1. Improve
power performance
After supercharging, the
circulating air flow into the cylinder increases greatly. The circulating fuel
supply increases accordingly, and the power of the diesel engine increase
obviously. Turbocharging can increase the power of a diesel engine by 30% or
more. At the same time, due to the increase of air burst pressure, friction
loss is increased, but the effective power of diesel engine is increased more,
so the mechanical efficiency of diesel engine is improved.
2. Improve
economic performance
The increase of mechanical
efficiency after supercharging reduces the fuel consumption. The increase of
intake pressure not only improves the scavenging process, but also makes the
pump work become positive, and the fuel consumption rate decrease. In addition,
the excess air coefficient after supercharging will be increased accordingly,
so that the fuel oil will become more perfect and the fuel consumption will
decrease.
3. Harmful
emission reduction
Due to the increase of excess air
coefficient, the oxygen content in the mixture is relatively increased, and the
combustion is more complete, and the CO, hydrocarbons and smoke content in the
exhaust air are decreased.
After the turbocharging of the diesel
engine, it also brings some problems, mainly as follows:
1. The compression pressure and
burst pressure are increased after supercharging, the load of the parts is
increased, and the wear is aggravated.
2. Due to the increase of heat
load of diesel engine after supercharging, the heat load of piston group,
cylinder (wall) and exhaust valve are increased, and the material strength is
decreased.
Structure and working principle
of exhaust air turbocharger for diesel generator set
The flow-off exhaust air
turbocharger of diesel generator set consists of two parts, including exhaust
air turbine and compressor. The compressor on the left and the exhaust turbine
on the right, coaxial. The turbine inlet is connected with the cylinder exhaust
pipe, and the outlet is connected with the diesel exhaust. The compressor inlet
is connected with the air filter of the diesel engine inlet and the outlet end
is connected with the cylinder inlet duct. The compressor inlet is connected
with air filter of the diesel engine inlet and the outlet end is connected with
the cylinder inlet duct.
1. Exhaust
driven air turbine
Exhaust air turbine consists of
volute, nozzle ring and working impeller. The nozzle ring consists of the
nozzle ring, the outer ring and the nozzle blade. The channels formed by the
nozzle blades form a contraction form from the inlet to the outlet. The working
impeller is composed of a rotary disc and am impeller, and is fixed with a
working blade on the outer edge of the rotary disc. A nozzle ring and adjacent
working impellers from a stage. Only one stage of the turbine is called a
single-stage turbine, and most turbochargers use single-stage turbines. When
the diesel engine works, the exhaust air passes through the exhaust pipe and
flows into the nozzle ring at a certain pressure and temperature. Because the
ares of the nozzle ring decreases gradually, the flow rate of the exhaust air
inside the nozzle ring increases. The high-speed exhaust from the nozzle enters
the passage in the impeller blade and the air is forced to turn. As a result of
centrifugal force, the air pressure is pressed to the concave surface of the
blade, which causes the pressure difference between the concave and convex
surfaces of the blade, and the combined force of the pressure difference acting
on all the blades produces an impact moment on the shaft of the rotor. This
causes the impeller to rotate in the direction of torque, and the exhaust air
from the impeller passes through the center of the turbine from the outlet.
2. Booster
The compressor is mainly composed
of inlet, working impeller, expanding press and volute. The compressor is
coaxial with the exhaust turbine, driven by the exhaust turbine, making the
working turbine rotate at high speed. The working turbine is the main component
of a compressor. Usually it consists of forward curved guide wheel and a
semi-open working wheel. The two parts are mounted on a rotating shaft
respectively. The straight blades are arranged along the radial direction on
the working wheel, and the expanding airflow channels are formed between the
blades. Because of the rotation of the working wheel, the inlet air is
compressed by centrifugal force, and the pressure, temperature and velocity of
the air are increased when thrown to the outer edge of the working wheel. Air
flow transforms the kinetic energy of air into pressure energy through
diffusive action. In the exhaust volute, the kinetic energy of air is gradually
transformed into pressure energy.
Cleaning and
inspection of exhaust air turbocharger for diesel generator set
Cleaning of exhaust air
turbocharger
1. Soaking parts in non-corrosive
cleaning fluids with carbon and sediment softens then. Among them, the thicker
layer of carbon deposit in the return cavity of the middle shell must be
completely eliminated.
2. Only plastic scrapers or mane
brushes can be used to clean up the deposits on aluminum and copper parts.
3. When cleaning with steam
impact, the journal and other bearing surface should be protected.
4. Apply compressed air to clean
all parts of the lubricating oil channel.
Inspection
of main parts of exhaust air turbocharger
1. Floating-ring bearing
The wear of the end surface and
the inner and outer surfaces of the floating ring was observed. In general, the
lead-tin coating on the inner and outer surface still exists after a long
period of operation, but the outer surface is more worn, and there is a slight
trace of wear on the end surface of the oil tank, which belongs to the normal
condition. The groove on the surface of the floating ring should be replaced
because the lubricating oil is not clean, more serious or beyond the wear
limit.
2. Middle
case
Observe whether there are
scratches and coke deposits on the surface adjacent to the back of the
compressor impeller and the black of the turbine impeller. If there is a
phenomenon of spraying, the floating bearing has a large wear and the surface
of the bearing inner hole is damaged, the inner hole surface should be ground
or wiped to remove the trace of copper and lead on the inner hole surface.
3.
Compressor impeller
Check the impeller back and blade
tip for rubbing phenomenon, check blade bending and fracture, blade inlet and
outlet edge cracks.
4. Elastic
seal ring
Check the wear and carbon
deposition on both sides of the ring, measure the thickness of the ring and the
opening clearance in free state should not be less than 2 mm, if less than 2mm,
it should be replaced.
5.
Compressor end seal
Check whether there is in the
contact part of the elastic seal ring pedestal hole between the air seal plate
and the middle shell at the turbine end.
Comments
Post a Comment