Experimental and Numerical Investigation on the Combustion Characteristics of Solid Fuels in Supersonic Combustors
Abstract
The proposed research will provide a fundamental understanding of the combustion characteristics of solid fuels in supersonic combustors. Scramjets offer the opportunity to increase missile and projectile range, while decreasing time to target by traveling in the hypersonic regime. Storing the fuel in solid formoffers many advantages including long term storage, mission readiness, and packagg and sustained combustion. Virginia Tech has two experimental facilities which can be leveraged for this effort that can simulate flight conditions slightly above Mach 4; 1) a continuous flow facility, 2) a blowdown facility. While providing similar flight conditions, each has its own advantages depending on the experimental goals. In the experimental investigation we will start by considering an optically accessible two dimensional slab combustor configuration. In the slab configuration we will systematically study the geometrical effects of cavity flame holders, fuel regression rates, skin friction on the combusting fuel surface, flame structure via chemiluminescence, and temperature measurements in the reacting boundary layer using color imaging pyrometry.During the latter part of this research effort, a second, modular combustor will be designed and fabricated to allow for performance assessment of various fuel geometries. We propose to study an elliptical fuel grain geometry which has not been previously considered in a solid fuel scramjet. Elliptical combustorshave been considered in liquid/gaseous fuel scramjets with the negative impact of increased viscous drag and heat transfer to the combustor walls. In a solid fuel configuration, increased heat transfer to the walls promotes fuel pyrolyzation which promotes ignition and combustion. In the modular combustor,measurements will be made of the axial pressure profile, fuel regression rates, and combustion efficiency. The experimental work will initially consider a baseline fuel, Polymethyl Methacrylate (PMMA), which lends itself to additive manufacturing techniques before progressing to cast-cure fuels such as Hydroxyl Terminated Polybutadiene (HTPB).The proposed research includes a closely coupled numerical investigation. Large eddy simulations (LES) hold a significant advantage over RANS in combustion modelling because scalar mixing is of paramount importance to chreover, the dissipation of kinetic energy and the pressurework due to dilatation in compressible turbulence are key initiation processes for supersonic combustion near walls. Sub-cell resolution and low numerical dissipation are the preferred characteristics of LES solvers capable to model the complex near-wall physics underlying solid-fuel scramjet. LES of thecompressible, reactive Navier-Stokes equations will be conducted on the coupled fluid-solid domain formed by the gas and the fuel grain. The proposed research will be performed using two computational frameworks: an in house Discontinuous Galerkin (DG) code currently developed by Massa and JENRE,the Naval Research Laboratorys high-order Discontinuous Galerkin code. The two codes have a very similar structure. The in-house code will be used and maintained only for a preliminary investigation to be conducted before the beginning of the funding period anopment and validation of ADER-DG for chemically reactive flow, second is the evaluation of gas-solid coupling effects on ignition and burning characteristics, third is the improvement of the accuracy of the source termevaluation in conditions representative of turbulent supersonic combustion, and the final task is the improvement of near wall combustion and heat transfer by considering a mult
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 05, 2021
- Source ID
- N000142112299
Entities
People
- Gregory Young
Organizations
- Office of Naval Research
- United States Navy
- Virginia Tech