## Definition of Leading/Trailing Edge Points

## Definition of Leading/Trailing Edge Points

(OP)

Hi All,

New to the forum and hoping I might be able to get some assistance. I work for a manufacturing company and we have just started large scale production of engine turbine blades. To meet the needs of our customers we are working on developing our own inspection and report generation software. I am tasked with most of this and am looking for help with the definition of leading edge and trailing edge points.

I am currently working with point curves generated from the 2D section profile (X,Y) of the blade. This section is, of course, an airfoil. In order to determine parameters such as chord length I need to determine the leading edge and trailing edge points. The only way I know how these are defined is from the mean camber line (MCL).

Method for MCL Determination:

Construct a MCL for my data using a modified voronoi approach to inscribed circles. This works until approximately 1 radius away from the edge.

Extrapolate a straight line from end point, find normals along the line and make sure the points are half the normal.

Fit new points to a polynomal, and contstruct normals. Make sure points are located halfway along the normal.

Iterate last step until convergence.

This method works reasonably well but my chord length still has error on the order of .005". I really need to be able to obtain values in the .0002" range of accuracy.

I am wondering if anyone here has experience with MCL or LE/TE point determination for an arbitrary airfoil. If not, perhaps you might able to assist with alternate MCL definitions to play with?

Thank YOU!

New to the forum and hoping I might be able to get some assistance. I work for a manufacturing company and we have just started large scale production of engine turbine blades. To meet the needs of our customers we are working on developing our own inspection and report generation software. I am tasked with most of this and am looking for help with the definition of leading edge and trailing edge points.

I am currently working with point curves generated from the 2D section profile (X,Y) of the blade. This section is, of course, an airfoil. In order to determine parameters such as chord length I need to determine the leading edge and trailing edge points. The only way I know how these are defined is from the mean camber line (MCL).

Method for MCL Determination:

Construct a MCL for my data using a modified voronoi approach to inscribed circles. This works until approximately 1 radius away from the edge.

Extrapolate a straight line from end point, find normals along the line and make sure the points are half the normal.

Fit new points to a polynomal, and contstruct normals. Make sure points are located halfway along the normal.

Iterate last step until convergence.

This method works reasonably well but my chord length still has error on the order of .005". I really need to be able to obtain values in the .0002" range of accuracy.

I am wondering if anyone here has experience with MCL or LE/TE point determination for an arbitrary airfoil. If not, perhaps you might able to assist with alternate MCL definitions to play with?

Thank YOU!

## RE: Definition of Leading/Trailing Edge Points

## RE: Definition of Leading/Trailing Edge Points

We deal with (X,Y) data because a coordinate measuring machine is used to obtain data points after manufacturing. My background in ME/Math so understanding a bit more of airfoil properities would be helpful.

If this approach to constructing airfoils seems elementary, could you please recommend a better way to do this with the measured data? As we are a manufactuing company we have no control over airfoil shape.

## RE: Definition of Leading/Trailing Edge Points

This process (the determination of a MCL from arbitrary data) is not well documented and seems not common. I have a found a few journals but the implementation of the topics was not successful.

Perhaps there are other ways to define the LE/TE points without the MCL?

## RE: Definition of Leading/Trailing Edge Points

## RE: Definition of Leading/Trailing Edge Points

## RE: Definition of Leading/Trailing Edge Points

Cheers

Greg Locock

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## RE: Definition of Leading/Trailing Edge Points

i would have thought that picking points with a vertical (ie along the Y axis) tangent would be adequate to define the LE and TE.

## RE: Definition of Leading/Trailing Edge Points

## RE: Definition of Leading/Trailing Edge Points

if you're doing engineering design development, just be consistent in your definition. if you've got several test results/prototypes, the best definition is the one that matches your data best and makes the best predictions.

## RE: Definition of Leading/Trailing Edge Points