Air system analysis and evaluation method based on complete machine energy efficiency

Abstract

The invention discloses a complete machine energy efficiency-based air system analysis and evaluation method, which comprises the following steps of: decomposing a turbine engine into an air inlet assembly, an exhaust assembly, an air compressor, a combustion chamber and a turbine according to parts, simulating by adopting flow characteristics and turbine characteristics, and establishing an engine performance one-dimensional calculation model by connecting elements in series; a mathematical model or flow characteristic simulation is adopted for throttling elements, local flow loss elements and the like in an engine air system, and an air system flow path one-dimensional calculation model is established; uniformly modeling the engine performance one-dimensional calculation model and the air system flow path one-dimensional calculation model, and establishing an engine overall performance and air system coupling calculation model; outputting a calculation result of the influence of the air system induced and exhausted air on the engine performance. Complete machine coupling analysis in a full envelope range can be carried out, air system air introduction and exhaust positions and flow parameters better conform to real conditions and change in real time according to states, and the precision of air system and overall performance calculation is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas turbine engines, and in particular, to an analysis and evaluation method for an air system based on the overall engine energy efficiency. Background Technique

[0002] The air system is an important subsystem of an aeroengine, which is responsible for important functions such as supplying air for air-cooled blades, cooling high-temperature turbine components, sealing the turbine disk cavity with gas, controlling the temperature of the compressor, adjusting the axial force load of the rotor, sealing and heat insulation of the bearing and lubrication system, and clearance control. The air system of an aeroengine usually draws air from the main passage of the engine, organizes the flow, distributes it to each chamber inside the engine, completes each basic function, and finally flows back to the main passage or is discharged to the outside of the engine. As Figure 1 shown. The air intake volume of the air system of modern aeroengines accounts for 20-30% of the total inlet flow of the engine, which has an obvious impact on the overall performance of the engine, and the impact on the specific fuel consumption of the engine is more than 6%.

[0003] The flow path of the air system is very complex and is usually composed of multiple parallel or series flow paths. Each flow path internally has air intake structures, holes, pipes, channels, elbows, chambers, sealing structures, exhaust structures, etc. Due to the complexity of the air system, the one-dimensional network method is usually mainly used for the overall air system analysis in engineering. The one-dimensional network method decomposes the air system flow structure into some basic flow resistance and heat transfer elements, such as pipes, holes, slits, sudden expansions, sudden contractions, elbows, labyrinth seals, etc. The air system is simplified into a network of air flow and heat transfer elements composed of multiple inlets, outlets, and branches. Based on classical theories such as gas dynamics and heat transfer, empirical correlation formulas or semi-empirical theories are used to establish calculation models for these elements, thereby establishing a flow network equation set, and the network analysis method is used to solve for the flow parameters such as pressure, temperature, and flow rate of each element and the flow rate distribution of each flow path branch.

[0004] For the gas discharged from the air system into the turbine, which part does work and which part does not do work? The engineering treatment method is to classify the exhaust gas at different positions of the air system. Taking the 1st-stage turbine as an example, the air system air flow introduced before the throat of the guide vane is considered to have reached the momentum at the outlet of the guide vane, so it will do work at this stage; the air system air flow introduced after the throat of the guide vane does not do work at this stage of the turbine and does work at the downstream stages of the turbine. Therefore, according to the flow rate distribution calculated by the one-dimensional network method, the air system is statistically classified according to whether it does work or not, and the total flow rate of the air system that has an obvious impact on the engine performance is simply estimated.

[0005] When calculating the overall performance, according to the flow rate distribution statistically classified by the air system, an overall calculation model considering the flow rate distribution and influence of the air system is established. Figure 2It is a calculation example of the overall performance calculation software GasTurb considering the air system. The bleed air flow paths at different positions simply give the ratio of the enthalpy value at the bleed air location to the enthalpy value at the compressor outlet and the bleed air ratio. Through the overall calculation model, the overall performance considering the influence of the air system and the parameters of each cross-section are obtained.

[0006] In the prior art, the air system and the overall performance analysis are carried out independently. The air system analysis obtains the distribution results of the intake and exhaust air flows, but it cannot directly evaluate the impact of the intake and exhaust air on the overall performance. When calculating the overall performance, only the influence of the air system can be simply considered, and the following problems exist:

[0007] 1) It is impossible to establish an overall performance model based on the actual intake and exhaust positions of the air system. Only the flow distribution can be carried out according to the intake and exhaust positions specified by the overall calculation model based on the classification and statistical results of the air system.

[0008] 2) It is impossible to consider the actual flow parameters at the intake and exhaust positions, such as pressure, temperature, etc. Only simple processing according to the enthalpy ratio can be carried out.

[0009] 3) When performing dynamic calculations, it is impossible to consider the changes in the air system flow distribution ratio and flow parameters (enthalpy ratio) under different engine states.

[0010] 4) The interactive influence between the air system model and the overall performance model is not considered. Summary of the Invention

[0011] The present invention provides a method for analyzing and evaluating the air system based on the overall engine energy efficiency to solve the technical problem that in the prior art, the air system and the overall engine performance analysis are carried out independently, and the flow distribution results obtained from the air system analysis cannot directly evaluate the impact on the overall engine performance.

[0012] According to one aspect of the present invention, a method for analyzing and evaluating the air system based on the overall engine energy efficiency is provided, including the following steps:

[0013] Step 1: Decompose the turbine engine into an intake component, an exhaust component, a compressor, a combustion chamber, a gas turbine, and a power turbine according to components, simulate using flow characteristics and turbomachinery characteristics, and establish a one-dimensional calculation model of the engine performance by connecting each component in series.

[0014] Step 2: For the throttle element, local flow loss element, chamber element, and heat exchange element in the engine air system, use a mathematical model or flow characteristic simulation to establish a one-dimensional calculation model of the air system flow path.

[0015] Step 3: Uniformly model the one-dimensional calculation model of engine performance and the one-dimensional calculation model of the air system flow path on the same software platform to establish a coupled calculation model of the overall engine performance and the air system, and realize coupled solution;

[0016] Step 4: Output the calculation results of the influence of the intake and exhaust of the air system on the engine performance under different engine states.

[0017] Furthermore, in the said Step 1, it includes establishing calculation models for the intake component, exhaust component, and flow path transition section components. When air flows through the intake and exhaust flow paths, total pressure losses are generated, and the formula is as follows:

[0018] p 2 =σp 1 (1)

[0019] In formula (1), p 1 , p 2 are respectively the inlet total pressure and outlet total pressure of the intake component and the exhaust component, and σ is the recovery coefficient.

[0020] Furthermore, in the said Step 1, it includes establishing calculation models for the compressor, gas turbine, and power turbine components. The relationship between the compressor, turbine flow rate and rotational speed, pressure, or expansion ratio is calculated by characteristic table interpolation, and the formula is as follows:

[0021]

[0022] In formula (2), is the mass flow rate, N is the rotational speed, π is the compressor pressure ratio or turbine expansion ratio, p, T are the inlet pressure and temperature;

[0023] And establish a calculation model for the rotor mechanical inertia component. The difference between the compressor required power and the turbine output power is the engine rotor acceleration, and the formula is as follows:

[0024]

[0025] In formula (3), P T , P T are respectively the compressor and turbine powers, J is the rotor moment of inertia, is the rotational acceleration.

[0026] Furthermore, in the said Step 1, it includes establishing a calculation model for the combustion chamber component, and directly calculating the fuel-air ratio of the combustion chamber by the isothermal enthalpy difference method, and the formula is as follows:

[0027]

[0028] In formula (4), f is the fuel-air ratio, η b is the combustion efficiency; H uis the lower calorific value of fuel; h in，a , h out，a are the inlet and outlet air enthalpy values of the combustion chamber respectively; H out is the isothermal enthalpy value at the outlet temperature of the combustion chamber;

[0029] Total pressure at the outlet of the combustion chamber: p out = p in σ b , where the total pressure recovery coefficient σ b takes values from 0.96 to 0.97.

[0030] Furthermore, in the said step 2, it includes establishing a calculation model for orifice and clearance throttling elements. When air flows through the intake and exhaust channels, total pressure losses are generated. The formula is as follows:

[0031]

[0032] In formula (5), A is the orifice area, T 1 * is the total temperature, P 1 * is the inlet total pressure, C d is the orifice flow coefficient, P 2 is the outlet static pressure, is the mass flow rate, R is the gas constant, and k is the adiabatic index.

[0033] Furthermore, in the said step 2, it includes establishing a calculation model for local flow loss elements. The formula is as follows:

[0034]

[0035] In formula (6), are the inlet total pressure and outlet total pressure of the flow element respectively, ζ is the resistance coefficient, ρ is the air density, and v is the air flow velocity.

[0036] Furthermore, in the said step 2, it includes establishing a calculation model for chamber elements. It has a certain volume, and the imbalance between the inlet and outlet flow rates leads to changes in the chamber pressure and temperature. The calculation formula is as follows:

[0037]

[0038] In formula (7), p, ρ, h, and T are the pressure, density, specific enthalpy, and temperature of the air in the chamber respectively, V is the chamber volume, m is the mass of air in the chamber, m i is the mass flow rate of air at each interface of the chamber, Q is the heat exchange amount between the air in the chamber and the outside, the subscript i represents the chamber interface number, and t is the time.

[0039] Furthermore, in the said step 2, it includes establishing a calculation model for heat exchange elements. The formula is as follows:

[0040] q = hA(T w - T c )(8)

[0041] In Equation (8), q is the heat transfer heat flow, A is the heat transfer area, T w and T c are the solid wall temperature and the air temperature respectively, and h is the heat transfer coefficient.

[0042] Furthermore, in Step 3, under the design point condition, the steady-state analysis of the overall engine performance and the air system coupling model achieves stable operation according to the performance data of each component at the design point; under the off-design point condition, initial parameter values are assigned to each component, and these initial parameter values are continuously updated through iterative calculations to satisfy the balance relationship of the flow rate and power among the components of the engine.

[0043] Furthermore, in Step 4, based on the overall engine performance and the air system coupling calculation model, steady-state and dynamic calculation analyses are carried out, and at the same time, the flow parameter distribution of the air system and the overall engine performance are obtained. The influence of the air extraction of the air system on the engine performance is evaluated through the engine performance of the overall engine performance and the air system coupling calculation model.

[0044] The present invention has the following beneficial effects:

[0045] The present invention proposes an overall engine performance and air system coupling integrated energy efficiency analysis method, establishes an overall machine coupling model including the air system and the overall engine performance. The engine performance model composed of components such as a compressor, a combustion chamber, a gas turbine, and a power turbine can evaluate overall engine parameters such as engine power, thermal efficiency, and fuel consumption rate. The one-dimensional network model of the air system can evaluate the air extraction volume of the air system, the flow parameters of each branch flow path and component, etc. Since a coupling analysis model of the air system and the overall engine performance is established, through the steady-state and dynamic analysis of the model, the steady-state and dynamic performance results of the influence of the air system on the overall engine performance can be directly obtained; and the overall machine coupling analysis within the full envelope range can be carried out, and the air extraction and exhaust positions and flow parameters of the air system are more in line with the actual situation and change in real time according to the state; in addition, the accuracy of the calculation of the air system and the overall performance is improved through the coupling analysis of the air system and the overall performance.

[0046] The present invention has been applied to a certain type of turboprop engine, carried out the coupling analysis of the air system and the overall performance, compared and studied the influence of single measures such as air extraction, precooling, and prewhirl of the air system on the air system and the engine performance, proposed a comprehensive improvement and optimization plan. Through the overall machine coupling analysis, the comprehensive improvement measures of the air system have increased the engine thermal efficiency by 2%, and intuitively evaluated the improvement effect of the air system.

[0047] In addition to the purposes, features and advantages described above, the present invention has other purposes, features and advantages. The present invention will be further described in detail below. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0049] Figure 1 is a schematic diagram of an engine air system;

[0050] Figure 2 is a calculation example of the GasTurb overall calculation considering the air system;

[0051] Figure 3 is a schematic diagram of a component for dealing with volume effect;

[0052] Figure 4 is an example of the coupling analysis of the air system and the overall performance. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0053] The embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention can be implemented in many different ways defined and covered by the following.

[0054] An embodiment of the first aspect of the present invention provides an air system analysis and evaluation method based on the overall engine energy efficiency, including the following steps:

[0055] Step 1: Decompose the turbine engine into an intake component, an exhaust component, a compressor, a combustion chamber, a gas turbine and a power turbine according to components, simulate using flow characteristics and turbomachinery characteristics, and establish a one-dimensional calculation model of the engine performance by connecting each element in series;

[0056] Step 2: For the throttle element, local flow loss element, chamber element and heat exchange element in the engine air system, use a mathematical model or flow characteristic simulation to establish a one-dimensional calculation model of the air system flow path; wherein the throttle element, local flow loss element, chamber element and heat exchange element are typical elements such as holes, pipes, gaps, cavities and channels in the engine air system;

[0057] Step 3: Uniformly model the one-dimensional calculation model of the engine performance and the one-dimensional calculation model of the air system flow path on the same software platform, establish a coupling calculation model of the overall engine performance and the air system, and realize coupling solution;

[0058] Step 4: Output the calculation results of the influence of the air system intake and exhaust on the engine performance under different engine states.

[0059] One-dimensional fluid network models are used for the calculation and analysis of the overall performance and air system of aero-engines. For the one-dimensional network model of engine performance, it mainly consists of a compressor, a combustor, a turbine, and intake and exhaust components; for the one-dimensional calculation model of the air system flow path, it mainly consists of pneumatic components such as holes, labyrinth clearances, pipelines, and cavities. Both are gas flow path systems, and their calculation methods have certain similarities. Therefore, a one-dimensional network total model that couples the overall performance of the engine and the air system can be established on the same software platform, and the relationship between the air intake and exhaust between the two can be reflected. Various types of flow components are connected in parallel or in series to form a one-dimensional flow path network, and each component is simulated and calculated using the corresponding mathematical model. Through the solution of the total network, the calculation results of the influence of the air system intake and exhaust on the engine performance under different engine conditions can be obtained.

[0060] The present invention proposes a method for analyzing the overall engine efficiency by coupling the overall performance of the engine and the air system, establishing an overall engine coupling model including the air system and the overall performance of the engine. The engine performance model composed of components such as a compressor, a combustor, a gas turbine, and a power turbine can evaluate the overall engine parameters such as engine power, thermal efficiency, and fuel consumption rate. The one-dimensional network model of the air system can evaluate the air intake volume of the air system, the flow parameters of each branch flow path and components, etc. Since a coupling analysis model of the air system and the overall performance of the engine is established, through the steady-state and dynamic analysis of the model, the steady-state and dynamic performance results of the influence of the air system on the overall performance of the engine can be directly obtained; and the overall engine coupling analysis within the full envelope range can be carried out, and the air intake and exhaust positions and flow parameters of the air system are more in line with the actual situation and change in real time according to the state; in addition, the accuracy of the calculation of the air system and the overall performance is improved through the coupling analysis of the air system and the overall performance.

[0061] The present invention has been applied to a certain type of turboprop engine, carried out the coupling analysis of the air system and the overall performance, compared and studied the influence of single measures such as air system injection, precooling, and prewhirl on the air system and engine performance, proposed a comprehensive improvement and optimization plan. Through the overall engine coupling analysis, the comprehensive improvement measures of the air system have increased the engine thermal efficiency by 2%, and intuitively evaluated the improvement effect of the air system.

[0062] In the embodiment of the present invention, the step 1 includes establishing a calculation model for the intake assembly, the exhaust assembly, and the flow path transition section components. When air flows through the intake and exhaust flow paths, a total pressure loss is generated, and the formula is as follows:

[0063] p 2 =σp 1 (1)

[0064] In formula (1), p 1 、p 2are the total inlet pressure and total outlet pressure of the intake component and the exhaust component respectively, and σ is the recovery coefficient.

[0065] In an embodiment of the present invention, in step 1, a calculation model of a compressor, a gas turbine, and a power turbine element is established. The relationship between the flow rate, rotational speed, pressure, or expansion ratio of the compressor and the turbine is calculated by interpolating a characteristic table, and the formula is as follows:

[0066]

[0067] In formula (2), is the mass flow rate, N is the rotational speed, π is the compressor pressure ratio or turbine expansion ratio, p and T are the inlet pressure and temperature, and f is a function;

[0068] And a calculation model of the rotor mechanical inertia element is established. The difference between the power required by the compressor and the power output by the turbine is the engine rotor acceleration, and the formula is as follows:

[0069]

[0070] In formula (3), P T 、P T are the compressor and turbine powers respectively, J is the rotor moment of inertia, is the rotational acceleration.

[0071] The total pressure loss element is used to evaluate the pressure loss at the inlet and outlet. The temperature, flow rate, and other parameters at the inlet and outlet of this element remain unchanged. According to the principle of flow conservation, the flow rate is consistent with that of the compressor, gas turbine, or power turbine element connected before and after, and the temperature is consistent with the outlet of the upstream connected element. The compressor, gas turbine, and power turbine elements establish a matching relationship between the flow rate, power, and pressure ratio (or expansion ratio) through the characteristic relationship curves of the flow rate, efficiency, rotational speed, and pressure ratio (or expansion ratio). The rotational speed, flow rate, and pressure ratio (or expansion ratio) of the compressor and turbine are determined by iterative calculation based on the principles of flow balance, power balance, and rotational speed balance.

[0072] In an embodiment of the present invention, in step 1, a calculation model of the combustion chamber element is established, and the fuel-air ratio of the combustion chamber is directly calculated by the isothermal enthalpy difference method, and the formula is as follows:

[0073]

[0074] In formula (4), f is the fuel-air ratio, η b is the combustion efficiency; H u is the lower calorific value of the fuel; h in，a , h out，a are the inlet and outlet air enthalpy values of the combustion chamber respectively; H out is the isothermal enthalpy value at the outlet temperature of the combustion chamber, which can be obtained by looking up the table according to the corresponding fuel;

[0075] Total pressure at the combustor outlet: p out = p in σ b , where the total pressure recovery coefficient σ b takes values from 0.96 to 0.97.

[0076] The present invention uses the characteristics of flow components and turbomachinery characteristics for simulation. By connecting in series components such as an intake assembly, a compressor, a combustor, a gas turbine, a power turbine, and an exhaust assembly, physical processes such as the gas mass flow balance through each series component, the power balance between the compressor and the gas turbine under the same rotational speed constraint, and the energy difference and output power balance of the gas at the inlet and outlet of the overall engine model are achieved, and a one-dimensional calculation model for engine performance simulation is established.

[0077] In an embodiment of the present invention, the step 2 includes establishing a calculation model for orifice and clearance throttling elements. When air flows through the intake and exhaust channels, a total pressure loss occurs, and the formula is as follows:

[0078]

[0079] In formula (5), A is the orifice area, T 1 * is the total temperature, P 1 * is the inlet total pressure, C d is the orifice flow coefficient, P 2 is the outlet static pressure, is the mass flow rate, R is the gas constant, and k is the adiabatic index.

[0080] The present invention uses the throttling principle of the air system orifice for the hydrodynamic calculation of the engine compressor and turbine, that is, according to the inlet and outlet pressures and temperatures, the through-flow mass flow rate of the turbomachinery is calculated, and the one-dimensional fluid network coupling calculation of the one-dimensional calculation model for engine performance and the one-dimensional calculation model for the air system flow path is realized.

[0081] In an embodiment of the present invention, the step 2 includes establishing a calculation model for local flow loss elements, and the formula is as follows:

[0082]

[0083] In formula (6), are respectively the inlet total pressure and the outlet total pressure of the flow element, ζ is the resistance coefficient, ρ is the air density, and v is the air flow velocity.

[0084] In an embodiment of the present invention, the step 2 includes establishing a calculation model for chamber elements, which have a certain volume. The imbalance between the inlet and outlet flow rates causes changes in the chamber pressure and temperature, and the calculation formula is as follows:

[0085]

[0086] In formula (7), p, ρ, h, and T are respectively the pressure, density, specific enthalpy, and temperature of the air in the cavity, V is the volume of the chamber, m is the mass of the air in the cavity, m i is the air mass flow rate at each interface of the chamber, Q is the heat exchange amount between the air in the cavity and the outside, the subscript i represents the chamber interface number, and t is the time.

[0087] Based on the values of the cavity pressure and cavity temperature at the previous moment, the integrator calculates the value at the current moment through the time derivatives of pressure and temperature and the time step.

[0088] According to the gas mass flow rate and enthalpy flow rate at each port of the chamber, calculate the change rates of the gas pressure, temperature, and mass in the chamber over time, and realize the actual transient response analysis of the chamber.

[0089] In the embodiment of the present invention, in step 2, it includes establishing a calculation model of the heat exchange element, and the formula is as follows:

[0090] q = hA(T w -T c ) (8)

[0091] In formula (8), q is the heat exchange heat flow, A is the heat exchange area, T w , T c are respectively the solid wall temperature and the air temperature, and h is the heat transfer coefficient.

[0092] The present invention uses a mathematical model or flow characteristics, etc. for simulation, connects typical elements such as throttle elements, local flow loss elements, chamber elements, and heat exchange elements in series, realizes the constraints of physical processes such as flow conservation and energy conservation in the model, and establishes a one-dimensional calculation model of the air system flow path.

[0093] The flow elements include throttle elements and flow loss elements, and their flow parameters include the flow rate, pressure, and temperature at the inlet and outlet. The relationship between the flow rate and the inlet and outlet pressure of this type of element is determined by the flow coefficient or resistance coefficient, and the inlet and outlet temperatures remain the same without considering heat exchange.

[0094] The heat exchange element mainly considers the heat exchange with the outside. The flow rate and pressure at the inlet and outlet of this element remain unchanged, and the relationship between the heat exchange amount and the inlet and outlet temperatures is established according to the principle of energy conservation.

[0095] The chamber element is mainly used for unsteady (dynamic / transient) calculations. The flow parameters at the inlet and outlet of this element remain the same during steady-state calculations. During unsteady calculations, the inlet and outlet temperatures, pressures, and flow rates all change.

[0096] A one-dimensional calculation model of the air system flow path is formed by connecting the flow element, heat exchange element, and chamber element in series or parallel. A control equation set for the fluid network is established to obtain the relationship between the mass flow rate of each element and the inlet / outlet pressure and temperature. The principle of mass conservation is followed during steady-state calculation, and the dynamic characteristics of the chamber element are considered during unsteady-state calculation. By solving the control equation set of the fluid network, the flow, pressure, temperature, and other flow parameters at the inlet and outlet of each element can be obtained.

[0097] In the embodiment of the present invention, in step 3, under the design point condition, the steady-state analysis of the overall engine performance and the air system coupling model achieves stable operation according to the performance data of each component at the design point; under off-design point conditions, initial parameter values are assigned to each component, and these initial parameter values are continuously updated through iterative calculation to satisfy the balance relationship of the flow rate and power among the engine components.

[0098] According to the intake and exhaust conditions of the engine air system, the one-dimensional calculation model of the engine performance and the one-dimensional calculation model of the air system flow path are unifiedly modeled on the same software platform. The actual intake and exhaust connection relationship is reflected between the two models to achieve coupled solution.

[0099] Under the design point condition, the steady-state analysis of the overall engine performance and the air system coupling model can achieve stable operation according to the performance data of each component at the design point; under off-design point conditions, there are no specific aerodynamic performance data of each component actually given, only the pressure ratio, efficiency, and dimensionless flow characteristics of the components; therefore, under off-design point conditions, the common working state needs to be calculated according to the characteristics of each component to achieve the steady-state performance calculation at off-design points. In this process, initial parameter values need to be assigned to the components. The initial parameter values can adopt one-dimensional parameters of overall performance matching, and these initial parameter values are continuously updated through iterative calculation to satisfy the balance relationship of the flow rate and power among the engine components.

[0100] According to the one-dimensional model solution principle, initial values need to be assigned before calculation, but the initial values are arbitrarily assigned and do not need to satisfy the balance of flow rate and power. Better initial values can improve the convergence speed of the calculation model.

[0101] The engine components work together and restrict each other, which exists both in the steady-state and dynamic processes, and each component must satisfy the common working equation at all times. Compared with the steady-state process, the common working equation of the engine dynamic process mainly has the inertia term brought by the acceleration of the rotor in the power balance equation:

[0102]

[0103] In formula (9), J L is the moment of inertia of the low-pressure rotor, is the acceleration of the low-pressure rotor, q TLis the low-pressure turbine flow rate, L TL is the low-pressure turbine power, q CL is the low-pressure compressor flow rate, L CL is the low-pressure compressor power, q a is the propeller flow rate, P pr is the propeller power, n L is the low-pressure shaft speed. The high-pressure shaft also has an inertia term brought by the rotor acceleration.

[0104] The inertia brought by the rotor acceleration in the dynamic process of the engine will affect the establishment of the one-dimensional network model of the air system in the later stage. The change in the rotational speed indicates that the operating condition of the engine has changed, resulting in changes in the boundary conditions of the air system, including the intake and exhaust pressures and temperatures, etc. This influence is reflected through the intake and exhaust boundaries of the air system connected to the corresponding positions of the engine performance model.

[0105] In fact, in addition to the power balance being affected by the dynamic process, the storage and release of gas mass and energy caused by the change of gas parameters in the cavities of each component over time also exist in the actual process. As Figure 3 shown, in order to simplify the model, a volume chamber is connected behind each component. The components are calculated according to the aerodynamic process without considering the volume effect, and the gas flowing through the volume chamber is considered to be affected by the volume effect, and the flow rate and energy of the outflowing air flow are recalculated. In the figure, W in , h in and W out , h out are the gas flow rate and enthalpy value at the inlet and outlet of the volume chamber respectively. Among them, W in and h in are essentially the gas flow rate and enthalpy value at the outlet of the component without considering the volume effect.

[0106] In the embodiment of the present invention, in step 4, based on the overall engine performance and the air system coupling calculation model, steady-state and dynamic calculation and analysis are carried out, and at the same time, the flow parameter distribution of the air system and the overall engine performance are obtained, and the influence of the air extraction of the air system on the engine performance is evaluated through the engine performance of the engine overall performance and the air system coupling calculation model.

[0107] The present invention adopts the throttling principle of the holes in the air system for the hydrodynamic calculation of the engine compressor and turbine, that is, according to the inlet and outlet pressures and temperatures, the through-flow mass flow rate of the turbomachinery is calculated, and the one-dimensional fluid network coupling calculation of the one-dimensional calculation model of the engine performance and the one-dimensional calculation model of the air system flow path is realized. Through the established one-dimensional network of the air system and the engine performance, the flow rate of each component and each branch flow path can be obtained after solution, and by summing the branch flow rates of the air extraction from the engine, the total air extraction amount of the air system from the engine can be obtained.

[0108] The evaluation of the engine's overall performance by the air system's bleed air mainly focuses on the effects on thermal efficiency, power, and specific fuel consumption. Taking the evaluation of the engine's thermal efficiency as an example, the engine's thermal efficiency is defined as η t = L e / q 0 , where L e is the effective work of the engine's thermodynamic cycle, and q 0 is the heat generated by the complete combustion of the fuel. The engine's thermal efficiency without considering the influence of the air system is η t0 , and the engine's thermal efficiency considering the influence of the air system is η ta . Then the influence ratio of the air system on the overall thermal efficiency of the engine is 1 - η ta / η t0 . The evaluation methods for the influence of the air system on other overall parameters are similar to this.

[0109] Based on the above models and calculation methods, using the AMESim platform, components such as total pressure loss components for intake and exhaust, compressor aerodynamic components, combustion chamber aerodynamic components, turbine aerodynamic components, and rotor inertia components were developed for calculating the engine's overall performance. Components such as holes, pipes, local losses, chambers, and heat exchange components were developed for calculating the air system. Figure 4 This is a coupled calculation model of the overall performance of a certain engine and the air system established based on the above components. This model can perform steady-state and dynamic calculation analyses. At the same time, parameters such as the flow rate distribution of the air system and the overall performance of the engine can be obtained. The influence of the air system's bleed air on the engine's performance can be directly evaluated through the engine performance of the coupled model.

[0110] The above description is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An air system analysis and evaluation method based on whole machine energy efficiency, characterized in that: The following steps are involved: Step 1: Decompose the turbine engine into intake assembly, exhaust assembly, compressor, combustion chamber, gas turbine and power turbine according to its components, simulate it using flow characteristics and impeller characteristics, and establish a one-dimensional calculation model of engine performance by connecting each component in series; Step 2: For the throttling elements, local flow loss elements, chamber elements and heat exchange elements in the engine air system, a mathematical model or flow characteristic simulation is used to establish a one-dimensional calculation model of the air system flow path; Step 3: Unify the one-dimensional calculation model of engine performance and the one-dimensional calculation model of air system flow path on the same software platform, establish the coupled calculation model of engine overall performance and air system, and realize coupled solution; Step 4: Output the calculation results of the effect of air system exhaust on engine performance under different engine conditions.

2. The air system analysis and evaluation method based on whole machine energy efficiency according to claim 1 is characterized in that: The step 1 includes establishing a calculation model of the intake assembly, the exhaust assembly and the flow passage transition section element. When the air flows through the intake and exhaust flow passages, the total pressure loss is generated, and the formula is as follows: P2=σp1 (1) In formula (1), p1 and p2 are the inlet total pressure and outlet total pressure of the intake component and the exhaust component, respectively, and σ is the recovery coefficient.

3. The air system analysis and evaluation method based on whole machine energy efficiency according to claim 1 is characterized in that: The step 1 includes establishing a calculation model of the compressor, gas turbine and power turbine components. The relationship between the compressor and turbine flow and the speed, pressure or expansion ratio is calculated by interpolation of the characteristic table. The formula is as follows: In formula (2), is the mass flow rate, N is the speed, π is the compressor pressure ratio or turbine expansion ratio, p, T are the inlet pressure and temperature; A calculation model of the rotor mechanical inertia element is established. The difference between the compressor demand power and the turbine output power is the engine rotor acceleration, and the formula is as follows: In formula (3), P T , P T are the compressor and turbine powers respectively, J is the rotor moment of inertia, is the rotational acceleration.

4. The air system analysis and evaluation method based on whole machine energy efficiency according to claim 1 is characterized in that: The step 1 includes establishing a calculation model of the combustion chamber components and directly calculating the oil-gas ratio of the combustion chamber using the isothermal enthalpy difference method, and the formula is as follows: In formula (4), f is the oil-gas ratio, η b is the combustion efficiency; H u is the lower calorific value of fuel oil; h in，a ,h out，a are the inlet and outlet air enthalpies of the combustion chamber respectively; H out is the isothermal enthalpy at the combustion chamber outlet temperature; Total pressure at combustion chamber outlet: p out =p in σ b , where the total pressure recovery coefficient σ b The value ranges from 0.96 to 0.

97.

5. The air system analysis and evaluation method based on whole machine energy efficiency according to claim 1 is characterized in that: The step 2 includes establishing a calculation model of the hole and gap throttling element. When the air flows through the intake and exhaust flow passages, the total pressure loss is generated. The formula is as follows: In formula (5), A is the hole area, T1* is the total temperature, P1* is the inlet total pressure, C d is the orifice flow coefficient, P2 is the outlet static pressure, is the mass flow rate, R is the gas constant, and k is the absolute index.

6. The air system analysis and evaluation method based on whole machine energy efficiency according to claim 1 is characterized in that: The step 2 includes establishing a calculation model of the local flow loss element, and the formula is as follows: In formula (6), are the inlet total pressure and outlet total pressure of the flow element respectively, ζ is the resistance coefficient, ρ is the air density, and v is the air flow rate.

7. The air system analysis and evaluation method based on whole machine energy efficiency according to claim 1 is characterized in that: The step 2 includes establishing a calculation model of a chamber element with a certain volume, and the imbalance of its inlet and outlet flow leads to changes in chamber pressure and temperature. The calculation formula is as follows: In formula (7), p, ρ, h, and T are the pressure, density, specific enthalpy, and temperature of the air in the cavity, respectively; V is the volume of the cavity; m is the mass of the air in the cavity; and m i is the air mass flow rate on each interface of the chamber, Q is the heat exchange between the air in the chamber and the outside, the subscript i represents the chamber interface number, and t is the time.

8. The air system analysis and evaluation method based on whole machine energy efficiency according to claim 1 is characterized in that: The step 2 includes establishing a calculation model of the heat exchange element, and the formula is as follows: q=hA(T w -T c ) (8) In formula (8), q is the heat transfer flux, A is the heat transfer area, and T w , T c are the solid wall temperature and air temperature respectively, and h is the heat transfer coefficient.

9. The air system analysis and evaluation method based on whole machine energy efficiency according to claim 1, characterized in that: In step 3, under the design point state, the steady-state analysis of the overall engine performance and the air system coupling model achieves stable operation according to the performance data of each component at the design point; under the non-design point state, initial parameter values ​​are assigned to each component, and these initial parameter values ​​are continuously updated through iterative calculations to satisfy the balance relationship between flow and power among the engine components.

10. The air system analysis and evaluation method based on whole machine energy efficiency according to claim 1, characterized in that: In step 4, based on the overall engine performance and the air system coupling calculation model, steady-state and dynamic calculation analysis are performed, and the flow parameter distribution of the air system and the overall engine performance are obtained at the same time. The influence of air system bleed air on the engine performance is evaluated through the overall engine performance and the engine performance in the air system coupling calculation model.

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