IRF: Institutional Repository FHNW
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Neuzugänge
Ignition behavior of marine diesel sprays. Investigation of marine diesel ignition and combustion at engine-like conditions by means of OH* chemiluminescence and soot incandescence
(Japan Society of Mechanical Engineers, 2012) Schmid, Andreas; von Rotz, Beat; Bombach, Rolf; Weisser, German; Herrmann, Kai; Boulouchos, Konstantinos
In this contribution, an initial investigation of the ignition behavior of large two-stroke marine diesel sprays has been performed. At engine-like conditions, the OH radical was traced with an intensified high speed camera and a sophisti-cated optical setup. A series of spectroscopic measurements showed, however, that the soot incandescence strongly con-tributes to the UV signal, superimposing with or even masking the chemiluminescence of the OH radical. As the com-bustion of typical fuels used in large two-stroke engines involves the formation of non-negligible amounts of soot, the signal is almost omnipresent during the oxidation process. A differentiation between the UV-light emitted by the OH radical and the UV-light emitted by soot incandescence is only possible when both signals are measured separately. Therefore, a second high speed camera recorded the light coming from soot incandescence. In addition, it recorded the background illuminated spray plume to make an exact positioning of the OH* signal relative to the spray possible. A comparison of the two images then allowed the differentiation between the two light sources. In a first measurement series, which included a temperature variation, ignition delay, ignition location and flame lift-off have been measured. The results are in accordance with literature, as they show a dramatic decrease in ignition delay towards higher gas temperature. On the other hand the standard deviation increases towards lower gas temperatures. The ignition location and lift-off showed similar behavior: Lower gas temperature corresponds to an increase of the distance between ignition location/lift-off and nozzle orifice along with increased standard deviation. It could be shown that the applied technique works for the investigation of large marine diesel engine combustion systems.
01A - Beitrag in wissenschaftlicher Zeitschrift
Berufsbildung gegen Bezahlung
(SAGW, 2023) Preite, Luca; Leemna, Regula Julia; Makarova, Elena
04A - Beitrag Sammelband
Reference data generation of spray characteristics in relation to large 2-stroke marine diesel engines using a novel spray combustion chamber concept
(2010) Herrmann, Kai; von Rotz, Beat; Weisser, German; Bouchoulous, Konstantinos; Schneider, Bruno
The availability of appropriate reference data for combustion in large 2-stroke marine diesel engines is a prerequisite for the further development of Computation Fluid Dynamics tools. In order to enable the acquisition of such data at relevant physical dimensions (bore) and operational parameters (pressure, temperature), including flow characteristics (swirl) and the low fuel qualities involved, a novel experimental test facility has been realized. The core element is a disk-shaped constant volume spray combustion chamber of diameter 500 mm with peripheral injection into a swirl flow. Thermo- and fluid dynamic conditions at start of injection similar to those in real engines are achieved by feeding the chamber via inclined intake channels with pressurized and heated process gas provided by a pressure vessel/heat regenerating system. The chamber design includes comprehensive possibilities for optical access as well as various injector arrangement options and the injection system is prepared for running on typical marine fuels. Reference data for the fuel spray propagation has been acquired by means of shadow-imaging measurements: This involved the variation of key parameters such as gas pressure and temperature (up to 9 MPa, 930 K), number of injector orifices (1/2/5) and the spray orientation (10 deg counter to 40 deg co-swirl) relative to the gas flow. The spray propagation data collected at conditions representative of the operation of large 2-stroke marine diesel engines contributes to a better understanding of the underlying phenomena and enable the validation of simulation tools at such conditions. The new spray combustion chamber thus fills a clear gap and must be considered a reference setup for those applications.
04B - Beitrag Konferenzschrift
Assessing the performance of spray and combustion simulation tools against reference data obtained in a spray combustion chamber representative of large two-stroke diesel engine combustion systems
(2010) Schulz, Reiner; Herrmann, Kai; von Rotz, Beat; Hensel, Sebastian; Seling, Fernando; Weisser, German; Wright, Yuri Martin; Bolla, Michelle; Boulouchos, Konstantinos
The optimization of the combustion systems of large Marine Diesel engines still relies largely on extensive testing; however, it is more and more supported by computational fluid dynamics (CFD) simulations – in spite of limitations regarding the applicability of the available spray, evaporation, combustion and emissions formation models to those systems. As combustion is particularly sensitive to the fuel vapour distribution, the accurate simulation of spray and evaporation processes is seen as a prerequisite for reliable combustion and emissions formation results.In order to enable the validation of such simulations at conditions relevant to large two stroke engines, a novel experimental setup was realized, consisting of an optically accessible, disk-shaped constant volume chamber of 500 mm diameter with peripheral injection into a swirling flow. In this setup, thermo- and fluid dynamic conditions similar to those applying at start of injection of an engine are obtained by feeding pressurized and heated air or nitrogen to the spray combustion chamber (SCC) via inclined intake ports. The SCC has been used extensively for visualizing spray phenomena by means of shadow imaging techniques, thereby covering a large range of operating conditions, including non-reactive and reactive cases, as well as a variety of configurations, specifically with respect to the injector nozzle. In the present paper, those data are used for the validation of different CFD sub-models for spray and evaporation, based on initial conditions at start of injection, which have been derived on the basis of comprehensive simulations of the filling of the chamber, verified separately through flow measurements. Additionally, since each spray is also affected by the conditions upstream the orifice, the flow inside the injector is simulated in order to identify its effect on the injection boundary conditions, thereby taking into account the geometry of the nozzle tip actually used in the SCC tests, which is determined by means of computer tomography. This investigation hence focuses on the key aspects of spray and evaporation simulation, including different fuel modelling approaches and injector geometry effects. It allows identifying the most suitable models and model combinations, thereby establishing a basis for the simulation of combustion and emissions formation, and thus represents a major step towards the application of CFD for actual combustion system optimization.
04B - Beitrag Konferenzschrift