CN109638652B - Method for improving strength of insulator at discharge end of ignition nozzle of aero-engine - Google Patents
Method for improving strength of insulator at discharge end of ignition nozzle of aero-engine Download PDFInfo
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- CN109638652B CN109638652B CN201811461357.4A CN201811461357A CN109638652B CN 109638652 B CN109638652 B CN 109638652B CN 201811461357 A CN201811461357 A CN 201811461357A CN 109638652 B CN109638652 B CN 109638652B
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- insulator
- central electrode
- discharge end
- conical surface
- electric nozzle
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01T—SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES
- H01T13/00—Sparking plugs
- H01T13/20—Sparking plugs characterised by features of the electrodes or insulation
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
- F02C7/00—Features, components parts, details or accessories, not provided for in, or of interest apart form groups F02C1/00 - F02C6/00; Air intakes for jet-propulsion plants
- F02C7/26—Starting; Ignition
- F02C7/264—Ignition
- F02C7/266—Electric
Abstract
The invention provides a method for improving the strength of an insulator at a discharge end of an ignition nozzle of an aircraft engine, which keeps the total length of the insulator and a central electrode unchanged, changes the size of a part of the insulator and the size of a part of the central electrode, and realizes that the conical surface matching of the central electrode and the insulator is changed into the straight surface matching; for the insulator, the discharge end of the insulator is changed into a straight surface from a conical surface, the wall thickness of the end part is increased by 0.5mm, and the size of an inner hole of the discharge end is
The end part is chamfered by 60 degrees, and the axial length of the end part chamfer is 0.5 mm; a straight platform is added on the outer circle of the insulator, so that the bottom surface of the shell cannot be completely back-gouged to prevent point contact; for the central electrode, the discharge end of the central electrode is changed into a straight surface from a conical surface, and the diameter of the discharge end of the central electrode
The invention keeps the characteristics of centralized ignition and high efficiency of the concave structure, reduces the stress of the discharge end part of the insulator, meets the use requirement of adapting to the engine environment and provides a main ignition electric nozzle with high reliability for the engine.
Description
Technical Field
The invention belongs to the field of aviation and aerospace engine ignition, and particularly relates to a method for improving the strength of an insulator at a discharge end of an ignition nozzle of an aero-engine.
Background
At present, in the process of engine test run, an ignition electric nozzle of a certain aeroengine has insulator crack faults at a plurality of discharge ends, and cannot meet the use requirements of the engine in environments such as high temperature, vibration and the like.
The ignition electric nozzle adopts a concave structure, namely a central electrode and an insulator are in a conical surface matching mode (figure 1). In the process of high-temperature cold recovery along with an engine, because the axial shrinkage of the metal central electrode is greater than that of the ceramic insulator, the outer cone of the central electrode generates axial pressure on the inner cone surface of the insulator, and when the concentrated stress exceeds the yield stress of the insulator material, the end surface of the insulator is cracked.
Disclosure of Invention
In order to solve the problem that the existing ignition nozzle is easy to have insulator cracks at the discharge end, the invention provides a method for improving the strength of an insulator at the discharge end of the ignition nozzle of an aero-engine, which keeps the characteristics of centralized ignition and high efficiency of a concave structure, reduces the stress of the discharge end part of the insulator, meets the use requirement of adapting to the environment of the engine, and provides a main ignition nozzle with high reliability for the engine.
The technical scheme of the invention is as follows:
the method for improving the strength of the insulator at the discharge end of the ignition nozzle of the aircraft engine is characterized by comprising the following steps of: the total length of the insulator and the central electrode is kept unchanged, the size of the insulator part and the size of the central electrode part are changed, and the conical surface matching of the central electrode and the insulator is changed into straight surface matching;
for the insulator, the discharge end of the insulator is changed into a straight surface from a conical surface, the wall thickness of the end part is increased by 0.5mm, and the size of an inner hole of the discharge end is
The end part is chamfered by 60 degrees, and the axial length of the end part chamfer is 0.5 mm; a straight platform is added on the outer circle of the insulator, so that the bottom surface of the shell cannot be completely back-gouged to prevent point contact;
for the central electrode, the discharge end of the central electrode is changed into a straight surface from a conical surface, and the diameter of the discharge end of the central electrode
Advantageous effects
The invention improves the size of the insulator part and the size of the central electrode part of the ignition nozzle of the aero-engine, maintains the characteristics of centralized ignition and high efficiency of the concave structure, reduces the stress of the discharge end part of the insulator, meets the use requirement of adapting to the environment of the engine, and provides the main ignition nozzle with high reliability for the engine.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1: the structure of the existing discharge end;
FIG. 2: the using state structure diagram of the electric nozzle on the engine;
FIG. 3: the using state of the electric nozzle on the engine is analyzed;
FIG. 4: the non-working state of the electric nozzle uses scene description;
FIG. 5: a schematic diagram of the stress of the cold-back shrinkage;
FIG. 6: comparing the improved structure of the discharge end before and after; (a) modifying the front structure, (b) modifying the rear structure;
FIG. 7: BDZ-47A main ignition nozzle insulator improvement front and back comparison graphs; (a) modifying the front insulator, (b) modifying the rear insulator;
FIG. 8: a comparison diagram before and after the central electrode of the BDZ-47A main ignition nozzle is improved; (a) a modified front center electrode, (b) a modified rear center electrode;
Detailed Description
The following detailed description of embodiments of the invention is intended to be illustrative, and not to be construed as limiting the invention.
In the embodiment, the insulator material and the use environment scene are analyzed, the stress of the insulator is theoretically calculated, an improvement scheme is determined, and simulation verification is performed.
1. Insulator material analysis
The insulator material is GLC-58 alumina ceramic and Al2O3As a main component, Al2O3The content is more than 95 percent, other metal oxide components used as additives are added, and the mixture is prepared by calcining, ball milling, sieving, plasticizing, molding, ageing, biscuit firing, roasting and performance test processing after being uniformly mixed according to a certain proportion. The sintering temperature is 1650-1700 ℃.
The ceramic material belongs to brittle material, the fracture of the brittle material has no yield stage and ultimate stress sigmabIs the only index for measuring the strength. For brittle materials, the part is subjected to a stress exceeding the ultimate stress σ of the materialbCracks are generated.
2. Usage environment scenario analysis
The use scene of the electric nozzle on the engine is analyzed, the main ignition electric nozzle is in threaded connection with an outer casing of a combustion chamber casing, the threaded connection part bears mechanical impact such as vibration, impact and acceleration transmitted by the engine, a discharge end extends into an outer ring cylinder of the flame tube by 0-1 mm, the electric nozzle floating sleeve is in floating connection with the flame tube, the floating gap is 1.5mm, and the electric nozzle is not stressed in a hot state. The flame tube outer ring tube body where the electric nozzle is located adopts slot air film and multi-inclined hole diffusion cooling, and the highest temperature of the flame tube body at the electric nozzle is about 1000 ℃ when the flame tube body works. The electric nozzle seat on the flame tube at the electric nozzle mounting position is arranged at three positions right facing the airflow direction
The small holes are used for reinforcing the cooling air film covering of the discharge end of the electric nozzle, so that the electric nozzle does not bear mechanical force caused by thermal expansion in the installation and use process (the visual inspection result of the fault electric nozzle close to the discharge end has no abnormal abrasion). The maximum temperature is equivalent to the maximum wall temperature of the flame tube cylinder body under the influence of mechanical impact such as vibration, impact, acceleration and the like transmitted by the engine and thermal load.
After ignition is finished, the main ignition nozzle is in a non-working state and is in threaded connection with the combustion chamber casing through the mounting seat, and in the working process of an engine, the main ignition nozzle can be continuously influenced by mechanical impact such as vibration, impact and acceleration of the engine and thermal load, and meanwhile, the discharge end is cooled under airflow.
The root of the electric nozzle is arranged on an electric nozzle mounting seat of a casing of an engine combustion chamber, the discharge end of the electric nozzle is connected with the flame tube in a floating mode through a floating sleeve, and the discharge end and the floating sleeve are in small clearance fit. When the main ignition electric nozzle is installed on an engine, mechanical impact such as vibration, impact and acceleration transmitted by the engine is borne by the installation thread structure of the electric nozzle, the electric nozzle is of a cantilever type installation structure, the discharge end is free to expand and is not stressed, extra shearing force cannot be caused, meanwhile, the electric nozzle adopts an integral sealing structure, and the electric nozzle is integrally affected by mechanical impact such as vibration, impact and acceleration, so that the head of an insulator cannot be subjected to overstress to cause cracks of the insulator.
3. Stress calculation
3.1 high temperature thermal expansion stress
The center electrode and the shell expand in both the axial and radial directions in a thermal environment. According to the technical protocol requirements of the BDZ-47A electric nozzle, the highest temperature of the ignition end of the electric nozzle is 1000 ℃, the central electrode material is GH3044, and the linear expansion coefficient of the GH3044 material is 16.28 multiplied by 10 (20 ℃ -1000 ℃) at the working temperature of 1000 DEG C-6℃-1The insulator material is GLC-58 with linear expansion coefficient of 8.5 × 10 (20-1000 deg.C)-6℃-1Thus, therefore, it is
Axial elongation Δ L of center electrode1＝L1αΔt＝8.9×16.28×10-6×980＝0.14mm
Axial elongation Δ L of insulator2＝L2αΔt＝8.9×8.5×10-6×980＝0.074mm
The axial elongation Δ L3 ═ L3 α Δ t ═ 18.9 × 16.28 × 10 of the housing-6×980＝0.3mm
L1＝L28.9mm is the distance from the bottom end face of the gasket to the end face of the central electrode
L318.9mm is the length from the threaded part to the end part of the shell
The axial elongation of the top end of the central electrode and the axial elongation of the shell are larger than the axial elongation of the insulator under the environment of 1000 ℃, and no axial pressure is formed on the insulator.
The diameter of the center electrode after thermal expansion is d1+Δd1＝d1αΔt＝4.3+4.3×16.28×10-6×980＝4.368mm
The diameter of the insulator is 4.4+4.4 multiplied by 7 multiplied by 10 after thermal expansion-6×980＝4.43mm
It can be seen that the center electrode does not generate thermal expansion compressive stress to the inner wall of the conical surface of the insulator when the electric nozzle is at high temperature.
3.2 stress of cold-recovery shrinkage
The specific heat of the metal part is much smaller than that of the insulator part, the specific heat of the high-temperature alloy is 440J/(Kg ℃), the specific heat of the ceramic insulator is about 850J/(Kg ℃), the central electrode and the shell are quickly cooled back to 500 ℃ in the air flow cooling process in the non-working state, the insulator is only reduced to 800 ℃, and the linear expansion coefficient of the GH3044 material is 13.31 multiplied by 10 when the working temperature is 500 ℃ (20 ℃ -500 ℃), and the linear expansion coefficient of the GH3044 material is 13.31 multiplied by 10-6℃-1The insulator material is GLC-58, and its linear expansion coefficient is 8.5X 10 (20-800 deg.C)-6℃-1Thus, therefore, it is
Axial elongation Δ L of center electrode1＝L1αΔt＝8.9×13.31×10-6×480＝0.05mm
Axial elongation Δ L of insulator2＝L2αΔt＝8.9×8.5×10-6×780＝0.059mm
Axial elongation Δ L of housing3＝L3αΔt＝18.9×13.31×10-6×480＝0.12mm
L1＝L28.9mm is the distance from the bottom end face of the gasket to the end face of the central electrode
L318.9mm is the length from the threaded part to the end part of the shell
It can be seen that when the electric nozzle contracts after high-temperature cooling, the contraction quantity of the central electrode is greater than the axial extension quantity of the insulator, and the conical surface of the central electrode is contacted with the inner wall of the conical surface of the insulator to generate axial pressure.
3.3 Experimental validation
In order to verify the influence of the stress of the insulator on the insulator during the cold-back shrinkage of the central electrode, the following high-temperature cold-back test is carried out: placing 2 discharge end components in a high-temperature furnace at 1000 ℃ for 15min, taking out the components from the high-temperature furnace, blowing the insulator by using compressed air until the insulator is cooled, and inspecting the end face of the insulator after the cooling, wherein 2 cracks appear in 1 component, and 3 cracks appear in the other 1 component.
In order to further verify the influence of the acting force in the insulator of the product, 5 insulators are placed in a high-temperature furnace at 1000 ℃ for 15min, the parts are taken out of the high-temperature furnace, the insulators are blown by compressed air until the insulators are cooled, and after the cooling, the end faces of the insulators are inspected, so that the insulators have no cracks.
4. Design of new structure
4.1 determination protocol
Through the analysis, the end part of the insulator end part crack is caused by the compressive stress of the central electrode to the conical surface and the spark impact force, in order to eliminate the compressive stress of the central electrode to the conical surface of the insulator, the scheme that the conical surface matching of the central electrode and the insulator is changed into the straight surface matching is adopted, and in order to improve the spark impact resistance of the insulator, the scheme that the end surface thickness of the insulator is increased, so that the strength of the insulator is increased is adopted, as shown in fig. 6.
In order to change the conical surface fit of the central electrode and the insulator into the straight surface fit, the sizes of the insulator part and the central electrode part need to be improved. The total length of the insulator and the center electrode is not changed, the taper angle of the connecting end of the insulator and the copper bush is not changed, and only the taper angle size of the discharge end is improved, as shown in fig. 7 and 8.
TABLE 1BDZ-47A comparison of primary ignition nozzle insulator dimensions
TABLE 2BDZ-47A comparison of center electrode sizes for main firing tips
5. Simulation verification
The stress simulation is carried out on the product before and after the design is improved, and the simulation result shows that the acting force exists on the conical surfaces of the central electrode and the insulator in the product before the design is improved, the acting force does not exist after the design is improved, and the stress distribution of the end surface of the insulator is obviously improved before the improvement.
To verify the improved strength of the structural insulator of the present invention, the following test verifications were performed:
1. part strength verification
The insulator parts were machined to the dimensions after the modification and subjected to a bending strength test, which was superior in strength to the insulator before the modification, as compared with the insulator before the modification. The test results are as follows:
TABLE 3 insulation improvement front and rear bending strength comparison
| Test piece 1 | Test piece 2 | Test piece 3 | Test piece 4 | Test piece 5 | |
| Original structure insulator | 1.86kN | 1.94kN | 1.90kN | 2.15kN | 2.2kN |
| New structure insulator | 4.22kN | 4.06kN | 4.08kN | 4.34kN | 4.27kN |
2. Electric nozzle product performance verification
2 with the structure processing test spare after the improvement, after the assembly, the test spare carries out the performance contrast with S1501010# electric nozzle, and the performance is equivalent, and the homoenergetic satisfies technical agreement' S requirement, specifically as follows:
TABLE 4 comparison of product Performance parameters before and after improvement
3. Electric nozzle use environment verification
The improved structure is verified by environment tests such as a high-temperature cold-back test, an oil dripping life test, a high-temperature life test, a vibration test, a low-temperature test, a temperature impact test and the like, and the insulator at the discharge end of the electric nozzle has no crack.
From the above results, it can be seen that the present invention achieves the objects of the invention.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made in the above embodiments by those of ordinary skill in the art without departing from the principle and spirit of the present invention.
Claims (1)
1. A method for improving the strength of an insulator at a discharge end of an ignition nozzle of an aircraft engine is characterized in that: the insulator material of the electric nozzle adopts GLC-58 alumina ceramic, and the central electrode material adopts GH3044 alloy; the discharge end of the insulator before improvement has a cone angle of 40 degrees, an axial length of 3mm and a bottom inner hole size
The discharge end of the central electrode is a conical surface with a cone angle of 40 degrees;
the method comprises the following steps:
step 1: the material of the insulator is analyzed and,determining that the insulator material is brittle, when the insulator is stressed beyond the limit stress sigmabCracking is generated;
step 2: analyzing the scene of the using environment of the electric nozzle, and determining that the electric nozzle does not bear mechanical force caused by thermal expansion in the using process of the installation machine, and the electric nozzle is not subjected to mechanical impact action of vibration, impact and acceleration to the whole body so as not to generate overstress on the head of the insulator to cause insulator cracks;
and step 3: according to the highest temperature of the ignition end of the electric nozzle, the expansion of the central electrode and the shell in the axial direction and the radial direction under a thermal environment is calculated, and the fact that the central electrode does not generate thermal expansion pressure stress on the inner wall of the conical surface of the insulator when the electric nozzle is at the high temperature is determined;
and 4, step 4: after the electric nozzle is cooled and shrunk at high temperature, the elongation of the central electrode is smaller than the axial elongation of the insulator, and the fact that the conical surface of the central electrode is in contact with the inner wall of the conical surface of the insulator is determined to generate axial pressure;
and 5: it was determined that the insulator end cracking was due to the insulator end being subjected to compressive stress and spark impact of the center electrode against the conical surface, and that the improvement was designed to:
for the insulator, the total length of the insulator is kept unchanged, the taper angle of the connecting end of the insulator and the copper bush is kept unchanged at 14 degrees, the discharge end of the insulator is changed into a straight surface from a taper surface, the wall thickness of the end is increased by 0.5mm, and the size of the inner hole of the discharge end of the improved insulator is equal to
The end part is chamfered by 60 degrees, and the axial length of the end part chamfer is 0.5 mm; a straight platform is added on the outer circle of the insulator, so that the bottom surface of the shell cannot be completely back-gouged to prevent point contact;
for the central electrode, the total length of the central electrode is kept unchanged, the discharge end of the central electrode is changed into a straight surface from a conical surface, and the diameter of the discharge end of the central electrode
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| CN111271204B (en) * | 2019-11-15 | 2022-03-29 | 陕西航空电气有限责任公司 | High-temperature test method for boosting ignition electric nozzle of aircraft engine |
| CN112736649A (en) * | 2020-12-18 | 2021-04-30 | 陕西航空电气有限责任公司 | Ignition electric nozzle with high-voltage insulator |
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| CN204143971U (en) * | 2014-09-17 | 2015-02-04 | 陕西航空电气有限责任公司 | Along face ignition electric nozzle ceramic insulator |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5406249B2 (en) * | 2011-07-06 | 2014-02-05 | 日本特殊陶業株式会社 | Igniter plug and igniter plug manufacturing method |
| JP6666371B2 (en) * | 2017-10-11 | 2020-03-13 | 日本特殊陶業株式会社 | Spark plug |
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Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5367871A (en) * | 1992-07-27 | 1994-11-29 | General Electric Company | Aircraft engine ignition system |
| CN204143971U (en) * | 2014-09-17 | 2015-02-04 | 陕西航空电气有限责任公司 | Along face ignition electric nozzle ceramic insulator |
| CN204253189U (en) * | 2014-11-26 | 2015-04-08 | 陕西航空电气有限责任公司 | Macro-energy long-life semiconductor discharge plug discharge end structure |
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| CN205120317U (en) * | 2015-11-16 | 2016-03-30 | 陕西航空电气有限责任公司 | Electric nozzle air -tight test frock |
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