WO2002075127A1

WO2002075127A1 - Apparatus and method for treating exhaust emissions

Info

Publication number: WO2002075127A1
Application number: PCT/GB2002/001227
Authority: WO
Inventors: James Stuart Moray Edmiston; John Wright-Bailey
Original assignee: James Stuart Moray Edmiston; John Wright-Bailey
Priority date: 2001-03-15
Filing date: 2002-03-15
Publication date: 2002-09-26
Also published as: GB2373197A; GB0106452D0

Abstract

The present invention relates to an apparatus and method for treating exhaust emissions. Apparatus (2) is provided comprising a fluid pathway (4) for receiving a flow of exhaust emissions, said fluid pathway (4) being provided with a restriction (18) for accelerating said flow and being provided with an opening (16) located adjacent said restriction (18) so as to be exposed to said accelerated flow during use, said opening (16) communicating with a source of air.

Description

APPARATUS AND METHOD FOR TREATING EXHAUST EMISSIONS

The present invention relates to an apparatus and method for treating exhaust emissions and particularly, but not exclusively, to an apparatus and method for treating the exhaust emissions of a reciprocating internal combustion engine. Furthermore, the invention particularly, but not exclusively, relates to the treatment of exhaust emissions in the areas of mixture formation and ignition systems.

It is well known that the exhaust emissions of internal combustion engines can have an undesirable effect on the environment. The present invention seeks to address this problem by reducing the proportion of noxious materials in exhausts (such as carbon monoxide CO, hydrocarbons CH and nitric oxides NO_x) to levels that are no longer a threat to the environment.

A first aspect of the present invention provides a method for treating exhaust emissions, said method comprising the step of mixing air with exhaust emissions. The step of mixing air with exhaust emissions may comprise the step of accelerating a flow of exhaust emissions so as to reduce the static pressure thereof and thereby induce a flow of air. Ideally, the step of accelerating the exhaust emissions comprises the step of directing a flow of said exhaust emissions through a converging passageway. The method may also comprise the step of compressing the mixture of air and exhaust emissions. Preferably, the method also comprises the step of expanding said mixture following the compression thereof. The air and exhaust emissions mixture is preferably expanded so as to separate exhaust gases. Following expansion of the air and exhaust emissions mixture, said mixture is preferably passed through a filter. It is also desirable to cool the air and exhaust emissions following the step of expanding said mixture.

A second aspect of the present invention provides apparatus for treating exhaust emissions, said apparatus comprising a fluid pathway for receiving a flow of exhaust emissions, said fluid pathway being provided with a restriction for accelerating said flow and being provided with an opening located adjacent said restriction so as to be exposed to said accelerated flow during use, said opening communicating with a source of air. Said opening preferably communicates with air by means of a tube. Said tube preferably comprises a nozzle. Said source of air is preferably atmospheric air surrounding said apparatus. The tube is preferably arranged so as to comprise a longitudinal axis located parallel with a longitudinal axis

/ of said fluid pathway. It is also preferable for said apparatus to comprise a straight portion of fluid pathway located downstream of said restriction. It is further preferable for said apparatus to comprise an expansion region downstream of said straight portion of fluid pathway. Also, said apparatus may comprise means for collecting carbon particles.

Embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a schematic cross-sectional side view of a first embodiment of the present invention;

Figure 2 is a schematic cross-sectional side view of a second embodiment of the present invention;

Figure 3 is a schematic cross-sectional side view of a third embodiment of the present invention

Figure 4 is a schematic cross-sectional side view of a fourth embodiment of the present invention.

The first exhaust treatment system 2 shown in Figure 1 of the accompanying drawings comprises an elongate ram tube 4 for receiving exhaust emissions from an exhaust inlet (not shown) and conveying said exhaust emissions to an exhaust outlet (not shown). An upstream end 6 of the ram tube 4 is provided with an air induction valve 8 which provides for the introduction of air into the ram tube 4 as a result of a vacuum effect generated by the flow of exhaust gas emissions within the system 2. In order to facilitate the required positioning of the air induction valve

8, the upstream end 6 of the ram tube 4 is provided with a 90° bend 10. This allows a conical tube 12 of the air induction valve 8 to extend through a wail 14 of the ram tube 4 and to be located coaxially within said ram tube 4. The conical tube 12 thereby provides a passageway for allowing air in the surrounding environment into the exhaust treatment system 2.

It will be seen from Figure 1 that the cross-sectional area of the conical tube 12 decreases in the direction of exhaust gas flow through the straight portion of ram tube 4 located downstream of the 90° bend 10. Thus, the conical tube 12 provides a converging passageway for air flowing therethrough into the ram tube 4. A downstream end 16 of the conical tube 12 opens at a position within the ram tube 4 where a constriction or convergence 18 (emulsifier) is provided. It will be appreciated by those skilled in the art that, during use of the exhaust treatment system 2, exhaust gas emissions flowing through the ram tube 4 will flow about the external surface of the conical tube 12 (as indicated by arrows.20 in Figure 1) and accelerate through the convergence 18 so as to maintain a constant flow rate in accordance with known fluid dynamics principles. As the exhaust gas emissions accelerate through the convergence 18, the dynamic pressure of said exhaust increases and the associated static pressure decreases. Accordingly, the fluid local to the downstream end 16 of the conical tube 12 may be thereby provided with a static pressure lower than the static atmospheric pressure external to the exhaust treatment system 2. As a result, the static pressure gradient across the convergence 18 generates a flow of air from the atmosphere external to the system into the ram tube 4 via the air induction valve 8. This flow of air is indicated by arrows 22 in Figure 1.

It will be noted that, in addition to the conical tube 12, the air induction valve 8 further comprises a cover member 24 located over an upstream end 26 of the conical tube 12. The cover member 24 is provided with suitable passageways and guide veins for facilitating a ready flow of air from the environment into the conical tube 12. If necessary, the air induction valve 8 may comprise a filter (located, for example, in the cover member 24) for removing undesirable particulates..

Downstream of the convergence 18, the cross-sectional area of the ram tube 4 increases. In the system 2 of Figure 1, this increase in area is an instantaneous step increase. Beyond the convergence 18, the ram tube 4 defines a straight compression zone 28. At the downstream end of said compression zone 28, the ram tube 4 is provided with a second 90° bend 30. Downstream of the second bend 30, the ram tube 4 communicates with the exhaust outlet via further tubing.

During use of the exhaust treatment system 2, exhaust gas emissions flow from an associated engine into the exhaust inlet and towards the first 90° bend 10. As the exhaust gas flows around the first bend 10, the gas envelopes the portion of conical tube 12 projecting into the ram tube 4 and begins to flow in an axial direction along the external surface of said conical tube 12. As the exhaust gas approaches the downstream end 16 of the conical tube 12, said gas enters the convergence 18 within the ram tube 4 and accelerates. As a result, the static pressure in the region of said downstream end 16 is sufficiently reduced to provide a flow of air into the system 2 via the cover member 24 and conical tube 12 (i.e. via the air induction valve 8). The reducing cross-sectional area of the conical tube 12 in the direction of air flow causes an acceleration of the air flow. The conical tube 12 accordingly acts as a nozzle and projects a jet 32 of air into the ram tube 4. The jet 32 of air subsequently mixes with the exhaust gas flowing through the convergence 18. As the air and exhaust gas flow from the convergence 18 into the compression zone 28, the air is absorbed by the exhaust gas and the product gas is compressed within the ram tube 4.

Following the compression of the aforementioned product gas, said gas is permitted to expand. This expansion may occur within an expansion chamber (not shown in Figure 1). If required, the expanded gas product may be further treated.

A second exhaust treatment system 102 is shown in Figure 2. The second system 102 has components corresponding to the first system 2 and like components are shown in the drawings and referred to hereinafter with like reference numerals. The second system 102 comprises the same components as the first system; however, at the downstream end of the compression zone 28, the ram tube 4 opens into an expansion region 34 (defined by a filter housing 36) rather than immediately connecting with further tubing. The filter housing 36 is a cylindrical member having a diameter greater than that of the ram tube 4 and is located concentrically about the ram tube 4. Each end of the filter housing 36 is sealed, the second end of the filter housing 36 adjacent the downstream open end of the ram tube 4 being sealed by means of a removable reverse flow deflector 38. The filter housing 36 is provided with a removable filter assembly comprising an annular carbon chip media filter 42 located between two annular ceramic media filters 44, 46. The removable filter assembly 40 is located concentrically with the ram tube 4 and filter housing 36 and fills the annular space between the external surface of the ram tube 4 and the internal surface of the filter housing 36. Thus, product gas deflected in use by the reverse flow deflector 38 must flow through the filter assembly 40.

At the bottom of the expansion region 34 and adjacent the open end of the ram tube 4, a sludge trap 48 is provided for receiving carbon particles which have coagulated with atmospheric water vapour. The sludge trap 48 comprises a drain tap 50 for allowing ready removal of collected sludge.

An annular space 52 defined between the filter housing 36, ram tube 4, filter assembly 40and the second sealed end of the filter housing 36 (i.e. the end of the filter housing 36 distal to the open end of the ram tube 4) opens into further tubing 54 for receiving both treated product gas and transmitting said gas to the exhaust outlet.

Thus, in use of the second exhaust treatment system 102, a mixture of air and exhaust gas emissions flows from the open end of the ram tube 4 and expands in the expansion region 34. Upon expansion, the air/exhaust mixture separates into carbon oxides, sulphur oxides and carbon particles. The carbon particles tend to coagulate with atmospheric water vapour and fall to the bottom of the expansion region 34 under the action of gravity. The remaining fluid flow is deflected radially outwardly and back on itself by means of the reverse flow deflector 38. In this way, the coagulated carbon particles are blown towards the sludge trap 48 and the carbon oxides and sulphur oxides are directed towards the filter assembly 40. The ceramic media filters 44, 46 act to remove the carbon oxides whereas the carbon chip media filter 42 acts to crystallise and thereby remove the sulphur oxides.

On passing through the filter assembly 40, the product gas flows into the annular space 52 and through the further tubing 54. In so doing, the product gas is cooled and, if necessary, filtered before expulsion to the atmosphere via the exhaust outlet. Both the first and second exhaust treatment systems 2, 102 may be manufactured from light steel, carbon fibre, Polypenco Torlon plastics, and ceramic and carbon discs, plates or granules. All of these materials are readily available.

In view of the above description, it will be apparent that the two exhaust treatment systems 2, 102 benefit from the three functions of air induction, gas separation and aerobic treatment.

A third exhaust treatment system 202 is shown in Figure 3. The third system 202 is similar to the previously described systems according to the invention in that an elongate ram tube 204 is provided for receiving exhaust emissions from an exhaust inlet (not shown) and for conveying said exhaust emissions to an exhaust outlet (not shown). An upstream end 206 of the ram tube 204 is provided with a variable air induction valve 208 which provides for a controlled and variable introduction of air into the ram tube 204 as a result of varying the exposure of a source of air to a vacuum effect generated by the flow of exhaust gas emissions within the ram tube 204. In order to facilitate the required positioning of the air induction valve 208 within the ram tube 204, the upstream end 206 of the ram tube 204 is provided with a 90° bend 210. This allows the positioning of a tapering air intake tube 212 of the air induction valve 208 to extend coaxially with the ram tube 204. The air intake tube 212 has an external diameter less than the internal diameter of the ram tube 204 so that an annular space between the air intake tube 212 and the ram tube 204 is provided for receiving a flow of exhaust emissions. The interior of the air intake tube 212 defines a fluid passageway which reduces in diameter in the direction of air flow so that air flowing into the ram tube 204 is accelerated.

A downstream end of the air intake tube 212 defines an opening in the form of a nozzle 214. The nozzle 214 is located adjacent a deflector 216 in the ram tube 204. The deflector 216 is shaped as a dome with an aperture located at the dome apex for allowing passage of exhaust flow. The purpose of the deflector 216 is to accelerate a flow of exhaust emissions and thereby reduce the static pressure thereof. Optionally, the deflector 216 may be arranged so as to impart a swirl motion to the flow of exhaust emissions and thereby reduce static pressure. Alternative means may be used for reducing the static pressure of the exhaust emissions. For example, a deflector for inducing turbulence may be provided. It will be seen from Figure 3 that a cover member 224 is located over an upstream end of the air intake tube 212. The cover member 224 is provided with a plurality of passageways 217 and guide veins (not shown) for facilitating a ready flow of air from the environment into the intake tube 212. If necessary, the air induction valve 208 may comprise a filter (located, for example, in the cover member 224) for removing undesirable particulates in the intake air.

The air intake tube 212 is itself mounted within the ram tube 204 by means of a linear bearing assembly 218. More specifically, the bearing assembly 218 is secured to a flange member 220 which is itself secured to the ram tube 204. The arrangement is such that the air intake tube 212 and associated cover member 224 may move axially within the ram tube 204 relative to the deflector 216.

An actuator 222 is connected to the cover member 224 by means of a plurality of pivotally linked arm members 224, 226. It will be clear to the skilled person that an alternative arrangement for connecting the actuator 220 with the air intake 212 can be provided. The actuator 222 may be in the form of a hydraulically driven piston cylinder arrangement. It will be seen from Figure 3 that the actuator 222 is attached to a flange 228 which is itself secured to the exterior of the ram tube 204. The actuator 222 operates in response to variations in the temperature of the exhaust emissions. In a simple and preferred form of the actuator 222, heat from the ram tube 204 is conducted via the flange 228 to a fluid retained within the piston/cylinder arrangement. The fluid (e.g. air) may be held within a pleated bag. Thus, as the temperature of the exhaust emissions increases, the fluid retained in the actuator 222 expands and displaces the piston. In turn, the air intake tube 212 is moved axially within the ram tube 204. Similarly, as the temperature of the exhaust emissions decreases, the retained fluid contracts and the air intake tube 212 is moved in the opposite direction.

It will also been seen from Figure 3 that the upstream end of the air intake tube 212 is provided with a reed valve 224 which serves to allow air to flow into the intake tube 212 but to prevent air from flowing out of the system via the cover member 224 due to exhaust back pressure.

It will be appreciated that the system 202 shown in Figure 3 may be provided with the same compression, expansion and filtering components downstream of the deflector 216 (emulsifier) as described in relation to the systems of Figure 1 and

2.

The preferred materials for use in manufacturing the exhaust treatment system shown in Figure 3 (and also the systems shown in Figures 1 and 2) are as follows. The ram tube is preferably manufactured from 13 IS high quality stainless steel, the deflector (or restriction) is preferably manufactured from E93A high tensile steel, and the air intake tube is preferably manufactured from E938 mild steel. The material for the air intake tube preferably expands rapidly with an increase in temperature so that as exhaust temperature increases and more intake air is required, the air intake tube expands so as to more readily accept an increase in air flow rate.

In use, it will be seen with reference to Figure 3 that exhaust emissions flow over the exterior of the air intake tube 212 towards the deflector 216. When the engine associated with the exhaust treatment system 212 is shut down and the system is cool, the nozzle 214 locates in the aperture of the deflector 216. In the embodiment shown in Figure 3, the aperture of the deflector 216 is illustrated as being of a slightly larger diameter that the nozzle 214. However, the nozzle 214 may be dimensioned so as to abut the deflector 216 and thereby seal the aperture of the deflector 216. When the engine associated with the exhaust treatment system 202 is started, back pressure from the exhaust gases immediately tends to press the air intake tube 212 away from the deflector 216 in the direction of arrow A shown in Figure 3. The characteristics of the actuator 222 will be such that a small amount of movement of the intake tube 212 (for example, 1 or 2 mm) will be permitted so that exhaust emissions may flow through the aperture in the deflector 216.

The exhaust treatment system 202 is shown in Figure 3 arranged in the configuration for an engine idling speed. Exhaust emissions flow over the exterior of the air intake tube 212 and through the aperture in the deflector 216. In so doing, the exhaust gas accelerates due to a reduction in cross-sectional area of the flow path. It will be understood therefore that the static pressure of the exhaust gas at the nozzle 214 is substantially reduced. In fact, the static pressure of the exhaust emissions at the nozzle 214 is reduced to below atmospheric pressure which in turn causes an induction of air through the cover member 24 and into the air intake tube 212. The deflector 216 may be located near the exhaust system outlet so that the static pressure of the exhaust emissions flow has reduced sufficiently for the deflector 216 (in combination with the air intake tube 212) to further reduce static pressure to below atmospheric pressure. The induced air accelerates through the intake tube 212 (due to the narrowing of the internal diameter of this tube 212) and mixes with the exhaust emissions downstream of the nozzle 214. The mixture of air and exhaust emissions then flows downstream of the deflector 216 and reacts with the stainless steel material of the ram tube 204 so as to reduce the harmful effects of the emitted exhaust.

As engine speed and exhaust flow rate is increased, the temperature of the exhaust increases also. This temperature rise is conducted to the actuator 222 which expands moving the air intake tube 212 in the direction of arrow A away from the deflector 216. This movement of the air intake tube 212 is assisted by exhaust back pressure. The nozzle 214 is thereby displaced further from the aperture of the deflector 216 allowing for a greater flow of exhaust emissions. The arrangement of the exhaust treatment system 202 is such that the exhaust temperature associated with a particular flow rate of exhaust emissions results in a particular placement of the nozzle 214 relative to the deflector 216. This particular placement of the nozzle 214 ensures that the static pressure of the exhaust flow at the nozzle 214 is such as to induce a flow rate of air specifically required for the given flow rate of exhaust emissions. The required air flow rate is that which maximise the reduction of the harmful effects of the emissions.

When the engine running speed is reduced, the temperature of the exhaust also reduces and the air intake tube 212 moves in a direction opposite to that indicated by that of arrow A. It should be understood that any means may be provided for locating the nozzle 214 relative to the deflector 216 in dependence upon the exhaust emissions characteristics and the flow thereof. For example, means may be provided for positioning the air intake tube 212 directly in response to engine running speed.

A fourth embodiment of the present invention is shown in Figure 4 of the accompanying drawings. The fourth exhaust treatment system 302 shown in Figure 4 comprises the exhaust treatment system 202 shown in Figure 3 in combination with a pre-treatment system 303. The pre-treatment system 303 is arranged so that exhaust emissions first flow through a carbon chip media filter 304 and then into a reservoir 306 for collecting carbon deposits and manufactured water.

The exhaust emissions are then passed via a filter 308 into a gas separator chamber

310 before entering the exhaust treatment system 202 illustrated in Figure 3. It should be noted that each ^"of the systems shown in the accompanying drawings are exhaust gas reactors rather than catalytic converters.

As a general observation in respect of the above embodiments, it is to be understood that static air pressure is utilised to induce a chemical reaction to bring about the separation of the two main exhaust gases (sulphur oxide and carbon oxide). They are not being diluted by the introduction of air pressure, but are actually broken down and separated. In order to sustain the effectiveness of the process at idling speeds (i.e. below 1000 rpm), it may be necessary to introduce a simple mechanical impeller, or a simple automatically opening orifice, or a pump merely to ensure the necessary flow. It may also be necessary to provide a water injection system for introducing water to assist the reaction process.

The present invention is not limited to the specific embodiments and methods described above. Alternative arrangements and suitable materials will be apparent to a skilled reader.

Claims

CLAIMS:

1. Apparatus for treating exhaust emissions, said apparatus comprising a fluid pathway for receiving a flow of exhaust emissions, said fluid pathway being provided with means for deflecting said flow of exhaust emissions in such a way as to reduce the static pressure thereof, and said fluid pathway being further provided with an opening communicating with a source of air, said opening being located said deflecting means so as to be exposed during use to a flow of exhaust emissions having a reduced static pressure.

2. Apparatus as claimed in claim 1, wherein means are provided for moving the location of said opening relative to the deflecting means during use of the apparatus.

3. Apparatus as claimed in claim 2, wherein said means for moving the location of said opening operates so as to move said opening to a location in the flow of exhaust emissions at which the static pressure is such as to generate a required flow of air through said opening.

4. Apparatus as claimed in claim 2 or 3, wherein said moving means operates in response to the temperature of the exhaust emissions.

5. Apparatus as claimed in claim 4, wherein said moving means comprises an expandable chamber in which a fluid is retained for heating by the exhaust emissions.

6. Apparatus as claimed in any of the preceding claims, wherein said opening communicates with air by means of a tube.

7. Apparatus as claimed in claim 6, wherein said tube comprises a nozzle defining said opening.

8. Apparatus as claimed in claim 6 or 7, wherein said tube is arranged so as to comprise a longitudinal axis located parallel with a longitudinal axis of said fluid pathway.

9. Apparatus as claimed in any of the preceding claims, wherein said source of air is atmospheric air surrounding said apparatus.

10. Apparatus as claimed in any of the preceding claims, wherein said appears comprises a straight portion of fluid pathway located downstream of said deflecting means.

11. Apparatus as claimed in claim 10, wherein said apparatus comprises an expansion region downstream of said straight portion of fluid pathway.

12. Apparatus as claimed in any of the preceding claims, wherein said apparatus comprises means for collecting carbon particles.

13. A method for treating exhaust emissions, said method comprising the step of mixing air with exhaust emissions prior to release of the exhaust emissions to the atmosphere.

14. A method as claimed in claim 13, wherein the step of mixing air with exhaust emissions comprises the step of accelerating a flow of exhaust emissions so as to reduce the static pressure thereof and thereby induce a flow of air.

15. A method as claimed in claim 14, wherein the step of accelerating the exhaust emissions comprises the step of directing a flow of said exhaust emissions through a converging passageway.

16. A method as claimed in claim 15, wherein the step of mixing air with exhaust emissions comprises the step of varying the geometry of the converging passageway so as to reduce the static pressure to a particular level and thereby induce air at a particular flow rate.

17. A method as claimed in any of claims 13 to 16, wherein said method further comprises the step of compressing the mixture of air and exhaust emissions.

18. A method as claimed in claim 17, wherein said method also comprises the step of expanding said mixture following the compression thereof.

19. A method as claimed in claim 18, wherein the air and exhaust emissions mixture is expanded so as to separate exhaust gases.

20. A method as claimed in claim 18 or 19, wherein following expansion of the air and exhaust emissions mixture, said mixture is passed through a filter.

21. A method as claimed in any of claims 18 to 20, wherein the mixture of air and exhaust emissions is cooled following the step of expanding said mixture, fluid pathway for receiving a flow of exhaust emissions^ said fluid pathway being provided with a restriction for accelerating said flow and being provided with an opening located adjacent said restriction so as to be exposed to said accelerated flow during use, said opening communicating with a source of air.