256 research outputs found
Design of an Optically Accessible Intake Manifold for Characterization of Liquid and Gaseous Jets in PFI Operating Conditions
No full textThe intake manifold and its components play a key role in the proper formation of air–fuel mixtures suitable for correct engine operation. In this article, starting from the original intake manifold design fitted to an optically accessible spark-ignited engine, a new solution was developed so as to allow the application of high-speed imaging of the fuel jet located between the runner and intake valves (Port Fuel Injection). To compare the two designs in terms of overall engine performance parameters such as volumetric efficiency, 0D/1D simulations were performed in motored conditions. Measurements at different crankshaft speed values were used for calibrating the intake line parameters and providing boundary conditions. Finite Element Analysis (FEM) was performed in SolidWorks to verify the structural strength of the new design when operating in the most critical conditions, i.e., boosted operation. As an overall conclusion, the results show that the new design guarantees a wider range of intake pressure values during the intake stroke, thus expanding the possible operative points. This can be obtained without compromising structural integrity, given that predicted safety factors were well above acceptable limits even for relatively high boost levels
Wasted spark duration measurement as a method for firing TDC identification in small engines
No full textDistributed generation represents a valid option for reducing
transmission losses and overall power system complexity.
Back-up power is another option that can ensure valuable
safety margins in the scenario of extensive penetration of
renewables, and can also act as balancing sources. Spark
ignition (SI) engines are often the prime choice for such
applications with sizes ranging from single cylinder
configurations to large bore units. Augmenting control
margins without increasing the number of sensors is an
essential aspect for small size engines. Common practice for
such power units is to employ fixed ignition timing with so
called wasted spark systems, i.e. two events per cycle one
during compression and one during the exhaust stroke.
Nonetheless, application of more complex control systems
such as fuel injection are becoming more and more
widespread even for this engine category. Within this
context, a method was developed for identifying TDC
phasing based on current measurements in the secondary
ignition circuit for engines that feature wasted spark
systems. The method was applied on a 50 cc SI unit
connected to a 1 kW power generator. The only
modification to the ignition system was to substitute the coil
with an automotive type piece; this was required because the
original component featured common ground wiring for the
primary and secondary side, thus rendering current
measurements much more difficult to implement. Duration
of the actual spark event was found to be a good parameter
for distinguishing between ignition occurring during the
compression stroke or during exhaust. Statistical distribution
during sequences of 200 cycles recorded at three different
levels of load was used for testing the identification
algorithm. The developed method was verified with pressure
measurements to distinguish between the two events, i.e.
compression and exhaust. Limitations of the method are
discussed and the possible ways of improving its application
were identified
System Design and Stress–Strain Analysis for Cranking and Motoring Small-Size Engines
No full textThe characterization of small-size engines requires dedicated rigs that are usually used for loading the power unit. Adding the possibility of motoring the engine is an important advantage that allows more detailed information on operating characteristics. It can be used for obtaining precious data that contribute to the development of more accurate numerical models and subsequent validation. Cost competitiveness is another essential aspect of small-size engines, given that development efforts need to be contained as much as possible. Within this context, the present work developed and tested a setup capable of cranking and motoring a small-size 50 cc spark ignition engine. Two configurations were considered for coupling an electric motor to the power unit: the first through a pulley-belt transmission and the second via a plastic clutch assembly. The main idea was to ensure the capability of motoring the engine up to a rotational velocity of 6000 rpm. Engine load was applied through a 1 kW electric generator connected directly to the crankshaft. The overall setup was designed in the two configurations and a stress–strain analysis was performed. The belt-driven option was found to be more favorable in terms of mechanical component requirements, showing a safety factor of around 4.0, while the plastic clutch assembly involved a more complex design phase and turned out to be more demanding, with a safety factor of around 2.9
0D/1D Modeling of Lean-Burn Conditions in a Hydrogen SI Engine for Closer Correlation of In-Cylinder Chemical Species with Optical Data
No full textSupplements, Plain Language Summary and Video abstract for Article Merola JF, et al. JAAD 2024 (DUPISTAD 24 weeks)
No full textSupplement, Plain language Summary and author narrated video abstract to accompany the research letter "Improved sleep parallels improvements in atopic dermatitis signs, symptoms, and quality of life in adult patients treated with dupilumab: 24-week results from the DUPISTAD study" Journal: Journal of the American Academy of Dermatology Authors: Joseph F. Merola, MD,a Albert S. Chiou, MD,b Emmanuel During, MD,c,d Peter Foley, MD,e,f,g Jiangming Wu, PhD,h Marius Ardeleanu, MD,i and Zafer E. Ozturk, MDjTHIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV
"Dislivelli stilistici e configurazioni sintattiche delle costruzioni participiali del Codex Diplomaticus Cavensis"
No full textIl lavoro analizza le costruzioni participiali rilevate nei documenti legali del IX secolo appartenenti al cosiddetto Codex Diplomaticus Cavensis. In particolare, è messa in evidenza la rilevanza della relazione tra le caratteristiche linguistiche di queste costruzioni e il livello stilistico e sociolinguistico del documento.This paper focuses on the participle constructions found in the ninth-century legal documents from the so called Codex Diplomaticus Cavensis. In particular, it demonstrates the relevance of the relationship between the linguistic features displayed by these constructions and the stylistic and sociolinguistic level of the document
ASO Author Reflection: Risk of Recurrence After Radical Resection in Entero-Pancreatic Neuroendocrine Tumors
No full textFlame Front and Burned Gas Characteristics for Different Split Injection Ratios and Phasing in an Optical GDI Engine
No full textDirect-injection in spark-ignition engines has long been recognized as a valid option for improving fuel economy, reducing CO2 emissions and avoiding knock occurrence due to higher flexibility in control strategies. However, problems associated with mixture formation are responsible for soot emissions, one of the most limiting factors of this technology. Therefore, the combustion process and soot formation were investigated with different injection strategies on a gasoline direct injection (GDI) engine. The experimental analysis was realized on an optically accessible single cylinder engine when applying single, double and triple injection strategies. Moreover, the effect of fuel delivery phasing was also scrutinized by changing the start of the injection during late intake- and early compression-strokes. The duration of injection was split in different percentages between two or three pulses, so as to obtain close to stoichiometric operation in all conditions. The engine was operated at fixed rotational speed and spark timing, with wide-open throttle. Optical diagnostics based on cycle resolved digital imaging was applied during the early and late stages of the combustion process. Detailed information on the flame front morphology and soot formation were obtained. The optical data were correlated to in-cylinder pressure traces and exhaust gas emission measurements. The results suggest that the split injection of the fuel has advantages in terms of reduction of soot formation and NOx emissions and a similar combustion performance with respect to the single injection timing. Moreover, an early injection resulted in higher rates of heat release and in-cylinder pressure, together with a reduction of soot formation and flame distortion. The double injection strategy with higher percentage of fuel injected in the first pulse and early second injection pulse showed the best results in terms of combustion evolution and pollutant emissions. For the operative condition studied, a higher time for mixture homogenization and split of fuel injected in the intake stroke shows the best results
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