CN118821434A - A method for calculating the evaporation amount of inlet jet precooling droplets based on mass conservation - Google Patents

Abstract

The invention discloses a method for calculating precooling liquid drop evaporation capacity of jet flow of an air inlet channel based on mass conservation, and relates to the technical field of precooling of the air inlet channel of a turbine engine. According to the method, the measurement of the evaporation quantity of the liquid drops can be converted into the measurement of the total temperature and the total pressure of the inlet and the outlet and other parameters in the given turbine engine air inlet channel inlet parameters and outlet parameters, so that the evaporation quantity of the liquid drops can be rapidly determined, the air inlet channel jet precooling effect can be effectively evaluated, the method for measuring the inlet and outlet parameters is perfect, the accuracy is high, and the method has guiding significance for practical engineering experiments.

Description

A method for calculating the evaporation amount of inlet jet precooling droplets based on mass conservation

Technical Field

The invention belongs to the technical field of turbine engine inlet precooling, and in particular relates to a method for calculating the evaporation amount of inlet jet precooling droplets based on mass conservation.

Background Art

In order to solve the adverse effects of high stagnation temperature at the engine inlet on the engine and achieve a smooth connection between thrust and speed, precooling technology for cooling the air entering the engine has received increasing attention. The so-called precooling refers to cooling the high-temperature air entering the engine to reduce the temperature to the normal operating temperature of the turbine engine. Jet precooling by spraying cooling medium at the compressor inlet is one of the main ways of precooling. Jet precooling technology has the potential advantages of low cost and fast formation, which makes the turbine engine not limited to higher flight altitudes and Mach numbers. Therefore, jet precooling technology is an effective way to expand the flight envelope of turbine engines and an important development direction.

Jet precooling may bring many benefits: in hypersonic flight, lowering the intake temperature can expand the Mach number flight range, improve the climb rate and actual ceiling, optimize the thermal management of various components, and improve the high temperature protection of the engine body; lowering the intake temperature can increase the intake density to increase the intake mass flow rate, thereby increasing the thrust; through appropriate cycle design, the proper use of high-speed stagnation heat can provide cycle thermal efficiency. At present, there is no mature theoretical calculation basis for the droplet evaporation amount as a key parameter to measure the quality of jet technology. Calculating the droplet evaporation amount through the law of conservation of mass has become a feasible method.

Summary of the invention

In response to the current technical difficulties, the present invention provides a method for calculating the evaporation amount of inlet jet precooling droplets based on the law of mass conservation. The evaporation mass of droplets in the inlet jet precooling of a turbine engine is calculated by the law of mass conservation, thereby effectively characterizing the improvement effect of the jet precooling technology on the engine performance.

In order to achieve the above object, a method for calculating the evaporation amount of inlet jet precooling droplets based on mass conservation is provided, comprising the following steps:

Step 1: Measure the turbine engine inlet duct to determine the inlet and outlet parameters of the inlet duct;

The inlet parameters and outlet parameters of the air inlet duct include inlet area A ₁ , inlet total pressure P ₀₁ , inlet static pressure P _S1 , inlet total temperature T ₀₁ , inlet air constant R ₁ , air gas constant R _air , inlet air adiabatic index γ ₁ , outlet area A ₂ , outlet total pressure P ₀₂ , outlet static pressure P _S2 , outlet total temperature T ₀₂ , outlet humid air gas constant R ₂ , outlet humid air adiabatic index γ ₂ , steam gas constant R _steam ;

Step 2: Calculate the inlet Mach number and inlet static temperature according to the determined inlet parameters and outlet parameters, and find the air constant pressure specific heat and air adiabatic index corresponding to the inlet static temperature;

The calculation formulas for the inlet Mach number, the inlet static temperature, the air constant pressure specific heat corresponding to the inlet static temperature, and the air adiabatic index corresponding to the inlet static temperature are as follows:

_CV1 ＝ _CP1 - _R1 (4)

Wherein, Ma ₁ is the inlet Mach number, _TS1 is the inlet static temperature, _CP1 is the air constant pressure specific heat corresponding to the inlet static temperature, γ ₁ ′ is the air adiabatic index corresponding to the inlet static temperature, and _CV1 is the air constant volume specific heat corresponding to the inlet static temperature;

Step 3: Determine whether the air adiabatic index corresponding to the inlet static temperature meets the error requirement. If yes, output the air adiabatic index corresponding to the inlet static temperature and execute step 4. Otherwise, replace the inlet air adiabatic index with the air adiabatic index corresponding to the inlet static temperature and return to step 2 to continue calculation.

The criterion for determining whether the air adiabatic index corresponding to the inlet static temperature meets the error requirement is: γ ₁ ′-γ ₁ <10 ^-m , where m is a given error limit;

Step 4: Calculate the inlet sound velocity, inlet velocity and inlet density based on the obtained inlet Mach number, inlet static temperature, air specific heat corresponding to the inlet static temperature, air adiabatic index corresponding to the inlet static temperature, inlet parameters and outlet parameters to obtain the inlet mass flow rate;

The calculation formulas for the inlet sound velocity, inlet velocity, inlet density and inlet mass flow rate are:

v ₁ =Ma ₁ ·a ₁ (7)

Where _a1 is the inlet sound velocity, _v1 is the inlet velocity, _ρ1 is the inlet density, is the inlet mass flow rate;

Step 5: According to the inlet mass flow rate, inlet parameters and outlet parameters, calculate the outlet Mach number, outlet static temperature, outlet sound velocity, outlet velocity and outlet density, obtain the outlet mass flow rate, and calculate the droplet evaporation amount;

The calculation formulas for the outlet Mach number, outlet static temperature, outlet sound velocity, outlet velocity, outlet density, outlet mass flow rate and droplet evaporation amount are as follows:

v ₂ =Ma ₂ ·a ₂ (13)

Where Ma ₂ is the outlet Mach number, T _s2 is the outlet static temperature, a ₂ is the outlet sound velocity, v ₂ is the outlet velocity, ρ ₂ is the outlet density, is the outlet mass flow rate, is the droplet evaporation amount;

Step 6: Calculate the air constant pressure specific heat and steam constant pressure specific heat corresponding to the outlet static temperature according to the outlet static temperature, the inlet mass flow rate, the droplet evaporation amount, the inlet parameters and the outlet parameters, and obtain the air constant pressure specific heat and steam constant pressure specific heat corresponding to the outlet static temperature together with the gas constants of air and steam to obtain the air and steam constant volume specific heat, and at the same time obtain the outlet humid air constant volume specific heat, the updated outlet humid air gas constant and the outlet humid air constant pressure specific heat, and calculate the updated humid air adiabatic index;

_Cvair ＝ _CPair - _Rair

(19)

C _{v steam} = C _{P steam} - R _steam (20)

C _p =C _v +R ₂ '(23)

Wherein, _CPair is the specific heat of air at constant pressure corresponding to the outlet static temperature, _CPsteam is the specific heat of steam at constant pressure corresponding to the outlet static temperature, _Cvair is the specific heat of air at constant volume, _Cvsteam is the specific heat of steam at constant volume, _Cv is the specific heat of outlet humid air at constant volume, _CP is the specific heat of outlet humid air at constant pressure, γ ₂ ′ is the updated humid air adiabatic index, and R ₂ ′ is the updated gas constant of outlet humid air;

Step 7: Replace the outlet wet air adiabatic index with the updated wet air adiabatic index calculated in step 6 and substitute it into step 5, calculate the droplet evaporation amount as the updated droplet evaporation amount, and judge whether the updated droplet evaporation amount meets the error requirement. If yes, output the updated droplet evaporation amount, otherwise return the updated wet air adiabatic index to step 5 to continue calculation;

The criteria for judging whether the updated droplet evaporation amount meets the error requirement are: in is the updated droplet evaporation amount, and n is the given error limit.

Compared with the prior art, the present invention has the following beneficial effects:

Under current experimental conditions, the measurement of droplet evaporation requires measuring the mass flow rate of droplets at the outlet, etc., and it is difficult to guarantee the accuracy of the measurement. Through this calculation method, given the inlet and outlet parameters of the turbine engine inlet duct, the measurement of droplet evaporation can be converted into measuring parameters such as the inlet and outlet total temperature and total pressure, and then the droplet evaporation amount can be quickly determined, thereby effectively evaluating the inlet jet precooling effect. The method for measuring the inlet and outlet parameters is perfect and accurate, which has guiding significance for actual engineering experiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a calculation flow chart of a method for calculating the evaporation amount of inlet jet precooling droplets based on mass conservation in an embodiment of the present invention.

DETAILED DESCRIPTION

The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

A method for calculating the evaporation amount of inlet jet precooling droplets based on mass conservation, as shown in FIG1 , includes the following steps:

Step 1: Measure the turbine engine inlet duct to determine the inlet and outlet parameters of the inlet duct;

The inlet parameters and outlet parameters of the air inlet duct include inlet area A ₁ , inlet total pressure P ₀₁ , inlet static pressure P _S1 , inlet total temperature T ₀₁ , inlet air constant R ₁ , air gas constant R _air , inlet air adiabatic index γ ₁ , outlet area A ₂ , outlet total pressure P ₀₂ , outlet static pressure P _S2 , outlet total temperature T ₀₂ , outlet humid air gas constant R ₂ , outlet humid air adiabatic index γ ₂ , steam gas constant R _steam ;

The inlet parameters and outlet parameters determined in this embodiment are shown in Table 1, including inlet area A ₁ =0.09m ² , inlet total pressure P ₀₁ =220700Pa, inlet static pressure P _s1 =204103.52Pa, inlet total temperature T ₀₁ =601K, inlet air constant R ₁ =287 (J/kg·K), inlet air adiabatic index γ ₁ =1.4, outlet area A ₂ =0.09m ² , outlet total pressure P ₀₂ =221927.54Pa, outlet static pressure P _S2 =207154Pa, outlet total temperature T ₀₂ =464.9939K, outlet humid air gas constant R ₂ =300 (J/kg·K), outlet humid air adiabatic index γ ₂ =1.4, steam gas constant R _steam =461 (J/kg·K);

Table 1 Case initial conditions

Step 2: Calculate the inlet Mach number and inlet static temperature according to the determined inlet parameters and outlet parameters, and find the air constant pressure specific heat and air adiabatic index corresponding to the inlet static temperature;

The calculation formulas for the inlet Mach number, the inlet static temperature, the air constant pressure specific heat corresponding to the inlet static temperature, and the air adiabatic index corresponding to the inlet static temperature are as follows:

_CV1 ＝ _CP1 - _R1 (4)

Wherein, Ma ₁ is the inlet Mach number, _TS1 is the inlet static temperature, _CP1 is the air constant pressure specific heat corresponding to the inlet static temperature, γ ₁ ′ is the air adiabatic index corresponding to the inlet static temperature, and _CV1 is the air constant volume specific heat corresponding to the inlet static temperature;

In this embodiment, the inlet Mach number Ma ₁ =0.3390, the inlet static temperature T _S1 =588.3246K, the air specific heat C _p1 =1052.6 (J/kg·K), and the air adiabatic index γ ₁ ′=1.3749 are calculated;

Step 3: Determine whether the air adiabatic index corresponding to the inlet static temperature meets the error requirement. If yes, output the air adiabatic index corresponding to the inlet static temperature and execute step 4. Otherwise, replace the inlet air adiabatic index with the air adiabatic index corresponding to the inlet static temperature and return to step 2 to continue calculation.

The criterion for determining whether the air adiabatic index corresponding to the inlet static temperature meets the error requirement is: γ ₁ ′-γ ₁ <10 ^-m , where m is a given error limit;

In this implementation, if γ ₁ ′-γ ₁ ＜10 ^-3 , then γ ₁ ′ is output, otherwise, the result is substituted into step 2 to continue iterative calculation;

Step 4: Calculate the inlet sound velocity, inlet velocity and inlet density based on the obtained inlet Mach number, inlet static temperature, air specific heat corresponding to the inlet static temperature, air adiabatic index corresponding to the inlet static temperature, inlet parameters and outlet parameters to obtain the inlet mass flow rate;

The calculation formulas for the inlet sound velocity, inlet velocity, inlet density and inlet mass flow rate are:

v ₁ =Ma ₁ ·a ₁ (7)

Where _a1 is the inlet sound velocity, _v1 is the inlet velocity, _ρ1 is the inlet density, is the inlet mass flow rate;

In this embodiment, the calculated inlet sound velocity a ₁ =481.8167 m/s, the inlet velocity V ₁ =163.3512 m/s, and the inlet density ρ ₁ =1.2088 kg/m ³ , yielding the inlet mass flow rate:

Step 5: According to the inlet mass flow rate, inlet parameters and outlet parameters, calculate the outlet Mach number, outlet static temperature, outlet sound velocity, outlet velocity and outlet density, obtain the outlet mass flow rate, and calculate the droplet evaporation amount;

The calculation formulas for the outlet Mach number, outlet static temperature, outlet sound velocity, outlet velocity, outlet density, outlet mass flow rate and droplet evaporation amount are as follows:

v ₂ =Ma ₂ ·a ₂ (13)

Where Ma ₂ is the outlet Mach number, T _s2 is the outlet static temperature, a ₂ is the outlet sound velocity, v ₂ is the outlet velocity, ρ ₂ is the outlet density, is the outlet mass flow rate, is the droplet evaporation amount;

The outlet Mach number Ma ₂ calculated in this embodiment is 0.3176, the outlet static temperature T _S2 is 456.2765K, the outlet sound velocity a ₂ is 432.4209m/s, the outlet velocity v ₂ is 137.3424m/s, the outlet density ρ ₂ is 1.5275kg/m ³ , and the outlet mass flow rate is obtained: Calculate the evaporation rate of the droplet

Step 6: Calculate the air constant pressure specific heat and steam constant pressure specific heat corresponding to the outlet static temperature according to the outlet static temperature, the inlet mass flow rate, the droplet evaporation amount, the inlet parameters and the outlet parameters, and obtain the air constant pressure specific heat and steam constant pressure specific heat corresponding to the outlet static temperature together with the gas constants of air and steam to obtain the air and steam constant volume specific heat, and at the same time obtain the outlet humid air constant volume specific heat C _v , the updated outlet humid air gas constant R ₂ ' and the outlet humid air constant pressure specific heat C _P , and calculate the updated humid air adiabatic index γ ₂ ′;

_Cvair ＝ _CPair - _Rair

(19)

C _{v steam} = C _{P steam} - R _steam (20)

C _p =C _v +R ₂ '(23)

Wherein, _CPair is the specific heat of air at constant pressure corresponding to the outlet static temperature, _CPsteam is the specific heat of steam at constant pressure corresponding to the outlet static temperature, _Cvair is the specific heat of air at constant volume, _Cvsteam is the specific heat of steam at constant volume, _Cv is the specific heat of outlet humid air at constant volume, _CP is the specific heat of outlet humid air at constant pressure, γ ₂ ′ is the updated humid air adiabatic index, and R ₂ ′ is the updated gas constant of outlet humid air;

The outlet static temperature calculated in this embodiment corresponds to the air constant pressure specific heat C _{P air} = 1028.1 (J/kg·K), the steam constant pressure specific heat C _{P steam} = 1942.9 (J/kg·K), the air constant volume specific heat C _{V air} = 741.1478 (J/kg·K), the steam constant volume specific heat C _{V steam} = 1481.9 (J/kg·K), the outlet humid air constant volume specific heat C _v = 784.6844 (J/kg·K), the humid air constant pressure specific heat C _P = 1081.9 (J/kg·K), the humid air gas constant R ₂ ' = 297.2271 (J/kg·K), and the humid air adiabatic index γ ₂ ' = 1.3788;

Step 7: Replace the outlet wet air adiabatic index with the updated wet air adiabatic index calculated in step 6 and substitute it into step 5, calculate the droplet evaporation amount as the updated droplet evaporation amount, and judge whether the updated droplet evaporation amount meets the error requirement. If yes, output the updated droplet evaporation amount, otherwise return the updated wet air adiabatic index to step 5 to continue calculation;

The criteria for judging whether the updated droplet evaporation amount meets the error requirement are: in is the updated droplet evaporation amount, and n is the given error limit.

In this embodiment, the above calculation steps are performed and the error limit is required. Calculate the final droplet evaporation amount

The solutions in the embodiments are not intended to limit the patent protection scope of the present invention. All equivalent implementations or changes that do not deviate from the present invention are included in the patent scope of this case.

Claims (8)

1. The method for calculating the evaporation capacity of the precooled liquid drops of the jet flow of the air inlet channel based on mass conservation is characterized by comprising the following steps:

step one: measuring an air inlet channel of a turbine engine, and determining inlet parameters and outlet parameters of the air inlet channel;

Step two: calculating inlet Mach number and inlet static temperature according to the determined inlet parameter and outlet parameter, and solving air constant pressure specific heat and air heat insulation index corresponding to the inlet static temperature;

step three: judging whether the obtained air insulation index corresponding to the inlet static temperature meets the error requirement, if so, outputting the air insulation index corresponding to the inlet static temperature and executing the fourth step, otherwise, replacing the inlet air insulation index with the obtained air insulation index corresponding to the inlet static temperature and returning to the second step for continuous calculation;

step four: calculating inlet sound velocity, inlet speed and inlet density according to the obtained inlet Mach number, inlet static temperature, air specific heat corresponding to the inlet static temperature, air adiabatic index corresponding to the inlet static temperature, inlet parameters and outlet parameters to obtain inlet mass flow;

Step five: calculating an outlet Mach number, an outlet static temperature, an outlet sound velocity, an outlet speed and an outlet density according to the inlet mass flow, the inlet parameter and the outlet parameter to obtain an outlet mass flow, and solving the evaporation capacity of liquid drops;

Step six: calculating air constant pressure specific heat and steam constant pressure specific heat corresponding to the outlet static temperature according to the outlet static temperature, the inlet mass flow, the liquid drop evaporation capacity, the inlet parameter and the outlet parameter, combining the air constant pressure specific heat and the steam constant pressure specific heat corresponding to the outlet static temperature with the gas constants of air and steam to obtain the constant volume specific heat of air and steam, simultaneously obtaining the outlet wet air constant volume specific heat, updated outlet wet air gas constant and outlet wet air constant pressure specific heat, and calculating updated wet air insulation index;

Step seven: substituting the updated wet air adiabatic index obtained in the step six for the outlet wet air adiabatic index to the step five, calculating to obtain the liquid drop evaporation capacity as the updated liquid drop evaporation capacity, judging whether the updated liquid drop evaporation capacity meets the error requirement, if so, outputting the updated liquid drop evaporation capacity, otherwise, returning the updated wet air adiabatic index to the step five for continuous calculation.

2. The method according to claim 1, wherein the inlet and outlet parameters of the inlet in the first step include an inlet area a ₁, an inlet total pressure P ₀₁, an inlet static pressure P _S1, an inlet total temperature T ₀₁, an inlet air constant R ₁, an air gas constant R _{Air-conditioner} , an inlet air insulation index γ ₁, an outlet area a ₂, an outlet total pressure P ₀₂, an outlet static pressure P _S2, an outlet total temperature T ₀₂, an outlet wet air gas constant R ₂, an outlet wet air insulation index γ ₂, and a steam gas constant R _{Steam generation} .

3. The method for calculating the evaporation capacity of precooled liquid drops of the jet flow of the air inlet based on mass conservation according to claim 2, wherein in the second step, the calculation formulas of the inlet Mach number, the inlet static temperature, the air constant pressure specific heat corresponding to the inlet static temperature and the air heat insulation index corresponding to the inlet static temperature are as follows:

C_V1＝C_P1-R₁ (4)

Wherein, ma ₁ is inlet mach number, T _S1 is inlet static temperature, C _P1 is air constant pressure specific heat corresponding to inlet static temperature, γ ₁' is air insulation index corresponding to inlet static temperature, and C _V1 is air constant heat corresponding to inlet static temperature.

4. The method for calculating the evaporation capacity of precooled liquid drops of the jet flow of the air inlet based on mass conservation according to claim 3, wherein the judging criterion of whether the air insulation index corresponding to the inlet static temperature obtained by judgment in the step three meets the error requirement is as follows: gamma ₁′-γ₁|＜10^-m, where m is the given error limit.

5. The method for calculating the evaporation capacity of precooled liquid droplets of an air inlet jet based on mass conservation according to claim 3, wherein in the fourth step, the calculation formulas of the inlet sound velocity, the inlet speed, the inlet density and the inlet mass flow are as follows:

v₁＝Ma₁·a₁ (7)

Where a ₁ is the inlet sound speed, v ₁ is the inlet speed, ρ ₁ is the inlet density, Is the inlet mass flow.

6. The method for calculating the evaporation capacity of precooled liquid drops of an air inlet jet based on mass conservation according to claim 5, wherein the calculation formulas of the outlet mach number, the outlet static temperature, the outlet sound velocity, the outlet speed, the outlet density, the outlet mass flow and the evaporation capacity of liquid drops in the fifth step are as follows:

v₂＝Ma₂·a₂ (13)

Wherein, ma ₂ is the exit Mach number, T _s2 is the exit static temperature, a ₂ is the exit sound velocity, v ₂ is the exit velocity, ρ ₂ is the exit density, For the outlet mass flow rate,Is the evaporation amount of the liquid drop.

7. The method for calculating the evaporation capacity of precooled liquid drops of an air inlet jet based on mass conservation according to claim 6, wherein in the step six, the calculation formulas of the air constant pressure specific heat corresponding to the outlet static temperature, the steam constant pressure specific heat corresponding to the outlet static temperature, the air constant volume specific heat, the steam constant volume specific heat, the outlet wet air constant volume specific heat, the updated outlet wet air gas constant, the outlet wet air constant pressure specific heat and the updated wet air adiabatic index are as follows:

C_{v Air-conditioner} ＝C_{P Air-conditioner} -R _{Air-conditioner}

(19)

C_{v Steam generation} ＝C_{P Steam generation} -R _{Steam generation} (20)

C_p＝C_v+R₂' (23)

wherein, C _{P Air-conditioner} is the air constant pressure specific heat corresponding to the outlet static temperature, C _{P Steam generation} is the steam constant pressure specific heat corresponding to the outlet static temperature, C _{v Air-conditioner} is the air constant pressure specific heat, C _{v Steam generation} is the steam constant pressure specific heat, C _v is the outlet wet air constant pressure specific heat, C _P is the outlet wet air constant pressure specific heat, gamma ₂ 'is the updated wet air insulation index, and R ₂' is the updated outlet wet air gas constant.

8. The method for calculating the evaporation capacity of precooled liquid drops of the jet flow of the air inlet channel based on mass conservation according to claim 7, wherein the judgment criterion for judging whether the updated evaporation capacity of liquid drops meets the error requirement in the seventh step is as follows: Wherein the method comprises the steps of N is a given error limit for the updated drop evaporation.