Exhaust gas recirculation

Exhaust gas recirculation:-

In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide (NOx) emissions reduction technique used in petrol/gasoline and diesel engines. In many countries around the world, the emissions of NOx from diesel and gasoline vehicles are restricted by legislation. NOx is formed in the combustion chamber of engines, when high temperatures cause oxygen and nitrogen (both found in the air supplied for combustion) to combine.EGR works by recirculating a portion of an engine's exhaust gas back to the engine cylinders. Exhaust gas is routed back into the combustion chamber because the exhausted air is much hotter than the intake air. EGR works by diluting the N2 and providing gases inert to combustion (CO2 primarily) to act as an absorbent of combustion heat to reduce peak in-cylinder temperatures. NOx is produced in a narrow band of high cylinder temperatures and pressures.

Gas Welding

Gas Welding

Although the oxyacetylene process has been introduced long time ago it is still applied for its flexibility and mobility. Equipment for oxyacetylene welding consists of just a few elements, the energy necessary for welding can be transported in cylinders.Process energy is obtained from the exothermal chemical reaction between oxygen and a combustible gas, . Suitable combustible gases are C2H2, lighting gas, H2, C3H8 and natural gas; here C3H8 has the highest calorific value. The highest flame intensity from point of view of calorific value and flame propagation speed is, however, obtained with C2H2. C2H2 is produced in acetylene gas generators by the exothermal transformation of calcium carbide with water, Carbide is obtained from the reaction of lime and car- bon in the arc furnace.C2H2 tends to decompose already at a pressure of 0.2 MPa. Nonetheless, commercial quantities can be stored when C2H2 is dis- solved in acetone.

Acetone disintegrates at a pressure of more than 1.8 MPa, i.e., with a filling pressure of 1.5 MPa the storage of 6m3 of C2H2 is possible in a standard cylinder (40 l). For gas ex- change (storage and drawing of quantities up to 700 l/h) a larger surface is necessary, therefore the gas cylinders are filled with a porous mass (diatomite). Gas consumption during welding can be observed from the weight reduction of the gas cylinder.

ANTILOCK BRAKING SYSTEM

ABS is an abbreviation for Anti-lock Braking System. The ABS is a system that prevents wheel lock-up by automatically modulating the brake pressure during an emergency stop. By preventing the wheels from locking, it enables the driver to maintain steering control and to stop in the shortest possible distance under most conditions. It was designed to help the driver maintain some steering ability and avoid skidding while braking.ABS allows you to maintain control of the vehicle. Since four-wheel ABS prevents all wheels from skidding, it allows you to steer the vehicle and still maintain braking.

How does it work?

ABS uses wheel speed sensors to determine if one or more wheels are trying to lock up during braking. If a wheel tries to lock up, a series of hydraulic valves limit or reduce the braking on that wheel. This prevents skidding and allows you to maintain steering control.

In a recent Canadian Automobile Association survey of some 1700 members, 66% correctly associated ABS with vehicle stability in an emergency, and 53% correctly stated that ABS allows the driver to steer while braking.

Since the ABS will not allow the tire to stop rotating, you can brake and steer at the same time. The braking and steering ability of the vehicle is limited by the amount of traction the tire can generate.

If you demand steering while braking, the 100% of traction that the tire can generate will be divided between both tasks. For example, if you require 50% for steering then there is 50% of available traction left for braking. If you require 10% for steering then there is 90% left for braking. Be aware that 100% traction on a dry road is a great deal more traction than 100% traction on ice! Therefore, your vehicle is unable to steer and brake as well on a slippery surface as it can on a dry road.