Engine multi-fuel identification device based on fuel fluid characteristics and closed-loop regulation and control system

Abstract

The invention discloses an engine multi-fuel recognition device based on fuel fluid characteristics and a closed-loop regulation and control system. The engine multi-fuel recognition device comprises at least two fuel conveying pipelines. The fuel conveying pipeline is connected with the fuel storage device and the fuel mixing system, and a pressure adjusting device and a fuel recognition device are arranged on the fuel conveying pipeline. On the basis of the Bernoulli principle, when fuel is introduced into a pipeline P, the pressure in the pipeline changes, a floating valve ascends and descends, a spring is driven to deform, the displacement of the floating valve is converted into a spring stress signal, finally, data on a resistance strain sensor is compared with data of a pre-stored fuel type-stress database, and the current fuel type is recognized. In the closed-loop regulation and control system, an ECU (Electronic Control Unit) takes parameters such as engine thermal efficiency, oil consumption and emission as regulation targets, and regulates fuel flow through a flow regulation and control device according to information such as current working conditions of an engine, fuel types, a fuel mixing ratio, fuel remaining amount and fuel thermal efficiency, so that closed-loop regulation and control of the mixing ratio are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of engine control, and particularly to an engine multi-fuel identification device and a closed-loop regulation system based on fuel fluid characteristics, which can realize automatic fuel identification, mixture ratio calculation and precise regulation. For engines burning multiple fuels, it can not only improve the fuel utilization rate, but also improve the economy and power performance of the engine. Background Art

[0002] With the transformation of the automotive development towards the new energy direction, more and more fuels (such as clean fuels like biomass fuels, hydrogen, ammonia, etc.) will be used in engines in the future, and the types of fuels are becoming more and more diverse. With the diversified development of engine fuels, the regulation system of engine fuels has become more complex.

[0003] At present, most engines on the market use a single fuel, and the existing regulation systems of engines on the market are mostly designed for single fuels, lacking the automatic identification technology for multiple types of engine fuels, being difficult to be compatible with multi-fuel collaborative optimization, and having relatively low regulation reliability. Summary of the Invention

[0004] In order to solve the deficiencies existing in the prior art, the present application proposes an engine multi-fuel identification device and a closed-loop regulation system based on fuel fluid characteristics; based on the principle of fluid mechanics, a mechanical structure is used to automatically identify the types of engine fuels, effectively promoting the application of multiple fuels in engines. The present invention uses two signals of fuel type and mixture ratio for parameter regulation, which is more reliable than the traditional regulation system.

[0005] The technical solution adopted by the present invention is as follows:

[0006] An engine multi-fuel identification device based on fuel fluid characteristics, comprising:

[0007] At least two fuel delivery pipelines; one end of each fuel delivery pipeline is connected to a fuel storage, and the other end is connected to a fuel mixing system.

[0008] A pressure regulating device and a fuel identification device are arranged on each fuel delivery pipeline. The pressure regulating device includes a pressure intercepting valve, a pressure regulator, a differential pressure valve, and a temperature compensator; the fuel identification device includes a rigid housing, a floating valve movably installed inside the rigid housing, the floating valve is sequentially connected to a spring and a resistance strain sensor through a sensitive filament, and the resistance strain sensor is sequentially connected to a correction unit and a pre-stored fuel type - force database in signal.

[0009] Further, a correction unit corrects the tensile force value measured by the resistive strain sensor. The correction coefficients include b and A. b is used to compensate for the errors caused by the actual fluid characteristics and mechanical friction, and A is used to compensate for the deviations brought about by the pipe cross-sectional area and the pressure adjustment within the pipe.

[0010] Further, a standard fuel delivery pipe is arranged. Fuel with a known standard pressure is input into the standard pipe. After passing through the fuel identification device, the tensile force value of the spring is read by the resistive strain sensor, forming a pre-stored fuel type - force database.

[0011] Further, the spring and the resistive strain sensor are installed inside an insulating cover. The bottom of the insulating cover is connected to a rigid outer shell through a rigid sleeve, and a vacuum chamber is formed between the inner cavity of the rigid outer shell above the floating valve and the insulating cover.

[0012] Further, there is a clearance fit between the sensitive filament and the rigid sleeve and lubricating oil is applied.

[0013] Further, the elastic strain range of the sensitive filament is approximately 0.01% - 0.5%. The tensile strength of the sensitive filament needs to reach 1500 - 2000 MPa, and the thermal expansion coefficient needs to be controlled at ≤ 1.5×10 -6 / °C. The tensile strength of the spring needs to be maintained at 1200 - 1800 MPa, and the thermal expansion coefficient needs to meet ≤ 5×10 -6 / °C.

[0014] A closed-loop control system for multi-fuels of an engine based on fuel fluid characteristics includes a fuel flow control device, a flow control valve, a flow velocity sensor, a fuel ratio calculation module, and an ECU.

[0015] The fuel flow control device controls the opening degree of the flow control valve on the fuel delivery pipe.

[0016] The flow velocity sensor detects the fuel flow velocity signal in the fuel delivery pipe.

[0017] The fuel ratio calculation module calculates the fuel mixing ratio based on the fuel flow velocity signal.

[0018] The ECU 11 receives the information of fuel type X and mixing ratio α, and based on the current working condition G of the engine, fuel type X, current fuel mixing ratio α, remaining fuel quantity M, and engine thermal efficiency η, outputs a flow control signal to the fuel flow control device.

[0019] Further, the fuel mixing ratio α:

[0020] α = (ρ x V x ) / (ρ1V1 + ρ2V2 +... + ρ n V n ) x ∈ [1, n]

[0021] In the formula, ρ x represents the density of a certain fuel in the multi-fuel, ρ1 and ρ2 respectively represent the densities of each fuel, the fuel type is obtained by the fuel identification device, and the density can be obtained; V n represents the volume of a certain fuel in the multi-fuel, V1 and V2 respectively represent the flow rates of each fuel, and can be obtained from the flowmeter.

[0022] Furthermore, a function of the fuel mass flow rate and the engine operating state parameters is pre-stored in the ECU 11, denoted as:

[0023] g(m) = g(G, X, α, M, η)

[0024] In the formula, m represents the fuel mass flow rate, including m1 and m 2， respectively represent the mass flow rates of fuel A and fuel B; G represents the engine operating conditions, including speed and load; X represents the fuel type; α represents the current fuel mixing ratio; M represents the remaining fuel amount; η represents the fuel thermal efficiency.

[0025] Furthermore, the driver's active control always takes precedence over the feedback regulation of the ECU.

[0026] Advantages of the present invention:

[0027] 1. The present invention uses a mechanical structure that utilizes the fluid characteristics of the fuel to identify the incoming fuel, converts the differences in the fluid characteristics of different fuels into the tensile force value of the spring, and screens and compares it with the pre-stored fuel type-force database, thereby automatically identifying the fuel type. Compared with manual fuel identification, the present invention can achieve automatic fuel identification and adapt to the trend of automotive automation development.

[0028] 2. With the application of multi-fuels in the engine, manual identification not only consumes a large amount of time, but also has subjectivity and inaccurate identification. The present invention identifies based on the fluid characteristics of the fuel, with high identification accuracy. In addition, the fuel identification device can also report errors for unrecognized fuels, enhancing the reliability of fuel identification.

[0029] 3. The present invention has no special requirements for the structural sizes of pipelines P and Q and the pipeline pressure, and different pressures or pipeline cross-sectional areas can be used according to the application conditions of each fuel. When performing combustion identification, the correction unit will automatically correct the tensile force signal, unify the initial conditions such as the pipeline structural size and pressure into the initial conditions in the pre-stored fuel type-force database, greatly improving the fuel adaptability and reducing the pipeline manufacturing difficulty.

[0030] 4. In the fuel identification device of the present invention, the identification of fuel types is not limited to single fuel or dual fuel. Based on the pre-stored fuel type - force database, multiple fuel types can be identified. For fuels not recorded in the pre-stored fuel type - force database, according to the collection principle, fuels not recorded in the pre-stored fuel type - force database are plastic and can be continuously updated to adapt to new development trends.

[0031] 5. In the closed-loop control system of the present invention, two signals of fuel mixture ratio and fuel type are transmitted to the ECU, enabling the ECU to perform control based on the engine operating state parameters, and the control effect is more reliable. In addition, the closed-loop control system uses neural networks and genetic algorithm optimization methods to control the fuel flow, which can not only improve the engine power performance but also reduce fuel consumption. Brief Description of the Drawings

[0032] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0033] Figure 2 It is a schematic diagram of the structure of the closed-loop control system of the present invention.

[0034] Figure 3 It is a schematic diagram of the structure of the fuel identification device of the present invention.

[0035] Figure 4 It is an enlarged cross-sectional view of some sensitive filaments of the present invention. Detailed Embodiments

[0036] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] The orientation or positional relationship indicated by terms such as "upper", "lower", "front", "rear", "left", "right", "vertical", "straight", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. As Figure 1 shown, the present invention designs an engine multi-fuel identification device based on fuel fluid characteristics, including:

[0038] At least two fuel delivery pipes, respectively used to deliver different types of fuels; one end of each fuel delivery pipe is connected to the fuel storage 1. The other end of each fuel delivery pipe is connected to the fuel mixing system, and the fuel is transported to the fuel mixing system through the fuel delivery pipe for mixing.

[0039] A pressure regulating device and a fuel identification device 6 are provided on each fuel delivery pipeline; the pressure regulating device includes a pressure cut-off valve 2, a pressure regulator 3, a differential pressure valve 4, and a temperature compensator 5 that are sequentially installed on the fuel delivery pipeline. The pressure regulator 3 regulates the pressure, the differential pressure valve 4 maintains the pressure, and the temperature compensator 5 eliminates the errors caused by thermal expansion and contraction, controlling the fuel delivery pipeline pressure to adapt to the fuel delivery conditions. The temperature compensator 5 plays roles such as dynamically adjusting the differential pressure or throttle area, ensuring stable fuel flow, and eliminating the deviation caused by the signal of thermal expansion and contraction.

[0040] The structure of the fuel identification device 6 is as Figure 3 shown, and it includes a rigid housing 14, a floating valve 15, a sensitive filament 16, a rigid sleeve 17, a spring 18, a resistance strain sensor 19, an insulating cover 20, a correction unit 22, and a pre-stored fuel type-force database 23. The rigid housing 14 is cylindrical and perpendicular to the surface of the fuel delivery pipeline. The floating valve 15 is movably installed inside the rigid housing 14. One side of the floating valve 15 is in contact with the medium in the fuel delivery pipeline, and the other side is sequentially connected to the sensitive filament 16, the spring 18, and the resistance strain sensor 19, and the resistance strain sensor 19 is sequentially connected to the correction unit 22 and the pre-stored fuel type-force database 23 by signals. The spring 18 and the resistance strain sensor 19 are installed in the insulating cover 20. The bottom of the insulating cover 20 is connected to the rigid housing 14 through the rigid sleeve 17, and a vacuum chamber is formed between the inner cavity of the rigid housing 14 above the floating valve 15 and the insulating cover 20.

[0041] As Figure 4 shown, the sensitive filament 16 is connected to the spring 18 through the rigid sleeve 17; there is a clearance fit between the sensitive filament 16 and the rigid sleeve and lubricating oil is applied.

[0042] More specifically, the elastic strain range of the sensitive filament 16 is about 0.01%-0.5%, so as to accurately transmit the small displacement of the floating valve 15 and ensure that the stretching amount of the spring 18 accurately reflects the flow rate change; both the sensitive filament 16 and the spring 18 need to have high tensile strength and low thermal expansion coefficient. The tensile strength of the sensitive filament 16 generally needs to reach 1500-2000 MPa, and the thermal expansion coefficient needs to be controlled at ≤1.5×10 -6 / ℃, the tensile strength of the spring 18 needs to be maintained at 1200-1800 MPa, and the thermal expansion coefficient needs to meet

[0043] ≤5×10 -6 / ℃, avoiding fracture or fatigue failure and preventing the length change caused by temperature change from affecting the accuracy.

[0044] More specifically, the spring 18 and the resistance strain sensor 19 are protected by an insulating cover 20 to reduce external interference and spring oxidation, and a small hole 21 is provided at the upper end of the insulating cover 20 to relieve the pressure difference inside and outside the insulating cover 20 caused by the displacement of the float valve 15.

[0045] More specifically, for the fuel identification device 6, when fuel enters the pipeline P or the pipeline Q, based on the Bernoulli principle (p + 1 / 2ρv 2 + ρgh = C), the relationship between the fluid's own characteristics (such as flow velocity and viscosity, etc.) and pressure, the pressure inside the pipeline changes, the float valve 15 displaces, the displacement of the float valve 15 drives the sensitive filament 16, the sensitive filament 16 pulls the spring 18, causing the spring 18 to deform, and the resistance strain sensor 19 obtains the pulling force value at this time. After the pulling force value is corrected by the correction unit 22, it is compared one by one with the pre-stored fuel type - force database 23, and the fuel type can be identified.

[0046] More specifically, the correction coefficients of the correction unit 22 are b and A. Among them, the correction coefficient b is used to compensate for the errors that may be caused by non-ideal factors such as actual fluid characteristics and mechanical friction. That is, the pulling force value:

[0047] F = k * Δx + b

[0048] Where k is the spring stiffness coefficient, Δx is the spring elongation length, and Δx follows Δx ∝ Δh ∝ Δp, Δh is the displacement of the float valve, and Δp is the pressure change at the fuel identification device.

[0049] Due to the differences in the storage pressure and the structure of the transportation pipeline of different fuels, based on the Bernoulli principle, it is necessary to adjust factors such as the measured pipeline cross-sectional area S and the pipeline internal pressure P to be consistent with the initial conditions in the database according to the initial conditions for calculating the pulling force in the pre-stored fuel type - force database 23. The correction coefficient A is used to compensate for the deviation caused by the data adjustment of factors such as the pipeline cross-sectional area and the pipeline internal pressure. The specific compensation calculation formula is as follows:

[0050] F(S 1， P 1， ...) = F(S 0， P 0， ...) + A

[0051] F(S 0， P 0， ...) is the pulling force value of the spring when the actual fuel is introduced into the transportation pipeline; F(S 1， P 1， ...) is the pulling force value after correcting the actual fuel test parameters (pipeline cross-sectional area, pipeline internal pressure, etc.); A is the correction coefficient.

[0052] More specifically, the data collection principle of the pre-stored fuel type - force database 23 is as follows: First, arrange a standard fuel delivery pipeline, input fuel with a known standard pressure into the standard pipeline, pass through the fuel identification device 6, read the tensile force value of the spring 18 at this time by the resistance strain sensor 19, and upload it to the pre-stored fuel type - force database 23. Repeat the above actions to upload the tensile force values of various fuels of the engine, and form the pre-stored fuel type - force database 23.

[0053] More specifically, compare the tensile force value F(S 1， P 1， ... ) of the measured fuel after correction with the tensile forces in the pre-stored fuel type - force database 23 one by one. If the error < 5%, then screen out the type of the current fuel; if after traversing and querying, the comparison errors are all > 5%, then trigger the alarm system of the pre-stored fuel type - force database. At this time, the database will display an error page to remind the user that this fuel may not be in the pre-stored fuel type - force database 23. When using it for the first time, start traversing and querying from the first group of data in the database, and store and remember the queried fuel data; during subsequent use, preferentially start traversing and querying from the fuel data stored last time to improve the query efficiency and intelligence level.

[0054] More specifically, the rigid housing 14 and the float valve 15 in the fuel identification device 6 are made of corrosion-resistant titanium alloy to cope with corrosive fuels such as formaldehyde, gasoline, and diesel. There is a clearance fit between the rigid housing 14 and the float valve 15 and a little lubricating oil is applied.

[0055] More specifically, the fuel mixing system includes a fuel mixer 13 and an air filter 12.

[0056] Combined with Figure 1 A detailed introduction to the working process of this device is as follows:

[0057] When fuel A enters pipeline P, fuel identification is carried out by fuel identification device 6. The identification principle is as follows: Since fuel A flows in, the pressure of fuel identification device 6 changes, the floating valve 15 rises and falls significantly, the sensitive filament 16 pulls the spring 18, and the stretching degree is digitized by the resistance strain sensor 19 and corrected by the correction unit 22. At this time, the pulling force value is taken as x; the pulling force value x is input into the pre-stored fuel type - force database 23 for fuel comparison to identify the type of fuel A; when fuel B also enters pipeline Q, fuel identification is carried out by fuel identification device 6. Since fuel B flows in, the pressure of fuel identification device 6 changes, the floating valve 15 rises and falls, the sensitive filament 16 pulls the spring 18, and the stretching degree is digitized by the resistance strain sensor 19 and corrected by the correction unit 22. At this time, the pulling force value is taken as y. The pulling force value y is input into the pre-stored fuel type - force database 23 for fuel comparison to identify the type of fuel B. Based on Bernoulli's principle, due to the differences in fluid characteristics such as fuel flow velocity and viscosity, the pressures of the two fuels at the fuel identification device are different at this time. Therefore, the pulling force value x is completely different from the pulling force value y.

[0058] Based on the multi-fuel identification results of the above device, the present invention also proposes a closed-loop regulation system for multi-fuels of an engine based on fuel fluid characteristics, including a fuel flow regulation device 7, a flow control valve 8, a flow velocity sensor 9, a fuel ratio calculation module 10, and an ECU 11.

[0059] The fuel flow regulation device 7 regulates the fuel flow in the pipeline by controlling the opening of the flow control valve 8;

[0060] The flow velocity sensor 9 detects the fuel flow velocity signal and transmits the fuel flow velocity signal to the fuel ratio calculation module 10 for calculating the fuel mixing ratio; the fuel mixing ratio α:

[0061] α = (ρ x V x ) / (ρ1V1 + ρ2V2 +... + ρ n V n ) x ∈ [1, n]

[0062] In the formula, ρ x represents the density of a certain fuel in the multi-fuels, ρ1 and ρ2 respectively represent the densities of each fuel. After the fuel type is obtained by the fuel identification device, the density can be obtained; V n represents the volume of a certain fuel in the multi-fuels, V1 and V2 respectively represent the flow velocities of each fuel, which can be obtained from the flow velocity device. The fuel identification module of the present invention can identify more than two types of fuels, and can identify multiple fuels according to the pre-stored fuel type - force database.

[0063] The ECU 11 receives information on the fuel type X and the air-fuel ratio α, and based on the operating condition G of the current engine, the fuel type X, the current air-fuel ratio α of the fuel, the remaining fuel quantity M, and the engine thermal efficiency η, outputs a flow control signal to the fuel flow control device 7; a closed-loop control loop of fuel identification → air-fuel ratio calculation → flow control → information feedback is formed.

[0064] More specifically, a functional relationship between the fuel mass flow rate and the engine operating state parameters is constructed:

[0065] g(m) = g(G, X, α, M, η)

[0066] In the formula, m represents the fuel mass flow rate, including m1 and m 2， respectively representing the mass flow rates of fuel A and fuel B; G represents the operating condition of the engine, including the rotational speed and load; X represents the fuel type; α represents the current air-fuel ratio of the fuel; M represents the remaining fuel quantity; η represents the fuel thermal efficiency. The flow rate of m can be controlled by adjusting the opening degree of the fuel control valve; the operating condition G can be obtained by collecting from in-vehicle sensors, X can be obtained from the fuel identification device; the remaining fuel quantity M is judged based on the level in the fuel storage tank 1; the fuel thermal efficiency η is based on big data simulation combined with the engine operating condition.

[0067] More specifically, since the engine operating condition G, the fuel type X, the current air-fuel ratio α of the fuel, the remaining fuel quantity M, and the fuel thermal efficiency η are important parameters for changing the fuel mass flow rate m, the numerical obtaining method is as follows: taking the engine operating condition G, the fuel type X, the current air-fuel ratio α of the fuel, the remaining fuel quantity M, and the fuel thermal efficiency η as the input layer, training through a neural network, using the MATLAB software cftool interactive interface for multi-variable fitting, and optimizing with a genetic algorithm to obtain the output layer, that is, the fuel mass flow rate m; for adjusting the fuel mass flow rate, this neural network can mainly select types such as a genetic algorithm optimized network, a recurrent neural network, and a conditional convolutional neural network.

[0068] More specifically, when the engine uses two fuels A and B, if fuel A is about to run out or the difference in the remaining amounts of fuel A and fuel B exceeds 80%, at this time, the ECU 11 increases the opening degree of the flow control valve of fuel B to ensure timely fuel supply. The driver's active control always takes precedence over the feedback control of the ECU 11, and the driver intervenes in the control of the ECU 11 according to the selection.

[0069] Combined Figure 2 , the working principle of the closed-loop control system:

[0070] The type signals of fuel A and fuel B are input into the ECU 11; the fuel flow control device 7 controls the flow control valve 8. After that, fuel A and fuel B respectively transmit the flow rate information to the fuel ratio calculation module 10 via the flow rate sensors 9. Finally, the fuel identification device 6 and the fuel ratio calculation module 10 respectively identify the types of fuel A and fuel B and calculate the fuel mixing ratio, and transmit the fuel type and fuel mixing ratio signals to the ECU 11. The ECU 11 takes parameters such as engine thermal efficiency, fuel consumption, and emissions as the adjustment targets. According to information such as the current engine operating condition G, fuel type X, fuel mixing ratio α, remaining fuel quantity M, and engine thermal efficiency η, the ECU 11 adjusts the fuel flow through the flow control device 7 to achieve closed-loop control of the mixing ratio and convey the fuel type and mixing ratio to the ECU 11. The ECU 11 forms a closed-loop control loop including fuel identification → mixing ratio calculation → flow control → information feedback based on information such as the current engine operating condition, temperature, fuel type, fuel mixing ratio, remaining fuel quantity, and fuel thermal efficiency. The dual signals of fuel type and mixing ratio increase the reliability and accuracy of the ECU 11 control.

[0071] The ECU 11 obtains the fuel type and mixing ratio signals and feedback-controls the fuel flow control device 7. The fuel flow control device 7 realizes fuel flow control by controlling the flow control valve 8. Among them, when the engine uses two fuels A and B, if fuel A is about to run out or the difference in the remaining amounts of fuel A and fuel B exceeds 80%, at this time, the ECU 11 increases the opening degree of the flow control valve of fuel B to ensure timely fuel supply. The driver's active control always takes precedence over the feedback control of the ECU 11, and the driver intervenes in the control of the ECU according to the selection.

[0072] The above embodiments are only used to illustrate the design concept and features of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications made according to the principles and design concepts disclosed by the present invention are within the protection scope of the present invention.

Claims

1. An engine multi-fuel identification device based on fuel fluid characteristics, characterized in that, Comprising: At least two fuel delivery pipelines; one end of each fuel delivery pipeline is connected to a fuel storage (1), and the other end is connected to a fuel mixing system. A pressure regulating device and a fuel identification device (6) are provided on each fuel delivery pipeline. The pressure regulating device includes a pressure cut-off valve (2), a pressure regulator (3), a differential pressure valve (4), and a temperature compensator (5); the fuel identification device (6) includes a rigid housing (14), a float valve (15) movably installed inside the rigid housing (14), and the float valve (15) is sequentially connected to a spring (18) and a resistance strain sensor (19) through a sensitive filament (16). The resistance strain sensor (19) is sequentially connected to a correction unit (22) and a pre-stored fuel type - force database (23) in signal.

2. The engine multi-fuel identification device based on fuel fluid characteristics according to claim 1, characterized in that: The correction unit (22) corrects the tensile force value measured by the resistance strain sensor (19). The correction coefficients include b and A. b is used to compensate for the error caused by the actual fluid characteristics and mechanical friction, and A is used to compensate for the deviation caused by the pipeline cross-sectional area and the pipeline internal pressure adjustment.

3. The multi-fuel identification device for an engine based on fuel fluid characteristics according to claim 1, characterized in that Arrange a standard fuel delivery pipeline, input fuel with a known standard pressure into the standard pipeline, pass through the fuel identification device (6), and read the tensile force value of the spring (18) at this time by the resistance strain sensor (19) to form a pre-stored fuel type - force database (23).

4. An engine multi-fuel identification device based on fuel fluid characteristics according to claim 1, characterized in that The spring (18) and the resistance strain sensor (19) are installed in an insulating cover (20). The bottom of the insulating cover (20) is connected to the rigid housing (14) through a rigid sleeve (17), and a vacuum chamber is formed between the inner cavity of the rigid housing (14) above the float valve (15) and the insulating cover (20).

5. The engine multi-fuel identification device based on fuel fluid characteristics according to claim 1, characterized in that: The sensitive filament (16) and the rigid sleeve are in clearance fit and coated with lubricating oil.

6. The multi-fuel identification device for an engine based on fuel fluid characteristics according to claim 1, characterized in that, The elastic strain range of the sensitive filament (16) is about 0.01% - 0.5%, the tensile strength of the sensitive filament (16) needs to reach 1500 - 2000 MPa, and the coefficient of thermal expansion needs to be controlled at ≤ 1.5×10 -6 / °C; the tensile strength of the spring (18) needs to be maintained at 1200 - 1800 MPa, and the coefficient of thermal expansion needs to meet ≤ 5×10 -6 / °C.

7. A closed-loop control system for multi-fuels of an engine based on fuel fluid characteristics, characterized in that, Based on an engine multi-fuel identification device based on fuel fluid characteristics, the system includes a fuel flow control device (7), a flow control valve (8), a flow velocity sensor (9), a fuel ratio calculation module (10), and an ECU11; The fuel flow control device (7) controls the opening degree of the flow control valve (8) on the fuel delivery pipeline; The flow velocity sensor (9) detects the fuel flow velocity signal in the fuel delivery pipeline; The fuel ratio calculation module (10) calculates the fuel mixing ratio according to the fuel flow velocity signal; The ECU11 receives the fuel type X and mixing ratio α information, and based on the current engine operating condition G, fuel type X, current fuel mixing ratio α, fuel remaining amount M, and engine thermal efficiency η, outputs a flow control signal to the fuel flow control device (7).

8. A closed-loop control system for an engine multi-fuel based on fuel fluid characteristics according to claim 7, characterized in that, Fuel mixing ratio α: α = (ρ x V x ) / (ρ1V1 + ρ2V2 +... + ρ n V n ) where x ∈ [1, n] where ρ x represents the density of a certain fuel in the multi-fuel, ρ1 and ρ2 respectively represent the densities of each fuel, and the fuel type is obtained by the fuel identification device, then the density can be obtained; V n represents the volume of a certain fuel in the multi-fuel, V1 and V2 respectively represent the flow rates of each fuel, which can be obtained from the flow meter.

9. A closed-loop control system for an engine multi-fuel based on fuel fluid characteristics according to claim 7, characterized in that, The function of the pre-stored fuel mass flow and engine operating state parameters in the ECU (11) is denoted as: g(m) = g(G, X, α, M, η) In the formula, m represents the mass flow rate of the fuel, including m1 and m 2， which respectively represent the mass flow rates of fuel A and fuel B; G represents the operating conditions of the engine, including the rotational speed and load; X represents the fuel type; α represents the current fuel mixing ratio; M represents the remaining fuel quantity; η represents the fuel thermal efficiency.

10. A closed-loop control system for an engine multi-fuel based on fuel fluid characteristics according to claim 7, characterized in that, The driver's active control always takes precedence over the feedback control of the ECU (11).

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