scholarly journals Fuel-to-air ratio control under short-circuit conditions through UEGO sensor signal analysis

2019 ◽  
Vol 21 (9) ◽  
pp. 1577-1583
Author(s):  
Carlos Guardiola ◽  
Benjamín Pla ◽  
Marcelo Real ◽  
Cyril Travaillard ◽  
Frederic Dambricourt
Keyword(s):  
Signal Analysis ◽  
Equivalence Ratio ◽  
Short Circuit ◽  
Experimental Tests ◽  
Pollutant Emissions ◽  
Frequency Content ◽  
Novel Approach ◽  
Wide Range ◽  
The Impact ◽  
Three Way Catalyst

The impact of short-circuit pulses on the after-treatment system of a spark-ignited engine must be taken into account to keep the fuel-to-air equivalence ratio within the three-way catalyst window, thereby reducing pollutant emissions. The fuel-to-air equivalence ratio overestimation that suffers the wide-range λ-sensor upstream three-way catalyst in the presence of short circuit is especially relevant. In this study, a novel approach to deal with the fuel-to-air equivalence ratio control under short-circuit conditions is introduced. Under this scope, this work proposes a strategy for the on-board correction of the aforementioned fuel-to-air equivalence ratio overestimation, by means of the information regarding short-circuit level that provides the frequency content of the λ-sensor at the engine frequency. Finally, the potential of this approach to minimize pollutant emissions, in particular the NO x penalty arisen as a consequence of running the engine under leaner conditions than expected, is assessed through experimental tests.

The fate of infiltrated stormwater from infiltration basins to the stream: quantifying the impact of the urban karst

2020 ◽  
Author(s):  
Abolfazl Poozan ◽  
ََAndrew Western ◽  
Meenakshi Arora ◽  
Matthew Burns ◽  
Tim Fletcher
Keyword(s):  
Short Circuit ◽  
Control Measures ◽  
Sewer Pipes ◽  
Groundwater Levels ◽  
Novel Approach ◽  
Wide Range ◽  
Underground Infrastructure ◽  
Receiving Waters ◽  
Stormwater Control Measures ◽  
The Impact

<p>Urbanization leads to severe alterations to the flow regime of receiving waters, including increased frequency and magnitude of storm flows as well as reduced baseflows. Infiltration basins are among the most widely applied stormwater control measures worldwide, in part for their ability to intercept stormwater runoff and allow it to infiltrate into the ground, with the assumption that this will recharge groundwater and thus help in restoring clean, filtered baseflows to receiving waters. Recent research has highlighted that in fact, the fate of infiltrated stormwater is highly uncertain, particularly because of likely interactions with underground infrastructure—e.g. sewer pipes, telecommunication cables, etc. These infrastructures are typically surrounded by highly permeable material which has the potential to substantially alter the way infiltrated stormwater moves through the subsurface (a phenomenon known as the urban karst).</p><p>This study aimed to predict and generalize the impact of the urban karst on infiltrated stormwater as it can provide a preferential flowpath and thus may prevent infiltrated stormwater from reaching receiving waters or may short circuit subsurface storages that can increase routing time delays and thus baseflow. In doing so, a modelling study using HYDRUS-3D was undertaken. In addition, a novel approach to generalize the results was proposed based on groundwater level and the hydraulic conductivities of soil and gravel/sand. We predicted that the impact of the urban karst on infiltrated stormwater increases whit higher groundwater levels, and greater contrasts between the hydraulic conductivity of regional soil and gravel. The HYDRUS results for a wide range of scenarios are compared with the generalization, which captures the impact of Urban Karst well.</p><p>It is important to consider the impact of the urban karst where one of the goals of building infiltration basins is to recharge the baseflow of the stream downslope. This suggests that decision on basin location is important where urban infrastructure is located between potential infiltration basin sites and downslope stream. The impact of the urban karst should be investigated at each specific site before implementing infiltration systems and this study works towards simplified representations of impact for design.</p>

Effects of H2 Addition to CNG Blends on Cycle-to-Cycle and Cylinder-to-Cylinder Combustion Variation in an SI Engine

2012 ◽  
Author(s):  
Mirko Baratta ◽  
Stefano d’Ambrosio ◽  
Daniela Misul ◽  
Ezio Spessa
Keyword(s):  
Diagnostic Tool ◽  
Combustion Process ◽  
Experimental Tests ◽  
Test Point ◽  
Pollutant Emissions ◽  
Engine Operation ◽  
Pressure Transducers ◽  
Rate Analysis ◽  
Spark Plug ◽  
Wide Range

An experimental investigation and a burning-rate analysis have been performed on a production 1.4 liter CNG (compressed natural gas) engine fueled with methane-hydrogen blends. The engine features a pent-roof combustion chamber, four valves per cylinder and a centrally located spark plug. The experimental tests have been carried out in order to quantify the cycle-to-cycle and the cylinder-to-cylinder combustion variation. Therefore, the engine has been equipped with four dedicated piezoelectric pressure transducers placed on each cylinder and located by the spark plug. At each test point, in-cylinder pressure, fuel consumption, induced air mass flow rate, pressure and temperature at different locations on the engine intake and exhaust systems as well as ‘engine-out’ pollutant emissions have been measured. The signals correlated to the engine operation have been acquired by means of a National Instruments PXI-DAQ system and a home developed software. The acquired data have then been processed through a combustion diagnostic tool resulting from the integration of an original multizone thermodynamic model with a CAD procedure for the evaluation of the burned-gas front geometry. The diagnostic tool allows the burning velocities to be computed. The tests have been performed over a wide range of engine speeds, loads and relative air-fuel ratios (up to the lean operation). For stoichiometric operation, the addition of hydrogen to CNG has produced a bsfc reduction ranging between 2 to 7% and a bsTHC decrease up to the 40%. These benefits have appeared to be even higher for lean mixtures. Moreover, hydrogen has shown to significantly enhance the combustion process, thus leading to a sensibly lower cycle-to-cycle variability. As a matter of fact, hydrogen addition has generally resulted into extended operation up to RAFR = 1.8. Still, a discrepancy in the abovementioned conclusions was observed depending on the engine cylinder considered.

Comparative Analysis of EGR and Air Dilution in Spark-Ignited Natural Gas Engines

2017 ◽  
Author(s):  
William Glewen ◽  
Chris Hoops ◽  
Joel Hiltner ◽  
Michael Flory
Keyword(s):  
Natural Gas ◽  
Power Density ◽  
Thermal Efficiency ◽  
Gas Temperature ◽  
Natural Gas Engines ◽  
Cycle Simulation ◽  
Wide Range ◽  
Charge Mixture ◽  
The Impact ◽  
Three Way Catalyst

Industrial natural gas engines are used in a wide range of applications, each with unique requirements in terms of power density, initial cost, thermal efficiency, and other factors. As a result of these requirements, distinct engine designs have evolved to serve various applications. Heavy-duty spark-ignited engines can generally be divided into two broad categories based on their charge characteristics and method of emissions control. Stoichiometric engines are widely used in applications where first cost, absolute emissions and relative engine simplicity are more important than fuel consumption. In most of the developed world, stoichiometric engines are equipped with a three-way catalyst to control emissions of nitrogen oxides (NOx) as well as products of incomplete combustion and raw unburned fuel. Dilution of the charge mixture with excess air reduces the peak combustion gas temperature and associated heat rejection. As a result, lean burn engines are generally able to achieve higher efficiency and power density without inducing excessive component temperatures or end gas knock. NOx formation is mitigated by the reduced gas temperatures, such that most regulatory standards can currently be met in-cylinder. Significant obstacles exist to meeting more stringent future emissions regulations in this manner, however. Another possible strategy is to dilute the charge mixture with recirculated exhaust gas. This offers similar benefits as air dilution while maintaining the ability to use a three-way catalyst for emissions after-treatment. While similar principles apply in either case, the choice of diluent can have a significant impact on knock resistance, emissions formation, thermal efficiency, and other parameters of importance to engine developers and operators. This work aimed to examine the unique characteristics of EGR and air dilution from a thermodynamic and combustion perspective. A combination of cycle simulation tools and experimental data from a single-cylinder test engine was applied to demonstrate the impact of diluent properties on a fundamental level, and to illustrate departures from idealized behavior and practical considerations specific to the development of combustion systems for spark-ignited natural gas engines.

scholarly journals Short-circuit effects on spark ignition engine after-treatment and fuel-to-air ratio control

2018 ◽  
Vol 21 (5) ◽  
pp. 885-894
Author(s):  
Carlos Guardiola ◽  
Benjamín Pla ◽  
Marcelo Real ◽  
Cyril Travaillard ◽  
Frederic Dambricourt
Keyword(s):  
Control Strategy ◽  
Short Circuit ◽  
Point Of View ◽  
Spark Ignition Engine ◽  
Exhaust Gas ◽  
Gas Composition ◽  
Engine Emissions ◽  
The Impact ◽  
Three Way Catalyst ◽  
Catalyst Efficiency

The short circuit of fresh air is a more and more extended strategy to deal with low-end torque issues, very common in small turbocharged and spark-ignited four-stroke engines. Therefore, from the author’s point of view, it is interesting to check whether the after-treatment system can work properly under these conditions. In the present study, the effect of the fresh air short-circuit on engine emissions has been assessed through its impact on the wideband [Formula: see text] sensor and the three-way catalyst behaviour, which are the key elements of the fuel-to-air ratio control strategy. In particular, the analysis of the sensor dynamic response shows that the [Formula: see text] sensor overestimates the fuel-to-air ratio under short-circuit conditions. The sensor overestimation leads the actual fuel-to-air ratio out of the proper three-way catalyst window; in this sense, results show a non-negligible emissions increase, especially in terms of NOx. Regarding the impact on the three-way catalyst behaviour, the study shows how short-circuit pulses change the exhaust gas composition for a given fuel-to-air ratio at catalyst inlet, which also contributes to a penalty in the three-way catalyst efficiency.

Approach to Validate Simulation-Based Distribution Predictions Combining the Gamma-Method and Uncertainty Assessment: Application to Focused Ultrasound

2016 ◽  
Vol 1 (3) ◽  
Author(s):  
Esra Neufeld ◽  
Adamos Kyriacou ◽  
Wolfgang Kainz ◽  
Niels Kuster
Keyword(s):  
Computational Models ◽  
Focused Ultrasound ◽  
Uncertainty Assessment ◽  
Comparison Method ◽  
Verification And Validation ◽  
Pressure Distributions ◽  
Novel Approach ◽  
Wide Range ◽  
The Impact ◽  
Gamma Method

This paper presents a novel approach for simulation validation by combining systematic, National Institute of Standards and Technology-guideline-based uncertainty assessment with the gamma dose distribution comparison method, and applies the approach to simulated and measured complicated pressure distributions in the field of focused ultrasound. Simulations require verification and validation to demonstrate that they correctly implement the underlying model and sufficiently capture the real-world behavior of the system of interest within the context-of-use. Uncertainty assessment is necessary to determine the quality (strength, success, and range) of the validation. The combined approach of systematic uncertainty evaluation and the gamma-method presented herein permits thorough validation with meaningful and reasonable tolerances (expanded uncertainty: 1.04 dB = 12.7%, 1.88 wavelengths), whereas point-wise comparison would have resulted in an unacceptably large uncertainty (>10 dB) due to the impact of distortion. The approach presented also provides a scalar agreement metric and a natural means of visualizing areas of disagreement. Verification is achieved by identifying the critical physical and numerical phenomena and ascertaining correct handling by means of analytical and numerical benchmarks. The generality of the verification and validation approach presented makes it applicable to a wide range of computational models, beyond the highlighted acoustic simulations.

Simulations of High Velocity Impacts of Ice on Carbon/Epoxy Composite Laminates

2014 ◽  
Vol 566 ◽  
pp. 505-510 ◽  
Author(s):  
Jesús Pernas-Sánchez ◽  
José Alfonso Artero-Guerrero ◽  
David Varas ◽  
Jorge López-Puente
Keyword(s):  
Mechanical Behavior ◽  
High Velocity ◽  
Composite Laminates ◽  
Epoxy Composite ◽  
Experimental Tests ◽  
High Velocity Impact ◽  
Velocity Impact ◽  
Wide Range ◽  
High Velocity Impacts ◽  
The Impact

In this work simulations of high velocity impacts of ice spheres on carbon/epoxy laminates are accomplished. The Drucker-Prager model has been chosen to describe the mechanical behavior of the ice under high velocity impact conditions. Results have been validated by means of experimental tests performed in a wide range of impact velocities. The delaminated area was chosen as comparison variable, and reflects that the model predicts adequately the impact process.

scholarly journals Modified Distance Transformation for Image Enhancement in NIR Imaging of Finger Vein System

Sensors ◽  
2020 ◽  
Vol 20 (6) ◽  
pp. 1644 ◽  
Author(s):  
Krzysztof Bernacki ◽  
Tomasz Moroń ◽  
Adam Popowicz
Keyword(s):  
Near Infrared ◽  
Infrared Imaging ◽  
Vascular System ◽  
Selective Extraction ◽  
Identification Accuracy ◽  
Dark Line ◽  
Distance Transformation ◽  
Novel Approach ◽  
Wide Range ◽  
The Impact

Most of the current image processing methods used in the near-infrared imaging of finger vascular system concentrate on the extraction of internal structures (veins). In this paper, we propose a novel approach which allows to enhance both internal and external features of a finger. The method is based on the Distance Transformation and allows for selective extraction of physiological structures from an observed finger. We evaluate the impact of its parameters on the effectiveness of the already established processing pipeline used for biometric identification. The new method was compared with five state-of-the-art approaches to features extraction (position-gray-profile-curve—PGPGC, maximum curvature points in image profiles—MC, Niblack image adaptive thresholding—NAT, repeated dark line tracking—RDLT, and wide line detector—WD) on the GustoDB database of images obtained in a wide range of NIR wavelengths (730–950 nm). The results indicate a clear superiority of the proposed approach over the remaining alternatives. The method managed to reach over 90 % identification accuracy for all analyzed datasets.

scholarly journals Performance Evaluation of Java Programming Strategies

2021 ◽  
Vol 10 (4) ◽  
pp. 146-159
Author(s):  
Qusay Idrees Sarhan
Keyword(s):  
Programming Languages ◽  
Web Applications ◽  
Experimental Studies ◽  
Experimental Tests ◽  
Performance Improvements ◽  
Java Programming ◽  
Software Applications ◽  
Wide Range ◽  
Significant Performance ◽  
The Impact

Java is one of the most demanding programming languages nowadays and it is used for developing a wide range of software applications including desktop, mobile, embedded, and web applications. Writing efficient Java codes for those various types of applications (which some are critical and time-sensitive) is crucial and recommended best practices that every Java developer should consider. To date, there is a lack of in-depth experimental studies in the literature that evaluate the impact of writing efficient Java programming strategies on the performance of desktop applications in terms of runtime. Thus, this paper aims to perform a variety of experimental tests that have been carefully chosen and implemented to evaluate the most important aspects of desktop efficient Java programming in terms of runtime. The results of this study show that significant performance improvements can be achieved by applying different programming strategies.

THE IMPACT OF LEADERSHIP PRACTICES TO TEAM MEMBERS’ SATISFACTION

2009 ◽  
Vol 8 (1) ◽  
Author(s):  
Chalimah .
Keyword(s):  
Conflict Resolution ◽  
Leadership Practices ◽  
Hotel Industry ◽  
Leader Behavior ◽  
Team Leader ◽  
Shop Floor ◽  
Team Members ◽  
Top Executives ◽  
Wide Range ◽  
The Impact

eamwork is becoming increasingly important to wide range of operations. It applies to all levels of the company. It is just as important for top executives as it is to middle management, supervisors and shop floor workers. Poor teamwork at any level or between levels can seriously damage organizational effectiveness. The focus of this paper was therefore to examine whether leadership practices consist of team leader behavior, conflict resolution style and openness in communication significantly influenced the team member’s satisfaction in hotel industry. Result indicates that team leader behavior and the conflict resolution style significantly influenced team member satisfaction. It was surprising that openness in communication did not affect significantly to the team members’ satisfaction.

Stress, anxiety, depression and burnout in frontline health care workers during COVID-19 pandemic: a brief systematic review and new data from Russia

2021 ◽  
Author(s):  
Ekaterina Mosolova ◽  
Dmitry Sosin ◽  
Sergey Mosolov
Keyword(s):  
Risk Factors ◽  
Systematic Review ◽  
Female Gender ◽  
Assessment Tools ◽  
Care Workers ◽  
Younger Age ◽  
Wide Range ◽  
Associated Risk Factors ◽  
Anxiety Depression ◽  
The Impact

During the COVID-19 pandemic, healthcare workers (HCWs) have been subject to increased workload while also exposed to many psychosocial stressors. In a systematic review we analyze the impact that the pandemic has had on HCWs mental state and associated risk factors. Most studies reported high levels of depression and anxiety among HCWs worldwide, however, due to a wide range of assessment tools, cut-off scores, and number of frontline participants in the studies, results were difficult to compare. Our study is based on two online surveys of 2195 HCWs from different regions of Russia during spring and autumn epidemic outbreaks revealed the rates of anxiety, stress, depression, emotional exhaustion and depersonalization and perceived stress as 32.3%, 31.1%, 45.5%, 74.2%, 37.7% ,67.8%, respectively. Moreover, 2.4% of HCWs reported suicidal thoughts. The most common risk factors include: female gender, nurse as an occupation, younger age, working for over 6 months, chronic diseases, smoking, high working demands, lack of personal protective equipment, low salary, lack of social support, isolation from families, the fear of relatives getting infected. These results demonstrate the need for urgent supportive programs for HCWs fighting COVID-19 that fall into higher risk factors groups.

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