Ignition

Engines may be of two types: a spark ignition (S.I.) engine and a compression ignition (C.I.) engine.

Let us consider fuel-system layout and function in a spark ignition engine. There are two versions: one uses petrol for starting and vaporizing-oil for running; the other uses petrol only. The petrol/vaporizing system includes all the components of the petrol version, plus those peculiar to itself.

The essential assemblies are as follows air cleaner petrol tank, vaporized-oil tank, fuel pipes, filters, carburettor, inlet manifold, exhaust manifold, governor and controls.

The air outlet of the air-cleaner is connected by the carburettor and inlet manifold to the engine cylinders. When the air passes out of the cleaner through the carburettor, it mixes with fuel there and enters the cylinders via the inlet manifold.

In most vaporizing-oil systems, one carburettor usually handles petrol for - starting and vaporizing-oil during work. But there are a few systems that employ a carburettor for each fuel.

A small machine known as a magneto is used for producing the spark to ignite the explosive mixture in the cylinder of the engine. The main essentials of the magneto are a coil of insulated wire, a condenser and a contact breaker. The wire is wound round a soft-iron core. One end is earthed to the magneto frame, whilst the other is electrically connected to one of a pair of contact-breaker points. The contact point to which the wire is connected is electrically insulated from all but the other point, which, in turn, is earthed to the magneto body. The contacts open and close continuously in use. The condenser is "bridged" (включен параллельно) across the contact.

The secondary circuit extends outside the magneto. Its main essentials are about a mile of fine wire, a secondary lead out (or pick-up) (провод высокого напряжения) rotor, distributor cover, plug cables, spark plugs, engine cylinder block and magneto body. The fine wire is coiled round the primary, and is heavily insulated.

When the magneto shaft is rotated, a low-voltage current is magnetically induced into the primary circuit. The contact points in this circuit separate mechanically each time one of the pistons reaches the firing-point of its com­pression stroke.

The separation of the points cuts the primary current. If it were not for the condenser, the current would refuse to be cut.

When the primary current is cut, a high-voltage (approx. 10,000-20,000) current is induced in the secondary circuit.

At a fantastic speed, this current passes from the secondary coil, along the pick-up to the rotor, which is timed to deliver it to the cable attached to a given spark plug. It passes down the insulated centre of the plug and jumps the plug points - causing a spark and consequent ignition of the air/fuel mixture.

1. Study the following words:

spark ignition, pipes, manifold, inlet, magneto, wire, insulated, core, whilst, circuit, current, plug, piston, coiled, condenser.

2. Define the part of speech of the following words:

wire, heavily, insulated, refuse,separate, plug, high-voltage, magnetically, rotated,

lead out, timed, outside

3. Insert the missing adjectives:

A) The separation of the points cuts the …current.

b) A …machine known as a magneto is used for producing the spark.

С) The … essentials of the magneto are a coil of insulated wire.

d) The wire is wound … a soft-iron core.

4. Insert prepositions if necessary:

a) When the primary current is cut, a high-voltage (approx. 10,000-20,000) current is induced … the secondary circuit.

b)The contacts open and close continuously …use.

С) Engines may be … two types: a spark ignition (S.I.) engine and a compression ignition (C.I.) engine.

d) The separation … the points cuts the primary current

5. Exercises in translation:

1. The troubles C. I. (=a compression ignition engine be­cause its fuel is ignited by heat generated from the com­pression of air within its cylinders) and S.I. (=a spark ignition engine because its fuel is ignited by an electric spark) versions of the 4-cylinder water-cooled 4-stroke en­gine are subject to can be separated into those common to both, those confined to S.L, and those found only with C. I. 2. Advancement of the ignition is measured by the po­sition at the time the advanced spark occurs, in relation to T.D.C. 3. The filter should be washed in clean fuel and allowed to dry before it is replaced; do this each time the oil is changed. 4. Clean the element and inlet pipe each time the engine is decarbonized. 5. The ice had melted by the time the engine had been dismantled in the workshop.

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