Calculation Method for Overall Performance of Pulse Detonation Turbofan Engine

Abstract

The present invention relates to a method for calculating the overall performance of a pulse detonation turbofan engine. Design point performance calculations are performed based on the pulse detonation turbofan engine's air inlet, fan components, compressor components, mixing chamber, and tail nozzle. Performance calculations are then performed sequentially on the compressor components, pulse detonation combustion chamber, and turbine components within the inner and outer ducts. The obtained inner and outer duct outlet parameters are compared and judged with iterative fan pressure ratios until the inner and outer ducts achieve static pressure equilibrium, thereby ultimately obtaining the engine's performance parameters, including engine thrust FN, engine unit thrust FS, and engine unit fuel consumption SFC. When performing overall aeroengine design, the present invention can effectively reduce the pressure ratio of the pulse detonation turbine engine's compression components, thereby reducing the number of compressor and turbine stages, reducing engine mass, improving the engine thrust-to-weight ratio, and ultimately enhancing engine performance, effectively shortening the iteration cycle of the pulse detonation turbine engine's overall design.

Description

Technical Field

[0001] The present invention relates to the field of aviation turbine engines, and in particular to a method for calculating the overall performance of a turbofan engine taking into account a pulse detonation combustion chamber. Background Art

[0002] As the epitome of high-end equipment manufacturing, aircraft turbine engines are hailed as the crown jewel of industry due to their extremely demanding and complex design and manufacturing requirements. Their technology embodies a country's scientific and technological level and comprehensive technical capabilities, and can be used to measure a country's overall national strength. The overall design of an aircraft engine is the top-level design of R&D technology and the soul of the aircraft engine.

[0003] The pulse detonation engine (PDE) uses periodic detonation waves to generate high-temperature and high-pressure combustion gas to generate thrust, and has the advantages of high cycle thermal efficiency and simple structure.

[0004] Based on the turbofan engine, a pulse detonation combustor (PDC) is used to replace the isobaric combustion chamber in the traditional turbojet engine to form a turbofan-pulse detonation combination engine, namely a pulse detonation turbofan engine, which transforms the engine from an isobaric cycle to a detonation cycle (approximately a constant volume cycle) and thus improves the thermal efficiency of the cycle.

[0005] The overall performance parameters of a pulse detonation turbofan engine are key to its overall design and determine the engine's level of sophistication. Accurately calculating the overall performance of a pulse detonation turbofan engine can help designers quickly determine whether its performance parameters meet requirements, shortening the overall design iteration cycle and improving design efficiency. Therefore, a method for calculating the overall performance of a pulse detonation turbofan engine is urgently needed. Summary of the Invention

[0006] The purpose of the present invention is to avoid the shortcomings of the existing technology and provide a method that can quickly and accurately estimate the average parameters of the pulse detonation combustion chamber outlet and construct a high-precision whole-machine component-level variable specific heat performance calculation model.

[0007] To achieve the above object, the present invention adopts a technical solution: a method for calculating the overall performance of a pulse detonation turbofan engine, comprising the following steps:

[0008] Step 1: Using a variable specific heat calculation method, the design point performance calculation is performed on the air inlet, fan components, compressor components, mixing chamber and tail nozzle of the pulse detonation turbofan engine in sequence, and the inner and outer bypass ducts of the pulse detonation turbofan engine are determined according to the engine bypass ratio BPR and fan pressure ratio PRF at the design point;

[0009] Step 2: Calculate the outlet total temperature T3 and outlet total pressure P3 of the compressor components in the inner channel, and then according to the compressor outlet total temperature T3 and outlet total pressure P3 and the number of detonation tubes NUMB, tube length L, tube diameter D, operating frequency f and detonation combustion chamber outlet total temperature T4 of the detonation combustion chamber, and take the total temperature and total pressure of the pressure platform area at the thrust wall of the detonation chamber as the equivalent total temperature and total pressure at the detonation chamber outlet, and according to the detonation wave structure model, obtain the average parameters of the pulse detonation combustion chamber outlet;

[0010] Step 3: According to the total temperature T4, total pressure P4 and high-pressure turbine efficiency ET of the detonation combustion chamber outlet HP , low-pressure turbine efficiency ET LP , the total temperature T5 and total pressure P5 of the turbine outlet are obtained by iterative calculation, which are the intrinsic channel outlet parameters of the pulse detonation engine;

[0011] Step 4: Based on the known total pressure loss DP in the outer duct DU , Mach number Ma, judge whether the static pressure of inner and outer duct is balanced. If they are close, perform the design point performance calculation of the mixing chamber and tail nozzle. Otherwise, continue to iteratively calculate the fan pressure ratio PRF until the static pressure of inner and outer duct is balanced. At this time, the static pressure residual of inner and outer duct is ≤e -4 ;

[0012] Finally, the engine performance parameters are obtained, including engine thrust FN, engine unit thrust FS, and engine unit fuel consumption SFC.

[0013] Furthermore, the specific process of calculating the outlet total temperature T3 and outlet total pressure P3 of the compressor components in the inner channel in step 2 is as follows:

[0014] Step 21: Under the conditions of a given flight Mach number Ma and a flight altitude H of zero, according to the atmospheric temperature T of the standard atmosphere at sea level s0 With atmospheric pressure P s0 The total temperature T1 and total pressure P1 of the air in the intake duct are calculated using the calculation formula of total parameters and static parameters;

[0015] Step 22: Calculate the total outlet temperature T of the fan component using the fan / compressor pressure ratio calculation formula based on the engine bypass ratio BPR, the fan pressure ratio PRF of the fan component, the fan efficiency ETAF, the compressor pressure ratio CPR, the compressor efficiency ETAC, and the air flow Wa. 21 and outlet total pressure P 21 And the compressor outlet total temperature T3 and outlet total pressure P3.

[0016] Furthermore, the specific calculation process of the average parameters of the pulse detonation combustion chamber outlet in step 2 is:

[0017] According to the detonation wave structure model, the calculation formulas for the total pressure and total temperature at the thrust wall of the detonation chamber are:

[0018]

[0019] T H =T CJ [1-(γ2-1) / 2Ma CJ ] 2 ,

[0020] Where: P H is the pressure at the thrust wall; P CJ is the pressure at point CJ of the detonation wave; T H is the temperature at the thrust wall; T CJ is the detonation wave CJ point temperature, γ is the specific heat ratio; Ma CJ is the detonation wave Mach number;

[0021] The filling Mach number Ma given by the design point fill The static pressure and static temperature inside the pulse detonation combustion chamber are obtained after the filling stage is completed by using the static temperature and static pressure stagnation parameters. The specific heat capacity and enthalpy of the working fluid are calculated by REFPROP, and the detonation wave Mach number Ma CJ , speed V CJ The parameters were calculated using NASA's chemical equilibrium application software.

[0022] The working medium in the pulse detonation combustion chamber flows radially and uniformly, the flow rates at the inlet and outlet of the pulse detonation combustion chamber are equal in the same detonation cycle, the pressure platform, pressure decay and filling stages of the pulse detonation combustion chamber are all isentropic thermodynamic processes, the back propagation of the detonation wave of the pulse detonation combustion chamber is ignored, and under ideal conditions with only 20-25% pressure loss and no time lag between the filling stage of the pulse detonation combustion chamber and the formation of the detonation wave at the closed end, the average parameters of the outlet of the pulse detonation combustion chamber are calculated using NASA's chemical balance application software, and the average parameters of the outlet include the flow rate W at the outlet of the pulse detonation combustion chamber. g4 , outlet total temperature T4, outlet total pressure P t , the outlet oil-gas ratio FAR4, is used as the equivalent total parameter of the detonation combustion chamber outlet to calculate the performance of the pulse detonation turbine engine.

[0023] Furthermore, the outlet total temperature T4, outlet total pressure P t The specific calculation process is:

[0024] First, the total pressure in the pressure plateau area is:

[0025] p plateau =δ A1 p s,fill ,

[0026]

[0027] Where p s，fill is the static pressure in the pulse detonation combustion chamber after filling is completed, δ A1 It is a gas characteristic parameter, which characterizes the pressure increase ratio of the total pressure in the pressure platform area relative to the static pressure in the filling stage. k1 and k2 are the specific heat ratios of the fuel and air mixture before detonation and the specific heat ratios of the products after detonation, respectively.

[0028] Under isentropic conditions, according to the relationship between sound speed and temperature, the total temperature of the pressure platform area after the detonation wave is initiating, the sound speed c after the detonation is obtained. b Calculated by the following formula, δ A2 is the characteristic parameter that characterizes the pressure decay.

[0029] c b =V CJ / δ A2 ,

[0030]

[0031] The propagation time of the blast wave is t CJ It is obtained from the following formula, L is the length of the pulse detonation combustion chamber, V fill is the filling velocity of the pulse detonation combustion chamber at the initial moment.

[0032]

[0033] Duration of pressure plateau area t plateau Calculated by the following formula, where δ B is the gas characteristic parameter, which characterizes the propagation time t of the detonation wave CJ The ratio of:

[0034] t plateau =δ B t CJ ,

[0035]

[0036] Duration of the pressure decay phase t decay Calculated by the following formula, where function f n (δ A2 ) According to the thrust wall pressure decay function table with time:

[0037] t decay =t CJ δ A2 [f n (δ A2 )-1];

[0038] Finally, the calculation formula for filling time is:

[0039]

[0040] Based on the above formulas, the total parameters and corresponding times of the filling stage, pressure platform stage, and pressure decay stage are calculated. The calculation formula for the detonation chamber working time is:

[0041] t cycle =t CJ +t plateau +t decay ,

[0042] The average total temperature and total pressure at the outlet of the pulse detonation combustion chamber can also be calculated:

[0043]

[0044] in:

[0045]

[0046] Where u(t) is the air velocity at time t, D tube is the pipe diameter, N tube is the number of tubes, f is the operating frequency, P tout That is equivalent to the total pressure P4 at the detonation chamber outlet, T tout That is equivalent to the total temperature T4 at the detonation chamber outlet.

[0047] Furthermore, the specific calculation process of the total pressure P5 in step 3 is:

[0048] The residual equation of the whole machine performance model is established:

[0049] ERR=(P 5I -P 5O ) / P 5I

[0050] P5=f(FanPR),

[0051] Where, P 5I is the total pressure at the outlet of the low-pressure turbine, P 5O is the total pressure at the duct outlet, and the independent variable is the fan pressure ratio; that is, by changing the fan pressure ratio, the total pressure of the two sections is adjusted to make them basically consistent, reducing mixing losses and ensuring stable operation of the mixing chamber.

[0052] Furthermore, the design point of the mixing chamber in step 4 is obtained by the static pressure balance equation of the inner and outer ducts at the mixing chamber inlet, the total temperature T6 of the mixing chamber outlet, the total pressure P6 of the mixing chamber outlet, the total temperature and pressure of the tail nozzle inlet, and the velocity coefficient C V After isentropic calculation, the tail nozzle outlet area A9 and air flow velocity V9 are obtained.

[0053] The beneficial effect of the present invention is that when performing performance calculations, the present invention replaces the isobaric combustion chamber in a traditional turbojet engine with a pulse detonation combustion chamber, so that the engine is converted from an isobaric cycle to a detonation cycle (approximately a constant volume cycle) to improve the thermal efficiency of the cycle. That is, after calculating the average parameters of the pulse detonation combustion chamber outlet, the pulse detonation combustion chamber is taken as a conventional engine component and brought into the overall performance model to obtain more accurate performance results.

[0054] The pulse detonation combustion chamber has the characteristic of self-pressurization. When conducting the overall design of an aero-engine, it can effectively reduce the compression ratio of the compression components of the pulse detonation turbine engine, thereby reducing the number of compressor and turbine stages, thereby reducing the engine mass, further improving the engine thrust-to-weight ratio, and ultimately improving the engine performance, effectively shortening the iteration cycle of the overall design of the pulse detonation turbine engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 It is a flow chart of the whole machine performance calculation. DETAILED DESCRIPTION

[0056] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0057] In order to achieve the above object, the present invention provides the following specific implementation methods:

[0058] Example 1: A method for calculating the overall performance of a pulse detonation turbofan engine, comprising the following steps:

[0059] Step 1: Using the variable specific heat calculation method, the design point performance calculations are performed on the pulse detonation turbofan engine's inlet, fan components, compressor components, mixing chamber, and tail nozzle in sequence. Based on the engine bypass ratio BPR and fan pressure ratio PRF at the design point, the inner and outer bypass ducts of the pulse detonation turbofan engine are determined;

[0060] Step 2: Calculate the outlet total temperature T3 and outlet total pressure P3 of the compressor components in the inner channel, and then according to the compressor outlet total temperature T3 and outlet total pressure P3 and the detonation tube number NUMB, tube length L, tube diameter D, operating frequency f and detonation combustion chamber outlet total temperature T4, and take the total temperature and total pressure of the pressure platform area at the thrust wall of the detonation chamber as the equivalent total temperature and total pressure at the detonation chamber outlet, and according to the detonation wave structure model, obtain the average parameters of the pulse detonation combustion chamber outlet;

[0061] The specific process of calculating the outlet total temperature T3 and outlet total pressure P3 of the compressor components in the inner channel is:

[0062] Step 21: Under the conditions of a given flight Mach number Ma and a flight altitude H of zero, according to the atmospheric temperature T of the standard atmosphere at sea level s0 With atmospheric pressure P s0 The total temperature T1 and total pressure P1 of the air in the intake duct are calculated using the calculation formula of total parameters and static parameters;

[0063] Step 22: Based on the engine bypass ratio BPR, the fan pressure ratio PRF of the fan component, the fan efficiency ETAF, the compressor pressure ratio CPR, the compressor efficiency ETAC, and the air flow Wa, the fan component outlet total temperature T is calculated using the fan / compressor pressure ratio calculation formula. 21 and outlet total pressure P 21 And the compressor outlet total temperature T3 and outlet total pressure P3.

[0064] The specific calculation process of the average parameters of the pulse detonation combustion chamber outlet is as follows:

[0065] According to the detonation wave structure model, the calculation formulas for the total pressure and total temperature at the thrust wall of the detonation chamber are:

[0066]

[0067] T H =T CJ [1-(γ2-1) / 2Ma CJ ] 2 ,

[0068] Where: P H is the pressure at the thrust wall; P CJ is the pressure at point CJ of the detonation wave; T H is the temperature at the thrust wall; T CJ is the detonation wave CJ point temperature, γ is the specific heat ratio; Ma CJ Mach number of the detonation wave CJ point;

[0069] In the pulse detonation combustion chamber, the working fluid flows radially uniformly. The flow rates at the inlet and outlet of the pulse detonation combustion chamber are equal in the same detonation cycle. The pressure platform, pressure decay and filling stages of the pulse detonation combustion chamber are all isentropic thermodynamic processes. The back propagation of the detonation wave of the pulse detonation combustion chamber is ignored. Under ideal conditions with only 20-25% pressure loss and no time lag between the filling stage of the pulse detonation combustion chamber and the formation of the detonation wave at the closed end, the average parameters of the pulse detonation combustion chamber outlet are calculated using NASA's chemical equilibrium application software. The average parameters of the outlet include the flow rate W at the outlet of the pulse detonation combustion chamber. g4 , outlet total temperature T4, outlet total pressure P t , the outlet oil-gas ratio FAR4, is used as the equivalent total parameter of the detonation combustion chamber outlet to calculate the performance of the pulse detonation turbine engine.

[0070] Furthermore, the outlet total temperature T4, outlet total pressure P t The specific calculation process is:

[0071] First, the total pressure in the pressure plateau area is:

[0072] p plateau =δ A1 p s,fill ,

[0073]

[0074] Where p s，fill is the static pressure in the pulse detonation combustion chamber after filling is completed, δ A1 It is a gas characteristic parameter, which characterizes the pressure increase ratio of the total pressure in the pressure platform area relative to the static pressure in the filling stage. k1 and k2 are the specific heat ratios of the fuel and air mixture before detonation and the specific heat ratios of the products after detonation, respectively.

[0075] Under isentropic conditions, according to the relationship between sound speed and temperature, the total temperature of the pressure platform area after the detonation wave is initiating, the sound speed c after the detonation is obtained. b Calculated by the following formula, δ A2 is the characteristic parameter to characterize the pressure decay;

[0076] c b =V CJ / δ A2 ,

[0077]

[0078] The propagation time of the blast wave is t CJ It is obtained from the following formula, L is the length of the pulse detonation combustion chamber, V fill is the filling velocity of the pulse detonation combustion chamber at the initial moment;

[0079]

[0080] Duration of pressure plateau area t plateau Calculated by the following formula, where δ B is the gas characteristic parameter, which characterizes the propagation time t of the detonation wave CJ The ratio of:

[0081] t plateau =δ B t CJ ,

[0082]

[0083] Duration of the pressure decay phase t decay Calculated by the following formula, where function f n (δA2 ) According to the thrust wall pressure decay function table with time, as shown in Table 1:

[0084] t decay =t CJ δ A2 [f n (δ A2 )-1];

[0085] Table 1 Thrust wall pressure decay function with time

[0086]

[0087] Finally, the calculation formula for filling time is:

[0088]

[0089] Based on the above formulas, the total parameters and corresponding times of the filling stage, pressure platform stage, and pressure decay stage are calculated. The calculation formula for the detonation chamber working time is:

[0090] t cycle =t CJ +t plateau +t decay ,

[0091] The average total temperature and total pressure at the outlet of the pulse detonation combustion chamber can also be calculated:

[0092]

[0093] in:

[0094]

[0095] Where u(t) is the air velocity at time t, D tube is the pipe diameter, N tube is the number of tubes, f is the operating frequency, P tout That is equivalent to the total pressure P4 at the detonation chamber outlet, T tout That is equivalent to the total temperature T4 at the detonation chamber outlet.

[0096] Step 3: According to the total temperature T4, total pressure P4 and high-pressure turbine efficiency ET of the detonation combustion chamber outlet HP , low-pressure turbine efficiency ET LP , the total temperature T5 and total pressure P5 of the turbine outlet are obtained through iterative calculation, which are the intrinsic outlet parameters of the pulse detonation engine;

[0097] Among them, the specific calculation process of the total pressure P5 is:

[0098] The residual equation of the whole machine performance model is established:

[0099] ERR=(P 5I -P 5O ) / P 5I

[0100] P5=f(FanPR),

[0101] Where, P 5I is the total pressure at the outlet of the low-pressure turbine, P 5O is the total pressure at the duct outlet, and the independent variable is the fan pressure ratio; that is, by changing the fan pressure ratio, the total pressure of the two sections is adjusted to make them basically consistent, reducing mixing losses and ensuring stable operation of the mixing chamber.

[0102] Step 4: Based on the known total pressure loss DP in the outer duct DU , Mach number Ma, judge whether the static pressure of inner and outer duct is balanced. If it is close, perform the design point performance calculation of mixing chamber and tail nozzle. Otherwise, continue to iteratively calculate the fan pressure ratio PRF until the static pressure of inner and outer duct is balanced. At this time, the static pressure residual of inner and outer duct is ≤e -4 ;

[0103] Among them, the design point of the mixing chamber is the static pressure balance equation of the inner and outer ducts at the mixing chamber inlet, and the total temperature T6 and total pressure P6 of the mixing chamber outlet are obtained. The total temperature and total pressure of the tail nozzle inlet are known, and the velocity coefficient C is V After isentropic calculation, the tail nozzle outlet area A9 and air flow velocity V9 are obtained.

[0104] Finally, the engine performance parameters are obtained, including engine thrust FN, engine unit thrust FS, and engine unit fuel consumption SFC.

[0105] In order to further illustrate the technical solutions and effects of the present invention, the following specific examples are provided:

[0106] Specific example: A method for calculating the performance of a pulse engine includes the following calculation steps:

[0107] (1) This specific implementation plan takes the calculation of the design point of a 500kgf turbofan engine as an example. Before calculating the performance parameters of the entire engine, it is necessary to first calculate the average parameters of the PDC outlet section;

[0108] (2) First, input the atmospheric conditions of the engine: altitude and Mach number are both 0. The program calculates the total temperature of the air in the inlet duct, T1 = 288.15K, and the total pressure, P1 = 101325Pa;

[0109] (3) Before calculating the compression component, input fan pressure ratio PRF = 2.5, bypass ratio BPR = 2.7, fan efficiency ETAF = 0.845, compressor pressure ratio PRC = 4.0, compressor efficiency ETAC = 0.82, and air flow rate Wa = 9.5 kg / s. The calculation yields:

[0110] Fan outlet total temperature T 21 =391.6993K, total pressure at fan outlet P 21 =253312.5Pa, total temperature at compressor outlet T3 = 681.8113K, total pressure at compressor outlet P3 = 1418550.0Pa.

[0111] (4) The compressor outlet parameters are passed to the pulse detonation combustor module, and the number of detonation combustor tubes NUMB = 8, tube length L = 1.2m, tube diameter D = 0.06m, operating frequency f = 40, and total temperature T4 at the combustor outlet = 1500K are entered. Calculation yields:

[0112] The total pressure at the combustion chamber outlet P4 = 1892190.3 Pa, the oil-gas ratio FAR4 = 0.02471, and the outlet gas flow rate W f =9.734745kg / s, equivalent pressure ratio PR PDE =1.33389;

[0113] (5) Turbine module inlet parameters, (or:) given the total temperature and pressure at the combustion chamber outlet, the power input calculated by the high and low pressure compressor modules, and the high and low turbine efficiencies ET HP =0.86, ET LP =0.87, through iterative calculation we can get:

[0114] The total temperature at the turbine outlet is T5 = 1482.0625K, the total pressure at the turbine outlet is P5 = 867997.3125Pa,

[0115] (6) Total pressure loss DP in the bypass duct DU =0.045, Mach number Ma=0.6. Determine whether the total pressure of the inner and outer ducts is similar. If not, continue to iterate the fan pressure ratio until the pressure is balanced. After mixing:

[0116] The total temperature at the mixing chamber outlet is T6 = 606.5755K, and the total pressure at the mixing chamber outlet is P6 = 242611.7500Pa;

[0117] (7) The total temperature and pressure at the tail nozzle inlet are known, and the velocity coefficient C V =0.985, after isentropic calculation we know:

[0118] Nozzle outlet area A9 = 0.0248 m 2 , air flow velocity V9=443.0268m / s;

[0119] (8) In summary, the engine performance parameters can be calculated as follows:

[0120] Engine thrust FN = 494.1491 kgf;

[0121] Engine unit thrust FS = 52.0157 kgf / (kg / s);

[0122] Engine specific fuel consumption SFC = 0.5504 kg / (kgf*h).

[0123] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for calculating the overall performance of a pulse detonation turbofan engine, characterized in that: The following steps are involved: Step 1: Using a variable specific heat calculation method, the design point performance calculation is performed on the air inlet, fan components, compressor components, mixing chamber and tail nozzle of the pulse detonation turbofan engine in sequence, and the inner and outer bypass ducts of the pulse detonation turbofan engine are determined according to the engine bypass ratio BPR and fan pressure ratio PRF at the design point; Step 2: Calculate the outlet total temperature T3 and outlet total pressure P3 of the compressor components in the inner channel, and then according to the compressor outlet total temperature T3 and outlet total pressure P3 and the number of detonation tubes NUMB, tube length L, tube diameter D, operating frequency f and detonation combustion chamber outlet total temperature T4 of the detonation combustion chamber, and take the total temperature and total pressure of the pressure platform area at the thrust wall of the detonation chamber as the equivalent total temperature and total pressure at the detonation chamber outlet, and according to the detonation wave structure model, obtain the average parameters of the pulse detonation combustion chamber outlet; Step 3: According to the total temperature T4, total pressure P4 and high-pressure turbine efficiency ET of the detonation combustion chamber outlet HP , low-pressure turbine efficiency ET LP , the total temperature T5 and total pressure P5 of the turbine outlet are obtained by iterative calculation, which are the intrinsic channel outlet parameters of the pulse detonation engine; Step 4: Based on the known total pressure loss DP in the outer duct DU , Mach number Ma, judge whether the static pressure of inner and outer duct is balanced. If they are close, perform the design point performance calculation of the mixing chamber and tail nozzle. Otherwise, continue to iteratively calculate the fan pressure ratio PRF until the static pressure of inner and outer duct is balanced. At this time, the static pressure residual of inner and outer duct is ≤e -4 ; Finally, the engine performance parameters are obtained, including engine thrust FN, engine unit thrust FS, and engine unit fuel consumption SFC.

2. The method for calculating the overall performance of a pulse detonation turbofan engine according to claim 1, wherein: The specific process of calculating the outlet total temperature T3 and outlet total pressure P3 of the compressor components in the inner channel in step 2 is as follows: Step 21: Under the conditions of a given flight Mach number Ma and a flight altitude H of zero, according to the atmospheric temperature T of the standard atmosphere at sea level s0 With atmospheric pressure P s0 The total temperature T1 and total pressure P1 of the air in the intake duct are calculated using the calculation formula of total parameters and static parameters; Step 22: Calculate the total outlet temperature T of the fan component using the fan / compressor pressure ratio calculation formula based on the engine bypass ratio BPR, the fan pressure ratio PRF of the fan component, the fan efficiency ETAF, the compressor pressure ratio CPR, the compressor efficiency ETAC, and the air flow Wa. 21 and outlet total pressure P 21 And the compressor outlet total temperature T3 and outlet total pressure P3.

3. The method for calculating the overall performance of a pulse detonation turbofan engine according to claim 1, wherein: The specific calculation process of the average parameters of the pulse detonation combustion chamber outlet in step 2 is: According to the detonation wave structure model, the calculation formulas for the total pressure and total temperature at the thrust wall of the detonation chamber are: T H =T CJ [1-(γ2-1) / 2Ma CJ ] 2 , Where: P H is the pressure at the thrust wall; P CJ is the pressure at point CJ of the detonation wave; T H is the temperature at the thrust wall; T CJ is the detonation wave CJ point temperature, γ is the specific heat ratio; Ma CJ Mach number of the detonation wave CJ point; The working medium in the pulse detonation combustion chamber flows radially and uniformly, the flow rates at the inlet and outlet of the pulse detonation combustion chamber are equal in the same detonation cycle, the pressure platform, pressure decay and filling stages of the pulse detonation combustion chamber are all isentropic thermodynamic processes, the back propagation of the detonation wave of the pulse detonation combustion chamber is ignored, and under ideal conditions with only 20-25% pressure loss and no time lag between the filling stage of the pulse detonation combustion chamber and the formation of the detonation wave at the closed end, the average parameters of the outlet of the pulse detonation combustion chamber are calculated using NASA's chemical balance application software, and the average parameters of the outlet include the flow rate W at the outlet of the pulse detonation combustion chamber. g4 , outlet total temperature T4, outlet total pressure P t , the outlet oil-gas ratio FAR4, is used as the equivalent total parameter of the detonation combustion chamber outlet to calculate the performance of the pulse detonation turbine engine.

4. The method for calculating the overall performance of a pulse detonation turbofan engine according to claim 3, wherein: The outlet total temperature T4, outlet total pressure P t The specific calculation process is: First, the total pressure in the pressure plateau area is: p plateau =d A1 p s,fill , Where p s，fill is the static pressure in the pulse detonation combustion chamber after filling is completed, δ A1 It is a gas characteristic parameter, which characterizes the pressure increase ratio of the total pressure in the pressure platform area relative to the static pressure in the filling stage. k1 and k2 are the specific heat ratios of the fuel and air mixture before detonation and the specific heat ratios of the products after detonation, respectively. Under isentropic conditions, according to the relationship between sound speed and temperature, the total temperature of the pressure platform area after the detonation wave is initiating, the sound speed c after the detonation is obtained. b Calculated by the following formula, δ A2 is the characteristic parameter that characterizes the pressure decay. c b =V CJ / d A2 , The propagation time of the blast wave is t CJ It is obtained from the following formula, L is the length of the pulse detonation combustion chamber, V fill is the filling velocity of the pulse detonation combustion chamber at the initial moment. Duration of pressure plateau area t plateau Calculated by the following formula, where δ B is the gas characteristic parameter, which characterizes the propagation time t of the detonation wave CJ The ratio of: t plateau =δ B t CJ , Duration of the pressure decay phase t decay Calculated by the following formula, where function f n (δ A2 ) According to the thrust wall pressure decay function table with time: t decay =t CJ d A2 [f n (d A2 )-1]; Finally, the calculation formula for the filling duration is: Based on the above formulas, the total parameters and corresponding times of the filling stage, pressure platform stage, and pressure decay stage are calculated. The calculation formula for the detonation chamber working time is: t cycle =t CJ +t plateau +t decay , The average total temperature and total pressure at the outlet of the pulse detonation combustion chamber can also be calculated: in: Where, u(t) is the air velocity at time t, D tube is the pipe diameter, N tube is the number of tubes, f is the operating frequency, P tout That is equivalent to the total pressure P4 at the detonation chamber outlet, T tout That is equivalent to the total temperature T4 at the detonation chamber outlet.

5. The method for calculating the overall performance of a pulse detonation turbofan engine according to claim 1, wherein: The specific calculation process of the total pressure P5 in step 3 is: Establish the residual equation of the whole machine performance model: ERR=(P 5I -P 5O ) / P 5I P5=f(FanPR), Where, P 5I is the total pressure at the outlet of the low-pressure turbine, P 5O is the total pressure at the duct outlet, and the independent variable is the fan pressure ratio; that is, by changing the fan pressure ratio, the total pressure of the two sections is adjusted to make them basically consistent, reducing mixing losses and ensuring stable operation of the mixing chamber.

6. The method for calculating the overall performance of a pulse detonation turbofan engine according to claim 1, wherein: The design point of the mixing chamber in step 4 is obtained by the static pressure balance equation of the inner and outer ducts at the mixing chamber inlet, and the total temperature T6 and total pressure P6 of the mixing chamber outlet are obtained. The total temperature and total pressure of the tail nozzle inlet are known, and the velocity coefficient C is V After isentropic calculation, the tail nozzle outlet area A9 and air flow velocity V9 are obtained.

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