Search Results

The likelihood of transmission of potential disease agents between animals and man during spaceflight is a real concern. Development of disease exclusion lists for animals and refinement of animal containment units have been the principal means of providing protection to the crew members. Awareness of potential latent infections and a judicious use of the higher risk category of animals such as wild-caught nonhuman primates provides another level of protection. Use of high efficiency filters, gasketing, and differential air pressures have all enabled increasing levels of safety through containment of potential aerosol escape from animal habitats.

AS81044 covers single conductor electric wires made as specified in the applicable detail specification with tin-coated, silver-coated, or nickel-coated copper or copper alloy conductors insulated with crosslinked polyalkene, crosslinked alkane-imide polymer, or polyarylene. The crosslinked polyalkene, crosslinked alkane-imide polymer, or polyarylene may be used alone or in combination with other insulation materials as specified in the detail specification.

The design and development of an encoding altimeter incorporating a new method of display and an improved coding scheme for the transmission of altitude information to air traffic controllers is presented.

The two combustion products which future technology will be unable to eliminate from present day jet engines are carbon dioxide and water vapor. The potential climatic change effects of carbon dioxide are considered to be a small part of a larger CO2 problem. Water vapor added to the troposphere forms contrails. The paper will assess the non-conclusive evidence of increased cirrus cloudiness at certain locations. Finally the potential climatic effects of added water vapor in the stratosphere on the radiation budget, the small decrease in ozone, and polar night cloudiness is evaluated in the light of future commercial aviation injections of water vapor.

Describing how the total weight of an airship becomes less as its flight continues and how its elevators can be used to keep the airship's nose pointed downward, thus balancing the excess lift by “dynamic lift,” the author says that 5 hr. is about the limit of flight for which the too great lightness can be overcome in this fashion safely, explains how different the conditions become on long flights and gives details of the means used to counteract this rising tendency. Valving of gas to overcome airship lightness is wasteful and costly, especially when the craft is inflated with helium gas but, if this is not done, some substance must be collected and stored at the same rate as that at which fuel is consumed in the engines and the most practicable method seems to be to recover water from the exhaust gases.

Through microscopic visualization experiments, a process generally known as depth filtration was shown to be caused by surface pores. Moreover, the existence of a soot cake layer was an important advantage for filtration performance because it could trap most of the particulates. We proposed an ideal diesel particulate filter (DPF), in which a silicon carbide (SiC) nanoparticle membrane (made from a mixture of 80 nm and 500 nm powders) instead of a soot cake was sintered on the DPF wall surface; this improved the filtration performance at the beginning of the trapping process and reduced energy consumption during the regeneration process. The proposed filter was called a diesel particulate membrane filter (DPMF). A diesel fuel lamp was used in the trapping process to verify the trapping and oxidation mechanisms of ultrafine particulate matter. Thus, the filtration performance of the membrane filters was shown to be better than that of conventional DPFs.

We discuss three factors that could alter human operators' perception of a remote worksite and adversely affect their task performance. First, we discuss the effect of image degradation on task performance. Our experimental results are similar to corresponding visual psychophysical experimental results, suggesting that the psychophysical results might be helpful for predicting the performance under other viewing conditions. The second factor is the control of the different viewing parameters. Dynamic control could be disorienting, but if the parameters are fixed, the operator might not feel telepresent. The interface through which the parameters are controlled also requires careful consideration and we discuss the advantages of using a helmet-mounted display. The third factor, the display update rate, can be affected by hardware limitations, transmission delays, or long rendering times.

Concern over the vibroacoustic environment within manned space platforms has been raised by astronauts on recent Spacelab missions. As a result, hardware being designed for the International Space Station is being subjected to stricter acoustic requirements and waivers allowing noise levels above the specified levels will be extremely difficult to obtain. The Space Station Biological Research Project (SSBRP) is developing Life Sciences hardware for the Space Station and is sensitive to the need for well defined requirements and allocations for acoustic noise. Statistical Energy Analysis (SEA) is being used to develop acoustic models of the main system hardware including sources, transmission paths and dissipation paths to ensure that acoustic requirements and allocations are adequate and consistent with hardware capabilities. Preliminary SEA models have been developed to predict the noise levels within the working volume of the Centrifuge Accommodation Module on Space Station.

Comparative studies between competing engineering techniques are complex, since the comparison depends upon the application. This paper focuses upon periodic vibration and noise in regional turboprops and in fuselage-mounted twin-jets. The vibrations under discussion are propeller harmonics of the turboprop and unbalance tones of the turbojet. Broadband noise (wind noise and combustion noise) is not discussed since no mature active technology is applicable to this type of noise. A large body of both active and adaptive/passive technology is applicable to periodic noise. Much of this technology is proprietary and unavailable to the public. Competing approaches are not openly compared; rather each technology is selectively promoted by its marketing team. This paper attempts a comparison. The authors of this paper are members of an engineering team that has recently finished the development of some adaptive/passive technologies.

A spatially periodic structure is a longitudinal array of identical substructures. A method of free and forced vibration analysis of periodic structures with simply supported and guided ends is presented. The computational effort required roughly equals the effort to analyze a single substructure. All natural modes and frequencies of an extensive structure can be found from a characteristic equation of order equal to the degrees of freedom on one substructure boundary. A modal reduction further simplifies the computations; applications are presented. The method is expected to be useful in structural vibration, sound transmission, and sonic fatigue analysis.

The development of exhaust nozzles and their application in operational military aircraft are discussed. Prime consideration is given to installation factors such as engine bay and nozzle cooling, inlet-engine flow matching, and aerodynamic effects on external afterbody drag. Examples of various operational exhaust systems are given which show how the aircraft-exhaust nozzle characteristics are integrated to achieve maximum system compatibility and performance. Results from one flight test program are presented which show how an aircraft-exhaust nozzle system was integrated to achieve maximum installed performance.

This paper traces the historical development of the BICERI variable compression ratio piston and its use in a number of engines. In early petrol experiments a variable compression piston covering the range from 6.5:1 to 16.5:1 showed significant efficiency improvements on 70 octane petrol. In the diesel engine field, Teledyne Continental increased the power of a V12 direct injection tank engine from 550 hp (30 hp per litre) to 1475hp (80 hp per litre) retaining the original crankcase and structure. At BICERI the output of a supercharged research engine was increased to 40 bar bmep with a peak cylinder pressure of only 165 bar. Military application lapsed with the preference for gas turbine engines, but the time is now right to explore the capabilities of variable compression within the wider automotive scene. Volkswagen have been working on a variable compression engine and have shown fuel consumption improvements up to 13% together with lower emissions.

This paper presents an experimental study of the vapour space flammability of Fuel Ethanol (a high-ethanol fuel for Flexible Fuel Vehicles, commonly known as “E85”) and gasoline containing up to 10% ethanol (commonly known as “E10”). The seasonal minimum vapour pressure limits in specifications for automotive spark ignition fuels are intended, in part, to minimize the formation of flammable mixtures in the headspace of vehicle fuel tanks. This is particularly important at subzero temperatures, where the headspace mixture may not be rich enough to prevent combustion in the presence of an ignition source such as a faulty electrical fuel pump. In the current study, the upper temperature limits of flammability were measured for field samples of “E85” and “E10”, and a series of laboratory-prepared blends of denatured ethanol, Before Oxygenate Blending (BOB) gasoline, and n-butane.

Abstract Constant area section length downstream to the fuel injection point is a crucial dimension of scramjet duct geometry. It has a major contribution in creating the maximum effective pressure inside the combustor that is required for propulsion. The length is limited by the thermal choking phenomenon, which occurs when heat is added in a flow through constant area duct. As per theory, to avoid thermal choking the constant area section length depends upon the inlet conditions and the rate of heat addition. The complexity related to mixing and combustion process inside the supersonic stream makes it difficult to predict the rate of heat addition and in turn the length. Recent efforts of simulating the reacting flow inside scramjet combustors are encouraging and can be useful in this regard. The presented work attempts to use simulation results of scramjet combustion for predicting the constant area section length for a typical scramjet combustor.

An accurate air flow rate model is critical for high-quality air-fuel ratio control in Spark-Ignition engines using a Three-Way-Catalyst. Emerging Variable Valve Timing technology complicates cylinder air charge estimation by increasing the number of independent variables. In our previous study (SAE 2004-01-3054), an Artificial Neural Network (ANN) has been used successfully to represent the air flow rate as a function of four independent variables: intake camshaft position, exhaust camshaft position, engine speed and intake manifold pressure. However, in more general terms the air flow rate also depends on ambient temperature and pressure, the latter being largely a function of altitude. With arbitrary cam phasing combinations, the ambient pressure effects in particular can be very complex. In this study, we propose using a separate neural network to compensate the effects of altitude on the air flow rate.

In order to meet the stricter and stricter emission regulations, cleaner combustion concepts for Diesel engines are being progressively introduced. These new combustion approaches often requires closed loop control systems with real time information about combustion quality. The most important parameter for the evaluation of combustion quality in internal combustion engines is the in-cylinder pressure, but its direct measurement is very expensive and involves an intrusive approach to the cylinder. Previous researches demonstrated the direct relationship existing between in-cylinder pressure and engine block vibration signal and several authors tried to reconstruct the pressure cycle on the basis of information coming from accelerometers mounted on engine block. This paper proposes a method, based on the analysis of the engine vibration signal, for the diagnosis of combustion process in a Diesel engine.

Butanol, a four-carbon alcohol, is considered in the last years as an interesting alternative fuel, both for Diesel and for gasoline application. Its advantages for engine operation are: good miscibility with gasoline and diesel fuels, higher calorific value than ethanol, lower hygroscopicity, lower corrosivity and possibility of replacing aviation fuels. Like ethanol, butanol can be produced as a biomass-based renewable fuel or from fossil sources. In the research project, DiBut (Diesel and butanol) addition of butanol to Diesel fuel was investigated from the points of view of engine combustion and of influences on exhaust aftertreatment systems and emissions. One investigated engine (E1) was with emission class “EU Stage 3A” for construction machines, another one, engine (E2) was HD Euro VI. The most important findings are: with higher butanol content, there is a lower heat value of the fuel and there is lower torque at full load.

Urea-SCR systems have become one effective method for meeting the ever tightening NOx emission control regulations for diesel engines. Higher activity of SCR catalysts in the low temperature region is crucial for meeting emission regulations and improving fuel economy. Some of the new catalytic components in the literature have shown good low temperature SCR activity, but they have not been fully confirmed to be durable enough for mobile applications. Fe-zeolite has been widely used in mobile applications due to its wide operating temperature window, but after exposure to large amounts of HCs at low temperatures, it is easily deactivated. We developed new SCR catalysts with improved low temperature activity and improved durability against HC fouling and thermal sintering by combining OSC (oxygen storage component) with Fe-zeolite.

Recently, there has been an increasing interest in Fiber Optic Sensors (FOS) for aircraft applications. Many of the FOS are based on different transducer mechanisms and hence, employ sensor-specific readout systems. However, for ease of maintenance and cost saving purposes, a ‘universal interrogator’ that can be used with at least a large sub-group of sensors is the preferred option for deployment in aircraft. Oxsensis has been developing sensors for harsh environments with focus on land based gas-turbine monitoring and combustion control and more recently is also looking at applying its technology to other areas such as Aerospace and Oil & Gas. In this paper we report on recent progress on the development of a number of FOS and how these could find application in aircraft with a ‘universal interrogator’ concept in mind.

Although the aerospace production process is much better controlled than the process in other industries, it remains true that very small manufacturing variability exists in the geometrical parameters (flange thicknesses, hole diameters …) as well as in material properties.). Also the medical, nuclear, and even the toy industry manufacturers assemble their products to very controlled and tight tolerances, thus receiving the always more stringent quality requirements imposed by customers, regulations and safety. However, despite this clear trend towards improved quality in products, in the current design process, the effect of this manufacturing variability is usually compensated for by applying safety factors. This is not an ideal situation, as it may lead to slightly over-designed structures. A much more promising approach is to include probabilistic models of design variables into the mechanical simulation process.