Water Pump
3
Refrigerant
2
4
Air
W
Figure 2-.9. Thermal storage inlet system.
isothermal compression process as shown in Figure 2-40. The water injected is usually mechanically atomi.ed so that very fine droplets are entered into the air. The water is evaporated as it comes in contact with the high pressure andtemperature air stream. As water evaporates， it consumes about 1058 BT. (1117 kJ) (latent heat of vapori.ation) at the higher pressure and temperature resulting in lowering the temperature of the air stream entering the next stage. This lowers the work required to drive the compressor.
The intercooling of the compressed air has been very successfully applied to high-pressure engines. This system can be combined with any of the previously described systems.
Injection of .umidified and .eated Compressed Air. Compressed air from a separate compressor is heated and humidified to about 60% relative humidity by the use of an HRSGand then injected into the compressor discharge. Figure 2-41 is a simplified schematic of a compressed air injectionplant， which consists of the following major components:
1. A commercial combustion turbine with the provision toinject， at anypoint upstream of the combustor， the externally supplied humidified and preheated supplementary compressed air. Engineering and mechanical aspects of the air injection for the compressed air injection plant concepts are similar to the steam injection for the power aug-mentation， which has accumulated significant operating experience.
Water
W
1
Air
2. A supplementary compressor (consisting of commercial off-the-shelf compressor or standard compressor modules) to provide the supple-mentary airflow up-stream of combustors.
3. A saturation column for the supplementary air humidification and preheating.
4. Heat recovery water heater and the saturated air preheater.
5.
Balance-of-plant equipment and systems， including interconnectingpiping， valves， controls， etc.
Injection of Water or Steam at the Gas Turbine Compressor Exit. Steam injection or water injection has been often used to augment the power gen-erated from the turbine as seen in Figure 2-42. Steam can be generated from the exhaust gases of the gas turbine. The HRSGfor such a unit is very elementary as the pressures are low. This technique augments power and also increases the turbine efficiency. The amount of steam is limited to about 12% of the airflow， which can result in a power increase of about 25%. The limits of the generator may restrict theamount of power， which can be added. The cost for such systems runs around .100jkW.
Injection of Steam in the Combustor of the Gas Turbines Utilizing .resent .ual Fuel Nozzles. Steam injection in the combustor has been commonly used for NOxcontrol as seen in Figure 2-43. The amount of steam，which can be added， is limited due to combustion concerns. This is limited to about 2-3% of the airflow. This would provide an additional 3-5% of the rated power. The dual fuel no..les on many of the industrial turbines could easily be retrofitted to achieve the goal of steam injection. The steam would be produced using an HRSG. Multiple turbines could also be tied into one HRSG.
Combination of Evaporative Cooling and Steam Injection. The combin-ation of the above techniques must also be investigated as none of these techniques is exclusive of the other techniques and can be easily used in conjunction with each other. Figure 2-44 is a schematic of combining the inlet evaporative cooling with injection of steam in both the compressor exitand the combustor. ln thissystem， the power is augmented benefiting from
Exhaust
the cooling of theair， and then augmented further by the addition of the steam.
Summation of the .o.er Augmentation Systems
The analysis of the different cycles examinedhere， which range from the simplest cycle such as evaporative cooling to the more complex cycles suchas the humidified and heated compressed aircycle， are rated to their effec-tiveness and to their cost is shown in Table 2-1. The cycles examined herehave been used in actual operation of major power plants， thus there are no cycles evaluated that are only conceptual in nature. The results show addi-tion from 3-21% in power and the increase in efficiency from 0.4-24%
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