Experimental and Numerical Investigation of a Direct Injection Spark Ignition Hydrogen Engine for Heavy-Duty Applications

International audienceThe H2 internal combustion engine is gaining increasing interest especially for commercial vehicles. Regarding the optimization of the combustion process, results of experimental investigations on a H2 heavy-duty single-cylinder engine in combination with numerical 3D-CFD investigations are presented. In addition to a Direct Injection (DI) Spark Ignited (SI) configuration, Port Fuel Injection (PFI) is explored to provide a reference with near homogeneous cylinder charge. The main objective is to assess a 3D-CFD-RANS framework based on ECFM and state-of-the art sub-models to describe the most important phenomena occurring in H2 spark ignition engines and to support the experimental analysis. Experimental results show that the PFI configuration provides efficiency and emissions benefits at the expense of volumetric efficiency. The proposed CFD model demonstrates the ability to successfully simulate different engine operating conditions for both PFI and DI systems. In particular, it is shown that the charge stratification typical for DI systems is not beneficial for the studied configuration as it increases wall heat losses and NOx formation

Evolution of Recrystallization Texture in AISI300 Series Austenitic Stainless Steels After Cold Rolling to Large Strain

The present paper deals with the evolution of texture in austenitic stainless steels during annealing after 95% cold rolling. After 95% cold rolling, the texture is mainly of the brass type {110} along with a scatter towards the S orientation {123} and Goss orientation {011} . Weak evidence of Cu component is observed at this high deformation level. During annealing, recovery is observed before any detectable recrystallization. After recrystallization, the overall texture intensity was weak; however, there are some discernible texture components. There was no existence of the brass component at this stage. Major components are centered on Goss orientation and Cu component {112} as well as the BR component {236} . Also, there are some few orientations which come up after recrystallization i.e. {142} and {012} . With increase in annealing temperature the textural evolution shows emergence of weak texture with another new component i.e. {197} . The evolution of texture was correlated with the deformation texture through twin chain reaction

Spatio-temporal leaf growth patterns of Arabidopsis thaliana and evidence for sugar control of the diel leaf growth cycle

Leaf growth dynamics are driven by diel rhythms. The analysis of spatio-temporal leaf growth patterns in Arabidopsis thaliana wild type and mutants of interest is a promising approach to elucidate molecular mechanisms controlling growth. The diel availability of carbohydrates is thought to affect diel growth. A digital image sequence processing (DISP)-based noninvasive technique for visualizing and quantifying highly resolved spatio-temporal leaf growth was adapted for the model plant A. thaliana. Diel growth patterns were analysed for the wild type and for a mutant with altered diel carbohydrate metabolism. A. thaliana leaves showed highest relative growth rates (RGRs) at dawn and lowest RGRs at the beginning of the night. Along the lamina, a clear basipetal gradient of growth rate distribution was found, similar to that in many other dicotyledonous species. The starch-free 1 (stf1) mutant revealed changed temporal growth patterns with reduced nocturnal, and increased afternoon, growth activity. The established DISP technique is presented as a valuable tool to detect altered temporal growth patterns in A. thaliana mutants. Endogenous changes in the diel carbohydrate availability of the starch-free mutant clearly affected its diel growth rhythms