OpenLaval — Supersonic Impulse Turbine Blade Generator

OpenLaval is a numerical tool for generating supersonic impulse turbine blade geometry using the method of characteristics and classical vortex‑flow theory.

It implements the design approach described in several NACA and NASA technical reports and produces upper and lower blade surfaces, interpolated contours, and derived quantities such as solidity.

This repository is a refactored and modular version of the original project published by Interstellar Technologies Inc.:
https://github.com/istellartech/OpenLaval

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Features

• Supersonic impulse turbine blade design based on Prandtl–Meyer expansion theory
• Method of characteristics for upper and lower surface construction
• Circular arcs, concave/convex transitions, and leading‑edge shaping
• Interpolated blade contour suitable for CAD or CFD preprocessing
• Aerodynamic performance evaluation (isentropic loss coefficients, shock losses, turning efficiency, curvature smoothness)
• Benchmarking and validation against historical NTRS cascade datasets
  (NACA RM L52B06, NASA TN D‑4421/4422)
• Automated blade performance optimization workflows using scipy.optimize
• Export of geometry, metadata, and CSV files
• Export of CAD/CFD formats (.dat and coordinate CSVs)
• Plotting of raw geometry, interpolated contours, thickness, camber, curvature, combined curvature, raw‑vs‑interpolated, asymmetry, and Prandtl–Meyer diagrams
• Automated batch processing of multiple configuration files
• Parametric design sweeps with CSV summary generation
• Validation of design constraints and configuration parameters
• Configuration through a simple TOML file
• Asymmetric blade support

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Installation

OpenLaval requires Python 3.12 or newer.

Install in editable mode:

pip install -e .

This installs the openlaval CLI.

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Usage

Prepare a configuration file, for example:

example.toml

Or store multiple configurations under a directory:

configs/example.toml
configs/asymmetric.toml
configs/high_mach.toml

Compute geometry

openlaval run configs/example.toml

Plot the interpolated blade contour

openlaval plot configs/example.toml

If save_fig = true, the plot is saved to:

result/<name>_contour.png

Export geometry, metadata, and CSV files

openlaval export configs/example.toml --outdir result/

This writes:

• interpolated geometry CSV
• raw geometry CSV
• metadata JSON
• optional Excel file (save_excel = true)

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Additional plot commands

All plots respect save_fig = true and write PNG files to result/.

Raw geometry

openlaval plot-raw <config>

Thickness distribution

openlaval plot-thickness <config>

Camber line

openlaval plot-camber <config>

Curvature distribution

openlaval plot-curvature <config>

Combined curvature view

openlaval plot-curvature-combined <config>

Raw vs interpolated

openlaval plot-raw-vs-interp <config>

Asymmetry

openlaval plot-asymmetry <config>

Prandtl–Meyer diagram

openlaval plot-nu <config>

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Advanced CLI operations

Validate configuration

openlaval validate configs/example.toml

Evaluate blade performance

openlaval evaluate configs/example.toml

Validate against cascade data

openlaval validate-cascade configs/example.toml

Automated optimization

openlaval optimize configs/example.toml

Export CAD and CFD formats

openlaval export-cad configs/example.toml --outdir result/

Batch processing

openlaval batch "configs/*.toml" --output-dir batch_results/

Parameter sweep

openlaval sweep configs/example.toml --param mach_in --start 1.5 --end 2.5 --steps 5 --output-dir sweep_results/

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Input parameters

The configuration file defines:

• specific heat ratio
• inlet and outlet Mach numbers
• inlet flow angle
• symmetric or asymmetric Prandtl–Meyer angles
• leading‑edge parameters
• number of interpolation points
• output options (save_fig, save_excel)

See example.toml for a reference.

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References

OpenLaval implements the design methods described in:

1. NACA RM L52B06 — Application of Supersonic Vortex‑Flow Theory to the Design of Supersonic Impulse Compressor or Turbine‑Blade Sections
2. Design of Turbine Blades Suitable for Supersonic Relative Inlet Velocities — Part I: Theory and Design
3. Design of Turbine Blades Suitable for Supersonic Relative Inlet Velocities — Part II: Experiments, Results and Discussion
4. NASA TN D‑4421 — Analytical Investigation of Supersonic Turbomachinery Blading: I — Computer Program for Blading Design
5. NASA TN D‑4422 — Analytical Investigation of Supersonic Turbomachinery Blading: II — Analysis of Impulse Turbine‑Blade Sections

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Status and future work

The refactored version provides a modular structure suitable for extension.

Possible future additions:

• Additional export formats: STEP, DXF, STL using libraries like trimesh, CadQuery, or gmsh.