The performance improvement of diesel generator set with exhaust air turbocharging is mainly shown in the following aspects:
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.
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.
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 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.
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.