An overview of in-flight plume diagnostics for rocket engines

An overview and progress report of the work performed or sponsored by LeRC toward the development of in-flight plume spectroscopy technology for health and performance monitoring of liquid propellant rocket engines are presented. The primary objective of this effort is to develop technology that can be utilized on any flight engine. This technology will be validated by a hardware demonstration of a system capable of being retrofitted onto the Space Shuttle Main Engines for spectroscopic measurements during flight. The philosophy on system definition and status on the development of instrumentation, optics, and signal processing with respect to implementation on a flight engine are discussed

Integrated control and health management. Orbit transfer rocket engine technology program

To insure controllability of the baseline design for a 7500 pound thrust, 10:1 throttleable, dual expanded cycle, Hydrogen-Oxygen, orbit transfer rocket engine, an Integrated Controls and Health Monitoring concept was developed. This included: (1) Dynamic engine simulations using a TUTSIM derived computer code; (2) analysis of various control methods; (3) Failure Modes Analysis to identify critical sensors; (4) Survey of applicable sensors technology; and, (5) Study of Health Monitoring philosophies. The engine design was found to be controllable over the full throttling range by using 13 valves, including an oxygen turbine bypass valve to control mixture ratio, and a hydrogen turbine bypass valve, used in conjunction with the oxygen bypass to control thrust. Classic feedback control methods are proposed along with specific requirements for valves, sensors, and the controller. Expanding on the control system, a Health Monitoring system is proposed including suggested computing methods and the following recommended sensors: (1) Fiber optic and silicon bearing deflectometers; (2) Capacitive shaft displacement sensors; and (3) Hot spot thermocouple arrays. Further work is needed to refine and verify the dynamic simulations and control algorithms, to advance sensor capabilities, and to develop the Health Monitoring computational methods

Investigation of Combustion Phenomena in a Single-Cylinder Spark-Ignited Natural Gas Engine with Optical Access

More demanding efficiency and emissions standards for internal combustion (IC) engines require novel combustion strategies, alternative fuels, and improved after-treatment systems. However, their development depends on improved understanding of in-cylinder processes. For example, the lower efficiency of conventional spark-ignited (SI) natural-gas (NG) engines reduces their utilization in the transportation sector. Single-cylinder optical-access research engines allow the use of non-intrusive visualization techniques that study in-cylinder flow, fuel-oxidizer mixing, and combustion and emissions phenomena under conditions representative of production engines. These visualization techniques can provide qualitative and quantitative answers to fundamental combustion-phenomena questions such as the effects of engine design, operating conditions, fuel composition, fuel delivery strategy, and ignition techniques.;The thesis is divided in two main parts. The first part focuses on the setup of a single-cylinder research engine with optical access including the design of its control system and the acquisition of in-cylinder pressure data and high-speed combustion images. The second part focuses on measurements of the turbulent flame speed using the high-speed combustion images. Crank-angle-resolved images of methane combustion were taken with a high-speed CMOS camera at a rate of 15,000 Hz. The optical engine was operated in a skip-firing mode (one fired cycle followed by 5 motored cycles) at 900 RPM and a load of 5.93 bar IMEP. The images show that flow turbulence and flame stretch resulted in flame velocities several order of magnitude higher compared to the laminar flame velocity. In addition, both in-cylinder pressure and optical data were used to determine the cycle-to cycle variability of the combustion phenomena

Simulation and Measurement of Transient Fluid Phenomena within Diesel Injection

Rail pressures of modern diesel fuel injection systems have increased significantly over recent years, greatly improving atomisation of the main fuel injection event and air utilisation of the combustion process. Continued improvement in controlling the process of introducing fuel into the cylinder has led to focussing on fluid phenomena related to transient response. High-speed microscopy has been employed to visualise the detailed fluid dynamics around the near nozzle region of an automotive diesel fuel injector, during the opening, closing and post injection events. Complementary computational fluid dynamic (CFD) simulations have been undertaken to elucidate the interaction of the liquid and gas phases during these highly transient events, including an assessment of close-coupled injections. Microscopic imaging shows the development of a plug flow in the initial stages of injection, with rapid transition into a primary breakup regime, transitioning to a finely atomised spray and subsequent vaporisation of the fuel. During closuring of the injector the spray collapses, with evidence of swirling breakup structures together with unstable ligaments of fuel breaking into large slow-moving droplets. This leads to sub-optimal combustion in the developing flame fronts established by the earlier, more fully-developed spray. The simulation results predict these observed phenomena, including injector surface wetting as a result of large slow-moving droplets and post-injection discharge of liquid fuel. This work suggests that post-injection discharges of fuel play a part in the mechanism of the initial formation, and subsequent accumulation of deposits on the exterior surface of the injector. For multiple injections, opening events are influenced by the dynamics of the previous injection closure; these phenomena have been investigated within the simulations