Cabin air compressor bypass for surge avoidance
An environmental control system for a vehicle includes an environmental control system pack including a ram air circuit and a thermodynamic device. The ram air circuit includes a ram air shell having a ram inlet and a ram outlet and at least one ram air heat exchanger arranged within the ram air shell. A ram air fan is fluidly coupled to the ram air shell. A bypass conduit is fluidly connected to a source of compressed medium. The bypass conduit has an outlet end positioned adjacent to a surface of the ram air fan for delivering a compressed medium to the surface.
1 . An environmental control system for a vehicle comprising:
an environmental control system pack including a ram air circuit and a thermodynamic device, the ram air circuit including:
a ram air shell having a ram inlet and a ram outlet;
at least one ram air heat exchanger arranged within the ram air shell; and
a ram air fan fluidly coupled to the ram air shell;
a bypass conduit fluidly connected to a source of compressed medium, wherein the bypass conduit has an outlet end positioned adjacent to a surface of the ram air fan for delivering a compressed medium to the surface;
wherein in a first mode of operation, ram air is drawn through the ram air shell via the ram air fan and in a second mode of operation, ram air is drawn through the ram air shell via compressed medium output from the bypass conduit, wherein in the second mode of operation, the ram air fan is either non-operational or configured as a generator.
2 . The environmental control system of claim 1 , wherein the ram air fan further comprises a casing, and the outlet end is positioned adjacent to the surface of the casing.
3 . The environmental control system of claim 2 , wherein the ram air fan further comprises a fan rotor arranged within the casing.
4 . The environmental control system of claim 1 , wherein the compressed medium includes a bleed air.
5 . The environmental control system of claim 1 , wherein the compressed medium includes a fresh air.
6 . The environmental control system of claim 1 , further comprising at least one cabin air compressing device including a compressor having a compressor outlet, wherein the compressor outlet is the source of compressed medium.
7 . The environmental control system of claim 6 , wherein a conduit fluidly connects the compressor outlet to the environmental control system pack and the bypass conduit is fluidly connected to the compressor outlet at a location upstream from the conduit.
8 . The environmental control system of claim 6 , wherein the at least one cabin air compressing device further comprises:
a shaft connected to the compressor; and
an electric motor operably connected to the shaft and configured to drive the compressor.
9 . The environmental control system of claim 1 , wherein the ram air fan is arranged at the ram outlet.
10 . The environmental control system of claim 1 , further comprising a valve associated with the bypass conduit, the valve being operable to control a supply of the compressed medium provided to the surface of the ram air fan.
11 . The environmental control system of claim 1 , wherein the vehicle is an aircraft.
12 . A method of operating an environmental control system of a vehicle, the method comprising:
providing a compressed medium to a surface of a ram air fan of a ram air circuit;
entraining a flow of ram air within the compressed medium as the compressed medium moves across the surface;
generating electricity via movement of the compressed medium having the flow of ram air entrained therein across the surface; and
exhausting the compressed medium having the flow of ram air entrained therein to an ambient atmosphere surrounding the vehicle.
13 . The method of claim 12 , wherein providing the compressed medium to the surface of the ram air fan further comprises diverting the compressed medium from a compressor outlet of a cabin air compressing device to the ram air fan via a bypass conduit.
14 . The method of claim 13 , wherein diverting the compressed medium from the compressor outlet to the ram air fan further comprises operating a valve associated with the bypass conduit.
15 . The method of claim 12 , wherein the vehicle is an aircraft.
16 . An environmental control system for a vehicle comprising:
an environmental control system pack including a ram air circuit and a thermodynamic device, the ram air circuit including:
a ram air shell having a ram inlet and a ram outlet;
at least one ram air heat exchanger arranged within the ram air shell; and
a ram air fan fluidly coupled to the ram air shell, the ram air fan including a casing; and
a bypass conduit fluidly connected to a source of compressed medium, wherein the bypass conduit has an outlet end positioned adjacent to an interior surface of the casing of the ram air fan for delivering a compressed medium to the surface;
wherein the interior surface is a Coanda surface and the ram air fan is configured as an air amplifier, the ram air fan being drivable by the compressed medium provided to the ram air fan such that ram air is entrained within the compressed medium in response to a Coanda effect at the interior surface.