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(1 - 5 of 5)
- Title
- DESIGN AND PERFORMANCE EVALUATION OF AN INTEGRATED MINIATURE SINGLE STAGE CENTRIFUGAL COMPRESSOR AND PERMANENT MAGNET SYNCHRONOUS MOTOR.
- Creator
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ACHARYA, DIPJYOTI, Kapat, Jayanta, University of Central Florida
- Abstract / Description
-
An attempt has been made in this present work to design, fabricate and performance evaluate an integrated single stage centrifugal compressor and permanent magnet synchronous motor which is a key component of the reverse brayton cycle cryocooler. An off the shelf compressor – the driven and electric motor – the driver was not available commercially to suffice the requirements of the reverse brayton cryocooler. The integrated compressor-motor system was designed and tested with air...
Show moreAn attempt has been made in this present work to design, fabricate and performance evaluate an integrated single stage centrifugal compressor and permanent magnet synchronous motor which is a key component of the reverse brayton cycle cryocooler. An off the shelf compressor – the driven and electric motor – the driver was not available commercially to suffice the requirements of the reverse brayton cryocooler. The integrated compressor-motor system was designed and tested with air as the working fluid at mass flow rate of 7.3 grams per sec, with a compression ratio of 1.58 and driven by a 2 KW permanent magnet synchronous motor at a design speed of 108,000 rpm. A permanent magnet synchronous motor rotor was designed to operate to operate over 200,000 rpm at 77 Kelvin temperature. It involved iterative processes involving structural, thermal and rotordynamic analysis of the rotor. Selection of high speed ceramic ball bearings, their mounting, fit and pre-load played prominent role. Attempts were made to resolve misalignment issues for the compressor – motor system, which had severe impact on the rotordynamic performance of the system and therefore losses at high speeds , . A custom designed flexible coupler was designed and fabricated to run the compressor – motor system. An integrated compressor – motor system was an innovative design to resolve considerably several factors which hinder a high operational speed. Elimination of the coupler, reduction of number of bearings in the system and usage of fewer components on the rotor to increase the stiffness were distinct features of the integrated system. Several custom designed test-rigs were built which involved precision translation stages and angle brackets. Motor control software, an emulator, a DSP and a custom designed motor controller was assembled to run the motor. A cooling system was specially designed to cool the stator – rotor system. A pre-loading structure was fabricated to adequately pre-load the bearings. Flow measurement instruments such as mass flow meter, pressure transducers and thermocouples were used at several locations on the test rig to monitor the flow. An adjustable inlet guide vane was designed to control the tip clearance of the impeller.
Show less - Date Issued
- 2006
- Identifier
- CFE0001207, ucf:46955
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001207
- Title
- NUMERICAL STUDY OF A HIGH-SPEED MINIATURE CENTRIFUGAL COMPRESSOR.
- Creator
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Li, Xiaoyi, Kapat, Jayanta, University of Central Florida
- Abstract / Description
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A miniature centrifugal compressor is a key component of a reverse Brayton cycle cryogenic cooling system. The system is commonly used to generate a low cryogenic temperature environment for electronics to increase their efficiency, or generate, store and transport cryogenic liquids, such as liquid hydrogen and oxygen, where space limit is also an issue. Because of space limitation, the compressor is composed of a radial inlet guide vane, a radial impeller and an axial-direction diffuser ...
Show moreA miniature centrifugal compressor is a key component of a reverse Brayton cycle cryogenic cooling system. The system is commonly used to generate a low cryogenic temperature environment for electronics to increase their efficiency, or generate, store and transport cryogenic liquids, such as liquid hydrogen and oxygen, where space limit is also an issue. Because of space limitation, the compressor is composed of a radial inlet guide vane, a radial impeller and an axial-direction diffuser (which reduces the radial size because of smaller diameter). As a result of reduction in size, in order to obtain the required static pressure ratio/rise, the rotating speed of the impeller is as high as 313 KRPM, if Helium is used as the working fluid. Two main characteristics of the compressor – miniature and high-speed, make it distinct from conventional compressors. Higher compressor efficiency is required to obtain a higher COP (coefficient of performance) system. Even though miniature centrifugal compressors start to draw researchers' attention in recent years, understanding of the performance and loss mechanism is still lacking. Since current experimental techniques are not advanced enough to capture details of flow at miniature scale, numerical methods dominate miniature turbomachinery study. This work numerically studied a high speed miniature centrifugal compressor. The length and diameter are 7 cm and 6 cm, respectively. The study was done on the same physical compressor but with three different combinations of working fluid and operating speed combinations: air and 108 KRPM, helium and 313 KRPM, and neon and 141 KRPM. The overall performance of the compressor was predicted with consideration of interaction between blade rows by using a sliding mesh model. It was found that the specific heat ratio needs to be considered when similarity law is applied. But Reynolds number effect can be neglected. The maximum efficiency observed without any tip leakage was 70.2% for air 64.8% for helium 64.9% for neon. The loss mechanism of each component was analyzed. Loss due to turning bend was found to be significant in each component, even up to 30%. Tip leakage loss of small scale turbomachines has more impact on the impeller performance than that of large scale ones. Use of 10% tip gap was found to reduce impeller efficiency from 99% to 90%. Because the splitter was located downstream of the impeller leading edge, any incidence at the impeller leading edge leads to poorer splitter performance. Therefore, the impeller with twenty blades had higher isentropic efficiency than the impeller with ten blades and ten splitters. Based on numerical study, a four-row vaned diffuser was used to replace a two-row vaned diffuser. It was found that the four-row vaned diffuser had much higher pressure recovery coefficient than the two-row vaned diffuser. However, most of pressure is found to be recovered at the first two rows of diffuser vanes. Consequently, the following suggestions were given to further improve the performance of the miniature centrifugal compressor. 1. Redesign inlet guide vane based on the numerical simulation and experimental results. 2. Add de-swirl vanes in front of the diffuser and before the bend. 3. Replace the current impeller with a twenty-blade impeller. 4. Remove the last row of diffuser.
Show less - Date Issued
- 2005
- Identifier
- CFE0000702, ucf:46605
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000702
- Title
- DESIGN OF SEA WATER HEAT EXCHANGERFOR MINIATURE VAPOR COMPRESSION CYCLE.
- Creator
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Hughes, James, Chow, Louis, University of Central Florida
- Abstract / Description
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Recent advances in the development of miniature vapor compression cycle components have created unique opportunities for heating and cooling applications, specifically to human physiological requirements that arise in extreme environments. Diving in very cold water between 1.7 and 5°C requires active heating because passive thermal insulation has proven inadequate for long durations. To maintain diver mobility and cognitive performance, it is desirable to provide 250 to 300 W of heat from...
Show moreRecent advances in the development of miniature vapor compression cycle components have created unique opportunities for heating and cooling applications, specifically to human physiological requirements that arise in extreme environments. Diving in very cold water between 1.7 and 5°C requires active heating because passive thermal insulation has proven inadequate for long durations. To maintain diver mobility and cognitive performance, it is desirable to provide 250 to 300 W of heat from an un-tethered power source. The use of a miniature vapor compression cycle reduces the amount of power (batteries or fuel cell) that the diver must carry by 2.5 times over a standard resistive heater. This study develops the compact evaporator used to extract heat from the sea water to provide heat to the diver. The performance is calculated through the application of traditional single-phase and two-phase heat transfer correlations using numerical methods. Fabrication methods were investigated and then a prototype was manufactured. A test stand was developed to fully characterize the evaporator at various conditions. The evaporator is then evaluated for the conditions of interest. Test results suggest the correlations applied over predict performance up to 20%. The evaporator tested meets the performance specifications and design criteria and is ready for system integration.
Show less - Date Issued
- 2009
- Identifier
- CFE0002917, ucf:48016
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002917
- Title
- Ancient Maya Stone Polishers and Issues with the Terminology for the Artifacts Polished with These Tools.
- Creator
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Landry, Rachael, Chase, Arlen, Walker, John, Barber, Sarah, University of Central Florida
- Abstract / Description
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The ancient Maya adorned themselves with ornamental objects. This study investigates a type of polishing tool used by the ancient Maya to manufacture certain types of ornaments. Five stone polishing tools used by the ancient Maya are presented and analyzed. Relevant artifact forms are examined to establish which types of artifacts were being polished with these tools. An extensive discussion of the archaeological record and artistic representations of miniature earflares and buttons, which...
Show moreThe ancient Maya adorned themselves with ornamental objects. This study investigates a type of polishing tool used by the ancient Maya to manufacture certain types of ornaments. Five stone polishing tools used by the ancient Maya are presented and analyzed. Relevant artifact forms are examined to establish which types of artifacts were being polished with these tools. An extensive discussion of the archaeological record and artistic representations of miniature earflares and buttons, which were polished with many of these stone polishing tools, is also included because the terminology used to refer to these objects has varied throughout the academic literature and is in need of clarification.
Show less - Date Issued
- 2013
- Identifier
- CFE0005020, ucf:50012
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005020
- Title
- A Framework for Miniaturized Mechanical Characterization of Tensile, Creep, and Fatigue Properties of SLM Alloys.
- Creator
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Torres-Caceres, Jonathan, Orlovskaya, Nina, Xu, Yunjun, Das, Tuhin, University of Central Florida
- Abstract / Description
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With the heightened design complexity that may be achieved through additive manufacturing (AM) comes an equally complex set of distinct material characteristics. To properly characterize new materials for use in selective laser melting (SLM), extensive analysis is necessary. Traditional testing techniques, however, can be prohibitive in time and cost incurred. The small punch test (SPT) has been developed for such purposes, where material is scarce or costly. Although lacking standardization,...
Show moreWith the heightened design complexity that may be achieved through additive manufacturing (AM) comes an equally complex set of distinct material characteristics. To properly characterize new materials for use in selective laser melting (SLM), extensive analysis is necessary. Traditional testing techniques, however, can be prohibitive in time and cost incurred. The small punch test (SPT) has been developed for such purposes, where material is scarce or costly. Although lacking standardization, SPT has been successfully employed with various materials to assess material properties such as the yield and ultimate strength and verified by traditional testing results. With the accompaniment of numerical simulations for use in the inverse method and determining correlation factors, several methods exist for equating SPT results with traditional results. There are, however, areas of weakness with SPT which require development, and the solution of the inverse method can be demanding of time and resources. Additionally, the combination of SPT and SLM is relatively unexplored in literature, though studies have shown that SPT is sensitive to the types of structures and unique material characteristics present in SLM components. The present research therefore focuses on developing a framework for characterizing SLM materials via the small punch test. Several types of SLM materials in various orientations and processing states are small punch tested to evaluate the ability of the SPT to track the effects of these as they cause the materials to evolve. A novel cyclic test method is proposed to fill the gap in SPT fatigue testing. Results from these tests are evaluated via numerical modelling using the inverse method solved with the least squares method. Samples were also inspected using digital microscopy to connect fracture morphology to processing parameter variations. A framework is thus presented with which SPT may be utilized to more economically and expeditiously characterize SLM materials.
Show less - Date Issued
- 2018
- Identifier
- CFE0007109, ucf:51952
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007109
