Steam Engine Design/Historic

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Engine

(Reference the Wikipedia article here)

Engine Valve Design

There are several common styles of conventional valves in steam engines

• slide valve
• piston slide valve
• cam actuated poppet valve
• bump (or bash) valve
• slide valve

Some illustration of slide valve designs:

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Each of these has their own advantages and disadvantages often depending on steam conditions and desired durability. Please consult an engineering manual such as Valves And Valve Gears for a detailed discussion of this.

For the simple valves shown above it is not possible to vary the steam cutoff ratio during operation. This usually detrimentally impacts efficiency as one has to set the cutoff ratio higher than needed to keep the engine from stalling during load variation. For this reason a multitude of valve gears were developed for the three basic types of valve designs. The valve gears allow for the adjustment of the cutoff ratio during operation.

Slide Valve and Piston Slide Valve Valve Gears

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Poppet Valve Valve Gears

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