This paper reviews the latest accomplishments in controlling gas emissions from large two-stroke diesel engines. During the last few decades several alternative methods have been developed, tested in service and evaluated for reduction of the exhaust gas emission. NOx emission can be reduced by Water Emulsion Fuel, High-pressure Water Injection, Exhaust Gas Recirculation (EGR), Scavenging Air Moistening (SAM), Low NOx Fuel Injectors and the Emission Mode of the ME Engine. With regard to SOx emission it can be solved by Exhaust Gas Treatment. Operation on low-sulphur fuel Will also solve the problem. However, this requires special operational procedures. The HC and particulate emission is the result of an insufficient combustion process. It is preferable to trace the reasons, as the resultant heat load and contamination has a negative influence on the engine's performance.
This paper explains what SCW (Super Critical Water) diesel is, what sort of combined system it is, how effective it can be, why the authors develop it and how the system can be realized. One may, in a word, consider it as a kind of parallel combined systems by means of comparatively large diesel engines. This paper clarifies the reason why the parallel combined system for diesel engines is regarded as“SCW diesel system”. This paper introduces Super Critical Water (SCW) diesel as a parallel combined system and explains its efficacy and output focusing on the difference between parallel combined systems and series combined systems, referring to GT (gas turbine) parallel combined system and GT series combined system. One often calls the former system GT-Cheng cycle and the latter system GTCC (gas turbine combined cycle) . This paper points out that SCW diesel is not a simple regenerative or economizing system but a remarkable power & efficiency amplifier for prime movers. This paper also details how a parallel combined system for diesel engines could be materialized. Consequently, how to estimate the system equilibrium is studied. Here the system equilibrium means a balance between prime movers and waste heat exchangers and a balance between the air·gas cycle work and the SCW cycle work in the cylinders. In solving the equilibrium (especially as to the latter balance), the authors introduced the concept of“designing the cycle process of reciprocators”. Without this concept, it is almost impossible even to work out SCW diesel system and/or to make a plan of confirmation tests. Concept verification tests are still in progress. This paper touches on the test preparation. However, the expected outcomes for power increase, efficiency improvement and emission reduction are discussed.
The authors have studied the influence of common rail system on the injection characteristics and engine performance for reducing exhaust emissions and noise at low load of high-speed diesel engine. The effects of the parameters of injection timing, common rail pressure, pre-injection timing, pre-injection quantity and its interval etc. on especially the engine performance and noise at low load have been examined. As it is able to increase the fuel injection pressure at low speed, Bosch smoke number at low speed with torque rich operation was reduced by optimizing the injection pressure. And fuel consumption was reduced. In addition, NOx and PM were decreased by optimizing the injection timing for the engine operation condition. The pre-injection at idle and low load operation is one of the effective methods for reducing the noise. In this paper, the above test and analyses results are presented.
At present, air pollution Annex to Marpol 73/78 convention is being compiled to regulate NOx and SOx emission limits. The paper describes the application of a CFD combustion model - KIVAII3v for a large bore, slow speed marine diesel engine and explores the feasibility of using fuel timing injection variables to estimate NOx exhaust emissions levels, at steady running conditions. The correlation analysis between the measured and calculated gaseous emission caused by fuel variable injection timing (VIT) was performed. The analysis is based on experimental data from Wärtsila RTA engines test bed trials. Extracted and averaged measured history of NOx, and other gas components emission concentration were used as a comparison basis for calculation results. An examination of the measured and calculated results, particularly NOx concentrations, generally reveals a difference of emission levels associated with engine load and VIT setting.
This paper presents the simulation of operation of a turbocharged medium-speed marine diesel engine, incorporating two prototype modifications to counteract fuel-air mismatch during transient loading - injection of high pressure air on the compressor impeller and variable path exhaust manifold allowing pulse or constant pressure turbocharging. The simulation work was performed using the MOTHER code, an in-house developed thermodynamic code, applied to the MAN B&W 5L16/24 test engine, installed in the Laboratory of Marine Engineering NTUA. For typical transient engine loading profiles, obtained from ship-board measurements, the simulation results clearly show the improved response of the turbocharger compressor. The simulation results were used in the design of related experiments, with the prototype components installed on a test engine.
Thanks to the progress in both computer system hardware and software, the engine performance and exhaust emission precisely can be simulated by using virtual engine model of one dimension with codes. Therefore, it came to be able to shift from a relative evaluation by the single cylinder model with the overall turbocharger efficiency to an absolute evaluation by the multi cylinder model (full model) with the turbocharger map. As a result, the simulation accuracy for the engine performance and exhaust emission estimation has been improved. This paper presents the improvement of engine performance simulation technology by using the examples of engine simulation calculations and engine experimental results. In these analyses, the multi cylinder model is introduced for simulating the engine performance and exhaust emission and the results are compared with the experimental results.
Maintenance and inspection work during operation for the low speed diesel engines have to be minimized to rationalize the work and reduce the maintenance cost. For higher reliability and automatic surveillance, the detection of abnormal conditions and diagnosis of troubles have become necessary for engines. This study analyses the temperature of combustion chamber of the low speed diesel engine at simulated operation. The heat flux inside the combustion chamber rises up suddenly at severe conditions of operation, and that results in the abnormal temperature change, especially at piston, piston ring and cylinder liner. The temperature distribution is estimated by calculations and analyzed by finite element method (FEM) . Time-aging effect of diesel engines raises heat flux on combustion chamber to the trouble of engines.
FIA (Fuel Ignitability Analyzer) from Fueltech, Norway has already achieved plenty of ignitability evaluation of many kinds of marine diesel fuels over the world. In this study, a total fuel evaluation method on FIA measurement was newly proposed through constructing electronically controlled injection systems. These systems realized near square-shaped injection rate and good repeatability. In the course of the measurement progress, the experimental conditions required to evaluate fuel combustibility became clearer than before. Indexes introduced to evaluate fuel combustibility on the heat release process in FIA successfully determined the troublemaking fuels. Supplementary indexes on simple composition analysis also succeeded in defining the boundary of troublemaking fuels. With all the examinations, combustibility analysis of bunker fuel oil on HA system brought into reality for the first time.
The Shipbuilding Research Association of Japan started a project in 2003 to develop a direct water injection (DWI) system to decrease NOx formation through the reduction of flame temperatures at the combustion stage in marine diesel engines. In this project, it was decided that an 80% reduction in NOx emission must be achieved with a less than 3% increase in specific fuel consumption. To evaluate this system, high-speed photography of combustion was carried out using a visual test engine that had the same construction as a low-speed marine engine. Flame temperature decreases were visualized using the two-color method of digital photo data analysis. CFD calculations using KIVA code and StarCD were also made, and the behavior of sprays/flames and the temperature distribution in flames were successfully simulated. Furthermore, experiments to optimize the water injection system design, ensuring NOx reduction, were carried out using a constant volume combustion chamber simulating the engine running conditions.
Fundamental concept for low emission engines in the present study is utilization of alternative fuels such as natural gas and methanol with low evaporation temperature for reducing smoke, and high EGR engine operation for reducing NOx. The final goal is to achieve the extremely low levels of both NOx and smoke without deteriorating high thermal efficiency in a dual fuel diesel engine. Natural gas or methanol was charged into the suction air, and a small amount of gas oil as an ignition source was injected directly into the combustion chamber of a four-cylinder DI diesel engine. The injection amount of gas oil, intake temperature, compression ratio and EGR ratio were changed in the experiments. The effects of these parameters on ignition delay, maximum rate of heat release, knock limit and misfire limit were clarified for the premixture of natural gas or methanol respectively.
A technique to monitor abnormal vibration of crosshead bearings in large two-stroke diesel engines has been developed using a dynamically loaded bearing seizure test rig. The test rig is able to simulate the load pattern and oscillatory motion of the actual crosshead bearing. Normal vibration spikes occur around crank angles of -90deg and +90deg where the oscillating speed is zero. When the lubrication condition deteriorates, an abnommal vibration spike caused by severe metal-to-metal contact is frequently generated at a crank angle of +90deg where the oil film thickness is a minimum. If careful measures against seizure are carried out immediately after detecting abnommal vibration, the bearing surface would be able to recover, thereby avoiding severe metal-to-metal contact damage. Thus the early detection of abnormal vibration can be effective inpreventing seizure of the bearings.
Drain oils in 2-stoke marine engines are receiving a lot of attention as they are expected to become a major contributor to optimise cylinder unit operation or define their predictive maintenance. Given the complexity of drain oil analysis and adequate interpretation, the objective of this study is to simulate and understand the transformation of Marine Cylinder Lubricant from “fresh oil” to “drain oil” during the engine running. It is also to establish a performance profile along the liner wall of the lubricant in use, in terms of thermal stability, neutralisation capacity and protection from abrasive and corrosive wear. Two different mechanistic approaches are proposed to describe the transformation process, combining neutralisation with oxidation reactions. Validation of the test conditions is done through comparative testing of proven formulations of MCL, and simulation of drain oils sampled in the field. The study finally proposes a preferred mechanism. This will allow to further optimise formulations of Marine Cylinder Lubricants to the actual and future engine demands.
The analysis on the mixed lubrication of piston rings in a 4-stroke cycle diesel engine is made. The analysis uses the average Reynolds equation developed by Patir and Cheng, which governs the mean hydrodynamic pressure generated between two partially lubricated surfaces. The asperity contact pressure and the real contact area are estimated by the formulas of Lee and Ren, which are functions of the statistical surface roughness parameters, material hardness and load. Effects of statistical surface roughness parameters, which include the surface pattern parameter, combined rms roughness and auto-correlation length, on the film thickness and friction characteristics between piston rings and a liner are investigated. The cyclic variations of the minimum film thickness and friction force are significantly affected by the surface pattern parameter. The film thickness and friction characteristics of barrel-faced ring are also examined.
A unique device for separating oil from oil-contaminated seawater by the magnetohydrodynamics (MHID) method, so-called the MIID separation device, is improved on the basis of the results of observation of the inside of MHD separation cells. The MHID method is based on the difference in electric conductivity between seawater and oil; the separation force applied to oil as a reaction of the electromagnetic force is used for oil separation. The performance of the improved device with a mixture of artificial seawater and simulation particles instead of oil droplets is tested using a 10-T class superconducting magnet. The results show perfect separation at a magnetic field of 5 T 10.1 A or higher.
This report treats the design procedures for the crank-angle arrangements and firing sequences for multicylinder reciprocating engines. The authors developed the most powerful design method of finding uneven crankangle arrangements for four and two stroke cycle reciprocating engines of multi-cylinders. The study reveals how the various kinds of engine-exciting forces and/or moments are simply expressed and how the procedure contributes toward the vibration reduction of multi-cylinder engines. In order to build the design procedure, a new type of optimization algorithm is introduced: a method in which the feasible domain due to the constraint conditions is clarified. In other words, the idea of “modified cyclotomic polynomial (MCP) ” analysis is contrived. This report points out that the introduced concept is significant not only for the reciprocating engine design but also for general engineering and science. Actually new and effective crank-angle arrangements have been looked for. This paper also establishes new ways in solving non-linear optimization problems with non-linear constraint conditions.
Torsional vibrations in a ship propulsion plant comprising a low-speed two-stroke engine directly coupled to a propeller may be calculated with a one-dimensional mathematical model but, owing to the particular geometry of the engine crankshaft, for reliable results a three-dimensional model should be used for all other vibration calculations. And even for static calculations like alignment there are good reasons to use such an advanced calculation model. This paper introduces a computer program developed by the Wärtsilä Corporation which provides a threedimensional model of the shafting for the calculation of coupled vibrations, alignment and whirling in such a ship propulsion plant. Based on the finite-element method the program covers both dynamic and static problems. Each node has six degrees of freedom. The following features are included: calculation in frequency range and time domain, linear and nonlinear bearing characteristic, consideration of variation of running gear inertia, and optimization of engine parameters. The mathematical model of the shaft line with all associated parameters and boundary conditions are represented by calculation results and validated by measurement. Some everyday examples of calculation results for axial vibrations with the associated measured data are shown in this paper. Furthermore the influence of the variation of torsional inertia is demonstrated and a possibility for reduction of torsional stress in the crankshaft by injection timing optimization is explained. As an example for the static capabilities the reverse bearing offset calculation based on measured web deflections, bearing loads and bending moments is demonstrated.
In recent years, technology for achieving higher compressor pressure ratio, higher performance and compactness has become an essential requirement in the design of turbochargers installed on 4 stroke diesel engines from the viewpoint of preventing global warming and air pollution and for achieving higher engine output and higher efficiency. Under these circumstances, IHI has developed the radial type AT14 turbocharger with high reliability and durability. This new turbocharger was designed based on abundant experiences of IHI in field. AT14 turbocharger was subjected to run on the test-rig over a long period of time and confirmation tests with reliability and durability were conducted at various stages of development. The longest running hours of AT14 turbochargers reached almost 8, 000 hours without any problem and the condition of the bearings are good for such long operating hours. These results show that AT14 turbocharger has enough reliability and durability even under the heavy fuel oil application.
In response to the requirement for higher output of diesel engines in the recent years, IHI (Ishikawajima-Harima Industries Co., Ltd.) has recognized that a turbocharger with higher pressure-ratio and volume-flow rate will be required, and has commenced the development of such a turbocharger. One of the important technologies to develop the turbocharger with floating bush bearings is the evaluation of design parameters such as bearing peripheral temperatures and rotational speed of floating bush bearings. The present paper describes some measurements in a small size marine turbocharger to evaluate peripheral temperatures of the bearing, rotor vibration and rotational speed of 3-arc geometry floating bush bearings by using a slip ring system. Then for the rotational speed of floating bush bearings we have compared the prediction by a infinite length theory with measurements. The acquired results will be applied for designing of floating bush bearings.
Gas hydrate is generally formed at comparatively high pressure or low temperature. But, in recent years, some researchers reported that CH4 hydrate remains meta-stable even under some conditions outside its stability region. If the meta-stable property of gas hydrate can be utilized economically, it is possible to store and transport stranded natural gas at higher temperature, compared to conventional LNG method. Although the‘self-preservation’property of gas hydrate has been gradually clarified, its mechanism has been still poorly understood. There is a disparity among the obtained experimental data, and the reason for the data gap has not been still elucidated. In order to understand the‘genuine’self-preservation property of gas hydrate, we made gas hydrate samples from small ice particles and CH4 with hydrate particle size controlled and with no pelletization processed, and experimentally examined their self-preservation property at 0.1 MPa. We compared the results with our previous data obtained for both‘non-pelletized’and‘pelletized’CH4 hydrate samples, and pointed out that there was a possibility that we observed such the data gap mainly owing to several factors of differences in both manufacturing method and thermal history of the hydrate samples, besides influence of pelletization process.
Carbon dioxide (CO2) ocean sequestration technologies, such as dissolution into seawater, are important to mitigate global warming. In this study, solution processes of CO2 gas in seawater and pure water were experimentally studied under various pressures and temperatures to evaluate the solubilities of CO2 in seawater. The solubilities of CO2 in seawater and pure water were measured by a change in pressure due to absorption at pressures up to 30 MPa and the temperatures ranged from 4°C to 60°C. It was obtained that the solubilities of CO2 were between 0.27 × 10-3 and 1.26 × 10-3 in seawater, and between 0.26 × 10-3 and 0.6 × 10-3 in pure water near atmospheric pressure. The values increase with an increase in pressure, but decrease with an increase in temperature. The Henry's law constant of CO2 was about 105 MPa at a temperature of 4°C in seawater under atmospheric pressure, and increased with an increase in temperature. The solubility of CO2 in seawater was lower than that in pure water. Empirical correlations for solubilities of C02 in seawater and pure water at various temperatures under atmospheric pressure were obtained based on the experimental data.
The dissolution rate of CO2 drops with CO2 hydrate films was investigated to estimate the environmental impacts of the ocean storage of CO2. The diameter of dissolving CO2 drops was measured and compared with that from a theoretical model, where the mass transfer coefficient is provided by Ranz-Marshall's equation to involve the effect of water flow on the dissolution rate. The pH in ambient water around the drops was also measured to obtain the CO2 concentration in ambient water, which is also incorporated into the model. The dissolution rate of the CO2 drop was obtained from both the model and the experimental results. The experimental dissolution rate was enhanced by an increase in flow velocity similar to the predicted rate; however, the experimental dissolution rate was lower than that predicted. Moreover, the difference between the experimental and predicted dissolution rates became higher due to an increase in flow velocity.
A submersible vehicle based on sea turtles was developed to investigate the possibilities of flapping fin propulsion and maneuvering. This vehicle has two forefins with two degrees of freedom, representing flapping and feathering motions. It uses them for propulsion and maneuvering. Flapping motion is realized by a combination of a stepping motor, a crank mechanism and a universal joint for each forefin; the feathering motion is realized by a servomotor for each fin. Hindfins were also equipped with one degree of freedom, and a buoyancy controller for the vehicle was designed. In experiments, this vehicle swam at 0.06 m/s when the forefin frequency was 0.53 Hz, and the maximum swimming number was 0.24 when the fin frequency was 0.35 Hz. This vehicle still presents many problems, such as limited flapping frequency. By assessing those drawbacks, this kind of vehicle might be improved and investigated for possible use.
In recent years, speech recognition systems have been employed in vehicle instrumentation in a wide variety of environments. Speech recognition plays an important role in the chief engineering systems on ships. In this type of system, speech recognition supports the engine room controls, and lower than 0-dB signal-to-noise ratio (SNR) operability is required. In such a low SNR environment, a noise signal can be misjudged as speech, dramatically decreasing the recognition rate. Therefore, this study focuses on a recognition system that uses body-conducted signals. Since noise is not introduced within body-conducted signals that are conducted in solids, even within sites which are low SNR environments such as engine rooms, it is necessary to construct a system with a high recognition rate. However, when constructing such systems, in order to create models specialized for body-conducted speech, it is necessary to use leaming data consisting of sentences that must be read numerous times. Therefore, in the present study we applied a method in which the specific nature of body-conducted speech is reflected within an existing speech recognition system with only small numbers of vocalizations. Because two of the prerequisites for operation within a site such as an engine room where noise exists are both“hands-free” and“eyes-free”operations, we also investigated the effects of making this type of system wireless.
Nowadays the container transportation service has become an increasingly important means of transportation. Berth resource allocation plays an important role in operation management at container terminals. It directly influences the efficiency of the loading/unloading operation process as well as the service level. This paper establishes a berth allocation model for the container terminals. The model considers the utilization of the berth and quay crane resources, and the distances between the positions of the vessels and the stacks. A case is given and a satisfying alternative of the berthlquay crane distribution can be obtained in terms of the model. It can be used to help planners to make out a berth schedule quickly and reasonably. It is helpful to raise the efficiency of the berth planning, especially for the new planners.
This paper, for the purpose of machinery plant operation training by means of Engine Room Simulator (ERS) based on PC, describes the features of human errors by the unskilled trainees in the marine engine plant operation and shows the necessary improvement in the training in order to decrease such errors from the viewpoint of educational technology. Human error data were collected out of the simulator operation record and observation of the trainees in VIMARU (Vietnam Maritime University) . The examination of such data has shown that error occurs mainly by omission error and extraneous act. Further analysis was made on such errors by the trainees to find out the characteristics of errors caused in the process of acquiring procedural knowledge for the operation. The analysis has revealed that the human errors occur for the following reasons: (1) Lack of knowledge on the over all system and fundamental operation (2) Insufficient confirmation to operation (3) Incomplete knowledge on the operational sequence In this paper, the roles of instructor will be described in order to reduce the cause for such human errors and to enhance the educational performance.