CN102933810A

CN102933810A - Ring reductant mixer

Info

Publication number: CN102933810A
Application number: CN2011800273357A
Authority: CN
Inventors: Y·T·布伊; 古玉祥; 孙金辉
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2010-04-05
Filing date: 2011-04-01
Publication date: 2013-02-13
Anticipated expiration: 2031-04-01
Also published as: US20110239631A1; CN102933810B; WO2011126930A3; WO2011126930A2; DE112011101199T5; GB201217708D0; GB2491777A

Abstract

An engine exhaust aftertreatment system including a ring disposed in an exhaust conduit. The ring assists in the introduction and conversion of a reductant introduced by an injector.

Description

Ring type reducing agent mixer

Technical field

The present invention relates to the engine exhaust after-treatment system, and relate more specifically to adopt the exhaust after treatment system for the reducing agent of NOx reduction technique.

Background technique

Can comprise selective catalytic reduction (SCR) system at the pump-down process or the after-treatment system that are used for power system, to remove or to reduce nitrogen oxide (NOx or NO) effulent from engine exhaust.The SCR system uses the reducing agent that is imported in the vent systems, for example urea.

US Patent No. 7,581,387 disclose a kind of hybrid system that comprises be used to the hybrid blade that urea is mixed with exhaust stream.

Summary of the invention

The invention provides and be configured to reducing agent is imported the sparger in the exhaust duct and is configured in the engine exhaust after-treatment system of the ring in the exhaust stream a kind of comprising.

Description of drawings

Fig. 1 comprises motor and with the skeleton diagram of the power system of the after-treatment system of mixer.

Fig. 2 is the front view of mixer.

Fig. 3 is another embodiment's of mixer front view.

Fig. 4 is another embodiment's of mixer front view.

Fig. 5 is another embodiment's of mixer front view.

Fig. 6 is another embodiment's of mixer front view.

Fig. 7 is the skeleton diagram that has added the double branch pipe after-treatment system of mixer.

Embodiment

As shown in Figure 1, power system 10 comprises motor 12 and for the treatment of the after-treatment system 14 of the exhaust stream 16 that is produced by motor 12.Motor 12 can comprise other unshowned feature structures, such as controller, fuel system, air system, cooling system, peripheral equipment, power train member, turbosupercharger, exhaust gas recycling system etc.

Motor 12 can be the motor (internal combustion, gas, diesel oil, vaporized fuel, rock gas, propane etc.) of any type, can have any size, with any amount of cylinder, and adopts any structure (" V " type, array, radially wait).Motor 12 can be used for driving any machine or other devices, comprises highway truck or vehicle, open-air truck or machinery, earth-moving equipment, generator, AEROSPACE APPLICATION, locomotive application, ocean application, pump, static equipment or other engine-driven application.

After-treatment system 14 comprises exhaust duct 18 and selective catalytic reduction (SCR) system 20.SCR system 20 comprises SCR catalyzer 22, mixing duct 24, mixer 26 and reductant supply system 28.

SCR catalyzer 22 comprises and is configured in suprabasil catalyst material.Substrate can be comprised of steinheilite, silicon carbide, other potteries or metal.Substrate can comprise the passage of a plurality of perforations and can form cellular structure.

Reductant supply system 28 can comprise reducing agent 30, reducing agent source 32, pump 34, valve 36, reductant line 38 and sparger 40.Reducing agent 30 is sucked from reducing agent source 32 via pump 34 and controls to the conveying of sparger 40 via valve 36.Also can control flowing of reducing agent 30 by the running of pump 34.

Mixing duct 24 is sections of the exhaust duct 18 that is imported into of reducing agent 30.Mixing duct 24 comprises inwall 25 and outer wall 27.Mixing duct 24 is also limited by inner width 29.

Reductant supply system 28 also can comprise the reducing agent 30 that freezes be used to thawing, prevent that reducing agent 30 from freezing or prevent the heat management system that reducing agent 30 is overheated.The member of reductant supply system 28 also can be adiabatic, and is overheated to prevent reducing agent 30.Reductant supply system 28 also can comprise for importing pressurized air to aid in the air auxiliary system of reducing agent spraying 44 formation droplets.The air auxiliary system also can be used to when not using reductant line 38 and other reductant supply system 28 members are driven send reducing agent 30.

Reducing agent 30 is from nozzle or the injector tip 42 of sparger 40, to form reducing agent spraying 44 or otherwise to import in exhaust stream 16 or the SCR catalyzer 22.The position of injector tip 42 can be so that along the direct guiding downwards of the center line of mixing duct 24 and mixer 26 reducing agent spraying 44.

After-treatment system 14 also can comprise diesel oxidation catalyst (DOC) 46, diesel particulate filter (DPF) 48 and cleaning catalyst 50.DOC 46 and DPF 48 can be arranged in as shown in the figure the same pot or separate.SCR catalyzer 22 and cleaning catalyst 50 also can be arranged in as shown in the figure the same pot or separate.

After-treatment system 14 is configured to remove, collect or transform undesirable composition from exhaust stream 16.DOC 46 changes into carbon dioxide (CO2) with carbon monoxide (CO) and unburned hydrocarbon (HC).DPF 48 collecting granules materials or charcoal cigarette.SCR catalyzer 22 is configured to the amount of the NOx of minimizing reduction exhaust stream 16 in the situation that has reducing agent 30.

Also can comprise thermal source 52, to remove the charcoal cigarette from DPF 48, heat management SCR catalyzer 22, DOC 46 or cleaning catalyst 50 to remove desulfuration from SCR catalyzer 22, are perhaps removed the sludge of the established reducing agent 30 of possibility.Thermal source 52 can be presented as burner, be used for forming at DOC 46 hydrocarbon metering supply system, electrical heating elements, microwave device or other thermals source of exothermic reaction.Thermal source 52 also can be presented as motor 12 is turned round under the state that produces exhaust stream 16 temperature that raise.Thermal source 52 also can be presented as back pressure valve or another confining device in the exhaust, so that exhaust stream 16 temperature raise.

In illustrated embodiment, exhaust stream 16 leaves motor 12, gets around or process thermal source 52, through DOC 46, DPF 48, then passes through SCR system 20, and then via exhaust duct 18 process cleaning catalysts 50.

Also can other exhaust gas treatment devices be set in SCR system 20 upstreams, downstream or its inside.In illustrated embodiment, SCR system 20 is positioned at DPF 48 downstreams and DOC 46 is positioned at DPF 48 upstreams.Thermal source 52 is positioned at DOC 46 upstreams.Cleaning catalyst 50 is positioned at SCR system 20 downstreams.In other embodiments, these devices can adopt various arranged in order and can be combined in together.In one embodiment, SCR catalyzer 22 can make up with DPF 48, and wherein catalyst material is deposited on the DPF 48.

Although other reducing agents 30 are possible, urea is the source of the most general reducing agent 30.Carbamide reducing agent 30 decomposes or hydrolysis ammonification (NH3) and then be absorbed or otherwise be stored in the SCR catalyzer 22.Mixing duct 24 can be very long, with the mixing of assisting reducing agent 30 or be evenly distributed in the exhaust stream 16 and be provided for the waiting time that carbamide reducing agent 30 changes into NH3.NH3 is reduced into nitrogen (N2) by NOx and is consumed in SCR catalyzer 22.

Cleaning catalyst 50 can be presented as ammoxidation catalyst (AMOX).Cleaning catalyst 50 is configured to catch, storage, oxidation, reduction and/or transform the NH3 that can slip over or pass SCR catalyzer 22.Cleaning catalyst 50 also can be configured to catch, storage, oxidation, reduction and/or transform the composition of other existence.

Also can comprise controller and sensing system, with other members in control engine 12, thermal source 52, reductant supply system 28 and power system 10 or its application.

Mixer 26 comprises around parts or encircles 54.Ring 54 is smooth as shown in the figure, has toroidal shape and rectangular cross-section, is similar to packing ring.In other embodiments, ring 54 can have various other cross sections, comprises circle.

Ring 54 comprises front face surface (face surface) 55, internal surface 56 and outer surface 57.Ring 54 is limited by the thickness 58 on the flow direction of exhaust stream 16, internal diameter 60, external diameter 61 and ring width 62.Ring width 62 be form ring 54 parts width and be internal diameter 60 and half of the difference of external diameter 61.The internal diameter 60 of ring 54 limits central opening 64.

Because ring 54 can be smooth, so the surface of ring can impenetrating thickness 58 be consistent and identical with front face surface 55.Transverse plane 65 passes mixer and cuts mixing duct 24.Transverse plane 65 comprises the plane group parallel with it.Transverse plane 65 can be arranged or extensible another part of passing mixer 26 along front face surface 55.Transverse plane 65 can be perpendicular to exhaust stream 16, as shown in the figure.Transverse plane 65 also can be perpendicular to the inwall 25 of mixing duct 24.In other embodiments, Transverse plane 65 can with 26 one-tenth various angle configurations of exhaust stream 16 and inwall.

Describe and be depicted as toroid and circular and have " diameter " although will encircle 54, encircling 54 also can be rectangle, octagonal, leg-of-mutton or any other shape.Ring 54 shape can be consistent with the interior week of mixing duct 24 and at least a portion of shape that can corresponding mixing duct 24 with holding it mate.Ring 54 also can have the shape and the size that are different from mixing duct 24 and be adapted to fit in (for example, ring 54 can have the square shape that is engaged in the circular mixing duct 24) in the mixing duct 24.Ring width 62 is can yes or no constant.The profile of ring 54 also can be different from interior shape (for example, profile can be circular, and interior shape and central opening 64 can be rectangles).

Mixer 26 also can comprise the spacer element 66 that ring 54 and the inwall 25 of mixing duct 24 are separated.Spacer element 66 also can be used to installing ring 54.

The outer surface 57 of ring 54 and the separation between the inwall 25 limit gap 68.Gap 68 can be annular or have a difformity.Gap 68 can have gap width 70.It is constant that gap width 70 can yes or no around ring 54.In certain embodiments, can there be gap 68 at some positions of ring 54.

Some size situations of mixer 26 below are provided.These size situations can be depending on a large amount of variablees that can change to some extent between different power system 10.For example, suitable mixer 26 sizes can be depending on that exhaust stream 16 speed, mixing duct 24 sizes, motor 12 duty cycle, motor 12 back pressures require, reducing agent is sprayed 44 drop sizes, reducing agent is sprayed 44 speed.For these variablees are described, aspect ratio, limit following size and scope is provided.

Gap width 70 can be about 1/8 inch.In other embodiments, gap width 70 can be between 1/16 and 1/4 inch.In other other embodiments, gap width 70 can be between 1/16 and 1/2 inch.

The size of gap width 70 also can be the function of inner width 29.In one embodiment, gap 68 transversely the area on plane 65 can be mixing duct transversely plane 65 area about 1.3%.In other embodiments, gap 68 transversely plane 65 area can between mixing duct transversely plane 65 area 0.5% and 5% between, between 0.1% and 10% or between 0.7% and 2%.

Ring width 62 can be about 2 inches.In other embodiments, ring width 62 can be between 1 and 3 inch.In other other embodiments, ring width 62 can be between 0.5 and 5 inch.

The size of ring width 62 also can be the function of inner width 29.In one embodiment, ring width 62 can be about 10% of inner width 29.In other embodiments, ring width 62 can between inner width 29 5% and 15% between or between 2% and 25%.

Gap width 70 and ring width 62 also may be selected to the given size of realizing central opening 64 according to inner width 29.In one embodiment, central opening 64 transversely the area on plane 65 can be mixing duct 24 transversely plane 65 area about 62%.In other embodiments, central opening 64 transversely plane 65 area can between mixing duct 24 transversely plane 65 area 50% and 70% between, between 40% and 80%, between 30% and 80% or between 20% and 90%.

Ring 54 can be made of sheet metal, and therefore thickness 58 can be smaller, but it can be various sizes.In one embodiment, this thickness can be less than 1(one) inch.In another embodiment, this thickness can be less than 1/4 inch.Thickness 58 also can be less than ring width 62.

Fig. 2-6 shows the various embodiments of the mixer 26 with various features as described below.Mixer 26 can comprise any combination of the feature of describing in the literary composition.Fig. 2 will encircle 54 and illustrate as solid surface.Fig. 2 also illustrates spacer element 66 can be separated with inwall 25 and the spot welding 72 of installing or be connected to inwall 25 forms by encircling 54.

Fig. 3 shows ring 54 can comprise the one or more openings 73 that pass front face surface 55.Opening 73 can have the various positions on ring 54 and can form various patterns.Fig. 3 also illustrates spacer element 66 can be by forming from encircling the contact pin (tab) 74 that 54 outer surface 57 extends.Then the far-end of contact pin 74 can weld, inserts or be otherwise connected to mixing duct 24, separates with inwall 25 and installs or be connected to inwall 25 will encircle 54, and form gap 68.

Fig. 4 shows mixer 26 can comprise the central construct 76 that extends in the central opening 64.These central construct 76 can from encircle 54 internal surface 56 from another position or body extend.Central construct 76 can be presented as large parts, little wire or silk screen.

Fig. 5 shows can increase guide plate 78 at mixer 26.Guide plate 78 comprises guide plate opening 80 and inflector 82.16 one-tenth of inflector 82 and exhaust streams less than the angle configurations of 90 degree and thus directing exhaust gas stream 16 at a certain angle by guide plate opening 80.Guide plate 78 can form by curved cuts 84 or punching press sector part (scallop) 86.Fig. 6 illustrates inflector 82 and also can be formed by spacer element 66 or central construct 76.

Fig. 1 shows the position of mixer 26 in mixing duct 24.Mixer 26 is configured in the inwall 25 at mixer distance 88 places of distance injector tip 42.Mixer distance 88 can be such: when reducing agent spraying 44 arrival encircled 54, the size of spraying 44 when it expands was roughly the size of central opening 64.

Fig. 7 shows mixer 26 and can be used in the double branch pipe after-treatment system 90.Double branch pipe after-treatment system 90 comprises and receives exhaust stream 16 and from the first and

second SCR arms

91 and 92 of the reducing agent 30 of reductant supply system 28.

Exhaust stream 16 divided or separation in the separation section 93 of exhaust duct 18 from mixing duct 24.Separation section 93 can be positioned at separation distance 94 places in mixer 26 downstreams.Separation distance 94 comparable mixer distance 88 length.In one embodiment, separation distance can be the function of inner width 29.Separation distance 94 can be about 1.2 times of inner width 29.In other embodiments, separation distance 94 can be inner width 29 more than between 1.2 times, 1 and 2 times or between 1 and 3 times.

Double branch pipe after-treatment system 90 can comprise that also exhaust stream 16 is delivered to first and second of reductant supply system 28 enters arm 95 and 96.From the first and second exhaust stream 16 divided or separations in the merging section 97 of exhaust duct 18 that enter

arm

95 and 96.

First and second

enter arm

95 and 96 is shown as and comprises DPF 48 and DOC 46, but can not comprise above-mentioned any one, perhaps can comprise other members.In one embodiment, first and

second enter arm

95 and 96 and do not comprise DPF 48.First and second

enter arm

95 and 96 also can be shown as with respect to the first and

second SCR arms

91 and 92 configuration that meets at right angles, but can become various other angle configurations or can dispose linearly.Double branch pipe after-treatment system 90 also can be accommodated in the box structure with the inwall of separating exhaust stream.

Mixer 26 members can be made of steel or any other various materials.Mixer 26 also can be coated with the material of assisting reducing agent 30 to transform or be hydrolyzed into NH3.

Industrial applicibility

Mixer 26 helps reducing agent 30 to be distributed equably or be mixed in the exhaust stream 16, promotes that reducing agent 30 changes into NH3, and prevents sedimentary formation.Mixer 26 also should cheap, little and formation no minimum.Yet these features are mutually conflict usually.For example, larger and complicated structure can reducing agent 30 being assigned to equably in the exhaust stream 16 and promoting reducing agent 30 to change into aspect the NH3 effectively but not cheap, occupy too much space, and usually form a large amount of back pressures.

Reducing agent 30 is assigned in the exhaust stream 16 equably by all passages that NH3 are directed to equably the SCR catalyzer improved the efficient of SCR system 20 and therefore in a large number conversion can occur.Reducing agent 30 is assigned to equably the amount that also can reduce the required reducing agent 30 of the larger efficient of realization in the exhaust stream 16.Reducing agent 30 is assigned to equably also can prevents from the exhaust stream 16 too much NH3 is directed to a part of SCR catalyst area that can cause NH3 to slip over.

When reducing agent 30 does not resolve into NH3 rapidly, may form sludge, and assemble the thick-layer of reducing agent 30.These layers are can be along with increasing reducing agent 30 injected or collect and accumulate, and this can have and stops the cooling action of resolving into NH3.As a result, reducing agent 30 is sublimed into crystal or otherwise is transformed into solid constituent and forms sludge.The sludge component can comprise biuret (NH2CONHCONH2) or cyanuric acid ((NHCO) 3) or another kind of component, depends on temperature and other conditions.In the zone that these sludges can be formed on reducing agent spraying 44 bumps, precipitate or stagnate or on the surface.

These sludges can have adverse effect to the running of power system 10.Sludge can block exhaust stream 16 and flow, and causes higher back pressure and reduces motor 12 and after-treatment system 14 performances and efficient.Sludge also can interrupt reducing agent 30 and flow and be mixed in the exhaust stream 16, reduces thus and resolves into NH3 and reduce the NOx reduction efficiency.Sedimentary formation has also consumed reducing agent 30, makes the control of injection more difficult and reduced potentially the NOx reduction efficiency.The sludge member of SCR system 20 that also may corrode and degrade.

The increase of restriction back pressure is also very important.High back pressure can endanger motor 12 performances.High back pressure can cause that also sludge forms and exhaust gas leakage.

Ring 54 can form limited back pressure, realizes still that simultaneously higher reducing agent 30 is mixed into the degree in the exhaust stream 16.The large scale of central opening 64 has limited restriction and has formed the rolling (tumbling) of exhaust stream 16, and this rolling is effective for reducing agent 30 is mixed in the exhaust stream 16.Many other mixer design have realized by the eddy flow mixing or have formed high turbulent level.These mixers have complicated and huge structure, and therefore very expensive and generation back pressure often.On the contrary, found that simultaneously production is got up also cheap, and can not produce the back pressure of the so large amount of other mixers by encircling 54 rollings that realize for mixing effectively.The even shape of ring 54 is conducive to its manufacturing by cutting cheap simple sheet material.More complicated mixer needs expensive more complicated cutting, bending and welding.

Can adopt gap 68 to allow exhaust stream 16 to flow through, still realize above-mentioned rolling effect simultaneously.Thisly flow through the stagnation that prevents otherwise will form sedimentary reducing agent 30 and assemble.This flowing through also helps to reduce back pressure.If gap 68 is excessive, then above-mentioned rolling effect may be hindered, and will only carry out around ring 54 rather than roll through central opening 64 because flow in a large number.If gap 68 is too small, then describedly flow through the remarkable minimizing that may be not enough to prevent sludge or realize back pressure.

Gap 68 can be along the periphery location along ring 54 outer surface 57, because this is that reducing agent is with the position of assembling.In certain embodiments, gap 68 can only be positioned at ring 54 bottom, reducing agent 30 otherwise can assemble here.

Mixer 26 can affect sedimentary formation and mix effectiveness with the mixer distance 88 of injector tip 42.If mixer distance 88 is too short, then reducing agent spraying 44 will concentrate in the little space, because spray 44 also not expansions.Correspondingly, the accurate central part of central opening 64 can be only passed through in reducing agent spraying 44.Because spraying 44 will concentrate in the little space and the center by central opening only, so above-mentioned rolling effect may not can work, and reducing agent 30 is mixed into the degree that it(?) may not can in the exhaust stream 16 reaches expectation.If mixer distance 88 is long, then reducing agent spraying 44 will expand into larger volume and can impinge upon before being converted into NH3 on ring 54 or the inwall 25.This bump may cause forming as mentioned above sludge.

But can adopt opening 73 to help reduce back pressure and weight reduction.Also can form flowing through and discharging area of reducing agent 30 gatherings with opening 73, prevent thus sludge.

Central construct 76 can help to make reducing agent spray 44 fragmentations and atomizing, helps thus to be converted into NH3.Central construct 76 also can import the turbulent flow that can help to be converted into NH3 in the exhaust stream 16.Central construct 76 can not form sludge, because they are positioned at the zone with high flow rate and high-temperature.Central construct 76 also can increase rigidity and the structural strength of mixer 26.

Can adopt guide plate 78 except rolling, also eddy flow is imported in the exhaust stream 16 to be used for other mixing.In certain embodiments, guide plate 78 can produce the counterrotating eddy flow.The same with opening 73, but guide plate 78 also can help to reduce back pressure and weight reduction.Also can form flowing through and discharging area of reducing agent 30 gatherings with guide plate 78, prevent thus sludge.

Mixer 26 also can be suitable for double branch pipe after-treatment system 90.Double branch pipe after-treatment system 90 usually with relatively large engine system coupling.Double branch pipe after-treatment system 90 can allow to use less reprocessing substrate.Because these substrates usually are complicated ceramic bodies, so they can adopt less size to produce more economically.Less size also can be improved the packing selection and improve the Flow Distribution of striding basal surface.

Because mixer 26 imports limited back pressure, thus it can be equably in conjunction with from the first and second exhaust streams 16 that enter arm 95 and 96.The rolling that forms by mixer 26 also can help exhaust stream 16 flowed and be separated into first and second and leave in arm 91 and 92.The mixer that greatly depends on eddy flow and turbulent flow can form any one the bias current of leaving in

arm

91 and 92 towards first and second.

Separation distance 94 can affect exhaust stream 16 and flow and evenly be separated into first and second and leave in

arm

91 and 92 and prevent from forming sludge.

Separation distance 94 can affect exhaust stream 16 and flow and evenly be separated into first and second and leave in arm 91 and 92.If separation distance 94 is too short, then reducing agent 30 may have no time to change into NH3 and large from the rolling effect possibility of mixer 26.May impinge upon on the wall and produce sludge along with reducing agent separating the section 93 front bad NH3 of changing into.Large rolling may cause being partial to the first and second one of leaving in arm 91 and 92.If separation distance is long, then may causes the packing difficulty of double branch pipe after-treatment system 90 and may cause losing and activate SCR catalyzer 22 and prevent from forming the required heat of sludge.

Although above mixer 26 is described as assisting reducing agent is imported exhaust stream, also can imagine, mixer 26 can be used to assist any various materials are imported in any various flowing.Do not break away from the scope of following claim although embodiments of the invention as described herein can merge, it is evident that to those skilled in the art, can make various remodeling and modification.According to specification with to practice of the present invention, other embodiments for a person skilled in the art will be apparent.Should think specification and example only for exemplary, true scope of the present invention is indicated by following claim and their equivalent.

Claims

1. an engine exhaust after-treatment system (14) comprising:

Be configured to that reducing agent (30) imported the sparger (40) in the exhaust duct (24) of motor (12) and be configured in ring (54) in the described exhaust duct (24).

2. engine exhaust after-treatment system according to claim 1 (14), wherein, described ring (54) is smooth.

3. each described engine exhaust after-treatment system (14) according to claim 1-2, wherein, described ring (54) is toroidal and has the rectangular cross-section.

4. each described engine exhaust after-treatment system (14) according to claim 1-3, wherein, described ring (54) limits central opening (64), described central opening along the area of the Transverse plane (65) of described exhaust duct (24) between the area of described Transverse plane (65) in described exhaust duct (24) 50% and 70% between.

5. each described engine exhaust after-treatment system (14) according to claim 1-4, wherein, described ring (54) limits the gap (68) of extending around the periphery of described ring (54), and described gap is formed by the spacer element (66) between the inwall (25) of the outer surface (57) of described ring and described exhaust duct (24).

6. engine exhaust after-treatment system according to claim 5 (14), wherein, described gap (68) have the width (70) between 1/16 and 1/2 inch.

7. engine exhaust after-treatment system according to claim 5 (14), wherein, described gap (68) have between the area of Transverse plane (65) in described exhaust duct (24) of described exhaust duct (24) 0.5% and 5% between the area along described Transverse plane (65).

8. each described engine exhaust after-treatment system (14) according to claim 1-7, wherein, described ring (54) is positioned at apart from the certain distance (88) of described sparger (40) to be located, so that when the spraying (44) of described reducing agent (30) arrived described ring (54), described spraying (44) was not more than central opening (64).

9. each described engine exhaust after-treatment system (14) according to claim 1-8, wherein, described exhaust duct (24) is punished greater than the distance (94) of the width (29) of described exhaust duct (24) at described ring (54) the downstream described ring of distance (54) and is divided into 2 or more arm (91,92).

10. each described engine exhaust after-treatment system (14) according to claim 1-9, wherein, described ring (54) comprises a plurality of openings (73), inflector (82) and extends to central construct (76) in the central opening (64) in the described ring (54).