Exhaust Gas Recirculation is an effective method for NOx control. The exhaust gases mainly consist of carbon dioxide, nitrogen, etc. and the mixture has higher specific heat compared to atmospheric air. Re-circulated exhaust gas displaces fresh air entering the combustion chamber with carbon dioxide and water vapor present in engine exhaust. As a consequence of this air displacement, lower amount of oxygen in the intake mixture is available for combustion. Reduced oxygen available for combustion lowers the effective air–fuel ratio. This effective reduction in air–fuel ratio affects exhaust emissions

1. EXHAUST GAS RECIRCULATION SYSTEM
(EGR)
Prepared By: Engr. Mohammad Imam Hossain (Rubel),
Skype ID: mdimam, Email: rubelduet04@gmail.com

2. AIR POLLUTION

3. According to EPA six common air pollutants are:
1.Ozone
2.Particulate Matters
3.Carbon Monoxides
4.Sulfur Dioxide
5.Lead
6.Nitrogen Dioxide
CAUSES OF AIR POLLUTION

4. WHAT IS NOx? WHERE DOES IT COME FROM?
• NOx is a generic term for mono-nitrogen
oxides (NO and NO2).
• Major sources are diesel engines.
• NOx formation is depends upon
temperature (i.e. 2000k).

6. NOx LEVELS RISING STEADILY

7. HOW TO REDUCE NOx EMISSION IN DIESEL ENGINES
• NOx are formed when temperatures
in the combustion chamber
get too hot (2000 k).
• In diesel engines NOx formation
can be reduced by:
1. Late injection of fuel.
2. Enriching A/F ratio.
3. Recirculating some exhaust gas.
(i.e. EGR system)

8. EXHAUST RECIRCULATION SYSTEM (EGR)

9. EXHAUST RECIRCULATION SYSTEM (EGR)
In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction
technique used in petrol/gasoline and diesel engines. EGR works by recirculating a portion of an engine's exhaust gas
back to the engine cylinders.
Usually, an engine recirculates exhaust gas by piping it from the exhaust manifold to the inlet manifold. This design is
called external EGR. A control valve (the EGR valve) within the circuit regulates and times the gas flow. Some engines
incorporate a camshaft with relatively large overlap during which both the intake valve and the exhaust valve are
open, thus trapping exhaust gas within the cylinder by not fully expelling it during the exhaust stroke

10. THE EFFECTS OF EGR
The addition of Exhaust-Gas has many effects on diesel engine combustion and pollutant formation. They are:
1. Decreased flame temperature due to increased heat capacity of the intake charge .
2. Lower O2 concentration due to dilution of the intake charge. Exhaust gas contains much lower O2 levels than ambient air.
3. Increasing the inlet temperature due to introduction of hot combustion products
4. Changes in Ignition Delay and combustion characteristics like flame structure
5. Increased inlet concentration of pollutants due to re-circulation, leading mainly to greater in-cylinder wear rates.
6. Thermal throttling’ effect: the hot exhaust-gases mix with cooler air in the intake manifold. This reduces the density of
the intake mixture and hence the mass of the inducted charge decreases. This causes an overall increase in cylinder
temperatures.

11. CLASSIFICATION OF EGR SYSTEM
 Based on operating condition:
1. High EGR flow.
2. Low EGR flow.
3. NO EGR flow.
 Based on temperature :
1. Hot EGR.
2. Fully cooled EGR.
3. Partly cooled EGR.
 Based on Pressure :
1. Low pressure route system.
2. High pressure route system.

12. Working of EGR system :
 EGR is a useful technique for reducing NOx formation in the
combustion chamber.
 EGR works by recirculating a portion of an engine's exhaust
gas back to the engine cylinders.
 In C.I. Engines EGR :
1. Increased ignition delay.
2. Increased heat capacity.
3. Dilution of combustion mixture (A/F Mixture).
EXHAUST GAS RECIRCULATION SYSTEM (EGR)-1

13. EXHAUST GAS RECIRCULATION SYSTEM (EGR)-2
EGR System for a Low-Speed Two-Stroke Marine Application

14. DIAGRAM OF AN EGR SYSTEM
Hybrid EGR System for US EPA Tier 2 Bin 5 Diesel Application

15. BASIC PARTS OF EGR SYSTEM
EGR Valve
EGR Cooler
EGR Transfer Pipe

16. TYPES OF 4-STROKE DIESEL ENGINE WITH BASIC PARTS OF EGR

17. TYPES OF 4-STROKE DIESEL ENGINE WITH BASIC PARTS OF EGR

18. EGR OPERATING CONDITION
• High EGR flow
• Low EGR flow
• No EGR flow

19. EGR THEORY OF OPERATION
 The purpose of the EGR system is to precisely regulate the flow under different operating conditions.
 By integrating the fuel and spark control with the EGR metering system, engine performance and the
fuel economy can be enhanced
 For this an ECM (Electronic Control Machine) is used to regulate the EGR flow. When EGR is required
ECM opens the EGR valve.
 The ECM is capable of neutralizing the negative aspects of EGR by programming additional spark
advance and decreased fuel injection duration during periods EGR flow.

20. EGR THEORY OF OPERATION

21. TECHNICAL ISSSUES
 Combustion Contamination
 Exhaust gas from any combustion process may have certain contaminants
 May lead to serious combustion degradation and instability, and shorter component life.
 Control System Stability
 Control systems for modern engines have been developed over two decades to maintain emissions control at
varying loads, speeds, and fuel conditions.
 Adding EGR into the combustion process introduces further complexity that must be carefully integrated into
the entire engine control system approach for successful operation over a wide range of conditions.

22. TECHNICAL ISSSUES
Materials and Durability
 EGR systems may decrease long-term life of the components affected, including the EGR coolers and control
valves, the pistons and cylinder heads, exhaust manifolds and sensors
 Continuous duty applications may cause materials breakdown, shorter component life, and even
unexpected, engine failures.

23. TECHNICAL ISSSUES

24. CONCLUSION
Thermal efficiency of the engine are not affected significantly by EGR.
Use of EGR technology to treat diesel exhaust shows promise for meeting strict 2010 EPA requirements.
This method is very reliable in terms of fuel consumption.
EGR is the most effective method for reducing the nitrous oxide emissions from the engine exhaust.
Exhaust Gas Recirculation is a very simple method. It has proven to be very useful and it is being modified
further to attain better standards.
The increase in particulate matter emissions due to EGR can be taken care by employing particulate traps
and adequate regeneration techniques.

25. Everyone to realize their responsibility towards Mother Earth. Saving
Environment is the need of today, the way we are destroying environment
will lead to the destruction of life on this earth. Therefore, it’s necessary
that we should Save Environment and everyone should contribute to the
cause and should do something to save Environment. The best way to
encourage others for the cause of saving environment is to write and
share some short effective messages on saving environment.
Eliminating pollution is the best solution to save the environment

26. THANKS A LOT …………..