Article
Energy & Fuels
Khawar Mohiuddin, Heesun Kwon, Minhoo Choi, Sungwook Park
Summary: This study investigated the combined effects of engine compression ratio, start of injection timing, and exhaust gas recirculation rate on performance and emissions from a diesel engine, with a special focus on particle number emissions. Results showed that increasing compression ratio led to higher in-cylinder pressure, reduced ignition delay, and slightly improved fuel consumption, while also resulting in higher NOx production. Additionally, interesting trends were observed for particle number and soot emissions as compression ratio increased.
Article
Environmental Sciences
Gavaskar Thodda, Arun Kathapillai, Venkata Ramanan Madhavan, Murugapoopathi Saravanamuthu
Summary: The predicted scarcity, increasing cost of petroleum fuels, and environmental degradation are driving researchers to find alternative fuels. This study investigated the use of a dual-fuel system (acetylene gas and diesel) in a compression ignition engine to reduce emissions and improve fuel efficiency. The results showed that a gas rate of 6 lpm provided the best fuel consumption efficiency of 30.7%.
ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
(2023)
Article
Energy & Fuels
Amin Yousefi, Hongsheng Guo, Shouvik Dev, Brian Liko, Simon Lafrance
Summary: This study investigates the feasibility of an ammonia/diesel dual-fuel engine in reducing greenhouse gas emissions while maintaining diesel-like efficiency. Results show that increasing the ammonia energy fraction reduces nitrogen oxide emissions but increases nitrous oxide emissions, resulting in higher overall greenhouse gas emissions compared to diesel-only combustion. Advancing the start of diesel injection helps reduce nitrous oxide and overall greenhouse gas emissions while achieving diesel-like thermal efficiency.
Article
Green & Sustainable Science & Technology
Wanchen Sun, Mengqi Jiang, Liang Guo, Hao Zhang, Zhiqin Jia, Zhenshan Qin, Wenpeng Zeng, Shaodian Lin, Genan Zhu, Shenyue Ji, Yimo Zhu
Summary: This study explores the application potential of renewable methanol and direct dual fuel stratification (DDFS) technology in marine internal combustion engines. By optimizing the fuel injection strategy for a marine methanol/diesel DDFS engine, it is found that the fuel mixing process plays a crucial role in the combustion state switching. A strategy with earlier start of diesel injection (SOID) compared to the start of methanol injection (SOIM) and an appropriately extended injection interval achieves better engine performance. Furthermore, the optimized methanol two-stage injection strategy improves fuel economy while causing a decrease in combustion completeness and increase in emissions.
JOURNAL OF CLEANER PRODUCTION
(2023)
Article
Energy & Fuels
Abdulvahap Cakmak, Hakan Ozcan
Summary: In this research, the effect of a glycerol tert-butyl ethers mixture on combustion and emissions characteristics of a diesel engine was experimentally investigated. The results showed that the addition of the mixture resulted in a decrease in NOx emission and an increase in HC emission. The blending ratio of 2% v/v of the mixture with a diesel-biodiesel blend provided a simultaneous decrease in NOx and CO emissions.
Article
Chemistry, Physical
Patrick Rorimpandey, Ho Lung Yip, Ales Srna, Guanxiong Zhai, Armin Wehrfritz, Sanghoon Kook, Evatt R. Hawkes, Qing Nian Chan
Summary: This study investigates the ignition and combustion characteristics of diesel pilot and hydrogen jets under simulated compression-ignition engine conditions. The results show that the injection sequence and timing between injections significantly affect the combustion process. Igniting the hydrogen jet before the diesel pilot leads to better combustion performance, while delaying the ignition of the hydrogen jet reduces its combustion efficiency.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2023)
Article
Energy & Fuels
S. Ouchikh, M. S. Lounici, K. Loubar, L. Tarabet, M. Tazerout
Summary: Experimental research on the diesel injection strategy for a methane/diesel dual-fuel engine revealed that the split injection strategy significantly improved combustion efficiency and reduced NOx emissions at low load conditions.
Article
Energy & Fuels
Zhongshu Wang, Fangyuan Zhang, Ye Xia, Dan Wang, Yun Xu, Guizhi Du
Summary: This study investigated the impact of pilot diesel injection timing on combustion phases of diesel and natural gas in a dual fuel engine, showing that injection timing plays a crucial role in determining engine thermal efficiency and exhaust emissions level. The results revealed a clear correspondence between the lengths of combustion period of two fuels, with advancing pilot diesel injection resulting in shortened combustion durations and increased combustion overlap periods.
Article
Energy & Fuels
Shouying Jin, Binyang Wu, Zhenyuan Zi, Puze Yang, Taifeng Shi, Junhong Zhang
Summary: As the greenhouse effect worsens, ammonia, a carbon-free fuel, is gaining attention. The ammonia-diesel dual-fuel (ADDF) engine can effectively overcome the drawbacks of ammonia's high auto-ignition temperature and slow flame speed, making it an effective solution for reducing greenhouse gas emissions. By studying the effects of ammonia energy ratio (AER) and injection strategy on combustion and emissions, it was found that increasing AER led to a decrease in gross indicated thermal efficiency (ITEg) and an increase in unburned ammonia emissions. Optimizing the injection strategy and combustion process can significantly improve ITEg and reduce greenhouse gas emissions.
Article
Thermodynamics
Kailin Yang, Zhongshu Wang, Kechao Zhang, Dan Wang, Fangxi Xie, Yun Xu, Kaiqiang Yang
Summary: A detailed investigation was conducted to understand the effect of natural gas injection timing on the combustion and emissions performance of a dual-direct-injection diesel/natural gas engine. The results showed that advancing the injection timing of natural gas can achieve higher thermal efficiency.
Article
Energy & Fuels
Zhijie Zhu, Xingyu Liang, Lei Cui, Kun Wang, Xiaohui Wang, Shihao Zhu
Summary: Currently, most ships still rely on fossil fuels as the main source for marine engines. However, diesel as a fuel for marine engines is no longer sufficient to meet the economic requirements of shipping and emission restrictions imposed by regulations. This research examined the viability of employing hydrogen-carrying fuel ammonia (NH3) in marine engines to develop a low-carbon combustion technology, to address the carbon emission problem of marine diesel engines.
Article
Energy & Fuels
Wenhui Tao, Tao Sun, Wenjun Guo, Kangbo Lu, Lei Shi, He Lin
Summary: Diesel fuel pilot injection timing, pilot mass percent, and methanol substitution rate were experimentally investigated to study their effects on the combustion and emissions of a diesel-methanol dual fuel engine. The results showed that adding pilot injection advanced the ignition time and increased the heat release rate. With the increase in pilot mass percent, the peak in-cylinder pressure and heat release rate increased. Furthermore, at high methanol substitution rates, advancing the pilot injection timing, increasing the pilot mass percent, and combining exhaust gas recirculation (EGR) were found to improve combustion performance and reduce emissions.
Article
Energy & Fuels
Amin Yousefi, Hongsheng Guo, Shouvik Dev, Simon Lafrance, Brian Liko
Summary: This study investigates the effect of split diesel injection strategy on an ammonia/diesel dual-fuel engine under medium load conditions. Results show that the use of split diesel injection strategy increases the thermal efficiency and reduces the unburned ammonia emissions. Two optimized split diesel injection strategies are suggested to reduce greenhouse gas emissions while improving combustion efficiency, although they result in higher nitrogen oxides emissions.
Article
Energy & Fuels
Zhiyong Li, Yang Wang, Yongjian Wang, Zibin Yin, Zhanbin Gao, Zixiao Ye, Xudong Zhen
Summary: A methanol/diesel/methanol (M/D/M) strategy is proposed to improve fuel economy and reduce emissions of a diesel/methanol dual-fuel direct injection engine. The study shows that the timing of fuel injection and the methanol split ratio (SR) have significant effects on the engine performance. An appropriate combination of M-SOI-30, D-SOI-5, and M-SOI-3 is found to be the best overall configuration.
Article
Energy & Fuels
Changchun Xu, Yuan Zhuang, Yejian Qian, Haengmuk Cho
Summary: In methanol/diesel combined injection mode engines, the high latent heat of vaporization of methanol reduces the combustion temperature, effectively reducing NOx emissions. However, this can lead to combustion deterioration under high blending ratio conditions. The study aimed to improve this negative effect by changing methanol injection positions. The results showed different effects on combustion and emissions under varying load and methanol substitution rates.
Review
Energy & Fuels
Panagiotis Grammelis, Nikolaos Margaritis, Petros Dallas, Dimitrios Rakopoulos, Georgios Mavrias
Summary: Approximately 3 billion tires are commercially transacted worldwide each year, with an equivalent amount disposed of. Despite efforts to increase tire life, the number of discarded tires is expected to rise due to the growing demand for vehicles globally. Around 70% of discarded tires are currently recovered for energy production or production of various materials, while approximately 95% of them can be reused.
Article
Energy & Fuels
Stefanos Petridis, Orestis Blanas, Dimitrios Rakopoulos, Fotis Stergiopoulos, Nikos Nikolopoulos, Spyros Voutetakis
Summary: The study introduces an improved backward-forward sweep power flow algorithm for unbalanced three-phase distribution networks, which produces accurate results with minimal computational resources and time. The algorithm represents the network in a tree-like structure, avoiding redundant computations and unnecessary data storage.
Article
Energy & Fuels
Dimitrios C. Rakopoulos
Summary: This study assesses the impact of exhaust gas recirculation (EGR) on combustion, performance, and exhaust emissions in direct injection (DI) diesel engines under different EGR rates and strategies. By using numerical simulations and comparing the results with experimental data, the study highlights the importance of using a consistent fueling rate (FR) or air/fuel ratio (AFR) strategy in EGR applications to avoid misleading interpretations and comparisons.
JOURNAL OF ENERGY ENGINEERING
(2021)
Article
Chemistry, Physical
G. M. Kosmadakis, D. C. Rakopoulos, C. D. Rakopoulos
Summary: The study investigates the cyclic variability in a spark-ignition engine fueled with methane/hydrogen blends using an in-house CFD code. It follows a recent methodology to accurately predict the COV of IMEP in a fraction of time. Results show that the methodology provides reliable predictions for a range of operating conditions, with a focus on engine cycle variations and NO emissions.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2021)
Article
Energy & Fuels
Dimitrios C. Rakopoulos, Constantine D. Rakopoulos, Evangelos G. Giakoumis, George M. Kosmadakis
Summary: This study developed a comprehensive, quasi-dimensional, two-zone combustion model to predict the combustion characteristics, performance, and emissions of high-speed spark-ignition engines. The validated model showed good agreement with experimental data, providing insights into engine performance and emission attributes. The results shed light on the underlying physical and chemical mechanisms influencing SI engine performance and emissions.
JOURNAL OF ENERGY ENGINEERING
(2021)
Review
Energy & Fuels
Theodoros C. Zannis, John S. Katsanis, Georgios P. Christopoulos, Elias A. Yfantis, Roussos G. Papagiannakis, Efthimios G. Pariotis, Dimitrios C. Rakopoulos, Constantine D. Rakopoulos, Athanasios G. Vallis
Summary: This paper reviews the contemporary exhaust gas treatment systems (EGTS) used in shipping for SOx, PM, and NOx emission control. Various after-treatment technologies are analyzed, and their operational principles, performance characteristics, and investment and operation details are thoroughly explained. The effectiveness of different technologies in reducing NOx emissions is compared, and actual data on the installation and cost of seawater scrubbers are provided. The study concludes that closed-loop wet scrubbers with NaOH solution are the most effective in reducing SOx emissions, while SCR systems can effectively reduce NOx emissions and comply with IMO Tier III limits.
Article
Thermodynamics
Constantine D. Rakopoulos, Dimitrios C. Rakopoulos, Dimitrios C. Kyritsis, Eleftherios C. Andritsakis, George C. Mavropoulos
Summary: This study is based on a validated combustion model and predicts the performance and emissions of spark-ignition engines. The model is extended by considering exergy terms and applied to experimental test results. The study provides detailed information on chemical exergy, irreversibility, and exergy losses.
Article
Energy & Fuels
Theodoros C. Zannis, Roussos G. Papagiannakis, Efthimios G. Pariotis, Dimitrios C. Rakopoulos, Athanasios G. Vallis
Summary: This theoretical study examines the impact of intake-air nitrogen enrichment on the performance and emissions of a high-speed direct injection diesel engine. The results show that increasing intake-air nitrogen content can achieve NO emissions-free operation, but it leads to higher levels of soot emissions. In addition, using biodiesel such as RME under certain conditions can reduce both soot and NO emissions.
JOURNAL OF ENERGY ENGINEERING
(2022)
Review
Chemistry, Multidisciplinary
Maria Fotopoulou, Stefanos Petridis, Ioannis Karachalios, Dimitrios Rakopoulos
Summary: This paper reviews the algorithms for Distribution System State Estimation (DSSE), focusing on their specific requirements, mathematical formulation, existing model-based and data-driven approaches, and recommended solutions. The paper also highlights DSSE applications and future trends, emphasizing the business-related aspects.
APPLIED SCIENCES-BASEL
(2022)
Article
Energy & Fuels
George M. Kosmadakis, Dimitrios C. Rakopoulos, Constantine D. Rakopoulos
Summary: The effect of two mechanisms on the cyclic variability of a lean methane-hydrogen fueled SI engine was investigated using computational fluid dynamics (CFD) simulations. The first mechanism involves gas turbulent properties near the spark plug, while the second mechanism involves fuel mass variation per cycle. Linear regression and Monte Carlo-based approaches were used to analyze engine performance and emissions. The results showed that the first mechanism significantly affects the initial flame propagation, while the second mechanism affects the combustion process and CO emissions with high variability.
JOURNAL OF ENERGY ENGINEERING
(2023)
Article
Chemistry, Analytical
Maria Fotopoulou, Dimitrios Rakopoulos, Stefanos Petridis
Summary: This paper introduces an optimal Decision Support System (DSS) to assist microgrid operators in handling various emergencies and optimizing the autonomy of the microgrid while prioritizing renewable energy production. The DSS is aligned with the ongoing energy transition and considers multiple types of Distributed Energy Resources (DER), including Renewable Energy Sources (RES) and Battery Energy Storage Systems (BESS) that can only be charged with renewable energy.
Article
Green & Sustainable Science & Technology
Myrto Zeneli, Alessandro Bellucci, Gianfranco Sabbatella, Maria Fotopoulou, Vasilis Apostolopoulos, Panagiotis Stamatopoulos, Daniele M. M. Trucchi, Aristeidis Nikolopoulos, Dimitrios Rakopoulos
Summary: Dielectric microspacers (DMS) are used to achieve a fixed gap distance between the emitter and the PV cell of a near-field thermophotovoltaic converter. This study investigates the integration of DMS technology into a hybrid thermionic-photovoltaic converter operating at ultra-high temperatures without the risk of overheating and mechanical failure. A 3-D CFD model was developed to simulate the thermal behavior of the system under different conditions. Results show that DMS pattern does not affect thermal performance, but mechanical failure is possible at high cathode temperatures.
Article
Energy & Fuels
Renos Rotas, Maria Fotopoulou, Panagiotis Drosatos, Dimitrios Rakopoulos, Nikos Nikolopoulos
Summary: This study assesses the annual performance improvement of two actual building spaces retrofitted with Adaptive Dynamic Building Envelopes (ADBEs) and evaluates their potential to contribute to the electricity and heating load of the spaces. The results demonstrate that the ADBE system can significantly benefit the energy consumption of the buildings in Cardiff and Grevena.
Review
Computer Science, Information Systems
David Cervero, Maria Fotopoulou, Jesus Munoz-Cruzado, Dimitrios Rakopoulos, Fotis Stergiopoulos, Nikos Nikolopoulos, Spyros Voutetakis, Jose Francisco Sanz
Summary: The paper provides a practical review of the solid state transformer (SST), which is considered to be the dominant solution for the changing architecture of electricity networks. It presents the main functionalities and possible applications of SST, including smart grids, data centres, railways, and offshore wind farms. The analysis of SST prototypes and future trends and challenges in wider implementation of SST technology in the electrical grid are also discussed.