International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

In this paper is presented an exergy analysis of low power steam turbine with one Curtis stage which drives the main feed water pump (MFPT) in the conventional LNG carrier steam propulsion system. It was obtained an insight into the exergy efficiency and the exergy destruction change during the variation in turbine developed power. Measurements of necessary steam operating parameters were performed in seven different turbine operating points. Increase in turbine developed power from 50 kW up to maximum power of 570 kW causes a continuous increase in turbine exergy efficiency and highest exergy efficiency was obtained at the maximum turbine power. Turbine exergy destruction is influenced by steam operating parameters, steam mass flow and turbine current power. MFPT is balanced as the most of the other steam system components – maximum exergy efficiency will be obtained at the highest turbine (steam propulsion system) load on which can be expected the majority of LNG carrier operation.

Four-stroke air cooled, direct injection diesel engine Torpedo BT4L912 during rotational speed variation was investigated in this paper. By using the measurement results obtained at engine brake was calculated several main operating parameters in each engine rotational speed. Rotational speed was varied from 1000 rpm to 2300 rpm. Calculated engine operating parameters are engine torque, effective power, engine brake mean effective pressure, specific effective fuel consumption and volume fuel consumption per engine process. The highest obtained engine torque amounts 338.8 Nm and the highest engine effective power amounts 71.76 kW. Specific effective fuel consumption has the lowest value of 197.42 g/kWh at engine rotational speed of 1800 rpm. Regarding several calculated engine operating parameters, optimal operating point of the analyzed engine is at 1800 rpm.

A change in essential operating parameters of a high speed direct injection turbocharged diesel engine MAN D0826 LOH15 during the injected fuel mass flow variation was presented. Based on two measurement sets, performed with standard diesel fuel, several operating parameters were calculated: engine torque, effective power, excess air ratio, specific effective fuel consumption and heat released per engine process. All of the calculated parameters are presented for a wide engine operating range. Along with calculated, several important parameters were measured, in addition to those presented in measurement sets. Additional measured parameters were lubrication oil temperature and exhaust gas temperature before and after the turbocharger turbine. Those calculated and measured parameters allow deep insight not just into the engine process, but also in the process of turbocharging, which is very important in the analyzed diesel engine operation.

During the engine experimental investigation usually was obtained engine effective power and rotational speed. In order to obtain engine mechanical efficiency and engine indicated power from experimental data, must be used equation for calculation of engine mean pressure of mechanical losses along with its proper coefficients. This equation gives correct values if engine mechanical efficiency and engine indicated power was obtained in the range ±1.5%, when compared with experimentally obtained ones. For marine slow speed twostroke diesel engine 6S50MC MAN B&W was analyzed this equation along with its coefficients during the whole range of engine loads. The mean pressure of mechanical losses equation, when obtained coefficients was applied, gives a percentage difference in the range ±0.79% for the engine mechanical efficiency and percentage difference in the range ±0.85% for the engine indicated power when compared with experimentally obtained values. For the higher engine loads presented equation is even more accurate and precise.

Turbo-generator (TG) steam turbine energy efficiency and energy power losses in a wide range of turbine loads were presented in this analysis. For TG steam turbine was investigated influence of steam specific entropy increment from the real (polytropic) steam expansion on energy power losses and energy efficiency. TG turbine energy power losses, during the all observed loads, were in the range from 646.1 kW to 685.5 kW. The most influenced parameter which defines change in TG turbine energy power losses is steam mass flow change, while for small steam mass flow changes, influence of steam specific entropy increment on steam turbine energy power losses is the most influential. Steam specific entropy incremental change can be used to estimate the change of TG steam turbine energy efficiency. Increase in steam specific entropy increment resulted with a decrease in TG turbine energy efficiency and vice versa. Analyzed steam turbine energy efficiency ranges from 53.84 % to 60.12 %, what is an expected range for low power steam turbines.

This paper presents numerical analysis of efficiencies and non-measured operating parameters for the marine two-stroke slow speed turbocharged diesel engine 6S50MC MAN B&W with direct fuel injection. Numerical analysis was based on a measurement set performed at different engine loads. Calculated efficiencies were mechanical, indicated and effective efficiency, while the calculated important operating parameters were power of engine mechanical losses, mean effective pressure, effective engine torque and specific effective fuel consumption. Engine load was presented in percentage of maximum continuous rating (MCR). The highest engine mechanical efficiency of 94.52 % was obtained at the highest engine load, while the highest engine effective efficiency of 49.34 % was obtained at the engine load 75 % of MCR. Available engine effective torque was from 267380 Nm on the lowest up to 643594 Nm on the highest engine load, while effective fuel consumption was between 171.18 g/kWh and 186.83 g/kWh.

Energy and exergy analysis of sea water pump which is used for the main condenser cooling at lower steam propulsion system loads on conventional LNG carrier is presented in this paper. By using the measured variables from the exploitation, it is presented different influences of pump used power on cumulative energy and exergy power inputs. Energy and exergy pump power losses are reverse proportional, while pump energy and exergy efficiencies are directly proportional to increase in pump load. The highest obtained pump energy efficiency amounts 59.61 %, while the highest obtained pump exergy efficiency amounts 60.25 %. From the viewpoint of efficiencies and power losses, it will be optimal that analyzed pump operates at the highest possible loads.

Paper presents an exhaust gas emission investigation for a high speed turbocharged direct injection diesel engine MAN D0826 LOH15 during the fuel and air mass flow variation. Emission analysis is based on a two measurement sets at two different engine rotational speeds (1500 rpm and 2400 rpm). The analyzed diesel engine operates with a standard diesel fuel. Measured emissions were nitrogen oxides (NO_x), unburned hydrocarbons (HC) and soot emissions. Calculated emissions were carbon dioxide (CO₂) emissions by using equations from the literature. For the observed diesel engine, much higher NO_x and HC emissions were obtained at the lower engine rotational speed. Soot emission of the analyzed engine, in general, does not have to depend on engine rotational speed. Calculated CO₂ emissions depend primarily on the fuel mass flow and the carbon mass fraction in used fuel.

Exergy flow motion insight and analysis of plant requirements for a typical conventional LNG carrier with Rankine regenerative feed water heating steam cycle is given in this paper to clarify and distinguish auxiliary flow streams from the useful ones. Auxiliary flow supports the plant operation, but reduces exergy efficiency by certain amounts. Main boilers exergy flow streams are divided into two major groups: superheated and de-superheated flow stream consumers. A plant run test was carried out by varying main shaft revolutions to collect required thermodynamic data at various plant locations. In the presented marine steam plant is explained exergy flow streams for considering components and flow streams ratios of particular plant components. It is detected and explained the points of excessive auxiliary stream flows consumption and recommendations for possible reduction in saving auxiliary power or steam consumption are given.

Distribution of volumes and their change in the diesel engine cylinder is an essential parameter of each numerical model. Quasidimensional numerical model divide space inside the engine cylinder into two main areas: fuel spray packages and a large surrounding area without combustion, which is used for air distribution into the fuel spray packages. This paper analyzes the four-stroke diesel engine for thelight truck drive in several operating modes. Numerical model is validated by using laboratory measurements. In a selected engine operating mode are presented the results of a numerical model for the observed volumes inside the engine cylinder. The observed volume change provides insight into the details of the air-fuel mixing process and fuel evaporation. Described changes are the basis for the calculation of heat-release and pressure changes in the cylinder. The developed numerical model provides insight into the details of the process inside the engine cylinder which cannot be measured with standard measuring equipment.

For the analyzed LNG carrier with Rankine regenerative feed water cycle, energy analysis is presented. The intention was to determine auxiliary flow streams from the useful ones. Auxiliary energy flow supports plant operation on the one side, but reduces overall efficiency on the other. Steam generators energy streams are divided into two major groups, for the main and auxiliary stream consumers. The steam system test was performed by varying main propulsion shaft revolutions. The required thermodynamic data are collected at various steam system locations. For considered plant energy flow streams components are explained and analyzed. In this paper the recommendations for possible energy savings for the mentioned propulsion plant are proposed.