Fuels For Internal Combustion Engines Research Articles

Comparative Analysis Of Cycle-To-Cycle Variabilities And Combustion Development In An Optical Spark-Ignition Engine Fueled By Pure Hydrogen And Propane: Insights From Chemiluminescence and PI

Hydrogen, derived from renewable sources and devoid of carbon emissions, is a pivotal energy carrier for the future. Representing a viable substitute for fossil fuels in internal combustion engines (ICEs), contemporary studies advocate using very-lean and ultra-lean hydrogen-air mixtures, with a fuel-air equivalence ratio below 0.5, as a potent strategy to reduce NOx emissions in hydrogen-fueled ICEs. An experimental setup with an optical spark-ignition engine was devised to investigate the primary factors influencing cycle-to-cycle variations in H2ICEs by optimizing mixture homogeneity and focusing the study on flame interaction with in-cylinder aerodynamics. Simultaneous in-cylinder pressure, chemiluminescence, and PIV analyses were performed to characterize and compare the behaviors of ultra-lean hydrogen-air and propane-air flames, assessing flame development and cyclic variation features. Results indicate that the flame development of hydrogen and propane is significantly different. Propane exhibited increased in-cylinder pressure trace variability at lean and rich flammability limits with a high flame development difference between fast and slow cycles. In contrast, hydrogen-air mixtures under various equivalence ratios (from very-lean to ultra-lean) presented much more stable in-cylinder pressures. Furthermore, fast propane flames were mainly advected to the cylinder's symmetrical axes, while fast hydrogen flames started further away from the spark plug. Horizontal and vertical PIV measurements showed a single structure flow field over the studied conditions with mainly intensity variations over the measured cycles. Fast flames were associated with more intense tumble motion. The differences between fast and slow flames for hydrogen are attributed to the early flame development. However, after initial differences in flame development over several crank angles, there are similarities in all cycles, suggesting that the low variability in in-cylinder pressures is mostly due to the robustness of hydrogen flame ignition and its independence from in-cylinder flow small variations at the early development phase.

3E analyses of different blend fuels in an internal combustion engine

AbstractIn response to the escalating emphasis on sustainability across diverse sectors, this study addresses the imperative to combat environmental degradation through conscientious development. The primary focus is on assessing the feasibility of replacing fossil fuels with renewable alternatives in internal combustion engines (ICEs) equipped with direct fuel injection. The research employs energy and exergy analyses, coupled with economic analysis, to comprehensively evaluate the performance of fuels and blends. Applying the Lotus Engine software, computational analyses are conducted, taking into account the specific geometry of the engine. Simulations explore different λ‐factors to identify optimal performance configurations for each fuel or blend. Noteworthy outcomes reveal that blends featuring green hydrogen yield remarkable improvements, showing high torque (max. +11.5%), power (max. +14.35%), thermal efficiency (max. +3%), and exergy efficiency (max. +21.56%). These blends also demonstrate reduced operating costs (max. −10%), although with higher exergy losses, indicating areas for potential enhancement. Conversely, fuels containing ethanol show intermediate values between the blends and pure fuels. Consequently, this study effectively establishes the significance of these fuels in ICEs, supported by comprehensive energy, exergy, and economic analyses. The findings underscore the promising potential of renewable fuels as viable alternatives to fossil fuels, marking a substantial stride towards sustainable energy solutions and environmental preservation.

The criteria for qualifying fuels as a replacement fuels for internal combustion engines

The article presents the classification of motor fuels into conventional and unconventional. The concept of replacement fuels is formalized as fuels that can replace conventional petroleum fuels for spark ignition and self-ignition engines without any structural or regulatory changes. The criteria for qualification unconventional fuels as replacement fuels are presented. This article also introduces the results of empirical research conducted on a single-cylinder research engine powered by diesel fuel and rapeseed methyl esters (RME) in summer version and winter version. The engine was tested and the combustion phenomenon in the cylinder was analyzed. Very similar engine properties were observed for diesel fuel and rapeseed methyl esters (RME) in the summer version, while greater differences were found for rapeseed methyl esters (RME) with winter additives. In light of the empirical research and the physicochemical properties of the fuels, it is concluded that RME warrants consideration as replacement fuel for engines with self-ignition, especially in the case of biofuel in the summer version.

Effect of recycled polyethylene catalyst for Mediterranean pine seed shell biomass pyrolysis on hydrogen and methane production

ABSTRACT The present study exhibits the potential of hydrogen and methane gases production from the Mediterranean pine tree seed shell biomass over recycled polyethylene wastes as catalyst. In the study, firstly, the viscosity and density of polyethylene materials and degassing point were determined. The pyrolysis was carried out at a rate of 50 °C/min at 600°C temperature. The obtained gases were analyzed with gas chromatography device. At the last step of the experiments, solid residues were observed under an optical microscope, and their microstructures were also examined. The results showed that Mediterranean pine seed shell biomass and its mixture with low-density polyethylene may produce methane and hydrogen gases. M8 catalyst, which has one of the lowest viscosity values (0.45 gr/10 min.) and highest density values (0.950 gr/cm3) produced the highest methane and hydrogen gas yields. In the pyrolysis experiments, 38.44% CH4, 19.50% CO2 and 42.06% H2 gases were obtained from Mediterranean pine seed shell biomass. Moreover, CO2 emission values of biomass were calculated and compared with DEFRA values. The study demonstrated that, since hydrogen and methane can be obtained through the pyrolysis process, Mediterranean pine tree seed shell can be classified as a new biomass source and has potential to alternative fuel to fossil-based fuels for internal combustion engines.

Comparison and optimization of strategies for ammonia-diesel dual-fuel engine based on reactivity assisted jet ignition and reactivity turbulent jet disturbance under high load conditions

Ammonia (NH3), as a zero carbon, easy to synthesize, and easily obtainable fuel, is one of the choices for future internal combustion engine fuels. However, the slow laminar flames speed and high ignition temperature of NH3 seriously hinder the development of NH3 engines. Efficiently igniting NH3 and ensuring its stable combustion is currently a challenging research topic. Utilizing diesel to optimize the NH3 combustion process is one effective solution. However, the increase of unburned ammonia (UNH3) and unstable combustion, under high load conditions have always been technical challenges that constrain the development of ammonia-diesel dual-fuel (ADDF) engines. Previous studies have found that pre-chambers (PC) have a significant effect on improving ammonia combustion characteristics. Therefore, based on the PC system, this study proposes two combustion modes: Reactivity Assisted Jet Ignition (RAJI) and Reactivity Turbulent Jet Disturbance (RTJD), which greatly optimize the combustion characteristics of ADDF engines under high load conditions. The research results indicate that the RAJI mode effectively improves the thermal environment inside the cylinder. Setting the start of diesel injection of pre-chamber (SODI-PC) at −14 °CA after top dead center (ATDC) can increase the cylinder temperature by 25.05% before the start of diesel injection of main chamber (SODI-MC). The improvement of thermal environment reduces the average generation of N2O to 13.56% of the traditional mode. However, if SODI-PC is postponed to −8 °CA ATDC, the effect of creating a thermal environment is no longer significant. Research on the RTJD mode has found that adopting the RTJD mode can significantly optimize emissions. Compared with traditional modes, N2O, UNH3, and Soot decreased by 28.81%, 27.79%, and 35.08%, respectively. Additionally, SODI-PC is delayed until after 4 °CA ATDC, CO and UHC will be further reduced to 50.00% and 12.24% of the traditional mode, respectively. In addition, the RTJD mode overcomes the deficiency of the slow laminar flame speed of NH3, shortening the combustion duration by 23.46%, and effectively improving the gross indicated thermal efficiency (ITEg) by an average increase of 1.08%, with the highest increase reaching 47.57%. This paper provides ideas for optimizing the structure and strategy of ADDF engines, as well as theoretical support and empirical reference for achieving clean and efficient combustion of engines.

Characteristics of High-Pressure Injection Pump Operated with Renewable Fuel for Diesel Engines

The use of renewable fuels for internal combustion engines marks a significant stride towards sustainability in transportation and power generation. Ensuring the compatibility of these fuels with existing diesel engines and infrastructure is paramount for a smooth transition. Diesel engines capable of harnessing the advantages of alternative fuels without extensive modifications offer a pragmatic approach to sustainable power for vehicles and industries. This article investigates the impact of carbon-neutral renewable fuel types (hydrogenated vegetable oils, or HVOs, and biodiesel) on the operation of a high-pressure injection pump, focusing on rotational speed and delivery pressure as key parameters. Our investigation, based on pump operating cycle analysis and volumetric efficiency measurements, aimed to investigate to what extent shaft speed and fuel type influence pump performance. Hydrogenated carbon-neutral fluids (HVOs) demonstrate adequate hydraulic capabilities compared to conventional fossil fuels. The findings underscore that while the fluids under consideration vary in viscosity and compressibility modulus, it is the compressibility modulus that predominantly affects the pump’s operation cycle. Diesel (fossil) fluid exhibits intermediate characteristics compared to hydrogenated fossil diesel fluids and biodiesel. The differences in terms of volumetric efficiency are finally reported, showing that hydrogenated carbon-neutral fluids do not significantly hinder the pump’s flow rate transfer capability.

An enhanced automated machine learning model for optimizing cycle-to-cycle variation in hydrogen-enriched methanol engines

Renewable methanol and hydrogen have emerged as great potential alternative fuels for internal combustion engines in recent research. Hydrogen exhibits the ability to mitigate cycle-to-cycle variations in methanol engines thanks to its rapid combustion rate. Furthermore, the integration of machine learning with genetic algorithms provides a solution to achieve efficient and clean combustion in hydrogen-enriched methanol engines. Nevertheless, this approach is constrained due to the limited predictive accuracy in small-sample learning. This study aims at introducing an enhanced model based on the automated machine learning framework, and provide a comparative analysis of the enhanced model and computational fluid dynamics simulations in terms of multi-objective optimization performance and computational time. Additionally, this study further considered the effect of engine cycle-to-cycle variations on performance, ultimately attaining optimal operating parameters for stable combustion. The results indicate that datasets actively created by genetic algorithms are more effective than those generated through Latin hypercube sampling. The introduction of a classification model for the identification of misfires has enhanced the efficiency of dataset utilization. Through feature construction, the automated machine learning model demonstrates improvements in R-square and mean-squared error for all parameters on the test dataset. Furthermore, by employing a larger overall population size, the automated machine learning model has not only achieved a higher-quality Pareto fronts compared to the computational fluid dynamics method but has also significantly reduced computation time, particularly upon introducing additional engine cycle-to-cycle variations constraints.

Aspects of the combustion variability analysis at an automotive engine fuelled with hydrogen

Over the last decades, the use of the alternative fuels was one of the main research activities for specialists in the field of internal combustion engines. The development of the modern automotive engines is constantly challenged by the more severe emission legislation. The engine emissions levels and the fuel efficiency are directly influenced by the engine operation, reproduction of the combustion phases from one cycle to other, cyclic dispersion during combustion process being important. In general, the use of alternative fuels in internal combustion engines provides an improvement of the energetic and pollution performance, or just a slight improvement of them, but the study of the combustion process must be completed with aspects regarding the cyclic variability. In particular, using this alternative fuel, a study of cyclic variation of the combustion process would be necessary in order to establish if the normal operation of the engine can be ensured. The paper presents some aspects of the analysis of the cyclic variability at a spark ignition engine fuelled with gasoline and hydrogen. During the engine operation at the regime of 2500 rev/min speed and 55% engine load, a number of 250 consecutive combustion cycles was recorded for classic fuel use and for hydrogen use. The coefficient of cyclic variation (CCV) or the coefficient of variation (COV) is determined for different combustion parameters such as maximum pressure, maximum pressure rise rate and mass fraction burned, defined by angles at which the conventional fractions of 10%, 50% and 90% of the heat of reaction is released. Thus, the values of the COV for maximum pressure (COV)pmax, maximum pressure rise rate (COV)dp/dα, angles of 10, 50 and 90% heat release as (COV)10%, (COV)50% and (COV)90% were calculated and compared with the admissible limit of 10%. The combustion variability analysis establishes the limits of the normal operation of the spark ignition engine fuelled with gasoline and hydrogen compared with the classic fuelling method.

Evaluation of CI Engine Performance Using Compression Ratio for Palm Oil Biodiesel

The experiment explores vegetable oils as potential future fuels for internal combustion engines, particularly compression ignition engines designed for diesel. However, these oils have distinct properties from diesel, requiring modifications for direct use. Integration approaches include adjusting oil properties or adapting engines. Commonly, transesterification aligns oil properties, but using biodiesel often affects engine performance. In this study palm oil biodiesel as a diesel substitute, evaluating engine performance and emissions. In a short-term test, engine performance and emission traits by employing biodiesel compression ratio of 12:1, 14:1 and 18:1 with diesel at full load. Findings indicated that 14:1 and 18:1 exhibited 1.01 % and 1.02 % higher brake power than pure diesel. Volumetric efficiency percentages were 82.33 for 14:1, 82.36 for 18:1, and 82.30 for 12:1. Notably, 14:1 and 18:1 showed 5.44% and 10.90 % increased brake thermal efficiency compared to diesel. Interestingly, 14:1 and 18:1 displayed 2.35 % and 2.61 % higher mechanical efficiency than diesel. The exhaust gas temperature was notably decreased in 12:1 to 18:1 compression ratio. Nitric oxide concentrations were 65.07 ppm for 12:1, 124.44 ppm for 14:1, and 126.48 ppm for 18:1. Carbon dioxide levels increased by 9.79 % for 14:1 and 62.47 % for 18:1 relative to diesel. Carbon monoxide concentrations were 0.07 % for 14:1 and 0.05% for 18:1, in contrast to diesel's 0.12%.

EXPERIMENTAL AND REGRESSION ANALYSIS OF COMPRESSION IGNITION ENGINE POWERED BY DIESEL SURROGATE FUEL FROM USED LUBRICATING OIL USING MICROWAVE PYROLYSIS

Fossil fuels are depleting rapidly, and the search for alternative fuels has become inevitable. The researchers investigated the usage of surrogate fuels for internal combustion engines due to the high demand for diesel fuel in all sectors. Diesel surrogate fuels (DSFs) from used lubricating oil seem to be a solution for the future. The disposal of used lube oils poses a major environmental issue that affects the entire planet. This study aims to anticipate the exhaust emissions, brake-specific fuel consumption (BSFC), and brake thermal efficiency (BTE) of a compression ignition engine powered by blends. The blends used are B10 (DSF10% + diesel 90%), B20 (DSF20% + diesel 80%), B30 (DSF30% + diesel 70%), and B50 (DSF50% + diesel 50%) of DSF with diesel through microwave-assisted pyrolysis of used lubricating oil as fuel. Experimental findings were applied to predict each condition's performance characteristics. To estimate the performance characteristics, regression analysis was employed using experimental data in Microsoft Excel and Design Expert-12 software. The experimental data were compared to the simulated data. It was observed that fuel obtained from used lubricating oil using microwave-assisted pyrolysis could be used to power diesel engines without making any changes to the existing engines because the chemical characteristics of the diesel surrogate fuel were almost identical to those of diesel. The BTE of a compression ignition engine with DSF was close when compared to diesel up to full loading condition. At 1.924 kW brake power, the DSF30% has a higher efficiency than the other three blends. It was also observed that the rise in brake power also raises BSFC, thereby lowering thermal efficiency.

Effects of Injection Parameters and EHN Mixing on the Combustion Characteristics of Fueling Pure Methanol in a Compression Ignition Engine

As one of the most ideal alternative fuels for internal combustion engines, methanol can achieve near-zero carbon emissions. The main problem of methanol application in compression combustion engines is the phase lag caused by its poor combustion characteristics, but under low load conditions, the fuel activity can be improved by adding the cetane number improver EHN (Isooctyl nitrate), and the dependence on intake heating can be reduced to a certain extent. Based on a three-dimensional CFD simulation, the effects of methanol injection parameters and the addition of EHN on the combustion characteristics of a four-stroke exhaust turbocharged diesel engine were studied in this paper. With or without EHN, the increase in injection pressure and the advance in injection timing lead to an increase in the peak temperature, pressure, and heat release rate, as well as a shortening of the combustion duration. Adding EHN witnesses reduced requirements for methanol ignition, including a decreased peak temperature, pressure, and heat release rate, a significantly shortened ignition delay period, and an extended combustion duration, which thus results in a reduced indicated thermal efficiency. This study innovatively develops a 3D model of a compression combustion engine applicable to in-cylinder direct injection pure methanol fuel and EHN under small load conditions, which provides a reference for future research and development of small-load pure methanol compression combustion engines and has certain guiding significance.

Direct Numerical Simulation of Atomization Characteristics of ECN Spray-G Injector: In-Nozzle Fluid Flow and Breakup Processes

AbstractIn order to sustain applications dealing with various liquid fuels in internal combustion engine (ICE), it is essential to make available prediction methodologies that allow an early evaluation of the potential usefulness of such fuels in terms of favourable mixture preparation process already in realistic configurations. Since the air-mixture formation and subsequent processes are predominantly governed by the fuel injection, a DNS based numerical investigation coupled with VOF as an interface tracking method is carried out in this paper to gain better insight on the fuel injection from an industrial injector "Spray G" configuration. Chosen from Engine Combustion Network (ECN), this is a gasoline direct injector (GDI) featuring 8-holes orifices and operating with high injection pressure (200 bar). Under consideration of the required computational cost associated with DNS, only the 1/8 of the nozzle geometry including one orifice is used. The numerical simulation is accomplished for the quasi-steady injection condition with nozzle needle fully opened. The obtained results are first validated with available experimental data for nozzle mass flow rate and spray spread angle showing a good agreement. Then, a detailed numerical analysis is provided for the in/near nozzle flow evolution especially for flow turbulence, primary and secondary atomization. Furthermore, droplet statistics in terms of droplet shape, and droplet size-velocity distribution together with a breakup regime map are reported. Finally, a 2-D data curation technique is proposed to extract the droplet statistics along selected planes and evaluated by direct comparison with three-dimensional droplet data, which may allow handling of the DNS data in more feasible and economical way especially for time series data with higher frequency. The comprehensive DNS data generated by this DNS-VOF approach enable not only to carry out detailed numerical analysis of in- and near-nozzle physical phenomena for which experimental data are still scarce, but also to provide a hint of more reliable injector boundary conditions useful for lower order spray injection method based on Lagrangian particle tracking.

Experimental Analysis of Hydrogen Enrichment in Waste Plastic Oil Blends for Dual-Fuel Common Rail Direct Injection Diesel Engines

Abstract Growing global concerns about fossil fuels highlight the importance of alternative fuels for internal combustion engines. Proper management of plastic waste is crucial due to its environmental impact. The pyrolysis oil process offers a sustainable solution to address plastic waste accumulation. This study explores the impact of a hydrogen-waste plastic oil blend on a modern diesel engine. The research delves into plastic oil and diesel blends at 10%, 20%, and 30% concentrations, with hydrogen provided at 8 L/min. Experiments are conducted at various loads, and hydrogen-enriched fuel blends are analyzed for combustion characteristics, performance parameters, and emissions. Higher blended fuel ratios lead to extended ignition delays, decreased thermal efficiency, and increased emissions. Hydrogen enrichment reduces carbon dioxide, hydrocarbon, and carbon monoxide emissions but raises nitrogen oxide emissions due to higher exhaust gas temperatures. The comparative analysis shows significant improvements in brake thermal efficiency and brake-specific fuel consumption under full load conditions. The blend demonstrates notable reductions in hydrocarbon, carbon monoxide, and carbon dioxide emissions but an increase in nitrogen oxide emissions compared to diesel. The findings indicate that integrating hydrogen into diesel engines enhances performance measures and reduces overall emissions.

Preliminary assessment of the potential for rapid combustion of pure ammonia in engine cylinders using the multiple spark ignition strategy

In pursuit of carbon neutrality, the adoption of zero-carbon fuels in internal combustion engines offers a path to zero carbon emissions. Among such fuels, ammonia (NH3) stands out as an effective hydrogen energy carrier with a higher energy density and a more advanced production-storage-transportation lifecycle than hydrogen (H2) fuel, making it a superior alternative. Nevertheless, achieving high combustion efficiencies in engine cylinders requires the use of fuels with fast flame speeds, since the time scales of the combustion event are practically milliseconds. The inherent flame speed of NH3 falls short, typically necessitating augmentation with H2. Yet, the in-situ generation of H2 from NH3 remains constrained, rendering the flame speed of NH3 less competitive against traditional fuels like gasoline and natural gas. To address the dual challenges of slow flame speed of NH3 and the difficulty of generating large amounts of H2 from NH3 onboard, this study evaluates an alternative method of accelerating the ammonia combustion in the engine combustion chamber through the use of multiple spark plugs, which is limited discussed in existing research. Numerical simulations performed in this study show that the application of the multi-spark strategy increases the mass burn rate, advances the combustion phasing, shortens the combustion duration, increases the engine power output, improves the fuel economy, and reduces the unburned ammonia emissions, all of which indicate that rapid combustion of pure ammonia is achieved in the combustion chamber. Moreover, the use of multiple spark points does not lead to a marked increase in nitrogen oxides emissions, thereby ensuring no added stress on exhaust aftertreatment systems. In addition, pure ammonia combustion appears to be very well adapted to this strategy, as evidenced by the avoidance of excessive cylinder pressures and pressure rise rates—a challenge faced by conventional spark ignition engines, given ammonia notably slower flame speed relative to conventional petroleum-based fuels. Overall, all these findings strongly support that the multi-spark ignition system presents a compelling direction for future zero-carbon ammonia engines. However, it is crucial to address design challenges to ensure that the engine head layout provides sufficient cooling, structural robustness, optimal breathing efficiency, and reliable multi-ignition events within the confined space.

A Review of Isobutanol as a Fuel for Internal Combustion Engines

Isobutanol, one of the four isomers of butanol (C4H9OH), possesses some favorable properties that make it an attractive fuel for internal combustion engines. For instance, when compared to ethanol, isobutanol features a higher heating value and lower hygroscopicity (which prevents corrosion and enables it to be transported via pipelines). Moreover, its addition to gasoline does not distort the fuel blend’s vapor pressure to the same extent as ethanol does. All of this while having a high octane rating. Those advantages over ethanol suggest that isobutanol has the potential to be used as a gasoline oxygenate or even as a neat fuel. Furthermore, the advances made in biotechnology have enabled isobutanol to be produced from biomass more efficiently, allowing it to be used in compliance with existing renewable energy mandates. This article reviews some of the relevant literature dedicated to isobutanol as a motor fuel, covering its merits and drawbacks. Several studies on its combustion characteristics are also discussed. Most of the included literature refers to the use of isobutanol in spark-ignition (SI) engines, as its properties naturally lend themselves to such applications. However, isobutanol’s utilization in diesel engines is also addressed, along with a couple of low-temperature combustion examples.

Comparative analysis of waste tire pyrolysis oil and gasoline as low reactivity fuel in RCCI engine

ABSTRACT The utilization of alternative fuels in internal combustion engines has gained significant attention due to concerns about energy security and environmental sustainability. Waste tire pyrolysis oil (WTPO) is a potential alternative fuel that can be produced from waste vehicle tires through a pyrolysis process. In this study, the possible use of WTPO in a diesel engine operating under Reactivity Controlled Compression Ignition (RCCI) mode was investigated. In the study, the use of WTPO as a low-reactivity fuel in RCCI engines is examined, highlighting the importance of innovative approaches to alternative fuels with varying reactivity levels for effective combustion control and emission reduction. In the experimental work, WTPO was tested at different energy rates of 15%, 30%, and 45% into the intake port using the PFI system, while conventional diesel fuel was injected directly into the cylinder by the CRDI system. The tests were carried out under different engine load conditions while maintaining a constant engine speed of 2400 rpm. The performance, combustion, and emission characteristics of the engine were analyzed and compared between WTPO and conventional gasoline fuel as LRF. The study results show that using WTPO in RCCI operation with sustainable ringing intensity leads to significant increases in Brake Thermal Efficiency (BTE) compared to gasoline usage, with BTE increments of up to 5%, 3.3%, and 6.3% observed with increasing engine load. Furthermore, WTPO usage in RCCI engines effectively reduced hydrocarbon (HC) emissions, addressing a significant issue, and maintaining the known benefits of reactivity-controlled combustion. These findings suggest that WTPO can be utilized as a viable low-reactivity fuel in RCCI engines with acceptable performance, combustion, and emission characteristics.

A review on ammonia-hydrogen fueled internal combustion engines

In the face of the electrification trend in transportation, the internal combustion engine (ICE) is expected to continue playing a vital role in generating electricity for power systems or directly propelling vehicles in certain sectors. However, ICEs are also under significant pressure to achieve carbon neutrality, with the key lying in carbon-free fuels. Ammonia, compared to hydrogen, offers advantages in terms of hydrogen-carrying capacity, storage and transportation convenience, and safety, making it a promising carbon-free fuel for large-scale use in ICEs. Nonetheless, ammonia's combustion inertness poses challenges for its application, requiring efforts to enhance its combustion. Hydrogen, as a carbon-free and highly reactive fuel, serves as a powerful combustion promoter, maximizing the carbon-free effect of ammonia. Furthermore, on-board ammonia decomposition can produce hydrogen, ensuring a stable hydrogen supply and enabling ammonia-hydrogen synergy combustion while carrying only ammonia. This ammonia-hydrogen synergy combustion, based on on-board hydrogen production, presents a highly promising development direction for ammonia engines. When combined with hybridization, it further enhances the overall energy efficiency of ammonia. The objective of this paper is to review recent advancements in ammonia-hydrogen engines, covering topics such as ignition methods and combustion strategies, fuel supply, pollutants, and after-treatment. Based on this review, a conceptual ammonia-hydrogen engine for hybrid power systems is proposed. This engine ignites the ammonia-hydrogen mixture in the main chamber using hydrogen active jet ignition, achieving spark-assisted compression ignition. Technical measures for efficient engine combustion, synergistic utilization of exhaust heat for hydrogen production, and effective after-treatment of NOx, unburned NH3, and N2O are discussed. At last, some perspectives on the development of ammonia-hydrogen engines are also presented.

Assessment of CI Engine Performance Utilizing Palm Oil Biodiesel Blend

Experiment was explores vegetable oils as potential future fuels for internal combustion engines, particularly compression ignition engines designed for diesel. However, these oils have distinct properties from diesel, requiring modifications for direct use. Integration approaches include adjusting oil properties or adapting engines. Commonly, transesterification aligns oil properties, but using biodiesel often affects engine performance. In this study palm oil biodiesel as a diesel substitute, evaluating engine performance and emissions. In a short-term test, engine performance and emission traits by employing biodiesel blends of 0, 20, and 50 % with diesel at full load. Findings indicated that B20 and B50 exhibited 2.40% and 3.88% lower brake power than pure diesel. Volumetric efficiency percentages were 82.44 for B20, 81.64 for B50, and 82.93 for diesel. Notably, B20 and B50 showed 9.35% and 10.70 % decreased brake thermal efficiency compared to diesel. Interestingly, B20 and B50 displayed 1.09 and 2.44 % higher mechanical efficiency than diesel. Exhaust gas temperature was notably elevated in B20 and B50 blends. Nitric oxide concentrations were 98.74 ppm for diesel, 105.48 ppm for B20, and 111.78 ppm for B50. Carbon dioxide levels decreased by 4.14% for B20 and 7.86% for B50 relative to diesel. Carbon monoxide concentrations were 0.082% for B20 and 0.080% for B50, in contrast to diesel's 0.10%.

Large eddy simulation of spray and combustion characteristics of biodiesel and biodiesel/butanol blend fuels in internal combustion engines

Biofuel is a crucial renewable and environmentally friendly energy source for addressing greenhouse gas emissions and other energy-related issues. Biodiesel and butanol, among alternative biofuels, possess complementary physical and chemical properties, offering multiple possibilities for their use in existing internal combustion engines. However, biodiesel’s distinctly different physical and combustion properties from conventional diesel fuels make its combustion process substantially different. The complex composition of biodiesel presents significant challenges in accurately simulating its spray combustion characteristics. This paper presents a systematic evaluation of six single-component surrogate fuel models and a five-component model for the prediction of biodiesel spray characteristics under various conditions using large-eddy simulation (LES). The results show that single-component surrogate fuel models can only predict the gaseous penetration of biodiesel but not the liquid-phase penetration. A five-component fatty acid methyl ester surrogate fuel model is proposed, demonstrating an accurate simulation of biodiesel spray evaporation characteristics under different conditions. Based on the five-component evaporation model, LES is utilized to examine three strategies of biodiesel/butanol-fueled internal combustion engines: direct injection of pure biodiesel in conventional diffusion-controlled combustion (CDC) engines, direct injection of biodiesel–butanol blend in CDC engines, and biodiesel/butanol reactivity-controlled compression ignition (RCCI) engines. The simulation results are validated against engine experiment results, showing that the five-component model can successfully predict spray and combustion characteristics in internal combustion engines. The RCCI concept can significantly reduce NOx emissions; however, CO and UHC emissions are higher than in the CDC engines due to incomplete combustion in the fuel-lean butanol/air mixture.

Influence of injection strategies on ignition patterns of RCCI combustion engine fuelled with hydrogen enriched natural gas

The depletion of fossil fuel and the concerns for harmful emissions and global warming has instigated researchers to use alternative fuels. Hydrogen (H2) and natural gas (NG) are attractive fuels for internal combustion engines. The dual-fuel combustion strategy is promising to reduce emissions with efficient engine operation. The concern for using NG in this strategy is the lower efficiency at low load conditions and the emission of exhaust gases like carbon monoxide and unburnt hydrocarbon. Mixing fuel with a wide flammability limit and a faster burning rate with NG is an effective method to compensate for the limitations of using NG alone. Hydrogen (H2) is the best fuel added with NG to cover NG limitations. This study investigates the in-cylinder combustion phenomenon of reactivity-controlled compression ignition (RCCI) engines using hydrogen-added NG as a low-reactive fuel (H2 addition to NG on a 5% energy basis) and diesel as a highly reactive fuel. The numerical study was done on a 2.44 L heavy-duty engine using CONVERGE CFD code. Three low, mid, and high load conditions were analyzed in six stages by varying the diesel injection timing from −11 to −21 O after top dead centre (ATDC). The H2 addition to NG had shown deficient harmful emissions generation like carbon monoxide (CO) and unburnt hydrocarbon with marginal NOx generation. At low load conditions, the maximum imep was achieved at the advanced injection timing of −21OATDC, but with the increase in load, the optimum timing was retarded. The diesel injection timing varied the optimum performance of the engine for these three load conditions.