Introduction to GAS Turbine

To discussion Gas Turbine we must Know thermo dynamic 

1.1   Introduction for thermodynamic cycles:-

Brayton cycle & Rankine cycle

   Ø  Brayton cycle

The Brayton cycle is a thermodynamic cycle that describes the workings of a constant pressure heat engine. Gas turbine engines and air breathing jet engines use the Brayton Cycle. Although the Brayton cycle is usually run as an open system (and indeed must be run as such if internal combustion is used), it is conventionally assumed for the purposes of thermodynamic analysis that the exhaust gases are reused in the intake, enabling analysis as a closed system.

-        A Brayton-type engine consists of three components:

         ·         Gas compressor

         ·         Burner (or combustion chamber)

         ·         An expansion turbine

-       Ideal Brayton cycle:

 Ambient air is drawn into the compressor, where it is pressurized, the compressed air then runs through a combustion chamber, where fuel is burned, heating that air—a constant-pressure process, since the chamber is open to flow in and out.

The heated, pressurized air then gives up its energy, expanding through a turbine (or series of turbines). Some of the work extracted by the turbine is used to drive the compressor, heat rejection (in the atmosphere).

-        

       ·         Adiabatic process - compression.

       ·         Isobaric process - heat addition.

       ·         Adiabatic process - expansion.

       ·         Isobaric process - heat rejection.

    Since neither the compression nor the expansion can be truly isentropic, losses through the compressor and the expander represent sources of inescapable working inefficiencies. In general, increasing the compression ratio is the most direct way to increase the overall power output of a Brayton system.

COMPRESSOR CLEANING SYSTEM

MANUAL COMPRESSOR CLEANING SYSTEM 

يستخدم لازالة الاتربة  الموجوده على ريش الكباس والتى تسبب فى تقليل كفاءة الوحدة الغازيه

        يتكون نظام غسيل الكباس من الاتى:

1-    تنك مياه بسعة 750 لتر يتم ملئ التانك بخليط من الماء ومادة منظفه

2- يتم ضخ الخليط باستخدام طلمبة متعددة المراحل بمحرك تيار متردد, فى مدخل الهواء يوجد نوعين من nozzles لعمل 

inject for water لتنظيف الكباس :

2 jet nozzles(for off line), 20 spray nozzles (for off line and on line)

note that:

- It is recommended to perform off line washing once a week.
 -  the off line should be performed at least once every month,If we can not do it due to load of gas turbine

 - If frequent on line washing shall be carried out,can be 
   (1 / 2 per week) according to the environmental conditions.

  Compressor Cleaning at Operating Speed (ON LINE WASHING)

  - If the gas turbine cannot be shut down for compressor washing,The compressor cleaning can be performed at rated speed and on-load. 

  - Compressor washing is suggested at base load 

 with fully opened IGV.

  - Peak load  is not admissible .

Warning: Never use jet nozzles but only the spray nozzles. 
                Do not open drain valves.

Note: Compressor washing at nominal speed is less 
          effective than the washing procedure at
           washing speed. 
          It could be necessary to repeat the procedure
          several times.

finally:

   -   On Line cleaning (GT on load)

   IGV fully open

   Spray nozzles

          Less deep cleaning (repeat the operation few times)

Compressor Washing at Washing Speed (OFF LINE WASHING)

  -  Off Line Washing is performed in four steps: max 700 dm3

     (dm3 = L ) during washing (water + detergent) max 700 dm3 during each rinsing
    (water only) (to be considered the number of rinsing,

    for instance 1400 dm3 in case of 2 rinsing cycles).  
    The tank capacity is approximately 750 liters 

finally:

- Off line cleaning( GT on Turning Gear):

     Jet nozzles

     Spray nozzles

     Deep Cleaning (Always after a GT extended outage)

Ansaldo Gas turbine_component_HCO or RDS_part3

Ansaldo Gas turbine_component_HCO or RDS_part3

in this part we will discussion the most problems for HCO 
system during operation

click her for part1

click her for part2

1-    Load rejection and GT fast unloading: the RDS is automatically deactivated

A fast unloading == a load rejection it is considered fast unloading when:

a-      The load gradient is > EK.LEIST.101 (load change of about 13 MW/min)

b-      The load reduction is > E.LEIST.101 (load difference of about – 15 MW).

                   In case the rotor is not in the NULL position G.HSO.01 after delay K.HSO.11, a GT trip.

                When the RDS has been deactivated due to a load rejection, it is necessary to wait that

                K.HSO.04 (e.g. 1 h) has elapsed before a new activation of the RDS. 

  

2-        GT Shut Down: It is automatically disconnected after the fuel stop valve(s) closure   

3-         GT Turning gear operation and standstill:

a-    During turning gear operation for cooling, the RDS system is under pressure and the secondary chamber is pressurized

b-    In case of fault to the RDS system, the turning gear operation is performed also with the depressurized RDS system. However in this condition a GT start is NOT ALLOWED since the shaft shall be in the NULL position before attempting

       a GT start up.

c-    In case of interval turning and GT standstill the RDS system is not pressurized

d-    Maintenance on the RDS system

                 Warning: In case it is required to totally exclude the RDS system with the GT at        

                               Standstill or in turning gear mode in order to perform maintenance job, 

                                 it is Necessary to switch off manually all pumps, to deactivate all manual

                                  Sequences and to interlock pumps (otherwise they will start again due to

                                  The low pressure protection logic).To perform maintenance job, all system                                            Shall be TOTALLY DEPRESSURIZED

4-     The following actions are required (necessary fundamental condition: GT speed < S.TURB.05):

a. Switch off the RDS pump (if just in operation) and disconnect the pumps at the  

     Switchboard by smooth action (in order to avoid undesired automatic start).

b. Switch off the RDS‐SEQUENCE

c. Open SEC CH return valve (MBA53AA005)

5-      When the pressure in the RDS system has decayed it is possible to perform work on the RDS system

6-      When the lube oil has been removed from the RDS system, after work completion, the RDS system must be refilled with oil, after that, during cool down turning, the RDS system is pressurized.

When the RDS system is filled with lube oil, the RDS‐Sequence shall be switched on for automatic operation. This action activates automatically the shutdown branch of the RDS sequence. Since during the depressurization of the system the RDS pressure has dropped below P.HSO.02, the main and secondary channels are at first vented and purged. Then the solenoid valves are positioned by the RDS sequence in order to bring the shaft in the NULL position and the secondary channel is pressurized.

7-      Additional warnings:

a-    The accumulator pre‐charge is monitored by the control system via the filling time of the accumulators. The accumulator pre‐charge shall be controlled at regular intervals.

b-    The closure of not used optional tapping points must be checked at regularly maintenance activity in order to avoid potential leak.

c-    Before activating again the RDS system when the RDS system has been deactivated due to a fault, it is necessary that the fault event has been removed.

  

Ansaldo Gas Turbine_component_HCO_part2

  HCO   ( Hydraulic clearance optimization ) 

                 
    او RDS ( Rotor Displacement system)
Part_2

لمشاهدة الجزء الاول اضغط على هذا الرابط http://goo.gl/ypDQVu

فى هذا الجزء سوف نتناقش المشاكل اللى ممكن تواجهنا بالنسبه لتشغيل نظام HCO وكيفية التغلب عليها

The following events may occur:

1-    High pressure in the not‐loaded chamber: bearing stress condition

      When a channel is not activated, the pressure must be low. A pressure increase can indicate a

       Bearing stress and a damage.

      In case of pressure > P.HSO.07 all feed valves in the main and secondary channels are closed and the return valves opened. If 10s after opening the return valves, no pressure reduction still takes place, then a GT trip is issued and corresponding alarms issued

2-      High pressure in the loaded secondary chamber

      In case of special conditions during GT start up (cold bearing and cold lube oil), it is possible that

      Pressure in the secondary chamber increases due to thermal expansion of the lube oil.

       The following Actions must be taken:

      If the pressure is > P.HSO.100 for more than 10 s, the secondary return valve must be opened and The alarm issued. The valve is closed again when the pressure is < P.HSO.101.

      In case the pressure is > P.HSO.102 for more than 10 s, a GT Trip shall be issued for too high pressure in secondary chamber.

3-      Low pressure in the loaded chamber

      When a channel is activated, the pressure must be higher  than P.HSO.09 otherwise a defined axial position of the rotor is no more guaranteed.

      In case of pressure < P.HSO.09, an alarm is issued.

     GT trip occurs in case of fault to both (2v2) pressure transducers in return main line or in return secondary line.

Notes that:

1-    When low pressure is in the main channel (RDS ON), the RDS system shall be manually deselected by the operator

2-    When low pressure is in the secondary channel (RDS OFF), the RDS system shall be manually selected by the operator

3-      Warning: In case the RDS selection is not possible or not desired, the GT shall be operated       

                 as much as possible in a stable way (i.e. avoid sudden load change)

4-      The axial position of the shaft is monitored through the linear transducers MBA10CG101 /102.

5-      When the RDS is activated (main channel pressurized), the shaft shall reach the proper position G.HSO.02 within the time K.HSO.05 otherwise a deactivation of the RDS system occurs.

6-      in case the position is attained too quickly (<K.HSO.10) an alarm is issued but automatic

deselection of RDS does not occur

7-      When the RDS is de‐activated (secondary channel pressurized), the shaft shall reach the proper position G.HSO.01 within the time K.HSO.11 otherwise the RDS pre‐selection is reset and an alarm is issued.

8-      in case the null position is attained too quickly (<K.HSO.10) an alarm is issued and the RDS preselection is reset.

9-      Warning: In case of too quick movement of the shaft (to G.HSO.01 or G.HSO.02 position), a bearing damage can occur.

10-   Before any GT start up, the main and secondary channels are purged in order to remove any air via the return line to the lube oil tank.

11-   Warning: In case the shaft in not in the NULL position, it shall be brought to the NULL position (< G.HSO.01) before initiating the GT start up (manual command).

                              Activation of the RDS is possible only 1 hour after reaching FSNL 

                           condition (time K.HSO.04). Loading / unloading according to the allowed

                                gradients can be performed with the operating RDS system
اى يتم تشغيل HCO بعد مرور ساعه من وصول الوحده الى الـ  full speed  

فى الجزء الثالث سوف نتحدث عن وضع الـHCO  فى حالة الـ trip or shut dowun