Air-blast injection

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[1] makes it only suitable for stationary applications and watercraft.

[4] The air-blast injection system was first used by George Bailey Brayton in 1890 for a four-stroke kerosene fueled engine.

[5] Due to the highly viscous fuels Diesel used and thermal afterburning occurring, the principle of accumulating did not work sufficiently.

[7] Nevertheless, this improved system was still insufficient and Diesel considered direct injection without a huge compressor „unfeasible“.

[9] Initially, sieve-type atomisers were used for the injections nozzles, until the sieves were widely replaced by discs.

[12] For engines with disc-type atomisers, the injection pressure should be in sync with the rotational frequency of the crankshaft.

Julius Magg recommends a disc hole diameter depending on the indicated cylinder power output:

The injection nozzle is supplied with fuel from the fuel-feed-pump while constantly being fed with compressed air from the compressed-air tank.

5 and on the two-cylinder Johann-Weitzer-engine on the right) would activate the injection valve so the compressed air would then press the fuel into the combustion chamber.

Before the injection valve opens, neither fuel nor compressed air can enter the combustion chamber.

[16] The closed nozzle design allowed for a good air-fuel-mixture at the time which made it very useful for high capacity engines.

Biggest disadvantages were the higher manufacturing cost and the injection nozzle restrictions that made designing engines with horizontal cylinders considerably difficult,[17] since in horizontal cylinder engines, compressed air can easily enter the cylinder without pressing a sufficient quantity of fuel into the combustion chamber which leads to engine misfire or post-ignition.

At injection, the compressed air would then press the fuel through the disc-type atomisers into the combustion chamber.