ANTILOCK BRAKING SYSTEM

Requirement of ABS Technology:

We know that when we apply brake, it pushes the brake pad on running drum or disk. For heavy loaded vehicle we need to high braking force
to stop of slow down the vehicle. This braking force generate by some means like hydraulic pressure, Air pressure etc. When the vehicle is running and we want to stop the vehicle we push the brake pedal. Due to excessive braking causes skidding. This skidding jam the wheel but due to inertia the vehicle tends to skid on the road and it became out of control from driver. This is called locking of the wheel.

This is understood by that when we run on the floor and eventually tends to stop we slip down on it. This is exactly true for the vehicle. This type of locking is harmful for driving and may cause accident. So we have to remove it use of a new safety system. This system is called ABS.

Working of ABS Technology:

We have been already explained how locking of road wheels due to excessive braking causes skidding. Modern antilock brake systems not only cause the vehicle to stop without deviating from its straight line path, these also provide directional stability since there is no skidding of the wheels.

Skidding is avoided by releasing the braking pressure just before the wheels lock up, and then reapplying the same. These releasing and reapplying the brakes in succession is what an antilock system does and this process is called pressure modulation. This system can modulate the pressure to the brakes about 15 times per second.  The feel of brake pedal in case of ABS equipped brakes is quite similar to that of conventional power brake system.

An ABS consist of an electronic control unit, one sensor on each wheel, an electrically driven hydraulic pump and a pressure accumulator. Accumulator is used to store hydraulic fluid to maintain high pressure in the braking system and to provide residual pressure for power assisted braking. ECU monitors and controls the antilock function when required. Its function is based on inputs from the wheel speed sensors and feedback from the hydraulic unit to determine whether the ABS is operating precisely and also to decide when the antilock operation is required. In some antilock braking system, a lateral acceleration sensor is also provided to monitor the side movement of the vehicle while taking a turn. This ensures proper braking during turns also.

When the front wheels of vehicle are locked, its maneuverability is reduced, whereas in case of rear wheel locking, the vehicle stability is reduced. ABS calculates the required slip rate of the wheels accurately based on the vehicle speed and the speed of the wheels and then controls the brake fluid pressure to achieve the target slip rate. Although ABS prevents complete locking of the wheel.

ABS is manufactured by Bendix, Delco Moraine, Kelsey-Hayes Lucas Girling, Bosch etc. 

IMPORTANT TECHNICAL TERMS OF AUTOMOTIVE VEHICLES

1.)AERODYNAMIC DRAG– is the air resistance to the motion of the vehicle.This consists of profile drag, induced drag, skin friction drag, interference drag, and cooling and ventilation drag.

2.)AERODYNAMIC LIFT– is the vertical component of the resultant force caused by the pressure distribution on the vehicle body.

3.)AIR BRAKE – A braking system which uses compressed air to supply the effort required to apply brakes.

4.)BOOSTER – Device incorporated in a car system (such as brake and steering),to increase pressure output or decrease amount of effort required to operate or both.

5.)CAMBER ANGLE – The outward (positive) or inward (negative) angle of the wheel centre line to absolute vertical.

6.)CASTER ANGLE – The rearward (positive) or forward (negative) angle of the steering axis to absolute vertical.

7.)CLUTCH PEDAL – A pedal in the drivers compartment that operates the clutch.

8.)CLUTCH SLIPPAGE – A condition in which the engine over revs during shifting or acceleration.

9.)DUAL BRAKE SYSTEM – Tandem or dual master cylinder to provide a brake system that has two separate hydraulic systems, one operating the front brakes, the other operating the rear brakes.

10.)EPICYCLIC GEAR– In the epicyclic gearing, at least one gear not only rotates about its own axis, but also rotates about some other axis.

What are the different uses for gas turbines?

if you want to know, What are the different uses for gas turbines then you came to right place because this gas turbine power plant lecture is about applications of gas turbine. The continued developments in gas turbine materials toward increasing the turbine inlet temperature and improving the components efficiency over the past decade has enlarged the spectrum of gas turbine applications to area such as power generation, utility industry, space, marine, automotive propulsion etc.. The main reasons of such a wide popularity being employed by the gas turbine is its advantages of simplicity, high power/weight ratio, smooth running, less maintenance, multi-fuel capability for combined cycle and reliability. The gas turbine applications can be divided in the following categories: 1) For electric power generation: The gas turbine are very popular for electric power generation because of the ability of starting and brought up-to full load quickly less cost of installation and maintenance. - Majority of the gas turbine power plants are used for peak load service with other types of power plants(steam and hydro power plants) - A large number of gas turbine power plants is also used as stand by power plants in hydro electric power plants. - Gas turbine power plants are also used as base load power plants where fuel oil or natural gas are cheap and easily available, water supply is scarce and load factor is very low(15-18%) - Now a day gas turbine plants are used to operate as combustion plants with steam plants, called as combined cycle power plant. 2) For jet propulsion engine: Every turbojet and turbo-propeller engine has a gas turbine. The turbine supplies power only to drive the air compressor in the turbojet engines while in the turbo propeller engines they may drive the propeller in addition to the compressor. 3) For supercharging: A small gas turbine run by the hot exhaust gases which is used to run supercharger(compressor) for aviation gasoline engines and for heavy duty diesel engines. 4) For marine field: A gas turbine can be also used for propulsion of ships or power generation on the ships. 5) Railway and road transport: Gas turbine can be also used for rail propulsion and high speeds road vehicles like racing cars. 6) Industry: Gas turbine are also employed for industrial applications like blast of air for blast furnace in steel industries, oil and other chemical industries. Gas turbine is also used to supply preheated combustion air, hot gases for an industrial process in petrochemical industries.

working principle of gas turbine power plant

working principle of gas turbine power plant :

in a gas turbine first air is obtained from the atmosphere and compressed in an air compressor. this high prsuure air is then pased into the combustion chamber, where it is heated due to  combustion of fuel. The product of combustion(hot gases) of high pressure and temperature passes through the passages formed by the stationary and rotating blades of gas turbine. Ajet of hot gases is made to flow over ring of blades imparting rotary motion to the shaft of turbine. A large part of power developed by the turbine rotor is consumed for a driving a compressor which supplies air under pressure of combustion chamber, while remaining power is utilized for doing the external work.

Gas turbine engines derive their power from burning fuel in a combustion chamber and using the fast flowing combustion gases to drive a turbine in much the same way as the high pressure steam drives a steam turbine. A simple gas turbine is comprised of three main sections a compressor, a combustor, and a power turbine. The gas-turbine operates on the principle of the Brayton cycle, where compressed air is mixed with fuel, and burned under constant pressure conditions. The resulting hot gas is allowed to expand through a turbine to perform work.

In an ideal gas turbine, gases undergo four thermodynamic processes: an isentropic compression, an isobaric (constant pressure) combustion, an isentropic expansion and heat rejection. Together, these make up the Brayton cycle.

In a real gas turbine, mechanical energy is changed irreversibly (due to internal friction and turbulence) into pressure and thermal energy when the gas is compressed (in either a centrifugal or axial compressor). Heat is added in the combustion chamber and the specific volume of the gas increases, accompanied by a slight loss in pressure. During expansion through the stator and rotor passages in the turbine, irreversible energy transformation once again occurs. Fresh air is taken in, in place of the heat rejection.