102.Flapper nozzle

It is a transducer which converts varying mechanical input signal into varying air output signal.

Air is fed to the nozzle at constant pressure via an orifice. Air leaks to atmosphere via nozzle is depend on the gap between nozzle and flapper.

When mechanical input is higher, it will push flapper against the spring thus gap between flapper and nozzle reduces and output pressure will increase(As amount of air leak between flapper and nozzle decreases)

When mechanical input is low , the gap between flapper and nozzle increases. as a result output decreases.