitationBiBTeX, EndNote, RefMan
External Links: Patentscope, Espacenet
High lift rotor or stator blades with multiple adjacent airfoils cross-section
WO 2005040559 A1
Abstract
High lift rotor or stator blades with multiple adjacent airfoils cross-section, constituted from a main fin 1 and from at least one other secondary fin 2 and/or 3 joined through a root h and a tip t, and in the span between the root and tip is always imaginable a main airfoil P that circumscribes all the fin's airfoils. The peculiarity of this blades consists in the slots between the fins that enables transfering part of the air-flow with high energy, from the lower to the upper surface of the blades, with consequent increases of the boundary layer energy on the upper surface. Adopting the slots is possible to design blades that have both the camber and the surface greater than the actual blades in use, consequently increasing the lift and delaying the onset of the stall flutter.
Claims  (OCR text may contain errors)
Claims 1. High lift rotor or stator blades having multiple adjacent airfoils cross-section, said airfoils being partially or completely placed on themselves; the blades being constituted by a main fin (1) and by at least a second fin (2) placed nearby the leading edge of the main fin (1) , and/or at least a third fin (3) placed nearby the trailing edge of the main fin; the secondary fin being located close to the upper and/or lower surface of the main fin (1); said fins (1,2,3) being joined through a root (h) and a tip (t) forming, in the span between them, a main airfoil (p) that circumscribes all the airfoils of the fins; each of said blades having at least one slot (S) that provide to transfer part of the flow, with high energy, from the lower to the upper surface of the blades, with consequent increases of the boundary layer energy on the upper surface .
2. High lift rotor or stator blades according to claim 1, characterised in that the second fins (2) are two or more .
3. High lift rotor or stator blades according to claim 1, characterised in that the third fins (2) are two or more.
4. High lift rotor or stator blades according to claim 1, characterized in that the blades, as well the fins (1,2,3), are twisted and/or untwisted, tapered and/or with a constant chord, with or without a movable part, completely adjustable or fixed.
5. High lift rotor or stator blades according to claim 1, characterized in that each blade on the whole is single, being the fins joined through a root (h) and a tip (t) that reduce the external free vortices; said blades being realized both from several assembled pieces or from a single one.
6. High lift rotor or stator blades according to the claim 1, characterized in that the dimensions of the slots (S) are similar and/or different to the dimensions of the fin's chords.
7. High lift rotor or stator blades according to the claim 1, characterized in that the dimension of the main fin chord is similar and/or different to the dimensions of the secondary fins chords.
8. High lift rotor or stator blades according to the claim 1, characterized in that the airflow and the boundary layer across the slots (S) are of the laminar and/or turbulent types.
9. High lift rotor or stator blades according to claim 1, characterized in that the airfoils of the fins, as well the main airfoil (p) , are thick or thin are of the symmetrical, conventional cambered, reflexed, aft-loaded, supercritical type or a combination of the former characteristics.
10. High lift rotor or stator blades according to claim 1, characterized in that the slots (S) are of the convergent, divergent and/or with constant area type, in the axial and radial directions.
11. High lift rotor or stator blades according to claim 1, characterized in that among the fins is placed at least one laminar or curved projection (a) that strengths the blades, protects the shape of the slot and avoids vortices propagation.
12. High lift rotor or stator blades according to claim 11, characterized in that the projection (a) has the plane shape coincident with the main airfoil (P) or a different shape; the shape of said projection is thus contained in the main airfoil (P) perimeter or not.
13. High lift rotor or stator blades according to claim 1, characterized in that at least one fin is rotatable in respect of the other ones so that to modify the shape of the slot (S) .
14. High lift rotor or stator blades according to claim 1, characterized in that at least in one section of the blade the flow is transonic or supersonic; and the upstream fin produces shock waves allowing to the following fins to work with subsonic flow.
15. High lift rotor or stator blades according to claim 1, characterized in that the blades are realized in superconductor material ad they are crossed from high density electrical currents so that to generate high magnetic field.
16. High lift rotor or stator blades according to claim 1, characterized in that a plurality of the bladesw are employed in turbine engine, axial & centrifugal compressors, axial & centrifugal ventilator, propeller, fan, axial & centrifugal pumps, axial & centrifugal turbines in aeronautical, maritime and space fields.
Description  (OCR text may contain errors)

High lift rotor or stator blades with multiple adjacent airfoils cross-section.

Description

This invention relates to high performance rotor or stator blades and more particularly for applications in variable pitch fan (adopting- the twisted stator row upstream the rotor as well the rotor blades described in the patent application WO02055845 "A Turbine Engine"), turbo-machinery and wind turbine. The variable pitch systems, especially applied to fan assemblies, introduce problems in the achievable performance and in the stall flutter because of the reduced number of blades. Indeed, the lower the number of blades and: the lower the efficiency; the lower the performance; and the ligher the pressure losses. The fact is that reducing the number of blades: both the work and the lift coefficient decrease because of the reduced stream line deflection amongst the airfoils leading and trailing edges; the aerodynamic forces decrrease because of the lower rotor blades surface and the lower lift coefficient; the pressure loses increase and the efficiency decrease because of the boundary layer detachment point, on the airfoils upper surface, moves towards the leading edge. It is therefore the main object of this invention to provide blades which have big surfaces, big camber and boundary layer detachment points closed to the trailing edge; even if applied in stator and rotor rows with both low number of blades and high attach angles .

The blades according to the invention will be referred hereafter with the acronym MAB "Multiple Airfoils Blade"; instead the multiple adjacent airfoils cross-section will be referred hereafter with the acronym MAS "Multiple Airfoils Section". The objects of this invention will become readily apparent from the following description of the drawing in which:

Fig. la and lb show the main geometric characteristics of the airfoils (a is the trailing edge, u is the leading edge, d is the upper surface, u is the lower surface, c is the chord and m is the middle line) and the attach angles α, respectively, in a traditional concave-convex airfoil and in a MAS concave-convex one; Fig. 2a and 2b outline the streamlines path and the average speeds v in the boundary layer on the upper surface, respectively, in a traditional airfoil and in a MAS one (note that the main airfoil P, the attach angle and the external conditions are the same in both the airfoils) ;

Fig. 3a, 3b and 3c define, respectively, the speed triangle upstream an axial compressor stage and the speed triangles downstream the same compressor stage realized with traditional airfoils and with MAS ones; Fig. 4a7 4b and 4c define, respectively, the speed triangle upstream an axial turbine stage and the speed triangles downstream the same turbine stage realized with traditional airfoils and with MAS ones; Fig. 5 show few examples of MAS airfoils: 1 is the main fin; 2¸2n' are the fin located upstream the leading edge; 3¸3n' is the fin located downstream the trailing edge; S¸Sn' are the slots; and P is the main airfoils which circumscribes all the fin's airfoils; Fig. 6a, 6b and βc, respectively, show the rotor blade of a variable pitch fan in frontal, lateral and perspective views and the relative cross-sections in which are recognizable the multiple adjacent airfoils fins 1 and 2 as well the main airfoils P;

Fig. 7 sketch out few examples of general MAB plane shapes;

Fig. 8, 9 and 10 show few examples of rotor MAB;

Fig. 11 shows few different design chose of the same tapered rotor MAB: 1 is the main fin; 2 is the secondary fin; t is the tip fin that reduces the free vortex generation and has a structural function while t' is the 'tip fin further useful to achieves the blades performance; h is the root fin that has only structural function (It's the hub in fix pitch or the base-plate in variable pitch) while h' is the root fin useful also to achieves the blades performance; and a is the projection among the fins needed to strengths the blades, protects the shape of the slots and avoids vortices propagation; it is underlined that it is possible to design any combination among the shape and type of MAB, with several MAS and projections a both for rotor or stator blades;

Fig. 12 shows the example of a twisted stator blade

20, partially constituted from MAS airfoils, lodged inside one Air-Intake 100; Fig. 13 shows the example of the variable pitch rotor 110 with the MAB 30 shown in Fig. 6;

Fig. 14 shows the example of the rotor 120 of an axial compressor with the MAB 40;

Fig. 15 shows the example of the rotor 130 of a centrifugal pump with the MAB 50.

Referring to Fig. 2, with positive attach angles, the air-flow that encircles the upper surface increases continuously the speed and decreases the pressure from the leading edge towards the airfoil thickest point. Instead, from the thickest point moving towards the trailing edge the air-speed decreases and there is the pressure recovery; but, inside the boundary layer, the particles closer to the airfoil surface endure a greater air-speed deceleration than the expected one because of the energy loses due to the friction. In this latter case, it can be considered that the particles assume an opposite direction to the motion and are generated vortices. Thus, on the upper surface of the airfoil there is the separation of the boundary layer. When the separation point moves towards the leading edge the streamlines don't follow anymore the airfoil deflection (see point D in Fig. 2a) and a lot of vortices becomes generated; it does appear the stall flutter. It's clear that the vortices always dissolve energy and the higher the vortices propagation beyond the trailing edge and the lower are both the aerodynamic and acoustic efficiencies. The separation point moves towards, the leading edge increasing the camber and the attach angles. Moreover, both in stator and rotor row applications, the stall flutter depends from the number of the blades and more particularly depends from the solidity, the ratio between the chords and the mechanical pitch (distance between the airfoils) : the separation point moves towards the trailing edge increasing the solidity. Thus, with the traditional technique, it is possible to design airfoil with high camber that work with high values of attach angles only when the solidity has very high values. For example it can be considered the different camber of the propeller airfoils in the actual turbo-fan: the airfoils camber increase closer to the hub. After this consideration it is simpler to understand the reason that didn't allows to the variable pitch rotor to be developed in turbo-fan and turbo- machinery. Indeed, in these latter applications the benefits concerning the variable pitch technique become sensibly reduced with the reduction of the rotor blades (reduced values of the solidity) . It is therefore the first object of this invention to provide rotor blades to increase both the lift and the efficiency of the propellers, especially with low values of the solidity. In order to achieve this objective it has to be increased the rotor blades camber but moving the boundary layer separation points towards the trailing edges. Therefore it's necessary to increase the energy of the boundary layer on the upper surface of the airfoils. A useful solution is the MAB. Indeed introducing the slots S, shaped between the fins, part of the energy of the lower-surface7 s boundary layer is carried to the upper-surface's one. Referring to the Fig. 2b, the particles of the boundary layer in the point D are mixed with the higher energy particles that come from the slot S. Thus, in the point C the energy of the boundary layer is bigger than in the traditional airfoil and the separation point is moved towards the trailing edge even with high camber. Furthermore it's possible to increase the lift because of the increased surface. Referring to Fig. 1 and Fig. 2, it's evident that the total surface of a traditional airfoil is lower than the surface of a MAS one which has the same main airfoil P.

It is a still further object of this invention to provide rotor blades to increase the compressors and fans pressure ratio, especially with low values of the solidity. In order to achieve this objective it's necessary to increases the work L that the rotor blades supply to the flow. The following description it has been referred to axial applications, but the same theory and results can be applied to centrifugal ones. From the energetic equations of the fluid, it's obtained a relation called "equation of the work to the differences of kinetic energies" that it's suitable to estimate the pressure rise by the propeller and the axial compressors. The work is expressed in relation to the absolute kinetic energies C, of the relative energies W and of the driving energies U; and the work L is dues to the change of these speeds amongst the sections upstream and downstream the rotor blades. In the compressors, pumps, fans, propellers, and more generally in the operating machine:

L = (C2 2 - C?) I2 + (W2 - W?)I 2 + (U2 2 - U )l' 2

In axial machines, it's possible to consider the same driving speed U for both the leading and trailing edges (Ui = U2 = U = Cost.) . Defining y the angles between the absolute speeds C and the driving ones U, and referring to the Carnot theorem, is obtained the "Euler" equation of the work: = U2 • C2 cos.y2 - Ul Cl cosyl = U (C2 cosy2 - Cl cos^)

It's clear that to increase the work it's necessary

to increase C2 - cosy2 and/or decrease , • cosy1. In

practice it's necessary to increase the deflection of the streamlines among the rotor airfoils. That can be done in one hand increasing the camber of the rotor airfoils, in the other hand increasing the attach angles. Thus the proposed solution is again the MAB. Fig. 3, show a graphical comparison between two similar stages of an axial compressor. The stagger angles, the mechanical pitch and the operating conditions are the same in both the configurations, but not the airfoils. Thus the speed triangle upstream the rotors rows is the same; instead the speed triangles downstream the rotor row are sketched out considering the maximum deflection allowed by the airfoils without incur in the stall flutter. It's

evident that C2 ' - cosy2' is bigger than C2-cos'2 and

therefore that increasing the streamline deflection it's increased the work conferred to the gas or fluid.

It is a still further object of this invention to provide stator blades to increase both the rotor efficiency and the rotor pressure ratio, especially with low values of the solidity. In order to achieve this objective it has to be increased the stator blades camber but moving the boundary layer separation points towards the trailing edges. Indeed, increasing the streamline deflections of the stator row without incur in the stall flutter, the rotor stagger angles can be decreased (increasing the rotor efficiency) and the attach angles increase (increasing the rotor pressure ratio) . The solution is therefore to adopt stator MAB. It is a still further object of this invention to provide rotor blades to increase the energy achievable from the turbines, especially with low values of the solidity. In order to achieve this objective it's necessary to increase the work L that the rotor blades capture from the flow. With the same theory illustrated above for the operating machine, it is known that the energy absorbed from the axial turbines is proportional to the following equation:

L = U - (Cl COSJ/J -C2 -cos >2)

As described for the axial compressor stage, to

increase the work it's necessary to increase C2-cos_>2

and/or decreaseC, -cos . In practice it's again

necessary to increase the deflection of the streamlines among the rotor airfoils. That can be done in one hand increasing the camber of the rotor airfoils, in the other hand increasing the attach angles. Thus the proposed solution is again the MAB. Fig. 4, show a graphical comparison between two similar stages of an axial turbine. The stagger angles, the mechanical pitch and the operating conditions are the same in both the configurations, but not the airfoils. Thus the speed triangle upstream the rotors rows is the same; instead the speed triangles downstream the rotor row are sketched out considering the maximum deflection allowed by the airfoils without incur in the stall flutter. It's

evident that C2 ' - cosy2 is bigger than C2-cos'2 and

therefore that increasing both the gas and fluid streamline deflection it's increased the attainable energy.

Patent Citations
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DE390486C *14 Jul 192220 Feb 1924Rudolf Wagner DrSchaufel, insbesondere fuer Dampf- und Gasturbinen
GB2106193A * Title not available
US1553627 *7 Jun 192215 Sep 1925Allis Chalmers Mfg CoRotor
US1724456 *25 May 192913 Aug 1929Louis H CrookAerodynamic control of airplane wings
US2135887 *3 Jun 19368 Nov 1938Fairey Charles RichardBlade for airscrews and the like
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US2938662 *16 Mar 195431 May 1960Daimler Benz AgTurbo compressor
US3692425 *2 Jan 196919 Sep 1972Gen ElectricCompressor for handling gases at velocities exceeding a sonic value
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
WO2007105174A113 Mar 200720 Sep 2007Tecsis Tecnologia E Sistemas Avanšados LtdaMulti-element blade with aerodynamic profiles
WO2009121927A1 *2 Apr 20098 Oct 2009Lm Glasfiber A/SA wind turbine blade with an auxiliary airfoil
WO2010125599A3 *23 Apr 20103 Jun 2011Leonardo ValentiniRotor blade with aerodynamic flow static diverter for vertical axis wind turbine
WO2015044615A129 Sep 20142 Apr 2015Electricfil AutomotiveRotor for a vertical-axis wind turbine
CN103195572A *4 Jan 201310 Jul 2013通用电气公司涡轮扩散器
CN105275872A *22 Jul 201527 Jan 2016航空技术空间股份有限公司Blade with branches for an axial-flow turbomachine compressor
DE102014203601A1 *27 Feb 201427 Aug 2015Rolls-Royce Deutschland Ltd & Co KgSchaufelreihengruppe
DE102014203604A1 *27 Feb 201427 Aug 2015Rolls-Royce Deutschland Ltd & Co KgSchaufelreihengruppe
EP1947293A1 *18 Jan 200723 Jul 2008Siemens AktiengesellschaftGuide vane for a gas turbine
EP2078824A1 *9 Jan 200915 Jul 2009SnecmaDouble-blade with wings
EP2092163A1 *14 Nov 200626 Aug 2009Volvo Aero CorporationVane assembly configured for turning a flow ina a gas turbine engine, a stator component comprising the vane assembly, a gas turbine and an aircraft jet engine
EP2092163A4 *14 Nov 200617 Apr 2013Volvo Aero CorpVane assembly configured for turning a flow ina a gas turbine engine, a stator component comprising the vane assembly, a gas turbine and an aircraft jet engine
EP2107235A1 *2 Apr 20087 Oct 2009Lm Glasfiber A/SA wind turbine blade with an auxiliary airfoil
EP2463480A3 *29 Nov 201123 Jul 2014Rolls-Royce Deutschland Ltd & Co KGBlade with hybrid airfoil
EP2977548A1 *22 Jul 201427 Jan 2016Techspace Aero S.A.Axial turbomachine compressor blade with branches
EP3070264A4 *10 Oct 201421 Jun 2017Ihi CorpVane structure for axial flow turbomachine and gas turbine engine
US80211139 Jan 200920 Sep 2011SnecmaTwin-airfoil blade with spacer strips
US825703217 Jan 20084 Sep 2012Siemens AktiengesellschaftGas turbine with a guide vane
US82823573 Nov 20089 Oct 2012Rolls-Royce PlcTurbine blade
US864706313 Mar 200711 Feb 2014Tecsis Tecnologia Sistemas Avanšados S.A.Multi-element blade with aerodynamic profiles
US88341302 Apr 200916 Sep 2014Peter FuglsangWind turbine blade with an auxiliary airfoil
US93947948 Dec 201119 Jul 2016Rolls-Royce Deutschland Ltd & Co KgFluid-flow machine—blade with hybrid profile configuration
US20120148396 *8 Dec 201114 Jun 2012Rolls-Royce Deutschland Ltd & Co KgFluid-flow machine - blade with hybrid profile configuration
US20130170969 *4 Jan 20124 Jul 2013General Electric CompanyTurbine Diffuser
US20130209224 *6 Feb 201315 Aug 2013Mtu Aero Engines GmbhTurbomachine
US20160024932 *20 Jul 201528 Jan 2016Techspace Aero S.A.Axial turbomachine compressor blade with branches at the base and at the head of the blade
US20160024933 *21 Jul 201528 Jan 2016Techspace Aero S.A.Blading with branches on the shroud of an axial-flow turbomachine compressor
Classifications
International ClassificationF01D5/14
Cooperative ClassificationF04D29/544, F05D2240/301, F01D5/146
European ClassificationF01D5/14B4
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