Unvalved

Unvalved refers to a state where something lacks a valve. Valves are mechanical devices that regulate, direct, or control the flow of a fluid (liquids, gases, slurries, or a combination of these) by opening, closing, or partially obstructing various passageways. Therefore, an unvalved system or component is one where this control mechanism is absent.

In plumbing, an unvalved pipe would allow fluid to flow freely in both directions or simply not be able to be stopped, unlike a valved pipe which can be opened or closed to control flow. In engines, unvalved designs, such as certain two-stroke engines or some types of gas turbines, rely on different mechanisms to control the intake and exhaust of gases, rather than traditional poppet valves. These mechanisms might include ports in the cylinder wall that are uncovered by the piston's movement or rotary valves.

The absence of valves can simplify a design, potentially reducing cost and maintenance requirements. However, it often comes with trade-offs in terms of efficiency, control, or the ability to manage fluid flow precisely. For instance, unvalved engines may have less efficient fuel combustion or greater emissions compared to valved engines. The term "unvalved" is primarily used to describe the specific absence of these control components in various mechanical and engineering contexts.