CFD Simulation of a Bag Filter for a 200MW Power Plant

The combustion of pulverized coal inevitably produces dust and other harmful substances.For these reasons,the optimization of de-dusting procedure and equipments is an aspect of crucial importance towards the final goal of making this source of energy more sustainable.In the present work,the behaviour of a“bag filter”is simulated using Computational Fluid Dynamics(CFD).More specifically,three possible approaches are used,differing with respect to the level of fidelity and the partial utilization of empirical data.The outcome of these simulations is mutually compared and finally discussed critically in the light of available experimental results.

Numerical Simulation of Retrofit Scheme of a Boiler Tail Flue

Aiming at the problem that the total pressure loss of the flue of the electric precipitator of the 350 MW unit of a power plant to the inlet of the draft fan is too large,the numerical simulation software Fluent and the standard k-εmodel was used to simulate the flue,the results show that the main part of the flue mean total pressure loss is derived from the confluence header and elbow.In order to reduce the loss and consider the cost of transformation,the concept of twodimensional feature surface is established,gradually proposed three sets of flue transformation program and analysis of the flue transformation program drag reduction effect,the results show that the total reduction of the flue can be reduced from 486 Pa to 89 Pa and the reduction rate is 81.7%,which is the best solution;The concept of two-dimensional feature plane is helpful for quick condensing of flue;Double V-type structure of the convergence of the box has a better drag reduction effect.

Comparative study of surface energy and land-surface parameters in different climate zones in Northwest China

Based on observational data of arid,semi-arid and semi-humid areas in Northwest China,the characteristics of surface-wa ter heat transfer and land-surface parameters were compared and analyzed.The results show that the annual mean net radi ation was largest in the semi-humid area,followed by the semi-arid area,and then the arid area:77.72 W/m^2,67.73 W/m^2,and 55.47 W/m^2,respectively.The annual mean sensible heat flux was largest in the arid area,followed by the semi-arid and semi-humid areas,while latent heat flux showed the reverse.The annual mean sensible heat flux in arid,semi-arid,and semi-humid areas was 85.7 W/m^2,37.59 W/m^2,and 27.55 W/m^2,respectively.The annual mean latent heat flux was 0 W/m^2,26.08 W/m^2,and 51.19 W/m2,respectively.The annual mean soil-heat flux at the 5-cm soil layer in arid,semi-arid,and semi-humid areas was 1.00 W/m^2,0.82 W/m^2,and 1.25 W/m^2,respectively.The annual mean surface albedo was larg est in the arid area,followed by the semi-humid area;and the smallest was in the semi-arid area:0.24,0.21,and 0.18,re spectively.The annual mean Bowen ratio in the semi-arid area was about 2.06,and that in semi-humid area was about 0.03.The annual mean soil thermal conductivity in the arid,semi-arid,and semi-humid areas was 0.26 W/(m k),1.15 W/(m k),and 1.20 W/(m k),respectively.

The Elaboration of Flow Resistance Model for a Bag Filter Serving a 200 MW Power Plant

On the basis of a macro flow resistance method and the Darcy Theory,a mathematical model is elaborated to characterize the flow resistance of a bag filter serving a coal-fired power plant.The development of the theoretical model is supported through acquisition of relevant data obtained by scanning the micro structure of the bag filter by means of an electron microscope.The influence of the running time and boiler load on the flow resistance and the impact of the flow resistance on the efficiency of the induced draft fan are analyzed by comparing the results of on-site operation tests.We show that the initial operation time and the table operation time are linearly related to the flow resistance of the bag filter;with the increase of boiler load,the flow resistance of the bag filter rises approximately as a quadratic function;with the rise of resistance,the power consumption of the induced draft fan increases while the efficiency of the induced draft fan decreases.

Simulation of Electric Field Distribution along Insulator Surface in Polluted Environments

In recent years,more than 50%of the cities in the inland area of our country have suffered from moderate pollution.It can affect the distribution of electric field along the surface of insulator and the pollution characteristics of its surface area,even endanger the safe operation of transmission lines.This paper takes the XSP-160 porcelain three umbrella insulator under the action of 0–±30 kV DC voltage as the research object,and establishes the physical model of the insulator;uses COMSOL software to simulate the electric field of the insulator.The comparison with the results of the wind tunnel test of North China Electric Power University verifies the rationality of the simulation method.In view of the medium pollution environment which often occurs in the inland area,the force of the polluted particles deposited on the insulator under 110 kV DC voltage was analyzed.The distribution characteristics of the electric field along the surface in the clean and three kinds of pollution environment(light,medium and heavy)were simulated and compared.The results showed that:1)In the moderate pollution environment,the influence of fluid drag force on the movement of polluted particles is greater at the initial stage(0.28–0.33 s);at the late stage(after 0.33 s),the influence of the electric field force begins to increase,and gradually plays a major role in the process of fouling.2)In the three different polluted environments,the potential along the surface of each umbrella skirt of the insulator increases non-linearly with the increasing of the pollution concentration,and there are apparent potential inflection points near b and l.3)The pollution particle concentration has the most obvious influence on the electric field along the low-voltage umbrella skirt,whose potential distortion rate can be up to 220 times in the heavy polluted environment.

Performance of the CRA-40/Land,CMFD,and ERA-Interim Datasets in Reflecting Changes in Surface Air Temperature over the Tibetan Plateau

We analyzed the spatiotemporal variations in surface air temperature and key climate change indicators over the Tibetan Plateau during a common valid period from 1979 to 2018 to evaluate the performance of different datasets on various timescales.We used observations from 22 in-situ observation sites,the CRA-40/Land(CRA)reanalysis dataset,the China Meteorological Forcing Dataset(CMFD),and the ERA-Interim(ERA)reanalysis dataset.The three datasets are spatially consistent with the in-situ observations,but slightly underestimate the annual mean surface air temperature.The daily mean surface air temperature estimated by the CRA,CMFD,and ERA datasets is closer to the in-situ observations after correction for elevation.The CMFD shows the best performance in simulating the annual mean surface air temperature over the Tibetan Plateau,followed by the CRA and ERA datasets with comparable performances.The CMFD is relatively accurate in simulating the daily mean surface air temperature over the Tibetan Plateau on an annual scale,whereas both the CRA and ERA datasets perform better in summer than in winter.The increasing trends in the annual mean surface air temperature over the Tibetan Plateau from 1979 to 2018 reflected by the CRA dataset and the CMFD are 0.5℃(10 yr)^(-1),similar to the in-situ observations,whereas the warming rate in the ERA dataset is only 0.3℃(10 yr)^(-1).The trends in the length of the growing season derived from the in-situ observations,the CRA,CMFD,and ERA datasets are 5.3,4.8,6.1,and 3.2 day(10 yr)^(-1),respectively.Our analyses suggest that both the CRA dataset and the CMFD perform better than the ERA dataset in modeling the changes in surface air temperature over the Tibetan Plateau.

Auto Insurance Fraud Detection with Multimodal Learning

In recent years,feature engineering-based machine learning models have made significant progress in auto insurance fraud detection.However,most models or systems focused only on structural data and did not utilize multi-modal data to improve fraud detection efficiency.To solve this problem,we adapt both natural language processing and computer vision techniques to our knowledge-based algorithm and construct an Auto Insurance Multi-modal Learning(AIML)framework.We then apply AIML to detect fraud behavior in auto insurance cases with data from real scenarios and conduct experiments to examine the improvement in model performance with multi-modal data compared to baseline model with structural data only.A selfdesigned Semi-Auto Feature Engineer(SAFE)algorithm to process auto insurance data and a visual data processing framework are embedded within AIML.Results show that AIML substantially improves the model performance in detecting fraud behavior compared to models that only use structural data.

Temporal patterns of energy intake and cognitive function and its decline:a community-based cohort study in China

Dear Editor,Worldwide,around 55 million people had prevalent dementia in 2019,which is expected to triple by 2050,especially in low-and middle-income countries[1].Lacking timely diagnosis and limited effective treatment for dementia make identifying risk factors crucial for its early prevention,among which dietary factors have received increasing attention[1].Recently,accumulating evidence from population-based studies has linked the temporal patterns of energy intake(TPEI),usually defined as the temporal distribution of energy intake during a day,to mortality and metabolic diseases[2],such as diabetes and hypertension.In vitro and in vivo studies also revealed that meal timing could drive metabolic alterations and circadian regulation[3],and disrupted meal timing altered the peripheral circadian clocks in the hippocampus and consequently affected cognitive function[4].