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Despite significant benefits in terms of the ignition enhancement, the strength and timing of the turbulent flame jets subsequently issuing into the main chamber strongly depend on the pre-chamber combustion process and, thus, are sensitive to the specific engine operating conditions it experienced. This poses considerable difficulties in optimizing engine operating conditions as well as controlling engine performance. This paper investigates the influence of engine operating conditions on the pre-chamber combustion event using both experimental and numerical methods. A miniaturized piezo-electric pressure transducer was designed to be placed inside the engine cylinder head to record the pre-chamber inner volume pressure, in addition to conventional pressure indication inside the main chamber.

Modern Diesel engines have become ever more complex systems with many degrees of freedom. Simultaneously, with increasing computational power, simulations of engines have become more popular, and can be used to find the optimum set up of engine operation parameters which result in the desired point in the emission-efficiency trade off. With increasing number of engine operation parameter combinations, the number of calculations increase exponentially. Therefore, adequate models for combustion and emissions with limited calculation costs are required. For obvious reasons, the accuracy of the ignition timing is a key point for the following combustion and emission model quality. Furthermore, the combination of mixing and chemical processes during the ignition delay is very challenging to model in a fast way for a wide range of operation conditions.

Three-dimensional reactive computational fluid dynamics (CFD) plays a crucial role in IC engine development tasks complementing experimental efforts by providing improved understanding of the combustion process. A widely adopted combustion model in the engine community for (partially) premixed combustion is the G-Equation where the flame front is represented by an iso-level of an arbitrary scalar G. A convective-reactive equation for this iso-surface is solved, for which the turbulent flame speed ST must be provided. In this study, the commonly used and well-established Damköhler approach is compared to a novel correlation, derived from an algebraic closure for the scalar dissipation of reaction progress as proposed by Kolla et al. [1].