1,721,444 research outputs found
Instantaneous engine speed analysis for cylinder isolation in multiple misfire events
No full textMisfire detection is a subject that has been deep studied during the last years and many methodologies have been developed for this purpose. Affordably detecting the misfire event and isolating the cylinder where the missing combustion took place can be considered a solved problem for engines with a limited number of cylinders. Misfire detection and in particular cylinder isolation is still challenging for engine operating conditions at very low load and high engine speed, for engines with a high number of cylinders, or when more than one misfire event is present within the same engine cycle (multiple misfire). In particular this last malfunctioning condition is very challenging, and its detection is enforced by the international regulations without requiring cylinder isolation, but only the number of misfiring cylinders. Many methodologies have been developed in the past based on the analysis of the instantaneous engine speed. The missing combustion effect on this signal is anyway very low when the number of cylinders is high and for engine operating conditions at low engine speed, giving rise to misdetection or false alarms as already mentioned. In addition when a misfire event takes place a torsional vibration is excited and shows up in the instantaneous engine speed waveform. If a multiple misfire occurs this torsional vibration is excited more than once in a very short time interval. The interaction among these successive vibrations can further generate false alarms or misdetection, and an increased complexity when dealing with cylinder isolation is necessary. The approach here presented permits enhancing existing misfire detection methods through optimized algorithm that allows correctly isolating the multiple misfiring cylinders over the entire engine operating range. This has been obtained by proper identifying the effect of the torsional vibration over the instantaneous engine speed. The identified waveform has been then used to filter out the torsional vibration effects in order to enlighten the effects of the missing combustions. In addition a proper instantaneous engine speed windowing has been introduced in order to increase the detection signal to noise ratio over the whole engine operating range. The integration of these two signal processing techniques has proven to be very effective on the engine investigated in this study, and it is easily extendible to other engine architectures. Particular care has been devoted to satisfy on-board implementation requirements in terms of memory allocation and computational power. The tests have been conducted on an L4 1.2 liter spark ignition engine mounted in a test cell. In-cylinder pressure signals have been acquired in order to validate the methodology here developed. Copyright © 2003 by ASME
Formula 1 Engine Evolution Analysis Using the Engine Acoustic Emission
No full textThis paper presents some results of a methodology capable of extracting instantaneous engine speed information from acoustic emission measurements, obtained from Formula 1 (F1) vehicles during qualifying or race sessions, from the early races in 50s-60s until present days. The results presented in the paper show that, from this signal, it is possible to gain information regarding the instantaneous engine speed (that in racing engines is strongly related to the power developed by the engine itself), but also regarding the way the combustions are distributed within an engine cycle, the time needed for a gear shift, the gear ratios employed, the driving strategy and so on. The analysis conducted in this work is applied to acoustic emission data recorded by microphones placed on-board the investigated cars. In recent years each F1 vehicle has been equipped with its own microphone while, in early races, in-car microphones had not been systematically used. It is anyway possible to find in the literature some recordings coming from microphones placed on board, during tests or even qualifying and race sessions. The analysis has shown to be insensitive from the type of microphone employed and from its position on-board the vehicle; even the signal coming from a low-cost microphone showed to be good enough for successfully applying the developed methodology. This made possible a useful comparison between the information obtained from all the engine acoustic emission signals available in the literature, thus allowing to analyze F1 powertrain evolution over the last four decades. Copyright © 2002 SAE International
Engine torque non-uniformity evaluation using instantaneous crankshaft speed signal
No full textThe paper presents the development of a methodology for evaluating the torque non-uniformity between the various cylinders of an Internal Combustion Engine (ICE). This non-uniformity can be due, for example, to pathological operating conditions such as misfires or misfuels, as well as to other abnormal operating conditions. Between the nominal torque production and the one corresponding to the absence of combustion there exist, in fact, a series of possible intermediate conditions. Each of them corresponds to a value of produced torque that lies between the nominal value and the one corresponding to the lack of combustion (due for example to statistical dispersion in manufacturing or aging in the injection system). The diagnosis of this type of non-uniformity is a very important issue in today's engine control strategies design. The use of the developed methodology should in fact allow the control strategy to adopt the appropriate interventions if the diagnosed non-uniformity is related to different behavior of the injectors. In order to evaluate this torque production variability between the various cylinders, information hidden in the instantaneous crankshaft speed fluctuations has been processed using a suitable methodology. The procedure has been validated running a supercharged 2.0 liters V6 engine, and a 1.2 liters L4 engine, in a test cell. During the tests, the in-cylinder pressure signal has been acquired together with the instantaneous engine speed, in order to determine a correlation between speed fluctuations and the indicated torque produced by each cylinder. The actual cylinder by cylinder torque non-uniformity can then be evaluated on-board by processing engine speed. The procedure is able to diagnose the absence of combustion (due for example to a misfire or a misfuel) as well as abnormal combustions that do not necessarily involve lack of combustion, with the accuracy needed for on-board use. Control interventions to injection and ignition time commands of one or more cylinders should in most cases be able to re-establish torque production uniformity
Air fuel ratio estimation using in-cylinder pressure frequency analysis
No full textThis paper presents an original approach to estimate the air-fuel ratio (AFR) of the mixture that burned inside a given cylinder of a spark-ignited (SI) internal combustion engine, using the information hidden in the corresponding in-cylinder pressure signal. In modern closed-loop fuel injection control strategies, the feedback signal is usually given by one (or more) heated exhaust gas oxygen (HEGO) sensor(s), mounted in the exhaust manifold(s). The information that such sensors give is related to the stoichiometry of the mixture that burned inside the cylinders. The HEGO sensor is not able to evaluate the AFR value precisely, being only able to determine whether the mixture was rich or lean. This information is sufficient to allow the implementation of a closed-loop strategy for injection time control. Generally speaking, such strategy could be improved in terms of readiness and precision by directly measuring (or by estimating) the actual AFR. Universal exhaust gas oxygen (UEGO) sensors are still considered expensive and their use is mostly limited to laboratory and racing applications, even if some automotive manufacturers have started installing such sensors on board passenger cars, as part of an effort to comply with ULEV (ultra low emission vehicles) regulations. For this reason the idea of estimating AFR values from other signals has received great attention in the past few years. A new approach based on in-cylinder pressure frequency analysis is presented here
Strategies for early prediction and timely recognition of drug-induced liver injury: The case of cyclin-dependent kinase 4/6 inhibitors
Full text linkThe idiosyncratic nature of drug-induced liver injury (Dili) represents a current challenge for drug developers, regulators and clinicians. The myriad of agents (including medications, herbals, and dietary supplements) with recognized Dili potential not only strengthens the importance of the post-marketing phase, when urgent withdrawal sometimes occurs for rare unanticipated liver toxicity, but also shows the imperfect predictivity of pre-clinical models and the lack of validated biomarkers beyond traditional, non-specific liver function tests. After briefly reviewing proposed key mechanisms of Dili, we will focus on drug-related risk factors (physiochemical and pharmacokinetic properties) recently proposed as predictors of Dili and use cyclin-dependent kinase 4/6 inhibitors, relatively novel oral anticancer medications approved for breast cancer, as a case study to discuss the feasibility of early detection of Dili signals during drug development: published data from pivotal clinical trials, unpublished post-marketing reports of liver adverse events, and pharmacokinetic properties will be used to provide a comparative evaluation of their liver safety and gain insight into drug-related risk factors likely to explain the observed differences
Targeting the arrhythmogenic substrate in atrial fibrillation: focus on structural remodeling
No full textAtrial fibrillation (AF) is an emerging clinical problem with multifaceted issues: current and expected prevalence, significant morbidity, potentially fatal outcome (e.g., stroke) and gaps in therapeutic approaches. Current antiarrhythmic strategies not only fail to guarantee effective rhythm control, but also cause “on target” (i.e., pro-arrhythmia, namely torsade de pointes) and “off target” (i.e., extra-cardiac toxicities) side effects. Although a number of drugs have just come out of the pipeline with promising results (e.g., dronedarone), the question arises whether channel-targeted drugs represent the only viable approach. A body of evidence has emerged supporting structural remodeling as the main arrhythmogenic substrate perpetuating AF. Fibrosis, inflammation and oxidative stress appear strongly interconnected in the pathogenesis of remodeling-induced abnormalities. Moreover, insights into extracellular matrix network strongly suggested an active cross-talk within the cardiac microenvironment, which should be further investigated as promising “anti-remodeling” approach. Therefore, pharmacological modulation of non-ionic targets (the so called “upstream” therapy) has gained interest as a preventive strategy in AF. At the present state of knowledge, renin-angiotensinaldosterone system blockers and statins offer evidence for potential clinical exploitation, while several remodeling targeted therapies have been tested only experimentally or failed when studied for human validation. Fascinating and innovative strategies have been proposed (e.g., miRNAs modulation), but the actual benefit is debated. This review will provide mechanistic insights into structural remodeling and highlight emerging upstream strategies in AF management
A review of remote-control strategies for reactivity controlled compression ignition combustion
Full text linkOver the past years, the increasingly stringent emission regulations for Internal Combustion Engines (ICE) have led to the development of non-conventional combustion strategies like Low Temperature Combustions (LTC) characterized by high efficiency and low pollutant emissions. One of the most relevant LTC strategies is the Reactivity Controlled Compression Ignition (RCCI), characterized by the combustion of a lean mixture composed by air and a low reactivity fuel (LRF, gasoline in the case under study) ignited by a high reactivity fuel (HRF, Diesel in this study), directly injected in the combustion chamber, due to the high pressure and temperature in the cylinder. The proper management of this combustion strategy results in high efficiency and low engine-out emissions, with the simultaneous mitigation of both nitrogen oxides (NOx) and particulate matter (Soot). On the other hand, this combustion methodology is affected by high instability and high sensitivity to slight variations of the in-cylinder thermal conditions. Previous works demonstrate that combustion stability can be guaranteed through closed-loop control strategies that vary the injection parameters to keep the center of combustion (CA50, i.e. the angular position when the 50% of fuel burned within the engine cycle) at a proper target value. Although the center of combustion can be directly evaluated from in-cylinder pressure measurement, the on-board installation of in-cylinder sensors is still uncommon, mainly because they would increase the cost of the whole engine management system. Due to the above considerations, two different closed-loop control strategies have been developed by the authors of this paper to evaluate combustion characteristics using low-cost sensor, that are already present on-board for other management purposes. The current work summarizes these different strategies and demonstrate how a feed-forward estimation of the ignition delay, based on the estimation of the in-cylinder temperature, can improve the transient behavior of the control and how it is possible to replace all the information from in-cylinder pressure signal
Reduced neuropsychiatric events as “beneficial reactions” to drugs: Seek associations with caution
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