Patent Application
20170030296
The disclosure generally relates to aircraft propulsion system, and more particular, to aircraft engine thrust reversers.
Recent trends in aviation engineering have led to the pursuit of higher bypass ratio nacelle designs in order to improve the engine thrust specific fuel consumption (TSFC) and thereby overall system efficiency. Very High Bypass Ratio (VHBR) engines are being pursued to increase propulsive efficiencies. In large engines, VHBR results in large fans and associated fan ducts, and thus must be designed with a larger exhaust area to accommodate the increased fan airflow. However, these VHBR engines require the nacelle surfaces to be minimized to obtain acceptable airframe integration losses.
Typical VHBR engines have a nacelle with reduced fineness ratio due to the requirement for minimization of the wetted surface areas. The exhaust area available through the cascade array and leakage paths during thrust reverser operation must be able to meet the increased fan exit area necessary to maintain adequate engine operating margins. These requirements result in a nacelle having a reduced volume within the nacelle interior to accommodate the packaging of cascade thrust reverser. The cascade arrays included in the nacelle are shorter than the length typically required to satisfy both the fan exhaust area and the reverse thrust specifications. This additional area can be provided by allowing for increased leakage around the periphery of the blocker doors.
According to a non-limiting embodiment, a thrust reverser included in an aircraft nacelle includes an annular nacelle, a blocker door assembly, and a cascade assembly. The annular nacelle has an inner hollowed area defining a fan duct that extends longitudinally along an axis between an upstream inlet and a downstream outlet. The blocker door assembly is disposed in the fan duct and between the upstream inlet and the downstream outlet. The blocker door assembly is configured to selectively deploy a plurality of blocker doors that extend radially from the nacelle into the fan duct so as to form a plurality of air leakage paths that define a total leakage area (AL). The cascade assembly is circumferentially disposed upstream from the blocker door assembly. The cascade assembly including a plurality of vents that define an inner circumferential area (AC2) of the cascade assembly as a ratio (RC) with respect to the AL.
According to another non-limiting embodiment, a method of controlling a thrust reverser installed in a fan duct of an aircraft nacelle includes deploying a plurality of blocker doors interposed between an upstream portion of the fan duct and a downstream portion of the fan duct. The blocker doors define a plurality of air leakage passages between the upstream portion and the downstream portion. The method further includes directing a first portion of an airflow stream flowing in the upstream portion through a cascade assembly disposed in the upstream portion of the fan duct. The method further includes directing a second portion of the airflow stream through the air leakage passages defined by the blocker doors and into the downstream portion, wherein approximately 80 percent of the airflow stream is passed through the cascade assembly while approximately 20 percent of the airflow stream is passed through the air leakage passages.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
With reference now to
The annular nacelle system 104 further includes a thrust reverser 114 interposed between the upstream portion 108 and the downstream portion 110. The thrust reverser 114 includes a translating sleeve 116, a blocker door assembly 118 having a plurality of blocker doors 120, and a cascade assembly 122. The translating sleeve 116 slides forward and backward in the direction of the longitudinal axis 102 so as to mechanically operate the thrust reverser 114 as discussed in greater detail below.
The blocker doors 120 are positionable between a fully deployed state and a fully stowed state. When initiating the blocker doors 120 into the fully deployed state (see
When initiating the blocker doors 120 into the fully stowed state (not shown), the translating sleeve 116 with respect to the fixed case of the annular nacelle 104 and slides forward toward the upstream portion 108. As the translating sleeve 116 slides forward, the blocker door assembly 118 is operated such that the blocker doors 120 are retracted into respective recesses 126 formed in the inner surface of the translating sleeve 116. In addition, the cascade assemblies 122 are covered so as to prevent airflow from exhausting therethrough. In this manner, essentially the full airflow entering the inlet 108 is directed past the blocker door assembly 118 and through the fan duct 112 where it is exhausted from the fan nozzle exit 110 to promote forward thrust of the aircraft.
Turning to
The uppermost blocker doors 120a are spaced apart from an upper bifurcation 137 by a distance (D4) to define upper bifurcation leakage paths 124d. Similarly, the lowermost blocker 120b doors are spaced apart from a lower bifurcation 139 by a distance (D5) to define lower bifurcation air paths 124e. The annular ring of blocker doors 120 therefore essentially forms a wall that directs the majority of the airflow in the upstream portion 108 through the cascades assembly 122 (not shown in
According to at least one embodiment, the spacings (e.g., D1-D5) defined by the blocker doors 120 are sized larger and formed at locations not found in conventional thrust reversers. For instance, conventional blocker doors as designed so as to minimize the air leakage past the thrust reverser, and instead maximize the airflow exhausted through the cascade array. In this manner, a minimal amount of airflow is allowed to pass by the blocker door assembly so as to minimize the amount of airflow that enters the downstream portion of the fan duct when the conventional blocker doors are fully deployed. For instance, conventional thrust reversers typically allow approximately 7% of the air flow to leak past conventionally shaped blocker doors.
Unlike conventional thrust reversers, however, at least one embodiment includes an arrangement of blocker doors 120 that defines spaces (e.g., D1-D3) between the tapered side edges 128, proximate edges 130 and distal edges 132, respectively. In this manner, a greater amount of airflow is allowed to leak past the blocker doors 120 and into the downstream portion 110 of the fan duct 112 when the blocker doors 120 are fully deployed, as compared to conventional thrust reversers. According to a non-limiting embodiment, the distances D1, D2, D4, and D5 defining the leakage paths 124a, 124b, 124d and 124e, respectively, are minimized while the distance D3 defining the distal edge leakage path 124c is maximized. In this manner, the lowest potential of the air flow in the fan duct 112 during thrust reverser deployed operation exists nearest to the IFS 106 surface. To maximize the reverse thrust for a given exhaust area provided by the thrust reverser 114, it is preferable to inhibit air flow from proceeding past the blocker doors 120 primarily through leakage paths 124d and 124e, while inhibiting air flow through leakage paths 124a and 124b as a secondary measure.
Turning now to
For instance, a first length (L1) parallel with the longitudinal axis 102 and a first circumferential length (LC1) of the cascade assembly 122 define a first overall circumferential area (AC1). The first length (L1) and a second circumferential length (LC2) defined by the turning vanes 144 forming the inner cascade array surface 140 define a second (e.g. inner) circumferential area (AC2). The second circumferential length (LC2) defined by the turning vanes 144 can be defined as the first circumferential length (LC1), less the areas occupied by the solid non-vented areas 147 (e.g., the actuators).
Turning now to
The input air flow stream (AF) flowing into the upstream portion 108 of the fan duct 112 is divided into one or more first airflow streams 148 and one or more second airflow streams 150. The first airflow streams 148 are forced to exit the fan duct 112 via the cascade assembly 122, while the second airflow streams 150 flow through the leakage paths 124a-124e and exit at the downstream portion of the fan duct (not shown in
The blocker doors 120 are also designed so as to define the total leakage area as a percentage of the inner circumferential area (AC2) of the inner cascade array surface 140. That is, the inner circumferential area (AC2) of the inner cascade array surface 140 is expressed as a cascade ratio (RC) with respect to the total leakage area (AL) defined by the plurality of blocker doors 120, i.e., RC=AC2:AL. In this manner, the leakage area (AL) can be structured as a function of the circumferential area (AC2) of the inner cascade array surface 140 so as to achieve the desired mass air flow ratio described above (e.g., RMAF=80upstream:20downstream). According to a non-limiting embodiment, the Rc ranges from approximately 0.15 (e.g., 15%) to approximately 0.35 (35%). For example, if the plurality of blocker doors 120 define an AL of approximately 900 in2, then the A2 of the inner cascade array 138 is approximately 6000 in2. Conventional engine systems have a RC ranging from about 0.06 (6%) to about 0.1 (10%). Therefore, at least one embodiment provides a RC that is more than twice the conventional RC.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
