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The effect of the introduction of low-emission vehicles on potential air quality improvement in the Los Angeles area was predicted using a three-dimensional airshed simulation model. The simulations were based on ozone concentration estimates made on the basis of data released by the California Air Resources Board concerning projected quantities of emissions from various sources in 2010. Analyses were made of three scenarios. One assumed that LEV, ULEV and ZEV regulations were enforced as planned, a second assumed that these planned regulations were modified; and a third assumed that emission levels from various sources were reduced in line with the goals of the Air Quality Management Plan formulated by the South Coast Air Quality Management District.

An experimental and theoretical investigation has been performed on the flow and pressure loss in axisymmetric catalytic converters and isolated monoliths under steady, isothermal flow conditions. Monolith resistance has been measured with a uniform, low turbulence, incident flow field. It has been found that the pressure loss expression for fully developed laminar flow is a good approximation to observations for x+ greater than 0.2. However, for x+ less than 0.2 the additional pressure loss due to developing flow is no longer negligible and a better approach is to use the correlation proposed by Shah (16). From experimental studies on the axisymmetric catalytic converters non-dimensional power law relationships have been derived relating maldistribution and pressure drop to expansion length, Re, and monolith length. These expressions are shown to generally fit the data well within ±5%.

This paper investigates the use of several zero-ozone depleting potential (zero-ODP) HFC refrigerants, including HFC-134a, HFC-227ca, HFC-227ea, HFC-236ea, HFC-236cb, HFC-236fa, HFC-245cb, and HFC-254cb, for centrifugal chiller applications. We took into account the thermodynamic properties of the refrigerant and aerodynamic characteristics of the impeller compression process in this evaluation.. For a given operating temperature lift, there are significant differences in the pressure ratio required by each refrigerant and this variation in pressure ratio directly affects compressor size, efficiency, and performance. A comparison of the HFC refrigerant candidates with CFC-114 shows that HFC-236ea, HFC-227ca and HFC-227ea are viable alternatives for centrifugal water chillers. HFC-236ea has properties closest to CFC-114, and will result in comparible performance, but will require a slightly larger impeller and a purge system.

This paper will describe the screening and development of absorbents for HFC-134a in the chemical/mechanical heat pump. The absorbents must have low volatility, low melting point, high solubility for HFC-134a vapor, high heat of mixing with HFC-134a, suitable vapor pressure/temperature concentration characteristics when mixed with HFC-134a, low toxicity, low flammability, and thermal stability. A screening procedure was used to select approximately 15 absorbents for experimental evaluation. Measurement of the key physical and thermodynamic properties of the absorbent/HFC-134a mixtures, such as vapor pressure/temperature/concentration properties, materials compatibility, and thermal stability, is described. From these measurements, activity coefficients, enthalpy of mixing, and entropy of mixing of the liquid solution were determined.

Phase Change Materials once were an interesting phenomena in search of applications. This is no longer true. Advances in encapsulating phase change materials into microscopically thin shells permits their insertion into a wide varity of host materials. As the technology has developed, new applications are being found in a wide variety of areas. Some applications include temperature controlled suits for firefighters and military personnel, structural panels that absorb transient heat loads, and high heat capacity cooling fluids. This paper will cover the current applications being studied for these materials and propose possible future applications. In many cases, the application of these materials is only hampered by not enough people being aware of their capabilities. This paper will detail the Phase Change Materials (PCM) effort and future directions as developed by the U.S. Air Force Wright Laboratory's Flight Dynamics Directorate.

A Computer Aided Engineering (CAE) tool has been developed for the design of flight control and hydraulic systems. The CAE tool consists of independent modules that build on each others results. For the programing of each of these modules it was necessary to thoroughly review the state-of-the-art. This paper presents a structured design procedure for hydraulic systems of transport category aircraft aiming at maximum performance at minimum weight (and cost). Reference is made to CAE modules written to support a substantial part of this design procedure. The module for the steady state calculation of hydraulic systems is further detailed.

The effect of Gurney flaps on a NACA 0011 airfoil was investigated. Gurney flaps provide a substantial increase in lift while the penalty in drag is small. With the Gurney flap, the airfoil pressure distribution shows increased suction on the upper surface and higher pressure on the lower surface compared to the clean airfoil. This change in pressure is most profound on the lower surface just in front of the Gurney flap. Since separation occurs on the upper surface upon stall, this higher pressure condition on the lower surface continues into the post-stall regime. Thus, the NACA 0011 airfoil with Gurney flaps generates lift coefficients greater than one even under post-stall conditions.

The current trend in military avionics design is to physically move electronics closer to the components they control. This saves on weight, increases component maintainability, reduces aircraft manufacturing costs, and reduces the amount of electromagnetic shielding required. A disadvantage to this trend is the difficulty in achieving thermal control of these remotely located electronics. Accordingly, this thermal control issue is being addressed through the development of a loop heat pipe cold plate (LHPCP). The LHPCP is different than previous hardware of its kind by the fact that it operates in any orientation. The prototype LHPCP that was fabricated and tested was 30 inches long and weighed 1.2 pounds and was able to transport a minimum of 160 watts in any orientation. Future LHPCPs will be made flexible to allow relative motion between the package to be cooled and the heat sink.

New and powerful methods of characterizing existing and new airfoil geometries with mathematical equations are presented. The methods are applicable to a wide range of airfoil shapes representing traditional, cusped, reflexed, flat-bottom, laminar, transonic, and supersonic designs. With the emphasis on low-speed airfoils, several existing airfoils are first closely matched with the math-modeling methods. Then, to support the design of new airfoil geometries, a new interpretation of Theodorsen's potential flow method is outlined for the calculation and presentation of surface velocity in inviscid flow. Also, a vector approach is introduced for the calculation of pitching moment. Finally, new math-modeled airfoils are proposed for conventional and unique aircraft configurations.

This paper describes the transfer of Russian fine pore sintered powder metal wick structure fabrication technology to the United States for use in the construction of U.S. made loop heat pipes (LHPs), capillary pumped loops (CPLs) and heat pipes. Sintered powder metal wick structures have been used in U.S. made heat pipes for over twenty-five years. The typical pore radii for these wick structures range from 10 to 100 microns. Use of a wick material with a pore radius less than 10 microns was limited due to the high pressure drop encountered when used in a standard heat pipe. Conversely, the Russian loop heat pipe is able to get around this high pressure drop constraint due to its unique evaporator design. Prior to the work presented in this paper, the U.S. concentrated on the development of wick structure materials above 10 microns which created a technology void with the advent of the LHP.

Pavement texture plays a vital role in the development of both pavement friction and tire wear. Hence, knowledge of the effect of texture parameters on friction and tire wear will certainly assist pavement engineers in designing pavements that improve tire life without compromising the all-important skid-resistance. This paper describes the second stage of a research project undertaken to identify the fundamental texture properties that are associated with friction and wear. A analytical methodology for computer modeling of pavement texture formulated during the previous stage is now applied to model actual pavement surfaces made of asphalt and concrete. The pavement surface profiles measured by a SURTRONIX 3+ profilometer in two perpendicular directions are converted to Auto Regressive Moving Average (ARMA) models. Then, these models are used to graphically regenerate the pavement surface using a Fast Fourier Transform (FFT) technique.

The comparison of CFD predictions with aerodynamic heating data must be preceded by a careful analysis of the experimental data. Of primary interest is the location of transition since boundary layer state is still a user input for most CFD codes and an error here can result in large variations between the numerical and experimental results. Transition can usually be located by observing the associated sharp rise in surface heating rate with increasing Reynolds number. However, on complex vehicles the distributions of laminar, transitional, and turbulent flow will also be complex, and a rise in heating rate may be produced by flow phenomena other than transition. This paper reviews the method used to determine boundary layer state using experimental surface pressure and heat transfer data.

This paper presents the methodology employed to measure the T-46 nose landing gear shimmy parameters. In the course of the presentation, the experimental test set-up using the T-46 static test article is described, the parameters to be measured are defined, tables of force-deflection data are presented, the data reduction techniques are described, the final calculated values are given, and the experimental measurement of the torsional freeplay of the gear is discussed.

The development of an in-line, full flow oil debris sensor for the F119-PW-100 Advanced Tactical Fighter Engine is described. The sensor continuously counts and sizes wear metal particles, both ferrous and non-ferrous, in the main oil supply line of the engine. The design requirements, principle of operation, mechanical design features and electronic design features of the sensor are discussed. The performance characteristics of the sensor as measured during development testing are also presented.

We apply artificial neural networks to helicopter hydraulic pump condition monitoring. Several neural net models are used to perform pattern classification on the vibration measurements. Various pump conditions are examined using data from accelerometers in different places on the pump. The fundamental pump frequencies and its harmonics are used as input features to two neural net models: (1) a multi-layer neural net using back-propagation and (2) a Kohonen's feature map. Both neural net models have the ability to distinguish between pumps with different flow rates and mechanical conditions. A fundamental result is that the vibration signature can be used to classify pump condition.

This paper has been written to put in perspective the airline maintenance environment for the benefit of those individuals who are unfamiliar with its workings. The paper will discuss the various factors that effect airline maintenance, the impact of delays and cancellations and the cost of maintenance operations. The paper will also provide a general overview of airline maintenance programs and goes on to illustrate the role that condition monitoring plays in those programs. The paper will conclude with a discussion of the role of the maintenance community in airline safety.

This paper applies a wheel fatigue life prediction technique based on strain survey data to predicting the fatigue life of two F-16 main landing gear wheels. Parametric studies were performed on inflation pressure, tire type and loading condition. The results of this study indicate that for the block 30 wheel, the radial tire distributes the load to the wheel much differently than the bias tire. Also, the F-16 block 40 wheel is stressed much greater than the block 30 wheel for the same tire type during qualification testing.

This paper presents an optical technique called fringe projection to measure three dimensional tire deformation subjected to different loads, percentages of deflection and yaw angles. Unlike the well-known Moire method, the proposed technique uses a single light source and a grating, thus requiring no image superposition. As a result, the measurement is not as sensitive to vibration as the Moire method. The fringe projection also differs from the commonly used optical inspection technique in manufacturing industry via line scanning known as structured light, which cannot be applied to dynamic deformation measurements. The recently developed subpixel resolution was employed to accurately locate the optical fringe centers, which in turn improves the accuracy in 3-D geometry determination. A fiber-optic displacement sensor was also placed close to the tire sidewall in order to measure the deformational change of a selected reference point.

Real-time emissions measurement and analysis at AEDC are performed by the Applied Technology Department. During fiscal year 1995, there was a major increase in the number of requirements for emissions measurements in support of ground testing at AEDC. This ambitious schedule required the best path through research, design, and implementation of data acquisition and analysis procedures. Therefore, the preparations for each test included improvements to emissions measurement methodology. These improvements could then be implemented on all subsequent tests so that overall testing methodology was continuously improved, and the time between testing and final data analysis was minimized. The objectives of this paper are to identify accomplishments in real-time emissions monitoring and improvements in emissions measurement and analysis capability at AEDC.

Advancing the USAF's capabilities in engine life measurement and diagnostic monitoring of critical engine components is necessary to improve engine availability, minimize performance degradation, and reduce life cycle costs. Proven artificial intelligence (AI) technologies such as neural networks, fuzzy logic and expert systems present an opportunity to significantly enhance current trending and diagnostic capabilities in a real-time monitoring environment. This paper outlines the strategy adopted by the USAF to develop a state-of-the-art engine health monitoring system. In addition, the status of an R&D program whose ultimate aim is to demonstrate the perceived capability is also discussed. Engine data currently sensed and recorded for post flight processing will be analyzed in a continuous real-time mode.