Economical operation of modern engines is not imaginable without exhaust gas turbochargers. The already high requirements for propulsion systems and energy producing units concerning efficiency and longevity are being continuously increased under the aspects of fuel utilization and environmental load. In this, the components of exhaust gas turbochargers are subject to extreme operating conditions.
1) Exhaust gases of up to 650 °C continuously flow through the turbine and heat up its components, without an own counteractive cooling system. Especially the shaft bearing must withstand the high operating temperatures without the lubricating film ever breaking.
2)On the compressor side, the air is heated to over 200 °C.
3) The high temperatures lead to extreme thermal loads of the material at many locations.
4) Speeds are extremely high: The MAN Diesel exhaust gas turbochargers are operated with speeds ranging from 10 000 to 35 000 rpm, depending on size. In this, circumferential velocities of 530 m/s and more are reached at the compressor wheel, which amounts to 1.7 times the speed of sound or 2 000 km/h.
5)The centrifugal forces are extremely high: Forces of several 100 kN can easily apply at the foot of the turbine blade.
6)The complete gas exchange of the engine is performed by the exhaust gas turbocharger. For this machine, the throughput of combustion air can amount to 34 m3/s.
7)Simplified, it can be said that approx. 1/3 of the power produced by the engine is converted on minute space within the exhaust gas turbocharger. These requirements can be fulfilled only with use of the most recent material and manufacturing technologies, introduced into the series by MAN Diesel with use of the latest developmental results, and based on decades of experience in building diesel engines and exhaust gas turbochargers.
Turbochargers consist mainly of a turbine and a compressor, which are seated on the same shaft. The exhaust gas of the engine drives the turbine;the compressor draws in fresh air and compresses.
The turbocharger consists of the following main subassemblies:
1)Rotating element
Turbine wheel and shaft are firmly connected together; the turbine
blades are individually set into the turbine wheel. The compressor wheel is mounted on the shaft and can be removed.
2)Bearing casing:
The interior bearing of the rotating element consists of two bearing
bushes and a thrust bearing. Lubrication of the bearing is carried out via the lube oil circuit of the engine. Lubricating oil pipes, lube oil venting and sealing air pipes are integrated in the bearing casing.
3)Gas-admission casing:
The nozzle ring is built into the gas-admission casing. It enables opti-
mum adaptation of the turbocharger to the engine.
4)Gas outlet casing:
The gas outlet diffuser in the outlet casing is flow-technically optimized.
The outlet casing is fitted with 5 offset connections for the washing wateroutlet. Depending on the build-in position of the turbocharger, the connection positioned lowest is used.The outlet casing is designed so that together with the flanged-on gas-admission casing, it offers optimum burst protection for the turbine wheel.
5)Silencer or air intake casing
Compressor casing optional with one or two discharge connections.
The compressor casing houses the diffuser, which allows for optimum adaptation of the turbocharger to the engine. Additionally, the diffuser functions as burst protection.
OPERATION-The exhaust gas of the engine flows through the gas-admission casing and the nozzle ring, and runs axially onto the turbine wheel. The exhaust gasdrives the turbine wheel; in this process, the energy contained in the exhaust gas is transformed into mechanical rotation energy at the turbine wheel. As the turbine wheel and the compressor wheel are seated on the same shaft,the compressor wheel is driven at the same time. The exhaust gas exits the turbocharger through the gas outlet diffuser and the gas outlet casing. The compressor wheel draws in fresh air through the silencer or the intake casing and the insert. The fresh air is compressed in the compressor wheel, diffuser and compressor casing. The compressed fresh air is forced into the cylinders of the engine via charge air cooler and charge air pipe.The rotating element of the turbocharger is led radially by two bearing bushes, which are situated in the bearing casing between turbine wheel and compressor wheel. The thrust bearing positioned on the compressor side not only handles the axial guidance, but also transfers the thrust in axial direction. A bearing body holds the bearing seat and at the same time is used as insulation against the hot exhaust-gas side of the turbocharger. The turbocharger is intended for use on diesel and heavy-fuel-oil engines. It produces the required amount of air for engine operation and the charge
pressure. Any application beyond this must be discussed with and
approved by MAN Diesel , otherwise MAN Diesel will refuse any and all
liability.
LUBE OIL DIAGRAM
The lubrication and cooling of the high-stressed bearing bushes in the turbocharger takes place by means of a lube oil system, which is integrated mainly in the bearing casing.
The lubricating oil is supplied from the lube oil system of the engine to the lube oil system of the turbocharger via a supply pipe (1). An orifice (2) adjusts the required lube oil pressure. The lube oil pressure is controlled behind the non-return valve (4) by means of a pressure monitor (5) and a pressure gauge
(6). Air bubbles may not be contained in the oil being supplied. This could lead to bearing damage at lubrication of the turbocharger.
The lubrication oil flows through the non-return valve (4) into the turbo-
charger casing, from where it reaches the thrust bearing (8) and the bearing bushes (9) via passages in the bearing casing (7) and the bearing body. The lubricating oil flows to the gap between bearing and shaft as well as to the face-sided lubrication point of the thrust bearing via bores in the bearing bushes. The lubricating oil leaves the gap between the bearing and the shaft
and is splashed against the wall of the bearing casing by the rotation of the shaft. The lubricating oil exits the bearing casing through the drain pipe (10) and flows back into the lube oil system of the engine (11).
The gravitiation tank (18) above the turbocharger ensures the lubrication of the bearings after the engine is switched off, while the rotating element runs out and the bearings still must cool down.
During operation the non-return valve (13) is shut. The gravitiation tank is
filled with lubricating oil via a small bypass bore in the valve plate of the non-return valve (13). As soon as the lube ail level reaches the height of the overflow pipe (17) , lubricating oil flows back into the bearing casing through the overflow pipe.
If the engine is shut off, the pressure in the lube oil system is reduced. This causes the non-return valve (13) to open and the non-return valve (4) to shut.
Das lubrication oil flows out of the gravitiation tank back into the turbo-
charger and cools the bearing points in the process.In case of a „blackout“, the gravitation tank serves as an oil reservoir for approx. 10 seconds of emergency operation of the turbocharger without lube-oil supply.
BEARING HOUSING ARRANGEMENT;
SEALING AIR SYSTEM(Check the diagram below)--The sealing air prevents hot exhaust gas from entering the bearing casing and the lubricating oil from seeping into the turbine (oil coke). Additionally,undesirable axial thrust on the bearing bush is reduced.The sealing air system is fully integrated in the bearing casing (11). A part of the air compressed by the compressor wheel (C) is diverted and flows out of the compressor casing (1) into a ring duct (2) in the bearing casing. From
there, the air is led into the sealing air pipe (4), whereby an orifice (3) reduces the pressure to the required sealing air pressure. The air is led to a ring duct(5) on the turbine side of the bearing casing. There, the sealing air emerges
between shaft and turbine labyrinth.
▪ A small amount of the sealing air flows back into the bearing casing,
presses against the turbine-sided bearing bush (9), and thus holds back
the lubricating oil.
▪ The other part of the sealing air is led past the rotor shaft, through the
labyrinth seal on the turbine side, and into the gas outlet casing (12).
This develops a thrust-compensating piston between the labyrinths on the
turbine disc and bearing casing.
The sealing air pressure is factory set via the orifice (3) and must not be
controlled or readjusted by the user.
2.Fit the hanging sling tool on compressor casing and then remove it. The compressor casing houses the diffuser.
3.Remove the diffuser from compressor casing.
4. Take out the gas admission casing .The nozzle ring is built into the gas-admission casing.
7. Now removing the compressor.
8.Now removing the labyrinth disc from compressor side.
1) Exhaust gases of up to 650 °C continuously flow through the turbine and heat up its components, without an own counteractive cooling system. Especially the shaft bearing must withstand the high operating temperatures without the lubricating film ever breaking.
2)On the compressor side, the air is heated to over 200 °C.
3) The high temperatures lead to extreme thermal loads of the material at many locations.
4) Speeds are extremely high: The MAN Diesel exhaust gas turbochargers are operated with speeds ranging from 10 000 to 35 000 rpm, depending on size. In this, circumferential velocities of 530 m/s and more are reached at the compressor wheel, which amounts to 1.7 times the speed of sound or 2 000 km/h.
5)The centrifugal forces are extremely high: Forces of several 100 kN can easily apply at the foot of the turbine blade.
6)The complete gas exchange of the engine is performed by the exhaust gas turbocharger. For this machine, the throughput of combustion air can amount to 34 m3/s.
7)Simplified, it can be said that approx. 1/3 of the power produced by the engine is converted on minute space within the exhaust gas turbocharger. These requirements can be fulfilled only with use of the most recent material and manufacturing technologies, introduced into the series by MAN Diesel with use of the latest developmental results, and based on decades of experience in building diesel engines and exhaust gas turbochargers.
Turbochargers consist mainly of a turbine and a compressor, which are seated on the same shaft. The exhaust gas of the engine drives the turbine;the compressor draws in fresh air and compresses.
1)Rotating element
Turbine wheel and shaft are firmly connected together; the turbine
blades are individually set into the turbine wheel. The compressor wheel is mounted on the shaft and can be removed.
2)Bearing casing:
The interior bearing of the rotating element consists of two bearing
bushes and a thrust bearing. Lubrication of the bearing is carried out via the lube oil circuit of the engine. Lubricating oil pipes, lube oil venting and sealing air pipes are integrated in the bearing casing.
3)Gas-admission casing:
The nozzle ring is built into the gas-admission casing. It enables opti-
mum adaptation of the turbocharger to the engine.
4)Gas outlet casing:
The gas outlet diffuser in the outlet casing is flow-technically optimized.
The outlet casing is fitted with 5 offset connections for the washing wateroutlet. Depending on the build-in position of the turbocharger, the connection positioned lowest is used.The outlet casing is designed so that together with the flanged-on gas-admission casing, it offers optimum burst protection for the turbine wheel.
5)Silencer or air intake casing
Compressor casing optional with one or two discharge connections.
The compressor casing houses the diffuser, which allows for optimum adaptation of the turbocharger to the engine. Additionally, the diffuser functions as burst protection.
OPERATION-The exhaust gas of the engine flows through the gas-admission casing and the nozzle ring, and runs axially onto the turbine wheel. The exhaust gasdrives the turbine wheel; in this process, the energy contained in the exhaust gas is transformed into mechanical rotation energy at the turbine wheel. As the turbine wheel and the compressor wheel are seated on the same shaft,the compressor wheel is driven at the same time. The exhaust gas exits the turbocharger through the gas outlet diffuser and the gas outlet casing. The compressor wheel draws in fresh air through the silencer or the intake casing and the insert. The fresh air is compressed in the compressor wheel, diffuser and compressor casing. The compressed fresh air is forced into the cylinders of the engine via charge air cooler and charge air pipe.The rotating element of the turbocharger is led radially by two bearing bushes, which are situated in the bearing casing between turbine wheel and compressor wheel. The thrust bearing positioned on the compressor side not only handles the axial guidance, but also transfers the thrust in axial direction. A bearing body holds the bearing seat and at the same time is used as insulation against the hot exhaust-gas side of the turbocharger. The turbocharger is intended for use on diesel and heavy-fuel-oil engines. It produces the required amount of air for engine operation and the charge
pressure. Any application beyond this must be discussed with and
approved by MAN Diesel , otherwise MAN Diesel will refuse any and all
liability.
LUBE OIL DIAGRAM
The lubrication and cooling of the high-stressed bearing bushes in the turbocharger takes place by means of a lube oil system, which is integrated mainly in the bearing casing.
The lubricating oil is supplied from the lube oil system of the engine to the lube oil system of the turbocharger via a supply pipe (1). An orifice (2) adjusts the required lube oil pressure. The lube oil pressure is controlled behind the non-return valve (4) by means of a pressure monitor (5) and a pressure gauge
(6). Air bubbles may not be contained in the oil being supplied. This could lead to bearing damage at lubrication of the turbocharger.
The lubrication oil flows through the non-return valve (4) into the turbo-
charger casing, from where it reaches the thrust bearing (8) and the bearing bushes (9) via passages in the bearing casing (7) and the bearing body. The lubricating oil flows to the gap between bearing and shaft as well as to the face-sided lubrication point of the thrust bearing via bores in the bearing bushes. The lubricating oil leaves the gap between the bearing and the shaft
and is splashed against the wall of the bearing casing by the rotation of the shaft. The lubricating oil exits the bearing casing through the drain pipe (10) and flows back into the lube oil system of the engine (11).
The gravitiation tank (18) above the turbocharger ensures the lubrication of the bearings after the engine is switched off, while the rotating element runs out and the bearings still must cool down.
During operation the non-return valve (13) is shut. The gravitiation tank is
filled with lubricating oil via a small bypass bore in the valve plate of the non-return valve (13). As soon as the lube ail level reaches the height of the overflow pipe (17) , lubricating oil flows back into the bearing casing through the overflow pipe.
If the engine is shut off, the pressure in the lube oil system is reduced. This causes the non-return valve (13) to open and the non-return valve (4) to shut.
Das lubrication oil flows out of the gravitiation tank back into the turbo-
charger and cools the bearing points in the process.In case of a „blackout“, the gravitation tank serves as an oil reservoir for approx. 10 seconds of emergency operation of the turbocharger without lube-oil supply.
BEARING HOUSING ARRANGEMENT;
SEALING AIR SYSTEM(Check the diagram below)--The sealing air prevents hot exhaust gas from entering the bearing casing and the lubricating oil from seeping into the turbine (oil coke). Additionally,undesirable axial thrust on the bearing bush is reduced.The sealing air system is fully integrated in the bearing casing (11). A part of the air compressed by the compressor wheel (C) is diverted and flows out of the compressor casing (1) into a ring duct (2) in the bearing casing. From
there, the air is led into the sealing air pipe (4), whereby an orifice (3) reduces the pressure to the required sealing air pressure. The air is led to a ring duct(5) on the turbine side of the bearing casing. There, the sealing air emerges
between shaft and turbine labyrinth.
▪ A small amount of the sealing air flows back into the bearing casing,
presses against the turbine-sided bearing bush (9), and thus holds back
the lubricating oil.
▪ The other part of the sealing air is led past the rotor shaft, through the
labyrinth seal on the turbine side, and into the gas outlet casing (12).
This develops a thrust-compensating piston between the labyrinths on the
turbine disc and bearing casing.
The sealing air pressure is factory set via the orifice (3) and must not be
controlled or readjusted by the user.
STEPS FOR OVERHAULING TURBOCHARGER ARE AS FOLLOWS;
1)Remove the retaining nut from the silencer , and then remove the silencer.
2.Fit the hanging sling tool on compressor casing and then remove it. The compressor casing houses the diffuser.
5. Measure the clearance between the gas outlet guide and turbine blade.
7. Now removing the compressor.
