Removal of Aircraft.Engine.REFERENCE_DIAMETER#1047
Open
xjjiang wants to merge 30 commits intoOpenMDAO:mainfrom
Open
Removal of Aircraft.Engine.REFERENCE_DIAMETER#1047xjjiang wants to merge 30 commits intoOpenMDAO:mainfrom
xjjiang wants to merge 30 commits intoOpenMDAO:mainfrom
Conversation
…or engine sizing. still a work in progress.
…to engine_ref_diameter
xjjiang
changed the title
ehariton
reviewed
Mar 31, 2026
jkirk5
reviewed
Apr 17, 2026
Contributor
jkirk5
left a comment
jkirk5
left a comment
There was a problem hiding this comment.
One quick request before approval
Co-authored-by: Jason Kirk <110835404+jkirk5@users.noreply.github.com>
jkirk5
approved these changes
Apr 17, 2026
github-merge-queue
bot
removed this pull request from the merge queue due to failed status checks
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Summary
Engine reference diameter never existed in GASP. This PR replaces it with a different algorithm.
Suppose
AE= Engine cross-sectional area (inlet/frontal area). The current GASP algorithm computesAEas follows:AE = 0.3×WG/1500/ENP, whereWGis the gross weight andENPis the number of engines. The factor0.3is the Thrust-to-Weight ratio and1500.0is engine size constant.From our existing engine library, we establish the following table:
See the graph below:
Today’s engines are in the 1.4 to 1.65 range.
If we know the fan pressure ratio, then we can do a curve fitting (polynomially or exponentially):
The problem is that the fan pressure ratio is not always available. Notice that for the modern engines, this ratio usually stays in the upper range in which a value of
800for the engine size constant is pretty close. Therefore, it is recommended that we pick800to replace1500. When we do so, we get an equation:AE = 0.3×WG/800/ENP = 0.000375×WG/ENPThis result is very close to our models.
Related Issues
Backwards incompatibilities
None
New Dependencies
None