Fuel tank inerting system based on engine tail gas and control method thereof

Abstract

The invention belongs to the electromechanical technology of helicopters, and relates to a fuel tank inerting system based on engine tail gas and a control method of the fuel tank inerting system. One end of a pipeline blows air from an engine exhaust nozzle, and the other end of the pipeline is connected with upper air of a fuel tank; a fan, a pressure safety valve, a temperature adjusting unit, a three-way catalyst, an oxygen monitoring unit, a cooling unit and a temperature monitoring unit are sequentially arranged in the pipeline; a fuel tank oxygen sensor is arranged at the upper part of the fuel tank; the fuel tank is further connected with the outside atmosphere through a ventilation pipeline.

Description

Technical Field

[0001] This invention belongs to helicopter electromechanical technology and relates to a fuel tank inerting system based on engine exhaust gas and its control method. Background Technology

[0002] Studies have shown that when the oxygen concentration in the gas phase space of the fuel tank is reduced to below 9% by using an inerting device, the inerting device can prevent combustion and explosion caused by electrical sparks or localized high temperatures due to mechanical friction of internal components or aging of cables.

[0003] The safety of modern aircraft has always been a major concern, and fuel system combustion and explosion are among the leading causes of aircraft crashes. Helicopters in Europe and America have been using fuel tank inerting devices to proactively prevent fuel tank explosions for decades.

[0004] Common aircraft fuel tank inerting technologies include liquid nitrogen inerting, Halon 1301 inerting, molecular sieve technology, membrane separation technology, and catalytic combustion technology.

[0005] On-Board InertGas Generator System (OBIGGS) using hollow fiber membranes to produce nitrogen-rich gas is currently the most economical and practical technology for suppressing combustion and explosion in aircraft fuel tanks. However, OBIGGS technology still has many problems, such as the need to draw gas from the engine compressor in some cases, low separation membrane efficiency leading to large aircraft compensation losses, gradual clogging of fine membrane fibers and permeate pores, severe membrane performance degradation due to ozone in the gas source, and fuel vapor leakage and environmental pollution when nitrogen-rich gas is filled into the fuel tank.

[0006] Catalytic combustion is a method that reduces the flammability risk of fuel tanks by consuming oxygen and combustible vapors in the gas phase space. This method requires virtually no preheating, has a fast start-up speed, and, due to the consumption of oxygen in the reactor, achieves high inerting efficiency and a short time; it also does not release fuel vapors, making it environmentally friendly. However, this technology still has drawbacks such as incomplete reaction and low concentration of nitrogen gas produced as inerting.

[0007] Currently, in research on energy integration in electromechanical systems, the utilization of engine exhaust gas is limited to some waste heat recovery and utilization.

[0008] To avoid reducing engine power by drawing air from the engine compressor outlet and to address the shortcomings of incomplete catalytic combustion, such as low nitrogen concentration in inert gas, it is necessary to fully utilize the low oxygen concentration in engine exhaust and use it in an inert fuel tank. This requires filtering, catalyzing, and cooling many particles and harmful gases in the engine exhaust, such as CO, HC, and NOx. Summary of the Invention

[0009] Purpose of the invention: This invention provides a fuel tank inerting system and its control method based on engine exhaust gas. Engine exhaust gas is drawn from the engine tailpipe, filtered for particulate impurities by a vortex filter, further reduced by a three-way catalytic converter to reduce the oxygen concentration, separated by water, removed by sulfides, and cooled before being sent to the fuel tank. This achieves the purpose of inerting the fuel tank, avoiding the reduction of engine power by drawing air from the engine compressor, and improving energy utilization.

[0010] To address the aforementioned technical issues, this application provides a fuel tank inerting system based on engine exhaust gases, comprising: One end of the pipeline draws air from the engine's exhaust nozzle, while the other end connects to the air in the upper part of the fuel tank. The pipeline is sequentially equipped with a fan, a pressure safety valve, a temperature regulation unit, a three-way catalytic converter, an oxygen monitoring unit, a cooling unit, and another temperature monitoring unit. A fuel tank oxygen sensor is located on the upper part of the fuel tank; The fuel tank is also connected to the outside atmosphere via a vent pipe.

[0011] Furthermore, a vortex filter is installed in the pipeline between the fan and the engine exhaust nozzle, with a built-in gas adsorption medium and a built-in high-temperature resistant metal filter element for filtering particulate matter.

[0012] Furthermore, the temperature control unit includes: a front-end cooler unit connected in parallel / series and an electric heater; The front-end cooler unit cools the front-end cooler via a front-end cooling fan; The front end of the front cooler and the front end of the electric heater are respectively connected to the first shut-off valve and the second shut-off valve. The front end temperature and pressure sensor is installed in the pipeline after the output ends of the front cooler and the electric heater converge.

[0013] Furthermore, the back-end cooling unit includes a back-end cooling fan and a back-end cooler. A water separation filter is installed between the back-end cooling unit and the temperature monitoring unit, and the unit includes a built-in water separation filter device and activated carbon for removing sulfides.

[0014] Furthermore, the temperature monitoring unit includes a rear-end temperature and pressure sensor, a venting valve, and a rear-end shut-off valve arranged sequentially. When the temperature exceeds the standard, close the back-end shut-off valve and open the vent valve to release the gas in the pipeline to the outside atmosphere.

[0015] Furthermore, the oxygen monitoring unit includes a front-end oxygen sensor; When the front-end oxygen sensor detects that the oxygen concentration exceeds the standard, the vent valve of the temperature monitoring unit is opened to release the gas in the pipeline to the outside atmosphere.

[0016] Furthermore, a front-end flame suppressor is installed between the temperature monitoring unit and the fuel tank.

[0017] Furthermore, it also includes a controller; Controller connections: fan, first shut-off valve, second shut-off valve, electric heater, front cooling fan, rear cooling fan, front oxygen sensor, fuel tank oxygen sensor, rear shut-off valve, and vent valve.

[0018] Furthermore, a rear flame suppressor is installed at the outer end of the venting pipe, and a venting valve is installed inside the venting pipe.

[0019] A control method for a fuel tank inerting system based on engine exhaust gases, the process of which is as follows: Through ground tests, with the fuel tank oxygen concentration threshold and safety value as control targets, the opening values ​​of the first, second and rear shut-off valves were determined respectively. Set the fuel tank oxygen concentration threshold and safety value in the controller; the threshold should be lower than the safety value. When the system starts up, the first and second shut-off valves and the vent valve are fully open, the rear shut-off valve is closed, and the rear cooling fan is on. Normal control: Start the fan to extract engine exhaust gas; When the front-end temperature and pressure sensor detects that the exhaust gas temperature does not meet the requirements, if the temperature is lower than the lower limit of the temperature threshold, the electric heater is controlled to heat the exhaust gas; if the temperature is higher than the upper limit of the temperature threshold, the cooling fan is controlled to start to cool the exhaust gas. The first and second shut-off valves are initially fully open. Then, based on the data collected by the electric heater and front-end cooling fan over a period of time, as well as the data collected by the front-end temperature and pressure sensors, and combined with the opening degree of the first and second shut-off valves determined by the ground test, a fixed opening degree is given to each valve to avoid the electric heater and front-end cooling fan from frequently starting up. When the oxygen concentration collected by the front oxygen sensor is less than the safe value and the temperature value of the rear temperature and pressure sensor is less than the specified temperature, the vent valve is closed and the rear shut-off valve is opened to inflate the upper space of the fuel tank to inertize the fuel tank. The values ​​collected from the back-end temperature and pressure sensors are used to control the back-end cooling fan, so that the exhaust gas outlet temperature of the back-end cooler is lower than the specified temperature. When the data collected by the fuel tank oxygen sensor is greater than the threshold, the first, second, and rear shut-off valves are fully opened, and the system reaches the fully open state. When the data collected by the fuel tank oxygen sensor is less than the safe value, the first and second shut-off valves are set to the previously determined opening degree. When the data collected by the fuel tank oxygen sensor is less than the threshold, the rear shut-off valve is reduced to the specified value, and the fuel tank oxygen concentration enters the maintenance phase. When the data collected by the fuel tank oxygen sensor is greater than the threshold, the back-end shut-off valve is fully opened. When the data collected by the fuel tank oxygen sensor is greater than the safety value, the first, second, and back-end shut-off valves are fully opened. The system enters the fully open state and enters the rapid inertization state of the fuel tank. Exception handling: If the oxygen concentration detected by the front-end oxygen sensor is greater than the safe value, the back-end shut-off valve will be closed, the vent valve will be opened, an alarm will be issued, and the system will continue to run for a specified time. If the oxygen concentration detected by the front-end oxygen sensor is still greater than the safe value, the system will be shut down. If the oxygen concentration detected by the front-end oxygen sensor is less than the safe value, the system will be controlled normally as described above. When the temperature or pressure collected by the back-end temperature and pressure sensor exceeds the specified safe temperature or pressure threshold, the shut-off valve is closed, the vent valve is opened, an alarm is issued, and the system continues to run for a specified time. If the temperature or pressure collected by the back-end temperature and pressure sensor exceeds the specified safe temperature or pressure threshold, the system is shut down. If the temperature or pressure collected by the back-end temperature and pressure sensor is less than the specified safe temperature or pressure threshold, the system operates normally as described above.

[0020] In summary, the beneficial effects of the present invention are as follows: This invention applies engine exhaust gas to a fuel tank inerting system. Engine exhaust gas is drawn from the engine exhaust nozzle, treated, and then sent to the fuel tank, thus inerting the fuel tank, avoiding the need to draw air from the engine compressor to reduce engine power, and improving energy utilization. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a hydraulic system for a tilting mechanism used in a tiltrotor aircraft. Detailed Implementation

[0022] Inerting systems that utilize engine exhaust gases to inertate fuel tanks, such as Figure 1 It consists of an engine tail nozzle 1; a vortex filter 2; a fan 3; a pressure relief valve 4; a first shut-off valve 5, a second shut-off valve 8, and a rear shut-off valve 17; a front cooler 6 and a rear cooler 13; a front cooling fan 7 and a rear cooling fan 15; an electric heater 9; a front temperature and pressure sensor 10 and a rear temperature and pressure sensor 16; a three-way catalytic converter 11; a front oxygen sensor 12 and a fuel tank oxygen sensor 20; a water separator filter 14; a front flame suppressor 18 and a rear flame suppressor 22; a fuel tank 19; a vent valve 21; pipelines; a controller 23; a vent valve 24; and measurement and control circuits, etc.

[0023] Principle: The oxygen concentration in the engine exhaust gas after combustion is relatively low. A suitable location is selected from the engine tailpipe as the exhaust gas collection inlet, so that the temperature of the exhaust gas drawn by the fan is usually between 550℃ and 700℃. The drawn exhaust gas passes through a vortex filter to remove particulate impurities. If the temperature of the drawn exhaust gas is too high or too low, it is controlled between 550℃ and 700℃ by an electric heater or cooler to meet the temperature requirements of the three-way catalytic converter. After passing through the three-way catalytic converter, the exhaust gas undergoes an oxidation-reduction reaction, further reducing the oxygen concentration. At this point, the exhaust gas temperature rises slightly. After passing through a water separator to remove moisture and sulfides, it is cooled to room temperature and then sent to the fuel tank, achieving the purpose of fuel tank inerting.

[0024] The outlet of the engine exhaust nozzle 1 is connected to the inlet of the vortex filter 2 via a pipeline; the outlet of the vortex filter 2 is connected to the inlet of the blower 3 via a pipeline; the outlet of the blower 3 is connected to the inlet of the pressure relief valve 4 via a pipeline; the outlet of the pressure relief valve 4 is connected to the inlets of the first shut-off valve 5 and the second shut-off valve 8 via a pipeline; the outlet of the first shut-off valve 5 is connected to the exhaust gas passage inlet of the front-end cooler 6 via a pipeline; the outlet of the second shut-off valve 8 is connected to the inlet of the electric heater 9 via a pipeline; the exhaust gas passage outlet of the front-end cooler 6 and the outlet of the electric heater 9 are connected to the inlet of the three-way catalytic converter 11 via a pipeline, and a front-end temperature and pressure sensor 10 is installed on the pipeline between them; the outlet of the three-way catalytic converter 11 is connected to the rear-end cooler via a pipeline. The exhaust gas passage inlet of the rear cooler 13 is connected; the exhaust gas passage outlet of the rear cooler 13 is connected to the inlet of the water separator filter 14 via a pipeline; the outlet of the water separator filter 14 is connected to the inlet of the rear shut-off valve 17 via a pipeline, and a rear temperature and pressure sensor 16 is installed on the pipeline between them; a branch pipeline between the water separator filter 14 and the rear temperature and pressure sensor 16 is installed with a vent valve 24; the outlet of the rear shut-off valve 17 is connected to the inlet of the front flame suppressor 18 via a pipeline; the outlet of the front flame suppressor 18 is connected to the fuel tank 19 via a pipeline; the fuel tank 19 is connected to the vent valve 21 via a pipeline; the vent valve 21 is connected to the rear flame suppressor 22 via a pipeline.

[0025] The controller 23 is connected to the fan 3, the first shut-off valve 5, the front cooling fan 7, the second shut-off valve 8, the electric heater 9, the front temperature and pressure sensor 10, the front oxygen sensor 12, the rear cooling fan 15, the rear temperature and pressure sensor 16, the rear shut-off valve 17, the fuel tank oxygen sensor 20, etc. via control lines.

[0026] The vortex filter 2 is mainly used to form a vortex flow of exhaust gas. Particulate impurities and moisture in the exhaust gas are thrown to the edge by centrifugal force. After filtration, the clean exhaust gas flows to the fan. Fan 3 uses a centrifugal fan to provide the power required for exhaust gas flow.

[0027] Pressure safety valve 4 is used to prevent system overpressure.

[0028] The front cooler 6 and the rear cooler 13 are forced air-cooled radiators used to cool the exhaust gas, while the front cooling fan 7 and the rear cooler 15 provide power for the cold air.

[0029] The electric heater 9 is used to heat the exhaust gas.

[0030] The three-way catalytic converter 11 is used to perform an oxidation-reduction reaction on the exhaust gas, thereby further reducing the oxygen concentration. The water separation filter 14 is used to dehumidify and adsorb sulfides from the gas after the three-way catalytic reaction and cooling.

[0031] The front flame suppressor 18 and the rear flame suppressor 22 are used to prevent external flames from spreading into the fuel tank.

[0032] The vent valve 21 is a two-way vent valve, which can maintain a certain positive pressure in the fuel tank and allow air to pass into the fuel tank when the fuel tank is under negative pressure.

[0033] Control strategy: Through ground tests, with the fuel tank oxygen concentration threshold and safety value as control targets, the opening values ​​of the first, second and rear shut-off valves were determined respectively.

[0034] The fuel tank oxygen concentration threshold and safety value are set in controller 23. The threshold is lower than the safety value. When the system starts up, the first shut-off valve 5, the second shut-off valve 8, and the vent valve 24 are fully open, the rear shut-off valve 17 is closed, and the rear cooling fan is on.

[0035] Start fan 3 to extract engine exhaust gas; When the front-end temperature and pressure sensor detects that the exhaust gas temperature does not meet the requirements, if the temperature is lower than the lower limit of the temperature threshold, the electric heater is controlled to heat the exhaust gas; if the temperature is higher than the upper limit of the temperature threshold, the cooling fan is controlled to start to cool the exhaust gas. The first shut-off valve 5 and the second shut-off valve 5 are initially fully open. Then, based on the data collected by the electric heater and the front-end cooling fan during a period of time, as well as the data collected by the front-end temperature and pressure sensor 10, and combined with the opening degree of the first and second shut-off valves determined by the ground test, a fixed opening degree is given to each valve to avoid the electric heater 9 and the front-end cooling fan 7 from being frequently turned on.

[0036] When the oxygen concentration collected by the front oxygen sensor 12 is less than the safe value and the temperature value of the rear temperature and pressure sensor 16 is less than the specified temperature, the vent valve 24 is closed and the rear shut-off valve 17 is opened to inflate the upper space of the fuel tank 10 to inertize the fuel tank.

[0037] The values ​​collected from the rear temperature and pressure sensor 16 are used to control the rear cooling fan 15 so that the exhaust gas outlet temperature of the rear cooler 13 is lower than the specified temperature.

[0038] When the data collected by the fuel tank oxygen sensor 20 is greater than the threshold, the first, second and rear shut-off valves are fully opened, and the system reaches the fully open state. When the data collected by the fuel tank oxygen sensor 20 is less than the safe value, the first and second shut-off valves are set to the previously determined opening degree. When the data collected by the fuel tank oxygen sensor 20 is less than the threshold, the rear shut-off valve is reduced to the specified value, and the fuel tank oxygen concentration enters the maintenance phase.

[0039] When the data collected by the fuel tank oxygen sensor 20 exceeds the threshold, the rear shut-off valve 17 is fully opened. When the data collected by the fuel tank oxygen sensor 20 exceeds the safety value, the first, second, and rear shut-off valves are fully opened. The system enters the fully open state and enters the rapid inertization state of the fuel tank.

[0040] Exception handling: If the oxygen concentration collected by the front-end oxygen sensor 12 is greater than the safe value, the back-end shut-off valve 17 is closed, the vent valve 24 is opened, an alarm is issued, and the system continues to run for a specified time. If the oxygen concentration collected by the front-end oxygen sensor 12 is still greater than the safe value, the system is shut down. If the oxygen concentration collected by the front-end oxygen sensor 12 is less than the safe value, the system is controlled normally as described above.

[0041] When the temperature or pressure collected by the back-end temperature and pressure sensor 16 exceeds the specified safe temperature or pressure threshold, the shut-off valve 17 is closed, the vent valve 24 is opened, an alarm is issued, and the system continues to run for a specified time. If the temperature or pressure collected by the back-end temperature and pressure sensor 16 exceeds the specified safe temperature or pressure threshold, the system is shut down. If the temperature or pressure collected by the back-end temperature and pressure sensor 16 is less than the specified safe temperature or pressure threshold, the system is controlled normally as described above.

Claims

1. A fuel tank inerting system based on engine exhaust gases, characterized in that: The system includes: One end of the pipeline draws air from the engine's exhaust nozzle, while the other end connects to the air in the upper part of the fuel tank. The pipeline is sequentially equipped with a fan, a pressure safety valve, a temperature regulation unit, a three-way catalytic converter, an oxygen monitoring unit, a downstream cooling unit, and a temperature monitoring unit. A fuel tank oxygen sensor is located on the upper part of the fuel tank; The fuel tank is also connected to the outside atmosphere via a vent pipe.

2. The system according to claim 1, characterized in that: A vortex filter with a built-in high-temperature resistant metal filter element is installed in the pipeline between the fan and the engine exhaust nozzle to filter particulate matter.

3. The system according to claim 2, characterized in that: The temperature control unit includes: a front-end cooler unit connected in parallel / series and an electric heater; The front-end cooler unit includes a front-end cooler and a front-end cooling fan, which cools the front-end cooler. The front end of the front cooler and the front end of the electric heater are respectively connected to the first shut-off valve and the second shut-off valve. The front end temperature and pressure sensor is installed in the pipeline after the output ends of the front cooler and the electric heater converge.

4. The system according to claim 3, characterized in that: The rear cooling unit includes a rear cooling fan and a rear cooler. A water separation filter is installed between the rear cooling unit and the temperature monitoring unit. The unit has a built-in water separation filter and activated carbon for removing sulfides.

5. The system according to claim 4, characterized in that: The temperature monitoring unit includes a rear-end temperature and pressure sensor, a vent valve, and a rear-end shut-off valve arranged sequentially. When the temperature exceeds the standard, close the back-end shut-off valve and open the vent valve to release the gas in the pipeline to the outside atmosphere.

6. The system according to claim 5, characterized in that: The oxygen monitoring unit includes a front-end oxygen sensor; When the front-end oxygen sensor detects that the oxygen concentration exceeds the standard, the vent valve of the temperature monitoring unit is opened to release the gas in the pipeline to the outside atmosphere.

7. The system according to claim 6, characterized in that: A front-end flame suppressor is installed between the temperature monitoring unit and the fuel tank.

8. The system according to claim 7, characterized in that: It also includes the controller; Controller connections: fan, first shut-off valve, second shut-off valve, electric heater, front cooling fan, rear cooling fan, front oxygen sensor, fuel tank oxygen sensor, rear shut-off valve, and vent valve.

9. The system according to claim 2, characterized in that: A rear flame suppressor is installed at the outer end of the venting pipe, and a venting valve is installed inside the venting pipe.

10. A control method for a fuel tank inerting system based on engine exhaust gases, used to control the system according to any one of claims 1-9, characterized in that: The steps are as follows: Through ground tests, with the fuel tank oxygen concentration threshold and safety value as control targets, the opening values ​​of the first, second and rear shut-off valves were determined respectively. Set the fuel tank oxygen concentration threshold and safety value in the controller; the threshold should be lower than the safety value. When the system starts up, the first and second shut-off valves and the vent valve are fully open, the rear shut-off valve is closed, and the rear cooling fan is on. Normal control: Start the fan to extract engine exhaust gas; When the front-end temperature and pressure sensor detects that the exhaust gas temperature does not meet the requirements, if the temperature is lower than the lower limit of the temperature threshold, the electric heater is controlled to heat the exhaust gas; if the temperature is higher than the upper limit of the temperature threshold, the cooling fan is controlled to start to cool the exhaust gas. The first and second shut-off valves are initially fully open. Then, based on the data collected by the electric heater and front-end cooling fan over a period of time, as well as the data collected by the front-end temperature and pressure sensors, and combined with the opening degree of the first and second shut-off valves determined by the ground test, a fixed opening degree is given to each valve to avoid the electric heater and front-end cooling fan from frequently starting up. When the oxygen concentration collected by the front oxygen sensor is less than the safe value and the temperature value of the rear temperature and pressure sensor is less than the specified temperature, the vent valve is closed and the rear shut-off valve is opened to inflate the upper space of the fuel tank to inertize the fuel tank. The values ​​collected from the back-end temperature and pressure sensors are used to control the back-end cooling fan, so that the exhaust gas outlet temperature of the back-end cooler is lower than the specified temperature. When the data collected by the fuel tank oxygen sensor is greater than the threshold, the first, second, and rear shut-off valves are fully opened, and the system reaches the fully open state. When the data collected by the fuel tank oxygen sensor is less than the safe value, the first and second shut-off valves are set to the previously determined opening degree. When the data collected by the fuel tank oxygen sensor is less than the threshold, the rear shut-off valve is reduced to the specified value, and the fuel tank oxygen concentration enters the maintenance phase. When the data collected by the fuel tank oxygen sensor is greater than the threshold, the back-end shut-off valve is fully opened. When the data collected by the fuel tank oxygen sensor is greater than the safety value, the first, second, and back-end shut-off valves are fully opened. The system enters the fully open state and enters the rapid inertization state of the fuel tank. Exception handling: If the oxygen concentration detected by the front-end oxygen sensor is greater than the safe value, the back-end shut-off valve will be closed, the vent valve will be opened, an alarm will be issued, and the system will continue to run for a specified time. If the oxygen concentration detected by the front-end oxygen sensor is still greater than the safe value, the system will be shut down. If the oxygen concentration detected by the front-end oxygen sensor is less than the safe value, the system will be controlled normally as described above. When the temperature or pressure collected by the back-end temperature and pressure sensor exceeds the specified safe temperature or pressure threshold, the shut-off valve is closed, the vent valve is opened, an alarm is issued, and the system continues to run for a specified time. If the temperature or pressure collected by the back-end temperature and pressure sensor exceeds the specified safe temperature or pressure threshold, the system is shut down. If the temperature or pressure collected by the back-end temperature and pressure sensor is less than the specified safe temperature or pressure threshold, the system operates normally as described above.

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