N22A-T002 TITLE: Multifunctional Heat Exchanger for Aerodynamic Aircraft Inlets

OUSD (R&E) MODERNIZATION PRIORITY: Directed Energy (DE);General Warfighting Requirements (GWR)

TECHNOLOGY AREA(S): Air Platforms

OBJECTIVE: Develop an aerodynamic, multifunctional heat exchanger that is capable of dissipating a large amount of aircraft waste heat while improving inlet flow distortion upstream of a gas turbine engine.

DESCRIPTION: Inlet guide vanes offer a potentially attractive way to remove heat from aircraft and engine coolants. Doing so, however, adds complexity and volume to conventional guide vanes, which are also ill-suited for convoluted inlets with complex aerodynamics. The volume added to conventional guide vanes results in aerodynamic losses and weight penalties that can negate the gains from multifunctionality. More elegant, combined aerodynamic/heat exchanger solutions may be feasible given the current state-of-the-art in multi-objective optimization, additive manufacturing, and custom flow tailoring. Advanced diffuser designs often involve flow separation and large-scale unsteady flow features which reduce the diffuser efficiency and subject the downstream turbomachinery to extreme flow distortions. Solutions are sought for a new heat exchanger technology that can simultaneously improve inlet diffuser aerodynamic performance. The heat transfer and aerodynamic flow field characteristics of the proposed technology need to be fully understood to ensure gas turbine engine compatibility and enable future, advanced Navy propulsion systems.

The proposed solutions will be required to demonstrate the following criteria:

• Heat exchanger effectiveness greater than, or equal to, 0.4.
• A total pressure drop across the heat exchanger no greater than 8%.
• A decrease in the element average circumferential and radial distortions as defined in SAE AIR 1419C [Ref 5].
• The front face of the heat exchanger positioned no more than two (2) diameters upstream of the Aerodynamic Interface Plane (AIP).

Though not required criteria, proposed solutions are encouraged to consider impacts and capabilities on the air platform as a whole. Metrics such as weight, serviceability, propulsion performance, and working fluid are important aspects to overall feasibility and utility. Values are not imposed so that the design space is not overly constrained. It is advised that total system estimated weight (including installation and plumbing) not to exceed 50lbm, and must fit within an existing inlet geometry (Ref 3 may be used for a defined geometry).

It is recommended to collaborate with an original equipment manufacturer (OEM) for Phase II studies, and Phase III integrated testing to identify representative installation configurations and performance needs.

PHASE I: Demonstrate feasibility of the proposed technology through computational and system-level analysis of a proposed concept, and in a simplified flow environment at the bench level. Detailed benefits of this concept, relative to existing technologies, should be identified. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: A prototype device should be designed, built, and tested to evaluate heat exchanger effectiveness, pressure loss, and distortion reduction in a representatively complex inlet (serpentine, varying cross-sectional area and shape; Ref 3).

PHASE III DUAL USE APPLICATIONS: Integrated test should be performed to evaluate the impact the multifunctional heat exchanger has on power plant performance. Transition the technology to applicable naval platform or lab.

Heat dissipation and flow straightening are not military specific concerns. Commercial aircraft/rotorcraft could also take advantage of this topic. Improvements to air flow into engines provide great operational safety and reliance for air vehicles.

Commercialization of this technology may include industrial applications for flow conditioning and heat exchangers, as well as advanced concepts for commercial transport aircraft and automotive applications.

This technology could also be applied for regenerative engine cycles. The ability to utilize the waste exhaust thermal energy of a power cycle to heat incoming air can provide an increase in cycle efficiency and decrease in fuel consumption. Additive manufacturing could provide the opportunity to retrofit existing systems to take advantage of regeneration.

REFERENCES:

1. Guimarães, T., Lowe, K. T., & O�Brien, W. F. (2017, October 31). "StreamVane turbofan inlet swirl distortion generator: Mean flow and turbulence structure." AIAA Journal of Propulsion and Power, 34(2), 340-353. https://doi.org/10.2514/1.B36422.
2. Nessler, C. A., Copenhaver, W. W., & List, M. G. (2013, January 7-10). "Serpentine diffuser performance with emphasis on future introduction to a transonic fan [Paper presentation]." In 51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition, Grapevine (Dallas/Ft. Worth Region), TX, United States. https://doi.org/10.2514/6.2013-219.
3. Maghsoudi, I., Mahmoodi, M., & Vaziri, M. A. (2020, January 28). "Numerical design and optimization of mechanical vane-type vortex generators in a serpentine air inlet duct." European Physical Journal Plus, 135(2), 139. https://doi.org/10.1140/epjp/s13360-020-00124-1.
4. Reichert, B. A., & Wendt, B. J. (1996). "Improving curved subsonic diffuser performance with vortex generators." AIAA Journal, 34(1), 65-72. https://doi.org/10.2514/3.13022.
5. SAE International Aerospace Council Divisional Technical Committee S-16. (2017, November 20). "AIR1419C: Inlet total-pressure-distortion considerations for gas-turbine engines." SAE International, November 20, 2017. https://www.sae.org/standards/content/air1419c/.

KEYWORDS: Thermal management; Inlets; Heat Exchangers; Propulsion Performance; Inlet Distortion; Additive Manufacturing