“Combine Effect of Exhaust Gas Recirculation (EGR) and Inlet Air Pressure on Emission and Performance of Constant Speed Compression

Ignition Engine”

SUBMITTED BY:

HARSHRAJ DANGAREnrollment No: 110300721011

GUIDED BY:Prof. Gaurav Rathod

Associate Professor, LDRP-ITR

A Thesis Submitted to Gujarat Technology University

in Partial Fulfilment of Requirement forthe Degree of Master of Engineering

in (Thermal Engineering)

Dec-2012

LDRP-ITR, Near ITI, KH-5 Circle, Gandhinagar-382015.

i

CERTIFICATE

This is to certify that research work embodied in this thesis entitled “Combine

effect of exhaust gas recirculation (EGR) and inlet air pressure/temperature on

performance and emission of compressed ignition diesel engine” was carried out by

Mr. Harshraj Dangar (110300721011) at LDRP-ITR, Gandhinagar for partial

fulfillment of M.E degree to be awarded by Gujarat Technological University. This

research work has been carried out under my supervision and is to satisfaction of

department. The students work has been published/accepted for publication.

Date:

Place:

Prof. Gaurav P. Rathod Prof. A. R. Patel

Associate Professor, H.O.D,Mech.Dept.

LDRP-ITR, LDRP-ITR,

Gandhinagar.-382015 Gandhinagar.-382015

Dr. Gargi Rajpara

Principal,

LDRP-ITR

Gandhinagar-382015

Seal of Institute

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THESIS APPROVAL

This is to certify that research work in this entitled "Combine Effect of Exhaust Gas Recirculation (EGR) and Inlet Air Pressure/Temperature on Performance and Emission of Compressed Ignition Diesel Engine” was carried out by Mr. Harshraj Dangar, Enrollment No.: 110300721011 at LDRP-ITR is approved for award of the degree of Masters of Engineering (M. E.) by Gujarat Technological University.

Date: -

Place: -

Examiner(s):-

___________ ___________ ___________( ) ( ) ( )

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DECLARATION OF ORIGINAL WORK

I hereby certify that I am the sole author of this thesis and that neither any part

of this thesis nor the whole of the thesis has been submitted for a degree to any other

University or Institution.

I certify that, to the best of my knowledge, my thesis does not infringe upon

anyone’s copyright nor violate any proprietary rights and that any ideas, techniques,

quotations, or any other material from the work of other people included in my thesis,

published or otherwise, are fully acknowledged in accordance with the standard

referencing practices. Furthermore, to the extent that I have included copyrighted

material that surpasses the bounds of fair dealing within the meaning of the Indian

Copyright Act, I certify that I have obtained a written permission from the copyright

owner(s) to include such material(s) in my thesis and have included copies of such

copyright clearances to my appendix.

I declare that this is a true copy of my thesis, including any final revisions, as

approved by my thesis review committee.

Date:

Place:

Mr. Harsahraj Dangar.Enrollment No.: 110300721011

Verified

Prof. Gaurav P. Rathod Asso. Prof., Mechanical Engg. Dept. LDRP-ITR, Gandhingar-382015

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ACKNOWLEDGEMENT

It is indeed a pleasure for me to express my sincere gratitude to those who

have always helped me for this dissertation work.

First I thanks to almighty god who gave strength, courage and sense to

complete this dissertation work.

I am humbly expressing thanks to my respected guide Prof. Gaurav P.

Rathod for his valuable time and constant help given to me. He provided me this

opportunity to work in this inspiring project. With his enthusiasm, inspiration, and

great efforts to explain things clearly and simply, he helped to make this work fun.

Throughout my dissertation period, he provided encouragement, sound advice, good

teaching, good company, and lots of good ideas. I would have been lost without him.

I have learned many things from him such as the way of thinking and the way of

conducting speech.

I would also like to thank Prof. A. R. Patel, H.O.D., Mechanical Engineering

Department, LDRP-ITR, who has always been prepared to offer me help at any time,

in spite of having busy schedule.

Finally, I am thankful to all the faculty members of Mechanical Engineering

Department and my parents, all my friends who have directly or indirectly helped me

during this dissertation work.

HARSHRAJ DANGAR

110300721011

M.E-Thermal Engg.

LDRP-ITR, Gandhinagar

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Table of content

Titles Page No.

Title Page i

Certificate ii

Thesis Approval iii

Declaration of Original Work iv

Acknowledgement v

Tables of Contents vi

List of Figures viii

List of Tables ix

Abstract x

Chapter 1 Introduction 1.1 – 1.6

1.1 Introduction to Chapter 1.1

1.2 Problem Statement 1.2

1.3 Objective of Study 1.4

1.4 Scope of Study 1.4

1.5 Methodology 1.5

1.6 Work Plan for Dissertation 1.5

1.7 Structure of Thesis 1.6

Chapter 2 Literature Survey 2.1 – 2.26

2.1 Diesel Engine 2.1

2.2 Emission Legislation 2.1

2.3 Emission Formation in Diesel Combustion 2.2

2.3.1 Nitrogen Oxide 2.2

2.3.2 Particulate Matter 2.5

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2.3.3 Sulphur Oxides 2.6

2.3.4 Hydrocarbons 2.7

2.3.5 Carbon Monoxide and Carbon Dioxide 2.7

2.4 Technology use to reduce Exhaust Gas 2.8

2.5 Scope of the Work 2.26

Chapter 3 Exhaust Gas Recirculation (EGR) Systems 3.1 – 3.6

3.1 Introduction to Chapter 3.1

3.2 Concept of EG 3.2

3.3 Classification of EGR systems 3.4

3.4 Advantages of EGR 3.5

3.5 Disadvantages and Difficulties of EGR 3.5

3.6 Application of Cambusiton Analyzers to EGR Development 3.6

Chapter 4 Experimental Setup

4.1 Experimental Setup Description 4.1

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List of figure and tables

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“Combine Effect of Exhaust Gas Recirculation (EGR) and Inlet Air Pressure on Emission and Performance of Constant Speed Compression Ignition Engine”

Submitted by

DANGAR HARSHRAJ GOKALBHAIEnrolment No.:110300721011

Supervised By

Prof. Gaurav Rathod, M.E. ThermalAsso. Professor

Mechanical Engineering Department LDRP-ITR, Gandhinagar-382015

ABSTRACT

An experimental study has been carried out for combined effect of Exhaust Gas Recirculation (EGR) system and inlet air pressure on performance and emission of diesel engine. As we know that the diesel engine are known for their high NOx formation and Exhaust Gas Recirculation (EGR) is being used widely to reduce and control the oxides of nitrogen (NOx) emission from diesel engines. EGR controls the NOx because it lowers oxygen concentration and flame temperature of the working fluid in the combustion chamber. However, the use of EGR leads to a trade-off in terms of soot emissions moreover it exhausted more unburned hydrocarbons (20–30%) compared to conventional engines and it also affect the efficiency and bsfc of engine performance. Present experimental study will be carrying out in a single cylinder, water cooled and constant speed direct injection four stroke diesel engine to experimentally evaluate the performance and emissions for three different EGR rates and three different values of inlet air pressure of the engine. This experiment is conducted to see the potential of EGR combine with inlet air pressure. Three different rates: 5%, 10% and 15% of this exhaust gas will recirculate in engine and inlet air pressure ranges from 1 bar to 5 bar is selected to check the effect EGR on different loading conditions.

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CHAPTER-1

INTRODUCTION

1.1 Introduction

In today’s World the Energy Consumption Has Been Increased Due To Rapid Growth in Industrialization and individual mobility. Such causes a growth in transportation sector owing increased fuel consumption and environmental problems. The engineers are developing the power units for the fulfilment of the industrial growth and to provide transportations. In the development of the power units the diesel engines are the widely used and well established machines. Now a day’s diesel engine because of its unique combination of energy efficiency, power, reliability, and durability, diesel technology plays a vital role in important sectors of the economy. More than 90 percent of commercial trucks are powered by diesel engines, as are two-thirds of all farm and construction equipment, and 100 percent of all freight locomotives, river barges and other marine work vessels. Diesel engines also power electric generators used for distributed generation or as emergency back-up power such as those used by hospitals, different diesel power plants are universally adapted to supplement hydroelectric or thermal stations and as central stations for small capacity in the range of 2 to 50 MW capacity. The diesel engines are more favourable compare to others because of their inherently high thermal efficiencies, resulting from their high compression ratio and fuel lean operations. The high temperature is produced due to the higher compression ratio required for the achievement of auto-ignition point for the combustion of diesel. Higher compression ratio leads to higher expansion ratio which tends to discharge less thermal energy in the exhaust system. The most difficult problems that an engineer and manufacturers faces during diesel engine development are the control and reduction in pollutant emissions.

Climate change is potentially one of the most serious environmental threats facing the world today. While it is difficult to determine whether individual events are the direct result of man-made changes to the climate, at the global level, temperatures rise by approximately 0.6° centigrade during the last century. Awareness of the global scale of emissions of greenhouse gases (carbon dioxide CO2, methane CH4, chlorofluorocarbons CFC and nitrous oxide N2O) has increased over recent years. Scientists warn that we are about to enter a global warming phase during which the Earth’s temperature is expected to rise significantly. The Intergovernmental Panel on Climate Change (IPCC) has forecast that global temperatures will rise between 1° and 2° by 2020 and between 2° and 5° by 2070. Naturally occurring greenhouse gases include water vapour, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3). Emissions from transport, and especially motor vehicles, add considerably to the levels of greenhouse gases in the atmosphere. Road transport generally accounts for approximately 55-99% of greenhouse gases from transport. Of this, two-thirds are attributable to the private car. Technologies and actions which promote energy efficiency, energy independence and greenhouse gas (GHG) emission reductions are increasingly attractive to national, state and local policymakers.

The exhorting anticipation of additional improvements in diesel fuel and diesel vehicle sales in future has forced to upgrade the technology in terms of power, fuel economy, and emissions. Global energy consumption has been increasing around the world, owing to the

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rapid growth of industrialization and improvements in the standard of living. As a result, more carbon dioxide and nitrogen oxide being released into the environment.

Table- 1.1: Car Production (Year Wise)

Year Car produced in the world

% Change (YOY)

Car produced in the India

% Change (YOY)

2011 79,989,155 3.1 3,926,517 10.4

2010 77,703,987 25.9 3,557,073 34.7

2009 61,791,868 -12.4 2,641,550 13.3

2008 70,520,493 -3.7 2,332,328 3.5

2007 73,266,061 5.8 2,253,729 11.6

2006 69,222,975 4.1 2,019,808 24.2

1.2 Problem Statements

The diesel engine is the most efficient prime mover commonly available today. Diesel engines move a large portion of the world's goods, power much of the world's equipment, and generate electricity more economically than any other device in their size range. But the diesel is one of the largest contributors to environmental pollution problems worldwide, and will remain so, with large increases expected in vehicle population and vehicle miles travelled (VMT) causing ever-increasing global emissions. Diesel emissions contribute to the development of cancer; cardiovascular and respiratory health effects; pollution of air, water, and soil; soiling; reductions in visibility; and global climate change. Where instituted, control programs have been effective in reducing diesel fleet emissions. Fuel changes, such as reduced sulphur and aromatics content, have resulted in immediate improvements across the entire diesel on- and off-road fleet, and promise more improvements with future control. Off road diesel fuel sulphur content is 10 times higher than that of national on-road diesel fuel. Significantly reducing this sulphur content would reduce secondary particulate matter (PM) formation and allow the use of control technologies that have proven effective in the on-road arena. The use of essentially zero-sulphur fuels, such as natural gas, in heavy-duty applications is also expected to continue.

Diesel-powered vehicles and equipment account for nearly half of all nitrogen oxides (NOx) and more than two-thirds of all particulate matter (PM) emissions from US transportation sources.  

Diesel emissions of nitrogen oxides contribute to the formation of ground level ozone, which irritates the respiratory system, causing coughing, choking, and reduced lung capacity. Ground level ozone pollution, formed when nitrogen oxides and hydrocarbon emissions combine in the presence of sunlight, presents a hazard for both healthy adults and individuals suffering from respiratory problems. 

Technology changes, such as engine modifications, exhaust gas recirculation, and catalytic after treatment, take longer to fully implement, due to slow fleet turnover. However, they eventually result in significant emission reductions and will be continued on an ever-widening basis in the country and worldwide. New technologies, such as hybrids and fuel

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cells, show significant promise in reducing emissions from sources currently dominated by diesel use. Lastly, the turnover of trucks and especially off-road equipment is slow; pollution control agencies need to address existing emissions with in-use programs, such as exhaust trap retrofits and smoke inspections. These and other steps that can be continued and improved will allow the use of the diesel engine, with its superior fuel consumption, to continue to benefit society while greatly reducing its negative environmental and health impacts. The next ten years can and must become the "Decade of Clean Diesel."

The first Indian emission regulations were idle emission limits which became effective in 1989. These idle emission regulations were soon replaced by mass emission limits for both petrol (1991) and diesel (1992) vehicles, which were gradually tightened during the 1990s. Since the year 2000, India started adopting European emission and fuel regulations for four-wheeled light-duty and for heavy-dc. Indian own emission regulations still apply to two- and three-wheeled vehicles.Current requirement is that all transport vehicles carry a fitness certificate that is renewed each year after the first two years of new vehicle registration.On October 6, 2003, the National Auto Fuel Policy has been announced, which envisages a phased program for introducing Euro 2 - 4 emission and fuel regulations by 2010. The implementation schedule of EU emission standards in India is summarized in Table 1.

Table- 1.2: Indian Emission Standards (4-Wheel Vehicles)

Standard Reference Date RegionIndia 2000 Euro 1 2000 Nationwide

Bharat Stage II Euro 22001 NCR*, Mumbai, Kolkata, Chennai2003.04 NCR*, 12 Cities†2005.04 Nationwide

Bharat Stage III Euro 32005.04 NCR*, 12 Cities†2010.04 Nationwide

Bharat Stage IV Euro 4 2010.04 NCR*, 12 Cities†* National Capital Region (Delhi)

† Mumbai, Kolkata, Chennai, Bengaluru, Hyderabad, Ahmedabad, Pune, Surat, Kanpur, Lucknow, Sholapur, and Agra

Table- 1.3: Emission Standards for Diesel Truck and Bus Engines, g/kWh

Year Reference CO HC NOx PM1992 - 17.3-32.6 2.7-3.7 - -1996 - 11.20 2.40 14.4 -2000 Euro I 4.5 1.1 8.0 0.36*2005† Euro II 4.0 1.1 7.0 0.152010† Euro III 2.1 0.66 5.0 0.10* 0.612 for engines below 85 kW

† earlier introduction in selected regions, see Table 1Table- 1.4: Emission Standards for Light-Duty Diesel Vehicles, g/km

Year Reference CO HC HC+NOx PM

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1992 - 17.3-32.6 2.7-3.7 - -1996 - 5.0-9.0 - 2.0-4.0 -2000 Euro 1 2.72-6.90 - 0.97-1.70 0.14-0.252005† Euro 2 1.0-1.5 - 0.7-1.2 0.08-0.17† earlier introduction in selected regions, see Table 1.1

Figure- 1.1: Comparison between European, US, and Bharat Stage (Indian) emission standards for diesel passenger cars, based on NOx, CO and particulate matter. The sizes of the green circles represent the

permissible limits for particulate matter.

So, there are different methods which are employed to achieve above fulfilment of emission control. To accomplish such a problem there are many ways, one of them is to reduce the emission inside the cylinder chamber. In another cases different after-treatment process are used to maintain the emission legislation.

This research is aimed to find out the answers for the following questions:

i. What are the influences on engine performance and NOx emission by combine effect of EGR with varying inlet air pressure and temperature?

ii. What is the most significant value of EGR with inlet air pressure and temperature for better engine performance and reducing NOx emission?

1.3 Objective of the Study

The objective of this study is to find out the effect of different values of combined effect of EGR with inlet air pressure and temperature on engine performance and reducing NOx emission and to find out the optimum value and by analyzing different values to improve the engine performance and reducing the NOx emission.Objective of this study are as follows:

1. To find out the most significant value of EGR with inlet air pressure and temperature for better engine performance and reducing NOx emission.

2. To analyze the different values by using Design of Experiments (DOE).

1.4 Scope of Study

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This project will involve experimentation by using single cylinder DI water cooled

diesel engine. This experiment will concern about the different values as stated in this project

like EGR rate, inlet air pressure/temperature. EGR is one of the most suitable techniques to

reduce the tail pipe emission from the engine. The scope of this work is to examine the effect

of EGR rate with inlet air pressure/ temperature. EGR have many positive and negative

effects on the engine performance and emission. So, main motive for this study is to

understand these effects and work to minimize the undesired effect.

1.5 Methodology:

For this experimental work to find the combine effect of EGR rate and inlet air

pressure/temperature on single cylinder water cooled DI diesel engine was selected. To

recirculate the exhaust gas in to intake with different inlet air pressure/temperature a pipe

work is provided. A compressed cylinder is used to varying inlet air pressure.

This experiment contains study for three different EGR rate with inlet air

pressure/temperature. Jacob and hochheiser method is introduced to measure the NOx and a

simple gas analyzer is used to measure the HC from engine exhaust.

1.6 Structure of Thesis:

The structure of thesis work is shown below:

Chapter - 1 Introduction

In this chapter the problem identification, objective, scope, methodology, dissertation planning of work and structure has been carried out.

Chapter - 2 Literature survey

In this chapter complete survey of literature work is described.Chapter - 3 EGR systems

In this chapter emissions from diesel engine along with techniques to reduce has been reviewed. Basics of EGR system is also carried out in this chapter.

Chapter - 4 Experimental setup

Detail of experimental setup along with the description of different measuring and controlling devices is shown in this chapter.

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CHAPTER 3 EGR SYSTEMS

1.1 Introduction:

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The diesel engine provides a high efficiency and hence it can help to reduce O 2 emissions, which are believed to be the main cause of global warming. Diesel exhaust also contains toxic gases, mainly nitrogen oxides (NOx) and soot particles. These emissions are therefore limited by the authorities in most countries.

The following table provides a summary for the pollutants.

Emission Source

SOx Function of fuel oil sulphur contentCO2 Function of combustionCO Function of the air excess ratio and combustion temperature and

air/fuel mixture.HC Very engine dependant but a function of the amount of fuel and lube

oil left unburned during combustion.Smoke/

ParticulatesOriginates from unburned fuel, ash content in fuel and lube oil.

NOx Function of peak combustion temperatures, oxygen content and residence time.

Table- 3.1: - Summary of pollutants

Instead of using after-treatment systems to comply with exhaust emission legislation, it is also possible to avoid the formation of emissions during the combustion. The raw emissions are reduced and thus no after-treatment is needed. It is common practice nowadays, to use EGR to reduce the formation of NOX emissions. A way to reduce the nitrogen oxide emissions of a diesel engine is the use of exhaust gas recirculation, EGR. The Exhaust Gas Recirculation (EGR) system is designed to reduce the amount of Oxide of Nitrogen (NOx) created by engine during operating periods that usually result in high combustion temperatures. NOx is formed in high concentrations whenever combustion temperatures exceed about 2500’F. The EGR system reduces NOx production by recirculating small amount of exhaust gases into the intake manifold where it mixes with the incoming air/fuel charge. By diluting the air/fuel mixture under these conditions, peak combustion temperature and pressures are reduced resulting in an overall reduction of NOx output. Increasing the EGR volume lowers NOx production to a point, but excessive EGR volume causes incomplete combustion, raising the particulate levels. Achieving the opposing goals of lower NOx production and lower particulate levels requires carefully tuned EGR levels.

3.2 Exhaust Gas Recirculation (EGR)

A widely adopted route to reduce NOx emissions is Exhaust Gas Recirculation (EGR). This involves recirculating a controllable proportion of the engine's exhaust back into the intake air. A valve is usually used to control the flow of gas, and the valve may be closed completely if required. The substitution of burnt gas (which takes no further part in combustion) for oxygen rich air reduces the proportion of the cylinder contents available for combustion. This causes a correspondingly lower heat release and peak cylinder temperature, and reduces the formation of NOx. The presence of an inert gas in the cylinder further limits the peak temperature (more than throttling alone in a spark ignition engine).

The gas to be recirculated may also be passed through an EGR cooler, which is usually of the air/water type. This reduces the temperature of the gas, which reduces the

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cylinder charge temperature when EGR is employed. This has two benefits- the reduction of charge temperature results in lower peak temperature, and the greater density of cooled EGR gas allows a higher proportion of EGR to be used. On a diesel engine the recirculated fraction may be as high as 50% under some operating conditions.

Figure- 3.1: Exhaust Gas Recirculation

The exhaust gas acts as an inert gas in the combustion chamber, it does not participate in the combustion reaction. This leads to a reduction of the combustion temperature by different effects. The fuel molecules need more time to find an oxygen molecule to react with, as there are inert molecules around. This slows down the combustion speed and thus reduces the peak combustion temperature, as the same amount of energy is released over a longer period of time.

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Figure- 3.2: Temperature dependency of NOX formation

The X-axis shows the mass-percentage of oxygen. This is a way to express the amount of EGR that is recirculated. More EGR leads to a lower oxygen concentration. Another way to express the amount of EGR is the EGR-rate, which is defined as follows:

Several difficulties have to be taken into account when EGR is used. When the exhaust gas is taken out of the exhaust system upstream of the turbocharger, the energy of this gas is lost for the turbocharger. This decreases the useable exhaust energy for compressing the intake air and thus the amount of air that gets into the cylinder. This amount of air is directly coupled to the amount of EGR that the engine can run, because the limiting factor is the air/fuel ratio in the cylinder. Another problematic area is the control of emissions during transients. As it is desirable to get a maximum acceleration, the EGR is usually shut off when the load is increased, to provide the maximum amount of available air. This strategy leads to NOx peaks in the transient parts of the MNEDC as can be seen in Figure 3.3.

Figure- 3.3: NOX formation during the MNEDC

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The configuration of an EGR system depends on the required EGR rate and other demands of the particular application. Most EGR systems include the following main hardware components:

One or more EGR control valves One or more EGR coolers Piping, flanges and gaskets

Other specialized components are possible in certain types of systems, such as venturi mixer devices or EGR pumps.

3.2.1 Advantages of EGR Reduced NOx.

Potential reduction of throttling losses on spark ignition engines at part load. Improved engine life through reduced cylinder temperatures (particularly exhaust

valve life).

3.2.2 Disadvantages and Difficulties of EGR

Since EGR reduces the available oxygen in the cylinder, the production of particulates (fuel which has only partially combusted) is increased when EGR is applied. This has traditionally been a problem with diesel engines, where the trade-off between NOx and particulates is a familiar one to calibrators.

The deliberate reduction of the oxygen available in the cylinder will reduce the peak power available from the engine. For this reason the EGR is usually shut off when full power is demanded, so the EGR approach to controlling NOx fails in this situation.

The EGR valve cannot respond instantly to changes in demand, and the exhaust gas takes time to flow around the EGR circuit. This makes the calibration of transient EGR behavior particularly complex- traditionally the EGR valve has been closed during transients and then re-opened once steady state is achieved. However, the spike in NOx / particulate associated with poor EGR control makes transient EGR behavior of interest.

The recirculated gas is normally introduced into the intake system before the intakes divide in a multi-cylinder engine. Despite this, perfect mixing of the gas is impossible to achieve at all engine speeds / loads and particularly during transient operation. For example poor EGR distribution cylinder-to-cylinder may result in one cylinder receiving too much EGR, causing high particulate emissions, while another cylinder receives too little, resulting in high NOx emissions from that cylinder.

Although the term EGR usually refers to deliberate, external EGR, there is also a level of internal EGR. This occurs because the residual combustion gas remaining in the cylinder at the end of the exhaust stroke is mixed with the incoming charge. There is therefore a proportion of internal EGR which must be taken into account when planning EGR strategies. The scavenging efficiency will vary with engine load, and in an engine fitted with variable valve timing a further parameter must be considered.

3.2.3 Application of Cambustion Analyzers to EGR Development Cambustion’s CLD500 NOx analyzer offers two channels of simultaneous NOx

measurement, with a T10-90% of 10ms or less. This allows NOx concentrations in the

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exhaust to be measured for each firing cycle, allowing cyclic variability to be observed.

Cambustion's NDIR500 CO&CO2 analyzer offers two channels of simultaneous CO & CO2 measurement, with a T10-90% of 8ms. This allows a variety of applications:

Sampling with the NDIR500 in the intake allows measurement of CO2 concentration in the intake charge. Measurement of exhaust CO2 with the other channel of the NDIR allows calculation of the external EGR rate, on a cycle by cycle basis.

Depending on the location of the intake probe, either the overall EGR rate or the EGR rate specific to one cylinder may be measured. This allows verification and improvement of EGR modelling and EGR distribution, including transients.

Sampling with the NDIR probes at different points through the EGR loop allows characterization of EGR system delays and behaviour.

Comparison of the CO2 concentration in the pre-combustion gas with the exhaust gas from the previous cycle allows total EGR (internal + external) to be calculated. This technique can therefore reveal cyclical variation, as well as cylinder to cylinder variation. Such a capability may also be useful when verifying the effects of variable valve timing.

Cambustion’s DMS Series particulate analyzers are capable of making exhaust particulate concentration measurements (both particle number and particle mass) and have a T10-90% response time as low as 200ms. While this is not fast enough for cycle by cycle resolutions, the DMS series allows fine tuning of EGR for particulate emissions, and the ability to measure directly in the exhaust allows comparison of different cylinders.

1.2 Classification of EGR Systems

Various EGR systems are classified mainly into three groups as discussed below:

3.3.1 Based on the method of trapping the exhaust gas

EGR is classified mainly into two categories.1) Internal EGR2) External EGR

1) Internal EGR

This type of EGR differs from the other EGR owing to the fact that it has no external routing through which the exhaust gas is routed from the exhaust manifold to the intake manifold.

For all other types of EGR, we use an external piping to stream the exhaust into the cylinder of the engine. The internal EGR is more disadvantageous when compared to external EGR. Internal EGR is inefficient and reduces fuel economy.

2) External EGR

This type of EGR is the most common type of EGR. This, unlike internal EGR, has an external routing through which the required amount of exhaust gas is re - circulated into the engine.

This has many advantages over the internal EGR that, in this system, the exhaust

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routed from the engine can be cooled externally with additional equipment’s like the EGR cooler or even, the exhaust can be filtered to avoid particulate matter (PM) entering the cylinder, which can cause over wear of the moving parts inside the engine.

3.2.2 Based on the path of exhaust gas

Based on the path of exhaust gas, the EGR is classified into two categories, basically.1) Short path EGR2) Long path EGR

1) Short path EGR

In this kind of EGR system, a portion of the exhaust is routed into the engine to the downstream of the compressor of the turbocharger, which is normally at a pressure well below the exhaust pressure.

2) Long path EGR

The exhaust formed in the cylinder is routed into the turbine of the turbocharger at first to run the compressor turbine of the same. A portion of the exhaust is taken to the EGR cooler to cool the exhaust and then its flow is regulated by the EGR valve which has links to the engine management system.

3.2.3 Based on the temperature of the exhaust gas admitted

Based on the temperature of the exhaust gas admitted, the EGR is classified into two categories, basically

1) Hot EGR2) Cooled EGR

1) Hot EGR

This kind is not that popular since it increases the temperature of the intake mixture , the Hot EGR is the type of EGR in which the exhaust gas is re-circulated as such.It reduces the life of the engine.

2) Cooled EGR

Here, the exhaust routed from the engine is cooled to a desired level before admitting it into the engine. This is more popular than Hot EGR due to the reduced risk of knocking and formation of hot-spots inside the cylinder of the engine.

Greenhouse Gas

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EGR – Exhaust Gas RecirculationDOE – Design of Experiments

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