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。For combustion engines, performance and safe operation are largely a function of the maintenance quality of the engine and related systems. Some faults are inherently more critical than others and often also dependent on the operating conditions. Fault identification, isolation and assessment facilitate decision making, whether to reschedule the needed maintenance and continue operation, potentially on a different operating point, or stopping the engine immediately to repair the fault. To manually assess the fault situation requires extensive skills and experience of combustion engines and is typically only possible to do after the fault event has occurred. Historical trends of measurements can be used, but usually these are on a very low time resolution, which is not sufficient for rapidly progressing faults. Within the automotive industry, fault diagnostic methods, i.e. automatic fault identification and isolation that is embedded in the engine control system, have been used for over two decades with good results. Many different methods have been applied, but model-based fault diagnostics can be regarded as one of the most promising approaches within this industry. However, as automotive engines are highly standardized with high sales volumes, the additional cost of maintaining models and parameters for a large set of models becomes insignificant. In contrast, for large medium- and low-speed engines, the volumes are low and the ratio of variants to total sales is typically high. To overcome this situation, new fault diagnostic approaches need to be considered with the target to reduce the parameter management problem, while still securing the quality of the diagnostics. In this paper, the opportunity and value of fault diagnostics of large medium-speed engines will be discussed. Practical aspects will moreover be highlighted along with a set of fault diagnostics case studies for specific sensors and actuators. Test results from full-scale engine tests will be provided for evidence of the performance of the fault diagnostics methods.

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 prime mover of merchant ships has been for more than a century the marine Diesel engine, which is nowadays predominantly a low-speed, two-stroke, crosshead-type, reversible, uniflow-scavenged, turbocharged, electronic engine. The low speed engine is, because of its size, the most efficient thermal machine and, due to its fewer cylinders and consequently fewer moving parts, particularly reliable. The two-stroke cycle is applied to maximise the power to weight ratio and minimise engine size. Due to the low speed required and the finite maximum piston speed achievable, the marine engine features a very high stroke to bore ratio, which in turn is the main reason for the crosshead design and the uniflow-scavenging concept. Since the long two-stroke engine needs to be forcescavenged, the two-stroke marine Diesel engine is invariably also turbocharged. Finally, the demand for flexible engine tuning, optimised throughout the load range dictates the use of electronic engine control. The market requirements for a two-stroke marine Diesel Engine differ profoundly from engines in other segments of the marine and automotive industries. The engine designer is obliged to correctly select the power output and the speed of the engine independently, since the engine is directly connected to the propeller without a gearbox. This attribute of the low speed engine, added to the low production volumes characteristic of the merchant shipbuilding market, makes the low-speed engine a highly customised product, tailor made for each application. The purpose of this paper is to give an overview of the development of the modern low-speed two-stroke marine Diesel engine from the engine designer’s point of view starting from the market requirements for power and speed, with insights that are relevant for the whole industry. A presentation will be made of - the basic thermodynamic layout of the engine, - the dimensioning and design criteria determining the size and design concept of the powertrain and structure parts, - the design concepts for the hot parts and cylinder lubrication, - the choices the engine designer has to make regarding core ancillary systems such as the fuel injection and exhaust valve actuation systems, - the automation & control systems governing the modern electronic engine. Particular focus will be placed on the trade-off the engine designer (licensor) is challenged with in terms of reliability, cost, manufacturability and serviceability of the engine, in order to make a competitive product for his customers, which are obviously shipowners, but also engine makers (licensees) and shipyards. Additionally, the tools and methods that the engine designer of the modern two-stroke marine Diesel engine has at his disposal will be described in the context of the development process.

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。Recent trends in gas engine design have focused on improving power output and efficiency while reducing emissions. Despite the fact that gas engines may be similar to other engines in their appearance and specifications, lubrication requirement of a gas engine is quite different from the conventional diesel or gasoline engine, owing to their higher combustion temperatures, engine loads and very different engine operation. Gas engines operate at high temperatures greater than 200 °C. At these high temperatures, especially, in a piston environment, lubricating oil is prone to severe thermal oxidation. Nitration is the most common route cause for many maladies of a gas engine lubricant which occurs due to the reaction of the oil with the oxides of nitrogen (NOX) generated during combustion. Several engine operating factors which will contribute to nitration are air to fuel ratio, load, cylinder liner temperatures, blow-by ingress, poor crankcase ventilation etc. Impact of nitration on lubricant would be excessive sludge/varnish formation, premature oil thickening, insoluble increase and ring and liner wear. To sustain these operational eventualities, natural gas engine lubricants are to be robust in nature. This robustness is important to achieve longer drain potentials which is one of the customer demand, as frequent oil changes not only pushes up the oil bill but also will lead to consequential power loss arising out of shut downs. Oils not properly designed specifically for gas engines can reduce head rebuild cycles, filter plugging and accelerate ring and liner wear. Natural Gas Engine Oils are classified according to their ash content- low, medium and high. Ash comes from the detergent additives used in these formulations. While too low an ash leads to valve seat recession, to high an ash leads to valve guttering and torching. Hence optimum balance is to be achieved. Since gaseous fuel per se is much cleaner and devoid of sulphur compared to liquid fuels, low ash (<0.6% Wt) is generally preferred for these oils. Regarding base oils, API Gp. II base oils –hydro-treated, branched paraffinic- are more preferred owing to their higher oxidation stability than Gp. I oils. Gp.III oils, though are more oxidatively stable, may not be suitable because of their lower viscosity. Further, lubricants based on off-the shelf additive packages from various additive suppliers may not be as robust as they ought to be. The present paper describes the development of a new generation, component based, low ash natural gas engine oil for stationary gas engines formulated with API Gp.II base oil. Performance assessment methodology devised involves effective lab screening tests, with each test simulating a condition that the oil would experience in service. Selection of test methods involve adoption of those severe deposit formation tests which are commonly used for passenger car and heavy duty diesel engine segments- where pass/fail criteria and test conditions for these parameters are far more severe. Three types of thermo-oxidation tests – static, bubbling oxygen, dynamic catalytic oxidation tests were used coupled with blotter test to establish the oxidation stability of the oil. A specially designed nitration bench test was employed to assess the oil resistance to degradation from nitration. Friction, wear and film strength characteristics were screened in widely accepted tribological test rigs. All the test data were benchmarked against a very high industry reference oil. The candidate oil delivers better performance than industry reference product in tests related to Nitration, Oxidation, Deposits, Corrosion, TBN Retention, Acid Control, Wear, Film Thickness, Friction and Sludge Dispersancy. Single cylinder engine tests were conducted to demonstrate that the formulation offers superior control of deposits and bearing corrosion protection.

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。During the last years alternative fuels beside Diesel and HFO have been gaining higher importance within the different applications of Large Engines. This was mainly driven by improved availability and lower price of such alternative fuels ( i.e. Natural Gas ). Meanwhile have this Dual-Fuel and Gas engines proven their robustness in all major stationary Large Engine applications and tests on mobile applications are under process. ( i.e. Locomotives ) The extended system demands, pushed by upcoming emission legislation and fuel flexibility needs, will be supported by a new Bosch Large Engine specific engine control unit (LE-ECU). It will support the stable trend towards electronically controlled Fuel Injection Equipment (FIE) for Diesel, Gas and Dual Fuel engines. The LE-ECU is based on Bosch´s latest automotive control unit technology (MDG1) incl. a new powerful microcontroller generation and an AUTOSAR 4 compatible basis software. This LE-ECU extends the application spectrum of the already available marine certified ECU, which is mainly used in small high speed diesel engines, towards more complex engine applications and provides increased performance and scalability for current and future customer requirements. Corresponding to the market requirements Bosch already offers a broad and acknowledged Diesel-FIE portfolio (electrical Unit-Pump-System, modular Common-Rail-System). In combination with a modular set of Gas Admission valves, which is close to production, Pilot Injection-capable Injectors and field-proven sensors the LE-ECU allows the application and calibration of future Dual Fuel and Gas Engines. This paper gives an overview on the requirements considered for the specification of the control unit and how it fits to the existing FIE portfolio of Bosch for Large Engine applications. We will describe the system approach of Bosch for Diesel, Gas and DF engines, including all main components, to support the applications from small truck-derivative Large Engines up to medium speed engines used for Marine, Rail or GenSet applications.

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。Liquefied natural gas (LNG) is becoming an attractive alternative to traditional transportation fuels such as diesel and heavy fuel oil. The major advantages in terms of reduced pollutant emissions and its worldwide availability make it an attractive fuel for powering ships. This has resulted in a rapidly growing number of LNG-fuelled ships. The natural boiloff gas (NBOG), which is taken from the top of the tank, can directly be used as fuel gas for the engines. The NBOG typically has a high methane content and hence a high knock resistance. However, when the power demand is higher than the power that can be generated using NBOG, forced boil-off gas (FBOG, obtained by vaporizing liquid LNG) is mixed with the NBOG. Gas from forced boil off contains all the hydrocarbons present in the LNG and usually has a lower knock resistance than that produced by natural boil off. Thus, adding FBOG to NBOG reduces the knock resistance of the fuel and appropriate precautions should be taken in situation when the knock resistance of the LNG is low to avoid the occurrence of engine knock. Mild engine knock increases pollutant emissions and can damage the engine in the long term, while severe knock can physically destroy the engine in seconds. Thus, engine knock should be avoided. There is a wide variety of engine types used in LNG-fuelled ships. Both engine manufacturers and fleet owners must be certain that the engines chosen can accept the range of LNG compositions available in the ports at which they bunker. To ensure that the engines to be used in LNG-fuelled ships are matched with the expected variations in fuel composition, the knock resistance of the LNG fuels must be determined, and subsequently specified, unambiguously. Recently, DNV GL developed a method to characterize gases with respect to their knock resistance. The DNV GL method is based on the physics and chemistry of combustion, and is uniquely flexible in being adaptable for any engine type and gas composition. Furthermore, it has been demonstrated to have superior accuracy for predicting the knock resistance for different gas compositions than the existing methods. In addition, to be able to predict the effect of boil off on the knock resistance of NBOG and FBOG of typical LNGs during a voyage, we coupled the knock model to a dynamic model that computes the evaporation of LNG in tanks. This model is part of the DNV GL COSSMOS modeling framework for ship machinery systems. The model employs coupled thermodynamic non-linear vapourliquid phase equilibrium equations and differential conservation equations describing the evolution of LNG quantity and composition with time. The boil-off model is used to calculate the variation in composition of the LNG and the boiloff gas, during typical voyage profiles derived from a case study LNG vessel. The gas compositions calculated from the boil-off model are then used as input to the knock model to calculate the knock resistance of the LNG (thus, the FBOG) and NBOG during the voyage. The results provide valuable input and insight regarding the acceptability of the range of LNG qualities in the ports at which ships bunker.

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 development time for new engines is getting shorter and tests are, in case of large bore medium speed engines, very expensive. An accurate assessment of the expected engine performance is required at an early stage of a project. Cylinder pressure traces and the main mass flows are required to support the engine design. The general setup, mass flows and pressure requirements are necessary to define the auxiliary systems and the turbo charger. And last but not least the fuel consumption is important to support the sales activities. Information about the restrictions concerning ambient conditions such as altitude, temperature and gas quality are required in a later stage as well. It is impossible to measure all of these values even with detailed single cylinder tests in advance. To deliver the information a detailed and reliable simulation model of the engine is required without or with only a few measured values for the validation. 1-D-simulation tools like GT-Power are well known and effective tools to predict the performance of a combustion engine. Without an empirical combustion model at least it is not possible to set up the model prior to measurements. A fully integrated physical Diesel-Gas combustion model for GT-Power is available at Caterpillar and will be presented in this paper. The Model is validated with a broad range of single cylinder measurements. It shows a very good correlation for the required range of Air/Fuel-Ratios, start of injection (SOI), ignition fuel quantities and gas qualities. The influence of engine speed and load is covered and a validation with different engine sizes was successful. The physical combustion model is a co-development of Hiltner Combustion Systems (HCS) and Caterpillar. Models are available for the combustion in liquid fuel ignited Diesel-Gas and spark ignited pre chamber and open chamber Otto-Gas engines. The topic of this presentation is the Diesel-Gas engine combustion model and the use during the development of the M46DF. An outlook for future projects, like a possible power upgrade and the use of alternative fuels as Methanol and associated gas will be given at the end of the presentation. It was possible to support the development of the recent engine families at Caterpillar Motoren Kiel.

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 importance of natural gas as a primary fuel in internal combustion engines is steadily increasing. While in the energy sector it has been considered a viable option for decades, its use in the maritime sector has been limited. Despite the recent improvements to the infrastructure available for natural gas, the reason for this is still mainly due to fuel related concerns (storage, bunkering). However, poor transient performance can disqualify gas engines for certain applications even in areas where the infrastructure is sufficiently developed. Particularly in applications with expected severe transient loading, the increasing importance placed on system integration requires studies of dynamic behaviour to be carried out by potential users of the system. The air-excess ratio in the cylinder influences efficiency and emissions through its effects on the combustion process. Furthermore, its range is severely constrained by misfire and knock. These two factors make engines running primarily on natural gas particularly sensitive to transient operations. This paper investigates the transient behaviour of engines using natural gas as primary fuel. In order to achieve this, two existing diesel engine models have been adapted to simulate the operating principle of such engines. The first model focuses on the cylinder processes and has a crank angle time scale. It is used to gain insight into the combustion process of gas and dual-fuel engines. The second model simulates the entire system and has a revolution time scale. It includes three different versions of controlling the air-excess ratio in the cylinder: waste gate, blow-off valve and variable valve timing. The simulation results show the trade-off between cost and efficiency on the one side and transient response on the other. By increasing the extent to which the air-excess control system is used, bigger load steps can be taken without the occurrence of knock or misfire. This would, however, also imply a bigger waste gate/blow-off valve and more losses, as these would be opened over a larger range. Variable valve timing could theoretically be used to eliminate this choice entirely, so it is expected that manufacturers will work on the development of this technology. The difference in performance observed between a waste gate and a blow-off valve was negligible. Much more important proved to be the sizing of the valves mentioned above and the parameters of the control system. The models developed give an initial indication to potential users whether a gas or dual-fuel engine can comply with the transient requirements for a certain application. Furthermore, the results can be used to identify changes that would increase the transient capabilities of the engine up to the desired level. This could give potential users the required confidence and might help engines running primarily on natural gas to enter previously un-accessible markets.

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。As a response to market demand and fluctuating fuel costs, engine combustion concepts and subsystems must be characterized by maximum flexibility. Researchers, manufacturers and suppliers are forced to develop and optimize combustion concepts for fuel-efficient multi-application engines in a shorter amount of time. With little change in hardware, these engines must be capable of running on different types of fuel with varying properties and meeting emission limits that depend on the area of application and national legislation. The well-known ‘Design of Experiments’ method, or DoE, can help meet these multiple challenges. Making use of a statistical approach is not an innovation itself, but today DoE can be employed to do much more than just optimize a test plan and minimize test bed time. By examining a variety of concrete cases, this article will explore the range of ways the DoE method can be used to advance engine development from its classic application to DoE based model development to purely simulation-based DoS (‘Design of Simulations’) system optimization. In the section on classic application of DoE, the advantages of a statistical approach are compared to a full factorial collection of measurement data in the examination of a high-speed diesel engine focusing on PM emissions. With this approach multiple applications (gen-set, locomotive, etc.) were optimized in terms of fuel consumption and emissions. Two further examples of areas of application to be discussed are the pre-optimization of efficiency and nitric oxides in the case of a dual fuel engine as well as the investigation of the influence of different fuel gas compositions on the operating range (knocking) in the case of a gas engine. In addition, the DoE method can also lay the foundations for model development, e.g. for describing the combustion process. Originating from experimental investigations, measurement-based functions provide the input required for system optimization. With this input, multi-cylinder engine simulation following a statistical approach can be applied to vary engine parameters in order to optimize efficiency while respecting the constraints of emissions, knocking and misfire. Within this paper this process is demonstrated for a pre-chamber gas engine. Finally, optimization work involving multiple parameters can also be conducted entirely with simulation without using any measurement data. Using simulation instead of measurements can result in long processing times, e.g. detailed reaction kinetic determination of ignition delay, laminar flame speeds, etc. Therefore, these simulation tasks are treated separately; the results can once again be described by functions and serve as input for system optimization.

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。Retaining and improving the performance and efficiency of shipboard power plants, as well as performing condition monitoring towards efficient fault diagnosis and asset management, requires Monitoring (measuring) and Evaluation (benchmarking). On the monitoring side, any in-service measurements may occasionally prove to be untrustworthy, taking into account sensor and recording accuracy issues. Performance evaluation and fault diagnosis rely on dependable and accurate benchmark/reference, against which measurements can be compared. The core of the novel methodology, presented in this paper, involves the use of a thermodynamic simulation model for each specific shipboard engine. This model is tuned to be an exact replica of the actual engine in operation, reflecting the physical relationships of all primary parameters (temperatures, pressures, rpm) and resultant values (torque, fuel consumption, emissions etc.). Once tuning is performed, the model predicts engine performance as influenced by ambient conditions, load, speed and fuel, at any operating point. Based on the premise that the operating envelope of the engine is known, a great number of simulations are performed a-priori, for combinations of all possible engine settings, ambient conditions and fuels. Thus an engine performance hyper-map (Engine Hyper Cube) is generated. This hyper-map database can provide the “expected” values of performance parameters at any engine operating condition. These “expected” values are then compared to the “measured” values offering diagnostics based on the residual differences between the two. Euronav Shipping Company has installed Engine Hyper Cube models, as produced by Propulsion Analytics, for seven Suezmax tankers (sister ships). The ships’ main engines have various measuring and data acquisition systems installed onboard, with the Engine Hyper Cube methodology capable of working with any such system and/or sensor. To ascertain the accuracy of the methodology and the predictive potential, a single blind validation was performed where the engine settings from service performance reports for some years in the past, were input into the Engine Hyper Cube software. Any observed swing in residuals (measured-expected) in the timeline, were then compared with the known engine maintenance events. The results indicated recognizable shift in performance, following maintenance events in the ship’s records, confirming the validity and accuracy of the Engine Hyper Cube methodology. Another case is presented, where a fuel injection problem was investigated. An in-depth analysis using measured cylinder pressure diagrams compared with pressure trace predictions and the use of heat release analysis pinpointed the cylinder with fuel injection issues. The methodology also allows the shipping company to perform optimization studies (e.g., VIT optimization) as well as execute a number of ‘what-if’ scenarios for examining how the vessel engine performs in regimes it had not operated in the past. One such case is also presented. The shipping company is using these methodologies and technologies for monitoring and evaluation, aiming at optimum vessel operation.

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。To obtain NOx emissions that fall below the increasingly lower NOx limits with prechamber gas engines, it is not enough to merely increase the excess air ratio in the main combustion chamber; this would result in significant losses in engine efficiency. Instead, it is necessary to focus on the NOx emissions created in the prechamber in particular since these greatly contribute to the total amount of NOx emissions. Thus when developing combustion concepts for prechamber gas engines, attention must be paid to finding ways to reduce NOx in the prechamber without compromising the effectiveness of flame torches in initiating combustion in the main combustion chamber. This article will make use of engine measurements to show what challenges arise as a result of high prechamber NOx emissions. The main emphasis is placed on a methodology that is capable of characterizing the origin of NOx emissions. Next, the causes of NOx formation in the scavenged prechamber are investigated by conducting detailed analyses of test bed measurements. Advanced analytical tools that rely mainly on 0D models and analysis methods are applied to perform calculations of the thermodynamic conditions in the prechamber in order to calculate prechamber NOx. These tools are also capable of calculating the charge composition in the prechamber at ignition timing which is relevant information for ignition and flame propagation. The flow of nitric oxides between prechamber and main combustion chamber is considered as well. Thorough knowledge of parameters related to the prechamber such as prechamber pressure curve and prechamber gas amount, composition of the scavenging gas and timing of the admission is imperative. The described methodology is used for developing combustion concepts for highest efficiencies that are able to accomplish also future low NOx emissions levels prescribed by law. In addition, it is shown what impact various prechamber parameters (amount of prechamber gas, prechamber geometry, etc.) and different types of scavenging gases such as hydrogen and reformer gas have on prechamber NOx formation. The interaction between the prechamber and the main combustion chamber will be analyzed in detail.