An aero-engine cold start auxiliary staged preheating system and control method

Abstract

The present application relates to a kind of aero-engine cold start auxiliary staged preheating system and control method, belong to aero-engine starting technical field;The present application is integrated preheating treatment to engine fuel, in-cylinder mixture thermodynamic state (in-cylinder thermal atmosphere before ignition) and lubricating oil by pipeline fuel preheating device, oil outlet preheating device, cylinder sleeve preheating device and lubricating oil heat preservation preheating device, coupling combustion parameter control strategy, according to the temperature gradient of plateau alpine low temperature environment, design four levels of plateau alpine cold start feedback control strategy, so that aviation kerosene pressure combustion engine provides and implements reasonable preheating scheme according to different low temperature low pressure environment outside in plateau alpine condition, can effectively solve the problem that aviation kerosene pressure combustion engine is difficult to cold start, starting time is long, engine parts wear seriously and cold start stability is poor and the like in plateau alpine environment.

Description

A cold start auxiliary staged preheating system and control method for aero-engines Technical Field

[0001] This invention relates to an auxiliary graded preheating system and control method for cold start of aero-engines, belonging to the field of aero-engine starting technology. Background Technology

[0002] Due to the high altitude, harsh climate, and low atmospheric temperature in the high-altitude and frigid environment of aviation kerosene compression ignition engines, the fresh charge temperature entering the engines is reduced, resulting in poor fuel atomization and inadequate fuel-air synergy. This leads to deteriorated combustion in the cylinder, prolonged ignition delay, lower pressure and temperature at the end of compression, and slower formation of a high-temperature atmosphere in the cylinder, making cold start ignition difficult. Furthermore, the engine's lubrication system is severely affected, accelerating wear on engine components and reducing engine life and reliability. Conventional cold start optimization technologies do not comprehensively consider the main key factors during engine cold starts, optimizing only one or a few factors, resulting in problems such as difficulty in cold starting, long starting times, severe wear on engine components, and poor cold start stability.

[0003] Conventional crankcase preheating optimization technology only optimizes engine block temperature. It uses heating rods to gradually raise the engine block temperature, creating a high-temperature atmosphere to optimize kerosene atomization and facilitate cold engine starts. While this method does promote cold starts, it is overly reliant on engine block temperature. Furthermore, the heat transfer is relatively slow, requiring time for the engine block temperature to reach the engine's cold-start temperature. This leads to increased fuel atomization time and poor lubrication system optimization in high-altitude and cold-weather environments, resulting in prolonged cold start times and severe wear on engine components.

[0004] Conventional air-assisted atomization optimization technology only optimizes fuel atomization by blowing high-pressure air supplied by a mechanical air pump through air nozzles, thereby improving fuel atomization and further shortening engine cold start time. However, this optimization method does not make targeted improvements to the engine's lubrication system. Furthermore, the operation of the mechanical air pump consumes the engine crankshaft's output power, resulting in severe wear of engine components and poor cold start stability even in high-altitude and cold-weather environments.

[0005] In summary, in conventional optimization methods for starting kerosene compression ignition engines in high-altitude and cold-weather environments, crankcase preheating and air-assisted atomization can optimize the engine's cold start problem to some extent. However, both conventional optimization techniques have certain limitations. Summary of the Invention

[0006] To overcome the problems existing in the background technology, the present invention preheats the engine fuel and lubricating oil through a pipeline fuel preheating device, an oil outlet preheating device, a cylinder liner preheating device, and a lubricating oil insulation preheating device. At the same time, it also couples combustion control parameter adjustment to further optimize the in-cylinder combustion of the engine. It can effectively solve the problems of long cold start time, severe wear of engine parts, and poor cold start stability of aviation kerosene compression ignition engines in high-altitude and cold environments.

[0007] To overcome the problems existing in the background art and to solve the above problems, the present invention is achieved through the following technical solution:

[0008] A cold start auxiliary staged preheating system for an aircraft engine includes an engine, cylinder liners, an adjustable throttle valve, a pipeline fuel preheating device, a fuel preheating device, an engine ECU (8), a battery, a fuel tank, an oil pan, an oil pump, a lubricating oil insulation and preheating device, a cylinder liner preheating device, a lubricating oil temperature sensor I, a lubricating oil temperature sensor II, a fuel temperature sensor I, and a fuel temperature sensor II. The fuel preheating device is installed on the fuel tank outlet pipe, the pipeline fuel preheating device is installed on the fuel pipe between the fuel preheating device and the engine, the cylinder liner preheating device is installed on the cylinder liner inside the engine, and the lubricating oil insulation and preheating device is connected to the oil pan inside the engine via the oil pump. The system includes a bottom housing; a lubricating oil temperature sensor I installed inside the oil pan, a lubricating oil temperature sensor II installed inside the lubricating oil insulation and preheating device, a fuel temperature sensor I installed inside the fuel tank, and a fuel temperature sensor II installed on the pipeline between the engine and the fuel preheating device. The lubricating oil temperature sensor and the fuel temperature sensor are connected to the input terminal of the engine ECU. The output terminal of the engine ECU is connected to the adjustable throttle valve, the fuel preheating device, the fuel preheating device, the lubricating oil insulation and preheating device, and the cylinder liner preheating device, respectively. An adjustable throttle valve is installed in the engine's air intake circuit. The battery supplies power to the preheating device, sensors, engine ECU, and adjustable throttle valve.

[0009] Preferably, the fuel preheating device at the fuel outlet includes a silicon carbide ceramic body, a nickel-iron-aluminum alloy heating rod, a cesium tungsten bronze nano-insulating coating, a fuel inlet, a fuel inlet distributor, a stainless steel shell, a fuel outlet, a fuel outlet manifold, and a distribution pipe. The fuel inlet is connected to the fuel tank, the fuel inlet distributor is connected to the fuel inlet, the fuel inlet distributor is connected to the fuel outlet manifold through the distribution pipe, the fuel outlet manifold is connected to the fuel outlet, and the fuel outlet is connected to the fuel inlet pipe of the engine. The silicon carbide ceramic body is embedded inside the stainless steel shell so that the fuel in the distribution pipe can be heated evenly. The nickel-iron-aluminum alloy heating rod is embedded inside the silicon carbide ceramic body to heat the fuel in the distribution pipe. A cesium tungsten bronze nano-insulating coating is provided between the stainless steel shell and the silicon carbide ceramic body to reduce heat loss.

[0010] Preferably, the pipeline fuel preheating device includes a stainless steel shell, a silicon carbide ceramic body, a nickel-iron-aluminum alloy heating rod, and a cesium tungsten bronze nano-insulating coating. Two channels are provided inside the stainless steel shell and the silicon carbide ceramic body. One channel is used to install the pipeline fuel preheating device onto the fuel inlet pipe, and the other channel is used to install the nickel-iron-aluminum alloy heating rod. A cesium tungsten bronze nano-insulating coating is also provided between the stainless steel shell and the silicon carbide ceramic body.

[0011] Preferably, the cylinder liner preheating device includes a cylinder liner, a silicon carbide ceramic body, a nickel-iron-aluminum alloy heating rod, a cesium tungsten bronze nano-insulating coating, and an engine block cylinder wall. The cylinder liner and the engine block cylinder wall form the outer shell of the cylinder liner preheating device. The inner surface of the engine block cylinder wall is uniformly provided with crescent-shaped channels for embedding the silicon carbide ceramic body and the nickel-iron-aluminum alloy heating rod, so that the lubricating oil at the cylinder liner is uniformly heated. All crescent-shaped channels are non-penetrating channels. A cesium tungsten bronze nano-insulating coating is provided between the crescent-shaped channels and the silicon carbide ceramic body.

[0012] Preferably, the lubricating oil heat preservation and preheating device includes a stainless steel outer shell, a stainless steel inner shell, a silicon carbide ceramic body, a nickel-iron-aluminum alloy heating rod, and a cesium tungsten bronze nano-insulating coating. The silicon carbide ceramic body with adapted uniform channels is embedded between the stainless steel inner and outer shells to preheat the lubricating oil uniformly. The designed uniform channels are all non-penetrating. The nickel-iron-aluminum alloy heating rod is installed in the insulating silicon carbide ceramic body. A layer of cesium tungsten bronze nano-insulating coating is designed between the stainless steel outer shell and the silicon carbide ceramic body to reduce heat loss.

[0013] Preferably, the battery is a storage battery made using lithium iron phosphate technology.

[0014] A graded preheating control method for cold start of an aero-engine is disclosed. The method involves setting the temperature measured by lubricating oil temperature sensor I as T1, lubricating oil temperature sensor II as T2, fuel temperature sensor I as T3, fuel temperature sensor II as T4, and ambient temperature as T5. A graded feedback control strategy is implemented with four levels of control based on T1, T2, T3, T4, and T5. Fuel and lubricating oil are heated separately according to the ambient temperature T5. The engine ECU regulates the throttle opening to adjust the intake air volume during cold start. Simultaneously, a high-pressure common rail injection strategy is coupled to flexibly adjust the injection parameters during cold start, resulting in better matching of the air-fuel mixture and maintaining the air-fuel ratio within the optimal range. This promotes efficient combustion of the combustible mixture and avoids in-cylinder afterburning, accelerating the combustion rate, increasing the compression end temperature and pressure, and accelerating the formation of a high-temperature atmosphere in the cylinder, further improving the stability of the engine during cold start.

[0015] Preferably, the hierarchical feedback control strategy, based on the four-level control set according to T1, T2, T3, T4, and T5, is as follows:

[0016] Primary regulation: When -20°C < T5 < 0°C, the ambient temperature T5 does not reach the freezing point temperatures of aviation kerosene and lubricating oil. At this time, the ambient temperature T5 has a small impact on the viscosities of aviation kerosene and lubricating oil. Only the problem of poor stability during cold start of the aviation kerosene compression ignition engine needs to be considered. The stability during cold start of the engine is optimized by adjusting and optimizing the engine combustion parameters to improve the in-cylinder combustion during cold start of the engine.

[0017] Secondary regulation: When -30°C < T5 < -20°C, the viscosity of the lubricating oil is greatly affected. On the basis of the primary regulation, this level of regulation adds the lubricating oil heat preservation and preheating treatment. The temperature T1 measured by the lubricating oil temperature sensor I is fed back to the engine ECU to control the start of the motor oil pump. Part of the lubricating oil in the oil sump is pumped out to the lubricating oil heat preservation and preheating device for preheating treatment. When T2 reaches the normal working temperature of the lubricating oil during cold start of the engine, the heating of the lubricating oil in the lubricating oil heat preservation and preheating device is stopped to save the energy of the battery. When the engine stops operating, at this time T1 has reached the working temperature of the lubricating oil. In order to save the power supply energy of the battery, part of the hot lubricating oil is pumped into the lubricating oil heat preservation and preheating device for heat preservation treatment. If the interval between the next start is long and T2 cannot meet the temperature of the lubricating oil during cold start of the engine, the lubricating oil heat preservation and preheating device preheats the lubricating oil again.

[0018] Tertiary regulation: When -40°C < T5 < -30°C, the temperature has reached the freezing point temperature of the lubricating oil, which has a great impact on the viscosity and fluidity of the lubricating oil. On the basis of the secondary regulation, this level of regulation adds cylinder liner preheating. The engine ECU controls the cylinder liner preheating device to preheat and optimize the thermodynamic state of the lubricating oil at the cylinder liner and the in-cylinder mixture. When T1 reaches the working temperature of the lubricating oil during cold start of the engine, the heating of the cylinder liner preheating device is stopped.

[0019] Quaternary regulation: When T1 or T5 < -40°C, the temperature has a great impact on the viscosity of aviation kerosene. In order to enhance the fuel atomization effect and further shorten the cold start time of the engine, on the basis of the tertiary regulation, this level of regulation adds fuel preheating. The fuel is preheated by the fuel preheating device at the oil outlet. Since the fuel inlet pipe is long, in order to enhance the fuel preheating efficiency and further improve the fuel atomization effect, according to the length of the inlet pipe, the remaining parts of the inlet pipe are installed with pipeline fuel preheating devices to preheat the pipeline fuel again. When the T4 temperature reaches the working temperature of the fuel during cold start of the engine, the power supply of the fuel preheating device at the oil outlet and the pipeline fuel preheating device is stopped.

[0020] The high-pressure common rail injection strategy involves flexibly controlling the injection pressure via the engine ECU, based on the engine's cold start conditions in high-altitude and cold environments. This maintains optimal injection pressure to promote thorough air-fuel mixing during cold starts. Furthermore, the engine ECU adjusts the injection timing and rate to maintain optimal pre-injection timing, pre-injection frequency, main injection timing, and pre-main injection intervals to accelerate the formation of a high-temperature atmosphere in the cylinder. The strategy also involves adjusting the high-pressure common rail injection pressure via the engine ECU. The solenoid valves in the high-pressure common rail injection system flexibly control the engine's fuel injection quantity, preventing air bubbles and zero residual pressure in the engine's high-pressure fuel circuit. Simultaneously, it maintains optimal starting fuel injection, pre-injection, and main injection quantities under high-altitude and cold-weather starting conditions, ensuring a reasonable amount of combustible mixture in the cylinder. Through the aforementioned high-pressure common rail injection strategy, combined with reasonable intake regulation, the engine's fuel-air synergy is better matched, and in-cylinder combustion is optimized and improved, thereby further enhancing the stability of aviation kerosene compression ignition engines during cold starts in high-altitude and cold-weather environments.

[0021] The specific air-fuel ratio control method is as follows: based on the amount of fuel injected by the high-pressure common rail injection strategy, the engine ECU adjusts the opening of the adjustable valve to control the intake air volume during cold start of the engine in high-altitude and cold environments. This ensures that the fuel-air mixture is properly matched during cold start of the aviation kerosene compression ignition engine in extreme environments, thereby maintaining the engine's air-fuel ratio within the optimal range. This promotes the formation of the air-fuel mixture and improves its ignition performance, thus improving the stability of the aviation kerosene compression ignition engine during cold start in high-altitude and cold environments.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention preheats engine fuel and lubricating oil through a pipeline fuel preheating device, an oil outlet preheating device, a cylinder liner preheating device, and a lubricating oil insulation preheating device. At the same time, it also couples combustion control parameter adjustment to further optimize the in-cylinder combustion of the engine. It can effectively solve the problems of long cold start time, severe wear of engine parts, and poor cold start stability of aviation kerosene compression ignition engines in high-altitude and cold environments.

[0024] The preheating device achieves rapid heating through nickel-iron-aluminum alloy heating rods, and the silicon carbide ceramic body makes the fuel and lubricating oil preheat more evenly. The cesium tungsten bronze nano heat insulation coating reduces the heat loss of the preheating device and improves the energy utilization efficiency.

[0025] Furthermore, this invention is based on a pipeline fuel preheating device, an oil outlet preheating device, a cylinder liner preheating device, and a lubricating oil insulation preheating device, coupled with a combustion parameter control strategy. According to the temperature gradient of the low-temperature environment in high-altitude and cold regions, a four-level high-altitude and cold-start feedback control strategy is designed, enabling aviation kerosene compression ignition engines to provide and implement reasonable preheating schemes according to different low-temperature and low-pressure environments in high-altitude and cold regions, thereby achieving efficient, reliable, and energy-saving cold starts of the engine. Attached Figure Description

[0026] Figure 1 is a schematic diagram of the auxiliary preheating system of the present invention;

[0027] Figure 2 is a cross-sectional view of the fuel preheating device at the oil outlet of the present invention.

[0028] Figure 3 is a schematic diagram of the structure of the fuel preheating device at the oil outlet of the present invention.

[0029] Figure 4 is a cross-sectional view of the pipeline fuel preheating device of the present invention;

[0030] Figure 5 is a schematic diagram of the pipeline fuel preheating device of the present invention;

[0031] Figure 6 is a cross-sectional view of the cylinder liner preheating device of the present invention;

[0032] Figure 7 is a schematic diagram of the cylinder liner preheating device of the present invention;

[0033] Figure 8 is a cross-sectional view of the lubricating oil heat preservation and preheating device of the present invention.

[0034] Figure 9 is a schematic diagram of the structure of the lubricating oil heat preservation and preheating device of the present invention;

[0035] Figure 10 is a schematic diagram of the cold start control process of the aero-engine of the present invention.

[0036] The diagram is labeled as follows: 1-Engine; 2-Cylinder liner; 3-Silicon carbide ceramic body; 4-Nickel-iron-aluminum alloy heating rod; 5-Adjustable throttle body; 6-Fuel preheating device; 7-Fuel preheating device; 8-Engine ECU; 9-Battery; 10-Fuel tank; 11-Starter motor; 12-Oil pan; 13-Oil pump; 14-Lubricating oil heat preservation and preheating device; 15-Cesium tungsten bronze nano-insulation coating; 16-Oil inlet; 17-Oil inlet distributor; 18-Stainless steel housing; 19-Oil outlet; 20-Oil outlet manifold; 21-Distribution pipe; 22-Oil inlet pipe; 23-Cylinder wall; 24-Stainless steel outer shell; 25-Stainless steel inner shell; 26-Lubricating oil pipe; 27-Cylinder liner preheating device; 28-Lubricating oil temperature sensor I; 29-Lubricating oil temperature sensor II; 30-Fuel temperature sensor I; 31-Fuel temperature sensor II. Detailed Implementation

[0037] To make the objectives, technical solutions, and beneficial effects of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so as to facilitate understanding by those skilled in the art.

[0038] As shown in Figure 1, a cold start auxiliary staged preheating system for an aircraft engine includes an engine 1, a cylinder liner 2, an adjustable throttle valve 5, a fuel preheating device 6, a fuel preheating device 7, an engine ECU 8, a battery 9, a fuel tank 10, an oil pan 12, an oil pump 13, a lubricating oil insulation and preheating device 14, a cylinder liner preheating device 27, a lubricating oil temperature sensor I 28, a lubricating oil temperature sensor II 29, a fuel temperature sensor I 30, and a fuel temperature sensor II 31. The fuel preheating device 7 is installed on the fuel outlet pipe of the fuel tank 10. The fuel preheating device 6 is installed on the fuel pipe between the fuel preheating device 7 and the engine 1. The cylinder liner preheating device 27 is installed on the cylinder liner inside the engine. The lubricating oil insulation and preheating device 14 is connected to the oil pan 12 inside the engine 1 via the oil pump 13. An adjustable throttle valve 5 is installed in the air intake circuit of the engine 1.

[0039] Lubricating oil temperature sensor I 28 is installed inside the oil pan 12, lubricating oil temperature sensor II 29 is installed inside the lubricating oil insulation and preheating device 14, fuel temperature sensor I 30 is installed inside the fuel tank 10, and fuel temperature sensor II 31 is installed on the pipeline between the engine 1 and the fuel preheating device 6. The lubricating oil temperature sensor and the fuel temperature sensor are connected to the input terminal of the engine ECU 8, respectively providing feedback on the real-time temperature of the lubricating oil or fuel in the oil pan 12, the lubricating oil insulation and preheating device 14, the fuel tank 10, and the fuel inlet pipeline 22. The output terminal of the engine ECU 8 is connected to the adjustable throttle valve 5, the fuel preheating device 6, the fuel preheating device 7, the lubricating oil insulation and preheating device 14, and the cylinder liner preheating device 27, respectively, controlling the start switches of these electrical devices to achieve remote intelligent control.

[0040] The battery 9 is connected to the preheating device, sensors, engine ECU 8, and adjustable throttle valve 5 for power supply. The battery 9 is preferably a lithium iron phosphate battery.

[0041] The fuel preheating device 7 at the fuel outlet, as shown in Figures 2 and 3, includes a silicon carbide ceramic body 3, a nickel-iron-aluminum alloy heating rod 4, a cesium tungsten bronze nano-insulation coating 15, a fuel inlet 16, a fuel inlet distributor 17, a stainless steel shell 18, a fuel outlet 19, a fuel outlet manifold 20, and a distribution pipe 21. The fuel inlet distributor 17 is connected to the fuel inlet 16, which is connected to the fuel tank 10. The fuel outlet manifold 20 is connected to the fuel outlet 19, and the fuel outlet 16 is connected to the fuel inlet pipe 22. The fuel inlet distributor 17 and the fuel outlet manifold 20 are connected by five distribution pipes 21. The silicon carbide ceramic body 3, the nickel-iron-aluminum alloy heating rod 4, the cesium tungsten bronze nano-insulating coating 15, and the stainless steel shell 18 constitute the preheating body of the fuel preheating device 7 at the fuel outlet. The silicon carbide ceramic body 3 is embedded inside the stainless steel shell 18 to ensure that the fuel in the distribution pipe 21 is heated evenly. The nickel-iron-aluminum alloy heating rod 4 is embedded inside the silicon carbide ceramic body 3 to heat the fuel in the distribution pipe 21. At the same time, a layer of cesium tungsten bronze nano-insulating coating 15 is provided between the stainless steel shell 18 and the silicon carbide ceramic body 3 to reduce heat loss.

[0042] The pipeline fuel preheating device 6, as shown in Figures 4 and 5, consists of a stainless steel shell 18, a silicon carbide ceramic body 3, a nickel-iron-aluminum alloy heating rod 4, and a cesium tungsten bronze nano-insulating coating 15. Two channels are provided inside the stainless steel shell 18 and the silicon carbide ceramic body 3. One channel facilitates the installation of the pipeline fuel preheating device 6 onto the fuel inlet pipe 22, and the other channel is used to insert the nickel-iron-aluminum alloy heating rod 4 to heat the fuel in the fuel inlet pipe 22. Simultaneously, a layer of cesium tungsten bronze nano-insulating coating 15 is also provided between the stainless steel shell 18 and the silicon carbide ceramic body 3 to reduce heat loss.

[0043] The cylinder liner preheating device 27, as shown in Figures 6 and 7, consists of a cylinder liner 2, a silicon carbide ceramic body 3, a nickel-iron-aluminum alloy heating rod 4, a cesium tungsten bronze nano-insulating coating 15, and an engine block cylinder wall 23. The cylinder liner 2 and the engine block cylinder wall 23 form the outer shell of the preheating device, while the silicon carbide ceramic body 3, the nickel-iron-aluminum alloy heating rod 4, and the cesium tungsten bronze nano-insulating coating 15 form the preheating body of the cylinder liner preheating device 27. To facilitate the embedding of the silicon carbide ceramic body 3 and the nickel-iron-aluminum alloy heating rod 4 and to increase the heating area, eight crescent-shaped channels are uniformly designed on the inner surface of the engine block cylinder wall 23. The silicon carbide ceramic body 3 and the nickel-iron-aluminum alloy heating rod 4 are embedded in each crescent-shaped channel to ensure that the lubricating oil at the cylinder liner 2 is heated uniformly. To avoid safety issues caused by the conductivity of the nickel-iron-aluminum alloy heating rod 4, all eight crescent-shaped channels are designed as non-penetrating channels. Simultaneously, the insulating properties of the silicon carbide ceramic body 3 are used to encase the nickel-iron-aluminum alloy heating rod 4 to prevent direct contact between the heating rod 4 and the cylinder wall 3. To reduce heat loss, a cesium tungsten bronze nano-insulating coating 15 is placed between each crescent-shaped channel and the silicon carbide ceramic body 3.

[0044] The lubricating oil heat preservation and preheating device 14, as shown in Figures 7 and 8, consists of a stainless steel outer shell 24, a stainless steel inner shell 25, a lubricating oil pipe 26, a silicon carbide ceramic body 3, a nickel-iron-aluminum alloy heating rod 4, and a cesium tungsten bronze nano-insulating coating 15. The lubricating oil pipe 26 is connected to the oil pan 12. Multiple channels are evenly arranged between the stainless steel outer shell 24 and the stainless steel inner shell 25 to allow the insertion of the nickel-iron-aluminum alloy heating rod 4 to heat the lubricating oil. The silicon carbide ceramic body 3, adapted to the uniform channels, is embedded between the stainless steel inner and outer shells to ensure uniform preheating of the lubricating oil. To avoid unnecessary safety hazards caused by the conductivity of the nickel-iron-aluminum alloy heating rod 4, the designed uniform channels are all non-penetrating; at the same time, the nickel-iron-aluminum alloy heating rod 4 is wrapped in the insulating silicon carbide ceramic body 3 to prevent it from directly contacting the stainless steel outer shell 24 and the stainless steel inner shell 25. To enhance the heat preservation effect of the lubricating oil heat preservation and preheating device 14, a cesium tungsten bronze nano heat insulation coating 15 is designed between the stainless steel shell 24 and the matching silicon carbide ceramic body 3 to reduce heat loss.

[0045] The graded feedback regulation optimization strategy of the aero-engine cold start auxiliary graded preheating control method is as follows:

[0046] Let T1 be the temperature measured by lubricating oil temperature sensor I28; T2 be the temperature measured by lubricating oil temperature sensor II29; T3 be the temperature measured by fuel temperature sensor I30; T4 be the temperature measured by fuel temperature sensor II31; and T5 be the ambient temperature. A graded feedback control strategy is implemented with four levels of control based on T1, T2, T3, T4, and T5. Engine combustion parameters are adjusted and optimized to improve in-cylinder combustion during cold starts, thereby optimizing engine stability. An adjustable throttle valve 5 is installed at the intake manifold to adjust the air-fuel ratio during cold starts. The air-fuel ratio refers to the ratio of the mass of air entering the engine to the mass of fuel injected into the engine. Based on the amount of fuel injected according to the high-pressure common rail injection strategy, the intake air volume of the engine during cold start is controlled by adjusting the opening of the adjustable valve through the engine ECU8. This ensures that the fuel-air mixture of the aviation kerosene compression ignition engine during cold start in extreme environments is properly matched, thereby maintaining the air-fuel ratio of the engine within the optimal range. This promotes the formation of the air-fuel mixture and improves the ignition performance of the mixture, thus improving the stability of the aviation kerosene compression ignition engine during cold start in high-altitude and cold environments.

[0047] Meanwhile, this application also couples a relatively advanced high-pressure common rail fuel injection strategy to flexibly adjust the fuel injection parameters of the engine. The regulation of the high-pressure common rail fuel injection strategy is mainly controlled by the engine ECU8. According to the working condition of the engine during cold start in the high-altitude and cold environment, the engine ECU8 adjusts the high-pressure common rail fuel injection strategy to flexibly control the fuel injection pressure, so that the engine maintains the optimal fuel injection pressure during cold start in the high-altitude and cold environment to promote the full mixing of air and fuel; the engine ECU8 adjusts the high-pressure common rail fuel injection strategy to flexibly control the fuel injection timing and the change of fuel injection rate, so that the engine maintains the optimal pre-injection moment, pre-injection number, main injection moment and pre-main injection interval during cold start in the high-altitude and cold environment to accelerate the formation of a high-temperature atmosphere in the cylinder; the engine ECU8 adjusts the solenoid valve in the high-pressure common rail fuel injection system to flexibly control the fuel injection volume of the engine, so that there are no bubbles and the residual pressure is zero in the high-pressure fuel circuit of the engine, and at the same time, the engine maintains the optimal starting fuel injection volume, pre-injection fuel volume and main injection fuel volume during cold start in the high-altitude and cold environment, so that the quantity of the combustible mixture in the cylinder is reasonable. Through the adjustment of the above high-pressure common rail fuel injection strategy and combined with reasonable intake air adjustment, the fuel-air synergy of the engine is better matched, and the in-cylinder combustion of the engine is better optimized and improved, thereby further optimizing the stability of the aviation kerosene compression ignition engine during cold start in the high-altitude and cold environment.

[0048] Primary regulation: When -20°C < T5 < 0°C, since the ambient temperature T5 at this time does not reach the freezing point temperatures of aviation kerosene and lubricating oil (freezing point of aviation kerosene RP-3: -47°C, freezing point of lubricating oil: -30°C), the influence of the ambient temperature T5 on the viscosities of aviation kerosene and lubricating oil is relatively small at this time. Only the problem of poor stability during cold start of the aviation kerosene compression ignition engine needs to be considered at this time. Therefore, within this ambient temperature T5 range, the stability during cold start of the engine is optimized by adjusting and optimizing the engine combustion parameters to improve the in-cylinder combustion during cold start of the engine. The engine ECU8 controls the air-fuel ratio of the engine to be maintained within the optimal range to promote the formation of the mixture and improve the ignition performance of the mixture. At the same time, a relatively advanced high-pressure common rail fuel injection strategy is coupled to adjust the fuel injection parameters during cold start. The engine ECU controls the engine to couple relatively appropriate fuel injection parameters during cold start to optimize the in-cylinder combustion during cold start and further improve the stability during cold start of the engine.

[0049] Secondary regulation: When -30°C < T5 < -20°C, at this temperature, the viscosity of the lubricating oil is greatly affected. The engine ECU8 regulates to start the auxiliary preheating system to feedback preheat and optimize the lubricating oil in the oil pan 12. The engine ECU controls the motor oil pump 13 to start, and pumps out part of the lubricating oil in the oil pan 12 to the lubricating oil heat preservation and preheating device 14 for preheating treatment. When T2 reaches the normal working temperature of the lubricating oil during cold start of the engine, the power supply to the nickel-iron-aluminum alloy heating rod 4 in the lubricating oil heat preservation and preheating device 14 is stopped to save the energy of the battery 9. When the engine 1 stops working, at this time, the lubricating oil temperature T1 is at the working temperature. In order to save the power supply energy of the battery, part of the hot lubricating oil is pumped into the lubricating oil heat preservation and preheating device 14 for heat preservation treatment for use during the next start. If the interval to the next start is long and T2 cannot meet the temperature of the lubricating oil during cold start of the engine, the engine ECU8 regulates to preheat the lubricating oil again. At the same time, in order to further enhance the stability during cold start of the engine at this temperature, this level of regulation will combine with the regulation and optimization of the engine combustion parameters in the primary regulation to further enhance the cold start stability.

[0050] Tertiary regulation: When -40°C < T5 < -30°C, at this time, the temperature has reached the pour point temperature of the lubricating oil (pour point of lubricating oil: -30°C), which has a great impact on the viscosity and fluidity of the lubricating oil. In order to better improve the problem of serious wear of engine parts, this level of regulation will add cylinder liner preheating on the basis of secondary regulation. Since only part of the lubricating oil is pumped out for preheating or heat preservation in secondary regulation, at this temperature, the temperature of the lubricating oil in the oil pan 12 will be affected after pumping it back again. Therefore, this level of regulation will further preheat and optimize the thermodynamic state of the lubricating oil at the cylinder liner 2 and the in-cylinder mixture. When T1 reaches the working temperature of the lubricating oil during cold start of the engine, in order to save the energy of the battery in time, the power supply to the nickel-iron-aluminum alloy heating rod 4 in the cylinder liner preheating device 27 is stopped.

[0051] Level 4 Control: When T1 or T5 < -40℃, the temperature significantly affects the viscosity of aviation kerosene (the pour point of aviation kerosene is -47℃). To enhance fuel atomization and further shorten engine cold start time, this level of control adds a fuel preheating module to the level 3 control. A fuel preheating device 7 is installed at the fuel inlet pipe near the fuel tank 10 to preheat the fuel. Due to the relatively long fuel inlet pipe, to enhance preheating efficiency and further improve fuel atomization, one or more pipeline fuel preheating devices 6 are installed on the remaining portion of the fuel inlet pipe to reheat the fuel at the inlet pipe. When the T4 temperature reaches the operating temperature of the engine cold start fuel, power supply to the nickel-iron-aluminum alloy heating rod 4 in the fuel preheating device 7 and the pipeline fuel preheating device 6 is stopped.

[0052] This invention preheats engine fuel and lubricating oil through a pipeline fuel preheating device, an oil outlet preheating device, a cylinder liner preheating device, and a lubricating oil insulation preheating device. At the same time, it also couples combustion control parameter adjustment to further optimize the in-cylinder combustion of the engine. It can effectively solve the problems of long cold start time, severe wear of engine parts, and poor cold start stability of aviation kerosene compression ignition engines in high-altitude and cold environments.

[0053] The preheating device achieves rapid heating through nickel-iron-aluminum alloy heating rods, and the silicon carbide ceramic body makes the fuel and lubricating oil preheat more evenly. The cesium tungsten bronze nano heat insulation coating reduces the heat loss of the preheating device and improves the energy utilization efficiency.

[0054] Furthermore, this invention is based on a pipeline fuel preheating device, an oil outlet preheating device, a cylinder liner preheating device, and a lubricating oil insulation preheating device, coupled with a combustion parameter control strategy. According to the temperature gradient of the low-temperature environment in high-altitude and cold regions, a four-level high-altitude and cold-start feedback control strategy is designed, enabling aviation kerosene compression ignition engines to provide and implement reasonable preheating schemes according to different low-temperature and low-pressure environments in high-altitude and cold regions, thereby achieving efficient, reliable, and energy-saving cold starts of the engine.

[0055] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for auxiliary graded preheating control for cold start of an aircraft engine, applied to an auxiliary graded preheating system for cold start of an aircraft engine, the auxiliary graded preheating system for cold start of an aircraft engine includes an engine (1), a cylinder liner (2), an adjustable throttle valve (5), a pipeline fuel preheating device (6), a fuel preheating device (7), an engine ECU (8), a battery (9), a fuel tank (10), an oil pan (12), an oil pump (13), a lubricating oil heat preservation and preheating device (14), a cylinder liner preheating device (27), a lubricating oil temperature sensor I (28), a lubricating oil temperature sensor II (29), a fuel temperature sensor I (30), and a fuel temperature sensor II (31); the fuel preheating device (7) is installed on the oil outlet pipe of the fuel tank (10), the pipeline fuel preheating device (6) is installed on the fuel pipeline between the fuel preheating device (7) and the engine (1), the cylinder liner preheating device (27) is installed on the cylinder liner (2) inside the engine, the lubricating oil heat preservation and preheating device (6) is installed on the fuel pipeline between the fuel preheating device (7) and the engine (1), the cylinder liner preheating device (27) is installed on the cylinder liner (2) inside the engine, and the lubricating oil heat preservation and preheating device (6) is installed on the oil outlet pipe of the fuel tank (10). The heating device (14) is connected to the oil pan (12) inside the engine (1) via the oil pump (13); the lubricating oil temperature sensor I (28) is installed inside the oil pan (12), the lubricating oil temperature sensor II (29) is installed inside the lubricating oil heat preservation and preheating device (14), the fuel temperature sensor I (30) is installed inside the fuel tank (10), and the fuel temperature sensor II (31) is installed on the pipeline between the engine (1) and the pipeline fuel preheating device (6). The lubricating oil temperature sensor and the fuel temperature sensor are connected to the input terminal of the engine ECU (8), and the output terminal of the engine ECU (8) is connected to the adjustable throttle valve (5), the pipeline fuel preheating device (6), the fuel preheating device (7), the lubricating oil heat preservation and preheating device (14), and the cylinder liner preheating device (27), respectively; the adjustable throttle valve (5) is installed on the air circuit of the engine (1); the battery (9) supplies power to the preheating device, the sensor, the engine ECU (8), and the adjustable throttle valve (5); the characteristic is that, The cold start auxiliary hierarchical preheating control method for an aeroengine includes: setting the temperature measured by the lubricating oil temperature sensor I as T1, the temperature measured by the lubricating oil temperature sensor II as T2, the temperature measured by the fuel temperature sensor I as T3, the temperature measured by the fuel temperature sensor II as T4, and the ambient temperature as T5. The hierarchical feedback control strategy sets four levels of control according to T1, T2, T3, T4, and T5. The fuel and lubricating oil are heated separately according to the ambient temperature T5. The throttle opening is adjusted through the engine ECU to regulate the intake air volume during the cold start of the engine. At the same time, the high-pressure common rail injection strategy is coupled to flexibly adjust the injection parameters during the cold start, so that the air-fuel coordination of the engine is better matched, and the engine air-fuel ratio is maintained within the optimal range, thereby promoting the efficient combustion of the combustible mixture and avoiding afterburning in the cylinder, accelerating the combustion rate, increasing the temperature and pressure at the end of compression, and accelerating the formation of a high-temperature atmosphere in the cylinder, further improving the stability during the cold start of the engine; among them, the hierarchical feedback control strategy sets four levels of control according to T1, T2, T3, T4, and T5, including: First-level control: When -20°C < T5 < 0°C, the ambient temperature T5 does not reach the freezing point temperatures of aviation kerosene and lubricating oil. At this time, the ambient temperature T5 has little effect on the viscosities of aviation kerosene and lubricating oil. Only the problem of poor stability during the cold start of the aviation kerosene compression ignition engine needs to be considered. The stability during the cold start of the engine is optimized by adjusting and optimizing the engine combustion parameters to improve the in-cylinder combustion during the cold start of the engine; Second-level control: When -30°C < T5 < -20°C, the viscosity of the lubricating oil is greatly affected. This level of control adds lubricating oil heat preservation and preheating treatment on the basis of the first-level control. The temperature T1 measured by the lubricating oil temperature sensor I is fed back to the engine ECU to control the start of the motor oil pump, and part of the lubricating oil in the oil pan is pumped out to the lubricating oil heat preservation and preheating device for preheating treatment. When T2 reaches the normal operating temperature of the lubricating oil during the cold start of the engine, the heating of the lubricating oil in the lubricating oil heat preservation and preheating device is stopped to save the energy of the battery. When the engine stops operating, at this time T1 has reached the operating temperature of the lubricating oil. In order to save the power supply energy of the battery, part of the hot lubricating oil is pumped into the lubricating oil heat preservation and preheating device for heat preservation treatment. If the interval between the next start is long and T2 cannot meet the temperature of the lubricating oil during the cold start of the engine, the lubricating oil heat preservation and preheating device preheats the lubricating oil again; Third-level control: When -40°C < T5 < -30°C, the temperature has reached the freezing point temperature of the lubricating oil, which has a great impact on the viscosity and fluidity of the lubricating oil. This level of control adds cylinder jacket preheating on the basis of the second-level control. The engine ECU is used to control the cylinder jacket preheating device to preheat and optimize the thermodynamic state of the lubricating oil at the cylinder jacket and the in-cylinder mixture. When T1 reaches the operating temperature of the lubricating oil during the cold start of the engine, the heating of the cylinder jacket preheating device is stopped;Level 4 control: When T1 or T5 < -40℃, the temperature significantly affects the viscosity of aviation kerosene. To enhance fuel atomization and further shorten engine cold start time, this level of control adds fuel preheating to the level 3 control. The fuel is preheated through a fuel preheating device at the fuel outlet. Due to the long fuel inlet line, to further enhance fuel preheating efficiency and improve atomization, a fuel preheating device is installed on the remaining section of the fuel inlet line to preheat the fuel again. When the T4 temperature reaches the fuel's operating temperature for engine cold start, power supply to both the fuel preheating device at the fuel outlet and the fuel preheating device in the fuel line is stopped.

2. The aero-engine cold start auxiliary graded preheating control method according to claim 1, characterized in that, The high-pressure common rail injection strategy includes: flexibly controlling the injection pressure by adjusting the high-pressure common rail injection strategy according to the engine's cold start conditions in high-altitude and cold environments, so as to maintain optimal injection pressure to promote thorough air-fuel mixing; flexibly controlling and adjusting the injection timing and injection rate by adjusting the high-pressure common rail injection strategy by the engine ECU, so as to maintain optimal pre-injection timing, pre-injection frequency, main injection timing, and pre-main injection interval to accelerate the formation of a high-temperature atmosphere in the cylinder under high-altitude and cold start conditions; and adjusting the injection timing and injection rate by the engine ECU. The solenoid valves in the high-pressure common rail injection system flexibly control the engine's fuel injection quantity, preventing air bubbles and zero residual pressure in the engine's high-pressure fuel circuit. Simultaneously, it maintains optimal starting fuel injection, pre-injection, and main injection quantities under high-altitude and cold-weather starting conditions, ensuring a reasonable amount of combustible mixture in the cylinder. Through the aforementioned high-pressure common rail injection strategy, combined with reasonable intake regulation, the engine's fuel-air synergy is better matched, and in-cylinder combustion is optimized and improved, thereby further enhancing the stability of aviation kerosene compression ignition engines during cold starts in high-altitude and cold-weather environments.

3. The aero-engine cold start auxiliary graded preheating control method according to claim 1, characterized in that, The specific air-fuel ratio control method includes: controlling the intake air volume of the engine during cold start in high-altitude and cold environments by adjusting the opening of the adjustable throttle valve through the engine ECU according to the amount of fuel injected by the high-pressure common rail injection strategy. This ensures that the fuel-air mixture of the aviation kerosene compression ignition engine during cold start in extreme environments is reasonably matched, thereby maintaining the air-fuel ratio of the engine within the optimal range. This promotes the formation of the air-fuel mixture and improves the ignition performance of the mixture, thus improving the stability of the aviation kerosene compression ignition engine during cold start in high-altitude and cold environments.

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