Patent Publication Number: US-2017370287-A1

Title: Inlet particle separator system with pre-cleaner flow passage

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with Government support under W911W6-08-2-0001 awarded by the US Army. The Government has certain rights in the invention. 
    
    
     TECHNICAL FIELD 
     The present disclosure generally relates to an inlet particle separator system for a vehicle engine, and more particularly relates to an inlet particle separator system with a pre-cleaner flow passage for improving fine particulate separation efficiency. 
     BACKGROUND 
     During operation of a vehicle, such as an aeronautical vehicle, air is induced into an engine and, when mixed with a combustible fuel, is used to generate energy to propel or provide power to the vehicle. The induced air may contain undesirable particles, such as sand and dust, which may degrade engine components. In order to prevent or at least minimize such degradation, many vehicles use an inlet particle separator system, disposed upstream of the engine, to remove at least a portion of the undesirable particles. The inlet particle separator may be configured to direct flow of particulates away from the engine and to direct relatively clean air into the engine. 
     Furthermore, other desirable features and characteristics of the present disclosure will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. 
     BRIEF SUMMARY 
     In one embodiment, an inlet particle separator system for a vehicle engine includes a shroud section and a hub section. The hub section is at least partly surrounded by the shroud section. The hub section is spaced apart from the shroud section. The inlet particle separator system also includes a flow passageway with an air inlet defined between the hub section and the shroud section. The flow passageway branches downstream of the air inlet into a main passage and a pre-cleaner passage. The main passage is defined between the hub section and the shroud section. The pre-cleaner passage includes a pre-cleaner inlet and extends at least partially through the hub section. Furthermore, the inlet particle separator system includes a splitter that is disposed within the main passage, downstream of the pre-cleaner inlet. The splitter divides the main passage into a scavenge flow path and an engine flow path. The pre-cleaner inlet is partly defined by a first surface of the hub section. The first surface faces in an upstream direction substantially toward the air inlet. 
     In another embodiment, an inlet particle separator system for a vehicle engine includes a shroud section and a hub section that is at least partly surrounded by the shroud section. The hub section is spaced apart from the shroud section. The inlet particle separator system also includes a flow passageway with an air inlet defined between the hub section and the shroud section. The air inlet directs flow substantially along a first direction. The flow passageway branches downstream of the air inlet into a main passage and a pre-cleaner passage. The main passage is defined between the hub section and the shroud section. The pre-cleaner passage extends at least partially through the hub section. The inlet particle separator system further includes a splitter that is disposed within the main passage. The splitter divides the main passage into a scavenge flow path and an engine flow path. The pre-cleaner passage re-directs flow from the air inlet along a second direction. The second direction is transverse to the first direction. 
     In yet another embodiment, an inlet particle separator system for a vehicle engine includes a shroud section and a hub section that is at least partly surrounded by the shroud section. The hub section is spaced apart from the shroud section. The inlet particle separator system also includes a flow passageway with an air inlet defined between the hub section and the shroud section. The flow passageway branches downstream of the air inlet into a main passage and a pre-cleaner passage. The main passage is defined between the hub section and the shroud section, and the pre-cleaner passage includes a pre-cleaner inlet and extends at least partially through the hub section. Additionally, the inlet particle separator system also includes a splitter that is disposed within the main passage, downstream of the pre-cleaner inlet. The splitter divides the main passage into a scavenge flow path and an engine flow path. The pre-cleaner inlet is partly defined by a first surface of the hub section. The first surface faces in an upstream direction substantially toward the air inlet. The first surface re-directs flow from the air inlet at least eighty degrees (80°) outwardly in a radial direction. 
     Furthermore, other desirable features and characteristics of the inlet particle separator system will become apparent from the above background, the subsequent detailed description, and the appended claims, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
         FIG. 1  is a functional block diagram of an exemplary gas turbine engine; 
         FIG. 2  is a cross-sectional view of an exemplary inlet particle separator system that may be implemented in the gas turbine engine of  FIG. 1 , wherein the cross-section is taken along a longitudinal axis of the inlet particle separator system; 
         FIG. 3  is a cross-sectional view of the inlet particle separator system taken along the longitudinal axis according to various embodiments of the present disclosure; 
         FIG. 4  is a perspective view of a hub section of the gas turbine engine, which defines portions of the inlet particle separator system according to various embodiments of the present disclosure; 
         FIG. 5  is a cross-sectional view of the inlet particle separator system, which includes the hub section of  FIG. 4 , and which is sectioned along the line  5 - 5  of  FIG. 4 ; and 
         FIG. 6  is a cross-sectional view of the inlet particle separator system taken along the line  5 - 5  of  FIG. 4  according to various embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the present disclosure or the application and uses of the present disclosure. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description. 
     Turning now to  FIG. 1 , a functional block diagram of an exemplary gas turbine engine is depicted. The engine  100  may be included on a vehicle  101  of any suitable type, such as an aircraft, rotorcraft, marine vessel, train, or other vehicle, and the engine  100  can propel or provide auxiliary power to the vehicle. In other embodiments, the engine  100  may be included on a stationary object. 
     In some embodiments, the depicted engine  100  may be a single-spool turbo-shaft gas turbine propulsion engine, which includes a compressor section  102 , a combustion section  104 , a turbine section  106 , and an exhaust section  108 . The compressor section  102 , which may include one or more compressors  112 , draws air into the engine  100  and compresses the air to raise its pressure. In the depicted embodiment, only a single compressor  112  is shown, though it will be appreciated that one or more additional compressors could be used. 
     No matter the particular number of compressors  112  that are included in the compressor section  102 , the compressed air is directed into the combustion section  104 . In the combustion section  104 , which includes a combustor assembly  114 , the compressed air is mixed with fuel supplied from a non-illustrated fuel source. The fuel and air mixture is combusted in the combustion section  104 , and the high energy combusted air mixture is then directed into the turbine section  106 . 
     The turbine section  106  includes one or more turbines. In the depicted embodiment, the turbine section  106  includes two turbines: a high pressure turbine  116  and a low pressure turbine  118 . However, it will be appreciated that the engine  100  could be configured with more or less than this number of turbines. No matter the particular number, the combusted air mixture from the combustion section  104  expands through each turbine  116 ,  118 , causing it to rotate a power shaft  122 . The combusted air mixture is then exhausted via the exhaust section  108 . The power shaft  122  may be used to drive various devices within the engine or vehicle. For example, in the context of a helicopter, the power shaft may be used to drive one or more rotors. 
     As  FIG. 1  further depicts, the gas turbine engine  100  also includes an inlet particle separator system  150 . The inlet particle separator system  150  is coupled to, and disposed upstream of, the compressor section  102 . The air that the compressor section  102  draws into the engine  100  first enters the inlet particle separator system  150 . The inlet particle separator system  150 , as will be described in more detail further below, is generally configured to separate the air that is drawn into the engine  100  into compressor inlet air  152  and scavenge air  154 . The compressor inlet air  152  is drawn into the compressor section  102 , and the scavenge air  154  is drawn into, for example, a scavenge scroll  156  via, for example, an air pump  158  (e.g., a blower or the like), and is then discharged into the atmosphere. The particle separator system  150  is additionally configured such that at least a portion of any particulate that is suspended in the air that is drawn into the engine  100  is separated therefrom and is discharged with the scavenge air  154 . Thus, the compressor inlet air  152  that is drawn into the compressor section  102  is relatively clean, particulate-free air. 
     A longitudinal axis  160  and a radial axis  162  are included in  FIG. 1  for reference purposes. As will be discussed, the engine  100  may include various passageways for the air to move along the longitudinal axis  160  and the radial axis  162 . It will be appreciated that a “downstream direction” may be defined along the longitudinal axis  160  from the inlet particle separator system  150  generally toward the low pressure turbine  118 , and an “upstream direction” may be defined along the longitudinal axis  160  opposite the “downstream direction”. It will also be appreciated that an “outboard direction” may be defined along the radial axis  162 , away from a centerline of the engine  100 . Furthermore, it will be appreciated that an “inboard direction” may be defined along the radial axis  162 , toward the centerline of the engine  100 . It will be understood that these directions can be distinguished from each other by referring to one as a “first direction” and others as a “second direction,” a “third direction,” and so on. 
     Referring now to  FIG. 2 , a cross section view of portions of the inlet particle separator system  150  is depicted and will be described according to exemplary embodiments of the present disclosure. The inlet particle separator system  150  may generally include a shroud section  202 , a hub section  204 , and a splitter  206 . It will be appreciated that this cross section illustrates a representative portion of the inlet particle separator system  150 . The shroud section  202 , hub section  204 , and/or splitter  206  may each be generally annular in shape and can be substantially symmetrical about the longitudinal axis  160   
     Thus hub section  204  will be discussed initially according to exemplary embodiments. The hub section  204  may be generally annular in shape and centered about the longitudinal axis  160 . The hub section  204  can include an outer surface  205 . In some embodiments, the hub section  204  may be substantially symmetrical with respect to the longitudinal axis  160 . The diameter (measured along the radial axis  162 ) of the outer surface  205  can vary along the longitudinal axis  160 . The hub section  204  may include an upstream portion  215 , a downstream portion  217 , and an intermediate portion  216  disposed between the upstream and downstream portions  215 ,  217 , relative to the longitudinal axis  160 . The intermediate portion  216  may have a greater diameter than both the upstream and downstream portions  215 ,  217 . 
     The shroud section  202  may be generally annular in shape and centered about the longitudinal axis  160  so as to be substantially concentric with respect to the hub section  204 . The shroud section  202  may surround at least a portion of the hub section  204 . An inner surface  203  of the shroud section  202  may have a greater diameter than the outer surface  205  of the hub section  204  (measured along the radial axis  162 ). Thus, the shroud section  202  may be spaced apart from the hub section  204 . In some embodiments, one or more struts or other support structures can extend between the shroud section  202  and the hub section  204  to maintain the separation between the shroud section  202  and the hub section  204 . In some embodiments, the shroud section  202  may be made from the same materials as the hub section  204 ; however, in other embodiments, the shroud section  202  may be made from different materials than the hub section  204 . 
     A flow passageway  208  may be defined between the shroud section  202  and the hub section  204 . The flow passageway  208  may have an air inlet  212  defined between the shroud section  202  and the upstream portion  215  of the hub section  204 . The air inlet  212  is configured to receive inlet air  207  that is drawn into the engine  100 . 
     The flow passageway  208  may branch downstream of the air inlet  212  into a main passage  210  and at least one pre-cleaner passage  213 . The main passage  210  may be defined between the outer surface  205  of the hub section  204  and the inner surface  203  of the shroud section  202 , whereas the pre-cleaner passage  213  may extend at least partly through the hub section  204 . In some embodiments, the pre-cleaner passage  213  may include a pre-cleaner inlet  220  defined within the intermediate portion  216  of the hub section  204 . Downstream segments of the pre-cleaner passage  213  may extend through the intermediate portion  216  as will be discussed in detail below. 
     The main passage  210  of the flow passageway  208  may be sub-divided into a main passage inlet  211 , a throat section  214 , and a separation section  218 . The main passage inlet  211  may be defined between the shroud section  202  and an outer lip  209  of the intermediate portion  216  of the hub section  204 . The throat section  214  may be defined between a concave portion  221  of the inner surface  203  of the shroud section  202  and the intermediate portion  216  of the hub section  204 . The separation section  218  may be defined between the shroud section  202  and the hub section  204 , proximate the splitter  206 . The shroud section  202  and the hub section  204  may be configured such that the cross sectional flow area of the main passage  210  increases gradually from the main passage inlet  211 , through the throat section  214 , and to the separation section  218 . Specifically, a first cross sectional flow area  223  proximate the main passage inlet  211 , a second cross sectional flow area  231  proximate the throat section  214 , and a third cross sectional flow area  229  are indicated in  FIG. 2 . It will be appreciated that the first cross sectional flow area  223  may be less than the second cross sectional flow area  231 , and that the second cross sectional flow area  231  may be less than the third cross sectional flow area  229 . Also, the flow area can gradually increase along the longitudinal axis  160 . 
     The separation section  218  is where the air that is drawn into the engine  100 , and more specifically the air that is drawn into the air inlet  212 , is separated into the compressor inlet air  152  and the scavenge air  154 . The separation section  218  is also where the splitter  206  is disposed. The splitter  206  may be an annular member that is substantially symmetrical with respect to the longitudinal axis  160 . The splitter  206  may also be concentric with both the shroud section  202  and the hub section  204 . The splitter  206  may be attached to the shroud section  202  and/or the hub section  204 . In some embodiments, the splitter  206  may be spaced apart from the shroud section  202  and the hub section  204  along the radial axis  162 . In some embodiments, the splitter  206  may be integrally attached to the shroud section  202  so that the splitter  206  is unitary with other portions of the shroud section  202 . In other embodiments, the splitter  206  is an independent part that is attached (e.g., via struts or other supporting structure) to the shroud section  202 . Likewise, the splitter  206  can be integrally attached or removably attached to the hub section  204 . The splitter  206  may be disposed within and may extend into the main passage  210 , downstream of the air inlet  212 , the pre-cleaner inlet  220 , and the throat section  214 . More specifically, the splitter  206  may be disposed within the separation section  218 . The splitter  206  divides the main passage  210  into a scavenge flow path  222 , into which the scavenge air  154  flows, and an engine flow path  224 , into which the compressor inlet air  152  flows. 
     Air  207  that is drawn into the engine  100  may have particles entrained therein. The inlet particle separator  150  may be configured to prevent (or at least reduce the amount of) particles flowing further into the engine  100 . Accordingly, the inlet particle separator  150  can ameliorate problems that particles would otherwise cause the engine  100 , such as particles plugging secondary flow lines, particles melting and forming glass on relatively hot engine components, particles decreasing core pressure loss, or particles otherwise reducing engine performance. 
     Specifically, the inlet particle separator  150  may cause air containing such particles to be directed toward the scavenge flow path  222  and cleaner air (i.e., air that contains less particulate) to be directed toward the engine flow path  224 . Due to inertia, relatively larger (e.g., &gt;80 microns) entrained particles may tend to collect adjacent the shroud section  202 , and may thus flow with the scavenge air  154  into the scavenge flow path  222 . As previously noted, the scavenge air  154  is drawn into the scavenge scroll  156  via the air pump  158  and is then discharged into the atmosphere. The compressor inlet air  152 , which has none (or at least very few) relatively large particles entrained therein, flows downstream into the engine flow path  224 , and ultimately into the compressor section  102  (not depicted in  FIG. 2 ). 
     In some instances, relatively small entrained particles (e.g., &lt;80 microns) may flow with the compressor inlet air  152  into the engine flow path  224 , and thus be ingested into the engine. To prevent, or at least inhibit, a large portion of the relatively small particles from flowing into the compressor section  102 , the depicted inlet particle separator system  150  includes the pre-cleaner passage  213 . 
     In some embodiments, the air pump  158  ( FIG. 1 ) may provide suction to the pre-cleaner passage  213  as well as to the scavenge flow path  222 . In other embodiments that will be discussed, the pre-cleaner passage  213  may include a dedicated air pump that pumps air through the passage  213 , and the air pump  158  may separately pump air through the scavenge flow path  222 . 
     As mentioned above, the pre-cleaner passage  213  may include a pre-cleaner inlet  220 . The pre-cleaner inlet  220  may be defined by an upstream surface  226  and the upstream lip  209  of the intermediate portion  216  of the hub section  204 . The upstream surface  226  may face in an upstream direction substantially toward the air inlet  212 . In some embodiments, for example, the upstream surface  226  may extend in a direction that is transverse to the longitudinal axis  160  (e.g., substantially along the radial axis  162  or at a relatively small angle relative to the radial axis  162 ). Stated differently, the outer surface  205  of the upstream portion  215  of the hub section  204  may extend along (i.e., substantially parallel to) the longitudinal axis  160 , and the upstream surface  226  may project outwardly therefrom, substantially along the radial axis  162 . In other words, the upstream surface  226  may be disposed at an angle  228  relative to the longitudinal axis  160 . In some embodiments, the angle  228  may be at least eighty degrees (80°) relative to the longitudinal axis  160 . In additional embodiments, the angle  228  may be between approximately eighty degrees (80°) and one hundred twenty degrees (120°) relative to the longitudinal axis  160 . 
     Furthermore, the hub section  204  may include a transition surface  227  between the outer surface of the upstream portion  215  of the hub section  204  and the upstream surface  226 . Moving in the downstream direction along the longitudinal axis  160 , the diameter of the transition surface  227  may gradually increase and may have a predetermined radius. In some embodiments, the contoured transition surface  227  may occupy between approximately ten and fifty percent (10%-50%) of the width  232  of the inlet  230 , measured along the radial axis  162 . 
     Also, the upstream surface  226  may be spaced apart from the lip  209  along the longitudinal axis  160 . The lip  209  may also curve slightly in an inboard direction along the radial axis  162  toward the upstream portion  215  of the hub section  204 . Accordingly, air that travels along the outer surface  205  of the hub section  204  can be re-directed by the transition surface  227  and the upstream surface  226  and directed into the pre-cleaner passage  213  by the lip  209 . 
     Moreover, as shown in the cross section of  FIG. 2 , the pre-cleaner inlet  220  may have a relatively large width  230 , especially in relation to the width  232  of the air inlet  212 . More specifically, the width  230  of the pre-cleaner inlet  220  may be measured along the radial axis  162 , from the upstream lip  209  to the outer surface  205  of the upstream portion  215  of the hub section  204 . In contrast, the width  232  of the air inlet  212  may be measured along the radial direction  162 , from the inner surface  203  of the shroud section  202  to the outer surface  205  of the upstream portion  215  of the hub section  204 . In some embodiments, the width  230  of the pre-cleaner inlet  220  may be at least half of the width  232  of the air inlet  212 . 
     Accordingly, as air  207  flows through the inlet  212  along the longitudinal axis  160 , a predetermined portion of the air  207  enters the pre-cleaner passage  213  (indicated as air  240  in  FIG. 2 ), depending on the amount of suction applied to the pre-cleaner passage  213 . The remaining air undergoes a large change in flow direction to continue along the main passage  210 . This large change in flow direction causes more relatively fine particles from inlet air  207  to gather near the hub  205  and be captured by the pre-cleaner passageway  220  as part of air  240 . 
     The air  240  flowing into the pre-cleaner passage  213 , while initially flowing along the longitudinal axis  160 , is re-directed in another direction by the upstream surface  226  of the pre-cleaner inlet  220 . Stated differently, the upstream surface  226  may re-direct flow of the air  240  in a direction that is transverse to the longitudinal axis  160 . Specifically, this air may be re-directed outwardly substantially along the radial axis  162  as it flows further into the pre-cleaner passage  213 . The upstream surface  226  may re-direct flow generally toward an inner diameter surface  225  of the intermediate portion  216  of the hub section  204 . More specifically, as air flows along the longitudinal axis  160 , the upstream surface  226  re-directs the flow substantially along a vector corresponding to the angle  228 . 
     The pre-cleaner passage  213  may also include a longitudinal segment  234 , which extends from the pre-cleaner inlet  220  substantially along the longitudinal axis  160 . Additionally, the pre-cleaner passage  213  may include a radial segment  236 , which extends from the longitudinal segment  234  inwardly and substantially along the radial axis  162 . In some embodiments, the cross sectional area of the pre-cleaner passage reduces from the pre-cleaner inlet  220  to the radial segment  236 . 
     The pre-cleaner passage  213  may include an outlet  238 . The outlet  238  is partially shown in  FIG. 2 . In some embodiments, the outlet  238  may be fluidly disconnected from the scavenge flow path  222 . In other embodiments, the outlet  238  may be fluidly connected to the scavenge flow path  222 . For example, in some embodiments, the pre-cleaner passage  213  may extend through a strut, through the splitter  206 , to fluidly connect to the scavenge flow path  222  as disclosed in U.S. patent application Ser. No. 13/961,284, filed on Aug. 7, 2013 and published as U.S. Patent Publication No. 2015/0040535, the disclosure of which is incorporated by reference in its entirety. Other embodiments in which the outlet  238  of the pre-cleaner passage  213  is fluidly connected to the scavenge flow path  222  will be discussed in greater detail below. 
     Accordingly, the pre-cleaner passage  213  may receive particulate-containing air  240  so that it does not enter the engine flow path  224 . More specifically, the relatively large width  230  of the pre-cleaner inlet  220  may allow the pre-cleaner passage  213  to receive air  240  which has undergone a large change in flow direction (i.e., initially flowing substantially along the longitudinal axis  160  and turning such that it flows substantially along the radial axis  162 ). The air  240  is thus re-directed by the upstream surface  226  through a high degree of curvature to flow through the pre-cleaner passage  213 . As the air  240  is re-directed, the inertia of particles therein may cause them to gather nearer the hub section  204 . Then, the particles may be captured by the pre-cleaner inlet  220  and may eventually be exhausted from the engine  100 . 
     In some embodiments represented in  FIG. 3 , the pre-cleaner passage  213  may include a flow control member, which is schematically represented and indicated at  250 . Generally, the flow control member  250  may be configured for selectively varying the flow through the pre-cleaner passage  213 . Although the flow control member  250  is illustrated in  FIG. 3  within the longitudinal segment  234 , it will be appreciated that the flow control member  250  may be operably coupled to the passage  213  at any suitable location without departing from the scope of the present disclosure. 
     In some additional embodiments, the flow control member  250  may selectively allow flow through the pre-cleaner passage  213  and, conversely, inhibit flow through the pre-cleaner passage  213 . Thus, for example, the flow control member  250  may allow flow through the pre-cleaner passage  213  when the engine  100  operates in an area with a relatively high degree of airborne particulate (e.g., close to the ground, in a dust storm, etc.). In contrast, the flow control member  250  may shut off and prevent flow through the pre-cleaner passage  213  when the engine  100  operates in an area with a relatively low degree of airborne particulate (e.g., at higher elevations, etc.), so that the engine  100  may operate at higher efficiency. 
     Specifically, in some embodiments, the flow control member  250  may be (or may include) a valve. The valve may have an open position, allowing flow through the pre-cleaner passage  213 . The valve may also have a closed position, preventing flow through the pre-cleaner passage  213 . Additionally, the valve may have one or more intermediate positions between the open and closed positions. In some embodiments, the valve may be manually opened and closed. In other embodiments, the valve may be automatically moved between the open and closed positions and may be operatively coupled to a controller  252 . 
     The controller  252  may be a computerized device that may generate and send control signals (e.g., to an actuator) for opening and closing the valve. The controller  252  may also include any hardware, software, firmware, electronic control component, processing logic, and/or processor device, individually or in any combination, including without limitation: application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. 
     In additional embodiments, the flow control member  250  may be an ejector, which selectively blows high-pressure air through the pre-cleaner passage  213 . For example, the ejector may be a nozzle that is directed downstream within the pre-cleaner passage  213 . At a selected time, the controller  252  may send a control signal, causing the ejector to blow pressurized air into the pre-cleaner passage  213  to entrain additional air through the passage  213 , thus increasing the total amount of particle-laden airflow that enters passage  213 , or to clean the passage  213  of accumulated particles. 
     In further embodiments, the flow control member  250  may be an air pump that blows or sucks air through the pre-cleaner passage  213 . This air pump may operate independent of the air pump  158  of the scavenge flow path  222  in some embodiments. The controller  252  may send control signals to the air pump for increasing air flow and/or decreasing air flow through the pre-cleaner passage  213 . 
     Referring now to  FIGS. 4 and 5 , additional embodiments of the hub section  1204  and the associated inlet particle separator system  1150  are illustrated according to exemplary embodiments. The embodiments of  FIGS. 4 and 5  may be substantially similar to the embodiments discussed above, except as noted. Thus, the embodiments of  FIGS. 4 and 5  may include components that correspond with those of  FIGS. 1-3 . Descriptions of those corresponding components will not be repeated for purposes of brevity. Components that correspond to those of  FIGS. 1-3  are indicated with corresponding reference numerals increased by 1000. 
     As shown in  FIG. 4 , the hub section  1204  may include a plurality of the pre-cleaner passages  1213 . The pre-cleaner passages  1213  may be spaced apart evenly in a circumferential direction about the intermediate portion  1216  of the hub section  1204 . 
     Also, as is most clearly shown in  FIG. 4 , the hub section  1204  may include a plurality of projecting members  1600 . Each of the projecting members  1600  may be operatively coupled to one of the pre-cleaner passages  1213 . The projecting members  1600  may project from the intermediate portion  1216  of the hub section  1204 . In some embodiments, the projecting members  1600  may project in a downstream direction substantially along the longitudinal axis  1160 . In additional embodiments, the projecting members  1600  may project outward, substantially along the radial axis  1162 . As will be discussed, the projecting members  1600  may be directed generally toward the shroud  1202  and/or toward the scavenge passage  1222  to direct particles within the projecting member  1600  toward the shroud  1202  and/or scavenge passage  1222 . 
     Each projecting member  1600  may be hollow and tubular so as to include a respective snorkel passage  1602  as shown in  FIG. 5 . The snorkel passage  1602  may be in fluid communication with the respective pre-cleaner inlet  1220 . Moreover, the snorkel passage  1602  may include a downstream end  1604 . The downstream end  1604  may define the outlet  1238  of the pre-cleaner passage  1213 . 
     A representative projecting member  1600  is shown in  FIG. 5 . As shown, the projecting member  1600  may be at least partly disposed within the main passage  1210 . Also, the snorkel passage  1602  may be in fluid communication with the scavenge flow path  1222 . Thus, particles within the pre-cleaner passage  1213  may flow into the scavenge flow path  1222 . Also, because of this configuration, the air pump  158  ( FIG. 1 ) may provide suction to both the pre-cleaner passage  1213  and the scavenge flow path  1222 . 
     In some embodiments, the downstream end  1604  of the snorkel passage  1602  may be proximate an inlet  1606  of the scavenge flow path  1222 . Specifically, as shown in  FIG. 5 , the downstream end  1604  may be spaced apart and disposed upstream relative to the inlet  1606  of the scavenge flow path  1222 . The downstream end  1604  may be directed generally toward the concavity of the inner surface  1203  of the shroud section  1202 . It will be appreciated that this arrangement may facilitate packaging, manufacturing, and/or assembly of the inlet particle separator system  1150 . 
     In other embodiments that are not specifically illustrated, at least one projecting member  1600  may project through the splitter  1206  and/or the shroud section  1202  such that the downstream end  1604  is in fluid communication with the scavenge flow path  1222 . In this example, however, the downstream end  1604  may be disposed upstream of the inlet  1606  of the scavenge flow path  1222 . 
     In additional embodiments represented in  FIG. 6 , the pre-cleaner passage  1213  may include the flow control member  1250  discussed above with reference to  FIG. 3 . As stated above, the flow control member  1250  may be configured for selectively varying the flow through the pre-cleaner passage  1213 . 
     In the embodiment of  FIG. 6 , the flow control member  1250  may be an ejector. The ejector may selectively blow high-pressure air through the pre-cleaner passage  1213 . This may increase entrainment of particle-laden air through the passage  1213 . 
     The inlet particle separator systems  150 ,  1150  described herein may increase the separation efficiency of relatively small particles from engine inlet air without an unreasonable increase in core pressure loss. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the present disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the present disclosure. It is understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the present disclosure as set forth in the appended claims.