Reverse Engineering

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Reverse Engineering

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Reverse Engineering (RE) is the process transforming 3D geometry from neutral file formats (STEP, IGES, Parasolid, BREP) into a parametric CFturbo model.

The process is semi-automatic and consists of the following basic stages:

1.Creating/opening a CFturbo-project considering the desired machine type

2.Specifying the design point and the direction of impeller rotation of the 3D-model to be redesigned (Global setup)

3.Defining 3D geometry to be redesigned

4.Specifying parameters for automatic computation of the CFturbo model

5.Manual adjusting the CFturbo model to improve alignment with the initial 3D geometry

The stages 1. and 2. serve the purpose of specifying the turbomachinery's operating point as usual. The stages 3. and 4. are performed inside a separate dialog enabling the user to create a CFturbo model quickly and efficiently. In stage 5. the user can modify the redesigned CFturbo-model as needed within the ordinary design process (impellers, stators).

RE-dialog

The RE-dialog is divided into the following parts:

1.Steps (top)

selecting the current active RE-step (loading 3D geometry, meridional redesign, blade redesign)

contains information related to the current step

2.Imported geometry (left)

loading external 3D geometry

displaying the imported 3D geometry

aligning geometry to 3D coordinate system of CFturbo model

specifying CFturbo semantics for related geometry-elements (e. g. hub, shroud, blade)

3.Redesigned geometry (middle)

presenting computation results of the CFturbo model as 3D geometry and meridional view

4.Settings (right)

specifying parameters for computation of the CFturbo model

5.Message tree (bottom right)

contains information, warnings and errors occurred during the RE-process
 

 

Detailed description of the import process

1. Vorbereiten des CFturbo-Projektes

Creating/opening a CFturbo-project considering the desired machine type

Within Global setup:

oSpecifying the design point suitable for the model to be redesigned

oSpecifying the rotation direction of the model to be redesigned (rotation direction must coincide with the definition for the CFturbo-project)

 

2. Load external 3D geometry

Preconditions:

oRE-step Import must be selected at the top

oinput geometry must be represented by parametric surface data
(e. g. B-Spline surface, Cylindrical surface, etc.)

oinput geometry can be defined within a single or multiple files representing neutral file formats STEP, IGES, Parasolid or BREP

Load geometry by clicking Load CAD data button or via drag & drop from a file explorer into the 3D-view.

Loaded geometry is displayed in the 3D view and contained geometry elements are listed in the model tree left.

3. 3D alignment of loaded 3D geometry

In order to obtain an accurate CFturbo model the loaded geometry has to be aligned sufficiently to the 3D coordinate system of the CFturbo-model.

This essentially includes aligning rotation/symmetry axis of loaded geometry with the z-axis of the global coordinate system.

Achieving a valid alignment can directly be done inside the Imported geometry section using Transformation panel.

4. Defining CFturbo-semantics on geometry elements

In order to compute a CFturbo model from external 3D geometry a classification of imported 3D faces representing a specific CFturbo model part (e. g. hub, shroud, blade) must be applied (mapping).

Mappings are applied context sensitive related to the currently selected RE-step (Meridian: Hub, Shroud/Tip, Blade: Main blade, Splitter blade) at the top.

This can be achieved by selecting a single or multiple 3D face(s) in the 3D view or model tree and using one of the following options:

oopening the context menu by clicking right mouse button and selecting an appropriate CFturbo model part (see left image below)

oclicking buttons representing CFturbo model parts next to the model tree (see left image below)

ousing drag & drop of a model tree node from the Imported geometry section onto the model tree node related to a CFturbo model part in the Redesigned geometry section (see right image below)

Mappings of 3D face(s) to CFturbo-model parts are represented by an information in the model tree of the Imported geometry section and by explicit nodes in the model tree of the Redesigned geometry section.

Mappings can be deleted using one of the following options:

oopening the context menu of the related tree node in the Redesigned geometry section and choosing the option Remove mapping

oclicking button Remove mapping next to the model tree

 

5. Computation of CFturbo model

Updating redesigned model:

owithin RE-step Meridian: computation of the CFturbo model is performed automatically related to user inputs

owithin RE-step Blade: computation of the CFturbo model is started manually by pressing Update design in the Settings section or is performed automatically related to user inputs in case of activated Automatic design update

oAutomatic computations are triggered by adding/removing assignments of 3D-faces to CFturbo model parts and by changing parameters in the Settings section

Parameters:

RE-step

Parameter

Description

Meridian

Unshrouded

Closed (shrouded) or open (unshrouded) geometry at blade tip side

Tip clearance

Gap between blade tip and casing

Extend shroud at inlet/outlet

In case the computed Shroud contour is too short in order to obtain a valid Meridian, it can be extended to user-defined z,r coordinates.

With blades [Stator only]

Definition of a vaned or vaneless stator

Blade

Number of blades

Defines the number of blades of the CFturbo model.

Splitter blades

Defines whether geometry has splitter blades.

Number of spans

Defines number of intersections of the user-defined blade geometry used for blade profile computation.

Offset Hub/Shroud/Tip

Blade intersections are evenly distributed between Hub and Shroud. The area of intersections can be limited by offsets on Hub- and on Shroud-/Tip-side in order to avoid inaccurate blade profiles due to blade root fillets.

Suggestion: Remove blade root fillets from initial CAD-data, if possible.

Blade edge shape (Leading/Trailing edge)

Defines the shape of the Leading/Trailing edge of the user-defined blade geometry (blade profile computation depends on shape of blade's Leading/Trailing edge).

Results of computations are displayed inside the Redesigned geometry section:

o2D contours in z,r coordinate system inside 2D diagram:

Hub / Shroud / Tip contours

Blade's Leading / Trailing edge

Spans (light grey: contours for blade intersection; black: valid blade intersection; orange: invalid blade intersection)

o3D design model in the 3D-view (incl. model tree)

oIndication of validity of user-defined input geometry assigned to CFturbo model parts by model tree node color
(green: valid, red: invalid/incomplete)

oWarnings/Errors during computation inside the message list bottom right

6. Finalization of import process

After computation of a valid CFturbo model the Reverse engineering dialog can be closed by pressing OK button (irreversible)

Now the CFturbo project contains the new component which has to be activated finally

Example

In this section the RE-process from initial input geometry to a CFturbo design is documented for a mixed-flow pump exemplarily. Any redesigned CFturbo model can further be modified as needed inside the ordinary design process.

1. Preparing the CFturbo-project

Creating a new CFturbo-project

 

Specifying the design point and direction of rotation within Global setup

Adding a new component and specifying the import-format

   

2. Loading and preparing external 3D geometry

load external 3D geometry from neutral 3D file formats

align loaded geometry with the coordinate system of the CFturbo model

ocollinear alignment of rotation axis with the z-axis

ofluid flow direction in positive z-axis direction (for turbines: opposite direction!)

check whether desired rotation direction of the redesigned model fits the project's rotation direction defined in Global setup
(If that's not the case project's rotation direction must be changed inside Global setup before performing the RE-process. This can't be corrected afterwards!)

3. Meridional redesign

Selection of Step ❷ Meridian

Map 3D-faces to Hub / Shroud

It's not necessary to select all 3D-faces representing the complete hub-/shroud-surface. Instead a single face covering the surface from inlet to outlet is sufficient.

4. Blade redesign

Selection of Step ❸ Blade

Map 3D-faces of a single blade to Main blade

select the Blade edge shape of the loaded blade geometry (Round, Angular)

choose sufficient Blade intersection parameters

odefault Number of spans is sufficient in general

ooffsets can be increased in case of large blade root fillets (optional)

press Update design in order to compute the redesigned geometry

5. Finalization

close RE-dialog by pressing OK after a valid design model is computed
(initially opened/created project now contains the redesigned CFturbo-model)

activate the redesigned component (in order to modify the design)

save the created design by saving the project

 

Possible warnings

Problem

Possible solutions

Hub / Shroud: Rotation axis of selected faces not collinear with global z-axis.

3D-alignment of specified Hub/ Shroud faces is inaccurate. Symmetry axis is not collinear with global z-axis.

Update 3D-transformation of imported geometry by aligning symmetry axis to global z-axis.

Calculation of following blade profile(s) failed: [span number(s)].

Cutting selected blade faces by span surfaces results in open blade profile(s). Redesigned blade shape may differ significantly from given blade faces.

Ensure there are no gaps between specified blade faces in the range of span surfaces.

Improve redesigned blade shape manually in the ordinary design process after finishing the RE-process.

M-distribution of following meanline(s) is not strictly increasing: [span number(s)].

Unsupported meanline shape (no strictly increasing m-distribution in m,t-coordinate system). Redesigned blade shape may differ significantly from given blade faces.

Improve redesigned blade shape manually in the ordinary design process after finishing the RE-process.

Hub / Shroud / Blade tip / Main blade / Splitter blade:
No valid geometry defined.

A valid Hub / Shroud / Blade tip / Main blade / Splitter blade could not be computed due to insufficient or not defined geometry.

Map loaded 3D-faces to Hub / Shroud / Blade tip / Main blade / Splitter blade.

Check whether mapped geometry indeed represents Hub / Shroud / Blade tip / Main blade / Splitter blade.

Ensure correct 3D-alignment of specified faces with the global coordinate system of the CFturbo model.

No valid Hub / Shroud / Blade tip contour could be computed.

A 2D meridional contour couldn't be computed from given 3D-faces.

Ensure all specified faces represent the Hub and Shroud/ Blade tip of the model.

Ensure correct 3D-alignment of specified faces with the global coordinate system of the CFturbo model.

Shroud / Blade tip has self-intersections.

2D meridional contour intersects itself.

Reduce tip clearance or change shroud extension.

Zero length meridional contour(s).

2D meridional contour of Inlet / Outlet has zero length.

Ensure specified faces for Hub and for Shroud/ Blade tip are not connected to each other.

Meridional contours intersect each other.

2D meridional contours of Hub and Shroud intersect each other.

Ensure all specified faces represent the Hub and Shroud/ Blade tip of the model.

Update point of extension in case of activated Shroud extension.

Calculation of blade profiles failed.

A redesigned blade could not be computed due to too less successfully computed blade profiles (at least two valid blade profiles must be available).

Ensure there are no gaps between specified blade faces in the range of span surfaces.

Ensure all specified faces represent the Main/Splitter blade of the model.

Ensure blade does not exceed meridional boundaries.

Unconnected blade faces selected.

There are blade faces specified not being connected to others.

Ensure specified blade faces are connected to each other.