Large Marine Engine Research Articles

Numerical investigation on the effects of pilot fuel and natural gas injection pressures on methane slip in a large marine dual-fuel engine

Numerical investigation on the effects of pilot fuel and natural gas injection pressures on methane slip in a large marine dual-fuel engine

Control strategies for mode switching of a large marine two-stroke engine equipped with exhaust gas recirculation and turbocharger cut-off systems

To meet the stringent nitrogen oxides emissions regulations, the recent marine two-stroke engines are equipped with exhaust gas recirculation (EGR) systems. Crossing the boundaries of exhaust control areas requires switching between the engine operating modes associated with the activation or deactivation the EGR system, which imposes challenges to the engine operation. This study aims to develop and numerically test effective control strategies for improving the mode switching of marine two-stroke engines with EGR systems. The investigated engine dynamic model is developed by integrating a zero-dimensional thermodynamic model developed in GT-POWER and the control model developed in MATLAB/Simulink. This model is first validated against the experimentally measured engine performance parameters, and subsequently employed to simulate the engine dynamic operation with mode switching. The simulation results are assessed to quantify the impact of several control strategies on the engine performance. The derived perrformannce parameters time variations demonstrate that the deactivation of the EGR branch and the small engine–turbocharger result in exceeding the manufacturer limits at high loads and increasing the fuel consumption. The proposed load-based control strategies, which employ load thresholds and time delays for the control of the EGR and turbocharging systems activation/deactivation, are proved effective, as the engine performance parameters are retained within their limits and fuel consumption penalties are minimised. This study provides insights for developing the control of the marine engines after-treatment systems, hence contributing towards enhancing shipping sustainability.

Experimental study on reducing BC emissions from a low-speed marine engine by using blended biodiesel and a nitro additive

The aim of this study was to evaluate the emission reduction effect of using waste oil biodiesel/diesel binary fuel and a nitro additive on black carbon (BC) emissions from a large marine engine fueled by heavy fuel oil (HFO). We conducted steady-state conditions tests on a low-speed two-stroke marine engine, where pure distillate diesel (D100), blended biodiesel (blending ratios of 10%, 30%, and 50%), low-sulfur heavy fuel oil (LSFO), high-sulfur heavy fuel oil (HSFO), and a nitro additive were tested, and the BC emission concentrations from the engine were measured under different conditions using a filter-type smoke meter (FSM) and a photoacoustic smoke meter (PAS). The results indicated that BC emissions from the engine were significantly decreased when blended biodiesels were used, with the decline rate increasing as the engine load increased, reaching a maximum reduction of 73% and 94% under 75% and 100% load compared to the use of HFOs, respectively. However, the use of biodiesel slightly increased the brake specific fuel consumption (BSFC) and NOx emissions. The nitro additive was blended with LSFO and HSFO at a ratio of 1:1200, respectively. It was observed that the introduction of the nitro additive led to a significant reduction in BC emissions compared to the use of pure HFOs. But different from the case of using blended biodiesels, the decline rate of BC decreased with increasing engine load. The BC emissions from LSFO and HSFO were decreased by approximately 10% and 25% under 25% load, respectively, the corresponding BSFC decreased by 5.88% and 3.71%, respectively, while the NOx emissions increased by 11.59% and 34.58%, respectively. In addition, the BC emissions measured by the FSM were on average 38.56% and 43.53% higher than those of the PAS when LSFO and HSFO were used, respectively.

High Quality Multi-Zone and 3D CFD Model of Combustion in Marine Diesel Engine Cylinder

Abstract The paper presents a 3D model of the processes taking place in the cylinder of a large 4-stroke marine engine. The model is based on CFD calculations performed on the moving mesh. The modelling range includes the full duty cycle (720° crankshaft position) and the complete geometry of the cylinder with inlet and exhaust ducts. The input data, boundary conditions and validation data were obtained by direct measurements on the real object. Fuel injection characteristics were obtained by Mie scattering measurements in a fixed-volume chamber. The modelling results have been validated in terms of the pressure characteristics of the engine’s cylinder within the entire range of its loads. The mean error did not exceed 1.42% for the maximum combustion pressure and 1.13% for the MIP (Mean Indicated Pressure). The model was also positively validated in terms of the O2 and NOx content of the exhaust gas. The mean error in this case was 1.2% for NOx fractions in the exhaust gas and 0.4% for O2 fractions. The complete model data has been made available in the research data repository on an open access basis.

Determination of Geometrical Deviations of Large-Size Crankshafts with Limited Detection Possibilities Resulting from the Assumed Measuring Conditions

This article deals with the geometrical deviation measurements of crankshafts of large marine engines fuelled with conventional or alternative fuels, taking into account the problem of their deformability. Since the detectability of geometrical deviations of a crankshaft supported by prisms depends largely on the support conditions assumed and the parameters of the method, the study was carried out for two cases of crankshaft support. The first case concerned measurements of the main journals of a crankshaft seated on a set of supports pre-positioned at an equal height. In contrast, the second case involved measurements of the main journals of a crankshaft seated on supports pre-positioned at various heights. In particular, the research focused on evaluating the effect of sensor location angle on the results of measurements of deviations and contour profiles of the crankshaft main journal system. The results of the research are the developed procedures, the application of which in practical measurements under workshop conditions, where there is no access to coordinate measuring machines, enables correct interpretation of the measurement results and evaluation of the geometrical state of the measured crankshaft.

Experimental study of combustion process of NH3 stratified spray using imaging methods for NH3 fueled large two-stroke marine engine

To achieve greenhouse gas emission reductions from the maritime sector, there is a growing demand for the development of NH3 fueled marine engines. Since NH3 is difficult to ignite and burn, it is valid to assist the NH3 combustion by a supporting fuel, which is easily ignited and burned. A new NH3 spray combustion concept for a large two-stroke marine engine has been proposed, which is a “three-layer stratified fuel injection comprising supporting fuel / liquid NH3 / supporting fuel (i.e., NH3 stratified injection)”. The advantages of the NH3 stratified injection concept are the symmetrical combustion support effect in the spray axis at important timing (ignition and late combustion). The supporting fuel used was n-hexadecane (nC16H34, cetane). The characteristics of the NH3 stratified spray under non-combustion conditions were investigated in an optically accessible constant volume combustion chamber using a reflective shadowgraph imaging system. The spray penetration length and the spray cone angle were similar to those of the 100% nC16H34 spray and typically estimated equations. Moreover, the combustion process of an NH3 stratified spray was investigated using high-speed direct imaging. The flame lift-off position moved downward and the rapid combustion by the third layer was different compared to those of the 100% nC16H34 spray. The burnt gas lump was confirmed to have initially played an important role in the flame lift-off position. The rapid combustion stems from the multipoint ignition, flame propagation, and downward movement of the flame by the jet stream. Additionally, the NH3 combustion in the NH3 stratified spray was investigated using imaging spectroscopy. The spectra of chemiluminescence revealed that the NH3 combustion progressed after forming the initial burnt gas lump, and the NH2* ammonia α-band was observed in the combustion area. Consequently, the combustion process of an NH3 stratified spray was clarified from these experimental results.

Health assessment framework of marine engines enabled by digital twins

The advancements in digital twins when combined with the use of the machine learning tools can facilitate the effective health assessment and diagnostics of safety critical systems. This study aims at developing a framework to address the health assessment of marine engines utilising digital twins based on first-principles. This framework follows four distinct stages, with the former two including the marine engine digital-twin set up by customising the required thermodynamic models, as well as its calibration using tests trials data representing the engine healthy conditions. In the third stage, measurements from actual operating conditions are corrected and subsequently employed to develop the digital twin representing the prevailing conditions. The fourth stage deals with the engine health assessment by assessing health metrics derived from the developed digital twins. This framework is demonstrated in a case study of a large marine four-stroke nine-cylinder propulsion engine. The results demonstrate that three cylinders are identified to be underperforming leading to an average increase of the engine Brake Specific Fuel Consumption (BSFC) by 2.1%, whereas an average decreases of 6.8% in Indicated Mean Effective Pressure (IMEP) and 6.1% in the Exhaust Gas Temperature (EGT) are exhibited for the underperforming cylinders across the entire operating envelope. The developed digital twins facilitate the effective mapping of the engine performance for the entire operating envelope under several health conditions, providing enhanced insights for the current engine health status. The advantages of the proposed framework include the use of easily obtained data, and its application to several engine types including two and four-stroke engines for both propulsion and auxiliary use.

중대형 선박 엔진용 냉각수 펌프 개발

The cooling pump for medium and large marine engines is a centrifugal pump, which circulates the coolant to cool the engine, lubricating oil and fresh water. As the built-in engine cooling water pump uses a large amount of power compared to other auxiliary equipment driven by the engine power of a ship, proper design of components, such as the impeller, is required to improve the pump efficiency to 60% or more, and without appearance of cavitation. In this study, the impeller, volute casing, and housing that correspond to various engine specifications of marine engine manufacturers, were used. The pump installed marine engines with a total efficiency of 60% or more were designed with CFturbo S/W. Performance tests of prototypes were conducted and the results were compared and reviewed. Ultimately, high efficiency and cavitation avoidance design technology of cooling water pump were acquired.

Investigation on the potential of using carbon-free ammonia in large two-stroke marine engines by dual-fuel combustion strategy

Ammonia (NH3) as a carbon-free fuel is gaining much attention in the shipping industry for its enormous potential of global decarbonization, which is expected to achieve large-scale applications in marine engines by dual-fuel (DF) combustion technology. As such, this study was conducted to explore the emission reduction potential of NH3/diesel DF combustion strategy via low-pressure gas injection in large low-speed two-stroke marine engines using computational fluid dynamics (CFD) modeling coupled with chemical kinetics. An established in-house CFD platform, KIVA-CHEMKIN-CDAC, was employed to perform engine simulations, while an DF combustion mechanism was constructed in this work to mimic the oxidation behaviors of NH3 and diesel as well as the emissions formation. It was found that NH3 admission exhibits a significant inhibiting effect on the autoignition of pilot fuel. Increasing ammonia substitution ratio (ASR) will prolong the ignition delay, resulting in high intensity of premixed combustion. Generally, NH3/diesel DF combustion mode shows two-stage heat release shape. The first stage is characterized by the premixed combustion of diesel–NH3–air mixtures, whereas the dominant combustion regime of the second stage highly depends on the NH3 concentration in the premixed charge. In the very lean NH3-air mixtures, the second stage corresponds to the mixing-controlled diffusion combustion phase; but for the richer NH3-air mixtures, it could be controlled by the turbulent flame propagation. NOx emission decreases when the ASR does not exceed 40%, otherwise increases significantly. The former is probably due to the Thermal DeNOx process dominated by NH2 + NO = N2 + H2O, while the latter is due to the fuel-bound nitrogen. As expected, CO2 emission is reduced monotonically for the same total fuel energy with the increase of ASR, confirming that the utilization of zero-carbon fuel is the most direct means to reduce CO2 emissions. Moreover, there is a trade-off relationship between NOx and N2O emissions. This is because N2O formation usually occurs at lower temperatures (i.e., T < 1400 K). Furthermore, advancing the pilot-fuel injection timing could reduce the unburned NH3 and N2O emissions. Therefore, optimization of injection timing can achieve lower emissions while maintain higher efficiency.

DEVELOPMENT OF METHODS FOR EVALUATION OF TECHNICAL CONDITION OF ENGINES ACCORDING TO THE RESULTS OF INDICATION OF WORKING PROCESS ON MODES DIFFERENT FROM NOMINAL

Technical condition assessment of marine internal combustion engines by the parameters and nature of the workflow is a common practice in their operation. Taking and analysis of indicator diagrams is a mandatory procedure provided by the rules of technical operation for the main range of large and medium-sized marine engines. There is a whole arsenal of indication means for such evaluation: from classical mechanical systems to electronic means of periodic or continuous action. The rapid development of electronic control systems and changes in approaches to logistics operations in maritime transport have imposed a number of limitations, somewhat narrowing the possibilities of using these methods. Most of the vessels that form the basis of the world merchant fleet were built 10...15 years ago. Information about the results of the indication of the engines of such vessels during bench tests is presented in the form of raster images. This complicates the process of using them as the reference needed to compare them with the actual diagrams obtained in operation by means of electronic control systems, which have replaced mechanical indicators over the past few years. In addition, tendencies to reduce the speed of vessels complicate, and often make it impossible to indicate the engines in the specified operating modes. As a result, the efficiency of using indicator diagrams to assess the current technical condition is sharply reduced. In this regard, there is an objective need to compare different methods of obtaining and storing information about the results of indication and in a unified method of presenting this information, convenient for processing and analysis. In addition, there is a need to develop methods for obtaining reference diagrams for nonspecific modes on the basis of processing the results of acceptance and commissioning bench tests of a particular engine to assess its technical condition by the results of indication on the partial load modes. This study is devoted to the comparison of different methods of presenting information and obtaining reference indicator diagrams for non-specific operating modes of engines.

Parameter Variation Study of Two-Stroke Low-Speed Diesel Engine Using Multi-Zone Combustion Model

The latest electronically controlled marine engines have a control system that allows the operator to view all the essential parameters of the engine in real conditions during operation. The system is connected to the electronic control system (ECS) through the control network, thus controlling the engine. The operator has various management and monitoring options. The objective of this paper was to become familiar with the specific factors that affect engine operation and optimize engine operation. A model of a large marine engine was developed and calibrated with measured data. Simulations were performed, and the combustion process was analyzed. The parameter study was performed by varying the fuel injection and the gas exchange timing. Fuel consumption decreases by 6 g/kWh, and NOx emissions decrease by 0.5 g/kWh. The research conducted in this work will be used by engineers to understand the potential of new technologies to optimize combustion in real-world conditions during operation and for the future development of an expert system to continuously monitor, diagnose, and optimize engine health during operation.

Parameter investigation of the pilot fuel post-injection strategy on performance and emissions characteristics of a large marine two-stroke natural gas-diesel dual-fuel engine

This study aimed to conduct a parametric study to investigate the effect arising from pilot fuel post-injection strategy on engine combustion, performance, and emissions of a large two-stroke natural gas-diesel dual-fuel engine for marine applications. The one-dimensional and three-dimensional simulation models were built in AVL-BOOST and CONVERGE, respectively, and validated according to experimental results. The effects of post-injection strategies on post-injection timing and mass ratio on engine combustion, performance, and emissions were investigated. As revealed by the results, an appropriate pilot fuel post-injection strategy could achieve lower NOx emissions with less loss of performance. As post-injection timing was delayed, the NOx emission first decreased and then increased. Subsequently, it decreased to the lowest and finally increased. With the increase in the post-injection mass ratio, the NOx emission was kept decreasing. Compared with the original engine, the NOx emission decreased by 81.85 ppm with a post-injection timing of 18 deg after top dead center and with a mass ratio of 0.7. However, the indicated power only decreased by 4.82 kW, and the indicated specific fuel consumption only increased by 0.2 g/kWh. This study can provide some theoretical guidance for the injection strategy optimization of the marine two-stroke natural gas-diesel dual-fuel engines and provide technical suggestions for practical application.

NH3 combustion using three-layer stratified fuel injection for a large two-stroke marine engine: Experimental verification of the concept

A unique liquid NH3 spray combustion concept for a compression ignition engine, which applies a "three-layer stratified fuel injection comprising a supporting fuel / liquid NH3 / supporting fuel (i.e., NH3 stratified injection)” concept, in which the liquid NH3 is sandwiched by the supporting fuels, is proposed for a large two-stroke marine engine. The supporting fuel is a liquid fuel which can be ignited and burnt easily, such as marine gas oil, marine diesel oil, biodiesel oil and synthetic diesel oil produced from renewable energies. The three layers were injected sequentially from a single nozzle, and a three-layered spray was formed. To verify the combustion concept, a constant volume combustion chamber and a stratified fuel injection system were developed to simulate combustion in the cylinder of a large two-stroke engine. We then confirmed that the stratified fuel injection system can very nearly realize a two- or three-layer spray, by measuring the energy injection rate during one injection period. In the experiments, the heat release rates and combustion gas compositions for the NH3 stratified injection were evaluated. From the experimental results, and using the combustion concept, we found that the fuel is ignited and burns up the NH3 in the NH3 stratified injection; it also suppresses N2O production via the combustion of the supporting fuel in the third layer. Consequently, it was found that the combustion concept is effective for liquid NH3 spray diffusion combustion in large two-stroke marine engines.

Computational exploration of bio-oil blend effects on large two-stroke marine engines

Maritime shipping is an essential and growing component of international trade, with over 90% of all the world’s goods being transported on large ocean-going vessels. The sector is also among the last to reduce criteria pollutants and is responsible for up to 3% of global CO2 emissions. For the first time, the maritime sector is facing regulatory action on multiple fronts: reductions in fuel sulfur content, CO2 emissions, and NOx emissions, as well as expected upcoming limits on black carbon emissions. Decarbonizing the maritime sector requires the development of new fuel sources that do not compete with other transportation fuels in the global market. Because of the extremely large physical size of the internal combustion engines present in shipping vessels, experimental development of the engine-fuel system is often cost prohibitive. This work aims to develop a computational model of a scaled marine engine. The scaled model is representative of a custom-built 1:10 scale research engine commissioned for lubricant research at Oak Ridge National Laboratory. Reduced chemical mechanisms are developed for diesel, biodiesel, bio-oil, and polycyclic aromatic hydrocarbons (PAH). The mechanisms are combined, and the impact of these fuel blends on the emissions of NOx and PAHs (as a surrogate for soot) is assessed. The model is validated against experimental data, and details of the differences in the combustion process between the different fuels are discussed.

Comparative Assessment and Parametric Optimisation of Large Marine Two-Stroke Engines with Exhaust Gas Recirculation and Alternative Turbocharging Systems

Although the exhaust gas recirculation (EGR) technology has been proven effective to decrease the marine engine’s nitrogen oxides (NOx) emissions, it is associated with a considerable fuel consumption increase and challenges to the engine–turbocharger matching. This study aims to parametrically optimise the EGR and turbocharging system settings of a large marine two-stroke engine with the objective of obtaining the highest engine efficiency whilst ensuring compliance with the prevailing NOx emissions limits. Two typical configurations of the investigated engine (baseline and alternative) are modelled in the GT-SUITE software. Parametric simulations are performed with EGR rates up to 40% along with cylinder bypass rates up to 50%, and the simulation results are analysed to quantify the impact of the engine operation with EGR on the performance and NOx emissions parameters. For the baseline engine configuration, the EGR rate increase considerably deteriorates the brake specific fuel consumption (BSFC), which is attenuated by opening the cylinder bypass valve. The optimal combinations of the EGR and cylinder bypass rates for each operating point are identified for both configurations. Following the comparative assessment between the two engine configurations, recommendations for the engine operating modes are proposed, leading to BSFC improvement in the region of 0.7 to 2.9 g/kWh. This study provides insights for the operational settings optimisation of two-stroke engines equipped with EGR systems, contributing towards the reduction of the associated environmental carbon footprint.

Optimisation of Maintenance Policies Based on Right-Censored Failure Data Using a Semi-Markovian Approach.

This paper exposes the existing problems for optimal industrial preventive maintenance intervals when decisions are made with right-censored data obtained from a network of sensors or other sources. A methodology based on the use of the z transform and a semi-Markovian approach is presented to solve these problems and obtain a much more consistent mathematical solution. This methodology is applied to a real case study of the maintenance of large marine engines of vessels dedicated to coastal surveillance in Spain to illustrate its usefulness. It is shown that the use of right-censored failure data significantly decreases the value of the optimal preventive interval calculated by the model. In addition, that optimal preventive interval increases as we consider older failure data. In sum, applying the proposed methodology, the maintenance manager can modify the preventive maintenance interval, obtaining a noticeable economic improvement. The results obtained are relevant, regardless of the number of data considered, provided that data are available with a duration of at least 75% of the value of the preventive interval.

An experimental study of the effect of condensing water vapour on the cold corrosion wear of marine engine cylinder liners

AbstractThis work presents an experimental study of the cold corrosion wear phenomenon that is experienced on the cylinder liners in large two‐stroke marine diesel engines that burn heavy fuel oil containing sulfur. The wear is caused by condensing sulfuric acid‐ and water vapours (H2SO4 and H2O, respectively) that are formed during combustion. In this work, cold corrosion is studied experimentally with a modified and motored light duty engine that operates at 98 revolutions per minute, in order to match the rotational speed of a large marine engine. The engine works as a tribotester where multiple charge gas compositions with up to 10% H2O and 80 ppm H2SO4 (mole/mole) in dry air are fed to its cylinders to produce realistic marine engine H2O and H2SO4 partial pressures. A lube oil blend that is composed by a conventional two‐stroke marine engine cylinder lube oil and a base oil is used in the experiments. By extracting oil samples from the engine oil swamp during an experiment (that are analysed for iron and sulfur content using an energy dispersive X‐ray fluorescence spectrometer) the cylinder liner wear rate and sulfuric acid condensation rate are determined for the applied charge gas composition and liner surface temperature (primarily 80°C). The method shows that the different charge gas compositions yield distinct liner wear rates and the highest wear rates are experienced at elevated H2O concentrations where the influence of H2SO4 is comparably low.

CFD Analysis of a Large Marine Engine Scavenging Process

The scavenging process is an important part of the two-stroke engine operation. Its efficiency affects the global engine performance such as power, fuel consumption, and pollutant emissions. Slow speed marine diesel engines are uniflow scavenged, which implies inlet scavenging ports on the bottom of the liner and an exhaust valve on the top of the cylinder. A CFD model of such an engine process was developed with the OpenFOAM software tools. A 12-degree sector of the mesh was used corresponding to one of the 30 scavenging ports. A mesh sensitivity test was performed, and the cylinder pressure was compared to experimental data for the analyzed part of the process. The scavenging performances were analyzed for real operation parameters. The influence of the scavenge air pressure and inlet ports geometric orientation was analyzed. The scavenging process is analyzed by means of a passive scalar representing fresh air in the cylinder. Isosurfaces that show the concentration of fresh air were presented. The variation of oxygen and carbon dioxide with time and the axial and angular momentum in the cylinder were calculated. Finally, the scavenging performance for the various operation parameters was evaluated by means of scavenging efficiency, charging efficiency, trapping efficiency, and delivery ratio. It was found that the scavenging efficiency decreases with the engine load due to the shorter time for the process. The scavenging efficiency increases with the pressure difference between the exhaust and scavenging port, and the scavenging efficiency decreases with the increase in the angle of the scavenging ports. It was concluded that smaller angles than the industry standard of 20° could be beneficial to the scavenging efficiency. In the investigation, the charging efficiency ranged from 0.91 to over 0.99, the trapping efficiency ranged from 0.54 to 0.83, the charging efficiency ranged from 0.78 to 0.92, and the delivery ratio ranged from 1.21 to 2.03.

A Novel Process for Manufacturing High-Friction Rings with a Closely Defined Coefficient of Static Friction (Relative Standard Deviation 3.5%) for Application in Ship Engine Components.

In recent years, there has been an increased uptake for surface functionalization through the means of laser surface processing. The constant evolution of low-cost, easily automatable, and highly repeatable nanosecond fibre lasers has significantly aided this. In this paper, we present a laser surface-texturing technique to manufacture a surface with a tailored high static friction coefficient for application within driveshafts of large marine engines. The requirement in this application is not only a high friction coefficient, but a friction coefficient kept within a narrow range. This is obtained by using nanosecond-pulsed fibre lasers to generate a hexagonal pattern of craters on the surface. To provide a suitable friction coefficient, after laser processing the surface was hardened using a chromium-based hardening process, so that the textured surface would embed into its counterpart when the normal force was applied in the engine application. Using the combination of the laser texturing and surface hardening, it is possible to tailor the surface properties to achieve a static friction coefficient of ≥0.7 with ~3–4% relative standard deviation. The laser-textured and hardened parts were installed in driveshafts for ship testing. After successfully performing in 1500 h of operation, it is planned to adopt the solution into production.

Parametric investigation of a large marine two-stroke diesel engine equipped with exhaust gas recirculation and turbocharger cut out systems

Albeit the exhaust gas recirculation (EGR) is widely used to reduce the nitrogen oxides (NOx) emissions from large marine two-stroke engines, several challenges emerge for the engine–turbocharging system matching considering the contradictory requirements of the engine and its subsystems operation. Such challenges become more pronounced in complex engine configurations that include parallel turbochargers and the EGR system along with cut out and bypass branches. This study aims at parametrically investigating a large marine two-stroke engine equipped with an EGR system, two parallel turbochargers of different size, and cut out branches. The turbocharging system characteristics are selected targeting the minimisation of the engine specific fuel consumption whilst ensuring compliance with the respective NOx emissions limits and satisfying imposed constraints for the compressors operation. A detailed model of the zero/one dimensional type is developed in the GT-SUITE software and used to simulate the investigated engine along with its subsystems. Simulation runs are performed to investigate the engine with four different turbocharger configurations of varying capacity ratio and under various operating conditions in terms of the EGR rate and engine load. The simulation results are analysed to reveal the impact of the turbocharger selection of the engine performance and emissions parameters. Furthermore, modulation schemes with EGR blower speed control, exhaust gas bypass and cylinder bypass are investigated to overcome the mismatch on the engine components flow rates and avoid turbocharger operational issues. The derived results demonstrate that the lowest weighted BSFC is achieved for the case of 70:30 capacity ratio between the large and small turbochargers, whilst the engine operation with the EGR is associated with a 2.6% penalty in the weighted BSFC. The EGR blower speed control is found sufficient to avoid the compressor overspeed at high engine loads exhibiting the lower BSFC penalty, whereas the cylinder bypass control is appropriate for controlling the compressor speed at low engine loads. This study contributes on delineating the underlying parameters and interactions between the engine components for the investigated marine two-stroke engine and provides recommendations for the engine–turbocharging system matching procedure.