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

The Civil Standard of Proof – What is it, Actually?

Common Law distinguishes two standards of proof applicable in civil and criminal matters, respectively. The criminal standard of beyond reasonable doubt is much higher than the preponderance of the evidence standard used in civil cases. Continental European Civil Law, on the other hand, recognizes just one standard of full conviction applicable in both criminal and civil cases. This study is the first to look at the standard of proof actually used by judges and judicial clerks in a Civil Law country (Switzerland). It is shown that, when asked directly, the members of court express a high decision threshold in line with legal doctrine and case law. But when Swiss judges are asked to estimate the error costs associated with each outcome and the error-cost-minimizing decision threshold is calculated based on the responses, the resulting standard is no different from the Common Law's preponderance of the evidence standard. When using the stated degree of belief in the truth of the plaintiff's allegations as a predictor for the grant of the plaintiff's request in a civil action, the probability of grant is 50% at a stated conviction of only 63%. It is further shown that the decision threshold is influenced by the individual's loss aversion, with individuals with a higher loss aversion having a higher decision threshold. No difference between the estimated decision threshold for members of the courts and members of the general population is found. The results suggest that the standard of proof actually employed by Swiss judges is not much different from the Common Law's preponderance of the evidence standard, despite the doctrinal insistence to the contrary