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Analysis of EGR/Air Mixing by 1-D Simulation, 3-D Simulation and Experiments
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. (CCGEx)
Lund University.
Lund University.
KTH, School of Engineering Sciences (SCI), Mechanics. (CCGEx)
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(English)Article in journal (Other academic) Submitted
Abstract [en]

The use of EGR for NOX reduction is today a standard technology for diesel engines. The mixing of air and EGR is an important issue, especially for high-pressure EGR systems. Anuneven distribution of EGR between the cylinders can lead tohigher overall engine emissions when some cylinders producemore soot, others more NOX than they would with a perfectlyeven distribution.It is therefore important to understand the processes thatcontrol the mixing between air and EGR. The mixing isinfluenced by both the geometry of the mixing area and thepulsating nature of the flow.The aim of this work is to point out the high importance of thepulses present in the EGR-flow. By simulation in 1-D and 3-Das well as by a fast measurement method, it is shown that theEGR is transported in the air flow in packets. This implies thatthe timing between intake valve opening and the positioning ofthe EGR packets has a high influence of the distribution ofEGR between the cylinders.The ability of 1-D and 3-D simulation to predict the behavior isevaluated. It is shown how standard 1-D simulations fail topredict the pulsation effects. Furthermore, it is shown how 1-Dmodels can be modified to give results reasonably close to the3-D simulation results.

Keyword [en]
EGR, mixing, pulsating flow
National Category
Vehicle Engineering
URN: urn:nbn:se:kth:diva-140848OAI: diva2:692861

QS 2014

Available from: 2014-02-02 Created: 2014-02-02 Last updated: 2014-02-03Bibliographically approved
In thesis
1. Efficiency and Mixing Analysis of EGR-Systems for Diesel Engines
Open this publication in new window or tab >>Efficiency and Mixing Analysis of EGR-Systems for Diesel Engines
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The reduction of fuel consumption and the reduction of toxic emissions are the main goals of research and development in the area of internal combustion engines. The use of exhaust gas recirculation (EGR) to come further in that direction is today an established method for diesel engines. EGR reduces the emissions of nitrogen oxides with a low penalty in fuel consumption.

The increasingly hard regulations on emissions put high pressure on the manufacturers to improve these systems. The present work aims at increasing the knowledge in the area of EGR. Two of the main challenges when applying EGR are addressed, efficiency and mixing.

The efficiency of the EGR-system is analyzed, focusing on keeping the fuel penalty low for a given EGR-rate. Different layouts of the EGR system are studied and compared regarding their stationary and transient properties. Exergy analysis is used to show the potential for improvement in different system components. In the same time, exergy analysis as a tool is introduced and compared to energy analysis of a system. The usefulness of exergy analysis of the entire gas exchange is shown by the example of a heavy-duty diesel engine.

The problem of EGR and air mixing is approached by a detailed study of the mixing process in a heavy-duty diesel engine. Different methods for the measurement of EGR distribution are presented and compared. Additionally, the possibility to predict the mixing effects by 1-D and 3-D simulation is assessed. It is shown that the mixing between air and EGR is highly dependent on the pulsating nature of the flow. The EGR is shown to be transported in packets in the air flow. This leads to the conclusion that mixing not only at the mixing point, but also mixing in flow direction needs to be optimized, as the distribution of EGR between the cylinders is dependent on the timing between the passage of the EGR packets and the valve opening time.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. viii, 75 p.
TRITA-MMK, ISSN 1400-1179 ; 2014:01
EGR, Exergy, mixing, pulsating flow, HP-EGR, LP-EGR, high-pressure EGR, low-pressure EGR
National Category
Other Mechanical Engineering
urn:nbn:se:kth:diva-140850 (URN)978-91-7501-997-0 (ISBN)
Public defence
2014-02-28, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 14:00 (English)

QC 20140203

Available from: 2014-02-03 Created: 2014-02-02 Last updated: 2014-02-03Bibliographically approved

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Reifarth, SimonSakowitz, AlexanderÅngström, Hans-Erik
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Internal Combustion EnginesMechanics
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