Low-speed Two-stroke Marine Diesel 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.

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.

Modelling of temporal and spatial evolution of sulphur oxides and sulphuric acid under large, two-stroke marine engine-like conditions using integrated CFD-chemical kinetics

In this work, three-dimensional computational fluid dynamics (CFD) studies of sulphur oxides (SOx) and sulphuric acid (H2SO4) formation processes in a large, low speed two-stroke marine diesel engine are carried out. The current numerical study aims to investigate the conversion of sulphuric dioxide (SO2) to sulphuric trioxide (SO3) and the possibility of H2SO4 condensation which are the prerequisites to better understand the corrosion-induced wear phenomenon. This is achieved with the aid of the implementation of a multicomponent surrogate model, which comprises a skeletal n-heptane mechanism and a reduced sulphur subset mechanism. In the present work, performance of the coupled CFD-chemical kinetic model is evaluated using both qualitative and quantitative methods. The modelling results show that the temporal and spatial evolutions of SOx predicted by the skeletal model are similar to those by the base mechanism. Predictions of the variations of SOx and the associated SO2 to SO3 conversion in response to the change of fuel sulphur content, swirl velocity, start of injection, scavenge pressure and humidity qualitatively agree with numerical and experimental results from the literature. The model is further evaluated using the measured SO2 to SO3 conversion levels in a low load, low scavenge pressure case and a low load, high scavenge pressure case. The absolute values of simulated and measured conversion levels are close, although the former appear to be higher. The current results show that the flame impinges at the cylinder liner near top dead centre. The gas is cooled rapidly by the wall temperature and H2SO4 is produced in the region where the local temperature is less than 600K. Based on the flue gas correlation, the acid dew point temperature is higher than the wall temperature, suggesting that acid condensation may begin early at the top part of the cylinder liner. The predicted distribution corresponds well with the distribution of corroded parts observed in service engines. The model is expected to serve as an important tool to simulate the rates of SO2 absorption into lubricating oil film and H2SO4 condensation in this combustion system.

20809 舶用2ストロークディーゼル機関から排出されるPMの粒径分布(第2報) : 機関負荷率およびシリンダ注油率の影響(一般講演 反応・複雑流れ)

In this paper, the particle size distribution of PM in the exhaust gas from low speed two-stroke marine diesel engine was investigated to know the emission characteristics of the PM. The measurement of particle size distribution was executed by Scanning Mobility Particle Sizer (SMPS) and Low Pressure Impactor (LPI). The effects of the cylinder oil feed rate and the engine load on particle size distribution of PM were examined. Particles of less than 100 nm in diameter decrease with a decrease in cylinder oil feed rate. As the engine load becomes higher, the peak of size distribution curve slightly shifts toward smaller particle size for under 100 nm particle.

20808 舶用2ストロークディーゼル機関から排出されるPMの粒径分布(第1報) : 希釈率の影響(一般講演 反応・複雑流れ)

Particulate matter (PM) exhausted from diesel engines has several serious effects on human health and the environment. Especially, the strong health effects of the fine particles are reported recently. In this paper, the measurement of the particle size distribution was executed with a low speed two-stroke marine diesel engine. The effect of the dilution ratio in the dilution tunnel on particle size distribution was examined using Scanning Mobility Particle Sizer (SMPS) and Low Pressure Impactor (LPI). The results show that particles in the diameter range from 50 to 100 nm decrease with an increase in the dilution ratio.