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At least 37 records · Page 2

Scaling of Performance in Liquid Propellant Rocket Engine Combustion Devices

This paper discusses scaling of combustion and combustion performance in liquid propellant rocket engine combustion devices. In development of new combustors, comparisons are often made between predicted performance in a new combustor and measured performance in another combustor with different geometric and thermodynamic characteristics. Without careful interpretation of some key features, the comparison can be misinterpreted and erroneous information used in the design of the new device. This paper provides a review of this performance comparison, including a brief review of the initial liquid rocket scaling research conducted during the 1950s and 1960s, a review of the typical performance losses encountered and how they scale, a description of the typical scaling procedures used in development programs today, and finally a review of several historical development programs to see what insight they can bring to the questions at hand.

Hulka, James R.↗

Simulation of liquid propellant rocket engine combustion instabilities

A simulation technique for studying the high frequency combustion instabilities of liquid propellant rocket engines has been developed and used to investigate various aspects of instability phenomena. Of importance was investigation of the significance of the method of coupling the combustion and the gas dynamics of the system. Two coupling processes were studied: linear response of the combustion process to pressure fluctuations, and the nature of the resulting instabilities; and nonlinear response of the combustion process to velocity fluctuations, and the nature of the resulting instabilities. For the combustion model studied, nonlinear (velocity) coupling was found to more closely characterize liquid propellant instabilities.

Ventrice, M. B.↗

Optimizing a liquid propellant rocket engine with an automated combustor design code (AUTOCOM)

A procedure for automatically designing a liquid propellant rocket engine combustion chamber in an optimal fashion is outlined. The procedure is contained in a digital computer code, AUTOCOM. The code is applied to an existing engine, and design modifications are generated which provide a substantial potential payload improvement over the existing design. Computer time requirements for this payload improvement were small, approximately four minutes in the CDC 6600 computer.

Hague, D. S.↗

Prediction of high frequency combustion instability in liquid propellant rocket engines

The present use of a numerical model developed for the prediction of high-frequency combustion stabilities in liquid propellant rocket engines focuses on (1) the overall behavior of nonlinear combustion instabilities (2) the effects of acoustic oscillations on the fuel-droplet vaporization and combustion process in stable and unstable engine operating conditions, oscillating flowfields, and liquid-fuel trajectories during combustion instability, and (3) the effects of such design parameters as inlet boundary conditions, initial spray conditions, and baffle length. The numerical model has yielded predictions of the tangential-mode combustion instability; baffle length and droplet size variations are noted to have significant effects on engine stability.

Kim, Y. M.↗

Nonlinear Longitudinal Mode Instability in Liquid Propellant Rocket Engine Preburners

Nonlinear pressure oscillations have been observed in liquid propellant rocket instability preburner devices. Unlike the familiar transverse mode instabilities that characterize primary combustion chambers, these oscillations appear as longitudinal gas motions with frequencies that are typical of the chamber axial acoustic modes. In several respects, the phenomenon is similar to longitudinal mode combustion instability appearing in low-smoke solid propellant motors. An important feature is evidence of steep-fronted wave motions with very high amplitude. Clearly, gas motions of this type threaten the mechanical integrity of associated engine components and create unacceptably high vibration levels. This paper focuses on development of the analytical tools needed to predict, diagnose, and correct instabilities of this type. For this purpose, mechanisms that lead to steep-fronted, high-amplitude pressure waves are described in detail. It is shown that such gas motions are the outcome of the natural steepening process in which initially low amplitude standing acoustic waves grow into shock-like disturbances. The energy source that promotes this behavior is a combination of unsteady combustion energy release and interactions with the quasi-steady mean chamber flow. Since shock waves characterize the gas motions, detonation-like mechanisms may well control the unsteady combustion processes. When the energy gains exceed the losses (represented mainly by nozzle and viscous damping), the waves can rapidly grow to a finite amplitude limit cycle. Analytical tools are described that allow the prediction of the limit cycle amplitude and show the dependence of this wave amplitude on the system geometry and other design parameters. This information can be used to guide corrective procedures that mitigate or eliminate the oscillations.

Sims, J. D.↗

Design of Liquid Propellant Rocket Engines Second Edition

This book intends to build a bridge for the student and the young engineer: to link the rocket propulsion fundamentals and elements (which are well covered in the literature) with the actual rocket engine design and development work as it is carried out in industry (which is very little, if at all covered in literature). The book attempts to further the understanding of the realistic application of liquid rocket propulsion theories, and to help avoid or at least reduce time and money consuming errors and disappointments. In so doing, it also attempts to digest and consolidate numerous closely related subjects, hitherto often treated as separate, bringing them up to date at the same time. The book was written "on the job" for use by those active in all phases of engine systems design, development, and application, in industry as well as government agencies. Since it addresses itself to human beings set out to create new machines, rather than describing machines about to dominate man, the language chosen may not always be "functional" in the strict sense of the word. The book presents sufficient detail to familiarize and educate thoroughly those responsible for various aspects of liquid propellant rocketry, including engine systems design, engine development, and flight vehicle application. It should enable the rocket engineer to conduct, independently, complete or partial engine systems preliminary detail designs and to understand and judge the activities in, and the problems, limitations, and "facts of life~ of the various subsystems making up a complete engine system. It also attempts to educate those ultimately interested in specialized subsystems and component design (thrust chamber, turbopump, control valves, etc.) about their own as well as neighboring subsystems and about the complete engine system. This should enable the student to prepare realistic analytical calculations and design layouts with a long headstart toward the final specialized designs for subsystem production release. Special emphasis has been placed on engine flight application to stimulate engine systems and subsystem designers to think in these terms from the outset. The book is intended as a textbook, with specific consideration of the teacher without industry experience. We hope it will stimulate those desiring to specialize in the area of a rocket engine subsystem by supplying adequate information to enable them to benefit fully from the specialized literature. Thus, it provides a realistic expert introduction for those joining the liquid propellant rocket engine field.

Dieter K Huzel↗

Sensing and actuation in a liquid propellant rocket engine

Equations describing the conservation of mass, momentum, and energy, and multicomponent transport and chemical reaction in a liquid propellant rocket (LPR) engine are given, along with appropriate boundary conditions. The formulation includes a detailed description of the two-phase (gas/liquid) flow in terms of a moving boundary problem, with droplets and vapor occupying time-dependent subdomains of the LPR chamber. Several sensor and actuator types are considered in detail, and their mathematical descriptions are incorporated into the differential equations and boundary conditions.

Bentsman, Joseph↗

Scaling of Performance in Liquid Propellant Rocket Engine Combustors

The objectives are: a) Re-introduce to you the concept of scaling; b) Describe the scaling research conducted in the 1950s and early 1960s, and present some of their conclusions; c) Narrow the focus to scaling for performance of combustion devices for liquid propellant rocket engines; and d) Present some results of subscale to full-scale performance from historical programs. Scaling is "The ability to develop new combustion devices with predictable performance on the basis of test experience with old devices." Scaling can be used to develop combustion devices of any thrust size from any thrust size. Scaling is applied mostly to increase thrust. Objective is to use scaling as a development tool. - Move injector design from an "art" to a "science"

Hulka, James↗

Thermal Insulative Elastomers for Clustered Large Liquid Propellant Rocket Engines

As thrust levels increase and as rocket engines fire for longer periods of time, the difficulties encountered in the protection of critical components from the effects of excessively high temperatures greatly increase. To protect these components a series of filled elastomeric composites have been evaluated. A brief discussion is presented of the problems of hot gas recirculation, radiation, and base plane heating with particular reference to large, clustered, liquid propellant rocket engines. The effect on components is discussed and an evaluation of a series of insulators based on filled elastomeric composites is presented. The evaluations are based on specialized thermal tests which were designed to simulate as far as possible, conditions during flight. The most promising of these elastomeric composites are compared to three alternative insulative systems, a filled, castable ceramic, a metal foil-silica fiber batting, and an asbestos-inconel wire mesh composite, in terms of weight, cost, and ease of fabrication and repair.

Peters, S. T.↗

Control-oriented modeling of combustion and flow processes in liquid propellant rocket engines

This paper presents a control-oriented model of the flow, reaction, and transport processes in liquid propellant rocket combustion chambers, based on the multicomponent conservation laws of gas dynamics. This model provides a framework for the inclusion of detailed chemical kinetic relations, viscous and other dissipative effects, a variety of actuators and sensors, as well as process and measurement disturbances. In addition to its potential usefulness to the designer in understanding the dynamical complexity of the system and the sources of model uncertainty, the model provides a rigorous basis for control system design. An appraisal of current and feasible actuators and sensors, and their mathematical representation are included.

Bentsman, Joseph↗

Fiberoptics for liquid propellant rocket engine environments

Interest is increasing in the use of fiberoptics on liquid-fueled rocket engines in recognition of their immunity to lightning and EMI, light weight, high-frequency response, and the possibility offered by optical technologies to measure additional important engine parameters for which present measurement methods are impractical. This paper discusses the requirements to be placed on fiberoptics applied to liquid-fueled rocket engines; identifies manufacturers of fibers that appear to have promise for the harsh rocket engine applications; and summarizes information on the characteristics of these fibers obtained from the manufacturers, program testing, and the general literature.

Delcher, R.↗

Fiber optics in liquid propellant rocket engine environments

Fiber optics have recently been seen to offer several major benefits in liquid-fuel rocket engine applications. Fiber-optic sensors can provide measurements that cannot be made with conventional techniques. Fiber optics also can reduce harness weight, provide lightning immunity, and increase frequency response. This paper discusses the results of feasibility testing optical fibers in simulated liquid-fuel rocket engine environments. The environments included cryogenic and high temperatures, and high vibration levels.

Delcher, R.↗