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Efficiency and Mixing Analysis of EGR-Systems for Diesel Engines
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Internal Combustion Engines. (CCGEx)
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.
Series
TRITA-MMK, ISSN 1400-1179 ; 2014:01
Keyword [en]
EGR, Exergy, mixing, pulsating flow, HP-EGR, LP-EGR, high-pressure EGR, low-pressure EGR
National Category
Other Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-140850ISBN: 978-91-7501-997-0 (print)OAI: oai:DiVA.org:kth-140850DiVA: diva2:692865
Public defence
2014-02-28, Kollegiesalen, Brinellvägen 8, KTH, Stockholm, 14:00 (English)
Opponent
Supervisors
Note

QC 20140203

Available from: 2014-02-03 Created: 2014-02-02 Last updated: 2014-02-03Bibliographically approved
List of papers
1. TRANSIENT EGR IN A LONG-ROUTE AND SHORT-ROUTE EGR-SYSTEM
Open this publication in new window or tab >>TRANSIENT EGR IN A LONG-ROUTE AND SHORT-ROUTE EGR-SYSTEM
2009 (English)In: PROCEEDINGS OF THE 2009 SPRING TECHNICAL CONFERENCE OF THE ASME INTERNAL COMBUSTION ENGINE DIVISION, NEW YORK: AMER SOC MECHANICAL ENGINEERS , 2009, 761-770 p.Conference paper, Published paper (Refereed)
Abstract [en]

The use of EGR to lower NOx-emissions from Diesel engines is a well-documented method. Recently, more and more research is done on alternative EGR routing systems such as long-route EGR. To reach future emission legislation goals it is not sufficient to focus on steady-state driving. The emission peaks during the transient parts of driving cycles are gaining importance. It is therefore interesting to analyze the EGR-flow in transients for different configurations of the EGR system. In this work, a 1-D simulation is performed in GT-Power for a Euro 4 passenger car diesel engine equipped with cooled short-route EGR and a variable geometry turbine. For calibration of the simulation, load transients were measured including the measurement of transient EGR-rates using a fast CO2-analyzer and cylinder pressure to obtain heat-release data. While the transient heat-release rates are used as an input for the combustion-simulation, the EGR response measurements are used as a reference for calibration of the EGR-system and its components. A long route EGR system and a short-route EGR system are then simulated and compared, focusing on transient response, availability of EGR during the transient and the fuel consumption in steady state. It is shown that the long-route system has advantages in both steady-state and transient driving conditions. In steady state it can decrease fuel consumption, in transient it can provide EGR without negative effect on the transient response.

Place, publisher, year, edition, pages
NEW YORK: AMER SOC MECHANICAL ENGINEERS, 2009
National Category
Computer and Information Science
Identifiers
urn:nbn:se:kth:diva-30229 (URN)10.1115/ICES2009-76107 (DOI)000273471300073 ()2-s2.0-77952868412 (Scopus ID)
Conference
Spring Technical Conference of the ASME-Internal-Combustion-Engine-Division Milwaukee, WI, MAY 03-06, 2009
Note
QC 20110221Available from: 2011-02-21 Created: 2011-02-21 Last updated: 2014-02-03Bibliographically approved
2. Transient EGR in a High-Speed DI Diesel Engine for a set of different EGR-routings
Open this publication in new window or tab >>Transient EGR in a High-Speed DI Diesel Engine for a set of different EGR-routings
2010 (English)In: SAE International Journal of Engines, ISSN 1946-3936, Vol. 3, no 1, 1071-1078 p.Article in journal (Refereed) Published
Abstract [en]

EGR has been proven to reduce NOx emissions from diesel engines significantly and is nowadays widely used in production engines. To reach future emission legislation standards, alternative EGR-routings that deliver higher EGR- rates get into the focus of researchers. As the steady-state emissions are reduced more and more, the emission peaks in transient parts of driving cycles gain importance. Therefore it is interesting to analyze the transient behavior of different EGR-routings. In this work, a 1-D simulation is performed in GT-Power for a 1.9 liter passenger car diesel engine equipped with cooled short-route EGR and a variable geometry turbine. For calibration of the simulation, load transients are measured including the measurement of transient EGR-rates using a fast CO2-analyzer and cylinder pressure to obtain heat-release data. A database with heat-release rates for transient combustion is collected to enable the simulation to run with real combustion data at all points of the transients. The transient EGR-rate as well as the intake pressure are used as criteria to chose the right heat-release rate for a certain cycle. A set of different ways of supplying EGR, namely hybrid EGR, pump-assisted EGR and a reed valve in the EGR- circuit are then implemented in the simulation software and analyzed with respect to transient response and fuel consumption. Another aspect of the analysis is the possibility to control the EGR-rate during the transient. This includes positive load transients with EGR-shutoff as well as negative load transients with need for fast EGR-delivery.

Keyword
EGR, transient EGR
National Category
Mechanical Engineering Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-71792 (URN)10.4271/2010-01-1271 (DOI)2-s2.0-78649716726 (Scopus ID)
Note

QC 20120131

Available from: 2012-01-31 Created: 2012-01-31 Last updated: 2014-04-11Bibliographically approved
3. Exergy and Energy Analysis of HP and LP EGR-system
Open this publication in new window or tab >>Exergy and Energy Analysis of HP and LP EGR-system
(English)Article in journal (Other academic) Submitted
Abstract [en]

The emission legislation throughout the world is getting moreand more stringent. Especially in the US and Europe, dieselengine manufacturers are facing big challenges in order tokeep their engine emissions within the limits. In addition totraditional legislation of harmful emissions, the emission ofCO2, i.e. the fuel consumption, is starting to be subject of newlegislation. Many measures that control the harmful emissionscounteract the reduction of fuel consumption. After treatmentsystems for example increase backpressure, thus lowering theengine efficiency.Exhaust gas recirculation (EGR) is an important tool foremission control in modern diesel engines. The EGR-loopinduces some pumping losses thus decreasing the overallengine efficiency. Many studies have been published that aimat minimizing these losses. The use of a low-pressure EGRloop is one of the most common ways to alternate the system.This study compares a low-pressure (LP) and a high-pressureHP) EGR-system with focus on single components.To analyze the gas exchange system, both energy and exergybalance methods can be used. In this study, both methods arecompared and specific advantages and disadvantages areshown. It is shown that the exergy analysis contains usefulinformation for engine development regarding the efficiencyof single components and their influence on the entire systems performance.

Keyword
high-pressure EGR, low-pressure EGR, HP-EGR, LP-EGR, EGR, Exergy
National Category
Energy Engineering
Identifiers
urn:nbn:se:kth:diva-140847 (URN)
Note

QS 2014

Available from: 2014-02-02 Created: 2014-02-02 Last updated: 2014-02-03Bibliographically approved
4. Analysis of EGR/Air Mixing by 1-D Simulation, 3-D Simulation and Experiments
Open this publication in new window or tab >>Analysis of EGR/Air Mixing by 1-D Simulation, 3-D Simulation and Experiments
Show others...
(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
EGR, mixing, pulsating flow
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-140848 (URN)
Note

QS 2014

Available from: 2014-02-02 Created: 2014-02-02 Last updated: 2014-02-03Bibliographically approved
5. Measuring and simulating EGR-distribution on a HD-diesel engine
Open this publication in new window or tab >>Measuring and simulating EGR-distribution on a HD-diesel engine
(English)In: SAE technical paper series, ISSN 0148-7191Article in journal (Other academic) Submitted
Abstract [en]

The distribution of EGR between the cylinders of an internalcombustion engine has been shown to have large impact onthe engine emissions. Especially at high EGR, the combustionreacts sensibly to variations in the EGR-rate. A cylinder thatreceives excessive EGR produces soot particles while acylinder with too little EGR has increased NOX-emission. It istherefore important to have knowledge about the mixing in anengine.This study compares two different EGR-mixing measurementmethods. The first is based on CO2 measurement withstandard probes, placed at 36 different locations in the engine.The second method uses a laser beam and a detector to gaininformation about the mixing with a high time-resolution.Additionally, 1-D simulations are used to gain informationabout the mixing process.To vary the mixing process on the engine, two differentair/EGR mixers are used and their mixing performance isevaluated.

Keyword
EGR, mixing, distribution measurement
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-140849 (URN)
Conference
SAE PFL 2014
Note

QS 2014

Available from: 2014-02-02 Created: 2014-02-02 Last updated: 2017-12-06Bibliographically approved

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