Intake valves for reciprocating expanders with nonmetallic disk plates

Abstract

The design of nonmetallic plates formed from a glass-fiber-base laminate is analyzed for potential use in intake valves of the "dry version" of rapidly reciprocating expanders, and results are cited for five types of plates. Promising use of nonmetallic plates as component parts of expander stages is noted.Provision for high efficiency and reliability of gas-distribution elements is one of the basic problems encountered in the development of reciprocating expanders. Considering the need to separate the "hot" and "cold" zones of the working chamber, preference is usually given to a direct-flow expander stage with the intake valve located in the face of the cylinder. In that case, the role of exhaust valve is played by a sliding device with exhaust ports (windows) of circular or arbitrary shape, which are located on the lateral surface of the cylinder in the zone of bottom dead center (BDC). With this gas-distribution system, maximum possible channel sections are achieved in the seat of the exhaust valve; with a fixed section in the slot, this makes it possible to reduce the displacement of the valve plates h va , their impact velocities with the seat w s and limiter w l , and the stresses σ in the valve plates to the maximum extent possible.For this design of the expander stage, it is expedient to replace the metallic valve plates with nonmetallic ones (formed from a pure, or copper-coated glass-fiber-base laminate), which offer a number of advantages:• low noise level during operation of the intake valves;• high heat resistance of the plates; this makes it possible to use them in expander-generator units with a gas temperature falling within the range from 150 to 300°C at the inlet; • airtightness of the closed valves, and absence of seat and limiter wear, as well as light weight of the nonmetallic plates predetermine the expediency of their use in lubricant-free stages in units with increased rotational speed of the shaft and moderate piston speed; • a very high level of operational safety, since breakdown of the valve plates will not result in even greater damages when components of the driving mechanism, the cylinder-piston groups (CPG), and expensive greaseless piston and rod seals malfunction; and • the simplicity with which the nonmetallic valve plates are fabricated, and also their maintainability not only enhance the reliability and longevity of the working components of the CPG, but also make it possible to lower operating expenditures considerably.