CN105224713A - A kind of derated design method of aeromotor intershaft bearing - Google Patents

A kind of derated design method of aeromotor intershaft bearing Download PDF

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CN105224713A
CN105224713A CN201510458891.XA CN201510458891A CN105224713A CN 105224713 A CN105224713 A CN 105224713A CN 201510458891 A CN201510458891 A CN 201510458891A CN 105224713 A CN105224713 A CN 105224713A
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fan blade
intershaft bearing
frequency
check
boundary line
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CN105224713B (en
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王俨剀
廖明夫
王四季
杨伸记
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Northwestern Polytechnical University
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    • Y02T10/82—Elements for improving aerodynamics

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Abstract

A kind of derated design method of aeromotor intershaft bearing, propose and make intershaft bearing from synchronous principle of impacting, in the working range of aeromotor from slow train rotating speed-maximum (top) speed, choose N number of rotating speed point, determine the defect characteristic octave frequency of intershaft bearing inner ring and the defect characteristic octave frequency of outer shroud under each rotating speed.Mark the lobe numbers of fan.Check fan blade number and integral multiple thereof whether with the defect characteristic octave frequency of inner ring and outer shroud the defect characteristic octave frequency at a distance of within 2%.If the rotating speed interval meeting this condition exceedes 10% of engine operating speed range, then adjust lobe numbers or high/low pressure rotor speed ratio, ensure in the engine operating speed range more than 90%, fan blade number and integral multiple thereof differ more than 2% with intershaft bearing inner ring and outer shroud the defect characteristic octave frequency, present invention effectively prevents intershaft bearing and occur synchronous impact.

Description

A kind of derated design method of aeromotor intershaft bearing
Technical field
The present invention relates to aeromotor Structural Dynamic Design field, specifically a kind of off-load method of aeromotor intershaft bearing.
Background technology
Intershaft bearing is load crucial in birotor aeromotor and drive disk assembly.Its outer shroud is arranged on High Pressure Turbine Rotor, and inner ring is arranged on Low Pressure Turbine Rotor; Or contrary, outer shroud is arranged on Low Pressure Turbine Rotor, and inner ring is arranged on High Pressure Turbine Rotor.Therefore, intershaft bearing inner and outer ring rotates simultaneously.Intershaft bearing works in high temperature, alternate load, the environment that not easily lubricates, easily breaks down, once break down the safe operation of serious threat engine, and the dynamic loading reducing intershaft bearing is the effective way reducing rate of breakdown.
For micro-damage point P in the intershaft bearing inner ring in Fig. 1, it often contacts a roller, is subject to one-shot, is f with the frequency of impact of Z roller p.Fig. 2 is the impulsive force schematic diagram of rolling body to inner ring.
Be arranged on low pressure rotor with inner ring, outer shroud is arranged on high pressure rotor, and two rotor rotating Vortex schemes are example, and for the intershaft bearing of Z rolling body, rolling body is respectively with the frequency point P in inner ring, outer shroud being put Q contact:
f P = 1 2 × 2 π | Ω H - Ω L | ( 1 + d D m c o s α ) z - - - ( 1 )
f Q = 1 2 × 2 π | Ω H - Ω L | ( 1 - d D m c o s α ) z - - - ( 2 )
In formula:
Ω h, Ω lthe angular velocity of rotation of high pressure rotor, low pressure rotor.
D rolling body diameter;
D mbearing pitch diameter;
α contact angle, center, abutment face and the angle between the rolling body line of centres and bearing sagittal plane.
As can be seen from the above equation: for single rotor system, due to outer shroud rotating speed Ω h=0, and general is not integer, therefore bearing inner ring characteristic frequency f p, outer shroud characteristic frequency f qcan not be equal with the frequency of rotor multiple frequency periodical exciting force.But for having the birotary engine of intershaft bearing, according to engine performance requirement, high pressure rotating speed Ω hwith low pressure rotating speed Ω lin in a big way change, completely likely make intershaft bearing inner ring characteristic frequency or outer shroud characteristic frequency equal with rotor excitation force frequency or close.
In the birotary engine course of work, the periodical exciting force of the periodical exciting force or low pressure rotor that act on high pressure rotor be intershaft bearing bear the main source of dynamic loading.When micro-damage point P a certain on raceway contacts with bearing roller, be also subject to the percussive action rotating exciting force, the dynamic loading of P point is rolling body impulsive force and rotates superposing of exciting force simultaneously.
Fig. 3 acts on epitrochanterian exciting force F interthe dynamic loading that raceway is formed.When roller IV, roller III and roller II roll across successively and inner ring put P, the load change that P point is subject to as shown in the figure.Wherein, Fig. 3 (a) is the dynamic loading under excitation force frequency and the unequal condition of inner ring characteristic frequency, and Fig. 3 (b) is the dynamic loading under excitation force frequency condition equal to inner ring characteristic frequency.τ in figure fthe cycle rotating exciting force, τ pit is the cycle of roller to inner ring impulsive force.
Can find out, the load that raceway bears is made up of two parts: rolling body impulsive force and rotation exciting force.Rotate excitation force frequency and inner ring characteristic frequency unequal time, the impulsive force that P point is subject to can not be always rolling body impulsive force and rotation exciting force width sum; But when rotation exciting force and rolling body impulsive force are with the same phase time of frequency, the impulsive force that some P is subject to is rolling body impulsive force and rotation exciting force width sum, and continuingly acts on P point.This phenomenon is referred to as synchronous impact.Under synchronous percussive action, the dynamic loading that intershaft bearing is subject to increases, and is easy to the local damage causing raceway, reduces the life-span of intershaft bearing.
Above-mentioned for inner ring, describe synchronous impact phenomenon.When rotating excitation force frequency and being equal with outer shroud characteristic frequency, also can obtain similar result, outer shroud be put Q and will be subject to synchronous impact.
For birotary engine, fan blade will produce periodic gas exciting force, and its frequency is fan blade number integral multiple and low pressure rotating speed Ω lproduct.The high/low pressure rotor speed of engine changes than according to engine performance control rate, intershaft bearing inner ring or outer shroud the defect characteristic octave frequency can be made within the specific limits to equal or close to fan blade number, fan blade will produce the frequency rotation exciting force equal with intershaft bearing inner ring or outer shroud characteristic frequency, this power superposes with the impulsive force of rolling body, will cause the synchronous impact of agency bearing.
For the ease of derated design, the characteristic frequency of intershaft bearing inner ring and the characteristic frequency of outer shroud are rewritten into the form of low pressure rotating speed multiple, i.e. inner and outer rings the defect characteristic octave frequency number.Formula (1) and formula (2) become:
X P = 1 2 · | Ω H Ω L - 1 | · ( 1 + d D m c o s α ) z - - - ( 3 )
X Q = 1 2 · | Ω H Ω L - 1 | · ( 1 - d D m c o s α ) z - - - ( 4 )
In formula (3) and (4), comprise high/low pressure rotor speed ratio during the change of high-low pressure rotating ratio, inner ring the defect characteristic octave frequency number X pwith outer shroud the defect characteristic octave frequency number X qchange thereupon.
In the past in design, generally do not consider rotor exciting force agency bearing bear the impact of dynamic loading.But for birotary engine, if fan blade number equals or close to intershaft bearing inner ring or outer shroud the defect characteristic octave frequency time, fan blade will produce the frequency rotation exciting force equal with intershaft bearing inner ring or outer shroud characteristic frequency.Now, the impulsive force that raceway bears is rolling body impulsive force and the power width sum rotating exciting force.The impulsive force acted on micro-damage point increases, and continues the effect being subject to impulsive force, makes damage aggravation, reduces the life-span of intershaft bearing thus.For this problem, the present invention proposes a kind of method of aeromotor intershaft bearing derated design.
At " aviation power journal " ISSN:1000-8055, " fault signature of aeromotor intershaft bearing and diagnostic method " literary composition that the 28th volume the 12nd periodical in 2013 is stepped on, establishes the method for diagnosis aeromotor intershaft bearing fault.Establish the method for diagnosis aeromotor intershaft bearing fault.Utilize the slip of engine high and low pressure as trigger pip, collection such as slip cycle such as grade is carried out to engine luggine signal, and in slip territory, frequency spectrum and envelope spectrum analysis is carried out to vibration signal.Utilize intershaft bearing failure response in " permanent spacing " characteristic sum " constant frequency " feature in slip territory, identification intershaft bearing local fault.But it does not relate to the method for designing how reducing intershaft bearing dynamic loading.
Chinese invention patent CN200910109202.9, a kind of method for testing service life of rolling bearings, has invented a kind of method of rolling bearing aging test, under equivalent stress level, implements strenuous test and the Fast Evaluation of rolling bearing life and reliability.But do not provide feature and the derated design method of test bearing component stress.
Chinese invention patent CN201410146849.X, a kind of method for designing of aeroengine rotor Structural Dynamics, by optimizing the parameter of rotor and supporting, when making the hot-die state of rotor-support-foundation system avoid supporting absolute rigidity, the mode of rotor, makes rotor-support-foundation system under hot-die state, meet the requirement of vibration standard.Its core ensures that rotor is in the whole operating rotational speed range of engine, all can smooth working.But optimal design object is rotor-support-foundation system, does not relate to intershaft bearing.
Russ P RU2110781 (C1) " METHODOFFORECASTINGOFMECHANICALCONDITIONOFINTERSHAFTANTI FRICTIONBEARINGINTWIN-SHAFTTURBOMACHINE " describes one sensor installation on birotary engine intershaft bearing, and judges the method for intershaft bearing state according to vibration signal.But it does not relate to the method for designing how reducing intershaft bearing dynamic loading.
United States Patent (USP) 20120070278 " GASTURBINEENGINEBEARINGARRANGEMENT ", describe a kind of reverse rotation rotor structure using intershaft bearing, a rotor-support-foundation system has rotor and stator structure, and another rotor-support-foundation system only has rotating part.Try hard to, by the retainer rotating speed of structural design control intershaft bearing, reduce the load of intershaft bearing, increase the serviceable life of bearing.It for two rotor reverse rotation rotor structures, can only can not be applicable to homodromal situation.
Summary of the invention
In operation process, there is synchronous problem of impacting for overcoming aeromotor intershaft bearing in prior art, to reduce intershaft bearing failure rate, the present invention proposes a kind of derated design method of aeromotor intershaft bearing.
Detailed process of the present invention is:
Step one, determine the rotating ratio of birotary engine mesohigh rotor and low pressure rotor.
Step 2, determine intershaft bearing inner ring characteristic frequency and outer shroud characteristic frequency.
Step 3, determine the defect characteristic octave frequency of intershaft bearing.
Step 4, the synchronous impact of drafting check figure.
Relation between the inner ring the defect characteristic octave frequency of fan blade number and intershaft bearing and outer shroud the defect characteristic octave frequency is showed by the mode of figure by described synchronous impact check figure, provides foundation for checking synchronous impact, and this figure is called and synchronously impacts check figure.
Check in figure in described synchronous impact, when intermediary's bearing roller is close with fan blade excitation force frequency to the impact force frequency of inner race, the two superposition is in inner race; When intermediary's bearing roller is close with fan blade excitation force frequency to the impact force frequency of outer-race ball track, the two superposition is in outer-race ball track.
The detailed process of drawing described synchronous impact check figure is:
I by the rule X of inner ring the defect characteristic octave frequency with rotation speed change inner, ibe plotted in synchronous impact on check figure, synchronously impacted the inner ring the defect characteristic octave frequency X in check figure inner, icurve.
II draws inner ring the defect characteristic octave frequency number X inner+ 2%X innerand X inner-2%X innerboundary line, synchronously impacted the X in check figure respectively inner+ 2%X innerboundary line and X inner-2%X innerboundary line.
III by the rule X of outer shroud the defect characteristic octave frequency with rotation speed change outerbe plotted in synchronous impact on check figure, synchronously impacted the outer shroud the defect characteristic octave frequency X in check figure outercurve.
IV draws outer shroud the defect characteristic octave frequency number X outer+ 2%X outerand X outer-2%X outerboundary line, synchronously impacted the X in check figure respectively outer+ 2%X outerboundary line and X outer-2%X outerboundary line.
V by 2 multiple F of fan blade number at different levels and this fan blade number at different levels bk, jbe marked on synchronous impact on check figure successively, obtain the straight line that a group shows fan blade numbers at different levels.
Dynamic loading state suffered by step 5, check intershaft bearing, avoids synchronous impact occurs.
Figure is checked, if any straight line showed in the straight line of fan blade number at different levels is in X according to synchronous impact inner+ 2%X innerboundary line and X inner-2%X innerbetween boundary line; Or any straight line showed in the straight line of fan blade number at different levels is in X outer+ 2%X outerboundary line and X outer-2%X outerbetween boundary line, then show intershaft bearing inner ring characteristic frequency or outer shroud characteristic frequency close with fan blade excitation force frequency, now may there is synchronous impact phenomenon in intershaft bearing.
When occurring synchronously to impact, the load that intershaft bearing inner race is subject to or the load that outer-race ball track is subject to are rolling body impulsive force and fan blade exciting force width sum.Under now intershaft bearing is in severe loaded-up condition, forbid long-term work in this case.
If there is the straight line of described performance fan blade number at different levels to be in by X inner+ 2%X innerboundary line and X inner-2%X innerin the hazardous location that boundary line is formed, and when exceeding 10% of engine operating speed range shown in horizontal ordinate; Or any straight line in the straight line of described performance fan blade at different levels number is in by X outer+ 2%X outerboundary line and X outer-2%X outerin the hazardous location that boundary line is formed, and when exceeding 10% of engine operating speed range, then necessary adjust design parameters, reduces the dynamic loading that intershaft bearing bears.
The dynamic loading that step 6, reduction intershaft bearing bear.Described reduction dynamic loading that intershaft bearing bears is by heightening or turn down high/low pressure rotor speed ratio, to reduce the dynamic loading that intershaft bearing inner race and outer shroud bear.
When reducing the dynamic loading that intershaft bearing inner race bears:
Check in figure, by X in the synchronous impact of drawing inner+ 2%X innerboundary line and X innerit is D that curve forms region 1, by X inner-2%X innerboundary line 4 and X innerit is D that curve forms region 2.
When the straight line of described performance fan blade number at different levels is in D 1length in inherent X-coordinate is greater than and is in D 2during length in inherent X-coordinate, high/low pressure rotor speed ratio need be turned down.Specifically, former high/low pressure rotor speed is progressively turned down than the step-length with 0.1%, until the straight line of described performance fan blade at different levels number is positioned at outside described hazardous location, and makes non hazardous areas be greater than 90% of engine operating speed range shown in horizontal ordinate.
When the straight line of described performance fan blade number at different levels is in D 1length in inherent X-coordinate is less than and is in D 2during length in inherent X-coordinate, high/low pressure rotor speed ratio need be heightened.Specifically, former high/low pressure rotor speed is progressively heightened than the step-length with 0.1%, until the straight line of described performance fan blade at different levels number is positioned at outside described hazardous location, and makes non hazardous areas be greater than 90% of engine operating speed range shown in horizontal ordinate.
When reducing the dynamic loading that intershaft bearing outer-race ball track bears:
Check in figure, by X in the synchronous impact of drawing outer+ 2%X outerboundary line and X outerit is D that curve forms region 3, by X outer-2%X outerboundary line and X outerit is D that curve forms region 4.
When the straight line of described performance fan blade number at different levels is in D 3length in inherent X-coordinate is greater than and is in D 4during length in inherent X-coordinate, high/low pressure rotor speed ratio need be turned down.Specifically, former high/low pressure rotor speed is progressively turned down than the step-length with 0.1%, until the straight line of described performance fan blade at different levels number is positioned at outside described hazardous location, and makes non hazardous areas be greater than 90% of engine operating speed range shown in horizontal ordinate.
When the straight line of described performance fan blade number at different levels is in D 3length in inherent X-coordinate is less than and is in D 4during length in inherent X-coordinate, high/low pressure rotor speed ratio need be heightened.Specifically, former high/low pressure rotor speed is progressively heightened than the step-length with 0.1%, until the straight line of described performance fan blade at different levels number is positioned at outside described hazardous location, and makes non hazardous areas be greater than 90% of engine operating speed range shown in horizontal ordinate.
So far, complete the adjustment to the high/low pressure rotor speed ratio of engine, avoid intershaft bearing and occur synchronous impact.
The present invention proposes and make intershaft bearing from synchronous principle of impacting, that is: the situation that intershaft bearing inner ring the defect characteristic octave frequency, outer shroud the defect characteristic octave frequency approach in the scope of 2% with fan blade number and integral multiple thereof is hazardous location, forbids that engine is in this region long-term work.
The present invention proposes and avoid intershaft bearing to be subject to synchronous method for designing of impacting.Fig. 4 is the process flow diagram of the method for designing that the present invention proposes.First in the working range of aeromotor from slow train rotating speed-maximum (top) speed, choose N number of rotating speed point, determine the defect characteristic octave frequency of intershaft bearing inner ring and the defect characteristic octave frequency of outer shroud under each rotating speed; Then the lobe numbers of fan is marked; Check fan blade number and integral multiple thereof whether with the defect characteristic octave frequency of inner ring and outer shroud the defect characteristic octave frequency at a distance of within 2%.If the rotating speed interval meeting this condition exceedes 10% of engine operating speed range, then adjust lobe numbers or high/low pressure rotor speed ratio, ensure in the engine operating speed range more than 90%, fan blade number and integral multiple thereof differ more than 2% with intershaft bearing inner ring and outer shroud the defect characteristic octave frequency.
The invention allows for and a kind ofly check the whether close graphic technique of fan blade number and integral multiple thereof and intershaft bearing inner ring the defect characteristic octave frequency and outer shroud the defect characteristic octave frequency, this figure is called and synchronously impacts check figure.In figure, horizontal ordinate is engine speed conditions, and coordinate range at least comprises from slow train to maximum rating, and unit is absolute rotating speed (r/min) or number percent rotating speed (%).Ordinate unit is frequency multiplication (X).Go out fan blade number at figure subscript, then draw bearing inner ring and the outer shroud the defect characteristic octave frequency change curve with rotating speed.Adjust high/low pressure rotor speed ratio, ensure in the engine operating speed range more than 90%, above-mentioned lobe numbers differs more than 2% with intershaft bearing inner ring the defect characteristic octave frequency and outer shroud the defect characteristic octave frequency.
By above-mentioned design procedure, intershaft bearing can be made from synchronous impact, effectively can reduce the dynamic loading on raceway, improve the fatigue lifetime of intershaft bearing.
Beneficial effect of the present invention is:
For the bearing that outer shroud is fixing, the situation that excitation force frequency is equal with bearing features frequency can not be there is.But for the intershaft bearing of birotary engine, if design improper, then synchronous impact phenomenon may occur, the dynamic loading making raceway bear sharply increases, for bearing reliability brings challenges.The present invention proposes to avoid synchronous principle of impacting to be that intershaft bearing derated design specifies direction.
Intershaft bearing can be made from synchronous impact by derated design step, avoid rolling body impulsive force and rotate exciting force in-phase stacking and act on same point on raceway, effectively can reduce the dynamic loading on inner race and outer-race ball track, then improve the fatigue lifetime of intershaft bearing.The theoretical analysis result of comparison diagram 3 (a) and Fig. 3 (b), clearly can find out the reduction of dynamic loading.
The synchronous impact check figure that the present invention proposes is effective derated design instrument, for the design engineer of this area, draw easy, statement physical significance is distinct, contributes to the efficiency improving intershaft bearing derated design.
Accompanying drawing explanation
Fig. 1 is intershaft bearing kinetic model schematic diagram.
Fig. 2 is the impulsive force schematic diagram of intershaft bearing rolling body to raceway.
Fig. 3 is the overlaying relation figure rotating exciting force and rolling body impulsive force, and wherein, 3a is the dynamic loading under excitation force frequency and the unequal condition of inner ring characteristic frequency, and 3b is the dynamic loading under excitation force frequency condition equal to inner ring characteristic frequency.
Fig. 4 is process flow diagram of the present invention.
Fig. 5 is intershaft bearing derated design process schematic.
Fig. 6 synchronously impacts check figure.
Fig. 7 is the synchronous impact check figure of prior art design.
Fig. 8 is the synchronous impact check figure of derated design of the present invention.
In figure: 1. the straight line showing fan blade number at different levels; 2.X inner+ 2%X innerboundary line; 3. inner ring the defect characteristic octave frequency X innercurve; 4.X inner-2%X innerboundary line; 5. hazardous location; 6.X outer+ 2%X outerboundary line; 7. outer shroud the defect characteristic octave frequency X outercurve; 8.X outer-2%X outerboundary line.
Embodiment
The present embodiment is a kind of method of aeromotor intershaft bearing derated design, and detailed process is:
Step one, determine the rotating ratio of birotary engine mesohigh rotor and low pressure rotor.
According to rotating speed principle at equal intervals, to the operating rotational speed range of maximum (top) speed, choose N number of speed conditions point from slow train rotating speed in aeromotor.According to engine high pressure rotor design rotating speed and low pressure rotor design speed, the high/low pressure rotor speed calculated under each speed conditions compares γ i=Ω h,i/ Ω l,i=n 2, i/ n 1, i, i=(1,2 ... N).Wherein, Ω hthe angular velocity of rotation of high pressure rotor, Ω lit is the angular velocity of rotation of low pressure rotor.N 2be high pressure rotor design speed, dimension is rev/min; n 1be low pressure rotor design speed, dimension is rev/min.
If be arranged on High Pressure Turbine Rotor for common outer shroud, inner ring is arranged on Low Pressure Turbine Rotor structure, then the high/low pressure rotor speed obtained compares γ ibe the outer shroud/inner ring rotating ratio of intershaft bearing.The high/low pressure rotor speed calculated compares γ iit is one of design parameter important in intershaft bearing derated design.
Step 2, determine intershaft bearing inner ring characteristic frequency and outer shroud characteristic frequency.
Determine intershaft bearing inner ring characteristic frequency:
Under determining each speed conditions by formula (5), intershaft bearing inner ring characteristic frequency f inner, i, i=(1,2 ... N)
f i n n e r , i = 1 2 × 60 · | n 2 , i ± n 1 , i | · ( 1 + d D m · c o s α ) · Z - - - ( 5 )
Determine intershaft bearing outer shroud characteristic frequency:
Under determining each speed conditions by formula (6), intershaft bearing outer shroud characteristic frequency f outer, i, i=(1,2 ... N)
f o u t e r , i = 1 2 × 60 · | n 2 , i ± n 1 , i | · ( 1 - d D m · c o s α ) · Z - - - ( 6 )
In formula (5) and (6), d is the diameter of rolling body in intershaft bearing, D mbe bearing pitch diameter, α is contact angle, and z is rolling body number.Described each parameter obtains by bearing design requirements.
When high pressure rotor and low pressure rotor rotating Vortex, get minus sign "-", during reverse rotation, get plus sige "+".
Step 3, determine the defect characteristic octave frequency of intershaft bearing.
Describedly determine the defect characteristic octave frequency that the defect characteristic octave frequency of intershaft bearing comprises the defect characteristic octave frequency and this intershaft bearing outer shroud determining this intershaft bearing inner ring.
By formula (7), by inner ring characteristic frequency f inner, ibe converted into the frequency multiplication of rotational speed of lower pressure turbine rotor:
X i n n e r , i = f i n n e r , i n 1 , i / 60 = 1 2 · | γ i ± 1 | · ( 1 + d D m · c o s α ) · Z - - - ( 7 )
Obtain the defect characteristic octave frequency X of intershaft bearing inner ring inner, i.
By formula (8), by outer shroud characteristic frequency f outer, ibe converted into the frequency multiplication of rotational speed of lower pressure turbine rotor:
X o u t e r , i = f o u t e r , i n 1 , i / 60 = 1 2 · | γ i ± 1 | · ( 1 - d D m · c o s α ) · Z - - - ( 8 )
Obtain the defect characteristic octave frequency X of intershaft bearing outer shroud outer, i.
Step 4, the synchronous impact of drafting check figure.
Relation between the inner ring the defect characteristic octave frequency of fan blade number and intershaft bearing and outer shroud the defect characteristic octave frequency is showed by the mode of figure by described synchronous impact check figure, provides foundation for checking synchronous impact, and this figure is called and synchronously impacts check figure.
Check in figure in described synchronous impact, when intermediary's bearing roller is close with fan blade excitation force frequency to the impact force frequency of inner race, the two superposition is in inner race, and power width is two force width sums; When intermediary's bearing roller is close with fan blade excitation force frequency to the impact force frequency of outer-race ball track, the two superposition is in outer-race ball track, and power width is two force width sums.
Drawing synchronous detailed process of impacting check figure Fig. 6 is:
I by the rule X of inner ring the defect characteristic octave frequency with rotation speed change inner, ibe plotted in synchronous impact on check figure, Z is synchronously impacted the inner ring the defect characteristic octave frequency X in check figure inner, icurve 3.
II draws inner ring the defect characteristic octave frequency number X inner+ 2%X innerand X inner-2%X innerboundary line, synchronously impacted the X in check figure respectively inner+ 2%X innerboundary line 2 and X inner-2%X innerboundary line 4.
III by the rule X of outer shroud the defect characteristic octave frequency with rotation speed change outerbe plotted in synchronous impact on check figure, synchronously impacted the outer shroud the defect characteristic octave frequency X in check figure outercurve 7.
IV draws outer shroud the defect characteristic octave frequency number X outer+ 2%X outerand X outer-2%X outerboundary line, synchronously impacted the X in check figure respectively outer+ 2%X outerboundary line 6 and X outer-2%X outerboundary line 8.
V by 2 multiple F of fan blade number at different levels and this fan blade number at different levels bk, jbe marked on synchronous impact on check figure successively, obtain the straight line that a group shows fan blade numbers at different levels.
In the present embodiment, described fan blade at different levels comprises 1 ~ 3 grade.Wherein, light breeze fan leaf has 37, and gentle breeze fan leaf has 45, and 3rd level fan blade has 43.Then check on figure synchronous impact, mark the F of light breeze fan successively 1,1=37 ×, F 1,2=74 ×; The F of gentle breeze fan 2,1=45 ×, F 2,2=90 ×; The F of 3rd level fan 3,1=43 ×, F 3,2=86 ×.
Dynamic loading state suffered by step 5, check intershaft bearing, avoids synchronous impact occurs.
Check in figure, if any straight line showed in the straight line 1 of fan blade number at different levels is in X synchronous impact inner+ 2%X innerboundary line 2 and X inner-2%X innerbetween boundary line 4; Or any straight line showed in the straight line 1 of fan blade number at different levels is in X outer+ 2%X outerboundary line 6 and X outer-2%X outerbetween boundary line 8, then show intershaft bearing inner ring characteristic frequency or outer shroud characteristic frequency close with fan blade excitation force frequency, now may there is synchronous impact phenomenon in intershaft bearing.
When occurring synchronously to impact, the load that intershaft bearing inner race is subject to or the load that outer-race ball track is subject to are rolling body impulsive force and fan blade exciting force width sum, under now intershaft bearing is in severe loaded-up condition, forbid long-term work in this case.
If there is the straight line 1 of described performance fan blade number at different levels to be in by X inner+ 2%X innerboundary line 2 and X inner-2%X innerin the hazardous location 5 that boundary line 4 is formed, and when exceeding 10% of engine operating speed range shown in horizontal ordinate; Or any straight line in the straight line 1 of described performance fan blade at different levels number is in by X outer+ 2%X outerboundary line 6 and X outer-2%X outerin the hazardous location 5 that boundary line 8 is formed, and when exceeding 10% of engine operating speed range, then necessary adjust design parameters, reduces the dynamic loading that intershaft bearing bears.
Step 6, reduce intershaft bearing bear the optimal design of dynamic loading.
Based on existing method for designing, there is the possibility that synchronous impact occurs in intershaft bearing.Such as, the synchronous impact of the existing design of Fig. 6 is checked in figure, and the straight line 1 showing gentle breeze fan leaf number is in X inner+ 2%X innercurve 2 and X inner-2%X innerrotating speed interval between curve 4 has exceeded 10% of engine operating speed range.
Now, by adjusting high/low pressure rotor speed ratio, changing the mutual relationship of fan blade excitation force frequency and rolling body impact force frequency, avoiding synchronous impact, reduce the dynamic loading that intershaft bearing raceway bears.
The high/low pressure rotor speed ratio of described adjustment is by adjustment control of engine speed rate, heightens or turn down high/low pressure rotor speed ratio, to reduce the dynamic loading that intershaft bearing inner race and outer shroud bear.Described control of engine speed rate is determined in engine design.
When reducing the dynamic loading that intershaft bearing inner race bears:
Check in figure, by X in the synchronous impact of drawing inner+ 2%X innerboundary line 2 and X innerit is D that curve 3 forms region 1, by X inner-2%X innerboundary line 4 and X innerit is D that curve 3 forms region 2.
When the straight line 1 of described performance fan blade number at different levels is in D 1length in inherent X-coordinate is greater than and is in D 2during length in inherent X-coordinate, high/low pressure rotor speed ratio need be turned down.Specifically, former high/low pressure rotor speed is progressively turned down than the step-length with 0.1%, until the straight line 1 of described performance fan blade at different levels number is positioned at outside described hazardous location 5, and non hazardous areas is made to be greater than 90% of engine operating speed range shown in horizontal ordinate.
When the straight line 1 of described performance fan blade number at different levels is in D 1length in inherent X-coordinate is less than and is in D 2during length in inherent X-coordinate, high/low pressure rotor speed ratio need be heightened.Specifically, former high/low pressure rotor speed is progressively heightened than the step-length with 0.1%, until the straight line 1 of described performance fan blade at different levels number is positioned at outside described hazardous location 5, and non hazardous areas is made to be greater than 90% of engine operating speed range shown in horizontal ordinate.
When reducing the dynamic loading that intershaft bearing outer-race ball track bears:
Check in figure, by X in the synchronous impact of drawing outer+ 2%X outerboundary line 6 and X outerit is D that curve 7 forms region 3, by X outer-2%X outerboundary line 8 and X outerit is D that curve 7 forms region 4.
When the straight line 1 of described performance fan blade number at different levels is in D 3length in inherent X-coordinate is greater than and is in D 4during length in inherent X-coordinate, high/low pressure rotor speed ratio need be turned down.Specifically, former high/low pressure rotor speed is progressively turned down than the step-length with 0.1%, until the straight line 1 of described performance fan blade at different levels number is positioned at outside described hazardous location 5, and non hazardous areas is made to be greater than 90% of engine operating speed range shown in horizontal ordinate.
When the straight line 1 of described performance fan blade number at different levels is in D 3length in inherent X-coordinate is less than and is in D 4during length in inherent X-coordinate, high/low pressure rotor speed ratio need be heightened.Specifically, former high/low pressure rotor speed is progressively heightened than the step-length with 0.1%, until the straight line 1 of described performance fan blade at different levels number is positioned at outside described hazardous location 5, and non hazardous areas is made to be greater than 90% of engine operating speed range shown in horizontal ordinate.
So far, complete the adjustment to the high/low pressure rotor speed ratio of engine, avoid intershaft bearing and occur synchronous impact.
By above-mentioned design procedure, intershaft bearing can be made from synchronous impact, effectively can reduce the dynamic loading on raceway, improve the fatigue lifetime of intershaft bearing.

Claims (4)

1. a derated design method for aeromotor intershaft bearing, it is characterized in that, detailed process is:
Step one, determine the rotating ratio of birotary engine mesohigh rotor and low pressure rotor;
Step 2, determine intershaft bearing inner ring characteristic frequency and outer shroud characteristic frequency;
Step 3, determine the defect characteristic octave frequency of intershaft bearing;
Step 4, the synchronous impact of drafting check figure;
Relation between the inner ring the defect characteristic octave frequency of fan blade number and intershaft bearing and outer shroud the defect characteristic octave frequency is showed by the mode of figure by described synchronous impact check figure, provides foundation for checking synchronous impact, and this figure is called and synchronously impacts check figure;
Check in figure in described synchronous impact, when intermediary's bearing roller is close with fan blade excitation force frequency to the impact force frequency of inner race, the two superposition is in inner race; When intermediary's bearing roller is close with fan blade excitation force frequency to the impact force frequency of outer-race ball track, the two superposition is in outer-race ball track;
Dynamic loading state suffered by step 5, check intershaft bearing, avoids synchronous impact occurs;
Figure is checked, if any straight line showed in the straight line of fan blade number at different levels is in X according to synchronous impact inner+ 2%X innerboundary line and X inner-2%X innerbetween boundary line; Or any straight line showed in the straight line of fan blade number at different levels is in X outer+ 2%X outerboundary line and X outer-2%X outerbetween boundary line, then show intershaft bearing inner ring characteristic frequency or outer shroud characteristic frequency close with fan blade excitation force frequency, now may there is synchronous impact phenomenon in intershaft bearing;
When occurring synchronously to impact, the load that intershaft bearing inner race is subject to or the load that outer-race ball track is subject to are rolling body impulsive force and fan blade exciting force width sum, under now intershaft bearing is in severe loaded-up condition, forbid long-term work in this case;
If there is the straight line of described performance fan blade number at different levels to be in by X inner+ 2%X innerboundary line and X inner-2%X innerin the hazardous location that boundary line is formed, and when exceeding 10% of engine operating speed range shown in horizontal ordinate; Or any straight line in the straight line of described performance fan blade at different levels number is in by X outer+ 2%X outerboundary line and X outer-2%X outerin the hazardous location that boundary line is formed, and when exceeding 10% of engine operating speed range, then necessary adjust design parameters, reduces the dynamic loading that intershaft bearing bears;
The dynamic loading that step 6, reduction intershaft bearing bear; Described reduction dynamic loading that intershaft bearing bears is by heightening or turn down high/low pressure rotor speed ratio, to reduce the dynamic loading that intershaft bearing inner race and outer shroud bear; So far, complete the adjustment to the high/low pressure rotor speed ratio of engine, avoid intershaft bearing and occur synchronous impact.
2. the derated design method of aeromotor intershaft bearing as claimed in claim 1, it is characterized in that, the detailed process of drawing described synchronous impact check figure is:
I by the rule X of inner ring the defect characteristic octave frequency with rotation speed change inner, ibe plotted in synchronous impact on check figure, obtain Z to the synchronous inner ring the defect characteristic octave frequency X impacted in check figure inner, icurve;
II draws inner ring the defect characteristic octave frequency number X inner+ 2%X innerand X inner-2%X innerboundary line, synchronously impacted the X in check figure respectively inner+ 2%X innerboundary line and X inner-2%X innerboundary line;
III by the rule X of outer shroud the defect characteristic octave frequency with rotation speed change outerbe plotted in synchronous impact on check figure, synchronously impacted the outer shroud the defect characteristic octave frequency X in check figure outercurve;
IV draws outer shroud the defect characteristic octave frequency number X outer+ 2%X outerand X outer-2%X outerboundary line, synchronously impacted the X in check figure respectively outer+ 2%X outerboundary line and X outer-2%X outerboundary line;
V by the multiple F of fan blade number at different levels and this fan blade number at different levels bk, jbe marked on synchronous impact on check figure successively, obtain the straight line that a group shows fan blade numbers at different levels.
3. the derated design method of aeromotor intershaft bearing as claimed in claim 1, is characterized in that, when reducing the dynamic loading that intershaft bearing inner race bears:
Check in figure, by X in the synchronous impact of drawing inner+ 2%X innerboundary line and X innerit is D that curve forms region 1, by X inner-2%X innerboundary line and X innerit is D that curve forms region 2;
When the straight line of described performance fan blade number at different levels is in D 1length in inherent X-coordinate is greater than and is in D 2during length in inherent X-coordinate, high/low pressure rotor speed ratio need be turned down; Specifically, former high/low pressure rotor speed is progressively turned down than the step-length with 0.1%, until the straight line of described performance fan blade at different levels number is positioned at outside described hazardous location, and makes non hazardous areas be greater than 90% of engine operating speed range shown in horizontal ordinate;
When the straight line of described performance fan blade number at different levels is in D 1length in inherent X-coordinate is less than and is in D 2during length in inherent X-coordinate, high/low pressure rotor speed ratio need be heightened; Specifically, former high/low pressure rotor speed is progressively heightened than the step-length with 0.1%, until the straight line of described performance fan blade at different levels number is positioned at outside described hazardous location, and makes non hazardous areas be greater than 90% of engine operating speed range shown in horizontal ordinate.
4. the derated design method of aeromotor intershaft bearing as claimed in claim 1, is characterized in that, when reducing the dynamic loading that intershaft bearing outer-race ball track bears:
Check in figure, by X in the synchronous impact of drawing outer+ 2%X outerboundary line and X outerit is D that curve forms region 3, by X outer-2%X outerboundary line and X outerit is D that curve forms region 4;
When the straight line of described performance fan blade number at different levels is in D 3length in inherent X-coordinate is greater than and is in D 4during length in inherent X-coordinate, high/low pressure rotor speed ratio need be turned down; Specifically, former high/low pressure rotor speed is progressively turned down than the step-length with 0.1%, until the straight line of described performance fan blade at different levels number is positioned at outside described hazardous location, and makes non hazardous areas be greater than 90% of engine operating speed range shown in horizontal ordinate;
When the straight line of described performance fan blade number at different levels is in D 3length in inherent X-coordinate is less than and is in D 4during length in inherent X-coordinate, high/low pressure rotor speed ratio need be heightened; Specifically, former high/low pressure rotor speed is progressively heightened than the step-length with 0.1%, until the straight line of described performance fan blade at different levels number is positioned at outside described hazardous location, and makes non hazardous areas be greater than 90% of engine operating speed range shown in horizontal ordinate.
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