CIMAC Congress - Schiff & Hafen

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<strong>CIMAC</strong> CONGRESS | BERGEN 2010 are tested combined with both high and low engine loads. The same setup with the highest rail pressure is used for all the run loads. The results show that there is a clear dependency between the injection parameters and the engine performance. An optimization may be possible but the overall view of all the main engine outcomes has to be taken into account. Predictive simulation and experimental validation of phenomenological combustion and pollutant models for medium-speed common rail diesel engines at varying inlet conditions P. Kyrtatos, P. Obrecht, K. Boulouchos, ETH Zürich, Switzerland, K. Hoyer, Paul Scherrer Institut, Switzerland As internal combustion engines are becoming ever more complex, there is increasing need for engine parameter optimization through simulation, to avoid numerous timely and costly test-bed measurements. When performing simulations for engine performance and emission optimization, the capability of the combustion model used to accurately predict NOx emission formation as well as heat release rates at varying engine conditions becomes increasingly important. Considering the trade-off between computational cost and accuracy of predictions of diesel engine combustion and pollutant models, phenomenological models have a clear advantage compared to their CFD and simple mathematical approximation alternatives. The detailed phenomenological model used in this study is able to capture changes in fuel injection system and charge-air thermal and chemical properties for direct injection diesel motors, while being computationally efficient. This paper aims to show the ability of these models to predict diesel combustion and emission formation during significantly varying inlet charge and injection conditions, in common rail medium-speed diesel engines. Initially the phenomenological models are calibrated using measurement data from a production common rail medium-speed Wärtsilä 6L20CR diesel engine, employing a state-of-the-art turbocharging system. The model calibration includes data from experiments where injection timing and pressure as well as engine load were varied, to determine their influence on combustion and NOx emissions. The models are then used to predict the heat release rate and NOx formation when the inlet valve timing is changed to earlier Miller timing and the charge air pressure is raised using twostage turbocharging. Additionally, the models are embedded in a 1-D simulation model of the engine to predict the resulting engine performance. The simulation results are compared with experimental results obtained from the test engine with matching hardware changes, giving an indication of the models’ ability to capture the most important combustion and emission formation characteristics. Results from the study show very good performance of the combustion and emission models, when used to perform operating map-wide simulations with varying fuel injection conditions. When the models are used to predict heat release rate in the two-stage turbocharged engine with Miller timing, the combustion rate is predicted well, with small discrepancies in ignition delay calculation. The emission model correctly forecasts the reduction in NOx emissions as a result of the advanced Miller valve timing, but underestimates the true level of NOx produced. Overall, the combustion and emission models show good performance, and their short calculation time allows them to be used for multi-variable engine optimization within the calibration ranges. With improvements in the ignition delay and NOx calculation, the models can additionally be used for preliminary engine concept design studies and turbocharger matching through simulation. Emission reduction potential of 3000 bar common rail injection and development trends S. Pflaum, J. Wloka, G. Wachtmeister, Technical University of Munich, Germany Due to the introduction of new emission limits, engine developers are forced to optimize both, combustion process and peripheral equipment of diesel engines. For this purpose peripherical systems like the cooling system, the exhaust-gas-recirculationsystem (EGR) and the injection system play a major role. Beside cooling- and EGRsystem highly affecting the generation of nitrogen oxide (NOx) emissions, the soot production is primarily influenced by the injection system. To investigate and develop new combustion processes the Chair of Internal Combustion Engines (LVK) at the Technische Universitaet Muenchen (TUM) developed a novel singlecylinder-research-engine, equipped with a special EGR system and a 3000 bar common rail system. This common rail system based on a standard 1800 bar system had to be adapted and redeveloped for the extremely high injection pressures. The LVK-Research-Engine itself was build for combustion pressures up to 300 bar, which is high above series. The first engine tests with the new 3000 bar injection system showed a great correlation between the injection pressure and the emission. As the extremely high injection pressures in combination with standard injector nozzles (designed for 1800 bar) did not yet produce satisfying emission results, the LVK started to adapt and design new nozzles for this high injection pressures. The development process of the new highpressure-nozzles is based on Computional Fluid Dynamic (CFD) calculations, which show the diesel flow in the injector nozzle holes. After adapting the calculations to the new high-pressure range, the influence of the different geometry parameters, like nozzle-hole number, diameter, conicity and degree of hydro erosive (HE)-rounding of the nozzle holes was studied. With consideration of the needs of a low-emission combustion process, the new, adapted nozzles for high pressures were designed by CFD and manufactured by drilling and HErounding. The high-pressure-nozzles were mounted in the LVK- Research-Engine for further investigations. The emission behaviour of the new nozzles was tested and validated in the research engine. With the new high-pressure-nozzles remarkable good emissionresults could be achieved. The 3000 bar common rail system with the new CFD-optimized nozzles showes big potential to comply with EURO VI in a distinctive area of the engine map. Beside the described development process the paper will discuss engine development trends concerning also costs, lifetime and potentials, like reduction of emission and fuel consumption by applying new, adapted highpressure-injection-systems (up to 3000 bar and above). In addition some future visions will be presented. NOx emission reduction by use of N 2 diluted charge air O. Melhus, I. J. Garasen, B. Haukebo, K. K. Langnes, Ecoxy AS, Norway, D. J. Stookey, Compact Membrane Systems, Inc., USA, J. E. Hustad, Norwegian University of Science and Technology (NTNU) In the years from 2004 to 2009 Ecoxy has tested three different ways to dilute the charge air for NOx reducing purposes. EGR is a wellknown measure to reduce NOx from diesel engines and has been extensively used for automotive diesel engines for a number of years. For marine diesel engines, which run on totally different types of 52 Ship & Offshore | 2010 | No. 3
Monday, 14 June Wednesday, 16 June Thursday, 17 June Tuesday, 15 June fuel, EGR may have draw-backs leading to a reluctant attitude among engine makers and users to this technology. The market for NOx reducing solutions for marine diesel engines in Norway was opened by the business sectors NOx fund established in May 2008. The cooperation between the pollution authorities and the industries established by this fund has been a big success for technology development and introduction of NOx reducing technologies in to the shipping market. The relation between O 2 content in the charge air and NOx emission from the engine is well known. A significant reduction of NOx emission will be obtained by using air separating membranes to reducing the O 2 content of the charge air. The O 2 lean charge air thus produced is always clean without particulate matter and has ambient temperature. The paper will describe the three different solutions Ecoxy has tested. All systems use Nitrogen Enriched Air (NEA) producing membranes, but operate quite differently: 1. NEA membrane system moderately pressurized by the Turbo Charger (TC) of the engine (
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