BACKGROUND

The present invention relates to an environmental control system. In particular, the invention relates to a ram air fan assembly for an environmental control system for an aircraft.

An environmental control system (ECS) aboard an aircraft provides conditioned air to an aircraft cabin. Conditioned air is air at a temperature, pressure, and humidity desirable for aircraft passenger comfort and safety. At or near ground level, the ambient air temperature and/or humidity is often sufficiently high that the air must be cooled as part of the conditioning process before being delivered to the aircraft cabin. At flight altitude, ambient air is often far cooler than desired, but at such a low pressure that it must be compressed to an acceptable pressure as part of the conditioning process. Compressing ambient air at flight altitude heats the resulting pressurized air sufficiently that it must be cooled, even if the ambient air temperature is very low. Thus, under most conditions, heat must be removed from air by the ECS before the air is delivered to the aircraft cabin. As heat is removed from the air, it is dissipated by the ECS into a separate stream of air that flows into the ECS, across heat exchangers in the ECS, and out of the aircraft, carrying the excess heat with it. Under conditions where the aircraft is moving fast enough, the pressure of air ramming into the aircraft is sufficient to move enough air through the ECS and over the heat exchangers to remove the excess heat.

While ram air works well under normal flight conditions, at lower flight speeds or when the aircraft is on the ground, ram air pressure is too low to provide enough air flow across the heat exchangers for sufficient heat removal from the ECS. Under these conditions, a fan within the ECS is employed to provide the necessary airflow across the ECS heat exchangers. This fan is called a ram air fan. As with any system aboard an aircraft, there is great value in an improved ram air fan that includes innovative components designed to improve the operational efficiency of the ram air fan and to reduce its weight.

SUMMARY

An outer hub portion for a fan rotor includes an upstream arm and a downstream arm opposite of the upstream arm. The upstream arm includes a radially inner surface, a radially outer surface opposite of the radially inner surface, and a compound contoured surface connecting the radially inner surface to the radially outer surface.

A fan rotor for a ram air fan includes a hub and blades extending radially outwards from the hub. The hub includes an inner hub portion, a disk portion connected to a radially outer surface of the inner hub portion, and an outer hub portion connected to a radially outer surface of the disk portion. The outer hub portion has an upstream arm with a compound contoured surface. The compound contoured surface is configured to direct air flow around the compound contoured surface and along roots of the blades.

A ram air fan includes a tie rod with a first end and a second end, a motor including a rotor that rotates with the tie rod and a stator positioned radially around the rotor, and a fan rotor attached to a first end of the tie rod that rotates with the tie rod. The fan rotor includes a hub and blades extending radially outwards from the hub. The hub has an inner hub portion, a disk portion connected to a radially outer surface of the inner hub portion, and an outer hub portion connected to a radially outer surface of the disk portion. The outer hub portion has an upstream arm with a radially inner surface, a radially outer surface opposite of the radially inner surface, and a compound contoured surface connecting the radially inner surface to the radially outer surface. The compound contoured surface is configured to direct air flow around the compound contoured surface and along roots of the blades.

