lm2500_heatrej

Heat Rejection and Temperature Limitations

The LM2500 Gas Turbine is designed to operate with inlet-air temperature from -65° to +130°F and engine-space ambient temperature from -20° to +140°F. It is recommended that the engine be installed inside an enclosure to protect it from the weather and shield operating personnel from engine heat and noise. The enclosure must be ventilated for cooling of the gas turbine. Although the enclosure can be negative or positive pressure, positive pressure is preferred from the gas turbine bearing sump sealing and venting system standpoint.

Heat is released from the gas turbine by radiation and convection from hot surfaces and by hot-air leakage from flanges and struts. Cooling must be provided to maintain casing temperature below the maximum allowable as shown on Figure 1.

Figures 2 through 4, for use in designing the cooling system, show estimated temperatures of the gas turbine casings and exhaust duct as functions of various values of heat flux for ambient temperature from -20° to +120°F and for various power settings. Sufficient cooling air must be provided to limit the engine casing temperatures as shown on Figures 2 through 4. The cooling air should be uniformly distributed to prevent warping of the engine; this applies both during operation and when the engine is shut down. Direct impingement of forced cooling air on the engine casings is to be avoided. The emissivity of the gas turbine casing surfaces is 0.8.

Figure 1. LM2500 Maximum Allowable Casing Temperatures

Page 1 of 6Heat Rejection

19/11/2005http://inside-aep.ps.ge.com/insideaep/aep/iad/engine_prod_delv/idms/lm2500/07templimi...

Figure 2. Estimated Engine Casing Temperatures for LM2500 Base Load Power, Ambient Temperature = 59qF

Figure 3. Estimated Engine Casing Temperatures for LM2500 Base Load Power, Ambient Temperature = - 20qF



Figure 4. Estimated Engine Casing Temperatures for LM2500 Base Load Power, Ambient Temperature = 130qF



If the gas turbine is installed within a building or open room, the room ventilating and cooling system should be designed to prevent any reingestion of hot exhaust gases into the room. Hot exhaust gases could prove detrimental to engine control devices, electrical devices and accessory components, as well as to other peripheral equipment within the room.

Figure 5 describes casing temperature as a function of time after the engine has been shut down. This figure applies to either (1) an emergency shutdown from full power or (2) a normal shutdown from idle and is based on no cooling airflow during the shutdown and no radiation from the surrounding surfaces.

Figure 5. LM2500 Estimated Non-dimensional Engine Average Surface Temperature after Shutdown from Full Power



Normally a secondary airflow of 15% to 30% of engine airflow is sufficient to keep the gas turbine exterior surfaces cool. The exact quantity is a function of the air velocity over the engine and the radiation characteristics of the Purchaser’s enclosure walls, and must be determined by heat transfer analysis. Cooling flow initial estimates of 32 lbs/s (14.5 Kg/s) for regions with ambient temperatures below 85F (30C), and a flow of 35 lbs/s (16 Kg/s) for regions with ambient temperatures above below 85F (30C) are recommended starting points. Air velocity of the cooling air should be at least 9.8 ft/s (3 m/s), average. The cooling air must meet as a minimum the same contaminant limits as the inlet air to the gas generator.



Scale model flow tests of the proposed engine cooling system should be considered as a part of the overall installation design. It is essential that local cooling flow velocities and flow directions through the engine compartment be considered to ensure a satisfactory installation. Such testing could be combined with any inlet/exhaust system model testing being done.

In addition to the casing temperature limits, there are limitations on the maximum temperatures of the electrical and instrumentation devices mounted on the Gas Turbine. Cooling air adjacent to the engine must be provided to maintain the engine electrical and instrumentation devices within the limits described below. The controls and accessories are only minor sources of heat. Components containing fuel and/or oil are cooled by the media they handle while the engine is operating and, therefore, only heat soak-back after shutdown must be considered for these items. During engine cooldown, the flow of air through the engine must not be restricted.

During commissioning the Purchaser should arrange to record actual skin temperatures of the components listed in this Table.

Maximum Allowable Temperatures of Engine Mounted Components.

Component Maximum Temperature, ºF (ºC)

Gas Generator Speed Pickup (2) 225 (107)

Lube Supply RTDs 220 (104)

Variable Stator Vane Actuators 350 (177)

Gas Generator Accelerometer Connector 400 (204)

T48 Sensors (At Lug) 600 (316)

T48 Interface Connector 400 (204)

T3 Sensor at Connector 400 (204)

Lube and Scavenge Pump 300 (149)

Chip Detectors 350 (177)

Starter (Optional) 250 (121)

UV Flame Detectors (Optional) 200 (93) Power Turbine Speed Sensor Connector 400 (204)

Vibration Sensor Connector 400 (204)



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