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A novel hybrid forecasting approach for NOx emission of coal-fired boiler combined with CEEMDAN and self-attention improved by LSTM

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ASIA-PACIFIC JOURNAL OF CHEMICAL engineering 2024年第4期19卷 e3057-e3057页

作者： Yan, Hua Chen, Yunchi Yang, Bin Yang, Yang Ni, Hu Wang, Ying Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Peoples R China Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai Peoples R China China Resources Power Wenzhou Co Ltd Wenzhou Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China

The precise prediction of NOx generation concentration in coal-fired boilers serves as the foundational cornerstone for the judicious optimization and control of selective catalytic reduction denitrification (SCR) systems. Owing to the intricate nature of the denitrification process within SCR, there exists a temporal delay in regulating the ammonia injection rate based on the monitored data of NOx concentration at the SCR inlet. Such delays can give rise to ammonia leakage and subsequent obstruction of the air preheater. In light of this, a predictive model, CEEMDAN-LSTM-SA, is proposed as an amalgamation of data decomposition and the LSTM (long short-term memory) fusion self-attention mechanism within a deep learning network, which is introduced to forecast the NOx emission concentration at the SCR inlet of coal-fired units. To mitigate the impact of data outliers on the training effectiveness of the model, a clustering method coupled with a statistical testing strategy is initially applied to refine the dataset first. CEEMDAN data decomposition technology is leveraged to facilitate the breakdown of data, alleviating its non-stationary and intricate characteristics. Subsequently, through spectral analysis, the decomposed components are grouped and aggregated to form novel data elements, which are then subjected to prediction by the constructed LSTM-SA deep learning network. The ultimate NOx emission concentration prediction value is derived through a process of fusion. Upon scrutinizing and comparing the predictions derived from various models using coal-fired power plant data, it is evident that the performance metrics of CEEMDAN-LSTM-SA predictions exhibit a mean absolute error of 7.425, mean absolute percentage error of 2.415%, root mean square error of 9.715, R-squared (R2) value of .789, mean absolute relative error of 2.109%, and a Theil's information criterion of .016. In contrast to other models, including traditional self-attention networks, LSTM, and LST

关键词： CEEMDAN data cleaning LSTM NOx emission self-attention mechanism

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Numerical study of heat transfer characteristics of phase change materials reinforced with porous media based on hybrid mesh

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SUSTAINABLE ENERGY TECHNOLOGIES AND ASSESSMENTS 2024年 65卷

作者： Wang, Zilong Zhu, Liucan Zhang, Hua Yu, Guoxin Li, Jing Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Qingdao Haier Smart Technol R&D Co Ltd 1 Haier Rd Qingdao Shandong Peoples R China

To address the drawbacks of inadequate energy density as well as utilization effectiveness in solar energy utilization, phase change energy storage offers a possible option. However, the low thermal conductivity of traditional phase change materials (PCMs) restricts the extent to which solar energy utilization can be enhanced. In this paper, the impact of the metal foam (MF) on the solid-liquid interface, the flow field, the enhancement heat transfer mechanism during the paraffin wax (PX) melting process and thermal storage characteristics was analyzed. Besides, a three-dimensional mathematical model of MF-PX using the hybrid mesh technique was established and software ANSYS-FLUENT was used for simulation. The results indicated that, the hybrid mesh exhibited a reduction of 52.75 % in mesh count compared to the unstructured mesh, resulting in 45 % reduction in computational time. Moreover, the hybrid mesh also showcased improved mesh quality that the unstructured mesh was mainly distributed in the range of 0.48-0.6, while within the range of 0.84-1.0 for the hybrid mesh. More important, the maximum relative error between experimental and simulation was 8.67 %, indicating that the model can make a reasonable prediction. With the proportions of MF increased from 0.11 % to 0.43 %, both the Rayleigh number (Ra) and its amplification decreased. At 800 s, the Ra decreased from 1.76E+07 to 1.20E+07, while the amplification of the Ra was reduced from 1.88E+07 to 1.30E+07. In addition, the natural convection proportions of CMF decreased from 96.31 % to 80.65 %. These observations indicated that natural convection was the primary heat transfer mechanism, and the conduction was enhanced by the increasing proportion of MF. Finally, in terms of heat storage characteristics, the heat storage capacity and heat storage rate of the composite PCM slightly decreased. The heat storage values decreased from 19.30 kJ to 18.66 kJ. Similarly, the heat storage rates decreased from 19.86 J/s

关键词： Phase change materials Numerical simulation Copper metal foam Hybrid mesh heat transfer enhancement

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Numerical Simulation Study on Two-Phase flow of Thermal Runaway Evolution and Jet Fire of 18650 Lithium-Ion Battery Under Thermal Abuse

SSRN

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SSRN 2023年

作者： Wang, Jia-Hao Mei, Mei Jiang, Ziqi Qiu, Huihe Wang, Ying Shanghai Key Laboratory of Multiphase Flow and Heat Transfer in Power Engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai200093 China Department of Mechanical and Aerospace Engineering The Hong Kong University of Science and Technology Clear Water Bay Hong Kong

This study investigates the impact of particles on the external jet flame of 18650 lithium-ion batteries using a two-dimensional transient numerical simulation. The mixing characteristics of jet flames and particles generated by battery combustion are analyzed using a multi-component Navier-Stokes equation and Lagrangian method. The model is validated by comparing it with experimental measurements of flame height. The results show that particles have a significant impact on the jet flame's characteristics and dynamic behavior during the battery's thermal runaway process. The study includes an analysis of the velocity field, temperature field, flow field, component concentration distribution, and lift-off height. Two stages of the jet flame are identified: unstable and stable. The presence of particles causes the unstable flame height to be 1-2 times higher than the stable flame height. This research provides reference for the safety assessment of actual batteries. © 2023, The Authors. All rights reserved.

关键词： Lithium-ion batteries

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heat transfer ENHANCEMENT OF A PARTIALLY SERRATED TWISTED FINNED TUBE WITH NON-GROOVING ON THE LEEWARD SIDE

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JOURNAL OF ENHANCED heat transfer 2022年第4期29卷 41-61页

作者： Wei, Hongyu Cong, Tao Jiang, Chen Zhou, Wenxue Bai, Bofeng Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Qingdao Haier Washing Machine Co Ltd Qingdao 266103 Peoples R China Shanghai Lanbin Petrochem Equipment Co Ltd Shanghai 201518 Peoples R China Lanzhou Heat Transfer & Energy Saving Engn & Tech Lanzhou 730070 Peoples R China

Fin-and-tube heat exchanger is a basic component widely used in many industrial processes such as air cooling and waste heat recovery. To obtain greater comprehensive heat transfer performance, a partially serrated twisted finned tube is proposed. Considering the uneven heat transfer between the windward side and the leeward side, the partially serrated twisted finned tube is serrated on the windward side to enhance the heat transfer and has a non-grooving area on the leeward side. Compared to the fully serrated finned tube, the non-grooving area on the leeward side can increase the heat transfer area and reduce flow resistance. The heat transfer and flow performance experiments on the partially serrated twisted finned tube are carried out to verify the simulation results. The correlations of Nu and f are proposed in the end. Nu of the partially serrated twisted finned tube increase by an average of 14.9% and j/ f(1/3) increases by an average of 9.2% comparing with the annular finned tube with Reynolds number from 5000 to 17,000.

关键词： partially serrated finned tube heat transfer friction factor non-grooving angle

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Experimental study on effect of structural parameters on pressure drop characteristics of multi-orifice plates

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flow MEASUREMENT AND INSTRUMENTATION 2023年第1期91卷

作者： Wu, Yuxin Ma, Youfu Lyu, Junfu Niu, Fangfang Jiao, Qianfeng Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Tsinghua Univ Dept Energy & Power Engn Key Lab Thermal Sci & Power Engn Minist Educ Beijing 100084 Peoples R China

Owing to the advantages of rectification, low noise, low pressure loss, and more stable pressure drop signal compared with the characteristics of the conventional single-orifice plate, multi-orifice plates (MOPs) offer a wide range of application prospects in various industrial pipelines. However, owing to its various orifice shapes and orifice layouts, the pressure drop characteristics of MOPs are not fully understood. In this study, the pressure drop characteristics of single-phase flow across a multi-orifice plate, which implies a stable zone (turbulent flow) pressure loss coefficient and the minimum critical Reynolds number of the stable zone, are experimentally investigated in the Reynolds number range of 29,000-146,000 using water as the fluid. Nine MOPs with circular holes evenly arranged in an equilateral triangle are tested. Their structures differ in terms of the equivalent diameter ratio (0.30-0.60), orifice number (64-400), and relative orifice thickness (0.40-1.60). The results show that the minimum critical Reynolds number deceases as the equivalent diameter ratio decreases, the relative orifice thickness increases, and the orifice number increases, which allows an enlarged Reynolds number range for the stable zone. As the equivalent diameter ratio, orifice number, and relative orifice thickness increase, the stable zone pressure loss coefficient of MOPs initially decreases rapidly and gradually approaches a constant. Finally, based on the experimental results of this study, a correlation of the stable zone pressure loss coefficient of MOPs is proposed, which provides a reference for using MOPs in various industrial applications.

关键词： Orifice plate Pressure drop Structural effect Throttling

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Syngas production from CO2 reforming of glycerol by mesoporous Ni/CeO2 catalysts

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FUEL 2023年第1期341卷

作者： Ren, Ruijia Dou, Binlin Zhang, Hua Wu, Kai Wang, Yadong Chen, Haisheng Xu, Yujie Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Chinese Acad Sci Inst Engn Thermophys Beijing 100190 Peoples R China

In this paper, the mesoporous Ni/CeO2 catalyst with high specific surface area was prepared by the colloidal solution combustion method and used for the production of syngas by glycerol dry reforming (GDR). The thermodynamic analysis was conducted by using a non-stoichiometric methodology based on the minimization of Gibbs's free energy. The characterization results show that the higher the Ni content, the weaker the interaction between Ni and the CeO2 support. 5Ni/CeO2 shows the most consistent Ni dispersion and uniform particle size, and it has the best catalytic activity in the GDR and the conversion of glycerol can reach 84.1 % at 750 degrees C. Besides, all catalysts exhibited excellent stability during the 10 h catalytic process. The temperature-programmed oxidation (TPO) results show that Ni loading ratio of 5 can reduce the production of filamentous carbon. Based on a kinetic model assuming a power law as a first-order reaction, the activation energy of the Ni-based catalyst for glycerol dry reforming was calculated.

关键词： Glycerol dry reforming Mesoporous Ni-based catalyst CO2 utilization

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A feature importance ranking based fault diagnosis method for variable-speed screw chiller

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SCIENCE AND TECHNOLOGY FOR THE BUILT ENVIRONMENT 2022年第2期28卷 137-151页

作者： Lu, Hailong Cui, Xiaoyu Han, Hua Fan, Yuqiang Zhang, Yunqian Univ Shanghai Sci & Technol Sch Energy & Power Engn 516 Jungong Rd Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China CQ Midea Gen Refrigerat Equipment CO LTD 15 Qiangwei Rd Chongqing 401336 Peoples R China Midea Grp Cent Air Conditioner BU Breakthrough Technol Ctr Foshan 528311 Guangdong Peoples R China

Fault detection and diagnosis (FDD) technology plays an important role in maintaining the stable and efficient operation of the chiller system, and screening the most important parameters for FDD is the key step that is far more critical than the selection of diagnosis methods. This study proposes a feature importance ranking method based on random forest (RF) to improve the FDD performance of a chiller while using fewer sensors, which is proved to be effective and efficient. When the product type or sensor configuration changes, the proposed method can be used to rank the feature importance efficiently based on the new fault simulation data, the FDD model using the features that are highly significant to fault indication and diagnosis can be established and the diagnosis performance can be promoted, accordingly. For verification and validation, fault simulation experiments of normal operation, refrigerant leakage and refrigerant overcharge have been carried out on a 200-ton variable-speed screw chiller. The importance of 15 parameters obtained from the experiments is ranked according to their contributions to the diagnosis of the corresponding faults using the proposed RF importance ranking method. Different critical features have also been discussed in terms of FDD performance and expertise knowledge for screw chiller. The optimal feature set for the investigated faults of the chiller is found to have just four parameters: Refrigerant Discharge Temperature (TR_dis), Condenser Water Temperature Difference (TWCD), Evaporator Water Temperature Difference (TWED) and Compressor power (kW). The overall diagnostic accuracy reaches 99.90%, higher than using all the parameters. Fewer sensors achieve better performance.

关键词： Screws

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Sorption-enhanced chemical looping steam reforming of glycerol with CO2 in-situ capture and utilization

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CHEMICAL engineering JOURNAL 2023年第Part4期452卷

作者： Dou, Binlin Wu, Kai Zhang, Hua Chen, Bingbing Chen, Haisheng Xu, Yujie Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Chinese Acad Sci Inst Engn Thermophys Beijing 100190 Peoples R China

Hydrogen production from chemical looping steam reforming using an oxygen transport catalyst is definitely enhanced by CO2 in-situ capture, which shifts the chemical equilibrium and reduces the energy demands. The utilization of CO2 from this process as a reactant for chemicals and fuels could help to improve economic reasons and mitigate its impact on climate. In this study, we proposed a sorption-enhanced chemical looping steam reforming of glycerol to realize the synergetic capture and conversion of CO2 in one integrated chemical looping hydrogen production process. The process is characterized to use the oxidized NiO/NiAl2O4 as a steam reforming catalyst, the reduced NiO/NiAl2O4 as a CO2-CH4 dry reforming catalyst, and the inexpensive dolomite as a CO2 sorbent. The surface carbon that would deactivate the catalyst is combusted by air after CO2-CH4 dry reforming and the Ni on the catalyst is re-oxidized. The coupling of these different processes of chemical looping steam reforming, CO2 in-situ capture, dolomite decomposition and CO2 in-situ utilization, results in simultaneous generation of high purity hydrogen and syngas. The results demonstrated that hydrogen of above 92.5% was one-step generated and CO2 was decreased to zero in the pre-CO2 breakthrough periods. The reduced NiO/NiAl2O4 catalysts favored the CO2-CH4 dry reforming at 850 degrees C. The syngas of H2-to-CO molar ratios of 0.8-1.1 through the conversion of CO2 from in-situ extraction of the absorbed CO2 dolomite, was produced. The NiO/Al2O4 with 15 wt% NiO gave the highest hydrogen and syngas yields, and maintained high performance for the proposed system. The catalysts and dolomite exhibited good stability with no obvious loss of activity in 10 cycles.

关键词： High-purity hydrogen production from sorption-enhanced chemical looping steam reforming (SE-CLSR) CO2 in-situ capture and utilization NiO Dolomite sorbent Syngas production from CO2-CH4 dry reforming (MDR)

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Sorption enhanced aqueous phase reforming of biodiesel byproduct glycerol for hydrogen production over Cu-Ni bimetallic catalysts supported on gelatinous MgO

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JOURNAL OF CLEANER PRODUCTION 2023年第1期383卷

作者： Liu, Dashuai Dou, Binlin Zhang, Hua Wu, Kai Luo, Chuanqi Du, Jinbo Gao, Dao Xing Chen, Haisheng Xu, Yujie Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Chinese Acad Sci Inst Engn Thermophys Beijing 100190 Peoples R China

Hydrogen production from sorption enhanced aqueous phase reforming (APR) of biodiesel byproduct glycerol was studied by Ni-based monometallic and bimetallic catalysts supported on gelatinous MgO supports. Compared with Ni-based monometallic catalyst, the H2 selectivity and glycerol conversion of the Cu-Ni bimetallic catalyst were found to be increased more than 3% and 30%, respectively. Meanwhile, higher reaction temperature was found to have higher H2 yield with lower H2 selectivity. The H2 yield using the catalyst with gelatinous MgO support was 1.25 times higher than that of calcined support. Through in-situ CO2 capture, the addition of CaO to the Cu-Ni bimetallic catalyst increased more than 58.3% and 14.4% of the H2 yield and selectivity, respectively. An analysis about liquid product component indicate that the presence of CaO promote the further cleavage of the C-C bond, which further increased the conversion of glycerol. Furthermore, it was found that the presence of CaO could also improve the stability of the catalyst through the control experiments.

关键词： Hydrogen production Gelatinous MgO Cu-Ni MgO catalyst Aqueous phase reforming of biodiesel byproduct glycerol In -situ CO 2 removal

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Modeling and experimental assessment of the novel HI-I2-H2O electrolysis for hydrogen generation in the sulfur-iodine cycle

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INTERNATIONAL JOURNAL OF ENERGY RESEARCH 2020年第8期44卷 6285-6296页

作者： Ying, Zhi Wang, Yabin Zheng, Xiaoyuan Geng, Zhen Dou, Binlin Cui, Guomin Univ Shanghai Sci & Technol Shanghai Key Lab Multiphase Flow & Heat Transfer Sch Energy & Power Engn Shanghai 200093 Peoples R China

To improve the sulfur-iodine (SI or IS) cycle for renewable hydrogen production, direct electrolysis of HIx solution (HI-I-2-H2O) from Bunsen reaction has been recently proposed. This work concerns the detailed microscopic physical performance and electrolytic processes of HIx electrolysis through theoretical simulation and experimental exploration. A two-dimensional mathematical model of the electrolytic cell for HIx electrolysis was developed, and was verified by the relevance between the simulated and experimental hydrogen production. The concentration, electric and flow field distributions were characterized. The decrease of anodic HI and increase of cathodic H-2 were found along the flow direction. The local potential distribution declined from anode to cathode region. Higher pressure drop from the inlet to outlet of channel as well as the pumping power were required for anolyte than catholyte. More detailed electrolytic processes along the flow channel at different operating conditions were analyzed. Increasing temperature from 303 K to 343 K improved the H-2 production rate. A low anode flow rate of 0.2 m/s was favorable for achieving high conversion rate of reactants and low consumed pumping power. The developed models and the clarified characteristics of HIx electrolysis will be further applied to the improved SI cycle.

关键词： HIx electrolysis hydrogen production model physical field sulfur-iodine cycle

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