WO2007113504A1

WO2007113504A1 - Treatment of exhaust gases

Info

Publication number: WO2007113504A1
Application number: PCT/GB2007/001162
Authority: WO
Inventors: Peter Kukla
Original assignee: Per-Tec Limited
Priority date: 2006-03-30
Filing date: 2007-03-30
Publication date: 2007-10-11
Also published as: EP2004961A1; GB0606410D0

Abstract

A particulate separator comprises a housing (2) which receives the exhaust gas from a diesel engine. The housing (2) contains a conduit (4) formed with elongate slits (5) alternating with elongate V-shaped channels (6). These channels (6) provide access to a collection chamber (7) arranged at the far end of the conduit (4). Exhaust gases flow out of the conduit (4) through the slits (5), and particulates entrained in the exhaust gases are trapped in the channels (6) and travel into the collection chamber (7) where they are burned off by a heater (10) in the form of a length of high-resistance wire (11). Although some of the heavy particulates are trapped in the channels (6), other particulates travel under their own momentum in an axial direction and are impelled towards the channels (6) by a diverter (14). A filter (15) made from layers of flexible, woven ceramic fibre surrounds the conduit (4). The housing (2) comprises one or more layers of expanded metal (16) wound around the filter (15) and an outer metal cage (17).

Description

TREATMENT OF EXHAUST GASES

The present invention relates to the treatment of exhaust gases, and in particular to arrangements for separating particulates from the exhaust gases of combustion processes, such as occur in internal combustion engines, e.g. diesel engines, or oil-fired boilers.

It is now well understood that the emission of carbon particulates in exhaust gases, such as from internal combustion engines, is undesirable from the point of view of atmospheric pollution and the resulting detriment to public health. Indeed, legislation is in force or being considered in many countries which will require a reduction in the pollutant output of internal combustion engines.

There have been many proposed systems for reducing the quantity of particulates in exhaust gases.

hi purely mechanical systems, the exhaust gases are caused to pass through a filter material which traps the particulates. Such arrangements suffer from the disadvantage that the filter becomes blocked with the particulates, giving rise to a back-pressure and a consequential reduction in engine efficiency. Although a by-pass channel can be provided to overcome this problem, some of the pollutant particulates will necessarily also pass into the by-pass channel and will not therefore be removed.

In electrostatic systems, the particulates in exhaust gases are charged by means of a high- voltage electrode, and the charged particulates are subsequently diverted by the application of an electric field into a path containing a filter. As with the purely mechanical systems described above, a by-pass channel is provided for the exhaust gases, but the diversion of the pollutant particles results in only a very small quantity of pollutant particles passing into the by-pass channel.

In both these purely mechanical systems and the electrostatic systems, the filters would, without special treatment, eventually become blocked with particulates and cease to function. In order to overcome this problem, the filters are periodically regenerated by heating them so as to burn off the trapped pollutant particulates. In Europe, emission standards for diesel engines in new vehicles are becoming increasingly rigorous. Thus, the 1992 standard, known as "Euro 1" provided a maximum level of particulate matter for passenger cars of 0.14 g/km, whereas the corresponding value adopted by the "Euro 3" standard which was introduced in 2000 was reduced to 0.05 g/km. Furthermore, the "Euro 5" standard, which is expected to be introduced in mid-2008, provides a maximum level of only 0.005 g/km. The corresponding maximum levels of particulate matter for heavy-duty diesel engines, which generally includes lorries and buses, have also been reduced.

The above systems work well with the relatively low levels of particulates typically found in the exhaust gases of the more modern internal combustion engines. However, older vehicles, and especially larger vehicles such as trucks and lorries which were designed to comply with the "Euro 1" standard, emit much higher levels of pollutant particulates, and, for such vehicles, these systems do not function efficiently.

It would therefore be desirable to provide arrangements for removing pollutant particulates from exhaust gases of internal combustion engines which emit higher levels of such particulates and which could be retro-fitted on to the vehicles.

The present inventor has observed that the high level of particulates which are emitted typically from older lorries and buses are due to the inclusion of a high proportion of large particulates, such as those having a diameter in the range of 2.5 to 10 microns.

In accordance with a first aspect of the present invention there is provided apparatus for separating pollutant particulates from the exhaust gases of a combustion process, the apparatus comprising: means for directing the exhaust gases along a relatively curved path; and means for guiding pollutant particulates entrained within the exhaust gases so that they are caused to move along a relatively straight path to a. collecting region.

Thus, this aspect of the present invention takes advantage of the high mass, and thereby the high momentum, of particulates in order to remove them from the exhaust gases. Indeed, by removing the high proportion of particulates which are of relatively high mass, it will be appreciated that a much higher proportion of the overall particulate mass is removed. Furthermore, by causing the particulates to be directed to the collecting region, there is no need to provide a filter for these particulates.

In a preferred arrangement, the apparatus further comprises a generally cylindrical housing defining an entrance at one end thereof for receiving the exhaust gases and a conduit extending from the entrance to the collecting region which functions both to direct the exhaust gases along the curved path and to guide the entrained pollutant particulates along the straight path. The conduit is provided with apertures through which the exhaust gases may pass, the arrangement being such that relatively massive particulates entrained in the exhaust gases are caused to be directed along the conduit to the collecting region, whereas the relatively light particulates entrained in the exhaust gases are allowed to pass through the apertures in the conduit.

With such an arrangement, the exhaust gases are forced under pressure into the apertures in the conduit and are thereby caused to move along a curved path, whereas the relatively heavy particulates continue, by virtue of their momentum, to travel within the conduit past the apertures.

By profiling the conduit so as to define guide channels for the particulates which extend in a generally axial direction within the housing, this facilitates the linear movement of the particulates from the entrance to the heating means.

The conduit is preferably in the form of a hollow circular cylinder, and the guide channels are arranged longitudinally along the cylinder.

The apertures are preferably in the form of elongated slits located between each pair of adjacent guide channels. Such an arrangement assists in the separation of particulates from the exhaust gas stream, since the particulates are likely to be trapped by the guide channels.

The guide channels preferably have a V-shaped cross-section, since this enhances the ability of the channels to trap the particulates. It will be appreciated that, once particulates are trapped in the apex of the "V", they will continue to travel along the channels and into the collecting region, and it is unlikely that the exhaust gas stream will cause them to become dislodged from the channels. Although with the above arrangements, most of the particulates will be directed to the heating means and burned off, there will still inevitably be at least some particulates, especially of lower mass, which follow the curved path of the exhaust gas stream and are not trapped. Thus, the exhaust gases which pass through the apertures in the conduit are preferably filtered to remove this relatively small proportion of lighter particulates.

The means for achieving this filtering may be in the form of a hollow cylinder of filter material disposed around the conduit. Such an arrangement enables the provision of a single filter for filtering the exhaust gases passing through all of the apertures within the conduit.

The hollow cylinder of filter material may be formed from a number of layers by winding a single sheet of the filter material around the conduit. Thus the filter material can be supplied in sheet form and cut into the desired size and shape for cylinders of different sizes. This also provides the technical advantage that the layers are compressed together by an amount which depends on the flow of exhaust gas. Thus, the higher the flow of exhaust gas, the greater is the filtration efficiency.

In a preferred arrangement, the sheet of filter material is wound around the conduit together with a sheet of expanded metal to form a double-roll structure. Expanded metal comprises a sheet of metal which has been slit and drawn into an open mesh pattern. This provides additional support for the file material.

Furthermore, the expanded metal is preferably coated with a catalyst for performing the standard functions of oxidising carbon monoxide to carbon dioxide, reducing nitrogen oxides to nitrogen and oxidising hydrocarbons to carbon dioxide and water.

The filter material is preferably flexible. This has been found to provide the advantage that particulates which pass through the apertures in the conduit and become trapped in the filter material are ejected back through the apertures as a result of the flexing of the filter material when subject to the vibrations typically encountered within a vehicle exhaust slincer. The filter material is preferably in the form of a woven fibre. The term, "woven" is used to refer to the structure of the filter material and is not intended to imply any limitation on the manner of manufacture. Thus, the fibres are interlinked in a pattern resembling a woven fabric. This feature also gives rise to an enhanced filtration efficiency at higher gas flow, but for the reason that the fibre strands of one layer tend to be compressed into the interstices between the fibre strands of the adjacent layers.

The filter material is preferably a ceramic fibre. Not only do ceramic fibres exhibit excellent filtering characteristics, but also serve to provide good acoustic insulation.

A clamp in the form of a metallic ring of circular cross-section is preferably provided at each end of the conduit so that the filter material in retained in position between the clamp and the housing. It will be appreciated that the filter material is subject to large forces, and the provision of such a clamp serves to stabilise the apparatus.

Furthermore, the ends of the filter material beyond the clamps are preferably tied, e.g. with a length of heat-resistant string, so as to reduce the diameter of the filter material at the ends, thereby enhancing the effect of the clamps. Alternatively, means may be provided for clamping the filter material about the ring clamps.

The housing may include one or more layers of expanded metal which surround the filter material. This therefore allows the exhaust gases to pass through the housing.

The housing preferably further comprises an outer cage structure for retaining the expanded metal in position. This enables the layer of expanded metal simply to be rolled around the filter material without any further means of support.

The apparatus preferably further comprises means for heating the collecting region so as to burn off the collected particulates. This provides a convenient arrangement for removal of the particulates which does not require dissembling the apparatus.

The heating means may comprise a length of high-resistance wire, which is preferably formed from an iron-chromium-aluminium alloy such as that marketed under the name Kanthal (Registered Trade Mark). Wire is more economical than the pressed sheet which has previously been used for the heaters used to regenerate exhaust gas filters, and iron-chromium-aluminium alloys have been found to exhibit the desired high electrical resistance over a wide range of voltages.

The heater wire is advantageously coiled around an insulating former made from a ceramic material which acts as both a thermal insulator and an electrical insulator.

In a preferred arrangement, the heating means is located within a generally cylindrical chamber provided with an entrance closure which acts, in conjunction with the conduit, as a barrier to the passage of exhaust gases but into which the relatively massive particulates entrained in the exhaust gases can pass via the guide channels in the conduit.

A diverter is preferably located upstream of the heater for diverting particulates entrained in the exhaust gases towards the guide channels. Although some of the heavy particulates will pass into the guide channels upstream of the diverter, the diverter serves to direct some of the remaining particulates into the channels, resulting in greater efficiency of separation.

The diverter may be in the form of one or more plates disposed in respective radial planes within the housing, or may alternatively be in the form of a conical surface. Thus any incoming particulates which hit the plates are redirected into the exhaust gas stream and can then be trapped by the guide channels.

When more than one diverter plate is provided, it is preferred that they are arranged in a sequence of increasing area in the direction of the collecting region. This provides an additional means of guiding the particulates towards the guide channels in the conduit.

An ionising electrode is preferably provided upstream of the guiding means for ionising particulates entrained in the exhaust gases, thereby to cause the particulates to be electrostatically attracted to the guiding means.

A by-pass channel is preferably arranged for the exhaust gases, so as to prevent undesirable back-pressures arising from the filter becoming blocked with particulates. The present invention extends to an apparatus for replacing the silencer of a vehicle powered by an internal combustion engine, the apparatus being in the form of a number of apparatuses of the above type connected in parallel to the supply of the exhaust gases.

The by-pass channel is preferably arranged to open automatically by means of a valve whenever the pressure of the exhaust gases exceeds a predetermined threshold.

The silencer of a vehicle is preferably replaced with a filtering apparatus of the above type within an outer housing. In the case of larger vehicles, the silencer may advantageously be replaced with two such filtering apparatuses within an outer housing.

The outer housing preferably comprises two industry-standard end-baffles.

The invention extends to a kit of parts comprising the two end-baffles in combination with flattened filter material for forming the hollow cylinder of filter material in the apparatus when constructed.

In accordance with a second aspect of the present invention there is provided a method of separating pollutant particulates from the exhaust gases of a combustion process, the method comprising: directing the exhaust gases along a relatively curved path; and guiding pollutant particulates entrained within the exhaust gases so that they are caused to move along a relatively straight path to a collecting region.

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

Figure 1 illustrates in part cross-section a preferred embodiment of a particulate separation apparatus in accordance with the present invention;

Figure 2 illustrates a cross-section of the arrangement shown in Figure 1, taken along the line II-II';

Figure 3 is an isometric view of the particulate separation apparatus of Figures 1 and 2;

Figure 4 illustrates the flow paths of the exhaust gases and the particulates, in the arrangement of Figures 1 to 3; Figure 5 illustrates an alternative embodiment to that of Figure 4;

Figures 6 and 7 illustrate first and second arrangements in which two particulate separation apparatuses are substituted for a silencer in a vehicle.

Referring to Figures 1 to 3 of the drawings, the particulate separator 1 comprises a circularly cylindrical housing 2 having an entrance chamber 3 for receiving the exhaust gas from a diesel engine.

The housing 2 contains a hollow circularly cylindrical conduit 4 which is formed with a plurality of elongate apertures 5 in the form of slits. In between each adjacent pair of apertures 5 there is formed in the conduit an elongate channel 6 having a V-shaped cross-section, which can be more readily appreciated from Figure 2. A collection chamber 7 defined by two end flanges 8, 9 is arranged at the far end of the conduit 4. The only access to the collection chamber 7 is via the peripheral V-shaped channels 6, since the upstream flange 8 serves to block the flow of exhaust gases through the central region within the conduit 4.

hi use, the exhaust gases are caused to flow out of the conduit 4 through the apertures 5. However, the V-shaped profile of the channels 6 serves to trap any heavy particulates entrained in the exhaust gases, and these are caused to travel along the channels 6 and into the collection chamber 7, by virtue of both the component of the gas flow in this direction and also the flow of subsequently deposited heavy particulates.

The collection chamber 7 is provided with a heater 10 for burning off the heavy particulates. The resulting carbon dioxide passes out of the collection chamber via the apertures 5 which extend into the collection chamber 7.

The heater 10 is in the form of a length of high-resistance wire 11 formed from an iron- chromium-aluminium alloy, marketed under the name Kanthal (Registered Trade Mark), which is coiled around a former 12 made from an insulating ceramic material. Electrical power is supplied to the heater 10 by means of a terminal 13. The voltage applied to the heater is normally 12V, but other applications could require voltages of e.g. 6V, 24V or 36V. The voltage will determine the length of the heater 10 and, in turn, the length of the collection chamber 7. A diverter 14 in the form of a flange of circular cross-section is located upstream of the heater 10 which serves to divert particulates which remain entrained in the exhaust gases towards the V- shaped channels 6. The diverter 14 comprises a circular diverting surface which faces the stream of exhaust gases and a skirt facing downstream.

Although only a single diverter 14 is illustrated in the drawings, alternative embodiments are envisaged in which a plurality of such diverters 14 of different diameters are provided, and which are ordered along the axis of the conduit 4 in increasing diameter towards the collection chamber 7.

Arranged within the housing 2 and surrounding the conduit 4 is a hollow circularly cylindrical filter 15 in the form of a number of layers of flexible, woven ceramic fibre wound around the conduit 4 from a single sheet of the fibre material. The housing 2 comprises one or more layers of expanded metal 16 wound around the filter 15 so as to create a region of overlap 16' and which retains the filter 15 in position. The housing 2 further comprises a metal cage 17 which retains the expanded metal 16 in position. The metal cage 17 comprises two end caps 18 which are joined together by two bars 19 having a V-shaped cross-section for enhanced rigidity and arranged parallel to the axis of the housing 2, which are in turn joined at their centres by a circumferential strap 20. The outer edge 21 of the sheet of expanded metal is arranged to be covered by one of the two axially oriented bars 19, as shown in Figure 2.

The filter 15 is further retained in position by virtue of a clamp 22 in the form of a metallic ring having a circular cross-section, which surrounds each end of the conduit 4 and which compresses the filter 15 against the outer layer or layers of expanded metal 16. The ends of the layers of the filter 15 are tied together by heat-resistant string 23. The string 23 also serves to retain the clamp 22 in position on the conduit 4 by causing the clamp 22 to bear against the V-shaped channels 6.

As mentioned above, some of the heavy particulates entrained in the exhaust gas become trapped in the V-shaped channels 6 and travel to the collecting chamber 7. In addition, the heavy particulates which, by virtue of their own momentum, travel in a generally axial direction along the central region of the conduit 4 are impelled towards the channels 6 by the diverter 14. However, since the material used for the filter 15 is flexible, the vibrations which arise in moving vehicles will tend to cause the layers of the filter 15 to flex and thereby cause some of the particulates which have passed through the apertures 5 in the conduit 4 to be ejected back into the entrance chamber 3.

Figure 4 illustrates the respective flow paths taken by the exhaust gases and the particulates. The solid lines indicate the curved paths of the exhaust gases, and it can be seen that the gases pass through the apertures 5 in the conduit 4 and into the filter 15. hi contrast, the particulates, either being trapped within the V-shaped channels 6 or being deflected by the diverter 14, adopt a relatively straight, axial path, shown by dotted lines in the figure, towards the collecting chamber 7.

Figure 5 shows an alternative embodiment in which the diverter is in the form of a cone 14'. This arrangement has been found by the inventor of the present invention to be particularly efficient in diverting the particulates into the collection chamber 7.

The above-described particulate separator 1 finds particular application in replacing the silencer of a diesel vehicle, since the filter material serves additionally to provide the necessary acoustic insulation.

In two such arrangements, as shown in Figures 6 and 7, two particulate separators 1, Y are connected in parallel to the supply of exhaust gases. The same reference numerals are used in these figures to indicate the corresponding parts shown in Figures 1 to 4.

hi the arrangement shown in Figure 6, two end-baffles 24, 25 support the two particulate separators 1, 1' and an outer housing (not shown). The upstream end-baffle 24 supports the separators 1, 1' via two respective supply channels 26, 26', and the downstream end-baffle 25 supports the separators 1, Y directly. Two spring-controlled by-pass valves 27, 27' are connected to the two respective supply channels 26, 26'. When the pressure in either of the two supply channels 26, 26' exceeds a predetermined value, the respective by-pass valve 27, 27' is opened, causing the exhaust gas to escape and to pass out of the outer housing via an aperture 28 in the downstream end-baffle 25. Thus, in the event of the filter 15 of one of the particulate separators 1 or 1' becoming blocked with trapped particulates, the resulting back-pressure will cause the respective by-pass valve 27 or 27' to open so as to enable the exhaust gases to escape.

Figure 7 illustrates an alternative arrangement in which a single by-pass valve 29 is connected to the upstream end-baffle 24. hi place of the two by-pass valves 27, 27' of the arrangement described above with reference to Figure 5, two respective open channels 30, 30 'are provided for diverting a proportion of the exhaust gases, together with relatively small particulates, into an auxiliary cylindrical filter 31 which removes these small particulates.

As with the particulate separators 1, 1 ', the filtered exhaust gases pass through the sides of the auxiliary filter 31 and escape from the outer housing via an aperture 32 provided in the downstream end-baffle 25.

It will be appreciated by those skilled in the art that numerous modifications may be made to the above preferred arrangements without departing from the scope of the invention.

For example, the filter material may be wound around the conduit together with a sheet of expanded metal to form a double-roll structure, and the expanded metal may be coated with a catalyst.

Alternatively, or in addition, a catalyst may be provided upstream of the particulate separator.

Claims

CLAIMS:

1. Apparatus for separating pollutant particulates from the exhaust gases of a combustion process, the apparatus comprising: means for directing the exhaust gases along a relatively curved path; and means for guiding pollutant particulates entrained within the exhaust gases so that they are caused to move along a relatively straight path to a collecting region.

2. Apparatus as claimed in claim 1, the apparatus further comprising: a generally cylindrical housing defining an entrance at one end thereof for receiving the exhaust gases; wherein the directing means and the guiding means are comprised by a conduit extending from the entrance of the housing to the collecting region and which is provided with apertures through which the exhaust gases may pass; the arrangement being such that relatively massive particulates entrained in the exhaust gases are caused to be directed along the conduit to the collecting region, whereas the relatively light particulates entrained in the exhaust gases are allowed to pass through the apertures in the conduit.

3. Apparatus as claimed in claim 2, wherein the conduit is profiled so as to define guide channels for the particulates which extend in a generally axial direction within the housing.

4. Apparatus as claimed in claim 3, wherein the conduit is substantially in the. form of a hollow circular cylinder and the guide channels arranged longitudinally along the cylinder.

5. Apparatus as claimed in claim 3 or claim 4, wherein the apertures comprise elongate slits located between each pair of adjacent guide channels.

6. Apparatus as claimed in any one of claims 3 to 5, wherein the guide channels have a V- shaped cross-section.

7. Apparatus as claimed in any one of claims 2 to 6, further comprising means for filtering the exhaust gases which pass through the apertures of the conduit.

8. Apparatus as claimed in claim 7, wherein the filtering means comprises a hollow cylinder of filter material disposed around the conduit.

9. Apparatus as claimed in claim 8, wherein the filter material is in the form of a plurality of layers wound around the conduit.

10. Apparatus as claimed in claim 9, further comprising a plurality of layers of catalyst material alternating with the plurality of layers of the filter material.

11. Apparatus as claimed in any one of claims 8 to 10, wherein the filter material is flexible.

12. Apparatus as claimed in any one of claims 8 to 11, wherein the filter material is in the form of a woven fibre.

13. Apparatus as claimed in any one of claims 8 to 12, wherein the filter material comprises a ceramic fibre.

14. Apparatus as claimed in any one of claims 8 to 13, further comprising a ring clamp disposed around the conduit at each end thereof, the arrangement being such that the filter material is retained in position between the ring clamps and the housing.

15. Apparatus as claimed in claim 14, further comprising means for tying each end of the filter material so as to reduce the diameter of the ends of the hollow cylinder of filter material and thereby enhance the retention of the filter material in position between the ring clamps and the housing.

16. Apparatus as claimed in claim 14, further comprising means for clamping the filter material about the ring clamps.

17. Apparatus as claimed in any one of claims 8 to 16, wherein the housing comprises a layer of expanded metal which surrounds the filter material, for allowing passage of the exhaust gases therethrough.

18. Apparatus as claimed in claim 17, wherein the housing further comprises an outer cage structure for retaining the layer of expanded metal in position.

19. Apparatus as claimed in any preceding claim, further comprising means for heating the collecting region so as to burn off the collected particulates.

20. Apparatus as claimed in claim 19, wherein the heating means comprises a length of high- resistance wire.

21. Apparatus as claimed in claim 20, wherein the high-resistance wire is formed from an iron-chromium-aluminium alloy.

22. Apparatus as claimed in claim 20 or claim 21, wherein the heater wire is coiled around an insulating former made from a ceramic material.

23. Apparatus as claimed in any one of claims 19 to 22, when dependent on claim 3, wherein the heating means is located within a generally cylindrical chamber provided with an entrance closure which acts, in conjunction with the conduit, as a barrier to the passage of exhaust gases but into which the relatively massive particulates entrained in the exhaust gases can pass via the guide channels in the conduit.

24. Apparatus as claimed in claim 23, further comprising means located upstream of the heater for diverting particulates entrained in the exhaust gases towards the guide channels.

25. Apparatus as claimed in claim 24, wherein the diverting means comprises one or more plates disposed in respective radial planes within the housing.

26. Apparatus as claimed in claim 25, wherein the diverting means comprises a sequence of such plates of increasing area along the axis of the housing in the direction of the collecting region.

27. Apparatus as claimed in claim 24, wherein the diverting means comprises a conical surface.

28. Apparatus as claimed in any preceding claim, further comprising an ionising electrode upstream of the guiding means for ionising particulates entrained in the exhaust gases, thereby the cause the particulates to be electrostatically attracted towards the guiding means.

29. Apparatus as claimed in any preceding claim, further comprising means defining a bypass channel for the exhaust gases.

30. Apparatus as claimed in claim 29, further comprising means for causing the by-pass channel to open whenever the pressure of the exhaust gases exceeds a predetermined threshold.

31. Apparatus for replacing the silencer of a vehicle powered by an internal combustion engine, the apparatus comprising a plurality of apparatuses as claimed in any one of claims 1 to 30 connected in parallel to the supply of exhaust gases.

32. Apparatus as claimed in claim 31, wherein the plurality of apparatuses comprises two apparatuses, the apparatus being provided with an outer housing.

33. Apparatus as claimed in claim 32, wherein the outer housing comprises two industry- standard end-baffles.

34. A kit of parts for apparatus as claimed in claim 33, the kit comprising the two end-baffles in combination with flattened filter material for forming the hollow cylinder of filter material in the apparatus when constructed.

35. A method of separating pollutant particulates from the exhaust gases of a combustion process, the method comprising: directing the exhaust gases along a relatively curved path; and guiding pollutant particulates entrained within the exhaust gases so that they are caused to move along a relatively straight path to a collecting region.

36. A method as claimed in claim 35, further comprising heating the collecting region so as to burn off the collected particulates.