Evaporative Emission Control For S.I Engine

Petrol Vapors from fuel tank escape into atmosphere by evaporation ( Or breathing ). This Vapor comes through filter cap vent or the tank vent tube. When the engine is not running , petrol will evaporate in the carburetor float chamber. It is estimated that the loses from the fuel tank are about 10% of the total Hydrocarbon Emission.

In this , fuel tank and carburetor float chamber are vented to a carbon canister. The canister absorbs the vapor and stores it. "Absorb" means the petrol vapors are trapped by stricking to the outside of the charcoal particles.

A vapor-liquid separator is provided on the top of fuel tank. Vapors go to the tap of the separator is filled with filter material that allows vapor, but not liquid to pure. A float type separator in which the float goes up and closes the orifice to the canister hose.

Carburetor float bowl has two vents. One is connected to the air cleaner and helps to compensate a clogged air cleaner. The other vents connect to charcoal canister. Various arrangements may control this vent. A special filter cap is provided on the fuel tank which maintains some pressure in the tank, that forces fuel vapors from the tank to the canister. Flow of Vapors from the fuel tank to the canister. Flow of vapors from the fuel tank may be controlled by a mechanically operated vent valve or an electrically operated solenoid valve. The throttle linkage operates the mechanical valve. By that, it allows the vapors from float chamber to canister during idling.

When the throttle is opened ,vent valve is closed. Likewise the electrical vent valve is opened with the ignition switch off. When the ignition switch is on the vent valve is closed by the energization of solenoid.

When the engine is operated, the fresh vapor enters through the canister and picks up the petrol vapor from the carbon in the canister. This air then flows into the intake manifold and becomes part of air-fuel mixture entering the engine cylinders to be burnt there. This action of clearing the trapped petrol vapor from the cannister is called purging.

Some Evaporative control systems have the purge valve in the purge line. It connects to the throttle body and discharges vapors just above the throttle valve into the intake air.

Comments

ELECTRICAL COMPARATORS AND ITS WORKING

Electrical Comparators are used as a means of detecting and amplifying small movements of a work contacting elements. An electrical comparator consists essentially of a pick-up head or transducer for converting a displacement into a corresponding change in current and a meter or recorder connected in the circuit to indicate the electrical change, calibrated to show in terms of displacement. Generally, an amplifier is needed to provide the requisite sensitivity and to match the characteristics of different parts of the circuit. Electrical comparators can be classified according to the electrical principle used in the pick-up head. Most of the comparators use either a differential transformer, an inductance bridge, a strain gauge or a capacitor as a means of detecting movement of the gauging element. There are different types of electrical comparators. One kind called an electrolimit gauge is used to check or measure the outside diameter of a roll. The objec...

SIMPLE CARBURETOR - CONSTRUCTION AND WORKING

CONSTRUCTION OF SIMPLE CARBURETOR : The main Components of Simple Carburetor are : Float Chamber, float, nozzle, venturi, throttle valve, inlet valve, and metering jet . In the float chamber, a constant level of petrol is maintained by the float and a needle valve. The float chamber is ventilated to atmosphere. This is used to maintain atmospheric pressure inside the chamber. The float which is normally a metallic hollow cylinder rises and closes the inlet valve as the fuel level in the float chamber increases to certain level. The mixing chamber contains venturi, nozzle and throttle valve. The venturi tube is fitted with the inlet manifold. This tube has a narrow opening called venturi. A nozzle is provided just below the centre of this venturi. The nozzle keeps the same level of petrol as that of the level in the float chamber. The mixing chamber has two butterfly valves. One is to allow air into the mixing chamber known as choke valve. The other is to al...

TOP POLLUTION RECORDED IN WORLD

CHERNOBYL NUCLEAR DISASTER (NUCLEAR POLLUTION) : In April 26,1986, the melt down of the Chernobyl nuclear reactor , in Russia, has leaked out the radioactive rays and radioactive materials. Effects : 1. In this Pollution nearly 2000 persons have been killed by the accident. 2. People suffered due to the illness such as, degeneration of the cells, severe bleeding, anemia, skin cancer. 3. Animals, Plants are also affected by nuclear radiation. MINAMATA EPIDEMIC (1953) : MARINE POLLUTION ( CASE STUDY ) Minamata is a small coastal village in Japan. The Chisso Chemical Company , which produces vinyl polymer plastics used organomercurial compound. The industry released its effluent into Minamata sea. The effluent containing mercury ions is converted into methyl mercury, which is highly toxic. The marine organisms like phytoplankton and zoo-planktons easily absorb the toxic methyl mercury compound. These organisms are consumed by small fishes and these are in ...

Mechinopedia For Mechanical Engineers

Search This Blog