RU225374U1 - Air flow temperature sensor - Google Patents

Abstract

Modern aircraft require very accurate airflow temperature measurements to calculate aircraft speed, control jet engine flight tests, meteorological research, ensure flight safety, and test ground equipment. Typically, temperature sensors are used that are installed externally on board the aircraft. To prevent the formation of ice on the surface when flying in icing conditions, the sensor housing is heated with a heating element, which entails an increase in the power of the aircraft's power system and, as a consequence, an increase in the aircraft's weight and fuel consumption.

Description

The utility model relates to measurement technology and can be used in aviation to determine the speed and altitude parameters necessary to control an aircraft and, more specifically, to air data systems.

Air temperature sensors have been used on commercial aircraft for about 50 years. The measured airflow temperature includes the outside or ambient air temperature plus additional heating of the air due to the kinetic energy of the fast moving aircraft.

The air intake duct of the sensor, protruding above the aircraft skin, is susceptible to the formation of ice on it under icing conditions. To eliminate these undesirable processes, the design of all modern temperature sensors includes a heating element, the power consumption of which ranges from 250 to 350 W, which entails an increase in the power of the aircraft's power system and, as a consequence, an increase in the aircraft's weight and fuel consumption.

An air flow temperature sensor is known, described in patent No. US 7441948, dated June 13, 2013, IPC G01K 13/02, containing an air intake opening that turns into an internal air channel, inside of which a temperature-sensitive element is located, and the air intake channel is removed from the surface of the aircraft and is located on an aerodynamically streamlined body. Part of the air flow flowing around the aircraft enters the air intake and is directed through the air channel to the sensing element.

The disadvantage of this design is that the streamlined body of the sensor itself protrudes into the air flow, which leads to the need to heat it.

An air flow temperature sensor is known, described in patent No. US 8182143 B2, dated 08/09/2006, IPC G01K 13/02, containing an air intake hole located near the outer surface of the aircraft, so that the surrounding air from the boundary layer adjacent to the outer surface passes into internal air channel and is directed to the sensing element.

The disadvantage of this design is that the air intake hole protrudes into the air flow, which, under icing conditions, leads to ice deposition and blockage of the air intake hole and the following internal air channel, which makes it impossible to reliably measure temperature.

The task to be solved by the claimed utility model is to reduce the load on the aircraft's power system.

The technical result consists in ensuring the operation of the air flow temperature sensor in icing conditions with minimal heating.

This technical result is achieved by the fact that in the inventive sensor the air intake and outlet openings are located on an aerodynamically streamlined surface having two zones, and the planes of the openings are parallel to the vector of the local air flow velocity. The air intake hole is in the high pressure zone, and the outlet hole is in the low pressure zone. The essence of the utility model is illustrated by the following drawings.

In fig. Figure 1 shows the proposed air flow temperature sensor, where:

1 - surface in the area of high pressure,

2 - surface in the area of low pressure,

3 - flow channel,

4 - sensor body,

5 - temperature-sensitive element,

6 - thermal insulating gasket,

7 - inlet,

8 - outlet,

9 - outer surface of the aircraft.

In fig. Figure 2 shows the proposed air flow temperature sensor with areas of high and low pressure formed by flat surfaces, with straight generatrices.

In fig. Figure 3 shows the proposed air flow temperature sensor with a heating element, where

10 - measuring cell,

11 - internal channel of the measuring cell,

12 - heating element,

13 - ring channel.

The proposed air flow temperature sensor Fig. 1 contains a sensor housing 4, installed flush with the outer surface of the aircraft 9, with a formed surface in the area of high pressure 1 with an inlet hole 7 and a surface in the area of low pressure 2 with an outlet hole 8, which are interconnected by a flow channel 3, inside which temperature-sensitive sensors are located elements 5. A thermal insulating gasket 6 is installed between the body 4 and the aircraft frame, while the body 4 is made of a material with a low heat transfer coefficient, for example, a composite material or stainless steel type 12Х18Н9Т.

Areas of high pressure 1 and low pressure 2 can be formed as spheres or ellipsoids of large radius, ogival bodies with high-order surfaces (Fig. 1, and flat surfaces with rectilinear generatrices Fig. 2.

In fig. Figure 3 shows an air flow temperature sensor with a heating element 12 installed around the outlet 8, while in order to weaken the effect of the heating element 12 on the sensor readings, a measuring cell 10 with an internal channel 11 is installed in the flow channel 3, containing sensitive elements 5 and isolated from sensor housing 4 with ring channel 13.

The formation of ice on a surface in an air flow occurs due to the presence in the atmosphere of supercooled water in a droplet-liquid state, which, due to the collision of drops with the surface of the aircraft, spreads and freezes.

The amount of moisture passing into the ice phase is calculated using the following formula (1)

The integral recovery coefficient E, relating to the entire recovery zone, is generally determined by the relation:

where G _yл is the mass of water falling on a unit surface length in 1 second, kg/s⋅m;

ω - water content of the cloud, kg/m ³ ;

C _max - reduced thickness of the midsection, m;

V - flow speed.

F (φ, Re, Re _drop ) is a function that depends on the scale parameter of the size of the drop and the streamlined body, on the Reynolds number of the drop and the air flow.

Since reducing the midsection of the surface located in the air flow makes it possible to reduce the formation of ice on its surface, the location of the inlet 7 parallel to the outer surface of the aircraft 9 will eliminate the capture of water droplets and, as a consequence, its icing.

The operation of the proposed utility model is similar to the operation of an air flow temperature sensor containing an air intake hole configured to admit ambient air into the internal flow channel where the sensitive elements are located.

Due to the fact that high-precision determination of the temperature of the air flow requires constant circulation of outside air over the surface of the sensitive elements 5, it is necessary to organize an air flow in channel 3. This is achieved due to the pressure difference between the inlet 7 and outlet 8 holes. When an air flow flows around a high-pressure surface 1, due to expansion, the flow slows down by an amount ΔV ₁ , which, according to Bernoulli’s law (2), leads to an increase in the pressure of the air flow P ₀ by an amount P ₁ , and around the low-pressure surface 2, on the contrary, it accelerates by an amount ΔV ₂ and the pressure P ₀ decreases by the amount ΔP ₂ , and the pressure P ₁ on surface 1 is greater than the pressure P ₂ on surface 2. The resulting pressure difference (P ₁ -P ₂ ) between the inlet 7 and the outlet 8 is equal to the sum of the pressures ( ΔP ₁ +ΔР ₂ ), creates an air flow in the flow channel 3 with a speed V _t .

P ₀ - air flow pressure;

P ₁ - pressure on surface 1;

P ₂ - pressure on surface 2;

ΔV ₁ and ΔV ₂ - respectively, the change in speed on surface 1 and 2;

ρ - air density.

Due to the absence of a flowing air channel located directly in the flow, as well as the slight protrusion of the aerodynamic surface into the flow, critical icing of the outer surface of the sensor does not occur, since supercooled water droplets and ice crystals, due to their inertia, cannot enter the inlet 7, and small Ice deposits on the surface in front of the outlet 8 will not lead to blockage of the flow channel 3.

When operating the sensor at angles greater than 5°, when the thickness of the midsection of the outlet hole 8 reaches a threshold value, to prevent its possible icing and deposition of even a small amount of ice, local heating is provided by the heating element 12. Coaxial arrangement of the measuring cell 10, in relation to the flow channel 3 forms an additional annular channel 13, which, when an air flow passes through it, reduces the heating of the measuring cell 10.

1. Aronin A.S. Practical aerodynamics. - M., Military Publishing House, 1962, p. 11-12.

2. Tenishev R.Kh. Aircraft anti-icing systems. - Publishing house "Mechanical Engineering", 1967.

Claims (3)

1. An external flow temperature sensor containing an inlet opening that transforms into a flow channel, inside which there is a temperature-sensitive element and an outlet opening, characterized in that the inlet opening and the outlet opening are configured to be positioned parallel to the outer surface of the aircraft, and the outer surface of the outer flow temperature sensor air is made of an aerodynamically streamlined curved shape and forms a zone of high pressure and a zone of low pressure, with the inlet hole located in the high pressure zone, and the outlet in the low pressure zone. 2. An external flow temperature sensor according to claim 1, characterized in that a heating element is installed around the outlet hole. 3. An external flow temperature sensor according to claim 1, characterized in that the temperature-sensitive element is located in a measuring cell isolated from the sensor body by a ring channel.