US2149402A - Air control device for combustion apparatus - Google Patents

Description

-March 7, 1939. '0. J; MOSSHART I AIR CONTROL DEVIQE FOR COMBUSTION APPARATUS Filed June 18, 1936 5 Sheets-Sheet l N Wu H TH. 1N N 5 Q R E5 O V o T W M D N m E E. W l 6 W March 7, 1939. MO HART 2,149,402

WITNESSES: INVENTOR DomvLu J. Mossrma'r- BY mama;

ATTORNEY March 7, 1939. MQSQSHART 2,149,402

AIR CONTROL DEVICE FOR COMBUSTION APPARATUS Filed June 18, 1936 5 Sheets-Sheet INVENTOR DONRLD J. Moss HHRT- ATTORNEY March 7, 1939. v J MQSSHART I 7 2,149,402

' AIR CONTROL DEVICE FOR COMBUSTION APPARATUS Filed June 18, 1936 5 Sheets-Sheet 4 F/ct. /0.

INVENTOR as DonnLu J. MOSSHRRT.

G-8: Ev

ATTORNEY March 7,1939. DQ H R 2,149,402

AIR CONTROL DEVICE FOR COMBUSTION APPARATUS v Fii ed June 18, 1936 s Sheets-Sheet 5 wmnzssrzs: C INVENTOR 2/ DONHLD J. MossnnR'r.

ATTORNEY Patented Mar. 7, 1939 AIR CONTROL DEVICE FOR COMBUSTION APPARATUS Donald J. Mosshart, Springfield, Pa., assignor to Westinghouse Electric &, Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania ApplicationJune 18, 1936, Serial No. 85,861

10 Claims.

My invention relates to means for controlling the flow of gaseous medium to a region of variable flow resistance and it has for an object to provide apparatus of this character which shall be effective to compensate for variation in flow resistance of the region to maintain a more regular or uniform flow condition of the gaseous medium.

I My improved apparatus for controlling the flow of gaseous medium is particularly applicable to stokers wherein irregularities in fuel bed conditions aifect the flow and distribution of air in such a way as to impair combustion. Ordinarily, if the fuel bed should diminish in resistance at a given region, because, for example, of being too thin, then an increased flow of air would tend to occur at that region, the increased flow causing an increased combustion rate and tending to retard restoration of the fuel bed at the region to a normal condition. With a thin spot, sometimes conditions may become so bad that combustible will be blown off the stoker exposing the latter to the combustion chamber. Aside from such undesired combustion at a thin spot or region, an undue proportion of the air may pass through the thin region at the expense of the remaining portions of the stoker. On the other hand, if the fuel bed resistance should increase at a given region, this tends to restrict the flow of air and to diminish the desired combustion rate at that region. A further object of my invention is to provide a duct construction for supplying gaseous medium from a suitable space to a region of variable flow resistance wherein the duct construction is provided with an orifice for admitting gaseous medium thereto from the space and with a throttle between the orifice and the region, the throttle having an element which is movable in response to differential pressure across the orifice to compensate for-variation in flow resistance of the region.

A further object of my invention is to provide a duct construction for supplying gaseous medium from a suitable space to a region of variable flow resistance wherein the duct construction has an orifice for admitting gaseous medium thereto from the space and has a throttle between the orifice and the region and which is provided with an element movable in response to diiferential pressure across the orifice to compensate for variation in fiow resistance of the region, the movable throttle element being partially submerged in liquid in the duct construction so as to provide opposed pressure areas above the liquid and subject to pressures at opposite sides of the orifice.

These and other objects are eifected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. 1 is a longitudinal sectional View of a stoker having my improved air supply means applied thereto;

Fig. 2 is a transverse sectional view taken along the line III-I of Fig. 1;

Fig. 3 is a detail view, partly in section, and showing one of the duct constructions;

Fig. 4 is a detail plan View taken on the line IV-IV of Fig. 3;

. Fig. 5 is a detail transverse sectional view taken on the line VV of Fig. 3 of one of the secondary chambers of a duct construction showing the interior bell aggregate;

Figs. 6, '7 and 8 show details of design in connection with the secondary orifice;

Fig. 9 is a detail sectional view showing a modified form of duct construction; and,

Fig. 10 is a view showing a further modified form of the invention.

While the invention is concerned with means for controlling the flow of gaseous medium, for example, air, to any suitable region having variable fiow resistance, it is particularly useful in connection with combustion apparatus. Therefore, in the drawings, the control apparatus is shown associated with an underfeed stoker, and, in the following description, the flow control apparatus is described in relation to parts of a stoker for the purpose of indicating utility for the apparatus as well as to give a clearer understanding thereof.

Referring to the drawings more in detail, there is shown combustion apparatus, for example, a multiple-retort underfeed stoker, at 10, arranged to carry a progressively moved fuel bed in the usual way at the bottom of the combustion chamber II.

The stoker II] has a plenum air chamber l2 arranged therebelow, the chamber being supplied with air through the duct l3 in the usual way. The stoker includes retorts I4 and rows of tuyeres I5, fuel being fed into the retorts from the hopper l6 by means of primary rams I1.

Each tuyere row has arranged therebelow an air channel i8, and each of the channels is divided by plates l 9 into a plurality of sections, for example, sections 20, 2 i, 22 and 23 supplied with air by means of duct constructions or devices 25, 26, 21 and 28, respectively.

Each duct construction 25, 26, 21 and28includes a duct 29 proper whose upper end communicates with a section of the air channel l8 and whose lower end communicates with the interior of a secondary chamber 30 forming a part of the duct construction.

Air under primary pressure is supplied from the plenum chamber [2 to the secondary chambers 3!) through orifices 3| and each secondary chamber 39 contains means therein which is movable in response to change in the pressure differential across its orifice to effect more or less throttling of the fiow of air from the secondary chamber through the duct portion 29 to the air channel.

Preferably, the means for throttling the flow of air through each duct 29 comprises a damper or Valve portion 33 cooperating with the lower end 34 of the duct to provide a variable throttle area 35, the damper, valve or throttling element 33 being operated by suitable means arranged within the secondary chamber 30.

Preferably, each chamber 3!] has a predetermined level of liquid therein, the liquid level being indicated by the dash line 36 in Fig. 3, and the damper or valve element 33 constitutes a part of a bell aggregate, at 31, which, in all positions of adjustment, has the major portion of its volume submerged in the liquid and has predetermined weight in excess of that of the liquid displaced.

The aggregate 3'! includes a liquid-sealed and partially submerged bell 38, a submerged float 39 and a keel or weight All.

The upper unsubmerged surface of the bell 38 is subject to" the pressure existing in the secondary chamber 3% and the lower sealed surface thereof is.arranged to be subject to primary or plenum chamber pressure, a conduit 4| extending upwardly through one of the openings 381) provided in the fioat 39 and having its upper end extending into the air space of the bell. Accordingly, the this arrangement, if there is a change in differential pressure across the primary orifice 3 I, the bell aggregate responds thereto and moves so as to vary the secondary orifice 35 in such a manner as to compensate for the change in fuel bed resistance producing the change in pressure differential across the primary orifice so that substantially normal differential pressure across the primary orifice is restored and variation in the rate of air flow through the duct construction is kept within very narrow limits irrespective of variation in fuel bed resistance.

Operation of parts so far described is as follows: If there is a change in fuel bed resistance at a region supplied by one of the duct constructions, then, due thereto, the flow of air through the duct construction changes and this is accompanied by a change in differential pressure across the orifice 3!, but change in the latter results in movement of the bell construction so as to vary the throttle area 35, the variation occurring in such a direction as to compensate for the change in fuel bed resistance, the throttle area being varied until such time as substantially normal differential pressure across the primary orifice is restored. In this way, each duct construction supplies an individual area of the stoker and has within itself means for maintaining the flow of air thereto approximately constant irrespective of variations in fuel bed resistance, the objective being toprevent the extreme variations of flow so as to permit a fuel bed to restore itself to normal condition.

With the arrangement so far described, regarding pressure in the plenary or primary chamber l2 as primary pressure, the pressure in each secondary chamber 30 between the orifice and the throttle as secondary chamber pressure, and the pressure in each duct beyond the throttle as tertiary pressure, unless measures to the contrary were taken, the bell aggregate, at 31, would be subject to the disturbing effect of tertiary pressure in the associated duct 29. Accordingly, in the preferred construction shown in Figs. 1 to 8, inclusive, the bell aggregate is constructed so as to provide a tubular passage 42, which is aligned with the passage of the duct 29 and is similar to and equal in area to the latter. As the lower end of the passage 32 extends into the liquid, no area of the bell aggregate is left for exposure to tertiary or duct pressure and the aggregate moves entirely in response to change in pressure differential across the primary orifice.

Aside from the avoidance of the effect of tertiary or duct pressure on the bell aggregate, the cooperating portions 33 and 34 of the duct and of the bell aggregate should be constructed so as to promote an easy turning of the current of air Without undesirable reaction effects, shocks and eddies. Accordingly, as may be seen from Figs. 3 and 8, the lower end 3 5 of the duct is rounded and the upper end 33 of the bell construction is also rounded and extends inwardly, the upper portion 33 extending slightly above the bell 38 to prevent reaction efiects, and such portion having inwardly extending flange 44 which substantially avoids eddying. Thus, it will be seen that the rounded lower end of the duct and the rounded upper end 33 of the bell construction form a circumferentially extending secondary orifice 35 which is convergent-divergent in the direction of flow and extends upwardly and inwardly.

I prefer to construct the bell constructionin such manner that it has a compensating effect in order to promote more rapid restoration of a region of the fuel bed to a normal condition. To this end, the bell 38 has an upwardly tapered portion 38a, with the result that, in case of upward movement of the bell construction, the projected or sealed area subject to primary and secondary pressure increases, and, instead of the bell construction coming to a stop in an equilibrium position where the differential pressure across the primary orifice is restored to the value it had before it changed due to change in fuel bed resistance, it is restored to a value somewhat less, whereby the fiow of airis reduced below normal to promote a more rapid restoration of the fuel bed at the region supplied by the duct. On the other hand, if the fuel bed or the region of resistance should increase, the contrary operation takes place, instead of a differential pressure across the primary orifice being restored to the value it has before the change in fuel bed resistance started, it is restored to a somewhat greater value to provide for increased flow in order that combustion may be carried on at an increased rate, thereby promoting reduction in fuel bed resistance to approximately the intended normal average value. The upwardly tapered portion of the bell construction is of advantage also when the stoker is operated at high rates of combustion in that the bell construction will secure the necessary increase in fiow with increase in fuel bed resistance and vice versa.

The taper 38a, already referred to, provides for an increase in area with upward movement and vice versa, with the result that, to produce equithe dashpot and fluid friction effect.

librium, the pressure differentials decrease with upward movement of the bell construction because of increase in areas at different equilibrium positions and such differentials increase with downward movements thereof because of decreasing areas.

. The bell is further tapered as indicated at 45, so that it will readily she-d particles of ash, etc., which might otherwise tend to disturb the equilibrium of the bell construction, such particles readily passing downwardly and around the bell construction into the bottom portion of the secondary chamber.

As already pointed out, the bell construction has unbuoyed weight, that is, without the application of a suificient pressure difference thereacross, it wouldrest on the supporting rods 46. The weight of the bell construction is so distributed that variation in the extent of the unsubmerged portion incident to rise and fall does not substantially vary the unbuoyed weight, with the result that, for practical purposes, the bell construction may be regarded as coming to an equilibrium position where the desired pressure differential across the primary orifice occurs.

Of course, as the float is submerged and the water space of the bell communicates with the water space of the chamber, there is a slight change in displacement for the full range of movement, the change in displacement corresponding to the very small volume of the thin walls which submerge and emerge. Due to the reduced displacement by the thin walls of the bell when the aggregate is in upper position the unbuoyed weight is slightly greater in that position than in the lowermost one. As the aggregate comes to a stop when all forces acting thereon are in balance or equilibrium, a slight change in differential pressure occurs for the full range of movement. In general, the equation for equilibrium is (P1P2)A=W, where P1-P2 is the differential pressure across the orifice, A is the projected area of the bell on which the pressures act, and W is the unbuoyed weight. If A were constant, then there would have to be a slight change in P2 to compensate for the change in unbuoyed weight for the full range of movement; however, as A is relatively large, the change in P2 is very small, so that, for all practical purposes, the normal differential pressure may be regarded as constant. The change in unbuoyed weight has a more important effect in providing a scale effect or opposing force for the aggregate, this result being aided by the dashpot action occurring when the aggregate moves. Assuming a change in differential pressure, the aggregate then starts to move because equilibrium is disturbed, but, movement results in changes in the forces acting on the aggregate tending to restore equilibrium. For example assume an increase in differential pressure, which means a drop in P2, then the aggregate rises, but, in rising the unbuoyed weight is increased to the extent of rise. Also, as the aggregate rises, increased throttling occurs tending to increase P2. At the same time, rapid movement of the aggregate is prevented by Hence, incident to the aggregate rising the force causing the rise is reduced and the more the aggregate rises the greater the force of the unbuoyed weight becomes with the result that the forces acting on the aggregate tend to restore an equilibrium condition, that is, the arrangement has an inherent opposing effect so that change in throttling is limited to that necessary to restore equilibrium.

Stated another Way, whenever there is a disturbance of equilibrium of forces acting on the aggregate, the latter moves in consequence, but movement brings about changes in forces in such directions as to restore equilibrium and stop movement.

Referring further to the dashpot effect, this is due to several contributing factors. First of all, each structural aggregate, including the bell, submerged float and weight, has a horizontal crosssection which is similar to that of the vertical chamber, but somewhat smaller than the latter. Also, the openings 38b providing for ingress and egress of fluid into and from the bell determine the rate of ingress and egress. Furthermore, the aggregate has considerable inertia and there is the element of fluid friction. Hence, the factors of flow resistance, provided by the close fit of the aggregate and the chamber and by the openings 38b, of fluid friction and of inertia contribute a dashpot effect or a certain amount of sluggishness preventing the aggregate from moving rapidly but, at the same time, with sufficient freedom to follow accurately trends of all forces.

In Fig. 9, there is shown a modified form of secondary chamber and bell. In this view, the inverted bell 48 cooperates with the lower end 49' of the duct 29 to provide a throttle, the secondary chamber 50 having an orifice As the inverted bell 48 would be subject to tertiary pressure in the duct 29, particularly as the bell approaches the lower end of the duct, it is desirable to neutralize the effect of such tertiary pressure. Accordingly, the inverted bell 48 contains therein a second or neutralizing bell 52 whose cross-sectional area corresponds to that of the duct 29 and a conduit 53 leads from the duct 29 and has its lower end extending upwardly into the air space of the neutralizing bell 52. Air from the primary or plenary chamber is supplied by the conduit 54 to the air space 55 within the bell 43 and about the neutralizing bell 52. With this arrangement, therefore, it will be seen that the bell 48 moves in response to the differential pressure across the orifice 5| in such manner that, when such differential changes, the bell moves in such a direction as to vary the throttle area so as to restore the differential back to the valueit had before the change started.

The bell aggregates 31, the secondary chambers 30, and the ducts 29 are so constructed and the water levels are so maintained that similar operations will occur. This means that the normal water level 36 in each secondary chamber should have a uniform distance from the lower end 34 of the duct and that equal unsubmerged portions of the bell constructions should extend upwardly to cooperate with the lower ends of the ducts to provide secondary orifices of equal area under the same conditions. Accordingly, each of the bell constructions 31 is of identical construction and has the same unbuoyed weight and is spaced in the same manner with respect to the lower end of its associated duct. To maintain equal water levels in the secondary chambers, the latter are provided with suitably placed overflows 5?; and, to economize in the use of Water and to maintain the water level in each secondary chamber, in Fig. l, I show a supply conduit 58 arranged to supply water into the secondary chambers of the uppermost duct construction 23 and the water is cascaded from the overflows 51 of the secondary chambers at the highest elevation to those of next lower elevation and so on,

water leaving the final overflows passing out through the discharge pipe 59.

As the stoker is of the multiple-retort type and contains a plurality of rows of tuyeres, there will be a plurality of duct constructions for each tuyere row; and, as shown in Fig. 2, the duct constructions of all the tuyre rows are arranged transversely in rows so that the secondary chambers may be connected by couplings 6|, an intermediate secondary chamber being made somewhat longer to provide a sump or receiver 62 for a purpose to be described. The water supply pipe 58 is preferably connected to this longer intermediate secondary chamber and the same is true with respect to the cascaded connections of the overflows 51. In this way, it will be seen that water supplied to the transverse row of secondary chambers at the front of the stoker attains a predetermined level in each of such chambers and overflows from the latter to the second transverse row of secondary chambers and so on, any excess of water above that necessary to maintain constant level in all of the chambers flowing out through the discharge pipe 59.

Referring again to Fig. 2, the secondary chambers are preferably aligned transverselyto facilitate flushing of material particles from all of the secondary chambers of a row. To this end, the sumps or receivers 62 of the intermediate secondary chambers are each provided with a drain connection 63 leading to a drain pipe 64, the connections having valves 65. Referring to Fig. 2, water jets 66 extend into the relatively narrow secondary chambers for the side wall tuyeres and are aligned with the couplings 6|. If the valve 65 of a connection 63 is opened and the corresponding jets 66 are rendered effective, it will be apparent that water and material particles will be drained from the sump or receiver 62, the jets flushing out and entraining material from the bottom portions of all of the secondary chambers to the intermediate sump or receiver connected to the drain.

Referring again to the secondary chambers 30, it will be apparent that, with the same differential pressure across the primary orifices ill, the flow may be varied by varying the area of such orifices. Therefore, as may be seen from Figs. 1 and 3, each orifice 3| has associated therewith a slide damper or gate 68, which is adjustable to vary the orifice area. The gates 68 are connected to actuating rods 69, which are pivotally connected to cranks. IE! on the crankshafts H, there preferably being a crankshaft H for each transverse row of secondary chambers. The crankshafts are connected together by means providing for relative adjustment of the gates or dampers 68 and for relative variation of movement thereof; and, to this end, each crankshaft H has a second crank arm 12 having openings 13 therein arranged at different radial distances from the radius of the crank shaft and links [4 connect adjacent arms l2, the links having turnbuckles 15 so that the lengths of the links may be suitably varied and the links being capable of having the ends thereof associated with any of the openings 13. By relative adjustment of the turnbuckles 15, any desired initial relative position of all the gates or dampers 68 may be secured, and, by selection of the openings 13 with which the ends of the links are to be associated and by adjustment of the turnbuckles, if necessary, the relative extent of variation of the primary orifices may be secured.

While the mechanism for adjusting all of the primary orifices may be operated in any suitable manner, I prefer to effect this result by any suita ble combustion controlling device, such a device being indicated generally, at 16, and which serves to impart motion to the first crankshaft H. With the latter type of device, if it is desired to increase the combustion rate of the stoker, this result is secured automatically through the device, at 16, the latter operating to change the orifice areas with the result that the air flow is changed without modification of the primary or plenary chamber pressure.

In Fig. 10, there is shown diagrammatically a further modified embodiment of my invention. In this view, the secondary chamber 18 has an orifice 19 and it is connected with a duct 80. The chamber has a bottom 8i which extends outwardly of the secondary chamber and is connected with vertical walls 82 forming a Well 83 which communicates by an opening 84 at the bottom with the interior of the secondary chamber 18. As the well 83 is open to the primary chamber, if liquid is placed in the well and in the secondary chamber, it will be apparent that the levels in the well and in the chamber will be different, dependent upon the differential pressure across the orifice 59. Therefore, as the water level in the secondary chamber 18 is dependent upon the differential pressure across the orifice 79, such water level may be used as an element of control. Accordingly, an inverted bell 85 is shown partially submerged in the water in the secondary chamber, such bell preferably having unbuoyed weight. A conduit 86 extends from the primary or plenary chamber and has its end extending upwardly into the air space of the bell. Accordingly, the sealed area of the bell 85 is subject to secondary pressure on top and to primary pressure underneath. If the bell 85 is connected by suitable linkage to a damper 81, the latter may be operated by the bell to provide a throttle between the secondary chamber and the duct and such secondary chamber will have its area varied dependent upon variation in dilferential pressure across the orifice E9, the operation being such that, in case of change of diiferential pressure across the orifices, the damper is adjusted in such a direction as to restore such differential pressure.

While I have shown my invention in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications. without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

1. In apparatus for supplying gaseous medium for passage through a region of variable flow resistance, means providing an enclosed space supplied with gaseous medium under pressure, means providing a chamber with a body of liquid therein and having an orifice for supplying gaseous medium from said space to the interior of the chamber above the liquid, a duct for supplying gaseous medium from the chamber to the region, a throttle providing a variable throttle area for controlling fiow through said duct and including a movable aggregate, said movable aggregate including an inverted bell having its lower portion submerged in said liquid and having its upper portion extending above the liquid to provide an upper pressure area subject to the pressure of gaseous medium in the chamber and a lower pressure area sealed from the upper area 75 by the liquid, and means providing for the application of gaseous medium under the pressure existing in said space to said lower pressure area.

2. In apparatus for supplying gaseous medium for passage through a region of variable flow resistance, means providing an enclosed space supplied with gaseous medium under pressure, means providing a chamber with a body of liquid therein and having an orifice for supplying gaseous medium from said space to the interior of the chamber above the liquid, a duct for supplying gaseous medium from the chamber to the region, a throttle providing a variable throttle area for controlling the flow through said duct and including a movable aggregate, said movable aggregate including an inverted bell having its lower portion submerged in said liquid and hav ing its upper portion extending above the liquid to provide an upper pressure area subject to pressure in the chamber and a lower pressure area sealed from the upper area by the liquid, said bell having the major portion of its volume submerged and having weight in excess of that of the liquid displaced thereby, and means providing for the application of gaseous medium under pressure existing in said space to said lower pressure area.

3. In apparatus for supplying gaseous medium for passage through a region of variable flow resistance, means providing an enclosed space supplied with gaseous medium under pressure, means providing a chamber with a body of liquid therein and having an orifice for supplying gaseous medium from said space to the interior of the chamber above the liquid, a duct for supplying gaseous medium from the chamber to the region, a throttle providing a variable throttle area for q controlling flow through said duct and including a movable aggregate, said movable aggregate including an inverted bell having an upper section which converges upwardly, said bell having its lower portion including the lower part of said section submerged in said liquid and having its upper portion extending above the liquid to provide an upper pressure area subject to pressure in the chamber and a lower pressure area sealed from the upper area by the liquid, and means providing for application of gaseous medium under pressure existing in said space to said lower pressure area.

4. In apparatus for supplying gaseous medium for passage through a region of variable flow resistance, means providing an enclosed space supplied with gaseous medium under pressure, means providing a chamber with a body of liquid therein and having an orifice for supplying gaseous medium from said space to the interior of the chamber above the level of liquid therein, a duct for supplying gaseous medium from the chamber to the region and having itsinlet end portion disposed vertically above the liquid, an inverted bell construction cooperating with the inlet end portion of said duo-t to provide a variable throttle area, said bell construction having its lower portion submerged in said liquid and having its upper portion extending above the liquid to provide an upper pressure area subject to the pressure in the chamber and a lower pressure area sealed from the upper area by the liquid, means providing for the application of gaseous medium under pressure existing in said space to said lower pressure area, and means providing for the avoidance of the effective application of pressure at the discharge side of the throttle to the bell construction.

5. In apparatus for supplying gaseous medium for passage through a region of variable flow resistance, means providing an enclosed space supplied with gaseous medium under pressure, means providing a chamber with a body of liquid therein and having an orifice for supplying gaseous medium from said space to the interior of the chamber above the level of liquid therein, a duct for supplying gaseous medium from the chamber to the region and having its inlet end portion disposed vertically above the liquid, an inverted bell construction cooperating with the inlet end portion of said duct to provide a variable throttle area, said bell construction having its lower portion submerged in said liquid and having its upper portion extending above the liquid to provide an upper pressure area subject to the pressure in the chamber and a lower pressure area sealed from the upper area by the liquid, said bell construction having an opening aligned with and approximately of the same size as the inlet end of the duct and serving to avoid the application of the pressure of gaseous medium at the discharge side of the throttle to the bell construction, and means providing for the application of gaseous medium under pressure existing in said space to said lower pressure area.

6. In apparatus for supplying gaseous medium for passage through a region of variable flow resistance, means providing an enclosed space supplied with gaseous medium under pressure, means providing a chamber with a body of liquid therein and having an orifice for supplying gaseous medium from said space to the interior of the chamber above the level of liquid therein, a duct for supplying gaseous medium from the chamber to the region and having its inlet end portion disposed vertically above the liquid, an inverted bell construction cooperating with the inlet end portion of the duct to provide a variable throttle area, said bell construction having its lower portion submerged in the liquid and having its upper portion sloping downwardly and extending above the liquid to provide an upper pressure area subject to the pressure in the chamber and a lower pressure area sealed from the upper area by the liquid, and means providing for the application of gaseous medium under pressure existing in said space to said lower pressure area.

7. In apparatus for supplying gaseous medium for passage through a region of variable flow resistance, means providing an enclosed space supplied with gaseous medium under pressure, means providing a chamber with a body of liquid therein and having an orifice for supplying gaseous medium from said space to the interior of the chamber above the level of liquid therein, a duct for supplying gaseous medium from the chamber to the region and having its inlet end portion disposed vertically above the liquid, an inverted bell construction cooperating with the inlet end portion of said duct to provide a variable throttle area, said bell construction having an upper section which converges upwardly and having its lower portion including the lower part of said section submerged in said liquid, said upper portion extending above the liquid to provide an upper pressure area subject to pressure in the chamber and alower pressure area sealed from the upper area by the liquid, and means providing for the application of gaseous medium under pressure existing in said space to said lower pressure area.

8. In apparatus for supplying gaseous medium for passage through a region of variable flow resistance, means providing an enclosed space supplied with gaseous medium under pressure, means providing a chamber with a body of liquid therein and having an orifice for supplying gaseous medium from said space to the interior of the chamber above the level of liquid therein, a duct for supplying gaseous medium from the chamber to the region and having its inlet end portion disposed vertically above the liquid, an inverted bell construction cooperating with the inlet end portion of said duct to provide a variable throttle area, said bell construction having its lower portion submerged in said liquid and having its upper portion extending above the liquid to provide an upper pressure area subject to pressure in the chamber and a lower pressure area sealed. from the upper area by the liquid, said bell having the major portion of its volume submerged and having weight in excess of that of the liquid displaced thereby, and means providing for the application of gaseous medium under the pressure existing in said space to said lower pressure area.

9. In apparatus for supplying gaseous medium for passage through a region of variable flow resistance, means providing an enclosed space supplied with gaseous medium under pressure, means providing a chamber with a body of liquid therein and having an orifice for supplying gaseous medium from said space to the interior of the chamber above the level of liquid therein, a duct for supplying gaseous medium from the chamber to the region and having its inlet end portion disposed vertically above the liquid, an inverted tubular bell construction cooperating with the inlet end portion of said duct to provide a variable throttle area, said bell construction having its lower portion submerged in said liquid and having its upper portion extending above the liquid to provide an upper pressure area subject to pressure existing in the chamber and a lower pressure area sealed from the upper pressure area by the liquid, the tubular opening of the bell construction being aligned with the duct and approximately of the same diameter as the latter, the inlet end portion of the duct and the upper end portion of the bell construction being rounded to provide a circumferentially extending convergentdivergent throttle passage, and means providing for the application of gaseous medium under the pressure existing in said space to said lower pressure area.

10. In apparatus for supplying gaseous medium for passage through a region of variable flow resistance, means providing an enclosed space supplied with gaseous medium under pressure; means providing a chamber with a body of liquid therein and having, an orifice for supplying gaseous medium from said space to the interior of the chamber above the level of liquid therein; a duct for supplying gaseous medium from the chamber to the region and having its inlet end portion disposed vertically above the liquid; an inverted bell construction cooperating with the inlet end portion of said duct to provide a variable throttle area; said bell construction having the lower and major portion of its volume submerged in said liquid, having its upper portion extending above the liquid to provide an upper pressure area subject to the pressure in the chamber and a lower pressure area sealed from the upper area by the liquid, and having weight in excess of the liquid displaced thereby; and means providing for the application of gaseous medium under pressure existing in said space to said lower pressure area; said vertical chamber having a substantially uniform horizontal cross-sectional area for a substantial portion of its length and the bell construction fitting within the chamber with sufiiciently close clearance to secure movement thereof with a dashpot eifect.

DONALD'J. MOSSHART.

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