Fluids Ch5

Carburetors and Torque Converters: Machines that use Accelerating Fluid to Generate Pressure Changes

Fluid machine

a machine that adds to, subtracts from, or converts energy of a fluid

streamlines

the trajectory of the instantaneous velocity field, i.e., a line that is everywhere tangent to the instantaneous fluid velocity vector

What is the purpose of a carburetor?

To mix fuel and air using pressure changes.

What is the purpose of a torque converter?

To transfer angular momentum between an engine and transmission.
Uses rotating airfoils to transfer angular momentum between two shafts.

How do these machines control pressure?

By accelerating fluid in the streamwise and normal directions.

Reynolds number (Re)

A dimensionless measure of inertial forces relative to viscous forces.

At high Reynolds numbers, inertial effects dominate viscous effects, making the inviscid approximation useful in appropriate flow regions.

irrotational flow

Flow in which the vorticity is zero

carburetor

a device that mixes fuel and air by passing the air through a Venturi to create a low-pressure region which sucks liquid fuel from a reservoir into the flow. Common in small engines e.g., chainsaws, lawn equipment, motorcycles

fluid machine

a machine that adds to, subtracts from, or converts energy of a fluid

Venturi

a tube with constriction whose purpose is to generate a low-pressure region in the throat

fuel injector

a device that injects fuel directly into a combustion chamber, usually with a spray atomizer

Bernoulli Equation

An equation relating pressure, kinetic energy, and gravitational potential energy along a streamline in inviscid (high Reynolds number), steady, incompressible flow.

Airfoil

In the context of fluid machines, a surface that turns flow and causes pressure changes

Clutch

A mechanical device that engages and disengages power transmission through frictional or viscous contact

casing

an enclosure. In a fluids context, usually an enclosure that contains the rotary elements of a turbomachine. Synonymous with housing.