Base heating scaling criteria for a four- engine rocket cluster operating at high altitude.
Base heating scaling criteria for four-engine rocket cluster operating at high altitude
NOZZLE WALL↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Advanced Intra-Cycle Detection of Pre-Ignition Events through Phase-Space Transforms of Cylinder Pressure Data
The widespread adoption of boosted, downsized SI engines has brought pre-ignition phenomena into greater focus, as the knock events resulting from pre-ignitions can cause significant hardware damage. Much attention has been given to understanding the causes of pre-ignition and identify lubricant or fuel properties and engine design and calibration considerations that impact its frequency. This helps to shift the pre-ignition limit to higher specific loads and allow further downsizing but does not fundamentally eliminate the problem. Real-time detection and mitigation of pre-ignition would thus be desirable to allow safe engine operation in pre-ignition-prone conditions. This study focuses on advancing the time of detection of pre-ignition in an engine cycle where it occurs. Furthermore, phase space transforms through time-delay embedding of cylinder pressure and principal component analysis were applied to same-cycle detection of pre-ignition and shown to enable detection on the order of a crank degree earlier than deviation in cylinder pressure can be identified through direct statistical observation of the pressure data. Additionally, it appears that the deviation of the trajectory in phase space may offer the opportunity to extend this method to further extend the detection window and allow more time for mitigation actions to occur.
42 ENGINEERING↗
Viking Mars hydrazine terminal descent engine thermal design considerations
A description is given of some of the more significant thermal design considerations employed in the development and qualification of the monopropellant hydrazine terminal descent engines on the Viking Mars lander spacecraft. The terminal descent engine operates in a blowdown and throttling mode, which results in an operating thrust range of 638 to 90 lbf. Martian entry thermal design boundary conditions are described, along with resulting radiative and conductive engine thermal isolation hardware. Test results are presented, showing engine thermal design performance as compared with specified requirements. General engine materials of construction are described, along with Hastelloy B shell structural characteristics, which were extended to 2000 F by test and are compared with limited existing MIL-HDBK-5 data. Subscale test results are presented, showing the maximum catalyst bed cylinder design temperature of 1970 F. Test results also are presented, showing local reactor internal convective heat-transfer coefficients. Such data are unique, since the engine employs a completely radial flow catalyst bed design. This design approach is the first of its kind in the monopropellant hydrazine gas generator field to be flight qualified.
Cunningham, C. R.↗
Engine Gaseous, Aerosol Precursor and Particulated Flight Altitude Conditions
The overall objective of the NASA Atmospheric Effects of Aviation Project (AEAP) is to develop scientific bases for assessing atmospheric impacts of the exhaust emissions by both current and future fleets of subsonic and supersonic aircraft. Among the six primary elements of the AEAP is Emissions Characterization. The objective of the Emission Characterization effort is to determine the exhaust emission constituents and concentrations at the engine exit plane. The specific objective of this engine test is to obtain a database of gaseous and particulate emissions as a function of fuel sulfur and engine operating conditions. The database of the particulate emission properties is to be used as a comparative baseline with subsequent flight measurement. The engine used in this test was a Pratt & Whitney F1OO-200E turbofan engine. Aviation fuel (Jet A) with a range of fuel sulfur was used. Low and high sulfur values are limited by commercially available fuels and by fuel specification limits of O.3% by weight. Test matrix was set by parametrically varying the combustor inlet temperature (T(sub 3) between idle and maximum power setting at simulated SLS and up to five other altitudes for each fuel. Four diagnostic systems, extractive and non-intrusive, were assembled for the gaseous and particulate emissions characterization measurements study. NASA extractive system includes smoke meter and analyzers for measurement of CO, CO2, NO, NOx, O2, total unburnt hydrocarbons (THC), and SO2. Particulate emissions were characterized by University of Missouri-Rolla Mobile Aerosol Sampling System. A chemical ionization mass spectrometer from the Air Force Research Laboratory at Hanscom AFB was used to measure SO2 and HNO3. Aerodyne Research. Inc. used infrared tunable diode laser absorption to measure SO2, SO3, NO, H2O and CO2.
Wey, C. C.↗
CMC Property Variability and Life Prediction Methods for Turbine Engine Component Application
The ever increasing need for lower density and higher temperature-capable materials for aircraft engines has led to the development of Ceramic Matrix Composites (CMCs). Today's aircraft engines operate with >3000"F gas temperatures at the entrance to the turbine section, but unless heavily cooled, metallic components cannot operate above approx.2000 F. CMCs attempt to push component capability to nearly 2700 F with much less cooling, which can help improve engine efficiency and performance in terms of better fuel efficiency, higher thrust, and reduced emissions. The NASA Glenn Research Center has been researching the benefits of the SiC/SiC CMC for engine applications. A CMC is made up of a matrix material, fibers, and an interphase, which is a protective coating over the fibers. There are several methods or architectures in which the orientation of the fibers can be manipulated to achieve a particular material property objective as well as a particular component geometric shape and size. The required shape manipulation can be a limiting factor in the design and performance of the component if there is a lack of bending capability of the fiber as making the fiber more flexible typically sacrifices strength and other fiber properties. Various analysis codes are available (pcGINA, CEMCAN) that can predict the effective Young's Moduli, thermal conductivities, coefficients of thermal expansion (CTE), and various other properties of a CMC. There are also various analysis codes (NASAlife) that can be used to predict the life of CMCs under expected engine service conditions. The objective of this summer study is to utilize and optimize these codes for examining the tradeoffs between CMC properties and the complex fiber architectures that will be needed for several different component designs. For example, for the pcGINA code, there are six variations of architecture available. Depending on which architecture is analyzed, the user is able to specify the fiber tow size, tow spacing, weave parameter, and angle of orientation of fibers. By holding the volume fraction of the fibers constant, variations in tow spacing can be explored for different architectures. The CMC material properties are usually calculated assuming the component is manufactured perfectly. However, this is typically not the case so that a quantification of the material property variability is needed to account for processing and/or manufacturing imperfections. The overall inputs and outputs are presented using a regression software to rapidly investigate the tradeoffs associated with fiber architecture, material properties, and ultimately cost. This information is then propagated through lifing models and Larson-Miller data to assess timehemperature-dependent CMC strength. In addition, a first order cost estimation will be quantified from a current qualitative perspective. This cost estimation includes the manufacturing challenges, such as tooling, as well as the component cost for a particular application. Ultimately, a cost to performance ratio should be established that compares the effectiveness of CMCs to their current rival, nickel superalloys.
Cheplak, Matthew L.↗
Preliminary Transient Performance Data on the J73 Turbojet Engine: Altitude, 45,000 Feet - 3
A program was undertaken to determine the J73 turbojet engine compressor stall and surge characteristics and combustor blow-out limits enc ountered during transient engine operation. Data were obtained in the form of oscillograph traces showing the time history of several engi ne parameters with changes in engine fuel flow. The data presented in this report are for step and ramp changes in fuel flow at an altitude of 45,000 feet and flight Mach numbers of 0 and 0.8.
McAulay, John E.↗
Operating Temperatures of a Sodium-Cooled Exhaust Valve as Measured by a Thermocouple
A thermocouple was installed in the crown of a sodium-cooled exhaust valve. The valve was then tested in an air-cooled engine cylinder and valve temperatures under various engine operating conditions were determined. A temperature of 1337 F was observed at a fuel-air ratio of 0.064, a brake mean effective pressure of 179 pounds per square inch, and an engine speed of 2000 rpm. Fuel-air ratio was found to have a large influence on valve temperature, but cooling-air pressure and variation in spark advance had little effect. An increase in engine power by change of speed or mean effective pressure increased the valve temperature. It was found that the temperature of the rear spark-plug bushing was not a satisfactory indication of the temperature of the exhaust valve.
FUEL-AIR MIXTURES↗
Method for determining component matching and operating characteristics for turbojet engines
Component matching and operating characteristics of turbojet engine
Evans, D. G.↗
Viscous Aerodynamic Shape Optimization with Installed Propulsion Effects
Aerodynamic shape optimization is demonstrated to tailor the under-track pressure signature of a conceptual low-boom supersonic aircraft. Primarily, the optimization reduces nearfield pressure waveforms induced by propulsion integration effects. For computational efficiency, gradient-based optimization is used and coupled to the discrete adjoint formulation of the Reynolds-averaged Navier Stokes equations. The engine outer nacelle, nozzle, and vertical tail fairing are axi-symmetrically parameterized, while the horizontal tail is shaped using a wing-based parameterization. Overall, 48 design variables are coupled to the geometry and used to deform the outer mold line. During the design process, an inequality drag constraint is enforced to avoid major compromise in aerodynamic performance. Linear elastic mesh morphing is used to deform volume grids between design iterations. The optimization is performed at Mach 1.6 cruise, assuming standard day altitude conditions at 51,707-ft. To reduce uncertainty, a coupled thermodynamic engine cycle model is employed that captures installed inlet performance effects on engine operation.
computational fluid dynamics↗
Comparison of the Combustion Performance of Shell UMF, Grade C, MIL-F-5624C, Grade JP-5, Fuels in a Heavy-Duty XRJ47-W-9 Ram-Jet Engine
Comparable combustion performance data for Shell UMF, grade C, and MIL-F-5624C, grade JP-5, fuels were obtained using a heavy-duty version of the XRJ47-W-9 ram-jet engine operated in a 2.75 Mach number free-jet facility. Data were obtained for the two fuels over a range of fuel-air ratios, engine airflows, and engine-inlet temperatures. The test conditions were selected to provide combustor-inlet temperatures. The test conditions were selected to provide combustor-inlet conditions approximately representative of those which would be encountered over a range of altitudes and flight Mach numbers. The variation of combustion efficiency with fuel-air ratio for the two fuels is compared at the several inlet conditions. The pilot-burner ignition and operating limits with both fuels are also included. In general, the combustion efficiency with Shell UMF, grade C, fuel was 1 to 4 points lower than with MIL-F-5624C, grade JP-5, fuel.
Ranscht, W. G.↗
Effects of blending C3-C4 alcohols on motor gasoline properties and performance of spark ignition engines: A review
Supplementing petroleum fuels with sustainable and renewable alternatives is a good option for increasing the sustainability of transportation fuels. Alcohols are particularly attractive blendstocks for spark ignition engines, mainly due to their desirable fuel properties including high octane, evaporative cooling, and reduced sooting propensity. Although the use of SI engines is widespread around the world, predominately for light duty vehicles, concerns about CO2 emissions and other sustainability issues necessitate increased engine efficiencies, reduced tailpipe pollutants, and lower lifecycle carbon emissions. The intelligent blending of C2-C4 alcohols into motor gasoline is a viable method for achieving these goals. There are a multitude of ways to produce renewable alcohols such as through fermentation from first-generation feedstocks (sugar and corn) and second-generation feedstocks (lignocellulosic biomass), or by gasification and mixed alcohol fuel synthesis routes from lignocellulosic biomass. Currently ethanol is extensively used in motor gasoline fuels worldwide and although many have proposed the use of C3 and C4 alcohols in motor gasoline as an improvement over ethanol, the higher cost of production and lack of clear definition as to their benefit over ethanol when blended into motor gasoline have led to slow acceptance into the market. In this review, special emphasis is placed on the effects of blending C3 and C4 alcohols into motor gasoline in terms of physicochemical properties, volatility behavior, and engine performance when compared to ethanol blends. Furthermore, the impact of blending C3 and C4 alcohols with gasoline on emission (particulate matter, nitrogen oxides, carbon monoxide, hydrocarbons, and unregulated oxygenates) and combustion (volumetric efficiency, thermal efficiency, fuel consumption, and cold performance) characteristics is discussed. Although there are some disagreements in the literature over the effect of alcohols predominately around the type of SI engine, i.e., port fuel injected versus direct fuel injected and engine operating mode, generally it is stated that alcohols can potentially reduce soot, unburned hydrocarbons and CO emissions while increasing thermal efficiency when proper engine configuration/calibration is used. Lastly, research that must be conducted to find the optimum combination of alcohol blends and engine configurations is highlighted and discussed.
09 BIOMASS FUELS↗
Ducted Fuel Injection and Cooled Spray Technologies for Particulate Control in Heavy-Duty Diesel Engines
Heavy-Duty diesel engine manufacturers are continuously in pursuit of simple and low-cost technologies that can reduce emissions. Ducted fuel injection (DFI) and Cooled Spray (CS) technologies are two technologies that continue to show promise for significant particulate emissions reductions. These technologies represent a breakthrough in diesel engine combustion from the potential of nearly sootless diesel combustion. This can provide a significant decrease in harmful PM emissions and may enable further system optimization for reduced NOx emissions and increased efficiency. Combustion vessel experiments and engine demonstrations at Sandia, together with the large bore engine tests performed by Wabtec show that this technology may be applicable to heavy duty diesel engines across a wide range of engine sizes and speeds representing the majority of off-road diesel engines. However, very little is known about the ideal geometry, scaling properties or effectiveness of these technologies over the engine operating map. This project will address those uncertainties through a series of experiments performed in an optical and a metal single-cylinder engine.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
An application of modern control theory to jet propulsion systems
The control of an airbreathing turbojet engine by an onboard digital computer is studied. The approach taken is to model the turbojet engine as a linear, multivariable system whose parameters vary with engine operating environment. From this model adaptive closed-loop or feedback control laws are designed and applied to the acceleration of the turbojet engine.
Merrill, W. C.↗
Determination of two-stroke engine exhaust noise by the method of characteristics
A computational technique was developed for the method of characteristics solution of a one-dimensional flow in a duct as applied to the wave action in an engine exhaust system. By using the method, it was possible to compute the unsteady flow in both straight pipe and tuned expansion chamber exhaust systems as matched to the flow from the cylinder of a small two-stroke engine. The radiated exhaust noise was then determined by assuming monopole radiation from the tailpipe outlet. Very good agreement with experiment on an operation engine was achieved in the calculation of both the third octave radiated noise and the associated pressure cycles at several locations in the different exhaust systems. Of particular interest is the significance of nonlinear behavior which results in wave steepening and shock wave formation. The method computes the precise paths on the x-t plane of a finite number of C(sub +), C(sub -) and P characteristics, thereby obtaining high accuracy in determining the tailpipe outlet velocity and the radiated noise.
Jones, A. D.↗
Generative engineering databases - Toward expert systems
Engineering data management, incorporating concepts of optimization with data representation, is receiving increasing attention as the amount and complexity of information necessary for performing engineering operations increases and the need to coordinate its representation and use increases. Research in this area promises advantages for a wide variety of engineering applications, particularly those which seek to use data in innovative ways in the engineering process. This paper presents a framework for a comprehensive, relational database management system that combines a knowledge base of design constraints with a database of engineering data items in order to achieve a 'generative database' - one which automatically generates new engineering design data according to the design constraints stored in the knowledge base. The representation requires a database that is able to store all of the data normally associated with engineering design and to accurately represent the interactions between constraints and the stored data while guaranteeing its integrity. The representation also requires a knowledge base that is able to store all the constraints imposed upon the engineering design process.
Rasdorf, W. J.↗
Investigation of Thermal High Cycle and Low Cycle Fatigue Mechanisms of Thick Thermal Barrier Coatings
Thick thermal barrier coating systems in a diesel engine experience severe thermal low cycle fatigue (LCF) and high cycle fatigue (HCF) during engine operation. In this paper, the mechanisms of fatigue crack initiation and propagation in a ZrO2-8wt.% Y2O3 thermal barrier coating, under simulated engine thermal LCF and HCF conditions, are investigated using a high power CO2 laser. Experiments showed that the combined LCF/HCF tests induced more severe coating surface cracking, microspallation and accelerated crack growth, as compared to the pure LCF test. Lateral crack branching and the ceramic/bond coat interface delaminations were also facilitated by HCF thermal loads, even in the absence of severe interfacial oxidation. Fatigue damages at crack wake surfaces, due to such phenomena as asperity/debris contact induced cracking and splat pull-out bending during cycling, were observed especially for the combined LCF/HCF tests. It is found that the failure associated with LCF is closely related to coating sintering and creep at high temperatures, which induce tensile stresses in the coating after cooling. The failure associated with HCF process, however, is mainly associated with a surface wedging mechanism. The interaction between the LCF, HCF and ceramic coating creep, and the relative importance of LCF and HCF in crack propagation are also discussed based on the experimental evidence.
Zhu, Dongming↗
Investigation of Thermal High Cycle and Low Cycle Fatigue Mechanisms of Thick Thermal Barrier Coatings
Thick thermal barrier coating systems in a diesel engine experience severe thermal low cycle fatigue (LCF) and high cycle fatigue (HCF) during engine operation. In this paper, the mechanisms of fatigue crack initiation and propagation in a ZrO2-8wt% Y2O3 thermal barrier coating, under simulated engine thermal LCF and HCF conditions, are investigated using a high power CO2 laser. Experiments showed that the combined LCF-HCF tests induced more severe coating surface cracking, microspallation and accelerated crack growth, as compared to the pure LCF test. Lateral crack branching and the ceramic/bond coat interface delaminations were also facilitated by HCF thermal loads, even in the absence of severe interfacial oxidation. Fatigue damage at crack wake surfaces, due to such phenomena as asperity/debris contact induced cracking and splat pull-out bending during cycling, was observed especially for the combined LCF-HCF tests. It is found that the failure associated with LCF is closely related to coating sintering and creep at high temperatures, which induce tensile stresses in the coating after cooling. The failure associated with HCF process, however, is mainly associated with a surface wedging mechanism. The interaction between the LCF, HCF and ceramic coating creep, and the relative importance of LCF and HCF in crack propagation are also discussed based on the experimental evidence.
Zhu, Dongming↗
Operating Temperatures of a Sodium-Cooled Exhaust Valve as Measured by a Thermocouple
Report presents the results of a thermocouple installed in the crown of a sodium-cooled exhaust valve. The valve was tested in an air-cooled engine cylinder and valve temperatures under various engine operating conditions were determined. A temperature of 1337 degrees F. was observed at a fuel-air ratio of 0.064, a brake mean effective pressure of 179 pounds per square inch, and an engine speed of 2000 r.p.m. Fuel-air ratio was found to have a large influence on valve temperature, but cooling-air pressure and variation in spark advance had little effect. An increase in engine power by change of speed or mean effective pressure increased the valve temperature. It was found that the temperature of the rear-spark-plug bushing was not a satisfactory indication of the temperature of the exhaust valve.
Sanders, J C↗