Free Stream Behavior of Hydrogen Released from a Fluidic Oscillating Nozzle

Abstract

The H2 internal combustion engine (ICE) is a key technology for complete decarbonization of the transport sector. To match or exceed the power density of conventional combustion engines, H2 direct injection (DI) is essential. Therefore, new injector concepts that meet the requirements of a H2 operation have to be developed. The macroscopic free stream behavior of H2 released from an innovative fluidic oscillating nozzle is investigated and compared with that of a conventional multi-hole nozzle. This work consists of H2 flow measurements and injection tests in a constant volume chamber using the Schlieren method and is accompanied by a LES simulation. The results show that an oscillating H2 free stream has a higher penetration velocity than the individual jets of a multi-hole nozzle. This behavior can be used to inject H2 far into the combustion chamber in the vertical direction while the piston is still near bottom dead center. As soon as the oscillation of the H2 free stream starts, the spray angle increases and therefore H2 is also distributed in the horizontal direction. In this phase of the injection process, spray angles comparable to those of a multi-hole nozzle are achieved. This behavior has a positive effect on H2 homogenization, which is desirable for the combustion process.

Editorial for the Special Issue on “Fluidic Oscillators—Devices and Applications”

“…Those can be harmful for the process and the device itself. Due to high frequencies and high entrainment, fluidic devices have shown that they are applicable for fuel-mixture preparation for liquid fuels in gas turbines [21] as well as for hydrogen in piston engines for trucks [22]. Furthermore, lean combustion devices often involve swirling flames that may be accompanied by a precessing vortex core, which can lead to combustion instabilities and suboptimal emission.…”