The authors would like to thank for the financial support of the Combustion Engineering Research Center(CERC).
An experimental and computational study of the nearwall combustion in a Homogeneous Charge Compression Ignition (HCCI) engine has been conducted by applying laser based diagnostic techniques in combination with numerical modeling. Our major intent was to characterize the combustion in the velocity- and thermal boundary layers. The progress of the combustion was studied by using fuel tracer LIF, the result of which was compared with LDA measurements of the velocity boundary layer along with numerical simulations of the reacting boundary layer. Time resolved images of the PLIF signal were taken and ensemble averaged images were calculated. In the fuel tracer LIF experiments, acetone was seeded into the fuel as a tracer. It is clear from the experiments that a proper set of backgrounds and laser profiles are necessary to resolve the near-wall concentration profiles, even at a qualitative level. Partial resolution of the velocity boundary layer was enabled by using a slightly inclined LDA probe operated in back-scatter mode. During these conditions, it was possible to acquire velocity data within 0.2 mm from the wall. A one-dimensional model of the flow field was devised to make the connection between the thermal and the velocity boundary layer. The investigations suggest that wall interaction is not the responsible mechanism for the rather high emissions of unburned hydrocarbons from HCCI engines. It is believed that the delayed oxidation, indicated by the fuel tracer LIF experiments and numerical simulations, is due to the thermal boundary layer. From the data at hand, it is concluded that the thermal boundary layer is on the order of 1 mm thick. In this boundary layer the reactions are delayed but not quenched. (Less)
Wavelength (nm)Figure I: AM 1.5 and AM 0 Spectral IntensityIntensity = 1.367 x 0.7(air mass)0.678 mW/cm 2 (I)In contrast to an air breathing engine, a solar powered aircraft has no exhaust andtherefore does not contaminate the atmosphere nor interfere with any delicate air measuringsensors on the aircraft. It also does not depend on the atmo:.phere for the production of power. Dueto the low wing loadings necessary on a solar aircraft they ire inherently slow which makes themwell suited for atmospheric studies. One obvious disadvantage of using solar power is that it is notavailable throughout the whole day. However battery or fu_.l cell power could be used to extendflight times.The ultimate goal for a solar powered aircraft is to be capable of continuous flight formonths or even years. In order to accomplish this a recharg,_'able energy storage system would beneeded. This energy storage system would need to be capat,le of supplying enough energy to sustainthe aircraft at the desired altitude throughout a nighttime p,;riod. Also the solar array would needto be capable of recharging this energy storage system duri lg the day time as well as maintain theaircraft power level tbr flight. Analysis of this type of cond mously flying solar power aircraft isgiven in references 4 and 5. In order to examine the solar p-3wer generating aspects of this type ofaircraft, a solar powered aircraft with minimal energy stora.ge capabilities was constructed. Thiswas done in order to further advance the development of a _olar powered aircraft as well as to gainan understanding of the operational constraints and probler is associated with the construction andflight of this type of aircraft. A GaAs/Ge solar array was us.'d as the power source for the aircraft.NASAFFM--1998-208652 2
A one-dimensional ring-pack lubrication model developed at MIT is applied to simulate the oil film behavior during the warm-up period of a Kohler spark ignition engine. This is done by making assumptions for the evolution of the oil temperatures during warm-up and that the oil control ring during downstrokes is fully flooded. The ring-pack lubrication model includes features such as three different lubrication regimes, i.e., pure hydrodynamic lubrication, boundary lubrication and pure asperity contact, nonsteady wetting of both inlet and outlet of the piston ring, capability to use all ring face profiles that can be approximated by piece-wise polynomials, and, finally, the ability to model the rheology of multigrade oils. Not surprisingly, the simulations show that by far the most important parameter is the temperature dependence of the oil viscosity.
Lightweight heat-resistant TiAl intermetallic compound has a high potential for a high performance exhaust valve material to improve power output and fuel economy by increasing engine speed and reduction in valvetrain friction. In this study, to apply TiAl to exhaust valves, alloy development, process development and evaluation of TiAl exhaust valve were carried out. A new TiAl(Ti-33.5Al-0.5Si-1Nb-0.5Cr ,mass%) with excellent oxidation, hot corrosion resistant and mechanical properties has been developed for an exhaust valve material. To manufacture TiAl exhaust valves, advanced technologies such as CLV investment casting, HIP treatment, Plasma carburization improving wear resistance of TiAl were employed. Engine tests of TiAl valves were successful. A durability test confirmed excellent high temperature performance and wear resistance of TiAl exhaust valves.
Locations of key body segments of Hybrid III dummies used in Federal Motor Vehicle Safety Standard (FMVSS) 208 compliance tests and New Car Assessment Program (NCAP) tests were measured and subjected to statistical analysis. Mean clearance dimensions and their standard deviations for selected body segments of driver and passenger occupants with respect to selected vehicle surfaces were determined for several vehicle classes. These occupant locations were investigated for correlation with impact responses measured in crash tests and by using a three dimensional human-dummy mathematical model in comparable settings. Based on these data, the importance of some of the clearance dimensions between the dummy and the vehicle surfaces was determined. The study also compares observed Hybrid III dummy positions within selected vehicles with real world occupant positions reported in published literature. (A) For the covering abstract of the conference see IRRD 882980.
Recent changes in regulatory practices have brought about a need for speciated analysis of the volatile organic components of vehicle exhaust. The purpose of this study was to allow interested laboratories to participate in a Round Robin so that each could assess their speciation methodologies. `Synthetic exhaust` samples were prepared of mixed DNPH-carbonyl standards deposited on DNPH cartridges, and solutions of alcohol in water. The fifteen participating laboratories included automotive, contract, petroleum and regulatory organizations. The results described in this paper consider only variability associated with the analyltical measurement of samples that have already been collected in impingers or on cartridges. In general, alcohols (methanol and ethanol) were quantified without difficulty. With the exception of acrolein and crotonaldehyde, the quantitation of the carbonyl samples was very good considering the variety of analytical methods that were used. 9 refs., 4 figs., 12 tabs.
Variable-valve timing allows for controlled scheduling of valve-timing events. When applied to spark-ignition engines, it yields improvements in emissions, economy, and performance. The benefits for diesel engines further include: improved starting, noise reduction, and the ability to vary compression ratios. A camlobe-phasing system which takes advantage of the merits of variable-valve timing has been developed. Some advantages of this advanced valve-timing approach are: 1. continuous control over valve-timing events, 2. independent control over valve opening and closing times, and 3. its application to engines with single- or twin-camshaft arrangements.
As the known reserves of natural petroleum-base gasoline diminish, synthetic full boiling range gasolines will assume a strategic importance. Gasolines from oil shale and coal will be prime candidates for replacing the petroleum-base fuel. In this paper, a shale derived, high paraffin gasoline is compared with a standard petroleum base fuel with respect of in-cylinder combustion characteristics, and overall power and emissions data. The results show that the performance of the synthetic fuel is comparable with the petroleum base fuel. However, optimization of engine combustion parameters for the synthetic shale blend gasoline is necessary to take full advantage of the synthetic fuel.
NASTRAN is a large digital computer program for static and dynamic structural analysis by the finite element approach. It is nearing completion after three years of development under NASA sponsorship. It will be made available to all interested users and it will be maintained by NASA. It is currently programmed for the IBM 360, the UNIVAC 1108, and the CDC 6600 computers.
Temperatures created in aircraft jet engines have given rise to concern over hot surface ignition of flammable fluids. For some time, 500° F has been accepted as the maximum safe surface temperature. Under the specific conditions reported here, it appears that this figure can be increased significantly.
A UNIQUE TEST method and apparatus now make it possible to reproduce conditions of vibration that are not only certain to loosen bolted joints but which also closely simulate actual conditions. It can be shown that properly preloaded fasteners loosen as a result of rotation as soon as relative motion occurs between the mating threads and between the bearing surfaces of the fastener and the clamped material.
