Research on Casing Treatments for Performance Enhancement of High-Speed Fans
Abstract
Aircraft engines operating in naval fighter applications have unique challenges, particularly for the fan. Inlet distortion due to aggressive flight maneuvers and carrier take-off constraints leads to reduced stall margin and reduced flutter margin, both limiting the operating range of the engine. Navy fans have operability limitations driven by: highly loaded airfoils, inlet distortion due to the shape of the inlet and aircraft maneuvers, and steam / hot gas ingestion. These threedemands not only pose significant challenges to the performance of the engine, but they will intensify with next generation aircraft and propulsion systems. Inlet distortion will worsen as inlets shorten and become more embedded for low-observability aircraft. Additionally, unmanned aircraft could execute maneuvers that would also exacerbate the distorted inlet flow. Fi aircraft catapulted off the deck of a carrier pass through a steam cloud produced by the catapult creating a temperature inlet distortion during takeoff. Therefore, there is a need to de-sensitize the fan to these harsh conditions while still maintaining good efficiency, directly impacting engine fuel consumption. One proven way to address reduced stall margin associated with inlet distortion is through the use of casing treatments. These can be liners or specially-shaped inserts applied to the casing (the engine housing) over the fan blade tips to adjust the air flow over the tips. Conventional casing treatments are nearly always accompanied with a decrease in engine efficiency, resulting in a tradeoff between increased stall margin with decreased efficiency. However, if the design of the fan integrated casing treatment from the start, rather than using it as a band aid after the fan design was complete, it could be possible to realize both an increase in stall margin and efficiency of the fan / casing treatment system. The major impediment to incorporating this design philosophy is that the computational design tools currently available exhibit significant shortcomings in accurately predicting endwall flows and tip leakage flows over the fan blades. The tools utilize models in these regions of the flow because direct calculation of these complex flow fields would take too long to be useful in an iterative design sense. To improve these models, an experimental research facility is needed, where a representative fan can be operated at relevant blade tip speeds and inlet distortion conditions, while still allowing access to the flow field for detailed measurements. These measurements will lead to an improved understanding of the flow physics in these regions, enabling model improvements so that the tools can be extended to this design philosophy. Therefore, a new military fan research facility is being developed at Purdue University for this research topic in collaboration with the Office of Naval Research. Honeywell has donated an 18-inch diameter fan rig to Purdue for this work. The first year of this 4-year, $2M project will be spent planning the layout of the test cell and ordering long-lead-time equipment needed to operate the fan so that the rig is operational in Year 2. By Year 3, repeatable baseline performance will be established and compared to previously acquired data on the rig. Relevant inlet distortion patterns will be generated and the impact on the fan performance and detailed flow features will be documented through careful experiments. New casing treatments will be designed and testing of those will occur in Year 4 to validate CFD models needed to design integrated fan / casingtreatment systems.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 20, 2019
- Source ID
- N000141912561
Entities
People
- Nicole Leanne Key
Organizations
- Office of Naval Research
- United States Navy
- University of Virginia