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Methods for Characterization of the Diesel Combustion and Emission Formation Processes
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). (Förbränningsmotorteknik)
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis various aspects of the diesel engine fuel injection, combustion and emission formation processes have been evaluated. Several types of evaluation tools and methods have been applied. Fuel spray momentum was used to characterize injection rate and hole-to-hole variations in fuel injectors. Using both instantaneous fuel impulse rates and instantaneous mass flow measurements, spray velocity and nozzle flow parameters were evaluated. Several other hole-to-hole resolved injector characterization methods were used to characterize a set of fuel injectors subjected to long term testing. Fuel injector nozzle hole-to-hole variations were found to have a large influence on engine efficiency and emissions. The degree of hole-to-hole variations for an injector has been shown to correlate well with the performance deterioration of that injector. The formation and atomization of fuel sprays, ignition onset and the development of diffusion flames were studied using an optical engine. Flame temperature evaluations have been made using two different methods. NO-formation depends strongly on flame temperature. By applying a NO-formation evaluation method based on both heat release rate and flame and gas temperature it was possible to achieve a reasonable degree of correlation with measured exhaust emissions for very varying operating conditions. The prediction capability of the NO-formation evaluation method was utilized to evaluate spatially and temporally resolved NO-formation from flame temperature distributions. This made it possible to pinpoint areas with a high degree of NO-formation. It was found that small hot zones in the flames can be responsible for a large part of the total amount of NO that is produced, especially in combustion cases where no EGR is used to lower the flame temperature. By applying optical diagnostics methods the combustion and emission formation phenomena encountered during production engine transients were evaluated. The transient strategy of the engine involved reducing the EGR-rate to zero during the initial parts of the transient. Increased general flame temperature and the occurrence of small hot zones were found to explain the increase in NO-emissions during these transients.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , 111 p.
Series
Trita-MMK, ISSN 1400-1179 ; 2011:10
Keyword [en]
diesel engine emissions
National Category
Vehicle Engineering
Research subject
SRA - Energy
Identifiers
URN: urn:nbn:se:kth:diva-34140ISBN: 978-91-7501-037-3 (print)OAI: oai:DiVA.org:kth-34140DiVA: diva2:419293
Public defence
2011-06-08, Sal F3, Lindstedtsvägen 26, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
StandUp
Note
QC 20110530Available from: 2011-05-30 Created: 2011-05-26 Last updated: 2011-09-13Bibliographically approved
List of papers
1. Development of a Fuel Spray Impulse Measurement Device and Correlation with Time Resolved Mass Flow
Open this publication in new window or tab >>Development of a Fuel Spray Impulse Measurement Device and Correlation with Time Resolved Mass Flow
2009 (English)In:  SAE Technical Paper 2009-01-1880, SAE International , 2009Conference paper, Published paper (Refereed)
Abstract [en]

The fuel injection process plays an important role in the combustion and emission formation processes of the DI diesel engine. One important fuel spray characteristic is the spray impulse. The most commonly used method to measure fuel spray impulse is the impingement method where the fuel spray impinges perpendicularly on the surface of a force transducer. This work deals with the theoretical background of such measurements as well as with developing and testing some different impulse measurement setups. The measured impulse is compared to measurements of the instantaneous mass flow and theoretical flow calculations. When measuring the impulse by impingement on the transducer membrane a fuel temperature related measurement error was encountered. This problem was solved by gluing a strike plate to the transducer membrane. The plate shielded the membrane from direct contact with the fuel. Initially plates made out of aluminum were used, they were however found to be sensitive to erosion. After a number of injections a small pit was formed and this led to an overestimation of the impulse as the fuel more effectively was reflected back towards the direction where it came from. It is crucial for the accuracy of the method that the spent fuel exits the plate perpendicularly, if some of the fuel bounces back towards the direction where it comes from the spray impulse is overestimated. With a flat strike plate it is difficult to be sure that all the spent fuel exits the plate perpendicularly. Therefore a plate with a rotationally symmetrical curvature which allows a gradual and thus more controlled direction change was manufactured and evaluated. When the injection rate of an injector is characterized using a conventional rate tube a number of problems are caused by pressure fluctuations in the fuel volume inside the rate tube. The measurements are disturbed by superimposed fluctuations which are especially problematic when small post injections are to be evaluated. The post injection rate can be disturbed by fluctuations introduced by the main injection, such fluctuations does not occur with impulse measurements. The new impulse measurement device produces measurements with high precision in both rate shape and absolute value. Because of this it is well suited for injection rate evaluation and when a high precision value of fuel spray impulse is required, for instance when calculating nozzle flow loss factors. Flow calculations based on the instantaneous mass flow and the fuel spray impulse are made.

Place, publisher, year, edition, pages
SAE International, 2009
Series
SAE Technical Paper Series, ISSN 0148-7191 ; 2009-01-1880
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-25552 (URN)10.4271/2009-01-1880 (DOI)2-s2.0-84877490425 (Scopus ID)
Conference
SAE World Congress 2009, Powertrains, Fuels and Lubricants Meeting. Florence, Italy 2009-06-15
Note
QC 20101027. Tidigare titel: "“Development and Testing of Some Variants of a Fuel Spray Momentum Measurement Device".Available from: 2010-10-27 Created: 2010-10-27 Last updated: 2011-05-30Bibliographically approved
2. A Study of Hole Properties in Diesel Fuel Injection Nozzles and its Influence on Smoke Emissions
Open this publication in new window or tab >>A Study of Hole Properties in Diesel Fuel Injection Nozzles and its Influence on Smoke Emissions
2008 (English)In: Proceedings Conference on Thermo- and Fluid Dynamic Processes in Diesel Engines, 2008Conference paper, Published paper (Refereed)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-25553 (URN)978-84-8363-313-7 (ISBN)
Conference
Thiesel 2008 Conference on Thermo- and Dynamic Processes in Diesel Engines,Conferences & symposia, Valencia, Spain
Note
QC 20101027Available from: 2010-10-27 Created: 2010-10-27 Last updated: 2011-05-30Bibliographically approved
3. A study of in-cylinder fuel spray formation and its influence on exhaust emissions using an optical diesel engine
Open this publication in new window or tab >>A study of in-cylinder fuel spray formation and its influence on exhaust emissions using an optical diesel engine
2010 (English)In: SAE Technical Papers, 2010, no 01-1498Conference paper, Published paper (Refereed)
Abstract [en]

Increasingly stringent emission legislation as well as increased demand on fuel efficiency calls for further research and development in the diesel engine field. Spray formation, evaporation and ignition delay are important factors that influence the combustion and emission formation processes in a diesel engine. Increased understanding of the mixture formation process is valuable in the development of low emission, high efficiency diesel engines. In this paper spray formation and ignition under real engine conditions have been studied in an optical engine capable of running close to full load for a real HD diesel engine. Powerful external lights were used to provide the required light intensity for high speed camera images in the combustion chamber prior to ignition. A specially developed software was used for spray edge detection and tracking. The software provides crank angle resolved spray penetration data. The images also provide data of ignition delay, ignition location and premixed flame propagation. The evaluation was made for an array of engine operation points with variations in fuel rail pressure, injection timing, boost pressure and charge air temperature. The influence of using pilot injections has also been investigated. This set of experiments makes it possible to analyze the impact of the various engine parameters on the spray formation and ignition processes. Some of the results are compared with the exhaust emission measurements in order to provide an insight into how the emission formation process is influenced by the spray formation and ignition processes.

Series
SAE Technical Papers, ISSN 0148-7191
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-34254 (URN)10.4271/2010-01-1498 (DOI)2-s2.0-84877187746 (Scopus ID)
Conference
International Powertrains, Fuels and Lubricants Meeting; Rio De Janeiro; Brazil; 5 May 2010 through 5 May 2010
Note

QC 20110530

Available from: 2011-05-30 Created: 2011-05-30 Last updated: 2014-08-19Bibliographically approved
4. In-Flame Evaluation of Emission Formation in Optical and Metal Engine Using High Speed Camera and Endoscope
Open this publication in new window or tab >>In-Flame Evaluation of Emission Formation in Optical and Metal Engine Using High Speed Camera and Endoscope
2010 (English)In: THIESEL 2010, 2010Conference paper, Published paper (Refereed)
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-34256 (URN)
Conference
Conference on Thermo and Fluid DYnamics Processes in Diesel Engines
Note
QC 20110530Available from: 2011-05-30 Created: 2011-05-30 Last updated: 2011-05-30Bibliographically approved
5. A study of combustion and emission formation characteristics during production engine transients using optical diagnostics
Open this publication in new window or tab >>A study of combustion and emission formation characteristics during production engine transients using optical diagnostics
2011 (English)In: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, Vol. 225, no D9, 1290-1303 p.Article in journal (Refereed) Published
Abstract [en]

In order to identify some of the special combustion and emission formation phenomena that occur in a turbocharged heavy-duty diesel engine during transient operation, the transient strategy of a production engine has been characterized at four different engine speeds. From each transient some points have been selected for further investigation by recreating these load points as steady-state points in a single-cylinder engine. This allows the emissions to be measured with a high degree of accuracy. An endoscope which makes it possible to evaluate flame temperatures was used in both engines. An empirically derived method of calculating nitric oxide (NO) formation from a combination of measured flame temperature, calculated gas temperature, and heat release rate has been developed and applied. This provides an increased understanding of combustion and emission formation phenomena during transient operation. An optical engine was also used to provide a full combustion chamber view for some of the operating points, and a specially developed software was used to calculate temperature distributions based on high-speed camera colour information. The NO formation formula was applied on these images, which resulted in spatially resolved NO formation distributions.

Keyword
diesel engine transients, NO formation, optical diagnostics, two-colour method
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-39535 (URN)10.1177/0954407011407143 (DOI)000294265300013 ()2-s2.0-80054987713 (Scopus ID)
Note
QC 20110913Available from: 2011-09-13 Created: 2011-09-12 Last updated: 2011-09-13Bibliographically approved

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