Swirl-Stabilized Injector Flow and Combustion Dynamics for Liquid Propellants at Supercritical Conditions


Book Description

An integrated modeling and simulation program has been conducted to substantially improve the fundamental knowledge of supercritical combustion of liquid propellants under conditions representative of contemporary rocket engines. Both shear and swirl co-axial injectors were considered. The formulation was based on the complete conservation equations in three dimensions. in addition, general-fluid thermodynamics and transport theories were incorporated to allow for a unified treatment of fluid properties over the entire range of thermodynamic states. Turbulence closure was achieved by means of the large-eddy-simulation (LES) technique. Special attention was given to the fluid behavior in the two-phase and transcritical regimes in which rapid property variations occur. Various underlying physiochemical mechanisms associated with co-axial injector dynamics were studied in detail. These included flow evolution, flame stabilization and spreading, heat transfer, and acoustic response. The effects of design attributes and operating conditions on injector characteristics were assessed. Results have not only enhanced the basic understanding of the subject problem, but also provided a quantitative basis for identifying and prioritizing the key design parameters and flow variables that exert dominant influences on the injector behavior in different environments.










Combustion Instabilities in Gas Turbine Engines


Book Description

This book offers gas turbine users and manufacturers a valuable resource to help them sort through issues associated with combustion instabilities. In the last ten years, substantial efforts have been made in the industrial, governmental, and academic communities to understand the unique issues associated with combustion instabilities in low-emission gas turbines. The objective of this book is to compile these results into a series of chapters that address the various facets of the problem. The Case Studies section speaks to specific manufacturer and user experiences with combustion instabilities in the development stage and in fielded turbine engines. The book then goes on to examine The Fundamental Mechanisms, The Combustor Modeling, and Control Approaches.







Swirl Coaxial Injector Development, Part II: CFD Modeling


Book Description

Injector design is critical to obtaining the dual goals of long engine life as well as providing high energy release efficiency in the main combustion chamber. Introducing a swirl component in the injector flow can enhance the propellant mixing and thus improve engine performance. A combined experimental and computational effort is underway to examine the properties of GOX-centered, swirl coaxial injectors to examine their performance and lifetime characteristics. These injectors can be easily manufactured and can be designed to maintain a low face temperature, which will improve engine life. Therefore, swirl coaxial injectors, which swirl liquid fuel around a gaseous oxygen core, show promise for the next generation of high performance staged combustion rocket engines utilizing hydrocarbon fuels. The purpose of this work is to not only examine the properties of these injectors, but also to develop a design methodology, utilizing a combination of high-pressure cold-flow testing, uni-element hot- fire testing, and computations to create a high performing, long life swirl coaxial injector for multi-element combustor use.




Liquid Rocket Thrust Chambers


Book Description

This is the first major publication on liquid-rocket combustion devices since 1960, and includes 20 chapters prepared by world-renowned experts. Each chapter focuses on a specific aspect of liquid-propellant combustion and thrust chamber dynamics, and is incorporated into the volume in a well-organized, cohesive manner. There are contributions from nine different countriesChina, France, Germany, Italy, Japan, the Netherlands, Russia, Sweden, and the United States.







Combustion Dynamics and Control in Liquid-Fueled Direct Injection Systems


Book Description

Experiments evaluating the performance of a closed-loop combustion stabilization algorithm show that the method can reduce the magnitude of pressure oscillations in a liquid-fueled combustor by more than 50%. This paper describes the gas-turbine type combustor facility used for the experiments, associated instrumentation, unsteady combustion experiments, and the control scheme employed to suppress the natural thermo-acoustic instability. The combustor exhibits a natural instability at 140 Hz, the result of dynamic coupling between the combustor pressure field and the combustion heat release. Experiments to characterize the influence of operating parameters on the behavior of the instability are described. The control algorithm, amplitude-based pulse-width modulation, is used to modulate flow through one stream of a dual-passage fuel injector at such a phase that the instability amplitude is reduced. The paper concludes with a discussion of the control experiments, showing that the algorithm was successful in reducing the pressure oscillation.




The Investigation on Dynamic Spray Characteristics of Gas-centered Swirl Coaxial Injector


Book Description

Due to the popularity in space exploration, the importance of liquid propellant rocket engines (LPRE) has increased. Gas-centered swirl coaxial (GCSC) injectors are widely implemented in gas-generation cycled LPREs. Thus, GCSC injectors has been a popular subject these years. The aims of this thesis were to establish a design process of LPRE and GCSC injector, and gain deeper understanding of the behavior of GCSC injector under large amplitude flowrate variation by conducting dynamic cold flow experiment using self-developed flowrate excitation ball valve. The LPRE and GCSC injector were firstly designed by theoretical formulae, and the detailed design were done with key geometric parameters acquired for future ground static test and cold flow experiments. After that, full-bridge gate driver and microcontroller chips were used to developed a DC motor controller. Angular position controller was realized by LabView, incremental encoder, DC motor and DC motor controller mentioned above. Finally, both steady and dynamic cold flow experiments were conducted with self-constructed backlight illumination observation system, fluid supply system, flowrate excitation ball valve, and GCSC injectors. After analyzing the results of cold flow experiment with self-developed computer program, four major conclusions were made: 1. The design of changing gas nozzle length to change recess ratio was found to be weakening the swirl strength. 2. The pressure oscillation in liquid manifold would create addition perturbation to liquid film, leading to the shortening of breakup length. 3. Large intact liquid films were more sensitive to change in gas momentum. 4. Momentum ratio was found to be a dominant factor determining the general breakup of liquid film based on the fact that spray cone structure was independent of phase difference in pressure oscillation.