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Gas Turbine Technology : Flying Machine to Ground Utilities. P M V Subbarao Professor Mechanical Engineering Department. A White Collar Power Generation Method…. Progress in Rankine Cycle. The most Unwanted Characteristic of Rankine Group of Power Generation Systems.
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Gas Turbine Technology : Flying Machine to Ground Utilities P M V Subbarao Professor Mechanical Engineering Department A White Collar Power Generation Method…
The most Unwanted Characteristic of Rankine Group of Power Generation Systems • The amount of cooling required by any steam-cycle power plant is determined by its thermal efficiency. • It has nothing essentially to do with whether it is fuelled by coal, gas or uranium. • Where availability of cooling water is limited, cooling does not need to be a constraint on new generating capacity. • Alternative cooling options are available at slightly higher cost. • Nuclear power plants have greater flexibility in location than coal-fired plants due to fuel logistics, giving them more potential for their siting to be determined by cooling considerations.
Cooling Problems !!!! • The bigger the temperature difference between the internal heat source and the external environment where the surplus heat is dumped, the more efficient is the process in achieving mechanical work. • The desirability of having a high temperature internally and a low temperature environmentally. • In a coal-fired or conventionally gas-fired plant it is possible to run the internal boilers at higher temperatures than those with finely-engineered nuclear fuel assemblies which must avoid damage. • The external consideration gives rise to desirably siting power plants alongside very cold water.
Steam Cycle Heat Transfer • For the heat transfer function the water is circulated continuously in a closed loop steam cycle and hardly any is lost. • The water needs to be clean and fairly pure. • This function is much the same whether the power plant is nuclear, coal-fired, or conventionally gas-fired. • Cooling to condense the steam and surplus heat discharge. • The second function for water in such a power plant is to cool the system so as to condense the low-pressure steam and recycle it. • This is a major consideration in siting power plants, and in the UK siting study in 2009 all recommendations were for sites within 2 km of abundant water - sea or estuary.
Water, Water & Water ….!!!!! • A nuclear or coal plant running at 33% thermal efficiency will need to dump about 14% more heat than one at 36% efficiency. • Nuclear plants currently being built have about 34-36% thermal efficiency, depending on site (especially water temperature). • Older ones are often only 32-33% efficient. • The relatively new Stanwell coal-fired plant in Queensland runs at 36%, but some new coal-fired plants approach 40% and one of the new nuclear reactors claims 39%.
History & Repetition • 1791: A patent was given to John Barber, an Englishman, for the first true gas turbine. • His invention had most of the elements present in the modern day gas turbines. • The turbine was designed to power a horseless carriage. • 1872: The first true gas turbine engine was designed by Dr Franz Stikze, but the engine never ran under its own power. • 1903: A Norwegian, Ægidius Elling, was able to build the first gas turbine that was able to produce more power than needed to run its own components, which was considered an achievement in a time when knowledge about aerodynamics was limited. • Using rotary compressors and turbines it produced 11 hp (massive for those days). • He further developed the concept, and by 1912 he had developed a gas turbine system with separate turbine unit and compressor in series, a combination that is now common.
1914: Application for a gas turbine engine filed by Charles Curtis. • 1918: One of the leading gas turbine manufacturers of today, General Electric, started their gas turbine division. • 1920: The practical theory of gas flow through passages was developed into the more formal (and applicable to turbines) theory of gas flow past airfoils by Dr A. A. Griffith. • 1930: Sir Frank Whittle patented the design for a gas turbine for jet propulsion.
First turbojet-powered aircraft – Ohain’s engine on He 178 The world’s first aircraft to fly purely on turbojet power, the Heinkel He 178. Its first true flight was on 27 August, 1939.
Steam Turbine Vs Gas Turbine : Power Generation • Experience gained from a large number of exhaust-gas turbines for diesel engines, a temp. of 538°C was considered absolutely safe for uncooled heat resisting steel turbine blades. • This would result in obtainable outputs of 2000-8000 KW with compressor turbine efficiencies of 73-75%, and an overall cycle efficiency of 17-18%. • First Gas turbine electro locomotive 2500 HP ordered from BBC by Swiss Federal Railways • The advent of high pressure and temperature steam turbine with regenerative heating of the condensate and air pre-heating, resulted in coupling efficiencies of approx. 25%. • The gas turbine having been considered competitive with steam turbine plant of 18% which was considered not quite satisfactory. • The Gas turbine was unable to compete with “modern” base load steam turbines of 25% efficiency. • There was a continuous development in steam power plant which led to increase of Power Generation Efficiencies of 35%+ • This hard reality required consideration of a different application for the gas turbine.
6 4 2 5 1 3 Anatomy of A Jet Engine
6f 7f 6p 7p Ideal Jet Cycles ~1970s Aero Rejected Engines & Aero Derivative Engines 4 TurboJet 3 5 6j T0 Turbofan 1 2 Turboprop Direction
Brayton Cycle 1-2 Isentropic compression (in a compressor) 2-3 Constant pressure heat addition 3-4 Isentropic expansion (in a turbine) 4-1 Constant pressure heat rejection
pv & Ts diagrams SSSF Analysis of Control Volumes Making a Brayton Cycle:
Specific Energy equation of SSSF : No Change in potential energy across any CV Calorically perfect and Ideal Gas as working fluid.
1 –2 : Specific work input : 2 – 3 : Specific heat input : 3 – 4 : Specific work output : 4 – 1 : Specific heat rejection : Isentropic Processes:
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