US-12626939-B2 - Emergency power units

Abstract

In accordance with at least one aspect of this disclosure, an emergency power unit system for an aircraft includes, a fuel cell system configured to generate power using a fuel and an oxidizer and to supply electrical power to an aircraft electrical bus in at least a fuel cell operational mode. An electrical storage is operatively connected to the aircraft electrical bus and directly connected to the fuel cell system to provide electrical power to the aircraft electrical bus and to the fuel cell system in a fuel cell start up mode.

Inventors

• Malcolm P. MacDonald

Assignees

• HAMILTON SUNDSTRAND CORPORATION

Dates

Publication Date

20260512

Application Date

20230130

Claims (20)

1. 1 . An emergency power unit system for an aircraft, comprising: a fuel cell system configured to generate power using a fuel and an oxidant and to supply electrical power to an aircraft electrical bus in at least a fuel cell operational mode; and an electrical storage operatively connected to the aircraft electrical bus and directly connected to the fuel cell system to provide electrical power to the aircraft electrical bus and to the fuel cell system in at least a fuel cell start up mode; wherein the electrical storage is a standalone electrical storage isolated from a main aircraft battery system.
2. 2 . The emergency power unit system of claim 1 , wherein, in the fuel cell start up mode, the electrical storage is configured to instantaneously provide electrical power to the aircraft electrical bus and to instantaneously provide electrical power to a starter motor of the fuel cell system to start the fuel cell system.
3. 3 . The emergency power unit system of claim 2 , wherein the fuel cell system further comprises: a fuel cell fluidly connected to an oxidizer supply line to receive the oxidant; and a compressor configured to receive the oxidant and compress the oxidant upstream of the fuel cell; wherein the starter motor of the fuel cell system is operatively connected to the compressor to drive the compressor for a first duration, wherein the first duration is a duration for the compressor to start and reach operational speed.
4. 4 . The emergency power unit system of claim 3 , wherein, in the fuel cell operational mode, only the fuel cell system is configured to supply electrical power to the aircraft electrical bus.
5. 5 . The emergency power unit system of claim 4 , wherein, in a parallel mode, after the first duration is reached, the electrical storage and the fuel cell system are configured to provide electrical power to the aircraft electrical bus in parallel for a second duration.
6. 6 . The emergency power unit system of claim 5 , further comprising a switching module configured to switch between the fuel cell start up mode, the fuel cell operational mode, and the parallel mode.
7. 7 . The emergency power unit system of claim 6 , wherein, to switch from the fuel cell start up mode to the fuel cell operational mode, the emergency power unit system is configured to disconnect the electrical storage from the aircraft electrical bus when the first duration is reached so that only the fuel cell system provides power to the aircraft electrical bus.
8. 8 . The emergency power unit system of claim 6 , wherein, to switch from the fuel cell start up mode to the parallel mode, the emergency power unit system is configured to continue to provide power to the aircraft electrical bus with the electrical storage while also providing power to the aircraft electrical bus with the fuel cell system, regardless of whether the second duration is reached.
9. 9 . The emergency power unit system of claim 6 , wherein, to switch from the parallel mode to the fuel cell operational mode, the emergency power unit system is configured to disconnect the electrical storage from the aircraft electrical bus when the second duration is reached so that only the fuel cell system provides power to the aircraft electrical bus.
10. 10 . The emergency power unit system of claim 1 , wherein the electrical storage is a battery.
11. 11 . The emergency power unit system of claim 10 , wherein the battery is smaller than a main aircraft battery.
12. 12 . The emergency power unit system of claim 1 , further comprising an oxidizer supply system fluidly connected to the fuel cell system to supply the oxidant to the fuel cell system via an oxidant supply line.
13. 13 . The emergency power unit system of claim 12 , further comprising a fuel supply system fluidly connected to the fuel cell system to supply the fuel to the fuel cell system via a fuel supply line, wherein a fuel cell is fluidly connected to the fuel supply line to receive the fuel.
14. 14 . The emergency power unit system of claim 1 , further comprising a thermal management system in thermal communication with the fuel cell system to divert heat from the fuel cell system to the thermal management system.
15. 15 . A method, comprising: supplying power from an electrical storage to an aircraft electrical bus; and directly supplying power from the electrical storage to a fuel cell system to power the aircraft electrical bus and the fuel cell system before supplying power to the aircraft electrical bus with only the fuel cell system; wherein the electrical storage is a standalone electrical storage isolated from a main aircraft battery system.
16. 16 . The method of claim 15 , further comprising switching between a fuel cell start up mode, a fuel cell operational mode, and a parallel mode as a function of a state of the fuel cell system.
17. 17 . The method of claim 16 , wherein switching from the fuel cell start up mode to the fuel cell operational mode includes disconnecting the electrical storage from the aircraft electrical bus when the state of the fuel cell system is fully operational so that only the fuel cell system provides power to the aircraft electrical bus.
18. 18 . The method of claim 16 , wherein switching from the fuel cell start up mode to the parallel mode includes continuing to provide power to the aircraft electrical bus with the electrical storage while also providing power to the aircraft electrical bus with the fuel cell system when the state of the fuel cell system is between start up and operational.
19. 19 . The method of claim 16 , wherein switching from the parallel mode to the fuel cell operational mode includes disconnecting the electrical storage from the aircraft electrical bus when the state of the fuel cell system is operational so that only the fuel cell system provides power to the aircraft electrical bus.
20. 20 . The method of claim 16 , wherein the electrical storage is a battery.

Description

TECHNICAL FIELD The present disclosure relates to emergency power units (e.g., for aircraft). BACKGROUND Typical emergency power units use a ram air turbine to generate power in an emergency. A fuel cell may be used as an emergency power unit over a ram air turbine, however, fuel cells require a supply of air and fuel to produce power, both of which are typically driven by a turbomachine (compressor, fan, or pump). In such instances, the response time of the turbomachine to reach its design pressure can lag behind the response time required for starting an emergency power unit. There is always a need in the art for improvements to emergency power units in the aerospace industry, and in particular, systems and methods for starting said emergency power units. This disclosure provides a solution for this need. SUMMARY In accordance with at least one aspect of this disclosure, an emergency power unit system for an aircraft includes, a fuel cell system configured to generate power using a fuel and an oxidizer and to supply electrical power to an aircraft electrical bus in at least a fuel cell operational mode. An electrical storage is operatively connected to the aircraft electrical bus and directly connected to the fuel cell system to provide electrical power to the aircraft electrical bus and to the fuel cell system in a fuel cell start up mode. In the fuel cell start up mode, the electrical storage can be configured to instantaneously provide electrical power to the aircraft electrical bus and to instantaneously provide electrical power to a starter motor of the fuel cell system to start the fuel cell system. The fuel cell system can include a fuel cell fluidly connected to an oxidizer supply line to receive the oxidizer and a compressor configured to receive the oxidizer and compress the oxidizer upstream of the fuel cell. The starter motor of the fuel cell system can be operatively connected to the compressor to drive the compressor for a first duration. The first duration can be a duration for the compressor to start and reach operational speed. In embodiments, the fuel cell can be or include a proton exchange membrane fuel cell. In certain embodiments, the fuel cell system may not include a solid oxide fuel cell. In embodiments, in the fuel cell operational mode, only the fuel cell system can be configured to supply electrical power to the aircraft bus alone. In embodiments, in a parallel mode, after the first duration is reached, the electrical storage and the fuel cell system can be configured to provide electrical power to the aircraft electrical bus in parallel for a second duration. In embodiments, the system can include a switching module and a controller configured to switch between the fuel cell start up mode, the fuel cell operational mode and the parallel mode. In embodiments, switching from the fuel cell start up mode to the fuel cell operational mode can include disconnecting the electrical storage from the aircraft electrical bus when the first duration is reached so that only the fuel cell system provides power to the aircraft electrical bus. In embodiments, switching from the fuel cell start up mode to the parallel mode can include continuing to provide power to the aircraft electrical bus with the electrical storage while also providing power to the aircraft electrical bus with the fuel cell system, regardless of whether the second duration is reached. In embodiments, switching from the parallel mode to the fuel cell operational mode can include disconnecting the electrical storage from the aircraft electrical bus when the second duration is reached so that only the fuel cell system provides power to the aircraft electrical bus. In certain embodiments, the electrical storage can be a battery. In embodiments, the battery can be a standalone battery, isolated from a main aircraft battery system. In embodiments, the battery can be smaller than a main aircraft battery. In embodiments, the system can include an oxidant supply system fluidly connected to the fuel cell system to supply the oxidant to the fuel cell system via the oxidant supply line. In embodiments, the system can further include a fuel supply system fluidly connected to the fuel cell system to supply the fuel to the fuel cell system via a fuel supply line. The fuel cell can be fluidly connected to the fuel supply line to receive the fuel. In embodiments, the fuel supply system can further include a fuel pump. In certain embodiments, the electrical storage can be operatively connected to provide electrical power to the fuel pump to power the fuel pump. A thermal management system can be in thermal communication with the fuel cell system to divert heat from the fuel cell system to the thermal management system. In accordance with at least one aspect of this disclosure, a method can include supplying power from an electrical storage to an aircraft electrical bus and directly supplying power from the electrical storage to a fuel cell