CN102737166B - Method for determining upper limit of environmental temperature in nacelle - Google Patents

Abstract

The invention belongs to the aircraft accessory design technology and relates to a method for determining the upper limit of the ambient temperature in the aircraft nacelle. The invention first obtains the temperature of the surface of the engine casing through experiments, then determines the ambient temperature of the aircraft, and then measures the section radius of the engine and the nacelle according to the data model or the real object of the engine and the nacelle. Finally, according to the principles of thermodynamics, aerodynamics, and the working characteristics of the aircraft nacelle ventilation and cooling system, combined with actual tests and engineering experience, the empirical formula is obtained through numerical fitting and calibration, and the upper limit of the ambient temperature of the nacelle is calculated. The invention is simple, convenient, easy to implement, has high precision and can meet the actual engineering requirements.

Description

A method for determining the upper limit of the ambient temperature in the nacelle

technical field

The invention belongs to the aircraft accessory design technology and relates to a method for determining the upper limit of the ambient temperature in the aircraft nacelle.

Background technique

The engine is one of the main heat-generating components of an aircraft, and there are usually many system components and working accessories around it, including some electronic components that are sensitive to temperature. This requires considering the influence of the high temperature environment caused by the engine, estimating the working ambient temperature of some engine accessories in the nacelle, and then calculating the upper limit of the nacelle ambient temperature as the design index of the engine accessories. How to predict the temperature field of the concerned parts more accurately, carry out targeted ventilation design and provide design input for other systems has become the focus and difficulty of ventilation and cooling system design.

The harshest ambient temperature of the aircraft nacelle usually occurs under ground conditions. At this time, the aircraft is stationary, the engine is running, and there is no effective forced ventilation in the nacelle. The components near the engine are in the most severe high-temperature working environment. In order to predict the ambient temperature of the nacelle under this state, the method of numerical simulation is usually used to obtain it, but because the implementation of the numerical simulation method of the heat transfer process of the nacelle is too complicated and the calculation period is long, it is not suitable for rapid engineering calculation.

Contents of the invention

The purpose of the present invention is to provide a method for quickly calculating the upper limit of the ambient temperature in the nacelle, which avoids the complexity of performing full three-dimensional numerical simulation.

The technical solution of the present invention is: a method for determining the upper limit of the ambient temperature in the nacelle, comprising the following steps:

Step 1: Obtain the average temperature of the engine surface;

The engine is divided into five sections according to each component (low-pressure compressor, high-pressure compressor, combustion chamber, turbine, exhaust pipe). The surface temperature of the engine casing is obtained from the engine test run, and the average surface temperature T _n of each section is obtained respectively; The maximum T _w among T _n is chosen.

Step 2: Determine the extreme temperature of the aircraft working environment;

According to the design requirements, determine the most severe ground working state of the aircraft, and obtain the corresponding ambient temperature T ₀ in this state.

Step 3: Obtain the geometric dimensions of the nacelle and the engine;

Measure the radius R1 of the engine case at the _Tw temperature range, and the corresponding radius R2 of the inner wall of the nacelle.

Step 4: Calculate the upper limit of the ambient temperature of the nacelle;

Form a new empirical formula based on engineering experience

T _max =0.5·(T _w +T ₀ )+k·(T _w -T ₀ )e ^(R1-R2)/R1 (k=1.5～2.0) (1)

Put T _w , T ₀ , R ₁ , and R ₂ into formula (1), select an appropriate coefficient k, and calculate the upper limit of the nacelle ambient temperature T _max .

The invention has the advantages that: the method for determining the upper limit of the ambient temperature in the aircraft nacelle is simple, convenient, easy to realize, and has high precision, which can meet the actual engineering requirements. It has been proved by experiments that the error between the upper temperature limit determined by this method and the actual measurement result does not exceed 10%.

Description of drawings

Fig. 1 is the flow chart of the method for determining the upper limit of ambient temperature in the aircraft nacelle for the present invention;

Fig. 2 is the structural representation of the engine and the nacelle in the method for determining the upper limit of the ambient temperature in the aircraft nacelle in a preferred embodiment of the present invention;

Fig. 3 is a schematic diagram of the surface temperature of each segmented casing of the engine in the method for determining the upper limit of the ambient temperature in the aircraft nacelle in a preferred embodiment of the present invention;

Among them, 1-nacelle wall 2-nacelle firewall 3-engine compressor section 4-engine combustion chamber section 5-engine turbine section 6-engine nozzle section 7-engine case radius 8-nacelle wall surface radius.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings.

The upper limit T _max of the ambient temperature in the aircraft nacelle depends on the engine wall temperature, atmospheric temperature and the geometric size of the nacelle engine. The difference between the engine wall temperature and the atmospheric temperature determines the strength of convective heat transfer in the nacelle. The higher the internal ambient temperature. The relative geometric size of the nacelle engine directly affects the gas flow, the size of the radiation heat transfer, and the comprehensive temperature difference, which characterizes the heat accumulation effect in the nacelle. The smaller the relative geometric size, the more significant the accumulation effect, and the higher the upper limit of the ambient temperature in the nacelle. high.

The method for determining the upper limit of the ambient temperature in the aircraft nacelle is based on thermodynamic principles, aerodynamics, and the operating characteristics of the aircraft nacelle ventilation and cooling system, combined with actual tests and engineering experience, numerical fitting calibration to obtain an empirical formula, and using the empirical formula Determine the upper limit of the ambient temperature in the nacelle, which is better in line with the actual temperature through test verification.

Below in conjunction with Fig. 1, provide the process steps of the method for the present invention to determine the ambient temperature upper limit in the aircraft nacelle:

Step 1: Obtain the average temperature of the engine surface

According to the core components of the engine, the engine is divided into several sections along the axial direction. The surface temperature of the engine case is obtained from the engine test run, and the average surface temperature T _n of each section of the case is obtained respectively; the maximum value T _w of T _n is selected;

Step 2: Determine the temperature extremes of the aircraft operating environment

According to the design requirements and the working environment of the aircraft, determine the most severe ground working state of the aircraft, and obtain the corresponding ambient temperature upper limit T ₀ under this state;

Step 3: Get nacelle and engine geometric dimensions

Measure the radius R1 of the engine case at the _Tw temperature range, and the corresponding radius R2 of the inner wall of the nacelle;

Step 4: Calculate the upper limit of the ambient temperature of the nacelle

According to engineering experience, test calibration is carried out to obtain a new empirical formula

T _max =0.5·(T _w +T ₀ )+k·(T _w -T ₀ )e ^(R1-R2)/R1 (k=1.5～2.0) (1)

Among them, T _max is the upper limit of the ambient temperature of the nacelle, and k is the empirical coefficient.

Put T _w , T ₀ , T ₁ , and R ₂ into formula (1), select an appropriate value of coefficient k (k=1.5～2.0), and calculate the upper limit T _max of the nacelle ambient temperature.

Example 1

The present invention determines the calculating method of ambient temperature upper limit in aircraft nacelle, and its flow process as shown in Figure 1, comprises the following steps:

Step 1: Obtain the average temperature of the engine surface

As shown in Figure 2, according to the core components of the engine, the engine is divided into four sections along the axial direction. The surface temperature of the engine casing is obtained from the engine test run, and the average surface temperature T _n of each section of the casing is obtained separately, as shown in Figure 3. The temperature of each section is expanded as follows: compressor section _T1 = 316K, combustion chamber section _T2 = 361K, turbine section _T3 = 366K, nozzle section _T4 = 373K; take the maximum value _Tw = _T4 = 373K;

Step 2: Determine the temperature extremes of the aircraft operating environment

According to the actual working conditions of the aircraft, it is determined that the severe working state of the aircraft is a hot day and high temperature environment on the ground (usually the highest will not exceed 50°C, which is 323K). In this embodiment, the working environment temperature T ₀ of the aircraft is set to 313K.

Step 3: Get nacelle and engine geometric dimensions

As shown in Figure 2, measure the radius R1 of the engine case at the _Tw temperature section = 0.60m, and the corresponding nacelle inner wall radius R2 = 0.80m;

Step 4: Calculate the upper limit of the ambient temperature of the nacelle

empirical formula

T _max =0.5·(T _w +T ₀ )+k·(T _w -T ₀ )e ^(R1-R2)/R1 (k=1.5～2.0) (1)

Substitute T _w , T ₀ , R1 and R2 into formula (1), and take 1.6 as k, and calculate the upper limit of nacelle ambient temperature T _max = 411.8K, which is 138.8°C.

The numerical test result of this embodiment is 129.3°C. Compared with the numerical simulation result and the actual temperature, the error of the result calculated by the method for determining the upper limit of the ambient temperature in the nacelle of the aircraft does not exceed 10%, which is within the allowable range of engineering errors.

Claims (1)

1. determine a method for upper limit of environmental temperature in nacelle, it is characterized in that, comprise the steps:

Step one: obtain engine surface medial temperature

According to engine core parts, vertically engine is divided into some sections, engine crankcase surface temperature is tested by engine run and is obtained, and obtains the average surface temperature T of every section of casing respectively _n, choose T _nin maximum of T _w;

Step 2: the extreme temperature determining aircraft working environment

According to designing requirement, determine the ground running that aircraft is the harshest, ambient temperature value T corresponding under obtaining this state ₀;

Step 3: obtain nacelle and engine geometry size

Measure T _wtemperature start casing radius R 1, and the nacelle inwall radius R 2 of correspondence;

Step 4: calculate the nacelle environment temperature upper limit

By T _w, T ₀, R1, R2 bring (1) formula into, and choose suitable experience factor k value, calculates T _max

T _max＝0.5·(T _w+T ₀)+k·(T _w-T ₀)e ^(R1-R2)/R1(1)

Wherein, T _maxfor the nacelle environment temperature upper limit, k is experience factor, k=1.5 ~ 2.0.