1,720,983 research outputs found
Low Head Hydraulic Pumping – Design, Simulation, and Field Validation of Ram and Turbine Pump in Indian River Basin
No full textWater energy is essential for economic expansion and human development. Social progress
and economic growth depend on meeting water energy needs sustainably. The use of non renewable energy sources for pumping water to high heads from a low head (surface flow or
groundwater) has led to a global imbalance, leaving society vulnerable to an uncertain future.
The thesis aims to bypass electrical energy for pumping water in a niche region of people near
river basins, promoting interdependence and minimizing consumption. Technical engineering
solutions applied in this work use the flow from rivers or streams as their primary input energy
sources to pump 5 to 10 percent of the water needed for sustenance at higher elevations while
returning 90 to 95 percent of the water that is used for pumping back to the stream. This
endeavour has the potential to assist around 5% of the world's population who currently live
along the river basins. The Taipadar village case study is illustrated, which is situated in the
Tiriya river basin of the Chhattisgarh state, Bastar, in central-east India, to demonstrate the
implementation of such technical solutions in the real world. The emphasis is given to the
effectiveness of converting two hydraulic powers: input river flow and head and output
delivered flow and delivery head.
Afterward, in this research, the two appropriate engineering solutions of the Taipadar village,
namely the Ram pump and Turbine pump, have been examined for their best performance, and
monograms have been created to enable technicians and field personnel to develop their
customized systems. A detailed comparison of two technologies (i.e., Ram pump and Turbine
pump) is made with a discussion of their working principles and the results of tests conducted
at a field station in central-east India. The H-Q-D (Head-Discharge-Diameter) chart is also
developed to serve as a helpful tool for interpreting the technology concerning boundary
circumstances and serves as a roadmap for upcoming innovations in such renewable hydro pumping devices.
It is crucial to investigate the technologies' combined or individual overall optimum
performance for the system design. To gain insights into the performance of the turbine pump,
its blade geometry, represented by the blade thickness to chord length ratio (t/l), is analysed.
This study on t/l highlights its effect on the specific speed of the turbine and, therefore, the
pumping efficiency. This comprehensive work on t/l is a novel area of investigation that has
been previously ignored or overlooked, but its findings have opened up new avenues for
optimizing the performance of hydro turbines. The scaling effect of axial flow propellers while
maintaining a constant t/l ratio, as well as varying chord lengths and blade numbers, is also
addressed. A comprehensive qualitative theory of energy transfer and corresponding loss
mechanisms is also provided, along with an analytical method.
Moreover, in order to examine the performance of a hydraulic ram, this study analysed the
stroke rate of the impulse valve, as well as the valve setting, drive head, and length, using two
analytical models. These models (i.e., Tacke and Iversen) have validated the results that show
good conformance with matching delivered flow. The analysis of the effect of control variables
on input variables demonstrates that the field setup outperformed the lab setup.
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The thesis, in the end, will provide the fundamentals, design, conceptualization, construction,
evaluation, and field validation guidelines for implementing low-head micro hydro pump
technologies to deliver water, generate electricity, and, most notably, convince society and
policymakers to shift their current reductionist approach. The scaling and design of the turbine
pump, pump selection, and flow output estimation with a technical-economic feasibility study
procedure are also discussed
Thermal Turbomachinery Design for Closed Thermal Cycles and Multiple Fluids
No full textClosed-cycle gas turbines can complement conventional power conversion systems due to their potential for improved efficiencies, compact system layouts, and the ability to exploit non-fossil fuel energy sources which leads to low carbon emissions. Moreover, they can be adopted for distributed power generation applications. This thesis provides an understanding of the true essence of closed-cycle gas turbines with a focus on the development of turbomachinery design methodologies. The methodologies have been applied for the radial turbomachinery design (small-scale power range) for supercritical Brayton cycles and other thermal cycles such as air cycle, organic Rankine cycle, cryogenic cycles, and steam Rankine cycle.
The thesis begins with an elaborate review of the potential of closed-cycle gas turbines. Thermodynamic analysis has been carried out for the recuperated closed Brayton cycle with and without intercooling employing different working fluids. It has shown that the supercritical carbon dioxide gives considerably higher efficiencies at mild turbine inlet temperatures of 400-700°C and helium can be considered at higher temperatures of above 800°C. The closed Brayton cycle turbomachinery designs with multiple fluids have been brought together uniquely on two charts, one in absolute scale (∆H-M-D) and other in non-dimensional scale (NS-DS) by carrying out a detailed survey of the closed-cycle gas turbine plants and concept designs, which can aid in the design of turbines and compressors for different applications.
Turbomachinery design can have two approaches. The first one is scaling a benchmark design for different fluids catering to a particular application. The second one is a thorough step-by-step meanline design methodology for both turbines and compressors for any new application. Turbomachinery development through scaling a good benchmark design using the power of similitude to adapt it to the different working fluids employed in various thermal cycles can save considerable amount of time and provide a quick solution with good performance. The scaling methodology has been used for the development of radial turbomachinery for a 50 kW supercritical carbon dioxide (SCO2) power plant. The CFD simulations along with experimental results have confirmed that the scaling technique is quite good. The radial inflow turbine had an isentropic efficiency of 77 % from the CFD simulation at the design point with SCO2 fluid. The torque coefficients, flow coefficients, and the efficiencies determined from the CFD simulations for the turbine, when superimposed on the benchmark turbine experimental curves, showed good agreement. The efficiencies for the compressor from CFD with SCO2 fluid were lower compared to the experimental efficiencies of the benchmark compressor, but the curves showed the same trend. The highest CFD efficiency of 77.2 % was obtained at a flow coefficient of around 0.46. Experiments were carried out for the developed turbine and compressor assembly using air as the fluid (aeroloop) to mainly observe the vibrations at high speeds. The assembly had run-up to a maximum speed of 70000 rpm. The turbine flow coefficients from the aeroloop experiment were not far away from the simulation and the NASA benchmark data. The compressor flow coefficient zone from the experiment coincided with the flow coefficient zone of open-type boundary condition simulation results of the compressor with air as the fluid. Also, the absolute plot of speed vs. mass flow rate for the compressor in the aeroloop test matched well with the open boundary type CFD simulation results.
The thesis has also presented a scaling procedure to develop turboexpanders from a benchmark air turbine having experimental characteristics. It has been applied for the design of turboexpanders for supercritical carbon dioxide (SCO2) Brayton cycle, R143a organic Rankine cycle, and helium cryogenic cycle. The dimensionless iso-Mach number characteristic curves and efficiency curves of the SCO2 turbine, helium turbine, and R143a turbine determined from the CFD simulations were superimposed on the experimental characteristics of the benchmark turbine. There was good conformance between both, which proved that the proposed scaling methodology can be adopted for the turboexpander design.
Detailed meanline design procedures were proposed in this thesis for radial inflow turbine and centrifugal compressor using specific speed and specific diameter parameters so that the design can be started from scratch for a new application. These were used for the development of a turbo-compressor for the 2 kW air cycle machine for DARE (DRDO) which is employed in aircraft cooling. The radial inflow turbine had an isentropic total efficiency of 85.6 %. The centrifugal compressor designed based on the proposed methodology had an isentropic total efficiency of 76 %. Another design of centrifugal compressor which was carried out in a different approach had attained an efficiency of 78.6 %.
Radial turbomachinery design for a 1 MW supercritical carbon dioxide power plant has been presented in which the radial turbine is designed using the proposed 1-D meanline design methodology and the centrifugal compressor is designed using the scaling school of thought. Numerical simulations showed isentropic total efficiencies of 91% for the radial inflow turbine and 77.25 % for the centrifugal compressor at the design point.
The last part of the thesis has discussed the design procedure of an unconventional turbine type called ‘radial outflow turbine’ for a 200 kW steam Rankine cycle and 1 MW supercritical carbon dioxide Brayton cycle. The design point CFD simulation of the 18-stage steam radial outflow turbine showed efficiency close to 75 %. A new zone was identified for the radial outflow turbine in Balje’s specific speed-specific diameter chart. The design point CFD efficiency of the supercritical carbon dioxide radial outflow turbine was 84.6 %
Analysis and Design of Organic Rankine Cycle based Power Plants
No full textSolving the world’s energy crisis, and mitigating anthropogenic climate change, requires efficiently harnessing non-polluting renewable energy. Organic Rankine cycle (ORC) can be useful in this regard. ORC is Rankine cycle using organic compounds (pure or mixture) as working fluid. It is applicable for heat sources with temperatures of about 100 ⁰C to 200 ⁰C, such as solar thermal energy, geo-thermal energy, bio-mass energy, and industrial waste heat. This M.Sc.Engg. research project explores ORC in the following 3 parts.
The first part of the thesis describes a computational analysis of working fluids for Rankine cycle. Rankine cycle converts heat energy into useful work. It consists of four basic components: pump, evaporator, expander (turbine), and condenser. An optional component is economizer: a heat exchanger to transfer heat, from low pressure vapour in section between expander and condenser, to high pressure liquid in section between pump and evaporator. This may increase efficiency, but it also increases setup cost, complexity, and maintenance. Hence, economizer’s use is justified if saving to investment ratio is high enough. Two ORC configurations are explored: without economizer, and with economizer. Based on a few inputs (working fluid, expander inlet temperature, pump outlet pressure, expander isentropic efficiency, pump isentropic efficiency, ambient temperature, and economizer’s pinch temperature difference if economizer is used), there are two outputs (net work output and overall efficiency).
Using REFPROP and MATLAB, 75 pure substances that are technically feasible as working fluids for Rankine cycle are analyzed. For each working fluid, expander inlet temperature is linearly varied in desired step (example 2 ⁰C) from 100 ⁰C to 200 ⁰C, and pump outlet pressure is linearly varied in desired step (example 1 bar) from 1 bar to working fluid’s critical pressure - 5 bar. Work output and efficiency are computed for each case. Best working fluids for work output and efficiency, and corresponding temperatures and pressures, are found.
Heat engine efficiency usually increases with heat source temperature. But planners of Rankine cycle setups may not have liberty to choose the expander inlet temperature, and may have to work with whatever is available. Thus, analysis is done for 75 substances as working fluids, with expander inlet’s temperatures of 200 ⁰C, 150 ⁰C, and 100 ⁰C. For 200 ⁰C expander inlet temperature, the top five for work output are water, heavy water, methanol, ethanol, and ammonia, and the top five for efficiency are methylcyclohexane, nonane, octane, n-propylcyclohexane, and heptane. For inlet temperature of 150 ⁰C, top five for work output are water, heavy water, methanol, ethanol, and ammonia, and the top five for efficiency are methylcyclohexane, benzene, isohexane, dimethyl carbonate, and cyclohexane. For 100 ⁰C, the top five for work output are methanol, ethanol, ammonia, acetone, cyclopentane, and top five for efficiency are pentane, R-365mfc, isohexane, cyclopentane, isopentane. Three dimensional graphs (work output or efficiency vs. expander inlet temperature vs. pump outlet pressure) are shown for R-245fa, toluene, cyclohexane, and benzene.
Mixtures are also explored as Rankine cycle working fluids. The number of possible mixtures can be very large (for example 8,060,931 mixtures, if ten components are varied in steps of 5 %). A super-computer may be needed for systematic analysis of a large number of mixtures. Here, two sample cases are presented: one mixture (mass composition of pentane 30 %, propane 35 %, butane 15 %, hexane 20 %); and fifteen mixtures (toluene, benzene, and cyclohexane varied in steps of 25 % by mass).
The second part of the thesis presents a case study on ORC at Challakere campus of Indian Institute of Science (gross power output up to about 100 kW). This ORC uses solar thermal energy and diesel combustion as heat sources. R-245fa is working fluid. There is no economizer. Thermodynamic analysis of this ORC is performed, and it is observed that the overall efficiency is about 9.6 %. We also explore what the performance would be if an economizer is used and its pinch temperature difference is 5 ⁰C. It is found that ORC efficiency increases to about 11.5 %.
Analysis and Design of Organic Rankine Cycle based Power Plants.
The third part of the thesis describes the design and construction of a laboratory scale ORC system at Bangalore campus of Indian Institute of Science (net power output up to around 10 kW). Thermodynamic analysis of this ORC is also performed to evaluate the performance of the system
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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