scholarly journals Impact of Condensation on the System Performance of a Fuel Cell Turbocharger

Machines ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 59
Author(s):  
Sebastian Lück ◽  
Tim Wittmann ◽  
Jan Göing ◽  
Christoph Bode ◽  
Jens Friedrichs

A mobile fuel cell systems power output can be increased by pressure amplification using an electric turbocharger. These devices are subject to frequent transient manoeuvres due to a multitude of load changes during the mission in automotive applications. In this paper, the authors describe a simulation approach for an electric turbocharger, considering the impact of moist air and condensation within the cathode gas supply system. Therefore, two simulation approaches are used: an iterative simulation method and one based on a set of ordinary differential equations. Additional information is included from turbine performance maps taking into account condensation using Euler–Lagrange CFD simulations, which are presented. The iterative calculation approach is well suited to show the impact of condensation and moist air on the steady state thermodynamic cycle and yields a significant shift of the steady state operating line towards the surge line. It is shown that a substantial risk of surge occurs during transient deceleration manoeuvres triggered by a load step.

2013 ◽  
Vol 385-386 ◽  
pp. 1011-1016
Author(s):  
Ying Yun Sun ◽  
Zhao Yu Jin ◽  
Tian Jiao Pu ◽  
Ting Yu ◽  
Wei Wang ◽  
...  

With the continuous improvement of wind power penetration, the impact of the random fluctuation characteristics of wind power on the frequency control of the power system is growing. Currently, researchers began to study the methods of wind farms participation in frequency control to reduce the frequency adjustment pressure of other power plants and increase the wind power penetration. However, the existing simulation software for the short and long term frequency control of the power system is not so good. So in order to analyze the impact of load fluctuations or wind farm power fluctuations on system frequency control, this paper propose a frequency fluctuation simulation method based on the quasi-steady-state method.


Author(s):  
Wenjuan Zhao ◽  
YiZhao Gao ◽  
Yongli Zhao ◽  
Xiaoya Deng ◽  
Jun Shao ◽  
...  

Generally, high bioelectroactivity of anodophilic biofilm favors high power generation of microbial fuel cell (MFC), however, it is not clear whether it can promote denitrification of MFC synchronously. In this study, the impact of anodophilic biofilms bioelectroactivity on denitrification behavior of single-chamber air-cathode MFC (SAMFC) in steady state was studied for the first time. Anodophilic biofilms of various bioelectroactivity were acclimated at conditions of open circuit (OC), Rext of 1000Ω and 20Ω (denoted as SAMFC-OC, SAMFC-1000Ω and SAMFC-20Ω, respectively) and run for 100 days in the presence of nitrate. Electrochemical tests and microbial analysis results showed that the anode of the SAMFC-20Ω delivered higher oxidation and denitrification current response and had a higher abundance of electroactive bacteria, like Geobacter, Pseudomonas and Comamonas, which possessed bidirectional electron transfer function, demonstrating a higher bioelectroactivity of the anodophilic biofilm. Moreover, these electroactive bacteria favored the accumulation of denitrifers, like Thauera and Alicycliphilus, probably by consuming trace oxygen through catalyzing oxygen reduction. The SAMFC-20Ω not only delivered a 61.7% higher power than the SAMFC-1000Ω, but also achieved a stable and high denitrification rate constant (kDN) of 1.9, which was 50% and 40% higher than that of the SAMFC-OC and SAMFC-1000Ω, respectively. It could be concluded that the high bioelectroactivity of the anodophilic biofilms not only favored high power generation of the SAMFC, but also promote the growth of denitrifers at the anodes and strengthened denitrification. This study provided an effective method and important theoretical basis for enhancing power generation and denitrification performance of the SAMFC synchronously.


2012 ◽  
Vol 43 (1-2) ◽  
pp. 54-63 ◽  
Author(s):  
Baohong Lu ◽  
Huanghe Gu ◽  
Ziyin Xie ◽  
Jiufu Liu ◽  
Lejun Ma ◽  
...  

Stochastic simulation is widely applied for estimating the design flood of various hydrosystems. The design flood at a reservoir site should consider the impact of upstream reservoirs, along with any development of hydropower. This paper investigates and applies a stochastic simulation approach for determining the design flood of a complex cascade of reservoirs in the Longtan watershed, southern China. The magnitude of the design flood when the impact of the upstream reservoirs is considered is less than that without considering them. In particular, the stochastic simulation model takes into account both systematic and historical flood records. As the reliability of the frequency analysis increases with more representative samples, it is desirable to incorporate historical flood records, if available, into the stochastic simulation model. This study shows that the design values from the stochastic simulation method with historical flood records are higher than those without historical flood records. The paper demonstrates the advantages of adopting a stochastic flow simulation approach to address design-flood-related issues for a complex cascade reservoir system.


Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1540
Author(s):  
Qianqian Ji ◽  
Zhe Gao ◽  
Xingyao Li ◽  
Jian’en Gao ◽  
Gen’guang Zhang ◽  
...  

The Loess Hilly–Gully region (LHGR) is the most serious soil erosion area in the world. For the small watershed with high management in this area, the scientific problem that has been paid attention to in recent years is the impact of the land consolidation project on the erosion environment in the gully region. In this study, the 3D simulation method of vegetation, eroded sediment and pollutant transport was innovated based on the principles of erosion sediment dynamics and similarity theory, and the impacts of GLCP were analyzed on the erosion environment at different scales. The verification results show that the design method and the scale conversion relationship (geometric scale: λl = 100) were reasonable and could simulate the transport process on the complex underlying surface of a small watershed. Compared with untreated watersheds, a significant change was the current flood peak lagging behind the sediment peak. There were two important critical values of GLCP impact on the erosion environment. The erosion transport in HMSW had no change when the proportion was less than 0.85%, and increased obviously when it was greater than 3.3%. The above results have important theoretical and practical significance for watershed simulation and land-use management in HMSW.


Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 367
Author(s):  
Konstantinos Giannokostas ◽  
Yannis Dimakopoulos ◽  
Andreas Anayiotos ◽  
John Tsamopoulos

The present work focuses on the in-silico investigation of the steady-state blood flow in straight microtubes, incorporating advanced constitutive modeling for human blood and blood plasma. The blood constitutive model accounts for the interplay between thixotropy and elasto-visco-plasticity via a scalar variable that describes the level of the local blood structure at any instance. The constitutive model is enhanced by the non-Newtonian modeling of the plasma phase, which features bulk viscoelasticity. Incorporating microcirculation phenomena such as the cell-free layer (CFL) formation or the Fåhraeus and the Fåhraeus-Lindqvist effects is an indispensable part of the blood flow investigation. The coupling between them and the momentum balance is achieved through correlations based on experimental observations. Notably, we propose a new simplified form for the dependence of the apparent viscosity on the hematocrit that predicts the CFL thickness correctly. Our investigation focuses on the impact of the microtube diameter and the pressure-gradient on velocity profiles, normal and shear viscoelastic stresses, and thixotropic properties. We demonstrate the microstructural configuration of blood in steady-state conditions, revealing that blood is highly aggregated in narrow tubes, promoting a flat velocity profile. Additionally, the proper accounting of the CFL thickness shows that for narrow microtubes, the reduction of discharged hematocrit is significant, which in some cases is up to 70%. At high pressure-gradients, the plasmatic proteins in both regions are extended in the flow direction, developing large axial normal stresses, which are more significant in the core region. We also provide normal stress predictions at both the blood/plasma interface (INS) and the tube wall (WNS), which are difficult to measure experimentally. Both decrease with the tube radius; however, they exhibit significant differences in magnitude and type of variation. INS varies linearly from 4.5 to 2 Pa, while WNS exhibits an exponential decrease taking values from 50 mPa to zero.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ai-Ling Jiang ◽  
Ming-Chieh Lee ◽  
Guofa Zhou ◽  
Daibin Zhong ◽  
Dawit Hawaria ◽  
...  

AbstractLarval source management has gained renewed interest as a malaria control strategy in Africa but the widespread and transient nature of larval breeding sites poses a challenge to its implementation. To address this problem, we propose combining an integrated high resolution (50 m) distributed hydrological model and remotely sensed data to simulate potential malaria vector aquatic habitats. The novelty of our approach lies in its consideration of irrigation practices and its ability to resolve complex ponding processes that contribute to potential larval habitats. The simulation was performed for the year of 2018 using ParFlow-Common Land Model (CLM) in a sugarcane plantation in the Oromia region, Ethiopia to examine the effects of rainfall and irrigation. The model was calibrated using field observations of larval habitats to successfully predict ponding at all surveyed locations from the validation dataset. Results show that without irrigation, at least half of the area inside the farms had a 40% probability of potential larval habitat occurrence. With irrigation, the probability increased to 56%. Irrigation dampened the seasonality of the potential larval habitats such that the peak larval habitat occurrence window during the rainy season was extended into the dry season. Furthermore, the stability of the habitats was prolonged, with a significant shift from semi-permanent to permanent habitats. Our study provides a hydrological perspective on the impact of environmental modification on malaria vector ecology, which can potentially inform malaria control strategies through better water management.


2021 ◽  
pp. ijgc-2020-002192
Author(s):  
Serena Cappuccio ◽  
Yanli Li ◽  
Chao Song ◽  
Emeline Liu ◽  
Gretchen Glaser ◽  
...  

ObjectiveTo evaluate trends in outpatient versus inpatient hysterectomy for endometrial cancer and assess enabling factors, cost and safety.MethodsIn this retrospective cohort study, patients aged 18 years or older who underwent hysterectomy for endometrial cancer between January 2008 and September 2015 were identified in the Premier Healthcare Database. The surgical approach for hysterectomy was classified as open/abdominal, vaginal, laparoscopic or robotic assisted. We described trends in surgical setting, perioperative costs and safety. The impact of patient, provider and hospital characteristics on outpatient migration was assessed using multivariate logistic regression.ResultsWe identified 41 246 patients who met inclusion criteria. During the time period studied, we observed a 41.3% shift from inpatient to outpatient hysterectomy (p<0.0001), an increase in robotic hysterectomy, and a decrease in abdominal hysterectomy. The robotic hysterectomy approach, more recent procedure (year), and mid-sized hospital were factors that enabled outpatient hysterectomies; while abdominal hysterectomy, older age, Medicare insurance, black ethnicity, higher number of comorbidities, and concomitant procedures were associated with an inpatient setting. The shift towards outpatient hysterectomy led to a $2500 savings per case during the study period, in parallel to the increased robotic hysterectomy rates (p<0.001). The post-discharge 30-day readmission and complications rate after outpatient hysterectomy remained stable at around 2%.ConclusionsA significant shift from inpatient to outpatient setting was observed for hysterectomies performed for endometrial cancer over time. Minimally invasive surgery, particularly the robotic approach, facilitated this migration, preserving clinical outcomes and leading to reduction in costs.


Author(s):  
Robert F Engle ◽  
Martin Klint Hansen ◽  
Ahmet K Karagozoglu ◽  
Asger Lunde

Abstract Motivated by the recent availability of extensive electronic news databases and advent of new empirical methods, there has been renewed interest in investigating the impact of financial news on market outcomes for individual stocks. We develop the information processing hypothesis of return volatility to investigate the relation between firm-specific news and volatility. We propose a novel dynamic econometric specification and test it using time series regressions employing a machine learning model selection procedure. Our empirical results are based on a comprehensive dataset comprised of more than 3 million news items for a sample of 28 large U.S. companies. Our proposed econometric specification for firm-specific return volatility is a simple mixture model with two components: public information and private processing of public information. The public information processing component is defined by the contemporaneous relation with public information and volatility, while the private processing of public information component is specified as a general autoregressive process corresponding to the sequential price discovery mechanism of investors as additional information, previously not publicly available, is generated and incorporated into prices. Our results show that changes in return volatility are related to public information arrival and that including indicators of public information arrival explains on average 26% (9–65%) of changes in firm-specific return volatility.


Mathematics ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 692
Author(s):  
Clara Calvo ◽  
Carlos Ivorra ◽  
Vicente Liern ◽  
Blanca Pérez-Gladish

Modern portfolio theory deals with the problem of selecting a portfolio of financial assets such that the expected return is maximized for a given level of risk. The forecast of the expected individual assets’ returns and risk is usually based on their historical returns. In this work, we consider a situation in which the investor has non-historical additional information that is used for the forecast of the expected returns. This implies that there is no obvious statistical risk measure any more, and it poses the problem of selecting an adequate set of diversification constraints to mitigate the risk of the selected portfolio without losing the value of the non-statistical information owned by the investor. To address this problem, we introduce an indicator, the historical reduction index, measuring the expected reduction of the expected return due to a given set of diversification constraints. We show that it can be used to grade the impact of each possible set of diversification constraints. Hence, the investor can choose from this gradation, the set better fitting his subjective risk-aversion level.


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