Simulation of a Two-Stroke Slow Speed Diesel Engine Using a Quasi-Dimensional Model

Poljak

2019

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This paper presents energy analysis of entire marine main propulsion steam turbine and both of its cylinders at three different loads. Marine steam propulsion plant in which main turbine operates is described in detail. Measured data from real exploitation at each required turbine operating point enables calculation of energy losses and efficiencies. Real developed power distribution between both turbine cylinders is not the same at all observed loads. Energy losses and efficiencies of main turbine cylinders and entire main steam turbine increases during the increase in turbine load. An increase in turbine load resulted with in a sharp increase in energy efficiency of HPC (High Pressure Cylinder) from 51.01 % to 74.13 %, while the increase in energy efficiency of LPC (Low Pressure Cylinder) is not as sharp (from 73.88 % to 78.50 %). The change in energy efficiency of the entire main steam turbine during the load increase (from 65.54 % to 79.45 %) is mostly influenced by a change in energy efficiency of HPC. Energy loss and real developed power ratio is reversely proportional to energy efficiencies and losses of both steam turbine cylinders and the entire turbine. Sažetak Ovaj članak prikazuje energijsku analizu čitave glavne propulzijske parne turbine i oba njezina kućišta pri trima različitim opterećenjima. Opisuje se podrobno, brodsko parno propulzijsko postrojenje u kojemu radi glavna turbina. Izmjereni podatci stvarne eksploatacije za svaku zahtijevanu radnu točka turbine omogućavaju izračun energijskih gubitaka i učinkovitosti. Stvaran raspored distribucije snage između oba kućišta turbine nije isti na svim promatranim opterećenjima. Energijski gubici i učinkovitosti turbinskih kućišta i cijele glavne turbine, povećavaju se za vrijeme porasta opterećenja turbine. Povećanje opterećenja turbine rezultira naglim rastom energijske učinkovitosti HPC (High Pressure Cylinder = kućište visokoga tlaka) od 51.01 % do 74.13 % dok povećanje energijske učinkovitosti LPC (Low Pressure Cylinder = kućište niskoga tlaka) nije tako naglo (od 73.88 % do 78.50 %). Promjena energijske učinkovitosti cijele glavne parne turbine, za vrijeme povećanja opterećenja (od 65.54 % do 79.45 %), najviše je pod utjecajem promjene energijske učinkovitosti HPC. Gubitak energije i stvarni omjer razvijene snage obrnuto je proporcionalan energijskim učinkovitostima i gubicima za oba kućišta i cijelu parnu turbinu. KEY WORDS main marine steam turbine marine propulsion plant energy analysis change in load conditions KLJUČNE RIJEČI glavna brodska parna turbina brodsko propulzijsko postrojenje energijska analiza promjena opterećenja

Section: Introduction / Uvodmentioning

confidence: 99%

Energy Analysis of Main Propulsion Steam Turbine from Conventional LNG Carrier at Three Different Loads

Poljak

2019

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“…QD models allow some insight into the formation of pollutants, but lack the dimensionality of 3D simulations. Mrzljak [18] implemented a QD model in order to simulate a large marine engine and obtained a very good agreement with measured data for power, maximum cylinder pressure, and fuel consumption for various load regimes.…”

mentioning

confidence: 77%

2D CFD Simulation of Water Injection Strategies in a Large Marine Engine

Senčić

Blecich

et al. 2019

JMSE

A two-dimensional computational fluid dynamics (2D CFD) simulation of a low-speed two-stroke marine engine simulation was performed in order to investigate the performance of 2D meshes that allow the use of more complex chemical schemes and pollutant formation analysis. Various mesh density simulations were compared with a 3D mesh simulation and with the experimentally obtained cylinder pressure. A heavy fuel model and a soot model were implemented in the software. Finally, the influences of three water injection strategies were simulated and evaluated in order to investigate the capability of the model and the influence of water injection on NOx formation, soot formation, and engine performance. We conclude that the direct water injection strategy reduces NOx emissions without adversely affecting the engine performance or soot emissions. The other two strategies-Intake air humidification and direct injection of fuel-water emulsion-reduced NOx emissions but at the cost of higher soot emissions or reduced engine performance.

“…The quasi-dimensional model presented in this paper is also tested on the large marine two-stroke slow speed diesel engine (Mrzljak et al, 2016b). The comparison of the model and the measurements at engine low-load show that this QD model has maximum relative errors of 2.1%, 4.3% and 2% for brake specific fuel consumption, peak firing pressure and peak compression pressure.…”

Section: Numerical Model Validationmentioning

confidence: 97%

Numerical analysis of the fuel spray packages penetration and gas inflow from quasi-dimensional di diesel engine numerical model

Zb. Veleuč. Rij. (Online)

Žarković

2019

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The paper presents two components of developed quasi-dimensional numerical model: spray package penetration and gas inflow from the zone without combustion into the spray packages. Correction of spray package penetration along the fuel spray radial axis is presented and described numerically. Numerical model simulation is validated in several measured operating points of direct injection diesel engine, after which the simulation results are presented. According to numerical model settings, each fuel spray was divided into packages (control volumes). In the same time interval, the shortest penetration was obtained for spray packages located at the fuel spray edge. Before reaching the break-up time spray package penetration was linear and after reaching the break-up time, package penetration had a curved form. Later injected spray packages quickly reached and surpassed earlier injected spray packages because earlier injected spray packages hit "gas wall" in the engine cylinder and they were "braked" with surrounding gas in comparison to packages injected later. Gas inflow from the zone without combustion into the spray packages is the most intensive for spray packages positioned at the fuel spray edge. The simulation shows that the inflow mass from the zone without combustion increases for spray packages injected later.