Increasing attention has been devoted to the use of biodiesel fuel in internal combustion diesel engine due to its positive attributes as compared to the other types of fuel: e.g., being a renewable source, non-petroleum-based, with lower carbon monoxide, hydrocarbon, and particulate matter emissions. This work investigates the performance and the air emission of a small displacement engine fueled with blends of distilled biodiesel (from this point forward biodiesel only) and ultralow-sulfur diesel fuel up to 40% by volume. The considered engine plays a leading role in city cars and urban vehicles; the urban congestion and the antipollution regulations for urban vehicles make this kind of engine very attractive in the near future, especially if it will be fueled with biodiesel blends for their potential of reducing the pollutant emissions in urban areas. The first part of this work aims at comparing the results obtained with biodiesel blends and those determined using diesel fuel as a reference under various operating regimes without any modification to the injection process. The impact of biodiesel blend fuels on the engine's power, specific fuel consumption, and emissions is analyzed. The second part of this work aims at investigating the influence of a variation of the injection parameters on the performance and emissions of the engine using biodiesel blends (20% and 40%). Five engine operation modes are considered, in which the engine is tested with split injection (preinjection and main injection) and various preinjection and main injection timings and durations.
■ INTRODUCTIONThe continuous tightening of regulations on engine exhaust emissions has led to new solutions capable of reducing nitrogen oxides (NO x ) and particulate matter (PM) and also limiting fuel consumption and related costs.It is well-known that performance and emission characteristics are strongly governed by injector design that has a key role in the atomization and spray development. 1,2 A number of researchers have investigated the effects of the injection parameter settings on diesel engine performance and emission characteristics. 3−6 According to these authors, NO x emissions are affected by injection timing and pressure. The increase of pressure and the advanced injection timing cause the gas temperatures to rise during the combustion process. A more homogeneous mixture is therefore realized, with an increase of NO x emissions due to the kinetic constants and oxygen concentration of the Zeldovich mechanism. Soot formation is enhanced by heterogeneous fuel/air mixtures and fuel droplets size. The increase of injection pressure and the advanced injection timing determines a decrease of soot emission. 7 In order to reduce harmful diesel engine emissions, considerable attention has been devoted to the investigation of the impact of fuel composition on diesel emissions.Numerous types of fuels have been alternatively proposed, and many studies have demonstrated the suitability of renewable nature fuels made from agricultural products to b...
Objective:Assessment of the knowledge and application as well as perceived utility by doctors of clinical governance tools in order to explore their impact on clinical units’ performance measured through mortality rates and efficiency indicators.Methods:This research is a cross-sectional study with a deterministic record-linkage procedure. The sample includes n = 1250 doctors (n = 249 chiefs of clinical units; n = 1001 physicians) working in six public hospitals located in the Emilia-Romagna Region in Italy. Survey instruments include a checklist and a research-made questionnaire which were used for data collection about doctors’ knowledge and application as well as perceived utility of clinical governance tools. The analysis was based on clinical units’ performance indicators which include patients’ mortality, extra-region active mobility rate, average hospital stay, bed occupancy, rotation and turnover rates, and the comparative performance index as efficiency indicators.Results:The clinical governance tools are known and applied differently in all the considered clinical units. Significant differences emerged between roles and organizational levels at which the medical leadership is carried out. The levels of knowledge and application of clinical governance practices are correlated with the clinical units’ efficiency indicators (bed occupancy rate, bed turnover interval, and extra-region mobility). These multiple linear regression analyses highlighted that the clinical governance knowledge and application is correlated with clinical units’ mortality rates (odds ratio, −8.677; 95% confidence interval, −16.654, −0.700).Conclusion:The knowledge and application, as well as perceived utility by medical professionals of clinical governance tools, are associated with the mortality rates of their units and with some efficiency indicators. However, the medical frontline staff seems to not consider homogeneously useful the clinical governance tools application on its own clinical practice.
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