WO2003000383A1

WO2003000383A1 - Particulate separator

Info

Publication number: WO2003000383A1
Application number: PCT/GB2002/002890
Authority: WO
Inventors: Abdelwahab Aroussi; Abdul Aziz Saud Abdulghani
Original assignee: The University Of Nottingham
Priority date: 2001-06-25
Filing date: 2002-06-25
Publication date: 2003-01-03
Also published as: GB0115456D0; WO2003000383B1

Abstract

A particle separator (300) is provided that mechanically separates airborne particles, such as dust, raindrops, pollen and cinders from fresh air taken into a motor vehicle heating, ventilation and air conditioning (HVAC) system (200). The particle separator (300) comprises at least one of disc (306a-d) mounted on a spindle (316). The separator (300) is integrated with the existing fan housing and is consequently independent of vehicle geometry and size.

Description

PARTICULATE SEPARATOR

This invention relates to a particulate separator. More particularly, but not exclusively, it relates to a particulate separator suitable for use with a vehicle heating ventilation and air conditioning (HVAC) system.

Since the 1940s, when vehicle HVAC became integrated fully with vehicle body design instead of being an add-on-unit, various climate control systems were introduced with the intention to create a comfortable climate inside the vehicle with its small interior volume (2-3m³) and its large surfaces of glass (2-3m²) . The penetration of rainwater through the heating ventilation and air conditioning system (HVAC) of a vehicle directly affects the provision of thermal comfort within the vehicle passenger compartment. Present vehicle designs restrict considerably the air-management processes due to reduced space and tighter packaging.

Alertness of the driver and his ability to concentrate on the traffic to a good extent depends on his level of comfort, particularly the humidity level. Furthermore, safe driving is possible only if the windshield and all other windows are clear. Hence the formation of mist on the inner surfaces of the glazed parts of the cabin must be avoided.

Parameters that have an impact on vehicle occupants' comfort fall into three groups. In-cabin parameters, which describe in vehicle temperature, micro- air velocity, in vehicle humidity, radiation from components, engine coolant temperature and particles/odour in the air. External parameters describe the ambient temperature, sun load, rain, snow, wind (force and direction), and vehicle cruising speed. Meanwhile, the human thermal physiology depends on the occupants' clothing, metabolism rate and their activity. Even for individuals, psychological and physical perception may vary at different times. In other words, the same ambient situation may be assessed differently, depending on whether the individual is tense or relaxed, tired or well rested.

A typical HVAC unit has a cowl box that is usually situated just behind grilles at the base of the vehicle's windshield. The cowl box directs air passing through the grilles into the HVAC unit. The cowl box is designed such that it separates some of the moisture from the air and then passes the air through a pollen filter, after that the air is is conditioned, heated or cooled as appropriate and blown into the vehicle's cabin, typically by a centrifugal fan blower through vents. The vents in the cabin direct the air onto the inside of the windshield and side windows, for thermal comfort and demisting purposes.

A recurring problem in automobile HVAC units is the ingress of water into the HVAC unit and consequently into the vehicle's cabin. The ingress of water into the HVAC unit causes a number of problems including the pollen filter becoming wet resulting in a reduction in its efficiency in removing dust particles. The reduced efficiency of the pollen filter results in a large pressure drop across it. This requires a more powerful fan to counteract the pressure drop.

In some cases, the pollen filter acts as a throttle in the flow path. If the filter swells due to water, this throttling effect increases as only part of its width is used and the lifetime of the filter is reduced.

Water that passes downstream, beyond the pollen filter, is sprayed onto the centrifugal fan and causes corrosion of the metal fan shaft. As is well known corrosion causes an acceleration of failure mechanisms thereby reducing the lifetime-to-failure of the fan shaft. Water in the HVAC system can also lead to corrosion of the vehicle's bodywork and can generate unpleasant smells in the vehicle's cabin. Moisture that passes through the HVAC and into the vehicle cabin causes misting of the vehicle's windows, resulting in poor driver visibility. Also, water collects in footwells of the vehicle leading to reduced comfort for both driver and passenger alike and corrosion.

Current HVAC systems attempt to overcome these problems by the use of baffles within the cowl box. This separates water and air such that air carried into the fan is nominally dry. The labarynthine flow path created by the baffles redirects the airflow so that the heavier water particles are unable to follow the flow path of the air. Such an arrangement is only partially successful in removing fluid particles entrained in air and whilst reducing the above mentioned problems does not eliminate them.

According to a first aspect of the present invention there is provided a particulate separator suitable for separating particles entrained in a gas comprising, a spindle, a drain, and at least one centrifuge member projecting outwards from the spindle and being arranged to rotate therewith such that a fraction of the entrained particles that contact the member is moved radially outward along the member to the drain.

This separator mechanically separates out particulate matter from air introduced into a vehicle's HVAC systems by use of the centrifuge principle.

Preferably the centrifuge member is an arm. More preferably there are a plurality of arms. The use of more than one arm increases the efficiency of the separator by providing an increased number surfaces with which particles can contact. Desirably the, or each, arm is comprised of a plurality of discrete fibres. Most desirably the, or each, arm may be in the form of a brush of filaments. The formation of each arm from a number of filaments further increases the surface area available to capture particulates. Also the use of a brush then minimises pressure drop associated with such an arrangement, reduces manufacturing problems and costs, and minimises noise associated with the separator. Alternatively the arm may be in the form of blades, rods, cones or any other suitable geometry.

The arm may be made of plastic, metal, ceramic or any other suitable material and may be perforated or solid. This allows the weight and strength of the separator to be modified in accordance with the stresses that are likely to be encountered in use.

The centrifuge member may be a disc. Preferably there are a plurality of discs that are typically spaced along the length of the spindle.

The separator may have a housing. Preferably the housing is arranged to be engageable with a fan housing of a vehicle's HVAC unit. More preferably the housing is releasably engageably with said fan housing.

Even more preferably the housing is arranged to occupy a space between the fan housing and an inner surface of the HVAC unit, typically around

30mm.

Thus the separator is easily mounted within a HVAC unit and may be easily removed for maintenance of the fan.

The spindle may be located in a collar in an opening in the housing. The opening may have a channel thereabout that is arranged to act as the drain. The opening may be of circular cross-section and the channel may be annular. The diameter of the opening may be approximately equal to twice the length of the, or each, arm. Alternatively the opening may be slightly larger than the diameter of the disc.

The spindle may be arranged to rotate freely in the collar, typically discrete from the fan spindle. The spindle may be unconnected to any drive means. Alternatively, the spindle may be connected to an air intake blower assembly through a gearbox. In a further alternative, the spindle may be connected to a spindle of the fan and may be arranged to be driven by a motor driving the fan.

Preferably the particles are at least one of the following: - water, pollen, cinders, dust, fibres, smoke, any particles sized lOμm or above (PM 10-20) .

Additionally preferable features of the first aspect of the present invention include one or more of the following :-

an integrated mechanically assisted particulate separator mounted in the system fan casing separates airborne rainwater, pollen, cinders and dust like objects which are found in the fresh air introduced to the system HVAC unit;

an integrated mechanically assisted particulate separator mounted on the fresh air intake blower shaft through a gearbox;

the particulate separator assembly is made of perforated plastic cones or a single brush like assembly, these are mounted inside the fan housing and are driven by the existing fan electric motor; the particulate separator efficiency is not affected by the fan rotational speed;

the particulate separator design is independent of the vehicle geometry and size or the external climate;

the particulate separator is light weight and does not require additional power from the fan's electric motor;

the separator's labyrinth arrangement does not impose additional and unaffordable pressure drop upstream of the blower;

the particulate separator does not generate any detectable aerodynamically generated noise; and

collecting said particles in a drain region adjacent to free end of said at least one arm.

Thus the separator is easily mounted with a HVAC unit and may be easily removable for maintenance of the fan.

According to a second aspect of this there is provided a method of separating particles from a gas comprising the steps of: i) providing a rotatable spindle having at least one centrifuge member projecting outwardly therefrom in a flow path of the air; ii) rotating said spindle such that a fraction of said particles collide with said at least one centrifuge member and migrate outwards along said centrifuge member under centrifugal action; and i) collecting said fraction of said particles in a drain region. According to a third aspect of the present invention there is provided a motor vehicle HVAC system including a particle separator according to a first aspect of the present invention.

According to a fourth aspect of the present invention there is provided a motor vehicle including a particle separator according to the first aspect of the present invention.

According to a fifth aspect of the present invention there is provided an air conditioning unit including a particle separator according to the first aspect of the present invention.

The air conditioning unit may be suitable for use in a clean room, a hospital, or a mineshaft.

According to a sixth aspect of the present invention there is provided a smoke filter including a particle separator according to the present invention.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic representation of an automobile showing factors that affect occupants' comfort;

Figure 2 is a schematic sectional view of a conventional vehicle HVAC unit;

Figure 3 is a plan sectional view of a vehicle HVAC unit incorporating a particle separator according to a first embodiment of the present invention; Figure 4 is a sectional view of the vehicle HVAC unit of figure 3;

Figure 5 is a plan view of a fan and separator arrangement according to a second embodiment of the present invention;

Figure 5a is a side view of part of a separator arrangement according to an embodiment of the present invention;

Figure 6 is a sectional view of the fan and separator of Figure 5; and

Figure 7 is a perspective view of part of a fibre of a brush of the separator of Figures 5 and 6.

Referring now to Figure 1, a vehicle 100 has an occupant's compartment 102 in which occupants 103a, b reside during a journey. The occupant's compartment 102 has glass windows 104 and air conditioning inlets 106. A number of factors affect the occupants' comfort, these can be divided into cabin parameters 108, external parameters 110 and human thermal physiology 112. Examples of such factors include sunload 114, rain 116, snow 118 and wind velocity 120.

Referring now to Figure 2, a conventional vehicle HVAC unit 200 comprises a cowl box 202, typically situated beneath a grille 204 adjacent the vehicle's windshield 205, connected to a pollen filter 206. A fan chamber 208 is on the opposite side of the filter 206 to the cowl box 202 and contains a blower fan 210 which is connected to an associated motor 212 by a drive spindle 213. An exit from the fan chamber 208 leads to a heater core 214. The heater core 214 has a footwell outlet 216, a face outlet 218 and a demister outlet 220. Additionally there is a recirculating channel 222 leading from inside the vehicle to the fan chamber 208. In use, air containing water and particles passes through the grille 204 into the cowl box 202, some of the water is separated from the air in the cowl box 202, typically by baffles (not shown) . In alternative embodiments the cowl box 202 may employ volume expansion, cyclonic action or any suitable form of obstruction to separate moisture from the air. The air and the remaining entrained particles and water pass through the paper pollen filter 206. The pollen filter 206 removes most particles down to a size of approximately lOμm. However, the entrained water causes the filter 206 to swell and become less efficient as the water is adsorbed by the filter 206. The air and water mixture passes into the fan chamber 208 where it is forced into the heater core 214 by the blower fan 210. The drive spindle 213 connecting the fan 210 to the motor can become corroded by the action of water leading to premature failure of the spindle 213. The fan 210 and heater core 214 are typically controlled by a microprocessor or user input controls in order to deliver this desired temperature to the vehicle's occupants.

Conditioned air is output into the vehicle's occupant compartment via the face outlet 216 and the footwell outlet 218 in order to maintain occupant comfort. Typically outlets can be closed should the occupants so choose. Conditioned air is output via the demisting outlet 220 onto an internal face of the windshield 205 in order to prevent the build up of water vapour on the windshield 205 and side windows, which reduces driver visibility.

The recirculating channel 222 removes a portion of air from the vehicle's occupant compartment and passes the air back into the fan chamber 208.

The recirculated air is forced into the heater core 214 by the fan 210. Recirculating the air reduces the load on the heater core 214 by presenting partially conditioned air to the core 214 thereby reducing the temperature variation required.

Referring now to Figures 3 and 4, a HVAC unit 300 incorporating a separator according to the present invention comprises a fresh air intake 302, having a pollen filter therein 303 leading to a fan 304. A plurality of separator discs 306a-d are located downstream of the fan 304. Air passes from the discs 306a-d via a dry air output 307 to an evaporator 308, a heater core 310, face, footwell and demister outlets 312, 314, 316. A recirculation air inlet 318 opens onto the fan 304, adjacent the fresh air intake 302 and operates substantially as hereinbefore described in relation to Figure 2.

In this embodiment a drive spindle 320 of the fan 304 is connected to the separator discs 306 by a gearbox 322, as will be described hereinafter, such that the separator discs 306 rotate on a spindle 324 at a rate that is linked to the -rate of rotation of the fan 304.

The discs 306 are typically conical but alternatively may be flat. The use of conical discs aids the migration of particles towards the outer edge of the discs 306 under gravity. The discs 306 have openings (not shown) therethrough in order to allow the passage of air.

An internal wall 326 of the separator 300 defines a duct 327 along which air can flow through the separator discs 306a-d and has a substantially U- shaped gutter 328 thereabout adjacent the downstream side of the edges of each of the discs 306 a-d in order to capture any captured particles that migrate over the discs' edges. The gutters 328 taper towards a drain region 329 through which the particles exit the separator 300. In use, air containing water droplets and solid particles is drawn into the fan 304 via the inlet 302. The air and the entrained particles pass along the duct 327 and collide with the first disc 306a and a fraction of the particles are captured on the disc 306a, with the air passing through holes in the disc 306a. The particles captured on the disc 306a are forced, centrifugally, towards the edge of the disc 306a. The particles eventually fall from the disc 306a into the gutter 328. The particles then move towards, and down, the drain region under gravity. Because the discs 306a-d are of substantially the same diameter as the duct 327, substantially all of the air flows through the discs 306a-d.

Each successive disc 306 b-d removes more of the particles entrained in the air until substantially dry air is output via the outlet 307.

Referring now to Figures 5 and 6, an alternative embodiment of a particle separator 500 according to the present invention comprises a housing 502 having an opening 504 therethrough, which is typically elliptical or circular in cross-section. An integrated cross-spar 506 extends diametrically across the opening 504 and has an annular collar 507 at the mid-point thereof. The collar 507 receives a spindle 508 that is free to rotate therein. The spindle 508 has two bunches of monofilament nylon fibres 510 a,b projecting radially therefrom. Alternatively, the spindle 508 has a disc, or a plurality of discs 511 a-c, of fibres projecting radially therefrom, as shown in Figure 5a. The opening 504 has a substantially grooved gutter 512 about an inner surface thereof. Free ends 514 a,b of the group of fibres 510 a,b lie above the gutter 512.

The housing 502 is attached on top of walls 515 of a fan 516 of a vehicle's HVAC unit. The fan 516 has a drive spindle 518 connected to a motor (not shown) with four equiangularly spaced blades 520 thereabout.

The housing 502 is typically 30 mm or less in height as this is typical of the clearance between the walls of the fan 516 and the HVAC's internal surface.

In this embodiment the spindle 508 is not connected to the drive spindle 518 and therefore the motor is not used to drive the spindle 508. This reduces the load on the motor and consequently the load on the vehicle's battery.

In use, the fan 516 is actuated and rotates. This causes air to be drawn through the housing 502. The passage of air through the housing 502 causes the bunches of fibres 510 a,b to rotate and forces the air through the bunches of fibres 510 a,b. Particles entrained in the air collide with the bunches of fibres 510 a,b and migrate radially outward along the bunches of fibres 510 a,b until they reach the free ends 514 a,b of the bunches of fibres 510 a,b centrifugally. Upon reaching the free ends 514 a,b of the bunches of fibres 510 a,b the particles drop under gravity, or are forced from the filaments 510 a,b centrifugally, into the gutter 512, or a drainage channel.

Referring now to Figure 7, an embodiment of a filament 700, suitable for use in a standard Class C saloon car, of the bunches of fibres 510a, b has four concave, curved outer surfaces 702a-d, typically quadrants of a circle each of which define a channel 704. Particles collected by the bunches of fibres 510a,b move outwards away from the spindle 508 along channels 704 under centrifugal action.

It will be appreciated that the filaments may be circular, rectangular, square, triangular in cross section, conical or of any convenient form.

The use of filaments provides only a small pressure drop, as little as O. lδPa, thus the vehicle's occupants experience of controlled airflow is unaffected. As a result of this the performance of the fan and the torque speed characteristics due to the added inertia of the brush mass are substantially unaltered by the addition of the separator.

The brush arrangement removes up to 90% of all water vapour entering the fan and can remove particles of a few microns, typically lOμm diameter or less.

Typically, the brush arrangement adds a maximum of 4dB to the existing noise level of the HVAC unit.

Whilst the invention has been described with reference to motor vehicle HVAC units it will be appreciated that it has applicability in any system where it is desirable to reduce particulate concentrations, for example clean rooms, hospitals or mineshafts.

It will be further appreciated that a particle separator according to the present invention can be used in smoke filters .

Claims

1. A particulate separator suitable for separating particles entrained in a gas comprising, a spindle, a drain, and at least one centrifuge member projecting outwards from the spindle and being arranged to rotate therewith such that a fraction of the entrained particles that contact the member is moved radially outward along the member to the drain.

2. A separator according to claim 1 wherein the at least one centrifuge member is an arm.

3. A separator according to claim 2 wherein there is provided a plurality of arms.

4. A separator according to claim 1 wherein the at least one centrifuge member comprises of a plurality of discrete fibres .

5. A separator according to either of claims 1 or 4 wherein the centrifuge member comprises a brush of fibres .

6. A separator according to claim 1 wherein the centrifuge member comprises a disc.

7. A separator according to claim 6 wherein there is a plurality of discs that is spaced along the length of the spindle.

8. A separator according to any preceding claim wherein the separator has a housing which is arranged to be engageable with a fan housing of a HVAC unit.

9. A separator according to claim 8 wherein the housing is arranged to occupy a space between the fan housing and an inner surface of the HVAC unit.

10. A separator according to either of claims 8 or 9 wherein the housing has an opening therethrough, the opening having a channel thereabout that is arranged to act as the drain.

11. A separator according to claim 10 wherein the opening forms a duct, through which gas is arranged to flow and in which the centrifuge member is located.

12. A separator according to either of claims 10 or 11 wherein the centrifuge member is arranged to sweep substantially all of the area of the opening.

13. A separator according to any preceding claim wherein the spindle is connected to an air intake blower assembly.

14. A separator according to claim 14 wherein the spindle is connected to the assembly through a gearbox.

15. A separator according to any preceding claim wherein the spindle is connected to a drive spindle of a fan.

16. A separator according to any one of claims 1 to 12 wherein the spindle is unconnected to any drive means .

17. A separator according to any preceding claim wherein the particles are at least any one of the following: water, pollen, cinders, dust, fibres, smoke, any particles sized lOμm or above.

18. A method of separating particles from a gas comprising the steps of:

iii) providing a rotatable spindle having at least one centrifuge member projecting outwardly therefrom in a flow path of the air; iv) rotating said spindle such that a fraction of said particles collide with said at least one centrifuge member and migrate outwards along said centrifuge member under centrifugal action; and v) collecting said fraction of said particles in a drain region.

19. A motor vehicle HVAC system including a particle separator according to any one of claims 1 to 17

20. A motor vehicle including a particle separator according to any one of claims 1 to 16

21. An air conditioning unit including a particle separator according to any one of claims 1 to 17.

22. A smoke filter including a particle separator according to any one of claims 1 to 17