METHOD AND APPARATUS FOR SEPARATING A PARTIAL FLOW FROM A FLOW OF GASES

Abstract: Method and apparatus (1) for separating, by means of a probe, a partial flow from a flow of gases coming from an exhaust pipe (8) of, for instance, an engine such as a diesel engine for a vehicle (9), the exhaust pipe being connected, by means of a sealingly connectable conduit (4), to a chamber formed by a number of walls, which chamber is surrounded by a housing (2) and communicates, by at least one wall passage, with a space defined between the housing and the chamber walls in which, by extraction means (3, 5, 6) and via optionally closable suction openings, an extraction flow to a remote location is generated, to which extraction flow the flow of gases coming from the exhaust pipe and fed to the chamber via the conduit, and the partial flow separated via the probe, are added.

Description: Title: Method and apparatus for separating a partial flow from a flow of gases The invention relates to a method for separating, by means of a probe, a partial flow from a flow of gases coming from an exhaust pipe of, for instance, an engine such as a diesel engine for a vehicle, wherein extraction means are present for receiving the flow of gases and discharging it to a location remote from the exhaust pipe, and to an apparatus for carrying out such method. Such method and apparatus are used inter alia for measuring the CO-content and the soot content of the exhaust gases of a motor vehicle. Such measuring is usually performed in a workshop, so that it is important to collect the exhaust gases and discharge them into the open air. For measuring the CO-content, it is conventional to sealingly couple a collecting hose to the exhaust pipe of the vehicle, which hose is connected to measuring equipment and to an extraction apparatus, so that the exhaust gases cannot end up in the working environment. Such method of operation is not possible for measuring the soot content, because this should take place under "free" pressure conditions, i.e. without the extraction apparatus affecting the pressure of the exhaust gases. For this reason, the soot measuring is effected by inserting a probe into the exhaust pipe and arranging an extraction hood at some distance behind the exhaust pipe, as is known from DE-U-9313492. However, it turned out that in this manner of operating, a part of the exhaust gases is not discharged via the extraction hood and ends up in the working environment. Moreover, a loose extraction hood has the drawback that the gases separated by the probe and fed to the soot meter are not collected, while the installation of a loose extraction hood is quite often forgotten, consciously or unconsciously. This may easily involve unpleasant and, most certainly, unhealthy working conditions. Further, the probe, inserted loosely into the exhaust pipe, is in an unstable position. Vibrations, in combination with exhaust gas flowing past, may cause ejection of the probe and may have an adverse effect on the measuring. The object of the invention is to improve the method described in the opening paragraph in such a manner that the above-described drawbacks no longer occur. This object is realized by the invention in that the exhaust pipe is connected, by means of a sealingly connectable conduit, to a chamber formed by a number of walls, which chamber is surrounded by a housing and communicates, by at least one wall passage, with a space defined between the housing and the chamber walls in which, by the extraction means and via suction openings communicating with the environment, an extraction flow to the remote location is generated, to which extraction flow the flow of gases coming from the exhaust pipe and fed to the chamber via the conduit, as well as the partial flow separated via the probe, are added. Through these features, the exhaust gases are passed from the exhaust pipe to a screened and properly ventilated environment and the exhaust gases are thus prevented from possibly ending up in the working environment. The specific arrangement of the chamber in the housing provides that the extraction flow does not affect the pressure of the exhaust gases, i.e. the exhaust pipe and the extraction apparatus are as it were uncoupled in terms of flow engineering, so that a soot measuring can be performed in the desired, correct manner, while on the other hand, the extraction flow along the wall passages actually provides that after measuring, the exhaust gases together with the partial flow separated therefrom are discharged to the outside environment in the desired manner. Through the use of the conduit which can be sealingly coupled to the exhaust pipe and thus constitutes an extension of that exhaust pipe, in accordance with a further embodiment of the invention, it can be provided that the separation of the partial flow from the flow of gases by the probe takes place in the conduit. The probe can then be arranged so as to be extremely stable, for instance by fixedly connecting it to the conduit . A further advantage of this arrangement is that the probe cannot be disposed in any other manner than by coupling the extraction means to the exhaust pipe, so that, accordingly, this cannot be forgotten. In order to enable the measuring operation to be optimally adjusted to the relevant engine, i.e. the quantity and the pressure of the gases coming from the exhaust pipe of that engine, in accordance with a further embodiment of the invention, it is provided that in the chamber, the conduit has an end having a free passage whose size is controlled depending on the quantity and/or pressure of the gases coming from the exhaust pipe and flowing to that passage. To have in each case optimum pressure conditions in the chamber, also if the extraction apparatus is operative but the engine to be measured is not yet running, in accordance with a further embodiment of the invention, it is preferred that the chamber be provided with means for the controlled feed of ambient air. In order to also ensure in each case optimum measuring conditions for the partial flow, it may further be provided that the partial flow separated by the probe is fed to a soot meter and, upon leaving the soot meter, is added, together with ambient air, to the extraction flow in the housing space. Exhaust gases usually have a relatively fairly high temperature, which requires cooling of the soot meter. This can be incorporated into the system in an advantageous manner if the soot meter is cooled with ambient air that after passing the soot meter is mixed with the partial flow coming from the soot meter and subsequently discharged, together with that partial flow, through the housing via the extraction apparatus. After the completion of the soot measurement, the vehicle engine is switched off and the fan can be allowed to continue rotating for some time for removing as many exhaust gases as possible from the housing and the chamber. To prevent the exhaust gases from ending up in the working environment as yet, by switching off the fan prematurely or when it fails unexpectedly, in accordance with a further embodiment of the invention, it can be provided that when the extraction means are switched off, the suction openings are closed off. Through such closure, it is also possible to omit after-rotation of the fan, if so desired, without this resulting in a pollution of the working environment. Although hereinabove, the emphasis is laid in particular on a soot measurement, the method is also suitable for measuring other components in the exhaust gases . To that end, it may be provided that in the conduit, at least one further partial flow is separated from the flow of gases, which further partial flow can then be fed to further measuring equipment and, after being fed back to the housing, discharged by the extraction apparatus. The invention also relates to an apparatus for performing a method as described hereinabove, i.e. an apparatus for separating a partial flow from a flow of gases coming from an exhaust pipe of, for instance, an engine such as a diesel engine for a vehicle, which apparatus comprises a housing which, on one side thereof, can be brought into open communication with the environment and, on another side thereof, is connected to an extraction tube in which, by extraction means, for instance a fan, an extraction flow can be generated, and a probe having an open front end for extracting a partial flow from a flow of gases coming from the exhaust pipe. To provide, with such apparatus, a guaranteed, optimum extraction of the exhaust gases without affecting the pressure at which the gases leave the exhaust pipe, in accordance with the invention, it is proposed that within the housing, a chamber formed by walls be arranged, into which chamber one end of a conduit opens, the other end of which is located outside the housing and comprises connecting means to enable the conduit to be sealingly coupled to the exhaust pipe, the chamber walls being provided with at least one passage which brings the chamber into open communication with a space in the housing outside the chamber, through which space the extraction flow can be generated and to which extraction flow the partial flow separated by the probe can also be added. With such apparatus, the entire system can be made ready for operation by merely coupling the conduit to the exhaust pipe, while it is guaranteed that in each case, an optimum extraction of the exhaust gases takes place as well; certainly if it is provided that the open front end of the probe is located in the conduit. To enable the exhaust pipe to be quickly and reliably connected to the apparatus, in accordance with a further embodiment of the invention, it may be provided that the connecting means for coupling the conduit to an exhaust pipe comprise a sleeve made from flexible, heat-resistant material and fastening means for securing the sleeve so as to clamp around the exhaust pipe with contraction. Such sleeve can readily be slid over the exhaust pipe and can quickly and reliably be sealingly adjusted to the diameter of the exhaust pipe by folding or wrinkling the sleeve together. The fastening means can be constructed in many ways, for instance in the form of a cord laced in a seam of the sleeve. However, according to the invention, it is preferred that the fastening means consist of Velcro attached to the sleeve. In this manner, a reliable face-wise abutment of the sleeve on the exhaust pipe can be obtained. To create conditions which, in terms of flow engineering, are as favorable as possible, in accordance with a further embodiment of the invention, it is preferred that the walls forming the chamber be arranged in the housing in such a manner that in the housing, from the open side which can be brought into open communication with the environment, longitudinal channels in the direction of the extraction tube are formed, and the part of the conduit which connects to the end in the chamber is also oriented in the direction of the extraction tube, while the open communication between chamber and housing space in the direction of the extraction tube is located beyond the end of the conduit in the chamber. The exhaust gases flowing from the conduit are then, in an advantageous manner, already oriented in the discharge direction of the extraction. To prevent exhaust gases from possibly ending up in the working environment when the measuring proceedings have ended, the fan may be allowed to continue rotating for some time after the vehicle engine has been switched off. Also, or instead, according to the invention, it may be provided that the side of the housing which can be brought into open communication with the environment is closable by means of valves. If, in addition, the valves can be displaced by a motor between an open and a closed position, with the valves being movable into the open position when the extraction means are activated and into the closed position when they are switched off, it is also guaranteed that when the fan is switched off or fails, no exhaust gases can end up in the working environment . To ensure in each case that optimum pressure conditions prevail in the chamber, and more in particular that no slight partial vacuum can be created therein by the extraction means, it is preferred that at least one chamber wall be provided with controllable connection openings to the environment outside the housing, whereby a longitudinal flow can be created in the chamber in the direction of the part of the conduit which connects to the end thereof in the chamber. To prevent exhaust gases from the chamber from possibly ending up in the working environment when the fan comes to a stop, the connection openings should then be closed. This can be realized in a simple manner if the controllable connecting openings are provided in a chamber wall located within the part of the housing which is closable by the valves. To enable adjusting the passage of the conduit to the pressure and quantity of the gases coming from the exhaust pipe, and precluding any suction action on the exhaust pipe when the engine is not running, without, however, affecting a correct measuring, in accordance with a further embodiment of the invention, it is preferred that the end of the conduit in the chamber comprise a non-return valve which is constructed and balanced so that a flow of gases passed through the conduit can open the valve substantially without loss of pressure. A soot meter should be cleaned with some regularity. To be able to do so in a convenient and quick manner, it is preferred that the housing be provided with means for detachably mounting a soot meter and with means for connecting the probe to the soot meter, so that the soot meter can readily be uncoupled from the housing for maintenance and the like. Further, it is also preferred to leave the partial flow, separated by the probe and passed to the soot meter, unaffected as much as possible, as far as pressure is concerned. To this end, in accordance with a further embodiment of the invention, it is preferred that the soot meter comprise an exhaust for the gases measured, which exhaust is arranged at a housing opening communicating with the space in which the extraction flow can be generated. If it is found desirable to cool the soot meter, that same housing opening can be used therefor, by passing ambient air through the soot meter and adding that air, after leaving the soot meter, to the extraction flow via the housing opening intended. Although only a slight quantity of exhaust gases egresses from the soot meter, that slight quantity, too, should preferably not end up in the working environment . This can be realized in a simple manner if the soot meter connects to the housing opening so as to be sealed relative to the environment, which housing opening, like the probe, can be closed by valve means when the extraction means are switched off, while by closing the probe, the last opening through which exhaust gases could escape is closed as well. Although hereinabove, soot measuring is mainly discussed, the apparatus can likewise be used for measuring all types of other components of the exhaust gases. If, in accordance with a further embodiment of the invention, means are provided in the conduit for separating at least one further partial flow, the apparatus is even suitable for performing different measurements at the same time. With reference to exemplary embodiments which are schematically shown in the accompanying drawings, the separating method and apparatus according to the invention will presently be further explained, by way of example only. In these drawings: Fig. 1 is an elevational view of a separator connected to an exhaust pipe of a motor vehicle; Fig. 2 shows, to an enlarged scale, a part of the separator shown in Fig. 1; Fig. 3 is a side elevational view of Fig. 2 ,- Fig. 4 is a further possible embodiment of the separator in elevational view; Fig. 5 is a slide elevational view of Fig. 4; and Fig. 6 shows, in perspective and to an enlarged scale, a connecting sleeve in its starting position. Fig. 1 shows a separator 1 comprising a housing 2 to which an extraction tube 3 connects on one side thereof, and a conduit 4 on the other. The extraction tube is connected to a fan 5, which in turn is in connection with a stack 6. Via coupling means 7, the conduit 4 is sealingly connected to an exhaust pipe 8 of a vehicle 9. The housing 2 is supported by a leg 10. Although the arrangement seems to be rather stationary, it will be understood that the necessary flexibility can be obtained by a flexible construction of at least a part of the extraction tube 3 and the conduit 4. Further, the leg 10 may be of a mobile and height-adjustable construction. As Figs. 2 and 3 demonstrate, the housing 2 is built up from a box-shaped bottom piece and a top piece having the shape of a chimney hood and constituting a transition between the box-shaped bottom piece and the extraction tube 3. In the housing 2, a chamber 14 is formed by walls 11, 12 and 13 extending throughout the depth of the housing 2. The edges of the wall 13 which are not connected to the housing are spaced from the adjacent edges of the deflected top parts of the walls 11 and 12, to form openings 15 and 16 via which openings the chamber 14 is in open communication with the other space within the housing 2, and more in particular with two longitudinal channels 17 and 18, which are created through the arrangement of the walls 11 and 12. The conduit 4 extends horizontally through the wall of the housing 2 and the chamber wall 12 into the chamber 14, the end of the conduit 4 in the chamber 14 being bent over at right angles to adopt a vertical position. The mouth of the conduit 4 comprises a valve 19 which is pivotable about an axis 20. The valve construction 19, 20 is of such design that normally, the valve 19 is in the closed position shown, yet opens directly at a slight excess pressure in the conduit 4, the degree of opening depending on the excess pressure and the quantity of the gases fed through the conduit 4. Provided in the conduit 4 is a probe 21, having the shape of a tube disposed in longitudinal direction of the conduit 4 and having an open end. The probe 21 does not follow the bend of the conduit 4, but extends straight on to a position outside the conduit 4, to be subsequently bent over at right angles parallel to the wall 11. In that position, the probe 21 breaks through the wall of the housing 2 to subsequently end in a part which is bent over upwards vertically and connected, by means of a coupling 22, to a soot meter 23. Supports 24 mounted on the housing 2 support the soot meter in a readily detachable manner, for instance by means of studs 25 hooked in L-shaped slots. In the conduit 4, a further probe 27 is indicated, which can be used for feeding gases extracted from the conduit 4 to other equipment , not shown . Below the soot meter 23, the housing 2 comprises a box- shaped built -on construction 28 which is in open communication with the longitudinal channels 17 and 18 and which comprises a perforated top wall 29. Further, the housing 2 is of open construction at its bottom side at the location of the longitudinal channels 17 and 18 and the bottom side of the chamber 14 is closed by a wall 30 comprising gratings 31 having controllable passage openings. For performing a soot measurement, the conduit 4 is connected, by the coupling means 7, to the exhaust pipe 8 of the vehicle 9. Next, the fan 5 is started, so that ambient air is drawn in through the longitudinal channels 17 and 18 and the extraction tube 3 connected thereto, while the pressure in the chamber 14 remains substantially unaffected. In this regard, depending on the extraction conditions, it may be preferred that the gratings 31 in the bottom of the chamber 14 be slightly opened, so that any influence of the longitudinal flows in the channels 17 and 18 directed along the openings 15 and 16 on the pressure in the chamber 14 can be compensated through the inflow of ambient air by means of the gratings 31, as a result of which an atmospheric pressure prevails in that chamber 14. Then, the engine of the vehicle 9 is started, the exhaust gases of which end up, via the exhaust pipe 8, in the conduit 4. When they reach the end of the conduit 4, the exhaust gases open the valve 19 and flow into the chamber 14, which is under atmospheric pressure; hence, this situation is comparable with the normal operating conditions of the vehicle 9, where the exhaust gases end up in the free space. The exhaust gases in the chamber 14 flow in the direction of the openings 15 and 16, where they are entrained by the longitudinal flows in the longitudinal channels 17 and 18 to • tn d d 0 xl CD i d XI 5 CD υ rd ft CD jd JJ 0 CD Jd JJ d JJ 5 o o o LΠ H ro ro The conduit 44 extends horizontally through the wall of the housing 42 and the chamber wall 52 into the chamber 54, the end of the conduit 44 in the chamber 54 being bent over at right angles into a vertical position. The mouth of the conduit 44 is closable by a valve in the manner as shown in Figs . 2 and 3. Provided in the conduit 44 is a probe 61 having the shape of a tube having an open end and disposed in longitudinal direction of the conduit 44. The probe 61 ends in a soot meter 63 which is detachably connected to the housing 42. The soot meter 63 is arranged on a box-shaped built-on construction 68 which is connected to the housing 42 and which is in open communication with the interior of the housing 42 but not with the chamber 54. Further, openings, not shown, are provided in the wall 53 of the chamber 54, which openings are closable by gratings having controllable passage openings. The housing 42, open at its bottom side, is closable at its bottom side by means of pivoting valves 69. The pivoting valves 69 are operated by a spindle motor 70 operating a rod mechanism 71. The rod mechanism 71 also operates a further lever mechanism 72 having valves 73 which can release or close an open passage between the soot meter 63 and the box- shaped built-on construction 68. If the apparatus is not in operation, the valves 69 and 73 are in the closed position and the housing 42 is closed relative to the direct working environment, which closure can be refined even further by providing another valve in the probe 61, preferably adjacent the location where the probe 61 enters the soot meter 63. Connecting the conduit 44 to the exhaust pipe 48 is effected by means of a connecting sleeve 47, shown to an enlarged scale in Fig. 6. The connecting sleeve 47 consists of a tubular part 75 manufactured from a flexible, heat- resistant material, one tube end being bent over and secured with a stitched seam 76. If so desired, the thus formed seam SH tn .. SH d X) ~ d rd tn rd TJ ^ rd 3Ϊ ft d rd υ CD TJ CD d 0 0 ft CD X! d CD jd rd ε ro ^ LΠ LΠ o LΠ o H CN ro ro also possible to arrange this extraction tube more or less horizontally in the direction of a wall of the workshop. Further, it has already been indicated that the separator can also be used for performing measurements other than a soot measurement. To that end, the partial flow separated by the probe can be used or a further partial flow which is separated by means of the further probe. In addition, a cylindrical bottom piece of the housing may also be considered, in which a cylindrical chamber is centrally arranged, so that this chamber is being flowed around by the extraction flow all over its circumference. In this arrangement, the open communication between the chamber and the other part of the housing may be located in the circumferential wall of the chamber as well as centrally in a conical top piece of the chamber. The closing of the housing when the apparatus is being switched off may be performed and controlled in any other suitable manner. For instance, nonreturn valves may further be arranged in the valves, enabling the fan to continue rotating for some time after the closing of the valves, so that the housing, which is then closed off for the rest, is entirely freed from exhaust gases.

Claims: Cl a i ms 1. A method for separating, by means of a probe, a partial flow from a flow of gases coming from an exhaust pipe of, for instance, an engine such as a diesel engine for a vehicle, extraction means being present for receiving the flow of gases and discharging it to a location remote from the exhaust pipe, characterized in that the exhaust pipe is connected, by means of a sealingly connectable conduit, to a chamber formed by a number of walls, which chamber is surrounded by a housing and communicates, by at least one wall passage, with a space defined between the housing and the chamber walls in which, by the extraction means and via suction openings communicating with the environment, an extraction flow to the remote location is generated, to which extraction flow the flow of gases coming from the exhaust pipe and fed to the chamber via the conduit, as well as the partial flow separated via the probe, are added. 2. A method according to claim 1, characterized in that the separation of the partial flow from the flow of gases by the probe takes place in the conduit . 3. A method according to claim 1 or 2 , characterized in that in the chamber, the conduit has an end having a free passage whose size is controlled depending on the quantity and/or pressure of the gases coming from the exhaust pipe and flowing to said passage. 4. A method according to any one of the preceding claims, characterized in that the chamber is provided with means for the controlled feed of ambient air. 5. A method according to any one of the preceding claims, characterized in that the partial flow separated by the probe is fed to a soot meter and, upon leaving the soot meter, is added, together with ambient air, to the extraction flow in the housing space. 6. A method according to claim 5, characterized in that the soot meter is cooled with ambient air that after passing the soot meter is mixed with the partial flow coming from the soot meter. 7. A method according to any one of the preceding claims, characterized in that when the extraction means are switched off, the suction openings are closed off. 8. A method according to any one of the preceding claims, characterized in that in the conduit, at least one further partial flow is separated from the flow of gases. 9. An apparatus for separating a partial flow from a flow of gases coming from an exhaust pipe of, for instance, an engine such as a diesel engine for a vehicle, said apparatus comprising a housing which, on one side thereof, can be brought into open communication with the environment and, on another side thereof, is connected to an extraction tube in which, by extraction means, for instance a fan, an extraction flow can be generated, and a probe having an open front end for extracting a partial flow from a flow of gases coming from the exhaust pipe, characterized in that within the housing, a chamber formed by walls is arranged, into which chamber one end of a conduit opens, the other end of which is located outside the housing and comprises connecting means to enable the conduit to be sealingly coupled to the exhaust pipe, the chamber walls being provided with at least one passage which brings the chamber into open communication with a space in the housing outside the chamber, through which space the extraction flow can be generated and to which extraction flow the partial flow separated by the probe can also be added. 10. An apparatus according to claim 9, characterized in that the open front end of the probe is located in the conduit. 11. An apparatus according to claim 9 or 10, characterized in that the connecting means for coupling the conduit to an exhaust pipe comprise a sleeve made from flexible, heat- resistant material and fastening means for securing the sleeve so as to clamp around the exhaust pipe with contraction. 12. An apparatus according to claim 11, characterized in that the fastening means consist of Velcro attached to the sleeve. 13. An apparatus according to any one of claims 9-12, characterized in that the walls forming the chamber are arranged in the housing in such a manner that in the housing, from the open side which can be brought into open communication with the environment, longitudinal channels in the direction of the extraction tube are formed, and the part of the conduit which connects to the end in the chamber is also oriented in the direction of the extraction tube, while the open communication between chamber and housing space in the direction of the extraction tube is located beyond the end of the conduit in the chamber . 14. An apparatus according to any one of claims 9-13, characterized in that the side of the housing which can be brought into open communication with the environment is closable by means of valves. 15. An apparatus according to claim 14, characterized in that the valves can be displaced by a motor between an open and a closed position, the valves being movable into the open position when the extraction means are activated and into the closed position when said extraction means are switched off. 16. An apparatus according to any one of claims 9-15, characterized in that at least one chamber wall is provided with controllable connection openings to the environment outside the housing, whereby a longitudinal flow can be created in the chamber in the direction of the part of the conduit which connects to the end thereof in the chamber. 17. An apparatus according to claim 16, characterized in that the controllable connecting openings are provided in a chamber wall located within the part of the housing which is closable by the valves. 18. An apparatus according to any one of claims 9-17, characterized in that the end of the conduit in the chamber comprises a non-return valve which is constructed and balanced so that a flow of gases passed through the conduit can open the valve substantially without loss of pressure. 19. An apparatus according to any one of claims 9-18, characterized in that the housing is provided with means for detachably mounting a soot meter and with means for connecting the probe to the soot meter. 20. An apparatus according to claim 19, characterized in that the soot meter comprises an exhaust for the gases measured, said exhaust being arranged at a housing opening communicating with the space in which the extraction flow can be generated. 21. An apparatus according to claim 20, characterized in that the soot meter can be cooled by passing ambient air through it, which ambient air, after leaving the soot meter, can be passed to the extraction flow via the housing opening. 22. An apparatus according to claim 20 or 21, characterized in that the soot meter connects to the housing opening so as to be sealed relative to the environment, which housing opening, like the probe, can be closed by valve means when the extraction means are switched off. 23. An apparatus according to any one of claims 9-22, characterized in that means are provided in the conduit for separating at least one further partial flow.

Inventors: DIJK SYBREN VAN, VAN DIJK, SYBREN
Applicants: DIJK SYBREN VAN, VAN DIJK, SYBREN
Application year: 1998
Main classification: G01M15
IPC codes: G01M15, G01N1, G01N33, H04N5