Patent Application
20140037441
Ram airflow is utilized in many aircraft applications such as cooling system and environmental control systems of the aircraft. During aircraft operation, movement of air is provided by the movement of the aircraft. However, when an aircraft is on the ground, such airflow is not provided and although still required, cannot be provided by movement of the aircraft. Accordingly, a ram air fan system is provided to draw air from around the aircraft through passages that communicate with the various systems that require cooling air. Typically, this cooling air is drawn by a fan driven by an electric motor. The flow of cooling air, and thus the performance of the fan and the electric motor are limited by the efficiency of airflow through the ram air fan system. Moreover, the flow of air through the ram air fan system can generate undesirable levels of noise during operation.
Accordingly, it is desirable to develop a ram air fan system that efficiently produce airflow while limiting noise to within desirable levels during operation.
An example disclosed ram air assembly includes a housing that defines an inlet and an inner cavity. A fan disposed at the inlet generates air flow and is driven by an electric motor. Airflow through the ram air fan assembly is directed through a passageway defined by a diffuser. The diffuser includes a first diameter at a forward end, and a second diameter at an aft end with the second diameter being larger than the first diameter to diffuse airflow and increase fan efficiency.
Although the different examples have the specific components shown in the illustrations, embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples.
These and other features disclosed herein can be best understood from the following specification and drawings, the following of which is a brief description.
Referring to
In a disclosed non-limiting dimensional embodiment, the first diameter 30 is between about 13.735 and 13.765 inches (34.9-35.0 cm) and the second diameter 34 is between about 15.800 and 15.830 inches (40.1-40.2 cm). In one disclosed example, a ratio between the first diameter 30 and the second diameter 34 is between approximately 0.85 and 0.089. In another example embodiment, the ratio between the first diameter 30 and the second diameter 34 is between about 0.86 and 0.88.
The forward end 28 is spaced an axial distance 52 from the aft end 32. The axial distance 52 combined with the difference between the first diameter 30 and the second diameter 34 provides the desired angle and increase in airflow area of the airflow passage 22. The disclosed example diffuser 26 includes a ratio of the second diameter 34 to the axial distance 52 that is between 1.30 and 1.36. In another disclosed example, the ratio of the second diameter 34 to the axial distance 52 is between 1.33 and 1.35. In one disclosed non-limiting dimensional example the axial distance is about 11.73 inches (29.8 cm). The ratio between the second diameter 34 and the axial distance 52 defines the increasing airflow area that provides a desired airflow efficiency of the fan 12.
A forward rim 36 is attached to an outer surface of the diffuser 26 at the forward end 28. An aft rim 38 is attached to the outer surface of the diffuser 26 at the aft end 32. The example forward rim 36 and the aft rim 38 are fabricated from a carbon matrix material and formed in a desired shape to interface with the inner surface 62 of the outer housing 16. In this example, the aft rim 38 defines a third diameter 44 (
The aft rim 38 includes a channel 68 that receives an aft seal 42 (
Referring to
Each of the plurality of openings 56 includes a diameter 54. In this example the diameter 70 is approximately 0.100 inches (0.3 cm). As appreciated, the specific open area and size of each of the plurality of openings 56 may differ to provide the desired communication through the perforated metal sheet 50.
Referring to
The example cavity 66 also includes an inner wrap 64 that is wrapped around an outer surface of the diffuser 26. This inner wrap 64 is comprised of a material that prevents the acoustic material 58 from being pulled through the plurality of openings 56 in response to the high velocity airflow through the passageway 22.
Accordingly, the example diffuser assembly 26 includes features providing improved fan operation while reducing generated noise.
Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the scope and content of this disclosure.
