Transport Physics in Reacting Turbulent Boundary Layers
Abstract
The interaction between a reacting ow and a solid surface is a ubiquitous factor in the design of any combustion device. After more procedation-quality, benchmark data to extend our fundamental understanding and develop predictive modeling capabilities.The solid fuel ramjet (SFRJ) is a high-speed propulsion device that has become a renewed focus for the Navy. These systems can achieve a significant improvement in special c impulse compared to solid rocket motors of comparable size because they harvest oxidizer from the atmosphere, ratherthan carrying that mass on the vehicle. Heat addition in an SFRJ combustor is fundamentally controlled by the mass, momentum, and energy transport processes between the low of oxidizer and the surface of the fuel grain. The global effect of these complex interactions is the regression of the fuel surface, which is the mechanism by which fuel is mixed and reacted with the owing air.The fundamental reacting ow - surface interaction is a three-way, coupled process where the ow, the flame, and the surface all mutually interact. Thermal effects are prominent, with wall heat flux that can be is high as O (10 6) W=m2 in high power density combustion devices, whichleads to flame quenching near the wall. Heat release near the wall alters the structure of the turbulent boundary layer, which feeds back into the flame propagation speed and reaction rates.Chemical kinetics within the reaction zone are also heavily ininfluenced by the presence of walls that act as heat and radical sinks, which can lead to incomplete combustion near walls. A detailed and accurate fundamental characterization of these transport processes is crucial to understand, model,and predict the thrust from an SFRJ.The interface physics of turbulent reacting mixing layers and boundary layers are highly sensitive to the local manifestation and relative strength of turbulent fluctuations, the thermochemical state of the gas, and the temperature of the wall. Our understanding of these processesis not sufficient for accurate modeling and prediction. Therefore, The principal thrust of this program is to quantify the rate-controlling physics of turbulent combustion in a solid fuel ramjet. The scientific objectives are to:(i) Develop a diagnostic capability to provide simultaneous, coincident measurements of the gas-phase ow temperature, oxygen mole fraction, and the turbulent ow velocity without presumed knowledge of the local ow composition.(ii) Apply the measurement technique to experimentally quantify the interactions between a canonical premixed flame and an inert solid surface.(iii) Extend the methodology to characterize the evaporation, mixing, and ignition physics within a turbulent reacting boundary layer of a regressing fuel grain at ow conditions that are representative of high-speed propulsion systems.The long-term vision for this program is to enable improvement in the accuracy of computational predictions of the near-wall processes in solid fuel ramjets and other combustion devices. The experimental measurements performed in this work will directly support ongoing efforts to achieve this goal, through collaborative eorts at the NAWCWD, then NRL, and other peer institutions.Moreover, the proposed experimental work-plan was strategically developed to complement and extended the impact of an ongoing ONR-funded project at Purdue (Grant Number N00014-19-1-2040). This fundamental first-principles based investigation will provide the detailed insight to needed to more fully realize the synergistic merits of both experimental and numerical tools to analyze these complex, multi-physics flows.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 08, 2020
- Source ID
- N000142012374
Entities
People
- Carson D. Slabaugh
Organizations
- Office of Naval Research
- United States Navy
- University of Virginia