Development of the Poppet Type Exhaust Valve in the Internal Combustion Engine: Part I 1860-1930

摘要

At a very early stage in the development of the internal combustion (IC) engine, poppet valves became the standard way of controlling the flow of the fuel/air mixture into the cylinder and the flow of exhaust gases out. Of the two valves, inlet and exhaust, the latter is more susceptible to failure. Exhaust valves are affected by creep, high temperature fatigue, and valve 'burning' from corrosion by the exhaust environment. As engine outputs increased, valve temperatures also increased and changes to fuel specification worsened the risk of corrosion. Initially, valve reliability was compromised by the limited range of alloys that were available, but the lack of scientific understanding of alloys also hindered development. After 1910, the mass-production automobile stimulated the need for better design and materials. Key advances were made in WWI when the Royal Aircraft Establishment investigated the first stainless steels for valves and the technique of cooling hollow valves using a sealed-in fluid. During and after WWI, work by Ricardo and others began to reveal the importance of octane rating, and towards the end of the 1920s fuels incorporating tetraethyl lead began to be utilized in American Naval aircraft, but this was the exception. In the automobile industry in the 1920s, much work was done on valve design. In this period both aircraft and automobile engines used Silchrome, a martensitic stainless steel containing silicon as well chromium, as the standard exhaust valve alloy. Silchrome had reasonable high-temperature strength and good resistance to the type of high-temperature corrosion from the unleaded fuels then in common use.