Demonstration Model of a Uniflow Valve for a Steam Engine

Demonstration Model of a Uniflow Valve for a Steam Engine

Usage conditions apply
This is a demonstration model of a uniflow steam engine valve introduced in 1908 by Johann Stumpf of Germany. The model was constructed by Severn-Lamb Ltd. of Stratford-upon-Avon, England. Engines using the uniflow valves have a significant thermal advantage over earlier designs. In those engines relatively cool, expanded steam was exhausted from the end of the cylinder, and hot, high pressure steam was then immediately fed to the same end. In the uniflow engine the relatively cold exhaust steam leaves through ports in the center of the cylinder. It does not wash back and cool the cylinder walls and face of the piston. This greatly reduces the efficiency robbing condensation of the steam entering on the next stroke of the engine.
Around the time of World War I reciprocating steam engine construction had declined rapidly due to increasing use of more efficient steam turbines and diesel engines. However, many U.S. engine manufacturers licensed the uniflow design to build new reciprocating engines. The commercial advantage was that the superb efficiency of the uniflow engine approached that of turbines and was achieved at lower cost, size and complexity than the earlier efficiency-increasing compound engine designs.
The model was built to operate and show how the uniflow design functioned. It shows a steam cylinder in cross section along with inlet valves of the poppet type at each end. The exhaust ports are shown in the middle of the cylinder. A steam pressure versus volume curve is shown below the cylinder. A label at the right of the model describes the functioning of the valve. A separate label on the top of the model case describes the advantages and goals of the uniflow valve design.
Object Name
Engine, Steam
engine, steam, uniflow, model
Severn-Lamb Ltd.
ID Number
catalog number
accession number
Steam Engines
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Work and Industry: Mechanical and Civil Engineering
Engineering, Building, and Architecture
Power Machinery
Exhibition Location
National Museum of American History
Data Source
National Museum of American History
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