Editorial

3 pages, 190 KiB

Open AccessEditorial

Shipping Emissions and Air Pollution: Latest Methodological Developments and Applications

by Yuanqing Zhu and Long Liu

Atmosphere 2023, 14(8), 1312; https://doi.org/10.3390/atmos14081312 - 20 Aug 2023

Viewed by 986

Shipping, which accounts for over 80% of international trade transportation, is the most cost-effective and efficient mode of transportation [...] Full article

(This article belongs to the Special Issue Shipping Emissions and Air Pollution)

Research

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13 pages, 7120 KiB

Open AccessArticle

Establishing Correlation between Cruise Ship Activities and Ambient PM Concentrations in the Kotor Bay Area Using a Low-Cost Sensor Network

by Radmila Gagic, Maja Skuric, Gordana Djukanovic and Danilo Nikolic

Atmosphere 2022, 13(11), 1819; https://doi.org/10.3390/atmos13111819 - 01 Nov 2022

Cited by 4 | Viewed by 1794

Abstract

The analysis of cruise ships is focusing on port areas where they may represent a significant source of anthropogenic emissions. In order to determine the correlation between cruise ship activities (hoteling and maneuvering) in ports with the ambient concentration of pollutants associated with [...] Read more.

The analysis of cruise ships is focusing on port areas where they may represent a significant source of anthropogenic emissions. In order to determine the correlation between cruise ship activities (hoteling and maneuvering) in ports with the ambient concentration of pollutants associated with marine diesel fuel combustion, the low-cost sensors are finding their market share due to lower prices compared to the referent ones. In this study, a network of four low-cost PM sensors was used to determine the correlation between ambient PM_2.5 and PM₁₀ mass concentrations with cruise ship activities in the Kotor Bay area during 27 days in the peak summer season, with a 10-min resolution. Recorded data and the Openair model were used to investigate the potential relationship between cruise ship operations and temporal fluctuations in PM concentrations in the ambient air. Additionally, an Tier 3 methodology developed through the European Monitoring and Evaluation Programme of the European Environmental Agency (EMEP/EEA) was applied in order to estimate the total cruise ship PM emissions. The study has shown that weather conditions play a significant role in local PM concentrations, so that, with predominant ENE wind directions, the west side of the Bay experienced on average higher concentrations of both PM_2.5 and PM₁₀. Rain precipitation and higher winds tend to decrease rapidly ambient PM concentrations. Higher PM levels are associated mainly with lower wind speeds and the inflows from neighboring berths/anchorages. During the maneuvering (arrival and departure) of cruise ships, higher spikes in PM values were detected, being more visible for PM₁₀ than PM_2.5. A significant correlation between daily average PM concentrations and cruise ships’ daily estimated PM emission was not found. As a result, higher temporal resolution demonstrated a stronger correlation. Full article

(This article belongs to the Special Issue Shipping Emissions and Air Pollution)

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22 pages, 6646 KiB

Open AccessArticle

Regional Predictions of Air Pollution in Guangzhou: Preliminary Results and Multi-Model Cross-Validations

by Zhi Qiao, Shengcheng Cui, Chenglei Pei, Zhou Ye, Xiaoqing Wu, Lei Lei, Tao Luo, Zihan Zhang, Xuebin Li and Wenyue Zhu

Atmosphere 2022, 13(10), 1527; https://doi.org/10.3390/atmos13101527 - 20 Sep 2022

Cited by 4 | Viewed by 1526

Abstract

A precise air pollution forecast is the basis for targeted pollution control and sustained improvements in air quality. It is desirable and crucial to select the most suitable model for air pollution forecasting (APF). To achieve this goal, this paper provides a comprehensive [...] Read more.

A precise air pollution forecast is the basis for targeted pollution control and sustained improvements in air quality. It is desirable and crucial to select the most suitable model for air pollution forecasting (APF). To achieve this goal, this paper provides a comprehensive evaluation of performances of different models in simulating the most common air pollutants (e.g., PM_2.5, NO₂, SO₂, and CO) in Guangzhou (23.13° N, 113.26° E), China. To simulate temporal variations of the above-mentioned air pollutant concentrations in Guangzhou in September and October 2020, we use a numerical forecasting model (i.e., the Weather Research and Forecasting model with Chemistry (WRF-Chem)) and two artificial intelligence models (i.e., the back propagation neural network (BPNN) model and the long short-term memory (LSTM) model). WRF-Chem is also used to simulate the meteorological elements (e.g., the 2 m temperature (T2), 2 m relative humidity (RH), and 10 m wind speed and direction (WS, WD)). In order to investigate the simulation accuracies of classical APF models, we simultaneously compare the simulations of the WRF-Chem, BPNN, and LSTM models to ground truth observations. Comparative assessment results show that WRF-Chem simulated air pollutant (i.e., PM_2.5, NO₂, SO₂, and CO) concentrations have the best correlations with ground measurements (i.e., Pearson correlation coefficient R = 0.88, 0.73, 0.61, and 0.61, respectively). Furthermore, to evaluate model performance in terms of accuracy and stability, the normalized mean bias (NMB, %) and mean fractional bias (MFB, %) are adopted as the standard performance metrics (SPMs) proposed by Boylan et al. The comparison results indicate that when simulating PM_2.5, WRF-Chem was more effective than the BPNN but less effective than the LSTM. While simulating concentrations of NO₂, SO₂, and CO, the WRF-Chem model performed better than the BPNN and LSTM models. With regards to WRF-Chem, the NMBs and MFBs for the PM_2.5 simulations are, respectively, 6.49% and 0.02%, –11.96% and –0.031% for NO₂, 7.93% and 0.019% for CO, and 5.04% and 0.012% for SO₂. Our results suggest that WRF-Chem has superior performance and better accuracy than the NN-based prediction models, making it a promising and useful tool to accurately predict and forecast regional air pollutant concentrations on a city scale. Full article

(This article belongs to the Special Issue Shipping Emissions and Air Pollution)

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18 pages, 8370 KiB

Open AccessArticle

Numerical Investigation on Mixing Characteristics and Mechanism of Natural Gas/Air in a Super-Large-Bore Dual-Fuel Marine Engine

by Long Liu, Shihai Liu, Qian Xia, Bo Liu and Xiuzhen Ma

Atmosphere 2022, 13(9), 1528; https://doi.org/10.3390/atmos13091528 - 19 Sep 2022

Cited by 3 | Viewed by 1495

Abstract

Premixed combustion mode dual-fuel (DF) engines are widely used in large-bore marine engines due to their great potential to solve the problem of CO₂ emissions. However, detonation is one of the main problems in the development of marine engines based on the [...] Read more.

Premixed combustion mode dual-fuel (DF) engines are widely used in large-bore marine engines due to their great potential to solve the problem of CO₂ emissions. However, detonation is one of the main problems in the development of marine engines based on the premixed combustion mode, which affects the popularization of liquefied natural gas (LNG) engines. Due to the large bore and long stroke, marine dual-fuel engines have unique flow characteristics and a mixture mechanism of natural gas and air. Therefore, the purpose of this study is to present a simulated investigation on the influence of swirl on multiscale mixing and the concentration field, which provides a new supplement for mass transfer theory and engineering applications. It is suggested that the phenomenon of abnormal combustion occurs on account of the distribution of the mixture being uneven in a super-large-bore dual-fuel engine. Further analysis showed that the level of swirl at the late compression stage and the turbulence intensity are the decisive factors affecting the transmission process of natural gas (NG) and distribution of methane (CH₄) concentration. Finally, a strategy of improving mixture quality and the distribution of the mixture was proposed. Full article

(This article belongs to the Special Issue Shipping Emissions and Air Pollution)

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20 pages, 4883 KiB

Open AccessArticle

Particulate Matter Forecasting Using Different Deep Neural Network Topologies and Wavelets for Feature Augmentation

by Stephanie Lima Jorge Galvão, Júnia Cristina Ortiz Matos, Yasmin Kaore Lago Kitagawa, Flávio Santos Conterato, Davidson Martins Moreira, Prashant Kumar and Erick Giovani Sperandio Nascimento

Atmosphere 2022, 13(9), 1451; https://doi.org/10.3390/atmos13091451 - 08 Sep 2022

Cited by 4 | Viewed by 2263

Abstract

The concern about air pollution in urban areas has substantially increased worldwide. One of its main components, particulate matter (PM) with aerodynamic diameter of ≤2.5 µm (PM_2.5), can be inhaled and deposited in deeper regions of the respiratory system, causing adverse [...] Read more.

The concern about air pollution in urban areas has substantially increased worldwide. One of its main components, particulate matter (PM) with aerodynamic diameter of ≤2.5 µm (PM_2.5), can be inhaled and deposited in deeper regions of the respiratory system, causing adverse effects on human health, which are even more harmful to children. In this sense, the use of deterministic and stochastic models has become a key tool for predicting atmospheric behavior and, thus, providing information for decision makers to adopt preventive actions to mitigate air pollution impacts. However, stochastic models present their own strengths and weaknesses. To overcome some of disadvantages of deterministic models, there has been an increasing interest in the use of deep learning, due to its simpler implementation and its success on multiple tasks, including time series and air quality forecasting. Thus, the objective of the present study is to develop and evaluate the use of four different topologies of deep artificial neural networks (DNNs), analyzing the impact of feature augmentation in the prediction of PM_2.5 concentrations by using five levels of discrete wavelet transform (DWT). The following types of deep neural networks were trained and tested on data collected from two living lab stations next to high-traffic roads in Guildford, UK: multi-layer perceptron (MLP), long short-term memory (LSTM), one-dimensional convolutional neural network (1D-CNN) and a hybrid neural network composed of LSTM and 1D-CNN. The performance of each model in making predictions up to twenty-four hours ahead was quantitatively assessed through statistical metrics. The results show that wavelets improved the forecasting results and that discrete wavelet transform is a relevant tool to enhance the performance of DNN topologies, with special emphasis on the hybrid topology that achieved the best results among the applied models. Full article

(This article belongs to the Special Issue Shipping Emissions and Air Pollution)

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24 pages, 11084 KiB

Open AccessArticle

Study on Characteristics Optimization of Combustion and Fuel Injection of Marine Diesel Engine

by Guixin Wang, Wenbin Yu, Zining Yu and Xiaobo Li

Atmosphere 2022, 13(8), 1301; https://doi.org/10.3390/atmos13081301 - 16 Aug 2022

Cited by 3 | Viewed by 1682

Abstract

The emission requirements of diesel engines are becoming increasingly strict and reducing emissions has become the key technology. In view of this development trend, the influence law of fuel injection on emission is studied in this paper. Numerical studies were performed to analyze [...] Read more.

The emission requirements of diesel engines are becoming increasingly strict and reducing emissions has become the key technology. In view of this development trend, the influence law of fuel injection on emission is studied in this paper. Numerical studies were performed to analyze the structural parameters of fuel injection system on combustion and emission characteristics of marine diesel engines. The numerical modelling was validated based on single-cylinder diesel engine tests and fuel injection tests. After investigating the single structural parameters on the fuel injection characteristics, the orthogonal method was used to design the double-parameter structural optimization scheme of the fuel injection system. There are 22 optimized cases selected to further investigate using the CFD method by visualizing scalar distributions in cylinder, which was helpful to explain the reason of pollutant formation. Comprehensively comparing the performance of each fuel injection system’s structural optimization scheme, moderate reduction of the discharge valve chamber volume and high-pressure tubing diameter would increase injection mass, along with faster injection rate and boosted injection pressure, leading to reduced Sauter mean diameter (SMD). Considering pollutant emission characteristics as well as economic and power concerns, case D6 with spray angle enlarging 5° showed best performance. Compared with the original condition, there was no NO deterioration and large reduction of soot emission by 65.4%, along with fuel consumption being lowered by 2.18% and more indicated power, by 2.21%. Therefore, reasonable optimization of spray angle can improve power, economy and emission performance simultaneously. Full article

(This article belongs to the Special Issue Shipping Emissions and Air Pollution)

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Review

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29 pages, 2175 KiB

Open AccessReview

A Prompt Decarbonization Pathway for Shipping: Green Hydrogen, Ammonia, and Methanol Production and Utilization in Marine Engines

by Jie Shi, Yuanqing Zhu, Yongming Feng, Jun Yang and Chong Xia

Atmosphere 2023, 14(3), 584; https://doi.org/10.3390/atmos14030584 - 17 Mar 2023

Cited by 35 | Viewed by 11135

Abstract

The shipping industry has reached a higher level of maturity in terms of its knowledge and awareness of decarbonization challenges. Carbon-free or carbon-neutralized green fuel, such as green hydrogen, green ammonia, and green methanol, are being widely discussed. However, little attention has paid [...] Read more.

The shipping industry has reached a higher level of maturity in terms of its knowledge and awareness of decarbonization challenges. Carbon-free or carbon-neutralized green fuel, such as green hydrogen, green ammonia, and green methanol, are being widely discussed. However, little attention has paid to the green fuel pathway from renewable energy to shipping. This paper, therefore, provides a review of the production methods for green power (green hydrogen, green ammonia, and green methanol) and analyzes the potential of green fuel for application to shipping. The review shows that the potential production methods for green hydrogen, green ammonia, and green methanol for the shipping industry are (1) hydrogen production from seawater electrolysis using green power; (2) ammonia production from green hydrogen + Haber–Bosch process; and (3) methanol production from CO₂ using green power. While the future of green fuel is bright, in the short term, the costs are expected to be higher than conventional fuel. Our recommendations are therefore as follows: improve green power production technology to reduce the production cost; develop electrochemical fuel production technology to increase the efficiency of green fuel production; and explore new technology. Strengthening the research and development of renewable energy and green fuel production technology and expanding fuel production capacity to ensure an adequate supply of low- and zero-emission marine fuel are important factors to achieve carbon reduction in shipping. Full article

(This article belongs to the Special Issue Shipping Emissions and Air Pollution)

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21 pages, 4749 KiB

Open AccessReview

Application and Development of Selective Catalytic Reduction Technology for Marine Low-Speed Diesel Engine: Trade-Off among High Sulfur Fuel, High Thermal Efficiency, and Low Pollution Emission

by Yuanqing Zhu, Weihao Zhou, Chong Xia and Qichen Hou

Atmosphere 2022, 13(5), 731; https://doi.org/10.3390/atmos13050731 - 02 May 2022

Cited by 43 | Viewed by 8609

Abstract

In recent years, the International Maritime Organization (IMO), Europe, and the United States and other countries have set up different emission control areas (ECA) for ship exhaust pollutants to enforce more stringent pollutant emission regulations. In order to meet the current IMO Tier [...] Read more.

In recent years, the International Maritime Organization (IMO), Europe, and the United States and other countries have set up different emission control areas (ECA) for ship exhaust pollutants to enforce more stringent pollutant emission regulations. In order to meet the current IMO Tier III emission regulations, an after-treatment device must be installed in the exhaust system of the ship power plant to reduce the ship NOx emissions. At present, selective catalytic reduction technology (SCR) is one of the main technical routes to resolve excess NO_x emissions of marine diesel engines, and is the only NO_x emission reduction technology recognized by the IMO that can be used for various ship engines. Compared with the conventional low-pressure SCR system, the high-pressure SCR system can be applied to low-speed marine diesel engines that burn inferior fuels, but its working conditions are relatively harsh, and it can be susceptible to operational problems such as sulfuric acid corrosion, salt blockage, and switching delay during the actual ship tests and ship applications. Therefore, it is necessary to improve the design method and matching strategy of the high-pressure SCR system to achieve a more efficient and reliable operation. This article summarizes the technical characteristics and application problems of marine diesel engine SCR systems in detail, tracks the development trend of the catalytic reaction mechanism, engine tuning, and control strategy under high sulfur exhaust gas conditions. Results showed that low temperature is an important reason for the formation of ammonium nitrate, ammonium sulfate, and other deposits. Additionally, the formed deposits will directly affect the working performance of the SCR systems. The development of SCR technology for marine low-speed engines should be the compromise solution under the requirements of high sulfur fuel, high thermal efficiency, and low pollution emissions. Under the dual restrictions of high sulfur fuel and low exhaust temperature, the low-speed diesel engine SCR systems will inevitably sacrifice part of the engine economy to obtain higher denitrification efficiency and operational reliability. Full article

(This article belongs to the Special Issue Shipping Emissions and Air Pollution)

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