TYPES OF BURNER USED IN BOILER

PRESSURE JET FUEL OIL BURNER



1. The basic assembly consists of a steel tube, or barrel, to which are attached swirl and orifice plates

2. The oil is supplied to the burner under pressure and , as it passes through, the burner performs two basic operations .

3. First it imparts rot ational energy to the oil as it passes through angled holes in the swirl plate .

4. Then rotating stream of oil thus formed is then forced under pressure through a small hole in the orifice plate which causes the jet to break up into fine droplets. This latter process is referred to as atomization.

5. Final result of these operations a hollow rotating cone, formed of fine
particles of oil , leaves the burner tip.

6. Burner control over the throughput of oil is obtained in two ways :-
By varying the oil supply pressure 
By changing the diameter of the hole in the orifice plate .

7. The ratio of the maximum to minimum oil throughput of the burner is known as the turn down ratio of the burner .

8. The turn down ratio with this type of burner is limited to a value of about  3·5.


ROTATING CUP TYPE OF FUEL OIL BURNER


1. A rotating cup oil burner atomizes the oil by throwing it off the edge of a tapered cup being rotated at high speeds  by an electric c motor.

2. It consists of a tapered cup fitted onto the end of a central rotating spindle mounted on ball or roller bearings.

3. The fuel oil is supplied to the inner surface of the cup through the hollow end of the spindle.

4. Here centrifugal force causes it to spread out evenly into a thin film, which then moves out along the taper until it reaches the lip of the cup.

5. where the radial components  of velocity cause  it to break up into fine particles  as it passes into the surrounding air stream. 

6. It performs two functions:
 First, supplying rotational energy to the oil.
 Second breaking it up into fine particles.

7. The final result is a hollow rotating cone of oil droplets leaving the burner.

8.The oil throughput is controlled by a regulating valve placed in the fuel supply system.

9. The wide turn down ratio available with this type of burner is a great advantage  value of over 10: 1 are possible.


STEAM BLAST JET TYPE FUEL OIL BURNER


1. These atomize the oil by spraying it int o the path of a high velocity jet of steam or air.

2. Steam flows along the central passage, and is then expanded through a
convergent divergent nozzle, where its pressure energy is converted to kinetic energy resulting in a high velocity jet of steam.

3. Oil sprayed into this jet is entrained by it, being torn to shreds and atomized in the process.

4. The exit ports are arranged tangentially, thus giving the necessary swirl to the oil droplets in order to form the hollow rotating cone of fine particles of oil.

5. The throughput of oil is controlled by varying the oil supply pressure.

6. Large turn down ratios of up to 20: 1 are therefore available with blast jet burners .



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