Marine Medium-speed Diesel Engine Research Articles

Research on Machining Quality Prediction Method Based on Machining Error Transfer Network and Grey Neural Network

Machining quality prediction is the critical link of quality control in parts machining. With the advent of the Industry 4.0 era, intelligent manufacturing and data-driven technologies bring new ideas for quality control in complex machining processes. Quality control is complicated for multi-process, multi-condition, small-batch, and high-precision parts processing requirements. To solve this problem, this paper proposes a machining quality prediction method based on the machining error transfer network and the grey neural network. Initially, by constructing a processing error transfer network, the error transfer law in part processing is described, and the PageRank algorithm and the influence degree of the nodes are used to determine the critical quality features. Additionally, the problem of low prediction accuracy due to small sample data and multiple coupling relationships is solved using the grey neural network algorithm, and a high accuracy prediction of critical quality features is achieved. Finally, the effectiveness and reliability of the method are verified by the case of medium-speed marine diesel engine fuselage processing. The results indicate that this method not only effectively identifies critical quality features in the machining process of complex parts, but it also maintains a high predictive accuracy for these features, even with small samples and limited data.

Research on Critical Quality Feature Recognition and Quality Prediction Method of Machining Based on Information Entropy and XGBoost Hyperparameter Optimization

To address the problem of predicting machining quality for critical features in the manufacturing process of mechanical products, a method that combines information entropy and XGBoost (version 2.1.1) hyperparameter optimization is proposed. Initially, machining data of mechanical products are analyzed based on information entropy theory to identify critical quality characteristics. Subsequently, a quality prediction model for these critical features is established using the XGBoost machine learning framework. The model’s hyperparameters are then optimized through Bayesian optimization. This method is applied as a case study to a medium-speed marine diesel engine piston. After the critical quality characteristics in the machining process are identified, the machining quality of these vital characteristics is predicted, and the results are compared with those obtained from a machine learning model without hyperparameter optimization. The findings demonstrate that the proposed method effectively predicts the machining quality of mechanical products.

Methodological Solutions for Predicting Energy Efficiency of Organic Rankine Cycle Waste Heat Recovery Systems Considering Technological Constraints

Solving strategic IMO tasks for the decarbonization of maritime transport and the dynamics of its controlling indicators (EEDI, EEXI, CII) involves the comprehensive use of renewable and low-carbon fuels (LNG, biodiesel, methanol in the mid-term perspective of 2030, ammonia, and hydrogen to achieve zero emissions by 2050) and energy-saving technologies. The technology of regenerating secondary heat sources of the ship’s power plant WHR in the form of an Organic Rankine Cycle (ORC) is considered one of the most promising solutions. The attractiveness of the ORC is justified by the share of the energy potential of WHR at 45–50%, almost half of which are low-temperature WHR (80–90 °C and below). However, according to DNV GL, the widespread adoption of WHR-ORC technologies, especially on operating ships, is hindered by the statistical lack of system prototypes combined with the high cost of implementation. Developing methodological tools for justifying the energy efficiency indicators of WHR–ORC cycle implementation is relevant at all stages of design. The methodological solutions proposed in this article are focused on the initial stages of comparative evaluation of alternative structural solutions (without the need to use detailed technical data of the ship’s systems, power plant, and ORC nodes), expected indicators of energy efficiency, and cycle performance. The development is based on generalized results of variation studies of the ORC in the structure of the widely used main marine medium-speed diesel engine Wärtsilä 12V46F (14,400 kW, 500 min−1) in the operational load cycle range of 25–100% of nominal power. The algorithm of the proposed solutions is based on the established interrelationship of the components of the ORC energy balance in the P-h diagram field of thermodynamic indicators of the cycle working fluid (R134a was used). The implemented strategy does allow, in graphical form, for justifying the choice of working fluid and evaluating the energy performance and efficiency of alternative WHR sources for the main engine, taking into account the design solutions of the power turbine and the technological constraints of the ORC condensation system. The verification of the developed methodological solutions is served by the results of comprehensive variation studies of the ORC performed by the authors using the professionally oriented thermoengineering tool “Thermoflow” and the specification data of Wärtsilä 12V46F with an achieved increase in energy efficiency indicators by 21.4–7%.

Complex Use of the Main Marine Diesel Engine High- and Low-Temperature Waste Heat in the Organic Rankine Cycle

The decarbonization problem of maritime transport and new restrictions on CO2 emissions (MARPOL Annex VI Chapter 4, COM (2021)562) have prompted the development and practical implementation of new decarbonization solutions. One of them, along with the use of renewable fuels, is the waste heat recovery of secondary heat sources from a ship’s main engine, whose energy potential reaches 45–55%. The organic Rankine cycle (ORC), which uses low-boiling organic working fluids, is considered one of the most promising and energy-efficient solutions for ship conditions. However, there remains uncertainty when choosing a rational cycle configuration, taking into account the energy consumption efficiency indicators of various low-temperature (cylinder cooling jacket and scavenging air cooling) and high-temperature (exhaust gas) secondary heat source combinations while the engine operates within the operational load range. It is also rational, especially at the initial stage, to evaluate possible constraints of ship technological systems for ORC implementation on the ship. The numerical investigation of these practical aspects of ORC applicability was conducted with widely used marine medium-speed diesel engines, such as the Wartsila 12V46F. Comprehensive waste heat recovery of all secondary heat sources in ORC provides a potential increase in the energy efficiency of the main engine by 13.5% to 21% in the engine load range of 100% to 25% of nominal power, while individual heat sources only achieve 3% to 8%. The average increase in energy efficiency over the operating cycle according to test cycles for the type approval engines ranges from 8% to 15% compared to 3% to 6.5%. From a practical implementation perspective, the most attractive potential for energy recovery is from the scavenging air cooling system, which, both separately (5% compared to 6.5% during the engine’s operating cycle) and in conjunction with other WHR sources, approaches the highest level of exhaust gas potential. The choice of a rational ORC structure for WHR composition allowed for achieving a waste heat recovery system energy efficiency coefficient of 15%. Based on the studied experimental and analytical relationships between the ORC (generated mechanical energy) energy performance (Pturb) and the technological constraints of shipboard systems (Gw), ranges for the use of secondary heat sources in diesel operational characteristic modes have been identified according to technological limits.

Use of biofuels in marine diesel engines for sustainable and safe maritime transport

The article presents results of research on the use of fuel mixtures, containing with biodiesel fuel. The research was carried out on specialized sea vessels with a deadweight of 10,820 tons and 29,420 tons, which made passages in the waters of South America and the Caribbean, as well as in the Sulphur Emission Control Areas of Northern Europe. The operation of the ship's power plants (main and auxiliary engines) was provided both on marine fuel of petroleum origin and on a fuel mixture that consisted of petroleum fuel and biodiesel fuel. The experiments were carried out on marine medium-speed diesel engines 5DC-17A Daihatsu Diesel, 16V32 Wärtsilä-Sulzer and Volvo Penta TWD1645GE. Various kinds of marine fuels and as biodiesel fuel Fatty Acid Methyl Esters B99.9 FAME and B99.6 FAME were used. The concentration of biodiesel fuel in the fuel mixture was 5–20 %. The environmental friendliness of the work of sea vessels was assessed by the value of the emission of nitrogen oxides, sulphur, and carbon. As a result of the research, a variant of adjusting the sea crossing was proposed to ensure the continuous operation of the ship's power plant using biodiesel fuel.

Study on the forming process of the cylinder wall fuel film and the piston top land ablation mechanism of a medium speed marine diesel engine under cold start condition

The study presents an explanation of the piston top land ablation mechanism in a specific type of marine medium-speed diesel engine, utilizing multi-dimensional Computational Fluid Dynamics (CFD) software. At present, there is a lack of research on the process analysis of fuel droplets attached to the cylinder wall at diesel engine cold start condition and the mechanism of piston top land ablation. The study results indicate that during low-speed cold start condition, a multitude of diesel droplets impact the wall, causing the combustion area concentrated near the wall of the combustion chamber. The last stage fuel spray droplets, driven by the vortex in the cylinder, adhere to the cylinder wall before evaporation during the post-combustion stage. After multi-cycle operation of the diesel engine under cold start condition, the mass of fuel film adhering to the cylinder wall and the cumulative fuel mass on the top of the gas ring increase. As the engine getting warm, higher cylinder wall temperature leads to rapid evaporation of the fuel film on the cylinder wall and the gas ring. Deflagration happens when the fuel vapor burns under high temperature and high-pressure condition, and subsequent pressure oscillation destroys the thermal boundary layer of the piston top land. Piston material ablation happens under high temperature and high-pressure shock.

Research on identification of key processes in machining process based on PageRank algorithm

Aiming at the difficulty of quantitatively evaluating the critical processes in the manufacturing process of complex mechanical products, a critical process identification method based on the PageRank algorithm is proposed with the goal of identifying key processes in the machining process. Based on the complex network theory, the error transfer network model of the machining process is established in this paper. Adopting the actual machining process as the data set of the complex network, the weights of the machining feature nodes are calculated by the PageRank ranking algorithm, and the nodes are ranked according to the weight values to assess the influence and importance of the nodes in the network model. Finally, taking the connecting rod machining process of a medium-speed marine diesel engine as an example, the results show that the method can quickly and effectively identify the key processes in the machining process.

Research on combustion process optimization of marine diesel engines based on dual-injector system

Marine diesel engines are widely used with their strong power and mature technology. However, in recent years, the emphasis on environmental protection has made combustion pollutants the focus of attention, and the new regulations of the International Maritime Organization (IMO) and various countries have put forward new requirements and challenges for diesel engine combustion and emission performance. Due to the large size and large amount of circulating fuel injection, the incomplete mixing of fuel in the cylinder and the local violent combustion of high-power medium-speed marine diesel engines are important reasons for low thermal efficiency and high pollutant emissions. To achieve efficient and clean combustion of fuel in the cylinder, a dual-injector combustion system is designed on a dual-fuel engine basis, aiming to add a micro-injection before the central injection and provide positive in-cylinder flow and hot atmosphere for the atomized combustion of the central-injection fuel, so that the combustion in the cylinder is reasonably arranged, the thermal efficiency is improved and NOx emissions are reduced. The 3D simulation model was established by CFD software CONVERGE, and the physical model was calibrated according to the data of the pure diesel mode of the dual-fuel engine, and the influence of the small pilot-injection fuel volume on the development of spray and combustion in the cylinder at high and low load was analyzed. It was found that the small pilot-injection fuel volume at a high load had little effect on the atomization evaporation of the main-injection fuel and the hot atmosphere in the cylinder, so the improvement effect of combustion quality was not obvious, while the pilot-injection volume with the same pilot-injection capacity as high load relatively accounted for a large proportion at the low load with a small cycle injection volume. Without changing the injector specification settings of the original dual-fuel engine, the thermal efficiency was increased by 6.13% and the NOx generation was reduced by 22.42% by optimizing the injection timing, injection duration, and injection amount.

Study on the impact mechanism of ammonia energy fraction on in-cylinder combustion and pollutant generation under wide operation conditions of medium-speed diesel engines

To expedite the utilization of ammonia in the domain of marine medium-speed diesel engines. The computational fluid dynamics (CFD) model combined with the ammonia/n-dodecane reaction mechanism were conducted to explore the impact mechanism of ammonia energy ratio (AER) and diesel injection timing on in-cylinder combustion and pollutant emission at low-mid-high loads of marine medium-speed diesel engines. Further, the formation laws of Thermal and Fuel nitrogen oxides (NOX) at various AER conditions were analyzed. At 10 % load, the rising AER advanced the CA50 by 57 % and increased the in-cylinder peak pressure by 3.5 % due to the enhanced premixed combustion stage. Whereas, at higher loads (50 % & 100 %), the effect of high specific heat capacity of ammonia played a crucial role in combustion progress with the increasing AER, which reduced the in-cylinder peak pressure by 1–3 %. The sensitivity of key combustion phases (CA10-CA90) to AER also gradually decreased with the rising loads because of the inhibited diffusion combustion stage. When the IT was 6°BTDC, the peak temperature in the cylinder decreased by 10 % at 10 % engine load; and the charge of excessive temperature in the cylinder was significantly reduced at 50 % and 100 % engine load. In terms of emission characteristics, HC and CO emission significantly reduced when AER was 45 %. And the proportion of Fuel NH3 in the fuel rose from 75.5 % to 91.4 % with the increasing AER. This means that the generation conditions of Thermal NOx were inhibited in the large proportion of ammonia-doped combustion conditions.

Experimental investigation on spray and flame characteristics of a marine diesel engine with single and double injection

Multiple injection is one of the advanced technologies employed in modern diesel engines to improve combustion efficiency, reduce pollutant emissions, and minimize combustion noise. The application of multiple injection in marine diesel engines differs from its use in vehicles or heavy-duty engines, as it is not commonly combined with Exhaust Gas Recirculation (EGR). However, there is a scarcity of studies specifically examining the combustion characteristics of medium-speed marine diesel engines utilizing multiple injection. Given the large space scale of marine diesel engine, a constant volume chamber with a visible diameter of 240 mm was used, and an injector with a nozzle diameter of 0.465 mm was employed in the experiment. The spray development and combustion process were recorded by Mie-scattering and flame natural luminosity imaging respectively. Both conventional and double injection combustion processes were analyzed in detail. The results show that although the liquid phase spray does not fully penetrate to the cylinder wall in marine diesel engines, the flame penetrates to the cylinder wall rapidly, the flame burns near the wall almost throughout the entire combustion duration. The combustion characteristics of the double injection are significantly different, the flame propagation speed of the pilot and main injection fuel is one-third to one-half of that of a single injection with a long duration. For single injection spray with long injection duration, the flame penetration velocity is determined by the sequential ignition velocity of the fuel. While the flame penetration velocity for sprays with short injection duration mainly depends on the jet penetration velocity. The investigation on the impact of dwell time, fuel distribution, and injection pressure on the combustion process of double injection also provides valuable insights for optimizing multiple injection strategies.

Fuel Consumption Rate Optimization Analysis of Dual-fuel Marine Diesel Engines Based on Orthogonal Design

To investigate the influence of diesel engine operating matching parameters on the comprehensive fuel consumption rate of butanol-diesel dual-fuel engines, a high-pressure combustion chamber cycle model of a 4190ZLC-2 marine medium-speed diesel engine was established using AVL-FIRE simulation software. After establishing the optimum blending ratio of butanol, the fuel system parameters were optimized using a one-time regression orthogonal experimental design method, and a mathematical model for fuel consumption rate prediction was constructed to find the combination of parameters with the lowest fuel consumption rate as the target. The study shows that inlet pressure has the greatest influence on the fuel consumption rate, followed by EGR and inlet air temperature. The lowest fuel consumption rate was achieved by combining the following parameters: (butanol blending ratio of 20%, EGR rate 0, inlet pressure 0.233 MPa, inlet temperature 325.15 K, Injection advance angle 22.6 °CA, the diameter of oil injection hole (0.26 mm); after optimization, the fuel consumption rate was reduced by 9.96% compared to the original machine.

The Impact of Slow Steaming on Fuel Consumption and CO2 Emissions of a Container Ship

Modern marine propulsion systems must be reliable, energy efficient, environmentally friendly, and economical. Efforts to reduce fuel costs and carbon dioxide (CO2) emissions per nautical mile have a significant impact on the choice of propulsion system. Considering that there is no alternative for maritime transport, various technical and technological solutions are being considered that aim to improve efficiency and reduce the negative impact on the environment. One of the ways to achieve this goal is slow steaming, which reduces fuel consumption and CO2 emissions. The designed speed of the vessel has a significant impact on the efficiency of slow steaming. Slow steaming is particularly suitable for large container ships with a design speed of more than 20 knots. In this paper, the effects of slow steaming are analyzed using the example of a container ship with diesel-engine propulsion. Propulsion systems with low-speed and medium-speed marine diesel engines with mechanical power transmission are investigated. Data on the required engine power and propeller speed were used for the study, obtained from calculations during testing of the ship’s hull model. The effects of speed reduction on specific fuel consumption and emission reduction were analyzed using numerical models of two-stroke and four-stroke diesel engines. The models were calibrated and validated using data provided by the engine manufacturers. The paper analyses four different cases where one or two low-speed diesel engines, or three or four medium-speed diesel engines, are used for propulsion. The analysis concludes that slow steaming can effectively reduce fuel consumption and CO2 emissions, but the choice of the optimal propulsion system is highly dependent on maritime market conditions in maritime transportation. The choice of propulsion system affects the potential of slow steaming.

Combustion and Exhaust Gas Characteristics of Residual Oil Mixed with Air-Fine Mixture in Medium-Speed Marine Diesel Engine

In the marine engineering field, research has been conducted to reduce fuel consumption and emissions of harmful exhaust gases from medium- and low-speed diesel engines by improving supercharging performance, scavenging efficiency, and introducing electronic control technology, etc., and these technologies have been put to practical use. However, most of these technologies have been applied to newly constructed vessels, and oxygen-containing fuels such as water-emulsion fuel and DME fuel have not yet been put to practical use. In this study, the effects of heating high viscosity residual oil and mixing air into the fuel as fine bubbles on the combustion and exhaust characteristics of the fuel were investigated using a practical medium-speed marine diesel engine. As a result, the fuel consumption reduction effect was confirmed when fine air bubbles were mixed in heated residual oil, as is the case with them being blended into marine diesel oil. In particular, the maximum reduction was 7% at 75% load and 0.2L/min air volume, and the average reduction was 3.2% at 75% load. In terms of the exhaust gas characteristics of the fuel, no significant reduction in NOx was observed when microbubbles were mixed, but smoke values were reduced by up to 33%.

Schlieren and mie-scattering visualization of an evaporating spray under marine diesel engine conditions

Due to the critical influence on combustion, extensive research has been carried out to deepen the understanding of diesel spray evolution. However, for the greater share of land-based diesel engines, most of the studies have focused on the injectors with small nozzle diameter and rare studies can be found on marine diesel engines, which has a larger mass flow rate and longer injection duration with large nozzle diameter. In this study, the influence of injection pressure, ambient temperature, ambient density and nozzle diameter on spray morphology for medium speed marine diesel engine injectors (with nozzle diameter up to 0.53 mm) were investigated under various non-reacting but evaporative conditions. The experiments were performed via a highly enhanced constant volume chamber (highest temperature of 900 K and highest pressure of 8 MPa) with an optical window diameter of 205 mm. Liquid and vapor penetration of sprays were recorded by Mie-scattering and schlieren optical configurations respectively. Results show that the vapor penetration velocity is mainly affected by injection pressure. Ambient temperature has the most significant effect on liquid penetration length, but less effect can be found on the vapor penetration velocity. Given the obvious deviation from heavy duty engine sprays, the empirical correlations for liquid penetration length and vapor spray evolution are updated to fit the spray characteristics of medium speed marine diesel engine injectors, which is helpful to understand the spray behavior for large nozzle diameter injector under marine diesel engine conditions.

Impact of Biofuel on the Environmental and Economic Performance of Marine Diesel Engines

The results of the research work on biofuel’s impact on the environmental and economic performance of marine diesel engines are presented. During the research, a fuel mixture was used that consisted of the diesel fuel RMA10 and FAME biofuel. The objective of the research was to determine the optimal concentration of biofuel mixed with diesel fuel. The research work was carried out on three of the same type of marine medium-speed diesel engine, 6N165LW Yanmar. One of the diesel engines only operated on diesel fuel, and the other two operated on a mixture of diesel fuel and 5–20% biofuel. During the experiment, the diesel engines operated at a load of 50–80% of the rated value. Experimentally, it was found that using biofuel improved the environmental friendliness of diesel engines: the emission of nitrogen oxides in exhaust gases was reduced by 8.7–23.4%, and the emission of carbon oxides in exhaust gases was reduced by 3.1–24%. However, when using biofuel, the economic efficiency of diesel operation decreased as the specific effective fuel consumption increased by 0.5–9.3%. The highest environmental efficiency was achieved when using a fuel mixture that included 10–15% biofuel in an 80% diesel load. In this case, the emission of nitrogen oxides was reduced by 21–23.5%, the emission of carbon oxides was reduced by 16.5–19.2%, and the magnification of the specific useful consumption of the diesel engine was 1–1.55%.

Effect of Mixed Firing Ethylene Glycol on Combustion and Emission Performance of Model 4190 Diesel Engine

In order to study the influence of ethylene glycol on the combustion and emission of marine diesel engine, a combustion chamber model was established based on 4190ZLC-2 marine medium speed diesel engine by AVL-FIRE simulation software, and the accuracy of the model was verified. The effects of ethylene glycol on the combustion and emission characteristics of diesel engine under different mixing ratios were studied by simulation experiments, and the optimal mixing ratio of ethylene glycol and diesel was obtained under the premise of ensuring the diesel engine to work at full load. The results show that the average pressure in the cylinder and the maximum burst pressure in the cylinder of the dual-fuel engine mixed with ethylene glycol are decreased compared with the original engine under different mixing ratios. Under full load condition, NOx and soot emissions are decreased by increasing ethylene glycol mixing ratio, and CO emission peak is increased but not significantly increased. Through analysis, it can be concluded that when mixing ratio is 15%, final CO emission decreases by 28.6%, final NO emission decreases by 7.9%, and Soot emission decreases by 16.9%.

Effect of Injection Advance Angle on the Performance of Butanol-Diesel Dual-fuel Engines

In order to further investigate the performance of the butanol-diesel dual-fuel engine, this paper uses the 4190ZLC-2 marine medium-speed diesel engine as a prototype and establishes a dual-fuel engine high-pressure cycle model using AVL-FIRE simulation software. The injection advance angle was set to 16.6°, 18.6°, 20.6° and 22.6° respectively, and its effect on the performance of the dual-fuel engine was investigated by varying the injection advance angle. The results show that as the injection advance angle increases, the incylinder pressure and temperature also increase. When the injection advance angle is 22.6°CA, compared with the original engine, CO emission is reduced by 16.8%, NO emission is increased by 7.4%, carbon smoke emission is reduced by 16.9%, and the indicated power is 52.6kW, which is increased by 1.8%.

Effect of assisted hydrogen on combustion and emission characteristics of a diesel engine fueled with biodiesel

In this paper, the effects of hydrogen assisted biodiesel with different fatty acid methyl esters (FAMEs) proportion on cylinder pressure, cylinder temperature, indicated thermal efficiency (ITE), NOx emission, HC emission and CO emission of a marine medium speed diesel engine are studied. The corresponding CFD model is executed by CONVERGE coupled to CHEMKIN, and a chemical kinetic mechanism with 314 reactions and 98 species is developed to accurately simulate the fuel injection and combustion processes. The results show that cylinder pressure, cylinder temperature and ITE increased with increasing HEF. Compared with rapeseed methyl ester (RME) and cottonseed methyl ester (CSME), the cylinder pressures are increased by 16.39% and 16.30% for CSME-6%H2 and RME-6%H2 at 100% load, respectively. The cylinder temperatures are increased by 7.42% and 7.14%, and ITE increased by 3.73% and 3.9%, respectively. In addition, the HC and CO emissions decreased significantly with the increase in HEF, while NOx emission increased. Compared with pure CSME and RME, HC emissions are reduced by 70.97% and 72.22% for CSME-6%H2 and RME-6% H2, and CO emissions are reduced by 41.89% and 38.12% for CSME-6%H2 and RME-6% H2 at 100% load, respectively. Overall, the strategy of using CSME-6% H2 mixed fuel for engine is not only economical and practical, but also can prevent performance loss and reduce emissions.

Miller Cycle with Early Intake Valve Closing in Marine Medium-Speed Diesel Engines

Miller Cycle with Early Intake Valve Closing in Marine Medium-Speed Diesel Engines

Test and Evaluation of Using Thermoelectric Technology to Monitor the Wear of the Journal Bearing of a Diesel Engine

Abstract The journal bearing is a key and vulnerable component of a large diesel engine. Once the journal bearing fails to work, it is very difficult repair. On-line monitoring of the wear of the journal bearing has always been one of the research hotspots. Firstly, the monitoring mechanism of the thermoelectric method is discussed in the article. Secondly, the structural characteristics of a 6DK20 marine medium speed diesel engine are analyzed. Thirdly, by using the thermoelectric sensor designed by the research and development team led by the author, the parameters of typical wear state with load conditions are measured. Finally, the directivity of thermoelectric signals is analyzed, and the variation law of the peak value of thermoelectric signals is researched corresponding to the ignition point of time of the diesel engine under typical wear states with load conditions. The results show that the thermoelectric signals reflect the wear and running state of journal bearings and have good directivity and transient feature. Therefore, it has great research value and application value to the evaluation of the wear and failure of journal bearings by thermoelectric technology.