A one type of compressors which is used to compressed the air for diffrent diffeent application

1. GUJARAT POWER ENGINEERING AND
RESEARCH INSTITUTE
NAME:- THAKKAR VIJAYKUMAR B.
ENROLL NO :- 161043119012
TOPIC :- ROOT BLOWERS
GUIDED BY :-
PROF. RAJESH J. PATEL SIR
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2.  ROOT BLOWERS
The Root blower is as shown in fig. 7.1, consists of two lobes. For
higher pressure ratio, three or four lobes may be used. Here the
pressure of air delivered is slightly above the atmosphere. The machine
consists of a fixed casing which contains two shafts fitted with two lobe
rotors. One of the rotor is driven by electric motor and other is driven
through the gear from first rotor. The air drawn through the inlet pipe
due to rotations of the rotor . The volume of the air is entrapped
between one rotor and casing for a very short interval. Due to rotation
of lobes trapped air is carried to the discharge side. Continued rotation
of rotor, opens the trapped space to the discharge part. The air is
pushed to the receiver due to the continued rotation of rotor. The detail
operation are shown in Fig 7.2
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4. Process 0-1 : Suction at constant pressure p1.
Process 1-2 : Irreversible compression process : Gas pressure is
increased at constant volume V2 due to backflow of gas from receiver.
Process 2-3 : Gas discharge at constant pressure p2.
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5. Work done per cycle :
W = [area 0-1-2-3 on p-V diagram]
Therefore, W= (p2-p1)*Vs, J/cycle where Vs = swept volume in m^3
If Vs in m^3/min, work done in J/min.
If compression process is reversible adiabatic (isentropic) process then
work done is given by,
Therefore,
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6. From above equation it is clear that roots efficiency decrease
with increase in pressure ratio p2/p1.
The roots blower normally is designed for capacities of from 0.14
m^3/min to 1400 m^3/min and pressure ratio is 2 to 1 for single stage
and 3 to 1 for two stage roots blower.
The root blower is must suitable for scavenging and supercharging task
of I.C. engines.
 Advantage of Root Blower.
1) There is no any reciprocating parts, only two rotating parts (normally
identical in shape and size), therefore it is very simple in construction.
2) Since rotors are symmetrical about their center of rotation and hence
it is dynamically balanced.
3) No clearance and it is positive displacement type machine.
4) It delivers gas/air continously.9/28/2017 6GPERI

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