Multi-dimensional knock control for lean operating HICEs

A carbon-free drive concept must be established as a long-term solution for meeting the climate targets. The hydrogen-powered internal combustion engine (HICE) represents a robust, cost-effective and CO2-free option. Therefore it can make a significant contribution to the transformation of the transportation sector. The unwanted self-ignition of the mixture that occurs in gasoline engines is also relevant in the HICE. But the underlying combustion process offers several opportunities to optimize the conventional knock control strategy. Instead of reducing the knocking tendency by means of ignition angle retardation, which entails disadvantages in combustion efficiency, a multi-dimensional control concept was developed. This is based on the adjustment of the air-fuel equivalence ratio for each individual cylinder and the overall exhaust gas recirculation rate. The ignition angle retardation is still available as a fallback level, which is used when the other two intervention parameters have been exhausted. The advantages of the new control method are demonstrated with the aid of tests on a real engine and a comparison with a conventional knock control. Besides slight efficiency advantages and an effective reduction of the knocking tendency, the flexibility of the application and the adaptability of the control method to the prevailing conditions increase.