Showing posts with label Technical Update. Show all posts
Showing posts with label Technical Update. Show all posts

How Air Bags Work ?

Air Bags:-
An airbag is a type of vehicle safety device and is an occupant restraint system. The airbag module is designed to inflate extremely rapidly then quickly deflate during a collision or impact with a surface or a rapid sudden deceleration. 

The purpose of the airbag is to provide the occupants a soft cushioning and restraint during a crash event to prevent any impact or impact-caused injuries between the flailing occupant and the interior of the vehicle. The airbag provides an energy absorbing surface between the vehicle's occupant and a steering wheel, instrumental panel, A-B-C- structural body frame pillars, headliner and windshield/windscreen.

There are three parts to an airbag that help to accomplish this feature:
>The bag itself is made of a thin, nylon fabric, which is folded into the steering wheel or dashboard or, more recently, the seat or door.
>The sensor is the device that tells the bag to inflate. Inflation happens when there is a collision force equal to running into a brick wall at 10 to 15 miles per hour (16 to 24 km per hour). A mechanical switch is flipped when there is a mass shift that closes an electrical contact, telling the sensors that a crash has occurred. The sensors receive information from an accelerometer built into a microchip.

>The airbag's inflation system reacts sodium azide (NaN3) with potassium nitrate (KNO3) to produce nitrogen gas. Hot blasts of the nitrogen inflate the airbag.


1.)CELSIUS – The scale of changes of temperature which uses 0 degree as the freezing point and 100 degree as the boiling point for water at standard pressure.

2.)CHARLE’S LAW – At constant pressure, the volume of a gas is proportional to its absolute temperature. At constant volume, the pressure is proportional to its absolute temperature.

3.)CLOSED SYSTEM – The system which will have boundaries across which both heat and work can penetrate, but no mass will be permitted to cross them.

4.)Cp– Specific heat at constant pressure-Heat to be supplied to raise the temperature of 1 kg of gas through 1°C, the pressure being kept constant (in other words external work is done).

5.)Cv– Specific heat at constant volume-Heat to be supplied to raise the temperature of 1 kg of gas through 1°C, the volume being kept constant (in other words no external work is done).

6.)DALTON’S LAW OF PARTIAL PRESSURES – At a common temperature, a mixture of gases will exert on the sides of the vessel a total pressure equal to the sum of the pressures which each constituent would exert separately if it alone occupied the vessel.

7.)DRY SATURATED STEAM – Saturated steam, as generated from water, that contains no moisture in suspension.

8.)EQUIVALENT EVAPORATION – Amount of water in kg. that would be evaporated from water at 100°C into steam at 100°C and 1.03 kscm, by the heat put into steam actually evaporated in one hour by 1 kg of fuel.

9.)FACTOR OF EVAPORATION – A quantity which when multiplied by the amount of steam generated at a given pressure from water at a given temperature, gives the equivalent evaporation from and at 100°C.

10.)FLOW WORK – The product PV (pressure and specific volume) represents flow work in a steady flow system.