Abstract:
An apparatus for use with an aircraft air conditioning machine to provide conditioned air to an aircraft cabin includes a recirculation air mixer to mix recirculation air and cold air from a turbine in the air conditioning machine as mixed air, the recirculation air mixer including a cold inlet, a plenum, a recirculation air inlet connected to an annulus and a plurality of injectors for injecting the recirculation air from the annulus into the plenum; and a condenser connected to the recirculation air mixer, the condenser including an inlet to receive air from a heat exchanger, a chamber where air from the recirculation air mixer enters to condense the air received through the inlet from the heat exchanger, an outlet for transferring the condensed air to the turbine, and an outlet for transferring conditioned air to the aircraft cabin.

Description:
BACKGROUND 
       [0001]    This invention relates generally to environmental control systems for an aircraft, and specifically to air conditioner systems. 
         [0002]    A typical environmental control system for an aircraft includes an air conditioning pack mounted to the outside of the pressure vessel of the aircraft. Pressurized air, such as bleed air from the engine, is provided and processed by going through primary and secondary heat exchangers. The output air from the air cycle machine is typically subfreezing air with moisture, ice or snow mixed in it. The output then goes through a duct to a condenser to flow through the condenser before it flows to the aircraft cabin. Sometimes heat is added to the system to prevent freezing and blockage within the system. 
       SUMMARY 
       [0003]    An apparatus for use with an aircraft air conditioning machine to provide conditioned air to an aircraft cabin includes a recirculation air mixer to mix recirculation air and cold air from a turbine in the air conditioning machine as mixed air, the recirculation air mixer including a cold inlet, a plenum, a recirculation air inlet connected to an annulus and a plurality of injectors for injecting the recirculation air from the annulus into the plenum; and a condenser connected to the recirculation air mixer, the condenser including an inlet to receive air from a heat exchanger, a chamber where air from the recirculation air mixer enters to condense the air received through the inlet from the heat exchanger, an outlet for transferring the condensed air to the turbine, and an outlet for transferring conditioned air to the aircraft cabin. 
         [0004]    A method of mixing air for use in an aircraft cabin includes condensing air through a condenser to remove moisture from the air; expanding the condensed air through a turbine to cool the air; mixing the expanded air flowing axially into a recirculation air mixer with recirculation air from the cabin flowing radially into the recirculation air mixer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1A  shows a perspective view of an air conditioning machine. 
           [0006]      FIG. 1B  shows a plan view of the air conditioning machine of  FIG. 1A . 
           [0007]      FIG. 2A  shows a perspective view of a condenser with hybrid recirculation air mixer. 
           [0008]      FIG. 2B  shows a perspective view of the hybrid recirculation air mixer of  FIG. 2A . 
       
    
    
     DETAILED DESCRIPTION 
       [0009]      FIG. 1A  shows a perspective view of air conditioning machine  10 , and  FIG. 1B  shows a plan view of air conditioning machine  10 . Air conditioning machine  10  includes hot air inlet  11 , ram air inlet  12 , dual heat exchanger  14 , ram air fan  16  with ram air outlet  17 , compressor  18 , turbine  20 , turbine bypass valve  21 , turbine diffuser cone  22 , recirculation air mixer  24 , condenser  26 , water collector  28  and outlet  30 . Dual heat exchanger  14  includes a primary heat exchanger and a secondary heat exchanger in series. Condenser  26  includes inlet  36  and outlet  38 . Recirculation air mixer  24  includes recirculation air inlet  40  and cold air inlet  42 . Dimension L is shown as the length of air conditioning machine, and can be about 42 inches (about 1067 mm). Arrows show flow direction through ducts in machine  10 . 
         [0010]    Ram air fan  16  connects to dual heat exchanger  14 . Dual heat exchanger  14  connects to compressor  18  through duct  45  connecting to primary heat exchanger, and connects to condenser  26  through duct  46  connecting to secondary heat exchanger. Condenser connects to turbine  20  through duct  49 , which includes water collector  28 . Turbine  20  connects to turbine diffuser cone  22 , which then connects to recirculation air mixer  24 , and through condenser  26  to outlet  30 . 
         [0011]    Air conditioning machine  10  can be mounted to the pressure vessel of an aircraft and works to supply conditioned air to the aircraft cabin at the proper pressure and temperature. Dual heat exchanger  14  receives compressed air from an engine at inlet  11 . Typically this air is bled off the engine and compressed, having gone through regulating valves to set the pressure. The bleed air goes into primary heat exchanger, where it is cooled using ram air fan  16 . Ram air fan  16  typically draws ambient air from outside the aircraft into heat exchanger  14  to cool process flow air and then exhausts the cooling ram air through outlet  17 . This ambient air acts to cool air entering primary heat exchanger. Primary heat exchanger can, in one example, cool air from about 400 degrees F. (204 degrees C. or 477 Kelvin (“K”)) to about 200 degrees F. (93 degrees C. or 366 K). This cooled air is then sent to compressor  18  through duct  45 , where it is compressed. A typical compression can be from about 45 psi (310 kPa) to about 80 psi (552 kPa) at 350 degrees F. (177 degrees C. or 450 K). Next air is transferred to secondary heat exchanger, which also uses ram air to cool the primary airflow further, for example, from about 350 degrees F. (177 degrees C. or 450 K) to about 150 degrees F. (66 degrees C. or 339 K). The process flow air then flows to condenser  26  through duct  46 . 
         [0012]    Condenser  26  condenses air by lowering the air temperature to a point where water condenses out of the airflow and into water collector  28 . This cooling is done by subjecting the flow to subfreezing air from turbine  20 . Process air flows through condenser  26  outlet  38  to turbine  20 . Turbine  20  expands the air to bring it to a subfreezing temperature. Turbine bypass valve  21  can be used to add heat to turbine  20  in some operating modes. Typically, valve  21  would be closed on warm days, when there is high humidity and large amounts of cooling from machine  10  are required. 
         [0013]    The cold air from turbine  20  is directed through turbine diffuser cone  22  to recirculation air mixer  24  inlet  42  axially. Recirculation air mixer  24  also receives recirculated air from the aircraft cabin at inlet  40 , directing it radially to mix with the process flow air, and then go through outlet  30  to be routed to aircraft cabin as mixed air. 
         [0014]    Because the air coming out of turbine  20  is subfreezing, and can sometimes contain ice and snow, it has the propensity to clog condenser  26  at inlet to condenser  26  from mixer  24 . This blockage can impede airflow in machine  10 , resulting in machine  10  providing less than acceptable airflow to the aircraft cabin. The insertion of recirculation air (which is warmer air from the cabin) into recirculation air mixer  24  warms overall air temperature, preventing clogging of airflow. 
         [0015]    Past systems included separate mixing and condenser systems. Past mixing systems typically brought all flow in radially, resulting in the need for additional mixing space to get desired mixing results. This resulted in air conditioning machines which were 52 inches (11 mm) in length or more. By combining condenser  26  and recirculation air mixer  24  into one piece, and mixing air radially and axially, air conditioning machine  10  is able to provide air to the aircraft cabin using much less space. Air conditioning machine  10  is about 42 inches (1067 mm) in length, reducing the length of air conditioning machine  10  by about 20% compared to previous air conditioning machines. Weight of the overall machine is also reduced, saving money and space. 
         [0016]      FIG. 2A  shows a perspective view of condenser  26  and recirculation air mixer  24 , and  FIG. 2B  shows a perspective view of recirculation air mixer  24 .  FIGS. 2A-2B  include condenser  26  with hot inlet  36 , hot outlet  38 ; recirculation air mixer  24  with recirculation air inlet  40 , cold air inlet  42 , plenum  44 , annulus  46  and injectors  48 . 
         [0017]    Condenser  26  and recirculation air mixer  24  can be cast from aluminum, or and other any other metals that can withstand operating temperatures and stresses. Alternatively, they could be molded from carbon fiber, or suitable plastics. Condenser  26  and recirculation air mixer  24  can be welded or bolted together. 
         [0018]    Recirculation air mixer  24  includes plenum  44 , which is generally an expanding rectangular shape, growing symmetrically in size from the cold inlet until it connects with the condenser. Around plenum  44 , there is an annulus  46 , which connects to recirculation air inlet  40  and injectors  48 . Inlet  40  receives recirculation air from the cabin and delivers it to annulus  46 . Injectors  48  are located on each side of plenum  44 , to inject air flowing in annulus  46  radially into plenum  44 . Airflow from turbine  20  enters plenum  44  axially. 
         [0019]    Condenser  26  includes a chamber which receives process air flow from secondary heat exchanger through inlet  36  and condenses air flow by lowering the temperature of process flow air through subjecting it to a subfreezing air flow from turbine  20  (see  FIGS. 1A-1B ). This causes vapor in the process air flow to condense, and any liquid is contained in water collector  28 . As mentioned above, due to the cold temperatures and ice and snow mixed in air flow coming from turbine  20 , inlet from mixer  24  to condenser  26  can freeze over, blocking air flow through air conditioning machine  10 . Recirculation air mixer  24  helps to combat this by injecting warmer recirculation air radially through injectors  48 . This radial injection of warm air through injectors  48  promotes quick mixing with the cold air flowing axially through inlet  42  (from turbine  20 ). The quick mixing warms the temperature of air through the system to prevent ice buildup, and radial injectors  48  directs some warm air flow directly at inlet. This helps to prevent freezing on the face of heat exchanger  14 , where the ice build-up commonly occurs. The teardrop shape of injectors  48  also promotes mixing to bring process flow air to a suitable temperature (in a smaller amount of space) for flowing through outlet  30  to cabin. 
         [0020]    Combining condenser  26  with recirculation air mixer  24  (with radial inejcetors) allows for a smaller overall air conditioning machine  10 , while preventing ice build ups which impeded flow through machine  10  in past systems. Radial teardrop shaped injectors  48  promote better mixing in a smaller amount of space. Radial injectors  48  also promote the prevention of ice buildup at inlet of condenser  26  by directing some of warm recirculation air directly towards inlet. Combining condenser  26  with mixer  24  reduces the number of parts associated with air conditioning machine  10 , which reduces the weight and volume required as compared to past system. 
         [0021]    While recirculation air mixer  24  is shown in the embodiment above to include four teardrop shaped injectors  48 , more or fewer injectors could be used. The shape of injectors  48  could also be varied to promote better mixing and prevent ice buildup. 
         [0022]    While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.