New technologies and applications
Smaller but more efficient23 August 2004
Donaldson Co has put on the market in Europe a new filter technology for gas turbine intake air systems. It is claimed to achieve high efficiency automatic self-cleaning performance with a system that is 40% smaller by volume. Designated XLR it is designed for very low maintenance with automatic self-cleaning, and is therefore suitable for remote or difficult-to-access locations.
The high density filter medium packaging technology applied to the XLR filter goes under the trade name PowerCore. It is designed to reduce the size of the intake filter system, reduce the complexity of the installation, shorten field installation time, and significantly reduce the cost of shipping. The key to this size reduction lies in PowerCore, a way of packaging the filter media that (says Donaldson) allows for twice the airflow per filter at the same initial pressure loss and filtration efficiency as the GDX model, regarded as an industry standard in self-cleaning filter systems.
Donaldson has marketed a medium similar to PowerCore as a replacement panel filter for the aftermarket, but this is the first time XLR has been offered to OEMs in a complete system. It has been applied very successfully in air filtration systems for diesel engines and automotive vehicles and is offered with a choice of Duratek or synthetic base media, both with ‘Spider-Web’ nanofibre technology.
Air flow through the XLR filter system is horizontal, with the filter elements mounted horizontally against a vertical tubesheet plenum. The filters are protected from direct exposure to rain and sun with an enclosed access area on the ‘dirty’ air side. Incoming air is pretreated with either a weather louvre, or a weather protection hood with optional inertial moisture separators. Incoming air is cleaned by pairs of PowerCore filter elements in an outside-to-inside airflow path. Cleaned air then passes to the turbine.
Filter cleaning is accomplished by a strong reverse pulse-jet of air automatically delivered when the pressure loss through the system exceeds a preset limit which varies depending on the environmental conditions. The filter elements are then cleaned in a top to bottom cycle until the system pressure loss returns below the automatic set point. The cleaned off dust settles to a collection hopper at the bottom of the unit for dust evacuation.
A walkway behind the louvres or inlet hoods provides easy service access to the filters and cleaning valves. The XLR is modular in construction, with module width limited for shipping purposes, and heights varying from 8 to 20 filter elements to accommodate a diverse range of large turbine airflows. The modular design is assembled onsite at the power plant.
PowerCore is a high-density corrugated flute media technology, and for XLR it is packaged in a V shape leading to a much higher packing density. This denser construction nonetheless reduces pressure loss owing to changes in air flow path through the filter.
This corrugated medium is constructed by layering alternating rows of flat sheet and corrugated media., The result is a dense, honeycomb-like structure of filter media. The resulting media pack consists of parallel rows of flutes that are open at only one end.