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In #20 above we read that Griffiths was predicting that compressor stage efficiencies of 90+% should be achievable and that tests corroborated it. This left me curious ... I listen to Radio 4 guerilla economist Tim Harford and the More or Less team investigate numbers in the news... "double the risk of" headlines that cause concern but actually mean going from 1 in a million to 2 in a million... we needn't worry after all.So what is the context of Griffiths' statement .... does it mean going from 88 to 91 or what?Not quite as easy to find the answer as I hoped but when I did it is obvious why people sat up and took notice.Charles Parsons who was our great Victorian/Edwardian pioneer of steam turbines for industrial and marine use (e.g. Turbinia) decided to use steam turbine blading in reverse and built an axial compressor.. it had less than 40% efficiency but he perservered because of other advantages over the reciprocating compressors that were used in mines and steelworks at the time. That is lack of pulsation, size, weight, and less maintenance. He managed to get the efficiency up to 55% and in the early years of the 20th century delivered 17 machines mainly for blast furnace use... then Rateau came along with multi stage centrifugal designs of 70% efficiency and the market for axials disappeared. So when in 1926 Griffith realised why the axial had such a low efficiency and had design methods to raise it 20% above the centrifugal people began to take the axials seriously again. At this stage work on industrial and aero applications diverged and did not come together again until Avons and Olympus were used in industrial/marine applications afte WW2.Picture from 'Galaxies and Machines' book on Parsons.
In #20 above we read that Griffiths was predicting that compressor stage efficiencies of 90+% should be achievable and that tests corroborated it. This left me curious ... I listen to Radio 4 guerilla economist Tim Harford and the More or Less team investigate numbers in the news... "double the risk of" headlines that cause concern but actually mean going from 1 in a million to 2 in a million... we needn't worry after all.
So what is the context of Griffiths' statement .... does it mean going from 88 to 91 or what?
Not quite as easy to find the answer as I hoped but when I did it is obvious why people sat up and took notice.Charles Parsons who was our great Victorian/Edwardian pioneer of steam turbines for industrial and marine use (e.g. Turbinia) decided to use steam turbine blading in reverse and built an axial compressor.. it had less than 40% efficiency but he perservered because of other advantages over the reciprocating compressors that were used in mines and steelworks at the time. That is lack of pulsation, size, weight, and less maintenance. He managed to get the efficiency up to 55% and in the early years of the 20th century delivered 17 machines mainly for blast furnace use... then Rateau came along with multi stage centrifugal designs of 70% efficiency and the market for axials disappeared. So when in 1926 Griffith realised why the axial had such a low efficiency and had design methods to raise it 20% above the centrifugal people began to take the axials seriously again. At this stage work on industrial and aero applications diverged and did not come together again until Avons and Olympus were used in industrial/marine applications afte WW2.
Picture from 'Galaxies and Machines' book on Parsons.
