该论文已在赫尔辛基举行的第28届CIMAC大会上发表，论文的版权归CIMAC所有。Gaseous fuels used for gas engines are composed primarily of methane (CH4), but also contain small hydrocarbons, ethane (C2H6), propane (C3H8) and butane (C4H10), and inert gases, carbon dioxide (CO2) and nitrogen (N2). In recent years, the productions of unconventional fuel gases, such as shale gas, and the increasing use of biogas and hydrogen (H2), have led to diversification in the constituents of gaseous fuels. Demand for higher thermal efficiency and greater power has led to high-pressure charging of gas engines, which results in knocking during operation under high loads. Knocking in a spark-ignition engine is occurred when the unburned mixture of end-gas region is ignited prior to flame propagation. The most important determinants of end-gas auto-ignition are the chemical reactivity and physical state of end-gas mixture. As for gaseous fuels containing small hydrocarbons and H2, ignitability, burning velocity and specific heat ratio are significantly different among those components. Accordingly, knock rating using two-component primary reference fuels, such as methane number, can be applied to a limited range. This study investigated the knocking characteristics of H2, C2H6, C3H8, n-C4H10, and iso-C4H10, and also investigated promoting/inhibiting effects of these minor components including CO2 on the incidence of knock with methane-based multi-component fuels. Firstly, engine tests were conducted using neat fuels. Among H2, C2H6, C3H8, n-C4H10, and i-C4H10, H2 possessed the highest knocking tendency. The knock-limited spark advance (KLSA) with H2 was 5 deg. ATDC, while that with n-butane was -23 deg. ATDC. The causes of high knock tendency of H2 were analyzed using zero-dimensional detail chemical kinetic computations, CHEMKIN-PRO. Computed ignition delay time was longest for CH4, followed by H2, C2H6, C3H8, i-C4H10, and n-C4H10. Thus, H2, which is a pro-knock reference fuel of methane number, was less ignitable than the other minor components. The test results were also simulated by setting measured pressure data to constrain pressure model of CHEMKIN-PRO. It was revealed that auto-ignition of H2 was due to the high temperature profile of unburned gas during compression and combustion phase. The higher unburned gas temperature with H2 during the compression stroke is due to the high specific heat ratio of H2 in the mixture. In addition to this effect, the unburned gas temperature with H2 is easy to increase during the combustion phase because of the high burning velocity of H2 which promote compression by flame front. Engine tests were also conducted using CH4-based dual-component fuels having H2, C2H6, C3H8, n-C4H10, or i-C4H10 as their secondary component, and ternary fuels of CH4/H2/CO2. When the proportion of secondary component was small, a CH4/H2 blend showed the lowest knocking tendency. However, as the proportion of secondary component increased, CH4/H2 showed a higher knocking tendency compared to CH4/C2H6. This is due to the high specific heat ratio and burning velocity of H2. Furthermore, addition of CO2 to CH4/H2 significantly increased knock resistance of CH4/H2. This is because CO2 mitigates the high specific heat ratio and burning velocity of H2. The impacts of minor components on knock can be more characteristic of gaseous fuels containing small hydrocarbons than of large hydrocarbons such as gasoline, in which the change in specific heat ratio and burning velocity for different fuel constituents is smaller. The authors believe that taking both of the chemical and physical properties of fuels into account for knock prediction could help to utilize diversified gaseous fuels in the future.

该论文已在赫尔辛基举行的第28届CIMAC大会上发表，论文的版权归CIMAC所有。The trend of shifting from HFO to alternative fuels is promoted by two circumstances: tighter regulations for emissions from ships imposed by the IMO including the SOx and NOx regulation; and the benefit for cost-effectiveness in operation achieved by the more affordable fuels. This paper investigates the potential of a number of alternative fuels as future environmentally-friendly marine fuels using a world-largest class visual combustion test facility, RCEM (Rapid Compression & Expansion Machine). Contents of the liquid fuel part are as follows: 1. Low sulfur but high aromatic fuel CLO (Clarified Oil = heavy cycle oil) is a residual from the FCC (Fluid Catalytic Cracking) process in the oil refinery, and is mainly composed of 2-3 ring aromatics. However, it has rather low-sulfur content and will be fit for the Global Cap of marine fuel from 2020. As a measure to improve the poor ignition quality of CLO, high CN (Cetane Number) component like GTL (Gas to Liquid) is mixed and the effect as an ignition improver is confirmed. 2. Large amount of water emulsion In this test, large amounts of water, even more than fuel (cracked gas oil) itself is mixed and ignited by a pilot injection. About twice the volume of emulsified fuel is injected from larger nozzle hole than the normal pure fuel case to obtain the same heat. This method is effective, not only to reduce NOx drastically to even clear the Tier3 regulation (-75%) but also to promote spray combustion to achieve shorter after-burning. The reason for improvement of spray combustion is examined according to the momentum theory of fuel spray. 3. Methanol As a zero-sulfur fuel, the combustion characteristics of methanol are investigated. Methanol spray combustion displays extremely short after-burning and reduced NOx, which can be explained in the same way as for the wateremulsion technology. As the gaseous fuel study, gases suitable for the GI (high pressure Gas Injection) type engine are investigated. Contents are as follows: 4. Natural gas Image of air-fuel mixture formation by high pressure natural gas jet is fundamentally near to that of liquid spray. Effect of gas injection pressure on GI combustion is investigated by raising it from the conventional 30 MPa level, and improvement of air-fuel mixture formation that leads to faster diffusive combustion is studied. 5. Ethane Ethane will be used as a marine fuel in the near future and GI combustion of ethane instead of methane is here demonstrated. Results indicate that ethane jet burns with more luminous flame because of higher C/H ratio at a little slower burning speed than methane. 6. Hydrogen-admixture to natural gas Adding hydrogen is one way to reduce CO2 further from the natural gas level. Moreover, the prominent effect to improve the natural gas diffusive combustion by added hydrogen is visualized. 7. Low calorie gas Since air entrainment into a gas jet depends on the injected gas momentum, adding even inert gas thus increases the momentum and could improve the diffusive combustion. It is the same theory as for the above-mentioned water emulsion. The admixture of natural gas and inert gas, equivalent to a low calorie gas shows a rather higher combustion rate during the injection than pure methane does. This is a unique feature of GI combustion, which is not seen in the lean-burn type engine. In addition, the inert gas, in contrast to hydrogen addition, has the merit of not increasing NOx.

该论文已在赫尔辛基举行的第28届CIMAC大会上发表，论文的版权归CIMAC所有。On-Board Diagnostic (OBD) is a tool for the condition based monitoring of MAN B&W Diesel two-stroke engines. Based on the data collected, expert advice is given to Chief Engineers, Owners and/or Managers via real time systems, and operational reports, on the reliability and economic operation of the main engine. The main component is the OBD software, which collects data from CoCos, PMI Auto-tuning, ships alarm system, external sensors, on-board and shore based laboratory measurements as well as wear measurements from scavenge port inspections, and liner calibrations. Uniquely amongst on-board systems, OBD compares and correlates this information to provide new and vital knowledge on the detailed engine condition, such as predicting ring packages lifetime and assessing the optimal cylinder lubricating oil feed rate. Unlike most real-time systems, the data from OBD is automatically replicated to the owners/managers office for further analysis and actions without expensive communication cost; additional expert systems can monitor and advise on main engine performance by correlating the data received from the vessel with current best practice and operational data. This paper focuses on the use of OBD in relation to Cylinder Condition. One example is the correlation between scavenge air temperature, wear measured manually and drain oil analysis to optimise the cylinder oil consumption and time between overhaul; both important issues for the operators in relation to reliability and cost. Other operational examples are given in the paper, such as documenting the relation between fuel quality, fuel treatment and engine tuning. The OBD system is also intended for the use of ship operators home office, offering an unique opportunity for the superintendents to get documentation of the main engine condition on individual ships and on the whole fleet under the superintendent’s supervision. In connection with condition based maintenance OBD could automatically provide the information required by Classification society.

该论文已在赫尔辛基举行的第28届CIMAC大会上发表，论文的版权归CIMAC所有。Mitsui Engineering & Co., Ltd. (MES) has developed a large size lean-burn gas engine MD36G jointly with DAIHATSU DIESEL MFG. CO., Ltd. (DAIHATSU). The base engine of MD36G is the medium-speed diesel engine DAIHATSU DK-36 which has a large number of records and experiences in both land and marine engines. Power output range of MD36G is 3 to 7 MW and put on the market from April 2008. Ignition system of MD36G is direct-injection micro pilot to the cylinder which is the significant feature of this gas engine. MD36G (6cylinder) as a power generation facility in MES has been working well and its reliability has been confirmed by operation more than 20,000 hours. To achieve higher generating efficiency we have improved gas engine (MD36G) itself and added heat recovery technology to the gas engine system. As one of the improvements of the gas engine itself we optimized the method of direct-injection micro pilot. This optimized method can increase combustion speed of the pre-mixture and generating efficiency of the gas engine will be increased. The most attractive point of this method is to suppress NOx increase in the exhaust gas and avoid abnormal combustion in cylinder together with increase generating efficiency of the gas engine. As a heat recovery technology, THS (Turbo Hydraulic System) and VPC (Variable Phase Cycle) system have been added to the gas engine system. THS can take the power from excess energy of Turbo Charger by converting it to hydraulic pressure. VPC system can take the power from low temperature exhaust gas after Turbo Charger which is not used before. THS can also assist Turbo Charger rotation and thereby the gas engine can respond more quickly against load fluctuation than before. We completed evaluation of these performance and reliability by the demonstrating test. It is confirmed that generating efficiency of the MD36G itself reaches 48.8 % in V-type and 47.8 % in L-type. Moreover especially for the customers who have demand mainly for electric power, generating efficiency will be improved further by adding THS and VPC to the MD36G gas engine system.

该论文已在赫尔辛基举行的第28届CIMAC大会上发表，论文的版权归CIMAC所有。The power generating world is living the change. Several countries have made the political decision to move away from conventional power generation towards more environmentally sustainable solutions. The currently available sustainable solutions, mainly solar and wind power, have the drawback, besides the high investment cost, of the rainy days without wind. The de-centralization of power generation is another obvious change. Partly related to the above, but also related to the overall efficiency, avoiding the losses induced by longer transportation distances, a need for smaller power plants can be foreseen. There are many actors on the market trying to seize this opportunity. Some are offering solutions to store the energy during those optimal sunny and windy days, then to be used during the rainy days without wind, others are offering smaller power plants, ranging from 10 – 500 MW, for flexibility. The most competitive solution, given the boundary conditions today, is the lean burning internal combustion piston engine running on gas. The Smart Power Generation™, enabling fast starting and stopping for the sudden clouds in the sky or lack of wind as the weather fronts move away, is a spinning reserve without spinning. The recent engine technology developments where over 50% of mechanical efficiency has been reached also speaks for the fact that smaller power plants can be made without compromising the efficiency. This article will focus on the recent technology developments on spark-ignited gas engines and how these will support the change the power generation is living today. In particular, the development regarding fast loading and unloading, as well as Grid Code Compliance and efficiency at high and partial load will be analyzed in greater detail. The lean burn gas engines are closing the gap to diesel engines in respect of load acceptance. The gas engines are well ahead regarding emissions, fulfilling today’s requirements without exhaust gas after treatment. The emission regulations of the future are met with lean burning gas engines with less effort than those using conventional liquid fuels.

该论文已在赫尔辛基举行的第28届CIMAC大会上发表，论文的版权归CIMAC所有。There is a global discussion if the excess power from renewable energy can be used for hydrogen production. Hydrogen is a good energy carrier. There has been some discussion that hydrogen could be used to be mixed into the natural gas in pipelines, and a small amount is already put in to the pipelines in Europe. As Wärtsilä engines can operate with limited amounts of hydrogen, the objective was to test and find the limits of hydrogen content in natural gas. Hydrogen mixing into natural gas has been tested at Wärtsilä engine laboratory. For this purpose, a tailor-made gas mixing station has been designed, built and used. The gas mixing station is built so that we can use different gases and ensure sure mixing ranges and a homogeneous blend. Hydrocarbons from methane to octane have been used as well as other gases like CO and H2. In the paper we will show the working principles of the gas mixing station and how the security was ensured in the engine cell. The testing safety in the cell was guaranteed to make sure that the system is built for safe operation. The air exchange was improved by an extra fan coupled to hoods over the vulnerable areas. Additional sniffers were distributed throughout the system to ensure that possible leakages and other risk situations could be monitored online. The access to the test cell was restricted, and additional measures were taken to ensure safe testing. The needed safety for application in power plants and marine installations will be discussed in this paper. Testing was done with mixing various contents of hydrogen in natural gas at different ambient conditions. We tested for both different applications and different contents of hydrogen, to ensure a wide applicability. Both power plant and marine applications were considered. The target was to find the limits for the hydrogen content in the fuel regarding engine performance and operability. The paper will show the test results.

该论文已在赫尔辛基举行的第28届CIMAC大会上发表，论文的版权归CIMAC所有。Active cylinder technology, cylinder deactivation or skip firing has been introduced for different applications for various reasons. The main driver in automotive industry has been to increase the fuel economy, especially on low load operation. Other drivers are emission control and operational benefits. The impact on the noise, vibration and harshness (NVH) has however always been an aspect to take into consideration when an active cylinder technology is introduced. The main drivers to introduce active cylinder technology (ACT) for Wärtsilä gas engines have been to reduce the unburned hydrocarbons as well as to improve the efficiency at part loads. These benefits have been proven by engine tests during the past years. The first successful field tests were made in 2003 on a power plant engine. During the past years, ACT has been developed both for marine applications and power plant applications. In order to make a robust introduction of the function, Wärtsilä is also focusing on the NVH. With a range of engine sizes from 20 cm up to 50 cm bore and cylinder configurations between 6 and 20 cylinders, extensive calculation and testing have been performed in order to find the best cylinder deactivation patterns for all Wärtsilä gas engines. The impact on the design of the base frame and mounting of the engine has been calculated and tested. The impact on the flexible coupling has also been calculated and measured on several engine sizes with different types of flexible couplings at different engine speeds. The measurement setup and the test procedures will be presented in this paper. The paper will present both optimized engine operation and operation patterns with high vibration levels. These results are then compared to standard operation and failure operation modes. Test results will be shown from performed tests on both small and bigger size Wärtsilä engines.

该论文已在赫尔辛基举行的第28届CIMAC大会上发表，论文的版权归CIMAC所有。In an effort to better protect the environment more stringent regulations are to be applied to marine exhaust emissions, with the IMO not only implementing their NOx Tier III requirements in Emission Control Areas from 2016 but also placing a global cap on SOx in all waters from 2020 or 2025. In order to satisfy these regulations in diesel engines fuel changes or ancillary systems must be employed, such as the SCR after-treatment system for NOx reduction and a scrubber system or low-sulphur fuel for SOx reduction. As a result operating costs for the vessels increases. On the other hand, the lean-burn combustion technology of natural gas has the sizable advantage that NOx, SOx, CO2 and PM can all be reduced at once. With increases in shale gas production also signalling a further decline in the market price of LNG, now more than ever are marine engines fuelled by natural gases, with their low environmental impact, attracting attention. In order to meet these market demands, Daihatsu Diesel Mfg. Co., Ltd. has developed a dual-fuel engine, the “DE28DF”. The DE28DF was developed according to the following concepts: - To satisfy the levels of reliability necessary for marine use; - To conform to the IGF code for inherently gas safe machinery spaces; - To comply with IMO NOx Tier III when in gas operation mode and Tier II in diesel operation mode; - To be able to change the operation mode from diesel to gas and vice versa without fluctuations in engine speed and load; and - To be acceptable for transient operation considering marine use on both diesel and gas operation mode. After addressing the above requirements the DE28DF underwent a type approval and NOx testing by classification societies in October 2014. It has now received the certificates for both tests. This paper describes the details of the engine structure and control system; its reliability and safety as required for marine engines; the engine performance and addressing of practical applications in LNG fuelled vessels.

该论文已在赫尔辛基举行的第28届CIMAC大会上发表，论文的版权归CIMAC所有。Dual fuel engines have become increasingly important in recent years thanks to their lower emissions compared to diesel engines, the possibility to easily switch between different fuels and the increasing availability of gaseous fuels at comparatively low prices. State-of-the-art diesel-gas engine concepts have the disadvantage of high system complexity because they are equipped with either two diesel injectors (one main injector for diesel operation and one pilot injector for dual fuel operation) or a double nozzle injector. In addition, the double injector concept suffers from the decentralized position of the pilot injector. Therefore, concepts with only one centrally located diesel injector that allows engine operation over the whole diesel range are the preferred solution. However, it is a challenge for injection system design to achieve the required injection accuracy especially at very small energetic diesel fractions of approximately 1%. The adjustment of nozzle geometry to obtain adequate spray behavior over the whole operating range with up to 100 % diesel also remains an important issue. This paper will provide a comparison of the injection behavior of an advanced L’Orange wide range diesel injector with that of a state-of-the-art pilot diesel injector. Their injection characteristics will be evaluated on the basis of rate of injection measurements and optical investigations in a spray box. Spray vapor phase and spray liquid phase will be characterized using high speed Schlieren and high speed Mie scattering visualization techniques. The focus of the investigations will be on small diesel fractions (1 - 10% of full load diesel operation) as applied to high speed dual fuel engines. Selected results of single cylinder engine measurements will be discussed once again by comparing the two different injectors. In order to avoid any influence of injector position on the evaluation, both injectors are mounted at the center of the cylinder head. The measurements will provide the limits with regard to very low diesel fractions which still result in stable combustion. In addition, the overall engine performance with the new injector design will be compared to that of the state-of-the-art pilot diesel injector at different engine operating conditions.

该论文已在赫尔辛基举行的第28届CIMAC大会上发表，论文的版权归CIMAC所有。The fuel nozzle of a Diesel engine can be seen as the interface between the injection system and the combustion chamber and it plays a pivotal role in achieving a fuel-effective combustion with low emissions. The injector is responsible for delivering and distributing the fuel into the combustion chamber, and to achieve good air-fuel mixing. To improve the design of injectors for 2-stroke Diesel engines both experimental and numerical development work has been performed to better understand the role of cavitation inside the fuel nozzles for large two-stroke Diesel engines. A number of experimental rigs have been used to investigate different aspects of the flow and cavitation properties in the fuel injector. A rig utilizing a full size injection system injecting into a standard atmosphere vessel has been used to evaluate the momentum flux produced by individual nozzle holes. This rig can be used to assess to what extent upstream geometrical features in the injector influence the momentum flux of the spray using force measurements. Furthermore an optically accessible rig mimicking the fully open injection valve has been used to measure the fuel velocity field inside the injector together with visualizations of the in-nozzle cavitation, using advanced optical measurement techniques. These techniques encompass microscopic Particle Imaging Velocimetry (PIV) using fluorescing seeding particles as well as Shadowgraph techniques using high spatial resolution with a pulsed laser and high temporal resolution with high speed imaging with frame rates as high as 400.000 frames per second. The rigs have shown to be useful in producing results suitable for the evaluation of Computational Fluid Dynamics models. The computed time averaged in-nozzle velocity fields as well as the prediction of the location of cavitation shows good agreement with the experiments. Furthermore, the predicted loss coefficients of the individual nozzle holes show excellent agreement with experimental results. Finally, visualizations of the near nozzle fuel spray inside a full size two-stoke low-speed test engine have been performed using high speed shadowgraphy with frame rates up to approx. 70.000 frames per second to assess the spray characteristics at engine conditions. The results obtained can be used to increase the understanding of the flow inside injectors and the cavitation produced.