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This article presents a study related to application of pre-chamber ignition system in heavy duty natural gas engine which, as previously shown by the authors, can extend the limit of fuel-lean combustion and hence improve fuel efficiency and reduce emissions. A previous study about the effect of pre-chamber volume and nozzle diameter on a single cylinder 2 liter truck-size engine resulted in recommendations for optimal pre-chamber geometry settings. The current study is to determine the dependency of those settings on the engine size. For this study, experiments are performed on a single cylinder 9 liter large bore marine engine with similar pre-chamber geometry and a test matrix of similar and scaled pre-chamber volume and nozzle diameter settings. The effect of these variations on main chamber ignition and the following combustion is studied to understand the scalability aspects of pre-chamber ignition. Indicated efficiency and engine-out emission data is also presented.

In computational fluid dynamic simulations of partially premixed combustion engines it is common to find simplifications of the in cylinder flow conditions in order to save computational cost. One common simplification is to start the simulation at the moment of intake valve closing with an assumed initial flow condition, rather than making a full scavenging simulation. Another common simplification is the periodic sector assumption, limiting all sector cuts of the full cylinder to be identical periodic copies of each other. This work studies how such flow simplifications affect the spray injection and in turn the fuel/air mixing at different injection timings. Focus is put on the stratification of fuel concentration and gas temperature due to interaction of the spray, turbulence and piston geometry. The investigated engine setup consists of a light duty engine with a piston bowl and a five-hole injector.

In the search for low greenhouse gas propulsion, the dual fuel engine provides a solution to use low carbon fuel at diesel-like high efficiency. Also a lower emission of NOx and particles can be achieved by replacing a substantial part of the diesel fuel by for example natural gas. Limitations can be found in excessively high heat release rate (combustion-knock), and high methane emissions. These limitations are strongly influenced by operating parameters and properties of the used (bio)-gas. To find the dominant relations between fuel properties, operating parameters and the heat release rate and methane emissions, a combustion model is beneficial. Such a model can be used for optimizing the process, or can even be used in real time control. As precursor for such a model, the current state of art of dual fuel combustion modelling is investigated in this work. The focus is on high speed dual fuel engines for heavy duty and marine applications, with a varying gas/diesel ratio.