Transportation accidents and the resulting fires are an important field of study. At the University of Waterloo Live Fire Research Facility (UWLFRF), an experiment was conducted in partnership with Sandia National Laboratories in Albuquerque, New Mexico. This experiment was designed to simulate an aircraft accident where fuel is spilled on the runway and is subsequently ignited. A crosswind pushes the 2.0 m diameter pool fire towards the aircraft fuselage and the conditions around the fire are monitored. Literature on the subject is examined first, examining the relationship between the fire, the crosswind, and the 2.7 m diameter blocking object (aircraft fuselage). A full wind characterization is then presented of the UWLFRF both with and without the blocking object in place, using five distinct wind speeds ranging from 3 m/s to 13.5 m/s. Turbulence intensity measurements are made on the centerline of the facility when possible. Details about the two sets of live fire tests are presented, a control experiment without the blocking object in place and then fire tests with the blocking object in place. Additionally, the control experiment has two different setups, one involving a floor surround in order to diminish the effect of the forward facing step on the front of the fuel pan. The fuel regression rate, the wind speed, the ambient conditions and the heat flux near the fuel pan are monitored during each live fire test. The fuel regression rate, defined as the rate at which the height of the liquid fuel level decreases as the fire burns, is then analyzed versus all other monitored variables. During no blocking object tests, trends of increasing wind speed and increasing heat flux on some gauges and decreasing flux on others was observed with increasing fuel regression rate when the floor surround was in place. During no blocking object tests without the floor surround and tests with the blocking object in place, no strong trends were observed when comparing the monitored variables. The ambient conditions were not observed to have an effect on any test. The average fuel regression for tests without the blocking object in place is 4.0 mm/min without the floor surround, and 4.4 mm/min with it in place. With the blocking object in place the average fuel regression rate was measured to be 4.8 mm/min using load cells and 4.1 mm/min using the sight glass.

Transportation accidents and the resulting fires are an important field of study. At the University of Waterloo Live Fire Research Facility (UWLFRF), an experiment was conducted in partnership with Sandia National Laboratories in Albuquerque, New Mexico. This experiment was designed to simulate an aircraft accident where fuel is spilled on the runway and is subsequently ignited. A crosswind pushes the 2.0 m diameter pool fire towards the aircraft fuselage and the conditions around the fire are monitored. Literature on the subject is examined first, examining the relationship between the fire, the crosswind, and the 2.7 m diameter blocking object (aircraft fuselage). A full wind characterization is then presented of the UWLFRF both with and without the blocking object in place, using five distinct wind speeds ranging from 3 m/s to 13.5 m/s. Turbulence intensity measurements are made on the centerline of the facility when possible. Details about the two sets of live fire tests are presented, a control experiment without the blocking object in place and then fire tests with the blocking object in place. Additionally, the control experiment has two different setups, one involving a floor surround in order to diminish the effect of the forward facing step on the front of the fuel pan. The fuel regression rate, the wind speed, the ambient conditions and the heat flux near the fuel pan are monitored during each live fire test. The fuel regression rate, defined as the rate at which the height of the liquid fuel level decreases as the fire burns, is then analyzed versus all other monitored variables. During no blocking object tests, trends of increasing wind speed and increasing heat flux on some gauges and decreasing flux on others was observed with increasing fuel regression rate when the floor surround was in place. During no blocking object tests without the floor surround and tests with the blocking object in place, no strong trends were observed when comparing the monitored variables. The ambient conditions were not observed to have an effect on any test. The average fuel regression for tests without the blocking object in place is 4.0 mm/min without the floor surround, and 4.4 mm/min with it in place. With the blocking object in place the average fuel regression rate was measured to be 4.8 mm/min using load cells and 4.1 mm/min using the sight glass.

<p dir="ltr">Instantaneous fuel regression rate within a solid fuel ramjet combustor was characterized using X-ray radiography and ultrasonic transducer measurements. Experiments were performed with cylindrical, center-perforated hydroxyl-terminated polybutadiene (HTPB) fuel grains at three mass fluxes (407-561 kg/m2-s) with consistent inlet total temperatures and chamber pressures. Ultrasonic transducer measurements demonstrated changes of web thickness ranging from 7.50-9.85 mm and regression rate measurements ranging from 1.35-1.74 mm/s. Local maxima of change in web thickness due to flow reattachment and erosive burning were consistently measured with the ultrasonic transducers. Changes in port radius on the order of 8-9 mm and regression rates of approximately 1.25 mm/s were deduced from the X-ray radiography images. Structure of the flow reattachment region was evident in measurements from the X-ray radiography images captured near the combustor entrance while images captured at the mid-length of the combustor exhibited more uniform fuel regression profiles. Ultrasonic measurements of change in web thickness were consistently greater in magnitude relative to X-ray radiography measurements. X-ray radiography imaging allowed for the more accurate measurement of fuel regression with the greatest axial spatial resolution while ultrasonic transducer measurements yielded the greatest radial spatial resolution. The change in web thickness calculated with weight-based techniques yielded smaller magnitude measurements of change in web thickness relative to X-ray radiography.</p><p dir="ltr">Time-dependent measurements of web thickness and regression rate along the port of aluminum-loaded and boron carbide-loaded, hydroxyl-terminated polybutadiene (HTPB) fuel grains were measured in a solid fuel ramjet combustor with X-ray radiography. The combustor was operated at three mass flux conditions, ranging from 397-532 kg/m2-s, with consistent chamber pressures and upstream-of-combustor total temperatures of 1313 kPa and 748 K, respectively. A cross-correlation-based edge detection scheme was used to extract the fuel grain edges within X-ray radiography images collected at 15 Hz. Cross-section photographs of the post-combustion fuel grain surfaces exhibited evidence of flow reattachment and large aft-end regression. Aluminized fuel grains exhibited average weight-based regression rates of 1.29-1.48 mm/s, and boron carbide-loaded fuel grains yielded average regression rates of 1.21-1.38 mm/s. Head-end X-ray measurements of change in port radius indicated flow reattachment, particularly for the bottom (theta = 180) edge of the fuel grain. The absolute maximum of change in port radius, which ranged between 8.56-10.31 mm for aluminized fuel grains and 8.22-9.40 mm for boron carbide-containing fuel grains, did not always coincide with the flow reattachment location. Time-averaged regression rate profiles measured with X-ray radiography were relatively uniform along the port axis but smaller in magnitude compared to the weight-based measurements; 1.17-1.35 mm/s for the aluminum-loaded fuel grains and 1.07-1.24 mm/s for the boron carbide-loaded fuel grains. Pre-ignition fuel regression, on the order of 1.5 mm, was determined to be the cause of the over-prediction of regression rate by weight-based measurements compared to X-ray measurements.</p><p dir="ltr">The weight-based average regression rates measured in tests conducted with the axisymmetric solid fuel ramjet test article in its various configurations were compared to quantify the effects of average port air mass flux, bypass air addition, carbon black addition, and metal particle addition on regression rate. Baseline tests without an aft-mixing section or bypass air addition fuel grains containing carbon black yielded a regression rate coefficient of a = 5.33E-2 and an exponent of n = 0.50 for p4 = 1179-1298 kPa. Including an aft-mixing section without bypass air addition yielded regression rates of 0.94-1.04 mm/s due to the increased residence time. Bypass air addition of 14\% bypass ratio reduced the regression rate to 0.83-0.92 mm/s, and 30% bypass ratio reduced the regression rate to 0.80-0.82 mm/s. For otherwise equal tests, adding carbon black to the fuel grain increased the regression rates from 0.76-0.78 mm/s to 0.83-0.92 mm/s (6-21%). Aluminized fuel grains exhibited an increase in regression rate coefficient over the baseline fuel grains from a = 5.33E-2 to a = 6.30E-2 (18%), but the regression rate exponent remained at n = 0.50. Boron carbide (B4C) addition reduced the regression rate exponent to n = 0.46 but increased the regression rate coefficient to a = 7.55E-2; a 42% increase.</p><p dir="ltr">A simplified solid fuel ramjet combustion model which includes (1) turbulent heat convection, (2) radiation, (3) radiation-coupled surface blowing, (4) unsteady sub-surface heat conduction, (5) solid fuel regression, (6) gas-phase combustion, and (7) fuel port hydrodynamics was developed for regression rate prediction over a range of combustor geometries and operating conditions. Turbulent convection was modeled with empirical correlations relating non-dimensional boundary layer transport numbers. Radiative heat transfer was estimated using modified empirical correlations for radiation in a slab hybrid rocket combustor. Hybrid rocket combustion theory was used to model surface blowing. The condensed-phase heat transfer was modeled by solving the unsteady, variable thermophysical property, regressing surface heat equation with an explicit time-integration, finite volume scheme on a non-uniform grid. A general Arrhenius expression was used to estimate the fuel regression rate. Chemical equilibrium calculations for a stoichiometric HTPB/air diffusion flame were used to model the gas-phase combustion. The port gas dynamics were modeled with compressible flow ordinary differential equations. The results of these individual physical processes were examined in detail for a high mass flux (G_air = 561 kg/m2-s) case. Experiments performed in the axisymmetric solid fuel ramjet combustor were simulated in the model, which yielded a lower regression rate versus mass flux exponent of n = 0.39 compared to the experimentally-obtained n = 0.50. A larger parameter sweep of the model yielded a mass flux exponent of n_1 = 0.30, a pressure exponent of n_2 = 0.04, and an inflow total temperature exponent of n_3 = 0.39. These exponents are less than those observed in other works, but the model successfully captured the relative influence of mass flux, chamber pressure, and inflow total temperature.</p><p dir="ltr">A combustion diagnostic consisting of X-ray radiography and thermocouples embedded within the fuel grain was successfully applied and demonstrated in a solid fuel ramjet slab combustor. One representative test condition with an air mass flowrate of 1 kg/s, an upstream-of-combustor static pressure of 560 kPa, and an upstream-of-combustor total temperature of 639 K was examined. Changes in web thickness of approximately 4 mm and steady-state regression rates of 0.35 mm/s were measured at the thermocouple locations. Condensed-phase temperature measurements yielded fuel grain surface temperatures of 820 K and temperature profiles which were compared to theoretical Michelson profiles. The Michelson profile closely matched the thermocouple-measured temperature profile at one axial location. Sub-surface conductive heat fluxes of 0.35 MW/m2, heat fluxes required to vaporize solid fuel of 0.60 MW/m2$, and surface heat fluxes of 0.95 MW/m2$ were estimated using the condensed-phase temperature profiles.</p>

Rocket propulsion using the hybrid-propellant scheme is a technology that offers much promise in applications where high-performance liquid rocket engines are deemed too complex and solid rocket motors are considered to lack performance or safety. However, despite extensive research, there is still a lack of knowledge in the theoretical aspects of hybrid rocketry, especially in the area of fuel-oxidizer mixing and fuel regression rate. This lack of a good theoretical model makes the implementation of good, practical solutions and mature, well-functioning designs more diffcult. This disadvantages the hybrid rocket engine when compared to liquid rocket engines or solid rocket motors.In this study, a hybrid rocket engine burning polymethyl methacrylate (PMMA) with compressed air has been designed to the point of a preliminary design defnition. PMMA is a transparent material, and this has been utilized to create a transparent-chamber rocket engine where engine processes can be studied with various optical methods withoutinterrupting or disturbing the operation of the engine. The function of hybrid rocket engines, the technological solutions involved in designing working hybrid rocket engines and the constituent parts of hybrid rocket engines have been studied. The nature of the trade-offs between performance and simplicity that occur when designing a rocket engine are also studied, with a focus on maximizing simplicity, safety and minimizing expenses, while still designing an engine that fulfills basic requirements. The results include a design defnition with a preliminary user’s guide, a feasibility study, and a summary of the results of the hybrid rocket performance model that was used to determine appropriate design parameters.

This thesis presents a research project in the field of oxygen system fire safety relating to the heterogeneous burning of iron in normal gravity and reduced gravity. Fires involving metallic components in oxygen systems often occur, with devastating and costly results, motivating continued research to improve the safety of these devices through a better understanding of the burning phenomena. Metallic materials typically burn in the liquid phase, referred to as heterogeneous burning. A review of the literature indicates that there is a need to improve the overall understanding of heterogeneous burning and better understand the factors that influence metal flammability in normal gravity and reduced gravity. Melting rates for metals burning in reduced gravity have been shown to be higher than those observed under similar conditions in normal gravity, indicating that there is a need for further insight into heterogeneous burning, especially in regard to the rate-limiting mechanism. The objective of the current research is to determine the cause of the higher melting rates observed for metals burning in reduced gravity to (a) identify the rate-limiting mechanism during heterogeneous burning and thus contribute to an improved fundamental understanding of the system, and (b) contribute to improved oxygen system fire safety for both ground-based and space-based applications. In support of the work, a 2-s duration ground-based drop tower reduced-gravity facility was commissioned and a reduced-gravity metals combustion test system was designed, constructed, commissioned and utilised. These experimental systems were used to conduct tests involving burning 3.2-mm diameter cylindrical iron rods in high-pressure oxygen in normal gravity and reduced gravity. Experimental results demonstrate that at the onset of reduced gravity, the burning liquid droplet rapidly attains a spherical shape and engulfs the solid rod, and that this is associated with a rapid increase in the observed melting rate. This link between the geometry of the solid/liquid interface and melting rate during heterogeneous burning is of particular interest in the current research. Heat transfer analysis was performed and shows that a proportional relationship exists between the surface area of the solid/liquid interface and the observed melting rate. This is confirmed through detailed microanalysis of quenched samples that shows excellent agreement between the proportional change in interfacial surface area and the observed melting rate. Thus, it is concluded that the increased melting rates observed for metals burning in reduced gravity are due to altered interfacial geometry, which increases the contact area for heat transfer between the liquid and solid phases. This leads to the conclusion that heat transfer across the solid/liquid interface is the rate-limiting mechanism for melting and burning, limited by the interfacial surface area. This is a fundamental result that applies in normal gravity and reduced gravity and clarifies that oxygen availability, as postulated in the literature, is not rate limiting. It is also established that, except for geometric changes at the solid/liquid interface, the heterogeneous burning phenomenon is the same at each gravity level. A conceptual framework for understanding and discussing the many factors that influence heterogeneous burning is proposed, which is relevant to the study of burning metals and to oxygen system fire safety in both normal-gravity and reduced-gravity applications.