Cycle-Resolved Hydrogen Flame Speed Measurements with High Speed Schlieren Technique in a Hydrogen Direct Injection SI Engine

The influence of internal mixture formation oil hydrogen combustion in a SI engine was investigated using high speed Schlieren photography. To this end a computer controlled high pressure injection system for direct injection of gaseous hydrogen was developed. The injection system for hydrogen direct injection consists of an electronic control unit, a solenoid valve and a purpose developed injector. The timing and the duration of the hydrogen injection are controlled by an electronic unit. The fuel-air ratio was varied by adjusting the opening time of the solenoid valve. The hydrogen was fed into the combustion chamber of the engine with a pressure of 6.0 MPa. With this injection system and injection pressure it, is possible to inject the hydrogen into the combustion chamber of the engine even during hydrogen combustion.

In order to compare the results of internal mixture formation, experiments with external mixture formation were also performed. Internal mixture formation showed distinct, advantages compared to external mixture formation. Engine operation could he achieved with fuel-air ratios up to Φ=1.0. The flame speeds obtained with internal mixture formation were significantly higher.