Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
  • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
  • F01D5/12—Blades
  • F01D5/14—Form or construction
  • F01D5/141—Shape, i.e. outer, aerodynamic form
  • F01D5/146—Shape, i.e. outer, aerodynamic form of blades with tandem configuration, split blades or slotted blades
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/40—Casings; Connections of working fluid
  • F04D29/52—Casings; Connections of working fluid for axial pumps
  • F04D29/54—Fluid-guiding means, e.g. diffusers
  • F04D29/541—Specially adapted for elastic fluid pumps
  • F04D29/542—Bladed diffusers
  • F04D29/544—Blade shapes
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/66—Combating cavitation, whirls, noise, vibration or the like; Balancing
  • F04D29/68—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers
  • F04D29/681—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers especially adapted for elastic fluid pumps
  • F04D29/682—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers especially adapted for elastic fluid pumps by fluid extraction
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/66—Combating cavitation, whirls, noise, vibration or the like; Balancing
  • F04D29/68—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers
  • F04D29/681—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers especially adapted for elastic fluid pumps
  • F04D29/684—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers especially adapted for elastic fluid pumps by fluid injection
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2240/00—Components
  • F05D2240/20—Rotors
  • F05D2240/30—Characteristics of rotor blades, i.e. of any element transforming dynamic fluid energy to or from rotational energy and being attached to a rotor
  • F05D2240/301—Cross-sectional characteristics

Definitions

• 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.
• 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.
• 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 ⁇ , 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. 4a 7 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.
• FIG. 6a, 6b and ⁇ c 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
• 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.
• 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.
• 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.
• 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.
• the airfoils camber increase closer to the hub.
• 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.
• 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-surface 7 s boundary layer is carried to the upper-surface's one. Referring to the Fig.
• the particles of the boundary layer in the point D are mixed with the higher energy particles that come from the slot S.
• 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.
• 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'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.
• 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.
• 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
• stator blades to increase both the rotor efficiency and the rotor pressure ratio, especially with low values of the solidity.
• 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.
• 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:
• 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.
• 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

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• 2003
  • 2003-10-17 IT IT000052A patent/ITBA20030052A1/it unknown
• 2004
  • 2004-10-14 WO PCT/EP2004/011546 patent/WO2005040559A1/en not_active Application Discontinuation
  • 2004-10-14 EP EP04790405A patent/EP1687511A1/en not_active Withdrawn

Non-Patent Citations (1)

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