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A thermodynamic simulation model for the performance of a 4-stroke, direct-injection (DI), variable compression ratio (rc), diesel engine is presented. The model investigates the effect of varying rc on engine performance over whole engine speed range. Simulation sub-models are fuel burning rate, combustion products, thermodynamic properties of working fluid, heat transfer, fluid flow, friction, and soot and NOx formation mechanisms. Comparison of model predications with some other published experimental works with constant rc under different operating conditions results in good agreement. A comprehensive optimization analysis is conducted to an engine with specifications similar to HELWAAN M114 under normal operating conditions for seeking an optimum variation of rc to achieve a constant minimum bsfc over whole engine speed range.

A GaAs-InGaP triangular-barrier optoelectronic switch, grown by metalorganic chemical vapor deposition (MOCVD), was fabricated. Owing to the avalanche multiplication and carrier confinement in the device operation, S-shaped negative-differential-resistance (NDR) performances were observed in the current-voltage (I-V) characteristics under normal and reverse operation modes. The device showed a flexible optical function related to the potential barrier height controllable by incident light. The dependence of the carrier transport mechanism on illumination was investigated.

Due to the high bandgap (Eg =1.9eV) and etching selectively of In0.5 Ga0.5P material, the InGaP/GaAs material system has been proposed to replace the AlGaAs/GaAs. Undoped or lighted doped InGaP, with a relatively high resistance, was considered well as an “insulator”. The wide bandgap characteristics enhance the breakdown voltage and, thus, the power handling capabilities of the device for high power applications. From the device point of view, the high breakdown voltage is an important requirement for high power operations. The wide-gap InGaP was also used to increase the collector breakdown voltage in an NpN double heterojunction bipolar transistors (DHBT's). For InGaP/GaAs DHBT's, the electron blocking effect associated with the presented ΔEC between B-C heterojunction could cause a degraded current gain. Therefore, it is necessary to suppress the electron blocking effect which mainly resulting from the ΔEC at BC heterojunction.

A high-breakdown-voltage n+-GaAs/δ (p+)-GaInP/n-GaAs camel-gate field-effect transistor with the triple-step doped-channel has been successfully fabricated and demonstrated. Experimentally, the high gate turn-on voltage of 1.6 V at a gate current of 1 mA/mm and a very high breakdown voltage of 40 V with the low gate leakage current of 400 μA/mm are obtained. The measured transconductance is 145 mS/mm with the current gain cut-off frequency fT of 17 GHz and the maximum oscillation frequency fmax of 33 GHz for a 1×100 um2 device. Consequently, based on the remarkable experimental results, the studied device shows a promise for high-power circuit applications.

In this work, the surface recombination effect of a GaAs-based heterostructure-emitter and heterostructure-base transistor (HEHBT) with a pseudomorphic base structure are compared and investigated. Due to the insertion of InGaAs quantum well between emitter-base (E-B) junction, the valence band discontinuity can be enhanced and high emitter injection efficiency may be achieved. The excellent transistor characteristics including high current gain of 280 and low offset voltage of 100 mV are obtained when the base metal is deposited on the lower surface recombination velocity InGaAs layer. However, lower current gain of only 135 and large offset voltage of 300 mV are acquired as the base metal is deposited on the GaAs layer. This is mainly attributed to the significant difference of surface recombination effect of the studied devices. The surface recombination velocity of InGaAs is substantially lower than that of GaAs layer.

A high breakdown-voltage and high-linearity field effect transistor based on n-p-n structure, i.e., camel-gate field-effect transistor (CAMFET), has successfully fabricated and demonstrated. The CAMFET employs very thin n+ and p+ layers together with the channel to form a majority-carrier camel diode for modulating the channel current. The breakdown voltage about 21 V is obtained Furthermore, the maximum drain saturation current and transconductance are as high as 770 mA/mm and 220 mS/mm, respectively. Consequently, for the tri-step doping channel CAMFET, not only have the voltage-independent but also the high transconductance are obtained.

“The Second Stirling Techno Rally” is held at Nov. 1998 near Tokyo. This time about 100 normal size cars (N-class) and 30 mini cars (M-class) came to the contest and got better records than last year. Moreover, for this second rally, race of manned big cars and bikes (L-class) with self made Stirling engines are taken place also, and, about ten cars came to the race. The preparation and wonderful results of this second techno rally are reported here in details. By those rallies, it is hoped that understanding and progress of Stirling engine itself will be stimulated very much towards glorious 21st century.

There is a significant paradigm shift occurring within the design of Uninhabited Combat Air Vehicles (UCAVs) in that all technology domains (both human and mechanical) are being evaluated against mission-level objectives and not the traditional stovepipe system and subsystem metrics. This shift provides the opportunity to evaluate the benefits of comprehensive integration of the air platform and propulsion system. The challenge is to develop engineering methods that allow designers to achieve the proper balance between vehicle performance and engine performance meeting the ultimate measure of merit: system level objectives.

Thermodynamic design and analyses have been carried out on a multiple extraction regenerative Rankine cycle employing a recent software called CyclePad. A synergistic combination of qualitative physics and artificial intelligence techniques have been used to develop Cycle-Pad to assist in teaching, design and research in applied thermodynamics and advanced energy conversion systems. It provides an articulate virtual laboratory, in terms of visualisation of the schematic combination of a variety of thermodynamic cycles. A thorough sensitivity analysis has been carried out to help optimise the regenerative Rankine cycle in terms of thermal efficiency as a function of the extraction pressures and the splitting fractions. Numerical results and trend plots are provided. Such studies demonstrate that analyses of complex cycles can now be carried out, as part of classroom instruction as well, employing such a tool.

The US EPA 40CFR certification label fuel economy mpg for 114 model types of 1998 model year passenger vehicles marketed in the United States (US) by European. Pacific Rim, and American manufacturers, was correlated with fuel economy mpg test data obtained by the Consumers Union (CU) of US, Inc., a nonprofit, independent consumer information organization. The 114 model types range in curb mass (empty weight) from 916 kg (2015 lbs) to largest 2425 kg (5335 lbs). This correlation shows that the manufacturers US EPA label values overstate city mpg and understate the highway mpg significantly; in comparison to the CU city mpg and CU highway mpg test data, for the 114 model types of motor vehicles, reported by Consumers Union in 1998.

As the maintenance and disposal costs of aircraft batteries have risen, it has become critical to increase battery lifetime and to reduce maintenance cycles. This has led to the development of charging techniques designed to increase battery life while continuing to satisfy battery performance requirements. However, the cost of battery chargers accounts for 60% to 80% of the battery/charger system cost. AFRL/PRPB has initiated an in-house project to evaluate F-16 batteries using the existing F-16 charger. The objective is to determine which batteries can pass all F-16 performance and lifetime requirements using this charger. Several batteries were procured from several sources and two F-16 chargers are on loan to us from Sacramento/ALC. Depending on the outcome of this phase the project may be extended to include other aircraft and other chemistries such as Nickel-Metal Hydride and Lithium-Ion. Results to date and future plans will be discussed in this paper.

Results of an extensive wind tunnel test program aimed at development of a Savonius rotor-based irrigation system are summarized. The system uses an optimum configuration of the turbine and a novel coil-pump. Results suggest the system to be quite effective, with the turbine speed and tube diameter of the pump influencing the flow-rate while the number of turn of the coil-pump governing the head attained. Thus appropriate design of the system can provide the desired performance. Simplicity of construction, self-starting character, low speed operation, ease of maintenance and economy make the system quite attractive.

Since the extracted power from a wind turbine is always fluctuating, due to the continuous variations of the wind speed. A new technique for controlled frequency supply generated from a stand alone wind turbine is designed and implemented in laboratory environment. This technique is based on a controller by which the output power of the wind turbine is divided into two parts, the first part is considered to be constant power which is kept at a constant frequency, the second part has the remaining output power. Two induction generators connected to the same shaft driven by the wind turbine simultaneously generate these two parts. The first induction generator generates the constant output power, which feeds a critical load, while the second induction generator, which generates the remaining output power, is connected to a non-critical load through a three-phase bridge converter.

In the paper is given the substantiation of application of multistage wind engines with vertical rotation axis. For this purpose is detected the regularity of variations of instantaneous average values of areas of windward surfaces of vanes for one -, two -, three- and four-stage windwheels. The rational way of equalisation of instantaneous areas of a windward surface obviously is the application of the multistage four-vane windwheel with the deviation phase of sail vanes from each other on an angle . It is proved that at increasing of the stage’s number the uniformity of rotation is increasing proportionate to the square of stage number and also is explained the technique of definition of basic sizes of vane’s sails.

A new model of gaseous fuel-air mixing that is based on the ideal gas law and the equation of continuity is applied to propane-air mixtures. The local degree of mixing and the rate of mixing are calculated using the mass fraction of fuel measured within an infinitesimal fluid element and the time rate of this mass fraction, respectively. According to the model, mixing is promoted by pressure, temperature and velocity gradients. High initial pressure reduces mixing caused by pressure gradients. Results presented here provide the isolated effects of pressure and velocity gradients on mixing. These results facilitate the development of high intensity and high efficiency combustors with special focus on reducing pollutants emission.

The Conductively Coupled Multi-Cell Thermionic Fuel Element combines the best aspects of the single cell and multi-cell TFE designs. The key element in this TFE design is the emitter tri-layer. The emitter tri-layer places strict requirements on material properties especially the insulator material. Emitter tri-layers composites consisting of scandium oxide and tungsten were fabricated and tested. Scandium oxide has met the requirements of thermal stability, mechanical strength and electrical resistance lifetime tests. Initial results on cesium plasma compatibility test indicate that scandium oxide will meet the chemical compatibility requirement.

The capacity and coefficient of utilization of the positive active material of nickel-hydrogen cells show a significant increase when the cells are charged at −20°C or subjected to extended overcharge at 50°C. An interesting aspect of cells in which the positive plates show very high utilization is the appearance of a second wave in the overcharge region. The second wave seems to indicate the formation of a higher-valent nickel. The additional capacity obtained at very low temperature is less stable than that of 10°C when cycled. Destructive physical analysis of these cells reveals increased positive plate swelling. Rapid reaction of oxygen with hydrogen, otherwise known as popping, is more likely to occur in cells that contain positive plates which have endured significant swelling, since swelling occludes the gas channels.

Regenerative Fuel Cell System (RFCS) technology for energy storage has been a NASA power system concept for many years. Compared to battery-based energy storage systems, RFCS has received relatively little attention or resources for development because the energy density and electrical efficiency were not sufficiently attractive relative to advanced battery systems. Even today, RFCS remains at a very low technology readiness level (TRL of about 2 indicating feasibility has been demonstrated). Commercial development of the Proton Exchange Membrane (PEM) fuel cells for automobiles and other terrestrial applications and improvements in lightweight pressure vessel design to reduce weight and improve performance make possible a high energy density RFCS energy storage system.

A fundamental study was performed to develop a high efficiency solar heat receiver for a solar energy experiment mission on the Japan experiment module - exposed facility of the international space station. It is composed of a solar heat absorber, thermal energy storage and heat pipes. This system is aimed to transport solar thermal energy to a bottoming system with an efficiency of 80 %. Thermal analysis of each component was performed to assess its design approach. One ground testing model of the solar receiver was designed and fabricated in 1998, and then would be experimentally evaluated in 1999 at a test vacuum chamber of National Aerospace Laboratory.

The USAF in conjunction with NASA and the Jet Propulsion Laboratory established the DoD/NASA joint program to competitively develop high power, lithium ion battery technology and to establish North American domestic sources for lithium ion batteries. The program was initiated in FY97 to meet DoD and NASA requirements not addressed by commercial battery developments. Four contracts were awarded for cylindrical and prismatic cell and battery systems development. Technical and program management advisory groups were established to coordinate program management and to verify and validate test results from individual contractors. Specific applications, contract deliverable items and the overall schedule are presented.