Combustion System Optimization of Commercial Vehicle Hydrogen Engines Via 3D CFD Simulations and Single Cylinder Engine Measurements: Injector Cap, Injection Strategy and Intake Duct Design

The development of hydrogen fueled engines has accelerated dramatically in recent years. They have gained much in operating reliability and the specific power outputs is at least comparable to those of current natural gas engines. This has been made possible by combining specific development tools derived from the development of compression ignition and spark ignition engines. These include jet visualization techniques (Schlieren, PIV, and LIF), video endoscopy on engine, and 3 D fluid dynamics simulations. In hydrogen engines for commercial vehicles, efforts have so far been made to keep engine components as unchanged as possible from similar diesel or gasoline versions. Similarly, some manufacturers have favored the port fueled injection (PFI) solution beca use it is easier to implement than the in cylinder (DI) injection one. The present work concerns the evaluation of the further improvement potential made possible by using direct injection (DI) technology, and intervening on both the geometry of the intake ducts and the design of the injector mounted cap. The analysis of these interventions makes use of single cylinder engine measurements and 3D CFD calculation of the fuel mixing process during the compression phase. Moreover, the flexibility of the direct injection system, that allows changing the injection timing with further improvement on the engine efficiency, was also considered . Despite the maturity already achieved by the hydrogen engine for commercial vehicle applications, the measurements and the simulations outlined in the present work throw a new light in the further (high) development potential of this technology.