Skip to main content

EGR SCR In Automobile Vehicle (Simplified)

Exhaust Gas Recirculation System

EGR AND SCR EXPLAINED


EGR system I.e. exhaust gas recirculation system is one of the processes of controlling pollution emitted from automobiles.

What is EGR?

The full form of EGR is an exhaust gas recirculation system. It reduces the formation of NOx gas from the combustion chamber. This is the main purpose of EGR.
The oxides of nitrogen are harmful to our environment so, in order to control it, a system is introduced in bs4 model vehicles.

How does EGR work?


The working of EGR is simple and clear to understand. As the name suggests, exhaust gas recirculation, means exhaust gases are recirculated and sent back to the intake manifold of the engine. Only 6 to 10% of exhaust gases are sent to the combustion chamber via the intake manifold. 
Between the intake manifold and exhaust manifold, an EGR valve is fitted. Which allows the exhaust gas to enter the intake manifold. The EGR valve is automatically controlled by ECU (engine control unit). An EGR position sensor gives data to ECU and ECU opens the valve with the help of an actuator. Here a stepper motor is used as an actuator.

At what RPM does EGR start working?
The EGR starts to work When the engine's RPM is between 1050 to 3050.


Process of Reducing NOx

The only suitable method of reducing NOx is to prevent the temperature of the combustion chamber to rise. The higher the temperature, the higher the formation of NOx, so if a few amounts of exhaust gas are mixed with the fresh air and sent into the combustion chamber then it could reduce the temperature inside the cylinder. 
Apart from this, it has some pros and cons also which you must need to know.

Advantage Of EGR

  • Reduce throttling losses 
  • Reduce heat rejection
  • Reduce chemical dissociation

Disadvantages Of EGR

  • Decrease in volumetric efficiency of an engine.
  • Reduce engine power and acceleration.
  • Reduce fuel efficiency.

As you can notice the pros and cons of using EGR is almost stable. There was no doubt that it was reducing NOx but using this system also reduces engine power and efficiency. 
So in order to make the engine more efficient and completely reduce NOx, engineers have added SCR with it. Let's get to know more about SCR.

What is SCR?


SCR in automobiles stands for Selective Catalytic Reduction. It is coupled with EGR in vehicles. EGR was not able to remove the NOx completely. So, SCR is introduced to reduce the NOx generated from the combustion chamber. After using this system 93% of NOx coming out with exhaust gases is reduced.

How does SCR work?


SCR purely works on chemical reactions. It uses a reduction process to change the oxides of nitrogen into nitrogen and water.
There are 4 major components of SCR
  1. DEF - Diesel Exhaust Fluid (A urea-based solution)
  2. DEF injector 
  3. Mixing Tube
  4. Some Catalyst

DEF is injected into the mixing tube. Due to the effect of higher temperature, it breaks into the molecules of ammonia and carbon dioxide. And in the presence of some catalyst ammonia is reacted with oxides of nitrogen and forms water and nitrogen. 

Conclusion


EGR system is used to reduce the production of NOx from the engine's combustion chamber and if somehow NOx is generated then SCR is used to reduce it completely into nitrogen and oxygen. Using both processes simultaneously the production of NOx is reduced to almost zero.

Also: Nowadays, Electric cars are also getting launched. Have you checked the new ola car which is battery-operated? And it doesn't have any EGR and does not emit any pollution.
Tags

Comments

Post a Comment

Popular Posts

Does EGR system Decreases Engine Power? (Must Know)

Does EGR system Decrease Engine Power? You will be shocked to know that the EGR system in automobiles decreases the volumetric efficiency as well as power output.  Yes, you heard it right. Then, you must be thinking. why are we using EGR? What it actually does? Does it do any other thing to the engine? All these doubts and topics are covered in this article. Let's get started. Little Intro to EGR EGR stands for Exhaust Gas Recirculation System . It is part of em mission control system in an automobile vehicle. It has zero roles in increasing engine power. It is used in vehicles to stop the formation of NOx gas. Which are very harmful to nature. Generally, when a vehicle runs on the road it produces lots of smoke and pollutants like carbon monoxide, carbon dioxide, and the most dangerous one i.e. oxides of nitrogen . Formation of NOx Fas Inside Engines Cylinder It is essential to know how and when NOx is formed inside an engine's combustion chamber. Nitrogen and oxygen are...
1 comment
Read more

What is Turbocharger? Turbo Lag, WasteGate Valve

What is Turbocharger? Turbo Lag, WasteGate Valve Getting a turbocharged vehicle is exciting but before you start the first thing that comes into your mind. In this article, I have shared the topics like What is Turbocharger , Turbo Lag , WasteGate Valve , and many other short questions and doubts related to the turbocharger. What is Turbocharger? How Does it Work? A turbocharger is a forced induction device which added to the engine to increase the volumetric efficiency of an engine. It is powered by the flow of exhaust gases coming out of the engine. It does not require any additional power or battery to run.  It compresses the intake air and forces more air into the intake manifold. Compressed air is cooled down with the help of an intercooler before sending it to the engine intake. Which helps to produce more power. A turbocharger helps to reduce emissions at high RPM. It is also known as a high-altitude compensation kit. Turbocharger Construction The design of the turbochar...
1 comment
Read more

CRDI (Explained In Very Simple Words)

CRDI - Common Rail Direct Injection (Hyundai) CRDI means a common rail direct injection system. It is a type of fuel delivery system used in most cars and vehicles. In this system, fuel is taken out and delivered into the engine's combustion chamber. CRDI is the name used by Hyundai and other brands that call the same system different names. Like, DICOR , CRDE, and DDIS , the three are the same but are used by various companies like TATA , Mahindra , and Maruti . What is CRDI? CRDI is the most advanced form of fuel delivery system which is fully automatic and controlled by ECU . And here, ECU works on the data provided by the actuators and sensors. This system is mostly used by Hyundai( a motor company).  Is CRDI and MPFI the same? No, both are different. CRDI is used in diesel engines whereas MPFI is used in petrol engines. Parts/components used in the CRDI system The main working components of the CRDI are: Fuel tank Fuel filter Pump Pressure Regulating Valve High-pressure Pu...
1 comment
Read more