Blades, axial impellers, fans and engines

Abstract

The present invention provides a blade, an axial flow impeller, a fan and an engine. The blade includes a blade front edge, a blade trailing edge, a blade root and a blade top. The blade profile frame of the blade is composed of a blade top profile line of the blade top, a blade root profile line of the blade root, a leading profile line of the blade front edge and a trailing profile line of the blade trailing edge. The blade cross-sectional profile line of the blade is controlled by the blade top profile line and the blade root profile line, and the blade cross-sectional profile of the blade is controlled by the leading profile line and the trailing profile line. In this way, by optimizing the blade leading profile line and the trailing profile line, using the blade top profile line and the blade root profile line to control the blade cross-sectional profile line, and controlling the blade cross-sectional profile by the leading profile line and the trailing profile line, the blade cross-sectional profile is guided to be swept from the blade root to the blade top, so that the blade profile presents a twisted uneven state in the blade height direction, which can effectively reduce the vortex on the blade suction surface, and inhibit the local vortex from spreading in the blade height direction, so as to achieve a good effect of reducing vortex noise and improving aerodynamic efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of fan equipment, and in particular, relates to a blade, an axial flow impeller, a fan and an engine. Background Art

[0002] With the continuous development of the domestic manufacturing industry, higher requirements are placed on the quality, noise, aerodynamic efficiency, etc. of fan impellers used for engine cooling. At present, domestic fan impellers used for engine cooling generally have problems of low aerodynamic efficiency and high noise. In order to solve the above problems, the blades of the fan impeller are generally swept forward and tilted forward to control the fan blades of the engine and engine cooling to produce as little noise as possible during operation. However, the low-noise blades with swept forward and tilted forward designs still have low aerodynamic performance and generate high noise during operation because the design is difficult to be precise and optimization cannot be in place. Summary of the invention

[0003] Based on the above-mentioned problems existing in the prior art, one of the purposes of an embodiment of the present invention is to provide a blade which is formed by optimizing the leading edge profile and the trailing edge profile of the blade, guiding the blade cross section to sweep from the blade root to the blade top, so that the blade profile is uneven in the blade height direction, so as to reduce the vortex on the suction surface of the blade and inhibit the diffusion of local vortex in the blade height direction, thereby achieving the effect of reducing vortex noise and improving aerodynamic efficiency.

[0004] To achieve the above object, the technical solution adopted by the present invention is: to provide a blade, comprising:

[0005] The leading edge of the blade is used to be placed on the air inlet side of the axial flow impeller;

[0006] The trailing edge of the blade is used to be placed on the air outlet side of the axial flow impeller;

[0007] a blade root extending from the bottom end of the leading edge of the blade to the bottom end of the trailing edge of the blade and used to be connected to the outer peripheral surface of the hub of the axial flow impeller; and

[0008] A blade tip extending from the top of the leading edge of the blade to the top of the trailing edge of the blade;

[0009] Among them, the blade profile frame of the blade is composed of the blade top profile line of the blade top, the blade root profile line of the blade root, the leading edge profile line of the blade front and the trailing edge profile line of the blade trailing edge, the blade cross-section profile line of the blade is controlled by the blade top profile line and the blade root profile line, the blade cross-section of the blade is controlled by the leading edge profile line and the trailing edge profile line, and the leading edge profile line and the trailing edge profile line respectively guide the blade cross-section to sweep from the blade root to the blade top, so that the blade profile of the blade presents a twisted and uneven state in the blade height direction.

[0010] Furthermore, the pressure surface profile of the blade tip satisfies the relationship: y = 0.0019x 2 -0.7729x+22.196; and the pressure surface profile of the blade tip satisfies the relationship: y=0.0042x 2 -0.855x+17.979; x is the X-axis coordinate point value on the corresponding X-axis, y is the Y-axis coordinate point value on the corresponding Y-axis, and the value range of x is -21.0252≤x≤60.706.

[0011] Furthermore, the intersection of the pressure surface profile of the blade tip and the suction surface profile of the blade tip is chamfered, and the fillet radius of the chamfer is 0.5≤R≤1.

[0012] Furthermore, the pressure surface profile of the blade root satisfies the relationship: y=0.0056x 2 -0.00005x+2.996; and the pressure surface profile of the blade root satisfies the relationship: x=0.0127y 2 -0.0009y-2.5387; x is the X-axis coordinate point value on the corresponding X-axis, y is the Y-axis coordinate point value on the corresponding Y-axis, and the value range of y is -22.9133≤y≤21.0573.

[0013] Furthermore, the intersection of the pressure surface profile of the blade root and the suction surface profile of the blade root is chamfered, and the fillet radius of the chamfer is 0.5≤R≤1.

[0014] Furthermore, the leading edge profile line and the trailing edge profile line are respectively formed by the intersection of axial and perpendicular curved surfaces, and in the curved surfaces constructed by the leading edge profile line and the trailing edge profile line: the curved surfaces perpendicular to the axial direction have a single hump-shaped feature with a protruding belly, the axial curved surface construction lines in the leading edge profile line construction curved surfaces are wavy, and the axial curved surface construction lines in the trailing edge profile line construction curved surfaces are sickle-shaped.

[0015] Based on the above-mentioned problems existing in the prior art, the second purpose of the embodiment of the present invention is to provide an axial flow impeller which optimizes the leading edge profile and the trailing edge profile of the blade, guides the blade cross section to sweep from the blade root to the blade top, and makes the blade profile present an uneven state in the blade height direction, so as to reduce the vortex on the suction surface of the blade and inhibit the diffusion of local vortex in the blade height direction, thereby achieving the effect of reducing vortex noise and improving aerodynamic efficiency.

[0016] To achieve the above object, the technical solution adopted by the present invention is: to provide an axial flow impeller, comprising a hub and the blades, wherein the blades are arranged on the outer peripheral surface of the hub at intervals along the circumferential direction.

[0017] Furthermore, the ratio of the diameter of the hub to the outer diameter of the axial flow impeller is 0.18 to 0.22.

[0018] Based on the above-mentioned problems existing in the prior art, the third purpose of the embodiment of the present invention is to provide a fan which optimizes the leading edge profile and the trailing edge profile of the blade to guide the blade cross section to sweep from the blade root to the blade top, so that the blade profile is uneven in the blade height direction, so as to reduce the vortex on the suction surface of the blade and inhibit the diffusion of local vortex in the blade height direction, thereby achieving the effect of reducing vortex noise and improving aerodynamic efficiency.

[0019] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: to provide a fan, including the blades or the axial flow impeller.

[0020] Based on the above-mentioned problems existing in the prior art, the fourth purpose of the embodiment of the present invention is to provide an engine which optimizes the leading edge profile and the trailing edge profile of the blade to guide the blade cross section to sweep from the blade root to the blade top, so that the blade profile is uneven in the blade height direction, so as to reduce the vortex on the suction surface of the blade and inhibit the diffusion of local vortex in the blade height direction, thereby achieving the effect of reducing vortex noise and improving aerodynamic efficiency.

[0021] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: to provide an engine, including the above-mentioned fan.

[0022] Compared with the prior art, the above one or more technical solutions in the embodiments of the present invention have at least one of the following beneficial effects:

[0023] The blades, axial flow impellers, fans and engines in the embodiments of the present invention are formed by optimizing the leading edge profile and the trailing edge profile of the blades, controlling the blade cross-sectional profile using the blade top profile and the blade root profile, and controlling the blade cross-section by the leading edge profile and the trailing edge profile, guiding the blade cross-section to sweep from the blade root to the blade top, so that the blade profile presents a twisted and uneven state in the blade height direction, thereby forming a blade that can minimize the vortex on the suction surface of the blade, effectively reducing the vortex on the suction surface of the blade, and inhibiting the diffusion of local vortex in the blade height direction, thereby achieving the good effect of reducing vortex noise and improving aerodynamic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0025] Figure 1 A schematic diagram of the three-dimensional structure of a blade provided in an embodiment of the present invention;

[0026] Figure 2Another schematic diagram of the three-dimensional structure of a blade provided by an embodiment of the present invention;

[0027] Figure 3 A side view of a blade provided by an embodiment of the present invention;

[0028] Figure 4 A schematic diagram of the three-dimensional structure of an axial flow impeller provided in an embodiment of the present invention;

[0029] Figure 5 A front view of a blade provided by an embodiment of the present invention;

[0030] Figure 6 A rear view of a blade provided by an embodiment of the present invention;

[0031] Figure 7 A side view of a blade provided by an embodiment of the present invention;

[0032] Figure 8 Another schematic diagram of the three-dimensional structure of the axial flow impeller provided in an embodiment of the present invention;

[0033] Fig. 9 Another schematic diagram of the three-dimensional structure of the axial flow impeller provided in an embodiment of the present invention;

[0034] Fig.10 A blade root profile diagram of a blade provided by an embodiment of the present invention;

[0035] Fig.11 A tip line diagram of a blade provided by an embodiment of the present invention;

[0036] Fig.12 A trailing edge profile diagram of a blade provided in an embodiment of the present invention;

[0037] Fig.13 A leading edge profile diagram of a blade provided by an embodiment of the present invention;

[0038] Fig.14 Noise spectrum analysis diagram for an axial impeller fan tested with existing blades;

[0039] Fig.15 A noise spectrum analysis diagram of a test of an axial flow impeller fan having blades provided by an embodiment of the present invention.

[0040] Among them, the reference numerals in the figure are:

[0041] 1-axial flow impeller; 11-hub; 12-blade; 121-blade leading edge; 122-blade trailing edge; 123-blade root; 124-blade tip. DETAILED DESCRIPTION

[0042] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0043] It should be noted that when an element is referred to as being "connected to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0044] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0045] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0046] Reference throughout the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Thus, when the phrases "in one embodiment," "in some embodiments," or "in some of these embodiments" appear in various places throughout the specification, not all references are to the same embodiment. Furthermore, in one or more embodiments, the particular features, structures, or characteristics may be combined in any suitable manner.

[0047] See also Figures 1 to 3, the blade provided by the embodiment of the present invention is now described. The blade 12 provided by the embodiment of the present invention can be used for the axial flow impeller 1. The blade 12 includes a blade front 121, a blade trailing edge 122, a blade root 123 and a blade top 124. The blade front 121 is used to be placed on the air inlet side of the axial flow impeller 1, the blade trailing edge 122 is used to be placed on the air outlet side of the axial flow impeller 1, the blade root 123 extends from the bottom end of the blade front 121 to the bottom end of the blade trailing edge 122, the blade is connected to the outer peripheral surface of the hub 11 of the axial flow impeller 1 through the blade root 123, and the blade top 124 extends from the top end of the blade front 121 to the top end of the blade trailing edge 122. Among them, the blade profile frame of the blade is composed of the blade tip 124 profile line of the blade tip 124, the blade root 123 profile line of the blade root 123, the front profile line of the blade front edge 121 and the trailing profile line of the blade trailing edge 122. The blade cross-sectional profile of the blade is controlled by the blade tip 124 profile line and the blade root 123 profile line, and the blade cross section of the blade is controlled by the front profile line and the trailing profile line, and the front profile line and the trailing profile line respectively guide the blade cross section to sweep from the blade root 123 to the blade tip 124. In this way, since the blade cross-sectional profile is controlled by the blade tip 124 profile line and the blade root 123 profile line, the spatial change of the blade cross section is controlled by the front profile line and the trailing profile line, and the cross section is guided to sweep from the blade root 123 to the blade tip 124, the blade profile can present a twisted uneven state in the blade height direction, which can effectively suppress the diffusion of local vortices along the blade height direction on the blade suction surface, reduce vortex noise and improve aerodynamic efficiency.

[0048] Compared with the prior art, the blade 12 provided in the embodiment of the present invention optimizes the blade leading edge 121 profile line and the trailing edge profile line, uses the blade top 124 profile line and the blade root 123 profile line to control the blade cross-sectional profile line, and controls the blade cross-section through the leading edge profile line and the trailing edge profile line, guides the blade cross-section to be swept from the blade root 123 to the blade top 124, so that the blade profile presents a twisted and uneven state in the blade height direction, thereby forming a blade 12 that can minimize the vortex on the blade suction surface to the greatest extent, which can effectively reduce the vortex on the blade suction surface and inhibit the diffusion of local vortex in the blade height direction, thereby achieving the good effect of reducing vortex noise and improving aerodynamic efficiency.

[0049] Specifically, see Fig.11 In some embodiments, the pressure surface profile of the blade tip 124 satisfies the relationship: y = 0.0019x 2 -0.7729x+22.196; and the pressure surface profile of the blade tip 124 satisfies the relationship: y=0.0042x 2 -0.855x+17.979; x is the X-axis coordinate point value on the corresponding X-axis, y is the Y-axis coordinate point value on the corresponding Y-axis, and the value range of x is -21.0252≤x≤60.706.

[0050] In some of the embodiments, the pressure surface profile of the blade tip 124 and the suction surface profile of the blade tip 124 are connected by a fillet, and the fillet radius of the fillet is 0.5≤R≤1.

[0051] Specifically, see Fig.10 In some embodiments, the pressure surface profile of the blade root 123 satisfies the relationship: y = 0.0056x 2 -0.00005x+2.996; and the pressure surface profile of the blade root 123 satisfies the relationship: x=0.0127y 2 -0.0009y-2.5387; x is the X-axis coordinate point value on the corresponding X-axis, y is the Y-axis coordinate point value on the corresponding Y-axis, and the value range of y is -22.9133≤y≤21.0573.

[0052] In some of the embodiments, the pressure surface profile of the blade root 123 and the suction surface profile of the blade root 123 are connected by a rounded corner, and the fillet radius of the rounded corner is 0.5≤R≤1.

[0053] Please refer to Fig.12 and Fig.13 In some embodiments, the leading edge profile and the trailing edge profile are formed by the intersection of axial and perpendicular curved surfaces respectively, and in the curved surfaces constructed by the leading edge profile and the trailing edge profile: the curved surfaces perpendicular to the axial direction have a single hump-shaped feature with a protruding belly, the axial curved surface construction lines in the leading edge profile construction curved surface are wavy, and the axial curved surface construction lines in the trailing edge profile construction curved surface are sickle-shaped.

[0054] In order to better illustrate the present invention, this embodiment is described by taking the diameter d=100 of the hub 11 and the outer diameter D=490 of the axial flow impeller 1 as an example, wherein -21.0252≤x≤60.706 in the blade tip 124 profile, and -22.9133≤y≤21.0573 in the blade root 123 profile, wherein the pressure surface profile and the suction surface profile are intersected by a fillet, and the fillet radius of the fillet is 0.5≤R≤1, and the specific leading edge profile and trailing edge profile coordinate points are shown in Table 1.

[0055] Table 1 The data table of the corresponding coordinate points of the leading edge and trailing edge in three-dimensional space

[0056]

[0057]

[0058] By inputting the coordinate points of the leading edge profile and the trailing edge profile in Table 1 for three-dimensional modeling, the surface models of the leading edge profile 121 and the trailing edge profile of the blade are respectively as follows: Fig.12 , Fig.13As shown, it is formed by the intersection of axial and perpendicular surfaces. Among the curved surfaces of the leading edge profile and the trailing edge profile, the curved surfaces perpendicular to the axial direction have a single hump-shaped feature with a protruding abdomen; the axial curved surface construction line in the trailing edge profile construction surface is sickle-shaped, and the axial curved surface construction line in the leading edge profile construction surface is wavy. In this way, the blade 12 provided in the embodiment of the present invention optimizes the leading edge 121 profile and the trailing edge profile, uses the blade top 124 profile and the blade root 123 profile to control the blade cross-sectional profile, and controls the blade cross section through the leading edge profile and the trailing edge profile, guides the blade cross section to sweep from the blade root 123 to the blade top 124, so that the blade shape presents a twisted uneven state in the blade height direction, thereby forming a blade 12 that can minimize the vortex on the suction surface of the blade, effectively reduce the vortex on the suction surface of the blade, and inhibit the diffusion of local vortices in the blade height direction, so as to achieve a good effect of reducing vortex noise and improving aerodynamic efficiency. It can be understood that the blade 12 provided in the embodiment of the present invention can be applied to a fan for cooling an engine, but is not limited to being applied to a fan for cooling an engine. According to the actual use requirements of the application, the blade 12 provided in the embodiment of the present invention can also be modified according to similar laws to be applied to other applications such as air cooling and heat dissipation or driving to generate airflow, such as overall enlarging the blade for use in a dust suppression vehicle fog cannon, or reducing the blade for use in small-sized heat dissipation applications such as computers.

[0059] By testing the existing axial flow impeller 1 fan and the impeller fan with the above blades 12 respectively, the test results shown in Table 2 are obtained.

[0060] Table 2 The coordinate point data table of the leading edge line and the trailing edge line in three-dimensional space

[0061] plan Speed ​​rpm <![CDATA[Flow rate m 3 / s]]> Total pressure Pa Shaft power kw Full pressure efficiency Sound pressure level at 1 meter Existing solutions 2000 3.908 459.8 2.51 71.6％ 91.8dB Solution of the present invention 2000 4.092 470.2 2.32 82.8％ 85.6dB

[0062] It can be seen from Table 2 that the total sound pressure level of the existing axial flow impeller 1 fan is 91.8dB, and the total pressure efficiency is 71.6%. The total sound pressure level of the impeller fan with the above blades 12 of the present invention is 85.6dB, and the total pressure efficiency is 82.8%. Fig.14 , Fig.15 Comparative analysis shows that compared with the prior art blades, under the same rotation speed conditions, the solution of the present invention can increase the flow rate by 4.7%, increase the total pressure efficiency by 11.2%, and reduce the noise by 6.2dB. In summary, the blade 12 of the present invention has an uneven blade profile in the blade height direction, which can effectively inhibit the diffusion of vortex along the blade height direction on the blade suction surface, reduce vortex noise, and effectively improve aerodynamic efficiency.

[0063] See also Figures 4 to 6The embodiment of the present invention further provides an axial flow impeller 1, comprising a hub 11 and blades 12 provided in any of the above embodiments, wherein the blades 12 are arranged on the outer peripheral surface of the hub 11 at intervals along the circumferential direction. Since the axial flow impeller 1 has all the technical features of the blades 12 provided in any of the above embodiments, it has the same technical effects as the above blades 12.

[0064] See also Figures 5 to 7 In some embodiments, the ratio of the diameter of the hub 11 to the outer diameter of the axial impeller 1 is 0.18 to 0.22. By adopting the above technical solution, by optimizing the front edge 121 profile and the trailing edge profile of the blade, and designing the optimal hub 11 ratio of the blade profile, a blade 12 capable of minimizing the vortex on the suction surface of the blade is formed, which can effectively reduce the vortex on the suction surface of the blade and inhibit the diffusion of the local vortex in the blade height direction, thereby achieving a good effect of reducing vortex noise and improving aerodynamic efficiency.

[0065] See also Figures 8 to 9 In some of the embodiments, eight blades 12 are disposed on the outer circumferential surface of the hub 11 , and the eight blades 12 are arranged at equal intervals along the circumference of the hub 11 .

[0066] The embodiment of the present invention further provides a fan, comprising the axial flow impeller 1 provided in any of the above embodiments. Since the fan has all the technical features of the blade 12 or the axial flow impeller 1 provided in any of the above embodiments, it has the same technical effects as the above blade 12 or the axial flow impeller 1.

[0067] The embodiment of the present invention further provides an engine, comprising the fan provided in any of the above embodiments. Since the engine has all the technical features of the fan provided in any of the above embodiments, it has the same technical effects as the above fans.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A blade for an axial flow impeller, characterized in that: include: The leading edge of the blade is used to be placed on the air inlet side of the axial flow impeller; The trailing edge of the blade is used to be placed on the air outlet side of the axial flow impeller; A blade root, extending from the bottom end of the leading edge of the blade to the bottom end of the trailing edge of the blade, and used to be connected to the outer peripheral surface of the hub of the axial flow impeller; as well as A blade tip extending from the top of the leading edge of the blade to the top of the trailing edge of the blade; The blade profile frame of the blade is composed of the blade top profile line of the blade top, the blade root profile line of the blade root, the front profile line of the blade front and the trailing edge profile line of the blade trailing edge, the blade cross-section profile line of the blade is controlled by the blade top profile line and the blade root profile line, the blade cross-section of the blade is controlled by the front profile line and the trailing edge profile line, and the front profile line and the trailing edge profile line respectively guide the blade cross-section to sweep from the blade root to the blade top, so that the blade profile of the blade presents a twisted and uneven state in the blade height direction; the front profile line and the trailing edge profile line are respectively formed by the intersection of axial and axially perpendicular curved surfaces, and in the curved surfaces constructed by the front profile line and the trailing edge profile line: the curved surfaces perpendicular to the axial direction all have a single hump-shaped feature with a protruding abdomen, the axial curved surface construction line in the front profile line construction curved surface is wavy, and the axial curved surface construction line in the trailing edge line construction curved surface is sickle-shaped.

2. The blade according to claim 1, characterized in that The pressure surface profile of the blade tip satisfies the relationship: y = 0.0019x 2 -0.7729x+22.196; and the pressure surface profile of the blade tip satisfies the relationship: y=0.0042x 2 -0.855x+17.979; x is the X-axis coordinate point value on the corresponding X-axis, y is the Y-axis coordinate point value on the corresponding Y-axis, and the value range of x is -21.0252≤x≤60.

706.

3. The blade according to claim 2, characterized in that The intersection of the pressure surface profile line of the blade tip and the suction surface profile line of the blade tip is chamfered, and the fillet radius of the chamfer is 0.5≤R≤1.

4. The blade according to claim 1, characterized in that The pressure surface profile of the blade root satisfies the relationship: y = 0.0056x 2 -0.00005x+2.996; and the pressure surface profile of the blade root satisfies the relationship: x=0.0127y 2 -0.0009y-2.5387; x is the X-axis coordinate point value on the corresponding X-axis, y is the Y-axis coordinate point value on the corresponding Y-axis, and the value range of y is -22.9133≤y≤21.0573.

5. The blade according to claim 4, characterized in that The pressure surface profile line of the blade root and the suction surface profile line of the blade root are connected in a rounded corner, and the fillet radius of the rounded corner is 0.5≤R≤1.

6. An axial flow impeller, characterized in that: The invention comprises a hub and a plurality of blades according to any one of claims 1 to 5, wherein the blades are arranged on the outer peripheral surface of the hub at intervals in the circumferential direction.

7. The axial flow impeller according to claim 6, characterized in that: The ratio of the diameter of the hub to the outer diameter of the axial flow impeller is 0.18 to 0.

22.

8. A fan, characterized in that: It comprises the blade according to any one of claims 1 to 5 or the axial flow impeller according to any one of claims 6 to 7.

9. An engine, characterized in that: Comprising the fan as claimed in claim 8.

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