# Use of Design point for a gas turbine engine

by avinod4all
Tags: design, engine, point, turbine
 P: 8 In order to test the performance of a specific engine, is it necessary to find a design point? If so could anyone tell me how to find the design point for gas turbine engine and suggest any useful materials that gives good information about Design point performance. Thank you!
 P: 478 Generally when testing engines part of the criteria is that it should meet the design point, usually, power and heat rate at a set of specified inlet conditions. There is no reason why you couldn't test an engine just to develop a performance curve, but it's an expensive way to get something that the manufacturer should be able to provide.
 P: 8 Thank you! I want to draw a design point for a turbofan engine using a carpet plot, can i draw graph to find out the design point just by using the range of BPR and FPR values?
 P: 478 Use of Design point for a gas turbine engine Sorry you've lost me, what are BPR and FPR values? Are you trying to design an engine or do you have engine data and want to analyse it?
P: 8
 Quote by Jobrag Sorry you've lost me, what are BPR and FPR values? Are you trying to design an engine or do you have engine data and want to analyse it?
BPR- Bypass ratio; FPR- Fan pressure ratio
I am trying to develop a model of an existing engine and later, test the outputs with the original data. So first, I am looking to find the design point of the engine.
 P: 490 I'm confused as to what you are trying to do. The customer will specify the design point. Normally is is something like a sea level take off under full load. Then they will request best performance on various secondary points. Then you discuss trade offs. On a commercial airline application, the customer might make the primary design point "best fuel ecconomy at cruise," which is at idle power at altitude; but then also specify what worst case take off loads are.
P: 87
 Quote by avinod4all Thank you! I want to draw a design point for a turbofan engine using a carpet plot, can i draw graph to find out the design point just by using the range of BPR and FPR values?
Hi there,
i don't think u can obtain the design point just by predicting/from previous data from BPR and FPR, it should be an overall pressure ratio and TET as well for example take some X, X1 and X2 engines (all three should be either be turbo jet or turbofan, better try thrust levels not being out of range) try finding the data for it like TET, BPR etc now try plotting BPR vs Engine X and overall Pressure vs Eng etc for engine X1 and X2 also, then you can get series of results where you can obtain some specific range of values, i think the values you get may be matched to the one you are saying the carpet plot(i dont know anything about caper plot).

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