Discussion on circumferential non-uniform temperature distribution and deformation in aero-engines

[Chaos2Max]

hello guys, im recently study the non-uniform temperature distribution and deformation in aero-engines(turbojet turbofan turboshaft), and the un-uniform deformation is a typical problem remains unsloved, but I cant find any material to learn from(for example, OTDF is a factor to define the temperature distribution of the combustion chamber outlet). so is anybody knows how to deal with this kind of problems? maybe we can discuss it?

 

[SWComposites]

i suspect this info is proprietary to the engine manufacturers

 

[WKTaylor]

Maybe some useful info in AIAA or SAE or documents/reports/standards...

SAE AIRxxx, ARPxxx, ARPxx, text books, published papers, etc. Example...
SAE AS681 Gas Turbine Engine Performance Presentation for Computer Programs
SAE AIR1419 Inlet Total-Pressure Distortion Considerations for Gas-Turbine Engines

AIAA has thousands of papers, every topic.

Bla bla bla...

 

[Chaos2Max]

i suspect this info is proprietary to the engine manufacturers

Thx~ but its also a problem related to manufacturers, but the contribution is not so significant. you know for turbine casing, due to the circumferential non-uniform temperature distribution(high temp gas and maybe ACC) the deformation is the non-uniform. which will lead to non-uniform tip clearance, you cant just evaluate the performance of your engine with a single 1D valve of Tip Clearance. you need 3D INFO~

 

[Chaos2Max]

Maybe some useful info in AIAA or SAE or documents/reports/standards...

SAE AIRxxx, ARPxxx, ARPxx, text books, published papers, etc. Example...
SAE AS681 Gas Turbine Engine Performance Presentation for Computer Programs
SAE AIR1419 Inlet Total-Pressure Distortion Considerations for Gas-Turbine Engines

AIAA has thousands of papers, every topic.

Bla bla bla...

YES Taylor. i've search those website, not much useful information.

 

[rb1957]

Have you answered your own question ?

I'd've thought that engines were very susceptible to even small loads, but if this is a thing that OEMs don't worry about, then why you ?

I'd've thought (like SWC) that OEMs did worry about this, and do so in a proprietary manner, so you may not find open sources on this.

I'd've thought that OEMs worried extensively about thermal effects (the the impact of these effects on the small clearances inside the engine.
Now maybe the combustion chambers massively overrule other thermal effects (like temperature rise due to compression).

Maybe you can explain your problem some more ... "the non-uniform temperature distribution and deformation in aero-engines". Are you looking at the engine shaft specifically ? A multi-shaft engine ??.

In my ignorance I'd expect that the combustion chambers are the biggest heat source, and the engine gradually heat soaks as it runs for several hours.
But outside air is at something like -30degC, so there's a bunch of thermal modelling going on.
So by "non-uniform temperature", do you mean some of the shaft is feeling the combustion chamber temp and some other parts are feeling the outside air ?

 

[jaceb]

what you are asking for is strictly controlled, properietary information, part of specific DPs, directly related to engine performance - you will have no access to this untill you will be a member of inner circle of trust at GE, PW, RR or Safran.... not just emplyee, but you have to work for a team which has access to this type of information on "need to know" basis

 

[SWComposites]

So Chaos, are you a student? Or do you work for an engine company? Or what motivates your interest in this topic?

 

[Green 123]

hello guys, im recently study the non-uniform temperature distribution and deformation in aero-engines(turbojet turbofan turboshaft), and the un-uniform deformation is a typical problem remains unsloved, but I cant find any material to learn from(for example, OTDF is a factor to define the temperature distribution of the combustion chamber outlet). so is anybody knows how to deal with this kind of problems? maybe we can discuss it?

Circumferential Non-Uniformity in Temperature Distribution and Resulting Deformation in Jet Engines​

1. Circumferential Non-Uniformity in Temperature Distribution​

In jet engines — especially in the turbine section — the temperature field is ideally expected to be uniform circumferentially around the engine centerline. However, in practice, due to various reasons like:

• Non-uniform combustion (hot streaks from burners)
• Secondary airflows (cooling air leaks, purge flows)
• Disturbances from upstream components (like distorted flow from compressors)
• Manufacturing tolerances and operational wear

the temperature field varies as you move around the circumference at a fixed axial location.


This non-uniformity is often called:

• Hot streaks (regions of locally higher temperature)
• Cold sectors (regions of locally lower temperature)

Typically, these circumferential differences can be on the order of tens to hundreds of degrees Kelvin, depending on operating conditions.

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2. Mechanisms Leading to Temperature Non-Uniformity​

• Combustor Pattern Factors: In annular combustors, even if designed symmetrically, imperfect fuel-air mixing leads to discrete "hot spots."
• Cooling Flows: Turbine blades and vanes are film-cooled. The coolant might not be perfectly uniform, causing local cold regions.
• Burner Misalignment or Malfunction: Faulty nozzles or injectors create localized rich or lean zones.
• Thermal Boundary Layers: Differences in the cooling efficiency along casing or hub walls can create temperature gradients.

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3. Resulting Deformation Phenomena​

Now, non-uniform temperatures cause non-uniform thermal expansion in engine components.


Key phenomena include:

3.1 Thermally Induced Ovalization ("Thermal Bowing")​

• Turbine casings, disks, and rotors, which are typically circular, can deform into an oval shape due to uneven expansion.
• Hot sectors expand more → pushing the casing outward locally.
• Cold sectors expand less → staying closer to original dimensions.

This ovalization leads to variations in tip clearances between blades and casing around the circumference, impacting efficiency and potentially causing rubs (physical contact).

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3.2 Rotor Disk "Tilt" and "Wobble"​

• Non-uniform heating across the disk face can create disk coning or wobble, where the rotor hub gets displaced axially and radially.
• This introduces unwanted vibrations and can accelerate fatigue damage.

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3.3 Creep and Material Fatigue​

• Areas under higher temperatures creep more (plastic deformation over time), leading to out-of-roundness even when the engine cools down.
• Fatigue cycles are exacerbated where temperature gradients cause large thermomechanical stresses.

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3.4 Thermomechanical Stress​

Thermal non-uniformities cause localized stresses because different parts of the component try to expand differently, but are mechanically connected:

• In extreme cases, this stress can cause cracks, especially at cooling holes or blade roots.
• In disks, it can also drive Low Cycle Fatigue (LCF) or Thermal Mechanical Fatigue (TMF) failure modes.

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4. Engineering Mitigation Strategies​

To control circumferential temperature non-uniformity and deformation effects, engineers design:

• Advanced combustors with better fuel-air mixing (e.g., lean-premixed, pre-vaporized combustors).
• Careful cooling flow management: optimizing the distribution and flow rates of coolant air.
• Flexible components: casings and mounts that can accommodate thermal growth.
• Tip clearance control systems: using active clearance control with cooling air to shrink or expand the casing dynamically.
• Thermal barrier coatings (TBCs) to equalize surface temperatures.

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