阅读说明：本技术 滑阀和薄膜节流器组合内置式干气密封静环结构 (Dry gas sealing static ring structure with built-in combination of slide valve and film throttler ) 是由 江锦波 蔡浩楠 彭旭东 孟祥铠 马艺 李纪云 于 2021-08-31 设计创作，主要内容包括：滑阀和薄膜节流器组合内置式干气密封静环结构,包括静环压盖、静环环体、滑阀节流器组件、薄膜节流器组件；滑阀节流器组件位于静环环体的外侧,在滑阀节流器组件中,滑阀节流腔体与阀片之间形成一级节流间隙,静环环体的一侧为密封端面,密封端面上开设有两列径向分布的节流孔；静环环体的另一侧为静环背面,静环背面上设有圆形腔室,圆形腔室内设有薄膜节流器组件；薄膜节流器组件的弹性膜片与下喷嘴之间形成二级下节流间隙,弹性膜片与上喷嘴之间形成二级上节流间隙,一级节流间隙与静环压盖上的节流气进气口相连通,二级下节流间隙与一级节流间隙、外侧节流孔相连通,二级上节流间隙与一级节流间隙、内侧节流孔相连通。(The dry gas sealing static ring structure with the built-in combination of the slide valve and the film throttler comprises a static ring gland, a static ring body, a slide valve throttler assembly and a film throttler assembly; the slide valve restrictor assembly is positioned on the outer side of the static ring body, a primary throttling gap is formed between a slide valve throttling cavity and a valve plate in the slide valve restrictor assembly, one side of the static ring body is a sealing end face, and two rows of throttling holes distributed radially are formed in the sealing end face; the other side of the static ring body is a static ring back, a circular cavity is arranged on the static ring back, and a thin film restrictor assembly is arranged in the circular cavity; a secondary lower throttling gap is formed between an elastic diaphragm and a lower nozzle of the film throttling device assembly, a secondary upper throttling gap is formed between the elastic diaphragm and an upper nozzle, the primary throttling gap is communicated with a throttling air inlet on a static ring gland, the secondary lower throttling gap is communicated with the primary throttling gap and an outer throttling hole, and the secondary upper throttling gap is communicated with the primary throttling gap and an inner throttling hole.)

1. The utility model provides a built-in dry gas seal quiet ring structure of slide valve and film flow controller combination which characterized in that: the slide valve restrictor assembly comprises a static ring gland (1), a static ring body (2), a slide valve restrictor assembly (3) and a film restrictor assembly (4). The slide valve restrictor assembly (3) is located on the outer side of the stationary ring body (2), and the slide valve restrictor assembly (3) comprises a valve plate (31), a spring (32), a valve seat (33) and a slide valve throttling cavity (34). A first-stage throttling gap R (1) is formed between the valve plate (31) and the throttling cavity (34) of the slide valve, and the first-stage throttling gap R (1) is communicated with the upper-stage throttling back through hole (361) and the lower-stage throttling back through hole (362).

One side of the static ring body (2) is a sealing end face (21), two rows of radially distributed throttling holes (211) and (212) are formed in the sealing end face (21), the outer side throttling hole (211) is close to the outer diameter side of the sealing end face, and the inner side throttling hole (212) is close to the inner diameter side of the sealing end face. The other side of the static ring body (2) is a static ring back surface (22), and a plurality of circular chambers (221) which are uniformly distributed in the circumferential direction are arranged on the static ring back surface (22);

a film restrictor assembly (4) is arranged in the circular chamber (221), and the film restrictor assembly (4) comprises an upper nozzle (432), a positioning sleeve, an elastic diaphragm (42) and a lower nozzle (431). A secondary lower throttling gap (R21) and a lower throttling air inlet cavity (441) are arranged between the elastic membrane (42) and the lower nozzle (431), the lower throttling air inlet cavity (441) is communicated with a lower-stage throttling rear through hole (362), a lower throttling air outlet cavity (451) is arranged between the lower nozzle (431) and the stationary ring body (2), and the lower throttling air outlet cavity (451) is communicated with the outer throttling hole (211). A secondary upper throttling gap (R22) and an upper throttling air inlet cavity (442) are arranged between the elastic diaphragm (42) and the upper nozzle (432), the upper throttling air inlet cavity (442) circulates through an upper throttling rear through hole (361) and an upper throttling level, an upper throttling air outlet cavity (452) is arranged between the upper nozzle (432) and the gland (1), and the upper throttling air outlet cavity (452) is communicated with the inner side throttling hole (212).

2. The combined built-in dry gas seal static ring structure of the slide valve and the film restrictor of claim 1, characterized in that: the static ring body (2) is fixedly connected with the static ring gland (1), and the sliding valve restrictor assembly (3) is fixedly connected with the static ring gland (1).

3. The combined built-in dry gas seal static ring structure of the slide valve and the film restrictor of claim 1, characterized in that: a slide valve pressure balance cavity (35) is formed between the back of the valve plate (31) and the valve seat (33), and the spring (32) is located in the slide valve pressure balance cavity (35).

4. The combined built-in dry gas seal static ring structure of the slide valve and the film restrictor of claim 1, characterized in that: the film restrictor assembly (4) sequentially comprises an upper locating sleeve (413), an upper nozzle (432), a middle locating sleeve (412), an elastic membrane (42), a lower locating sleeve (411) and a lower nozzle (431) from top to bottom.

5. The combined built-in dry gas seal static ring structure of the slide valve and the film restrictor of claim 1, characterized in that: the head of the valve plate (31) is of a conical structure, and the part, matched with the valve plate (31), in the slide valve throttling cavity (34) is also a conical cavity.

Technical Field

The invention relates to a dry gas sealing static ring structure, in particular to a dry gas sealing static ring structure with a slide valve and a film variable restrictor, which can be used for shaft end sealing of various rotating devices such as compressors, centrifugal pumps, stirring devices and the like.

Background

The static pressure dry gas seal has wide application prospect on low-speed stirring equipment due to the advantages of small abrasion, strong adaptability, long service life and the like. However, the low-speed rotating equipment is often long in rotating shaft or complex and changeable in working condition, and angular deflection and axial movement often occur in the shaft system in the running process. When the static pressure dry gas seal arranged at the shaft end of the rotating shaft runs in a multi-direction complex disturbance state such as axial direction and angular direction, the collision and grinding of the seal end surface are easy to occur, the abrasion of the seal end surface is easy to occur if the static pressure dry gas seal is light, and the sealing ring is cracked and rapidly fails if the static pressure dry gas seal is heavy; meanwhile, for the application occasions of some food-grade stirring equipment, the requirement on abrasion control of the shaft end seal is extremely strict, and seal abrasive dust is not allowed to enter the equipment so that food or medicines cannot be used.

The adoption of a variable restrictor such as a film restrictor or a slide valve restrictor is expected to remarkably improve the self-adaptive capacity of static pressure dry gas seal to external disturbance. Although the traditional film restrictor or slide valve restrictor solves the problem of self-adaption of the static pressure dry gas seal to axial vibration to a certain extent, the traditional film restrictor or slide valve restrictor is generally arranged outside the static pressure dry gas seal, and the problems of complex sealing system, untimely vibration response and the like are caused. On the other hand, the static pressure dry gas seal is subjected to complex disturbance from axial and angular directions in the operation process, the self-adaptive regulating capacity of the existing single film restrictor or slide valve restrictor for external complex disturbance is still insufficient, and a scheme for utilizing the advantages of different variable restrictors to adapt to the complex external disturbance needs to be researched.

Disclosure of Invention

In order to overcome the defects that the static pressure dry gas seal with the film restrictor cannot be adaptively controlled under axial and angular multi-direction disturbance and a structural system is complex, the invention provides the built-in dry gas seal static ring structure of the restrictor, which has a compact structure and strong adaptability to axial vibration and angular deflection disturbance.

The technical scheme of the invention is as follows:

a dry gas sealing static ring structure with a built-in combination of a sliding valve and a film restrictor comprises a static ring gland 1, a static ring body 2, a sliding valve restrictor component 3 and a film restrictor component 4. The slide valve restrictor assembly 3 is positioned on the outer side of the stationary ring body 2, and the slide valve restrictor assembly 3 comprises a valve plate 31, a spring 32, a valve seat 33 and a slide valve restrictor cavity 34. And a primary throttle gap R1 is formed between the valve plate 31 and the slide valve throttle cavity 34, and the primary throttle gap R1 is communicated with the upper-stage throttle rear through hole 361 and the lower-stage throttle rear through hole 362.

One side of the stationary ring body 2 is a sealing end face 21, two rows of radially distributed throttle holes 211 and 212 are formed in the sealing end face 21, the outer throttle hole 211 is close to the outer diameter side of the sealing end face, and the inner throttle hole 212 is close to the inner diameter side of the sealing end face. The other side of the stationary ring body 2 is a stationary ring back 22, and a plurality of circular chambers 221 which are uniformly distributed in the circumferential direction are arranged on the stationary ring back 22;

a film restrictor assembly 4 is arranged in the circular chamber 221, and the film restrictor assembly 4 comprises an upper nozzle 432, a positioning sleeve, an elastic diaphragm 42 and a lower nozzle 431. A secondary lower throttling gap R21 and a lower throttling air inlet cavity 441 are arranged between the elastic diaphragm 42 and the lower nozzle 431, the lower throttling air inlet cavity 441 is communicated with a lower-stage throttling rear through hole 362, a lower throttling air outlet cavity 451 is arranged between the lower nozzle 431 and the stationary ring body 2, and the lower throttling air outlet cavity 451 is communicated with the outer throttling hole 211. A secondary upper throttling gap R22 and an upper throttling air inlet cavity 442 are arranged between the elastic diaphragm 42 and the upper nozzle 432, the upper throttling air inlet cavity 442 flows through the upper primary throttling rear through hole 361, an upper throttling air outlet cavity 452 is arranged between the upper nozzle 432 and the gland 1, and the upper throttling air outlet cavity 452 is communicated with the inner side throttling hole 212.

Furthermore, the slide valve throttling cavity 2 is fixedly connected with the static ring gland 1, and the static ring body 3 is fixedly connected with the static ring gland 1.

Further, a spool pressure balance chamber 35 is formed between the back of the valve plate 31 and the valve seat 33 in the spool restrictor assembly, and the spring 32 is located in the spool pressure balance chamber 35.

Further, the film restrictor assembly 4 includes, from top to bottom, an upper positioning sleeve 413, an upper nozzle 432, a middle positioning sleeve 412, the elastic diaphragm 42, a lower positioning sleeve 411, and a lower nozzle 431 in sequence.

Further, the head of the valve plate 31 is of a conical structure, and the part of the throttle cavity 34 of the slide valve, which is matched with the valve plate 31, is also a conical chamber.

The working principle of the invention is as follows:

the film restrictor and the slide valve restrictor are two types of variable restrictors commonly used in the static pressure gas bearing, and can theoretically realize infinite axial gas film rigidity of a fluid film of the static pressure gas bearing, so that the adaptability of the fluid film to external axial disturbance is improved.

The core components of the film restrictor are an elastic diaphragm and a nozzle, a layer of throttling gap is arranged between the elastic diaphragm and the end face of the nozzle, the throttling gap has the functions of flow resistance and pressure reduction on gas flowing through, the elastic diaphragm can deform under the action of gas pressure in the throttling gap, and the intelligent regulation and control on output pressure can be realized by utilizing the pressure self-adaptive deformation characteristic of the elastic diaphragm. The specific working principle is as follows: when the static pressure gas bearing is disturbed by the outside and the gap is reduced, the gas flow resistance in the bearing gap is increased at the moment, so that the outlet pressure of the film restrictor is increased, the deformation of the elastic diaphragm is increased to increase the restriction gap, the restriction gap has weakened gas flow resistance and pressure reduction effects, and the outlet pressure of the film restrictor is further increased as a result, the feedback result of the increase of the gas pressure is that the gas film bearing capacity of the bearing gap is increased, and finally the bearing gap is increased and restored to the original gap value.

The core part of the slide valve restrictor is a valve plate, a spring and a slide valve throttling cavity, the head part of the valve plate is generally in a conical structure, and the valve plate is matched with the slide valve throttling cavity to form a layer of throttling gap, so that the flow-blocking and pressure-reducing effects are realized on flowing gas; a certain clearance is maintained under the combined action of a valve back spring and the outlet pressure of the valve plate, and the change of the throttling clearance by the micro displacement of the valve plate under the action of the gas pressure is utilized, so that the self-adaptive control of the output pressure is realized. The specific working principle is as follows: when the static pressure gas bearing is disturbed by the outside and the gap is reduced, the gas flow resistance in the bearing gap is increased at the moment, so that the outlet pressure of the slide valve restrictor is increased, the valve plate moves towards the spring side to increase the restriction gap, and as a result, the outlet pressure of the slide valve restrictor is further increased, and as a result, the bearing gas film bearing capacity of the bearing is increased and the bearing gap is restored to the original gap value.

Conventional diaphragm restrictors and slide valve restrictors have a strong adaptive control capability for the overall increase or decrease in bearing or seal clearance, but are significantly deficient for the occurrence of tilt clearance under angular disturbances. In order to enhance the adaptability of dry gas seal to external disturbance (especially angular deflection disturbance), the invention provides a throttling gas flow resistance system consisting of a slide valve restrictor, a film restrictor, a fixed orifice restrictor and a sealing gap restrictor, wherein the slide valve restrictor plays a main regulation role, and the film restrictor plays an auxiliary regulation role. Throttling gas entering from an initial inlet firstly enters the thin film restrictor assembly after the throttling pressure reduction effect of the throttling gap of the sliding valve restrictor. The film restrictor assembly comprises film restrictors positioned above and below the elastic diaphragm, the upper and lower sets of film restrictors share the elastic diaphragm, namely the deformation of the elastic diaphragm inevitably increases the flow resistance of one film restrictor and reduces the flow resistance of the other film restrictor; throttling gas flowing out of the two sets of film throttlers respectively enters the sealing gap through two rows of throttling holes on the sealing end face, and finally leaks to the inner diameter side and the outer diameter side of the sealing end face through the throttling action of the sealing gap.

When the dry gas seal is subjected to external axial disturbance and the whole gap is reduced, the flow resistance of the seal gap to throttling gas is increased, the pressure at the outlet of the throttling hole is increased, and the deformation of the elastic diaphragm is basically unchanged because the gas pressure above and below the elastic diaphragm is increased simultaneously; the increase of the medium further increases the stress of the valve plate head of the slide valve restrictor to move towards the spring side, the flow resistance of the slide valve restrictor is reduced to increase the pressure of an outlet cavity of the slide valve restrictor, and the feedback result is that the gas pressure in the sealing gap is increased to resist the disturbance force which reduces the gap from the outside, and finally the sealing gap is restored to the original value. Therefore, when axial disturbance is applied to increase or decrease the whole sealing gap, the self-adaptive adjusting function of the whole throttling airflow resistance system is mainly completed by the slide valve throttler.

When the dry gas seal is subjected to angular disturbance to generate an inclined gap, the flow resistance of the side with the reduced gap to the throttling gas is increased, and the flow resistance of the side with the increased gap to the throttling gas is reduced. Firstly, the sealing clearance at different positions of the circumferential direction of the sealing end surface is integrally increased or reduced, the regulation and control principle is similar to that when the clearance is increased or reduced due to axial disturbance of the dry gas seal, and the slide valve restrictor plays a main regulation role. Secondly, at a certain circumferential position, although the overall gap shows an increasing or decreasing trend, the gap values at different radial positions are slightly different, for example, for the gap increasing position, the gap close to the outer diameter side of the sealing end face is slightly larger, and the gap close to the inner diameter side of the end face is slightly smaller, so that the stress on two sides of the elastic diaphragm in the thin film restrictor is slightly different, the elastic diaphragm deforms to the side with smaller stress, the self-adaptive deformation causes the outlet pressure of the orifice at the side with larger sealing gap to be smaller, and the outlet pressure of the orifice at the side with smaller gap to be larger, and as a result, the sealing end face generates additional moment to restore the sealing gap to the parallel state.

Advantages and advantageous effects of the invention

(1) By combining the slide valve throttler and the film throttler, the slide valve throttler plays a main regulation role, and the film throttler plays an auxiliary regulation role when the sealing gap is inclined, so that the angular gas film rigidity of the sealing gas film is increased, and the adaptability of the static pressure dry gas seal to the angular deflection disturbance is obviously improved.

(2) Two rows of throttling holes distributed along the radial direction are arranged on the end face of the dry gas seal, and compared with a structure that the classical orifice throttling static pressure dry gas seal only has a single row of throttling holes in the radial direction, the structure has larger gas film bearing capacity and gas film rigidity.

(3) The slide valve throttler is arranged outside the stationary ring body, the film throttler is arranged in a back cavity of the stationary ring body, the two sets of film throttlers share one elastic diaphragm, and the designed dry gas sealing stationary ring is simple and compact in structure.

Drawings

FIG. 1 is a cross-sectional view of a dry gas seal static ring configuration of an embodiment of the present invention;

FIG. 2 is a cross-sectional view of a spool valve restrictor assembly of an embodiment of the present invention;

FIG. 3 is a cross-sectional view of a stationary ring configuration of an embodiment of the present invention;

FIG. 4 is a schematic end view of a stationary ring according to an embodiment of the present invention;

FIG. 5 is a cross-sectional view of a membrane restrictor assembly according to an embodiment of the present invention;

FIG. 6 is a schematic diagram illustrating the dry gas seal static ring and dynamic ring status during normal operation of an embodiment of the present invention;

FIG. 7 is a diagram showing the relationship between the flow resistance and the corresponding pressure of each stage of the throttle according to the embodiment of the present invention;

FIG. 8 is a schematic view of an embodiment of the present invention in a condition where the dry gas seal is axially disturbed and the gap is reduced;

FIG. 9 is a schematic view of a dry gas seal according to an embodiment of the present invention in a state in which the gap is inclined due to an angular disturbance.

Detailed Description

The invention is further described in detail with reference to the attached drawings.

Referring to fig. 1, 2, 3, 4 and 5, the dry gas sealing static ring structure with the built-in combination of the slide valve and the film restrictor comprises a static ring gland 1, a static ring body 2, a slide valve restrictor assembly 3 and a film restrictor assembly 4, wherein the static ring body 2 is fixedly connected with the static ring gland 1. The slide valve restrictor assembly 3 is located on the outer side of the stationary ring body 2, the slide valve restrictor assembly 3 is fixedly connected with the stationary ring gland 1, and the slide valve restrictor assembly 3 comprises a valve plate 31, a spring 32, a valve seat 33 and a slide valve restrictor cavity 34. The head of the valve plate 31 is of a conical structure, the part of the slide valve throttling cavity 34, which is matched with the valve plate 31, is also a conical cavity, a first-stage throttling gap R1 is formed between the valve plate 31 and the slide valve throttling cavity 34, and the first-stage throttling gap R1 is communicated with a previous-stage throttling rear through hole 361 and a next-stage throttling rear through hole 362. A spool pressure balance chamber 35 is formed between the back of the valve plate 31 and the valve seat 33, and the spring 32 is located in the spool pressure balance chamber 35.

One side of the stationary ring body 2 is a sealing end face 21, two rows of radially distributed throttle holes 211 and 212 are formed in the sealing end face 21, the outer throttle hole 211 is close to the outer diameter side of the sealing end face, and the inner throttle hole 212 is close to the inner diameter side of the sealing end face. The opposite side of quiet ring body 2 is quiet ring back 22, be equipped with the circular cavity 221 of 6 circumference equipartitions on the quiet ring back 22, be equipped with film flow controller subassembly 4 in the circular cavity 221, film flow controller subassembly 4 includes from last to down in proper order that go up position sleeve 413, go up nozzle 432, well position sleeve 412, elastic diaphragm 42, lower position sleeve 411, lower nozzle 431. A secondary lower throttling gap R21 and a lower throttling air inlet cavity 441 are arranged between the elastic diaphragm 42 and the lower nozzle 431, the lower throttling air inlet cavity 441 is communicated with a lower-stage throttling rear through hole 362, a lower throttling air outlet cavity 451 is arranged between the lower nozzle 431 and the stationary ring body 2, and the lower throttling air outlet cavity 451 is communicated with the outer throttling hole 211. A secondary upper throttling gap R22 and an upper throttling air inlet cavity 442 are arranged between the elastic diaphragm 42 and the upper nozzle 432, the upper throttling air inlet cavity 442 flows through the upper primary throttling rear through hole 361, an upper throttling air outlet cavity 452 is arranged between the upper nozzle 432 and the gland 1, and the upper throttling air outlet cavity 452 is communicated with the inner side throttling hole 212.

Referring to fig. 6 and 7, when the dry gas sealing stationary ring and the rotating ring 5 operate in a matching manner, the sealing gap between the stationary ring body end surface 21 and the rotating ring 5 is a parallel gap in a normal state. The throttling air which flows from the initial air inlet hole 11 on the static ring gland 1 and has the pressure of p0 enters the primary throttling clearance R1 through the through hole 37 on the throttling cavity 34 of the slide valve, is throttled and reduced to have the pressure of p1, and then enters the throttled through holes 361 and 362 respectively. Throttling air flowing out of the throttling back through hole 361 enters the lower throttling air inlet cavity 441 through the air inlet hole 231 on the static ring body 2, the throttling air enters a sealing gap between the moving ring and the static ring through the lower throttling air outlet cavity 451, the vent hole 241 on the static ring body 2 and the outer throttling hole 211, and the pressure is p31 after the throttling air passes through the air inlet hole 231 on the static ring body 2, the pressure is p21 after the throttling air is reduced through the secondary lower throttling gap R21 between the elastic diaphragm 42 and the lower nozzle 431, and the pressure is p31 after the throttling air passes through the outer throttling hole 211; the throttling gas enters a sealed outer cavity with the pressure of p41 after passing through the throttling and pressure reduction effect of the outer side sealing gap R41. Similarly, the throttling air flowing out of the throttling back through hole 362 enters the upper throttling air inlet cavity 442 through the air inlet hole 232 on the stationary ring body 2, the pressure is p22 after the throttling and pressure reduction is carried out through the secondary upper throttling gap R22 between the elastic diaphragm 42 and the upper nozzle 432, the throttling air enters the sealing gap through the upper throttling air outlet cavity 452, the vent hole 242 on the stationary ring body 2 and the inner diameter throttling hole 212, and the pressure after the throttling is carried out through the inner side throttling hole 212 is p 32; the throttling gas enters the sealed inner cavity with the pressure of p42 after the throttling and pressure reduction of the inner side sealing gap R42.

Referring to fig. 8, when the dry gas seal is disturbed axially by the outside and the seal gaps R41 and R42 are reduced as a whole, the seal gaps are kept parallel, the post-orifice pressures p31 and p32 are increased equally at the same time, and this increase is transmitted to the lower throttle outlet chamber 451 and the upper throttle outlet chamber 452 through the orifice holes 211 and 212 and the vent holes 241 and 242, while the secondary lower throttle gap R21 below the elastic diaphragm 42 and the secondary upper throttle gap R22 above the elastic diaphragm 42 are kept constant, the pressure p1 in the lower throttle inlet chamber 441 and the upper throttle inlet chamber 442 is increased and transmitted to the head of the valve plate 31 through the inlet holes 231 and 232 on the stationary ring body 2 and the post-throttle through holes 361 and 362 on the throttle chamber 34 of the spool valve, the head of the valve plate 31 is forced to be increased and moved slightly to the spring 32 side, the primary throttle gap R1 is increased, and the primary post-throttle pressure p1 is increased because the initial inlet pressure p0 is constant, this feedback of pressure increase increases the pressure p31, p32 after throttling of the orifices 211, 212. The increased gas pressure in the sealing gap forms larger gas film bearing capacity, and the sealing gap is gradually increased and restored to the original gap value.

Referring to fig. 9, when the dry gas seal is subjected to external angular deflection and the seal gap is inclined, the seal gap h1 on one circumferential side of the seal end surface is integrally increased, and the seal gap h2 on the other circumferential side is integrally decreased; further, the clearance on the outer diameter side of the seal clearance increasing side is slightly larger than the clearance on the inner diameter side, and the clearance on the outer diameter side of the seal clearance decreasing side is slightly smaller than the clearance on the inner diameter side. Taking the entire increase side of the seal gap as an example, since the flow resistance of the seal gap to the throttle air is reduced, the pressure p31 after the throttle hole 211 and the pressure p32 after the throttle hole 212 are both reduced as a whole, the force applied to the head of the valve plate 31 is reduced by this, the valve plate 31 slightly moves in a direction away from the spring 32, the primary throttle gap R1 is reduced, the primary throttle back pressure p1 is reduced, and as a result of the feedback, the pressures p31 and p32 after the throttle holes 211 and 212 are reduced, and the adjustment function of the slide valve restrictor is dominant. Further, the post-throttle pressure p31 is slightly smaller than the post-throttle pressure p32, so the force applied below the elastic diaphragm 42 is smaller than the force applied above, the elastic diaphragm 42 deforms toward the lower nozzle 431, the secondary lower throttle gap R21 decreases and the secondary upper throttle gap R22 increases, the pressure p31 after the throttle hole 211 slightly decreases and the pressure p32 after the throttle hole 212 slightly increases as a result of the feedback action, the adjusting action of the film restrictor is used as an auxiliary fine adjustment, and the adjusting amount is far smaller than the adjusting effect of the slide valve restrictor.

The embodiments described in this specification are merely illustrative of implementations of the inventive concept and the scope of the present invention should not be considered limited to the specific forms set forth in the embodiments but rather by the equivalents thereof as would occur to those skilled in the art upon consideration of the present inventive concept.