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In this paper a new dc-side active filtering system is proposed for aircraft electric power systems. The proposed active filter provides a continuous adjustable reactive power (both in phase and frequency) in the dc-link to meet the changing requirements which arise due to unbalanced and nonlinear loads at the 400(Hz) output. Furthermore, the active filter eliminate the additional capacitive kVA required in the dc-link caused by unbalanced and nonlinear loads. Results from a laboratory prototype active filter are also discussed.

In this study, a molten salt-based high temperature nanofluid is explored for solar thermal energy conversion applications. The efficacy of the nanofluid as a heat transfer fluid (HTF) in concentrating solar power systems is explored in this study. The molten salt can enable higher operating temperature resulting in enhancement of the overall system efficiency for power generation (using, for example, a Rankine cycle or Stirling cycle). However, the usage of the molten salt as the HTF is limited due to their low specific heat capacity values (compared with, for example, water or silicone oils). The low specific heat of molten salt can be enhanced by doping small amount of nanoparticles. Solvents doped with minute concentration of nanoparticles are termed as "Nanofluids." Nanofluids are considered as attractive coolants for thermal management applications due to their anomalously enhanced thermal properties (compared with the neat solvent).

The aim of this study is to explore the anomalous variation of thermo-physical properties of aqueous nanofluids. The specific heat of three water-based nanofluids containing silicon dioxide (SiO₂), titanium dioxide (TiO₂), and aluminum oxide (Al₂O₃) nanoparticles were measured using a differential scanning calorimeter (DSC). Measurements were performed over a temperature range of 30°C - 80°C which was chosen to be between melting point and boiling point of water. The experiments were implemented with different sizes of nanoparticles to investigate the effect of the size of nanoparticles on the specific heat of nanofluids. The specific heat of the nanofluids was plotted as a function of the diameter of nanoparticles and the mass concentration of nanoparticles. The results indicate that the specific heat of aqueous nanofluids decreases as the mass concentration of nanoparticles increases from 0.5% to 20%.

The possible use of a dual-loop, model-based adaptive control system for load-following in static space nuclear power systems is investigated. The objective of the fault-tolerant, autonomous control system is to deliver the demanded electric power at the desired voltage level, by appropriately manipulating the neutron power through the control drums. As a result sufficient thermal power is produced to meet the required demand in the presence of dynamically changing system operating conditions and potential sensor failures. Even though the proposed approach has thus far been applied only to a thermoelectric space nuclear power system, it is equally applicable to other static space nuclear power systems, such as thermionic systems. This is because of the considerable similarities in the underlying operational issues and in the dynamics of these systems from a control engineering viewpoint.

Artificial Neural Network(ANN) techniques are used to develop a system to detect High Impedance Faults(HIFs) in electric power distribution lines. Encouraging results were observed with a simple Multi-layer Perceptron(MLP) trained with the backpropagation learning algorithm. Although the results are not significantly better than those reported with other algorithmic approaches, ANN techniques have potential advantages over the other approaches; namely, ability to train the system easily to accommodate different feeder characteristics, ability to adapt and so become a better detector with experience and better fault tolerance. When these features are incorporated, the system is expected to perform better than existing systems. The system we developed for the current phase, the training strategies used, the tests conducted and the results obtained are discussed in this paper. Also background discussions on existing HIF detection techniques, and ANN techniques can be found in this paper.

Jet Engines may experience severe vibration due to the sudden imbalance caused by blade failure. This research investigates employment of on board magnetic bearings or piezolectric actuators to cancel these forces in flight. This operation requires identification of the source of the vibrations via an expert system, determination of the required phase angles and amplitudes for the correction forces, and application of the desired control signals to the magnetic bearings or piezo electric actuators. This paper will show the architecture of the software system, details of the control algorithm used for the sudden imbalance correction project described above, and the laboratory test results.

A scoping thermal analysis was done to evaluate the general feasibility of capillary pumped heat engines. The analysis was motivated by recent advances in nanoscale materials science that have made it increasingly practical to manufacture high porosity wicks with a median pore diameter on the order of a few nanometers. Capillary pumped heat engines are shown to be generally feasible for wick evaporation rates equivalent to about 1 watt per square centimeter when wick material thermal conductivity on the order of a few W/m-K is assumed. A compact heat engine architecture, referred to as an integrated capillary engine, is introduced.

The thermal characteristic of nanofluid for flow in a micro-channel is reported in this study by using an array of temperature nano-sensors. In this study, K-Type Thermocouples (Chromel/Alumel) were fabricated by surface micromachining process on a silicon wafer to obtain the thin film thermocouple array (TFTA). The micro-channel with TFTA was mounted on a heater (calorimeter) for imposing a specified heat flux on the bottom surface of the micro-channel. De-ionized water (DIW) was used as the test fluid for recording the temperature profile on the wafer substrate at different flow rates and heat fluxes. Aqueous nanofluids containing alumina nanoparticles were then used to record the temperature profiles under similar heat flux and flow conditions. The temperature profile was measured with the TFTA in a linear array of 5 columns and 2 rows of sensors while the volume flow rate was varied from 5 μl/min, to 7 μl/min and to 9 μl/min.

Electric power generation and conditioning have experienced revolutionary development over the past two decades. Furthermore, new materials such as high energy magnets and high temperature superconductors are either available or on the horizon. Our work is based on the promise that new technologies are an important driver of new power system concepts and architectures. This observation is born out by the historical evolution of power systems both in terrestrial and aerospace applications. This paper will introduce new approaches to designing space power systems by using several new technologies.

Poly Alpha Olefins (PAO) are extensively used as cooling fluid for thermal management in avionics cooling applications owing to their superior physical and chemical properties, such as greater fluidity at low temperature, lower volatility, a higher viscosity index, lower pour point, better oxidative and thermal stability as well as low toxicity. Solvents doped with minute concentration of nanoparticles are termed as “Nanofluid”. Anomalous enhancements in thermo-physical property values as well as in heat transfer performance of nanofluids have been reported using nanofluids (compared to that for the neat solvent). The thermal interfacial resistance between the nanoparticle and the solvent molecules (Kapitza Resistance) is the dominant factor controlling the efficacy of the nanofluids for cooling applications.

New dc to dc converter topologies are presented which are suitable for high density high power supplies. Topological variations of the basic inverse dual converter (IDC) circuit such as the transformer coupled, the multiphase and the multipulse derivation of the single phase IDC have been analysed and some simulation results have been presented. It has been shown in a recent publication [1] that the single phase IDC offers a buck-boost operation over wide range without transformer, bidirectional power flow, and complementary commutation of the switches. The topologies examined in this paper have additional features such as lower device and component stresses, and smaller filter requirements, resulting in smaller size and weight. Some performance and possible applications are also examined. Finally the IDCs for serial and parallel power distribution, and ac tapping of the IDC are discussed.