[TOPIC 04] : Inlet distortions
Inlet distortions
motivation :
Inlet distortion is a known driver of blade vibration. Synchronous and asynchronous vibration are commonly sensitive to inlet distortion. Synchronous vibrations such as low engine order forced response are generated by blades passing through distorted flow. Asynchronous vibration such as flutter and rotating stall may also be adversely affected by distortion. Research is often focused on fan inlet distortion, but the principles may also apply to a compressor or turbine. Inlet distortion typically refers to circumferentially non-uniform flow. It’s often simplified typically considered as a total pressure distortion, but distortion of the flow angles (swirl), Mach number, and temperature can also be important. There are various potential sources of inlet distortion. For typical wing or tail mounted engines, these sources tend to include crosswind, ground vortices, upwash, asymmetrical inlets, and sometimes inflight lip separation. Atypical installations, such as embedded engines, boundary layer ingestion designs, dual mounted engines, inlet filters, and some turboprop inlets may generate unique inlet distortion patterns. This is not a comprehensive list. For aeromechanics, inlet distortion is often studied as a constant steady distortion. However, unsteady distortion may also be important for the phenomena mentioned above.
topics of interest :
Proposed research should shall progress the understanding in one or more of these topics. Research may be analytical or experimental. Analytical work should be validated with existing data or through partnerships within GUIde 8. Aeromechanics distortion (excitation drivers)
- Fan/Inlet interaction
- Define distortion descriptors for various flow parameters (radial, circumferential, angular, dynamic) in line with ARP1420 and other SAE ARPs.
- Study distortions from various configurations: Boundary Layer Ingestion (BLI), embedded engines, and other unique installations
- Advanced measurement techniques for inlet distortion
- Develop mitigation strategies employing inlet liners, casing treatments, non-uniform vanes, or other
Distortion transfer
- Distortion transfer across multi stage compressors
- Total pressure attenuation, total temperature generation across single stage configurations and the physics of distortion attenuation/amplification.
- Define distortion transfer across multi stage compressors in terms of total pressure and total temperature, including physics of distortion attenuation.
- Measurement techniques, including incidence, swirl, Pt, Tt and any flow field visualization (PIV, FRS etc)
- Aero installation and configuration impacts on distortion transfer, including exit static pressure screens
expected deliverables :
Deliverables may include the following, but other deliverables may be proposed.
- Experimental and/or analytical data showing distortion at the inlet and subsequent blade vibration response, either synchronous or asynchronous
- Experimental and analytical data showing total pressure and total temperature through multi stage compressors
- Damping measurements with aeromechanics distortion screens
- Data showing a comparison of pressure vs swirl distortion for specific scenarios and the importance of each
- Rules of describing distortion in terms meaningful to aeromechanics
- Rules for evaluating the important importance of unsteady distortion with respect to aeromechanics
- Recommendations for the mitigation of inlet distortion driven vibration
- Ideas for new or novel measurement techniques or data collected with a novel measurement system
- Demonstration of reduced order models for evaluation of inlet distortion
subtopics :
- Boundary Layer Ingestion (BLI)
- Embedded inlets: distortion descriptors (radial, circumferential, angular, dynamic)
- Measurement techniques for inlet distortion effects
- AIP distortion forcing level + response data
- Comparison of pressure vs swirl distortion
- Inlet/fan interaction.
- Inlet liner design considerations.
- Casing treatment options to mitigate flutter (e.g., circumferential ND variation)
Other contributors to RfP
- Shreyas Hegde (Duke)
- Mani Sadeghi (Pratt & Whitney)
- Jennifer Hall (Pratt & Whitney)
- Eijiro Kitamura (Honda)
- Kuen-Bae Lee (GE Aerospace)
- Michael Meyer (Rolls Royce)