choked flow

(redirected from Choke flow)

Choked flow

Fluid flow through a restricted area whose rate reaches a maximum when the fluid velocity reaches the sonic velocity at some point along the flow path. The phenomenon of choking exists only in compressible flow and can occur in several flow situations. See Compressible flow

Through varying-area duct

Choked flow can occur through a convergent flow area or nozzle attached to a huge reservoir. Flow exits the reservoir through the nozzle if the back pressure is less than the reservoir pressure. When the back pressure is decreased slightly below the reservoir pressure, a signal from beyond the nozzle exit is transmitted at sonic speed to the reservoir. The reservoir responds by sending fluid through the nozzle. Further, the maximum velocity of the fluid exists at the nozzle throat where the area is smallest.

When the back pressure is further decreased, fluid exits the reservoir more rapidly. Eventually, however, the velocity at the throat reaches the sonic velocity. Then the fluid velocity at the throat is sonic, and the velocity of the signal is also sonic. Therefore, further decreases in back pressure are not sensed by the reservoir, and correspondingly will not induce any greater flow to exit the reservoir. The nozzle is thus said to be choked, and the mass flow of fluid is a maximum. See Mach number, Sound

With friction

Choked flow can also occur through a long constant-area duct attached to a reservoir. As fluid flows through the duct, friction between the fluid and the duct wall reduces the pressure acting on the fluid. As pressure is reduced, other fluid properties are affected, such as sonic velocity, density, and temperature. The maximum Mach number occurs at the nozzle exit, and choked flow results when this Mach number reaches 1.

With heat addition

A reservoir with a constant-area duct attached may also be considered in the case that the flow through the duct is assumed to be frictionless but heat is added to the system along the duct wall. See FLuid flow, Gas dynamics

choked flow

[¦chōkt ′flō]

(fluid mechanics)

Flow in a duct or passage such that the flow upstream of a certain critical section cannot be increased by a reduction of downstream pressure.

Mentioned in ?

compressible flow

References in periodicals archive ?

Because of the wide variance in flow rate, the regulator could be led to operate in an unstable manner during low flow conditions or could create a choke flow condition during high flow.

Retrofitting customized valves and actuators for pipeline monitoring stations

Based on the flow regimes and also gas fraction in the fluid two choke flow models can be detected sonic (critical) or subsonic (sub- critical) flow.

A NEW CHOKE CORRELATION TO PREDICT LIQUID FLOW RATE

This well, on a 24/64-inch choke flow test, has produced at a rate of 3,450,000 cubic feet of gas per day with a flowing tubing pressure of 1,000 pounds per square inch, 912 barrels of water and 48 barrels of oil per day.

Mexco Energy Announces Exploration Results

The possible operating points of a centrifugal gas compressor are limited by maximum and minimum operating speed, maximum available power, choke flow and stability (surge) limit (Figure 1).

Surge prevention in centrifugal compression systems

In the choke flow condition, no additional gas can pass though the regulator unless inlet pressure is increased.

Newest flexible element regulators ease stress of increased performance demands

The former could result in choke flow or excessive, recycle line pressures while the latter often resulted in surge.

In previous systems, the only options were to fully open the recycle valve (which could result in choke flow or excessive recycle line pressures), or to fully close it (which often resulted in surge).