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In the previous article, the author gave an account of how the First Parsons steam turbine was designed. Here he discusses about the first little toy turbine, Parsons’ experiments with the Hero turbine and the subsequent developments.
The first little toy turbine first ran in mid 1884. It developed about 8 horse power and rotated at 18,000 RPM using 60 psig saturated steam. It is a wonder it ran at all. Parsons now had a toy he could play and experiment with. He did so for several years. He filed for a patent on this “parallel- flow” reaction multi-stage turbine on April 23, 1884. Other patents were soon to follow. Four years after the running of the first turbine, in 1888, Parsons designed a new steam turbine having a three-stepped cylindrical rotor and a three-stepped casing to match whereby the flow area could be increased and the blades lengthened as the steam expanded. The steam still entered the center of the casing for a balanced pressure. This new turbine initially developed 32 KW, but it soon was putting out 75KW. He and his company started selling them to generate electrical power.
Parsons denied use of his patents
In 1889, Parsons and his partners suddenly got into a scrap. Parsons was kicked out and was denied use of his parallel-flow (axial flow) steam turbine patents. Finally, the company was dissolved. For the next five years Parsons was in exile, so to speak, but he formed his own company called Messers. C. A. Parsons and Company. He and his loyal friend engineers continued to develop other types of turbine that did not infringe on his original patents. He designed and made inward flowing steam turbine that resembled multiple stage centrifugal compressors with reversed flow. These were expensive to make and were low in efficiency. He then went to making outward flowing mult-stage steam turbines with the steam expanding from the center near the shaft whereby there were two wheels, one that did not rotate and held stages of stationary blades at right angle to the wheel to the outside. The other wheel was attached to the shaft and had its blading also attached to the wheel at right angles. It was difficult to maintain tip clearance, but the turbines ran quite well and were called the ‘Mongrel’.
A number of these machines were made and sold but it was not as efficient as the parallel-flow machine. He experimented with the ‘Hero’ turbine and various combinations thereof with other turbine designs but none worked very well.
During this period of exile Parsons ran a lot of tests on various shapes of blades. He started making them with airfoil shapes and began to better understand streamline aerodynamic flow of steam. The drawings in the book clearly show the new airfoil shapes that resemble the shapes used in today's turbines. This effort proved to be fruitful and gone were the old flat paddle blades and in came the airfoil shapes which were far more efficient. These five years were not wasted in the development of the Parsons steam turbines. He had the new Heaton Works to make turbine.
In 1890, before Parsons got control of his patents again, he markedly improved his governor and throttle valve arrangement called the ‘Gust’ governor followed by better design in 1891 to get rid of condensation problems with the Gust design. Also, Parsons came out with a mechanical governor instead of the electrical design.
Back to parallel flow steam turbines
In 1894, Parsons got control of his parallel flow patents again and immediately dropped the development of the other types of turbines. He started again where he had left off five years earlier. The time was ripe for the steam turbine to take off all around the World and Parsons led the way. He started licensing his patent rights and designs to a number of companies including those in France, Germany, Switzerland, the United States as well as others. One of the first steam turbines he made in 1894 at the Heaton Works was a non-condensing 350 KW turbine with a dummy piston at one end to balance pressure and had the new airfoil designed blading. It ran at 3000 RPM to drive a 50 cycle AC generator.
Parson had designed a condensing turbine to go with the new stepped rotor high pressure 75 KW unit in 1889, but it was not built until 12 years later. The steam entered each end of the rotor to balance the pressure and exited at the center to the condenser. He used the new stepped casing/rotor design for better expansion velocities. It was sold to Newcastle and District Electric Lighting Company to go with the existing 75 KW non-condensing unit.
In 1902, Parsons made another improvement for his beloved steam turbines by finding a way to get the leakage air out of the condenser and keeping it out so that a much higher vacuum could be realized to improve the efficiency of the condensing end of the steam turbine. He came up with the vacuum augmenter system that sucked out the non-condensable air to improve steam turbine efficiency. This turned out to be a very important advancement as were many of his other ideas he fostered while in exile.
The use of electricity in 1900 started to surged and to take care of this sky rocketing demand of AC power, Parsons took on the task of designing and making larger and larger steam turbine generator sets using all of the improvements he had developed as a lame duck. Since 1900 the size had risen from 500 to over 6000 KW in ten years.
In the next part of this series, the author talks about Parsons marine steam turbine and its application in powering ships of all kinds.
Ivan G. Rice was past chairman of the South Texas Section of ASME (1974 - 75), past chairman of the ASME Gas Turbine Division (now IGTI) (1975 - 76). A Life Fellow Member of ASME and Life Member of NSPE/TSPE, he has authored many articles and ASME papers on gas turbines, inter-cooling, reheat, HRSGs, steam cooling and steam injection.