Preface 1.General Considerations 2.Basic Processes in Atomization 3.Drop Size Distributions of Sprays 4.Atomizers 5.Flow in Atomizers 6.Atomizer Performance 7.External Spray Charcteristics 8.Drop Evaporation 9.Drop Sizing Methods Index

Atomization and Sprays

Several nozzle concepts that promise a gain in performance over existing conventional nozzles are discussed in this paper. It is shown that signie cant performance gains result from the adaptation of the exhaust e ow to the ambient pressure. Special attention is then given to altitude-adaptive nozzle concepts, which have recently received new interest in the space industry. Current research results are presented for dual-bell nozzles and other nozzles with devices for forced e ow separation and for plug nozzles with external freestream expansion. In addition, results of former research on nozzles of dual-mode engines such as dual-throat and dual-expander engines and on expansion ‐dee ection nozzles are shown. In general, e ow adaptation induces shocks and expansion waves, which result in exit proe les that are quite different from idealized one-dimensional assumptions. Flow phenomena observed in experiments and numerical simulations during different nozzle operations are highlighted, critical design aspects and operation conditions are discussed, and performance characteristics of selected nozzles are presented. The consideration of derived performance characteristics in launcher and trajectory optimization calculations reveal signie cant payload gains at least for some of these advanced nozzle concepts.

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Advanced Rocket Nozzles.

Liquid-propellant rocket engines are capable of on-command variable thrust or thrust modulation, an operability advantage that has been studied intermittently since the late 1930s. Throttleable liquid-propellant rocket engines can be used for planetary entry and descent, space rendezvous, orbital maneuvering including orientation and stabilization in space, and hovering and hazard avoidance during planetary landing. Other applications have included control of aircraft rocket engines, limiting of vehicle acceleration or velocity using retrograde rockets, and ballistic missile defense trajectory control. Throttleable liquid-propellant rocket engines can also continuously follow the most economical thrust curve in a given situation, as opposed to making discrete throttling changes over a few select operating points. The effects of variable thrust on the mechanics and dynamics of an liquid-propellant rocket engine as well as difficulties and issues surrounding the throttling process are important aspects of throttling behavior. This review provides a detailed survey of liquid-propellant rocket engine throttling centered around engines from the United States. Several liquid-propellant rocket engine throttling methods are discussed, including high-pressure-drop systems, dual-injector manifolds, gas injection, multiple chambers, pulse modulation, throat throttling, movable injector components, and hydrodynamically dissipative injectors. Concerns and issues surrounding each method are examined, and the advantages and shortcomings compared.

/pdf/liquid-propellant-rocket-engine-throttling-a-comprehensive-2wvkh5zlte.pdf

Liquid-propellant rocket engine throttling: A comprehensive review

Injection and Atomization Propellant Injection Systems and Processes Dynamics of Liquid Rocket Injectors Atomization of Coaxial-Jet Injectors Atomization of Impinging-Liquid Jets Disintegration and Distortion of Liquid Streams Combustion and Ignition Modeling of Liquid-Propellant Combustion in Rocket Engine Combustor Liquid-Propellant Droplet Vaporization and Combustion Droplet Cluster Behavior in Dense and Dilute Regions of Sprays Supercritical Combustion CARS Measurements in Cryogenic LOX-GH2 Jet Flames Propellant Ignition and Flame Propagation Nozzle Concepts, Design, and Optimization Rocket Engine Nozzle Concepts Nozzle Design and Optimization Thrust Chamber Dynamics, Heat Transfer, and Performance Simulation and Analysis of Thruster Chamber Flowfields: Storable Propellant Rockets Simulation and Analysis of Thrust Chamber Flowfields: Cryogenic-Propellant Rockets Scaling Techniques in Liquid Rocket Engine Combustion Devices Testing Thrust Chamber Cooling and Heat Transfer Assessment of Thrust Chamber Performance Aspects of Engine System Design Thermodynamic Power Cycles for Pump-Fed Liquid Rocket Engines Tripropellant Liquid Rocket Engine Technology Oxidizer-Rich Preburner Technology for Oxygen/Hydrogen Full Flow Cycle Applications

Liquid rocket thrust chambers : aspects of modeling, analysis, and design

Liquid-Propellant Rocket Engines (LREs) are capable of on-command variable thrust or thrust modulation, an operability advantage that has been studied intermittently since the late 1930s. Throttleable LREs can be used for planetary entry and descent, space rendezvous, orbital maneuvering including orientation and stabilization in space, and hovering and hazard avoidance during planetary landing. Other applications have included control of aircraft rocket engines, limiting of vehicle acceleration or velocity using retrograde rockets, and ballistic missile defense trajectory control. Throttleable LREs can also continuously follow the most economical thrust curve in a given situation, compared to discrete throttling changes over a few select operating points. The effects of variable thrust on the mechanics and dynamics of an LRE as well as difficulties and issues surrounding the throttling process are important aspects of throttling behavior. This review provides a detailed survey of LRE throttling centered around engines from the United States. Several LRE throttling methods are discussed, including high-pressure-drop systems, dual-injector manifolds, gas injection, multiple chambers, pulse modulation, throat throttling, movable injector components, and hydrodynamically dissipative injectors. Concerns and issues surrounding each method are examined, and the advantages and shortcomings compared.

/pdf/liquid-propellant-rocket-engine-throttling-a-comprehensive-1uq0n39qtw.pdf

Liquid-Propellant Rocket Engine Throttling: A Comprehensive Review

The reduction of Earth-to-orbit launch costs in conjunction with an increase in launcher reliability and operational efe ciency are the key demands on future space transportation systems. Results of various system analyses indicate that these demands can be met with future single-stage-to-orbit (SSTO) vehicles using advanced technologies for both structure and propulsion systems. This paper will provide a classie cation and description of all turbopump feed liquid rocket engine cycles, followed by a combined vehicle/propulsion analysis of the design parameters for the propulsion systems and their associated thermodynamic cycles for the launch of future SSTO vehicles. Existing and projected rocket engine cycles capable of SSTO missions will be presented.

Cycles for Earth-to-Orbit Propulsion

Flight-qualified liquid propellant rocket engines from the Russian lunar launch program were received at Aerojet, modified to include reusable and restartable features with modern instrumentation and controls, and test fired to verify the modifications. The NK-33 liquid oxygen/kerosene propellant rocket engine was designed and manufactured by Samara State Scientific and Production Enterprise "TRUD" (now known as N.D. Kuznetsov Samara Scientific and Technical Company) of Samara, Russia, for the Soviet N-l launch vehicle. This staged combustion engine delivered high pressure (2109 psia chamber pressure) and high performance (331 seconds vacuum delivered specific impulse) that had never been available in the West for an hydrocarbon engine. Aerojet imported 36 NK-33 engines, along with 9 NK-43 engines, an upper stage version of the same engine, from N.D. Kuznetsov SSTC. The first of the NK33 engines was modified for use on the Kistler K-l launch vehicle. Modifications included replacement of pyrotechnic initiated valves with solenoid actuated valves; replacement of electromechan ical actuators for thrust and mixture ratio control; redesign of purge supply systems; replacement of solid propellant for the turbopump start spinup and the main chamber igniters; redesign and replacement of the thrust frame for addition of a gimbal and thrust vector control mount; addition of valves, pyrotechnics, and plumbing to restart the engine; and replacement of instrumentation and wiring harnesses. This engine was successfully test fired at Aerojet to verify

http://lpre.de/resources/articles/AIAA-1998-3361.pdf

Modification and verification testing of a russian nk-33 rocket engine for reusable and restartable applications

Scaling and throttling of combustion devices are important capabilities to demonstrate in development of liquid rocket engines for NASA's Space Exploration Mission. Scaling provides the ability to design new injectors and injection elements with predictable performance on the basis of test experience with existing injectors and elements, and could be a key aspect of future development programs. Throttling is the reduction of thrust with fixed designs and is a critical requirement in lunar and other planetary landing missions. A task in the Constellation University Institutes Program (CUIP) has been designed to evaluate spray characteristics when liquid propellant rocket engine injectors are scaled and throttled. The specific objectives of the present study are to characterize injection and primary atomization using cold flow simulations of the reacting sprays. These simulations can provide relevant information because the injection and primary atomization are believed to be the spray processes least affected by the propellant reaction. Cold flow studies also provide acceptable test conditions for a university environment. Three geometric scales - 1/4- scale, 1/2-scale, and full-scale - of two different injector element types - swirl coaxial and shear coaxial - will be designed, fabricated, and tested. A literature review is currently being conducted to revisit and compile the previous scaling documentation. Because it is simple to perform, throttling will also be examined in the present work by measuring primary atomization characteristics as the mass flow rate and pressure drop of the six injector element concepts are reduced, with corresponding changes in chamber backpressure. Simulants will include water and gaseous nitrogen, and an optically accessible chamber will be used for visual and laser-based diagnostics. The chamber will include curtain flow capability to repress recirculation, and additional gas injection to provide independent control of the backpressure. This paper provides a short review of the appropriate literature, as well as descriptions of plans for experimental hardware, test chamber instrumentation, diagnostics, and testing.

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Cold Flow Testing for Liquid Propellant Rocket Injector Scaling and Throttling

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.

/pdf/scaling-of-performance-in-liquid-propellant-rocket-engine-2d6h7eafl1.pdf

James R. Hulka

Papers

Cycles for Earth-to-Orbit Propulsion

Modification and verification testing of a russian nk-33 rocket engine for reusable and restartable applications

Cold Flow Testing for Liquid Propellant Rocket Injector Scaling and Throttling

Scaling of Performance in Liquid Propellant Rocket Engine Combustion Devices

Benchmark testing of an enhanced operability LO2/LH2 RD-0120 engine