7 семестр (Бормотов А) / 1man_bw_l23_30_chn_23_30_instruktsiya_po_ekspluatatsii_1 / MAN-BW L23-30h project-guide
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08028-0D\H5250\94.08.12
1639499-6.0 |
Water Washing of Turbocharger - Compressor |
B 15 05 1 |
Page 1 (1) |
General
During operation the compressor will gradually be fouled due to the presence of oil mist and dust in the inlet air.
The fouling reduces the efficiency of the turbocharger which will result in reduced engine performance.
Therefore manual cleaning of the compressor components is necessary in connection with overhauls. This situation requires dismantling of the turbocharger.
However, regular cleaning by injecting water into the compressor during normal operation of the engine has proved to reduce the fouling rate to such an extent that good performance can be maintained in the period between major overhauls of the turbocharger.
The cleaning effect of injecting pure fresh water is mainly based upon the mechanical effect arising, when the water droplets impinge the deposit layer on the compressor components.
The water is injected in a measured amount and within a measured period of time by means of the water washing equipment.
The water washing equipment, see fig 1, comprises two major parts. The transportable container (6) including a hand valve with handle (5) and a plug-in coupling (4) at the end of a lance.
Installed on the engine there is the injection tube (1), connected to a pipe (2) and a snap coupling (3).
The cleaning procedure is:
1. Fill the container (6) with a measured amount of fresh water. Blow air into the container by means of a blow gun, until the prescribed operation pressure is reached.
1 |
Injection tube |
5 |
Hand valve with handle |
2 |
Pipe |
6 |
Container |
3 |
Snap coupling |
7 |
Charge air line |
4 |
Plug-in coupling |
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Fig 1 Water washing equipment
2. Connect the plug-in coupling of the lance to the snap coupling on the pipe, and depress the handle on the hand valve.
3. The water is then injected into the compressor.
The washing procedure is executed with the engine running at normal operating temperature and with the engine load as high as possible, i.e. at a high compressor speed.
The frequency of water washing should be matched to the degree of fouling in each individual plant.
94.11
1639455-3.1 Page 1 (2)
Lambda Controller |
B 15 11 1 |
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L23/30H
Purpose
The purpose with the lambda controller is to prevent injection of more fuel in the combustion chamber than can be burned during a momentary load increase. This is carried out by controlling the relation between the fuel index and the charge air pressure.
Advantages
The lambda controller has the following advantages:
-Reduction of visible smoke in case of sudden momentary load increases.
-Improved load ability.
-Less fouling of the engines exhaust gas ways.
-Limitating of fuel oil index during starting procedure.
The above states that the working conditions are improved under difficult circumstances and that the maintenance expenses for an engine, working with many and major load changes, will be reduced.
Principles for functioning
Figure 1 illustrates the controller's operation mode. In case of a momentary load increase the regulating device will increase the index on the injection pumps and hereby the regulator arm (1) is turned, the switch
(2) will touch the piston arm (3) whereby the electrical circuit will be closed.
Thus the solenoid valve (4) opens. The jet system is activated, the turbocharger accelerates and increases the charge air pressure, thereby pressing the piston
(3) backwards in the lambda cylinder (5) when the lambda ratio is satisfactory the jet system will be deactivated.
At a 50% load change the system will be activated for about 3-8 seconds.
Fuel oil Limiting during start procedure
During the start procedure the controller is activated as an index limiter.
Hereby heavy smoke formation is prevented during the start and further the regulating device cannot over-react. The fuel limiter function stops when the engine has reached the nominal RPM.
The jet system is blocked during the starting procedure.
Air consumption
Jet air consumption at sudden stepload:
Air cons. = |
(step load % - 25) x N |
(Nm³) |
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179 |
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N = Cylinder number.
Example: At step load 50% the air consumption will be as follows:
Cyl. no. |
5 |
6 |
7 |
8 |
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Nm3 |
0.70 |
0.84 |
0.98 |
1.12 |
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93.45
B 15 11 1 |
Lambda Controller |
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L23/30H
1639455-3.1 Page 2 (2)
Fig. 1 Jet system
93.45
Exhaust Gas System
B 16
1609535-5.1 Page 1 (2)
Exhaust Gas System |
B 16 00 0 |
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Internal exhaust gas system
From the exhaust valves, the gas is led to the exhaust gas receiver where the fluctuating pressure from the individual cylinders is equalized and the total volume of gas led further on to the turbocharger, at a constant pressure. After the turbocharger, the gas is led to the exhaust pipe system.
The exhaust gas receiver is made of pipe sections, one for each cylinder, connected to each other, by means of compensators, to prevent excessive stress in the pipes due to heat expansion.
In the cooled intermediate piece a thermometer for reading the exhaust gas temperature is fitted and there is also possibility of fitting a sensor for remote reading.
To avoid excessive thermal loss and to ensure a reasonably low surface temperature the exhaust gas receiver is insulated.
External exhaust gas system
The exhaust back-pressure should be kept as low as possible.
It is therefore of the utmost importance that the exhaust piping is made as short as possible and with few and soft bends.
Long, curved, and narrow exhaust pipes result in higher back-pressure which may affect the engine combustion.
The exhaust back-pressure should not exceed 250 mmWC at MCR. An exhaust gas velocity through the pipe of maximum 35 m/sec is often suitable, but depends on the actual piping.
Holeby will be pleased to assist in making a calculation of the exhaust back-pressure.
The gas outlet of turbocharger, the expansion bellows, the exhaust pipe, and silencer, (in case of silencer with spark arrestor care must be taken that the cleaning parts are accessible), must be insulated with a suitable material.
General
The insulation should be shielded by a thin plating, and should comply with the requirements of the classification society and/or the local authorities.
Exhaust pipe dimensions
It should be noted that concerning the maximum exhaust gas velocity the pipe dimension after the expansion bellow should be increased for some of the engines.
The wall thickness of the external exhaust pipe should be min. 3 mm.
Exhaust pipe mounting
When the exhaust piping is mounted, the radiation of noise and heat must be taken into consideration.
Because of thermal fluctuations in the exhaust pipe, it is necessary to use flexible as well as rigid suspension points.
In order to compensate for thermal expansion in the longitudinal direction, expansion bellows must be inserted. The expansion bellows should preferably be placed at the rigid suspension points.
Note: The exhaust pipe must not exert any force against the gas outlet on the engine.
One sturdy fixed-point support must be provided for the expansion bellows on the turbocharger. It should be positioned, if possible, immediately above the expansion bellow in order to prevent the transmission of forces, resulting from the weight, thermal expansion or lateral displacement of the exhaust piping, to the turbocharger.
The exhaust piping should be mounted with a slope towards the gas outlet on the engine. It is recommended to have drain facilities in order to be able to remove condensate or rainwater.
91.32
B 16 00 0 |
Exhaust Gas System |
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General
1609535-5.1 Page 2 (2)
Position of gas outlet on turbocharger
B 16 02 0 shows turning alternatives positions of the exhaust gas outlet. Before dispatch of the engine from Holeby exhaust gas outlet will be turned to the wanted position.
The turbocharger is, as standard, mounted in the front end.
Exhaust gas boiler
To utilize the thermal energy from the exhaust, an exhaust gas boiler producing steam or hot water can be installed.
Each engine should have a separate exhaust gas boiler or, alternatively, a common boiler with separate gas ducts. Concerning exhaust gas quantities and temperature, see list of capacities D 10 05 0, and engine performance D 10 10 0.
The discharge temperature from the exhaust gas boiler should not be lower than 180° C (in order to avoid sulphuric acid formation in the funnel).
The exhaust gas boilers should be installed with bypass entering in function at low load operation.
The back-pressure over the boiler must be considered.
Expansion bellow
The expansion bellow, which is supplied separately, must be mounted directly on the exhaust gas outlet, see also E 16 01 1-2.
Exhaust silencer
The position of the silencer in the exhaust gas piping is not decisive for the silencing effect. It would be useful, however, to fit the silencer as high as possible to reduce fouling. The necessary silencing depends on the loudness of the exhaust sound and the discharge from the gas outlet to the bridge wing.
The exhaust silencer, see E 16 04 2-3-5-6 is supplied loose with counterflange, gaskets and bolts.
91.32
1607517-7.4 Page 1 (2)
Water Washing of Turbocharger - Turbine |
B 16 01 1 |
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General
The tendency to fouling on the gas side of turbochargers depends on the combustion conditions, which are a result of the load on and the maintenance condition of the engine as well as the quality of the fuel oil used.
Fouling of the gas ways will cause higher exhaust gas temperatures and higher surface temperatures of the combustion chamber components and will also lead to a lower performance.
Tests and practical experience have shown that radial-flow turbines can be successfully cleaned by injecting water into the inlet pipe of the turbine. The cleaning effect is based on the water solubility of the deposits and on the chemical action of the impinging water droplets and the water flow rate.
The necessary water flow is dependent on the gas flow and the gas temperature. Enough water must be injected per time unit so that, not the entire flow will evaporate, but about 0.25 l/min. will flow off through the drainage opening in the gas outlet. Ensuring that sufficient water has been injected.
Washing time : max. 10 min.
Service experience has shown that the above mentioned water flow gives the optimal cleaning effect. If the water flow is reduced, the cleaning effect will be reduced or dissappear. If the recommended water flow is exceeded, there is a certain risk of an accumulation of water in the turbine casing which may result speed reduction of turbocharger.
The best cleaning effect is obtained by cleaning at low engine load approx. 20% MCR. Cleaning at low load will also reduce temperature shocks.
08028-0D/H5250/94.08.12
Experience has shown, that washing at regular intervals is essential to successful cleaning, as excessive fouling is thus avoided. Washing every week during operation is therefore recommended.
The cleaning intervals can be shorter or longer based on operational experience.
The water should be supplied from the fresh water sanitary system and not from the fresh cooling water system or sea water system. No cleaning agents or solvents need to be added to the water. Water consumption 1.5-5 l/min.
Water Washing System
The water washing system consists of a pipe system equipped with a regulating valve, a valve, a 3-way cock and a drain pipe with a ball valve from the gas outlet.
The water for washing the turbine is supplied from the external fresh water system through a flexible hose with couplings. The flexible hose must be disconnected after water washing.
By activating the valve and the regulating valve, water is led through the 3-way cock to the exhaust pipe intermediate flange which is equipped with a channel to lead the water to the gas inlet of the turbocharger.
The water which has not evaporated is led out through the drain pipe in the gas outlet.
98.20
B 16 01 1 |
Water Washing of Turbocharger - Turbine |
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1607517-7.4 Page 2 (2)
General
08028-0D/H5250/94.08.12
98.20