Refrigeration – Automatic control – Air compessor – cooler and expander
Reexamination Certificate
2001-09-26
2003-01-14
Esquivel, Denise L. (Department: 3744)
Refrigeration
Automatic control
Air compessor, cooler and expander
C062S087000
Reexamination Certificate
active
06505474
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of The Invention
The invention relates to an air conditioning system for airplanes for conditioning the moisture containing air, which is under excess pressure, for air conditioning an airplane cabin.
2. Prior Art
The fresh air for air conditioning airplane cabins is conditioned from the air, the socalled bleed air, which is bled from the power plant at high pressure and high temperature. The air conditioning systems use the pressure and temperature potential of the power plant air to generate the requisite cooling capacity. The bleed air is cooled in the course of the fresh air conditioning process, dehumidified and expanded to the cabin pressure of approximately 1 bar during ground operations or approximately 0.8 bar during flight operations. Air dehumidification is especially relevant during the fresh air conditioning process in order to prevent the individual components of the air conditioning system from icing up and in particular to prevent the formation of ice crystals and mist in the fresh air to be conditioned. Of course, it is necessary to dehumidify predominantly in the ground area, because during flight operation, that is at high altitudes, the ambient air and thus the bled power plant air is extremely dry in any event.
The German patent application DE 100 36 443.8, which has not been previously published, proposed an air conditioning system for airplanes for conditioning the moisture containing air, which is under excess pressure, for air conditioning an airplane cabin. The system comprises at least one compressor for compressing the air, fed under excess pressure, to an even higher pressure; a first air expansion turbine for expanding the air to a lower pressure; a second air expansion turbine, which is downstream of the first one, to further expand the air; and a water separator, which is disposed between the first air expansion turbine and the second air expansion turbine. With this air conditioning system, the air can be largely dehumidified. Of course, this air conditioning system, like other prior art air conditioning systems, does not provide a control mechanism for the moisture content of the air that is available for air conditioning the airplane cabin.
SUMMARY OF THE INVENTION
Therefore, the object of the present invention is to improve this class of air conditioning system in such a manner that it is possible to control at the same time the moisture of the air that is available for air conditioning the airplane cabin without suffering any losses in the cooling capacity.
The invention solves this problem through a combination of features by providing an air conditioning system for airplanes that removes moisture contained in the air, under excess pressure. The air conditioning system comprises at least one compressor for compressing the air, which is already fed under excess pressure, to an even higher pressure. There is also a first air expansion turbine for expanding the air to a lower pressure, and a second air expansion turbine, which is downstream of the first air expansion turbine, to further expand the air. Another feature is a water separator which is positioned between the first air expansion turbine and the second air expansion turbine. The water separator selectively adjusts the air expansion in the first air expansion turbine.
In the inventive air conditioning system the component that serves the purpose of dehumidification is installed after the first air expansion turbine. Thus, the highly compressed, but still moist air, coming out of the main heat exchanger, is passed to the first air expansion turbine at approximately 45 degrees C.
From the air expansion turbine, the air that is expanded in a first step, but is still moist and in which the moisture condenses in very fine droplets due to the temperature drop, is passed into the water separator, which can comprise, for example, a drop coalescing unit and a water separator, which follows the drop coalescing unit.
The present invention benefits from the fact that the degree of condensed droplets depends on the temperature level, to which the highly compressed, but still moist air, which is passed into the turbine, is decreased. The higher the degree of air expansion is, the lower the temperature level of the air. As the temperature level decreases, the percentage of free water that condenses increases.
By adjusting selectively the degree of air expansion, the residual moisture in the air can be adjusted. Hence, the combination of the features of the air conditioning system which comprises at least one compressor for compressing the air to an even higher pressure, the first air expansion turbine that expands the air to a lower pressure, and the second air expansion turbine, positioned downstream from the first air expansion turbine, further expands the air.
Also, the water separator positioned between the first and second air expansion turbine removes water from the air which makes it possible to control the moisture of the air provided to air condition the airplane cabin.
Especially advantageous embodiments of the invention include the first air expansion turbine exhibiting variable nozzle cross sections, with the nozzle cross sections preferably changed by a gate valve.
In another embodiment, the first air expansion turbine of the air conditioning system exhibits a twin nozzle, which is connected to separate air feeds, so that one of the feeds can be blocked to selectively choose a desired nozzle.
A further embodiment includes a bypass for the first air expansion turbine. The bypass permits at least one substream of the air to be directed past the first air expansion turbine. Also, the bypass can be activated to open or close a gate valve.
In another embodiment of the air conditioning system, a fraction of the air stream can be controllably and directly fed by a control valve from the inlet or outlet of the second compressor behind the first air expansion turbine.
A still further embodiment provides for a humidifier for the air, bled from a power plant, disposed upstream of the primary heat exchanger.
In a still further embodiment, in addition to the degree of air expansion in the first air expansion turbine and the degree of air expansion in the second air expansion turbine, the air conditioning system can be selectively adjusted in several ways. Additionally, the second air expansion turbine can have variable nozzle cross sections. The nozzle cross sections of the secondary expansion turbine can be changed by a gate valve. Alternatively, the second air expansion turbine can have twin nozzles which are connected to separate air feeds, and one of the feeds can be blocked in the second air expansion turbine. A bypass is provided that can direct a substream of the air past the air expansion turbine, and a gate valve is provided to open and close the bypass.
The air conditioning system, can also have a fraction of the air controllably fed by a control valve at the inlet or outlet of the compressor behind the first air expansion turbine.
In another embodiment, the first and second air expansion turbines are on a common shaft and the nozzle cross sections are coupled for adjustments. Alternatively, the first and second air expansion turbines are on separate shafts, and the nozzle cross sections of the first and second air expansion turbines are separately adjustable as a function of each other.
Preferably, the first air expansion turbine exhibits variable nozzle cross sections. By adjusting the nozzle cross sections, the degree of expansion that can be achieved in the air expansion turbine can be adjusted in a simple manner. The smaller the nozzle cross section is set, the higher the degree of expansion can be achieved with the air expansion turbine. The nozzle cross section can be varied by means of suitably actuated gate valves.
According to another, but more complicated alternative, the degree of expansion can also be changed by adjusting the guide vanes in the air expansion turbine.
According to a simple embodiment, the first air expansion turbine exhibi
Sauterleute Alfred
Schlagenhaft Engelbert
Esquivel Denise L.
Jacobson & Holman PLLC
Liebherr-Aerospace Lindenberg GmbH
Norman Marc
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