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Manasra S.,Bayreuth Engine Research Center | Brueggemann D.,Bayreuth Engine Research Center
SAE Technical Papers | Year: 2012

This work capitalizes on the investigation of the effect of split injection on the combustion and in-cylinder soot formation performance of low Compression Ratio GTL-fueled DI diesel engine. An optically-accessed Rapid Compression Machine was deployed allowing the application of optical diagnostics. A shadowgraph imaging was used to analyze spray development and detect ignition zones while imaging of soot incandescence was used to determine the temporal and spatial development of soot. In addition the rate of heat release was calculated for the analysis of the combustion characteristics. It has been found that split injection shortens sprays length while increases their penetration velocity. It alters the combustion from fully premixed to two-mode, premixed and non-premixed. Soot with split injection was, therefore, significantly larger while combustion noise was reduced by factor of 4. Surprisingly, split injection has no effect on the time at which cylinder pressure peaks and the time between first and second injection was found to have no influence on the ignition delay of the second injection as a result varying pilot injection timing with split injection in the combination of low CR and GTL fuel requires no combustion phasing. Split injection did, however, altered the air-mixing quality. A quadratic relation governed this time to soot formation which was found to be inversely proportional to Lift-Off-Length. Interestingly, close split could utilize cooling effect which extended premixed combustion mode yielding lowest soot level, highest rate of heat release and combustion noise two times larger than far split. Copyright © 2012 SAE International. Source


Manasra S.,Bayreuth Engine Research Center | Brueggemann D.,Bayreuth Engine Research Center
SAE Technical Papers | Year: 2011

This work capitalizes on the investigation of the effect of injection pressure and timing on the in-cylinder soot formation performance of low CR GTL-fueled DI diesel engine. An optically-accessed Rapid Compression Machine capable of simulating compression and expansion strokes of diesel engine was deployed allowing the application of optical diagnostics. For the detection of flame zones aiming mainly at determining the Lift-Off-Length, imaging of flame self-luminescence technique was used, while for the assessment of in-cylinder soot formation the photodiode-based non-imaging soot incandescence acquisition optical technique has been applied. Through in-cylinder installed pressure transducer and piston position sensor, the rate of heat release was calculated for the analysis of the combustion development. It was found that soot formation rate and peak decrease with increasing injection pressure. The former decreases, however, non-linearly, while the later decreases linearly. Such linear relation is attributed to the linear dependency of Lift- Off-Length on injection pressure. Start of soot appearance seems to be independent of injection pressure probably due to stable ignition of GTL fuel under low Compression ratio conditions. The more injection timing is retarded, the later soot inception is and the higher the decrease in its formation. Thus, by retarding injection timing, the portion of sootless combustion increases. This suggests that for the case of GTL fuel, the combination of low CR, sufficiently high injection pressure and late injection, the combustion mode of Highly Premixed Late Injection or HCCI-like combustion are quite attainable. It seems that under the operating conditions deployed in this work, late injection or retarded injection timing strengthens the effect of cylinder charge cooling brought about by heat lost from the cylinder charge to fuel evaporation which in return lowers local temperatures decreasing as a result the propensity for soot formation. It seems that by retarding injection timing, the portion of heat released towards the expansion stroke increases and combined with higher mixing energy due to flow induced by piston motion, soot oxidation rate apparently increases yielding overall lower soot concentration. Copyright © 2011 SAE International. Source


Smallbone A.,Cmcl Innovations | Bhave A.,Cmcl Innovations | Morgan N.,Royal Dutch Shell | Muhlbauer W.,Bayreuth Engine Research Center | And 2 more authors.
SAE Technical Papers | Year: 2013

In recent years, there has been rapid progress in characterizing the detailed chemical kinetics associated with the oxidation of liquid hydrocarbons and their blends. However adding these fuel models to the industrial engineer's toolkit has proven a major challenge due to issues associated with high CPU cost and the poor suitability of many of the most promising and well known fuel models to IC engine applications. This paper demonstrates the state-of-the-art in the analysis and modelling of current and future transportation fuels or fuel blends for internal combustion engine applications. First-of-all, a benchmarking of eleven representative fuel models (39 to 1034 species in size) is carried out at engine/engine-like operating conditions by adopting the standard Research Octane and Cetane Number test data for comparison. Next, methods to construct a fuel model for a commercial fuel are outlined using a simple, yet robust surrogate mapping technique. Finally, this method is used together with an extensively validated IC engine simulator (based on PDF-based methods - characterizing all key engine sub-processes fuel injection, turbulence, heat transfer etc.), to analyze the performance of multiple fuels and fuel blends (six commercial gasoline and diesel fuels and two standard bio-diesel/diesel blends) in two CIDI engines. Copyright © 2013 SAE International and Copyright © 2013 KSAE. Source


Moos R.,Bayreuth Engine Research Center | Beulertz G.,Bayreuth Engine Research Center | Reiss S.,Bayreuth Engine Research Center | Hagen G.,Bayreuth Engine Research Center | And 3 more authors.
Topics in Catalysis | Year: 2013

The oxygen loading degree in TWCs, the amount of stored ammonia in SCR catalysts, the NOx loading degree in LNTs, or the soot loading of DPFs play a key role in automotive exhaust gas aftertreatment. Today's methods determine the catalyst state indirectly. They utilize gas sensors installed up- or downstream of the catalysts and the catalyst state is inferred from the sensor signals. This overview reports on the status of an alternative approach based on the interaction of electromagnetic microwaves with the catalyst material. Since the catalyst state is strongly correlated with the electrical properties of the catalyst material itself, this concept shows a great potential. © 2013 Springer Science+Business Media New York. Source


Beulertz G.,Bayreuth Engine Research Center | Beulertz G.,Umicore AG | Fritsch M.,Bayreuth Engine Research Center | Fritsch M.,Umicore AG | And 6 more authors.
Topics in Catalysis | Year: 2013

Three-way catalyst-based automotive exhaust gas aftertreatment is of high importance to meet today's emission standards. To determine in situ the oxygen loading state of three-way catalysts, a microwave cavity perturbation method is used. In this study, it is investigated whether this measurement setup that had originally been described for full-sized catalysts can be transferred to a lab test bench using cores of 1″ diameter. The initial tests were successful and a high correlation between the oxygen loading degree dependent resonance frequency and the conversion was found. As an application example of the new in situ characterization technique, the steady state degree of oxidation of a three way catalyst was measured as a function of the exhaust stoichiometry. The experimental results are compared with the prediction of a recently published improved kinetic model that takes into account the oxidation of reduced ceria by H2O and CO2. It is shown that the experimental observations agree very well with this improved model. This result provides evidence that under typical operating conditions, the degree of oxidation of the three way catalyst is controlled by equilibrium effects. © 2013 Springer Science+Business Media New York. Source

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