<Table> <Tr> <Td> </Td> <Td> This article may require cleanup to meet Wikipedia's quality standards . No cleanup reason has been specified . Please help improve this article if you can . (November 2009) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article may require cleanup to meet Wikipedia's quality standards . No cleanup reason has been specified . Please help improve this article if you can . (November 2009) (Learn how and when to remove this template message) </Td> </Tr> <P> In an internal combustion engine, a choke valve modifies the air pressure in the intake manifold, thereby altering the ratio of fuel and air quantity entering the engine . Choke valves are generally used in naturally aspirated engines with carburetors to supply a richer fuel mixture when starting the engine . Most choke valves in engines are butterfly valves mounted in the manifold upstream from the carburetor jet to produce a higher partial vacuum, which increases the fuel draw . </P> <P> In heavy industrial or fluid engineering contexts, a choke valve is a particular design of valve that raises and lowers a solid cylinder (called a "plug" or "stem") which is placed around or inside another cylinder that has holes or slots . The design of a choke valve means fluids flowing through the cage are coming from all sides and that the streams of flow (through the holes or slots) collide with each other at the center of the cage cylinder, thereby dissipating the energy of the fluid through "flow impingement". The main advantage of choke valves is that they can be designed to be totally linear in their flow rate . </P>

Function of choke valve in oil and gas