Browse Topic: Liquid propellant rocket engines

Items (102)

Large Eddy Simulations of Supercritical and Transcritical Jet Flows Using Real Fluid Thermophysical Properties

2020-01-115304/14/2020

In order to understand supercritical jet flows further, well resolved large eddy simulations (LES) of a n-dodecane jet mixing with surrounding nitrogen are conducted. A real fluid thermodynamic model is used to account for the fuel compressibility and variable thermophysical properties due to the solubility of ambient gas and liquid jet using the cubic Peng-Robinson equation of state (PR-EOS). A molar averaged homogeneous mixing rule is used to calculate the mixing properties. The thermodynamic model is coupled with a pressure-based solver to simulate multispecies reacting flows. The numerical model is based on a second order accurate method implemented in the open source OpenFOAM-6 software. First, to evaluate the present numerical model for sprays, 1D advection and shock tube benchmark problems at supercritical conditions are shown. Second, a cryogenic nitrogen injection with a jet velocity of 4.9 m/s into a supercritical nitrogen environment at 4 MPa and room temperature is

Ningegowda, B M, Rahantamialisoa, Faniry, Zembi, Jacopo, Pandal, Adrian, Im, Hong G., Battistoni, Michele

Effects of Engine Speed on the Performance at Extreme Vehicle Driving Conditions

2019-36-029701/13/2020

Nowadays, improvements in engine fuel economy and reduction in pollutant emissions have been much discussed. Downsizing and downspeeding are methods widely used in the automotive market, used to increase internal combustion engine efficiency. Fuel consumption is commonly measured through a specific cycle that could differ between countries. Federal Test Procedure (FTP-75) for Latin America and New European Driving Cycle (NEDC) for Europe are some examples. These cycles include normal driving conditions, low vehicle load and mild environmental conditions. The style of gear shifting is one of the main factors affecting fuel efficiency and performance of motor vehicles. At extreme diving conditions, parameters like coolant and air charge temperature could reach limit durability values of the system. In order to avoid knocking and maintain structural reliability, it becomes mandatory to control the engine speed. An increase in engine speed reduces engine load requirements and thus

Thomaz, Fabrício, Baeta, José Guilherme Coelho

A Target Cascading Method Using Model Based Simulation in Early Stage of Vehicle Development

2019-01-083604/02/2019

In the early stages of vehicle development, it is important for decision makers to understand a feasible constraint region that satisfies all system level requirements. The purpose of this paper is to propose a target cascading method to solve for a feasible design region which satisfies all constraints of the system based on model based simulation. In this method, the feasible design region is explored by using both global optimization methods and active learning techniques. In optimization problems, the inverse problem for understanding feasibility for specific designs is defined and solved. To determine the objective functions of the inverse problem, an index representing the achievement level of constraints from system requirements is introduced. To predict feasible regions in the specific design space, a surrogate model of minimized values of the index is trained by using a kriging model. Training data of the surrogate model is sequentially generated based on the expected

Shintani, Kohei, Abe, Atsuji, Yamamoto, Yasushi

Freeform Channel Close-Out for High-Performance Heat Exchangers

TBMG-2884005/01/2018

Large-scale liquid rocket engines with regeneratively cooled nozzles will enable reliable and reduced-cost access to space. The coolant that circulates through the internal channels within the nozzle helps maintain adequate wall temperatures to prevent failure, and is contained under high pressure. It has been a challenge to affordably manufacture the intricate nozzle channels and close-out of these channels. As such, NASA has leveraged cladding and additive manufacturing technology to build the nozzle liner and outer jacket that closes out the channels within, and contains the high-pressure coolant fluid. The new capability reduces the time to fabricate the nozzle and allows for real-time inspection during the build. It has been demonstrated on a series of different alloys, hot-fire testing is nearly complete, and micrograph examination has verified that the bonds are reliable with little deformation to the coolant channels. The technology provides new opportunities to manufacture

Novel Design of an Orifice Control Element

TBMG-2800612/01/2017

An orifice element is commonly used in liquid rocket engine test facilities either as a flow metering device, a damper for acoustic resonance, or to provide a large reduction in pressure over a very small distance in the piping system. The orifice as a device is largely effective in stepping down pressure; however, it is also susceptible to a wake-vortex instability that generates pressure fluctuations that propagate downstream and interact with other elements of the test facility, resulting in structural vibrations. Exacerbating the situation in cryogenic test facilities is the possibility of the formation of vapor clouds when the pressure in the wake falls below the vapor pressure, leading to cavitation. Cavitation has the potential for highamplitude fluctuations that can cause catastrophic damage to a facility.

Effect of High Frequency Acoustic Field on Atomization Behavior of Ethanol and Kerosene

2017-01-231810/08/2017

Combustion instability often occurs inside the combustion chamber of aero engine. Fuel atomization and evaporation, one of the controlling processes of combustion rate, is an important mechanism of the combustion instability. To tackle combustion instability, it challenges a deep understanding of the underlying mechanism of fuel atomization and evaporation. In this paper, acoustic field was established to simulate the pressure oscillation. Transient spray images of ethanol and kerosene were recorded using high-speed camera. The obtained images were processed by MATLAB to extract and analyze the related data. Spatial fuel atomization characteristics was analytically examined by multi-threshold image method to analyze the effect of the high frequency acoustic field on the fuel break-up and disintegration. The results show that the half spray cone angle on the side with speaker is suppressed by the presence of the imposed acoustic field compared with the case without speaker

Jia, Xiaoxu, Huang, Zhong, Ju, Dehao, Huang, Zhen, Lu, Xing-cai

Numerical Analysis on the Injection and Atomization Characteristics of Diesel Surrogates at Engine Conditions

2017-01-230610/08/2017

Recently, the shortage of fossil resources contributes to strict regulations of environmental protection. The research on the high efficiency and low emission of engines becomes an important direction all over the world. Technologies like high injection pressure, high levels of supercharging and higher levels of back pressure have come into application. Increasing the injection pressure and average cylinder pressure results in that parts of the spray can experience transcritical and supercritical regimes. In this paper, we established a surrogate fuel composed of n-Hexadecane, HMN and 1-Metylnaphthalene, to analyze the injection and atomization of diesel surrogate fuel with large eddy simulation (LES) in a cubic calculation region with high temperature and high pressure environment. The injection pressure was fixed to 150MPa, and the 900-K temperature and the 6-MPa pressure represented the ambient condition in constant volume vessel which is supercritical with respect to No.2 diesel

Sun, Xiaochuan, Li, Xiang, Huang, Zhong, Ju, Dehao, Lu, Xing-cai, Han, Dong, Huang, Zhen

Application of Solid State Welding and Superplastic Forming to Aerospace Vehicles

2017-01-214809/19/2017

In this paper, manufacturing of launcher structural components with superplastic forming (SPF) and solid state welding technologies is presented with several examples. Some of high strength aerospace alloys, like aluminum, titanium and superalloys, are known to have superplasticity so that complex shapes of aerospace components can be produced with this technology. A combination of superplastic forming and solid state welding processes produces lighter and stiffer components than one manufactured with conventional machining and welding. Solid state welding is an attractive method to weld materials without melting where mechanical properties are important since the welding interface is homogeneous without liquid phases. The results includes aluminum and titanium tanks cryogenic application, a scaled combustion chamber with duplex stainless steel and copper alloy, and lightweight aluminum-copper-lithium cylinder manufactured by superplastic forming and diffusion bonding or friction stir

Combustion Characteristics of Hydrocarbon Droplets Induced by Photoignition of Aluminum Nanoparticles

TBMG-2738108/01/2017

In the study of combustion characteristics of liquid rocket fuels, it is customary to either study the combustion of liquid fuel droplets or the combustion of fuel sprays. However, the two are closely related to each other, because in a typical rocket combustion chamber, the burning of droplets, droplet clusters, and fuel sprays occur simultaneously.

Combustion Characteristics of Hydrocarbon Droplets Induced by Photoignition of Aluminum Nanoparticles

17AERP08_0706/01/2017

Test methodology allows analysis of combustion dynamics for subscale rocket injectors under super critical conditions. Air Force Research Laboratory (AFMC), Edwards Air Force Base, California In the study of combustion characteristics of liquid rocket fuels, it is customary to either study the combustion of liquid fuel droplets or the combustion of fuel sprays. However, the two are closely related to each other, because in a typical rocket combustion chamber, the burning of droplets, droplet clusters, and fuel sprays occur simultaneously. The study of droplet burning is mostly focused either on single suspended droplets or free droplets, usually in a free fall. In either case, the conditions regarding the combustion of a single fuel droplet deviates from what is expected in typical liquid rocket engines (LREs). This not only concerns the chamber pressure and the temperature that is usually much lower in a typical droplet study, but also the droplet ignition process and the related

Low Solidity Vaned Diffuser (LSVD) Design for Improvement of Pressure Recovery

TBMG-2685205/01/2017

Many pump vaned diffuser designs are based on existing airfoil designs, with little attention given to the vane leading edge. There is a need for a vaned diffuser leading edge that helps resist flow separation and the resultant poor diffuser pressure recovery. Diffusers in pumps are often working with an incompressible fluid that makes potential flow methodologies — which have incompressibility as a boundary condition — attractive. The potential flow-based free-streamline analysis methods have been known to improve the aerodynamics of varied components at high incidence angles, such as diffusers, jet engine nacelles, and liquid rocket engine turbopump inducers.

Green Monopropellant Secondary Payload Propulsion System

TBMG-2683505/01/2017

Small satellites, launched as secondary payloads, are increasingly being fielded. Advances in liquid rocket propulsion that enhance the on-orbit maneuverability, increase the on-orbit life, and decrease the time between identified need for and deployment of such spacecraft are of great value. Replacing the nearly ubiquitous yet toxic hydrazine propellant with AF-M315E produces higher specific impulse and density specific impulse, resulting in improved overall velocity change capability and increased on-orbit life.

Study of Formulating Conserved Scalar Equations for Turbulent Reactive Flows with General Species Mass- Diffusion Coefficients for Utilization in Flamelet Models

TBMG-2616501/01/2017

The modeling of turbulent reactive flows is a subject of contemporary research. Current turbulent-reaction models cannot account for realistic complexities such as distinct species mass-diffusion coefficients. Under the assumption of a single, constant, mass-diffusion coefficient, a conserved-scalar equation is typically derived in turbulent reactive flows by taking the difference between chemical-species conservation equations having opposite reaction rates (in the sense that the reactant has an opposite reaction rate to the product), thereby creating an equation devoid of reaction terms. Assuming the reaction regions are very thin and are merely contorted by turbulence, chemistry and turbulence can be decoupled, and the evolving statistics of the conserved scalar describe the reaction progression. No such equation has yet been derived for distinct mass-diffusion coefficient cases where the single coefficient is now replaced by a full matrix. Considering that mass diffusion is

NASA's Software Answers Big Questions About Space and Earth

TBMG-2606312/01/2016

NASA’s next-generation Space Launch System (SLS) for deep space exploration consists of four RS-25 liquid rocket engines and two five-segment solid rocket boosters (SRBs). At ignition, the SRBs create a significant over-pressure event, known as the Ignition Over-Pressure (IOP) event. The IOP event experienced in the first space shuttle flight (STS-1) in 1981 damaged the space shuttle orbiter and motivated significant design changes to the launch pad at NASA’s Kennedy Space Center. The RS-25 liquid rocket engines aboard the SLS, along with the SRBs, also create a very significant acoustic environment that, if not mitigated, can harm the SLS launch vehicle. An Ignition Over-Pressure/Sound Suppression (IOP/SS) water system was developed to reduce the amplitude of both the IOP event and the acoustic environment caused by the firing of the RS-25 engines and the SRBs.

Uncertainty of In-Flight Thrust Determination

AIR1678B (Current)10/22/2016

This document defines and illustrates the process for determination of uncertainty of turbofan and turbojet engine in-flight thrust and other measured in-flight performance parameters. The reasons for requiring this information, as specified in the E-33 Charter, are: determination of high confidence aircraft drag; problem rectification if performance is low; interpolation of measured thrust and aircraft drag over a range of flight conditions by validation and development of high confidence analytical methods; establishment of a baseline for future engine modifications. This document describes systematic and random measurement uncertainties and methods for propagating the uncertainties to the more complicated parameter, in-flight thrust. Methods for combining the uncertainties to obtain given confidence levels are also addressed. Although the primary focus of the document is in-flight thrust, the statistical methods described are applicable to any measurement process. The E-33 Committee

E-33 In Flight Propulsion Measurement Committee

Eddy-Current-Minimizing Flow Plug for Use in Flow Conditioning and Flow Metering

TBMG-2551010/01/2016

Innovators at NASA’s Marshall Space Flight Center have developed a suite of prototype fluid plug technologies with an array of capabilities for fluid flow metering, mixing, and conditioning. Each innovation within this suite is based upon a core technology that has no moving parts, is simple to manufacture, and provides high reliability and efficiency. Also, the base fluid plug technology can be modified with very few or no hardware changes to achieve the desired effect or combination of mixing, metering, and conditioning capabilities depending on the application.

Distributed, Fast, Intelligent Infrastructure Health Monitoring System

TBMG-2426704/01/2016

NASA needed an innovative solution to conduct system assessments of frameworks and to characterize subsystems of interest. This tool would be required to determine anomalies; examine their causes (root-cause analysis); make predictive statements (prognostics); provide intelligent health monitoring with incremental knowledge for working with unknown scenarios; and provide maintenance support for a complex collection of systems, subsystems, and elements in rocket engine test platforms.

Aluminum Rocket Engine Injector Fabricated Using 3D Additive Manufacturing

06/01/2015

Liquid rocket engine injectors can be extremely expensive to manufacture and hard to iterate to achieve high performance. Internal sealing points can also be the source of reliability issues. The technology disclosed here covers the application of a 3D additive manufacturing (AM) process to produce a functional aluminum injector for liquid propellant rocket engines, along with injector and overall engine design features that optimize the application of such processes to improve performance, reliability, and affordability relative to components produced using standard machining processes and designs. Aluminum was used for the injector instead of higher- temperature metals like stainless steel because its thermal conductance properties provide more opportunity to leverage the cooling potential of liquid oxygen and other cryogenic propellants.

START-UP ABILITY OF UAVs ON TASK

14AERD09_0109/03/2014

Besides low cost, easy manufacturability, light weight, long operation time, and high durability, miniature UAVs need restart capability during flight. Small unmanned air vehicles (UAVs) are today extensively used for a wide range of applications, from amateur to military applications. Many UAVs use electrical energy for the thrust generation, making them flexible, simple, safe, and quiet. The main drawback of this traction strategy is the low energy density of batteries compared to energy stored in the liquid form, as well as the speed and flight range of the vehicle. This is the point where turbines make their entrance. However, micro turbines used for the bigger UAVs are complex and expensive. The small dimensions require small clearances to maintain reasonable efficiencies. On the other hand, the rotating parts should be able to expand due to the high temperature. As the scale of turbo machinery is reduced, the compressor efficiency decreases and, therefore, the efficiency non

Advanced Numerical Tools for Design and Analysis of In-Space Valve and Feed Systems

09/01/2014

A high-fidelity numerical simulation software (CRUNCH CFD®) predicts the transient performance of flight valve designs, provides design support by supplementing current empirical rules, and diagnoses system anomalies. Currently, transient analysis of valves is difficult to simulate because of the requirement to dynamically deform the grid due to the valve motion. For complex, transient problems such as engine startup or shutdown that also involve dynamic sealing of fluid flow paths due to valve/solid surface contact, it becomes nearly impossible to deform the grid in an automated fashion.

3-D Manufacturing of Titanium Components Takes Off

TBMG-2034208/01/2014

With such challenges as base closings, shrinking defense budgets, and sequestration, the worldwide maintenance, repair, and overhaul (MRO) sector is projected to experience a significant decline over the next few years.

3-D Manufacturing of Titanium Components Takes Off

14AERP08_0108/01/2014

MRO providers are discovering ways to innovate their procedures while remaining viable and profitable through the current downturn in government spending. With such challenges as base closings, shrinking defense budgets, and sequestration, the worldwide maintenance, repair, and overhaul (MRO) sector is projected to experience a significant decline over the next few years. According to Hal Chrisman, leading analyst and Vice President at aviation consultancy ICF SH&E, “it appears that defense operations and maintenance spending will drop nearly 8%.” He added “forecasting, which is especially critical in the aftermarket world, is very tricky this year.”

Elevated-Temperature, Highly Emissive Coating for Energy Dissipation of Large Surfaces

TBMG-1990306/01/2014

This coating demonstrates high emittance above 80% or better at broad wavelengths within the infrared spectrum. It has shown to have an extremely stable emittance at lower wavelengths within the infrared (IR) spectrum, where energy dissipation is critical at elevated temperatures. The coating has demonstrated increases in surface texturing, and ultimately an increase in emissivity when exposed to temperatures up to 2,050 °F (≈1,120 °C). It is also stable at continuous run, elevated temperatures, and shows no signs of spalling or erosion.

Liquid Propellant Gas Generation Systems

AIR1343B (Current)06/17/2013

This information report presents a preliminary discussion of liquid propellant gas generation (LPGG) systems. A LPGG system, as used herein, is defined as a system which stores a liquid propellant and, on command, discharges and converts the liquid propellant to a gas. The LPGG system can interface with a gas-to-mechanical energy conversion device to make up an auxiliary power system. Figure 1 shows a block diagram of LPGG system components which include a propellant tank, propellant expulsion system, propellant control and a decomposition (or combustion) chamber. The purpose of this report is to provide general information on the variety of components and system arrangements which can be considered in LPGG design, summarize advantages and disadvantages of various approaches and provide basic sizing methods suitable for initial tradeoff purposes.

A-6C4 Power Sources Committee

Simulation of Oxygen Disintegration and Mixing With Hydrogen or Helium at Supercritical Pressure

TBMG-1486810/01/2012

The simulation of high-pressure turbulent flows, where the pressure, p, is larger than the critical value, pc, for the species under consideration, is relevant to a wide array of propulsion systems, e.g. gas turbine, diesel, and liquid rocket engines. Most turbulence models, however, have been developed for atmospheric-p turbulent flows. The difference between atmospheric-p and supercritical-p turbulence is that, in the former situation, the coupling between dynamics and thermodynamics is moderate to negligible, but for the latter it is very significant, and can dominate the flow characteristics. The reason for this stems from the mathematical form of the equation of state (EOS), which is the perfect-gas EOS in the former case, and the real-gas EOS in the latter case.

Estimation of Measurement Uncertainty in Engine Tests Based on NATO AGARD Uniform Engine Test Program

AIR4979A (Current)05/29/2012

The primary objective of this document is to describe the systematic and random measurement uncertainties which may be expected when testing gas turbine engines in a range of different test facilities. The documentation covers a "traditional" method for estimating pretest uncertainties and a "new" method for computing and comparing posttest uncertainties. To determine these posttest uncertainties, data generated during the AGARD Uniform Engine Test Program (UETP) were analyzed and compared to the pretest estimates. The proposed procedure provides a mechanism for determining the expected accuracy of test results obtained from facilities which were not previously cross calibrated. Furthermore, the method can be used to assist in making cost-effective management decisions on the level of validation/cross calibration necessary when bringing a test facility on line. This document is also intended to act as a guide for improving uncertainty analyses in a broad spectrum of related industries

E-33 In Flight Propulsion Measurement Committee

Applications of Probabilistic Methods

AIR5109 (Current)05/08/2012

This SAE Aerospace Information Report (AIR) addresses the following: 1 Captures previous experience and lessons learned in the application of PM. 2 Tabulates public-domain applications, and several representative examples discussed in detail. 3 Notes relative merits and barriers to implementation. The document does not contain technical details of probabilistic methods, benchmarking of specific approaches or legal aspects. These subjects are covered in other AIRs, referenced in Section 2 and prepared by the Probabilistic Methods Committee of the G-11 Reliability, Maintainability, Supportability and Logistics (RMSL) Division of SAE.

G-11 Probabilistic Methods Committee

Nonlinear Combustion Instability Prediction

TBMG-843209/01/2010

The liquid rocket engine stability prediction software (LCI) predicts combustion stability of systems using LOX-LH2 propellants. Both longitudinal and transverse mode stability characteristics are calculated. This software has the unique feature of being able to predict system limit amplitude.

Liquid Propellant Gas Generation Systems

AIR1343A (Historical)11/06/2007

This information report presents a preliminary discussion of liquid propellant gas generation (LPGG) systems. A LPGG system, as used herein, is defined as a system which stores a liquid propellant and, on command, discharges and converts the liquid propellant to a gas. The LPGG system can interface with a gas-to-mechanical energy conversion device to make up an auxiliary power system. Figure 1 shows a block diagram of LPGG system components which include a propellant tank, propellant expulsion system, propellant control and a decomposition (or combustion) chamber. The purpose of this report is to provide general information on the variety of components and system arrangements which can be considered in LPGG design, summarize advantages and disadvantages of various approaches and provide basic sizing methods suitable for initial tradeoff purposes.

A-6C4 Power Sources Committee

Liquid Oxygen/Liquid Methane Rocket Engine Development

2007-01-387609/17/2007

Because of low toxicity and low reactivity, methane and oxygen are identified as “green propellants”, and have the highest performance (as measured in ISP) of any practical rocket propellants, except oxygen/hydrogen. Investigation into green propellant rocket engines identified liquid oxygen (LOX)/methane (CH4) as an excellent candidate for upper stage applications. This paper discusses work in LOX/CH4 engine development carried out by XCOR Aerospace, Inc.

DeLong, Dan, Greason, Jeff, McKee, Khaki Rodway

Uncertainty of In-Flight Thrust Determination

AIR1678A (Historical)06/11/2007

This document defines and illustrates the process for determination of uncertainty of turbofan and turbojet engine in-flight thrust and other measured in-flight performance parameters. The reasons for requiring this information, as specified in the E-33 Charter, are: - determination of high confidence aircraft drag - problem rectification if performance is low - interpolation of measured thrust and aircraft drag over a range of flight conditions by validation and development of high confidence analytical methods - establishment of a baseline for future engine modifications This document describes systematic and random measurement uncertainties and methods for propagating the uncertainties to the more complicated parameter, in-flight thrust. Methods for combining the uncertainties to obtain given confidence levels are also addressed. Although the primary focus of the document is in-flight thrust, the statistical methods described are applicable to any measurement process. The E-33

E-33 In Flight Propulsion Measurement Committee

Virtual SEA: Towards an Industrial Process

2007-01-230205/15/2007

In the high frequency range, the SEA method has been applied to air borne path with success to predict both internal and external sound environment. Nevertheless, structure-borne prediction is still at issue -especially for cars, in the range 200 to 2000 Hz- as results are widely dependant on subsystem partition and validity of various assumptions required by SEA. Experimental SEA test technique (ESEA), applied to car bodies, has brought to the fore that SEA power balanced equations could robustly describe structure-borne noise. To make ESEA predictive, the database of measured FRF is simply replaced and enlarged by synthesized data generated from a finite element (FE) model and a selected observation grid of nodes. This technique, called Virtual SEA (VSEA), has been presented at SAE/NVC 2003. Since then, many developments have been carried out to improve the general efficiency of the three main steps of VSEA: The generation of the band-integrated FRF database (between nodes of the

Borello, Gérard, Gagliardini, Laurent

Super-High-Strength Aluminum Alloy

TBMG-465806/01/2006

AFRL researchers developed a superhigh- strength aluminum alloy that engineers can use to improve the capability and performance of aerospace components—cryogenic rocket engine components, in particular. They created an aluminum alloy with specific strength and ductility characteristics surpassing those of the alpha titanium alloy currently used in rocket engine turbopumps. The aluminum alloy also demonstrates less sensitivity to hydrogen embrittlement, is lighter weight, and is potentially less costly to manufacture than the titanium alloy.

Theoretical and Experimental Studies of Electrospray for IC Engine

2006-01-138804/03/2006

The objective of this work was to investigate the potential of the electrostatic atomization for its application in internal combustion engines. In this paper, a theoretical model for secondary breakup of charged droplets was established. The electric force reduces the surface tension of liquid, whereby atomization is promoted. To improve the diesel droplet atomization remarkably by means of electrostatic charge, the charge-mass ratio should be at least at the order of 10-6C/g. In the interest of the practical application conditions in internal combustion engines, the high-pressure injected electrospray was generated and investigated under various injection pressures and electric conditions. By means of the Photron high-speed camera, the special features of electrospray were observed. The micro-characters including the drop size distribution and the variance of the drop diameter in the spray front area were investigated. The uniformity of the diesel droplet sizes in this area was

Li, Liguang, Yu, Shui, Hu, Zongjie

Design of D-B Injectors for Increasing Propulsive Force in Jets

2005-01-338810/03/2005

In this work the fundamentals of centrifugal injector calculation is reviewed and new design procedure is proposed for liquid-liquid injectors, based on both theory and experimental results. Then some special conditions related to dual based liquid-liquid injectors are studied and the corresponding results were considered in design manipulation. The behavior of injector in various service conditions, such as mutual effects on twin spray envelopes in dual-base injector is investigated, then the design procedure is presented based on obtained results. Finally the computer program for designing this sort of injector is proposed. Using this program, some injectors were designed and tested. The results were presented in details in this paper.

Ommi, F., Hossinalipour, M., Movahednejad, E.

Estimation of Measurement Uncertainty in Engine Tests Based on NATO AGARD Uniform Engine Test Program

AIR4979-TEST-REC (Historical)11/17/2004

The primary objective of this document is to describe the systematic and random measurement uncertainties which may be expected when testing gas turbine engines in a range of different test facilities. The documentation covers a "traditional" method for estimating pretest uncertainties and a "new" method for computing and comparing posttest uncertainties. To determine these posttest uncertainties, data generated during the AGARD Uniform Engine Test Program (UETP) were analyzed and compared to the pretest estimates. The proposed procedure provides a mechanism for determining the expected accuracy of test results obtained from facilities which were not previously cross calibrated. Furthermore, the method can be used to assist in making cost-effective management decisions on the level of validation/cross calibration necessary when bringing a test facility on line. This document is also intended to act as a guide for improving uncertainty analyses in a broad spectrum of related industries

E-33 In Flight Propulsion Measurement Committee

Estimation of Measurement Uncertainty in Engine Tests Based on NATO AGARD Uniform Engine Test Program

AIR4979 (Historical)

11/17/2004

The primary objective of this document is to describe the systematic and random measurement uncertainties which may be expected when testing gas turbine engines in a range of different test facilities. The documentation covers a "traditional" method for estimating pretest uncertainties and a "new" method for computing and comparing posttest uncertainties. To determine these posttest uncertainties, data generated during the AGARD Uniform Engine Test Program (UETP) were analyzed and compared to the pretest estimates. The proposed procedure provides a mechanism for determining the expected accuracy of test results obtained from facilities which were not previously cross calibrated. Furthermore, the method can be used to assist in making cost-effective management decisions on the level of validation/cross calibration necessary when bringing a test facility on line. This document is also intended to act as a guide for improving uncertainty analyses in a broad spectrum of related industries

E-33 In Flight Propulsion Measurement Committee

Calculating Mass Diffusion in High-Pressure Binary Fluids

TBMG-81505/01/2004

A comprehensive mathematical model of mass diffusion has been developed for binary fluids at high pressures, including critical and supercritical pressures. Heretofore, diverse expressions, valid for limited parameter ranges, have been used to correlate high-pressure binary mass- diffusion- coefficient data. This model will likely be especially useful in the computational simulation and analysis of combustion phenomena in diesel engines, gas turbines, and liquid rocket engines, wherein mass diffusion at high pressure plays a major role.

Update on Area Production in Mixing of Supercritical Fluids

TBMG-770011/01/2003

The paper “Turbulence and Area Production in Binary-Species, Super- critical Transitional Mixing Layers” presents a more recent account of the research sum- marized at an earlier stage in “Area Production in Super- critical, Transitional Mixing Layers” (NPO-30425), NASA Tech Briefs, Vol. 26, No. 5 (May 2002) page 79. The focus of this research is on supercritical C7H16/N2 and O2/H2 mixing layers undergoing transitions to turbulence. The C7H16/N2 system serves as a simplified model of hydrocarbon/air systems in gasturbine and diesel engines; the O2/H2 system is representative of liquid rocket engines. One goal of this research is to identify ways of controlling area production to increase disintegration of fluids and enhance combustion in such engines. As used in this research, “area production” signifies the fractional rate of change of surface area oriented perpendicular to the mass-fraction gradient of a mixing layer. In the study, a database of transitional states obtained from

The dawn of the jet age: the first 10 years

AEROAPR03_0104/01/2003

One of the ironies of aviation history is that the most obvious potential power source for a fixed-wing aircraft was barely considered by the early pioneers. Embryonic rockets first soared into the atmosphere of China almost seven centuries before the Wright brothers' biplane staggered into the air-and into history-at Kitty Hawk, NC, on December 17, 1903. Its feeble internal-combustion engine and crude wooden propeller sustained it for just about a dozen seconds. Yet 44 years later, it was to be a rocket engine that pushed the Bell XS-1 past Mach 1.0, and rockets that have taken man into space. However, rockets were, and are, challenging pieces of technology to harness, and the bravery (or foolhardiness) of those early pioneers was undoubtedly stretched sufficiently far without giving their flimsy flying machines the added dimension of a power-to-weight ratio of huge proportions with unpredictable results. In fact, if rocketry had been seriously pursued as a power source, it is

Area Production in Supercritical, Transitional Mixing Layers

TBMG-326005/01/2002

This paper presents a study of area production in mixing layers undergoing transition to turbulence. These layers evolve from the mixing of two initially segregated counterflowing streams under supercritical conditions. The study may contribute to development of means to control area production in order to increase disintegration of fluids and enhance combustion in diesel, gas turbine, and liquid rocket engines. As used here, “area production” signifies the fractional rate of change of surface area oriented perpendicular to the mass-fraction gradient in a mixing layer. In the study, a database of transitional states obtained from direct numerical simulations of temporal three-dimensional supercritical mixing layers for heptane/nitrogen and oxygen/hydrogen systems was analyzed. A few of the many conclusions drawn from the analysis are that area production is determined more by strain than by compressibility; area is produced by strain and convective effects; area is destroyed by species

Software for Simulation of 3D, Three-Phase Combusting Flow

TBMG-745310/01/2001

A computational fluid dynamics (CFD) code has been developed to enable simulation of spray combustion near the fuel injectors in a liquid-fueled rocket engine. This code reflects the three-dimensional (3D), multiphase nature of the flow field in a rocket engine and is capable of modeling even a flow field as complex as one that results from the use of impingement injectors. Unlike prior spray-combustion codes that emphasize physical constraints at the expense of geometric ones, this code implements a compromise between physical and geometric constraints in order to enable analysis and comparison of the performances of alternative engine designs that involve different injector geometries. In particular, this code was constructed to enable prediction of the interactive effects of injector-element impingement angles and impingement points, momenta of individual orifice flows, and the resulting combusting flow.

Vortex-Fired Liquid-Fuel Rocket Combustion Chambers

TBMG-694109/01/2000

Liquid-fuel rocket engines that utilize vortex flow fields to keep combustion-chamber walls cool have been investigated in computational simulations and experiments. In an engine of this type, the vortex flow establishes radial gradients of pressure and density that cause the lower-density hot combustion products to be confined near the central axis of the combustion chamber while cold gases yet to be burned are centrifuged to the combustion-chamber wall. Keeping combustion-chamber walls cool in this manner reduces or eliminates damage by heat and oxidation, thereby (1) eliminating the need for leak-prone cooling passages, (2) extending the operational lifetimes of combustion chambers, and (3) creating an opportunity to fabricate combustion-chamber walls more easily, using relatively inexpensive materials (possibly even lightweight composite materials) instead of expensive alloys.

Refractory Metal-Lined Composites for Lightweight High-Performance Propulsion omponents

2000-01-172005/16/2000

Requirements for advanced rocket propulsion systems are becoming increasingly more demanding. The use of high temperature capable materials in such systems, including applications in liquid rocket engines and solid rocket motors, offers potential benefits of increased performance and/or efficiency based on the engine operating cycle. For the ultimate in high temperature capability, refractory metals, ceramics, ceramic matrix composites (CMCs), and carbon/carbon (C/C)composites each provide particularly beneficial attributes, but with selected limitations. Refractory metals are relatively tough and durable, provide impermeable structures, and can be conventionally fabricated, but are relatively dense, leading to heavyweight structures. Monolithic ceramics generally lack desired toughness and durability. CMCs offer substantially improved toughness over their monolithic counterparts and are relatively lightweight, but are permeable and difficult to join to conventional structures. C/C is

Brockmeyer, Jerry W., Tuffias, Robert H., Williams, Brian E.

Quasi-Steady High-Pressure Droplet Model for Diesel Sprays

2000-01-058803/06/2000

Droplet vaporization models that are currently employed in simulating diesel engine sprays are based on a quasi-steady, low-pressure formulation. This formulation does not adequately represent many high-pressure effects, such as non-ideal gas behavior, solubility of gases into liquid, pressure dependence of liquid- and gas-phase thermophysical properties, and transient liquid transport in the droplet interior. More importantly, the quasi-steady assumption becomes increasingly questionable as the ambient pressure approaches and /or exceeds the fuel critical pressure. In the present study, a high-pressure, quasi-steady vaporization model is developed. Except for the quasi-steady assumption that is retained in the model, it incorporates all the other high-pressure effects. The applicability of this model for predicting droplet vaporization under diesel-like environment is evaluated by comparing its predictions with those from a more comprehensive transient model, which is first validated

Aggarwal, Suresh K., Zhu, Guang-Sheng, Reitz, Rolf D.

Interfacing a General Purpose Fluid Network Flow Program with the SINDA/G Thermal Analysis Program

1999-01-216207/12/1999

A general purpose, one dimensional fluid flow code is currently being interfaced with the thermal analysis program SINDA/G. The flow code, the Generalized Fluid System Simulation Program (GFSSP), is capable of analyzing steady state and transient flow in a complex network. The flow code is capable of modeling several physical phenomena including compressibility effects, phase changes, body forces (such as gravity and centrifugal) and mixture thermodynamics for multiple species. The addition of GFSSP to SINDA/G provides a significant improvement in convective heat transfer modeling for SINDA/G. The interface development is conducted in multiple phases. This paper describes the first phase of the interface which allows for steady and quasi-steady (unsteady solid, steady fluid) conjugate heat transfer modeling.

Schallhorn, Paul, Popok, Dan

Integrated Capillary Engine - Conceptual Overview

1999-01-209207/12/1999

A scoping thermal analysis was done to evaluate the general feasibility of capillary pumped heat engines. The analysis was motivated by recent advances in nanoscale materials science that have made it increasingly practical to manufacture high porosity wicks with a median pore diameter on the order of a few nanometers. Capillary pumped heat engines are shown to be generally feasible for wick evaporation rates equivalent to about 1 watt per square centimeter when wick material thermal conductivity on the order of a few W/m-K is assumed. A compact heat engine architecture, referred to as an integrated capillary engine, is introduced.

Williams, Rube B., Kobayashi, Yasunori

Does it Exist, the New Theoretical Limits for Specific Impulse of Rocket Engines

94212210/01/1994

The technical thermodynamics solution of rocket engine cycle optimization is introduced here. The traditional approximations of thrust production process are critically evaluated and, as a consequence, a noncontroversial thermodynamic approach is presented. This paper underlines the uniqueness of the physical nature of such a thrust production process. The thermodynamics analysis results show that new limits of theoretical rocket engine specific impulse exist within this approach, and this can lead in future to a reduction of launch costs, environmental benefits for space system use and development of a specific, more efficient rocket system, such as nuclear and SSTO. New investigations ought to be organised and directed toward finding the practical possibilities to implement the ideas introduced here.

Zakharov, Alexander M.

Carbon Phenolic Ablation Testing and Analysis for High Speed Earth Return

94136906/01/1994

Testing of carbon phenolic heatshield materials suitable for the forward heatshield of a high speed Earth return capsule is addressed. Critical aspects of the testing included thermocouple size, orientation and placement, and heat flux calibration to provide accurate data. Post-test examination provides evidence of char and pyrolysis depth, delamination and cracking. Analysis indicates the specific heat capacity has a heating rate dependency, this has been accounted for in the correlation of conductivity with temperature. A fissure model to account for delamination of the samples needed to be included.

Mariage, E., Lacoste, M.

The Variable Radioisotope Heater Unit for the Cassini Spacecraft

94126806/01/1994

This paper describes the Variable Radioisotope Heater Unit; its development, performance, and effectiveness at controlling the temperatures for the Cassini spacecraft thruster clusters. To explore the Saturn system, the Cassini spacecraft relies on the electrical power from three Radioisotope Thermoelectric Generators, but the large power demand for science and engineering functions severely limits the electrical power available for temperature control purposes. The Variable Radioisotope Heater Unit combines the heating- and temperature-control functions into one nonelectrical self-controlled unit, thereby freeing up electrical heater power for other uses on the spacecraft.

Lyra, Jacqueline C., Stultz, James W.

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