CN111797580B - CFX software-based three-dimensional CFD automatic calculation method for turbine characteristics - Google Patents
CFX software-based three-dimensional CFD automatic calculation method for turbine characteristics Download PDFInfo
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Abstract
The invention provides a CFX software-based three-dimensional CFD automatic calculation method for turbine characteristics, which belongs to the technical field of turbine characteristics and comprises the following steps: calculating the working condition of the turbine design point by adopting CFX software to generate a working condition result file of the turbine design point; defining an outlet pressure initial value, a reference rotating speed and an initial rotating speed of the turbine; in the expression of CFX-Pre, defining a rotating speed expression according to the reference rotating speed, the initial rotating speed and the accumulated iteration step number calculated by CFX solution; defining an outlet pressure expression according to the outlet pressure initial value and the accumulated iteration step number calculated by CFX solution; in the CFX-Pre expression, defining a turbine performance parameter expression; in the control setting of a solver of CFX-Pre, setting the maximum iteration step number and the convergence standard; generating a set def file in the CFX-Pre; and starting iterative computation by taking the working condition result file of the turbine design point as an initial field. The method has simple calculation process and small occupied space resource.
Description
Technical Field
The disclosure relates to the technical field of turbine characteristics, in particular to a CFX software-based three-dimensional CFD automatic calculation method for turbine characteristics.
Background
The turbine characteristic refers to the change condition of performance parameters such as flow rate, efficiency and the like of the turbine along with the expansion ratio and the rotating speed of the turbine, can reflect the performance of the turbine under various working conditions, is one of important judgment bases for the quality of the pneumatic design of the turbine, and is also a necessary input condition for the general specialty of the engine to perform engine general performance calculation and performance matching calculation of each component. Therefore, the calculation of the turbine characteristics is an essential element of the turbine aerodynamic design process.
The turbine characteristic calculation can be divided into one-dimensional characteristic calculation, two-dimensional CFD characteristic calculation and three-dimensional CFD characteristic calculation according to the space dimension. The one-dimensional characteristic calculation is to calculate each state point of the turbine according to a one-dimensional pneumatic thermodynamic relation in the turbine and a large number of empirical constants, so that the characteristic calculation result of the turbine can be quickly obtained, but the calculation result is inaccurate and the precision is poor due to the existence of a large number of empirical parameters. The two-dimensional CFD characteristic calculation is a calculation of turbine characteristics by using a inviscid S2 flow surface CFD calculation program, and the calculation accuracy thereof depends on the accuracy of the loss model. Since the loss model is usually only verified under certain specific conditions, the accuracy of the two-dimensional CFD characteristic calculation cannot be guaranteed for a wide range of conditions involved in the turbine characteristic calculation.
The three-dimensional CFD characteristic calculation is to perform three-dimensional viscosity calculation on each working condition point in the working condition range related to the turbine characteristic by using three-dimensional CFD calculation software. The three-dimensional CFD calculation is an N-S equation for solving viscosity, and does not involve empirical constants and loss models required by non-viscous calculation, so that the calculation result precision is high. However, the current three-dimensional CFD characteristic calculation operation is complicated, and a large amount of computer space resources are required to be occupied. Therefore, there is a need to further improve the three-dimensional CFD characteristic calculation.
The above information disclosed in the background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not constitute prior art that is known to a person of ordinary skill in the art.
Disclosure of Invention
The invention aims to provide a CFX software-based three-dimensional CFD automatic calculation method for turbine characteristics, which is simple in calculation process and small in occupied space resource.
In order to achieve the purpose, the technical scheme adopted by the disclosure is as follows:
according to a first aspect of the present disclosure, the present disclosure provides a method for automatically calculating a three-dimensional CFD of a turbine characteristic based on CFX software, comprising:
calculating the working condition of the turbine design point by CFX software to generate a working condition result file of the turbine design point;
defining an initial value of outlet pressure, a reference rotating speed and an initial rotating speed of the turbine;
in the expression of CFX-Pre, defining a rotating speed expression according to the reference rotating speed, the initial rotating speed and the accumulated iteration step number calculated by CFX solution; defining an outlet pressure expression according to the outlet pressure initial value and the accumulated iteration step number calculated by CFX solution;
in the CFX-Pre expression, defining a turbine performance parameter expression;
in the control setting of a solver of CFX-Pre, setting the maximum iteration step number and the convergence standard;
generating a set def file in the CFX-Pre;
and starting iterative computation by taking the working condition result file of the turbine design point as an initial field.
In an exemplary embodiment of the present disclosure, defining a rotation speed expression according to the reference rotation speed, the initial rotation speed, and the cumulative iteration step number of CFX solution calculation includes:
setting each first step length, wherein the rotating speed is increased by 1 rotating speed step value compared with the initial rotating speed, the first step length is 1000-2000 iterative steps, and the rotating speed step value is 5-15% of the reference rotating speed.
In an exemplary embodiment of the present disclosure, the rotation speed expression is:
SpeedR＝R 0 *(α+int(atstep/1000)*γ)[rpm]
wherein speedR is the rotational speed, R 0 The reference rotating speed is alpha, the proportion of the initial rotating speed to the reference rotating speed is atstep, the accumulative iteration step number calculated by CFX solving is atstep, and the proportion of the rotating speed stepping value to the reference rotating speed is gamma.
In an exemplary embodiment of the present disclosure, defining an outlet pressure expression according to the outlet pressure initial value and the cumulative iteration step number calculated by CFX solution includes:
and setting the outlet pressure to be increased by 1 pressure step value than the initial outlet pressure value in every 100 iterative steps, and setting the outlet pressure to return to the initial outlet pressure value in every second step length, wherein the pressure step value is 0.05-0.2Mpa, the second step length is 1000-2000 iterative steps, and the number of iterative steps in the second step length is correspondingly equal to that in the first step length.
In an exemplary embodiment of the present disclosure, the outlet pressure expression is:
Spout＝P 0 +int((atstep-int(atstep/1000)*1000)/100)*β[MPa]，
where Spout is the outlet pressure, P 0 For the initial value of the outlet pressure, atstep is the cumulative number of iteration steps calculated for the CFX solution, and β is the pressure step value.
In exemplary embodiments of the present disclosure, the turbine performance parameters include expansion ratio, percent rotational speed, inlet flow function, and efficiency.
In an exemplary embodiment of the present disclosure, in the solver control setting of CFX-Pre, setting the maximum iteration step number and the convergence criterion includes:
and setting the maximum iteration step number according to the equal rotating speed line number of the turbine to be calculated.
In the exemplary embodiment of the disclosure, the maximum iteration step number is set to be n times of the number of the equal rotating speed lines of the turbine to be calculated, the convergence criterion is set to be that the residual convergence criterion is not greater than 1.0E-8, wherein n is selected from an integer of 1000-2000, and the value of n is correspondingly equal to the number of the iteration steps in the first step size.
In an exemplary embodiment of the present disclosure, generating the set def file in the CFX-Pre further includes:
in the output control setting of CFX-Pre, the turbine performance parameter is set as a monitoring point.
In an exemplary embodiment of the present disclosure, the method for automatically calculating the three-dimensional CFD of the turbine characteristics further includes:
adding a monitoring graph of the monitoring points along with the iteration step in CFX-Solver management;
and exporting the monitoring graph data, and extracting a monitoring point data value to obtain a turbine characteristic calculation result.
The invention provides a CFX software-based three-dimensional CFD automatic calculation method for turbine characteristics, which defines the change relationship of outlet pressure along with the accumulated iteration step number calculated by CFX solution in the expression of CFX-Pre, and the change relationship of rotating speed along with the accumulated iteration step number calculated by CFX solution, and defines the turbine outlet pressure expression and the rotating speed expression, so that in the whole calculation process of the turbine characteristics, the definition of an initial pressure value, a reference rotating speed and an initial rotating speed is only needed once, namely the outlet pressure values of different subsequent working condition points can be obtained through the turbine outlet pressure expression, the rotating speeds of different subsequent working condition points are obtained according to the rotating speed expression, thereby when the calculation of turbine performance parameters is carried out, the automatic joint calculation of each working condition point can be completed, the calculation result of the turbine characteristics at each working condition point can be obtained, the calculation process is simple, and the occupied space resource is less. In addition, the three-dimensional CFD automatic calculation method for the turbine characteristics does not depend on empirical constants and loss models, and the accuracy of the obtained turbine characteristic calculation results is high.
Drawings
The above and other features and advantages of the present disclosure will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.
FIG. 1 illustrates a flow diagram of a CFX software based method for three-dimensional CFD automatic calculation of turbine characteristics in an exemplary embodiment of the present disclosure;
FIG. 2 illustrates a plot of turbo expansion ratio monitoring in an exemplary embodiment of the present disclosure;
FIG. 3 illustrates a turbine percent speed monitoring plot in an exemplary embodiment of the present disclosure;
FIG. 4 illustrates a turbine efficiency monitoring plot in an exemplary embodiment of the present disclosure;
FIG. 5 illustrates a turbine inlet flow function monitoring plot in an exemplary embodiment of the present disclosure.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in 1 or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure.
The same reference numerals in the drawings denote the same or similar structures, and thus a detailed description thereof will be omitted.
The described features, structures, or characteristics may be combined in any suitable manner in 1 or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the embodiments of the disclosure can be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring the primary technical ideas of the disclosure.
The term "said" is used to indicate the presence of 1 or more elements/components/etc.; the terms "comprising" and "having" are intended to be inclusive and mean that there may be additional elements/components/etc. other than the listed elements/components/etc.
In the related art, because the characteristic calculation requires a great number of operating points under different expansion ratios and rotating speeds, and the three-dimensional CFD calculation involves the processes of preprocessing setting such as boundary conditions, iterative calculation to convergence, result post-processing, and the like, if preprocessing setting, calculation, and result post-processing are performed on a per operating point basis, the operation of the characteristic calculation is very complicated, and a large amount of computer space resources are required to store the result file of the three-dimensional calculation.
As shown in fig. 1, the present disclosure provides a method for automatically calculating a three-dimensional CFD of turbine characteristics based on CFX software, comprising the following steps:
step S100, calculating the working condition of a turbine design point by CFX software to generate a working condition result file of the turbine design point;
step S200, defining an outlet pressure initial value, a reference rotating speed and an initial rotating speed of the turbine;
step S300, in the CFX-Pre expression, defining a rotation speed expression according to the reference rotation speed, the initial rotation speed and the CFX calculation accumulated iteration step number; defining an outlet pressure expression according to the outlet pressure initial value and the accumulated iteration step number calculated by CFX solution;
step S400, defining a turbine performance parameter expression in the CFX-Pre expression;
step S500, in the solver control setting of CFX-Pre, setting the maximum iteration step number and the convergence standard;
step S600, generating a set def file in CFX-Pre;
and S700, starting iterative computation by taking the turbine design point working condition result file as an initial field.
The invention provides a CFX software-based three-dimensional CFD automatic calculation method for turbine characteristics, which defines the change relationship of outlet pressure along with the accumulated iteration step number calculated by CFX solution in the expression of CFX-Pre, and the change relationship of rotating speed along with the accumulated iteration step number calculated by CFX solution, and defines the turbine outlet pressure expression and the rotating speed expression, so that in the whole calculation process of the turbine characteristics, the definition of an initial pressure value, a reference rotating speed and an initial rotating speed is only needed once, namely the outlet pressure values of different subsequent working condition points can be obtained through the turbine outlet pressure expression, the rotating speeds of different subsequent working condition points are obtained according to the rotating speed expression, thereby when the calculation of turbine performance parameters is carried out, the automatic joint calculation of each working condition point can be completed, the calculation result of the turbine characteristics at each working condition point can be obtained, the calculation process is simple, and the occupied space resource is less. In addition, the three-dimensional CFD automatic calculation method for the turbine characteristics does not depend on empirical constants and loss models, and the accuracy of the obtained turbine characteristic calculation results is high.
The detailed process of each step in fig. 1 will be explained below with reference to the accompanying drawings.
CFD is the abbreviation of Computational Fluid Dynamics (Computational Fluid Dynamics) and is the product of a combination of modern hydrodynamics, numerical mathematics and computer science. The method approximately expresses integral and differential terms in a fluid mechanics control equation into a discrete algebraic form to form an algebraic equation set, and then solves the discrete algebraic equation set through a computer to obtain a numerical solution on discrete time/space points.
CFX is software under the ANSYS flag specifically used for computational fluid dynamics simulation. The CFX adopts a finite volume method based on finite elements, and absorbs the numerical accuracy of the finite element method on the basis of ensuring the conservation characteristic of the finite volume method.
In step S100, a CFX software is used to calculate a turbine design point condition, and a turbine design point condition result file is generated.
In an exemplary embodiment of the present disclosure, the 1 particular operating state for the turbine performance parameter and geometry is the turbine design point. The design point conditions generally include performance parameters such as turbine outlet pressure, rotation speed, expansion ratio, inlet flow and the like.
In step S200, an outlet pressure initial value, a reference rotation speed, and an initial rotation speed of the turbine are defined.
In an exemplary embodiment of the present disclosure, an initial value of the outlet pressure, a reference rotation speed, and an initial rotation speed of the turbine are defined according to the turbine of the required calculation characteristics. In the exemplary embodiment of the present disclosure, the initial value of the outlet pressure is 0.4MPa, the reference rotation speed is 24000rpm, and the initial rotation speed is 60% of the reference rotation speed, i.e., the initial rotation speed is equal to the reference rotation speed × 60%, and the initial rotation speed is 14400 rpm. It should be noted that the initial value of the outlet pressure, the reference rotation speed, and the initial rotation speed are only exemplary, and the specific values are not limited.
In step S300, in the CFX-Pre expression, a rotation speed expression is defined according to the reference rotation speed, the initial rotation speed, and the cumulative iteration step number calculated by CFX solution; and defining an outlet pressure expression according to the outlet pressure initial value and the accumulative iteration step number calculated by CFX solution.
CFX-Pre, CFX-Slover and CFX-Post are submodules of CFX software for solving fluid mechanics analysis. The CFX-Pre is a preprocessing module, which completes preprocessing setting, and specifically may include boundary condition setting, solver control setting, definition of output data, and the like.
In the disclosed exemplary embodiment, a rotation speed expression and an outlet pressure expression are defined into an expression editor of CFX-Pre, i.e., Expressions of CFX-Pre. Specifically, a rotating speed expression is defined according to the reference rotating speed, the initial rotating speed and the accumulative iteration step of CFX solution calculation; and defining an outlet pressure expression according to the outlet pressure initial value and the accumulated iteration step number calculated by CFX solution. It should be noted that the cumulative iteration step number of the CFX solution calculation is the cumulative iteration step number of the CFX during the solution calculation, and the cumulative iteration step number is a changing value during the solution calculation and increases as the calculation continues.
In an exemplary embodiment of the present disclosure, in step S300, the step of defining a rotation speed expression according to the reference rotation speed, the initial rotation speed, and the cumulative iteration step number calculated by CFX solution includes:
step S310, setting the rotation speed to be 1 rotation speed step value more than the initial rotation speed every first step, wherein the first step is 1000 and 2000 iterative steps, and the rotation speed step value is 5-15% of the reference rotation speed.
For example, the first step is 1000-; or every 1500 iteration step rotating speeds are increased by 1 rotating speed stepping value compared with the initial rotating speed, and the rotating speed stepping value is 15 percent of the reference rotating speed; or the rotating speed of every 2000 iteration steps is increased by 1 rotating speed step value compared with the initial rotating speed, and the rotating speed step value is 10 percent of the reference rotating speed. It should be noted that the number of iteration steps included in the first step length and the rotation speed step value are not in a specific corresponding relationship, for example, when the rotation speed of every 1500 iteration steps is increased by 1 rotation speed step value from the initial rotation speed, the rotation speed step value may be 5% or 15% of the reference rotation speed, and the like.
In an exemplary embodiment of the present disclosure, the base rotation speed is 24000rpm, and the initial rotation speed is 60% of the base rotation speed, i.e., 14400 rpm. The first step length is 1000 iterative steps, the rotating speed of every 1000 iterative steps is increased by 1 rotating speed step value compared with the initial rotating speed, and the rotating speed step value is 10 percent of the reference rotating speed. For example, the cumulative iteration step number of the CFX solution calculation is 6000 steps, 1 rpm step value is added every 1000 steps, and 6 rpm step values 24000 × 10% are added in 6000 steps.
In an exemplary embodiment of the disclosure, the rotational speed expression is:
SpeedR＝R 0 *(α+int(atstep/1000)*γ)[rpm]
wherein speedR is the rotational speed, R 0 The reference rotating speed is alpha, the proportion of the initial rotating speed to the reference rotating speed is atstep, the accumulative iteration step number calculated by CFX solving is atstep, and the proportion of the rotating speed stepping value to the reference rotating speed is gamma. When the rotating speed expression is defined in the actual CFX software, R 0 Can be directly written as a specific value of the reference rotation speed, alpha is directly written as a specific value of the proportion of the initial rotation speed to the reference rotation speed, and gamma is directly written as the rotation speed stepA specific value of the ratio of the value to the reference rotation speed. For example, in exemplary embodiments of the present disclosure, R 0 24000rpm, alpha is 0.6, gamma is 0.1, and the rotating speed expression is as follows:
SpeedR＝24000*(0.6+int(atstep/1000)*0.1)[rpm]
for example, when atstep is 6000 steps,
SpeedR＝24000*(0.6+int(6000/1000)*0.1)[rpm]
＝24000*(0.6+0.6)＝28800rpm
for example, when atstep is 5500 steps,
SpeedR＝24000*(0.6+int(5500/1000)*0.1)[rpm]
＝24000*(0.6+0.5)＝26400rpm
in an exemplary embodiment of the disclosure, in step S300, defining an outlet pressure expression according to the outlet pressure initial value and the cumulative iteration step number calculated by CFX solution includes:
step S320, setting the outlet pressure to be increased by 1 pressure step value than the outlet pressure initial value in each 100 iteration steps, and setting the outlet pressure to return to the outlet pressure initial value in each second step, wherein the pressure step value is 0.05-0.2Mpa, the second step size is 1000-2000 iteration steps, and the number of the iteration steps in the second step size is correspondingly equal to the number of the iteration steps in the first step size.
For example, the pressure step value may be 0.05MPa, 0.1MPa, 0.15MPa, 0.2 MPa. In an exemplary embodiment of the present disclosure, the initial value of the outlet pressure is 0.4MPa, the pressure step value is 0.1MPa, and the outlet pressure is increased by 1 pressure step value per 100 iteration steps, for example, the cumulative iteration step number of the CFX solution calculation is 600 steps, 1 pressure step value is increased per 100 steps, 6 pressure step values are increased per 600 steps, and the outlet pressure at 600 steps is increased by 6 pressure step values than the initial value of the outlet pressure of 0.4MPa by 0.1 MPa. And returning the outlet pressure to the initial value of the outlet pressure every second step length, wherein the second step length is 1000-2000 iterative steps, and the iterative step number in the second step length is correspondingly equal to the iterative step number in the first step length. For example, when the first step size is 1000 iterative steps, the second step size is also 1000 iterative steps, that is, in this step, the outlet pressure returns to the initial value of the outlet pressure every 1000 iterative steps, that is, when the cumulative number of iterative steps calculated by CFX solution is 1000 steps, the outlet pressure when the 1000 steps are iterated returns to the initial value of the outlet pressure of 0.4 MPa.
In an exemplary embodiment of the present disclosure, the outlet pressure expression is:
Spout＝P 0 +int((atstep-int(atstep/1000)*1000)/100)*β[MPa]，
where Spout is the outlet pressure, P 0 For the initial value of the outlet pressure, atstep is the cumulative number of iteration steps calculated for the CFX solution, and β is the pressure step value. It should be noted here that when defining the outlet pressure expression in the actual CFX software, P is 0 The specific value of the initial value of the outlet pressure can be directly written, and the specific value of the pressure stepping value can be directly written. For example, in an exemplary embodiment of the present disclosure, the outlet pressure initial value is 0.4MPa, the pressure step value is 0.1MPa, and the outlet pressure expression is:
Spout＝0.4+int((atstep-int(atstep/1000)*1000)/100)*0.1[MPa]
for example, when atstep is 600 steps,
Spout＝0.4+int((600-int(600/1000)*1000)/100)*0.1[MPa]
＝0.4+0.6＝1MPa。
when the atstep is 1000 steps,
Spout＝0.4+int((1000-int(1000/1000)*1000)/100)*0.1[MPa]
＝0.4MPa。
when the atstep is at a step of 1500,
Spout＝0.4+int((1500-int(1500/1000)*1000)/100)*0.1[MPa]
＝0.4+0.5＝0.9MPa。
in step S400, in the CFX-Pre expression, a turbine performance parameter expression is defined.
The turbine characteristic refers to the variation of performance parameters such as flow rate and efficiency of the turbine along with the expansion ratio and the rotating speed of the turbine. In the step, an expression of the turbine performance parameters is defined, and a calculation result of the turbine performance parameters is obtained through subsequent solving calculation, so that a turbine characteristic analysis result is obtained.
In exemplary embodiments of the present disclosure, turbine performance parameters include expansion ratio, percent rotational speed, inlet flow function, and efficiency. In addition, turbine performance parameters may also include other performance parameters such as inlet flow, power, outlet flow angle, outlet Mach number, and the like. And obtaining an expansion ratio expression according to the outlet pressure expression and the like by giving the inlet total pressure value, wherein the expansion ratio is the inlet total pressure to the outlet total pressure, and the outlet pressure expression represents the outlet static pressure. The percentage rotation speed, i.e. the percentage of the rotation speed to the reference rotation speed with reference to the reference rotation speed, is 0.6 if the initial rotation speed is 60% of the reference rotation speed. Expressions of the inlet flow function, efficiency, inlet flow, power, outlet airflow angle, outlet mach number, and the like can be defined according to the knowledge of fluid mechanics in the prior art, and are not specifically described herein.
In step S500, in the solver control setting of CFX-Pre, the maximum iteration step number and the convergence criterion are set.
In the Solver Control (solution Control) setting of CFX-Pre, the maximum iteration step number and the convergence standard are set. In some embodiments of the present disclosure, step S500 includes:
and setting the maximum iteration step number according to the equal rotating speed line number of the turbine to be calculated. The number of equal speed lines of the turbine to be calculated here means that the number of equal speed lines to be calculated is counted according to the rotating speed condition of the turbine to be calculated, for example, in the exemplary embodiment of the present disclosure, the number of equal speed lines, that is, the number of equal percentage rotating speeds, for example, in some embodiments, the percentage rotating speed to be calculated is 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, the number of equal percentage rotating speed lines is 7, and the number of equal speed lines is also 7. The maximum number of iteration steps can be set from this data 7.
And setting the maximum iteration step number to be n times of the number of the equal rotation speed lines of the turbine to be calculated, wherein n is an integer of 1000-2000, and the value of n is correspondingly equal to the iteration step number in the first step length. For example, when the first step size is 1000 iteration steps, the value of n is also 1000, that is, in this step, the maximum iteration step number is set to be 1000 times of the number of the equal rotation speed lines of the turbine to be calculated, and for an equal rotation speed line of 7, the maximum iteration step number may be set to be 7000 steps.
Further, in the disclosed exemplary embodiment, the convergence criterion is set such that the residual convergence criterion is not greater than 1.0E-8. Here, the convergence criterion set value is extremely small. Therefore, the calculation of each operating point in the full operating condition range of the turbine characteristic calculation can be realized, and the condition points are prevented from stopping because the operating points are not calculated completely and the convergence standard is reached.
In step S600, a set def file is generated in CFX-Pre.
In this step, the Definition files (. def) file contains all parameters set in the CFX-Pre, such as expression setting, Solver control setting, and the like, and can be used for subsequent CFX-Solver solution calculation.
In an exemplary embodiment of the present disclosure, step S600 further includes, before:
step S510, in the output control setting of CFX-Pre, setting the turbine performance parameter as a monitoring point.
In the Output Control setting of CFX-Pre, a turbine performance parameter is set as a monitoring point. In this step, some or all of the turbine performance parameters defined in step S400 are set as monitoring points, which may include expansion ratio, percentage rotation speed, inlet flow function and efficiency, and may also include inlet flow, power, outlet flow angle, outlet mach number, and the like.
In step S700, an iterative calculation is started with the turbine design point operating condition result file as an initial field.
In the step, an initial field file is set, so that iterative convergence is facilitated, and resource occupation is reduced.
In an exemplary embodiment of the present disclosure, the present disclosure provides a CFX software-based three-dimensional CFD automatic calculation method for turbine characteristics, further comprising:
step S800, adding a monitoring graph of the monitoring points along with the iteration step in CFX-solution management;
and S900, exporting the monitoring graph data, and extracting a monitoring point data value to obtain a turbine characteristic calculation result.
In step S800, a monitoring graph of the monitoring points defined in step S510 following the iteration step is added in CFX-Solver management (Manager).
In the exemplary embodiment of the present disclosure, in step S900, after the iterative computation is completed, the monitoring graph data is derived, and the monitoring point data value at the end of each 100 iterative steps is extracted to obtain the turbine performance parameter computation result of each operating point, and finally obtain the turbine characteristic computation result. In one embodiment of the present disclosure, an expansion ratio monitoring plot is obtained as shown in FIG. 2, a percent rotation rate monitoring plot is obtained as shown in FIG. 3, an efficiency monitoring plot is obtained as shown in FIG. 4, and an inlet flow function monitoring plot is obtained as shown in FIG. 5.
The invention provides a CFX software-based three-dimensional CFD automatic calculation method for turbine characteristics, which defines the change relationship of outlet pressure along with the accumulated iteration step number calculated by CFX solution in the expression of CFX-Pre, and the change relationship of rotating speed along with the accumulated iteration step number calculated by CFX solution, and defines the turbine outlet pressure expression and the rotating speed expression, so that in the whole calculation process of the turbine characteristics, the definition of an initial pressure value, a reference rotating speed and an initial rotating speed is only needed once, namely the outlet pressure values of different subsequent working condition points can be obtained through the turbine outlet pressure expression, the rotating speeds of different subsequent working condition points are obtained according to the rotating speed expression, thereby when the calculation of turbine performance parameters is carried out, the automatic joint calculation of each working condition point can be completed, the calculation result of the turbine characteristics at each working condition point can be obtained, the calculation process is simple, and the occupied space resource is less. In addition, the maximum iteration step number is set to be 1000 times of the equal rotating speed line of the turbine to be calculated, and the convergence standard is set to be the residual convergence standard which is not more than 1.0E-8. Therefore, the calculation of each operating point in the full operating condition range of the turbine characteristic calculation can be realized, and the condition points are prevented from being stopped because the operating points are not calculated completely and the convergence standard is met.
It should be noted that although the various steps of the methods of the present disclosure are depicted in the drawings in a particular order, this does not require or imply that these steps must be performed in this particular order, or that all of the depicted steps must be performed, to achieve desirable results. Additionally or alternatively, certain steps may be omitted, multiple steps combined into a 1-step execution, and/or 1 step broken down into multiple step executions, etc., are all considered part of this disclosure.
It is to be understood that the disclosure is not limited in its application to the details of construction and the arrangements of the components set forth in the specification. The present disclosure is capable of other embodiments and of being practiced and carried out in various ways. The foregoing variations and modifications are within the scope of the present disclosure. It should be understood that the disclosure disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present disclosure. The embodiments of this specification illustrate the best mode known for carrying out the disclosure and will enable those skilled in the art to utilize the disclosure.
Claims (8)
1. A CFX software-based three-dimensional CFD automatic calculation method for turbine characteristics is characterized by comprising the following steps:
calculating the working condition of the turbine design point by adopting CFX software to generate a working condition result file of the turbine design point;
defining an initial value of outlet pressure, a reference rotating speed and an initial rotating speed of the turbine;
in the expression of CFX-Pre, defining a rotating speed expression according to the reference rotating speed, the initial rotating speed and the accumulated iteration step number calculated by CFX solution; defining an outlet pressure expression according to the outlet pressure initial value and the accumulated iteration step number calculated by CFX solution;
in the CFX-Pre expression, defining a turbine performance parameter expression;
in the control setting of a solver of the CFX-Pre, setting the maximum iteration step number and the convergence standard;
generating a set def file in the CFX-Pre;
starting iterative computation by taking the turbine design point working condition result file as an initial field;
wherein, the step of solving the calculated accumulated iteration steps according to the reference rotating speed, the initial rotating speed and the CFX to define a rotating speed expression comprises the following steps:
setting each first step that the rotating speed is increased by 1 rotating speed stepping value compared with the initial rotating speed, wherein the first step is 1000-2000 iterative steps, and the rotating speed stepping value is 5-15% of the reference rotating speed;
defining an outlet pressure expression according to the outlet pressure initial value and the accumulated iteration step number calculated by CFX solving comprises the following steps:
and setting the outlet pressure to be increased by 1 pressure step value every 100 iteration steps, and setting the outlet pressure to return to the outlet pressure initial value every second step, wherein the pressure step value is 0.05-0.2Mpa, the second step is 1000-2000 iteration steps, and the number of iteration steps in the second step is correspondingly equal to that in the first step.
2. The CFX software-based three-dimensional CFD automatic calculation method for the turbine characteristics is characterized in that the rotating speed expression is as follows:
SpeedR＝R 0 *(α+int(atstep/1000)*γ)[rpm]
wherein speedR is the rotational speed, R 0 The reference rotating speed is alpha, the proportion of the initial rotating speed to the reference rotating speed is atstep, the accumulative iteration step number calculated by CFX solving is atstep, and the proportion of the rotating speed stepping value to the reference rotating speed is gamma.
3. The CFX software-based three-dimensional CFD automatic calculation method for turbine characteristics according to claim 1, wherein the outlet pressure expression is as follows:
Spout＝P 0 +int((atstep-int(atstep/1000)*1000)/100)*β[MPa]，
where Spout is the outlet pressure, P 0 For the initial value of the outlet pressure, atstep is the cumulative number of iteration steps calculated for the CFX solution, and β is the pressure step value.
4. The CFX software based three-dimensional CFD automatic calculation method of turbine characteristics according to claim 1, wherein said turbine performance parameters include expansion ratio, percent rotation speed, inlet flow function and efficiency.
5. The CFX software-based three-dimensional CFD automatic calculation method for turbine characteristics according to claim 1, wherein in the solver control setting of CFX-Pre, setting the maximum iteration step number and the convergence criterion comprises:
and setting the maximum iteration step number according to the equal rotating speed line number of the turbine to be calculated.
6. The CFX software-based three-dimensional CFD automatic calculation method for the turbine characteristics is characterized in that the maximum iteration step number is set to be n times of the number of the equal rotation speed lines of the turbine to be calculated, the convergence standard is set to be that the residual convergence standard is not more than 1.0E-8, wherein n is an integer of 1000-2000, and the value of n is correspondingly equal to the iteration step number in the first step size.
7. The method for three-dimensional CFD automatic calculation of turbine characteristics based on CFX software according to claim 1, wherein before generating the set def file in CFX-Pre, further comprising:
in the output control setting of CFX-Pre, the turbine performance parameter is set as a monitoring point.
8. The CFX software based three-dimensional CFD automatic calculation method for turbine characteristics according to claim 7, further comprising:
adding a monitoring graph of the monitoring points along with the iteration step in CFX-Solver management;
and exporting the monitoring graph data, and extracting a monitoring point data value to obtain a turbine characteristic calculation result.
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