Working of Silencer Or Exhaust System

How does my exhaust system work?

It's only when you hear or drive a car with a damaged silencer that you realise what a huge difference it makes to reducing noise levels.

And the way a silencer works is quite fascinating. It contains a deceptively simple set of tubes that are finely tuned to reflect the sound waves produced by an engine so that they cancel each other out.
If there is a hole in the silencer then the sound waves are no longer forced through the tubes and escape outside - increasing the noise level.

Other key components of your exhaust include exhaust pipes that are designed specifically for each car model and route exhaust fumes to the exit at the back of the car.

The exhaust manifold acts as a funnel. It collects exhaust gases from all cylinders of the engine then releases them through a single opening, often referred to as the front pipe.

The exhaust centre section works with the silencer to reduce noise and the tail pipe at the rear carries gases away from the vehicle. All of the components of an exhaust system are connected with a series of clamps, hangers, flanges and gaskets.

 

How Catalytic Converters Reduce Pollution

In chemistry, a catalyst is a substance that causes or accelerates a chemical reaction without itself being affected. Catalysts participate in the reactions, but are neither reactants nor products of the reaction they catalyze. In the human body, enzymes are naturally occurring catalysts responsible for many essential biochemical reactions.

In the catalytic converter, there are two different types of catalyst at work, a reduction catalyst and an oxidation catalyst. Both types consist of a ceramic structure coated with a metal catalyst, usually platinum, rhodium and/or palladium. The idea is to create a structure that exposes the maximum surface area of catalyst to the exhaust stream, while also minimizing the amount of catalyst required, as the materials are extremely expensive. Some of the newest converters have even started to use gold mixed with the more traditional catalysts. Gold is cheaper than the other materials and could increase oxidation­, the chemical reaction that reduces pollutants, by up to 40 percent

Most modern cars are equipped with three-way catalytic converters. This refers to the three regulated emissions it helps to reduce.

­The reduction catalyst is the first stage of the catalytic converter. It uses platinum and rhodium to help reduce the NOx emissions. When an NO or NO2 molecule contacts the catalyst, the catalyst rips the nitrogen atom out of the molecule and holds on to it, freeing the oxygen in the form of O2. The nitrogen atoms bond with other nitrogen atoms that are also stuck to the catalyst, forming N2. For example:

2NO => N2 + O2 or 2NO2 => N2 + 2O2

2NO => N₂ + O₂ or 2NO₂ => N₂ + 2O₂

Ceramic honeycomb catalyst structure.

The oxidation catalyst is the second stage of the catalytic converter. It reduces the unburned hydrocarbons and carbon monoxide by burning (oxidizing) them over a platinum and palladium catalyst. This catalyst aids the reaction of the CO and hydrocarbons with the remaining oxygen in the exhaust gas. For example:
2CO + O₂ => 2CO₂

There are two main types of structures used in catalytic converters -- honeycomb and ceramic beads. Most cars today use a honeycomb structure.