论文已在中国上海举行的2013年CIMAC大会上发表，论文的版权归CIMAC所有。 In 2003 the first author of this paper presented a survey of gas engine current production and development trends. Since that time, interest in gas engines has continued to grow at an unprecedented rate as worldwide customers have sought the most cost-effective, emission compliant, and fuel efficient ways to meet increased electricity and heat and power demands. The improved efficiency while simultaneously meeting lower NOx standards projected in the earlier paper has proven to hold true, with such trends continuing in future developments. The same can be said regarding specific power output, with recent advances in turbocharging boost levels and control systems allowing significant BMEP improvements. This paper surveys the improvements in current natural gas engine performance and emissions and again projects forward with a look at current development efforts.

论文已在中国上海举行的2013年CIMAC大会上发表，论文的版权归CIMAC所有。 The aim of this paper is to present how to achieve a reduction of fuel oil consumption and maintenance cost through carried out optimization of diesel engines. Further more the paper also will handle combustion related problems of Marpol Annex VI emission TIER I low NOx settings of Diesel Engines and Diesel Engine optimisation in general. All presented cases are real and are backed up with real combustion diagrams, measurements and calculations carried out during Performance & Energy Audits onboard Stolt Tankers vessels by the Author of this paper. The Author has as well attended several Factory Acceptance Tests for Diesel Engines. A’ diesel engine combustion analyzer instrument' is used when carrying out the performance tests of the diesel engines onboard vessels. Based on the results from the combustion diagrams achieved from the combustion analyzer and other relevant performance data's the diesel engines are optimized for improved performance. The work process in the combustion diagrams will be explained and also how the diagrams should look like to achieve the most efficient combustion. The paper will show examples of diesel alternator engines with Marpol TIER I Low NOx emission settings. The paper reveals that newly installed diesel engines on vessels optimized in compliance according to low NOx emission limitations can be poorly optimized and therefore in a state of combustion unbalance. The paper shows that it is possible to optimize these poor factory adjusted diesel alternator engines to achieve a more efficient combustion and thereby a reduced fuel oil consumption and maintenance cost and still com-ply with the low NOx emission limitations. One special case of wrongly designed diesel alternator engines incompliance with low NO, emission limitation installed on the new vessels in the fleet is presented. In connection to this special case an older diesel alternator engine was optimized to make it possible to compare the design of the fuel injection on the two engines. Further on there will be examples of optimization of older diesel engines that don't need to be in compliance with Marpol TIER I low NOx regulation, both a2-stroke main engine and a 4-stroke diesel alternator engine. The Author believes that the paper can be enlightening for both Ship Owners and Engine Makers.

论文已在上海2013年CIMAC大会上发表，论文版权归CIMAC所有。 The regulations for exhaust emissions of nitrogen oxides, sulfur oxide and particulate matters from marine diesel engines have been strengthened. The exhaust emissions depend on fuel properties for combustion as well as the engine operating conditions. Therefore, it is very important to investigate flame temperature and soot concentration in a diesel spray from the viewpoint of fundamental study. The OCA (Optical Combustion Analyzer) was used to visualize a transient combustion of diesel spray. The OCA has been developed in our research group and used to judge ignitability, combustibility and after-burning quality of bunker fuel oils by analyzing the visualization images and photo-sensor signals. Oxygen, nitrogen and ethylene are introduced through mass flow controllers and mixed in a constant-volume vessel. The lean mixture with much oxygen is ignited by a spark. The oxygen concentration in the burned gas was set at 21% in advance. After the maximum pressure, the pressure and the temperature of the gas decrease with decrease in pressure due to heat loss. When the pressure reaches a certain pressure, a single spray is injected. A high-speed camera captures the time series of spray flame images and photo-sensors detects the light emissions from the flame. The repeatability of the history of injection pressure is very good. When exhaust emissions are discussed, the combustion properties of the fuel oil such as flame temperature and soot concentration have to be understood besides the ignition delay, combustibility and after-burning. The two-color method is widely used to measure the soot temperature and concentration. Based on the empirical correlation, soot concentration can be qualified by the KL factor. In this study, the two-color method developed with inhouse software was applied to analyze the flame temperature and KL value related to the soot concentration. A notch filter was used to divide the images into red and blue ones. The uncertainty for two-color method was discussed. At first, the accuracy of the calibration be-tween the color temperature and the light strength in both red and blue images was investigated because there is non-linear relation strongly. Next, the digitalization of the camera is also discussed. A diesel fuel oil was tested with OCA and analyzed with two-color method under the condition of some ambient temperature. The results of some bunker fuel oils were com-pared. The injection duration was set to 30 ms. As a result, the bunker fuel oil with longer ignition delay showed lower flame temperature and higher soot concentration while the fuel oil with shorter ignition delay showed higher flame temperature and lower soot concentration. These results were also compared to the results in diesel fuel oils.

论文已在上海2013年CIMAC大会上发表，论文版权归CIMAC所有。 The introduction of more stringent emission legislation (IMO Tierll, ECA, etc.) and the continuous requirement of fuel efficiency improvements set up new challenges in the marine sector. The gas operation was identified as one of the most promising solution for high and medium speed engine powered vessels to meet the required NOx emission level. But this approach is less attractive in comparison to traditional propulsion systems using diesel engines due to highly dynamic duty cycles,i.e. tug boats. In this case the transient engine control of a gas operated engine could become very difficult, setting unacceptable constraints to the vessel's dynamic. The excel-lent propulsion control and its dynamic behaviour are on the other hands one of the most important characteristics of an electrified propulsion systems. Nevertheless it is well know from other applications, that the biggest challenge of electric propulsion system is linked to the poor power and energy density of the currently available energy storage systems; moreover these are connected to their prohibitive costs, weight and dimensions. On the contrary a hybrid solution seems to be really promising: the combination of both approaches, gas engine operation to reduce fuel consumption and improve the emission levels with electric propulsion, seems to represent a feasible and flexible solution. A general receipt to dimension such hybrid systems doesn't exist: the best architecture need to be defined for each application, depending on many parameters, as vessel characteristics, duty cycles, power, costs, etc. In this paper the authors have performed an analysis on different hybrid architectures and configurations applied to a typical tugboat, assuming the following constraints and boundary conditions· operational only near port or in Emission Control Area(ECA)· need for an extremely compact design· power range 0.5 MW to 4 MW· fulfillment of new IMO legislations requirements (e.g. Energy Efficiency Design Index EEDI and NOx standard in Tier-ll) The modeling of tug boat powertrain has been performed using Ricardo software tools: performance simulation models will be built using Ricardo Wave for the gas engine as well as for the original diesel engine. The hybrid component's behaviour(i.e. energy storage system, electric drives, etc.) will be simulated and assessed with Ricardo V-Sim, defining different architectures and developing optimised control strategies. The defined technical solutions will be assessed and com-pared with current Diesel powertrains. The presence of auxiliary systems as well as the combination and integration with other powertrain components (gearbox, propeller, shafts, bearings, etc.) will be also taken into account. A cost and economical analysis for the different architectures will complete the assessment and close the paper.

论文已在中国上海举行的2013年CIMAC大会上发表，论文的版权归CIMAC所有。The BMEP of gas engines has been increasing for the last two decades thanks to the advancement in technology allowing for the efficiency of the latest gas engines to surpass that of diesel engines in several categories. But at the same time, the stochastic occurrence of high firing pressure resulting from abnormal combustion can be seen more in many types of premixed gas engines having higher BMEP. This situation is worse in the Japanese market where the Methane Number of gaseous fuel is much lower than typical natural gas and has negatively affected the stable operation of the engines in service. Research conducted by the authors confirmed that this type of abnormal combustion is caused by the auto ignition of lubricating oil in the cylinder. Lubricating oil existing in the cylinder undergoes auto ignition before the intentional ignition from electrical spark or injection of pilot fuel takes place. This phenomenon increases not only the firing pressure due to the advanced combustion timing but also the cyclic variation of firing pressure from the multiple ignition points created by the presence of lubricating oil mist. The trend of developing higher BMEP gas engines will continue along with the increase in variation of the Methane Number due to the expansion of utilization of LNG all over the world. Under these circumstances, the abnormal combustion caused by lubricating oil could become one of the crucial hurdles for the development of future premixed gas engines. Therefore, autoignition of lubricating oil must be carefully considered in the optimization of engine parameters required for the development of higher BMEP engines from now on. Recent developments in numerical techniques and computational processing power are now permitting time-dependent, multi-dimensional computational fluid dynamic(CFD) calculations with reduced chemical kinetic mechanisms. Tools, such as the CONVERGE CFD code, enable to predict diffusion combustion as well as premixed combustion phenomena. Further advancements in combustion CFD modeling were achieved at Prometheus as a result of abundant research with combustion visualization, accurate surface temperature boundary conditions and appropriate turbulent models coupled to an in-depth knowledge of experimental combustion physics of gas engines. Prometheus' combustion CFD modeling technology, using the CONVERGE CFD code, is capable of high fidelity simulations of ultra lean, high BMEP gas engine combustion with either spark ignited or pilot ignition systems. Even sensitive physics like ignition by electrical spark and knock phenomena, near wall or end-gas, can be accurately predicted. This capability offers the advantage to design highly optimized natural gas engine components such as pistons, intake ports, precombustion chambers, fuel systems and ignition systems. With this simulation technology, the authors have developed a CFD combustion simulation that enables to predict the auto ignition of lubricating oil that takes place prior to the intentional ignition event. This is a very useful designing tool not only to investigate more about the mechanism of this abnormal combustion and countermeasures but also to make careful optimization of engine parameters to avoid auto ignition of lubricating oil. This paper aims at describing the fundamental physics of lubricating oil autoignition by comparing the experimental observations to the results obtained with an advanced combustion modeling technology and CFD code.

论文已在上海2013年CIMAC大会上发表，论文版权归CIMAC所有。 For this investigation a high-speed Mie Scattering Technique will be used. In order to get the a better understanding of this effect and the impact on the spray pattern additionally a long distance microscope will be used for the investigations of the near nozzle field. With the long distance microscope, it is possible to zoom to the nozzle hole outlet and investigate whether needle chattering has an effect on the fuel atomization or not.

论文已在上海2013年CIMAC大会上发表，论文版权归CIMAC所有。 IMO NOx emission regulation Tier 3will come into force from 2016 and require the marine two-stroke diesel engines to reduce their emission below a cycle value of 3.4 g/kWh in Emission Control Area. To cope with this regulation, the combined EGR(exhaust gas recirculation)& WEF(water emulsified fuel) system, aiming at effective NOx reduction with the minimum penalty in fuel oil consumption, has been newly developed and provided for the full-scaled test engine Kawasaki-MAN B&W 2S50ME-C.EGR applied is so-called ' high pressured EGR' featuring compactness in components. Turbocharger cut-out system and VT (variable turbine nozzle area) turbocharger are incorporated in EGR system, which enables it to reduce NOx with only a minimal impact on fuel oil consumption, and to switch on/off depending on the sea area. Wet scrubber is also incorporated in EGR system to remove SOx and PM in the re-circulating gas, which prevents corrosion and contamination in the scavenging air system during EGR. Detection and control methods for water carry-over has been newly established and tested. Water treatment system is one of the most important systems for EGR and has been developed to remove PM in the washing water out of the scrubber. A special compact settling tank with unique ditches has been developed based on the sewerage treatment technologies and secures the efficient removal of PM. This paper describes 1) the characteristics of EGR system, such as relations between EGR ratio and NO, emission, EGR ratio and fuel oil consumption, etc. both on newly developed EGR system with turbocharger cutout system and VT and on conventional EGR system without them,2) the performance of scrubber including water carryover and 3) the capability of water treatment system. And then 4) the result of the combined EGR & WEF system measured on test engine is reported in comparison with EGR alone. In addition to the test results by the test engine, this paper describes outline of our original ' package type EGR system' for on-board test. The package EGR system that major components of EGR are equipped on the main engine is introduced to facilitate the installation of the system in the ship. On the other hand, WEF technique is preceding EGR and now provided for long term operation in order to accumulate experiences in service field. The latest condition is reported additionally.

论文已在中国上海举行的2013年CIMAC大会上发表。论文的版权归CIMAC所有。

论文已在上海2013年CIMAC大会上发表，论文版权归CIMAC所有。 This paper gives an overview of cur-rent possibilities and challenges in precisely simulating the engine cycle of large Diesel engines. Both the increasing demands of emission legislation and com-petition are forcing greater efforts to be made in the design phase to predict the emissions and efficiency of engine concepts for large Diesel engines. In recent years, the development of simulation tools has allowed great progress to be made in prediction. However, due to the highly complex processes during combustion and emission formation in Diesel operation very high demands are placed on the employed tools. While3D CFD simulation is used to optimize the details of the combustion and emission formation processes in the combustion chamber, the OD and 1D engine cycle simulation are applied to select the concepts and to preoptimize important engine parameters. One great advantage of 0D and 1D models is their short calculation time, which allows the investigation of a great amount of variations in parameters. This paper investigates, compares and evaluates several 0D, quasidimensional and 3D simulation models for calculating the burn rate and the formation of soot and NOx. The0D combustion model evaluated (LEC-DCM) is based on a global description of the injection spray, while the quasi-dimensional model uses a multi-zone approach (MZCM). The assessment of the 3D combustion modeling comprises the extended coherent flame model (ECFM-3Z). Besides the combustion models one key factor is the injection rate history that provides the foundation for the accurate simulation. While the simulation of the NOx emission is mainly influenced by the quality of the burn rate model, the simulation of the soot formation and oxidation processes depends on significantly more parameters. Different models in0D as well as in 3D simulation were investigated. In addition, optical measurements on the single-cylinder research engine are used to validate the soot models.

论文已在上海2013年CIMAC大会上发表，论文版权归CIMAC所有。 Based on existing marine engine oil technologies, marine engine OEM's advise that long term use of cylinder oils designed for high-sulfur fuels, when burning low-sulfur fuels, can lead to piston ring/cylinder liner micro-seizures and scuffing. The cited mechanisms are insufficient controlled corrosion of the cylinder liner and/or excessive piston crown land deposits. Therefore, they recommend that operators change to a lower-BN cylinder oil when engines are required to operate more than two-weeks on low-S fuels. This necessitates that some operators carry more than one cylinder oil product on their vessel, which de-creases their operational efficiency and increases their cost. In view of this and the recent and planned re-ductions in the sulfur content of heavy(residual) marine fuels and changes in engine designs, ExxonMobil saw the need to develop a new cylinder oil product that would be suitable for wider sulfur range operation(0.5-4.0%S).A product such as this can reduce the total cost of ownership of operators and provide them with a competitive advantage in terms of over-all vessel operation. Building upon ExxonMobil's well-proven and patented cylinder oil technology, a new,60 BN cylinder oil product, Mobilgard 560 VS was developed that uses components which are carefully selected and balanced to provide the high performance typical ExxonMobil's 70 BN cylinder oil with high-sulfur fuels and of ExxonMobi's 40 BN cylinder oil with low sulfur fuels, hence with a broader operating range to cover both high and low-sulfur heavy fuels. All this is accomplished at no increase in feed rate relative to that required for a 70 BN cylinder oil. Based on excel-lent field trial performance in MAN K98 and S-series engines and in Wartsila RT-flex and RTA engines, in some cases using the minimum recommended feed rate(as low as 0.6 g/kW-h) irrespective of fuel sulphur content, both MAN Diesel and Turbo and Wartsila granted Letters of No-Objection for the use of this new formulation with both high-sulfur and low-sulfur heavy fuels. A field trial with low sulfur fuel (<1.0% S) revealed that the pistons lubricated by the new formulation were significantly cleaner than the pistons lubricated by the reference 40 BN oil. An additional cylinder oil feed rate ' sweep' test was run with an MAN S70series engine operated at high load on high-S HFO that further validated the excellent performance of the new formulation, fully equivalent to the 70 BN reference oil, when used at the same feed rate. Successful field testing was also conducted in an MAN K98 engine that demonstrated the ultra-low feed rate potential for this new oil formulation. Wear rates measured after operation for an excess of 5,000 hours at the extremely low feed rate of 0.45 g/kW-h were seen to be low and equivalent to those obtained with Mobilgard570 under the same test conditions.