N161-011 TITLE: Turbomachinery Distortion Characterization by Non-intrusive Measurement Methods

TECHNOLOGY AREA(S): Air Platform, Sensors

ACQUISITION PROGRAM: Joint Strike Fighter - Propulsion

OBJECTIVE: Develop a non-intrusive measurement capability to quantify the distortion profile at the inlet of the fan and compressor of an aircraft engine.

DESCRIPTION: Characterization of distortion (pressure, temperature, flow angle, density) at the inlet of fans and compressors is typically done during development, or in a test environment, through the use of pitot probes [4]. These probes can only be used during developmental stages due to their intrusive nature and potential to dislodge or break loose, potentially causing domestic object damage (DOD). Within the engine operating envelope, complex distortion profiles are experienced due to aircraft maneuvers or environmental effects such as steam, armament or jet blast ingestion. These distortion profiles are not all tested due to their stochastic nature. The capability to characterize the inlet distortion for in-service aircraft engines is currently not available. While in service, fans/compressors on aircraft engines run into structural, operability or performance issues that are caused by inlet distortion that may be different from those modeled or replicated during static ground tests even with complex distortion screens. To determine root cause of a performance or structural issue, it is critical to have the ability to quantify the severity and intensity of these distortion profiles at the inlet of the affected compression system. Having this capability would allow identification and avoidance of critical inlet flow distortion that can negatively impact operability and performance as well as structural integrity.

Current systems used to characterize pressure and temperature distortion are arrays of probes arranged in rakes that are immersed in the flow path. Typically, flow angle is never measured due to measurement complexity, as such, it is usually analytically modelled. Aside from being intrusive, these systems are vulnerable to Foreign Object Damage (FOD) as they are exposed to whatever is ingested by the engine. Additionally, the probes themselves can be a potential source of internal domestic object damage to downstream components. To develop this capability with conventional technology would result in designing a set of rake and probe arrays specific to the aircraft engine application. This is a costly proposition and also would require a considerable amount of lead time.

Proposed sensor design should be non-intrusive to the flow stream, should avoid extraneous excitation and be easily accessible from turbomachinery exterior. Easy installation is desired on different Navy engines without adversely affecting the flow stream, the turbomachinery performance or becoming a source of domestic object damage. The system should be capable to characterize distortion to a better accuracy than the current methods that are available only during development and testing. The output should be able to be converted into numerical distortion descriptors that can be used in computational models to generate impact of distortion on performance or operability. The proposed sensor design should not create adverse effects such as pressure losses or introduction of a synchronous engine order forcing function.

During the design of the non-intrusive system, consideration of sensor design to characterize the distortion parameters (like, pressure, angle, temperature) as well as data acquisition and processing systems and their foot print on the engine carcass, should be kept as a high priority.

It is desired for the resulting technology to be configurable to various engine platforms.

It is recommended, though not required, to collaborate with original engine manufacturers (OEMs).

PHASE I: Demonstrate technical feasibility and proof-of-concept of the sensor system and data acquisition to quantify the distortion profile at the inlet of the fan and compressor of an aircraft engine. Provide conceptual design and cost estimate for the overall system.

PHASE II: Develop a detailed design, and perform fabrication and validation of a prototype for the sensor system, data acquisition and processing systems. The validation should include component type bench testing simulating engine operating conditions to demonstrate overall system capability. Demonstrate a fully functional system prototype. Proposers are encouraged to work with the OEM, academia or other institutions for testing opportunities. NAVAIR technical personnel will assist with access to engines for testing, if necessary.

PHASE III DUAL USE APPLICATIONS: Complete any operational testing required to prepare for and demonstrate a fully functional non-intrusive sensor system to characterize pressure and temperature distortion on a relevant engine platform if available or if the opportunity exists. Configure and transition validated system to appropriate platforms. The system developed should be useful in characterizing pressure and temperature distortion at the inlet of fans/compressors of propulsion systems (military and commercial). The system will be widely applicable not only in military aircraft engine application, but would also have usage in commercial, ground based, marine, automotive and other areas, where distortion plays a significant role in reduced performance and operability.

REFERENCES:

1. Rabe, D.C & Williams, C.; Inlet Flow Distortion and Unsteady Blade Response in a Transonic Axial-Compressor Rotor, ISABE 99-7287

2. Giess, P.A. & Kost, F.; (1997). Detailed Experimental Survey of the Transonic Flow Field in a Rotating Annular Turbine Cascade, Proceedings of the 2nd European Conference on Turbomachinery - Fluid Dynamics and Thermodynamics. Antwerpen (Belgium)

3. Gossweiler, C. & Gyarmathy, G.; (1996). Measuring Techniques for Transonic and Supersonic Flow in Cascades and Turbomachines. Proceedings of 13th Symposium, ETH Zurich, Institute of Energy Technology Turbomachinery Laboratory

4. Aerospace Recommended Practice, ARP 1420, Rev B. http://standards.sae.org/arp1420b/

KEYWORDS: Compressor; Distortion; Characterization; non-intrusive; Excitation; Foreign Object Damage (FOD)

TPOC-1: 301-757-0490

TPOC-2: 301-757-0472

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