EXPERIMENTAL AND THEORETICAL STUDY OF FUEL LEAK, COMBUSTION, AND QUENCHING OF LIQUID HYDROCARBON FUELS IN MICRO-SCALE FUEL-AIR HEAT EXCHANGERS
Creators: name: Swanson, Christopher Carter
Publisher: name: Purdue University Graduate School
Year: 2024
Subjects: classificationCode: 400103
subject: Aircraft performance and flight control systems
classificationCode: 400199
subject: Aerospace engineering not elsewhere classified

description: In Chapter 2 an experiment has been conducted to measure the quenching distance of a premixed fuel-air mixture. Quenching distance refers to the physical limit below which combustion of a fuel and an oxidizer, even if present in sufficient proportions, cannot maintain combustion and propagate a flame. It is dependent on the physical area that is present for the flame to travel through, the temperature and pressure conditions, the thermal conductivity of the walls, and the specific fuel and oxidizer present. Applicable in a wide variety of industries from the automotive industry to the aerospace industry, the ability to control a combustion reaction and where it occurs can lead to increased safety and efficiency in devices such as injectors, mixing chambers, engine pistons, combustors, propellant turbopumps, and fuel-air heat exchangers. Currently, little to no quenching distance data exists for heavier-than-air hydrocarbons. Using a parallel ceramic plate setup with spark rods inside a pressure vessel to contain the initial combustion reaction, the quenching distances of the hydrocarbons is measured and a relationship with equivalence ratio is found. This relationship is used to construct a model to apply to heavier-than-air hydrocarbons.
Chapter 3 focuses on an experiment designed to measure the flow rates of leaks in fuel-air heat exchangers. The ability to accurately quantify and understand these flow rates is crucial for assessing the performance and safety of such systems. Furthermore, the obtained flow rate data will be compared with a Computational Fluid Dynamics (CFD) model developed for micro-scale flows resulting from fuel leakage into a cross-flow of heated air within the heat exchanger. These flow rates provide a model of the volume and rate of fuel being injected into the air channels, aiding in the assessment of potential risks and hazards associated with the leakage. To validate the accuracy and reliability of the model developed for micro-scale flow, the measured flow rates obtained from the experimental setup are compared against the corresponding predictions of the model. By establishing a correlation between the experimental data and the model results, the validity of the model can be confirmed, ensuring its efficacy for future simulations and analyses.
Chapter 4 details the creation and analysis of a program developed in Python and MATLAB for assessing combustion risk in microscale fuel-air heat exchanger channels. The Safety Net for Unquenched Flame Fronts (SNUFF) is designed as a design assistance tool for microscale flows of fuel and oxidizer, specifically for heat exchangers. This application helps analyze combustion risks in these microscale flow channels due to leaks or unintended flows caused by damage or manufacturing defects. SNUFF integrates REFPROP and flame simulation data with the models for quenching distance and microscale flow from previous chapters to generate sensitivity plots for various design parameters. This tool enables engineers to assess combustion risks in fuel-air channels, allowing them to design processes that accommodate manufacturing limitations in numerous microscale channel applications.