In engines working on the constant pressure of Diesel principle it is necessary, apart from any regulation of the throttle-valve, in order to obtain complete combustion, that the quantity and pressure of the injection air be adjusted for varying engine speeds and for different working charges.
To effect this purpose the conduit supplying injection air at constant pressure to the mixing chamber is throttled, before reaching the mixing chamber, by mechanism controlled either by the governor, or by the liquid fuel regulating mechanism, these two mechanisms, which are actuated independently, operating on the injection air conduit either jointly or independently.
Throttling always takes place in front of the atomising chamber in which the air and the liquid fuel are mixed.