Product Code:SAE ARD50026
Title:A Current Assessment of Planar Waves
Issuing Committee:S-16 Turbine Engine Inlet Flow Distortion Committee
Scope: The subject of planar total pressure waves has been reviewed to determine the feasibility of developing a consensus methodology that can account for the effect of planar waves on inlet/engine compatibility. The review includes a problem assessment, a discussion of possible approaches to methodology definition, a description of testing requirements, conclusions, recommendations, and the results of a document review of planar wave material. The problem assessment showed that planar waves have occurred at propulsion system operating conditions within normal flight envelopes during a number of aircraft development programs. Planar waves generally occur at low mass flow ratio and become more severe with increasing Mach number and decreasing airflow. Other sources, both internal and external, also can generate planar waves. Planar waves usually occur in combination with spatial total pressure distortion. The peak destabilizing event may not correspond to either a peak planar excursion or a peak spatial distortion. Because of the complex nature of the combined disturbance problem and the practice of exercising avoidance procedures, no well-developed consensus method exists for treatment of the combined planar wave/spatial distortion problem. This report defines an approach that is useful in methodology development. A potential approach to methodology definition is discussed which includes the following four key elements: 1) categorization of inlet planar waves, 2) determination of engine response to planar waves, 3) planar wave analysis methods, and 4) combined spatial total-pressure distortion and planar waves, including stability accounting. Elements of methodology validation are discussed in Appendix C. Inlet and compression system component testing will be required to apply the proposed methodology to a specific system. Inlet testing is used to define the planar wave component at the AIP and compression system testing defines the response to planar waves. An assessment of the available data and published information from a document review identified some recent data that define the physical characteristics of planar waves. Several publications describe planar wave test techniques and compression system analytical models. This report recommends that a well-planned analytical and experimental program be conducted to explore the sensitivities of turbine engines to planar waves in combination with various spatial distortion patterns.