WO2022079316A1

WO2022079316A1 - Aerodynamic spolier for jetfan bellmouth

Info

Publication number: WO2022079316A1
Application number: PCT/EP2021/078826
Authority: WO
Inventors: Fathi Tarada
Original assignee: Mosen Ltd
Priority date: 2020-10-16
Filing date: 2021-10-18
Publication date: 2022-04-21
Also published as: GB2599949B; EP4229277A1; GB202016446D0; GB2599949A

Abstract

An aerodynamic spoiler (4) attached to a fraction of the circumference of a bellmouth (3) in order to eliminate separation of the inlet flow in fan assemblies used in ventilating tunnels and other internal spaces.

Description

AERODYNAMIC SPOILER FOR JETFAN BELLMOUTH

FIELD OF INVENTION

[0001] The present invention relates to an aerodynamic spoiler fitted to a jetfan bellmouth.

BACKGROUND OF THE INVENTION

[0002] Bellmouths are routinely used in the ventilation industry at fan inlets. They are conventionally designed to provide a smooth path with a monotonically decreasing flow area towards fan inlets, in order to prevent flow separation, and to ensure the uniformity of inlet flow.

[0003] A previous patent application number, GB2562091, filed by the present Applicant describes an improved jetfan, by tilting the nozzle trailing edge so that it forms an angle with respect to the fan centreline, with the surface of the nozzle throughbore being non-cylindrical in shape. Another patent application filed by the present Applicant, GB2562263, has the purpose of reducing the Coanda effect downstream of tunnel jetfans, in order to improve in-tunnel thrust and to enhance energy efficiency. This can be achieved by the installation of a bellmouth that can comprise a convergent section, a constant-area section and a divergent section.

[0004] In order to ensure that the flow entering the bellmouth at the inlet side of the jetfan does not separate at the vicinity of the shortest edge of the silencer throughbore, particularly for bench thrust tests, it is necessary to wrap the bellmouth throughbore around, to form a rounded nose facing the oncoming flow. This ensures that the air flowing from the discharge side of the jetfan is correctly shepherded into the bellmouth, without separating along the bellmouth or within the nozzle. [0005] The requirement for a wrap-around surface forming a rounded spoiler along the entire circumference of the bellmouth can cause production difficulties, particularly during the rolling of stainless steel sheet metal.

[0006] The Applicant believes that there remains scope to simplify the design of bellmouths for improving the efficiency of jetfans.

STATEMENTS OF THE INVENTION

[0007] According to one aspect of the invention, there is provided a fan assembly for installation in an internal space to provide ventilation in the internal space, the fan assembly being arranged or arrangeable such that a ventilating flow will pass through the nozzle throughbore before entering the fan; the assembly comprising: a fan for generating a ventilating flow, the inflow into the fan being substantially parallel to the outflow from the fan; a nozzle has a trailing edge at the distal end from the fan; and a bellmouth is attached to the nozzle trailing edge; wherein the angle made between the nozzle trailing edge and a centreline of the fan is not perpendicular; and wherein: the bellmouth throughbore is extended along part of its circumference to form an aerodynamic spoiler.

[0008] The invention provides a solution to the technical issue of how to avoid separation at the inlet to the nozzle described in GB2562091. The solution proposed in GB2562263 is feasible and proven using Computational Fluid Dynamics (CFD). However, the previous solution involved wrapping the leading edge of the bellmouth around its entire circumference. The process of rolling stainless steel sheet metal can cause significant distortions. [0009] The solution identified by the Applicant is to develop a solution that treats the flow separation issue where it originates, namely for the flow along the shortest edge of the nozzle throughbore. Without adequate precautions, the inlet flow along the shortest edge may lift up and separate from the nozzle throughbore, causing a significant pressure drop and additional power consumption.

[0010] Separation of the flow along the shortest edge of the nozzle throughbore can be particularly acute when a jetfan manufactured in accordance with GB2562091 is tested on a bench, as opposed to a tunnel installation. This is because the angle of flow incidence at the bellmouth is much greater on a test bench rather than in a tunnel with a background velocity flowing in the same direction as the air discharged from the jetfan.

[0011] The Applicant’s CFD analysis has shown that it is possible to eliminate the flow separation at the inlet by the simple expedient of using an aerodynamic spoiler to shepherd the airflow flowing from the discharge side of the jetfan. This spoiler can either be an integral part of the inlet bellmouth, or an external attachment to the inlet bellmouth. Using a spoiler described in this invention avoids the need to wrap the bellmouth surface around itself around its entire circumference.

[0012] For reversible jetfans, the present invention should preferably be used on both the inlet and outlet bellmouths. For unidirectional jetfans, the present invention should be used on the inlet bellmouth side.

[0013] The aerodynamic spoiler is preferably arranged as a rotational projection about the bellmouth axis. Such a geometry is readily manufactured using standard spinning, rolling and machining production techniques.

BRIEF DESCRIPTION OF THE DRAWINGS [0014] A number of preferred embodiments of the present invention will now be described by way of example only, and with reference to the accompanying drawings, in which:

[0015] Fig.l shows a vertical section through an embodiment of a ventilation apparatus with a bellmouth and aerodynamic spoiler as described in this invention installed on one side of a fan assembly;

[0016] Fig. 2 shows an end view of an embodiment of a ventilation apparatus with a bellmouth, and with the aerodynamic spoiler arranged at the bottom of the bellmouth; and

[0017] Fig. 3 shows a 3D isometric drawing of an embodiment of a ventilation apparatus with a bellmouth and aerodynamic spoiler as described in this invention installed at the end of a nozzle.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0018] Referring to Figure 1, this shows a sectional side view of an embodiment of the present invention within the inlet side of a ventilation apparatus.

[0019] In this embodiment, a fan assembly comprising a fan (1) extracting flow from the ambient via a nozzle (2) and a bellmouth (3). The bellmouth is extended along part of its circumference in the vicinity of the end of the shortest nozzle edge to form a partial loop which acts as an aerodynamic spoiler (4). The extension is only a fraction of the bellmouth circumference, typically in the range of a 10 to 180 degree angle measured about the bellmouth axis.

[0020] The aerodynamic spoiler (4) is shown as a thin sheet of metal in figure 1, but it could also be produced as a separate solid piece and attached to the bellmouth. The aerodynamic spoiler can also be produced as a separate sheet of metal and welded onto the bellmouth. [0021] Figure 2 shows an end view of an embodiment of the invention, with an aerodynamic spoiler (4) installed on a bellmouth (3). The spoiler (4) is formed by an extension of part of the bellmouth which curves back towards the assembly in a partial loop structure to form a rounded nose. The figure serves to highlight the limited angular extent of the aerodynamic spoiler. This figure indicates a preferred angular extent of 30 degrees about the bellmouth axis for the aerodynamic spoiler, but other angular extents are also possible.

[0022] This invention permits the under-hang of the bellmouth relative to the lower edge of the nozzle to be reduced or eliminated. This can be achieved by rotating the nozzle and bellmouth about the fan axis, such that the aerodynamic spoiler does not protrude into the occupied space. For reversible jetfan operation, the nozzle/bellmouth angle of rotation is preferably set by reference to the required discharge angle of the flow.

[0023] It would be possible to modify an existing fan assembly in order to fit nozzles as described in this invention to one or more sides of a fan, and hence reap the benefits of improved performance.

[0024] This invention is equally beneficial for the ventilation of tunnels, underground car parks and similar internal spaces.

[0025] It will be appreciated that the foregoing are merely examples of embodiments and just some examples of their use. The skilled reader will readily understand that modifications can be made thereto without departing from the true scope of the inventions.

Claims

CLAIMS:

1. A fan assembly for installation in an internal space to provide ventilation in the internal space, the fan assembly being arranged or arrangeable such that a ventilating flow will pass through the nozzle throughbore before entering the fan; the assembly comprising: a fan for generating a ventilating flow, the inflow into the fan being substantially parallel to the outflow from the fan; a nozzle has a trailing edge at the distal end from the fan; and a bellmouth is attached to the nozzle trailing edge; wherein the angle made between the nozzle trailing edge and a centreline of the fan is not perpendicular; and wherein: the bellmouth throughbore is extended along part of its circumference to form an aerodynamic spoiler.

2. A fan assembly according to claim 1, wherein the aerodynamic spoiler extends the bellmouth throughbore in a partial loop to form a rounded nose.

3. A fan assembly according to claim 1 or claim 2, wherein the aerodynamic spoiler is integral to the bellmouth.

4. A fan assembly according to claim 1 or claim 2, wherein the aerodynamic spoiler is a separate part from the bellmouth.

5. A fan assembly according to any of the preceding claims, wherein the aerodynamic spoiler is arranged as a rotational projection about the bellmouth axis.

6. A fan assembly according to any of the preceding claims, wherein the aerodynamic spoiler is installed on both the inlet and discharge sides of a fan assembly.