8.0 Combustion
There are two types of combustion arrangement for the TB. The original version requires that the gaps between the various elements (swirler, flame tube, extension and star ring) are carefully controlled to ensure the temperature spread and distribution around the annulus is within limits.
Temperature distribution within a can is limited to 80 Celsius and the maximum allowable difference between the can averages is 20 Celsius.
For flame monitoring the TB has 16 equally spaced thermocouples within the exhaust diffuser, starting with #1 at 12:30 and finishing with #16 at circa 11:30 when looking downstream. Because of the swirl within the gas path t/cs 16 to 3 monitor combustor 1; 4 to 7 look at combustor 2 etc.
Failure to achieve the required temperature spread can mean :-
• There is an offset or gap errors at the interface between the various components of the combustor.
• Liquid burners are partially blocked or coated with carbon which can cause flame distortion.
• Gas burners need balancing
If the problem is not linked to the above elements of the combustors can be exchanged 1and 4 and or 2 and 3. It is not usually possible to exchange components side to side because they are ‘handed’.
With the sealed assembly there is no option to adjust the fit of components because there is a tight sliding interface between the elements. If the burners themselves are ok then the only options are swap parts around. Again this is generally limited to left / right changes.
Steam and water injection modules are available for both power and emissions control, but there is no DLE option for the TB turbine range.
Skid edge gas pressure should be in the range 180 – 200 psi.
8.1 Ignition.
Combustion light up for a TB is by small pilot flame torches and spark devices situated in each can. These torches are often fuelled with bottled propane gas but if suitable main fuel gas can be used. If a 50kg. propane bottle is used it is expected that at least 25 full starts could be achieved although in reality is probably nearer the mark.
The TB does not utilise the high energy ignition system available for the current turbine range from Lincoln.
9.0 Gearbox
The gearbox casing is an integral part of the structure of the TB engine and cannot be omitted. It is capable of accepting several gear ration options which at full speed are: - two epicyclic designs at 1500 and 1800 rpm for alternator drive, a star design for 3550 rpm pump duty and two parallel shaft designs at 11720 rpm and 13500 rpm for compressor duty. There is also the option for a straight through direct drive shaft without gears.
The epicyclic and straight through designs have in-line drive and rotation in the same direction as the turbine rotor; i.e. anticlockwise when viewed upstream.
The main engine driven lubricating oil pump and the mechanical overspeed trip are both driven from a power take off wheel on the gear assembly.
10.0 Lubricating Oil
The usual oil grade for the TB is VG46 which when operating at a
temperature of 60/65 Celsius will give acceptable behaviour. It is also permissible to use VG32 and VG68 in cold and hot environments. The very minimum oil temperature at start up must be 10 Celsius although most units are set to 15 Celsius.
Originally three oil pump sizes were specified for the TB and the chosen one depended on the retirements of the gearbox and the driven unit (90 gpm, 120 gpm and 180 gpm). The smallest of these is no longer recommended and I believe almost all of them have been changed to the 120 gpm version. In most cases, the AC and engine driven pumps are identical.
The normal oil pressure for the TB is 50 psi with a low pressure shut down of 35 psi.
The emergency dc pump only supplies oil to the two hot bearings, namely the CT and PT shaft disc end locations. This supply is for cooling purposes only after a shut down if the AC system fails. It does not and cannot be used with an operating turbine.
With three lobed bearings the pressure from the dc pump may be as low as 15 psi. This is adequate for the provision of cooling flow.
Typical oil usage is in the range 3 – 5 gallons per week. Many turbines will be better than this, some not so good
There are two types of combustion arrangement for the TB. The original version requires that the gaps between the various elements (swirler, flame tube, extension and star ring) are carefully controlled to ensure the temperature spread and distribution around the annulus is within limits.
Temperature distribution within a can is limited to 80 Celsius and the maximum allowable difference between the can averages is 20 Celsius.
For flame monitoring the TB has 16 equally spaced thermocouples within the exhaust diffuser, starting with #1 at 12:30 and finishing with #16 at circa 11:30 when looking downstream. Because of the swirl within the gas path t/cs 16 to 3 monitor combustor 1; 4 to 7 look at combustor 2 etc.
Failure to achieve the required temperature spread can mean :-
• There is an offset or gap errors at the interface between the various components of the combustor.
• Liquid burners are partially blocked or coated with carbon which can cause flame distortion.
• Gas burners need balancing
If the problem is not linked to the above elements of the combustors can be exchanged 1and 4 and or 2 and 3. It is not usually possible to exchange components side to side because they are ‘handed’.
With the sealed assembly there is no option to adjust the fit of components because there is a tight sliding interface between the elements. If the burners themselves are ok then the only options are swap parts around. Again this is generally limited to left / right changes.
Steam and water injection modules are available for both power and emissions control, but there is no DLE option for the TB turbine range.
Skid edge gas pressure should be in the range 180 – 200 psi.
8.1 Ignition.
Combustion light up for a TB is by small pilot flame torches and spark devices situated in each can. These torches are often fuelled with bottled propane gas but if suitable main fuel gas can be used. If a 50kg. propane bottle is used it is expected that at least 25 full starts could be achieved although in reality is probably nearer the mark.
The TB does not utilise the high energy ignition system available for the current turbine range from Lincoln.
9.0 Gearbox
The gearbox casing is an integral part of the structure of the TB engine and cannot be omitted. It is capable of accepting several gear ration options which at full speed are: - two epicyclic designs at 1500 and 1800 rpm for alternator drive, a star design for 3550 rpm pump duty and two parallel shaft designs at 11720 rpm and 13500 rpm for compressor duty. There is also the option for a straight through direct drive shaft without gears.
The epicyclic and straight through designs have in-line drive and rotation in the same direction as the turbine rotor; i.e. anticlockwise when viewed upstream.
The main engine driven lubricating oil pump and the mechanical overspeed trip are both driven from a power take off wheel on the gear assembly.
10.0 Lubricating Oil
The usual oil grade for the TB is VG46 which when operating at a
temperature of 60/65 Celsius will give acceptable behaviour. It is also permissible to use VG32 and VG68 in cold and hot environments. The very minimum oil temperature at start up must be 10 Celsius although most units are set to 15 Celsius.
Originally three oil pump sizes were specified for the TB and the chosen one depended on the retirements of the gearbox and the driven unit (90 gpm, 120 gpm and 180 gpm). The smallest of these is no longer recommended and I believe almost all of them have been changed to the 120 gpm version. In most cases, the AC and engine driven pumps are identical.
The normal oil pressure for the TB is 50 psi with a low pressure shut down of 35 psi.
The emergency dc pump only supplies oil to the two hot bearings, namely the CT and PT shaft disc end locations. This supply is for cooling purposes only after a shut down if the AC system fails. It does not and cannot be used with an operating turbine.
With three lobed bearings the pressure from the dc pump may be as low as 15 psi. This is adequate for the provision of cooling flow.
Typical oil usage is in the range 3 – 5 gallons per week. Many turbines will be better than this, some not so good
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