Hydrogen has been identified as a promising decarbonization fuel in internal combustion engine (ICE) applications in many areas including heavy-duty on- and off-road, power-generation, marine, etc. Hydrogen ICEs can achieve high power density and very low tailpipe emissions. However, there are challenges; designing systems for a gaseous fuel with its own specific mixing, burn rate and combustion control needs, which can differ from legacy products.
Being able to determine the thermal distribution and temperatures of the power cylinder components has always been critical to the design and development of ICE. SAE-2023-01-1675 [1] presented an analytical FE-based tool, and validation using both FE and CFD methods for a Euro VI HD Diesel engine converted to operate on hydrogen gas using direct injection. In this study, updated methods and investigations are presented for Hydrogen ICE including applicability of the Woschni heat transfer correlation, use of CFD thermal wall functions and a modified flame speed model
The applicability of the Woschni correlation to hydrogen modelling has been a subject of several investigations. This paper investigates using the Hohenberg correlation as an alternative to the Woschni correlation to study the effect on heat flux, maximum gas cylinder pressure and structural temperatures using the two different correlations.
Furthermore, within this study, 3D CFD thermal wall functions were modified by incorporating a novel blending approach combining the Han-Reitz and Unified wall-function formulations to provide accurate heat transfer predictions across grids with large variations in near-wall resolution.
The novel model formulated to account for the changing influence of the thermo-diffusive instability on the laminar flame speed characteristic of lean and ultra-lean hydrogen flames presented in a previous publication (SAE 2023-01-0197 [2]) has been used. In this study, the tabulation method was improved to overcome the so called “cold boundary problem” which had prevented an accurate estimation of the flame characteristics at high pressure and temperature.
The simulation results are presented against a selected subset of available measured data from the previous study (SAE-2023-01-1675 [1]) covering a wide range of engine speeds, loads and fueling.