Optimised tunnel ventilation device

Abstract

A ventilation device that enhances the effective longitudinal thrust of a fan assembly installed within a tunnel or other internal space. The nozzle trailing edge (6) is tilted so that it forms an angle (13) with respect to the fan centreline (7), with the surface of the nozzle throughbore being non-cylindrical in shape. The discharged flow (5) is turned away from the surrounding surfaces by a convergent-divergent bellmouth (1).

Claims

1. A fan assembly for installation in an internal space to provide ventilation in the internal space, the fan assembly comprising: a fan rotor for generating a ventilating flow, the inflow into the fan rotor being substantially parallel to the outflow from the fan rotor; a nozzle throughbore having an edge which, in use, is in proximity to a surrounding surface in which the fan assembly is installed; wherein: the nozzle has a trailing edge at the distal end from the fan; the fan assembly is arranged or arrangeable such that a ventilating flow generated by the fan will pass through the nozzle before exiting the assembly to enter a space to be ventilated; a bellmouth extending from the nozzle trailing edge, wherein the angle made between the nozzle trailing edge and a centreline of the fan is not perpendicular; the sidewalls of the nozzle throughbore diverge at an angle with respect to the fan centreline; and the nozzle trailing edge forms a circle.

2. A fan assembly according to claim 1, having a nozzle installed on each side of a fan.

3. A fan assembly according to claim 1, wherein the angle between the trailing edge and a line normal to the fan centreline is within the range of 5 to 60 degrees.

4. A fan assembly according to claim 1, wherein the cross-sectional area of the bellmouth throughbore decreases from the location of its attachment to the nozzle in the direction away from the fan, to a minimum cross-sectional area.

5. A fan assembly according to claim 2, wherein the bellmouth is rotationally symmetrical about its own central axis.

6. A fan assembly according to claim 2, wherein the bellmouth throughbore is arranged to be parallel to the shortest edge of the nozzle throughbore, at its point of attachment to the nozzle.

7. A fan assembly according to claim 2, wherein the bellmouth throughbore is arranged to form part of an elliptical arc at its point of attachment to the nozzle.

8. A fan assembly according to claim 2, wherein the bellmouth is arranged to form a part of an elliptical arc at the distal end from the fan.

9. A fan assembly according to claim 2 having two bellmouths, one installed on each side of the fan assembly.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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:

(2) Like reference numerals are used for like components throughout the figures;

(3) FIG. 1 shows a vertical section through an embodiment of a ventilation apparatus with nozzles as described in this invention installed on both sides of a fan;

(4) FIG. 2 shows an embodiment of a ventilation apparatus with a nozzle as described in this invention installed on one side of a fan;

(5) FIG. 3 shows a horizontal section through an embodiment of a ventilation apparatus with nozzles as described in this invention installed on both sides of a fan; and

(6) FIG. 4 shows an end view through an embodiment of a ventilation apparatus.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

(7) Referring to FIG. 1, this shows a sectional side view of an embodiment of the present invention within a bidirectional ventilation apparatus installed underneath a tunnel soffit, which is designed to operate in a fully reversible manner.

(8) In this embodiment, a fan assembly comprising a fan rotor (3) driven by a motor (4) is installed within a fan housing (2). The fan rotor (3) is mounted along the fan centreline (7).

(9) Airflow (5) enters the fan rotor (3) through a bellmouth (1) and an inlet nozzle throughbore (8), before being discharged thorough an outlet nozzle throughbore (9) and a bellmouth (1). The inlet and outlet trailing edges of the nozzle (6) are tilted at an angle (13) with respect to the normal to the fan centreline (7). The discharged airflow is turned by the upper surface of the bellmouth (1) in a direction away from the tunnel surfaces, hence reducing the Coanda effect.

(10) Preferably, the angle (13) is between 5 degrees and 60 degrees. Preferably still, the angle (13) is approximately 25 degrees.

(11) A larger geometric throat (14) can be arranged at both the inlet and discharge sides of the nozzle, by tilting the nozzle trailing edge (6) by the angle (13) between the normal to the throughbore (14) and the trailing edge (6). The trailing edge (6) can thereby increase in length.

(12) We refer now to FIG. 2, which shows a side view of a particular embodiment of this invention which would normally (but not exclusively) be operated in a unidirectional manner.

(13) In this embodiment, the indicated airflow direction is from left to right, i.e. the airflow (5) enters into a conventional nozzle (16) first, prior to being accelerated by the fan rotor (3) into a shaped nozzle with an outlet throughbore (9). The discharged flow is turned by the upper surface of the bellmouth (1). The bellmouth (1) is installed at an angle (13) with respect to the normal to the fan centreline (7), such that in use, the discharged air flows away from the surrounding tunnel surfaces.

(14) In FIG. 2, the flow direction can if necessary be reversed by running the fan rotor in the opposite direction. Due to the increased Coanda effect, a reduction of the in-tunnel aerodynamic thrust can be expected in the reverse flow direction (i.e. from right to left) in the embodiment described in FIG. 2.

(15) Referring now to FIG. 3, which shows a horizontal sectional view of an embodiment of this invention, it can be seen that the sidewalls of the throughbore diverge at an angle (15) with respect to lines parallel to the fan centreline (7). This underlines the non-cylindrical nature of the throughbore surface, and highlights the increase in flow area at the inlet and outlet planes (14).

(16) FIG. 4 shows an end view through an embodiment of a ventilation apparatus, with the edge of the nozzle throughbore at the distal end from the fan in the form of a circle with a specified diameter (17).

(17) 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.

(18) This invention is equally beneficial for the ventilation of tunnels, underground car parks and similar internal spaces.

(19) It will be appreciated that the foregoing merely provides illustrations 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.