INLET AND EXHAUST SYSTEM

 

GENERAL INFORMATION:

Gas turbine performance and reliability are a function of the quality and cleanliness of the

inlet air entering the turbine. Therefore, for optimum operation, it is necessary to treat the

atmospheric air entering the turbine and filter out the contaminants. The air inlet system, with

its specially designed equipment and ducting, modifies the quality of the air under various

temperature, humidity and contamination conditions, and makes it more suitable for use in

the unit. For the system drawing, please refer to ventilation system paragraph.

Hot exhaust gases produced as a result of combustion in the turbine are attenuated in the

exhaust system ducting before being released to the atmosphere or to a waste heat recovery

unit. These exhaust emissions must meet certain environmental standards for cleanliness and

acoustic levels, depending on site location.

AIR INLET:

The air inlet system consists of an elevated air inlet compartment and inlet ducting with

silencers connected to the turbine inlet plenum. This system combines the function of filtering

and silencing the inlet air with the function of directing the air into the turbine compressor.

Inlet air enters the inlet compartment and flows through the parallel overhead ducting, with

built- in acoustic silencers and filtration units, to the inlet plenum and then into the turbine

compressor. The elevated ducting arrangement provides a compact system and minimizes

entrance of dust which settles near the ground level.

All the external and internal surface areas exposed to air flow are coated with a protective

corrosion- preventive primer.

INLET COMPARTMENT:

The inlet compartment, an all-weather enclosure, is located off-base and connects to the inlet

ducting. This compartment contains a self-cleaning filtration system. The self-cleaning filter

system contains high efficiency media filter cartridges that are cleaned sequentially by pulses of

pressurized air during turbine operation. Compressor discharge air from the gas turbine compressor is supplied to the self-cleaning inlet filters for use as pulse air during the cleaning

cycle. The filtration unit is required to provide adequate protection for the turbine unit against

the environmental conditions at the turbine site. To ensure that this protection is maintained,

proper filtration maintenance is required.

INLET DUCTING:

The inlet compartment, an all-weather enclosure, is located on a raised support structure,

removed from the gas turbine. The air inlet duct work connects the inlet compartment to the

inlet plenum. It includes the acoustically-treated plenum at the gas turbine compressor inlet, a

90 degree elbow, a silencer module and sections of inlet ducting.

Silencing is provided by the use of vertical baffles, consisting of acoustically perforated sheets

of encapsulated low-density insulating material. In addition, the interior wall of the ducting and

plenum chamber are lined with the same type of covering. The vertical parallel baffles are

specifically tuned to eliminate the fundamental compressor tone as well as attenuating the

noise of other frequencies. The perforated sheet used in the silencers and line ducts is made of

steel and requires no maintenance. The inlet support structure are made of galvanized carbon

steel with multiple coats of protective paint.

EXHAUST SYSTEM:

Hot exhaust gases produced as the result of combustion are sent to the discharge duct. These

exhaust emissions must meet certain environmental standards of cleanliness and acoustic

levels, depending on site location. The exhaust duct is provided with an expansion joint and an

external insulation to avoid heat dissipation In the exhaust section, the gases that have been

used to power the turbine wheels are redirected and released to customer Heat Recovery

Steam Generator. One component of the system is the exhaust plenum, on which an

expansion joint and transition duct are vertically mounted, extending from the side of the

turbine base. A silencing section is installed between the transition duct and the exhaust duct

system.

Exhaust Plenum:

The exhaust plenum is a rectangular boxlike structure into which the turbine exhaust gases are

discharged before being ducted to the silencers and then vented to the atmosphere. Located

at the aft end of the turbine base, it encloses the exhaust frame, diffuser and turbine vanes. A

wrapper covers the top and side and serves to enlarge the plenum volume, forcing the exhaust

gases out of the side opening into the transition duct. Insulation placed inside the plenum

provides thermal and acoustical protection.