CN115434802B - Multi-objective optimization control strategy and system for ammonia-hydrogen dual-fuel aviation rotor engine - Google Patents
Multi-objective optimization control strategy and system for ammonia-hydrogen dual-fuel aviation rotor engine Download PDFInfo
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 6
- 230000009977 dual effect Effects 0.000 description 5
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- 229910052799 carbon Inorganic materials 0.000 description 4
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B53/00—Internal-combustion aspects of rotary-piston or oscillating-piston engines
- F02B53/02—Methods of operating
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B77/00—Component parts, details or accessories, not otherwise provided for
- F02B77/08—Safety, indicating, or supervising devices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
- F02B77/00—Component parts, details or accessories, not otherwise provided for
- F02B77/08—Safety, indicating, or supervising devices
- F02B77/084—Safety, indicating, or supervising devices indicating economy
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D19/00—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures
- F02D19/06—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed
- F02D19/0639—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed characterised by the type of fuels
- F02D19/0642—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed characterised by the type of fuels at least one fuel being gaseous, the other fuels being gaseous or liquid at standard conditions
- F02D19/0644—Controlling engines characterised by their use of non-liquid fuels, pluralities of fuels, or non-fuel substances added to the combustible mixtures peculiar to engines working with pluralities of fuels, e.g. alternatively with light and heavy fuel oil, other than engines indifferent to the fuel consumed characterised by the type of fuels at least one fuel being gaseous, the other fuels being gaseous or liquid at standard conditions the gaseous fuel being hydrogen, ammonia or carbon monoxide
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D43/00—Conjoint electrical control of two or more functions, e.g. ignition, fuel-air mixture, recirculation, supercharging or exhaust-gas treatment
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D45/00—Electrical control not provided for in groups F02D41/00 - F02D43/00
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- Mechanical Engineering (AREA)
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- Output Control And Ontrol Of Special Type Engine (AREA)
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Abstract
The invention provides a multi-objective optimization control strategy and a multi-objective optimization control system for an ammonia-hydrogen dual-fuel aero-rotor engine, wherein S1 builds a single-region numerical simulation model of the ammonia-hydrogen dual-fuel aero-rotor engine based on a mass conservation law, an energy conservation law and an ideal gas state equation; s2, inputting structural parameters, control parameters and fuel parameters of different ammonia-hydrogen dual-fuel aviation rotor engines into a single-region numerical simulation model of the ammonia-hydrogen dual-fuel aviation rotor engine to obtain corresponding performance parameters, and establishing simulation data sets of the different structural parameters, the control parameters, the fuel parameters and the corresponding performance parameters; and S3, optimizing control parameters in the simulation data set by using a NSGA-2 algorithm by taking the performance parameters in the simulation data set as an optimization target to obtain optimal control parameters of the ammonia-hydrogen dual-fuel aero-rotor engine corresponding to the optimal performance parameters under different loads, thereby realizing the optimization adjustment of the parameters of the ammonia-hydrogen dual-fuel aero-rotor engine under different loads.
Description
Technical Field
The invention belongs to the technical field of aviation power, and particularly relates to a multi-target optimization control strategy and system of an ammonia-hydrogen dual-fuel aviation rotor engine.
Background
The rotor engine has the advantages of small volume, simple structure, stable transmission and high power-weight ratio, and plays a unique role in the aspect of a small aviation power system. But at the same time, the heat efficiency and the oil consumption are always the difficult problems which cannot be avoided due to the shape of the long and narrow combustion chamber and the shape change of the complex working chamber. In order to meet urgent requirements of engine oil saving and emission reduction, and simultaneously give consideration to engine performance, a novel structure rotor engine is proposed. The compression ratio of the ammonia-hydrogen dual-fuel aviation rotor engine is larger, the low volume duration at the top dead center is longer, and the defect of long and narrow combustion chamber of the engine is overcome.
In addition, in order to improve high fuel consumption, increase thermal efficiency, and reduce carbon emissions, a new combustion strategy needs to be sought. Hydrogen and ammonia were first considered as novel green energy sources. Compared with the traditional energy, the ammonia combustion speed is slower, but the problem of high emission of the engine can be reasonably solved, the hydrogen activation energy is low, the chemical reaction speed is high, and the ammonia doped with hydrogen is used as the engine fuel, so that a new idea is provided for solving the problems. The ammonia-hydrogen dual fuel is used for the rotor engine, so that the disadvantage of serious emission of the rotor engine can be improved while maintaining the output power and ensuring higher thermal efficiency. On the one hand, the ammonia-hydrogen dual-fuel combustion chemical property is different from the traditional energy source, on the other hand, in the actual working process, the engine usually needs to adjust the working state according to the load state, and in order to obtain more ideal engine performance, the optimal result under the current working condition is obtained, and the running parameters of the engine need to be adjusted accordingly.
Current research on rotary engines focuses on several methods: experimental testing, three-dimensional CFD, and single-region numerical model. Based on the research of measured data, the engine working state under different conditions is simulated through machine learning, and the accuracy of the model depends on a large number of tests, so that the model accuracy under the condition of lack of data cannot be ensured. While CFD tools are powerful, they are very time and computation costly.
The single-region numerical model calculates the research method of the engine performance through the working medium homogenization assumption, omits the research on the internal complex smoothness, focuses on the calculation of the whole engine output performance, and has the characteristics of rapidness and accuracy. However, existing zero-dimensional models are mostly applied to reciprocating engines and single considerations. In addition, with the increase of control parameters, the traditional single-parameter or double-parameter adjustment strategy also needs to be changed, and an optimized control strategy capable of realizing simultaneous regulation and control of multiple parameters is necessary.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a multi-objective optimization control strategy and system for an ammonia-hydrogen dual-fuel aero-rotor engine, which are based on the structure of the ammonia-hydrogen dual-fuel aero-rotor engine, and combine a single-region numerical model and an NSGA-2 multi-objective optimization algorithm to realize the optimization adjustment of parameters of the ammonia-hydrogen dual-fuel aero-rotor engine under different loads and improve the performance of the ammonia-hydrogen dual-fuel aero-rotor engine under different loads.
In order to achieve the above purpose, the present invention provides the following technical solutions: an ammonia-hydrogen dual-fuel aviation rotor engine multi-target optimization control strategy comprises the following specific steps:
S1, constructing a single-region numerical simulation model of an ammonia-hydrogen dual-fuel aviation rotor engine based on a mass conservation law and an energy conservation law and an ideal gas state equation;
S2, inputting structural parameters, control parameters and fuel parameters of different ammonia-hydrogen dual-fuel aviation rotor engines into a single-region numerical simulation model of the ammonia-hydrogen dual-fuel aviation rotor engine to obtain corresponding performance parameters, and establishing simulation data sets of the different structural parameters, the control parameters, the fuel parameters and the corresponding performance parameters;
and S3, optimizing the control parameters in the simulation data set by using the NSGA-2 algorithm with the performance parameters in the simulation data set as an optimization target, and obtaining the optimal control parameters of the ammonia-hydrogen dual-fuel aviation rotor engine corresponding to the optimal performance parameters under different loads.
Further, in S1, according to the thermodynamic process of the engine, the single-region numerical simulation model of the ammonia-hydrogen dual-fuel aviation rotor engine includes an intake process model, a compression process model, a combustion process model, an expansion process model and an exhaust process model, each process model includes a volume subsystem, a combustion subsystem, an air leakage flow subsystem, a heat transfer subsystem and a physical property parameter subsystem, and the outputs of the volume subsystem, the combustion subsystem, the air leakage flow subsystem, the heat transfer subsystem and the physical property parameter subsystem are connected through mass and energy conservation equations to obtain the total change of the mass m and the internal energy u of the working medium in a single combustion chamber; and obtaining the change rule of the cylinder pressure and the cylinder temperature in the cylinder through a thermodynamic law gas state equation, and obtaining the engine performance parameters according to the change rule of the cylinder pressure and the cylinder temperature in the cylinder.
Further, in S1, the volume subsystem is used for calculating the volume change V of the single combustion chamber, the volume change V of the combustion chamber of the engine and the rotation angle of the eccentric shaftThe relationship between them is as follows:
Wherein: k is an engine shape parameter; e is the eccentricity; b is the width of the cylinder body; v p is the combustion chamber pit volume.
Further, in S1, the combustion subsystem is used for calculating the fuel combustion heat release quantity Q and the unit heat release rateWith the rotation angle of the eccentric shaft/>The variation of (2) is as follows:
Wherein x is the percentage of fuel burned during combustion, ma is the combustion quality coefficient, coefficient c is the Weber coefficient, and Hu is the fuel calorific value; η b is combustion efficiency, m fuel is fuel quantity, calculated by the hydrogen loading Hf and the equivalence ratio β.
Further, in S1, the leakage flow subsystem is configured to calculate the leakage flow and the energy carried by the leakage flow, and the leakage flow q is calculated by the pressure difference Δp and the rotation speed U of the two chambers, as follows:
wherein l, b and delta respectively represent the length, width and height of the air leakage port; μ is the viscosity coefficient of the gas; for tip leakage, the rotating speed U takes the movement speed of the tip of the rotor, and for side leakage, the rotor is mainly in rotary movement, so that the influence on radial leakage is small, and the shear flow is negligible.
Further, in S1, the heat transfer subsystem is configured to calculate heat transferred to the outside, and the calculation formula of the heat transfer loss Q exc is as follows:
wherein, subscript i takes 1,2 and 3 to respectively represent three parts of an end cover, a cylinder body and a rotor; t i is the average temperature of the surface of each component, a i is the component heat transfer area, and α i is the heat transfer coefficient of the in-cylinder gas to each component, calculated by the Woschni model.
The heat transfer area A i is calculated by the engine structure and the molded line, and the calculation formula is as follows:
Wherein A1 is the heat transfer area of the end cover; a2 is the heat transfer area of the cylinder body; a 3 is the rotor heat transfer area.
Further, in S1, the physical property parameter subsystem is used for evaluating energy loss caused by the change of thermodynamic parameters of working medium; and the physical parameter subsystem is also connected with a correction model based on gas physical parameters, the correction model based on the gas physical parameters adopts zero-dimensional-REFPROP physical parameter library simultaneous simulation, and the component analysis method is used for calculating the change of the working medium components at each combustion moment.
Further, in S3, a pareto solution set about fuel consumption and thermal efficiency under different loads is obtained in the simulation data set by using NSGA-2 algorithm, and a pareto front solution is solved to obtain optimal fuel consumption and thermal efficiency under a determined load condition, so as to obtain control parameters corresponding to the fuel consumption and thermal efficiency in the simulation data set.
Further, in S3, the control parameters are a rotation speed, an equivalence ratio, and a hydrogen loading amount.
The invention also provides a multi-objective optimization control system of the ammonia-hydrogen dual-fuel aviation rotor engine, which comprises the following components:
The simulation model building module is used for building a single-region numerical simulation model of the ammonia-hydrogen dual-fuel aviation rotor engine based on a mass conservation law, an energy conservation law and an ideal gas state equation;
The simulation data set establishing module is used for inputting the structural parameters, the control parameters and the fuel parameters of the different ammonia-hydrogen dual-fuel aviation rotor engines into the single-region numerical simulation model of the ammonia-hydrogen dual-fuel aviation rotor engine to obtain corresponding performance parameters, and establishing simulation data sets of the different structural parameters, the control parameters, the fuel parameters and the corresponding performance parameters;
And the multi-target optimization control module is used for optimizing the control parameters in the simulation data set by taking the performance parameters in the simulation data set as an optimization target and adopting an NSGA-2 algorithm to obtain the optimal control parameters of the ammonia-hydrogen dual-fuel aero-rotor engine corresponding to the optimal performance parameters under different loads. Compared with the prior art, the invention has at least the following beneficial effects:
the invention provides a multi-target optimization control strategy of an ammonia-hydrogen dual-fuel aero-rotor engine, which combines a single-region numerical model of the rotor engine with an NSGA-2 multi-target optimization algorithm, realizes the optimization adjustment of parameters of the ammonia-hydrogen dual-fuel aero-rotor engine under different loads, improves the performance of the ammonia-hydrogen dual-fuel aero-rotor engine under different loads, and is specific:
1. By considering the energy loss caused by the physical property parameter change, heat transfer and leakage of the working medium, the engine performance parameters including average indicated pressure, fuel consumption, thermal efficiency, torque and the like can be realized, so that a single-region model of the ammonia-hydrogen dual-fuel aviation rotor engine is provided, the model has strong inclusion, the engine working states of different models, different ignition conditions and different fuel blending ratios can be simulated by modifying the input parameters, the simulation result accuracy is high, and the calculation speed is high.
2. The multi-objective optimization algorithm can simultaneously and parallelly optimize a plurality of objective parameters, more efficiently integrate different input and engine performance parameters of the engine, and obtain a better engine control strategy. On the premise of fixed output power, three controllable parameters of rotation speed, equivalence ratio and hydrogen loading are used as variables, and the parameters of thermal efficiency and fuel consumption rate of the engine are optimized through NAGA-2 algorithm, so that an adjustment strategy of engine control parameters under different loads is obtained, and the best performance of the engine is achieved.
Drawings
FIG. 1 is a multi-objective optimal control strategy for a hydrogen-loaded rotary engine;
FIG. 2 is a flow chart of a thermodynamic subsystem of a single process;
FIG. 3 is a schematic diagram of an ammonia-hydrogen dual fuel aircraft rotor engine profile;
FIG. 4 shows the combustion heat release rate as a function of eccentric shaft rotation angle;
FIG. 5 engine gas physical parameter subsystem;
FIG. 6 comparison of rotor engine simulation and test pressure results;
FIG. 7 is a graph of thermal efficiency, fuel consumption versus rotational speed for a hydrogen-loaded rotary engine;
FIG. 8 is a graph of thermal efficiency, fuel consumption versus equivalence ratio for a hydrogen-loaded rotary engine;
FIG. 9 shows the relationship between the thermal efficiency, fuel consumption and hydrogen loading of a hydrogen loading rotary engine;
FIG. 10NSGA-2 multi-objective optimization model flowchart;
The pareto front solution for the multi-objective optimization algorithm at the typical load of the engine of fig. 11;
FIG. 12 is a comparison of control parameters of a multi-objective optimization strategy with a single parameter adjustment strategy under different loads;
FIG. 13 compares engine performance for a multi-objective optimization strategy with a single parameter adjustment strategy at different loads.
Detailed Description
In order to make the purposes, technical effects and technical solutions of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention are clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention; it will be apparent that the described embodiments are some of the embodiments of the present invention. Other embodiments, which may be made by those of ordinary skill in the art based on the disclosed embodiments without undue burden, are within the scope of the present invention.
As shown in fig. 3, unlike the conventional rotary engine, the ammonia-hydrogen dual-fuel aviation rotor engine adopts an outer spiral line as a rotor profile, adopts an envelope line of the outer spiral line as an engine cylinder profile, wherein the outer spiral line is the rotor profile of the ammonia-hydrogen dual-fuel aviation rotor engine (meanwhile, the cylinder profile of the conventional rotor engine), the outer envelope line is the cylinder profile of the ammonia-hydrogen dual-fuel aviation rotor engine, and the inner envelope line is the conventional rotor engine profile.
As shown in fig. 1, the multi-objective optimization control strategy of the ammonia-hydrogen dual-fuel aero-rotor engine is based on the ammonia-hydrogen dual-fuel aero-rotor engine, integrates a single-region numerical model of the rotor engine and an NSGA-2 multi-objective optimization algorithm, and obtains the control strategy of parameters of the ammonia-hydrogen dual-fuel aero-rotor engine under different loads, and the control strategy is specific:
firstly, constructing a single-region numerical simulation model of the ammonia-hydrogen dual-fuel aviation rotor engine based on a mass conservation law, an energy conservation law and an ideal gas state equation:
1) Working medium mass m and internal energy u in single combustion chamber of engine along with eccentric shaft rotation angle The change of (2) is influenced by each subsystem, and should conform to the law of conservation of mass and energy, specifically as shown in the formula 1 and the formula 2.
Wherein: subscripts in, fuel, l, exc, out represent the intake, fuel, blow-by, heat transfer, and exhaust processes of the engine, respectively; h represents the enthalpy of the substance; q is the heat release of fuel combustion; Representing the engine volumetric work; hu is the vaporization heating value of the fuel.
2) The engine in-cylinder parameters (cylinder pressure, cylinder temperature) are calculated by the following formula:
gaseous fuels in ammonia-hydrogen dual fuel aviation rotor engines obey the thermodynamic law ideal gas state equation:
pV＝mRT (3)
Wherein P, V and T respectively represent the pressure, the volume and the temperature of the system; r is a universal gas constant.
The system temperature is expressed as:
Wherein u is the internal energy of the system; cv is the constant specific heat capacity of the working medium of the system. Thermodynamic parameters of the system are affected by cylinder temperature and cylinder pressure, and are calculated through a REFPROP database. The air component is considered to be a combination of nitrogen, oxygen, carbon dioxide, water. Fuel combustion is considered to be a process that consumes oxygen to produce the end products H 2 and CO 2, with intermediate stage reactions being omitted.
3) The single-region model calculates required input parameters including: the structural parameters, control parameters and fuel parameters are shown in table 1, and specifically, the structural parameters are used for calculating the geometric shape of the engine to obtain the change rule of the volume of the combustion chamber; the control parameters are used for determining the working state of the engine; the fuel parameter is used to calculate the combustion heat release rate. Wherein, among the control parameters: the speed, equivalence ratio, and loading were adjustable, and therefore were chosen here as independent variables, with performance parameters as an estimate of engine performance, and as dependent variables.
Table 1 input parameters for an ammonia-hydrogen dual fuel aero rotor engine
The output of the single-region numerical simulation model of the ammonia-hydrogen dual-fuel aviation rotor engine is an engine in-cylinder state parameter and a performance parameter, and the specific parameters are shown in table 2:
Table 2 output parameters of an ammonia-hydrogen dual fuel aero rotor engine
The single-region numerical simulation model of the ammonia-hydrogen dual-fuel aviation rotor engine is divided into an air inlet process model, a compression process model, a combustion process model, an expansion process model and an exhaust process model according to the thermodynamic process of the engine; each process model consists of a volume subsystem, a combustion subsystem, a leakage gas flow subsystem, a heat transfer subsystem and a physical parameter subsystem module, wherein the subsystems are mutually independent, respectively describe different thermodynamic processes occurring in a combustion chamber, and output the quality and energy of each subsystem. The output of each subsystem is connected through a mass and energy conservation equation to obtain the total mass and energy change of the combustion chamber, then the in-cylinder parameter change rule (cylinder pressure and cylinder temperature) is calculated through a thermodynamic law gas state equation, and finally the engine performance parameter is calculated through the in-cylinder parameter change rule. The whole calculation process forms a single-region numerical simulation model of the ammonia-hydrogen dual-fuel aero-rotor engine, and refer to fig. 2.
A volume subsystem for calculating the volume V change and the eccentric shaft rotation angle of the combustion chamber of the engineThe relationship between the individual working chamber volume changes V is given by equation 3:
Wherein: k is an engine shape parameter; e is the eccentricity; b is the width of the cylinder body; v p is the combustion chamber pit volume.
The combustion subsystem is used for calculating combustion heat release quantity, and a Weber function is adopted to simulate the heat release rule of the ammonia-hydrogen dual-fuel aviation rotor engine, and the unit heat release rate of the combustion subsystem is used for calculating the combustion heat release quantityWith the rotation angle of the eccentric shaft/>The change in (c) is calculated from equation 4:
Wherein x is the percentage of fuel burned during combustion, ma is the combustion quality coefficient, and 3 is taken in the model; the coefficient c is a Weber coefficient, and is generally-6.908; hu is the fuel heating value; η b is combustion efficiency, m fuel is fuel quantity, calculated by the hydrogen loading Hf and the equivalence ratio β.
Referring to fig. 4, the combustion heat release rate varies with the eccentric shaft rotation angle.
The air leakage subsystem is used for calculating air leakage and carrying energy thereof, and is simplified to flow velocity calculation flowing through a slit gap so as to describe the relationship between the flow velocity and pressure difference, an upper plate surface (sealing piece and cylinder body) is fixed, a lower plate surface (rotor) moves in parallel relative to the upper plate surface at a speed U, and working media between the plates flow in a laminar flow. Part of the leakage flow between the plates is flow caused by pressure difference, the speed is parabolic along the height, the other is shear flow caused by the movement of the lower plate, and the flow speed is linearly distributed. The leakage flow q is calculated by the two-chamber pressure difference Δp and the rotation speed U as in equation (3.17).
Wherein l, b and delta respectively represent the length, width and height of the air leakage port; μ is the viscosity coefficient of the gas; for tip leakage, U takes the rotor tip movement speed, and for side leakage, the rotor is mainly rotated, so that the influence on radial leakage is small, and the shear flow is negligible.
The heat transfer subsystem is used for calculating heat transferred outwards, is simplified into a convection heat exchange process, and has small change amplitude of the surface temperature of each component, so that the surface temperature is considered to be constant, and the heat transfer area of each part is determined by the position of the rotor. Calculation formulas of heat transfer loss Q exc such as
Wherein, subscript i takes 1,2 and 3 to respectively represent three parts of an end cover, a cylinder body and a rotor; t i is the average temperature of the surface of each component, a i is the component heat transfer area, and α i is the heat transfer coefficient of the in-cylinder gas to each component, calculated by the Woschni model.
The heat transfer area A i is calculated by the engine structure and the molded line, and the calculation formula is as follows:
Wherein A1 is the heat transfer area of the end cover; a2 is the heat transfer area of the cylinder body; a 3 is the rotor heat transfer area.
The physical property parameter subsystem is used for evaluating energy loss caused by the change of thermodynamic parameters of the working medium.
As shown in fig. 5, the single-zone numerical simulation model establishes a correction model based on gas physical properties parameters to consider the relationship between the thermodynamic properties of gas and the gas state. REFPROP is a physical property data source developed by National Institute of Standards and Technology (NIST), a correction model based on gas physical property parameters adopts zero-dimensional-REFPROP physical property parameter library simultaneous simulation, and a component analysis method is used for calculating the change of working medium components at each combustion moment.
The power, the thermal efficiency and the fuel consumption rate in the performance parameters are calculated as follows:
power:
Pi is the engine indication power, P is the instantaneous pressure in an engine cylinder, V is the instantaneous volume, t is the number of engine strokes, and the Wankel engine takes 2 as the engine has the special structural characteristics that the crankshaft rotates three times for three times per revolution of a rotor, so the engine is a two-stroke engine in a strict sense.
Thermal efficiency:
where η is engine thermal efficiency, hu is fuel low heating value, m fuel is fuel mass, and subscript j indicates fuel type.
Fuel consumption rate:
Wherein, ISFC indicates oil consumption for the engine; n is the engine speed.
Referring to fig. 6, comparing the results of the engine simulation and test, it can be seen that the response curves are well matched, the model error is less than 6%, and the method can be used for further calculating the engine performance and obtaining the optimal control strategy by coupling with the target optimization strategy of NAGA-2.
Referring to fig. 7-9, the fuel consumption rate varies with engine thermal efficiency at different speeds, equivalence ratios and hydrogen loading. It can be seen that the engine thermal efficiency increases with increasing rotational speed, indicating that the fuel consumption decreases with increasing rotational speed, and that both changes at high rotational speeds flatten out. This is because the fuel combustion is retarded at a high rotation speed, and the energy conversion efficiency is lowered. With the increase of the equivalence ratio, the fuel combustion speed is increased, when the equivalence ratio reaches 0.8, the heat release point of the combustion center reaches the ideal position, the heat efficiency reaches the maximum, and then the heat efficiency is reduced. In addition, an increase in the amount of hydrogen loading reduces the thermal efficiency of the engine and increases fuel consumption because hydrogen significantly improves the flame propagation speed of the engine, the cylinder pressure of the engine rises faster, and the combustion heat cannot be effectively converted into volumetric work.
And a second step of: and establishing a simulation data set according to different structural parameters, control parameters and fuel parameters of the single-region numerical simulation model of the input ammonia-hydrogen dual-fuel aero-rotor engine and the corresponding obtained performance parameters.
And a third step of: and introducing a multi-objective optimization algorithm to optimize the objective performance parameters to obtain control parameters, wherein the multi-objective optimization is based on an NSGA-2 algorithm and expands the actual working conditions of the engine.
As shown in fig. 10, the engine control parameters and performance parameters under the constant power in the simulation data set are first screened, and then the screened parameters are optimized to obtain an adjustment strategy for calculating the optimal control parameters under different loads of the engine.
The NSGA-2 algorithm is input into different control parameters and corresponding output performances, and the output is the optimal working conditions (maximum thermal efficiency and lowest fuel consumption) of the engine under different loads. The specific operation is that the engine power (expressed as a percentage of full load) is used as a limiting condition, the thermal efficiency and the fuel consumption rate are used as optimization targets, the rotating speed, the equivalence ratio and the hydrogen loading amount are used as control variables (input), and the iteration number is 500. The NSGA-2 algorithm firstly takes the heat efficiency and the fuel consumption rate in the simulation data set as the father to process data, and performs non-dominant sorting and crowding degree test on the processing results to generate a new father, and iterates accordingly. The final output is pareto solution set for thermal efficiency and fuel consumption, which is processed in the next step. The NSGA-2 algorithm can converge better at the pareto front solution, and can be effectively applied to handle the trade-off between optimization goals herein and give a solution set of optimization strategies.
Referring to fig. 11, the pareto front solution for a multi-objective optimization algorithm at typical engine load. The pareto front solution is the best solution selected after the pareto solution set is processed. Regarding the heat efficiency and fuel consumption rate pareto solution sets, points a and B are taken to represent the minimum value of fuel consumption rate and the maximum value of heat efficiency, respectively. An assumed point C, i.e. the interaction of maximum thermal efficiency and minimum carbon emissions, is introduced. The Pareto front solution (point D) closest to the point C is called the optimal solution of multi-objective optimization, and the optimal fuel consumption rate and the optimal thermal efficiency meeting the requirements under the condition of determining the engine power are obtained; then obtaining the optimal rotation speed, equivalent ratio and hydrogen loading amount corresponding to the fuel consumption rate and thermal efficiency of the engine under the power condition from the simulation data set; as an optimized control scheme under this load. In this way, a trade-off between minimum carbon emissions and maximum thermal efficiency is achieved.
Referring to FIG. 12, the adjustment strategy for the control parameters obtained by the multi-objective optimization is compared with the adjustment strategy for the single parameter at different engine loads. The hydrogen loading ratio of 10% -30% can meet the requirements of different loads, the increasing amplitude of the equivalence ratio is smaller along with the increase of the loads, and the rotating speed of the optimization control strategy is generally higher for the purpose of power and heat efficiency loss caused by hydrogen loading and small equivalence ratio.
Referring to FIG. 13, engine performance parameters obtained by multi-objective optimization at different engine loads are compared with conventional equivalence ratio and rotational speed parameter adjustment strategies. The performance of the engine under low and high load working conditions is obviously improved under the multi-objective optimization, and the thermal efficiency is slightly lower than the equivalence ratio optimization strategy under the medium load, but the engine has better performance in the aspect of fuel consumption. The thermal efficiencies of 25%, 50%, 75%, 100% and 120% under load reach 26.5%, 31.3%, 33.7%, 35.2% and 35.3%, respectively, and the fuel consumption is continuously stabilized at 175-245 g/(kw.h).
Claims (4)
1. The multi-target optimization control strategy for the ammonia-hydrogen dual-fuel aviation rotor engine is characterized by comprising the following specific steps of:
S1, constructing a single-region numerical simulation model of an ammonia-hydrogen dual-fuel aviation rotor engine based on a mass conservation law and an energy conservation law and an ideal gas state equation;
S2, inputting structural parameters, control parameters and fuel parameters of different ammonia-hydrogen dual-fuel aviation rotor engines into a single-region numerical simulation model of the ammonia-hydrogen dual-fuel aviation rotor engine to obtain corresponding performance parameters, and establishing simulation data sets of the different structural parameters, the control parameters, the fuel parameters and the corresponding performance parameters;
s3, optimizing control parameters in the simulation data set by using a NSGA-2 algorithm with performance parameters in the simulation data set as an optimization target to obtain optimal control parameters of the ammonia-hydrogen dual-fuel aviation rotor engine corresponding to the optimal performance parameters under different loads;
In the S1, according to the thermodynamic process of the engine, a single-region numerical simulation model of the ammonia-hydrogen dual-fuel aviation rotor engine comprises an air inlet process model, a compression process model, a combustion process model, an expansion process model and an exhaust process model, wherein each process model comprises a volume subsystem, a combustion subsystem, an air leakage flow subsystem, a heat transfer subsystem and a physical parameter subsystem, and the output of the volume subsystem, the combustion subsystem, the air leakage flow subsystem, the heat transfer subsystem and the physical parameter subsystem is connected through a mass conservation equation and an energy conservation equation to obtain the total change of the working medium mass m and the internal energy u in a single combustion chamber; obtaining a change rule of cylinder pressure and cylinder temperature in the cylinder through a thermodynamic law gas state equation, and obtaining engine performance parameters according to the change rule of the cylinder pressure and the cylinder temperature in the cylinder;
In S1, the volume subsystem is used for calculating the volume change of the single combustion chamber Engine combustion chamber volume change/>The relation with the eccentric shaft rotation angle phi is as follows:
wherein: k is an engine shape parameter; e is the eccentricity; b is the width of the cylinder body; v p is the combustion chamber pit volume;
In S1, the combustion subsystem is used for calculating the combustion heat release quantity Q of fuel, and the unit heat release rate dQ/dphi changes along with the rotation angle phi of the eccentric shaft as follows:
Wherein x is the percentage of fuel burned during combustion, ma is the combustion quality coefficient, coefficient c is the Weber coefficient, and Hu is the fuel calorific value; η b is combustion efficiency, m fuel is fuel quantity, calculated by hydrogen loading Hf and equivalence ratio beta;
In S1, the leakage flow subsystem is used for calculating the leakage flow and the energy carried by the leakage flow, and the leakage flow q is calculated by the pressure difference Δp and the rotation speed U of the two chambers, as follows:
Wherein l, b and delta respectively represent the length, width and height of the air leakage port; μ is the viscosity coefficient of the gas; for top leakage, the rotating speed U takes the movement speed of the tip of the rotor, and for side leakage, the rotor is mainly in rotary movement, so that the influence on radial leakage is small, and the shear flow is ignored;
In S1, the heat transfer subsystem is configured to calculate heat transferred to the outside, and the calculation formula of the heat transfer loss Q exc is as follows:
Wherein, subscript i takes 1,2 and 3 to respectively represent three parts of an end cover, a cylinder body and a rotor; t i is the average temperature of the surface of each component; a i is the component heat transfer area; alpha i is the heat transfer coefficient of the in-cylinder gas to each component; calculated by Woschni model;
The heat transfer area A i is calculated by the engine structure and the molded line, and the calculation formula is as follows:
Wherein, Heat transfer area for the end cap; /(I)The heat transfer area of the cylinder body is provided; /(I)A heat transfer area for the rotor;
In S1, a physical property parameter subsystem is used for evaluating energy loss caused by thermodynamic parameter change of working medium; and the physical parameter subsystem is also connected with a correction model based on gas physical parameters, the correction model based on the gas physical parameters adopts zero-dimensional-REFPROP physical parameter library simultaneous simulation, and the component analysis method is used for calculating the change of the working medium components at each combustion moment.
2. The multi-objective optimization control strategy of the ammonia-hydrogen dual-fuel aero rotor engine according to claim 1, wherein in the step S3, a pareto solution set of fuel consumption and thermal efficiency under different loads is obtained in a simulation data set by using an NSGA-2 algorithm, the pareto front solution is solved to obtain optimal fuel consumption and thermal efficiency under a determined load condition, and control parameters corresponding to the fuel consumption and the thermal efficiency in the simulation data set are obtained.
3. The multi-objective optimization control strategy of an ammonia-hydrogen dual-fuel aviation rotor engine according to claim 1 or 2, wherein in S3, the control parameters are rotation speed, equivalence ratio and hydrogen loading.
4. An ammonia-hydrogen dual-fuel aero-rotor engine multi-objective optimization control system, characterized in that the control system adopts the control strategy of any one of claims 1-3 to optimally design the rotor engine, and the control system comprises:
The simulation model building module is used for building a single-region numerical simulation model of the ammonia-hydrogen dual-fuel aviation rotor engine based on a mass conservation law, an energy conservation law and an ideal gas state equation;
The simulation data set establishing module is used for inputting the structural parameters, the control parameters and the fuel parameters of the different ammonia-hydrogen dual-fuel aviation rotor engines into the single-region numerical simulation model of the ammonia-hydrogen dual-fuel aviation rotor engine to obtain corresponding performance parameters, and establishing simulation data sets of the different structural parameters, the control parameters, the fuel parameters and the corresponding performance parameters;
And the multi-target optimization control module is used for optimizing the control parameters in the simulation data set by taking the performance parameters in the simulation data set as an optimization target and adopting an NSGA-2 algorithm to obtain the optimal control parameters of the ammonia-hydrogen dual-fuel aero-rotor engine corresponding to the optimal performance parameters under different loads.
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