Air Intake Filter

The GDX system is a single stage self-cleaning air filter utilizing conical and cylindrical filter cartridges sequentially cleaned by a reverse flow pulse of compressed air. Combustion air is aspirated by the turbine through the filter. The air intake is located at the front side of the filter. Entrance into the inlet plenum is protected by the inlet hoods.

These inlet hoods and plenum protect the cartridges against foreign object damage, excessive ingestion of rain, sunshine. Inside these inlet hoods, a trace heating cable is installed to prevent possible icing damage inside the inlet hoods. A quantity of high efficiency filter cartridges composed of a combination of a conical and cylindrical filter element is attached to the vertical module plate (tube sheet).During normal operation, ambient air flows downwards between the elements, through the filter cartridges into the clean air plenum. Blowpipes are installed in the clean air plenum; one in front of each filter element set.Cleaning is accomplished by intermittently injecting compressed air through the blowpipes. Each pulse of air from the blowpipe into the filter cartridge provides a shock wave inside the filter cartridge and a momentary reverse flow.

These actions together provide the necessary cleaning energy. Many of the dust particles agglomerate on the media to form a thin cake.

When pulsed, they come off in larger masses than when they were deposited.

The possibility that these larger particles will be re-entrained when the normal flow is re-established, is reduced. The clean air plenum pressure is monitored and cleaning is initiated when the differential pressure becomes higher than a pre-set value. Cleaning continues until the pressure decreases to a lower pre-set value. The dust which is pulsed-off from the cartridges drops down into the dust evacuation hoppers. Each of these hoppers is fitted with an exhaust fan. Since these fans are running at the same time as the cleaning cycle is in operation, the dust falling down into the hopper is automatically blown away into the atmosphere.

The single stage filtration of the filter is provided by conical and cylindrical filter elements Inertial separators and pre-filters, generally used as first or second stages of filtration in traditional "3-stage" turbine filter systems, are not required in the GDX design. These extra stages were required to reduce premature plugging of the rectangular filter cells used in these systems. In the GDX, the high efficiency filter elements are automatically cleaned during the turbine operation and they do not require these extra stages thanks to the automatic cleaning feature of the filter.

The cartridge filter medium has been used for several years in filtering combustion air for turbine engines.

Particle count efficiency on a clean element is remarkably high, even on particles of 0.5 μm. The capture efficiency is practically total on the particles of 5μm and virtually total on particles of 1 μm after an initial loading period of a few hundred grams.
These efficiencies, provided by the filter elements, assure proper protection of the machines against both dust and alkaline salts.

Both the airflow pattern and the specified flow rates have been calculated to improve filtration and pulse cleaning of the filters.

During pulse cleaning, normal flow through two element sets is interrupted for about 0.1 second.

The effect of this interruption on the nominal flow of the turbine is negligible.

The self-cleaning filter pressure drop begins at a lower value: about 300 Pa.

The dust accumulation on the filter elements increases the pressure drop gradually.

The module clean air plenum pressure (vacuum) is monitored and cleaning is initiated when this pressure drop reaches a pre-set level with reference to ambient.

Cleaning continues until the Δp decreases to a lower pre-set limit.

After some time, depending upon the environmental conditions, the lower set value may not be reached anymore and the filter house will pulse continuously.

The pressure drop will then become stabilized approximately between 750 and 1000 Pa depending on the environment and the dust type to be filtered.

Strong recommendation
The average pressure drop of the filter left continuously in the automatic cleaning mode could be reduced if, at each shut-down of the engine, the manual cleaning mode feature is used.


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