Medium Speed Marine Research Articles

Effects of Methanol Steam Reforming for Hydrogen-Rich Products on the Performance Enhancement of a Medium-Speed Marine Engine

Effects of Methanol Steam Reforming for Hydrogen-Rich Products on the Performance Enhancement of a Medium-Speed Marine Engine

Analysis of changes in the angular velocity of the crankshaft of the marine engine for diagnosing the wear and location the failure of the fuel injection system

Abstract The combustion process can be simply described as periodic explosions in a cylinder with its frequency dependent on the number of cylinders and the rotational speed of the shaft. In practice, uniformity of combustion parameters in every cylinder is almost impossible. Due to this fact, instantaneous angular acceleration does not remain the same at the ends of the crankshaft. These observations formed the basis for the investigation of the instantaneous angular speed of the crankshaft ends. To investigate the influence of the failure behavior of the fuel systems during a shaft's rotational movement, a series of experiments were planned. For the simulations, a medium-speed marine engine driving electro generator was selected. The failure simulation was based on the installation of clogged spray holes, draining of part of fuel dose from high-pressure pump and decreasing of injection pressure by a lower tension of the injector spring. The results of measurement were processed and analyzed through a comparison of the fast Fourier transform spectra. As a general conclusion, a difference between general harmonics order of magnitudes was detected.

Investigation of evaporating sprays in a medium speed marine engine

The understanding of diesel sprays is very important to enable a better and cleaner marine engine design, but unfortunately little knowledge is openly available on marine engine fuel sprays. In this paper, evaporating sprays for medium speed marine engines were studied in a constant volume combustion chamber by performing optical measurements through Schlieren and Mie diagnostic techniques. The effects of ambient gas temperature and ambient gas density on vapor and liquid penetration were investigated by changing the target condition in the combustion chamber. A comparative study of two injectors with different nozzle diameters (0.38 mm and 0.44 mm) was also carried out at ambient density of 22.5 kg/m3. Some empirical correlations of spray penetration have been modified to fit the spray measurement data. Due to the transient characteristics of the pump-line-nozzle injection system, a time-dependent injection pressure profile is suggested for calculation of spray penetration. The spray tip penetration at large distance under low density (7.6 and 15.2 kg/m3) conditions is expected to be proportional to t2/3, which is supported by the model considering spray-induced gas turbulence effect. The t1/2 law, where turbulence is not taken into account, is still valid under high density (22.5 kg/m3) conditions with higher engine load. The comparison of two models demonstrates that the effect of gas turbulence is influenced by the ambient gas density and engine load.

Effect of Early Closing of the Inlet Valve on Fuel Consumption and Temperature in a Medium Speed Marine Diesel Engine Cylinder

The energy efficiency and environmental friendliness of medium-speed marine diesel engines are to be improved through the application of various measures and technologies. Special attention will be paid to the reduction in NOx in order to comply with the conditions of the MARPOL Convention, Annex VI. The reduction in NOx emissions will be achieved by the application of primary and secondary measures. The primary measures relate to the process in the engine, while the secondary measures are based on the reduction in NOx emissions through the after-treatment of exhaust gases. Some primary measures such as exhaust gas recirculation, adding water to the fuel or injecting water into the cylinder give good results in reducing NOx emissions, but generally lead to an increase in fuel consumption. In contrast to the aforementioned methods, the use of an earlier inlet valve closure, referred to in the literature as the Miller process, not only reduces NOx emissions, but also increases the efficiency of the engine in conjunction with appropriate turbochargers. A previously developed numerical model to simulate diesel engine operation is used to analyse the effects of the Miller process on engine performance. Although the numerical model cannot completely replace experimental research, it is an effective tool for verifying the influence of various input parameters on engine performance. In this paper, the effect of an earlier closing of the intake valve and an increase in inlet manifold pressure on fuel consumption, pressure and temperature in the engine cylinder under steady-state conditions is analysed. The results obtained with the numerical model show the justification for using the Miller processes to reduce NOx emissions and fuel consumption.

FUEL INJECTION PROCESS AT SPEED CHARACTERISTICS OF MEDIUM-SPEED DIESEL ENGINE AT VARIABLE MODES

The results of an experimental study of the features of the fuel injection process on the speed response of a medium-speed marine diesel engine under variable conditions are presented. The study of hydrodynamic processes for these characteristics expands the possibilities for improving the operation of a diesel engine, and also allows to clarify the methods for calculating the processes associated with fuel injection. Experimental studies have been performed on an engineless test bench under various initial conditions with the refinement of the measuring complex. The first option - before starting the high-pressure fuel system was unloaded. The second option - the engineless test bench was started after a short stop. At the same time, the residual pressure remains in the system after the first start option. The generalized results of the experimental study allowed to evaluate the process of fuel supply development during the whole experiment. At the same time, in the first option, the essential feature is the absence of a noticeable increase in pressure in the nozzles during the first three injection cycles in the acceleration process, despite the rather high rotational speed of the camshaft. Only in the fourth cycle, a pressure increase of up to 40 bar was obtained, which is not enough to lift the nozzle needle. The first injection conditions are formed in the fifth cycle (stepwise injection phase). In the second option, with an initial pressure in the fuel system of 27 bar, during acceleration already on the first revolution with a relatively low rotational speed, the pressure value corresponds to the injection conditions and reaches 166 bar. Thus, the initial pressure in the fuel system during acceleration has a significant impact on the development of the injection characteristics, which is a specific feature of the diesel engine operation in variable modes. The peculiarity of the formation of injection parameters during coasting in both options does not depend on the initial conditions in the fuel system. Consideration of the injection process features at a continuously varying rotation speed will improve the reliability of marine diesel engines during maneuvering and will ensure the improvement of diesel engine working processes at variable modes.

Numerical analysis of methane slip source distribution in a four-stroke dual-fuel marine engine

We present the results of a numerical model which has been developed for estimating the contribution to the methane slip from different sources in a four-stroke dual-fuel marine engine running on natural gas. The model is a thermodynamic three-zone zero-dimensional full engine cycle model and considers methane slip contributions from short-circuiting, crevices and wall quenching. The model is applied to analyze the methane slip from a four-stroke dual-fuel medium speed marine engine using natural gas as primary fuel. At low loads, wall quenching is found to be the dominant contribution to the methane slip. At full load, the wall quenching contribution is comparable to the level of the short-circuiting and crevice contributions which only vary relatively little with load. At 75% load, the contribution from short-circuiting is highest. In addition, we found that in-cylinder post-oxidation of unburned fuel remaining after the main combustion is negligible.

A novel technique for detailed and time-efficient combustion modeling of fumigated dual-fuel internal combustion engines

The present work details a study of the 3D-modeling of dual-fuel engines, with a specific focus on medium speed marine engines. These operate under the fumigated approach, which means that the second fuel, which replaces most of the diesel fuel, is added in the intake duct. This type of engine requires the least amount of modifications to the current medium speed diesel engine and is therefore an ideal retrofit solution to tackle global warming and local air quality issues. In this work, the operation of such an engine has been modeled, with special care for the combustion modeling. Namely, it comprises both auto-ignition of the diesel pilot, and flame propagation in the premixed fuel-air mixture. A tabulated kinetics approach, currently being used to model diesel operation, has been extended to include this flame propagation. Both a Coherent Flame Model (CFM) and a Flame Surface Wrinkling Model (FSWM) have been implemented to handle this premixed combustion mode. Coupling a flame propagation model to the tabulated chemistry should provide a practical way of capturing both the complex dual-fuel combustion process as the chemistry information, while maintaining an acceptable computation time. Additionally, a tabulated laminar flame speed method has also been implemented. Experimental results were obtained on the operation of a medium-speed engine in diesel, natural gas/diesel dual-fuel and methanol/diesel dual-fuel mode, under varying operating loads and speeds. Results have been compared to the ones obtained from the simulations performed in OpenFOAM with the dedicated combustion modeling technique. It was found that while both FSWM and CFM capture some physical trends, they are currently not able of capturing the dual-fuel combustion process in total. Improvements with regards to the ignition and mixing-controlled combustion modeling are necessary, since the current approach is not able of fully capturing the dual-fuel phenomena. This work however provides insight in the complex combustion process and serves as a basis for further developments. It can also be used as an initial engine development tool for fast calculation and optimization of dual-fuel operation.

Cost efficiency of optimizing automatic temperature control parameters in a diesel engine cooling system on a cruising vessel: A case study

With the enforcement of international regulations aimed at reducing environmental pollution, various measures and procedures have been proposed to reduce fuel consumption and increase energy efficiency of ships. Cruising ships that are commonly visiting some of most sensitive and protected sea areas are of particularly interest. This case study outlines measure that can be applied to cruising vessels without installing new or modifications of existing systems and will require somewhat increased attention of chief engineer during voyage. Modern medium speed marine diesel engines, out of the total energy contained in the fuel, utilize slightly less than half while the rest is a thermal loss.Therefore, ships are equipped with waste heat recovery systems utilizing the excessive heat of diesel engine exhaust gases and cooling water. The findings in this paper shows that correct selection of parameters in automated control of cooling water temperature results with a significant improvement of diesel engine thermal efficiency, reduced fuel consumption and improved costs efficiency. The results are applicable for all similar marine or industrial power systems as well.

Research on effects of early intake valve closure (EIVC) miller cycle on combustion and emissions of marine diesel engines at medium and low loads

The Miller cycle with EIVC is applied to a medium-speed marine diesel engine to achieve high-efficiency combustion and low nitrogen oxide (NOx) emissions. The effects of Miller cycle on the state parameters, combustion characteristics, NO emissions, and the spatial distribution of working fluid were analyzed. A one-dimensional (1D) simulation model was established by using the BOOST software. The FIRE software was used to simulate the combustion process and emission characteristics of the diesel engine at medium and low loads. The results show that in the E3 cycle (four kinds of loads, 100%, 75%, 50%, 25%, according to Marine application propeller law), with the proper EIVC, the in-cylinder pressure, temperature and NO emission will be reduced. At the load of 50%, NO emissions were reduced by 17.8%, At 25% load NO emissions were reduced by 14.9%. During the fuel injection, the decrease of in-cylinder temperature causes a longer ignition delay period. When the EIVC is too early, the heat release rate increases sharply, at the same time, the NO generation also increases. Furthermore, it will lead to misfire at low load.

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.

Considerations in analysing elemental carbon from marine engine exhaust using residual, distillate and biofuels

Elemental carbon (EC) concentrations in the exhaust of a medium-speed marine engine was evaluated using thermal-optical analysis (TOA). Particulate matter (PM) samples were collected at 75% and 25% engine loads using residual and distillate fuels with sulphur contents of 2.5%, 0.5% and 0.1%, and a biofuel (30% of bio-component). The EC analysis of PM samples from a marine engine proved to be challenging. For example, transformations of structure of the sampled particles in the inert and the oxygen mode were observed for marine engine exhaust samples. The relationship between constituents present in the samples from the marine engine using different fuels, and phenomena observed in the thermograms are discussed. Temperature protocol selection and sample pre-treatment (extractions and drying) affected the reported EC mass. Modifications in the methodology were suggested to increase the accuracy of the analysis. Repeatability and reproducibility of the EC analysis was studied in the round-robin of three laboratories.

Increasing exhaust temperature to enable after-treatment operation on a two-stage turbo-charged medium speed marine diesel engine

Nitrogen-oxides (NOx) are becoming more and more regulated. In heavy duty, medium speed engines these emission limits are also being reduced steadily: Selective catalytic reduction is a proven technology which allows to reduce NOx emission with very high efficiency. However, operating temperature of the catalytic converter has to be maintained within certain limits as conversion efficiency and ammonia slip are very heavily influenced by temperature. In this work the engine calibration and hardware will be modified to allow for a wide engine operating range with Selective catalytic reduction. The studied engine has 4MW nominal power and runs at 750rpm engine speed, fuel consumption during engine tests becomes quite expensive (±750kg/h) for a measurement campaign. This is why a simulation model was developed and validated. This model was then used to investigate several strategies to control engine out temperature: different types of wastegates, injection variation and valve timing adjustments. Simulation showed that wastegate application had the best tradeoff between fuel consumption and exhaust temperature. Finally, this configuration was built on the engine test bench and results from both measurements and simulation agreed very well.

Comparative performance of a thermal denuder and a catalytic stripper in sampling laboratory and marine exhaust aerosols

The performance of a thermal denuder (thermodenuder—TD) and a fresh catalytic stripper (CS) was assessed by sampling laboratory aerosol, produced by different combinations of sulfuric acid, octacosane, and soot particles, and marine exhaust aerosol produced by a medium-speed marine engine using high sulfur fuels. The intention was to study the efficiency in separating non-volatile particles. No particles could be detected downstream of either device when challenged with neat octacosane particles at high concentration. Both laboratory and marine exhaust aerosol measurements showed that sub-23 nm semi-volatile particles are formed downstream of the thermodenuder when upstream sulfuric acid approached 100 ppbv. Charge measurements revealed that these are formed by re-nucleation rather than incomplete evaporation of upstream aerosol. Sufficient dilution to control upstream sulfates concentration and moderate TD operation temperature (250°C) are both required to eliminate their formation. Use of the CS following an evaporation tube seemed to eliminate the risk for particle re-nucleation, even at a ten-fold higher concentration of semi-volatiles than in case of the TD. Particles detected downstream of the CS due to incomplete evaporation of sulfuric acid and octacosane aerosol, did not exceed 0.01% of upstream concentration. Despite the superior performance of CS in separating non-volatile particles, the TD may still be useful in cases where increased sensitivity over the traditional evaporation tube method is needed and where high sulfur exhaust concentration may fast deplete the catalytic stripper adsorption capacity.

МЕТОД БЕЗГРАДИЕНТНОЙ МИНИМИЗАЦИИ POWELL'64 В ЗАДАЧАХ МОНИТОРИНГА РАБОЧЕГО ПРОЦЕССА СУДОВЫХ ДИЗЕЛЕЙ

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.

INFLUENCE OF THE AIR SUPPLYING CONDITIONS ON THE FUEL--AIR MIXTURE INJECTION CHARACTERISTICS BY THE MARINE MIDDLE SPEED DIESEL ENGINE FUEL SYSTEM

The results of an experimental study of an alternative medium-speed marine diesel engine of fuel injection system operating on fuel-air mixture (FAM) has been analyzed. The influence of air supplying on the working processes in the fuel equipment was investigated. It is noted that an increase in the duration of the air inlet directly affects the amount of air entering the system, which has a significant impact on the parameters of the fuel injection, the timing has the impact on the working process only when overlapping of the air and base system supply phases occurs.

Research and development of electronic speed control strategies for medium-speed marine diesel engines

Modern diesel engine systems rely more and more on electronic control systems. The benefits of such electronic control systems include reduced fuel consumption, limited emissions and enhanced performance. Following the trend, this article aims to derive an appropriate methodology for improving the performance of the speed regulation by upgrading an existing mechanical governing control system to an electronic one for the marine diesel engine. Hardware-in-loop simulations and the diesel engine test-bed experiments are applied to realize a V-type mode study of the speed control strategies for the marine medium-speed diesel engines. First, the algorithm of the strategies and the functions of the electronic control unit are verified through hardware-in-loop test bench which is established using hardware devices and a software tool chain from ETAS GmbH. Additionally, the specific parameters are modified and calibrated finely on the test bed with an online debugging system. Finally, to demonstrate the performances and the generality of the proposed control strategies, the test-bed results of the two types of marine diesel engines are illustrated. The experimental results indicate that a better performance is achieved by replacing the original controller with the proposed controller. And the methodology of the control strategies development is proven to be efficient.

Modelling of the fuel injection of medium speed marine diesel engines

The article presents the stages of fuel injection modeling of the four-stroke marine diesel engines as a set of functional blocks the of the fuel waves flow. The elaborated model includes the values of changing pressures in the combustion chamber and the course of changes of the pressure in spaces of the injection pump, injection pipe and the injector. Linear and local losses, as well as the conditions for the functioning were taken into account in stages of the fuel flow. The influence of different values of the engine load on the pressure course of the in individual spaces of injection apparatus and in the engine cylinder during the working cycle depending on the crank angle of rotation of the crankshaft have been simulated. The mathematical relationships were selected and the structural and experimental data are used, allowing the calculation of the parameters of interest for the simulated process.

СИСТЕМА ОХОЛОДЖЕННЯ НАДДУВНОГО ПОВІТРЯ СУДНОВОГО ДВИГУНА ВНУТРІШНЬОГО ЗГОРЯННЯ ТЕРМОПРЕСОРОМ З УПОРСКУВАННЯМ ПЕРЕГРІТОЇ ВОДИ

The scheme solution by using thermopressor as the part of three-circuit cooling system of the medium-speed marine engine is analyzed. The way to improve of the efficiency of the water spray process in the thermopressor is considered. Using of overheated water injection in the thermopressor of the charge air cooling system makes it possible to increase the relative increase air pressure at the outlet thermopressor to 5...8 %, with a corresponding reduction in the power of the engine turbocharger.

Impact of diesel pilot distribution on the ignition process of a dual fuel medium speed marine engine

Recent emission legislation in the marine sector has emphasized the need to reduce nitrogen oxides (NOx) emissions as well as sulphur emissions. The fulfilment of emission legislation limits with conventional marine diesel oil (MDO) requires complex and expensive aftertreatment systems and in this framework lean burn pilot ignited dual fuel (diesel and natural gas) is revealed as one of the most suitable engine platforms to decrease pollutant formations at its source and therefore to mitigate aftertreatment system requirements. For this reason, an experimental study has been carried out in an 8.8l dual fuel single cylinder Wärtsilä 20DF engine in order to evaluate different diesel equivalence ratio distributions in the combustion chamber and to get a deeper insight into the interaction between the high reactivity (diesel) and the low reactivity (natural gas) fuels during the ignition process. Engine testing has been complemented with diesel spray pattern simulations for a better understanding of local combustion conditions. Results show the importance of local pilot fuel distribution as a way to control combustion phasing and consequently its impact on combustion instability, emissions and knock conditions. Stable combustion with engine-out NOx levels below legislation have been achieved without the need of after-treatment system using appropriate high reactivity fuel (HRF) distribution control.

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.