EP0865577A1 - Turbomachines et leur procede de fabrication - Google Patents

Turbomachines et leur procede de fabrication

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Publication number
EP0865577A1
EP0865577A1 EP95940361A EP95940361A EP0865577A1 EP 0865577 A1 EP0865577 A1 EP 0865577A1 EP 95940361 A EP95940361 A EP 95940361A EP 95940361 A EP95940361 A EP 95940361A EP 0865577 A1 EP0865577 A1 EP 0865577A1
Authority
EP
European Patent Office
Prior art keywords
impeller
meridional distance
dimensional
dimensional meridional
blade
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP95940361A
Other languages
German (de)
English (en)
Other versions
EP0865577B1 (fr
Inventor
Akira Goto
Mehrdad Zangeneh
Hideomi Harada
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
University College London
Ebara Corp
Ebara Research Co Ltd
Original Assignee
University College London
Ebara Corp
Ebara Research Co Ltd
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Application filed by University College London, Ebara Corp, Ebara Research Co Ltd filed Critical University College London
Publication of EP0865577A1 publication Critical patent/EP0865577A1/fr
Application granted granted Critical
Publication of EP0865577B1 publication Critical patent/EP0865577B1/fr
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/66—Combating cavitation, whirls, noise, vibration or the like; Balancing
    • F04D29/68—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers
    • F04D29/681—Combating cavitation, whirls, noise, vibration or the like; Balancing by influencing boundary layers especially adapted for elastic fluid pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/18—Rotors
    • F04D29/22—Rotors specially for centrifugal pumps
    • F04D29/2205—Conventional flow pattern
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D29/00—Details, component parts, or accessories
    • F04D29/26—Rotors specially for elastic fluids
    • F04D29/28—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps
    • F04D29/284—Rotors specially for elastic fluids for centrifugal or helico-centrifugal pumps for radial-flow or helico-centrifugal pumps for compressors

Definitions

  • the present invention relates to a turbomachinery and a method of manufacturing the turbomachinery which includes a centrifugal pump or a mixed flow pump for pumping liquid, a blower or a compressor for compression of gas, and more particularly to a turbomachinery having an impeller which has a fluid dynamically improved blade profile for suppressing meridional component of secondary flow, and a method of manufacturing such a turbomachinery.
  • the secondary flow is defined as flow which has a velocity component perpendicular to the main flow.
  • the total energy loss caused by the secondary flows is referred to as the secondary flow loss.
  • the low energy fluid accumulated at a certain region in the flow channel may cause a flow separation in a large scale, thus producing positively sloped characteristic curve and hence preventing the stable operation of the turbomachine.
  • the three-dimensional geometry of the impeller is defined as a meridional geometry formed by a hub surface and a shroud surface and a blade profile serving to transmit energy to fluid.
  • meridional geometry various geometries including a centrifugal type, a mixed flow type and an axial flow type are selected in accordance with design specification, including flow rate, pressure head and rotational speed, which is required in the individual turbomachinery.
  • N is the rotational speed in revolutions per minutes (rpm)
  • Q is the flow rate in cubic meter per minute (m 3 /min)
  • H is the head in meter (m) representing fluid energy which is imparted to the fluid by the turbomachinery.
  • the specific speed is determined if the design specification is given, and the meridional geometry of the impeller can be suitably selected in accordance with the specific speed.
  • Q is defined as volume flow rate, and in case of a compressor or the like, the volume flow rate at an impeller inlet is used for a compressible fluid whose volume is variable between the impeller inlet and the impeller exit.
  • the inlet blade angle is determined by the assumed inlet velocity triangle at each spanwise location to match the inlet blade angle with the inlet flow angle.
  • the exit blade angle is determined by the assumed exit velocity triangle at each spanwise location to satisfy the design head.
  • the inlet and the exit velocity triangles are calculated from the meridional geometry and the design flow rate and the design head, but can be updated based on the results of flow calculation of the impeller.
  • the design specification is input to determine the meridional geometry and the number of blades of the impeller.
  • a plurality of surfaces of revolution is defined on a meridional flow passage, and the tangential co-ordinate f 0 of a blade camber line at a point on each of surfaces of revolution is specified based on the past experience.
  • the location, where the tangential co-ordinate f 0 is specified, is selected at the leading edge or at the trailing edge of the impeller in many cases.
  • specified location of the tangential co-ordinate f 0 is referred as the stacking condition.
  • the blade angle at the impeller inlet is determined from the meridional geometry of the impeller obtained by the first step and design flow rate.
  • the blade angle at the impeller exit is determined from the meridional geometry of the impeller obtained by the first step, and design head.
  • a curve which connects smoothly the determined blade angle at the impeller inlet and the blade angle at the impeller exit is defined to determine the blade angle distribution along the location of non-dimensional meridional distance m.
  • the three-dimensional geometry of the impeller is determined by adding a certain thickness to the determined blade camber line to allow the blade to have a mechanical strength.
  • step of evaluating flow fields three-dimensional inviscid flow analysis which is a flow analysis without consideration of viscosity of fluid is applied to the three-dimensional geometry of the impeller determined by the third step, and a possibility of poor performance caused by a flow separation due to rapid deceleration of flow in the impeller is evaluated.
  • steps from the second step to the fourth step are repeated until the expected result is achieved.
  • the criteria (including the dependence on the specific speed of the impeller) for judging whether optimum pressure distribution in the flow channel is achieved to suppress the secondary flow is uncertain.
  • the state of generation of the secondary flows can be examined by the three-dimensional viscous flow analysis, enormous amount of calculations are required, thus optimization of the blade profile of the impeller by repeating the steps from the second step to the fourth step is practically infeasible.
  • the secondary flow in the impeller results from the action of Coriolis force caused by the rotation of the impeller and the effects of the streamline curvature.
  • the secondary flow in the impeller is divided broadly into two categories, one of which is blade-to-blade secondary flow generated along a shroud surface or a hub surface, the other of which is the meridional component of secondary flow generated along the pressure surface or the suction surface of a blade.
  • the purpose of the present invention is to suppress the meridional component of secondary flow in a centrifugal or a mixed flow turbomachine.
  • Figs. 1(A) and 1(B) the three-dimensional geometry of a closed type impeller is schematically shown in Figs. 1(A) and 1(B) in such a state that most part of shroud surface is removed.
  • Fig. 1(A) is a perspective view partly in section
  • Fig. 1(B) is a cross- sectional view taken along a line A-A' which is a meridional cross-sectional view.
  • a hub surface 2 extends radially outwardly from a rotating shaft 1 so that it has a curved surface similar to a corn surface.
  • a plurality of blades 3 are provided on the hub surface 2 so that they extend radially outward from the rotating shaft 1 and are disposed at equal intervals in the circumferential direction.
  • the blade tip 3a of the blades 3 are covered with a shroud surface 4 as shown in Fig " . 1(B).
  • a flow channel is defined by two blades 3 in confrontation with each other, the hub surface 2 and the shroud surface 4 so that fluid flows from an impeller inlet 6a toward an impeller exit 6b.
  • the surface facing the rotational direction is the pressure surface 3b
  • the opposite side of the pressure surface 3b is the suction surface 3c.
  • a casing (not shown in the drawing) for enclosing the impeller 6 serves as the shroud surface 4. Therefore, there is no basic fluid dynamical difference between the open type impeller and the closed type impeller in terms of the generation and the suppression of the meridional component of secondary flows, thus only the closed type impeller will be described below.
  • the impeller 6 having a plurality of blades 3 is incorporated as a main component, the rotating shaft 1 is coupled to a driving source, thereby jointly constituting a turbomachine. Fluid is introduced into the impeller inlet 6a through a suction pipe, pumped by the impeller 6 and discharged from the impeller exit 6b, and then delivered through a discharge pipe to the outside of the turbomachine.
  • the reduced static pressure distribution is formed by the action of a centrifugal force W 2 /R due to streamline curvature of the main flow and the action of Coriolis force 2 ⁇ W ⁇ due to the rotation of the impeller, where W is the relative velocity of flow, R is the radius of streamline curvature, ⁇ is the angular velocity of the impeller, W 9 is the component in the circumferential direction of W relative to the rotating shaft 1, p * is reduced static pressure, p is static pressure, p is density of fluid, u is peripheral velocity at a certain radius r from the rotating shaft 1.
  • the reduced static pressure p * has such a distribution in which the pressure is high at the hub side and low at the shroud side, so that the pressure gradient balances the centrifugal force W 2 /R and the Coriolis force 2 ⁇ W ⁇ directed toward the hub side.
  • the meridional component of secondary flow is generated on both surfaces of the suction surface 3c and the pressure surface 3b.
  • the secondary flow on the suction surface 3c has a greater influence on performance characteristics of turbomachinery.
  • the purpose of the present invention is to suppress the meridional component of secondary flow on the suction surface of the blade.
  • Fig. 2(B) which is a cross-sectional view taken along a line B-B' in Fig. 2(A)
  • a pair of vortices which have a different swirl direction from each other are formed in the flow channel between two blades as the flow goes towards exit. These vortices are referred to as secondary vortices.
  • a turbomachinery having an impeller, characterized in that the impeller is designed so that the reduced static pressure difference ⁇ Cp or the relative Mach number difference ⁇ M between the hub and the shroud on the suction surface of a blade shows a remarkable decreasing tendency along the location of non-dimensional meridional distance m toward the impeller exit.
  • the difference D between a minimum value ⁇ Cpm of reduced static pressure difference ⁇ Cp and a value ⁇ Cpm-o 4 of reduced static pressure difference ⁇ Cp at the location corresponding to non-dimensional meridional distance mm-0.4 obtained by subtracting non- dimensional meridional distance 0.4 from non-dimensional meridional distance mm representing the above minimum value ⁇ Cpm is selected to be not less than a specified value which is dependent on a specific speed Ns of the turbomachinery.
  • the pressure coefficient slope at the shroud side CPS-s on the suction surface of the blade is selected to be not less than -1.3 as the lower limit of the pressure coefficient slope at the shroud side CPS-s, LIM .
  • the pressure coefficient slope at the shroud side CPS- s on the suction surface of the blade is defined as a pressure gradient on the shroud surface at the location between the non- dimensional meridional distance mm representing the above minimum value ⁇ Cpm of reduced static pressure difference ⁇ Cp and the non- dimensional meridional distance mm-0.4 obtained by subtracting non-dimensional meridional distance 0.4 from non-dimensional meridional distance mm representing the above minimum value ⁇ Cpm.
  • the difference DM between a minimum value ⁇ Mm of relative Mach number difference ⁇ M and a value ⁇ M m -o.4 of relative Mach number difference ⁇ M at the location corresponding to non-dimensional meridional distance mm-0.4 obtained by subtracting non- dimensional meridional distance 0.4 from non-dimensional meridional distance mm representing the above minimum value ⁇ Mm is selected to be not less than a specified value which is dependent on a specific speed Ns of the turbomachinery.
  • the Mach number slope at the shroud side MS-s is selected to be not less than -0.8 as the lower limit of the Mach number slope at the shroud side MS-s, LIM .
  • the Mach number slope at the shroud side MS-s on the suction surface of the blade is defined as a gradient of Mach number on the shroud surface at the location between the non-dimensional meridional distance mm representing the above minimum value ⁇ Mm of relative Mach number difference ⁇ M and the non-dimensional meridional distance mm-0.4 obtained by subtracting non- dimensional meridional distance 0.4 from non-dimensional meridional distance mm representing the above minimum value.
  • the flow separation can be prevented in the downstream side of the location of non-dimensional meridional distance mm-0.4.
  • the impeller is designed so that the above-mentioned characteristic decreasing tendency in the reduced static pressure difference ⁇ Cp or the relative Mach number difference ⁇ M between the hub and the shroud on the suction surface of the blade is realized, and further the above-mentioned characteristic limit in the pressure coefficient slope at the shroud side CPS-s or the Mach number slope at the shroud side MS- s on the suction surface of the blade is realized.
  • the meridional component of secondary flow can be remarkably suppressed around and after the location of non-dimensional meridional distance mm-0.4 where the reduced static pressure difference ⁇ Cp or the relative Mach number difference ⁇ M shows a remarkably decreasing tendency toward the impeller exit.
  • the meridional component of secondary flow can be effectively suppressed in the overall area of the impeller.
  • the distribution of the reduce static pressure difference ⁇ Cp * along non-dimensional meridional distance m on the basis of the pressure coefficient Cp * which is normalized to clarify dependence on the specific speed Ns is characterized by a remarkable decreasing tendency toward the impeller exit.
  • the pressure coefficient Cp or the Mach number M, and thus the reduced static pressure difference ⁇ Cp or the relative Mach number difference ⁇ M are not defined as a function of a specific speed Ns, dependence of numerical values of them on the specific speed is not quantitatively clarified.
  • the difference D it is difficult to estimate the difference D at the specific speeds except for the specific speeds illustrated in Fig. 4 in the turbomachinery such as pumps which handle incompressible fluid, or the difference DM at the specific speeds illustrated in Fig. 5 in ⁇ the turbomachinery such as compressors which handle compressible fluid.
  • the normalized pressure coefficient Cp * is used, whereby the difference D * between a minimum value ⁇ Cp'm of the normalized reduced static pressure difference ⁇ Cp * and the normalized reduced static pressure difference ⁇ CpVo.4 at the location corresponding to non-dimensional meridional distance mm- 0.4 obtained by subtracting non-dimensional meridional distance 0.4 from non-dimensional meridional distance mm representing the above minimum value ⁇ Cp * m of the normalized reduced static pressure difference ⁇ Cp * can be expressed as a function of the specific speed Ns, as shown in Fig. 6, which is defined by the following equation:
  • the pressure coefficient Cp * in compressible fluid which is handled by the turbomachinery such as a compressor is expressed by the following equation.
  • M 0 *2 Ut/( ⁇ P 0 * /p 0 * ) 0 - 5
  • Ut is a peripheral speed of the impeller
  • W is a relative velocity
  • H 0 * is a rothalpy
  • y is a ratio of specific heats
  • P 0 * is rotary stagnation pressure
  • p 0 * is a density corresponding to P 0 * .
  • the second aspect of the present invention it is possible to select a wide range of specific speeds Ns in the turbomachinery and deal with every kind of fluid (compressible fluid and incompressible fluid) which is handled by the turbomachinery, and while selecting properly by trial and error the blade loading distribution along non-dimensional meridional distance m on the basis of the known close relationship between the pressure coefficient Cp and the angular momentum rV ⁇ , the pressure coefficient Cp * is increased or decreased.
  • the impeller is designed so that the above-mentioned characteristic deceasing tendency in the reduced static pressure difference ⁇ Cp * between the hub and the shroud on the suction surface of the blade is realized.
  • the meridional component of secondary flow can be remarkably suppressed after the location of non-dimensional meridional distance mm-0.4 where the normalized reduced static pressure difference ⁇ Cp * shows a remarkably decreasing tendency toward the impeller exit.
  • the meridional component of secondary flow can be effectively suppressed in the overall area of the impeller.
  • the turbomachinery having the impeller with the three-dimensional geometry which realizes the distribution of the reduced static pressure difference ⁇ Cp or the relative Mach number difference ⁇ M along non-dimensional distance m and is characterized by the first aspect of the present invention.
  • the turbomachinery having the impeller with the three-dimensional geometry which realizes the distribution of the reduced static pressure difference ⁇ Cp * on the basis of the normalized pressure coefficient Cp * along non-dimensional distance m and is characterized by the second aspect of the present invention.
  • the pressure coefficient Cp is increased or decreased, and by utilizing the known three-dimensional inverse design method using the blade loading distribution as input data, the three- dimensional geometry of the impeller which realizes the distribution characterizing the first and second aspects of the present invention is established.
  • the design specification is input to determine the meridional geometry of the impeller and the number of blades of the impeller.
  • a plurality of surfaces of revolution is defined in a meridional flow channel, and stacking condition f 0 representing tangential co-ordinate of blade camber line at a point on each of surfaces of revolution is determined.
  • the profile of the blade loading distribution d(rV ⁇ )/dm is selected so that the blade loading distribution has a peak on the shroud surface in the first half of the location of non-dimensional meridional distance m and a peak on the hub surface in the latter half of the location of non-dimensional meridional distance m.
  • the value obtained by integration of the blade loading distribution along the non- dimensional distance m is adjusted to satisfy design head of the impeller, the distribution of blade loading rV, along the location of non-dimensional meridional distance m is determined.
  • the blade shape is computed in an iterative manner by integrating
  • the fourth step step of evaluation of optimum reduced static pressure difference and the like
  • the fifth step (step of evaluating flow fields) a possibility of poor performance caused by a flow separation due to rapid deceleration of flow in the impeller determined by the third step is evaluated.
  • the secondary flow parameter is a satisfied value or not. In the case where it is judged that the pressure distribution in the impeller is not appropriate, after going back to the second step to modify the blade loading distribution, the steps from the second step to the fifth step are repeated until the expected result is achieved.
  • the blade loading distribution which is directly related to characteristics of flow fields of D, DM or D * which is criteria of judgement in the fourth process, is determined and is used as input data for the third step for determining blade profile. Therefore effective blade profile for suppressing secondary flow is promptly obtained, compared with the conventional manufacturing method using the blade angle distribution as a parameter related to the blade profile.
  • Figs. 1 and 2 are views for explaining the background art
  • Figs. 1(A) through 1(E) are views for explaining meridional component of secondary flow in three-dimensional geometry of a closed type impeller
  • Fig. 1(A) is a perspective view partly in section
  • Fig 1(B) is a meridional cross-sectional view taken along line A-A' of Fig. 1(A)
  • Fig 1(C) is a view for explaining a computational mesh in three-dimensional viscous calculation
  • Fig. 1(D) is a perspective view showing idspan and idpitch of the impeller
  • Fig. 1(E) is a view showing a blade profile of the impeller;
  • Figs. 2(A) and 2(B) are views for explaining secondary vortices caused by meridional component of secondary flow in the closed type impeller
  • Fig. 2(A) is a perspective view partly in section
  • Fig. 2(B) is a cross-sectional view taken along line B-B' of Fig. 2(A);
  • Figs. 3(A) and 3(B) are flow charts of numerical analysis by a computer to determine a three-dimensional shape of the impeller in the turbomachinery
  • Fig. 3(A) is a flow chart showing a conventional design method of designing the three- dimensional geometry of the impeller
  • Fig. 3(B) is a flow chart showing a three-dimensional inverse design method which has been put to practical use recently, according to the present invention
  • Fig. 4 is a graph showing verification data plotted on the plane defined by a vertical axis representing the pressure coefficient slope at the shroud side CPS-s and a horizontal axis representing the pressure coefficient slope at the hub side CPS- h, and further showing boundary lines defined by specific speeds Ns and ⁇ ⁇ the lower limit of the pressure coefficient slope at the shroud side CPS-s, LIM ;
  • Fig. 5 is a graph showing verification data plotted on the plane defined by a vertical axis representing the Mach number slope at the shroud side MS-s and a horizontal axis representing the Mach number slope at the hub side MS-h, and further showing boundary lines defined by specific speeds Ns and the lower limit of the Mach number slope at the shroud side MS-s, Llf1 ;
  • Fig. 6 is a graph showing verification data plotted on the plane defined by a vertical axis representing the difference D * between a minimum value ⁇ Cp * m of the normalized reduced static pressure difference ⁇ Cp * and a value ⁇ CpVo.4 of the normalized reduced static pressure difference ⁇ Cp * at the location corresponding to non-dimensional meridional distance mm-0.4 obtained by subtracting non-dimensional meridional distance 0.4 from non-dimensional meridional distance mm representing the above minimum value ⁇ Cp * m and a horizontal axis representing a specific speed Ns, and further showing boundary lines defined by specific speeds Ns, thereby expressing the above difference D * as a function of the specific speeds Ns;
  • Fig. 7(A) is a table showing the pressure coefficient slope at the shroud side CPS-s and the pressure coefficient slope at the hub side CPS-h read from characteristic graphs in verification examples, and MSF-angle calculated as secondary flow parameter
  • Fig. 7(B) is a table showing the difference D * on the basis of the normalized pressure coefficient Cp * shown in the same manner as Fig. 7(A);
  • Figs. 8 through 22 are characteristic graphs showing the distribution of the pressure coefficient Cp along non-dimensional meridional distance of the blade.
  • Fig. 8 is a graph showing a verification example "A”
  • Fig. 9 is a graph showing a verification example "B”
  • Fig. 10 is a graph showing a verification example "C”
  • FIG. 11 is a graph showing a verification example "D" Fig. 12 is a graph showing a verification example "E Fig. 13 is a graph showing a verification example "F” Fig. 14 is a graph showing a verification example "G” Fig. 15 is a graph showing a verification example "H” Fig. 16 is a graph showing a verification example Fig. 17 is a graph showing a verification example "J” Fig. 18 is a graph showing a verification example "K” Fig. 19 is a graph showing a verification example Fig. 20 is a graph showing a verification example ⁇ M' Fig. 21 is a graph showing a verification example "N", and Fig. 22 is a graph showing a verification example "0";
  • Fig. 23 is a flow vector diagram showing the state of flow separation in the verification example "0";
  • Figs. 24 through Fig. 29 are characteristic graphs showing the distribution of the Mach number along non-dimensional meridional distance m of the blade
  • Fig. 24 is a graph showing a verification example "P”
  • Fig. 25 is a graph showing a verification example "Q”
  • Fig. 26 is a graph showing a verification example "R”
  • Fig. 27 is a graph showing a verification example "S”
  • Fig. 28 is a graph showing a verification example "T”
  • Fig. 29 is a graph showing a verification example "U”;
  • Fig. 30 is a flow vector diagram showing the state of flow separation in the verification example "U" .
  • pressure coefficient Cp is defined by the following equation:
  • the pressure coefficient Cp is large at the shroud where reduced static pressure p * is low, and is small at the hub where reduced static pressure p * is high.
  • the meridional component of secondary flow on the blade suction surface is directed to the shroud side having low reduced static pressure p * from the hub side having high reduced static pressure p * , suppression of meridional component of secondary flow can be expected by reducing pressure difference ⁇ Cp between them.
  • the pressure coefficient Cp is equal to (W/Ut) 2 , where W is relative velocity.
  • W relative velocity
  • the physical variable being related to the behavior of secondary flow is relative Mach number.
  • the present invention proposes the structure for suppressing meridional component of secondary flow on the suction surface of the blade, considering distribution of the pressure coefficient Cp mainly in the latter half of the impeller. That is, the blade profile is designed so as to have the pressure distribution so that the pressure difference ⁇ Cp between the shroud side and the hub side on the suction surface shows a remarkably decreasing tendency along the location of non- dimensional meridional distance m toward the impeller exit.
  • Fig. 8 is a characteristic graph showing distribution of the pressure coefficient Cp obtained by the three-dimensional steady inviscid flow calculations, and thus the reduced static pressure difference ⁇ Cp of a pump according to a best mode of the first " aspect of the present invention.
  • the vertical axis represents the pressure coefficient Cp
  • Fig. 8 the vertical axis represents the pressure coefficient Cp
  • a solid curve at the upper part of the graph shows a pressure coefficient curve representing values of the pressure coefficient on the suction surface of the blade at the shroud side along the location of non-dimensional meridional distance m, and an alternative long and short dash curve extending substantially along the above solid line shows values of the pressure coefficient at the midpitch location on the shroud surface.
  • a solid curve at the lower part of the graph shows a pressure coefficient curve representing values of the pressure coefficient on the suction surface of the blade at the hub side along the location of non- dimensional meridional distance m, and an alternative long and short dash curve extending substantially along the above solid line shows values of the pressure coefficient at the midpitch location on the hub surface.
  • the distance between the solid curves adjacent to each other along the vertical axis i.e. the difference between a value on the pressure coefficient curve at the shroud side and a value on the pressure coefficient curve at the hub " side at the same location of non-dimensional meridional distance m corresponds to the reduced static pressure difference ⁇ Cp.
  • the gradient of inclined straight line which connects the value Cp s m . 04 on the pressure coefficient curve on the shroud surface at the location of non-dimensional meridional distance mm-0.4 and the value Cp s ffl on the pressure coefficient curve on the shroud surface at the location of non-dimensional meridional distance mm, i.e. (Cp s m -Cp s m.Q 4 )/0.4 is defined as a pressure coefficient slope at the shroud side CPS-s. In the example of Fig. 8, the pressure coefficient slope at the shroud side CPS-s is negative. Similarly, the gradient of straight line which connects the value Cp h m .
  • Cp h m on the pressure coefficient curve on the hub surface at the location of non-dimensional meridional distance mm-0.4 and the value Cp h m on the pressure coefficient curve on the hub surface at the location of non- dimensional meridional distance mm, i.e. (Cp h m -Cp h ra . 04 )/0.4 is defined as a pressure coefficient gradient at the hub side CPS-h.
  • the pressure coefficient slope at the hub side CPS-h is positive.
  • the difference between the value on the pressure coefficient curve at the shroud side at the location of non-dimensional meridional distance mm-0.4 and the value on the pressure coefficient curve at the hub side at the location of non-dimensional meridional distance mm-0.4 that is, the difference D between the reduced static pressure difference ⁇ Cp m -o.4 at the location of non- dimensional distance mm-0.4 and the minimum value ⁇ Cpm of the reduced static pressure difference ⁇ Cp is the essential factor which govern suppression of the secondary flow in the impeller of the turbomachinery.
  • the difference D is derived from cooperative contribution of the pressure coefficient slope at the shroud side CPS-s and the pressure coefficient slope at the hub side CPS-h, thus the differences D between the reduced static pressure difference ⁇ Cpm-o 4 at the location of non-dimensional meridional distance mm-0.4 and the minimum value ⁇ Cpm of the reduced static pressure difference ⁇ Cp in principal verification examples were plotted in Fig. 4 on the plane defined by horizontal and vertical axes representing the above respective slopes or gradients.
  • the vertical axis represents the pressure coefficient slope at the shroud side CPS-s
  • the horizontal axis represents the pressure coefficient slope at the hub side CPS-h.
  • open symbols ( ⁇ , D, 0) represent adaptation to the quantitative criterion (describe latter) of judgement about suppression of the secondary flow
  • solid symbols (A, I, •) represent nonadaptation to the above criterion.
  • Fig. 7(A) is a table showing data in principal verification examples.
  • Concerning four examples A, B, C and D, four pairs of data as to values of the pressure coefficient slope at the shroud side CPS-s and the pressure coefficient slope at the hub side CPS-h were read from the pressure coefficient curves of the verification examples shown in Figs. 8 through 11 in the order of A, B, C and D, and four ⁇ symbols were plotted on the plane between two axes from the readings.
  • Concerning two examples 1 and 2 the pressure coefficient curves in the verification examples are not shown, but the resultant data were represented for reference as a part of large amount of other verification examples.
  • open and solid symbols represent adaptation or nonadaptation to the quantitative criterion of judgement about suppression of the secondary flow.
  • the quantitative criterion of judgement will be described below.
  • Fig. 1(C) is an explanatory view used for the three- dimensional viscous flow calculation and showing the relationship between the computational meshes inside the bladed region and the secondary flow angle a defined in each of the computational meshes. Since the secondary flow is defined as flow which has a velocity component deviating from the direction of the computational mesh, the computational mesh to be used as a basis is required to have a certain regularity. That is, mesh is divided regularly (i.e.
  • MSF-angle used as the quantitative criterion of judgement about suppression of the secondary flow is expressed by the following equation.
  • ⁇ is an angle between the tangential direction along the streamwise mesh (J direction) and the direction of meridional velocity vector at the location near the suction surface of the blade in each computational mesh in the bladed region in Fig. 1(C);
  • Vm is meridional velocity
  • s is non-dimensional meridional span length in K direction, s being 0 on the hub surface and 1 on the shroud surface on each of Jth Quasi-orthogonal line (mesh line of K direction)
  • m is non-dimensional meridional distance in J direction, m being 0 at the blade leading edge and 1 at the blade trailing edge on each of Kth stream surface;
  • [ ]ss is integrated value in the first mesh from the suction surface of the blade.
  • MSF-angle is defined as mass-averaged value of the magnitude of the flow deviation angle from the streamwise mesh direction over the entire suction surface of the blade.
  • the value of MSF-angle in each of verification example equal to or larger than the value of MSF- angle as the criterion of judgement means nonadaptation to the above criterion of judgement (insufficient action of secondary flow suppression)
  • the value of MSF-angle in each of verification example smaller than the value of MSF-angle as the criterion of judgement means adaptation to the above criterion of judgement (sufficient action of secondary flow suppression).
  • the data of the nonadaptation are shown by solid symbols, and the data of the adaptation are shown by open symbols in Fig. 4.
  • a boundary line between data area of solid symbols which show nonadaptation to the criterion and data area of open symbols which show adaptation to the criterion can be drawn on the basis of data plotted in Fig. 4 for each of specific speeds Ns.
  • data area located at the lower right side of the boundary line corresponds to data area of adaptation to the criterion.
  • data area of open symbols which are suitable for suppression of the secondary flow on the plane between the pressure coefficient slope at the shroud side CPS-s and the pressure coefficient slope at the hub side CPS-h means that the difference D between ⁇ Cp m -o. 4 at the location of non-dimensional meridional distance mm-0.4 and the minimum value ⁇ Cpm of the reduced static pressure difference ⁇ Cp at the location of non-dimensional meridional distance mm can not be less than a certain value which is dependent on the criterion of judgement about suppression of the secondary flow.
  • the value of the difference D is the result of cooperative contribution of the value of the pressure coefficient slope at the shroud side CPS-s on the vertical axis on the boundary line and the value of the pressure coefficient slope at the hub side CPS-h on the horizontal axis.
  • the degree of contribution of both slopes varies in a wide range; there are three cases, i.e. the first case ( 1 ) which is largely dependent on the decreasing tendency of the pressure coefficient slope at the shroud side, the second case (2) which is dependent on the increasing tendency of the pressure coefficient slope at the hub side, and the third case (3) which is dependent on moderate harmonization of the decreasing tendency and the increasing tendency of both slopes.
  • the first case ( 1 ) which is largely dependent on the decreasing tendency of the pressure coefficient slope at the shroud side
  • the second case (2) which is dependent on the increasing tendency of the pressure coefficient slope at the hub side
  • the third case (3) which is dependent on moderate harmonization of the decreasing tendency and the increasing tendency of both slopes.
  • Fig. 2- _s a flow vector diagram showing the state of flow separation in the verification example of 0.
  • the pressure coefficient slope at the shroud side CPS-s and the pressure coefficient slope at the hub side CPS-h correspond to the Mach number slope at the shroud side MS-s and the Mach number slope at the hub side MS-h, respectively.
  • the plane in Fig. 5 is defined by a vertical axis representing the Mach number slope at the shroud side MS-s and a horizontal line representing the Mach number slope at the hub side MS-h.
  • Fig. 30 is a flow vector diagram showing the state of flow separation in the verification example of U.
  • the D 280 value is lower than D 400 and D 560 value
  • D 400 value is lower than D 560 value. So, the critical value of D has a tendency to have lower value for an impeller having a lower specific speed, although the quantitative dependency on the specific speed is not clear in Fig. 4 (the quantitative dependency is clarified in the following second aspect of the present invention).
  • the impeller having suppressed meridional secondary flow
  • the boundary lines of the inclined straight lines are confirmed and drawn in Fig. 4 or Fig. 5 dispersively for each of the specific speeds of the turbomachinery or sorts of fluid (incompressible fluid or compressible fluid), and the dependence of data on the specific speed is not made evident quantitatively.
  • the second aspect of the present invention with respect to the difference D between a minimum value ⁇ Cpm of the reduced static pressure difference ⁇ Cp and a value ⁇ Cpm-0.4 of the reduced static pressure difference ⁇ Cp or the difference DM between a minimum value ⁇ Mm of the relative Mach number difference ⁇ M and a value ⁇ Mm-o. 4 of the relative Mach number difference ⁇ M, the dependence on the specific speed is clarified in spite of sorts of fluid. That is, concerning the difference D or DM, the pressure coefficient Cp * which is normalized by the pressure coefficient Cp,mid-mid in the center of fluid passage is introduced and newly defined, whereby the boundary line according to the first aspect of the presen- invention can be expressed as a function of the specific spee Ns.
  • Fig. 6 shows the plotted data about the above difference on the basis of the normalized pressure difference Cp * in verification examples.
  • the vertical axis represents the difference D * between the normalized reduced static pressure difference ⁇ Cp * m-o.4 at the location of non- dimensional meridional distance mm-0.4 and a minimum value ⁇ Cp * m the normalized reduced static pressure difference ⁇ Cp * at the location of non-dimensional meridional distance mm
  • the horizontal axis represents a specific speed Ns of the turbomachinery.
  • Data plotted on the plane defined by both axes are the same as the data plotted on the plane of Figs. 4 and 5.
  • a boundary line of an negatively sloped straight line can be drawn so that data shown by open symbols representing adaptation to the quantitative criterion of judgement about suppression of the secondary flow are located on the data area at the upper right of the drawing, and data shown by solid symbols representing nonadaptation to the quantitative criterion of judgement about suppression of the secondary flow are located on the data area at the lower left of the drawing.
  • Cp * Cp/Cp, mid-mid where Cp, mid-mid is a pressure coefficient in the center of the flow channel as shown in Fig. 1(D).
  • the relative Mach number M can be related to the pressure coefficient Cp by the following equation, thus the normalized pressure coefficient Cp * is applicable to every kinds of fluid.
  • M 0 * ut/( Y P 0 * /p 0 * ) 0 - 5
  • Ut is a peripheral speed of the impeller
  • W is a relative velocity
  • H 0 * is a rothalpy
  • ⁇ is a ratio of specific heats
  • P 0 * is a rotary stagnation pressure
  • p 0 * is a density corresponding to P 0 * .
  • the design method comprises a first step of determining the meridional geometry, a second step of determining the blade loading distribution, a third step of determining blade profile, a fourth step of judging the optimum reduced static pressure difference ⁇ Cp and the like, and a fifth step of evaluating flow fields.
  • the pressure coefficient Cp is increased or decreased.
  • the three-dimensional shape of the impeller which realize a characteristic distribution characterized by the first and second aspects of the present invention is determined.
  • the design method is processed by the flow chart shown in Fig. 3(B).
  • the meridional shape of hub and the shroud and the position of the leading edge of the blade and the trailing edge of the blade are defined, and the number of blades of the impeller is selected.
  • Mesh required for numerical calculation is formed at an equal interval or unequal interval along the hub and the shroud surfaces. This mesh is extended to the upstream of the leading edge of the blade and the downstream of the trailing edge of the blade. The mesh is similar to that in Fig. 1(C) of the mesh for viscous flow calculations.
  • Quasi-Orthogonal line (Q-O line) is drawn by connecting the corresponding points on the hub and the shroud.
  • a plurality of surfaces of revolution is defined in the meridional flow channel, and the stacking condition f 0 ( tangential co-ordinate of the blade camber line at a point on each of surfaces of revolution).
  • the process in the first step is essentially the same as the process in the first step of the conventional design method shown in Fig. 3(A).
  • the shape of the blade loading distribution d(r ⁇ ⁇ )/dm is selected so that the blade loading distribution has a peak on the shroud surface in the first half of the non- dimens ' ional meridional distance m along the shroud and a peak on the hub surface in the latter half of the non-dimensional meridional distance m along the hub.
  • the distribution of d(r " V ⁇ )/r3m along the hub and shroud is integrated along the non-
  • the resultant value on the hub and the shroud surfaces obtained by integration along the non-dimensional meridional distance m is adjusted to satisfy the exit velocity triangles (i.e. the "may values on the hub and the shroud at the impeller exit determined, in the similar manner as the conventional method, from the design head of the impeller), and the rV 9 distribution between the hub and the shroud is determined by the linear interpolation along Q-0 line determined by the first step.
  • the blade camber line is obtained by applying the condition that the velocity is along the blade at the blade camber line, i.e. there is no flow through the blade camber.
  • f the tangential co-ordinate of the blade camber line (or wrap angle)
  • ⁇ the tangential co-ordinate of cylindrical polar co-ordinate system
  • B the number of blades (as shown in Fig. 1(E) ) .
  • the above equation is a first order hyperbolic partial differential equation.
  • the value of f 0 along an arbitrary Q-0 line in the blade (the stacking condition) is used as initial value, and the above equation is integrated along the non- dimensional meridional distance m, and the tangential co-ordinate of the blade camber line f in the location of non-dimensional meridional distance m is determined.
  • the three-dimensional geometry of the impeller is determined by adding a certain thickness to the determined blade camber line to allow the blade to have required mechanical strength.
  • the stacking condition can be specified by, for example, setting the zero value of f 0 along the Q-0 line at the blade trailing edge, or setting a moderate distribution of f 0 value along the Q-0 line at the blade trailing edge.
  • the velocity terms v rbl , v zbl and v 9bl are obtained from the solution of the tangentially periodic flow.
  • the Clebsch formulation of the velocity field is used for the solution of the periodic flow.
  • the velocity field is split into an unknown irrotational part (represented by a velocity potential function) and a known rotational part which is related to the blade circulation 2 ⁇ rV 9 .
  • the governing equation of the unknown potential function is then found by using Clebsch formulation for the velocity field in the continuity equation of the periodic flow. In this way a 3D Poisson's equation is obtained which can then be integrated by a suitable numerical technique, subject to vanishing periodic tangential velocity and spanwise velocity at upstream and downstream boundaries and no- flow conditions through the hub and shroud surface.
  • velocity field as well as blade loading of the impeller i.e. the pressure difference p( + ) - p(-) between the pressure p( + ) on pressure surface and the pressure p(-) on the suction surface of the blade can be obtained in the following equation.
  • the normalized pressure coefficient Cp * is defined as follows.
  • Cp * Cp/Cp,mid-mid
  • Cp,mid-mid is the pressure coefficient at the center of the flow channel (midspan and midpitch) at the location of non- dimensional meridional distance m.
  • the pressure coefficient Cp in compressible fluid is defined in the following equation.
  • M 0 *2 ut/( ⁇ p 0 * /p 0 * ) 0 - 5
  • Ut is a peripheral speed of the impeller
  • W is a relative velocity
  • H 0 * is a rothalpy
  • ⁇ is a ratio of specific heats
  • P 0 * is a rotary stagnation pressure
  • p 0 * is a density corresponding to P 0 * .
  • the decreasing tendency in the reduced static pressure difference ⁇ Cp is realized by (a) the degree of dependence on a variation at the shroud side, (b) the degree of dependence on a variation at the hub side, and (c) the degree of dependence on both variation at the shroud side and the hub side.
  • the pressure coefficient slope on the suction surface of the blade at the shroud side CPS-s and the pressure coefficient slope on the suction surface of the blade at the hub side CPS-h between the location of a minimum value ⁇ Cpm of the reduced static pressure difference ⁇ Cp and the location of non-dimensional meridional distance mm-0.4 obtained by subtracting non- dimensional meridional distance 0.4 from non-dimensional meridional distance mm representing the minimum value ⁇ Cpm are defined, and it is judged whether this value satisfies the criteria defined in the first aspect of the present invention.
  • the pressure coefficient Cp is equal to (W/U) 2 , where W is relative velocity.
  • W is relative velocity.
  • the physical variable related to the behavior of secondary flow is relative Mach number. Therefore, in case of compressible fluid, the same judgement concerning the reduced static pressure difference ⁇ Cp is applied to the relative Mach number difference ⁇ M based on the criteria defined in the first aspect of the present invention.
  • the fifth step step of evaluation of flow fields
  • a possibility of poor performance caused by the flow separation due to rapid deceleration or rapid pressure increase in the impeller determined by the third step is evaluated.
  • the steps from the second step to the fifth step are repeated until the expected result is achieved.
  • the characteristics of flow fields i.e. the blade loading distribution directly related to the flow physics, is used as input data for the third step to determine the blade profile, therefore the blade profile for suppressing the secondary flow can be promptly designed and the impeller having such blade profile can be easily manufactured, compared with the conventional manuf cturing method using the modification of blade angle distribution by trial and error.
  • a turbomachinery having an impeller, characterized in that the impeller is designed so that the reduced static pressure difference ⁇ Cp or the relative Mach number difference ⁇ M between the hub and the shroud on the suction surface of a blade shows a remarkably decreasing tendency along the location of non- dimensional meridional distance m toward the impeller exit.
  • the blade profile of the impeller is determined by utilizing the three-dimensional inverse design method using the blade loading distribution as input data so that the difference D between a minimum value ⁇ Cpm of the reduced static pressure difference ⁇ Cp and a value ⁇ Cp -0.4 of the reduced static pressure difference ⁇ Cp at the location corresponding to non-dimensional meridional distance mm-0.4 obtained by subtracting non- dimensional meridional distance 0.4 from non-dimensional meridional distance mm representing the above minimum value ⁇ Cpm is selected to be a specified value which is dependent on a specific speed of the turbomachinery.
  • the difference DM between a minimum value ⁇ Mm of the relative Mach number difference ⁇ M and a value ⁇ Mm-o.4 of the relative Mach number difference ⁇ M at the location corresponding to the above non- dimensional meridional distance mm-0.4 is also selected to be a specified value which is dependent on a specific speed of the turbomachinery.
  • the normalized pressure coefficient Cp * is commonly used for compressible fluid and incompressible fluid so that the normalized pressure coefficient difference D * corresponding to the above difference D or DM is expressed as a function of the specific speed Ns.
  • the blade profile of the impeller is determined by utilizing the three-dimensional inverse design method using the blade loading distribution as input data so that the above difference D * corresponding to the turbomachinery of a given specific speed is selected to be a specified value which complies with the above function.
  • the turbomachinery is designed and manufactured by utilizing the three-dimensional inverse design method using the aspects characterized by the above (1) and (2) as input data.
  • the meridional component of secondary flow can be effectively suppressed, a loss which occurs in the turbomachinery or the down stream flow channel can be reduced, emergence of positively sloped characteristic curve can be avoided, and stability of operation can be improved. Therefore, the present invention has a great utility value in industry.

Abstract

Rotor (6) de turbomachine muni d'ailettes (3) conçues de telle sorte que la différence de pression statique réduite ΔCp entre le moyeu (2) et la virole (4) sur la surface d'aspiration (3c) de l'ailette (3) présente une tendance notablement décroissante à proximité de la sortie du rotor (6b) dans la direction de la sortie du rotor (6b) entre l'entrée du rotor (6a) et la sortie du rotor (6b).
EP95940361A 1995-12-07 1995-12-07 Turbomachines et leur procede de fabrication Expired - Lifetime EP0865577B1 (fr)

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PCT/GB1995/002904 WO1997021035A1 (fr) 1995-12-07 1995-12-07 Turbomachines et leur procede de fabrication
CA002218692A CA2218692C (fr) 1995-12-07 1995-12-07 Turbomachines et leur procede de fabrication

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DE202005001875U1 (de) 2005-02-05 2005-05-19 Rewalux Markisenvertrieb Gmbh Verstellbares Sonnensegel mit einer Plane
KR101001056B1 (ko) 2010-02-19 2010-12-14 송길봉 구심력 동작형 수차
JP5611307B2 (ja) * 2012-11-06 2014-10-22 三菱重工業株式会社 遠心回転機械のインペラ、遠心回転機械
US10962021B2 (en) 2018-08-17 2021-03-30 Rolls-Royce Corporation Non-axisymmetric impeller hub flowpath
DE102021101419A1 (de) 2021-01-22 2022-07-28 Warema Renkhoff Se Sonnenschutzanlage mit einem Zugsystem
CN114251129A (zh) * 2021-11-29 2022-03-29 中国船舶工业集团公司第七0八研究所 用于透平机械二次流分析评估第三类流面及其设计方法
CN116306180B (zh) * 2023-05-22 2023-08-01 陕西空天信息技术有限公司 一种叶轮辅助分析方法、装置、设备及介质

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DE333336C (de) * 1920-04-30 1921-02-22 Alfred P Moessner Dipl Ing Kreisel-Laufrad fuer Gase oder Fluessigkeiten
US3481531A (en) * 1968-03-07 1969-12-02 United Aircraft Canada Impeller boundary layer control device
FR2550585B1 (fr) * 1983-08-09 1987-01-16 Foueillassar Jean Marie Moyens d'uniformiser la vitesse d'un fluide a la sortie d'un rouet centrifuge
US4615659A (en) * 1983-10-24 1986-10-07 Sundstrand Corporation Offset centrifugal compressor
GB2224083A (en) * 1988-10-19 1990-04-25 Rolls Royce Plc Radial or mixed flow bladed rotors

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CA2218692A1 (fr) 1997-06-12

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