RU2778104C1 - Local exhaust ventilation suction flare extension device - Google Patents

Abstract

FIELD: ventilation technology.

SUBSTANCE: invention relates to ventilation technology and can be used for local remote removal of harmful gases and fine aerosol near the source of their release, in particular in welding, soldering, painting, in the process of packaging powders, in electroplating, etc. The device for extending the suction torch of local exhaust ventilation contains a housing with a suction pipe coaxially placed in it, having a receiving opening at the cut, and a diffuser associated with it, located at the level of the cut of the suction pipe from the side of its receiving opening, while the walls of the diffuser have a bend with a radius of curvature R_d = γR_c, where R_c is the hull radius; 0.3 < γ < 1.2 bend shape factor. The body of the device is composite and includes an annular cylindrical section arranged in series with a tangential inlet pipe, a tapering transitional annular conical section and an annular cylindrical section associated with a profiled diffuser, the opening angle of which is 90° < β < 180°.

EFFECT: increase in elongation of the suction torch for local exhaust ventilation.

1 cl, 6 dwg

Description

The invention relates to ventilation technology and can be used for local remote removal of harmful gases and fine aerosol near the source of their release, in particular in welding, soldering, painting, in the process of packaging powders, in electroplating, etc.

An urgent problem in industrial enterprises is the cleaning of workplaces from air pollution by gases, smoke or dust. The most effective methods of ventilation are methods of removing harmful gaseous emissions near the source of their release, which prevents the spread of pollution throughout the room and reduces the cost of general ventilation.

There is a known disadvantage of the suction torch formed by a standard ventilation funnel. It is well known that in such a flow the velocity of the air flow falls inversely to the square of the distance from the entrance to the aperture of the funnel. A simple point flow model predicts the indicated pattern of exhaust velocity decay and, accordingly, explains the relatively short length of the suction plume created when polluted air is drawn through the funnel.

For a number of technologies, such as welding, soldering, etc., the specifics of the process require a certain free space for performing operations, which imposes restrictions on the positioning of the input element of the exhaust ventilation system. For example, in electric welding, it is recommended to remove ~ 1000 m ³ /h of welding aerosol from the area of the welding arc. When such a gas flow is taken using a standard funnel connected to an exhaust pipe with a diameter of 160 mm, a stable welding aerosol capture zone is formed only at a distance of less than 0.5 m along the axis from the funnel inlet. Taking into account the scale of the length of the operator's arm (~ 0.6 m), it can be concluded that in order to ensure the free operation of the electric welder, the suction element of the exhaust ventilation must be installed at a distance of 1 - 1.2 m.

It is known to use supply ventilation flows to direct (push) polluted air from the area of emissions to the exhaust device [US5063834, 12.11.1991, B08B15/02; US2007272230, 11/29/2007, F24C15/20, F24F7/06, F24F9/00, F26B21/00], thereby creating an increase in the effective distance of polluted air capture by the local ventilation system.

The disadvantage of the method of ‘pushing out’ polluted air into the area of direct action of the suction funnel or other exhaust device is the need for an appropriate spatial placement of sources of jet streams of supply ventilation so that the source of harmful emissions is located between the area of the supply jet and the area of operation of the hood. However, the specified coordinated separate placement of interacting devices for exhaust and supply ventilation is in many cases not possible due to the limitations of a particular production process or the specifics of the spatial arrangement of equipment.

Local ventilation devices are known, in which the means of exhaust and supply ventilation are concentrated in a single unit [US20070202791, 30.08.2007, B08B15/00; RU2428635, 08.12.2009, F24F 7/06, B08B 15/0; US20100126123, 05/27/2010, B01D45/08, B01D45/16, F24C15/20; RU2046258, 06/20/1992, F24F 7/06, B08B 15/00]. The inventions solve the problem of improving working conditions by increasing the efficiency of removing harmful substances by changing the structure of the suction torch of local ventilation.

An analysis of these solutions from the point of view of practical application requires consideration not only of estimating the dimensionless parameter of the elongation of the suction torch, expressed in calibers z / d, where z is the distance along the axis from the apparatus exit , d is the diameter of the exhaust channel, but also minimizing the relative size of the apparatus in the radial direction D/d, where D is the diameter of the entire device.

In known technical solutions [US20070202791, 08/30/2007, B08B15/00; RU2428635, 08.12.2009, F24F 7/06, B08B 15/02; US20100126123, 05/27/2010, B01D45/08, B01D45/16, F24C15/20] the peripheral supply air flow leaving the devices is swirled using swirlers of various types, while the radius of the source of the outgoing coaxial annular cylindrical or conical jet (deflected with slotted deflector [US20100126123]) is increased and is 3-4 times the diameter of the central intake hole of the hood. The latter is associated with preventing the direct interaction of oppositely directed flows and the occurrence of a significant velocity gradient in the radial direction and, accordingly, the generation of large-scale turbulence.

A significant drawback of these devices [US20070202791, 08/30/2007, B08B15/00; RU2428635, 08.12.2009, F24F 7/06, B08B 15/02; US20100126123, 05/27/2010, B01D45/08, B01D45/16, F24C15/20] to swirl the outgoing peripheral supply air flow using swirlers of various types, is a significant increase in the parameter D / d, i.e. dimensions in the radial direction, which significantly limits the conditions for the practical application of these devices. For example, the relative size of the apparatus in the radial direction D/d = 5 for the devices proposed in patents US20070202791 and RU2428635, D/d = 3.5 for option No. 6 of the device proposed in patent US20100126123.

In the device [US20100126123, May 27, 2010, B01D45/08, B01D45/16, F24C15/20] for removing kitchen smoke, an air curtain is created with the help of jet streams of supply air deflected by a deflector with respect to the exhaust axis, replacing bulky exhaust hoods. The induced circulation cell is used to transport kitchen smoke from the surface of the stove to the zone of direct action of the hood fan.

It should be noted here that the device proposed in the said patent and, especially, the essential condition for using the device above a plane, make it possible to attribute the generated flow structure to a wide class of vortex-plane interaction flows, including tornado-like flows. It is well known that the observed vortex updraft of a tornado is generated by the existence of a parent cloud supplying circulation due to the existence of a radial boundary layer above the plane. In other words, the solution described in the mentioned patent involves the removal of polluted air from the surface (plane), and it is the presence of the surface (plane) that ensures the adequate functioning of the device.

The disadvantage of the device is also the impossibility of continuous operation of the described type of deflector designed to deflect the peripheral flow.

The closest in technical essence to the claimed invention is a local exhaust ventilation device [RF patent No. 2046258, 06/20/1992, F24F 7/06, B08B 15/00], taken as a prototype. The specified device is a compact apparatus for extracting from an increased distance (z/d = 6 - 7.5) the capture of harmful substances from the area of its occurrence, regardless of the presence or absence of a plane located normal to the device, while D/d = 3.

The local exhaust ventilation device comprises a cylindrical body with a suction pipe coaxially placed in it, having a receiving opening at the cut, and with a conjugated diffuser located at the level of the cut of the suction pipe from the side of its receiving opening, a peripheral flow swirler located between the body and the branch pipe. The device makes it possible to form supply air into a swirling peripheral flow shielding the central suction torch in the form of an open radial fan jet.

The openness of the radial fan jet formed from the peripheral flow does not allow to fully realize the functionality of focusing central suction torch.

This device is characterized by complexity in the manufacture and installation of the bladed swirler in the body of the device. In addition, the profiled diffuser with an opening angle of 180° indicated in the device diagram does not provide the necessary condition for the separation angle of the peripheral air flow for the formation of a closed swirling jet regime.

Thus, the disadvantages of the known device are insufficient efficiency and functionality.

The problem to be solved by the claimed invention is to create a highly efficient device for extending the suction torch for local exhaust ventilation.

To solve this problem, a device for local exhaust ventilation is proposed. Due to the design features of the device, a supply air flow is formed in the form of a toroidal circulation area that shields the central suction torch, and thereby, due to the entrainment of air from the axial region in the direction of the exhaust, an increase in the length of the central suction torch is achieved.

According to the invention, the local exhaust ventilation device comprises a housing with a suction pipe coaxially placed in it, having an inlet at the cut, and a diffuser associated with it, located at the level of the cut of the suction pipe from the side of its inlet, while the walls of the diffuser have a bend with a radius of curvature R _d \u003d γR _to , where R _to - the radius of the body, γ - the coefficient of the form of the bend, 0.3 < γ < 1.2.

According to the invention, the body of the device is composite and includes a coaxial annular cylindrical section with a tangential inlet pipe, a coaxial tapering transitional annular conical section and a coaxial annular cylindrical section conjugated with a profiled diffuser, the opening angle of which is 90° < β < 180°.

The essence of the invention is illustrated by drawings.

Figure 1 shows the device in axial section and flow diagram.

Figure 2 - cross-section of the device at the level of the annular cylindrical section containing the tangential inlet pipe, view A-A.

Figure 3 - profile of the diffuser in the meridional section.

The figures indicate: 1 - suction pipe; 2 - tangential inlet pipe; 3 - coaxial annular cylindrical section containing a tangential inlet pipe;

4 - coaxial tapering transition annular conical section, 5 - coaxial annular cylindrical section; 6 - profiled diffuser; 7 - closed swirling jet; 8 - toroidal circulation area; 9 - suction torch; β - diffuser opening angle; R _d - radius of curvature of the diffuser profile arc in the meridional section.

The device comprises a suction pipe 1 and a composite housing coaxial with it, between which a coaxial channel is formed for the passage of supply air. Composite housing includes a coaxial annular cylindrical section 3 with a tangential inlet pipe 2 for directing the supply air through it, a coaxial tapering transitional annular conical section 4, a coaxial annular cylindrical section 5 associated with a profiled diffuser 6 with a given opening angle to induce the supply jet leaving the device into the shape of an annular cone.

The diffuser is made with smoothly expanding walls, profiled with a curvature that provides continuous flow around the surface of the diffuser by a peripheral air flow with a change in its direction from axial to radial. In the meridional section, the diffuser profile is an arc with curvature R _d = γR _k , where R _k is the radius at the level of conjugation of the diffuser with the device body, while 0.3<γ<1.3, where γ is the bend shape factor, and the angle diffuser opening β is determined by the condition 90° < β <180°; the lower edge of the diffuser 6 is at the level of the cut of the suction pipe.

The device works as follows.

The supply air enters through the tangential inlet pipe 2 into the coaxial annular cylindrical section 3 with peripheral flow swirling due to the tangential input of the supply air.

Then the swirling peripheral air flow passes through the coaxial tapering conical section 4 to equalize the unevenness of the velocity field and the coaxial cylindrical section 5 associated with a profiled diffuser 6 having a given opening angle, where it receives a uniform distribution of the tangential velocity component around the circumference (uniform swirl) and enters exit from the coaxial channel in the form of a hollow, intensely and uniformly swirling jet, the bulk of which is concentrated at the outer wall of the cylindrical section. The profiled diffuser forms an inlet jet leaving the device in the form of an annular cone 7 and provides a spatial regime of the jet stream lines closed to the exhaust opening.

The opening angle of the diffuser, selected from the range from 90° to 180°, provides a laminar suction flow, because there is no interaction of countercurrent flows. The profile of the diffuser, representing an arc with curvature R _d = γR _k , where 0.3 <γ< 1.2, provides a non-separated peripheral air flow around the diffuser surface with a change in its direction from axial to radial.

Thus, a toroidal circulation area 8 is formed, screening the exhaust flow, and thereby increasing the length of the suction torch 9 due to the entrainment of air from the axial region towards the exhaust zone.

Thus, in the claimed solution, unlike the prototype:

1. swirling of the peripheral flow is carried out without the use of a swirler, solely due to the design of the device, the body of which is made of sections of various shapes and a profiled diffuser arranged in series coaxially to the suction pipe 1;

2. The peripheral swirling flow of the supply air is organized in the form of a closed jet, while part of the flow lines of the supply flow penetrates into the outer part of the exhaust flow, thereby increasing the length of the suction torch.

To confirm the claimed technical result, experimental studies were performed to remove glycerin vapor from a local source located at a distance of 350 mm from the exhaust outlet of the local ventilation device, while the diameter of the suction pipe was 40 mm, i.e. z/d ≈ 8.8, and the flow velocity at the device inlet was 3 m/s.

The velocities in the complex three-dimensional flow field created by the device were studied using the LAD-06C developed at the IT SB RAS. The measurements were carried out by moving the LDA point measuring volume across and along the suction flow created by the device for diffuser opening angles of 45°, 90° and 180°.

In FIG. 4 shows a visualization of the transport of glycerol vapors by a local ventilation device with a 45° diffuser. The suction flow provided by a device with a diffuser opening angle of 45° is characterized by a high level of turbulence at the boundaries of the suction flow caused by the interaction of countercurrent flows, which indicates the unacceptability of such a device for local ventilation.

The suction flows provided by devices with diffuser opening angles of 90° and 180° are laminar (or quasi-laminar) as shown in FIG. 5.

The experimental results of non-intrusive flow velocity field diagnostics with LDA were used to test the retention and elongation of the suction plume area.

Experiments on measuring the axial velocity profile generated by the device using a laser anemometer showed higher values of velocity in the exhaust flow at a given distance from the inlet pipe compared to the velocity along the axis of the suction torch when the peripheral flow was turned off.

In FIG. 6 shows the axial (along the axis of the device) distribution of the velocity component V _z created by devices with different diffusers, where: 1 - calculated values of V _z in the absence of peripheral flow; 2 - experimental values of V _z in the absence of peripheral flow; 3 - calculated values of V _z for a device with a diffuser having an opening angle of 45°; 4 - experimental values of V _z for a device with a diffuser having an opening angle of 45°;

5 - calculated values of V _z for a device with a diffuser having an opening angle of 90°; 6 - experimental values of V _z for a device with a diffuser having an opening angle of 90°; 7 - calculated values of V _z for a device with a diffuser having an opening angle of 180°; 8 - experimental values of V _z for a device with a diffuser having an opening angle of 180°. The elongation of the suction torch area was confirmed by calculations and experimentally by increasing the speed along the axis of the device with diffusers having an opening angle of 90° (lines 5 and 6); and 180° (lines 7 and 8), compared with the velocity along the axis of the device in the absence of peripheral flow (lines 1 and 2).

Thus, the elongation of the suction torch of the local ventilation device was confirmed due to the organization of a closed swirling peripheral jet.

Claims (1)

A device for extending the suction torch of local exhaust ventilation, comprising a housing with a suction pipe coaxially placed in it, having an inlet at the cut, and a diffuser associated with it, located at the level of the cut of the suction pipe from the side of its inlet, while the walls of the diffuser have a bend with a radius curvature R_d = γR_to, where R_to hull radius; 0.3 < γ < 1.2 bend shape factor, characterized in that the body of the device is composite and includes an annular cylindrical section arranged in series with a tangential inlet pipe, a tapered transitional annular conical section and an annular cylindrical section associated with a profiled diffuser, the opening angle of which is 90° < β < 180°.

Images