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4 Gas Turbine Handbook: Principles and Practices
gases from a combustion chamber, which was fed from a compressor.
The turbine and compressor ran at 4,000 rpm and, in another early
example of steam injection, temperatures were kept down by injecting
steam upstream of the turbine nozzle. 1 Even at the turn of the
century turbine blade cooling was being integrated into the turbine
design as documented in 1914 by N. Davy who wrote, “In the experimental
turbine of Armengaud and Lemale the turbine wheel was a
double wheel of the Curtis type, water cooled throughout, even the
blades themselves being constructed with channels for the passage
of the water.” 3 Out of necessity (they did not possess the metallurgy
to withstand high temperatures) these early pioneers used steam
and water injection, and internal air and water cooling to reduce the
temperature effects on the combustor, turbine nozzles, and turbine
blades.
Later Brown Boveri and Co. went on to build a 500 horsepower
gas turbine with a three-stage centrifugal compressor, each stage having
25 impellers in series. This centrifugal compressor, specifically
built for a gas turbine application, was modeled from a A.C. Rateau
design. 4 It is sometimes difficult to separate, in retrospect, whether
these pioneers were augmenting their steam turbines with hot gas, or
their gas turbines with steam. But one thing is evident—their ideas
are still an important part of today’s gas turbine operation.
Throughout most of the first half of the 20th century the development
of the gas turbine continued slowly. Advances were hampered
primarily by manufacturing capability and the availability of high
strength, high temperature resistant materials for use in compressor,
turbine, and combustor components. As a result of these limitations
compressor pressure ratios, turbine temperatures, and efficiencies
were low. To overcome the turbine temperature limits, the injection
of steam and water to cool the combustor and turbine materials
was used extensively. As N. Davy noted in 1914, “From the purely
theoretical valuation of the cycle, the efficiency is lowered by any
addition of steam to the gaseous fluid, but in actual practice there
is a considerable gain in economy by so doing. Limits of temperature,
pressure, and peripheral speed, together with the inefficiencies
inherent in pump and turbine, reduce the efficiency of the machine
to a degree such that the addition of steam (under the conditions of
superheat, inaugurated by its injection into the products of combustion)
is of considerable economic value. It is also a great utility in