Improved visualization of pre-chamber combustion

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With the announcement of Maserati’s Nettuno enigne, pre-chamber ignition systems are finally set to see use in production vehicles. However, from a combustion analysis perspective, they present a fresh set of challenges to development engineers not present in traditional spark ignition systems.

To aid in their development, Kistler Group has now added a pre-chamber spark plug to its range of fiber-optic combustion analysis systems. This addition will enable insight into combustion occurring within the pre-chamber.

Fiber-optic analysis involves placing small viewing windows in the outer wall of the pre-chamber to capture a detailed record of processes in the engine so that optimization potential can be identified. The new design developed by Kistler allows analysis of more complex processes, taking account of different fuel mixes; until now it says, this measurement technology was only available for commonly used spark plugs.

Optical analyses provide spatial and time-based visualization of processes in the combustion chamber – such as knocking or pre-ignition – so researchers can understand them in detail.

Dr Frank Wytrykus, Kistler’s expert on optical technologies, said, “To optimize fuel consumption and emissions in the engines of the future, we need a precise understanding of pre-chamber ignition processes. Until now, this was impossible with such a level of detail. Our sensors make the effects of combustion visible, so we can work on eliminating the disruptive factors that reduce efficiency.”

Pre-chamber spark plugs ignite the fuel-air mix in a pre-chamber – hence their name. The expansion shoots the flame through small bore holes into the combustion chamber to trigger the main combustion over a large area. As a result, the main combustion is initiated at several points in the chamber: this makes it more likely that combustion will be uniform.

Correct dimensioning of the pre-chamber is the challenge here: even small changes to the design have a major impact on combustion. For example, engines with a pre-chamber spark plug are more susceptible to knocking. But to optimize engine efficiency and emission levels, it is essential to prevent uncontrolled combustion processes such as knocking or pre-ignition, and to avoid any formation of soot.

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