JP5903012B2 - Turbine design method, turbine manufacturing method, and method for determining unsteady force acting on moving blades, etc. - Google Patents

Description

  The present invention relates to a turbine design method, a turbine manufacturing method, and a method for determining an unsteady force acting on a moving blade and the like, and in particular, includes a stationary blade and a moving blade in a turbomachine such as a steam turbine or a gas turbine. The present invention relates to a turbine paragraph design method.

  The axial flow turbine includes a rotor, a plurality of moving blades, and stationary blades in a casing. A stationary blade converts the thermal energy of a fluid such as gas or steam into kinetic energy and rotates the moving blade. The stationary blades incorporated in the stator and the moving blades implanted in the rotor groove constitute a turbine stage.

  The stationary blades in the turbine stage cause periodic time fluctuations of the pressure field and the velocity field (nozzle wake) with respect to the moving blades located downstream. This becomes an unsteady force and acts on the moving blade. At this time, the moving blades are excited at a frequency obtained by multiplying the number of stationary blades by an integral multiple of the number of rotations. In general, interference that excites fluctuations in the pressure field is called potential interference, and interference that excites fluctuations in the velocity field is called wake interference. In the high-pressure stage and the intermediate-pressure stage of the steam turbine, the main components of unsteady force acting on the moving blade are potential interference and wake interference. The unsteady force generated by the interaction of the two interferences is called NPF (Nozzle Passing Frequency) excitation force. It is important to design so that the rotor blades are not broken by the NPF excitation force.

  It is known that the NPF excitation force acting on the moving blades varies depending on the axial distance between the stationary blades and the moving blades, the size of the stationary blades, the number ratio of the stationary blades to the moving blades, and the blade shape. It is known that the excitation force due to potential interference and wake interference, respectively, tends to increase as the axial distance between the trailing edge of the stationary blade and the leading edge of the stationary blade, that is, the distance between the stationary blades decreases. ing. However, it has also been found that the NPF excitation force, which is the sum of potential interference and wake interference, does not change monotonically with the distance between the stationary blades due to the combination of the phase of potential interference and wake interference. Since the phenomenon is complicated, the NPF excitation force is often obtained directly by non-stationary calculation of CFD (Computational Fluid Dynamics).

T. Nakajima, Y. Shikano, Y. Yamashita, Prediction of Effects of Potential Field Interaction and Wake Interaction on Unsteady Force for Buckets ： IGTC2011-0053, pp.1-8 (2011)

  NPF excitation force is often obtained directly by non-stationary calculation of CFD, but the calculation takes time. In addition, when trying to obtain a quantitative relationship between the distance between the stationary blades and the NPF excitation force, there was no other way than to perform many calculations using CFD and plot the points together. However, this method takes time to calculate. In addition, since regularity is not known, if the number of calculations is reduced, it is possible to know the tendency of the change in NPF excitation force with respect to the distance between the stationary blades. Quantify the NPF excitation force at any distance between the stationary blades. Difficult to predict. For this reason, it has been difficult in terms of design to flexibly change the distance between the stationary blades, the size of the stationary blades, and the number of blades while keeping the unsteady force below a predetermined threshold.

  On the other hand, when the distance between the stationary blades is shortened, the friction loss of the side walls is suppressed, and therefore an improvement in performance can be expected. In multi-stage turbines such as steam turbines, the distance between the stationary blades in each stage affects the length of the rotor, so shortening the distance between the stationary blades contributes to shortening the rotor length and increases the rotor rigidity. Can be expected.

  However, by design, it is easy to use a stationary blade that is well separated from NPF so that the blade is not broken by the NPF excitation force. Since this method limits the number of stationary blades that can be employed, depending on the detuning result, there may be a case where a stationary blade that degrades performance or a stationary blade that is long in the axial direction may be used. There is also a design method that limits the distance between the stationary blades and the size of the stationary blades in advance so that the NPF excitation force does not become excessive. However, since the NPF excitation force cannot be quantitatively evaluated, the NPF excitation force is easily overestimated. At this time, it may be unavoidable to use an unnecessarily large stationary blade or an unnecessarily long axial distance.

  Thus, the present inventors have proposed a new method for quantitatively predicting the NPF excitation force (Non-patent Document 1). In this new method, viscosity analysis and non-viscous analysis are performed on one cascade model, and the unsteady force (NPF excitation force) acting on the rotor blade and the excitation force due to potential interference are obtained by these analyses. The excitation force due to the wake interference acting on the rotor blades is obtained from the difference between the results of the non-viscous analysis. Then, by performing these for a plurality of stationary blade distances, the excitation force due to the potential interference and the wake interference is expressed as a function of the distance between the stationary blades, respectively, based on the formulated potential interference and the excitation force due to the wake interference. The unsteady force acting on the moving blades when the distance between the stationary blades is an arbitrary value is calculated. This method can quantitatively predict the NPF excitation force at any distance between the stationary blades. The present inventors use this new method for quantitatively predicting the NPF excitation force to reduce the unsteady force acting on the rotor blade, and to reduce the performance and increase the rotor shaft length. Japanese Patent Application No. 2011-180246 has proposed a turbine design method capable of easily constructing a turbine stage structure that can be prevented.

  In this design method, it is necessary to formulate the excitation force due to potential interference and the excitation force due to wake interference by changing the value of the distance between the stationary blades for both viscous analysis and inviscid analysis.

  To summarize the above, it is not practical to calculate the NPF excitation force directly by CFD and design the NPF excitation force to be below the specified threshold, and it is not practical to use other design methods. When the excitation force is set to be equal to or less than a predetermined threshold value, an excessively large nozzle or a distance between the stationary blades may be employed, which may cause performance degradation and increase of the rotor shaft length.

  With the new design method proposed by the present inventors, it is possible to solve the conventional problems, reduce unsteady force acting on the rotor blades, and prevent deterioration in performance and increase in rotor shaft length. It is possible to easily construct a possible turbine stage structure, but even with this new design method, both the viscosity analysis and the non-viscous analysis are carried out by changing the values of factors such as the distance between stationary blades. There is a need.

  In addition, the above-mentioned problem is also applied to the method of designing the unsteady force acting on the stationary blade of the turbine stage on the downstream side and the BPF (Bucket Passing Frequency) excitation force to be equal to or less than a predetermined threshold value.

  An object of the present invention is to provide a turbine stage structure capable of reducing unsteady force (NPF excitation force or BPF excitation force) acting on a moving blade or a stationary blade and preventing a decrease in performance and an increase in rotor shaft length. It is an object of the present invention to provide a new turbine design method that can be easily constructed.

  In order to solve the above problems, the present invention uses a stationary blade model and a moving blade model whose basic shape has been determined, and a non-stationary force acting on the moving blade and an excitation force due to potential interference, respectively. For the distance between the stationary blades, the excitation force due to the wake interference acting on the blade from the difference between the viscosity analysis result and the non-viscous analysis result is obtained for the distance between the stationary blades, and the potential interference and Based on the excitation force due to wake interference, the phase of the excitation force due to potential interference and the phase of the excitation force due to wake interference are expressed as a function of the distance between the stationary blades, and the phase difference between the calculated potential interference and the excitation force due to wake interference is the same. It is characterized in that the distance between the stationary blades is determined so that the phase does not become a phase or a phase that is somewhat away from the phase.

  In addition, instead of the stationary blade and the moving blade of the same turbine stage, the distance between the moving blade and the stationary blade is determined as a relationship between the moving blade of the upstream turbine stage and the stationary blade of the downstream turbine stage. To do.

  According to the present invention, in turbine design, it is possible to reduce unsteady force (NPF excitation force or BPF excitation force) acting on a moving blade or a stationary blade, and to prevent deterioration in performance and increase in rotor shaft length. A turbine stage structure can be easily constructed.

  For example, the NPF excitation force that acts on the rotor blades without unnecessarily degrading blade performance or increasing the rotor shaft length for the distance between the stator blades and the rotor blades in the turbine stage, which is the axial distance between the stator blades and the rotor blades. It is possible to easily determine the distance between the stationary blades that does not become excessive.

  And in this invention, the calculation case of the viscosity analysis and non-viscous analysis for calculating | requiring an exciting force can be made into 1 time, for example.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

The representative figure explaining the design method of the turbine paragraph of the Example of this invention. Sectional drawing which shows schematic structure of the turbine stage to which the Example of this invention is applied. Explanatory drawing of the turbine paragraph to which the Example of this invention is applied. The graph which shows an example of the relationship between the phase difference of NPF excitation force, excitation force by potential interference, and excitation force by wake interference. The graph which shows an example of the relationship between NPF excitation force and the distance between stationary blades explaining the distance setting method between stationary blades based on the Example of this invention. The graph which shows an example of the relationship of the moving blade turning angle and the distance between stationary blades explaining the distance setting method between stationary blades based on the Example of this invention. The figure explaining the design method of the turbine paragraph used as the basis of this invention. The graph which formulated the amplitude of the excitation force in the potential interference and wake interference in the cross section of a certain blade height. The graph which formulated the phase of the excitation force in the potential interference and the wake interference in the cross section of a certain blade height. The figure explaining the design method of the turbine paragraph which is the other Example of this invention. The graph which shows an example of the relationship between the NPF excitation force and the distance between stationary blades explaining the distance setting method based on the other Example of this invention. Sectional drawing of an example of the turbine stationary blade used with an actual machine. Sectional drawing of an example of a turbine stationary blade used for CFD unsteady calculation. Sectional drawing of the other example of the turbine stationary blade used for CFD unsteady calculation.

  Embodiments of the present invention will be described below with reference to the drawings. The present invention is applicable to a turbine stage (a pair of turbine stationary blades and turbine rotor blades) in a steam turbine, a gas turbine, or the like. In the following description, an embodiment in the case of being applied to a turbine stage of a steam turbine is described. explain. In addition, as described later, the present invention provides a case where the turbine blade generates an unsteady force (BPF (Bucket Passing Frequency) excitation force) that acts on the turbine stationary blade in the next turbine stage (the trailing edge of the blade). And the design of the distance between the moving and stationary blades at the leading edge of the stationary blade. Furthermore, 1.5 stages such as stationary blades-moving blades-stator blades or a plurality of stages may be targeted.

  FIG. 2 shows an example of a turbine stage to which the present invention is applied. FIG. 2 is a cross-sectional view showing a schematic configuration. On the downstream side of the stationary blade N fixed between the vehicle interior wall (or outer ring) 2 and the inner ring F on the stator side, the moving blade B implanted in the disk Rb of the rotor 3 is arranged. A blade cover Cb is provided at the tip of the blade. The turbine is provided with a plurality of turbine stages including a stationary blade N and a moving blade B. The stationary blade-to-blade distance d is the distance in the rotor axial direction X between the trailing edge a of the blade Bn of the stationary blade N and the leading edge b of the blade Bb of the blade B. The stationary blade-to-blade distance d is conventionally configured to have the same value from the blade tip t to the blade root r in the blade height direction Z, or in the blade height direction Z. Some are configured to increase from the blade root r toward the blade tip t. Hereinafter, the method for determining the distance d between the stationary blades in the turbine stage will be mainly described.

  In order to facilitate understanding of the embodiments of the present invention, first, the outline of the design method of the turbine stage which is the basis of the present invention will be described, and then the embodiments of the present invention will be described. The design method of the turbine paragraph which is the basis of the present invention was previously proposed by the present inventors as Japanese Patent Application No. 2011-180246.

  FIG. 7 is a flowchart for explaining the design method of the turbine stage which is the basis of the present invention. The first step 10 for determining the blade shape, the second step 20 for calculating the NPF excitation force, and the third step 30 for determining the distance between the stationary blades.

  The first step 10 includes a specification decision 11 and a blade basic shape decision 12. In the specification determination 11, the specification of the turbine to be designed, that is, the environmental condition is determined. Next, in the determination of the blade basic shape 12, the basic shape of the blade is determined so as to achieve the performance under a predetermined environmental condition and to withstand the bending and centrifugal tension of steam. This first step 10 is basically the same as the conventional one, and detailed description thereof is omitted.

  Using the stationary blades and moving blades determined in the first step 10, the second step 20 calculates the relationship between the stationary blade distance d and the NPF excitation force, and calculates the NPF excitation force at any stationary blade distance d. To do. Since the NPF excitation force varies in the blade height direction, the second step 20 is performed for about 1 to 10 cases as many as the required blade height.

  For the stationary blades and moving blades modeled in the first step 10, the viscosity analysis 21 and the non-viscous analysis 22 at an arbitrary distance between the stationary blades are performed by unsteady calculation of CFD (Computational Fluid Dynamics). These viscous analysis 21 and non-viscous analysis 22 are the distance between stationary blades so that the excitation force due to potential interference and the excitation force due to wake interference can be formulated (functions of the distance between stationary blades). Change the number of times. When the force obtained in each analysis is Fourier transformed, the amplitude and phase of the excitation force in each excitation order can be obtained.

The force obtained from the viscosity analysis 21 is the NPF excitation force. Except for paragraphs that operate under special conditions such as partial injection and paragraphs near the exhaust chamber, NPF excitation force F _N (t) is the sum of potential interference force and wake interference force, and can be expressed by equation (1). .

F _N (t) = A _N sin (ωt + α _N )
= A _p sin (ωt + α _p ) + A _w sin (ωt + α _w ) (1)
Here, A is the amplitude, ω is the angular velocity, t is the time, α is the phase, and the suffixes of the amplitude A and the phase α are p is a component caused by potential interference, w is a component caused by wake interference, and N is an NPF excitation. Indicates the force component.

Since the force obtained from the inviscid analysis 22 can be regarded as the excitation force F _p (t) (= A _p sin (ωt + α _p )) due to potential interference, the excitation force F _w (t) due to wake interference (= A _w sin a (ωt + α _w)), the force obtained by the viscosity analysis _{(= a p sin (ωt +} α p) + a w sin force obtained by inviscid analysis from _{(ωt + α w)) (} = a p sin (ωt + α p)) Obtained by drawing. As a result, an equation of amplitude and phase of the excitation force of each interference as a function of the distance between the stationary blades is obtained. The analysis is performed several times while changing the distance between the stationary blades and graphed as shown in FIGS. 8 (a) and 8 (b). In FIGS. 8A and 8B, the horizontal axis (x) is dimensionless by dividing the distance between the stationary blades by the nozzle cord length. As can be seen from FIG. 8A, the potential interference can be exponentially approximated and the wake interference can be approximated to a power. Further, as can be seen from FIG. 8B, the phase can be linearly approximated regardless of the type of interference. By thus graphed, the amplitude A _w and phase alpha _w amplitude A _p and phase alpha _p and wake interference potential interference, a mathematical formula as a function of the factor static and dynamic blades distance (FIG. 8 ( a) and numerical values of h, j, m, n, k _p , l _p , k _w , and l _w in the mathematical expressions in FIG. Through the above-described operation, it becomes possible to formulate 23b of the excitation force due to potential interference and the excitation force due to wake interference at an arbitrary blade height (it can be expressed as a function of the distance between the stationary blades).

Next, the calculation 24b of the NPF excitation force at an arbitrary distance between the stationary blades is performed. Since the NPF excitation force is the sum of the excitation force due to potential interference and the excitation force due to wake interference, any stationary blade based on the equation 23b or the graphs of FIGS. 8 (a) and 8 (b) The excitation force F _p (t) due to potential interference and the excitation force F _w (t) due to wake interference at the inter-space distance (arbitrary inter-blade distance including the inter-static blade distance not analyzed by CFD) are obtained, By calculating the excitation force F _p (t) caused by the potential interference and the excitation force F _w (t) caused by the wake interference, the calculation 24b of the NPF excitation force at an arbitrary distance between the stationary blades is performed.

Further, A _p , A _w , α _p , α _w at an arbitrary distance between the stationary blades are obtained from the graphs or equations in FIGS. 8A and 8B, and A _N and α in equation (1) are obtained. _N is obtained from the following formulas (2) and (3), and the NPF excitation force F _N (t) at an arbitrary distance between the stationary blades can be calculated based on the formula (1).

A _N = √ {(A _p cos α _p + A _w cos α _w ) ² + (A _p sin α _p + A _w sin α _w ) ² } (2)
α _N = tan ⁻¹ {(A _p sin α _p + A _w sin α _w ) / (A _p cos α _p + A _w cos α _w )} (3)
The second step 20 described above is performed while changing the blade height. Then, in the third step 30, the distance between the stationary blades is selected so that the NPF excitation force is equal to or less than the threshold value. The second step 20 and the third step 30 described above are performed for each paragraph in which the distance between the stationary blades needs to be determined.

  If the method of FIG. 7 described above is used, the calculation time can be reduced as compared with the case where the NPF excitation force is directly calculated by the conventional CFD non-stationary calculation. That is, the NPF excitation force differs in complexity from the excitation force due to potential interference and the excitation force due to wake interference, and regularity is not known (for example, it changes complicatedly as shown in FIG. 5 described later). For this reason, in order to obtain a smooth curve as shown in FIG. 5, although it depends on the type and range of factors given on the horizontal axis, it is necessary to calculate approximately 10 cases or more, which takes time. In addition, it is highly possible that the NPF excitation force at the uncalculated distance between the stationary blades cannot be predicted quantitatively.

  In the method shown in FIG. 7 described above, the excitation force due to potential interference and the excitation force due to wake interference are expressed as a function of the distance between the stationary blades, and based on these, the NPF excitation force at an arbitrary distance between the stationary blades is calculated. Can do. In other words, it is possible to generalize the NPF excitation force that was impossible in the past.

  However, also in the method shown in FIG. 7 described above, in order to formulate the amplitude and phase of potential interference and wake interference, the distance between the stationary blades is changed by about 3 to 6 cases, and both viscous analysis and inviscid analysis are performed. Must be implemented. For this reason, it is not easy to determine the optimum distance between the stationary blades even with the method of FIG.

  Therefore, in the embodiment of the present invention, the determination of the distance between the stationary blades is further facilitated.

  In the method shown in FIG. 7, in order to quantitatively determine the NPF excitation force, the excitation force due to potential interference and the excitation force due to wake interference are expressed as a function of the distance between the stationary blades. In order to formulate this, it is necessary to calculate by changing the distance between the stationary blades several times. However, as shown in Equation (1), the NPF excitation force is the sum of the excitation force due to potential interference and wake interference, and the two interferences. When the excitation force due to both interferences is in phase, the NPF excitation force is close to the maximum. When the phase is opposite, it becomes close to the minimum. In other words, even if the NPF excitation force itself is not calculated, the NPF excitation force acting on the moving blades can be reduced and the performance deteriorated by setting the space between the stationary blades while avoiding the range where the NPF excitation force is maximized. In addition, it is possible to easily construct a turbine stage structure that can prevent an increase in the rotor shaft length.

  Therefore, in the embodiment of the present invention, the phase of the excitation force due to the potential interference and the phase of the excitation force due to the wake interference are expressed as a function of the distance between the stationary blades, and the phase difference between the excitation force due to the potential interference and the wake interference is expressed as a formula. The distance between the stationary blades is determined so that the phase does not become the same phase or a phase separated from the same phase to some extent.

The phase α _p of the excitation force due to potential interference and the phase α _w of the excitation force due to wake interference can be linearly approximated regardless of the type of interference as shown in FIG. The distance between the stationary blades (horizontal axis x) is represented by d / C _n which is dimensionless with the nozzle code length C _n .

α _p = k _p * (d / C _n ) + l _p (4)
α _w = k _w * (d / C _n ) + l _w (5)
As will be described later in detail, it is known that the gradient k of the approximate expression of the phase can be obtained geometrically (Non-Patent Document 3). Therefore, if the phases α _p and α _w of the excitation force due to potential interference and the excitation force due to wake interference at an arbitrary distance between the stationary blades (one point) are known, intercepts l _p and l _w can be obtained, The phase of the excitation force due to potential interference and the phase of the excitation force due to wake interference can be respectively expressed as a function of the distance between the stationary blades. In order to formulate these, viscosity analysis and non-viscosity analysis can be performed for an arbitrary distance (1 point) between the stationary blades. Therefore, the number of calculations is larger than the design method proposed previously by the present inventors. Can be reduced.

  Next, the design method of the turbine stage which is one Example of this invention is demonstrated in detail using FIG.

  The first step 10 for determining the blade shape, the second step 20 for calculating the NPF excitation force, and the third step 30 for determining the distance between the stationary blades. The first step 10 is the same as the method of FIG.

  Using the stationary blade and the moving blade determined in the first step 10, the second step 20 obtains the phase difference between the excitation force due to potential interference and the excitation force due to wake interference that constitute the NPF excitation force. Since the NPF excitation force varies in the blade height direction, the second step 20 is performed for about 1 to 10 cases as many as the required blade height. In the method of FIG. 7, in the second step, the viscosity analysis 21 and the inviscidity analysis 22 are performed only for the required distance between the stationary blades, but in this embodiment, for any distance between the stationary blades (one point) Just do it.

For the stationary blades and moving blades modeled in the first step 10, the viscosity analysis 21 and the non-viscous analysis 22 at an arbitrary distance between the stationary blades are performed by unsteady calculation of CFD (Computational Fluid Dynamics). When the force obtained in each analysis is Fourier transformed, the amplitude and phase of the excitation force in each excitation order can be obtained. The point of obtaining NPF excitation force F _N (t) (= A _N sin (ωt + α _N )) in the viscosity analysis 21, and the excitation force F _p (t) (= A _p sin (ωt + α _p ) due to potential interference in the inviscid analysis 22 ) Is obtained by subtracting the force obtained by the inviscid analysis 22 from the force obtained by the viscosity analysis 21 to obtain the excitation force F _w (t) (= A _w sin (ωt + α _w )) by the wake interference. The method is the same as that shown in FIG. Therefore, these provide the amplitude and phase of the excitation force of each interference (at the point where the viscosity analysis 21 and the inviscid analysis 22 are performed) at any distance between the stationary blades.

As described above, it has been found that the phase can be linearly approximated with respect to the distance d between the stationary blades (see FIG. 8B and Non-Patent Document 3). It is also known that the slope k of the approximate phase equation can be obtained geometrically (see Non-Patent Document 3). For example, when the phase is linearly approximated by d / C _n where the distance d between the stationary blades is made dimensionless by the nozzle code length C _n , the phase gradient k in the above equations (4) and (5) is obtained by the following equation. It is done.

k _p = (tan γ _n + tan β _b ) * 360 * C _n / t _b * (N _n / N _b ) (6)
k _w =-(tan γ _n -tan β _b ) * 360 * C _n / t _b * (N _n / N _b ) (7)
Where β is the inlet angle, γ is the outlet angle, C is the cord length, t is the pitch, N is the number of blades, the subscript b is the moving blade, and n is the value relating to the nozzle (static blade) (see FIG. 3). . In this way, the slope of the approximate expression for the phase can be obtained geometrically. The geometric condition is determined in the first step 10 described above.

  On the other hand, it has been found that it is difficult to obtain an intercept geometrically, and CFD is the most effective means for obtaining an intercept quantitatively.

  Using the phase α of the excitation force due to potential interference and the excitation force due to wake interference obtained in the viscosity analysis 21 and the inviscid analysis 22, the intercept l can be obtained by the following equation.

l = α-k * (d / C _n ) (8)
When the slope k and the intercept l of the approximate expression of the phase are obtained, formula 23a of the phases α _p and α _w of each interference at an arbitrary distance between the stationary blades is executed (the above expressions (4) and (5) are performed). can get.).

  Next, a phase difference calculation 24a relating to an arbitrary distance between the stationary blades is executed using a phase expression (expressions (4) and (5)) of the excitation force due to potential interference and the excitation force due to wake interference. When the phase difference is an integral multiple of 360 deg, that is, the same phase, the NPF excitation force, which is the sum of the two interferences, is almost maximized. Note that the phase of the NPF excitation force is determined by the amplitude and phase of potential interference and wake interference as shown in the above equation (3). Therefore, between the stationary blades where the NPF excitation force reaches the maximum value only with the phase difference between the two interferences. Note that the distance cannot be accurately predicted.

  However, as shown in FIG. 4, the distance between the stationary blades when the phase difference between the excitation force due to potential interference and the excitation force due to wake interference becomes an extreme value is roughly the distance between the stationary blades where the NPF excitation force becomes an extreme value. I know it ’s close.

  Similarly, when the phase difference between the excitation force due to potential interference and the excitation force due to wake interference is a value obtained by adding 180 degrees to an integral multiple of 360 degrees, that is, an opposite phase, the NPF excitation force is close to a minimum value.

  The second step 20 described above is performed while changing the blade height.

  In the third step 30, the distance between the stationary blades is determined. In order to prevent the NPF excitation force from becoming excessive, the inter-stator blade distance is adopted so that the phase difference between the excitation force due to potential interference and the excitation force due to wake interference does not become the same phase, or a phase somewhat away from the same phase. .

  The second step 20 and the third step 30 described above are performed for each paragraph in which the distance between the stationary blades needs to be determined.

  According to the method of the embodiment of the present invention, the viscosity analysis and the inviscidity analysis need only be performed once, and the NPF excitation force is less likely to be excessive due to the phase difference between the excitation force due to potential interference and the excitation force due to wake interference. The distance between rotor blades can be adopted. Note that the maximum or minimum value of the NPF excitation force cannot be obtained when determining the distance between the stationary blades. Use this method when the amplitude of the excitation force due to potential interference and the excitation force due to wake interference can be estimated in advance. Is desirable. For example, it is effective when it can be predicted that the excitation force due to potential interference and the excitation force due to wake interference will be approximately the same in a blade having similar blade shape and thermal conditions. Further, the NPF excitation force at the distance between the stationary blades adopted by this method may be directly obtained by CFD, and it may be performed while confirming whether or not it is below a predetermined threshold.

  It should be noted that the number of surveys of the distance between the stationary blades in the above-described embodiment is the minimum necessary and may be considered with a larger distance between the stationary blades in order to improve the prediction accuracy.

  Next, an example of the third step in the embodiment of the present invention will be described with reference to FIGS.

  In FIG. 5, the horizontal axis is dimensionless by dividing the distance between the stationary blades by the nozzle cord length. The vertical axis is dimensionless with a threshold value V. The threshold value V corresponds to the blade breaking limit value (allowable value). If the adoption range of the phase difference between the excitation force due to potential interference and the excitation force due to wake interference is set as a margin of 70 deg with respect to the opposite phase in any blade cross section, the range of the distance between the stationary blades that can be adopted is shown in the figure. As shown in 5. The margin range can be freely changed according to the evaluation target paragraph and the wing height. In FIG. 5, the solid line indicates the NPF excitation force obtained quantitatively by the method of FIG. 7 in order to confirm the embodiment of the present invention.

  FIG. 6 shows another example of the third step. The horizontal axis is the blade turning angle, which is the value obtained by adding the blade inlet angle and the blade exit angle. In general, the blade root has a large blade turning angle, and the blade tip has a small blade turning angle. The vertical axis is dimensionless by dividing the distance between the stationary blades by the nozzle code length. For any given paragraph, the phase difference between the excitation force due to potential interference and the excitation force due to wake interference is obtained in the blade length direction with respect to the circumferential force FT and axial force FA, and the adoption range of the phase difference is, for example, antiphase On the other hand, if the 90 deg margin is set uniformly, the range of the distance between the stationary blades that can be adopted is the shaded area in FIG. The margin range can be freely changed according to the evaluation target paragraph and wing height. Although the circumferential force and the axial force are illustrated separately, the pressure (excitation force) on the blade surface obtained by analysis is the circumferential force (= FT) as the force applied in the blade surface normal direction. And axial force (= FA) can be decomposed, and when these are integrated, a circumferential force and an axial force are obtained as a resultant force acting on the blade.

  Next, another embodiment of the present invention will be described.

  FIG. 9 is a flowchart showing another embodiment of the present invention. The method shown in FIG. 9 compensates for the drawbacks of the methods shown in FIGS. That is, in this embodiment, the number of calculations is smaller than that of the method of FIG. 7, and there is an advantage that the NPF excitation force can be predicted quantitatively unlike the method of FIG. However, the prediction accuracy of the NPF excitation force is worse than the method of FIG.

  In the present embodiment, the first step 10 is the same as that shown in FIGS.

  In the second step 20, a viscosity analysis 21 and an inviscid analysis 22 are performed at an arbitrary distance between the stationary blades. As a result, similarly to FIG. 1, the phase conversion 23a and the phase difference calculation 24a of the excitation force due to potential interference and the excitation force due to wake interference are performed. Next, based on the phase difference, the distance 25 between the stationary blades is calculated so that the NPF excitation force is near the extreme value in the range of the distance between the stationary blades to be examined. Calculation of distance between stationary blades Calculate the viscosity of n + 2 in total by adding the minimum and maximum distances between the stationary blades to be evaluated to the n distance between the stationary blades obtained in 25 (analysis to obtain NPF excitation force) ) And connecting the points, the result is the dotted line in FIG. The solid line indicates the NPF excitation force obtained quantitatively by the method of FIG. As can be seen from FIG. 10, the NPF excitation force can be predicted almost quantitatively.

  In the third step 30, the distance between the stationary blades and the blade at which the NPF excitation force is equal to or less than the threshold value is determined using FIG.

  The second step 20 and the third step 30 described above are performed for each paragraph in which the distance between the stationary blades needs to be determined.

  According to the present embodiment, the number of calculations can be reduced as compared with the method of FIG. 7, and unlike the method of FIG. 1, the NPF excitation force can be predicted quantitatively to some extent.

  As in the embodiment of FIG. 1, the number of surveys of the distance between the stationary blades in the embodiment of FIG. 9 is the minimum necessary, and in order to improve the prediction accuracy, the distance between the stationary blades is larger. You may consider it.

  FIG. 11 shows a blade cross section as an example of a turbine stationary blade to which the present invention is applied. Usually, the trailing edge end a of the stationary blade N has a circular arc shape. When the turbine stage in which the effect of the wake interference cannot be ignored is designed, if the trailing edge of the stationary blade is round, the wake is generated in the inviscid analysis 22 in FIGS. The excitation force due to may not be obtained by CFD. Therefore, in this embodiment, the turbine vane used for CFD unsteady calculation is devised so that the excitation force due to potential interference can be obtained by CFD (non-viscous analysis 22).

  FIG. 12 shows a blade cross section of a turbine stationary blade used for CFD unsteady calculation in this embodiment. In this embodiment, without changing the trailing edge end shape (thickness, etc.) of the stationary blade shown in FIG. 11, the blade belly side surface and the blade back side surface are extended so that the trailing edge end portion a has a sharp pointed shape. ing. When the trailing edge a of the stationary blade N is sharply sharp, even if a turbine stage in which the effect of wake interference cannot be ignored is designed, the wake generation is performed in the inviscid analysis 22 of FIGS. Therefore, the excitation force due to potential interference can be obtained by CFD. In this case, the viscosity analysis 21 in FIGS. 1, 7, and 9 is also calculated with the same blade model, and the excitation force of the wake interference is obtained by subtracting the result of the inviscid analysis 22 from the result of the viscosity analysis 21. .

  FIG. 13 shows a blade cross section of another example of a turbine stationary blade used for CFD unsteady calculation. In this embodiment, the nozzle cord length of the stationary blade N is not changed, and the trailing edge thickness is smaller than that in FIG. Even when a turbine stage in which the effect of wake interference cannot be ignored is a design target, by reducing the thickness of the trailing edge of the stationary blade N, as in the embodiment of FIG. Since no wake is generated in the viscosity analysis 22, the excitation force due to potential interference can be obtained by CFD. Wake generation can be suppressed by reducing the thickness of the trailing edge of the stationary blade to be calculated to 25% or less compared to the original stationary blade. In order to reduce the thickness of the trailing edge, for example, on the ventral side of the stationary blade, the thickness of the blade from the central portion to the trailing edge is reduced, and the flow of the portion is the same as that of the base nozzle. I am trying to make it.

  In the above embodiment, the phase of the excitation force due to potential interference and the phase of the excitation force due to wake interference are expressed as a function of the distance between the stationary blades, and the phase difference between the excitation force due to potential interference and wake interference is the same phase. The distance between the stationary blades is determined so that it does not become a phase or a phase away from the same phase to some extent, but it is also possible to formulate it with a function of other factors and optimize for that factor . For example, by applying the above-described embodiments with the ratio of the number of moving blades / stator blades and the code length ratio of the moving blades / stator blades as factors, the ratio of the number of moving blades / stator blades, The code length ratio can be optimized.

  In the above-described embodiment, the design method for the unsteady force acting on the moving blade and the NPF excitation force has been described. However, the unsteady force acting on the stationary blade of the downstream turbine stage, BPF (Bucket Passing Frequency) Excitation force can also be predicted in the same way, and it can be used to design the axial distance between the trailing edge of the moving blade in the upstream turbine stage and the leading edge of the stationary blade in the downstream turbine stage, and the distance between the moving blade and stationary blade. It is also possible to apply.

  In addition, the analysis model to which the present invention is applied assumes a pair of stationary blades and moving blades (one paragraph), but it can be similarly examined in 1.5 stages such as stationary blades-moving blades-stator blades or multiple stages. It is.

  Based on the above-mentioned present invention, by designing the distance between the stationary blades and the stationary blades in the turbine stage, it acts on the blades without unnecessarily degrading the blade performance or increasing the rotor shaft length. The NPF excitation force to be applied and the BPF excitation force acting on the stationary blade can be quickly and effectively set to a threshold value or less. Then, by manufacturing the turbine based on the turbine stage designed by the design method of the present invention, the NPF excitation force or BPF excitation force is not excessive, and the blade performance is improved and the rotor shaft length is shortened. Can be realized.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

X: axial direction, Z: radial direction, 2 ... vehicle interior wall, 3 ... rotor, N ... stationary blade, Bn ... stationary blade wing, a ... stationary blade trailing edge, B ... moving blade, Bb ... moving blade wing, b ... rotor blade leading edge end, d ... static-dynamic wings distance, p ... wing central, r ... the blade root, t ... wing tip, of the excitation force by a p _... potential interference amplitude, a w _... wake interference Amplitude of excitation force due to α, α _p ... phase of excitation force due to potential interference, α _w ... phase of excitation force due to wake interference, FT ... circumferential force, FA ... axial force, V ... threshold, β ... blade inlet angle, γ ... blade exit angle, C ... code length, t ... pitch.

Claims (6)

A turbine design method for determining a distance between a stationary blade and a stationary blade, which is an axial distance between a trailing edge of the stationary blade and a leading edge of the blade in a turbine stage composed of a stationary blade and a moving blade, ,
Using the stationary blade and moving blade model for which the blade basic shape has been determined, the unsteady force acting on the moving blade at any distance between the stationary blades is determined by viscosity analysis,
Using the model to determine the excitation force due to potential interference acting on the rotor blades at the arbitrary inter-stator blade distance by inviscid analysis,
From the difference between the result of the viscosity analysis and the result of the non-viscous analysis, the excitation force due to the wake interference acting on the moving blade at the distance between the arbitrary stationary blades is obtained,
A turbine design method, wherein a distance between stationary blades is determined so that a phase difference between the obtained excitation force due to potential interference and the excitation force due to wake interference does not become a value close to the same phase.   The turbine design method according to claim 1, wherein the viscosity analysis and the inviscid analysis are performed using a stationary blade having a sharp trailing edge as the stationary blade in the model.   2. The stator blade according to claim 1, wherein the stator blade in the model is a stator blade having a trailing edge portion thinned so that a trailing edge end outlet thickness is 25% or less as compared with the stator blade having the determined blade basic shape. A turbine design method characterized by performing a viscosity analysis and the inviscid analysis. This is the axial distance between the single trailing edge of the moving blade of the upstream turbine stage and the leading edge of the stationary blade of the downstream turbine stage. A turbine design method for determining a distance between a moving blade and a stationary blade,
Using the moving blade and stationary blade model for which the blade basic shape has been determined, the unsteady force acting on the stationary blade at any distance between the moving and stationary blades is determined by viscosity analysis,
Using the model to determine the excitation force due to potential interference acting on the stationary blade at the arbitrary inter-blade blade distance by inviscid analysis,
From the difference between the result of the viscosity analysis and the result of the non-viscous analysis, the excitation force due to the wake interference acting on the stationary blade at the distance between the arbitrary moving and stationary blades is obtained,
A turbine design method characterized by determining a distance between a moving blade and a stationary blade so that a phase difference between the obtained excitation force due to potential interference and the excitation force due to wake interference does not become a value close to the same phase.   A method for manufacturing a turbine, wherein the turbine is manufactured using the design method according to claim 1. A method for determining unsteady force acting on a moving blade or a stationary blade in a turbine stage composed of a stationary blade and a moving blade,
Using the stationary blade and moving blade model for which the blade basic shape has been determined, the unsteady force acting on the moving blade or the stationary blade at any one point of the factor is obtained by viscosity analysis,
Using the model, the excitation force due to potential interference acting on the moving blade or stationary blade at the value of the arbitrary one point is obtained by inviscid analysis,
From the difference between the unsteady force obtained from the viscosity analysis and the excitation force due to potential interference obtained from the non-viscous analysis, the excitation force due to wake interference acting on the moving blade or stationary blade at the arbitrary value 1 point is obtained,
Based on the excitation force due to the potential interference and the excitation force due to the wake interference at the obtained arbitrary value at one point, the phase of each of the excitation force due to the potential interference and the excitation force due to the wake interference is expressed as a function of the factor. ,
Based on the equation of the phase of the excitation force due to the potential interference and the equation of the phase of the excitation force due to the wake interference, based on the excitation force due to the potential interference and the wake interference in the specific value of the factor (unsteady force determination target) The phase difference of the excitation force is obtained, and when the phase difference becomes the same phase, it is determined that the unsteady force acting on the moving blade or the stationary blade is almost maximized, and when the phase difference becomes the opposite phase, the moving blade Alternatively, a method for determining an unsteady force acting on a moving blade or a stationary blade, wherein the unsteady force acting on the stationary blade is determined to be substantially minimal .

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