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The processes addressed in this Aerospace Information Report (AIR) apply to the acquisition and validation of dynamic total-pressure and distortion data from CFD models simulating turbulent flows in inlets. The results of these processes can be used in the formation of an inlet-flow-distortion methodology that addresses turbine-engine operability assessments.

This document reviews the state of the art for data scaling issues associated with air induction system development for turbine-engine-powered aircraft. In particular, the document addresses issues with obtaining high quality aerodynamic data when testing inlets. These data are used in performance and inlet-engine compatibility analyses. Examples of such data are: inlet recovery, inlet turbulence, and steady-state and dynamic total-pressure inlet distortion indices. Achieving full-scale inlet/engine compatibility requires a deep understanding of three areas: 1) geometric scaling fidelity (referred to here as just “scaling”), 2) impact of Reynolds number, and 3) ground and flight-test techniques (including relevant environment simulation, data acquisition, and data reduction practices).

This document addresses many of the significant issues associated with effects of inlet total-pressure distortion on turbine-engine performance and stability. It provides a review of the development of techniques used to assess engine stability margins in the presence of inlet total-pressure distortion. Specific performance and stability issues that are covered by this document include total-pressure recovery and turbulence effects and steady and dynamic inlet total-pressure distortion.

This document addresses many of the significant issues associated with effects of inlet total-pressure distortion on turbine-engine performance and stability. It provides a review of the development of techniques used to assess engine stability margins in the presence of inlet total-pressure distortion. Specific performance and stability issues that are covered by this document include total-pressure recovery and turbulence effects and steady and dynamic inlet total-pressure distortion.

AIR1419 “Inlet Total Pressure Distortion Considerations for Gas Turbine Engines” documents engineering information for use as reference material and for guidance. Inlet total-pressure distortion and other forms of flow distortion that can influence inlet/engine compatibility require examination to establish their effect on engine stability and performance. This report centers on inlet-generated total-pressure distortion measured at the Aerodynamic Interface Plane (AIP), not because this is necessarily the sole concern, but because it has been given sufficient attention in the aircraft and engine communities to produce generally accepted engineering practices for dealing with it. The report does not address procedures for dealing with performance destabilizing influences other than those due to total-pressure distortion, or with the effects of any distortion on aeroelastic stability.

This document reviews the state of the art for data scaling issues associated with air induction system development for turbine-engine-powered aircraft. In particular, the document addresses issues with obtaining high quality aerodynamic data when testing inlets. These data are used in performance and inlet-engine compatibility analyses. Examples of such data are: inlet recovery, inlet turbulence, and steady-state and dynamic total-pressure inlet distortion indices. Achieving full-scale inlet/engine compatibility requires a deep understanding of three areas: 1) geometric scaling fidelity (referred to here as just “scaling”), 2) impact of Reynolds number, and 3) ground and flight-test techniques (including relevant environment simulation, data acquisition, and data reduction practices).

The turbine-engine-inlet flow distortion descriptors summarized in this document apply to the effects of inlet total-pressure, planar-wave, and total-temperature distortions. Guidelines on stability margin, destabilizing influences, types and purposes of inlet data, AIP definition, and data acquisition and handling are summarized from AIR5866, AIR5867, ARP1420, and AIR1419. The degree to which these recommendations are applied to a specific program should be consistent with the complexity of the inlet/engine integration. Total-pressure distortion is often the predominant destabilizing element that is encountered and is often the only type of distortion to be considered, i.e, not all types of distortion need to be considered for all vehicles.

The turbine-engine inlet flow distortion methodology addressed in this document applies only to the effects of inlet total-pressure distortion. Practices employed to quantify these effects continue to develop and, therefore, periodic updates are anticipated. The effects of other forms of distortion on flow stability and performance, and of any distortion on aeroelastic stability are not addressed. The guidelines can be used as necessary to create a development method to minimize the risk of inlet/engine compatibility problems. The degree to which guidelines for descriptor use, assessment techniques, and testing outlined in this document are applied to a specific program should be consistent with the expected severity of the compatibility problem.

The turbine-engine inlet flow distortion methodology addressed in this document applies only to the effects of inlet total-pressure distortion. Practices employed to quantify these effects are developing and therefore, periodic updates are anticipated. The effects of other forms of distortion on flow stability and performance and of any distortion on aeroelastic stability are not addressed. The guidelines can be used as necessary to create a development method to minimize the risk of inlet/engine compatibility problems. The degree to which guidelines for descriptor use, assessment techniques, and testing outlined in this document are applied to a specific program should be consistent with the expected severity of the compatibility problem.

The turbine-engine inlet flow distortion methodology addressed in this document applies only to the effects of inlet total-pressure distortion. Practices employed to quantify these effects continue to develop and, therefore, periodic updates are anticipated. The effects of other forms of distortion on flow stability and performance, and of any distortion on aeroelastic stability are not addressed. The guidelines can be used as necessary to create a development method to minimize the risk of inlet/engine compatibility problems. The degree to which guidelines for descriptor use, assessment techniques, and testing outlined in this document are applied to a specific program should be consistent with the expected severity of the compatibility problem.

The turbine-engine inlet flow distortion methodology addressed in this document applies only to the effects of inlet total-pressure distortion. Practices employed to quantify these effects are developing and therefore, periodic updates are anticipated. The effects of other forms of distortion on flow stability and performance and of any distortion on aeroelastic stability are not addressed. The guidelines can be used as necessary to create a development method to minimize the risk of inlet/engine compatibility problems. The degree to which guidelines for descriptor use, assessment techniques, and testing outlined in this document are applied to a specific program should be consistent with the expected severity of the compatibility problem.

This report revises ARD50015 document to the AIR format. This report, as was the original, is intended to complement ARP1420C and AIR1419C documents issued by the SAE S-16 Committee on spatial total-pressure distortion. These previous documents addressed only total-pressure distortion and excluded total temperature distortion. The subject of inlet total temperature distortion is addressed in this report with some background and identification of the problem area. The status of past efforts is reviewed, and an attempt is made to define where we are today. Deficiencies, voids, and limitations in knowledge and test techniques for total temperature distortion are identified.

This Aerospace Information Report (AIR) addresses the subject of aircraft inlet-swirl distortion. A structured methodology for characterizing steady-state swirl distortion in terms of swirl descriptors and for correlating the swirl descriptors with loss in stability pressure ratio is presented. The methodology is to be considered in conjunction with other SAE inlet distortion methodologies. In particular, the combined effects of swirl and total-pressure distortion on stability margin are considered. However, dynamic swirl, i.e., time-variant swirl, is not considered. The implementation of the swirl assessment methodology is shown through both computational and experimental examples. Different types of swirl distortion encountered in various engine installations and operations are described, and case studies which highlight the impact of swirl on engine stability are provided. Supplemental material is included in the appendices.