The use of hydrogen as an alternative fuel to power cogeneration gas engines has been a research topic over the last few decades and has currently gained importance, even more due to current circumstances related to decarbonisation efforts for the energy supply. A significant part of the research done is focused on the topic of combustion diagnostics, which can be fulfilled through different methods. This work investigates the feasibility of the ion current sensing for a pure hydrogen fueled series natural gas cogeneration engine. For this purpose, a variation of the fuel composition (100% natural gas to 100% hydrogen) was carried out while maintaining the indicated mean effective pressure (IMEP) and the combustion phasing (CA50). This demonstrated that the efficiency increased monotonically as the hydrogen concentration rose. Simultaneously, the ion current signal gradually dropped but was still detectable at 100% hydrogen combustion. To better understand this effect, 0D simulations with reaction kinetics (reaction mechanism: GriMech 3.0) were performed in AVL Boost. The observed ion current signal has been demonstrated to be linked to the mass fraction of OH- and O-radicals. Since the selection of a suitable spark plug entails a challenge in terms of its use for ion current sensing during hydrogen combustion, several spark plugs with different heat ranges were implemented in a further series of tests. Here, the spark was intentionally deactivated during selected engine cycles, while the ion current signal was measured and analyzed.
Session: RENEWABLE FUELS | | 15:00 - 15:30