The noise of generator set is mainly comes from engine and generator. To
reduce the noise of the generator set, it is necessary to control the noise
source. This article will show you the detailed information about the genset
noise source as well as the solution.
The main noise source of
engine is as follows:
Induction
noise
Exhaust
noise
Combustion
noise
Mechanical
noise
Cooling
fans noise
The
main noise source of generator is as follows:
Ventilation
noise
Electromagnetic
noise
Mechanical
noise
Main noise source of
engine
1. Air
intake and exhaust system noise is the most powerful noise source of the
engine.
The
main source of intake noise is as follows:
1) The
pressure fluctuation of air in the intake pipe, which results in low frequency
noise.
2) The
air flows through the flow area of the intake valve at high speed, which
results in high frequency eddy noise.
3) The
noise of turbocharger compressor
4) The
noise of scavenging pump for two-stroke diesel engine
The
main source of exhaust noise is as follows:
1) The
pressure fluctuation of exhaust gas in the exhaust pipe, which results in low
and intermediate frequency noise.
2) High
frequency eddy current noise at the flow area of exhaust valve.
2.
Combustion noise
Combustion
noise is the main noise source of internal combustion engine. The burning of
combustible mixture in the cylinder causes a sharp change of gas pressure. The
piston, cylinder liner, connecting rod, piston pin and crankshaft parts are
subjected to impact load, which causes structural vibration and noise.
3.
Mechanical noise
The
main components to cause mechanical noise include piston, cylinder head, cylinder
liner, cylinder block, connecting rod, piston pin, crankshaft, valve gear,
drive gear and fuel injection pump, etc. Therefore, the design of these parts,
manufacturing quality as well as the material selection have an important
effect on the noise. The diesel engine stiffness, rotating speed, and movement
clearance are the main factors to afftect the mechanical noise.
4.
Cooling fan noise
It
results from the sound of air being moved at high speed across the engine and
through the radiator.
Main
noise source of generator
1.
Ventilation noise
It
includes fan and other ventilation equipment as well as the gas weirl noise
formed by rotor. Fan rotation makes cooling gas periodic fluctuation so as to
produce the single frequency noise. Resonance of thin wall parts in wind path,
or the “piping” produced due to unreasonable return circuit design.
2.
Electromagnetic noise
The
noise refers that due to the interaction of stator and rotor magnetic field in
generator air gap, it produces radial force changing with time and space,
causing stator core and engine base to vibration due to periodic deformation
over time so as to produce noise.
3.
Mechanical noise
The
mechanical noise of generator includes the mechanical vibration noise (caused
by centrifugal force that is produced by rotor mechanical unbalance), bearing
ventilation noise, brush connector ring or commutator sliding contact noise,
and the axial vibration noise of end cap excited by bearing vibration.
Noise Reduction Measures
There
is no doubt that it will have certain effects on the surrounding environment
and personnel if the working noise of the machine is too large. Therefore, some
necessary noise reduction measures should be taken. In addition to reduce the
noise of generator set itself, it is also important to carry out special design
for generator room.
1. Room
sound insulation
The
room door and window should adopt fireproof sound insulation door and window.
Besides, the sound insulation requirement of brick wall needs more than 40dB
(a). On the other hand, it is also important to eliminate sound paths through
cracks in doors or walls.
2. Air
intake and exhaust
After
dealing with room sound insulation, you should turn to solve the problem
of ventilation and heat dissipation in the generator room. The air inlet shall
be in the same line as the generator set and the air outlet. The air inlet
shall be equipped with resistive chip muffler. Due to the air inlet pressure
loss is within the allowable range, it can make the air flow in the room reach
balance naturally, meanwhile, the effect of ventilation and heat dissipation is
obvious.
3.
Exhaust muffler
In
general, generator set is always equipped with an exhaust muffler to limit
exhaust noise from the machine. Exhaust silencer comes in a wide variety of
types, it is usually divided into two types: chamber-type silencer and spiral
type device. The chamber-type device tends to be more effective, but the
spiral-type device is more compact and may provide sufficient attenuation for
many equipments.
4.
Sound absorption treatment
In the
machine room, the five walls except for the ground can be used for sound
absorption treatment. According to the frequency spectral characteristic of the
generator set, the perforation board resonance sound absorption structure is
adopted. In addition, acoustic insulation – sound-absorbing materials are
available for lining air ducts and covering walls and ceilings. Reducing noise
at a wall covered in sound absorbing material can be very effective.
5. Air
exchange in the room
Good
sound insulation in the generator room will make there is no air convection in
the machine room when the closed water-cooled generator set power off, the high
temperature in the room can’t be lowered in time. To solve the problem, you can
adopt low noise axial flow fan and equip with a resistive chip muffler.
6.
Cooling air attenuation
Inlet
and outlet air attenuation baffles can help reduce the noise produced by the
cooling air as it moves across the engine and through the radiator.
7. Unit
vibration isolation
Before
installing the generator set,
users should strictly follow the relevant information provided by the
manufacturer to carry out vibration isolation treatment so as to avoid the
long-distance transmission of structural sound, which continuously radiate air
noise in the propagation so that the factory noise level fail to reach
standard. For the generator units that are required to deal with due to
exceed standard, the vibration of the ground near the unit must be measured. If
the vibration is obvious, the vibration isolation treatment of the generator
set must be carried out first.
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