Dual-fuel Engine Research Articles

The Experimental Investigation of the Effects on the Combustion, Performance, and Emission Characteristics of an RCCI Engine Using Methanol/Diesel Fuel

Reactivity-controlled compression ignition (RCCI) combustion is considered one of the most promising low-temperature combustion (LTC) concepts aimed at reducing greenhouse gases for the transportation and power generation sectors. RCCI combustion mode is achieved by combining different fuel types with low and high temperatures. The aim of this study is to investigate combustion characteristics and reduce nitrogen oxide (NOx) and carbon dioxide (CO2) emissions. In this experimental study, the effects of the RCCI strategy using methanol/diesel fuel on combustion characteristics (ignition delay, combustion duration), engine performance (brake-specific fuel consumption and brake-specific energy consumption), and emissions were examined in a four-cylinder, turbocharged, dual-fuel engine. The experiments were conducted at a constant speed of 1750 rpm at partial loads (40 Nm, 60 Nm, 80 Nm, and 100 Nm). The test results obtained with diesel fuel were compared with the test results obtained with methanol at different mass flow rates. When the results were examined, the minimum ignition delay (ID) occurred at 40 Nm torque, 5.63 crank angle (CA) with M12 fuel, while the maximum ID occurred with M26 fuel at 80 Nm torque, showing an increasing trend as engine load (EL) increased. The highest combustion time (CD) was achieved with M26 fuel at 100 Nm torque, whereas the lowest was achieved with the same fuel (M26) at 40 Nm. While the minimum brake-specific fuel consumption (bsfc) was 45.9 g/kWh for conventional diesel fuel at 40 Nm, the highest bsfc was 104.88 g/kWh for 100 Nm with M26 fuel. Generally, bsfc tends to increase with increasing load. Brake-specific energy consumption (bsec) had the lowest value of 1950.58 kJ/kWh with conventional diesel fuel at 40 Nm and the highest value of 4034.69 kJ/kWh with M26 fuel at 100 Nm. As the methanol content increased, significant improvements were observed in (NOx) and (CO2) emissions, while hydrocarbon (HC) and oxygen (O2) emissions increased as well. Smoke emissions decreased at low loads but tended to increase at high loads.

Experimental Investigation of Oxy-Hydrogen Injection in Natural Gas/Diesel Dual-Fuel Engine: Performance and Emission Analysis under Low Load Operation

The pursuit of achieving zero carbon emissions by 2050 has led to the implementation of green technologies in the maritime industry. One crucial aspect is the adoption of alternative fuels, with a focus on non-fossil fuels to enhance energy efficiency and minimize emissions during ship operations. This study explores the innovative dual fuel diesel – Compressed Natural Gas (CNG) technology, which offers relatively low emissions with uncomplicated modifications to the diesel engine. CNG is injected into the intake manifold, addressing the need for cleaner fuel options. However, the evolution of this technology has encountered challenges such as methane slip resulting from incomplete combustion. This research proposes an intervention using hydrogen within the combustion chamber to improve combustion quality. Oxy-hydrogen gas (HHO), a carbon-free fuel derived from water through electrolysis, is considered as a potential solution. The utilization of HHO serves as a substitute for pure H2 due to its more feasible production and application, considering the global limitations in hydrogen storage and usage in transportation. The study aims to investigate the impact of HHO on the performance and emissions of dual fuel engines. Experimental tests are conducted under low loads to simulate critical operational points of the engine. Results indicate that the dual fuel system exhibits significant fuel savings, particularly with increasing injection duration. However, the need for additional oxygen to enhance combustion perfection must be balanced. HHO injection demonstrates the potential to improve engine performance, leveraging the oxygen content in HHO and the positive characteristics of hydrogen with its high Lower Heating Value (LHV). Furthermore, the research suggests that HHO injection can mitigate methane slip issues associated with dual fuel engine operations, offering a promising avenue for emission reduction

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.

Experimental investigation and gray relational optimization of engine parameters to improve the output characteristics of an ammonia biodiesel powered dual fuel combustion engine

An innovative approach to this research is to evaluate the effects of different concentrations of biodiesel with premixed ammonia energy in a dual-fuel combustion engine and determine the best operating conditions for optimal engine responses. Experimental results of a 40% ammonia energy premixing fraction with direct injection of a biodiesel blend of 30% (40%AEPF + B30) at 80% load improved brake thermal efficiency (BTE) by 8.42% while reducing brake specific energy consumption (BSEC) by 13.28%. It also reduces the hydrocarbon (HC) emission by 16.8%, the carbon monoxide (CO) emission by 15.06%, and the smoke opacity by 26.8%. As opposed to this, carbon dioxide (CO2) and nitrogen oxide (NOx) emissions are elevated by 21.5% and 16.54%, respectively, relative to the 40% ammonia energy premixing fraction with direct injection of diesel (40%AEPF + Diesel). Thereafter, the ANOVA technique is also utilized to analyze the impact of operational parameters, and the findings show that the responses are statistically significant. Additionally, the results are utilized in a grey relational analysis (GRA) based optimization process to determine the appropriate operational variables. According to optimization results, 40%AEPF + B30 at 80% load provides the most efficiency and fuel economy. It is capable of being used as an alternate fuel instead of conventional diesel.

Effects of natural gas admission location and timing on performance and emissions characteristics of LPDF two-stroke engine at low load

Low-pressure gas-admission marine two-stroke engines have significant potential for reducing emissions in the shipping industry. However, they exhibit poor combustion quality under low-load conditions, leading to lower thermal efficiency and high levels of HC and CO emissions. This study numerically evaluated the impacts of the gas admission location and timing on engine performance and exhaust gas emissions under low load conditions. The study revealed that different gas admission locations form distinct NG-air stratifications. Lower gas admission locations resulted in longer ignition delays and shorter combustion durations. The unburned CH4 and CO emissions were significantly reduced by a maximum of 20.14% and 42.29%, respectively. A trade-off exists between NOx and N2O emissions owing to the different temperature conditions of their formation. The NOx emissions increased continuously as the gas admission location was lowered to a maximum of 3.4218 g/kWh; a value slightly above the Tier III emission standards. Advancing the timing of gas admission further decreased the ignition delay time, NOx, and unburned CH4 emissions. This study revealed that in-cylinder natural gas mixture stratification due to varying gas admission locations and timings can improve the combustion efficiency and exhaust gas emissions of a natural gas-diesel dual-fuel engine under low-load conditions.

Computational Investigation of the Influence of Combustion Chamber Characteristics on a Heavy-Duty Ammonia Diesel Dual Fuel Engine

In response to increasingly stringent emissions regulations and the depletion of conventional fuel sources, integrating carbon-free fuels into the transport sector has become imperative. While hydrogen (H2) presents significant technical challenges, ammonia (NH3) could present a better alternative offering ease of transport, storage, and distribution, with both ecological and economic advantages. However, ammonia substitution leads to high emissions of unburned NH3, particularly at high loads. Combustion chamber retrofitting has proven to be an effective approach to remedy this problem. In order to overcome the problems associated with the difficult combustion of ammonia in engines, this study aims to investigate the effect of the piston bowl shape of an ammonia/diesel dual fuel engine on the combustion process. The primary objective is to determine the optimal configuration that offers superior engine performance under high load conditions and with high ammonia rates. In this study, a multi-objective optimization approach is used to control the creation of geometries and the swirl rate under the CONVERGETM 3.1 code. To maximize indicated thermal efficiency and demonstrate the influence of hydrogen enrichment on ammonia combustion in ammonia/diesel dual fuel engines, a synergistic approach incorporating hydrogen enrichment of the primary fuel was implemented. Notably, the optimum configuration, featuring an 85% energy contribution from ammonia, outperforms others in terms of combustion efficiency and pollutant reduction. It achieves over 43% reduction in unburned NH3 emissions and a substantial 31% improvement in indicated thermal efficiency.

Optimization of methanol/diesel dual-fuel engines at low load condition for heavy-duty vehicles to operated at high substitution ratio by using single-hole injector for direct injection of methanol

Methanol, as a low-carbon and easily synthesizable fuel, is one of the promising directions for future internal combustion engine (ICE) fuels. However, methanol/diesel engines with high energy substitution ratios exhibit a significant drawback at low loads, namely poor fuel economy, which seriously hinders the development of dual fuel engines. Therefore, this paper conducts an optimization study on the combustion strategy of methanol/diesel in heavy-duty vehicle engines under high energy substitution ratios (70 %) and low loads. Innovatively combines single-hole injection with the direct dual fuel stratification (DDFS) technology. By coupling the longer injection duration of a single hole with higher injection pressure, and tailored combustion strategy adjustments, successfully achieving the goal of optimizing low-load methanol dual fuel engines. The research results indicate that when employing a methanol single-stage injection strategy, setting the start of diesel injection (SODI) of −25°CA after top dead center (ATDC) effectively enhances the combustion efficiency of methanol/diesel, especially when combined with a strategy that the start methanol injection (SOMI) is of −23°CA ATDC. This combination can boost the gross indicated thermal efficiency (ITEg) to 51.95 %. The research on utilizing a methanol two-stage injection strategy found that increasing the methanol premixing appropriately, within the engine's safe range, can effectively enhance ITEg. Specifically, with the methanol pre-injection ratio (MPR) of 10 % and the methanol two-stage injection interval (MII) of 20°CA, ITEg can be improved to 52.07 %. However, excessively of premixing can lead to premature combustion, causing an increase in negative work during the compression stroke and consequently reducing ITEg. This study has unveiled effective solutions for the application of methanol/diesel DDFS technology in the automotive engine field. It offers insights into the selection and optimization of methanol injectors and provides theoretical support and practical references for achieving clean and efficient combustion in engines.

Flame characteristics and abnormal combustion of ammonia-diesel dual-fuel engine with considering ammonia energy fractions

Carbon neutrality is a significant challenge but also an essential opportunity for internal combustion engines (ICE), and fueled with low-carbon fuels is the key for ICE to reduce carbon emissions. Ammonia is a carbon-free fuel, whereas ammonia-diesel dual-fuel (ADDF) combustion can provide efficient and clean combustion of ammonia. In this study, the flame characteristics and abnormal combustion of ADDF engines are studied by considering ammonia energy fractions and diesel injection timings. The results show that a high ammonia energy fraction led to an extended period of combustion, while the CA05 first advances and then decreases with the decrease of ammonia energy fraction. This phenomenon indicates that an easily ignitable ammonia-air mixture is also important for ammonia-diesel dual-fuel ignition. Besides, an optimal SOI is needed to maximize the promoting effect of ignited fuel on ammonia combustion, and the optimal SOI changes with the ammonia energy fraction. Flame images confirm that the weightiness of the auto-ignition and flame propagation changes with the SOI, and the auto-ignition kernels gradually reduce and flame propagation plays a more and more important role as the SOI advances. At high loads, knocking combustion will also occur for ADDF engines, although the knock intensity is low. Besides, due to the enhancement effect of the knocking pressure wave, the flames show a strong white light at the knocking onset. The current results can help understand the combustion process and thus find the optimization method of ADDF engines.

Performance and carbon emissions of a diesel/oxy-hydrogen dual-fuel engine with oxy-hydrogen injection variation under low and medium load conditions

Reducing carbon emissions such as carbon dioxide (CO2) and carbon monoxide (CO) from diesel engines struggled with engine performance challenges and fossil fuel limitations. Besides, huge transportation such as ships hardly replaced diesel engines due to the higher thermal efficiency and low operation cost. Oxy-hydrogen gas, as a carbon-free gas, could potentially improve diesel engine performance and carbon emissions. Most of the studies tried to identify the effect of oxy-hydrogen induction into diesel engine combustion on performance and emissions. However, this study evaluated oxy-hydrogen injector sizes to the diesel engine performance and carbon emissions at several loads and several engine speed conditions. Overall, the result showed that the oxy-hydrogen gas injection into the diesel engine’s intake port improved the performance and carbon emissions compared to the single diesel fuel as a baseline. High engine performance with low carbon emissions could be achieved at low and medium engine load conditions with high engine speeds. Moreover, smaller oxy-hydrogen injector sizes were suitable for the medium engine load and vice versa, to improve the performance and carbon emissions. At low load, the engine performance improvement of engine torque, specific fuel consumption, and thermal efficiency were 1800 to 2200 rpm. Moreover, the CO2 and CO emissions reductions were also suitable with 2200 rpm with a bigger oxy-hydrogen gas injector (6 mm). Furthermore, at medium load, the engine performance improved at 1400 rpm but the CO2 and CO emissions were lower at 2200 rpm with a small oxy-hydrogen gas injector (4 mm). The engine operation at 2200 rpm with a 4 mm injector also improved the engine performance regarding carbon emissions reduction. However, injecting oxy-hydrogen gas into diesel engines had the potential to enhance the engine performance and reduce carbon emissions, moving closer to achieving zero emissions

Experimental study on the effects of water addition in methanol on the performance of diesel-methanol diffusion combustion on a high-speed engine

Methanol is regarded as a low-carbon renewable fuel which is friendly to the environment. For purpose of investigating the impact of water introduction in methanol on diesel-methanol diffusion combustion, experimental tests were performed on a refitted dual-fuel high-speed diesel engine test bench. This research compared the differences between diesel-methanol diffusion combustion (DMDC) mode and diesel-hydrous methanol diffusion combustion (DHMDC) mode with a water mass content of 20%. The tests were performed by maintaining the engine speed of 3000 rpm and varying engine load as well as methanol injection timing (MIT). The results indicate that the heat release process in DHMDC mode begins later but is more rapid and concentrated compared to DMDC mode. The addition of 20% water in methanol does not significantly decreases the peak average in-cylinder temperature. However, it decreases the NOx emissions by up to approximately 40%. Water introduction leads to higher CO and THC emissions in DHMDC mode, but the retardation of MIT helps mitigate the increase in CO and THC emissions. The exhaust losses in DHMDC mode decrease by about 5%–8%, while the heat transfer losses increase by over 20%, resulting in a lower indicated thermal efficiency (ITE) in comparison with DMDC mode. The effects of the 20% water addition in methanol are sensitive to changes in engine load and MIT. Higher engine load and appropriately retarded MIT facilitate more efficient and cleaner combustion in DHMDC mode.

Techno-economic analysis of onboard CO[formula omitted] capture for ultra-large container ships

Decarbonising the naval shipping sector is of paramount importance to decrease global CO2 emissions. This work presents a techno-economic analysis of onboard solvent-based carbon capture for an ultra-large container ship, powered by two dual-fuel engines fed with either heavy fuel oil or liquefied natural gas. Different case studies are proposed depending on the fuel used by the ship and on the chosen design to supply the necessary heat and electricity to the carbon capture unit. Aside a conventional strategy based on heat provided via fuel combustion in a boiler, a novel configuration based on electric heat pump is investigated. The economic analysis is based on a real inter-continental journey. The results highlight that onboard carbon capture determines an increase in fuel consumption with respect to the unabated ship, that varies depending on the exhaust gas CO2 content (hence, on the ship fuel) and on the selected process design. The integration of the electric heat pump leads to a significant decrease in this additional fuel consumption and better results in terms of CO2 avoidance and costs. The carbon abatement cost is found in the range of 64–149 €/t of CO2 avoided.

Effect of Injection Timing on the Dual Fuel Engine Performance Operated with Hydrogen and Nano-Biodiesel Blends

In the current work, effect of nano-biodiesel blends and injection timing on the performance of hydrogen fueled dual fuel (DF) engine is presented. Hydrogen flow rate is maintained constant with a flow rate of 0.15 kg/h. For this B20 and nano-blends of Nigella sativa oil methyl ester (NLSTVAOME) and Jack fruit seed oil methyl ester (JKFSOME) fuel combinations are used. Nano-blends of respective B20 biodiesels are prepared using graphene amine (GA) nanoparticles with varied proportions ranging from 60 to 100 ppm using probe sonication method. Stabilization of the nano-blends are ensured with reference to quantity of nanoparticle, surfactant SDS (Sodium Dodecyl Sulfate) used and sonication time. Addition of the nanoparticles in the B20 biodiesel blends till 80 ppm showed considerable improvements on the performance of diesel engine with single fuel operation due to improved combustion compared to B20 biodiesel blends. Beyond 80 ppm the performance deteriorated due to non-homogeneous mixtures of nano-biodiesel blends. Injection timing (IT) for the modified DF engine IT is varied from 19 to 31oBTDC in steps of 4oBTDC. Further advancing the IT from 19 to 27oBTDC showed improved dual fuel engine performance with B20+GA80 blends of both biodiesels along with hydrogen induction when compared to B20 operation. Further mixing of air-hydrogen in the inlet manifold of dual fuel engine is studied using CFD analysis for varied hydrogen flow rates ranging from 0.10 to 0.2 kg/h in steps of 0.05 kg/h.

Cost-benefit analysis of emission reduction techniques: a case for container vessel

One of the most important issues in the maritime industry is controlling and reducing the amount of emissions caused by marine vessels. In this respect, the International Maritime Organization sets some air pollution-related regulations and encourages maritime companies to utilise current and innovative emission abatement methods on their ships. The application of these approaches to ships not only provides environmental benefits but also creates additional financial costs for the company. In this study, operational data of a container ship has been acquired and examined. Methods such as ammonia, LNG, scrubber, low sulphur fuel use, and selective catalytic reduction have been considered to determine the most appropriate emission reduction approach. Nine different scenarios have been created with the use of stated methods and each scenario is analysed both environmentally and economically and compared to each other. Finally, the most suitable scenario has been determined by calculating the payback period of each investment. Since there is a relatively longer period of redemption, using a dual-fuel engine could be more suitable for long-lasting and newly built ships. For the currently cruising ships, the use of scrubber systems with selective catalytic reduction is an effective solution to reduce the number of emissions.

Diesel and natural gas dual-fuel RCCI engine performance at high altitude

Diesel and natural gas dual-fuel RCCI engine performance at high altitude

Optimization of Combustion Cycle Energy Efficiency and Exhaust Gas Emissions of Marine Dual-Fuel Engine by Intensifying Ammonia Injection

The capability of operational marine diesel engines to adapt to renewable and low-carbon fuels is considered one of the most influential methods for decarbonizing maritime transport. In the medium and long term, ammonia is positively valued among renewable and low-carbon fuels in the marine transport sector because its chemical elemental composition does not contain carbon atoms which lead to the formation of CO2 emissions during fuel combustion in the cylinder. However, there are number of problematic aspects to using ammonia in diesel engines (DE): in-tensive formation of GHG component N2O; formation of toxic NOx emissions; and unburnt toxic NH3 slip to the exhaust system. The aim of this research was to evaluate the changes in combustion cycle parameters and exhaust gas emissions of a medium-speed Wartsila 6L46 marine diesel engine operating with ammonia, while optimizing ammonia injection intensity within the limits of Pmax, Tmax, and minimal engine structural changes. The high-pressure dual-fuel (HPDF) injection strategy for the D5/A95 dual-fuel ratio (5% diesel and 95% ammonia by energy value) was investigated within the liquid ammonia injection pressure range of 500 to 2000 bar at the identified optimal injection phases (A −10° CAD and D −3° CAD TDC). Increasing ammonia injection pressure from 500 bar (corresponding to diesel injection pressure) in the range of 800–2000 bar determines the single-phase heat release characteristic (HRC). Combustion duration decreases from 90° crank angle degrees (CAD) at D100 to 20–30° CAD, while indicative thermal efficiency (ITE) increases by ~4.6%. The physical cyclic deNOx process of NOx reduction was identified, and its efficiency was evaluated in relation to ammonia injection pressure by relating the dynamics of NOx formation to local combustion temperature field structure. The optimal ammonia injection pressure was found to be 1000 bar, based on combustion cycle parameters (ITE, Pmax, and Tmax) and exhaust gas emissions (NOx, NH3, and GHG). GHG emissions in a CO2 equivalent were reduced by 24% when ammonia injection pressure was increased from 500 bar to 1000 bar. For comparison, GHG emissions were also reduced by 45%, compared to the diesel combustion cycle.

Investigation of the combustion process in a dual-fuel engine

Modeling of in-cylinder processes occurring in a dual-fuel engine is necessary to obtain the ignition delay period as a function of the angle of rotation of the crankshaft and the subsequent calculation of its effective and environmental indicators. There is a need to identify the theoretical dependence of the fuel combustion process on the parameters that determine the operating modes of a dual-fuel engine, which leads to the need to create a mathematical model that allows the most accurate description of the combustion process, taking into account the maximum possible number of factors. The paper considers the optimization of the parameters of the workflow and the prediction of the performance of the projected and existing dual-fuel engines.

A Fault Diagnosis Method for Marine Engine Cross Working Conditions Based on Transfer Learning

Marine engines confront challenges of varying working conditions and intricate failures. Existing studies have primarily concentrated on fault diagnosis in a single condition, overlooking the adaptability of these methods in diverse working condition. To address the aforementioned issues, we propose a cross working condition fault diagnosis method named the Balanced Adaptation Domain Weighted Adversarial Network (BADWAN). This method combines transfer learning to tackle the challenges of cross working condition diagnosis with limited labels. Specifically tailored for scenarios with incomplete labeling in the target working conditions, we designed an Enhanced Centroid Balance scheme to balance the label space, thereby enhancing the model’s transfer capabilities. Additionally, we designed an Instance Affinity Weighting scheme on the foundation of Class-level Weighting, refining the model to the instance level for effective information interaction. Furthermore, we incorporated the Adaptive Uncertainty Suppression strategy to further boost the model’s classification prowess. Two experimental scenarios were designed to demonstrate the effectiveness of the proposed model using a Wärtsilä9L34DF dual-fuel engine as an experimental subject. The results demonstrate an over 90% diagnostic accuracy in scenarios with complete target working condition labels and 86% accuracy in scenarios with incomplete labels, outperforming other transfer learning models. The BADWAN model excels in cross-condition fault diagnosis tasks for marine engines with incomplete target working condition labels, offering a novel solution to this field.

Dynamics of heat release in a dual-fuel engine

The increasing attention to the use of dual-fuel engines with compression ignition leads to the need to study the thermal engineering processes occurring in them. A model for calculating the thermal engineering stages in a cylinder of a dual-fuel engine with a refined composition of the working fluid is presented, including the determination of fuel supply characteristics, fuel injection and evaporation functions and allowing theoretically to determine with high accuracy the pressure function, cycle operation, power, efficient and thermal criteria for the operation of a dual-fuel engine. The paper attempts to show the mutual relationship between the individual processes of heat generation, their influence on the design parameters under the operating conditions characteristic of a dual-fuel engine, as well as on the operating conditions of components and parts.

Optical diagnostics in impact of ammonia energy ratio and diesel split ratio on combustion process and flame propagation in an Ammonia-Diesel Dual-Fuel engine

In the context of ammonia-diesel dual-fuel (ADDF) engines, challenges such as ignition difficulties and misfires emerge prominently at elevated ammonia energy ratios. To alleviate these challenges, this study aims to elucidate the effects of ammonia energy ratios (AER) and diesel split ratios (DSR) on the combustion process and flame propagation in an optical ADDF engine configuration. Utilizing optical diagnostics, including flame luminescence and high-speed photography, the study provided insights into combustion boundary conditions specific to ADDF engine operation. The results highlight that an increase in AER to 60 % results in a marked decrease in peak cylinder pressure, peak apparent heat release rate (AHRR), and the in-cylinder pressure rise rate. This is accompanied by a reduction in IMEP from 4.16 bar to 3.24 bar, indicating a decline in combustion efficiency upon greater ammonia addition. Flame luminosity exhibits a shift from a diesel-like blue hue to an ammonia-tinted pale yellow. This change coincides with a significant reduction in soot formation and restrictions in flame area and propagation speed, largely due to ammonia's intrinsically slower burning velocity and its chemical interplay with diesel. Implementing a dual injection approach further accentuates the peak in-cylinder pressure and AHRR, with the second injection playing a crucial role in ignition. Optimizing the DSR to 40 % improves combustion efficiency, attributed to enhanced fuel-oxygen interactions. Conversely, DSR values of 60 % and 80 % pose challenges. A reduction in diesel content in the subsequent injection leads to a leaner blend, subsequently affecting combustion efficiency, as indicated by reduced heat release rate and diminished IMEP. This study emphasizes understanding the ammonia-diesel interaction and the importance of choosing the appropriate DSR to exploit the advantages of ADDF engines.

Utilization of hydrogen-diesel blends for the improvements of a dual-fuel engine based on the improved Taguchi methodology

A three-dimensional computational fluid dynamics model (CFD) of the diesel engine cylinder was developed using CONVERGE 3.0 software and a chemical reaction mechanism including 172 reactions and 62 components was developed using the CHEMKIN program. Then, the effects of nozzle diameter and spray cone angle on in-cylinder pressure, temperature, HC emission, NOx emission and soot emission of the hydrogen-diesel dual-fuel engine were investigated. Lastly, multi-objective optimization of HES, CR, nozzle diameter and spray cone angle were also carried out using Taguchi methodology. Analysis of variance and signal-to-noise ratio were performed using Minitab software. The results showed that higher in-cylinder pressure, temperature and NOx emission could be obtained with the decreasing nozzle diameters. But HC and soot emissions showed the opposite trend. Using the smaller spray cone angle was more favorable for in-cylinder pressure, temperature, HC, and NOx emissions. However, the small spray cone angle results in large amounts of soot emission. In addition, the factors that had the greatest impact on in-cylinder pressure, temperature, HC emission, and soot emission were all CR. And the factor that had the greatest impact on NOx emission was HES. This work provides a feasible technical approach to improve the marine diesel engine parameters.