HK1164408A - Fan blade - Google Patents

Abstract

The invention relates to a fan blade (6), in particular for smoke extractor fans, comprising fastening means (5) for mounting the fan blade (6) on a fan hub, and a blade section (7). In order to improve such a fan blade (6) in terms of the amount of material used and the mass, the blade section (7) has an outer casing (8) which encloses a hollow space.

Description

The present invention relates to a fan blade, particularly for smoke extraction fans, with fastening means for attaching the fan blade to a fan hub as well as with a blade section.

Fans for subways or tunnels and/or enclosed vehicle structures such as underground garages must operate reliably over very long periods of time under various load and environmental conditions. It is typical for fans to be installed in subways, tunnels, or underground garages designed for operation over several years or even decades. In particular, when fans are used as smoke extraction fans in subways or tunnels, the metro or tunnel operator has requirements regarding the operability of the fan at high temperatures, which occur especially during fires. Some of these requirements are legally defined. On the other hand, as is generally common practice, there is a desire to manufacture fans as cost-effectively and material-efficiently as possible.

Generally, fans, according to their basic structure, consist of a fan hub, to which a number of fan blades are radially attached. The attachment of the fan blades is done using fastening means such as, for example, bolts. See, for example, US 2,342,421 A1.

In view of the aforementioned general requirements for fans, different types of fan blades are conceivable. To keep the weight low, fan blades can be manufactured as solid parts from aluminum or an aluminum alloy. However, a disadvantage of fan blades made from aluminum is their limited applicability at temperatures above approximately 300°C. This is because the tensile strength of aluminum significantly decreases at these temperatures, causing the aluminum to gradually flow. Even special aluminum alloys cannot substantially improve this deficiency. As a result of this unfavorable property of aluminum, fan blades can change their shape and/or length at high temperatures, such as those that may occur during fires, thereby greatly impairing or even making their proper use during fires impossible.

Because of this inadequacy of aluminum fan blades, in the current state of the art for smoke extraction fans, solid steel fan blades are used under high loads, that is, at high rotational speeds and/or with long blade lengths. However, steel fan blades have the disadvantage of having a very high weight and being expensive to manufacture due to the large amount of material used.

It is therefore the object of the present invention to provide a fan blade of the aforementioned type which can be used without limitations even at high temperatures, such as those that may occur, for example, in tunnel fires, without having an undesirably high mass.

According to the invention, this object is achieved in a fan blade of the type mentioned at the beginning by having the feature combination of claim 1. In particular, the blade section has an outer casing enclosing a cavity. Thus, it is provided that the blade section of the fan blade is not solid throughout, as is the case in the prior art. This directly results in a saving of material and weight.

In order to improve the stability of the inventive fan blade, particularly its tensile strength, a support element is arranged in the cavity according to the invention.

In particular, in further preferred embodiments of the invention, the support element is formed integrally with the fastening means. In this way, the unit composed of the fastening means and the support element arranged in the cavity of the blade section can advantageously absorb all tensile forces during operation. The outer casing of the blade section mainly fulfills aerodynamic functions according to this advantageous embodiment of the invention. Advantageously, a material optimized for the purpose of strong fastening of the fan blade to the fan hub can be selected in this manner, while at the same time a material optimized for the aerodynamic shaping of the fan blade can be selected independently thereof. In particular, the support element can advantageously be made from a material having high high-temperature tensile strength and good creep resistance at high temperatures. According to the invention, an lightweight outer casing of the fan blade, for example made from a suitable steel alloy, can simultaneously be selected without adversely affecting the overall strength of the fan blades. Within the scope of the invention, however, other materials or alloys, for example based on titanium, can also be used.

If the carrier element is essentially made of a steel alloy and/or a titanium alloy, the invention provides, in a particularly advantageous embodiment, the advantage that the high-temperature strength and creep resistance of the turbine blade are especially high. This is particularly true for steel alloys. Because the high-temperature strength and creep resistance of steel are also excellent at temperatures above, for example, 300°C. In particular, the high-temperature strength at these temperatures is significantly better than that of aluminum.

According to the invention, the support element is designed as a module composed of several individual elements, in particular connectable to each other via a plug connection. The modular design of the support element allows for particularly cost-effective manufacturing based on standardized individual components, which can be adapted to different types of fans. Furthermore, the modular design enables the use of standardized parts in manufacturing for various fan blades, especially with regard to their length.

It is particularly advantageous in another embodiment of the invention if the support element has one or more profile tendons adapted to a shape of the outer casing. A profile shape of the fan blade can thus be manufactured technically by form-coupled bending of the outer casing to the profile tendons. Therefore, maintaining the aerodynamic profile of the fan blade even at high temperatures is advantageously ensured.

In another preferred embodiment of the invention, the cavity is filled with a foam-like filling mass. The foam-like filling mass should advantageously have a low mass or density. Advantageously, the outer casing can be supported according to the invention by the foam-like filling mass in order to maintain the aerodynamic profile. This effectively prevents dents in the outer casing, for example, in areas between the profile ribs of the support element. Moreover, filling the cavity with a foam-like filling mass advantageously prevents liquids from accumulating inside the cavity. The accumulation of liquids in the cavity would undesirably increase the effective mass of the fan blade. Furthermore, there is a risk of corrosion when water enters the cavity. Additionally, the vibration behavior and damping of the blade are improved by foaming. All these disadvantages are effectively prevented by filling the cavity with the foam-like filling mass. In particular, a two-component mixable foam has proven to be suitable as the filling mass.

If the outer casing according to another embodiment of the invention is provided with at least one opening leading into the cavity, a further advantageous embodiment of the invention is obtained. If the opening is located at the radially outer end of the fan blade, any liquid that has entered the cavity during operation is carried out of the cavity by centrifugal force. This advantageously avoids an unwanted increase in the mass of the fan blade due to accumulated condensate inside and an increased risk of corrosion. Providing an opening at the radially inner end of the fan blade particularly allows for inspection of internal weld seams, for example by means of endoscopic methods. This is advantageous when a welding connection between the outer casing and the support element exists.

Another advantageous embodiment of the invention provides that the outer sheath is coated with a corrosion protection on the hollow space side and/or is essentially made of a steel alloy. Both measures, individually or in combination, result in a significant improvement in the corrosion resistance of the outer sheath. This in turn allows for a thin-walled design of the outer sheath. For example, a material thickness of 1 mm may be sufficient for the outer sheath.

In another embodiment of the invention, the outer casing consists of two or more plate-like casing elements connected together.

In particular, the torsional strength of the inventive fan blade is advantageously improved in an embodiment of the invention when the outer casing is provided on the outside with stiffening elements for stiffening the fan blade (6).

The stiffening elements can be arranged on a pressure side and/or on a suction side of the outer casing in another embodiment of the invention. For example, the stiffening elements may be more pronounced on the suction side than on the pressure side.

The invention is described by way of example in a preferred embodiment with reference to a drawing, wherein further advantageous details can be found in the figures of the drawing.

Functionally identical parts are marked with the same reference designations.

The figures of the drawing show in detail: Figure 1: Supporting element for an inventive fan blade in a perspective view; Figure 2: Inventive fan blade (a) in an axial view and (b) in a radial cross-sectional view; Figure 3: Inventive fan blade in an alternative design, the views corresponding to those of Figure 2.

In Figure 1, a steel frame structure 1 is shown in a perspective view. The steel frame structure 1 consists of a total of three profile chords 2. The profile chords 2 are connected to each other via two cross bracings 3 by means of a plug-in connection. The profile chords are connected via the cross bracings 3 such that twisting of the profile of a fan blade manufactured from a profile chord 2 by applying an outer casing on the circumferential edges 4 of the profile chord 2 is generated. The profile chord 2 in the foreground of the figure is integrally connected with a fastening bolt 5. This is not visible in Figure 1. The fastening bolt 5 serves for attaching the fan blade to the steel frame structure 1 shown in Figure 1 within a not illustrated fan hub.

Figure 2 shows an inventive fan blade 6. The fan blade 6 has a fastening bolt 5 on its radial inner side, which was already mentioned in connection with Figure 1. The fan blade 6 has a blade section 7. The blade section 7 consists of an outer casing 8. The outer casing 8 is made of a number of individual steel plates with a material thickness of 1 mm. The steel plates are welded to the circumferential edges 4 of the profile chord 2 of the steel frame 1. In this way, the outer casing 8 encloses a cavity. Part of the cavity is filled with the steel frame 1. The remaining cavity can be filled with a filling mass. The radial view according to part (b) of Figure 2 clearly shows the aerodynamic profile of the fan blade 6. It can also be seen that a base plate 9 separates the blade section 7 from the fastening bolt 5. The fastening bolt 5 passes through the base plate 9.

In the radial top view according to Figure 2 (b), it is clearly visible that the profile of the outer casing 8 corresponds to the profile of the profile tendons 2 of the steel frame 1 according to Figure 1. The steel frame 1 is preferably made of steel. The outer casing 8 can be made of a steel alloy.

Within the outer sheath 8, a drainage hole 12 can be mounted radially on the outside. Furthermore, a endoscopic hole 13 can be present radially inside the outer sheath 8.

Figure 3 shows an alternative embodiment of an inventive fan blade. The representation and basic structure are essentially the same as those in Figure 2. However, the blade 6 according to Figure 3 is additionally provided with support plates 10, 11. The support plates 10, 11 are essentially perpendicular to the base plate 9. On the other hand, the support plates 10, 11 are essentially perpendicular to the surface of the outer casing 8 with their other edge. Thus, the support plates 10, 11 are essentially radially oriented, but are oriented substantially by 90° rotated relative to the outer casing 8 of the blade section 7. The overpressure-side support plate 11 is stronger than the underpressure-side support plate 10. The support plates 10, 11 can also be connected.

As shown in figures 1 to 3, the structure of an inventive fan blade 6 is thus illustrated. The inventive fan blade 6 is characterized in that an outer casing 8 made, for example, from a steel alloy is welded onto a steel frame 1. The welding takes place along the edge regions 4 of the profile ribs 2 of the steel frame 1. In this way, the outer casing 8 encloses a cavity in which the steel frame 1 is arranged. The remaining cavity can, according to the invention, be filled with a filler material. Thus, in accordance with the invention, a particularly lightweight, material-saving and yet robust design of a fan blade is obtained.

In the context of the invention, instead of steel, a titanium alloy or another material can also be used.

REFERENCE LIST

1 Steel frame 2 Profile cable 3 Cross brace 4 Perimeter edge 5 Fastening bolt 6 Fan blade 7 Blade section 8 Outer casing 9 Base plate 10 Support plate 11 Support plate 12 Drain hole 13 Endoscope hole

Claims (10)

1. Fan blade (6), in particular for smoke extractor fans, comprising fastening means (5) for fastening the fan blade (6) to a fan hub and comprising a blade portion (7), the blade portion (7) having an outer shell (8) that encloses a hollow space, a support element (1) being arranged in the hollow space, characterised in that the support element (1) is modularly formed from a plurality of individual elements that are in particular interconnected by a plug-in connection.
2. Fan blade (6) according to claim 1, characterised in that the support element (1) is integral with the fastening means (5).
3. Fan blade (6) according to any of the preceding claims, characterised in that the support element (1) is made substantially from a steel alloy and/or a titanium alloy,
4. Fan blade (6) according to any of the preceding claims, characterised in that the support element (1) has one or more chords (2) adapted to the shape of the outer shell (8).
5. Fan blade (6) according to any of the preceding claims, characterised in that the hollow space is filled with a foam-like filling material.
6. Fan blade (6) according to any of the preceding claims, characterised in that the outer shell (8) is provided with at least one through-bore (12, 13) going into the hollow space.
7. Fan blade (6) according to any of the preceding claims, characterised in that the outer shell (8) is provided with corrosion protection on the hollow-space side and/or is substantially made from a steel alloy.
8. Fan blade (6) according to any of the preceding claims, characterised in that the outer shell (8) consists of two or more interconnected plate-like shell elements.
9. Fan blade (6) according to any of the preceding claims, characterised in that the outer shell (8) is provided on the outside with reinforcing elements (10, 11) for reinforcing the fan blade (6).
10. Fan blade (6) according to claim 9, characterised in that the reinforcing elements (10, 11) are arranged on a pressure side and/or on a vacuum side of the outer shell (8),