CN109813540B - Design and monitoring operation method for avoiding disc cavity liquid accumulation instability rotor of aero-engine - Google Patents
Design and monitoring operation method for avoiding disc cavity liquid accumulation instability rotor of aero-engine Download PDFInfo
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Abstract
A design and monitoring operation method for avoiding disc cavity liquid accumulation instability of an aircraft engine comprises the steps of optimally designing a cavity structure of the aircraft engine rotor, introducing a checking criterion, deducing instability threshold liquid accumulation volume from instability threshold rotating speed of the aircraft engine rotor, comparing the instability threshold liquid accumulation volume with the rotor cavity volume, analyzing liquid accumulation instability risk of the rotor by comparing combination parameters of the rotor with critical combination parameters, and designing the aircraft engine rotor without disc cavity liquid accumulation risk. And a monitoring method is introduced in the running process of the rotor, the increase of the vibration total amplitude of the rotor, the subharmonic amplitude and the peak value of the vibration time domain waveform of the rotor are monitored, and the values are compared with corresponding values of a normally working rotor to judge whether the rotor has effusion instability, so that the rotor instability of most disc cavity effusion can be effectively avoided, or the rotor with instability risk can timely monitor effusion faults before the instability, and the normal running of the rotor with instability risk is ensured.
Description
Technical Field
The invention relates to the field of aeroengine dynamics design, in particular to a method for designing and monitoring the dynamics of an aeroengine rotor structure.
Technical Field
Disc cavity hydrops phenomenon happens occasionally in aeroengine working process, is one of the factors that arouse aeroengine vibration standard exceeding. When the aeroengine works under the conditions of high temperature and high pressure, the lubricating oil in the bearing cavity at the supporting position can be vaporized, when the sealing device is not tightly sealed in the working process, the vaporized lubricating oil and the water vapor in the air flow out through the sealing device, and the oil gas flows into the inner cavity of the disc drum structure of the aeroengine and can be condensed into liquid along with the reduction of the temperature, so that the disc cavity liquid accumulation phenomenon is formed. The phenomenon can cause self-excited vibration of a rotor system when reaching a certain condition, the vibration amplitude is generally large, great load can be brought to an engine, the structure of the engine can be damaged, and great harm is caused. Therefore, a rotor design method capable of avoiding disc cavity effusion instability or a monitoring method in the rotor operation process is needed to be found so as to improve the reliability of the rotor.
The invention with the publication number CN107025348A provides a method for identifying early effusion faults of a rotor. The unbalance fault and the liquid accumulation fault of the rotor to be identified are distinguished by drawing the amplitude-frequency characteristic curve of the rotor to be identified and the healthy rotor and dividing the area integral of the curve, so that the early-stage liquid accumulation fault of the rotor of the aircraft engine is identified. However, the invention only integrates the area of the first-order quantity of vibration before and after the first-order critical rotating speed, and does not consider the vibration condition before and after the unstable vibration of the rotor.
In the study of dynamic characteristics of a single-disc oil-accumulating rotor system, the phenomenon of aggregation and instability of an accumulated liquid rotor during operation are found, but the accumulated liquid instability of the rotor is not involved in the test process, and the matching degree of the rotor design and a real aircraft engine rotor is not high.
In the invention with the publication number of CN201410146849.X, a design method of the rotor structure dynamics of the aircraft engine is provided, and the parameters of the rotor and the support are optimized, so that the thermal mode of the rotor system avoids the mode of the rotor when the support is absolutely rigid, and the rotor system meets the requirement of the vibration standard in the thermal mode. The core of the engine is to ensure that the rotor can work stably in the whole working rotating speed range of the engine. However, in the working rotating speed, the risk of instability and vibration caused by accumulated liquid still exists, and the design process is not considered.
Therefore, the invention provides a rotor design and monitoring method capable of avoiding instability vibration caused by disc cavity effusion of an aircraft engine, provides a design method for avoiding instability vibration caused by disc cavity effusion of a rotor and an effusion rotor operation vibration monitoring method, and avoids effusion instability of most rotors or timely discovery and elimination of faults when few rotors have instability signs through optimized design of rotor parameters.
Disclosure of Invention
In order to overcome the defect that the instability vibration risk caused by liquid accumulation still exists in the prior art, the invention provides a design and monitoring operation method for avoiding liquid accumulation and instability of an aeroengine disc cavity.
The invention provides a design process of a rotor for avoiding disc cavity liquid accumulation instability of an aero-engine, which comprises the following steps:
step 1: determining the initial structural characteristics of the aeroengine rotor:
the initial structure characteristics comprise the initial structure and performance parameters of the aircraft engine rotor; wherein:
the aircraft engine rotor has an initial structure of an interlayer disc, and through shaft holes are formed in the centers of two end faces of the rotor. The determined structural parameters are the axial length H of the aircraft engine rotor, the outer diameter d of the rotor, the inner diameter R of the rotor and the aperture R of the shaft holei. The distance between the two inner surfaces of the rotor interlayer is L.
The performance parameter of the aircraft engine rotor is rotor density rhoiA rotor damping coefficient D and a stiffness coefficient K of the rotor.
Step 2: judging whether the rotor is unstable or not
Judging whether the rotor of the aircraft engine has the instability risk according to the instability criterion of the rotor;
when the rotor is checked according to the instability criterion, the rotor structure parameters preliminarily determined in the step 1 and the rotor performance parameters preliminarily determined are substituted into the instability criterion formula, and the combination parameters H and the critical combination parameters H are calculatedcAnd obtaining a critical combination parameter HcAs reference line a.
And comparing the obtained value of the combination parameter H with the value of the reference line A, wherein when the value of the combination parameter H is more than or equal to the value of the reference line A, the rotor has instability risk in the operation process.
When the combined parameter H is less than the value of the reference line a, the rotor is not at risk of instability during operation.
When the rotor has instability risk in the operation process, entering step 3, and carrying out optimization design and iterative check on the rotor again; when the rotor has no risk of instability during operation, the rotor is operated during monitoring.
The instability criterion is as follows:
the rotor structure combination parameter is noted as H. When the rotor begins to generate unstable vibration, the critical value of the rotor structure combination parameter is Hc；
If H belongs to [0, H ∈c) The accumulated liquid in the rotor cavity can not cause the unstable vibration of the rotor;
if H is not less than HcThe accumulated liquid in the rotor disc cavity reaches the unstable doorWhen the liquid accumulation amount is on the threshold, unstable vibration caused by the liquid accumulation in the disc cavity can be caused;
wherein:
in the above formula, RiIs the bore diameter of the shaft hole, R is the inner diameter of the rotor, L is the height of the interlayer, D is the damping coefficient of the rotor, K is the rigidity coefficient of the rotor, M is the mass of the rotor, mu is the viscosity coefficient of the effusion, rho is the density of the effusion, omeganThe first-order critical rotating speed of the rotor is obtained, and the gamma is a constant of instability frequency caused by effusion and is taken as 0.8.
And step 3: re-optimizing design and iteratively checking:
the specific process of re-optimizing design and iterative check of the rotor is as follows:
the outer cavity diameter R and/or the cavity width L of the rotor are varied. When the outer diameter R and the width L of the cavity of the rotor are changed, the outer diameter R and the width L of the cavity are respectively reduced by 5-10% on the basis of the original design size.
And (5) repeating the step (2) and judging whether the rotor with the changed structure size and weight is unstable or not. Specifically, each changed structural parameter is substituted into a checking criterion, and whether the rotor is unstable or not is judged. And if the judgment result is that the rotor is unstable, continuously changing the outer diameter R and/or the width L of the cavity of the rotor, and carrying out optimization design again.
In the repeated optimization design, if the design weight of the rotor exceeds the range after multiple times of optimization, the checking criterion still cannot be met, and the rotor needs to be operated in monitoring.
And if the judgment result is that the rotor cannot be unstabilized, the design of the rotor is completed, and the rotor operates in monitoring.
The invention provides a monitoring operation process for avoiding disc cavity liquid accumulation instability of an aircraft engine, which comprises the following steps:
the criterion for judging the instability of the effusion of the rotor disc cavity is as follows:
after the rotor crosses a first-order critical rotating speed, if the rotating speed variation range obtained through monitoring is within 50rpm, and the amplitude increment of the vibration total amount of the rotor exceeds 25%, the amplitude of the rotor is considered to be suddenly increased.
Where RPM1 is the rotational speed at normal vibration; RPM2 is the rotational speed at which the amplitude increases; a1 is the monitored amplitude at normal vibration and A2 is the monitored amplitude at increased amplitude.
II 0.5X-1X subharmonic component A of rotor vibration(0.5X,1X)Background noise amplitude A greater than twicenoiseJudging that the rotor is unstable;
A(0.5X,1X)≥2Anoise
in the formula A(0.5X,1X)The harmonic dominant amplitude of the vibration 0.5X-1X frequency component is extracted. Background noise amplitude AnoiseThe average value of the 0.5X-1X subharmonic component dominant amplitude when the rotor normally vibrates is taken, and the vibration amplitude before the first-order critical rotation speed can be approximated.
III when the vibration signal of the rotor, A in 4 groups of vibration periods in successionmaxp-p-Aminp-pAll exceed the normal vibration peak value Anormalp-p25% of the total amount, it is considered that the rotor rattles.
In the above formula, Amaxp-pFor the maximum peak-to-peak value within each group, Aminp-pThe minimum value of the peak value in each group is taken; i is a vibration period group, and i is 1,2,3 and 4.
And when the vibration period of the rotor is determined, recording a vibration signal of the rotor, and continuously monitoring the peak value of a vibration time domain waveform of the rotor. Take 8 consecutive vibration cycles as a group.
And 2, monitoring the vibration signal in the rotor operation process, and judging whether the rotor is unstable or has instability risk according to the monitored rotor vibration signal.
And when the subharmonic frequency amplitude is not monitored to be out of limit all the time in the running process of the rotor, namely the three instability standards are not met, the rotor normally runs without instability vibration risk caused by effusion.
When the subharmonic frequency amplitude is monitored to be out of limit in the operation process of the rotor, but the phenomenon of vibration beating does not occur to the amplitude sudden increase of the total vibration amount or the first frequency multiplication component of the vibration, namely the second criterion is met but the first criterion and the third criterion are not met, the temperature failure risk early warning is carried out, namely the rotor has the instability vibration risk caused by liquid accumulation, the operation of the rotor is stopped at the moment, and the operation can be carried out again after the fault is checked;
when the amplitude of subharmonic frequency is monitored to be out of limit in the operation process of the rotor, the phenomenon of beat vibration occurs when the amplitude of total vibration is suddenly increased or the first frequency multiplication component of vibration occurs simultaneously, namely the criterion two and the criterion three are met simultaneously, the rotor enters a destabilization vibration state caused by effusion, the effusion instability of a rotor disc cavity can be determined, the rotor operation is stopped, and faults are eliminated.
The invention can effectively avoid the instability of most rotors with disc cavity accumulated liquid, or can lead a few rotors which cannot avoid the instability, namely the rotors which must work under the condition of instability risk to be capable of monitoring the accumulated liquid fault in time before the instability, thereby ensuring the normal operation of the rotors with the instability risk.
In the invention, structural combination parameters are provided, and instability checking criteria are provided. Namely, the aero-engine rotor capable of normally working under the condition of no instability risk is designed through redesign and instability checking of the initial structure of the rotor.
The invention then proposes a process for monitoring the instability of the rotor without optimization conditions. And for the rotor which cannot pass the instability checking, carrying out instability monitoring in the running process of the rotor. The stable state of the rotor is identified by judging the stability criterion of the vibration subharmonic, the vibration total amount, the vibration fundamental frequency and the like, and the normal operation of the rotor with instability risk is ensured.
The invention provides a monitoring algorithm for an aircraft engine rotor instability fault. And judging whether the rotor has effusion instability or not by monitoring the amplitude increment of the total vibration quantity of the rotor, the subharmonic amplitude and the time domain waveform peak-to-peak value of the vibration of the rotor and comparing the values with corresponding values of a normally working rotor. Based on the methods, the vibration signals are processed, and early warning is performed before instability occurs.
Compared with the prior art, the invention has the beneficial effects that:
for the traditional design idea of the aero-engine rotor, the risk of instability of the rotor caused by disc cavity liquid accumulation is often ignored, or the rotor directly works under the risky condition. The design idea provided by the invention is to optimally design the cavity structure of the aircraft engine rotor and introduce a check criterion, wherein the check criterion is that the instability threshold liquid accumulation volume is deduced from the instability threshold rotating speed of the aircraft engine rotor and is compared with the cavity volume of the rotor, so that the comparison between critical combination parameters and combination parameters is simplified, the liquid accumulation instability risk of the rotor is analyzed by comparing the combination parameters and the critical combination parameters of the rotor, and the aircraft engine rotor without disc cavity liquid accumulation risk is designed.
And introducing a monitoring method in the running process of the rotor, analyzing the vibration signal of the rotor, monitoring the amplitude increment of the total vibration amount of the rotor, the subharmonic amplitude and the peak value of the time domain waveform of the vibration of the rotor, and comparing the values with the corresponding values of the rotor which normally works to judge whether the liquid accumulation instability occurs in the rotor.
The results obtained by the simulation experiment are shown in the figure, fig. 6a is a subharmonic frequency amplitude diagram when 34ml of oil is injected into the rotor cavity in the embodiment 2, and the subharmonic amplitude in the diagram rises but has smaller amplitude after the first-order critical rotating speed; FIG. 6b is a graph of the amplitude of the frequency doubled during the injection of 34ml of oil into the rotor cavity of example 2, which is substantially the same as the amplitude of the frequency doubled for a normally operating rotor.
FIG. 7a is a graph of the subharmonic frequency amplitude of the rotor cavity injected with 35ml of oil of example 2, in which the subharmonic amplitude increases abruptly after the first order critical speed and is significantly greater than the subharmonic amplitude at the first order critical speed; FIG. 7b is a graph of the amplitude of one-time frequency when 35ml of oil is injected into the cavity of the rotor in example 2, wherein the amplitude of one-time frequency after the first-order critical speed has obvious fluctuation and beat vibration occurs.
FIG. 8a is a graph of the subharmonic frequency amplitude of the rotor cavity injected with 36ml of oil of example 2, in which the subharmonic amplitude has a greatly increasing tendency after the rotor has crossed a first critical speed and cannot return to normal amplitude; FIG. 8b is a graph of the amplitude of one-time frequency of the rotor cavity filled with 36ml of oil in example 2, wherein the amplitude of one-time frequency of vibration also fluctuates significantly when the rotor crosses the first-order critical phase, and the beat vibration is more severe; FIG. 8c is an enlarged view of the second harmonic amplitude of the rotor cavity filled with 36ml of oil in example 2, with the beat amplitude of the rotor increasing continuously.
Drawings
FIG. 1 is a rotor design and monitoring process of the present invention;
FIG. 2 is a schematic representation of a rotor dynamics model of the present design;
FIG. 3 is a comparison chart of initial design parameter verification in the example;
FIG. 4 is a schematic diagram of rotor verification results optimized to be risk free;
FIG. 5 is a comparison chart of final design parameters of the rotor in the example;
FIG. 6a is a graph of the amplitude of the subharmonic frequency when 34ml of oil is injected in the embodiment;
FIG. 6b is a graph of the amplitude of 1X when injecting 34ml of oil in the embodiment;
FIG. 7a is a graph of the amplitude of the subharmonic frequency when 35ml of oil is injected in the example;
FIG. 7b is a graph of the amplitude of 1X when 35ml of oil is injected in the embodiment;
FIG. 8a is a graph of the amplitude of the subharmonic frequency when injecting 36ml of oil in the example;
FIG. 8b is a graph of the amplitude of 1X when injecting 36ml of oil in the embodiment;
FIG. 8c is an enlarged time domain waveform diagram of the amplitude increase position when injecting 36ml oil in the embodiment;
FIG. 9 is a flow chart of a design of a rotor for avoiding effusion instability in a disc cavity of an aircraft engine;
fig. 10 is a flowchart of a method for monitoring instability.
Detailed Description
The method comprises the steps of designing structural parameters of the rotor of the aircraft engine and checking whether the rotor has instability risks. The specific process is as follows:
step 1: determining the initial structure of the rotor of the aircraft engine:
and preliminarily determining the parameters of the aircraft engine rotor by using a transfer matrix method. The rotor structure is simplified to the rotor model shown in fig. 2.
The rotor is a sandwich disc, and the centers of two end faces of the rotor are provided with through shaft holes. The axial length of the rotor is H, the outer diameter of the rotor is d, and the inner diameter of the rotor is R. The aperture of the shaft hole is Ri. The distance between the two inner surfaces of the rotor interlayer is L. In this embodiment, the preliminarily determined rotor structural parameters are shown in table 1, and the preliminarily determined rotor performance parameters are shown in table 2.
TABLE 1 preliminary determination of rotor construction parameters
| Axial length H | Outer diameter d | Inner diameter R | Bore diameter R of through holei | Height L of the interlayer |
| 40mm | 300mm | 240mm | 100mm | 20mm |
TABLE 2 preliminary determination of rotor performance parameters
| Rotor density ρi | Damping coefficient D of rotor | Stiffness coefficient K of rotor |
| 7850kg/m3 | 0.04 | 1×106N/m |
The design weight of the rotor is between 10Kg and 15 Kg. In this embodiment, the weight of the rotor is 13.86 Kg.
Step 2: judging whether the rotor is unstable or not:
judging whether the rotor of the aircraft engine has the instability risk according to the instability criterion of the rotor;
the instability criterion is as follows:
the rotor structure combination parameter is noted as H. When the rotor begins to generate unstable vibration, the critical value of the rotor structure combination parameter is Hc；
If H belongs to [0, H ∈c) The accumulated liquid in the rotor cavity can not cause the unstable vibration of the rotor;
if H is not less than HcWhen the liquid accumulation amount in the rotor disc cavity reaches the instability threshold liquid accumulation amount, instability vibration caused by the liquid accumulation in the disc cavity can be caused;
wherein:
in the above formula, RiIs the bore diameter of the shaft hole, R is the inner diameter of the rotor, L is the height of the interlayer, D is the damping coefficient of the rotor, K is the rigidity coefficient of the rotor, M is the mass of the rotor, mu is the viscosity coefficient of the effusion, rho is the density of the effusion, omeganThe first-order critical rotating speed of the rotor is obtained, and the gamma is a constant of instability frequency caused by effusion and is taken as 0.8.
The density and viscosity coefficients of the conventional oil deposits are shown in Table 3:
TABLE 3 oil deposition parameters
| Density p | Coefficient of viscosity μ |
| 885kg/m3 | 7.3×103kg/(m·s) |
Checking the rotor according to the instability criterion of the rotor, specifically substituting the rotor structure parameters preliminarily determined in the step 1 and the rotor performance parameters preliminarily determined into an instability criterion formula, and calculating a combination parameter H and a critical combination parameter HcAnd obtaining a critical combination parameter HcAs reference line a.
Comparing the obtained value of the combination parameter H with the value of the reference line a, when the value of the combination parameter H is greater than or equal to the value of the reference line a, the rotor has a risk of instability during operation, as shown in fig. 3. The cylinder in fig. 3 is the value of the combination parameter H, and the value of the cylinder on the ordinate is the calculation result of the combination parameter H and is larger than the value of the reference line a on the ordinate.
When the combined parameter H is smaller than the value of said reference line a, the rotor is not at risk of instability during operation, as shown in fig. 4.
When the rotor has instability risk in the operation process, entering step 3, and carrying out optimization design and iterative check on the rotor again; when the rotor has no risk of instability during operation, the rotor is operated during monitoring.
And step 3: re-optimizing design and iteratively checking:
the specific process of re-optimizing design and iterative check of the rotor is as follows:
the outer cavity diameter R and/or the cavity width L of the rotor are varied. When the outer diameter R and the width L of the cavity of the rotor are changed, the outer diameter R and the width L of the cavity are respectively reduced by 5-10% on the basis of the original design size.
In this embodiment, the structural parameters of the modified rotor are as shown in table 4:
TABLE 4 rotor configuration optimization parameters
| Axial length H | Outer diameter d | Inner diameter R | Bore diameter R of through holei | Height L of the interlayer |
| 40mm | 300mm | 220mm | 100mm | 20mm |
And (5) repeating the step (2) and judging whether the rotor with the changed structure size and weight is unstable or not. Specifically, each changed structural parameter is substituted into a checking criterion, and whether the rotor is unstable or not is judged. And if the judgment result is that the rotor is unstable, continuously changing the outer diameter R and/or the width L of the cavity of the rotor, and carrying out optimization design again.
In the repeated optimization design, if the design weight of the rotor exceeds the range after multiple times of optimization, the checking criterion still cannot be met, and the rotor needs to be operated in monitoring.
And if the judgment result is that the rotor cannot be unstabilized, the design of the rotor is completed, and the rotor operates in monitoring.
In this embodiment, the new determination result is shown in fig. 5, the weight of the rotor is 14.99Kg, the height of the cylindrical body in the figure is the calculation result of the combination parameter H, and the calculated critical combination parameter H is used as the calculation resultcAs reference line a.
Comparing the obtained value of the combination parameter H with the value of the reference line a, when the value of the combination parameter H is greater than or equal to the value of the reference line a, the rotor has a risk of instability during operation, as shown in fig. 5. The cylinder in fig. 5 is the value of the combination parameter H, the value of the cylinder on the ordinate is the calculation result of the combination parameter H, and is greater than the value of the reference line a on the ordinate, and the rotor has a risk of effusion instability and needs to be operated in monitoring.
Example 2
This embodiment has still provided a rotor disc chamber hydrops unstability monitoring method of using, and the concrete process is:
the criterion for judging the instability of the effusion of the rotor disc cavity is as follows:
after the rotor crosses a first-order critical rotating speed, if the rotating speed variation range obtained through monitoring is within 50rpm, and the amplitude increment of the vibration total amount of the rotor exceeds 25%, the amplitude of the rotor is considered to be suddenly increased.
Where RPM1 is the rotational speed at normal vibration; RPM2 is the rotational speed at which the amplitude increases; a1 is the monitored amplitude at normal vibration and A2 is the monitored amplitude at increased amplitude.
II 0.5X-1X subharmonic component A of rotor vibration(0.5X,1X)Background noise amplitude A greater than twicenoise。
A(0.5X,1X)≥2Anoise
In the formula A(0.5X,1X)The harmonic dominant amplitude of the vibration 0.5X-1X frequency component is extracted. Background noise amplitude AnoiseThe average value of the 0.5X-1X subharmonic component dominant amplitude when the rotor normally vibrates is taken, and the vibration amplitude before the first-order critical rotation speed can be approximated.
III when the vibration signal of the rotor, A in 4 groups of vibration periods in successionmaxp-p-Aminp-pAll exceed the normal vibration peak value Anormalp-p25% of the total amount, it is considered that the rotor rattles.
In the above formula, Amaxp-pFor the maximum peak-to-peak value within each group, Aminp-pThe minimum value of the peak value in each group is taken; i is a vibration period group, and i is 1,2,3 and 4.
And when the vibration period of the rotor is determined, recording a vibration signal of the rotor, and continuously monitoring the peak value of a vibration time domain waveform of the rotor. Take 8 consecutive vibration cycles as a group.
And 2, monitoring the vibration signal in the rotor operation process, and judging whether the rotor is unstable or has instability risk according to the monitored rotor vibration signal.
And when the subharmonic frequency amplitude is not monitored to be out of limit all the time in the running process of the rotor, namely the three instability standards are not met, the rotor normally runs without instability vibration risk caused by effusion.
When the subharmonic frequency amplitude is monitored to be out of limit in the operation process of the rotor, but the phenomenon of vibration beating does not occur to the amplitude sudden increase of the total vibration amount or the first frequency multiplication component of the vibration, namely the second criterion is met but the first criterion and the third criterion are not met, the temperature failure risk early warning is carried out, namely the rotor has the instability vibration risk caused by liquid accumulation, the operation of the rotor is stopped at the moment, and the operation can be carried out again after the fault is checked;
when the amplitude of subharmonic frequency is monitored to be out of limit in the operation process of the rotor, the phenomenon of beat vibration occurs when the amplitude of total vibration is suddenly increased or the first frequency multiplication component of vibration occurs simultaneously, namely the criterion two and the criterion three are met simultaneously, the rotor enters a destabilization vibration state caused by effusion, the effusion instability of a rotor disc cavity can be determined, the rotor operation is stopped, and faults are eliminated.
The monitoring results of the rotor designed in the embodiment in the simulation experiment are as follows:
when 34ml of oil is injected, the first-frequency-multiplication amplitude of the rotor is the same as that of the rotor which normally works, but the subharmonic frequency amplitude of the rotor is raised, so that the instability risk exists; as shown in fig. 6a and 6 b.
When 35ml of oil is injected, the subharmonic frequency amplitude of the rotor is obviously increased after the first-order critical rotating speed, the vibration peak value is higher than the critical peak value of the first-order rotating speed, the vibration peak value is caused by disc cavity effusion, the beat vibration phenomenon of the rotor can be seen from a frequency doubling amplitude diagram, and the effusion instability of the rotor occurs at the moment. As shown in fig. 7a and 7 b.
When the oil is filled with 36ml, the subharmonic amplitude of the rotor after the rotor crosses the first-order critical rotating speed has a great rising trend, and when the rotor crosses the first-order critical, the first-order frequency multiplication amplitude of vibration also has a remarkable increase. After the first-order critical rotating speed is crossed, the rotor completely enters a destabilizing state and cannot be recovered along with the further increase of the rotating speed. As shown in fig. 8a and 8 b.
Through the amplification analysis of the fluctuation section of a frequency doubling amplitude, the rotor vibration has the process of continuous increase, and meanwhile, the obvious beat vibration phenomenon occurs, and the beat vibration amplitude is continuously increased. As shown in fig. 8 c.
Claims (4)
1. The utility model provides a avoid aeroengine dish chamber hydrops unstability rotor design method which characterized in that, concrete process is:
step 1: determining the initial structural characteristics of the aeroengine rotor:
the initial structure characteristics comprise the initial structure and performance parameters of the aircraft engine rotor; wherein:
the aircraft engine rotor has an initial structure of an interlayer disc, and the centers of two end faces of the rotor are provided with through shaft holes; the determined structural parameters are the axial length H of the aircraft engine rotor, the outer diameter d of the rotor, the inner diameter R of the rotor and the aperture R of the shaft holei(ii) a The distance between the two inner surfaces of the rotor interlayer is L;
the performance parameter of the aircraft engine rotor is rotor density rhoiA rotor damping coefficient D and a stiffness coefficient K of the rotor;
step 2: judging whether the rotor is unstable or not:
judging whether the rotor of the aircraft engine has instability risk according to the calibration criterion of the rotor;
when the rotor is checked according to the calibration criterion, the rotor structure parameters preliminarily determined in the step 1 and the rotor performance parameters preliminarily determined are substituted into a calibration criterion formula, and a combination parameter H and a critical combination parameter H are calculatedcAnd obtaining a critical combination parameter HcAs reference line A;
comparing the obtained value of the combination parameter H with the value of the reference line A, and when the value of the combination parameter H is more than or equal to the value of the reference line A, the rotor has instability risk in the operation process;
when the combined parameter H is smaller than the value of the reference line A, the rotor has no instability risk in the operation process;
when the rotor has instability risk in the operation process, entering step 3, and carrying out optimization design and iterative check on the rotor again; when the rotor has no instability risk in the operation process, the rotor is operated in monitoring;
and step 3: re-optimizing design and iteratively checking:
the specific process of re-optimizing design and iterative check of the rotor is as follows:
changing the outer diameter R of the cavity of the rotor and/or the distance L between two inner surfaces of the rotor interlayer; when the outer diameter R of the cavity of the rotor and the distance L between the two inner surfaces of the rotor interlayer are changed, the outer diameter R of the cavity and the distance L between the two inner surfaces of the rotor interlayer are respectively reduced by 5-10% on the basis of the original initial design size;
repeating the step 2, and judging whether the rotor with the changed structure size and weight is unstable or not; specifically, each changed structural parameter is substituted into a checking criterion, and whether the rotor is unstable or not is judged; if the judgment result shows that the rotor is unstable, continuously changing the outer diameter R of the cavity of the rotor and/or the distance L between the two inner surfaces of the rotor interlayer, and carrying out optimization design again;
in repeated optimization design, if the design weight of the rotor exceeds the range after multiple times of optimization, the checking criterion still cannot be met, and the rotor needs to operate in monitoring;
and if the judgment result is that the rotor cannot be unstabilized, the design of the rotor is completed, and the rotor operates in monitoring.
2. A design method for avoiding disc cavity liquid accumulation instability of an aircraft engine as defined in claim 1, wherein the calibration criterion in the step 2 is:
recording the rotor structure combination parameter as H; when the rotor begins to generate unstable vibration, the critical value of the rotor structure combination parameter is Hc；
If H belongs to [0, H ∈c) The accumulated liquid in the rotor cavity can not cause the unstable vibration of the rotor;
if H is not less than HcWhen the liquid accumulation amount in the rotor disc cavity reaches the instability threshold liquid accumulation amount, instability vibration caused by the liquid accumulation in the disc cavity can be caused;
wherein:
in the above formula, RiIs the bore diameter of the shaft hole, R is the inner diameter of the rotor, L is the distance between two inner surfaces of the rotor interlayer, D is the damping coefficient of the rotor, K is the rigidity coefficient of the rotor, M is the mass of the rotor, mu is the viscosity coefficient of the effusion, rho is the density of the effusion, omega isnThe first-order critical rotating speed of the rotor is obtained, and the gamma is a constant of instability frequency caused by effusion and is taken as 0.8.
3. The design method for avoiding the disc cavity liquid accumulation instability rotor of the aircraft engine as claimed in claim 1, wherein the specific process of the rotor monitoring is as follows:
step 1, determining a criterion for judging instability of effusion in a cavity of a rotor disc:
the criterion for judging the instability of the effusion of the rotor disc cavity is as follows:
after a rotor crosses a first-order critical rotating speed, if the rotating speed variation range obtained by monitoring is within 50rpm, and the amplitude increment of the vibration total amount of the rotor exceeds 25%, the amplitude of the rotor is considered to be suddenly increased;
where RPM1 is the rotational speed at normal vibration; RPM2 is the rotational speed at which the amplitude increases; a1 is the monitored amplitude at normal vibration, A2 is the monitored amplitude at increased amplitude;
II 0.5X-1X subharmonic component A of rotor vibration(0.5X,1X)Background noise amplitude A greater than twicenoiseJudging that the rotor is unstable;
A(0.5X,1X)≥2Anoise
in the formula A(0.5X,1X)The harmonic dominant amplitude of the vibration 0.5X-1X frequency component is extracted; background noise amplitude AnoiseTaking the average value of 0.5X-1X harmonic component dominant amplitude when the rotor normally vibrates, and approximating the vibration amplitude before the first-order critical rotation speed;
III when the vibration signal of the rotor, A in 4 groups of vibration periods in successionmaxp-p-Aminp-pAll exceed the normal vibration peak value Anormalp-p25% of the total weight, the rotor is considered to be beating;
in the above formula, Amaxp-pFor the maximum peak-to-peak value within each group, Aminp-pThe minimum value of the peak value in each group is taken; i is a vibration period group, i is 1,2,3, 4;
step 2, monitoring vibration signals in the rotor running process, and judging whether the rotor is unstable or has instability risks according to the monitored rotor vibration signals;
when the subharmonic frequency amplitude is not monitored to exceed the limit all the time in the running process of the rotor, namely the three instability criteria are not met, the rotor normally runs without instability vibration risk caused by liquid accumulation;
when the subharmonic frequency amplitude is monitored to be out of limit in the operation process of the rotor, but the phenomenon of vibration beating does not occur to the amplitude sudden increase of the total vibration amount or the first frequency multiplication component of the vibration, namely the second criterion is met but the first criterion and the third criterion are not met, the temperature failure risk early warning is carried out, namely the rotor has the instability vibration risk caused by liquid accumulation, the operation of the rotor is stopped at the moment, and the operation can be carried out again after the fault is checked;
when the amplitude of subharmonic frequency is monitored to be out of limit in the operation process of the rotor, the phenomenon of beat vibration occurs when the amplitude of total vibration is suddenly increased or the first frequency multiplication component of vibration occurs simultaneously, namely the criterion two and the criterion three are met simultaneously, the rotor enters a destabilization vibration state caused by effusion, the effusion instability of a rotor disc cavity can be determined, the rotor operation is stopped, and faults are eliminated.
4. The design method for avoiding the disc cavity liquid accumulation instability rotor of the aircraft engine as claimed in claim 3, wherein when the vibration period of the rotor is determined, the vibration signal of the rotor is recorded, and the peak-to-peak value of the vibration time domain waveform of the rotor is continuously monitored; take 8 consecutive vibration cycles as a group.
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