Refrigeration – Processes – Reducing pressure on compressed gas
Reexamination Certificate
2000-08-04
2001-07-10
Doerrler, William (Department: 3744)
Refrigeration
Processes
Reducing pressure on compressed gas
C062S402000
Reexamination Certificate
active
06257003
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to environmental control systems, and more particularly, to air cycle environmental control systems that condition water-vapor bearing compressed air for supply as conditioned air.
BACKGROUND OF THE INVENTION
Air cycle environmental control systems that condition air are well-known for the cooling and/or pressurization of heat loads such as passenger cabins and equipment compartments in both commercial and military aircraft. These systems are popular for a number of reasons, including the substantial amount of cooling available from air cycle systems of relatively modest size, and the adaptability of such systems to gas turbine engine powered vehicles such as aircraft and military land vehicles such as battle tanks.
In a typical installation, compressed ambient air provided by either the compressor section of a main engine or the compressor section of an auxiliary power unit, or both, is expanded in an air cycle turbo machine to provide a cool, fresh air supply for one or more cabins and/or equipment compartments of a vehicle.
One known air cycle environmental control system that utilizes a compressor (
36
) and a fan (
22
) driven by a pair of turbines (
24
) and (
26
) via a common shaft (
23
) is disclosed in U.S. Pat. No. 5,086,622, issued on Feb. 11, 1992 to John L. Warner and assigned to the Assignee of the present application, the entire disclosure of which is incorporated herein by reference. In Warner's system, compressed air is cooled in a primary heat exchanger (
16
), compressed in the compressor (
36
), and then cooled again in a secondary heat exchanger (
40
). The fan (
22
) drives a cooling ambient air flow through the primary and secondary heat exchangers (
16
) and (
40
). After passing through the primary and secondary heat exchangers (
16
) and (
40
), the compressed air is then further cooled in a condenser (
46
) that dehumidifies the compressed air by condensing water-vapor from the compressed air. The dehumidified compressed air is then directed through the turbine (
24
) where it is expanded to provide power to the shaft (
23
) and to cool the compressed air so that it may be used as the coolant in the condenser (
46
). The compressed air is then further expanded through the turbine (
26
) to power the shaft (
23
) and to cool the compressed air so that it may be supplied to a cabin (
62
). While this system is more than satisfactory for a number of applications, such as for large commercial aircraft, it may not be the optimum system for all applications, such as for small regional aircraft.
U.S. Pat. No. 5,887,445 issued Mar. 30, 1999 to Murry et al. discloses another air cycle environmental control system (
10
) that utilizes two air cycle machines (
39
) and (
40
) that rotate independent of each other. The air cycle machine (
39
) includes a compressor (
16
) that is driven by a high pressure turbine (
24
), and the air cycle machine (
40
) includes a fan (
32
) that is driven by a low pressure turbine (
28
) to supplement a ram air flow through primary and secondary heat exchangers (
12
,
13
). The system (
10
) also includes a reheater (
19
), condenser (
26
), and water extractor (
21
) that dehumidify the bleed air flow to the high pressure turbine (
24
). While the system (
10
) of Murry et al. may satisfactorily perform its intended function, for certain applications operation of the system (
10
) with an optimum power split between the turbines (
24
) and (
28
) may require that, under normal operating conditions, the bleed air be expanded through the high pressure turbine (
24
) to a point where the condensed water in the condenser (
26
) freezes, thereby creating icing in the condenser (
26
). This may require that the condenser (
26
) be designed to accommodate such icing, which can increase the size, weight, cost, and complexity of the condenser (
26
).
SUMMARY OF THE INVENTION
It is a primary object of the invention to provide an improved air cycle environmental control system.
It is another object of the invention to provide dehumidification in an air cycle environmental control system that can be optimized under normal operating conditions without requiring a condenser that is designed for icing of the condensed water from the compressed air flow.
It is another object of the invention to provide an air cycle environmental control system that can efficiently provide an increased conditioned air flow in an aircraft at cruising altitudes.
Having expressly identified a number of objects, it should be understood that some manifestations of the invention may not achieve all of the expressly identified objects.
In accordance with one aspect of the invention, a method is provided for conditioning water-vapor bearing compressed air for a supply as conditioned air.
In one form, the method includes the steps of further compressing the compressed air in a compressor, condensing and removing water vapor from the further compressed air to dehumidify the further compressed air, expanding the dehumidified air through a first turbine to cool the dehumidified air to a first temperature, rejecting heat from said further compressed air to said expanded dehumidified air in said condensing step, and, after the rejecting heat step, further expanding the dehumidified air through a second turbine to cool the dehumidified air to a second temperature and to power the compressor in the further compressing step in the absence of rotating engagement between the first and second turbines. As one feature, the method further includes the step of selectively directing a majority of the further compressed air to the second turbine to be expanded therein without the majority of the further compressed air undergoing the condensing step and the step of expanding the dehumidified air through a first turbine.
In accordance with one form of the invention, the method includes the steps of using a first air cycle machine including a first turbine powering a fan, using a second air cycle machine including a second turbine powering a compressor, flowing the compressed air first through the compressor, second through the first turbine, and third through the second turbine in the absence of rotating engagement between the first and second air cycle machines. As one feature, the method further includes the step of selectively directing the majority of the compressed air flow from the compressor to the second turbine without flowing the majority of compressed air flow through the condenser and the first turbine.
In accordance with another aspect of the invention, an environmental control system is provided for conditioning water-vapor bearing compressed air for supply as conditioned air. The system includes a compressor to further compress the compressed air and to deliver the further compressed air to the system, a condenser downstream of the compressor to receive the further compressed air and to condense at least a portion of the water-vapor in the further compressed air to deliver dehumidified compressed air to the system, a first turbine downstream of the condenser to receive the dehumidified compressed air and to expand the dehumidified compressed air to cool the dehumidified compressed air, and a second turbine downstream of the first turbine to receive the expanded dehumidified compressed air. The second turbine is rotatable independent from rotation of the first turbine to further expand the expanded dehumidified compressed air to cool the expanded dehumidified compressed air and to power the compressor.
As one feature, the environmental control system further includes a fan powered by the first turbine to produce a cooling air flow, and at least one heat exchanger upstream of the first turbine to reject heat to the cooling air flow from at least one of the compressed air and the further compressed air.
As one feature, the environmental control system further includes a bypass valve upstream of the condenser and the first turbine to selectively bypass a majority of the further compressed air to the second turbine without f
Doerrler William
Hamilton Sundstrand Corporation
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