J. S. Kapat

A Highly Efficient 200 000 RPM Permanent Magnet Motor System

This paper presents the development of an ultra-high-speed permanent magnet synchronous motor (PMSM) that produces output shaft power of 2000 W at 200 000 rpm with around 90% efficiency. Due to the guaranteed open-loop stability over the full operating speed range, the developed motor system is compact and low cost since it can avoid the design complexity of a closed-loop controller. This paper introduces the collaborative design approach of the motor system in order to ensure both performance requirements and stability over the full operating speed range. The actual implementation of the motor system is then discussed. Finally, computer simulation and experimental results are provided to validate the proposed design and its effectiveness

Design of a super-high speed permanent magnet synchronous motor for cryogenic applications

This paper gives the design and simulation of a permanent magnet synchronous motor (PMSM) for a super-high speed centrifugal compressor drive application. The PMSM has an output power of 2000 W at 200,000 rpm with 28 V dc power supply. It is designed for operation at a cryogenic temperature of 77 K. The designed PMSM is a 2-pole, 3-phase slotless structure. The permanent magnet is centrally located inside the hollow shaft. Multi-strand twisted Litz-wire is used to reduce eddy current loss in the winding. The criteria of selecting materials for the super-high speed and cryogenic application are presented. Possible structures of the rotor and stator are considered and simulated using finite element method (FEM). Mechanical stress simulation and rotor dynamic issues are also considered. The connections of low pass filters to reduce switching harmonics of pulse-width modulation (PWM) and to reduce circulating current are also discussed. The first prototype has been fabricated and tested at room temperature. Projected total efficiency of the motor is over 90%

Analysis and Test of a High-Speed Axial Flux Permanent Magnet Synchronous Motor

This paper gives the analysis and test of a surface mounted axial flux permanent magnet synchronous motor (PMSM) for a high-speed centrifugal compressor drive. Both analytical analysis and 3-D electromagnetic finite element method (FEM) are used to calculate flux density in the airgap, rotor back iron, and stator iron. 3-D FEM is used to simulate the electromotive force (back EMF) and torque. The motor has been tested up to 87,000 rpm using an open-loop controller. The advantages and disadvantages of this kind of structure are analyzed, and some improvements of this design are also considered and partially verified by experiments

Novel polymer derived ceramic-high temperature heat flux sensor for gas turbine environment

This paper attempts to prove the feasibility of a novel High Temperature Heat Flux (HTHF) sensor for gas turbine environment. Based on the latest improvement in a new type of Polymer-Derived Ceramic (PDC) material, the authors present the design and development of a HTHF sensor based on PDC material, and show that such a sensor is indeed feasible. The PDC-HTHF sensor is fabricated using newly developed polymer derived SiCN, whose conductivity is controlled by proper composition and treatment condition. Direct measurements and characterization of the relevant material properties are presented. Electrical conductivity can be varied from 0 (insulator) to 100 (ohm.cm)−1; in addition a value of 4000 ppm/°C (at 600 K) is obtained for temperature coefficient of resistance. This novel sensor is found to perform quite satisfactorily at about 1400 °C for long term as compared to conventional heat flux sensors available commercially. This type of PDC-HTHF sensor can be used in harsh environments due to its high temperature resistance and resistance to oxidation. This paper also discusses lithography as a microfabrication technique to manufacture the proposed PDC-HTHF sensor. In our current design, the sensor dimensions are 2.5mm in diameter and 250 µm thickness.

Design of an optimal V/f control for a super high speed permanent magnet synchronous motor

In this paper, a new design approach of an optimal V/f control for a super high speed permanent magnet synchronous motor (PMSM) is presented. The stator resistance of PMSM is generally neglected in design of a V/f control and compensated only by a boost voltage. However, due to the extra small size requirement of the proposed super high speed PMSM, stator resistance cannot be neglected any more. In this paper, the optimal design of a V/f control curve with consideration of the stator resistance is provided. The effect of the stator resistor to the V/f control curve is analyzed, it enables utilization of a simple and easy V/f control curve for an open-loop control of the super high speed PMSM. Simulation results are illustrated to show the effectiveness of the proposed design technique.

Multi-dimensional heat flux reconstruction using narrow-band thermochromic liquid crystal thermography

An inverse algorithm is developed to reconstruct multi-dimensional surface heat flux using transient surface temperature measurements provided by narrow-band thermal liquid crystals (TLC) or phase-change material (PCM). In this thermographic technique, the information provided is the time it took a certain location to reach the characteristic temperature of the TLC or PCM. A quadratic functional to be minimized is formulated. The Levenberg-Marquardt method and genetic algorithms are used to minimize the functional. It is shown that GAs can be used successfully to retrieve surface heat flux distributions with significant error in input times to arrival at the TLC or PCM critical temperature.

Multifunctional nanocomposite coating for wind turbine blades

In this study, multifunctional carbon nanofiber (CNF) paper-based nanocomposite coating was developed for wind turbine blades. The importance of vibration damping in relation to structural stability, dynamic response, position control, and durability of wind turbine blades cannot be underestimated. The vibration damping properties of the nanocomposite blades were significantly improved and the damping ratio of the nanocomposite increased by 300% compared to the baseline composite. In addition, the CNF paper-based composite exhibited good impact-friction resistance, with a wear rate as low as 1.78×10−4mm3/Nm. The nanocomposite also shows the potential to improve the blockage of water from entering the nanocomposite, being a superhydrophobic material, with a contact angle higher than 160.0°, which could improve the longevity of a wind turbine blade. Overall, multifunctional nanocomposite coating material shows great promise for usage with wind turbine blades, owing to its excellent damping properties, great friction resistance, and superhydrophobicity.

Modeling and Design of Super High Speed Permanent Magnet Synchronous Motor (PMSM)

Because of the advantages of compact size and high efficiency, today PMSM motor has attracted the attention in aerospace applications. We have designed a super high speed PMSM motor with 92% efficiency novel for a cryo-cooler compressor for NASA recently. The rated speed of the motor is 136 krpm and the rated output power is 1.85 kW. Considerable attention has been paid in the design due to the super high speed range of operation. In the paper, we will present our analysis and design approach based on computer modeling and simulation.

Impact of a Ceramic Microchannel Heat Exchanger on a Micro Turbine

A highly effective recuperator with low-pressure drop is a key enabling technology to increase the efficiency of a micro turbine. To achieve a cycle efficiency above 40%, the average micro turbine would require a recuperator that achieves close to 99% effectiveness with a pressure drop as low as 2%. This paper presents the design and analysis of a microchannel heat exchanger that could be used as a recuperator in a micro turbine as an alternative to the currently used metallic primary surface recuperators that achieve an effectiveness of 90% at most. In the proposed design, the recuperator will be a counter flow, multi-layer design of parallel ducts with wall thickness of 50 μm and will be constructed with SiCN or a similar polymer derived ceramics, and fabricated using micro-stereolithography technology. Two designs, one having ducts with square cross-sections and the other with equilateral triangle cross-sections, are proposed and compared. For each design, the geometric parameters are optimized to provide the highest overall cycle efficiency while the volume of the heat exchanger is kept limited to 0.125 m3 and other cycle parameters are kept constant at typical values. For the square cross section design, the optimization process provides a design with an effectiveness of 0.961 and pressure loss of 2.86% that correspond to a cycle efficiency of 39.4%. The corresponding values for the triangle cross-section design are 0.983, 2.4% and 42.2%, respectively. Both designs are expected to withstand temperatures up to 1300°C in combustion gases. Special strategy is needed to fabricate any of these two microchannel designs by existing or proposed micro-stereolithography systems. One possible option is to make the complete heat exchanger as a bundle of identical smaller segments so that overall performance is not affected.Copyright

COMPONENT FABRICATION AND TESTING FOR A MESO-SCALE REFRIGERATOR

Preliminary design of a meso-scale refrigerator is the focus of this paper. Two design variations for two different applications are presented here. The two intended applications are (1) an integrated heat removal system for electronics or photonic chips or modules, and (2) an actively cooled jacket for personnel. The proposed device is based on a vapor compression refrigeration cycle. The paper starts with a general system description and preliminary design along with a functional decomposition where the overall system function is decomposed into nine major sub-functions. Different alternatives for compression and actuation are considered. Design specifications and some design details for each application are presented next. The specifics of the design requirements were found to suggest the same thermodynamic cycle for both applications, with the same temperature lift of 48