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Heinrich Zoelly (1862–1937) was a Mexican-Swiss engineer. He developed steam turbines and turbine-driven locomotives and patented the geothermal heat pump in 1912.
1862 Heinrich Zoelly was the fifth child of Franz Xaver Zoelly. His father, originally from Switzerland near Klettgau, had emigrated to Mexico to seek better fortune. Heinrich was born in Mexico and received the Mexican citizenship. His father ran a hat factory in Mexico City with his brother John.
When Henry was still a child, his father left Mexico because of political unrest and returned to Switzerland. There, Henry attended primary school, before going to the Federal Polytechnic Institute (which later became ETH Zurich).
1882 He earned his degree in mechanical engineering, aged 20.
1886 After study trips to Mexico and Paris, Heinrich Zoelly went back to Switzerland.
1888 Zoelly applied in Fluntern for naturalization and became a Swiss citizen.
Heinrich Zoelly was married and had five children.
In 1886 Zoelly entered the service of Maschinenfabrik Escher Wyss and Cie of Zurich. He quickly became its technical director at the young age of 26. Thanks to him, the company flourished, which at this time manufactured steam engines, water turbines, locomotives, traction engines and vessels.
He is best known for his multi-stage pressure-compounded impulse steam turbine, developed in 1903 in collaboration with Professors Stodola and Wagner. The original machine of this type is now at the Deutsches Museum. See photo. This turbine competed with other types of steam turbine developed about the same time in the world (Parsons, Curtis, Laval, and others) and was licensed worldwide.
The multi-stage pressure-compounded impulse Zoelly turbine appears not to differ significantly in principle from that developed by Auguste Rateau. However, the Zoelly turbine was characterized by fewer stages than the Rateau, due to its higher blade speeds, permitted by the use of forged steel discs (Rateau’s discs were of sheet metal, riveted to a hub). Zoelly also introduced two-cylinder turbines with only one bearing between cylinders.<ref 'The Parsons Centenary - a Hundred Years of Steam Turbines' by F. R. Harris, IMechE, 1984</ref>
In 1912 Zoelly was awarded an honorary degree from the ETH Zurich, partly thanks to his work in turbine development.
Since Zoelly was convinced of the superiority of the steam turbine to the steam piston engine, in 1913 Escher Wyss abandoned the production of steam engines and concentrated fully on turbines. Zoelly's vision also extended to the use of turbine instead of piston power for steam locomotives.
Until his resignation from Escher-Wyss Zoelly devoted himself to the development of a steam turbine-driven locomotive, which he drove forward to serviceability (1926 Zoelly-SLM), and later in 1930 Krupp Zoelly). However, the steam locomotive was becoming obsolescent.
1937 Zoelly died in his adopted home town of Zurich