Johann Stumpf
Johann Stumpf of the Charlottenburg Technical College in Berlin is best known for popularising the uniflow steam engine, in the years around 1909.
Stumpf's 'Uniflow' system aroused interest among engine designers in the years before the First World War, at first in his native Germany and later elsewhere. The Uniflow principle was known previously, and Stumpf's work was really its practical application. In Stumpf's system steam was admitted at one end of the cylinder, and the used steam left through a ring of ports at the other end of the cylinder. This allowed the admission end to stay hot, as it was not cooled by the exhaust on its way out, and so improved efficiency. In a double-acting engine the exhaust ports were in the middle of the cylinder.
Almost all uniflow engines were large stationary types, but the system was tried by, among others, the North Eastern Railway in England. Briefly, the system worked well and obtained a small increase in economy by decreasing fuel consumption, but at the price structure prevailing at that time the extra constructional and maintenance costs were greater than the coal economy.