Boost Pressure Controlled Hot Exhaust Gas Re-circulation System
FIELD
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The present subject matter relates to a boost pressure controlled hot exhaust gas re¬circulation system. More particularly it relates to a controlling system to control the hot exhaust gas recirculation by sensing turbocharger boost, thereby reducing Nitrogen Oxide (NOx) emission.
BACKGROUND
Exhaust gas recirculation (hereinafter referred as "EGR") is a NOx (nitrogen oxide and nitrogen dioxide) reduction technique, used in most gasoline and diesel engines. EGR works by re-circulating a portion of an engine's exhaust gas back to the engine cylinders. Mixing the incoming air with re-circulated exhaust gas dilutes the mixture with inert gas, lowering the adiabatic flame temperature and (in diesel engines) reducing the amount of excess oxygen. The exhaust gas also increases the specific heat capacity of the mixture lowering the peak combustion temperature. Because NOx formation progresses much faster at high temperatures, EGR serves to limit the generation of NOx. NOx is primarily formed when a mixture of nitrogen and oxygen is subjected to high temperatures.
In current engines, for NOx reduction, cooled EGR system is used along with Common rail injection system engine. EGR is governed by EGR valve which is controlled by logic from Air mass flow sensor which is located before Turbocharger. Exhaust gases enters inside Intake manifold and mixes with fresh Air intake. This system is not very precise as it senses the airflow before turbocharger, which is non-controlled value, The disadvantages related to the said system are that, EGR cooler is costly and overall cost of the system is much higher and also the existing system is quiet complex and less precise.

Other technical solution used is, direct EGR system but there is no control on exhaust gas recirculation. A pipe is connected between exhaust manifold to intake manifold. Exhaust gas flows through this pipe to intake manifold without any control. The disadvantage of the said direct EGR system is that, the system is less reliable as it allows continuous flow of Exhaust gases to engine deteriorating engine component life.
To overcome the above mentioned drawba6ks of EGR system there is a need of a system which uses hot EGR for regulation of NOx and which is simple and cost effective.
OBJECTS
An object of the present invention is to provide a boost pressure controlled hot exhaust gas re-circulation system using turbocharger boost pressure in which turbocharger boost is sensed for controlling exhaust gas circulation to reduce peak combustion temperature thereby, reducing NOx (Nitrogen oxides) and support in meeting Central Pollution Control Board-II emission norms for Genset application.
Another object of the present invention is to provide a simple, reliable and cost effective hot EGR system.
BRIEF DESCRIPTIONS
Figure 1 shows a perspective view of a conventional cooled EGR system.
Figure 2 shows a perspective view of a hot EGR system, in accordance with the
present subject matter.
Figure 3 shows a perspective view of an EGR pipe, in accordance with the present subject matter.

Figure 4 shows a perspective view of an EGR valve, in accordance with the present subject matter.
DETAILED DESCRIPTIONS
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches may overcome by the present subject rilatter as described below in the preferred embodiments.
The present subject matter provides a boost pressure controlled hot exhaust gas re¬circulation system wherein, a turbocharger boost pressure is sensed thereby reducing Nitrogen Oxide (NOx) emission.
Hot EGR control from turbocharger boost pressure is a system in which turbocharger boost is sensed for controlling exhaust gas circulation to reduce peak combustion temperature which in turn helps in reducing NOx (Nitrogen oxides) and support in meeting CPCBII emission norms for Genset application. This is a simple and cost effective solution for Nitrogen Oxide (NOx) emission.
EGR is used to reduce NOx. NOx is produced during the combustion event in high. temperatures. Oxygen combines with nitrogen to form NO and N02. NOx combines with hydrocarbons or volatile organic compounds in sunlight to form SMOG. Modern engine uses exhaust gas recirculation or EGR to control NOx creation. EGR controls NOx by lowering the combustion temperature and reducing the oxygen content in the combustion chamber.

Referring now to figure 1, showing a perspective view of a conventional cooled EGR system (100).
The cooled EGR system (100) includes an exhaust manifold (5), a first EGR pipe (10), an EGR cooler (15), a second EGR pipe (20), an EGR valve (25), an inlet (50) for intake air, an intake manifold (30), an air mass flow sensor (35), an alternator (40), an inlet (55) to intake manifold, and a turbocharger (45),
In traditional practice of NOx reduction, cooled EGR system is used along with common rail injection system engine. EGR is governed by EGR valve (25) which is controlled by logic from Air mass flow sensor (35) which is located on the upper side of the turbocharger (45). Exhaust gases enter inside intake manifold through the inlet (55) and mixes with fresh Air intake. This cooled EGR system is not very precise as it senses the Airflow before turbocharger (45) which is not controlled value.
Other technical solution used is direct EGR system (not shown) in which there is no control on exhaust gas recirculation. A pipe connect exhaust manifold to intake manifold. Exhaust gas flows through this pipe to intake manifold without any control.
Disadvantages
1. EGR cooler is costly and overall cost of the system is much higher.
2. The existing system is quiet complex and less precise.
3. This system is less reliable as it allows continuous flow of Exhaust gases to engine deteriorating engine component life.
Referring now to figure 2, showing a perspective view of a hot EGR system, in accordance with the present subject matter.

The hot EGR system (200) includes an exhaust manifold (5), an EGR pipe (10),' an EGR Electronic Control Unit (hereinafter referred as "ECU") (65), an EGR valve (25), an inlet '(50) for compressed air, a boost pressure sensor (60), an intake manifold (30), an alternator (40), and a turbocharger (45).
Turbocharger (45) pumps air into intake manifold (30) at a pressure higher than atmospheric pressure to improve volumetric efficiency of engine. The air pressure produced by turbocharger (45) is called Boost pressure. This Boost pressure varies with respect to engine load conditions. For meeting CPCBII norms, boost pressure is taken as input to control the exhaust gas recirculation to intake manifold (30). This is achieved by using boost pressure sensor (60) which is located at entry of intake manifold. The boost pressure sensor (60) senses boost pressure and provides input to EGR ECU (65). Logic is prepared for controlling exhaust gases with respect to boost pressure. EGR ECU (65) sends signal to vacuum solenoid (not shown) which operates the pneumatic EGR valve (15). Exhaust gases recirculation to intake manifold is regulated through EGR Valve. Exhaust gases controls NOx by lowering the combustion temperature and reducing the oxygen content in the combustion chamber. This NOx reduction helps in meeting CPCBII Criteria.
Referring now to figure 3 and 4, there is shown a perspective view of an EGR pipe and a perspective view of an EGR valve, in accordance with the present subject matter. In order to achieve proper floe of exhaust gases, EGR pipes of different diameters ranging from 12.5 mm to 18 mm were taken for the trials and based on design of experiments 18mm diameter pipe is selected which provides the best results. Similarly, EGR valves of internal diameter ranging from 18 mm to 30 mm and of different diaphragm were taken for the trials and based on design of experiments, exhaust valve diameter of 18mm is selected. The location of EGR valve (25) is decided on intake manifold (30) itself to avoid no. of joints.

Development cycle for the Hot EGR System
1. EGR flow is calculated.
2. Design of experiments carried out with different EGR flow rates at different engine RPMs.
3. During Design of experiments (hereinafter referred as "DOE"), EGR flow is controlled through EGR valve which is controlled by boost pressure through sensor and ECR.
4. EGR Flow rate is finalized and EGR pipe and EGR valve diameter is finalized.
5. Calibration of ECU, boost pressure sensor and EGR flow through EGR valve.
6. Combustion optimization carried out for required engine performance and emission requirements.
7. Finally, validation of hot EGR system.
Validation of the System:
The complete system is validated for followings-
1. Performance test
2. Durability at parts and System level
Following are the results obtained after completing the Performance and Emission trials (combustion optimization) with Boost pressure controlled Hot EGR.


In an embodiment, the hot EGR system (100) is provided with Electric/Electronic EGR valve instead of Pneumatic EGR Valve.
Advantages of the present subject matter
1. Boost pressure controlled Hot EGR system not only results in meeting emission norms but also improve BSFC by approx. 4.6%.
2. Hot EGR is cost effective as compared to cooled EGR system or common rail system in meeting CPCB II Norms.
3. Controlled Hot EGR System Improves Engine Life as compared to uncontrolled EGR.
4. Hot EGR can be more accurately controlled by getting consistent value of Boost pressure with respect to Engine Revolution Per Minute (hereinafter referred as "RPM") and Engine load condition
5. It can be used for various Engine control parameters such as Fan Speed, Water cooling and Oil cooling.
9. The present invention is proved highly reliable for all related application requirements.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the

principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with 'various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.