Reactive Mixing in Liquid-Fueled Detonations: Droplet Breakup Under Complex Acceleration
Abstract
The purpose of this action is to provide a FY24 funding increment, in the amount of $154,844.00, for a new start Grant award. GRANT#14008282.--The next generation of compact high-performance propulsion and power generation devices require efficient and rapid combustion of liquid fuels. Detonations react fuels in a constant-volume-like process that improves the thermodynamic efficiency of heat engines and propulsion devices. Liquid fuels are required in applications where high-energy density storage is necessary, aircraft, missiles, and naval vessels. Detonation of liquid droplets is complicated by multiphase effects, such as droplet breakup and vaporization, occurring at small length (<10 um) and time (<1 us) scales. Detonations create complex unsteady conditions, processing droplets by shock and expansion waves creating unsteady accelerations. Our previous work aimed to understand how breakup and evaporation of dropletswith size distributions occurs under quais-1D detonation conditions. This work highlighted the important role of droplet lag in creating strong spatial perturbations in the equivalence ratio (ER). This proposed project will build on our previous results and examine the effect of ER and droplet/vapor mixing in detonations, and develop new methods for prescribing and measuring multiphase initial conditions. The overall goal of this project is to understand how droplet breakup and mixing perturb local equivalence ratios and affect detonation propagation. The proposed research will be guided by the hypothesis that lean equivalence ratios will result in faster detonation wave velocities for liquid-fueled detonations. This research will be conducted through simultaneous experimental andtheory-based modeling efforts. The experiments will be performed in our multiphase detonation tube leveraging our experience in creating liquid-fueled detonations and measuring high-speed droplet breakup events. A new mono-dispersed droplet seeding method will bedeveloped to ensure well-controlled initial conditions with precise droplet sizes. New methods will be developed to measure the spatial distribution of droplet sizes (providing local ER) for high density multiphase flows. Navy relevant reactants, O2/N2 and JP-5, will be studied. Detonation velocities will be measured for varying ERs, from 0.5-1.25, using monodispersed droplets at prescribed sizes from 20-50 um. Gas mixing will be estimated from chemiluminescence measurements of excited radicals. Temporally resolved breakup measurements will be made by laser induced fluorescence of rhodamine doped droplets using our high-speed imaging system, capable of up to 250 million frames per second. The experimental measurements will guide the development of a complex-acceleration droplet breakup model based on variable acceleration hydrodynamic instability theories. The merit of this work lies in developing new methods for prescribing and measuring multiphase initial conditions, providing high-fidelity data of liquid-fueled detonations, and in developing a new fundamental understanding of droplet breakup in complex high-strength accelerations. The project will deliver a new droplet breakup model with increased accuracy and efficiency for Navy simulations of detonation devices. The models, methods, and theory produced by this project will enable engineers to overcome challenges in advanced propulsion cycles and enable efficient naval aircraft with greater combat range and operational readiness. Additionally, this project will train students in areas vital to nationalsecurity and expose them to research opportunities with the Navy laboratories, enhancing the future naval research workforce. Approved for Public Release
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jun 13, 2024
- Source ID
- N000142412370
Entities
People
- Jacob McFarland
Organizations
- Office of Naval Research
- Texas Engineering Experiment Station
- United States Navy