Dual-fuel Internal Combustion Engines Research Articles

Prediction of Efficiency, Performance, and Emissions Based on a Validated Simulation Model in Hydrogen–Gasoline Dual-Fuel Internal Combustion Engines

This study explores the performance and emissions characteristics of a dual-fuel internal combustion engine operating on a blend of hydrogen and gasoline. This research began with a baseline simulation of a conventional gasoline engine, which was subsequently validated through experimental testing on an AVL testbed. The simulation results closely matched the testbed data, confirming the accuracy of the model, with deviations within 5%. Building on this validated model, a hydrogen–gasoline dual-fuel engine simulation was developed. The predictive simulation revealed an approximately 5% increase in overall engine efficiency at the optimal operating point, primarily due to hydrogen’s combustion properties. Additionally, the injected gasoline mass and CO₂ emissions were reduced by around 30% across the RPM range. However, the introduction of hydrogen also resulted in a slight reduction (~10%) in torque, attributed to the lower volumetric efficiency caused by hydrogen displacing intake air. While CO emissions were significantly reduced, NOₓ emissions nearly doubled due to the higher combustion temperatures associated with hydrogen. This research demonstrates the potential of hydrogen–gasoline dual-fuel systems in reducing carbon emissions, while highlighting the need for further optimization to balance performance with environmental impact.

Phenomenological model for unburned hydrocarbon emissions from spark-ignition, pre-chamber, and dual-fuel internal combustion engines

Considering the strict regulations on the transport sector emissions, predictive models for engine emissions are essential tools to optimize high-efficient low-emission internal combustion engines (ICE) for vehicles. This aspect is of major importance, especially for developing new combustion concepts (e.g. lean, pre-chamber) or using alternative fuels. Among the gaseous emissions from spark-ignition (SI) engines, unburned hydrocarbons (uHC) are the most challenging species to model due to the complexity of the formation mechanisms. Phenomenological models are successfully used in these cases to predict emissions with a reduced computational effort. In this work, uHC phenomenological model approaches by the authors are further developed to improve the model predictivity for multiple variations including engine design, engine operating parameters, as well as different fuels and ignition methods. The model accounts for uHC contributions from piston top-land crevice, wall flame quenching, oil film fuel adsorption/desorption and features a tabulated-chemistry approach to describe uHC post-oxidation. With the support of 3D-CFD simulations, multiple novel modelling assumptions are developed and verified. The model is validated against an extensive measurement database obtained with two small-bore single-cylinder engines (SCE) fuelled with gasoline-like fuel, one with SI and one with pre-chamber, as well as against data from two different ultra-lean large-bore engines fuelled with natural gas (one equipped with a pre-chamber and one dual-fuel with a diesel pilot). The model correctly predicts the trends and absolute values of uHC emissions for all the operating conditions and the engines with an accuracy on average of 11.4%. The results demonstrate the general applicability of the model to different engine designs, the correct description of the main mechanisms contributing to fuel partial oxidation, and the potential to be extended to predict unburned fuel emissions with other fuels.

Effect of liquid ammonia HPDI strategies on combustion characteristics and emission formation of ammonia-diesel dual-fuel heavy-duty engines

Reducing carbon emissions from internal combustion engines has become a crucial topic due to the pressure brought about by global warming. Ammonia, a carbon-free fuel, has significant potential for heavy-duty diesel engine applications. However, the laminar flame speed of ammonia fuel is relatively slow, resulting in suboptimal combustion performance. Therefore, the present study focuses on ammonia-diesel dual-fuel heavy-duty engines. A novel liquid ammonia high-pressure direct injection (HPDI) strategy has been developed to address the challenges associated with poor combustion performance and increased unburned ammonia emissions in ammonia-diesel dual-fuel internal combustion engines. Firstly, a three-dimensional numerical simulation method was utilized to establish and verify a model of a heavy-duty internal combustion engine that incorporates HPDI of liquid ammonia. Afterward, numerical studies comparing the engine's combustion and emission characteristics are conducted with varied ammonia energy fractions, liquid ammonia injection timings, and liquid ammonia injection directions. The results indicate that, compared to the pure diesel mode, the novel liquid ammonia HPDI strategy can alter the combustion mode, significantly improving fuel–air mixture efficiency. This leads to more thorough combustion. After replacing 80% of the fuel energy input with ammonia, there is still an increase of 8.9% in indicated mean effective pressure and a 10.6% improvement in indicated thermal efficiency. Moreover, modifying the HPDI strategy reduces greenhouse gas emissions effectively, and due to the thermal de-NOx reaction, there is a notable decrease in NOx emissions. Furthermore, by altering the liquid ammonia injection timing and direction, finer control of fuel combustion and pollutant generation can be achieved, thereby reducing unburned ammonia emissions in conditions of high ammonia energy fractions.

BACKGROUND FOR THE USE OF HYDROGEN IN UKRAINE IN THE ENERGY AND AUTOMOTIVE SECTORS

Based on the global trends, the article substantiates the place of hydrogen and hydrogen technologies in the further decarbonisation of the energy sector and road transport in Ukraine. The variety of methods of production, transportation and storage, and the use of hydrogen of different purity require complex trade-offs between the cost of the technology and the amount of possible emissions of harmful substances into the environment at all related stages of application of these technologies. Hydrogen fuels and hydrogen technologies should be positioned as one of the areas of energy transition of economic sectors to decarbonisation, which will lead to the development of climate-neutral technologies. Traditional reciprocating internal combustion engines (ICE) can be upgraded to run on purely hydrogen fuel, but this requires the use of new materials due to the high specific energy intensity of hydrogen. The combustion of hydrogen in ICE combustion chambers is hindered by nitrogen oxide (NOX) emission restrictions. A possible option is to use a mixture of hydrogen and natural gas or to upgrade dual-fuel internal combustion engines. This is the most realistic option for Ukraine at this point. In light of the decarbonisation process, the main advantage of fuel cells (FC) is the absence of hydrocarbon combustion and, accordingly, the ability to reduce air pollution with the greenhouse gas CO2. Existing FC can operate not only on hydrogen but also on natural gas. In the energy sector, hydrogen technologies compete not with traditional methods of generating heat and electricity, but with bioenergy, heat pumps, and technologies for capturing and storing carbon and its oxides. In the automotive sector, hydrogen technologies compete with liquid and gaseous biofuels, electric vehicles and hybrids with internal combustion engines and batteries. The potential application of hydrogen technologies for decarbonisation processes will only be unlocked once a hydrogen market and the relevant infrastructure are in place. The segment and price of hydrogen technologies depend on by the method of production process chosen, as well as the infrastructure components, including storage, transportation and fuelling stations. The safe operation and implementation of hydrogen technologies in Ukraine requires qualified engineering staff. The training of such specialists for the energy and transport sectors can be taken on by universities by universities in the speciality 142 – energy engineering.

Experimental study on the load control strategy of ammonia-hydrogen dual-fuel internal combustion engine for hybrid power system

The development of hybrid technology and the use of zero-carbon fuels are effective means to improve energy efficiency and reduce carbon emissions. In this study, the Miller cycle spark ignition engine was used, and four load control strategies of throttle, ammonia-hydrogen ratio, air–fuel ratio, and variable valve timing were used to conduct experimental research on the ammonia-hydrogen engine. The experimental results show that the throttle strategy provides the widest output range, and the BMEP is raised from a minimum of 1 bar to 7.4 bar. The ammonia-hydrogen mixing ratio strategy is suitable for cold start conditions, fully utilizing the good combustion characteristics of hydrogen, and at the same time reducing the amount of hydrogen used in the heat engine process as much as possible. The air–fuel ratio strategy provides the highest thermal efficiency with a maximum BTE approaching 40%. It satisfies the energy-saving demand under the single-point working condition of the engine in the series mode. The variable valve timing strategy can realize switching between BMEP between 3.5 bar and 6.5 bar, and keep BTE above 33%. The valve timing strategy can not only provide a wider load adjustment range but also maintain high thermal efficiency. Finally, combining the effects of the four control strategies and the typical operating modes of the hybrid system, this study suggests that the throttle strategy is suitable for the feed mode, the VVT strategy is suitable for the parallel mode, the ammonia-hydrogen mixture ratio strategy is suitable for the cold start condition, and the air–fuel ratio control is suitable for the series mode.

Special issue on “Optimal design and operation of energy systems”

Special issue on “Optimal design and operation of energy systems”

Impact of SOFC Power Generation Plant on Carbon Intensity Index (CII) Calculation for Cruise Ships

The International Maritime Organization (IMO) has recently discussed the introduction of a new design index called the Carbon Intensity Indicator (CII), which is a measure of the total carbon dioxide emissions divided by the amount of cargo carried and by the distance travelled on a one-year basis. In this study, authors have analysed a cruise ship assuming its size, the electrical and thermal power required, and its operative profile. CII is calculated with reference to a 180,000 GRT cruise ship equipped with different possible power plant configurations. Emissions in these scenarios are abated by employing alternative fuels like Liquefied Natural Gas (LNG), a shore connection, or innovative technologies like Solid Oxide Fuel Cells (SOFC). The analysis affirms that a cruise ship powered only by MGO from 2024 will not comply with the CII regulation. Results highlight the potential of LNG in reducing carbon dioxide emissions and, for the reference vessel, the use of LNG alone can guarantee a maximum CII rating up to 2026. The benefits of the installation of 10 MW of SOFC are relevant and similar to the one archived with a power plant composed of dual-fuel internal combustion engines and a shore connection.

Numerical investigation of droplet evaporation in high-pressure dual-fuel conditions using a tabulated real-fluid model

The substitution of diesel by cleaner renewable fuels such as short-chain alcohols in dual-fuel internal combustion engines is considered an attractive solution to reduce the pollutant emissions from internal combustion engines. In this context, two-phase flow models for multi-component mixtures considering the real-fluid thermodynamics are required for further understanding the evaporation and mixing processes in transcritical conditions. The present study proposes an efficient real-fluid model (RFM) based on a two-phase, fully compressible four-equation model under mechanical and thermal equilibrium assumptions with a diffused interface and closed by a thermodynamic equilibrium tabulation approach. Compared to previous research limited to binary mixtures tabulation, the proposed pre-tabulation approach can further handle ternary mixtures using a thermodynamic table that has been coupled to the CONVERGE CFD solver. The newly developed RFM model has been applied to investigate the evaporation of an n-dodecane droplet in a mixed ambient (methanol and nitrogen) relevant to dual-fuel configuration compared to pure nitrogen ambient. The four equation model is closed by a tabulated Cubic Plus Association (CPA) and Peng–Robinson (PR) equations of state for the droplet evaporation in a mixed and single component ambient, respectively. Numerical predictions show that the n-dodecane droplet lifetime decreases monotonically with increasing the methanol ambient concentration under the considered transcritical conditions. The performed thermodynamic analysis demonstrates that the droplet follows a different thermodynamic path as a function of the methanol ambient concentration. The different mechanisms contributing to the droplet lifetime behavior under varying ambient conditions are discussed.

Analysis of LNG carrier propulsion developments

The LNG market has undergone major changes and significant development in recent years. With the increase in the number of ships and the increase in the amount of gas transported, the propulsion machinery of LNG ships has also changed. For many years, the steam turbine was the only propulsion engine on this type of cargo ship. A negligible number of vessels powered by a traditional, low-speed, heavy-duty diesel engines are increasingly being replaced by new technologies. Versions of dual-fuel internal combustion engines that burn evaporated natural gas are increasingly replacing steam turbine propulsion systems. This phenomenon has been particularly pronounced in the last few years, when orders for steam turbine-powered LNG vessels have ceased. This article examines and presents the main reasons for these changes, which fall into two categories. The first is financial, as the use of new technologies can lead to significant financial savings in fuel consumption. Fuel costs can be reduced by more than 35% in some cases. The reduction in fuel consumption leads to a significant reduction in overall exhaust emissions and thus a reduction in air pollution and CO2 signature.

Current status of research on the effect of injection timing on the performance of dual-fuel internal combustion engines

In order to optimize the power, economy and emission of dual-fuel internal combustion engine, this paper summarizes the effect of different injection timings on the combustion performance and emission of mixed fuels such as natural gas diesel, and the selection of suitable injection timings in different mixed fuel combustion can significantly reduce carbon smoke and NOx emission, and can maintain the basic consistency with pure diesel combustion in terms of power and economy. Finally, it is pointed out that under the pressure of environmental pollution, global warming and energy crisis, new technologies of clean, efficient and energy-saving internal combustion engines are emerging, and China should pay full attention to clean and efficient internal combustion engine technology when formulating the development plan of automobiles, and on this basis, the research on the combustion performance of dual-fuel internal combustion engines relative to the injection timing also needs to be continuously deepened.

Development of thermosyphon controlled adsorptive natural gas storage system

Natural gas is considered a potentially available and ecologically preferable fuel, comparing to other liquid fossil fuels. Safe and sustainable energy storage device is one of the bases for changing the current energy systems. The system is to use tank packed with porous solid that can selectively adsorb methane at a gas pressure of 3.5–6 MPa. This low storage pressure in the gas tank reduces both the cost of compression and that of the storage tank, and poses less of a safety hazard than higher pressures used for compressed natural gas. The focus was the study of the effect exerted by the hybrid cooling technology and sorbent characteristics on the gas reserve. For dual-fuel internal combustion engines, a modular adsorbed natural gas (ANG) tank with an active and passive thermal control system was proposed. Dynamic charging is analyzed using a numerical model of the real properties of the sorbent and reservoir design. Novel thermosyphons with annular channels in long horizontal evaporators and a cold gas circulation loop made it possible to stimulate gas adsorption and avoid the rise of temperature in the sorbent bed during filling the tank with a gas at gas stations. They are capable of transporting energy for a distance of some meters which is difficult to be realized by horizontally disposed conventional thermosyphons and heat pipes.

Prospects, progress, challenges and policies for clean power generation from biomass resources

Worldwide primary energy needs are satisfied basically from non-renewable sources that are limited in supply and innately hazardous to the environment. Biomass-based power systems are very much potent to address the environmental issues fostering sustainable development, while being able to provide a secured and uninterrupted power supply at the same time. Biomass-based power generation systems not only reduce the GHG emissions but also have enormous opportunities of job creation and promote biomass re-growth through sustainable land management practices. This paper overviews the biomass scenario in Southeast Asian and EU countries to give an overview of the potential and scalable energy harnessed from biomass resources. Economic analyses presented on biomass gasification-based power generation have been evaluated with three specific cost estimations, namely low, average and high. Key economic performance metrics of biomass gasification-based dual-fuel internal combustion engine generator with low investment estimates are as follows: a positive net present value of USD 7.5 million; internal rate of return 14.45%; and a payback period of 5.45 years. A review of the technologies can provide a base for strategic energy policy for the next generation of sustainable energy policies and helps policymakers to frame strategies aiming for clean technology and sustainable development. Biomass integrated gasification combined cycle-based systems are found to be most suitable for power generation or biofuel synthesis.

A novel technique for detailed and time-efficient combustion modeling of fumigated dual-fuel internal combustion engines

The present work details a study of the 3D-modeling of dual-fuel engines, with a specific focus on medium speed marine engines. These operate under the fumigated approach, which means that the second fuel, which replaces most of the diesel fuel, is added in the intake duct. This type of engine requires the least amount of modifications to the current medium speed diesel engine and is therefore an ideal retrofit solution to tackle global warming and local air quality issues. In this work, the operation of such an engine has been modeled, with special care for the combustion modeling. Namely, it comprises both auto-ignition of the diesel pilot, and flame propagation in the premixed fuel-air mixture. A tabulated kinetics approach, currently being used to model diesel operation, has been extended to include this flame propagation. Both a Coherent Flame Model (CFM) and a Flame Surface Wrinkling Model (FSWM) have been implemented to handle this premixed combustion mode. Coupling a flame propagation model to the tabulated chemistry should provide a practical way of capturing both the complex dual-fuel combustion process as the chemistry information, while maintaining an acceptable computation time. Additionally, a tabulated laminar flame speed method has also been implemented. Experimental results were obtained on the operation of a medium-speed engine in diesel, natural gas/diesel dual-fuel and methanol/diesel dual-fuel mode, under varying operating loads and speeds. Results have been compared to the ones obtained from the simulations performed in OpenFOAM with the dedicated combustion modeling technique. It was found that while both FSWM and CFM capture some physical trends, they are currently not able of capturing the dual-fuel combustion process in total. Improvements with regards to the ignition and mixing-controlled combustion modeling are necessary, since the current approach is not able of fully capturing the dual-fuel phenomena. This work however provides insight in the complex combustion process and serves as a basis for further developments. It can also be used as an initial engine development tool for fast calculation and optimization of dual-fuel operation.

Auto Ignition Study of Methane and Bio Alcohol Fuel Blends

Abstract Methane (CH4) and bio alcohols have different ignition properties. These have been extensively studied and the resulting experimental data have been used to validate chemical kinetic models. Methane is the main component of natural gas, which is of interest because of its relative availability and lower emissions compared to other hydrocarbon fuels. Given growing interest in fuel-flexible systems, there can be situations in which the combustion properties of natural gas need to be modified by adding biofuels such as bio alcohols. This can occur in dual-fuel internal combustion engines or gas turbines with dual-fuel capabilities. The combustion behavior of such blends can be understood by studying the auto ignition properties in fundamental combustion experiments. Studies of the ignition of such blends are very limited in the literature. In this work, the auto ignition of methane and bio alcohol fuel blends is investigated using a shock tube facility. The chosen bio alcohols are ethanol (C2H5OH) and n-propanol (NC3H7OH). Experiments are carried out at 3 atm and 10 atm for stoichiometric and lean mixtures of fuel, oxygen, and argon. The ignition delay times of the pure fuels are first established at conditions of constant oxygen concentration and comparable pressures. The ignition delay times of blends with 50% methane are then measured. The pyrolysis kinetics of the blends is further explored by measuring CO formation during pyrolysis of the alcohol and methane–alcohol blends. The resulting experimental data are compared with the predictions of selected chemical kinetic models to establish the ability of these models to predict the disproportionate enhancement of methane ignition by the added alcohol.

Analysis of the Possibility of Using Low Speed Two-Stroke Dual-Fuel Engines for Propulsion of Sea-Going Vessels

Abstract The use of gas/LNG to supply marine engines in addition to tangible economic benefits is also a method of limiting emissions of harmful substances into the atmosphere and meeting strict environmental protection regulations, especially in special areas. The technology of supplying liquid and gas fuels (Dual Fuel) is most easily used in four-stroke engines but the highest thermal efficiency is ensured by combustion two-stroke piston engines. However, in the first two-stroke dual-fuel engines, the gas supply installation was more complicated than in the four-stroke engine. It resulted, among others from the necessity of compressing the gas to high pressures (15÷30 MPa), for which extremely energy-consuming multi-stage compression systems were needed. The complicated technical system is inherently prone to failures, which is why the dual-fuel low-speed two-stroke diesel engines remained for a long period in the design and experimental phase. In recent years, there has been a significant breakthrough thanks to the introduction of new solutions with the possibility of supplying two-stroke engines with low-pressure gas (less than 1.6 MPa). In recent years, many ships powered by two-stroke, dual-fuel internal combustion engines were commissioned. Some ship-owners owning a fleet of LNG carriers with two-stroke diesel engines that so far have been powered only by liquid fuels have decided to adapt them to gas combustion. This required the adaptation of the engine for gas combustion and the expansion of the supply gas fuel system. This paper is an attempt to analyse the legitimacy of introducing two-stroke, dual-fuel internal combustion engines into the propulsion system and adaptation of engines that are already used to burn gas in them. It presents the changes introduced on one of the LNG gas carriers consisting in adapting the engine to gas combustion through modification of the cylinder head and fuel supply installation. Parameter results of the modified engines obtained during sea trials have been presented. Both advantages and disadvantages resulting from gas combustion have been pointed out. Finally, the possibility of this solution application to other LNG carriers was assessed.

A fully renewable and efficient backup power system with a hydrogen-biodiesel-fueled IC engine

Renewable energy is free, abundant, clean and could contribute towards a significant reduction of the global warming emissions. It is massively introduced as a source of electricity production across the globe and is expected to become the primary source of energy within the following decades. However, despite the naturally replenished energy, the supply is not always available. For this reason, it is necessary at times of excess energy, any surplus quantity to be sufficiently captured, stored and later used when a deficit occurs. In this paper, an overview of a backup power system operating with a hydrogen-biodiesel dual-fuel internal combustion engine is provided. The system is utilizing the organic chemical hydride method for safe hydrogen storage and transportation. The high energy content of hydrogen stored in the form of an organic hydride under ambient conditions makes it an ideal energy backup medium for large-scale and long-term applications. The research work focusses on the operation and emissions output of the dual-fuel internal combustion engine running on fully renewable fuels and the results are compared with the conventional petroleum-derived diesel engine. Biodiesel-hydrogen operation shows significant benefits in the reduction of carbon and soot emissions but deteriorates the NOx formation compared to the conventional diesel-powered engines. The operation of the engine at high loads can provide high exhaust thermal energy while alternative combustion strategies are necessary to be implemented at low load conditions for the optimum operation of the backup power system.

Quantity and Quality of Dual Fuel IC Marine Engine Exhaust Sensible Waste Heat Considering Different Sulphur Content in Fuels

Maritime transport is facing a significant set of technical challenges due to planned by the International Maritime Organization implementation of ecological criterions on 01 January 2020 and 2021 regarding the emission of sulphur oxides, carbon dioxide and nitrogen oxides. The advantageous properties of natural gas (NG) as fuel in conjunction with dual fuel (DF) internal combustion (IC) engines potentially enables the fulfilment of all planned criterions. However, if the methane emission of DF IC is taken into consideration in CO2 emission balance it completely devaluates the advantages arising from high hydrogen to carbon ratio of NG. On the other hand, the planned global sulphur cap in combination with its low content in NG potentially enables to recover higher rates of waste heat and exergy of combustion products without the risk of low temperature corrosion (compared to liquid fuel). In this study the influence of sulphur content in NG and pilot fuel on the sulphuric acid condensation temperature was investigated in order to determine the rate of waste heat (quantity) and exergy (quality) of four stroke DF IC engine combustion products. In ideal process scenario (exergy based) the methane slip effect compensation was achieved only for a 0,5 engine load.

Використання п'єзоприводу для клапана подачі газу двохпаливного двигуна внутрішнього згоряння

Використання п'єзоприводу для клапана подачі газу двохпаливного двигуна внутрішнього згоряння

Modeling and control of fuel distribution in a dual-fuel internal combustion engine leveraging late intake valve closings

In internal combustion engines, cycle-to-cycle and cylinder-to-cylinder variations of the combustion process have been shown to negatively impact the fuel efficiency of the engine and lead to higher exhaust emissions. The combustion variations are generally tied to differences in the composition and condition of the trapped mass throughout each cycle and across individual cylinders. Thus, advanced engines featuring exhaust gas recirculation, flexible valve actuation systems, advanced fueling strategies, and turbocharging systems are prone to exhibit higher variations in the combustion process. In this study, the cylinder-to-cylinder variations of the combustion process in a dual-fuel internal combustion engine leveraging late intake valve closing are investigated and a model to predict and address one of the root causes for these variations across cylinders is developed. The study is conducted on an inline six-cylinder heavy-duty dual-fuel engine equipped with exhaust gas recirculation, a variable geometry turbocharger, and a fully flexible variable intake valve actuation system. The engine is operated with late intake valve closure timings in a dual-fuel combustion mode in which a high reactivity fuel is directly injected into the cylinders and a low reactivity fuel is port injected into the cylinders. The cylinder-to-cylinder variations observed in the study have been associated with the maldistribution of the port-injected fuel, which is exacerbated at late intake valve timings. The resulting difference in indicated mean effective pressure between the cylinders ranges from 9% at an intake valve closing of 570° after top dead center to 38% at an intake valve closing of 620° after top dead center and indicates an increasingly uneven fuel distribution. The study leverages both experimental and simulation studies to investigate the distribution of the port-injected fuel and its impact on cylinder-to-cylinder variation. The effects of intake valve closing as well as the impact of intake runner length on fuel distribution were quantitatively analyzed, and a model was developed that can be used to accurately predict the fuel distribution of the port-injected fuel at different operating conditions with an average estimation error of 1.5% in cylinder-specific fuel flow. A model-based control strategy is implemented to adjust the fueling at each port and shown to significantly reduce the cylinder-to-cylinder variations in fuel distribution.

Cylinder-to-Cylinder Variations in Power Production in a Dual Fuel Internal Combustion Engine Leveraging Late Intake Valve Closings

Cylinder-to-Cylinder Variations in Power Production in a Dual Fuel Internal Combustion Engine Leveraging Late Intake Valve Closings