Low-speed Marine Diesel Engine Research Articles

APPLICATION OF THE OPTIMIZATION METHOD IN THE OBJECTIVES OF THE ANALYSIS OF THE WORKING PROCESS OF SHIP DIESELS

The article touches upon the possibility of using the method of gradientless n-parametric minimization of Powell'64 in tasks of monitoring the working process of marine diesel engines. There is given an example of finding a global minimum of the Rosenbrock test function. Using the Powell'64 method, the Least-squares functionals in the synchronization and modelling tasks of compression-expansion curves in the working cylinder are minimized. The calculation results of data synchronization for low-speed two-stroke and medium-speed four-stroke marine diesel engines are shown. The synchronization problem can be solved in terms of equation P' = 0 derived for the sector from compression starting to combustion starting in the cylinder. The selection of the boundary conditions for simulation is shown. The advantage of Powell’64 method is its high efficiency for quadratic functionals. As opposed to gradient methods, the Powell'64 method does not require calculating derivatives and is universal for minimizing complex nonlinear general functionals. The original author's algorithm of data synchronization by analyzing the indicator diagrams using the Powell'64 method has been applied in the latest versions of monitoring systems of D4.0H marine diesel engine.

A tribological analysis on stuffing box-piston rod system of low-speed marine diesel engines

The stuffing box-piston rod system is widely used in the low-speed marine diesel engines to scrape oil and ensure sealing. Its friction power loss and wear rate are great, but the studies about the system are very limited. In this study, based on the special structure and working conditions of the stuffing box, the analytical model for the tribological properties of the stuffing box-piston rod system is developed considering the oil starvation and relative ring location effects. The minimum oil film thickness, friction, oil transportation, and asperity contact are calculated for the stuffing box. The analysis results show that compared with the fully flooded lubrication, the minimum oil film thicknesses of the rings reduce significantly in the middle of the strokes under the starved lubrication condition, but the friction losses of the rings are influenced by the comprehensive effects of the oil film thickness reduction and lubricating area reduction under the starved lubrication condition, which is related to the specific profiles of the rings. In addition, compared with the engine piston ring pack, the relative ring location effect is more obvious in the stuffing box ring pack because there are more rings and the ring intervals are larger. The relative ring location effect makes the minimum oil film thicknesses, friction forces, and asperity contacts of the rings have oscillations after bottom dead center and top dead center.

Study on Technical Features of Marine Low-Speed Diesel Engines

Study on Technical Features of Marine Low-Speed Diesel Engines

A new coupling tribodynamic model of crosshead slipper-guide system and piston skirt-liner system of low-speed marine diesel engines

In this paper, considering the coupling effects of the crosshead slipper-guide system and the piston skirt-liner system, a new tribodynamic model is established for the low-speed two-stroke marine diesel engine. Firstly, a dynamic model including the crosshead slipper, the piston, the piston rod, and the crosshead pin is proposed. Then, considering the disciplinary coupling between the dynamic model and the lubrication models, the stiff and nonlinear tribodynamic model is solved with the modified extended backward differentiation formulae (MEBDF). Finally the tribodynamic performances of the crosshead slipper and the piston skirt are analyzed. The simulation results show that the crosshead slipper bears the thrust force and its friction power loss is obviously larger than that of the piston skirt.

Impact of waste heat recovery systems on energy efficiency improvement of a heavy-duty diesel engine

Abstract The increase of ship’s energy utilization efficiency and the reduction of greenhouse gas emissions have been high lightened in recent years and have become an increasingly important subject for ship designers and owners. The International Maritime Organization (IMO) is seeking measures to reduce the CO2 emissions from ships, and their proposed energy efficiency design index (EEDI) and energy efficiency operational indicator (EEOI) aim at ensuring that future vessels will be more efficient. Waste heat recovery can be employed not only to improve energy utilization efficiency but also to reduce greenhouse gas emissions. In this paper, a typical conceptual large container ship employing a low speed marine diesel engine as the main propulsion machinery is introduced and three possible types of waste heat recovery systems are designed. To calculate the EEDI and EEOI of the given large container ship, two software packages are developed. From the viewpoint of operation and maintenance, lowering the ship speed and improving container load rate can greatly reduce EEOI and further reduce total fuel consumption. Although the large container ship itself can reach the IMO requirements of EEDI at the first stage with a reduction factor 10% under the reference line value, the proposed waste heat recovery systems can improve the ship EEDI reduction factor to 20% under the reference line value.

Effects of a turbocharger cut out system on vibration characteristics of a propulsion shafting system and a large low speed marine diesel engine

To cope with the long term recession in the shipping industry due to oversupply of ships and high oil prices and due to reinforcement of environmental regulations to reduce greenhouse gas emission from ships, large container vessels built recently have ultra-long stroke engines with high propulsion efficiency. For these, de-rated engine and tuning technologies are used to reduce fuel oil consumption. However, previously built vessels were optimized for high ship speed. In these case, lowering ship speed to reduce ship operating cost does not provide similar benefits. Therefore, engine manufacturers have developed a turbocharger cut-out system to reduce fuel oil consumption at low speed. This has the advantage of reducing fuel consumption at low speeds, but also has the characteristic of producing higher torsional exciting force than is typical in existing engines for low load ranges. In this paper, the performance and dynamic characteristics of a marine diesel engine were reviewed after applying a turbocharger cut-out system. Then the effects on the engine body vibration and the torsional vibration were examined for a corresponding propulsion shafting system in a Panamax container-vessel equipped with a turbocharger cut-out system optimized for slow steaming. As a result, the torsional vibratory stress in shafts was increased. This had a larger effect on the X-mode shape of the engine body vibration and on the upper structure vibration, when one of three turbochargers was cut out.

Research of NOx reduction on a low-speed two-stroke marine diesel engine by using EGR (exhaust gas recirculation)–CB (cylinder bypass) and EGB (exhaust gas bypass)

IMO Tier III, applied on 1 January 2016, forced that NOx emissions must not exceed 3.4 g/kWh for low-speed marine diesel engines (engine speed lower than 130 rpm) in NOx ECAs. And the best answer for propulsion of nautical ships presently and for the near decades is the low-speed two-stroke diesel engines. Any abatement technology that reduces NOx emissions to the expected point can be allowed. EGR is an effective technology that has been verified on automotive applications and marine diesel engines (high speed and medium speed). This paper provides an internal measure: EGR (exhaust gas recirculation) combined with CB (cylinder bypass) and EGB (exhaust gas bypass) to reduce NOx emissions. Combined with CB and EGB, the EGR system applied on the engine can reduce the NOx emissions under 3.4 g/kWh. To test the effects of the EGR system, three modes were set: non-EGR mode, low-EGR mode and ECA-EGR mode. The effects of different modes on NOx emissions, fuel consumption, engine power and emissions are investigated. As a result, it can be concluded when the engine run in the ECA-EGR mode, NOx emissions can meet the requirements of IMO Tier III.

A model to optimise the selection of marine dual-fuel low-speed diesel engines

This study aimed to address the state of the art of marine diesel engines computer simulation models and the main computer applications. There are simple models based on transfer function or more complex models based on computational fluid dynamics. The models may be either implemented through basic programming languages or simulated through dedicated packages of internal combustion engine simulation. Owing to the recent interest to reduce the gas emission, dual-fuel engines are increasingly being used as primary propulsion in merchant ships. In this context, a simplified model of marine dual-fuel low-speed diesel engine has been developed. Through the normalisation of specific fuel consumption and exhaust gas data, clear trends approachable by polynomial curves or surfaces were revealed. Thus, by using the proposed model and knowing the characteristics of an engine at its nominal maximum continuous rating, it is possible to predict the engine operation in any design point on the engine layout diagram, even at part load. The maximum deviations regarding the two simulated engines did not exceed −3.4%. Summarising, the developed model is a simple and effective tool for optimising the selection of dual-fuel low-speed diesel engines to be applied in ship propulsion systems.

NOx Reduction from Marine Low Speed Diesel Engines by Combination of EGR and WEF

NOx Reduction from Marine Low Speed Diesel Engines by Combination of EGR and WEF

NOx Reduction of Marine Low Speed Diesel Engine with Low Pressure EGR

NOx Reduction of Marine Low Speed Diesel Engine with Low Pressure EGR

The impact of the accuracy of indicator diagrams on the heat release characteristics calculation, used in the diagnosis of marine diesel engine

The paper analyzes the possibility to use the electronic type indicators in the diagnosis of marine engines. It has been shown that in-depth analysis of indicator diagrams would be useful – calculation of heat release characteristics. To make this possible, measuring indicated systems should meet a number of important requirements in or-der to ensure that they can be used for the diagnostic purposes. These includes: high precision sensors for the measurement of cylinder pressure, high speed and accuracy of measuring and recording of measured values. These also includes reliable determination of the top dead center piston (TDC). In order to demonstrate the impact of positional error TDC, simulation study was conducted in which indicated diagrams were used, obtained on a medium-speed four-stroke marine diesel engine type A25/30 and the low-speed two-stroke marine diesel engine type RTA76, Sulzer company.

Optimised selection of marine dual-fuel low-speed diesel engines: introducing relative specific fuel consumptions

Low-speed diesel engines are the most used ones in large ships as main propulsion, and due to severe environmental rules, there has been an intensive search for using alternative fuels which generate less emissions in these engines. In this context, dual-fuel diesel engines have been developed and their employment keeps growing. Therefore, the present study aimed to elaborate a simple and fast approach to assist the selection of the optimal marine dual-fuel low-speed diesel engine concerning fuel consumption to be fitted as primary mover. Relative specific fuel consumptions were introduced to develop unified expressions, and a polynomial approach was applied in order to fit curves. The accuracy of the method was verified through comparisons with a web-based application provided by an engine manufacturer and the highest deviation peaked at about 2.7 %. A practical liquefied natural gas carrier design of matching propeller/ship and engine was performed so that the convenience of the method could be explored. Thus, through the proposed optimisation methodology, annual savings of over 8.1 and 9.6 % were reached regarding heavy fuel oil and boil-off gas, respectively. At last, it was found that the optimal matching might not be due to the most efficient either propeller or engine.

Importance of Vanadium-Catalyzed Oxidation of SO2 to SO3 in Two-Stroke Marine Diesel Engines

Low-speed marine diesel engines are mostly operated on heavy fuel oils, which have a high content of sulfur and ash, including trace amounts of vanadium, nickel, and aluminum. In particular, vanadium oxides could catalyze in-cylinder oxidation of SO2 to SO3, promoting the formation of sulfuric acid and enhancing problems of corrosion. In the present work, the kinetics of the catalyzed oxidation was studied in a fixed-bed reactor at atmospheric pressure. Vanadium oxide nanoparticles were synthesized by spray flame pyrolysis, i.e., by a mechanism similar to the mechanism leading to the formation of the catalytic species within the engine. Experiments with different particle compositions (vanadium/sodium ratio) and temperatures (300–800 °C) show that both the temperature and sodium content have a major impact on the oxidation rate. Kinetic parameters for the catalyzed reaction are determined, and the proposed kinetic model fits well with the experimental data. The impact of the catalytic reaction is studied ...

Эволюция материалов ответственных компонентов малооборотных судовых дизелей

With the growth of average effective pressure in cylinders of marine lowspeed diesel engines the requirements increased to materials used for manufacturing their critical parts. This paper reports the dynamics of mechanical data changes in materials (steel and cast iron) of critical parts in diesel engines by the example of produce of the Bryansk engineering plant. From 1961 till 2008 the Bryansk engineering plant is the only manufacturer of powerful marine low-speed diesel engines in Russia. Diesel engines were being built under licence of “MAN Burmeister Diesel” Co. Diesel engines manufactures in different years differ with forcing degree. A diesel engine with a higher forcing degree has a higher value of mean effective pressure. In the paper there are shown types of diesel engines manufactured by the Bryansk engineering plant and is shown the evolution of mechanical data of cylinder iron bushes, piston rings, steel components of a bed frame, crankshafts. 
 It is pointed out that the application of new steel and cast iron kinds should follow considerable changes in the design of marine low-speed diesel engines of the type 6DKRN 50/200-14 of compact modification. 
 The conclusion is drawn of that with the growth of a forcing degree in diesel engines the mechanical data of steel and cast iron will increase at the expense of material chemistry changes by means of the introduction of alloying elements and application of modern metallurgical equipment for qualitative billet manufacturing.

高熱効率機関

高熱効率機関

A Study on Effects of Unsuitable Fuel and Insufficient Cylinder Lubricating Oil on Low Speed Marine Diesel Engine

A Study on Effects of Unsuitable Fuel and Insufficient Cylinder Lubricating Oil on Low Speed Marine Diesel Engine

APPLICABILITY STUDY OF THE FIBER-OPTIC GYRO IN PISTON ENGINES DIAGNOSING PROCESS

The Polish Naval Academy has been involved in marine reciprocating combustion engines indication tests for many years. Results of researches aiming to diagnostic using of measurement of engine crankshaft unsteady angular speed are presented in the paper. Up to now, adequate accuracy of angular speed measurement had not been achieved to make proper diagnostic decision. Commercially, measurement of unsteady rotation speed has been used only in MAPEX –TV system (Torsional Vibration detector) dedicated to SULZER engines, which can detect only the one engine cylinder switch out of work without any mistakes. For several years, mostly in navigation, more often are used optic gyroscopes which work on the base of Sagnac effect, assuring angular speed measurements with resolution of 0.001o/h. Such resolution is too high than needed in piston engines diagnostic, but range of measured rotation speed is much much lower than rpm of medium-or low-speed marine diesel engines. In scope of conducted research it was decided to build a model of Sagnac interferometer prepared to measure of instantaneous angular speed in range adequate to medium speed marine diesel engines. At rotational crankshaft speed equal 750 rpm 1mV change in output voltage had been achieved for the difference of 0,4 o/sec of rotational speed. Time of measurement is equal the time which need light ray to go through distance of 100 m fibber-optic line. In practice this method do not introduce any significant phase shifts and does not limit the number of samples per revolution.

Finite Element Analysis of Engine Fixed Parts Assembling Process

In order to select the best design method for stay bolts in the diesel engine assembling process, main fixed parts of some MAN low-speed marine diesel engine were analyzed based on finite element analysis software Hyperworks. The mechanical performance of bottom, frame and cylinder under the effect of the four kinds of assembling methods was investigated. Ultimately, the best assembling process was confirmed. Results indicated that the finite element analysis model was reliable and exactly. The middle to both sides assembly was the best among the four methods.

The Design Research on the Key Components of Low-Speed Marine Diesel Engine

This paper is mainly discussed the establishment of the unified constraint expression of simulation optimization model. Express all kinds of element constraints with unified physical mathematical mapping mechanism, uniform the model representation of product components in each domain and establish the unified expression model, in order to facilitate the follow-up simulation solution of multi-domain constraint system.

Study on the Combustion Noise Characteristic of Low Speed Diesel Engine

In recent years, the Low speed two stroke diesel engines are widely used as the main power device of big ship for its so many advantages such as the high power, better economical efficiency and good maintenance. However, the problem of diesel strong vibration and noise becomes a more and more serious at the same time. Because of the Construction Features of marine two-stroke low-speed diesel engine, the structure has to be suffered different kind of forces when it runs. In considering the source of vibration, the whole noise can be divided into combustion noise、machinery noise and aerodynamic noise. The combustion noise caused by cylinder pressure is the most important part of diesel noise. In this paper, the cylinder pressure curves are tested. The internal combustion engine dynamics and the equivalent node load are used in the calculation procedure to achieve the real condition simulation. The loading program is made to simulate the change of cylinder pressure and the move of piston. The transient response of the diesel engine is calculated. The characteristics of diesel caused by cylinder pressure are analyzed.The response analysis can be used to the vibration control.