BRIEF DESCRIPTION OF THE DRAWINGS
In the following, the present invention is described further on the basis of exemplary embodiments illustrated in the drawing.
FIG. 1: shows a schematic illustration of a first turbine having a filter device according to the present invention;
FIG. 2: shows a schematic illustration of a second gas turbine having a filter device according to the present invention;
FIG. 3: shows a top view of a first embodiment of the filter device according to the present invention having a vertical tubular electric filter, and
FIG. 4: shows a top view of a second embodiment of the filter device according to the present invention having multiple filter cells.
DETAILED DESCRIPTION
FIG. 1 schematically shows a gas turbine 100. Air 1 is sucked in from the outside by a compressor 3 and passes a filter device 2. In this embodiment, the filter device 2 has a tubular electric filter 20 and a downstream textile filter 22, which are only schematically shown in FIG. 1. The tubular electric filter is provided for the purpose of achieving high filtering, even of a damp gaseous fluid such as air, in a first filter stage. Dried air is thus supplied to the downstream textile filter, so that clumping of dirt particles no longer occurs and good air passage is provided. The air thus filtered enters the compressor 3 and is compressed there until it exits again at its outlet as compressed air 4. It is conducted there to a combustion chamber 5, where it is combusted together with a supplied fuel 7. Combustion gases 8 result, which are conducted to a downstream turbine 9 and drive the turbine. The flow energy of the combustion gases 8 is partially converted into mechanical energy by driving the compressor 3 and a generator 12. For this purpose, the compressor 3 and the turbine 9, as well as the generator 12, are mounted on a shared shaft 13. Finally, the combustion gas 8 exits the turbine 9 as hot exhaust gas 10 after passing the turbine 9.
The efficiency of a gas turbine may be increased if the heat of the hot exhaust gas 10 is used. This is performed, for example, by supplying the hot exhaust gas to a recuperator 5 (heat exchanger), which preheats the compressed air 4 before it reaches the combustion chamber 8, see FIG. 2. The quantity of the supplied fuel 7 may thus be reduced, so that less energy is required for operating the gas turbine. Less hot exhaust gas 11 subsequently exits from the recuperator 5.
A top view of a tubular electric filter 20, which is used in the filter device according to the present invention, is shown in FIG. 3. The tubular electric filter 20 has discharge electrodes 21, which project in needle shapes in the direction toward the precipitating electrode 23 enclosing them. The discharge electrodes are polarized cathodically, so that when a voltage is applied, electrons are emitted by the discharge electrodes. The electrons experience such a strong acceleration that from a specific voltage, ionization of the gaseous fluid which encloses the discharge electrodes and is to be filtered occurs. This ionization occurs far below the breakdown voltage.
On the way from the discharge electrodes to the precipitating electrode, the free electrons hit neutral gas molecules, so that gas ions and further electrons arise through impact ionization. An electron avalanche thus forms, which moves toward the precipitating electrode. If the discharge electrodes are sufficiently close to one another, the gas ion jets 22 are superimposed on one another, as shown in FIG. 3. The gas ions hit the precipitating electrode and release further electrons upon incidence there. In addition, the gas ions accumulate on dust particles and thus charge them. Under the effect of the electrical field between electrodes, the charged dust particles are transported transversely to the flow direction of the fluid toward the precipitating electrode, where they deliver their charges and accumulate on its surface because of adhesive forces, so that a deposited dust layer 24 is formed (only a part of the precipitating electrode surface having a deposited layer 24 is shown in FIG. 3). The entire flow which moves from the discharge electrodes toward the precipitating electrode is referred to as an electrical wind, this wind comprising negatively charged particles, neutral particles, electrons, and ions. The achievable current strength is a function, inter alia, of the dust content of the gas to be purified and the already existing dust deposits on the electrodes.
The precipitating electrode is to be implemented so that the interval between the electrodes is approximately equal to achieve a nearly constant electrical field between a discharge electrode and an associated precipitating electrode.
In the embodiment of the tubular electric filter shown in FIG. 3, the precipitating electrode is implemented as honeycombed and/or as a hexagonal tube. This is advantageous in regard to joining multiple filter cells 25 together in particular, see FIG. 4. A self-supporting structure of the filter device may thus be achieved without intermediate space between the individual cells, which requires relatively little material and is nonetheless stable. Through the honeycomb structure, it is easily possible to achieve a larger or smaller passage area for the fluid to be filtered by combining a desired number of filter cells with one another.
Patent Application
20080072759
