Air-blast injection

Air-blast injection is a historical direct injection system for Diesel engines. Unlike modern designs, air-blast injected Diesel engines do not have an injection pump. A simple low-pressure fuel-feed-pump is used instead to supply the injection nozzle with fuel. At injection, a blast of compressed air presses the fuel into the combustion chamber, hence the name air-blast injection.

The compressed air comes from compressed-air tanks which feed the injection nozzle. A large crankshaft-driven compressor is used to re-fill these tanks; the size of the compressor and the low rotational frequency of the engine's crankshaft means that air-blast injected Diesel engines are huge in size and mass, this, combined with the problem that air-blast injection does not allow for quick load alteration makes it only suitable for stationary applications and large watercraft.

Before the invention of precombustion chamber injection, air-blast injection was the only way a properly working internal air fuel mixture system required by a Diesel engine could be built. Rudolf Diesel was granted a patent on air-blast injection in November 1893 (DRP 82 168). By the 1920s, air-blast injection was rendered obsolete by superior injection system designs that allowed much smaller but more powerful engines.