1,721,171 research outputs found
Model-Based Estimation of Lithium Concentrations and Temperature in Batteries Using Soft-Constrained Dual Unscented Kalman Filtering
Full text linkThis brief proposes an electrochemical model-based estimator of the Lithium-ion (Li-ion) concentration and temperature of a Li-ion cell. The use of the electrochemical approach allows for the estimation of the spatial distribution of lithium concentration and temperature. The estimation is based on a soft-constrained dual unscented Kalman filter (DUKF) designed on the pseudo-2-D model of a Li-ion cell. The dual structure, along with parallelization, reduces the computational complexity, whereas the soft-constraint improves convergence. A simulation analysis validates the approach showing bulk state of charge (SoC) estimation error lower than 1.5%, solid-phase lithium concentration estimation errors of less than 4%, and temperature estimation errors within 0.2 °C from the true value in any point of the cell
Experimental investigation on surge phenomena in small centrifugal compressors
No full textCentrifugal compressors are key components in propulsion and energy production systems. They are commonly adopted in fuel cells, internal combustion engines, small cogeneration plants and many other systems. The main limitation to obtaining high performance and high boost pressures in centrifugal compressors is due to the instability phenomenon that occurs at low mass flow rates. A better knowledge of this phenomenon can consistently improve the performance of the systems in which centrifugal compressors are installed. The analysis of compressor instabilities, i.e., surge, is an important topic: during surge occurrence the operating flow can assume a highly unsteady behaviour with large fluctuations in pressure and mass flow rate. The compressor can be seriously damaged by phenomena of surge instability due to vibrations and thermal stress. In standard application it is common practice to reduce the operating area of the turbomachinery working away from the surge line to avoid any risk of damage. Usually, to avoid the surge occurrence, the maximum boost pressure is controlled with a by-pass valve commonly called dump valve, it is clear that this solution reduces the mass flow rate provided by the machine and therefore its performance. A better understanding of surge, which can be achieved through dedicated experimental investigations, is essential to develop simulation models capable of accurately predict compressor behaviour and surge occurrence. An in-depth experimental investigation was carried out on a small centrifugal compressor for automotive application at the test rig for components of propulsion system of the University of Genoa. A specific circuit adaptable in length and volume was set up to analyse the effect of different layout configurations on compressor performance with special reference to the low mass flow rate region. The instantaneous value of pressure and mass flow rate are measured in different sections upstream and downstream the compressor and along the circuit. Particular attention was paid in the transition from the steady to the unsteady operation of the compressor, considering different conditions and circuit configurations. Furthermore, the present work describes a methodology to analyse surge cycles, showing their variations with compressor speed and system configuration, applying time synchronous average of a large number of consecutive cycles to evaluate shapes and sizes of surge cycles. Then, this paper highlights the energy content of pressure and mass flow rate fluctuations considering the hysteresis loop during deep surge operations. Finally, a preliminary analysis on the surge precursor is performed by analysing the low and high frequency domain of the pressure fluctuations during the transition from the stable to the unstable zone
Experimental evaluation of the performance of an automotive electric supercharger
No full textNowadays, the electric supercharger for turbocharged downsized automotive engines is mainly used to improve torque at low engine speeds in order to obtain an enhancement of the time to boost. These components are usually designed to fill the gap in terms of torque in transient operation caused by the main turbocharger with reference to the typical turbo lag issues.
An advanced solution of the engine boosting system is taken into account, considering the adoption of an electrically assisted compressor (e-compressor) coupled to a waste-gated turbocharger, typically adopted alone, in order to provide a reduced turbo-lag.
In order to highlight the behavior of the electric supercharger coupled to the turbocharger, the first experimental investigation regarded the steady flow characterization of the compressor. Due to problems related to over temperature, the working time of the e-compressor is limited avoiding an accurate evaluation of compressor efficiency, which is related to the upstream and downstream temperature measurements. A driving system (instead of the electric machine) was designed by the authors to provide a more accurate evaluation of the compressor map. To this aim, a turbocharger turbine has been selected according to the requested power levels.
The experimental investigation was developed at the turbocharger test facility of the University of Genoa using different sensors for the measurements of the average levels of thermodynamic quantities. Besides, accelerometers and microphones were adopted to measure noise and vibrations operative levels in order to check the correct operative functionality of the system. Finally, the transient response of the e-compressor coupled to the main turbocharger is reported to highlight the benefit in terms of the engine time to boost
Experimental evaluation of isentropic efficiency in turbocharger twin-entry turbines
No full textTurbocharging plays a fundamental role not only in improving the performance of automotive engines, but also in reducing the fuel consumption and exhaust emissions of spark-ignited biofuel, diesel, liquid, and gaseous engines. Dedicated experimental investigations on turbochargers are therefore needed to evaluate a better understanding of its performance. The availability of experimental information on the steady flow performance of the turbocharger is an essential requirement to optimize the matching calculation. It is interesting to know the isentropic efficiency of the turbine in order to improve the coupling with the engine, in particular it is difficult to identify the definition of the turbine efficiency through a direct evaluation. In a radial turbine, the isentropic efficiency, evaluated directly starting from the measurement of the thermodynamic quantities at the inlet and outlet sections, can be affected by significant errors. This inaccuracy is mainly related to the incorrect evaluation of the turbine outlet temperature, due to the non-uniform distribution of the flow field in the measurement section. For this purpose, a flow conditioner was installed downstream the turbine. Tests were performed at different values of the rotational speed, and in quasi-adiabatic conditions. The flow field downstream the de-coupler was analysed through a hand-made three-hole probe with an exposed junction thermocouple inserted in the pipe with different protrusions. Thanks to this experimental campaign, it was possible to measure pressure, velocity, mass flow and temperature profiles necessary to examine the homogeneity of the flow field. As the turbocharger is fitted with a twin entry turbine, the thermodynamic quantities have been properly taken into account referring to each sector
Experimental analysis of the dynamic behavior of centrifugal compressors during the transition from stable to surge conditions
No full textDoes the Type of Multisystem Atrophy, Parkinsonism, or Cerebellar Ataxia Impact on the Nature of Sleep Disorders?
No full textMultiple system atrophy (MSA) is a neurodegenerative disease characterized by a combination of autonomic failure, parkinsonism, and/or cerebellar ataxia. The cause of MSA is unknown, but neuropathologically the disease is characterized by widespread α-synuclein-positive glial cytoplasmic inclusions and striatonigral and/or olivopontocerebellar neurodegeneration. Two motor phenotypes have been clinically identified: parkinsonian (MSA-P) and cerebellar (MSA-C). In order to elucidate if in addition to the motor abnormalities there are other significant differences between these two phenotypes, we performed a review of the studies on sleep disorders in the two MSA subtypes. Substantially, any significant difference in the sleep structure, as well as in the frequency and severity of the sleep disorders, has been found between MSA-P and MSA-C patients. Recent studies clearly showed similarities between the two MSA subtypes in terms of demographic distributions, natural history of the disease, and survivals. These findings suggest that although the dominant clinical presentations differ between MSA-C and MSA-P, a common pathophysiology may underlie both subtypes of MSA
Restless legs syndrome and painful legs/moving toes
No full textRestless legs syndrome (RLS), which has been recently renamed Willis-Ekbom disease (WED), is a neurological disorder characterized by unpleasant sensations in the legs, with an urge to move. Symptoms mainly occur at rest in the evening or at night, and they are alleviated by moving the affected extremity. In the general population, a RLS prevalence of 5 % has been reported. Concerning the pathophysiology of RLS, some possible primary factors as brain iron deficiency, central nervous system dopamine regulation, and genetics have been identified. Recent guidelines indicated that pharmacological treatment should be limited to those patients who suffer from clinically relevant RLS, that is, when symptoms significantly impair the patient’s daytime functioning, quality of life, and sleep. In patients affected by chronic RLS, a nonergot dopamine agonist or an a-2-d calcium channel ligand are indicated. In the clinical practice, a dopamine agonist is more appropriate in case of depression and overweight presence. In case of comorbidities, such as chronic pain, anxiety, or insomnia, the a-2-d ligands should be considered. RLS symptoms that are present through large part of the day and night may favor the use of long-acting agents, such as the rotigotine patch or gabapentin enacarbil. In refractory RLS patients, oral prolonged release oxycodone-naloxone should be appropriate. Painful legs and moving toes syndrome (PLMTS) is a rare and underdiagnosed disorder. The pathophysiology of PLMTS is unknown, but most reports suggest an association with a peripheral lesion. Treatment is often unsatisfactory, but botulinum toxin and pramipexole showed long-term beneficial effect
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