Marine Dual-fuel Engine Research Articles

Quantity and quality of marine dual-fuel engine’s exhaust sensible waste heat considering different sulfur content in fuels

Quantity and quality of marine dual-fuel engine’s exhaust sensible waste heat considering different sulfur content in fuels

Numerical study on the effect of a two-stage pilot injection strategy on the performance of medium-speed diesel/natural gas dual-fuel marine engine

The need to reduce marine engine emissions continues to grow with the implementation of stricter emission standards. Numerical simulations were conducted to study the effect of a two-stage pilot diesel injection strategy on combustion and emissions in a medium-speed diesel/natural gas dual-fuel marine engine. A comprehensive analysis was performed on the start of the first pilot diesel injection (SOI1) and the proportion of the first pilot diesel injection (POI1), identified as two coupling factors of the injection strategy. The results indicated a significant improvement in indicated thermal efficiency (ITE) of over 48% and a reduction in nitrogen oxide (NOx) emissions of over 50% compared to the baseline single-stage injection strategy can be achieved through the use of high POI1 and delayed SOI1. In addition, the first pilot diesel spray covered the squish and piston bowl regions, enhancing the reactivity of the fuel-air mixture in these regions. The mass fraction of CH2O and H2O2 radicals determined the distribution of reactivity in different regions and characterized the transition process from low-temperature reaction to high-temperature reaction. The strategy of high POI1 and delayed SOI1 resulted in a better low-temperature reaction distribution, reducing combustion duration, improving ITE, and decreasing NOx, HC, CO emissions at medium load condition.

A Techno-Environmental and Energy Efficiency Investigation of Marine Dual-Fuel Engines

The ship-based greenhouse gas emissions along with the volumetric growth in maritime transportation have increased significantly over the years. International Maritime Organization (IMO) has tightened the emission limits by putting new regulations into effect to overcome the environmental impacts and therefore, the maritime industry has focused on energy-efficient ship design and operation, recently. Regarding the latest developments, dual-fuel engines operated with different fuels have been installed and new technological developments in emission control have been implemented onboard ships. In this context, the selection of engine systems where there are many options available has been a substantial problem in the design process of a ship, recently. The latest marine engines are capable of operating with various types of fuels at different emission control modes, therefore, energy efficiency and emission performance of the prime movers should be analyzed in detail. In this study, VLSFO, methanol, LPG, LNG and MDO-fueled engines with the same power output are investigated and the NOX reduction device integrated engines’ technical specifications are compared. Then, the selected dual-fuel engines are thermodynamically analyzed and the environmental impacts are evaluated under different engine loads, Tier II, Tier III modes and ambient conditions. Moreover, EEDI calculations are conducted under the case study of powering a medium-range tanker and engine options are evaluated in terms of energy efficiency. Finally, a sensitivity analysis of engine performance is carried and the results are validated. According to the results, the energy efficiency of the ship can be increased by up to 20% by selecting the LNG-fueled engine as the prime mover while it requires more space and equipment compared to other engines.

Analysis of Carbon Particulate Matter Removal Performance of Dual-Fuel Marine Engine with DOC + CDPF

This study analyzes Diesel Oxidation Catalyst (DOC) and Carbon Diesel Particulate Filter (CDPF) after-treatment systems integrated into a WARTSILA W20DF marine dual-fuel engine. The CDPF was coated with a non-precious metal catalyst whose catalytic redox performance improved with increasing temperature. The carbon particulate matter combustion reached up to 12.5 mg/s at 800 K and over 20 mg/s at 900 K. Then, the W20DF running at 230 kW, 450 kW, 680 kW, and 810 kW with 1000 rpm; a Tisch 10-8xx; and an AVL SPC 478 were used to sample and analyze the carbon particulate matter (CPM) before and after DOC + CDPF. The gaseous emissions (O2, CO2, CO, HC, NOx, and NO2) were analyzed with the flue gas analyzer AVL i60. The results show that the collected carbon particulate matter simultaneously became darker as the load decreased. This study finds that the maximum amount of CPM per unit volume of exhaust gas occurs under 50% working conditions and the lowest amount under 90% working conditions. After DOC + CDPF treatment with a non-precious metal coating, the CPM was reduced by about 50%. Furthermore, this type of catalyst’s efficiency rises with the temperature increase. The CPM combustion efficiency reached up to 20 mg/s at 900 K. The other gas components in the exhaust gas before and after DOC + CDPF also changed. These research results have a significant reference value for DOC + CDPF optimization to decrease the carbon particulate matter in marine engines.

Investigation of rapid flame front controlled knock combustion and its suppression in natural gas dual-fuel marine engine

In this study, a new-type knock mechanism for large-bore marine engines, which differs from the existing end-gas auto-ignition knock theory and detonation wave theory, is fully revealed, using a high time resolution dynamic pressure difference method. The results indicate that the disparate enhancement effects of the flame front on the high-pressure region and the low-pressure region result in an increasing pressure difference, eventually forming the knock. The distinctions between this knock and the conventional end-gas auto-ignition knock were examined. Subsequently, the different functions of swirl in the two knock mechanisms were investigated. The results illustrate that, increasing swirl in end-gas auto-ignition knock can accelerate the termination of flame surface propagation and reduce the end-gas temperature by shortening the end-gas heat accumulation, thereby decreasing the knock intensity. However, reducing swirl in the new-type knock can diminish the combustion intensity of the flame front, thereby reducing its enhancement of the pressure wave. Consequently, a reduction to one-fourth of the initial swirl level can reduce knock intensity by 91%. Particularly, a novel knock suppression method of positioning the jet flame in the opposite direction of the swirl is proposed, which can avoid the local rapid combustion to effectively eliminate knock while maintaining power.

Experimental Investigation to Assess the Performance Characteristics of a Marine Two-Stroke Dual Fuel Engine under Diesel and Natural Gas Mode

With the aim of CO2 emissions reduction in the maritime sector, dual fuel engines operating on natural gas are the most prominent technical and commercially available solution. A promising variant is the two-stroke high-pressure natural gas injection engine, utilizing diesel pilot fuel injection for ignition of the gaseous fuel while being able to operate in diesel-only mode. In this study, a comparative analysis of the performance and the combustion mechanism of dual fuel and diesel mode for this engine type is conducted using experimental data. Studies based on measurements conducted on actual scale are limited in the literature due to the engines’ sheer size not allowing lab testing. The analysis was conducted using measurements acquired during the factory acceptance tests involving conventional operating data and cylinder pressure data acquired using a piezoelectric sensor. In terms of the mean pressure and temperature, only minor differences were found. The specific fuel consumption was improved under low load operation for the dual fuel mode by 1.8%, while a small increase of 1.2% was found near full load. Differences were found in the combustion process from 25 to 75% load with considerably faster premixed and diffusion combustion for the dual fuel mode leading to a 6–8% decrease in combustion duration. Despite the combustion process differences, the performance under dual fuel operation was overall close to that of conventional diesel with an acceptable 1.5% efficiency reduction on average. This confirms that modern dual fuel marine engines can achieve the performance standards of conventional ones while benefiting from low-carbon fuel use to reduce CO2 emissions.

Numerical investigations on charge motion and combustion of natural gas-enhanced ammonia in marine pre-chamber lean-burn engine with dual-fuel combustion system

Ammonia, an efficient hydrogen carrier with the advantages of lower storage cost and higher stability comparing to hydrogen, is becoming a potential solution for carbon dioxide emission reduction from marine engine. In this paper, the CH4/NH3 mechanism applied to simulate the combustion process of elevated-pressure engine was experimentally verified. Then, simulations were conducted on a marine pre-chamber lean-burn engine to investigate the feasibility of dual-fuel combustion with natural gas and ammonia. The results show that the combustion of the rich mixture ignited by spark in the pre-chamber produces high-speed turbulent jet flames into the main chamber, which promotes the combustion of the lean gas mixture. Additionally, an anomalous pre-ignition pressure rise is observed at 50% natural gas addition. Finally, the performance evaluation of engine indicates that for the design of marine dual-fuel engine, the ammonia fraction range of 50%∼80% should be employed to achieve good engine thermal efficiency.

Numerical simulation of lean premixed combustion characteristics and emissions of natural gas-ammonia dual-fuel marine engine with the pre-chamber ignition system

As an efficient hydrogen carrier, ammonia (NH3) has great potential to realize the target of carbon neutralization. In this paper, a natural gas-ammonia dual-fuel engine model has been established to evaluate the feasibility of ammonia application in a high-pressure medium-speed four-stroke natural gas marine engine. In order to achieve the efficient and clean combustion of ammonia, a method combining the pre-chamber ignition system with lean-burn combustion technology was proposed. In addition, a CH4/NH3 combustion mechanism with reasonable accuracy was developed to simulate the combustion process of the engine. Moreover, the effect of using various ammonia concentration in the fuel on jet flame formation, thermal efficiency, unburned ammonia, and NOx and N2O emissions were compared. The results showed that the pyrolysis of ammonia mixtures in the pre-combustion chamber promoted the formation of jet flame, which had a “chain effect” on the turbulent kinetic energy in the main combustion chamber and further enhanced the flame propagation in lean conditions. In addition, NOx emission showed a decreasing function of the split ratio of ammonia, which was caused by the NO reduction by unburned NH3. However, the low-temperature generation characteristics of N2O emissions led to the opposite trend. Furthermore, the application of ammonia increased N2O emissions by 0.18–0.49 g/kWh, which is about 0.06%–0.1% of nitrogen in ammonia fuel, resulting in a partial offset of CO2 emission reduction effect.

The Control-Oriented Heat Release Rate Model for a Marine Dual-Fuel Engine under All the Operating Modes and Loads

An accurate model plays an important role in control strategy development of smart ships. For the control-oriented engine models, calibration by experienced personnel is key to outputting high accuracy. However, the dual-fuel engine runs in liquid fuel mode, gas fuel mode, and fuel sharing mode. It is impossible to tune a single model or a set of parameters for the dual-fuel engine under all operating modes and loads. On the basis of our experience and practice, a Wiebe-based heat release rate model is used. To make the Wiebe model available for the dual-fuel engine, the Wiebe parameters are assumed to be linear functions. The combustion beginning angle is modeled as a function of fuel quantity in liquid fuel mode and as a look-up table in gas fuel mode for all loads. The combustion duration and the combustion distribution factor are modeled as a function of fuel quantity and engine revolution both in liquid fuel mode and in gas fuel mode. In fuel sharing mode, the heat release rate is modeled as a combination of the heat release rate models in liquid fuel mode and gas fuel mode. This model is called the SL model. For a further discussion, four types of combinations in fuel sharing mode are investigated. In addition, in liquid fuel mode and gas fuel mode, the combustion duration model and the combustion distribution factor model are replaced by the Woschni/Anisits model, which was specifically used in the diesel engine. This variation of model is called the WA model. To validate our hypothesis and models, the Wiebe parameters in liquid fuel mode and gas fuel mode are given, four types of combinations and two cases of comparisons in fuel sharing model are discussed, and the engine performance is checked and analysed. Results show that for the SL model, the average RMSE is 1.45% in the liquid fuel mode, 2.22% in the gas fuel mode, and 2.53% in the fuel sharing mode. For the WA model, the RMSE of the NOx is 9.79% in liquid fuel mode and 45.20% in gas fuel mode. Its maximum error reaches −65.54%. The proposed SL model is accurate and can generate Wiebe parameters that are better than the carefully tuned parameters. The WA model is not suitable for engine models that require NOx-emission-related parameters.

A Numerical Investigation on the Effects of Intake Swirl and Mixture Stratification on Combustion Characteristics in a Natural-Gas/Diesel Dual-Fuel Marine Engine

A Numerical Investigation on the Effects of Intake Swirl and Mixture Stratification on Combustion Characteristics in a Natural-Gas/Diesel Dual-Fuel Marine Engine

Modeling and Optimization of Fuel-Mode Switching and Control Systems for Marine Dual-Fuel Engine

The marine dual-fuel engine can switch between diesel and gas modes according to the requirements of sailing conditions, fuel cost, and other working conditions to make sure the ship is in the best operating condition. In fuel-mode switching in engines, problems such as unstable combustion and large speed fluctuations are prone to occur. However, there are some disadvantages, such as poor safety, environmental pollution, and easy damage to the engine, when the large, marine dual-fuel engine is directly tested on the bench. Therefore, in this paper, a joint simulation model of a dual-fuel engine is built using GT Power and MATLAB/Simulink to investigate the engine’s transient process of fuel-mode switching, and the conventional fuel PID(Proportion Integral Differential) control system is optimized using the cuckoo search (CS) algorithm. The simulation results show that the dual-fuel engine model has good accuracy, and the response in transient conditions meets the manufacturer’s requirements. In the process of switching from gas mode to diesel mode, due to the rapid change in fuel, the engine parameters, such as speed, fluctuate significantly, which is prone to safety accidents. In the process of switching from diesel to gas mode, because the fuel switching is gentle, all parameters are relatively stable, and the possibility of safety accidents is slight. The fuel PID control system optimized based on the cuckoo search algorithm has a better engine control effect than the traditional fuel control system.

Pilot diesel-ignited ammonia dual fuel low-speed marine engines: A comparative analysis of ammonia premixed and high-pressure spray combustion modes with CFD simulation

Decarbonization of global shipping plays an important role in avoiding the worst impacts of climate change, and ammonia is a promising sustainable and zero-carbon fuel in the maritime sector. The dual-fuel mode has the potential to compensate for the poor combustion property of ammonia, but the existing studies are mainly focused on automotive medium- and high-speed engines, researches on marine low-speed engines are rarely reported. In this paper, the numerical models of pilot diesel-ignited ammonia dual fuel engine under both the premixed and high-pressure spray combustion modes are established using a commercial low-speed marine diesel engine as the prototype, and verified against the experimental data of the spray mixture formation, ignition delay, in-cylinder pressure and pollutant emissions. Then, the engine performance and emissions of both two modes are studied and optimized. The results show that under the diesel replacement ratio of the commercial methane/diesel dual-fuel marine engine (i.e. around 98%–99%), both two modes can achieve an indicated thermal efficiency (ITE) of over 50%. At the optimized ammonia premixed combustion point, the ITE is increased by 5.1% owing to the significantly reduced cooling loss, but at the expense of 140.6% higher NOx emissions compared to the diesel-only mode. The optimized ammonia high-pressure spray combustion point can achieve a similar ITE and reduce the NOx emissions by around 47% compared to the diesel-only mode. For both the optimum points, the GHG emissions (i.e. CO2 + 300 × N2O) are reduced by around 97%, while the unburned NH3 emissions are negligibly small.

Effects of hydrogen mixture ratio and scavenging air temperature on combustion and emission characteristics of a 2-stroke marine engine

A numerical study was conducted to investigate the effects of hydrogen and scavenging air temperature (SAT) on the combustion and emission characteristics of a 2-stroke heavy-duty dual-fuel (DF) marine engine at full load. The engine had a 700 mm bore fuelled with hydrogen–methane (H2-CH4) mixtures. Three-dimensional simulations of the combustion and emission formation inside the engine cylinder with various H2 contents in the H2-CH4 mixture were performed. ANSYS FLUENT simulation software was used to analyse the engine performance, in-cylinder pressure, temperature, and emission characteristics. The CFD models were validated against the measured data recorded from the engine experiments. The results showed that an increase in the in-cylinder peak pressure increased the engine power when the H2 content in the H2-CH4 mixture increased. Notably, CO2 and soot emissions decreased (up to more than 65%) when the H2 content in the gaseous mixture increased to 50%. Specific NO emissions in the DF modes were lower than that of the diesel mode, when the H2 content in the gaseous mixture was lower than 40%. However, they increased compared to the diesel mode when the H2 content continued to increase. This limits the H2 amount that should be used in a gaseous mixture creating NO emissions. The results also showed that the SAT cooling method can further reduce emission problems while enhancing engine power. In particular, reducing the SAT to 28 °C in the gaseous mixture with 10% H2 ensured that the DF mode emitted the lowest NO emissions compared to the diesel mode. This reduced NO emissions by 37.92% compared to the measured NO emissions of the research engine (a Tier II marine engine). This study successfully analysed the benefits of using an H2-CH4 mixture as the primary fuel and the SAT cooling method in a 2-stroke ME-GI heavy-duty marine engine.

Numerical research of the in-cylinder natural gas stratification in a natural gas-diesel dual-fuel marine engine

The urgent need for decarbonization and emission reduction for marine engines is driving the development of alternative low-carbon fuels. One of the best alternative fuels for engines is natural gas, a clean energy source with vast reserves and a low price. However, low-pressure injection dual-fuel engines exhibit poor combustion characteristics at low engine loads, and extinction is likely to occur in the fuel mixture's dilution region. Thus, the Low Pressure Post Injection (LPPI) strategy was proposed in this paper. The major objective of the LPPI mode is to increase monocirculation combustion stability under low to moderate engine loads by achieving a reasonable distribution of NG in the combustion chamber. LPPI was compared with the Low Pressure Injection (LPI) strategy. Results indicate that the LPPI mode could successfully raise the swirl ratio in the cylinder upto 60.7 percent while perfectly avoiding the NG leakage phenomena. Additionally, with the aid of radial-wall distribution of NG and an improved swirl ratio in LPPI mode, the combustion duration is reduced by 33.6 percent, and the lean burn limit of the dual-fuel marine engine can be expanded to 0.30. Although local higher combustion temperature caused an large increase in NOx emission which is more than three times than LPI NOx emission, LPPI mode still meets Tier III NOx emission requirements.

Effects of the Injector Spray Angle on Combustion and Emissions of a 4-Stroke Natural Gas-Diesel DF Marine Engine

This work studied the effect of the injector spray angle (SA) on the combustion and emissions of a 4-stroke port-injection natural gas-diesel dual-fuel (NG-Diesel DF) marine engine to determine the optimal SA for the fuel injector, aiming to reduce exhaust gas emissions while keeping the engine performance. Three-dimensional (3D) simulations of the combustion process and emission formations occurring in the engine cylinder in both diesel and DF modes were carried out using the AVL FIRE R2018a code. The engine’s in-cylinder temperature, pressure, and emission characteristics were analyzed. To clarify the effect of the injector SA on the combustion and emission characteristics of the engine, only the injector SA has been varied from 145 to 160°. Meanwhile, all other boundary conditions for the simulations and operating conditions of the engine have remained unchanged. The simulation results have been compared and showed a good agreement with the engine experimental results. The study has successfully investigated the effects of the injector SA on the combustion and emission characteristics of the engine. A better SA for the fuel injector, to reduce the NO emissions (145°) or soot and CO2 emissions (150°), while keeping the engine power almost unchanged, without the use of any exhaust gas post-treatment equipment, has also been suggested.

Life-cycle cost analysis of an innovative marine dual-fuel engine under uncertainties

As innovative technologies are being deployed to accelerate shipping decarbonization in response to air emission regulations, there is considerable concern about the cost effectiveness of such technologies from a life-cycle perspective. This study conducts a life-cycle cost analysis (LCCA) on an innovative marine dual-fuel engine under uncertainties, comparing the total life-cycle cost performance of such an engine with that of a conventional diesel engine. By proposing several economic Key Performance Indicators (KPIs) such as the Net Present Cost (NPC), the Net Saving (NS) and the Saving-to-Investment Ratio (SIR), the findings indicate that the dual-fuel engine is more cost-effective than the diesel engine under a given fuel price scenario. The uncertainties are meticulously treated by using scenario sensitivity analyses and a Monte Carlo simulation. The scenario sensitivity analyses reveal that the cost effectiveness of the dual-fuel engine is sensitive to the high gas price scenarios. It is uncovered from the Monte Carlo simulation that there is an adequate degree of confidence when opting for the dual-fuel engine. Furthermore, fuel prices are found to be the most influential cost driver. Different foreseeable carbon pricing scenarios are also simulated to show that the dual-fuel engine is still the most favorable option. Regardless of fuel prices and carbon pricing scenarios, the dual-fuel engine provides a considerable environmental benefit with a CO2 emission reduction potential of 33%. The findings of this study are of interest within the field of shipping investment appraisals and relevant to decision-makers (i.e. ship-owners and investors).

Performance and emissions of a high-speed marine dual-fuel engine operating with methanol-water blends as a fuel

Dual-fuel (DF) operation with methanol-diesel allows to reduce CO2 emissions, increase efficiency and decrease NOx and soot. This paper describes the experimental results with methanol-water (MeOH-W) blends as a fuel, and has three objectives: (1) whether water acts as a knock suppressant, enabling higher diesel substitution ratios, (2) if water can be a measure to control engine-out NOx emissions given its cooling effect, and (3) to test the effect on brake thermal efficiency (BTE) of a blend of 90% methanol and 10% water by weight, which is interesting from a methanol fuel production cost perspective. Experiments were conducted on a dual-fuel marine Volvo Penta engine with methanol/water weight by weight shares of 50%/50% (MeOH-50), 64%/36% (MeOH-64), 90%/10% (MeOH-90) and 100%/0% (pure methanol, MeOH-100). A maximal increase in BTE of 3.3% and 4.9% were observed when going from respectively MeOH-100 and diesel-only operation to MeOH-50. The maximum methanol energy fraction (MEF) was obtained with pure methanol, equal to 76%, and decreased with increasing water content. NOx emissions decreased with pure methanol compared to diesel-only operation, and further decreased with increasing water content. It is concluded that MeOH-90 does not harm the BTE of the tested dual-fuel engine; and that MeOH-50 and MeOH-64 were able to reach IMO Tier III NOx legislation, but at the same time score worse for greenhouse gas reduction potential as less diesel can be substituted by methanol with these blends.

Performance Optimization and Knock Investigation of Marine Two-Stroke Pre-Mixed Dual-Fuel Engine Based on RSM and MOPSO

The two-stroke pre-mixed dual-fuel marine engine is prone to knocking at full load in gas mode, which affects the overall dynamic and economic performance of the engine. In this paper, the 7X82DF engine produced by Winterthur Gas & Diesel Ltd. (WinGD) was selected as the research object, aiming to investigate the effect of different parameters on engine power and knocking. Multi-objective optimizations were carried out. First, we used the one-dimensional simulation software AVL-BOOST to build the gas mode model of 7X82DF. Second, the pilot fuel start of combustion timing (SOC), the gas injection pressure, and the mass of diesel were taken as independent variables. The response surface methodology analysis of the independent variables was completed using the Design-Expert software and corresponding prediction model equations were generated. Finally, we took ringing intensity (RI) as the knock intensity evaluation index, combined with multi-objective particle swarm optimization (MOPSO) to optimize multiple-parameters to improve the overall performance and reduce combustion roughness of the engine. The optimization results showed that when the SOC was −8.36 °CA ATDC, the gas injection pressure was 20.00 bar, the mass of diesel was 14.96 g, the corresponding power was 22,668 kW, which increased by 0.68%, the brake-specific fuel consumption was 156.256 g/kWh, which was reduced by 3.58%, the RI was 4.4326 MW/m2, and the knock intensity decreased by 6.49%.

Supercritical CO2 Power Cycle and Ejector Refrigeration Cycle for Marine Dual Fuel Engine Efficiency Enhancement by Utilizing Exhaust Gas and Charge Air Heat

Dual fuel engines with LNG as fuel have become a feasible solution for ship power units in the current situation, but their fuel efficiency needs to be further enhanced to meet the increasingly stringent emission requirements. This paper designs a dual-loop system, including a supercritical CO2 power cycle and a thermally driven ejector refrigeration cycle, for recovering the exhaust gas and charge air heat of a marine dual fuel engine. The models of the waste heat recovery system, the evaluation indicators of the combined system, and the genetic algorithm optimization program are developed. Compared to the standalone machine, the waste heat recovery system can improve by about 9.3% of the engine’s fuel efficiency. The performance analysis shows that the ejector contributes to the highest share of exergy destruction and accounts for approximate 53% of the refrigeration cycle. There are optimal values for the compressor inlet temperature of about 8.1 MPa and for the turbine inlet temperature of about 305 °C. Finally, after optimization, the specific fuel consumption, fuel efficiency, and CO2 emissions of the combined system are around 137.9 g/kWh, 53.3%, and 537.4 g/kWh, respectively. It provides a feasible solution in which the charge air cooler can be wholly replaced by the ejector refrigeration cycle.

Numerical Investigation on Mixing Characteristics and Mechanism of Natural Gas/Air in a Super-Large-Bore Dual-Fuel Marine Engine

Premixed combustion mode dual-fuel (DF) engines are widely used in large-bore marine engines due to their great potential to solve the problem of CO2 emissions. However, detonation is one of the main problems in the development of marine engines based on the premixed combustion mode, which affects the popularization of liquefied natural gas (LNG) engines. Due to the large bore and long stroke, marine dual-fuel engines have unique flow characteristics and a mixture mechanism of natural gas and air. Therefore, the purpose of this study is to present a simulated investigation on the influence of swirl on multiscale mixing and the concentration field, which provides a new supplement for mass transfer theory and engineering applications. It is suggested that the phenomenon of abnormal combustion occurs on account of the distribution of the mixture being uneven in a super-large-bore dual-fuel engine. Further analysis showed that the level of swirl at the late compression stage and the turbulence intensity are the decisive factors affecting the transmission process of natural gas (NG) and distribution of methane (CH4) concentration. Finally, a strategy of improving mixture quality and the distribution of the mixture was proposed.