Marine Low-speed Engine Research Articles

Design, optimisation and evaluation of the S-CO2 Brayton cycle for marine low-speed engine flue gas

Five configurations of the S-CO2 Brayton cycle (SCBC) were constructed for flue gas waste heat recovery (WHR) of the marine low-speed engine HHM-6EX340EF on the EBSILON platform using the bench test data to save energy, reduce emissions and the efficient operation of ocean-going vessels. Experimental data from Sandia National Laboratories (SNL) was utilised to validate the accuracy of the model and the effect of Brayton cycle parameters on flue gas WHR for different configurations was analysed. The parameters of the SCRBC (S-CO2 recompression Brayton cycle) were optimised by combining the Neural Network Fitting (NNF) model, Multi-objective optimisation algorithms, and multi-criteria decision-making methods. Finally, the thermodynamic analysis of the low-speed engine was comprehensively evaluated by comparing five configurations of SCSBC (S-CO2 simple Brayton cycle), SCCBC (S-CO2 recuperative Brayton cycle), SCHBC (S-CO2 reheating Brayton cycle), SCIBC (S-CO2 intercooling Brayton cycle), and SCRBC. The optimised SCIBC configuration had the highest net recuperated work of 195.76 kW and the highest Brayton cycle efficiency of 20.13 %. The engine efficiency was improved by 0.82 %, 1.45 %, 1.78 %, 1.86 % and 1.68 %, the BSFC was decreased by 3.20 g/kW·h, 5.56 g/kW·h, 6.82 g/kW·h, 7.04 g/kW·h, and 6.43 g/kW·h, and the output power increased by 86.90 kW, 153.33 kW, 195.76 kW, 189.36 kW, and 178.14 kW, respectively. The maximum exergy loss of the cooler was 162.67 kW with an exergy loss efficiency of 14.54 % in the SCSBC configuration. Optimising the flue gas heat exchanger and cooler will further enhance the efficiency and reduce emissions. Research on the parameter and configuration optimisation of the SCBC for marine low-speed diesel engines can be extended to other low-speed engines.

Simulation and verification of cylinder head’s temperature field for marine low-speed engine

Abstract The high load capacity of marine low-speed engines poses a challenge to the thermal load of the cylinder head and temperature field simulation can guide its structural design and optimization. The 3-dimensional models of the fluid domain for the cooling water and the solid domain for the cylinder head are established and meshed, the fluid domain model is simulated to research the heat transfer pattern by Fluent software, and the surface temperature and heat transfer coefficient of the cooling water is calculated. The thermal boundary conditions of the gas in the cylinder are simulated through the analysis of the engine working process. The temperature of the cylinder head is calculated based on the fluid-structure interaction model with the thermal boundary conditions by Workbench software. The validation of the model is carried out by comparing the simulated and measured temperature data in the heated inner wall of the cylinder head. The research results show that compared with the measured value, the error of simulation results is small, which shows that the model and method are reasonable. The temperature in the inner wall of the combustion chamber is low, which can provide possibilities to appropriately improve the power density of the low-speed engine and reduce the risk of low-temperature corrosion.

Features of the operation of the lubrication system for lubricating ships' low-speed engines

The article examines the optimization of high-alkaline cylinder oil consumption in lubrication systems of marine low-speed engines (MODs), as well as the peculiarities of operation of the cylinder lubrication system in view of modern trends in the development of low-speed marine engines. An overview of the lubricator lubrication systems of the cylinders of marine main engines was carried out and possible prospects for improving the lubricator lubrication systems of the cylinders of marine diesel engines were considered. Attention is paid to the causes of occurrence and methods of combating a whole range of problems, which represent the possibility of increased wear of cylinder sleeves, pistons, piston rings, this is related to the type and grade of fuel and its sulfur content. Sulfur in the fuel is neutralized with the help of cylinder oils with high alkalinity, problems arise when changing the grade of fuel, this requires changing the brand of cylinder oil (CLO BN). The possibility of using a cylinder oil mixing system (ACOM) to neutralize sulfur in the fuel and improve protection against low-temperature corrosion of MOD cylinder liners is proposed and considered. This system mixes and doses cylinder oil depending on the load of the ship's engine and the type of fuel. ACOM allows the dosing of oil on marine engines operating in dual fuel consumption (SDF) modes, where the ratio between pilot (ignition) and gas fuel is defined, the system mixes two different types of cylinder oil into one with the required BN base number, it can be determined as the oil's ability to neutralize acids produced during use. The results of optimal consumption of cylinder oil, which ensures minimal wear of cylinder liners of a diesel engine, are given. Features of lubrication regimes and control of the technical condition of the cylinder group of marine low-speed diesel engines during their operation at reduced rotation frequency are described

Optimizations of energy fraction and injection strategy in the ammonia-diesel dual-fuel engine

Fuel consumption and emissions are growing concerns, driving the need for cleaner alternative fuels in engine research. Ammonia is a competitive alternative fuel. To enhance the effective utilization and provide a new direction for the marine application of ammonia, an ammonia-diesel dual-fuel engine model with the pre-combustion chamber structure was designed. Numerical simulations were carried out in this paper, considering variations in diesel energy fraction, ammonia injection timing, diesel injection pressure, and diesel injection timing. The findings indicate that an appropriate amount of pilot diesel accelerates jet flame formation, improving combustion efficiency. Advancing ammonia injection timing improves mixture homogeneity but increases ammonia slip, while delaying ammonia injection timing leads to mixture stratification. Locally rich areas in the mixture improve combustion efficiency. The timing and pressure of diesel injection significantly impact both combustion efficiency and emissions. Advancing diesel injection timing improves power output but increases NOX emissions. Increasing diesel injection pressure improves combustion efficiency, but excessive pressure leads to deterioration. Overall, this study provides valuable insights into the potential use of ammonia as a sustainable fuel for marine low-speed engines, selecting the optimal energy fraction and injection strategy to achieve efficient and environmentally friendly combustion.

Experimental Study of the Influences of Operating Parameters on the Performance, Energy and Exergy Characteristics of a Turbocharged Marine Low-Speed Engine

With appropriate strategy of EVC timing and fuel injection, the engine NOx emission could be reduced with acceptable deterioration of fuel consumption. However, for the mechanism of these favorable results, few studies focus on improving the fuel economy from the perspective of energy and exergy analysis, which could be helpful for providing a deeper comprehensive to researchers. Therefore, an experimental study for the combination of EVC timing and fuel injection strategy is conducted based on a marine low-speed engine with 340 mm bore, then the energy and the exergy analysis are separately carried out according to the obtained experimental results. The experimental results show that delaying the exhaust valve closing (EVC), complemented with an appropriate injection strategy, could improve the marine low-speed diesel engine brake specific fuel consumption (BSFC) with the NOx emission almost kept constant. The following energy balance analysis demonstrates that the losses from exhaust gas and heat transfer account for about 50% of total energy. However, from the perspective of exergy analysis, an opposite conclusion could be obtained; the proportion of exhaust gas and heat transfer exergy could reach about 15%, and the ratio of heat transfer could be higher relatively. The losses caused by irreversibility is the biggest source of all, and the irreversibility from combustion could takes about 70% of the total irreversibility. Finally, the reduction of total irreversibility could reach about 4% by optimizing the parameters of marine low-speed engines.

Possibility of Marine Low-Speed Engine Piston Ring Wear Prediction during Real Operational Conditions

A long-stroke, low-speed marine engine is used as the prime mover of a ship. During the operation of such engines, the excessive wear of the cylinder liners and piston rings frequently occurs. The breakdown of cylinder liners or piston rings is very dangerous for the safety of a vessel, the environment, and the people on board. The reliability of engine components is an extremely important topic, as it influences the efficient operation of the vessel. Therefore, to prevent such undesired events, it is essential that the condition of the cylinder liners and piston rings is frequently assessed. This paper presents research that finds prediction models for the rate of piston ring wear. The compiled prediction models are verified using verification tests. The models can be implemented to evaluate the tendency of piston rings to wear, and can be used to evaluate the quality of cylinder liner lubrication. Our findings will help to obtain the required optimal piston ring wear rates, maintain the good operational condition of the engine, reduce the costs of engine maintenance, and reduce the total consumption of lubricating oil and the emission of noxious substances into the atmosphere. All the mentioned benefits are related to a reduction in the ship’s operational costs and are directly related to energy efficiency.

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.

Experimental investigation of the high-pressure SCR reactor impact on a marine two-stroke diesel engine

The high-pressure selective catalytic reduction (HP-SCR) system arranged before the turbine is more suitable for high-power marine low-speed engines to reduce NOx emission. However, the HP-SCR reactor will cause an increase in engine exhaust back pressure, affecting its performance and brake-specific fuel consumption (BSFC). The 10WM marine low-speed two-stroke diesel engine and its HP-SCR system are taken as the research object in this paper. The engine performance and emissions in International Maritime Organization (IMO) Tier II and Tier III modes are tested by bench experiments. The effects of the HP-SCR reactor on engine performance parameters, emission characteristics, and pulse effect in exhaust pipe are obtained. The research showed that when the HP-SCR reactor is used, the BSFC of the engine will slightly increase, but the maximum will not exceed 1 g/kWh. The weighted specific emission of NOx is 2.09 g/kWh, which can meet Tier III emission regulations. In addition, under the Tier II mode, the engine exhaust pipe has a noticeable pulse effect. The exhaust gas temperature before the turbine is about 30 °C higher than that after the cylinder. However, under Tier III mode, the pulse effect in the exhaust pipe disappears completely. In addition to the fact that the HP-SCR reactor weakens the linear velocity of exhaust gas, the main reason is that the urea injection unit reduces exhaust gas temperature by 36 ∼ 47 °C.

Performance Modulation of S-CO2 Brayton Cycle for Marine Low-Speed Diesel Engine Flue Gas Waste Heat Recovery Based on MOGA.

(1) Background: the shipping industry forced ships to adopt new energy-saving technologies to improve energy efficiency. With the timing modulation for the marine low-speed diesel engine S-CO2 Brayton cycle, the waste heat recovery system is optimized to improve fuel economy. (2) Methods: with the 6EX340EF marine low-speed diesel engine established in AVL Cruise M and verified by the bench test data, the model of the S-CO2 Recompression Brayton Cycle (SCRBC) system for the low-speed engine flue gas waste heat recovery was developed in EBSILON, and verified by SANDIA experimental data. On this basis, the effects of injection timing and valve timing parameters on the comprehensive performance of the main engine and the waste heat recovery system were investigated. By optimizing the timing modulation parameters through multi-objective genetic algorithm (MOGA) and evaluating the flue gas waste heat recovery from the perspective of thermodynamic performance and emission reduction, the research on the performance modulation method of the S-CO2 Brayton Cycle for flue gas waste heat in marine low-speed engines has been completed. (3) Results: the SCRBC with waste heat modulation will further increase the total power and efficiency, which in turn brings about a reduction in the fuel consumption rate. The efficiency of the SCRBC system with the addition of waste heat modulation increases by 2.28%, 1.04% and 2.07% at 50%, 75% and 100%, respectively. After adding the residual heat modulation, the maximum annual CO2 emission reduction of 748.51 × 103 kg·a-1 occurred at 50% load; with the exergy analysis, the cooler has the largest system exergy loss of 165 kW, with the exergy loss efficiency of 2.06% under 100% load. (4) Conclusions: the research on the performance modulation method of S-CO2 Brayton cycle for flue gas waste heat in the marine low-speed engine has been completed, which further improves the efficiency of the system and can be extended to other engines.

Feasibility study of hydrogen jet flame ignition of ammonia fuel in marine low speed engine

As the global carbon emission reduction actions become more serious, the development of alternative fuel combustion solutions on engines has good prospect. Ammonia and hydrogen fuels have their own advantages and disadvantages, but the mixture of the two has good compatibility. However, in the current ammonia-hydrogen mixture combustion, spark ignition or compression ignition has certain limitations on large-bore marine engines. The development of a jet flame pilot scheme similar to pilot oil can effectively reduce the demand for hydrogen fuel and high ignition energy. A scheme of igniting ammonia fuel with a hydrogen jet flame was proposed, which realized the normal full-load power output of the marine low-speed engine. The temperature and reactivity atmosphere required for combustion brought by the jet flame to the cylinder, especially the high concentration of H radicals, helped to establish the OH and O radicals conditions required for combustion, and effectively promoted ammonia early combustion. In addition, NOx emission can meet the tier III standard by optimizing the ignition timing of the hydrogen jet flame in some case. This scheme has good potential in emissions, while relatively better power output and engine performance.

Empirical Model of Uniflow Scavenging for Ultra-Long-Two-Stroke Marine Diesel Engines

_ Low-speed two-stroke diesel engines are widely employed in the marine industry, especially in tanks, owing to their advantages of fuel economy and reliability. However, with the emerging ultra-long-stroke trend, existing scavenging models, which are based on the configuration of cylinders with short strokes, are no longer applicable. In this study, we investigate the flow field and residual exhaust gas distribution in a cylinder using particle image velocimetry and computational fluid dynamics (CFD) simulations. The result shows a strong Burgers vortex structure upstream of the scavenger flow and dissipates gradually as it moves downstream. Furthermore, the scavenging process comprises three processes according to the detailed CFD analysis: displacement, mixing scavenging, and short circuit. Inspired by the results, a tailored empirical model of ultra-long-stroke uniflow scavenging comprising three sub-models is proposed. Specifically, a logarithmic relationship between the concentration level and scavenging deliver ratio is proposed to describe the mixing scavenging process. Finally, the model was validated against CFD results. The results demonstrate that the discrepancy in the scavenging efficiency curve predicted by this model and CFD is less than 1%, thereby demonstrating model reliability. Introduction Owing to the advantages of a large power range, high thermal efficiency, low fuel consumption rate, and good reliability, marine low-speed engines are widely used to provide power to civil ships (Heywood 1999). The market for low-speed engines is vast and is improving the performance of low-speed engines through research has great economic and environmental significance (Woodyard 2004). To meet the requirements of ship owners for lower fuel consumption and the IMO’s regulation of halving the greenhouse gas emissions of newly built ships, the ultra-long stroke of low-speed engines has become a trend (Lamas & Vidal 2012). With an ultralong stroke, the combustion speed of low-quality fuel oil is slow, and an ultra-long-stroke cylinder can prolong the expansion process, improve the combustion process, and reduce the fuel consumption rate (Fenghua 2014). The ultra-long-stroke diesel engine further creates fuel savings of 3.5–7% based on the original low fuel consumption. Previously, ultra-long strokes could not be achieved, limited by materials and manufacturing processes. However, in recent years, with the advancement of materials and processes, ultra-long strokes have been widely adopted as they have demonstrated superior competitiveness.

Application and Development of Selective Catalytic Reduction Technology for Marine Low-Speed Diesel Engine: Trade-Off among High Sulfur Fuel, High Thermal Efficiency, and Low Pollution Emission

In recent years, the International Maritime Organization (IMO), Europe, and the United States and other countries have set up different emission control areas (ECA) for ship exhaust pollutants to enforce more stringent pollutant emission regulations. In order to meet the current IMO Tier III emission regulations, an after-treatment device must be installed in the exhaust system of the ship power plant to reduce the ship NOx emissions. At present, selective catalytic reduction technology (SCR) is one of the main technical routes to resolve excess NOx emissions of marine diesel engines, and is the only NOx emission reduction technology recognized by the IMO that can be used for various ship engines. Compared with the conventional low-pressure SCR system, the high-pressure SCR system can be applied to low-speed marine diesel engines that burn inferior fuels, but its working conditions are relatively harsh, and it can be susceptible to operational problems such as sulfuric acid corrosion, salt blockage, and switching delay during the actual ship tests and ship applications. Therefore, it is necessary to improve the design method and matching strategy of the high-pressure SCR system to achieve a more efficient and reliable operation. This article summarizes the technical characteristics and application problems of marine diesel engine SCR systems in detail, tracks the development trend of the catalytic reaction mechanism, engine tuning, and control strategy under high sulfur exhaust gas conditions. Results showed that low temperature is an important reason for the formation of ammonium nitrate, ammonium sulfate, and other deposits. Additionally, the formed deposits will directly affect the working performance of the SCR systems. The development of SCR technology for marine low-speed engines should be the compromise solution under the requirements of high sulfur fuel, high thermal efficiency, and low pollution emissions. Under the dual restrictions of high sulfur fuel and low exhaust temperature, the low-speed diesel engine SCR systems will inevitably sacrifice part of the engine economy to obtain higher denitrification efficiency and operational reliability.

Experimental energy and exergy analysis of turbocharged marine low-speed engine with high pressure exhaust gas recirculation

Exhaust gas recirculation (EGR) has been widely applied on marine low-speed engine for the Tier III standard. However, few studies focus on energy and exergy analysis to improve the deterioration of fuel economy caused by EGR. This study fills in this gap based on the related experiment. Results show that about 35% EGR rate could achieve the Tier III standard, while cylinder bypass (CB) may raise NOx due to the coupling of CB and exhaust receiver. Subsequent energy analysis shows that improving fuel consumption should start with reducing the energy of heat transfer and exhaust gas. But, the exergy analysis indicates that reducing the irreversibility will be more efficient. The irreversibility mainly comes from in-cylinder, turbocharger and intercoolers. According to the instantaneous in-cylinder exergy analysis, the corresponding irreversibility is due to charge mixing and combustion. Reducing temperature gradient and proportion of premixed combustion are effective methods to inhibit it. EGR has opposite impacts on in-cylinder irreversibility caused by combustion: it enhances this irreversibility by rising maximum temperature and prolonging combustion duration (25% load); but it also raises the proportion of premixed combustion, which will inhibit this irreversibility (100% and 75% load). As for the irreversibility from turbocharger, it is negatively correlated with EGR rate, because of CB reducing exhaust temperature. Whereas, due to the existence of EGR intercooler, the irreversibility caused by intercoolers are positively related with EGR rate.

Research on influence and demand of Miller cycle based on the coupling of marine low-speed engine and turbocharger

• Predictive model is built to study Miller cycle on the whole low-speed engine. • Impacts of Miller cycle is studied based on coupling of engine and turbocharger. • Uniflow scavenging is the fundamental reason for Miller cycle’s unique effect. • Turbine re-match and demand of Miller cycle is summarized by thermodynamics. • Above turbine re-match and demand are general in engine of uniflow scavenging. Miller cycle has been gradually applied on marine low-speed engines to reduce NOx emission, due to its convenient implement with lower cost. However, current studies about relevant effects, influence mechanism and turbocharger re-match all have neglected the coupling relationship between engine and turbocharger, which will have non-negligible impact on final results. Therefore, based on this relationship, the influence of Miller cycle is studied through a numerical simulation. Then, a thermodynamic analysis is conducted to summarize the relevant impact mechanism and provide guidance for turbocharger re-match. Numerical results show that the in-cylinder charger temperature is actually reduced, but the combustion duration is prolonged. Hence, the exhaust gas temperature is increased, causing compressor operating points moving to the direction with higher pressure ratio and mass flow rate. Furthermore, from the thermodynamic analysis, the fundamental reason of this phenomenon is the uniflow scavenging adopted by marine low-speed engine: for this scheme, the more the Miller cycle is applied, the more the mass will flow across the cylinder. For compensating the losses caused by Miller cycle, achieving the original cylinder compression pressure is an effective method, hence a higher boost pressure is needed and the turbocharger should be re-matched. Finally, based on the thermodynamic analysis, the demand of Miller cycle for turbocharger is summarized and the relevant guidance for turbocharger re-match is proposed: the relationship between boost pressure and Miller cycle should follow the original poly-tropic process in cylinder; the high efficiency area of compressor should include the operating point with maximum Miller cycle, where the pressure ratio and the mass flow rate are decided by the maximum Miller cycle and the index of original poly-tropic process.

Acoustic Method for Estimation of Marine Low-Speed Engine Turbocharger Parameters

The article presents the acoustic method of marine low-speed engine turbocharger parameter estimation under operating conditions when a prompt assessment of instantaneous turbocharger speed and rotor vibration level is required. The method lies in the analysis of the acoustic signal that is generated by the compressor of the turbocharger with the diesel engine running under load. The spectral analysis reveals that the compressor blades generate acoustic oscillations that are always present in the overall acoustic spectrum of the turbocharger regardless of its technical condition. The harmonic components corresponding to the blades can be detected in the spectrum using the limit method. The calculated instantaneous turbocharger speed makes it possible to analyze the main harmonic amplitude in the spectrum. The method presented in this paper helps eliminate discrete Fourier transform (DFT) spectral leakage so that the amplitude of the main harmonic can be estimated. Further analysis of the amplitude of the main harmonic allows for efficient estimation of the turbocharger rotor vibration level when in operation. The method can be practically applied by means of a smartphone or a computer that has the dedicated software installed. The proposed method lays the foundations for a permanent monitoring system of turbocharger speed and vibration in industrial and marine diesel engines.

Numerical and thermodynamic study on effects of high and low pressure exhaust gas recirculation on turbocharged marine low-speed engine

Marine low-speed engines are one of the most favorable power devices for oceangoing vessels. However, their energy consumption reduction is currently limited because of applying the exhaust gas recirculation (EGR) to reduce the NOx emission. Consequently, high pressure (HP) and low pressure (LP) EGR are studied in this study to explore the interactive relationship among the EGR, the turbocharger and the engine. The HP EGR reduces the turbine power, causing the deterioration of scavenge air pressure and compressor surge margin. As a solution, the cylinder bypass rate should be kept approximately equivalent to the EGR rate. Moreover, to avoid unfavorable impacts on the NOx emission, it should be decoupled with the exhaust gas receiver. While, the LP EGR has opposite effects on the turbocharger: the turbine power is raised and compressor operating points move to the opposite direction. It could be preliminarily attributed to the better utilization of the increased exhaust gas temperature. From a thermodynamic analysis, the fundamental reason is the difference of compressor inlet composition. Demands of them for the compressor are concluded subsequently: the HP EGR requires a wide high efficiency area at a constant pressure ratio, while the LP EGR needs the high efficiency area as long as possible in its demand direction. Finally, detailed comparisons between them are conducted based on the re-matched turbochargers and optimized engine parameters: the control and the structure of LP EGR are simpler and more effective, but its cost and compactness are inferior to the HP EGR.

ORGANIZATION OF INTERNAL MIXTURE FORMATION IN SHIP LOW-GAZODESEL

The observed increase in recent years in the price of fuel derived from petroleum, and tightening environmental regulations have forced manufacturers of marine low-speed engines to focus its efforts on the development of gas diesel engine options on the basis of existing models of marine diesel engines. At the same time there are two fundamentally different approaches to solving this problem. MAN Company established and successfully tested system with direct injection of gas into the combustion chamber under high pressure. An alternative approach is to feed gas into the working space of the engine under low pressure has been developed by Wärtsilä. The article is devoted to the search for new technical solutions that allow to combine advantages and eliminate shortcomings inherent in both schemes of the organization of internal mixture formation.

Improving the efficiency of marine low-speed engine by cooling charging air in thermotransformer

Improving the efficiency of marine low-speed engine by cooling charging air in thermotransformer

Lubrication Challenges in Shipping Industry - Reliable Lubrication of Marine Low-Speed Engines

For many decades, the marine industry has been a conservative environment with few changes in legislations and engine design. By the end of previous century, however, the demand for more engine power, followed by increased environmental awareness, triggered tremendous changes in this industry segment. Since the economic recession started several years ago, the marine industry faced an increasing need to reduce operating costs. This resulted in operational changes and triggered the need for new vessel-and engine designs. These changes also had an impact on the lubrication of low-speed marine engines. The selection of the correct cylinder oil and oil feed rate to balance these new conditions in the engine is more important than ever. Chevron has therefore developed its DOT.FAST service to accompany a full range of high quality cylinder oil grades available to guide its customers in achieving reliable and safe operation.