Adaptive Scanning for Compressor Airfoils
Navy SBIR 2015.1 - Topic N151-017
NAVAIR - Ms. Donna Moore -
Opens: January 15, 2015 - Closes: February 25, 2015 6:00am ET

N151-017 TITLE: Adaptive Scanning for Compressor Airfoils

TECHNOLOGY AREAS: Air Platform, Materials/Processes, Sensors


OBJECTIVE: Development of a commercialized measurement system for an integrally bladed rotor (IBR) and compressor blade inspection that will enable the accuracy of current commercial systems to be exceeded and will result in a reduction of measurement times.

DESCRIPTION: In the past several years, contact measurement systems have evolved from point, to line, to surface scanning methods. This evolution has led to an inherent decrease in scanning time for mapping the profile of military-sized engine IBRs from 100s of hours to less than 10 hours. In addition to contact measurement systems, there have been non-contact measurement systems that utilize optics for airfoil characterization. The contact and optical measurement methods each have their limitations. Contact measurement systems are inherently slower and are susceptible to dynamic effects such as vibration. Optical measurement systems use a line-of-sight technique which has highest integrity when performing measurements normal to the measured surface which makes small IBR measurements possessing small passages and closely spaced airfoils cumbersome. Optical techniques may be hindered by their susceptibility to characterize airfoils with high surface finish, as a smoother surface may saturate the receiving optics with diffused light. Airfoils with a "super-polished" finished are ideal for increased efficiency. A deficiency that both contact and optical methods exhibit is the inability to get accurate measurements of high-curvature entities, such as the leading and trailing edges of airfoils. It is the leading and trailing edge of airfoils that is considered the most critical with respect to geometry but also the most challenging to manufacture and thus the need for accurate inspection. Therefore, an innovative or hybrid singular system is necessary to accurately measure airfoil profiles, specifically high-curvature surfaces, while minimizing scan time.

The research will consist of two primary components. The first component of the research is system design. To increase measurement speed, it is expected that the solution will involve scanning of the desired airfoil sections that define the desired geometry. This will require extreme attention to the coordinated motion of multiple axes along with minimization / correction of geometric and positioning errors. The solution is recommended to be non-contact to eliminate speed-limiting, dynamic effects of the contact in conventional systems. The second component of the research is system control. A high-resolution, high bandwidth, non-contact probe has operating limits of angular orientation with respect to the surface being measured. Compressor airfoils have features with high curvature (e.g. leading and trailing edge) where the size of the feature is similar in magnitude to the location tolerance of the feature with respect to the overall part datum planes. These facts together mean that, in general, a multi-axis sensor path based on the nominal part geometry will not be sufficient to perform a successful measurement. A successful response will include a significant effort in the development of control algorithms including real-time signal conditioning, curve fitting, and optimization to quickly scan sections, IBRs and airfoils. These aspects of the research will certainly have implications to other applications and industries. Collaboration with engine/blade/IBR manufacturers to define system requirements and support commercialization is highly encouraged during all phases of the program.

PHASE I: Feasibility of measurement precision and measurement reduction time should be exhibited. Conceptual design for the final machine configuration should also be completed along with cost estimates. Assess the Technology Readiness Level (TRL)/Manufacturing Readiness Level (MRL) at the end of the Phase I base effort (and option, if applicable).

PHASE II: Detailed design, fabrication, and testing should be accomplished. Control algorithms should be optimized by tests on actual hardware. The optimization should include not only the control of the sensor for orientation but also, the use of redundant axes and location of probe with respect to rotational axis, taking into account part curvature to minimize inertial force. The result will be a functional working prototype and vehicle for future software/control revisions and testing. A fully functional prototype should be demonstrated and the TRL/MRL assessment updated. The final demonstration should be performed in a relative environment with the design incorporating basic commercial considerations such as safety and operator inputs.

PHASE III: The design and software should be fully functional and used for measurement of airfoils for axial compressors of propulsion systems (military and commercial) as well as for power turbines. Focus on certifying and qualifying the system for Navy use. Commercialize and transition the system to the Navy fleet, specifically the JSF platform. The measurement system will allow detailed post-manufacturing inspection in order to document manufacturing discrepancies and mitigate installation of flawed components within a reasonable duration.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The equipment developed will be useful for measurement of airfoils for axial compressors of propulsion systems (military and commercial) as well as power turbines. This is a substantial market on its own. In addition, the developed adaptive scanning will have potential benefit to any industry and application where coordinate metrology is used. Measurement times may be reduced for aerospace, automotive, optical, medical, electronics, semiconductor, etc. applications.

1. Sohn, A., Garrard, K.P., & Dow, T.A. (2011). Four-axis Spherical Geometry Measurement of Freeform Surfaces Polaris 3D. Proceedings of the 2011 ASPE Spring Topical Meeting. 511, 38-42. Retrieved from

2. Sohn, A., Garrard, K.P., & Dow, T.A. (2005). Polar coordinate-based profilometer and methods. U.S. Patent No. 6,895,682. Washington, DC: U.S. Patent and Trademark Office.

3. DoD 5000.2-R, Appendix 6, pg. 204. Technology Readiness Levels and Their Definitions.

4. Manufacturing Readiness Level (MRL) Deskbook, May 2011.

KEYWORDS: Inspection; Measurement; BLISK; IBR; MANUFACTURE; Compressor

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