Ignition Delay Model of Multiple Injections in CI Engines 2019-24-0071

In compression ignition engines, the combustion starts after the ignition delay period from the start of injection. The degree of mixing between air and fuel during this period impacts combustion characteristics, such as the pressure rise rate, which worsens combustion noise. The formation of soot and nitrogen oxides can also be affected. In addition, ignition delay is essential to estimate the in-cylinder pressure. Therefore, there have been many researches performed to estimate the ignition delay for model-based control applications considering the above relations.

In this study, a semiempirical and 0-dimensional ignition delay model is developed for real-time control applications. As the ignition delay consists of physical and chemical delays in compression ignition engines, the integrated ignition delay model considers both of these variables. The ignition delay was correlated with parameters such as in-cylinder charge density, local temperature, the oxygen concentration at which the fuel is injected, injection pressure and the previously injected fuel quantity. This model was applied to multiple injection conditions that are common among conventional diesel engines. A 1.6-liter diesel engine was used to verify the correlation between ignition delay and other parameters, and the established model was also validated with other engines that have different specifications than the test engine.

The new 0-dimensional ignition delay model can contribute to researches such as soot model, in-cylinder pressure model and study about combustion noise, which are requiring the ignition delay period and targeting the real-time application.