Emission Control Systems

Understanding Emission Control Systems: Types and Functions

Introduction:

Remember the time when the nation experienced a significant drop in air pollution during a lockdown? It highlighted the importance of reducing harmful emissions to create a cleaner and healthier environment. One crucial technology that helps minimize vehicle emissions is the emission control system. In this article, we will delve into the concept of emission control systems, explore the different types, and understand how they function to mitigate harmful pollutants.

What is an Emission Control System?

An emission control system refers to a series of functions designed to keep vehicle emissions at the lowest possible levels. These systems play a vital role in reducing harmful pollutants such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxide (NOx). Emission control methods can be broadly classified into two categories: prevention or active methods and destruction or passive methods. While modern engines have seen improvements in reducing emissions through various advancements, certain emission control methods are necessary to meet stringent emission norms effectively.

1. Catalytic Converters:

Catalytic converters are a popular and crucial component in all vehicles for destroying tailpipe emissions. Over the years, catalytic converters have evolved, with modern three-way converters capable of controlling CO, HC, and NOx emissions. These converters work by converting harmful gases into carbon dioxide (CO2) and water (H2O). Inside the cylindrical canister of a catalytic converter, precious metals like platinum (Pt), palladium (Pd), and rhodium (Rh) facilitate the oxidation process, transforming harmful gases into less harmful compounds.

Efficiency is essential for the catalytic converter to work optimally, and to address this, many car manufacturers employ a secondary battery to pre-heat the converter during cold starts. This ensures that emissions are controlled even when the engine is not operating at its peak temperature, making catalytic converters a critical emission control device.

2. Evaporative Emission Control:

The evaporative emission control system not only reduces emissions but also enhances fuel efficiency in vehicles. It prevents the evaporation of hydrocarbons from the fuel tank by channeling them into the combustion chamber. At the core of this system lies the carbon canister, which stores fuel vapors via loose chemical bonds. The purge solenoid, controlled by the onboard computer module, releases these stored vapors, directing them into the intake manifold for combustion.

This process not only saves fuel but also prevents harmful vapors from escaping through the fuel tank lid during refueling. By injecting the vapors into the engine's intake manifold through the Positive Crankcase Ventilation (PCV) valve, the evaporative emission control system aids in controlling emissions effectively.

3. Exhaust Gas Recirculation (EGR):

Exhaust Gas Recirculation (EGR) is a valuable method for reducing emissions and maintaining lower engine temperatures. Typically found in turbocharged petrol and diesel engines, EGR helps reduce NOx emissions in diesel engines and enhances efficiency in petrol engines.

The EGR system channels some of the exhaust gases back into the intake manifold, effectively reducing the combustion temperature and overall emissions. These exhaust gases are already inert, meaning they have already undergone combustion, so they limit the combustion capacity in each cylinder, resulting in lower heat production and subsequently fewer emissions. However, it's worth noting that EGR may slightly reduce engine power and typically only functions when the engine is running at optimal operating temperatures.

4. Diesel Particulate Filter (DPF):

The Diesel Particulate Filter (DPF) is a honeycomb-like filter installed in the exhaust manifold, responsible for trapping soot and solid particles after combustion. When the filter reaches a certain capacity, it undergoes regeneration, where the trapped substances are burned off. Car manufacturers recommend specific driving cycles to optimize the DPF's health, as slow speeds can hinder the regeneration process.

Modern cars often have systems that inform the driver about the DPF's activity levels and seamlessly carry out the regeneration process, ensuring the filter remains effective in controlling emissions.

5. Selective Catalyst Reduction (SCR):

Selective Catalyst Reduction (SCR) is an advanced emission control technology primarily used in high-capacity diesel engines. Also known as Adblue, SCR employs a form of liquid urea called Diesel Exhaust Fluid (DEF). When sprayed into the exhaust, Adblue reacts with NOx, converting it into nitrogen, water, and CO2. This conversion results in significantly less harmful gases being expelled through the exhaust pipe, helping diesel engines comply with stringent emission norms, such as BS6.

Frequently Asked Questions (FAQ) about Emission Control Systems

Q1: Does the catalytic converter affect emissions?

Answer: Yes, the catalytic converter plays a crucial role in reducing emissions in a vehicle. It acts as the main emission control unit and is responsible for trapping and converting harmful gases, such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxide (NOx), into less harmful compounds like nitrogen, water, and carbon dioxide. Without a catalytic converter, a vehicle would emit significantly higher levels of harmful pollutants, posing a threat to the environment and air quality.

Q2: How does the emission control system work?

Answer: The emission control system works through a series of interconnected processes, primarily falling into two categories: preventive and destructive methods. The system is designed to minimize emissions without compromising the vehicle's efficiency and performance. It employs technologies like catalytic converters, evaporative emission control, exhaust gas recirculation (EGR), diesel particulate filters (DPF), and selective catalyst reduction (SCR) to reduce harmful pollutants and promote cleaner air.

Q3: What are common faults with the emission control system?

Answer: The emission control system is complex, and modern vehicles are equipped with onboard computers that monitor its performance. One common issue is the clogging of the diesel particulate filter (DPF), which can be indicated on the vehicle's instrument cluster. In such cases, the car may require a regeneration process to clear the clog. If problems persist, it's best to consult an experienced mechanic for diagnosis and repairs.

Q4: How can I fix issues with the emission control system?

Answer: Due to the intricacies and concealed locations of emission control system components, it is recommended to seek assistance from a qualified mechanic when encountering problems. Attempting DIY fixes without proper knowledge and tools may lead to further complications. An experienced mechanic can diagnose the issue accurately and carry out the necessary repairs or replacements.

Q5: Why is the emission control system sometimes not ready?

Answer: Many emission control system components require specific conditions, such as optimum temperature and a sufficient concentration of oxygen, to function effectively. For instance, the catalytic converter and exhaust gas recirculation (EGR) may not operate efficiently when the engine temperature is low. Car manufacturers often tune these systems to function optimally under various environmental conditions, ensuring their effectiveness in reducing emissions throughout the vehicle's operation.

Conclusion:

Emission control systems are vital for minimizing harmful vehicle emissions and improving air quality. Through the use of technologies like catalytic converters, evaporative emission control, EGR, DPF, and SCR, we can work towards a cleaner and greener environment. As automotive technology continues to advance, these emission control methods will play an increasingly significant role in creating a sustainable future for our planet.