Heater improvement method, heater and ice detector

Abstract

The present invention discloses a method for improving a heater, a heater, and an ice detector. A copper shell (1) is used as the shell of a heater (5) in a probe of an ice detector; when the connecting end of the heater passes through a vibrating cylinder (4) of the ice detector, a silver solder is used to fill a passing gap (14) between the copper shell (1) and the vibrating cylinder (4) to ensure electrical conductivity between the heater shell and the vibrating cylinder. The present invention solves the technical problem that an aircraft ice detector cannot pass a 1A level lightning direct effect test.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental resistance design of sensors for aircraft, and relates to a method for improving a heater, a heater and an ice detector. Background Art

[0002] Ice detectors are essential instruments for large aircraft. Installed in the aircraft's lightning protection zone, 1A, they must pass a Level 1A lightning direct effects test. However, due to technical difficulties, ice detectors currently installed on Chinese aircraft fail the DO-160G Level 1A lightning direct effects test. Installation is only permitted after coordination to eliminate this test. With the increasing emphasis on aircraft safety in recent years, ice detectors that fail the Level 1A lightning direct effects test are no longer suitable for installation. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for improving a heater, a heater and an ice detector. The present invention solves the technical problem that an aircraft ice detector cannot pass the 1A level lightning direct effect test.

[0004] The technical solution of the present invention is: an improved method for a heater for an ice detector, wherein the outer shell of the heater in the probe of the ice detector is made of copper; when the connecting end of the heater passes through the vibrating tube of the ice detector, silver solder is used to fill the passing gap between the copper shell and the vibrating tube to ensure conductivity between the outer shell of the heater and the vibrating tube.

[0005] In the aforementioned improved method for the heater for the ice detector, the copper shell is made of pure copper T1 or T2, and the inner diameter of the copper shell is 0.9 mm and the outer diameter is 1.5 mm.

[0006] A heater improved by the above-mentioned improvement method comprises a copper shell, which is U-shaped as a whole. A heating wire is arranged along the axis of the copper shell, and an insulating material is filled between the heating wire and the copper shell.

[0007] In the aforementioned heater, the insulating material is magnesium oxide.

[0008] An ice detector using the aforementioned heater includes a base, a vibrating cylinder is provided on the base along the axial direction, a probe is provided in the vibrating cylinder, the top end of the probe passes through the vibrating cylinder and the base in sequence and then extends out, a spring is provided at the bottom end of the probe, and the bottom end of the spring is limited by a pressure plate provided at the bottom of the vibrating cylinder; a heater is provided in the probe, and the connecting ends at both ends of the heater pass through the vibrating cylinder and are connected to a connector provided on the outer wall of the vibrating cylinder; the vibrating cylinder is grounded.

[0009] In the aforementioned ice detector, a driving coil is also mounted on the probe located in the vibrating cylinder.

[0010] In the aforementioned ice detector, a feedback coil is also provided on the probe below the driving coil; the driving coil and the feedback coil are separated by an insulating spacer.

[0011] In the aforementioned ice detector, magnets are further provided on the outer wall of the vibrating cylinder at the positions of the driving coil and the feedback coil.

[0012] The advantages of the present invention are: compared with the existing technology, the present invention can pass the 1A level lightning direct effect test, and the test result shows that the probe is not broken or damaged. The present invention is simple to improve, does not change the overall structure of the ice detector, and cleverly integrates the improvement measures into the original structure. It only fine-tunes the thickness of the heater shell and the position where the vibration tube passes through the heater, and the improvement cost and technical difficulty are low. The present invention has a wide range of uses, and this improvement scheme can be applied to most of the current ice detectors. The present invention has achieved a major breakthrough for domestic ice detectors, enabling domestic ice detectors to pass the direct effect of lightning normally, rather than canceling the direct lightning test project, and helping domestic ice detectors obtain international airworthiness certificates.

[0013] In summary, the present invention solves the current situation in which my country's aircraft ice detectors cannot pass the 1A level lightning direct effect test. It has the characteristics of strong practicality, simple improvement, little impact on amplitude-frequency characteristics, and wide applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a diagram of the heater assembly;

[0015] Figure 2 This is a cross-sectional view of the ice detector;

[0016] Figure 3 Schematic diagram of the ice detector structure.

[0017] Figure numerals: 1-copper shell, 2-heating wire, 3-base, 4-vibration cylinder, 5-probe, 6-spring, 7-pressure plate, 8-heater, 9-connector, 10-driving coil, 11-feedback coil, 12-insulating gasket, 13-magnet, 14-through gap, 15-connecting end. DETAILED DESCRIPTION

[0018] The present invention will be further described below with reference to the accompanying drawings and examples, but they are not intended to limit the present invention.

[0019] Example 1. An improved method for an ice detector heater comprises using a copper outer shell for the heater within the probe of the ice detector. When the connecting end of the heater passes through the ice detector's vibrating cylinder, silver solder is used to fill the gap between the copper outer shell 1 and the vibrating cylinder 4 to ensure conductivity between the heater outer shell and the vibrating cylinder.

[0020] The aforementioned copper shell is made of pure copper T1 or T2, and the inner diameter of the copper shell is 0.9 mm and the outer diameter is 1.5 mm.

[0021] The heater obtained by the above-mentioned improvement method is composed of Figure 1 As shown, it includes a copper shell 1, which is U-shaped as a whole. A heating wire 2 is provided along the axis of the copper shell 1, and insulating material is filled between the heating wire 2 and the copper shell 1.

[0022] The aforementioned insulating material is magnesium oxide.

[0023] An ice detector using the aforementioned heater is constructed as follows Figure 1-3 As shown, it includes a base 3, a vibration tube 4 is axially provided on the base 3, a probe 5 is provided in the vibration tube 4, the top end of the probe 5 passes through the vibration tube 4 and the base 3 in sequence and then extends out, a spring 6 is provided at the bottom end of the probe 5, and the bottom end of the spring 6 is limited by a pressure plate 7 arranged at the bottom of the vibration tube 4; a heater 8 is provided in the probe 5, and the connecting ends of the two ends of the heater 8 (i.e., the two ends of the U-shape) pass through the vibration tube 4 and are connected to a connector 9 arranged on the outer wall of the vibration tube 4; the vibration tube is grounded.

[0024] The probe 5 in the vibrating cylinder 4 is also covered with a driving coil 10, which is used to provide a magnetic field so that the probe maintains its own natural frequency.

[0025] A feedback coil 11 is also provided on the probe 5 below the driving coil 10 ; the driving coil 10 and the feedback coil 11 are separated by an insulating spacer 12 .

[0026] Magnets 13 are further provided on the outer wall of the vibration cylinder 4 at the positions of the drive coil 10 and the feedback coil 11 .

[0027] When icing occurs, probe 5 freezes, causing its natural frequency to change. This signal is transmitted to the controller via feedback coil 11, which then outputs an icing alarm. When de-icing is required, the controller powers the heater, which is then fed through connector 9 and generates heat to de-icer.

[0028] During the lightning test, a large instantaneous current hits the top of the probe. The large current is transmitted to the vibration cylinder 4 through the copper shell of the heater without passing through the probe shell, thereby preventing the probe shell from heating up and being damaged.

[0029] Heater structure improvement:

[0030] The present invention changes the material of the heater shell from stainless steel to copper. Figure 1The following is a diagram of the heater structure. The original heater shell is made of stainless steel. After replacing it with a copper shell, the outer diameter increases from 1.2mm to 1.5mm. After replacing the heater, silver solder is used to fill the gap where the vibration tube passes through by flame brazing to enhance its conductivity. After replacing the probe assembly, the installation method remains unchanged. Figure 3 shown.

[0031] Analysis of the reasons for the failure of the original ice detector test:

[0032] The pulse specific energy is known to be

[0033]

[0034] The cross section is

[0035] S=q=10.28×10 -6 m 2

[0036] Resistivity

[0037] ρ O =1.1×10 -6 Ωm

[0038] density

[0039] γ=8×10 3 Kg / m 3

[0040] Specific heat capacity

[0041] C w =460J / Kg / k

[0042] Take L = 2cm length probe shell for research

[0043] volume

[0044] v = S × L = 2.056 × 10 -7 m 3

[0045] quality

[0046] m=V×γ=1.6448×10 -3 kg

[0047] L = 2cm length probe shell resistance is

[0048]

[0049] According to actual measurements, the probe shell resistance of L = 2cm is R2 = 0.9mΩ

[0050] Thermal energy

[0051]

[0052]

[0053] Temperature rise

[0054]

[0055]

[0056] The result of the brief temperature rise calculation is 2379K, while the simulated temperature rise is about 2000K, which shows that the calculation formula has certain reference significance.

[0057] A simple calculation of the internal pressure of the probe shell at high temperature

[0058] ρV=nRT

[0059]

[0060] When T changes from T1=293.15K to T2=2273.15K, then

[0061] ρ2 / ρ2=T2 / T1=7.75

[0062] ρ2=785.26875kPa

[0063] According to the formula, when the temperature rise reaches 2000℃, without considering the vent hole, the internal air will expand to 7.75 times the original volume, that is, the inside of the probe shell will be subjected to 7.75 times the atmospheric pressure.

[0064] P=0.5ρV 2

[0065]

[0066] Assuming the time is 1ms, then

[0067] V=SV 流 T=8.28×10 -8 m 3

[0068] V 原 =2.7*2.7*3.14*20=45.78× 10-8 m 3

[0069] Then the internal atmospheric pressure after escaping through the aperture is approximately

[0070]

[0071] ρ3=766.017kPa

[0072] According to the pressure vessel calculation formula:

[0073]

[0074] In the formula

[0075] δ=1.1mm——cylinder thickness;

[0076] ρ C =ρ3=0.766017MPa——calculated pressure;

[0077] D i =5.4mm——inner diameter of cylinder;

[0078] ——weld joint coefficient;

[0079] σ T =2.26MPa

[0080] According to the allowable stress table of materials specified in the American ASME standard, nickel-based alloys have a maximum allowable pressure of only at 649°C, and the allowable pressure at 200°C is generally ≥100MPa, while at 649°C the allowable pressure is generally less than 5MPa. It can be inferred that when nickel-based alloys approach the melting point, they are far from being able to withstand the allowable pressure of 2.26MPa.

[0081] Failure conclusion:

[0082] The lightning test caused the probe shell to heat up too high, and the high temperature reduced the strength of the probe shell. At the same time, the high temperature caused the air inside the probe shell to expand rapidly. The probe shell is a semi-closed structure, causing the expanded air to squeeze and explode the probe shell, resulting in the test phenomenon of the probe shell exploding.

[0083] Improved status analysis:

[0084] The structure after adding copper wire was simulated and calculated: the cross-sectional area of ​​the probe shell is 10.28×10 -6 m 2 The outer diameter of the copper shell is 1.5 mm, the inner diameter is 0.9 mm, and the cross-sectional area is 2.26×10 -6 m 2 .

[0085] After adding the copper shell, a brief temperature rise calculation is performed on the probe shell and the copper shell.

[0086] Copper related parameters are

[0087] ρ 铜 =1.75×10 -8 Ωm(resistivity)

[0088] q 铜=2.26×10 -6 m 2 (cross-sectional area)

[0089] γ 铜 =8.96×10 3 kg / m 3 (density)

[0090] C w铜 =390J / Kgk (specific heat capacity)

[0091] V 铜 =S×L=0.45×10 -7 m 3 (volume)

[0092] m 铜 =V×γ=0.405×10 -3 Kg(mass)

[0093]

[0094] I 铜 =170.6kA (current)

[0095] Q 铜 =0.225×10 3 J (calories)

[0096]

[0097] 3J58 related parameters are

[0098] ρ 3I58 =1.1×10 -6 Ωm(resistivity)

[0099] q 3I58 =10.28×10 -6 m 2 (cross-sectional area)

[0100] γ 3I58 =8×10 3 Kg / m 3 (density)

[0101] C w3I58 =460J / Kg k (specific heat capacity)

[0102] R2=0.9mΩ(resistance)

[0103] I 3I58 =29.3kA (current)

[0104] Q 3I58 =0.038×10 3J (calories)

[0105]

[0106] Based on theoretical calculations, the current flowing through the copper wire is 170.6kA, resulting in a temperature rise of 1426.6K. The current flowing through the housing is 29.3kA, resulting in a temperature rise of 51.25K. At this temperature, according to the ASME standard for allowable stresses for materials, nickel-based alloys generally have an allowable stress ≥ 100MPa, meeting the requirement of an allowable stress > 2.26MPa. However, a temperature rise of 1426.6K exceeds the melting point of the copper wire, potentially damaging it during the test. Although the lightning test process is complex, current calculations and test results showing the housing can withstand a 100kA current indicate that the housing can withstand the residual current after the copper wire is damaged. After direct lightning effects testing, the copper housing was found to pass the 1A level direct lightning effects test.

[0107] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the scope disclosed in the present invention should be covered by the protection scope of the present invention.

Claims

1. A method for improving a heater for an ice detector, characterized in that: The outer shell of the heater (8) in the probe of the ice detector is made of a copper shell (1); when the connecting end of the heater passes through the vibration tube (4) of the ice detector, a silver solder is used to fill the passing gap (14) between the copper shell (1) and the vibration tube (4) to ensure the conductivity between the outer shell of the heater and the vibration tube.

2. The method for improving the heater for an ice detector according to claim 1, characterized in that: The copper shell is made of pure copper T1 or T2, with an inner diameter of 0.9 mm and an outer diameter of 1.5 mm.

3. A heater improved by the improvement method according to claim 1 or 2, characterized in that: The invention comprises a copper shell (1), the copper shell (1) is U-shaped as a whole, a heating wire (2) is provided inside the copper shell (1) along the axis, and an insulating material is filled between the heating wire (2) and the copper shell (1).

4. The heater according to claim 3, characterized in that The insulating material is magnesium oxide.

5. An ice detector using the heater according to claim 3 or 4, characterized in that: The invention comprises a base (3), wherein the base (3) is provided with a vibration tube (4) along the axial direction, a probe (5) is provided in the vibration tube (4), the top end of the probe (5) passes through the vibration tube (4) and the base (3) in sequence and then extends out, a spring (6) is provided at the bottom end of the probe (5), and the bottom end of the spring (6) is limited by a pressure plate (7) arranged at the bottom of the vibration tube (4); a heater (8) is provided in the probe (5), and the connecting ends (15) at both ends of the heater (8) pass through the vibration tube (4) and are connected to a connector (9) arranged on the outer wall of the vibration tube (4); the vibration tube is grounded.

6. The ice detector according to claim 5, characterized in that: A driving coil (10) is also sleeved on the probe (5) in the vibrating cylinder (4).

7. The ice detector according to claim 6, characterized in that: A feedback coil (11) is also sleeved on the probe (5) below the driving coil (10); the driving coil (10) and the feedback coil (11) are separated by an insulating gasket (12).

8. The ice detector according to claim 7, characterized in that: A magnet (13) is also provided on the outer wall of the vibration cylinder (4) at the positions of the drive coil (10) and the feedback coil (11).

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