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Numerical and Experimental Study of Alternative Fuel Combustion in Internal Combustion Engines

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "I2: Energy and Combustion Science".

Deadline for manuscript submissions: 25 June 2026 | Viewed by 5566

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Dr. Diego Perrone

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Department of Mechanical, Energy and Management Engineering, University of Calabria, Ponte Bucci, Cubo 46 C, 87036 Rende, Italy
Interests: internal combustion engine fueled with alternative fuels; combustion processes; pollutant emissions; novel technologies for thermal management in internal combustion engines; oxy-MILD combustion technology; CHP/CCHP systems; computational fluid dynamics (CFDs)
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Dear Colleagues,

Internal combustion engines (ICEs) remain a cornerstone of energy production; they are a widely utilized and economically viable technology for transportation and power generation. However, the depletion of fossil fuel reserves and increasingly stringent emission regulations have driven the industry and research communities to explore alternative fuels.

The study of combustion processes is pivotal in advancing the use of alternative fuels in ICEs. Understanding the intricate mechanisms of fuel–air mixing, ignition, flame propagation, and pollutant formation is essential for optimizing engine performance and minimizing harmful emissions. Both numerical simulations and experimental investigations provide invaluable insights into these complex phenomena, offering pathways to enhance combustion efficiency and reduce the environmental impact of ICEs.

With this Special Issue, we aim to publish high-quality research papers and review articles focusing on combustion processes involving alternative fuels in internal combustion engines. Topics of interest include advances in the modeling and experimental analysis of combustion, with an emphasis on improving fuel conversion efficiency and reducing pollutant emissions.

Further topics of interest for this Special Issue include, but are not limited to, the following:

Numerical simulation of combustion processes and performance in ICEs using alternative fuels.
Experimental studies on ICE performance with biofuels, e-fuels, hydrogen, alcohol fuels, and other sustainable fuels.
Pollutant formation mechanisms and emission reduction technologies.
Comparative studies of alternative fuels and their impacts on engine performance and emissions.

We invite authors to contribute original research papers that align with these themes to advance our knowledge and the application of alternative fuels in ICEs. We look forward to receiving your valuable contributions to this exciting and impactful field.

Dr. Diego Perrone
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

internal combustion engines
alternative fuels
e-fuels
biofuels
numerical simulation
experimental study
combustion modeling
pollutant emissions

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Published Papers (6 papers)

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Research

24 pages, 14925 KB

Open AccessArticle

Numerical Study of a Swirled-Type Injector for Direct-Injection Hydrogen Engines

by Federico Ramognino, Lorenzo Sforza, Tommaso Lucchini, Angelo Onorati, Jeroen van Oijen and Nick Diepstraten

Energies 2026, 19(9), 2101; https://doi.org/10.3390/en19092101 - 27 Apr 2026

Viewed by 255

Abstract

The use of hydrogen direct injection (DI) plays a crucial role in decarbonizing internal combustion engine (ICE) technology. However, a suitable characterization of the injection process is required to control the mixture preparation before combustion, especially in the case of late injection timing. CFD modeling represents a useful tool to support experiments in addressing this goal. This study presents a numerical investigation of hydrogen DI using a swirled-type injector, seated in a constant-volume vessel. First, the selected numerical setup is validated against optical measurements of the jet penetration, demonstrating the reliability of the approach. Then, the analysis compares swirling and non-swirling configurations under different nozzle pressure ratios (nPRs) to evaluate the interaction between swirl-induced mixing and under-expanded jet structures. Results show that at lower nPR, swirl significantly alters the momentum distribution, reducing axial penetration. Instead, at higher nPR, where the H2 jets exhibit strong shock structures, the effects of swirl become negligible, with penetration and plume morphology nearly identical to non-swirling conditions. Analysis of the scalar dissipation rate showed the presence of a redistribution of mixing characteristics at low nPR due to swirl, while shock structures dominate at high nPR. This could have a significant impact on combustion and NO_x emissions in ICE operated with late injection strategies, where lower nPR are found. Full article

(This article belongs to the Special Issue Numerical and Experimental Study of Alternative Fuel Combustion in Internal Combustion Engines)

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26 pages, 3862 KB

Open AccessArticle

Development of a Refined Model for a Rapid Compression and Expansion Machine with Pre-Chamber Applied to Study the Effects of Pre-Chamber Geometry and Hydrogen Enrichment on Combustion and Extinction of Methane/Air Flames

by Fabio Bozza, Luigi Teodosio, Emanuele Ugliano, Ratnak Sok, Enrica Malfi and Jin Kusaka

Energies 2026, 19(4), 910; https://doi.org/10.3390/en19040910 - 9 Feb 2026

Viewed by 453

Abstract

In this paper, experimental and numerical analyses are performed with a Rapid Compression and Expansion Machine (RCEM) equipped with a passive pre-chamber (PC) and fueled with premixed stoichiometric air/methane mixture to replicate engine-like conditions. The main objective of this work is to study the effects of PC geometry, initial charge conditions and hydrogen addition to methane on combustion and flame extinction. From the experiments at different PC geometries, the combustion images acquired with a high-speed camera show the existence of a critical PC configuration (Long φ4) exhibiting the highest flame extinction probability (~54% under baseline conditions). The increase in the initial charge pressure and/or the enrichment of the methane with hydrogen (up to 30% H₂ by volume) help to mitigate the flame extinction by reducing its probability to about 10%. Subsequently, a 0D RCEM model is developed (GT-Power^TM) and enhanced with user sub-models of turbulent combustion and flame quenching. Once tuned, the model reproduces the impact of PC design, higher initial gas pressure and hydrogen enrichment on the combustion evolution. The quenching sub-model, calibrated for the side wall quenching configuration, is able to forecast the experimental flame extinction tendency for the critical PC by modifying the hydrogen enrichment or initial gas pressure. The proposed methodology, describing the flame extinction tendency in PC combustion systems through 0D quenching modeling, represents the novel aspect for PC-equipped devices aiming to support their study and supplement engine investigations during the development phase. Full article

(This article belongs to the Special Issue Numerical and Experimental Study of Alternative Fuel Combustion in Internal Combustion Engines)

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20 pages, 32561 KB

Open AccessArticle

CFD Analysis of Diesel Pilot Injection for Dual-Fuel Diesel–Hydrogen Engines

by Gianluca D’Errico, Giovanni Gaetano Gianetti, Tommaso Lucchini, Alastar Gordon Heaton and Sanghoon Kook

Energies 2026, 19(2), 380; https://doi.org/10.3390/en19020380 - 13 Jan 2026

Viewed by 944

Abstract

In the pursuit of cleaner and more efficient internal combustion engines, dual-fuel strategies combining diesel and hydrogen are gaining increasing attention. This study employs detailed computational fluid dynamics (CFD) simulations to investigate the behaviour of pilot diesel injections in dual-fuel diesel–hydrogen engines. The study aims to characterize spray formation, ignition delay and early combustion phenomena under various energy input levels. Two combustion models were evaluated to determine their performance under these specific conditions: Tabulated Well Mixed (TWM) and Representative Interactive Flamelet (RIF). After an initial numerical validation using dual-fuel constant-volume vessel experiments, the models are further validated using in-cylinder pressure measurements and high-speed natural combustion luminosity imaging acquired from a large-bore optical engine. Particular attention was given to ignition location due to its influence on subsequent hydrogen ignition. Results show that both combustion models reproduce the experimental behavior reasonably well at high energy input levels (EILs). At low EILs, the RIF model better captures the ignition delay; however, due to its single-flamelet formulation, it predicts an abrupt ignition of all available premixed charge in the computational domain once ignition conditions are reached in the mixture fraction space. Full article

(This article belongs to the Special Issue Numerical and Experimental Study of Alternative Fuel Combustion in Internal Combustion Engines)

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17 pages, 1971 KB

Open AccessArticle

Heavy Knocking Suppression and NO_X Emission Reduction by Means of Port Water Injection on a CFR SI Engine

by Emiliano Pipitone, Giuseppe Ingrassia and Michele Agueci

Energies 2026, 19(2), 339; https://doi.org/10.3390/en19020339 - 9 Jan 2026

Viewed by 619

Abstract

The energy transition in the transportation sector makes hydrogen a promising candidate as a fuel for internal combustion engines; however, its tendency to knock limits its use to lean mixtures, resulting in a reduction in performance. In this context, water injection represents a technical solution capable of reducing both the risk of knocking and the pollutant emissions of nitrogen oxide (NOx). Although several studies have been published on the benefits of water injection, its capacity to suppress high-intensity knocking phenomena was never investigated and is not traceable in the scientific literature. On account of this lack, the authors of the present paper experimentally evaluate the effectiveness of port water injection in suppressing high-intensity knock phenomena and its potential in terms of nitrogen oxide emission reduction. Differently from previous works, a highly reactive fuel (PRF60) was adopted to reproduce, as closely as possible, the knocking tendency of hydrogen. The tests were carried out on a single-cylinder CFR engine, suitably modified to allow port water injection, operating with stoichiometric air–fuel mixture (λ = 1) and at low engine speed, which constitutes the most critical condition, since it allows for heavy knocking and is less favorable for injected water evaporation. Moreover, aiming to assess the effect of spray atomization, the tests were repeated using three different water injection pressure levels. The study presented, however, is confined to the effects of port water injection on knock suppression and NOx emission reduction, while no engine performance or efficiency variation were considered. The results showed that port water injection, with water addition up to 40% by mass with respect to fuel, enables an almost complete suppression of high-intensity knocking phenomena, along with a significant reduction in NOx emissions (up to −62%). Full article

(This article belongs to the Special Issue Numerical and Experimental Study of Alternative Fuel Combustion in Internal Combustion Engines)

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19 pages, 3839 KB

Open AccessArticle

Usefulness of Rapeseed Oil Modified by n-Hexane and Ethanol as Diesel Fuel

by Rafał Longwic, Przemysław Sander, Anna Zdziennicka, Katarzyna Szymczyk, Bronisław Jańczuk, Jerzy Merkisz and Krzysztof Górski

Energies 2025, 18(24), 6455; https://doi.org/10.3390/en18246455 - 10 Dec 2025

Viewed by 663

Abstract

An attempt was made to adapt the physical and chemical characteristics of rapeseed oil (Ro), including its density, viscosity and surface tension to diesel oil in the aspect of its use as a biofuel in diesel engines by adding 10 and/or 15 percent n-hexane to the oil and contacting the obtained mixture with ethanol. After establishing an equilibrium of ethanol extraction in the phase containing a mixture of Ro and n-hexane and the mixture components in ethanol, measurements of the viscosity, surface tension and density of oil phases were performed. The obtained values of these physicochemical parameters for the Ro and n-hexane mixture phase were close to those of diesel oil. Next, engine tests were carried out on the Ro+n-hexane mixture after its contact with ethanol under real driving conditions. The tests showed that the mixture of rapeseed oil with 10% n-hexane in contact with ethanol achieved the highest torque and power values among all Ro-based fuels, and that the decrease in these parameters compared to diesel fuel was the smallest. Moreover, compared to Ro and the mixture of Ro with 10% n-hexane, a higher energy efficiency was obtained, which is due to the favorable physicochemical properties of the fuel—the reduced viscosity and improved volatility. Full article

(This article belongs to the Special Issue Numerical and Experimental Study of Alternative Fuel Combustion in Internal Combustion Engines)

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15 pages, 4479 KB

Open AccessArticle

Impact of Ethanol–Diesel Blend on CI Engine Performance and Emissions

by Mieczysław Sikora, Piotr Orliński and Mateusz Bednarski

Energies 2025, 18(9), 2277; https://doi.org/10.3390/en18092277 - 29 Apr 2025

Cited by 1 | Viewed by 1822

Abstract

The aim of this study was to assess the impact of adding ethanol to diesel fuel on particulate matter (PM) and nitrogen oxides (NOx) emissions in the Perkins 854E compression-ignition engine. Tests were carried out under European Stationary Cycle (ESC) conditions using the Horiba Mexa 1230 PM analyzer (HORIBA, Ltd., Kyoto, Japan) for particulate measurement and the AVL CEB II analyzer (AVL, Graz, Austria) for NO_x concentration. The engine under investigation featured direct injection, turbocharging, a common-rail fuel supply system, and complied with the Stage IIIB/Tier 4 emission standard. Two types of fuel were used: conventional diesel fuel (DF) and diesel with a 10% ethanol additive by volume (DFE10). In addition to emissions measurements, key engine performance parameters, such as torque, effective power, and fuel consumption, were analyzed. The ESC test was specifically chosen to isolate the influence of the fuel’s properties by avoiding the effects of changes in combustion control strategies. Due to the lower calorific value of DFE10 compared to DF, a slight increase in fuel consumption was observed under certain operating conditions. Nevertheless, overall engine performance remained largely unchanged. The test results showed that the use of DFE10 led to a significant 44% reduction in particulate matter emissions and a moderate 2.2% decrease in NO_x emissions compared to conventional diesel fuel. These findings highlight the potential of ethanol as a diesel fuel additive to reduce harmful exhaust emissions without negatively affecting the performance of modern diesel engines. Full article

(This article belongs to the Special Issue Numerical and Experimental Study of Alternative Fuel Combustion in Internal Combustion Engines)

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