CIMAC Congress - Schiff & Hafen

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<strong>CIMAC</strong> CONGRESS | BERGEN 2010 separation valve is installed just after exhaust valve, it must be easy to achieve the gas separation. The exhaust gas with mainly combustion gas shall be led into high temperature receiver and the exhaust gas with almost fresh air shall be led into low temperature receiver. The high temperature receiver is connected to turbocharger, and the low temperature receiver is connected to the scavenge receiver through EGS cooler and blower. The gas separation valve will be managed by electronic control units to adjust the valve timings for better total thermal efficiency. As a result of EGS system application, many kinds of advantages can be produced. • Waste Heat Recovery (WHR) rate of exhaust gas energy can be drastically improved by increased gas temperature in high temperature receiver • WHR system can be downsized by the decreased gas flow amount and increased temperature • Turbocharger can be downsized by the decreased gas flow amount • Conventional Selective Catalytic Reduction (SCR) can be placed after gas outlet of turbocharger instead of before turbocharger • SCR can be downsized by the decreased gas flow amount and concentrated density of NOx • Engine performance at part load can be improved by adjusted gas flow amount with the gas separation valve timing Some pre-tests have been carried out on our test engine to clarify the possibility of EGS implementation. Simulations of engine performance have been made after the pre-test to study EGS system from the viewpoints of WHR, SCR application, and so on. This paper begins with the explanation of EGS concept and deals with pre-tests results comparing the calculation results. Furthermore, prospective improvements of WHR and SCR installation are discussed as the investigation results of engine performance calculation and heat dissipation simulation as a whole system. PIV study of the effect of piston motion on the confined swirling flow in the scavenging process in 2-stroke marine diesel engines S. Haider, K. E. Meyer, J. Schramm, Technical University of Denmark (DTU), Denmark, S. Mayer, MAN Diesel & Turbo SE, Denmark The effect of piston motion on the incylinder swirling flow for a low speed, large two-stroke marine diesel engine is studied using the stereoscopic PIV technique. The measurements are conducted at 5 cross sectional planes along the cylinder length and at piston positions covering the air intake ports by 0%, 25%, 50% and 75%. The resulting swirling flow decays downstream the bulk flow direction and variation in Reynolds number has only effect in terms of magnitude. When the piston translates towards the top-deadcentre, it gradually starts closing the intake ports. The tangential velocity profile changes from Rankine/ Burgers vortex to forced vortex and axial velocity profile changes from wake-like to jet-like and then again to wake-like profile.. Design of experiments analysis of the NOx- SFOC trade-off in two-stroke marine engine A. E. Tuner, A. Andreasen, S. Mayer, MAN Diesel & Turbo SE, Denmark Conducting tests on large marine two-stroke engines is very expensive in terms of manpower, and the running costs – especially the fuel oil consumption – are significant. In order to achieve high quality and steady state results, the time required per test is also a major constrain on the extent of the test plan. In order to reduce the number of tests required to map the response surface of a given number of variables, the theory of design of experiments (DOE) is applied in the present study. Further, a strategy of achieving quasi steady state in which tests are conducted fast allowing only little time for engine stabilisation upon changing parameters is utilised in order to bring down the time required per test. In the present study we present results of the mapping of the response surfaces of NOx, SFOC, and maximum cylinder pressure with respect to start of injection, exhaust valve closing, injection pressure, injection nozzle hole size, injection profile characteristics, and turbocharger turbine area. Special emphasis is laid on the SFOC/ NOx trade-off and identifying the means to meet future NOx emissions legislation (IMO Tier II), while minimising the penalty in specific fuel oil consumption. Different scenarios are investigated by means of constrained optimisation mapping the results as function of usually measured performance parameters, such as scavenge pressure, compression pressure, maximum pressure, etc. 13:30 June 16th Room Troldtog (3–8) Environment, Fuel & Combustion – Diesel Engines – Modelling II Combustion chamber design to control particulate matter emission P. Tremuli, A. Skipton Carter, Ricardo UK Ltd., UK This paper outlines the possibility to comply with the exhaust emissions legislation faced by medium speed engine manufacturers, considering mainly the application of primary in-cylinder technologies. The potential for reduced particulate emissions at low NOx levels is the focus. Ricardo’s development of a combustion system for engines in the range of 170 – 230 mm bore assisted by 3D CFD analysis using Ricardo engine focused CFD code VECTIS is described. As well as reducing engine-out particulate matter (PM) emissions, the low soot combustion system should benefit engine first cost, whole life costs and engine and aftertreatment durability and reliability. Computational study of in-cylinder NOx reduction in a large marine diesel engine using water injection strategies C. Chryssakis, A. Frangopoulos, L. Kaiktsis, NTUA, Greece Recently imposed regulations by the International Maritime Organization (IMO) include a 16% reduction in Nitric Oxides (NOx) emissions between 2000 and 2011 for low-speed large marine Diesel engines, and an 80% reduction by 2016 for the Emission Control Areas (ECAs). Current research efforts for reducing NOx in large marine engines consider multiple injection strategies, water addition, Exhaust Gas Recirculation (EGR) and catalytic converters. In the present work, the potential for NOx emissions reduction in a large two-stroke marine diesel engine by means of Direct Water Injection (DWI), as well as intake water addition, is studied using Computational Fluid Dynamics (CFD) simulations. The modeling platform is a modified version of the CFD code KIVA-3V. For a given fuel injection profile, the effect of water mass on NOx emissions is first investigated, and compared to a reference case of zero water mass. The results indicate that Direct Water Injection is substantially more effective than intake water addition. Next, a variation of fuel injection profiles (for both techniques), as well as of water injectors’ locations (for DWI) is performed; the effects on NOx and soot 78 Ship & Offshore | 2010 | No. 3
Monday, 14 June Tuesday, 15 June Thursday, 17 June Wednesday, 16 June emissions, as well as on Specific Fuel Oil Consumption (SFOC) are quantified. For the cases of unmodified fuel injection, representative results indicate that a reduction in NOx of approximately 85% is achieved with DWI, and of 60% with intake water addition, for water mass levels of 50% and 200% of the injected fuel mass, respectively. Under those conditions, SFOC is increased by approximately 4.5% and 2.0%, respectively, accompanied by nonnegligible increase in the emitted soot levels. By systematically varying the locations of the water injectors, as well as fuel injection timing, it has been possible to maintain the same levels of NOx emissions reduction, with milder penalties in SFOC and soot emissions. The present detailed study suggests that: (a) the 2016 NOx emission standards could be met by proper water injection strategies, (b) further improvements in emissions levels and engine performance would be feasible in terms of optimized water and fuel injection, based on rigorous optimization studies. A combined numerical and experimental study on the influence of the injection system on the spray, the combustion and emissions in medium speed diesel engines C. Fink, H. Harndorf, Rostock University, Germany, M. Frobenius, AVL Deutschland GmbH, Germany, R. Pittermann, WTZ Rosslau gGmbH, Germany In cooperation with several partners a project funded by the German government was initiated in order to investigate the emission reduction potential of modern common-rail injectors using different marine fuels. The experimental and numerical study focuses on engine part load and low temperature (Miller-cycle) conditions, as these conditions are mainly causing high smoke and particulate emissions. The first part of the project includes the experimental and numerical analysis of injection sprays in a high pressure/high temperature research chamber at Rostock University. In order to account for nozzle internal effects, a coupled simulation method between the nozzle internal flow and the spray is applied. The CFD simulations have been performed using the CFD Code FIRE, which provides a modern nonlinear cavitation model combined with advanced turbulence modelling techniques to account for transient cavitation effects in the needle seat area and in the nozzle. By means of a special polymer moulding technique, real nozzle geometries were derived and considered in the simulation of the nozzle internal flow pattern. The obtained flow conditions are then used as input data for the spray simulation. Here, besides the droplet primary and secondary break-up and droplet collision models, a new advanced evaporation model considering droplet internal flows has been applied. The developed models have been validated against experimental data obtained in the optically accessible high pressure/ high temperature research chamber at Rostock University. Different optical methods are applied in order to quantify the characteristic spray parameters penetration length, cone angle, droplet size and velocity. Good correlations of the experimental and simulation results are observed, which confirm the applicability of the developed simulation models for the simulation of the mixture formation in the engine. In the second part of the project, the spray and mixture behaviour as well as the combustion and emission formation in a single-cylinder medium speed engine is investigated. The ECMF-3Zcombustion-model has been applied for the simulations together with an advanced NOx-model and a new developed kinetic soot model. The complex combustion and emission generation processes are investigated experimentally at the WTZ Rosslau gGmbH. A single cylinder medium speed research engine is equipped with the same common rail injector as used at Rostock University. Optical measurements of flame temperatures and soot concentration inside the cylinder are done for several variations. Filter smoke numbers (FSN), particulates (mass, composition, size distribution) and gaseous emissions are measured giving insight into emission generation mechanisms. As smoke emissions during low loads are mainly caused by oxygen lack, those conditions were counted for by a reduced charge air pressure of the auxiliary blowers. To investigate parameters for smoke emission reduction, the influence of the rail pressure, the injection timing and multiple injections on the smoke reduction was analysed. Good agreement of calculated and measured incylinder pressure traces as well as pollutant formation trends could be observed for the investigated arameter variations. The combined numerical and experimental study shows the potential of further emission reductions by the use of the flexible common-rail system. The developed coupled simulation method can improve the understanding of the influence of the nozzle flow conditions and the spray characteristics on combustion and emission behaviour. Predictive simulation of combustion and emissions in large diesel engines with multiple fuel injection G. Pirker, B. Losonczi, W. Fimml, A. Wimmer, F. Chmela, LEC - Large Engines Competencce Center, Austria Reliable simulation tools for preoptimization of the engine cycle are necessary in order to minimize the time and cost of development of a new engine and to fulfil future requirements for performance, efficiency and emissions. As the number of adjustable parameters in engine control continues to grow, an ever larger number of variants must be investigated when optimizing the entire system. Zerodimensional simulation processes with simple handling and short calculation times have proven to be advantageous. The shaping of the injection rate through multiple fuel injection has likewise proven to be an effective measure for reducing particulate emissions in large diesel engines, especially when using exhaust gas recirculation. Thus the reliable pre-calculation of combustion using different injection strategies is increasing in importance. A consistent simulation methodology describing the processes in internal combustion engines has been developed at the LEC in recent years. In this article, the continuing development of a combustion model for large diesel engines is presented with a special emphasis on the detailed modeling of the injection spray. An extended spray model succeeds in describing the mixing process for operating points with multiple fuel injection, which is a requirement for the prediction of burn rate and emissions. Exact knowledge of the injection parameters is essential as the basis for the burn rate calculation with multiple fuel injection in particular. To this end, a combined measuring system for determining the rate of injection, spray velocity and the amount of fuel injected has been developed at the LEC. 13:30 June 16th Room Klokkeklang (5–2) Component & Maintenance Technology – Piston Engines – Wear & Monitoring Contact pressure and temperature prediction in a marine piston ring D. Grunditz, H. Pedersen, H.-G. Qvist, S. Grahn, Daros Piston Rings, Sweden A novel simulation method is proposed for predicting temperature field and ring-liner contact pressure for a given top piston ring design and given engine operating conditions. The method employs AVL Excite to predict the blow-by gas flow rate and pressure difference No. 3 | 2010 | Ship & Offshore 79
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