Mixed-Flow Turbine Design Software – AxSTREAM® Platform Overview
The AxSTREAM® platform for multidisciplinary turbomachinery design, analysis and optimization software tools provides a fully integrated and streamlined solution for the complete flow path design process of radial-axial (mixed-flow) turbines.
Starting from the preliminary design (defining basic machine performance from just a few simple parameters such as geometrical constraints, inlet/outlet boundary conditions), AxSTREAM® progresses through a 1D inverse task solver optimizer, to continue with meanline (1D) and axisymmetric (2D) analysis, profiling and 3D blade design, 3D finite element analysis (FEA) for structural calculations, secondary air flow hydraulic and thermal calculations, rotor design, bearing analysis, rotor dynamics and 3D CFD calculations.
When the radial-axial flow turbine design project is finished, AxSTREAM® provides easy export of the blade geometry and its attachments (root, disk, wires, wheel and shroud) to the most common file formats allowing users to link with their existing capabilities for further analyses or creation of manufacturing drawings.
The tasks user can solve with AxSTREAM® include:
- Design new radial-axial turbines from scratch
- Analyze existing mixed-flow turbines and their performance at design and off-design conditions
- Redesign, optimize, rerate and upgrade existing radial and axial turbines/components
- Reverse engineer radial-axial turbine designs
- Troubleshoot and correct efficiency/reliability issues in existing hardware
As a fully integrated turbomachine design software platform, the AxSTREAM® platform provides users with the full array of axial and radial turbine design software solutions, whatever the compressible or incompressible working fluid (steam, gas, mixtures, organic fluids, refrigerants, sCO2, combustion products, etc.), across all of the crucial design stages for any number of stages and modules.
Loss models for profile, secondary, transient and leakages losses can be independently selected for each flow path element from a few standard ones (like Mitrohin-Stepanov, Craig-Cox or Kacker-Okapuu), from some corrected based on SoftInWay Inc experience or even customized as desired by the users.
The mixed-flow turbine Preliminary Design procedure is used to create thousands of machine flow path designs from scratch within seconds from a set of boundary conditions, geometrical parameters and constraints to design a radial turbine stage followed by any number of axial turbine stages.
AxSTREAM® can design mixed-flow turbines, with or without any pre-loaded profiles (special ATLAS profile database license required to design machines from scratch using specific profiles), with prismatic (cylindrical) or twisted blades, multiple extractions/injections, inter-stage heat exchangers, impulse & reaction designs, etc. for any number of stages and modules.
The Design Space Explorer allows the user to explore a set of radial and axial turbine stage design solution points generated with the Solution Generator. This gives users the possibility to select appropriate solutions by specifying different types of machine constraints and limitations.
The Post-design module provides the user with capabilities to adjust geometric parameters, pressure and heat drop distributions on the Mollier or the machine endwalls contour using splines, all while retaining the desired boundary conditions. An S1/S2 flow path adjustment option enables users to optimize separate components for efficiency and/or structural constraints based on variation of profile chord and relative pitch. The amount of reaction can also be optimized to ensure structural integrity of the machine under operation with very dense fluids.
The Streamline solver module allows performing meanline (1D) or axisymmetric (2D) calculation of turbomachines to determine streamwise and spanwise distribution of kinematics, thermodynamics and loss parameters as well as leakages and secondary air flows for a given set of boundary conditions.
AxSTREAM® is fully capable of mixed-flow turbine optimization calculations including through the use of a DOE approach (Design Of Experiment) in the AxPLAN module on both the axial and radial components.
This module uses the meanline and streamline solvers previously mentioned to optimize a given geometry by performing various tasks. This experiment planning option can be run for any combination of input and output parameters within hundreds available.
This AxSTREAM® module called AxMAP also uses the meanline and streamline solvers presented but in the present case they are used to automatically generate performance maps for any number of variables; this includes for example the dependency of efficiency on rotation speed and pressure ratio, the influence of throat and clearance degradation over time on machine performance, etc.
In addition to the map and AxSTREAM® project results experimental results can be stored for comparison purposes.
For Mixed-flow turbines the profiling of the blades in AxSTREAM® is performed individually for axial and radial components. Both are used to create and edit 3D airfoils using a wide range of geometric tools and interactive charts that allow users to configure the turbine blades easily.
The AxSTREAM®’s Axial Profiler and Blade Design software module includes several optimization methods and a potential flow solver which automatically calculates the distribution of several parameters along the axial turbine profile outline. This module can be used for 3D blade design, shaping and stacking (lean, sweep, etc.) Profiles can even be stored to/imported from the ATLAS Profile Database for use in different sections, blades or even projects.
The AxSTREAM®’s Radial Profiler and Blade Design software module allows designers to independently control beta, theta and thickness distributions at different sections of the radial blade with curvature monitoring. Forward and backward sweep can even be created. Leading and trailing edges can be cut-off, circular or elliptical as desired for 3D blades, ruled-surface blades and prismatic blades.
Finalized geometries can be exported in 3D to numerous CAD, CAE formats.
Once the aerodynamic shape of turbomachinery blades has been completed the AxSTRESS module inside AxSTREAM® can be used to perform express 3D structural, modal and harmonic analysis as well as Campbell and interference (SAFE) diagrams of the blades and their attachments (wheels, disks, roots, shrouds, wires) using a finite element analysis (FEA) method for both axial and radial components. Hot-to-cold and cold-to-hot calculations can also be performed.
Mixed-flow turbine boundary conditions are automatically taken from the corresponding AxSTREAM® project to optimize the aero-mechanical iteration process. Blade attachments can be added to the 3D blade providing the opportunity to analyze the complete 3D model without leaving AxSTREAM®. An automated mesh generator is included inside the module which allows refinement of cells in each part of the geometry.
Post-processing capabilities are pretty extensive and allow reviewing the stress and displacement values in different directions for any calculated mode on the blade surface and inside the blade.
Upon successful analysis the blade and its attachments can be exported for additional post-processing and manufacturing drawings creation.
AxSTREAM®’s Computational Fluid Dynamics (CFD) software, AxCFD, can be used for 3D flow analysis in blade-to-blade channels of mixed-flow turbines, for any given fluid, for subsonic, transonic and supersonic flows, using full 3D CFD formulation (Navier-Stokes, viscous with various turbulence models (standard k-e, k-e RNG, k-w, k-w SST models)). All of the data from the current AxSTREAM® project is transferred and used automatically by AxCFD to save significant time in the pre-processing phase while preventing human errors.
The mesh quality can be controlled at multiple locations to ensure the automated, embedded mesh generator produces a high quality segmentation of the blade channels for an individual row, stage or for the entire mixed-flow turbine.
Computations can be run for a given spanwise section throughout the domain or for the full 3D geometry.
To enhance the turbomachinery design process all the way through rotor dynamics the Rotor Design module can be used.
It allows opening an AxSTREAM® project to automatically import the flow path it contains. Blade attachments can then be imported from the AxSTRESS FEA tool where they were designed so that the rotor (shaft) geometry can be generated for given materials while accounting for structural constraints.
The resulting shaft geometry and its respective materials can then be automatically recognized in the AxSTREAM® RotorDynamics tool along with the blades and their attachments which are imported as mass-inertia elements.
AxSTREAM®’s Bearing software allows users to analyze detailed models of bearings of different configurations.
Steady-state, transient, and map analysis can be performed to accurately calculate the bearings different hydrodynamic and mechanical characteristics. The software features a flexible geometry configurator to model features such as pockets, lobes, oil supply channels, etc.
The static equilibrium and the bearing hydrodynamic characteristics including everything required to perform rotor dynamic calculations can be calculated for one or several rotation speeds and operation stability can be concluded.
Export of calculated projects allows automatic recognition of damping and stiffness coefficients in AxSTREAM® RotorDynamics.
The AxSTREAM® RotorDynamics software performs vibrational analysis (both lateral and torsional) of radial and axial turbine rotors (steam, gas, etc.) as well as centrifugal and axial compressor rotors, turbocharger trains, generators, electric motors, etc.
This versatile software can perform several types of analysis including Static Rotor Deflection, Lateral Critical Speeds calculation, Critical Speed Maps, Damped Unbalance Response, Train Torsional Modal and Transient, and Stability calculations.
Mixed-flow turbine cooling flows and secondary flows can be analyzed easily using AxSTREAM® NET. Users can benefit from a flexible modeling and representation of any fluid path and solid structure as a set of 1D elements which can be connected to form a thermal-fluid network whether the final blade geometry is known or unknown.
AxSTREAM® NET can even be used to model the entire thermal-fluid network of a complete gas turbine with compressor, extractions, injections, etc. for compressible and incompressible pure fluids and mixtures.
AxSTREAM®’s mixed-flow turbine reverse engineering module, AxSLICE, is used for the extraction of profile geometry from an axial or radial blade’s 3D model in STL, IGES or CURVE formats as a CAD file with surfaces or cloud of points obtained by 3D laser scan.
The recognized properties can immediately be loaded into an AxSTREAM® mixed-flow turbine project to calculate its performance, kinematic and thermodynamic parameters and losses at design point and off-design conditions using the meanline solver (1D), streamline solver (2D), or AxCFD (3D). In addition stress calculations on the recognized geometry can be performed as well as rerates, upgrades, optimizations, etc.