Patent Description:
Water removal from, or dehumidification of, airflow is one of the primary functions of aircraft ECSs. Traditionally, the water removal has been done via a high pressure water collector or via low pressure water separation.

In high pressure water collection, water is condensed out of the air by reducing temperature on the air while the air is in a high pressure condition, prior to any turbine expansion. Lowering temperature on the air is accomplished through heat exchangers typically known as a condenser and sometimes also a reheater, where the hot side is the hot, humid high pressure air and the cold side is the cold air that has been dehumidified and has undergone turbine expansion.

In low pressure water separation, water is condensed via turbine expansion prior to the air exiting the pack. The water coming off the turbine is often a very fine mist with a very small droplet size that would be difficult to gather using centrifugal forces and inertia alone. Therefore, water is coalesced into larger droplets with a cloth mesh filter prior to the water collecting can. This mesh is more burdensome because it needs regular schedule maintenance and the size of the water collecting can is also substantially bigger in order to lower air velocities such that any free moisture can be efficiently collected.

In some cases water is separated using both high and low pressure separation. This can happen, for example, in systems that include two turbines.

The management of free water within an ECS is particularly challenging in that the current art protective controls must conservatively limit the modes of system operation thereby not fully utilizing the performance capabilities of the system. An ECS is disclosed in <CIT>.

An environmental control system for an aircraft is provided as defined by claim <NUM>.

In embodiments, the system can further include a second humidity sensor disposed fluidly between the secondary heat exchanger and the dehumidification system that measures humidity of air that has left the compressor before it enters the dehumidification system.

In embodiments, the dehumidification system includes a condenser and a water extractor, and moisture is removed from air before entering the first turbine in the normal mode.

In embodiments, the system further includes a second humidity sensor disposed fluidly between the secondary heat exchanger and the dehumidification system that measures humidity of air that has left the compressor before it enters the dehumidification system.

In embodiments, air exiting the first turbine passes through the condenser before entering the second turbine.

In embodiments, the system can further include a bypass valve that diverts air around the dehumidification system such that air exiting the first turbine can enter the second turbine without passing though the dehumidification system when in a bypass mode. In some cases, the first humidity sensor is downstream of the bypass valve.

Also disclosed is an environmental control system of an aircraft, not covered by the claims, that includes an air cycle machine (ACM) with a first turbine but not the second. In particular, the environmental control system of this second embodiment includes: a primary heat exchanger; a secondary heat exchanger; and an air cycle machine. The ACM includes: a compressor fluidly coupled to an outlet of the primary heat exchanger and an inlet of the secondary heat exchanger; a dehumidification system arranged in fluid communication with the outlet of the secondary heat exchanger; a first turbine fluidly coupled to an outlet of the dehumidification system; and a humidity sensor disposed fluidly between second heat exchanger and the first turbine that measures humidity of air as it enters the first in the normal mode.

Referring now to <FIG>, illustrated is an environmental control system (ECS) <NUM> for an aircraft. The ECS <NUM> is supplied with, for example, bleed airflow <NUM> from a bleed air supply system <NUM> of a gas turbine engine.

The environmental control system (ECS) <NUM> includes a RAM air circuit <NUM> including a shell or duct <NUM> within which one or more heat exchangers are located. The shell <NUM> can receive and direct a medium, such as ram air flow <NUM> for example, through a ram inlet <NUM>.

The one or more heat exchangers <NUM>, <NUM> are devices built for efficient heat transfer from one medium to another. Examples of the type of heat exchangers that may be used, include, but are not limited to, double pipe, shell and tube, plate, plate and shell, adiabatic shell, plate fin, pillow plate, and fluid heat exchangers.

The bleed airflow <NUM> is input into a primary heat exchanger <NUM> of the ECS <NUM> where the bleed airflow <NUM> exchanges thermal energy with a RAM airflow <NUM>, or alternatively ambient airflow. The bleed airflow is then directed through a compressor <NUM> of an air cycle machine <NUM>. The compressor <NUM> and fan <NUM> are driven by, for example, turbine <NUM> that shares a common shaft <NUM> with the compressor <NUM> and fan <NUM>. After compression at the compressor <NUM>, the compressed bleed airflow <NUM> is directed to a secondary heat exchanger <NUM> where the compressed bleed airflow is cooled by thermal energy exchange with the RAM airflow <NUM>. The bleed airflow <NUM> is then directed towards an expansion device <NUM> connected to the shaft <NUM> for primary expansion.

As shown, the system includes at least one expansion device <NUM>. The expansion device <NUM> will also be referred to as a turbine or the first turbine herein.

The turbine <NUM> a mechanical device that includes components for performing thermodynamic work on air that leaves the compressor <NUM> (e.g., extracts work from or applies work to the compressed air by raising and/or lowering pressure and by raising and/or lowering temperature) and is used to drive the shaft <NUM> and thereby drive the fan <NUM> and the compressor <NUM>.

As illustrated, before being provided to the turbine <NUM>, the compressed air is passed through a dehumidification/water removal system <NUM>. This system is described as being part of the ACM for simplicity, but it shall be understood that any system <NUM> connected to a ACM such as ACM <NUM> shall be considered part of the ACM whether integrated with the ACM or implemented as a separate unit. This is applicable to all embodiments herein.

In the illustrated, non-limiting embodiment the dehumidification system <NUM> includes a condenser <NUM>, an optional reheater, and a water collector <NUM>. The condenser <NUM> is a particular type of heat exchanger and the water collector <NUM> is a mechanical device that performs a process of removing water from a medium. In an embodiment, the water collector <NUM> is a high pressure water separator that removes moisture from a medium at a highest pressure within the environmental control system <NUM> (e.g., downstream of the compressor <NUM> and ram air heat exchanger <NUM>). In an embodiment, the dehumidification system <NUM> further includes a reheater <NUM>. The reheater <NUM> is another type of heat exchanger configured to increase the temperature of the air as it passes there through. The reheater <NUM> may be arranged generally upstream from the condenser <NUM> such that compressed air exiting secondary heat exchange <NUM> flows through the reheater <NUM> and then the condenser <NUM> sequentially.

The air is then directed to the turbine <NUM> for expansion. After expansion, the air is then again directed through the condenser <NUM> and then into the cabin <NUM> or overboard. The above discussion has described operation in a normal or first mode.

As illustrated, the ECS <NUM> can also include a bypass or economy valve (ECV) <NUM>. When the ECV <NUM> is open, the air output from the ram air heat exchanger <NUM> has a temperature and pressure sufficient to meet the demands of the one or more loads, such as the cabin <NUM> for example. Herein, when ECV <NUM> is open, the system is said to be operating in a bypass mode. Accordingly, all or at least a portion of air output from the ram air heat exchanger <NUM> is configured to bypass including the dehumidification system <NUM> but not the turbine <NUM> in order to drive the compressor <NUM>.

In embodiments herein, a humidity sensor <NUM> is provided upstream of the turbine <NUM>. As illustrated, the humidity sensor <NUM> is directly upstream of the turbine <NUM> and downstream of the ECV <NUM>. In one embodiment, this humidity sensor <NUM> is the only sensor in the ECS <NUM>. In such an embodiment, the sensor <NUM> can be said to be in the "turbine inlet location. " Measuring humidity in such a position allows the ECS controls to minimize the risk of rotor icing effects in the turbine <NUM> (e.g. reduce ACM speed or raise turbine inlet temperature if required).

In prior systems, there was no directly measured humidity. Rather, only temperature and/or pressure was used to approximate it. It should be understood that the humidity sensor <NUM> (or any other humidity sensor herein, e.g., sensor <NUM> below) can be an integrated circuit (IC) sensor that can measure one or both temperature and pressure as well. This can simplify wiring in the system and may allow for a reduction in the number of separate sensors. More importantly, advanced ECV opening logic based on measured humidity can be utilized, further optimizing system performance. Also, knowing humidity values may help in root cause failure analyses for the ECS components.

Reference is now made to <FIG> that show two different installations that may be used when measuring humidity. In <FIG>, the turbine <NUM> is shown as having an inlet pipe <NUM>. The humidity sensor <NUM> can divert a small portion the air provided to the turbine <NUM> via an inlet and an outlet. The inlet is shown as measuring bypass channel <NUM>. The bypass channel <NUM> passes through the sensor <NUM> providing air to the sensor for measurements.

After being measured, the air exits the sensor <NUM> via an outlet shown as exhaust <NUM>. The rate of flow through the sensor can be controlled by an exhaust orifice <NUM> in the exhaust <NUM>. The orifice can be fixed or adjustable. As shown in <FIG>, the exhaust <NUM> can exhaust the air to an ambient environment. This environment can be overboard or the cabin, for example. As shown, the sensor <NUM> can receive power and can also provide data (measurements) to an ECS controller <NUM>.

In <FIG>, the turbine <NUM> is shown as having an inlet pipe <NUM>. The humidity sensor <NUM> can divert a small portion the air provided to the turbine <NUM> via a measuring bypass channel <NUM>. The bypass channel <NUM> passes through the sensor <NUM> providing air to the sensor for measurements. As shown, the sensor <NUM> can receive power and can also provide data (measurements) to an ECS controller <NUM>.

After being measured, the air exits the sensor <NUM> via exhaust <NUM>. The rate of flow through the sensor can be controlled by an exhaust orifice <NUM> in the exhaust <NUM>. The orifice can be fixed or adjustable. As shown in <FIG>, the exhaust <NUM> can be connected back to the outlet <NUM> of the turbine <NUM>.

In the above discussion, only a single sensor has been shown. It shall be understood that one or more optional additional sensors can be provided. For example, in <FIG>, an optional second humidity sensor <NUM> is shown upstream of the dehumidification system <NUM>. As the skilled artisan will realize, having such a second sensor can provide one more advantages. In particular, having two sensors (in addition to the above advantages of a single sensor) can allow for performance measurements of the dehumidification system <NUM> and may further provide additional information for a root cause failure analysis. The location of sensor <NUM> can also provide the benefit of more accurately determining if moisture is present in the system and therefore utilize the water removal system only when required.

The above, examples are directed to systems that includes one turbine in the ECS. It is also applicable to other configurations. For example, as shown <FIG>, the ECS <NUM> can include a pair of expansion devices <NUM> and <NUM>. The expansion devices <NUM>, <NUM> of the system <NUM>, may, but need not be substantially identical. In general, as above, the expansion devices are turbines. Herein turbine <NUM> can be referred to as a second turbine.

The first and second turbines <NUM>, <NUM> are both connected to the shaft <NUM> and, as above, are mechanical devices that include components for performing thermodynamic work on air that leaves the compressor <NUM> (e.g., extracts work from or applies work to the compressed air by raising and/or lowering pressure and by raising and/or lowering temperature) and is used to drive the shaft <NUM> and thereby drive the fan <NUM> and the compressor <NUM>.

As illustrated, before being provided to the first turbine <NUM>, the compressed air is passed through the dehumidification/water removal system <NUM>. In the illustrated, non-limiting embodiment the dehumidification system <NUM> includes a condenser <NUM>, an optional reheater, and a water collector <NUM>. The condenser <NUM> is a particular type of heat exchanger and the water collector <NUM> is a mechanical device that performs a process of removing water from a medium. In an embodiment, the water collector <NUM> is a high-pressure water separator that removes moisture from a medium at a highest pressure within the environmental control system <NUM> (e.g., downstream of the compressor <NUM> and ram air heat exchanger <NUM>). In an embodiment, the dehumidification system <NUM> further includes a reheater <NUM>. The reheater <NUM> is another type of heat exchanger configured to increase the temperature of the air as it passes there through. The reheater <NUM> may be arranged generally upstream from the condenser <NUM> such that compressed air exiting secondary heat exchange <NUM> flows through the reheater <NUM> and then the condenser <NUM> sequentially.

The air is then directed to the first turbine <NUM> via a first inlet tube <NUM>' for expansion. After expansion, the air it then again directed through the condenser <NUM> and then into the second turbine <NUM> via a second inlet tube <NUM>". The expanded air from the second turbine <NUM> can be provided to the cabin <NUM>.

Similar to the above, As illustrated, the ECS <NUM> can also include a bypass or economy valve (ECV) <NUM>. When the ECV <NUM> is open, the air output from the ram air heat exchanger <NUM> has a temperature and pressure sufficient to meet the demands of the one or more loads, such as the cabin <NUM> for example. Accordingly, all or at least a portion of air output from the ram air heat exchanger <NUM> is configured to bypass including the dehumidification system <NUM> and the first turbine <NUM> but not the second turbine <NUM>.

In embodiment shown in <FIG>, the humidity sensor <NUM> is provided upstream of the second turbine <NUM>. As illustrated, the humidity sensor <NUM> is directly upstream of the second turbine <NUM> in the second inlet tube <NUM>" and downstream of the ECV <NUM>. As above, the system of <FIG> can operate in normal and bypass modes based on the position of the ECV <NUM>.

In one embodiment, this humidity sensor <NUM> is the only sensor in the ECS <NUM>. In such an embodiment, the sensor <NUM> can be said to be in the "second turbine inlet location" on the second inlet tube <NUM>". Measuring humidity in such a position allows the ECS controls to minimize the risk of rotor icing effects in the turbine <NUM> (e.g., reduce ACM speed if required).

It shall be understood that sensor <NUM> can be arranged relative to any of turbines herein as shown in <FIG>.

In the above discussion of <FIG>, only a single sensor has been shown discussed. It shall be understood that one or more optional additional sensors can be provided. For example, in <FIG>, an optional second humidity sensor <NUM> is shown upstream of the dehumidification system <NUM>. As the skilled artisan will realize, having such a second sensor can provide one more advantages. In particular, having two sensors (in addition to the above advantages of a single sensor) can allow for performance measurements of the dehumidification system <NUM> be used to assess when the dehumidification system is needed and may further provide additional information in support of a root cause failure analysis of a field issue.

While in the above two humidity sensors are shown, additional humidity sensors could also be provided. Further, the location of the sensors could be varied. For example, the first sensor <NUM> could be moved such that it is in the first inlet tube <NUM>' of the first turbine <NUM> rather than the second inlet tube <NUM>" of the second turbine <NUM>.

In all embodiments disclosed herein, if two humidity sensors are provided, the dehumidification system <NUM> can be monitored. For example, the difference in humidity upstream of the dehumidification system <NUM> measured by the second humidity sensor <NUM> can be compared to the humidity measured by the first humidity sensor <NUM>. The difference will show the effectiveness of dehumidification system <NUM> at removing humidity. Further, the values can be tracked over time to see if the effectiveness of dehumidification system <NUM> at removing humidity is decreasing. Such a decrease may lead to determination that the dehumidification system <NUM> is failing or needs maintenance or both. Such data can also be used to determine a cause of a failure of the air cycle machine.

Claim 1:
An environmental control system for an aircraft, comprising:
a primary heat exchanger (<NUM>);
a secondary heat exchanger (<NUM>); and
an air cycle machine (<NUM>) including:
a compressor (<NUM>) fluidly coupled to an outlet of the primary heat exchanger and an inlet of the secondary heat exchanger;
a dehumidification system (<NUM>) arranged in fluid communication with the outlet of the secondary heat exchanger;
a first turbine (<NUM>) fluidly coupled to an outlet of the secondary heat exchanger;
a second turbine (<NUM>) disposed downstream of the first turbine that receives air from the first turbine in a normal mode and wherein the second turbine receives the air via a second turbine inlet; and
a first humidity sensor (<NUM>) including an inlet (<NUM>) and an exhaust (<NUM>), the first humidity sensor disposed fluidly between the first turbine and the second turbine that measures humidity of air that has left the first turbine as it enters the second turbine in the normal mode, and wherein the inlet of the first humidity sensor is connected to the second turbine inlet such that air is directed from the second turbine inlet through the first humidity sensor to the exhaust of the first humidity sensor, or
a first humidity sensor (<NUM>) disposed fluidly between second heat exchanger and the first turbine that measures humidity of air as it enters the first turbine in the normal mode; and wherein
the exhaust includes an exhaust orifice (<NUM>) disposed therein that is configured to control a rate of flow through the first humidity sensor.