Diesel fuel ignition temperature

Diesel fuel fnel nsed for internal combnstion in diesel engines usually, that fraction which distills within the temperature range approximately 200 to 370°C. A general term covering oils used as fuel in diesel and other compression ignition engines. 

In combustion of liquid oils such as heavy diesel fuels, the fuel is sprayed through nozzles into air. After ignition, a flame forms around the evaporating drops, driven by the vaporization of the drop in the hot boundary layer. The latent heat of vaporization strongly affects the temperature of the drop so that the heat release by the reaction is compensated by the heat absorbed in vaporizing the fuel and the heat lost to the cooler gas in the air. The composition profiles we might expect are shown in Figure 12-11, but the temperature will also vary around the particle. 

In a diesel engine, air is compressed to pressures of 1000 psi or greater. Upon compression, the air temperature increases to temperatures in the range of 600°F to 800°F (315.6°C to 426.7°C). At close to maximum compression, diesel fuel is injected into this hot, compressed air. Ignition of fuel within this environment is initiated whenever fuel components with the lowest autoignition temperature begin to combust. 

TEMPERATURE. The ignition delay of most Diesel fuels decreases as the temperature increases (50, 67, 94, 139). In certain temperature ranges highly-branched and cyclic compounds are exceptions (50). If it is assumed that the chemical delay is long in relation to the physical delay at low temperatures, then it is possible to estimate an apparent over-all energy of activation of the preflame reactions, as indicated in Figure 3 (71). Results similar to those shown in Figure 3 can be represented by an empirical relationship (43, 44) of the form ... 

The autoignition temperature of ethanol is significantly higher than that of gasoline or diesel fuel. This should make ethanol less susceptible to ignition when spilled on hot surfaces such as engine exhaust manifolds. 

The above parameters are relevant when pumping oils at low temperatures or for their use as alternative diesel fuel in ignition engines. The cloud points and pour points of the vegetable oils are higher than for diesel fuel. 

---