### 7.16.3. Ignition Delay Time

The ignition delay time, , is a function of local conditions, namely the fuel, pressure and temperature. You may either specify a custom correlation by CEL or chose from the built-in empirical correlations.

#### 7.16.3.1. Douaud and Eyzat

The ignition delay time of gasoline can be modeled using the empirical correlation by Douaud and Eyzat [183]:

| (7–107)

where the octane number, , is a user input parameter for the model. The correlation has been calibrated for the octane number range .

#### 7.16.3.2. Hardenberg and Hase

The ignition delay time of Diesel fuel can be modeled using the empirical correlation by Hardenberg and Hase [185]:

| (7–108)

where

The user input parameters are the mean piston speed, , the engine velocity in rounds per minute, , and the cetane number of the fuel, . The apparent activation energy, , has been calibrated for cetane number in the range .

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