Widening the operation limits of a SI engine running on neat ammonia

Present study aims to investigate the lean-burn characteristics of ammonia in a pre-mixed SI (Spark Ignition) engine and the influence of spark energy and discharge characteristics on engine performance and emissions. A wide range of engine operation conditions have been explored with particular focus on emission measurement. Engine parameters have been systematically swept to explore engine control strategies that would be operational in real engine application with a wide range of engine loads and tight emission regulations.Most previous studies required more than 5 % addition of hydrogen to the ammonia in order to achieve stable ignition for wide operation conditions. This has been a major obstacle in the application of ammonia for SI engines due to safety and system complexity issues. In present work, a comprehensive effort was made to understand and optimize the spark ignition system in order to mitigate the need for an ignition improver and all experiments have been performed with 100 % neat ammonia.With present engine modifications, emissions of unburned ammonia was measured to be between 5000 and 10000 ppm and with a combustion efficiency above 95 %. The unburned ammonia is believed to originate from crevices, particularly at the ring-pack. The NOx emission was between 4000 and 8000 ppm even at high excess air ratios. The emission of N2O is critical to minimize, as it is a strong greenhouse gas. It was measured to be between 20 and 80 ppm and appear to be related to post oxidation reactions of ammonia released from crevices during expansion.Advancing the ignition timing has proved to be an efficient handle for balancing the emissions of NH3 and NOx. These emissions will be reduced to H2O and N2 in an SCR catalyst if they are correctly balanced. Fortunately, advancing ignition timing also minimizes the formation of N2O.</div

Low-dose hydrocortisone in patients with COVID-19 and severe hypoxia: The COVID STEROID randomised, placebo-controlled trial.

BACKGROUND In the early phase of the pandemic, some guidelines recommended the use of corticosteroids for critically ill patients with COVID-19, whereas others recommended against the use despite lack of firm evidence of either benefit or harm. In the COVID STEROID trial, we aimed to assess the effects of low-dose hydrocortisone on patient-centred outcomes in adults with COVID-19 and severe hypoxia. METHODS In this multicentre, parallel-group, placebo-controlled, blinded, centrally randomised, stratified clinical trial, we randomly assigned adults with confirmed COVID-19 and severe hypoxia (use of mechanical ventilation or supplementary oxygen with a flow of at least 10 L/min) to either hydrocortisone (200 mg/d) vs a matching placebo for 7 days or until hospital discharge. The primary outcome was the number of days alive without life support at day 28 after randomisation. RESULTS The trial was terminated early when 30 out of 1000 participants had been enrolled because of external evidence indicating benefit from corticosteroids in severe COVID-19. At day 28, the median number of days alive without life support in the hydrocortisone vs placebo group were 7 vs 10 (adjusted mean difference: -1.1 days, 95% CI -9.5 to 7.3, P = .79); mortality was 6/16 vs 2/14; and the number of serious adverse reactions 1/16 vs 0/14. CONCLUSIONS In this trial of adults with COVID-19 and severe hypoxia, we were unable to provide precise estimates of the benefits and harms of hydrocortisone as compared with placebo as only 3% of the planned sample size were enrolled. TRIAL REGISTRATION ClinicalTrials.gov: NCT04348305. European Union Drug Regulation Authorities Clinical Trials (EudraCT) Database: 2020-001395-15