177,951 research outputs found
Analysis of a 115MW, 3 shaft, helium Brayton cycle
No full textThis research theme is originated from a development project that is going on in
South Africa, for the design and construction of a closed cycle gas turbine plant using
gas-cooled reactor as the heat source to generate 115 MW of electricity. South African
Power utility company, Eskom, promotes this developmental work through its
subsidiary called PBMR (Pebble Bed Modular Reactor). Some of the attractive features
of this plant are the inherent and passive safety features, modular geometry, small
evacuation area, small infrastructure requirements for the installation and running of the
plant, small construction time, quick starting and stopping and also low operational
cost.
This exercise is looking at the operational aspects of a closed cycle gas turbine,
the finding of which will have a direct input towards the successful development and
commissioning of the plant. A thorough understanding of the fluid dynamics in this
three-shaft system and its transient performance analysis were the two main objectives
of this research work. A computer programme called GTSI, developed by a previous
Cranfield University research student, has been used in this as a base programme for the
performance analysis. Some modifications were done on this programme to improve its
control abilities. The areas covered in the performance analysis are Start-up, Shutdown
and Load ramping. A detailed literature survey has been conducted to learn from the
helium Turbo machinery experiences, though it is very limited. A critical analysis on
the design philosophy of the PBMR is also carried out as part of this research work.
The performance analysis has shown the advantage, disadvantage and impact of
various power modulation methods suggested for the PBMR. It has tracked the effect of
the operations of the various valves included in the PBMR design. The start-up using a
hot gas injection has been analysed in detail and a successful start region has been
mapped. A start-up procedure is also written based on this. The analysis on the normal
and emergency load rejection using various power modulation devices has been done
and it stress the importance of more control facilities during full load rejection due to
generator faults.
A computational fluid dynamics (CFD) analysis, using commercial software, has
been carried out on some geometry of the PBMR design to find out whether its flow
characteristic will have any serious impact on the performance on the cycle during the
load control of the plant. The analysis has demonstrated that there will not be much
impact on the performance, during load control using pressure level changes, from this
geometry. However, some locations in the geometry have been identified as areas where
the flow is experiencing comparatively high pressure losses. Recommendations, which
include modification in the physical design, were made to improve this.
The CFD analysis has extended to a cascade to compare the flow behaviour of
Air and Helium with an objective of using air, being inexpensive, to test the helium
flow characteristic in a test rig to simulate the behavioural pattern of helium in the
PBMR pressure vessel. The specification of a hypothetical test rig and the necessary
scaling parameters has been derived from this exercise. This will be useful for designing
test rigs during the developmental and operational stage of the PBMR project
COMBINED BRAYTON, INVERSE BRAYTON and STEAM CYCLES POWER PLANT
No full textNowadays, more significant effort is needed to improve power generation efficiency to respond to environmental concerns. Several innovative technological options are under development and, among them, the integration of different energy systems is one remarkable opportunity. In this work, a combination of three different thermodynamic cycles has been proposed and studied: an Inverted Brayton cycle (IBC) is used to exploit the exhaust gas enthalpy of a Brayton-Joule cycle and a Steam Power Plant is bottomed to the Inverted Brayton Cycle, in order to recover the high thermal power wasted in its cooling section. In other words, a quite conventional natural gas combined cycle power plant is repowered introducing the Inverted Brayton Cycle to exploit the gas thermal power between the gas turbine and the heat recovery steam generator. In this integration, each parameter has a strong influence on the overall performance of the system: pressure ratio of the gas cycle, sub-atmospheric pressure of the inverted one, turbines inlet and outlet temperatures and heat recovery grade in the bottom steam section have been investigated in order to optimize the working conditions and find a best operating point. A post combustion opportunity was also considered, exploring for the best position to place it along the gases path and to get the maximum additional power through the repowering intervention
An elementary construction of Anick's fibration
No full textspheres and Moore spaces, as well as the first author’s work on the secondary suspension, predicted the existence of a p–local fibration S2n?1?T2n?1??S2n+1 whose connecting map is degree pr. In a long and complex monograph, Anick constructed such a fibration for p ? 5 and r ? 1. Using new methods we give a much more conceptual construction which is also valid for p = 3 and r ? 1. We go on to establish an H space structure on T2n?1 and use this to construct a secondary EHP sequence for the Moore space spectrum
Colonel H. R. Brayton of Texas A.& M. College\u27s chemical warfare service
No full textColonel H. R. Brayton of Texas A.& M. College\u27s chemical warfare service.https://mavmatrix.uta.edu/specialcollections_startelegram1940s/15347/thumbnail.jp
Subatmospheric Brayton-cycle Engine Program Review
No full textA solar energy powered electrical generator utilizing a Subatmospheric Brayton cycle engine is examined. The generator consists of a subatmospheric, Brayton-cycle engine and a permanent magnet (PM) alternator. The electrical power is generated by an alternator driven directly by the Brayton-cycle engine rotating group. Features that enhance reliability and performance include air foil bearings on both the Brayton-cycle engine rotating group and the PM alternator, an atmospheric-pressure solar receiver and gas-fired trim heater, and a high temperature recuperator. The subatmospheric Brayton-cycle engine design is based on that of the gas fired heat pump engine
Preliminary thermal performance analysis of the solar Brayton heat receiver
No full textThermal performance analysis of solar Brayton heat receiver in transferring heat to working gas of Brayton engin
Complemented circuits
No full textWe study a three-level form, called complemented circuit, which implements a special type of decomposition of a Boolean function into two logic blocks, e.g., SOP forms, whose outputs feed a two-input Boolean operator or a two-input programmable LUT. Such structures have been studied previously with a final fixed two-input operator, say an AND or an XOR, resulting in an AND-OR-AND implementation or an AND-OR-XOR implementation. We characterize the problem of all legal implementations of such a model, by defining Boolean relations that capture all the don’t care conditions induced by the chosen logic structure. For all 10 non-trivial two-input Boolean operators, we performed experiments using a Boolean relation minimizer to compare such realizations vs. SOP forms and other three-level forms, comparing areas and delays
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