US3883265A

US3883265A - Turbine

Info

Publication number: US3883265A
Application number: US396998A
Authority: US
Inventors: Jan Schrieken
Original assignee: Koninklijke Machinefabriek Stork BV
Current assignee: Koninklijke Machinefabriek Stork BV
Priority date: 1973-09-12
Filing date: 1973-09-12
Publication date: 1975-05-13
Anticipated expiration: 1992-05-13

Abstract

A turbine for a compressible medium in which one or more regulating valves directly communicate(s) with the distribution duct(s) around the wheel of a centripetal stage, regulating valves first converging gradually and then gradually diverging a valve body extending into the diverging part of the housing by a portion whose sectional area gradually decreases in accordance with a linear function of the place of said section on the longitudinal axis of the valve body, in the closed state the valve body being in contact on the upstream side of the converging part with the housing along a common tangential plane which is at an angle to the direction of movement of the valve body, which angle exceeds the friction angle between the valve body and the housing.

Description

United States Patent Schrieken TURBINE Inventor: Jan Schrieken, Delden, Netherlands Koninklijke Machinefabriek Stork B.V., Hengelo, Netherlands Sept. 12, 1973 Assignee:

Filed:

Appl. No.:

References Cited UNITED STATES PATENTS 1451 May 13, 1975 Primary Examiner-Henry F. Raduazo Attorney, Agent, or Firm-Snyder, Brown and Ramik [5 7] ABSTRACT into the diverging part of the housing by a portion whose sectional area gradually decreases in accordance with a linear function of the place of said sec tion on the longitudinal axis of the valve body, in the closed state the valve body being in contact on the upstream side of the converging part with the housing along a common tangential plane which is at an angle 1,412,257 4/1922 Petsche 415/151 29 4 7 950 Ange" 1 4 5 205 to the d1rect1on of movement of the valve body, whlch 3,479,124 11/1969 Hendriks 1. 415/159 angle exceeds the friction angle between the valve FOREIGN PATENTS 0R APPLICATIONS and housmg' 474,916 7/1951 Canada ,1 415/151 9 Claims, 4 Drawing Figures 3 L 1 l2 1 n 9 8 l0 TURBINE The invention relates to a turbine for a compressible medium comprising one or more wheels, among which at least the wheel of the first stage is traversed in the centripetal direction by the driving medium and operates in accordance with the equal-pressure principle, said stage being surrounded by one or more distribution ducts arranged around the centripetal wheel, in which one or more regulating valves in which an enthalpy difference of the medium is converted into velocity, is (are) directly connected by the outlet opening with the inlet side of the distribution duct (s) and, viewed from the inlet end, the distribution duct (s) exhibit(s) a gradually decreasing flow passage and directly join(s) along the whole inner circumference the centripetal wheel, said regulating valves being formed by a housing provided with a valve body, the passage of which first converges and subsequently diverges. The invention has for its object to provide such a turbine in which the regulating valve in which the velocity of the compressible medium is produced has a particularly advantageous structure. According to the invention the regulating valve is formed by a valve housing whose passage in the direction of flow first converges gradually and then gradually diverges, there being provided a valve body which leaves free a narrow gap at the area of the smallest diameter of the housing in the closed state and extends into the diverging part of the housing by a portion whose sectional area gradually decreases according to a linear function of the place of said sectional area on the longitudinal axis of the valve body, whilst in the closed state of the valve body it is in contact on the upstream side of the converging part, with the housing along a common tangential plane which is at an angle to the direction of movement of the valve body, which angle exceeds the friction angle between the valve body and the housing.

Thus a valve housing is obtained which comprises a portion whose passage gradually converges, in which the flow is subsonically accelerated, a narrowest place, the neck, where the velocity of sound is attained and a portion whose passage gradually diverges, in which the flow is supersonically accelerated after the valve with a sufficiently low pressure. It should be noted that in the turbine according to the invention one is not concerned with an optimum restoration of pressure, but it is intended to produce an optimally matching high velocity.

Since beyond the narrowest part of the passage of the housing the valve body extends in the diverging portion, the divergence of the available passage of the pressurized medium continues varying gradually in all states of partial load. Owing to the linear variation of the surface of the sectional area of the valve body the quantity of medium allowed to pass through the valve varies linearly with the stroke of the valve body. Since closure of the passage with the aid of the valve body does not take place at the narrowest section of the passage, it can be avoided that the valve body becomes jammed in the housing. Since the closing area is located in a considerably larger section than that of the smallest passage of the housing, the gap at the area of the narrowest passage of the housing will exhibit the smallest passage already at a very slight displacement of the valve body and will become determinative for the quantity of passing medium. Consequently, the linear control occurs not until the valve has performed a small stroke. At the area of closure the shape of the valve body and of the housing is very disadvantageous from the view-point of flow technology. However, owing to the large section in which the closure is made this disadvantage is negligible because in this area the velocity remains very low as compared with that in the narrowest section.

The invention will now be described more fully with reference to an embodiment of a regulating valve. In the drawing FIG. 1 is a schematic cross sectional view of a turbine embodying the invention.

FIG. 2 is a schematic sectional view of a valve body with the co-operating portion of the housing in the closed state,

FIG. 3 shows the valve body of FIG. 2 in the semiopened state and FIG. 4 shows the valve body of FIG. 2 in the completely opened state.

The turbine shown in FIG. 1 comprises a housing 1 in which the centripetal stage is arranged. The wheel 2 of the centripetal stage is arranged in a housing 3, which is suspended in the housing 1. The housing 3 comprises

distribution ducts

4 and 5, with which communicate regulating valves 6 and 7 respectively. As is shown in detail for the regulating valve 6, it comprises a housing 8 fastened to the housing I by flanges 9. The housing 8 accomodates a guide 10 for guiding a valve stem 11 holding a valve body 12. The valve body 12 is adapted to co-operate with an exchangeable part 13, which is secured in the housing 8. The exchangeable part 13 joins the housing 3 through a gap 14. It is thus avoided that in the event of temperature differences between the components high stresses would be produced. FIGS. 2, 3 and 4 show the valve body 12 on an enlarged scale, whilst in addition the portion of the exchangeable part 13 co-operating with the valve body 12 is shown.

The shape of the part 13 is such that, as is shown in FIG. 4, first a converging portion 15, in which the flow can be subsonically accelerated and then a narrowest place at 16, where the velocity of sound is attained and then a portion 17, in which the passage gradually diverges. With a sufficiently low pressure after the valve body 12 the flow is further accelerated supersonically. Between I8 and 19 the valve body I2 exhibits a variation in section which is linear with respect to the longitudinal axis of the body. As a result the narrowest passage between the valve body 12 and the part 13 and hence the passed quantity of medium will vary linearly with the stroke. This is desirable for the technical control.

At 20 the valve body 12 has a thickened part. In the closed state of the valve body shown in FIG. 2 this thickened part is in contact with the wall of the part I3 ofthe housing. In the closed state the thickened part 20 is in contact at 21 with the part 13. The

closing area

20, 21 is located upstream from the narrowest part 16 in a much larger sectional area than that of the part 16. This results in that at the movement of the valve body 12 out of the position shown in FIG. 2 the narrowest passage is initially located at 20 and 21, but fairly immediately the narrowest passage will be located at 16. Thus the linear control characteristic occurs as soon as the valve body has performed a very slight stroke. In FIG. 2 the angle between the contact planes at 20 and 21 and the direction of movement, when the valve body is in the closed state, is designated by a. The angle a to the direction of movement of the valve body exceeds the friction angle between the valve body 12 and housing part 13. Thus in operation the valve body will never be jammed due to self-braking.

The technically disadvantageous shape of the part 13 at 21 and of the valve body at is unobjectionable since in the opened states illustrated in FIGS. 3 and 4 these parts are located in a zone where only low veloc ity prevails owing to the large passage. When the turbine is located only partially, the drop in pressure across the centripetal stage will increase. This means that in order to maintain a low degree of reaction also the drop in pressure across the regulating valve has to increase. For this purpose a larger divergence of the passage available is required beyond the narrowest passage at 16. The passage of the portion 17 is constant and since with partial load the portion located between 18 and 19 co-operates with the portion 17, a larger divergence is, indeed, obtained beyond the narrowest passage in the position shown in FIG. 3 than in the case of full load, when the valve body is in the position shown in FIG. 4. Since in all partial load positions the part of the valve body located between 18 and 19 extends as far as into the portion 17 a gradual variation of the divergence is obtained in all positions.

What we claim is:

l. A turbine for a compressible medium having at least a first stage wheel which is traversed in the centripetal direction by the driving medium and operates in accordance with the equal pressure principle, said stage being at least partially surrounded by a distribution duct of decreasing cross section, a regulating valve controlling flow into said distribution duct and at which an enthalpy difference of the medium is converted into velocity, said valve comprising a housing provided with a valve body and having a passage which first converges and then diverges and characterised in that in the direction of flow the passage of the valve housing first converges abruptly and then gradually diverges and in that the valve body leaves free, in the closed state, a narrow gap at the area of the smallest section of the housing and extends into the diverging part of the housing by a portion whose sectional area gradually decreases in accordance with a linear function of the place of said sec tion on the longitudinal axis of the valve body and in that in the closed state the valve body is in contact on the upstream side of the converging part with the housing along a common tangential plane which is at an angle to the direction of movement of the valve body, which angle exceeds the friction angle between the valve body and the housing.

2. In a turbine driven by a compressible fluid and including at least one turbine wheel having radial vanes, a housing surrounding said turbine wheel and defining at least one distribution duct having an inlet end and extending from said inlet end circumferentially of said turbine wheel in progressively decreasing cross section, the improvement which comprises a body portion defining a valve-controlled discharge passage which discharges the compressible fluid axially into said inlet end of the distribution duct;

said discharge passage being defined by the inner surface of said body portion and having a constriction spaced from said inlet end of the distribution duct, a divergent portion leading from said constriction to said inlet opening, and a convergent portion leading to said constriction;

a valve member concentrically disposed and axially movable within said discharge passage, said valve member including a head having a shoulder portion presenting a downstream face engagable with essentially only line contact with said convergent portion of the discharge passage upstream of said constriction when the valve is closed, and a rounded, generally conical nose having its base merging with said downstream face and presenting throughout a cross section smaller than that of said constriction, said convergent portion of the discharge passage leading abruptly into said constriction to provide an annular clearance area around said shoulder portion of the valve member, when same is closed, which is substantially larger than the annular clearance between said nose and said constriction whereby the angle of engagement between said valve member and said body portion along said line contact is greater than the friction angle between such members and wherein the clearance between the nose and the constriction establishes flow control substantially as soon as said line contact between said downstream face of the valve member and said convergent portion of the discharge passage is broken; and

means for axially shifting said valve member between said closed position and a fully open position in which the tip of said nose of the valve member remains within said constriction.

3. In a turbine as defined in claim 2 wherein said nose is contoured to establish a substantially linear relation between axial shifting of said valve member and the change of cross sectional clearance area between the nose and constriction effected by such shifting throughout the range of movement of said valve member.

4. In a turbine as defined in claim 3 wherein said downstream face of the valve member is concave.

5. In a turbine as defined in claim 4 wherein that portion of said convergent portion of the discharge passage upstream of and immediately adjacent line contact is concave whereas that portion thereof downstream of and leading to said constriction is convex.

6. In a turbine as defined in claim 2 wherein said downstream face of the valve member is concave.

7. In a turbine as defined in claim 6 wherein that portion of said convergent portion of the discharge passage upstream of and immediately adjacent line contact is concave whereas that portion thereof downstream of and leading to said constriction is convex.

8. In a turbine as defined in claim 2 wherein that portion of said convergent portion of the discharge passage upstream of and immediately adjacent line contact is concave whereas that portion thereof downstream of and leading to said constriction is convex.

9. In a turbine as defined in claim 3 wherein that portion of said convergent portion of the discharge passage upstream of and immediately adjacent line contact is concave whereas that portion thereof downstream of and leading to said constriction is convex.

Claims

1. A turbine for a compressible medium having at least a first stage wheel which is traversed in the centripetal direction by the driving medium and operates in accordance with the equal pressure principle, said stage being at least partially surrounded by a distribution duct of decreasing cross section, a regulating valve controlling flow into said distribution duct and at which an enthalpy difference of the medium is converted into velocity, said valve comprising a housing provided with a valve body and having a passage which first converges and then diverges and characterised in that in the direction of flow the passage of the valve housing first converges abruptly and then gradually diverges and in that the valve body leaves free, in the closed state, a narrow gap at the area of the smallest section of the housing and extends into the diverging part of the housing by a portion whose sectional area gradually decreases in accordance with a linear function of the place of said section on the longitudinal axis of the valve body and in that in the closed state the valve body is in contact on the upstream side of the converging part with the housing along a common tangential plane which is at an angle to the direction of movement of the valve body, which angle exceeds the friction angle between the valve body and the housing.

2. In a turbine driven by a compressible fluid and including at least one turbine wheel having radial vanes, a housing surrounding said turbine wheel and defining at least one distribution duct having an inlet end and extending from said inlet end circumferentially of said turbine wheel in progressively decreasing cross section, the improvement which comprises a body portion defining a valve-controlled discharge passage which discharges the compressible fluid axially into said inlet end of the distribution duct; said discharge passage being defined by the inner surface of said body portion and having a constriction spaced from said inlet end of the distribution duct, a divergent portion leading from said constriction to said inlet opening, and a convergent portion leading to said constriction; a valve member concentrically disposed and axially movable within said discharge passage, said valve member including a head having a shoulder portion presenting a downstream face engagable with essentially only line contact with said convergent portion of the discharge passage upstream of said constrictIon when the valve is closed, and a rounded, generally conical nose having its base merging with said downstream face and presenting throughout a cross section smaller than that of said constriction, said convergent portion of the discharge passage leading abruptly into said constriction to provide an annular clearance area around said shoulder portion of the valve member, when same is closed, which is substantially larger than the annular clearance between said nose and said constriction whereby the angle of engagement between said valve member and said body portion along said line contact is greater than the friction angle between such members and wherein the clearance between the nose and the constriction establishes flow control substantially as soon as said line contact between said downstream face of the valve member and said convergent portion of the discharge passage is broken; and means for axially shifting said valve member between said closed position and a fully open position in which the tip of said nose of the valve member remains within said constriction.