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A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Energy Systems".

Deadline for manuscript submissions: closed (10 October 2023) | Viewed by 17275

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Prof. Dr. Jiangping Tian

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College of Power and Energy Engineering, Dalian University of Technology, Dalian 116023, China
Interests: fuel injection technology; spray; combustion theory
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

With the large-scale use of fossil fuels, environmental problems such as the greenhouse effect have become increasingly serious. At the COP26 summit in Glasgow, Scotland in November 2021, countries were asked to come forward with ambitious 2030 emissions reductions targets (NDCs, Nationally Determined Contributions) that align with reaching net zero by the middle of the century. To deliver on these targets, countries will need to accelerate the phase-out of coal, encourage investment in renewables, curtail deforestation and speed up the switch to electric vehicles. However, electric vehicles have a long way to go before they can replace internal combustion engine vehicles, especially outside the area of passenger cars. Oil is no longer indispensable in the field of automobile transportation, but it will still be widely used in the near future. The development of new combustion technologies and the utilization of clean energy have become more urgent and important for internal combustion engines. The fulfilment of the Paris Agreement requires the decarbonization of energy production by using carbon-neutral and carbon-free fuels produced from renewable energy. Green methanol, ammonia and hydrogen are most promising alternative carbon-neutral and carbon-free fuels for the near future. The combustion processes of internal combustion engines with alternative fuels might be quite different due to the physical and chemical properties of the fuels, and comprehensive study should be conducted before internal combustion engines with alternative fuels can fulfil the power, economic and emission demands and regulations.

This Special Issue on “Internal Combustion Engine Combustion Processes” aims to curate novel advances in the development and application of low-carbon, carbon-neutral and carbon-free fuels to internal combustion engines, and in the development and application of novel combustion techniques with traditional fossil fuels. Topics include, but are not limited to:

Fuel injection systems and processes for carbon-neutral and carbon-free fuels;
Atomization and spray processes of carbon-neutral and carbon-free fuels;
Development of combustion mechanisms for carbon-neutral and carbon-free fuels;
Innovative combustion processes with traditional fuels;
Optical diagnostics and numerical simulation for flow, spray and combustion processes in internal combustion engines;
Emission control technology and equipment for carbon-neutral and carbon-free fuels;
Abnormal combustion suppression technologies for carbon-neutral and carbon-free fuels.

Prof. Dr. Jiangping Tian
Guest Editor

Manuscript Submission Information

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Keywords

combustion
optical diagnostics
numerical simulation
carbon-neutral
carbon-free

Published Papers (11 papers)

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Research

24 pages, 36653 KiB

Open AccessArticle

Numerical Research on Effects of Variable Port Timing on Performance of Marine Low-Speed Two-Stroke Engine

by Heng Zhang, Wuqiang Long, Ge Xiao, Bo Li and Yuehua Qian

Processes 2023, 11(10), 2811; https://doi.org/10.3390/pr11102811 - 22 Sep 2023

Viewed by 798

Abstract

Enhancing the effective expansion ratio to further improve the fuel consumption, this study implemented a kind of Variable Port Timing (VPT) by designing a vertically moving sleeve on the outside of the scavenging port of a low-speed two-stroke diesel engine with a 340 mm bore. A 3D Computational Fluid Dynamics (CFD) model was constructed and calibrated to investigate the influence of the VPT strategy on the engine performance and the internal gas exchange process. The results indicated that the VPT can reduce the negative work from the compression stroke and increase the expansion work from the expansion stroke, which effectively enhances the fuel economy. However, the reduction in the mass flow rate would lead to the severe deterioration of the turbocharging system’s performance. The related matching analysis between the sleeve and the scavenging ports revealed that the sleeve velocity had a minimal influence on the scavenging flow rate, while increasing the height of the scavenging port can restore a certain mass flow rate, but will decrease the in-cylinder swirl intensity, deteriorating the combustion in the cylinders. The optimal approach is to raise the position of the scavenging port, achieving a Scavenging Port Closing (SPC) at a 235°CA, which will restore the scavenging flow rate of the original level to 90.7% and improve the indicated fuel consumption by 2.9 g/kWh. Full article

(This article belongs to the Special Issue Internal Combustion Engine Combustion Processes)

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14 pages, 4452 KiB

Open AccessArticle

Combustion Process of the Compound Supply CNG Engine

by Zhiqiang Zhu, Defu Zhang and Yunjing Jiao

Processes 2023, 11(9), 2725; https://doi.org/10.3390/pr11092725 - 12 Sep 2023

Viewed by 1106

Abstract

Objective: In order to study the lean combustion process of a natural gas engine by separating the combustor, a spark ignition natural gas engine with separated combustors was retrofitted from a S195 single-cylinder diesel engine. Methods: The electronic control system controlled the gas supply and the spark plug ignition. A low pressure injection valve was set in the inlet pipe to form a lean mixture while a high pressure injection valve was placed in the subsidiary chamber to create a rich mixture, which was then ignited and injected into the main combustor, where the lean mixture was subsequently ignited again to achieve stratified combustion. Results: The test results showed that steady ignition is feasible in the system and verified the impact of the shape of the main combustor on HC, the impact of channel diameter on NO_X production, and the impact of the ratios of high-pressure gas and low-pressure gas on HC and NO_X. The combustion conditions of high-pressure gas and low-pressure gas in the engine combustor vary greatly. Our results signify that the shape of the main combustor has a great impact on the performance of the engine, that is, a shorter propagation distance can reduce the generation of HC. Conclusion: The best ignition advance angle under different conditions was determined using a spark ignition natural gas engine. The ratios of high-pressure gas and low-pressure gas greatly impact the performance and emission of the engine. The reduced diameter of the channels between the main and subsidiary combustors can enhance the stratification and facilitate the secondary ignition. Full article

(This article belongs to the Special Issue Internal Combustion Engine Combustion Processes)

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12 pages, 4954 KiB

Open AccessArticle

Homogeneous Field Measurement and Simulation Study of Injector Nozzle Internal Flow and Near-Field Spray

by Ping Chen, Rongwu Xu, Zhenming Liu, Jingbin Liu and Xusheng Zhang

Processes 2023, 11(9), 2533; https://doi.org/10.3390/pr11092533 - 24 Aug 2023

Viewed by 696

Abstract

The homogeneous field measurement of internal flow and spray of internal combustion engine injector nozzles under high pressure has always been one of the difficulties in experimental research. In this paper, an actual-size aluminum alloy nozzle is designed, and the simultaneous measurement of internal flow and near-field spray is successfully realized with the help of synchrotron radiation X-ray phase contrast imaging technology under an injection pressure of 30~90 MPa. For a 0.25 mm aperture nozzle, different radii of the inlet corner can induce different cavitation layer thicknesses, and the measured flow section shrinkage ratio is 0.70. The flow characteristics in the nozzle are entirely connected to the jet characteristics, indicating a tight correlation between internal flow and jet morphology. Finally, the internal cavitation of the nozzle was studied by the CFD simulation, and the simulation results are in good agreement with the experiment. Full article

(This article belongs to the Special Issue Internal Combustion Engine Combustion Processes)

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21 pages, 8478 KiB

Open AccessArticle

Study on the Combustion Mechanism of Diesel/Hydrogen Dual Fuel and the Influence of Pilot Injection and Main Injection

by Longlong Xu, Haochuan Dong, Shaohua Liu, Lizhong Shen and Yuhua Bi

Processes 2023, 11(7), 2122; https://doi.org/10.3390/pr11072122 - 16 Jul 2023

Viewed by 1816

Abstract

Hydrogen is a clean and renewable alternative fuel. In this paper, the combustion mechanism of diesel/hydrogen dual fuel is constructed and verified. The mechanism is combined with three-dimensional numerical simulation to study the effects of pilot injection and main injection on the combustion and emissions of a diesel/hydrogen dual fuel engine. The mechanism uses a 70% mole fraction of n-decane and 30% mole fraction of α-methylnaphthalene as diesel substitutes, and it combines n-decane, α-methylnaphthalene, NO_X, PAH, soot and H₂/C₁-C₃ sub-mechanisms to form a diesel/hydrogen dual fuel combustion mechanism. The mechanism was verified by chemical kinetics, including the ignition delay time, JSR (Jet Stirred Reactor) oxidation and laminar flame speed, and then, it was verified by computational fluid dynamics. The results show that the simulated values are in good agreement with the experimental values of cylinder pressure, heat release rate and emissions data. The mechanism can well predict the combustion and emissions of a diesel/hydrogen dual fuel engine. Compared with single injection, the peak heat release rate, peak cylinder pressure and MPIR (Maximum Pressure Rise Rate) increase with the increase in pilot mass percent from 5% to 20%, which makes the phase of CA10 and CA50 advance and reduces CO emissions, but NO_X emissions increase. With the advance of pilot injection timing from 10° CA BTDC to 30° CA BTDC, the peak cylinder pressure increases, the peak heat release rate decreases, CA10 and CA50 advance, CO emissions decrease, NO_X emissions increase and NO_X emissions peak at 30° CA BTDC. When the pilot injection timing is further advanced from 30° CA BTDC to 50° CA BTDC, the peak cylinder pressure decreases, the peak heat release rate increases, CA10 and CA50 are delayed, CO and NO_X emissions are reduced, and NO_X emissions at 50° CA BTDC are lower than those at 10° CA BTDC. With the advance of main injection timing from 0° CA BTDC to 8° CA BTDC, CO emissions decrease, NO_X emissions increase, the peak cylinder pressure increases, the peak heat release rate decreases slightly first and then increases, and the peak cylinder pressure and peak heat release rate corresponding to the overall phase shift forward. When the main injection timing is advanced to 6° CA BTDC, MPIR is 1.3 MPa/° CA, exceeding the MPIR limit of diesel engine 1.2 MPa/° CA. Full article

(This article belongs to the Special Issue Internal Combustion Engine Combustion Processes)

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17 pages, 3157 KiB

Open AccessArticle

Study on the Skeleton Mechanism of Second-Generation Biofuels Derived from Platform Molecules

by Weiwei Fan, Aichun Du, Gang Liu, Qing Liu and Yuan Gao

Processes 2023, 11(6), 1589; https://doi.org/10.3390/pr11061589 - 23 May 2023

Viewed by 725

Abstract

This paper focuses on the combustion mechanism of furan-based fuels synthesized from lignocellulose. The fuel is a binary alternative fuel consisting of 2-methylfuran and 2,5-dimethylfuran derived from furfural. The key reactions affecting the combustion mechanism of this fuel were identified via path analysis, and the initial reaction kinetic mechanism was constructed using a decoupling methodology. Then, a genetic algorithm was used to optimize the initial mechanism. The final skeleton mechanism consisted of 67 species and 228 reactions. By comparing experimental data on ignition delay, component concentration, and laminar flame velocity under a wide range of conditions over various fundamental reactors, it was shown that the mechanism has the ability to predict the combustion process of this fuel well. Full article

(This article belongs to the Special Issue Internal Combustion Engine Combustion Processes)

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17 pages, 7065 KiB

Open AccessArticle

Experimental Study of the Effects of Pre-Chamber Geometry on the Combustion Characteristics of an Ammonia/Air Pre-Mixture Ignited by a Jet Flame

by Zechuan Cui, Jiangping Tian, Xiaolei Zhang, Shuo Yin, Wuqiang Long and Hui Song

Processes 2022, 10(10), 2102; https://doi.org/10.3390/pr10102102 - 17 Oct 2022

Cited by 11 | Viewed by 1769

Abstract

In the future, ammonia is expected to become a carbon-free fuel for internal combustion engines. However, the flammability of ammonia is poorer compared to conventional fuels such as gasoline and diesel fuel. Pre-chamber jet ignition may be an effective way to ensure stable ignition and enhance the combustion of ammonia. In this paper, the effects of pre-chamber geometric parameters, including volume and orifice diameter, on the jet ignition and combustion processes were studied using visualization methods, combined with pressure acquisition. The results showed that ignition energy increased and the jet duration was prolonged with the increase in pre-chamber volume, resulting in a higher maximum pressure and pressure rise rate in the main chamber. The jet characteristics of a larger volume pre-chamber exhibited higher stability when the ambient parameters were changed. The smaller volume pre-chamber showed the superiority of a shorter flame propagation distance inside the pre-chamber, which advanced the timing of the jet appearance and shortened the ignition delay when the flammability of the pre-mixture was adequate. The larger pre-chamber orifice diameter caused an earlier jet ignition timing, shorter ignition delay, and higher ignition location. The jet duration for the pre-chamber with a smaller orifice was longer, which was beneficial for increasing the pressure rise rate in the main chamber. Too small a pre-chamber orifice led to ignition failure in the main chamber. Full article

(This article belongs to the Special Issue Internal Combustion Engine Combustion Processes)

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25 pages, 11137 KiB

Open AccessArticle

Numerical Simulation Study on the Effect of Port Water Injector Position on the Gasoline Direct Injection Engine

by Zhongjie Zhang, Xuejiao Dai and Zhaolei Zheng

Processes 2022, 10(10), 1909; https://doi.org/10.3390/pr10101909 - 21 Sep 2022

Viewed by 1309

Abstract

This paper explores the effects of six different cases of port water injection on the combustion, knock suppression and emissions of a supercharged gasoline direct injection (GDI) engine through numerical simulation. The six different intake port water injection cases included three vertical distances from cylinder center to water injector and two different injection directions. The results showed that cases 2 and 4 allowed more water and air to enter the cylinder and thus suppressed the knock, so the pressure oscillation was small. Case 2 had the largest turbulent kinetic energy in the center of the cylinder, which in turn facilitated the propagation of flame to the cylinder wall and suppressed the knock. The water injection cases shortened the combustion delay period compared to the no water cases. At the same time, the strong low temperature reaction of the end mixture produced a large amount of CH₂O that decomposed into HCO. A high concentration and a large area of HCO distribution can predict the occurrence of a knock. In addition, the water injection cases (except for case 6) reduced the in-cylinder soot, unburned hydrocarbon (UHC) and CO emissions compared to the no water cases, but it increased NO_X emissions. Full article

(This article belongs to the Special Issue Internal Combustion Engine Combustion Processes)

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20 pages, 9986 KiB

Open AccessArticle

Numerical Study on Primary Breakup of Disturbed Liquid Jet Sprays Using a VOF Model and LES Method

by Zhenming Liu, Ziming Li, Jingbin Liu, Jiechang Wu, Yusong Yu and Jiawei Ding

Processes 2022, 10(6), 1148; https://doi.org/10.3390/pr10061148 - 08 Jun 2022

Cited by 7 | Viewed by 1709

Abstract

In this study, the primary breakup of a high-speed diesel jet is investigated using a CFD methodology that combines an LES model with a VOF technique for free surface capture. Inner-nozzle turbulence and cavitation are simplified as the sinusoidal radial velocity with a given amplitude and frequency. The ligament and droplet formation process are captured, the liquid jet is disturbed by the radial velocity, and umbrella-shaped crests are created. Meanwhile, ligaments are formed from the edges of crests because of shear stress and surface tension. We investigate the effect on the characteristics of the surface wave and the liquid structure of different disturbance frequencies and amplitudes. The variation in the disturbance amplitude and frequency facilitates the formation of a variety of liquid structures, such as waves, upstream/downstream-directed bells, and droplet chains. Increasing the disturbance frequency reduces the growth rate of the surface waves of the liquid jet. With an increase in disturbance amplitude, the amplitude of surface waves evidently increases. Furthermore, as the disturbance frequency and amplitude increase, the thickness and Weber number of the radial liquid sheet decrease, and this causes the ligament diameter of the primary breakup to become small. Finally, the primary breakup time is investigated, and the time scale of the liquid jet primary breakup decreases as the disturbance amplitude increases, which indicates that an increase in the disturbance amplitude promotes the atomization of a disturbed liquid jet. Full article

(This article belongs to the Special Issue Internal Combustion Engine Combustion Processes)

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23 pages, 7583 KiB

Open AccessArticle

Characteristics of Evaporating Spray for Direct Injection Methanol Engine: Comparison between Methanol and Diesel Spray

by Yang Wang, Pengbo Dong, Wuqiang Long, Jiangping Tian, Fuxing Wei, Qianming Wang, Zechuan Cui and Bo Li

Processes 2022, 10(6), 1132; https://doi.org/10.3390/pr10061132 - 06 Jun 2022

Cited by 3 | Viewed by 2652

Abstract

In the context of global efforts to pursue carbon neutrality, the research on the application technology of methanol fuel in internal combustion engines has ushered in a new peak. In order to provide a theoretical basis for the development of direct injection methanol engines, the spray characteristics of methanol with high-pressure direct injection were studied. Based on the visualization experimental device of constant volume vessels, the diffused background-illumination extinction imaging (DBI) and schlieren methods were applied to examine the distinctions in the evaporating spray properties between methanol and diesel under different injection pressures and ambient temperature conditions. Furthermore, aiming to maximize the potential of methanol fuel in compression ignition engines, under the premise that the alternative fuel can obtain the same total fuel energy as diesel, two different injection strategies of methanol were proposed and evaluated through the coordination of the nozzle hole diameter, injection pressure and injection duration. It reveals that it is easier for methanol spray to evaporate because of the lower boiling point, which results in a shorter spray tip penetration and wider spray angle compared with those of diesel, especially under the middle-level ambient temperature (600 K) condition. These deviations are also observed under different injection pressure conditions. However, affected by the lower energy density, the strategies of injecting the same fuel energy of methanol with that of diesel prolong the methanol spray tip penetration, enlarge its spray area and sacrifice the methanol evaporation performance. It is necessary for the geometrical design of the combustion chamber to coordinate with the hole diameter and injection pressure selection to deal with the huge distinctions in the spray characteristics between methanol and diesel fuel. Full article

(This article belongs to the Special Issue Internal Combustion Engine Combustion Processes)

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22 pages, 10663 KiB

Open AccessArticle

The Engine Combustion Phasing Prediction Based on the Support Vector Regression Method

by Qifan Wang, Ruomiao Yang, Xiaoxia Sun, Zhentao Liu, Yu Zhang, Jiahong Fu and Ruijie Li

Processes 2022, 10(4), 717; https://doi.org/10.3390/pr10040717 - 08 Apr 2022

Cited by 3 | Viewed by 1568

Abstract

While traditional one-dimensional and three-dimensional numerical simulation techniques require a lot of tests and time, emerging Machine Learning (ML) methods can use fewer data to obtain more information to assist in engine development. Combustion phasing is an important parameter of the spark-ignition (SI) engine, which determines the emission and power performance of the engine. In the engine calibration process, it is necessary to determine the maximum brake torque timing (MBT) for different operating conditions to obtain the best engine dynamics performance. Additionally, the determination of the combustion phasing enables the Wiebe function to predict the combustion process. Existing studies have unacceptable errors in the prediction of combustion phasing parameters. This study aimed to find a solution to reduce prediction errors, which will help to improve the calibration accuracy of the engine. In this paper, we used Support Vector Regression (SVR) to reconstruct the mapping relationship between engine inputs and responses, with the hyperparametric optimization method Gray Wolf Optimization (GWO) algorithm. We chose the engine speed, load, and spark timing as engine inputs. Combustion phasing parameters were selected as engine responses. After machine learning training, we found that the prediction accuracy of the SVR model was high, and the R² of CA10−ST, CA50, CA90, and DOC were all close to 1. The RMSE of these indicators were close to 0. Consequently, SVR can be applied to the prediction of combustion phasing in SI gasoline engines and can provide some reference for combustion phasing control. Full article

(This article belongs to the Special Issue Internal Combustion Engine Combustion Processes)

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16 pages, 5481 KiB

Open AccessArticle

Simulation Analysis of Fuel Economy of the GDI Engine with a Miller Cycle and EGR Based on GT-Power

by Shengli Wei, Zhicheng Zhang, Xuan Li, Chengcheng Wu and Fan Yang

Processes 2022, 10(2), 319; https://doi.org/10.3390/pr10020319 - 07 Feb 2022

Cited by 4 | Viewed by 2098

Abstract

A one-dimensional (1D) simulation calculation model was created using GT-Power software to investigate the effect of an exhaust gas recirculation (EGR) in concert with the Miller cycle on engine fuel economy and using a 1.5 T gasoline direct injection (GDI) engine as the source engine. The engine was tested under partial loading, full loading, and declared working conditions. The results show that under partial load, the Miller cycle could improve engine fuel economy by reducing pumping losses. In the low-speed 1000 r/min full load region, the Miller cycle had a significant effect on increasing the engine fuel economy. When the Miller intensity was −29 °CA, the fuel consumption decreased by a maximum of 10.5%. At medium speeds, 2000 r/min to 3600 r/min, the Miller cycle did not improve fuel economy significantly. For the Miller cycle with late intake valve closure (LIVC), when the EGR rate was about 7%, the fuel consumption was reduced by about 1.3% compared with the original engine at the same EGR rate. When opposed to the original engine without EGR, the fuel consumption was lowered by approximately 3.2 percent. Full article

(This article belongs to the Special Issue Internal Combustion Engine Combustion Processes)

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