阅读说明：本技术 用于飞行器的辅助动力单元的控制方法 (Method for controlling an auxiliary power unit for an aircraft ) 是由 薛勇 郭军亮 胡锦旋 岳鹏 周云 黄春光 于 2020-05-26 设计创作，主要内容包括：本发明涉及一种用于飞行器的辅助动力单元的控制方法,包括以下步骤：启动辅助动力单元(10)；确定飞行器处于飞行阶段还是地面阶段(20、30)；若确定飞行器处于飞行阶段期间,检测是否有应急情况(40)；以及在未检测到应急情况时,启动飞行器的燃油箱惰化系统的引气(50),即,将辅助动力单元产生的引气提供给燃油箱惰化系统。通过将辅助动力单元提供惰化引气作为其飞行期间的主要功能,使得辅助动力单元在提供惰化引气时,其工作处于高效率状态,即为该特定工况设计的一种工作状态,其燃油燃烧转化为引气增压的效率较高,同时该压力下惰化系统制取氮气的效率较高。(The invention relates to a method for controlling an auxiliary power unit for an aircraft, comprising the following steps: starting the auxiliary power unit (10); determining whether the aircraft is in a flight phase or a ground phase (20, 30); if it is determined that the aircraft is in the flight phase, detecting whether an emergency situation exists (40); and starting bleed air (50) of a fuel tank inerting system of the aircraft when the emergency situation is not detected, i.e. providing bleed air generated by the auxiliary power unit to the fuel tank inerting system. The auxiliary power unit provides inerted bleed air as a main function during the flight, so that when the auxiliary power unit provides the inerted bleed air, the auxiliary power unit works in a high-efficiency state, namely a working state designed under the specific working condition, the efficiency of converting fuel oil combustion into the bleed air and increasing the pressure is high, and meanwhile, the efficiency of preparing nitrogen by an inerting system under the pressure is high.)

1. A method for controlling an auxiliary power unit for an aircraft, characterized by comprising the steps of:

-activating the auxiliary power unit (10);

determining whether the aircraft is in a flight phase or a ground phase (20, 30);

if it is determined that the aircraft is in the flight phase, detecting whether an emergency situation exists (40); and

when the emergency situation is not detected, bleed air (50) of a fuel tank inerting system of the aircraft is started, i.e. bleed air generated by the auxiliary power unit is supplied to the fuel tank inerting system.

2. Control method according to claim 1, characterized in that, upon detection of the emergency situation, the auxiliary power unit is brought back into normal operation (60), in particular comprising stopping the supply of bleed air generated by the auxiliary power unit to a fuel tank inerting system of the aircraft and, depending on the kind of emergency situation, performing at least one of the following conditions:

(i) providing bleed air generated by the auxiliary power unit to an engine of the aircraft;

(ii) providing bleed air generated by the auxiliary power unit to an air conditioning assembly of the aircraft; and

(iii) providing mechanical power to a generator of the aircraft.

3. Control method according to claim 1, characterized in that the operational priority of the supply of bleed air generated by the auxiliary power unit to the fuel tank inerting system is placed after normal operation of the auxiliary power unit during a determination that the aircraft is in the ground phase.

4. A control method according to claim 3, characterized in that the operating priority with which bleed air generated by the auxiliary power unit is supplied to the fuel tank inerting system is increased to before normal operation of the auxiliary power unit when the fuel temperature exceeds a predetermined temperature value.

5. A control method according to claim 4, characterized in that the predetermined temperature value is the flash point of the fuel.

6. A control method according to claim 3, characterised in that bleed air generated by the auxiliary power unit is supplied to the fuel tank inerting system before passengers board the aircraft.

7. Control method according to claim 6, characterized in that the auxiliary power unit is brought back to normal operation (60) in the ground phase when the oxygen concentration in the fuel tank drops below a prescribed concentration.

8. The control method according to claim 7, wherein the prescribed concentration is 12%.

9. A control method as set forth in claim 3, characterized in that the supply of bleed air generated by the auxiliary power unit to the fuel tank inerting system is stopped and only the bleed air generated by the auxiliary power unit is supplied to the air-conditioning packs of the aircraft when a passenger starts boarding the aircraft.

10. Control method according to claim 1, characterized in that bleed air produced by the auxiliary power unit (100) is supplied to a fuel tank inerting system (200) of the aircraft and nitrogen-rich gas is obtained from the fuel tank inerting system (200) upon detection of a fire alarm in the auxiliary power unit (100) or in a compartment (400) in which the auxiliary power unit (100) is located, nitrogen-rich gas being introduced into the auxiliary power unit (100) or into the compartment (400) to prevent combustion.

Technical Field

The invention relates to a control method of an Auxiliary Power Unit (APU) for an aircraft, in particular to a control method of the APU with inerted bleed air as a main flight condition.

Background

The upper space of the fuel tank of the aircraft is filled with combustible oil-gas mixture, and the characteristics of flammability and explosiveness seriously threaten the flight safety, so that effective measures must be taken to reduce the probability of explosion and reduce the hazard level of the explosion and explosion. In the fuel tank protection system, the reduction of the oxygen concentration in the upper space of the fuel tank can effectively prevent the fuel tank from being exploded due to fire, and ensure the safety of passengers and aircrafts.

Reducing the oxygen concentration in the fuel tank is currently generally accomplished by supplying the fuel tank with an inert gas (e.g., nitrogen or carbon dioxide) using an inerting system. Specifically, the engine supplies air to an inerting system, the inerting system cools the bleed air and then leads the bleed air into an air separator, and the air separator is utilized to separate nitrogen in the bleed air to prepare nitrogen-rich gas. The nitrogen-rich gas is introduced into the fuel tank to reduce the oxygen concentration in the gas phase space in the fuel tank, so as to prevent the fuel tank from exploding and protect the safety of the fuel tank.

The APU is similar to a simplified small engine that provides emergency bleed air for engines, air conditioning systems, or emergency mechanical power for generators by burning fuel, and is a backup to conventional bleed air and power generation systems and is used only in emergency situations.

When the engines of the aircraft are not started, the APU may provide auxiliary bleed air and mechanical power to the aircraft, with typical operating conditions as follows:

(a) at a height of 4,572 meters (i.e., 15,000 feet) at ground level, the following two are satisfied:

(i) the air-bleed air can be provided for starting an air-conditioning system or a main engine;

(ii) the air-entraining and the generator shaft power can be simultaneously provided;

(b) providing shaft power to the generator below 12,131 meters (i.e., 39,800 feet) of altitude in the air;

(c) below 8,382 meters (i.e., 27,500 feet) height in the air, providing bleed air for the main engine start while also providing shaft power for the generator;

(d) below the 6,096 meter (i.e., 20,000 feet) elevation in the air, bleed air is provided for the environmental control system while shaft power is also provided for the generator.

The APU is provided not only to reduce the possibility of accidents in flight, but also to reduce the dependence on ground equipment, and thus its in-flight functions are not fully developed. Typically, the APU is off in flight and is only started when the engine is off or has failed, either to provide bleed air for engine starting or to provide mechanical power for the generator. However, the probability of these emergency situations occurring is low. The consequence of this is that the APU does not operate normally, becoming an idle weight in flight. Taking a model 150 base unit APU as an example, the weight of the APU is about 170kg, which not only increases the fuel consumption rate, but also reduces the economy.

Currently, there are some patent documents relating to the development of idle functions of APUs.

For example, the operating performance of an enhanced APU is disclosed in U.S. patent application US20160369700a1 filed 24/6/2014 by U.S. technical shares inc. In this document, the use of oxygen from the ASM to supply the APU to burn fuel to facilitate APU combustion is primarily mentioned.

Also for example, an aircraft system and method with an integrated tank and energy generator is disclosed in U.S. patent US9731834B2 filed by honeywell, 2, 16, 2017. In this document, re-inerting of the fuel tank by means of carbon dioxide generated by combustion of fuel vapour in the fuel tank is mainly mentioned.

However, these above techniques do not associate the APU with the fuel tank inerting system mentioned previously and therefore do not provide any facilitation to the inerting system.

Therefore, an APU control method taking inerted bleed air as a main flight condition needs to be designed. When an emergency situation occurs, the APU may shut off bleed air to the inerting system, switch it to an emergency state, provide start bleed air to the engine or bleed air to the air conditioning components, or provide mechanical power for emergency power generation to the generator.

Disclosure of Invention

The invention aims to provide an APU control method taking inerted bleed air as a main flight working condition. When an emergency situation occurs, the APU device may shut off bleed air to the inerting system, switch it to an emergency state, provide start bleed air to the engine or bleed air to the air conditioning components, or provide mechanical power for emergency power generation to the generator.

The invention relates to a method for controlling an auxiliary power unit for an aircraft, comprising the following steps:

starting the auxiliary power unit;

determining whether the aircraft is in a flight phase or a ground phase;

if the aircraft is determined to be in the flight phase, detecting whether an emergency situation exists; and

when an emergency situation is not detected, bleed air of a fuel tank inerting system of the aircraft is started, i.e. bleed air generated by the auxiliary power unit is supplied to the fuel tank inerting system.

Preferably, the auxiliary power unit is brought back into normal operation when an emergency situation is detected, in particular comprising stopping the supply of bleed air generated by the auxiliary power unit to a fuel tank inerting system of the aircraft, and performing at least one of the following conditions depending on the nature of the emergency situation: :

(i) providing bleed air generated by the auxiliary power unit to an engine of the aircraft;

(ii) providing bleed air generated by the auxiliary power unit to an air conditioning assembly of the aircraft; and

(iii) mechanical power is provided to the aircraft's generator.

On the other hand, during the determination that the aircraft is in the ground phase, the operational priority of the bleed air generated by the auxiliary power unit being provided to the fuel tank inerting system is placed after normal operation of the auxiliary power unit.

Preferably, the operating priority with which bleed air generated by the auxiliary power unit is supplied to the fuel tank inerting system is increased to before normal operation of the auxiliary power unit when the fuel temperature exceeds a predetermined temperature value.

More preferably, the predetermined temperature value is the flash point of the fuel.

In a further preferred embodiment, bleed air generated by the auxiliary power unit is supplied to the fuel tank inerting system before passengers board the aircraft.

Preferably, the auxiliary power unit is returned to normal operation during the ground phase when the oxygen concentration in the fuel tank falls below a specified concentration.

More preferably, the predetermined concentration is 12%.

In a further preferred embodiment, the supply of bleed air generated by the auxiliary power unit to the fuel tank inerting system is stopped when a passenger starts boarding the aircraft, and only the bleed air generated by the auxiliary power unit is supplied to the air conditioning components of the aircraft.

In a further preferred embodiment, upon detection of a fire alarm in the auxiliary power unit or in a compartment in which the auxiliary power unit is located, bleed air produced by the auxiliary power unit is supplied to a fuel tank inerting system of the aircraft and nitrogen-rich gas is obtained from the fuel tank inerting system, which is introduced into the auxiliary power unit or the compartment to prevent combustion.

The APU control method taking inerted bleed air as the main flight condition can obtain the following advantages:

(1) the APU provides the inerting bleed air as the main function of the APU during the flight, so that when the APU provides the inerting bleed air, the operation of the APU is in a high-efficiency state, namely, the APU is in a working state designed under the specific working condition, the efficiency of converting fuel oil combustion into the bleed air pressurization is higher, and meanwhile, the efficiency of preparing nitrogen by an inerting system under the pressure is higher. (2) When the aircraft is on the ground, the inerting system does not work, so that the damage of tail gas to the air separator can be reduced, the service life of the aircraft is prolonged, the maintenance cost is reduced, and the economy is improved.

(3) The Auxiliary Power Unit (APU) replaces an engine to bleed air, so that the APU is changed from useless weight to a system capable of providing the bleed air during flight, the consumption of the bleed air of the engine is reduced, the thrust of the engine is enhanced, and the economy is improved.

(4) Besides the mode of adding an APU manual control switch to start inerting bleed air, the starting can be realized through automatic logic of the system. In particular, by means of automatic logic or manual control, it is possible to shut down the inerting system in cold weather. Since the fuel temperature is now well below its flash point, it is safe without inerting the fuel tank at all.

(5) When the APU or the APU cabin generates a fire alarm, nitrogen-rich gas is introduced into the APU cabin to prevent combustion. Compared with the fuel tank, the APU cabin is small, and the nitrogen-rich gas can reduce the oxygen concentration of the fuel tank to below 12 percent in a short time, so that the combustion is effectively prevented.

(6) For an aircraft which does not use engine bleed air, such as an inerting system which uses cabin bleed air pressurization, the APU can be used as backup bleed air, and the reliability of the inerting system is improved. This is important to meet the inerting system reliability requirements specified by airworthiness provisions.

Drawings

To further illustrate the technical effects of the method for controlling an auxiliary power unit for an aircraft according to the invention, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments, in which:

FIG. 1 is a flow chart of a control method for an auxiliary power unit for an aircraft according to the present disclosure; and

fig. 2 is a schematic view of a scenario in which the control method for an auxiliary power unit for an aircraft according to the invention is applied.

Reference numerals

10 Start APU

20 determine if the aircraft is in a flight phase?

30 determine if the aircraft is in the ground phase?

40 detect if there is an emergency?

50 start-up inerting system bleed air

60 restoring normal operation to the APU

100 APU

200 fuel tank inerting system

300 fuel tank

400 APU cabin

Detailed Description

The technical effect of the control method for an auxiliary power unit for an aircraft according to the invention is explained below with reference to the drawings.

Fig. 1 is a flow chart of a control method for an auxiliary power unit of an aircraft according to the invention. As shown in fig. 1, the starting step 10 of the APU is first carried out, after which it is determined whether the aircraft is in the flight phase or in the ground phase. When the aircraft flies in the air or in the process of taking off and landing, determining that the aircraft is in a flight phase; when the aircraft is resident on the ground, it is determined that the aircraft is in the ground stage. Although the above determination steps are broken down into two steps in fig. 1, namely determination steps 20 and 30, it will be readily understood by those skilled in the art that the stage at which the aircraft is located may also be determined directly from manual input results, so that the above two determination steps are omitted. Such variations are intended to fall within the scope of the present invention.

If it is determined that the aircraft is in the flight phase, it continues to check whether there is an emergency condition 40. If no emergency situation is detected, the emergency bleed air generated by the APU is supplied to the fuel tank inerting system of the aircraft, i.e. the bleed air 50 of the fuel tank inerting system is started.

The Auxiliary Power Unit (APU) replaces an engine to bleed air, so that the APU is changed from useless weight to a system capable of providing the bleed air during flight, the consumption of the bleed air of the engine is reduced, the thrust of the engine is enhanced, and the economy is improved.

However, if an emergency situation, such as an engine shutdown, is detected, the supply of emergency bleed air generated by the APU to the fuel tank inerting system of the aircraft is stopped, i.e. the APU is brought back to normal operation 60, and at least one of the following conditions is performed depending on the kind of emergency situation:

(i) providing emergency bleed air generated by the APU for an engine of an aircraft to ensure the normal work of the engine;

(ii) providing emergency bleed air generated by the APU for an air conditioning component of the aircraft, ensuring air supply in an engine room and ensuring normal breathing of personnel in the aircraft; and

(iii) mechanical power is provided to the aircraft's generator to ensure that critical systems for safe flight are working properly.

On the other hand, during the determination that the aircraft is in the ground phase, the start bleed air is preferentially provided to the engines or the bleed air is provided to the air conditioning packs, i.e. the operational priority of providing emergency bleed air generated by the APU to the fuel tank inerting system is placed after the normal operation of the APU.

When the aircraft is on the ground, the inerting system does not work, so that the damage of tail gas to the air separator can be reduced, the service life of the aircraft is prolonged, the maintenance cost is reduced, and the economy is improved.

If the ground temperature is high, which results in the fuel temperature exceeding a preset temperature value, the priority of the bleed air of the inerting system is increased, namely the operation priority of providing the emergency bleed air generated by the APU to the fuel tank inerting system is increased to be before the normal operation of the APU, so as to protect the safety of the fuel tank.

The previously mentioned predetermined temperature value is typically the flash point of the fuel. As is well known, JETA or RP3 has a flash point of about 37-38 deg.C, and therefore, in the preferred embodiment of the present invention, the predetermined temperature value can be set to 37-38 deg.C.

In a preferred embodiment of the invention, it is also possible to provide emergency bleed air generated by the APU to the fuel tank inerting system before the passengers board the aircraft, in order to protect the safety of the passengers in general.

When the oxygen concentration in the fuel tank drops below a specified concentration (typically 12%) during the ground phase, the supply of emergency bleed air generated by the APU to the fuel tank inerting system is stopped, i.e. the APU is returned to normal operation 60. This is because when the oxygen concentration in the fuel tank is reduced to 12% or less, the inerted state of the fuel tank can be maintained for a long time without continuing the operation.

Alternatively, when the passengers start boarding the aircraft, the supply of emergency bleed air generated by the APU to the fuel tank inerting system is stopped, i.e. the APU is brought back to normal operation 60. In this case, the emergency bleed air generated by the APU need only be supplied to the air conditioning packs of the aircraft in order to reduce the aircraft temperature to a comfortable level.

Therefore, after the working condition of the APU is increased, a person skilled in the art can obtain a specific working condition with a specific function, namely bleed air is provided for the inerting system in the full flight envelope range, so that the inerting system can prepare nitrogen-rich gas. When the APU provides the inerting bleed air, the APU works in a high-efficiency state, namely a working state customized for the specific working condition, the efficiency of converting fuel oil combustion into the bleed air pressurization is higher, and the efficiency of preparing nitrogen by the inerting system under the pressure is higher.

For an aircraft which does not use engine bleed air, such as an inerting system which uses cabin bleed air pressurization, the APU can be used as backup bleed air, and the reliability of the inerting system is improved. This is important to meet the inerting system reliability requirements specified by airworthiness provisions.

Fig. 2 is a schematic view of a scenario in which the control method for an auxiliary power unit for an aircraft according to the invention is applied.

As shown in FIG. 2, APU100 is disposed within APU bay 400. When a fire alarm is detected in the APU100 or the APU compartment 400 in which the APU100 is located, emergency bleed air generated by the APU100 is supplied to a fuel tank inerting system 200 of the aircraft and nitrogen-rich gas is obtained from the fuel tank inerting system 200 and introduced into the APU100 or the APU compartment 400 to prevent combustion. Due to the small size of the APU compartment 400 compared to the fuel tank, the nitrogen rich gas can reduce the oxygen concentration of the fuel tank 300 to below 12% in a short period of time, thereby effectively preventing combustion.

Although the operational steps of the control method for an auxiliary power unit for an aircraft and its applications according to the invention have been described above with reference to a preferred embodiment and the accompanying drawings, it will be appreciated by those skilled in the art that the above examples are given by way of illustration only and are not to be construed as limiting the invention. Therefore, modifications and variations of the present invention may be made within the true spirit and scope of the claims, and these modifications and variations are intended to fall within the scope of the claims of the present invention.