maintenancecenter, writer
115
edits
Difference between revisions of "MultiPlane Balancing Turbocharger Aplication"
Jump to navigation
Jump to search
m
MultiPlane Balancing Turbocharger Aplication (view source)
Revision as of 20:05, 24 June 2020
, 20:05, 24 June 2020English edits
m (English edits) |
|||
| Line 6: | Line 6: | ||
Turbocharger rotors are small items but because of their high rotational speed, they may experience several critical speeds and should be considered as flexible. For that reason it is not possible to balance the rotor at only one speed: several speeds should be considered: so a run-up or a run-down. | Turbocharger rotors are small items but because of their high rotational speed, they may experience several critical speeds and should be considered as flexible. For that reason it is not possible to balance the rotor at only one speed: several speeds should be considered: so a run-up or a run-down. | ||
The number of possible balancing planes are typically up to 4: 2 on the compressor side and 2 on the turbine side. Depending on the | The number of possible balancing planes are typically up to 4: 2 on the compressor side and 2 on the turbine side. Depending on the case, it may not be possible to add or remove weight depending on the material characteristics (drilling, scrapping, grinding) on each of the planes. Then, a selection of the planes has to be considered: typically the plate of compressor side may be a good selection. The blades stay in principle untouched. | ||
[[Image:Best_practices_for_flexible_balancing_03.png|framed|none]] | [[Image:Best_practices_for_flexible_balancing_03.png|framed|none]] | ||
Possible balancing planes on turbochargers | Possible balancing planes on turbochargers: | ||
The balancing procedure should be considered similarly to a modal analysis. The idea is to determine the relationship between the response (vibration measured at the bearing) and the exciting force (the imbalance). So adding a known weight is like impacting a structure with an impact hammer and measuring the injected force. Once the relationship is known (the influence coefficient matrix), it is easy to locate the original force (imbalance) and propose and correction weight. | The balancing procedure should be considered similarly to a modal analysis. The idea is to determine the relationship between the response (vibration measured at the bearing) and the exciting force (the imbalance). So adding a known weight is like impacting a structure with an impact hammer and measuring the injected force. Once the relationship is known (the influence coefficient matrix), it is easy to locate the original force (imbalance) and propose and correction weight. | ||
| Line 22: | Line 22: | ||
* '''Setting of the input range:''' After the initial balancing, it may appear that the 1X component becomes smaller. It may be necessary to adapt the input range (doing an auto range for example). | * '''Setting of the input range:''' After the initial balancing, it may appear that the 1X component becomes smaller. It may be necessary to adapt the input range (doing an auto range for example). | ||
* '''Trial weights positioning: '''The trial weights position is important as well as it should bring new information compared to the original run or other trials. | * '''Trial weights positioning: '''The trial weights position is important as well as it should bring new information compared to the original run or other trials. | ||
* '''RPM run up/down rate:''' It is important to have the same rotor acceleration between the initial runs and the trial runs. The structure may not behave in the same way depending on how | * '''RPM run up/down rate:''' It is important to have the same rotor acceleration between the initial runs and the trial runs. The structure may not behave in the same way depending on how quickly speed increases or decreases. | ||
* '''Data:''' Data of the different runs should be synchronized from one to another. For calculating the influence coefficients matrix, the data of the different runs (Initial, Test 1, Test 2 etc. …) should be comparable at the exact same RPM value. | * '''Data:''' Data of the different runs should be synchronized from one to another. For calculating the influence coefficients matrix, the data of the different runs (Initial, Test 1, Test 2 etc. …) should be comparable at the exact same RPM value. | ||
* '''RPM selection:''' it is '''probably the most sensitive point to take into account''' when achieving balancing. The data should be selected with care because the wrong data or too much data would get the user to biased results. | * '''RPM selection:''' it is '''probably the most sensitive point to take into account''' when achieving balancing. The data should be selected with care because the wrong data or too much data would get the user to biased results. | ||
| Line 37: | Line 37: | ||
Other types of sensors such as force sensors or proximity probes can be used. | Other types of sensors such as force sensors or proximity probes can be used. | ||
During balancing, the purpose is to concentrate on the rotor independently from the surrounding supporting or driving structure. It is very comparable to modal analysis when a structure is | During balancing, the purpose is to concentrate on the rotor independently from the surrounding supporting or driving structure. It is very comparable to modal analysis when a structure is hung with rubber band. In this way, one wants to measure the response of only the test item independently from the rest. | ||
===Trial weights positioning=== | ===Trial weights positioning=== | ||
Trial weights should be positioned in order to excite the modes that should be balanced. In the example below, the 3 first modes are excited by the weights. Run 1 | Trial weights should be positioned in order to excite the modes that should be balanced. In the example below, the 3 first modes are excited by the weights. Run 1 excites the first rigid mode, Run 2 the second one and Run 3 excites the first bending mode. | ||
[[File:trail.png|framed|none]] | [[File:trail.png|framed|none]] | ||
| Line 71: | Line 71: | ||
====One should avoid==== | ====One should avoid==== | ||
* | * Structural resonances of the support (impact testing of the support/bearing may be useful prior to the balancing test). | ||
* | * Stationary phase (not much information). | ||
* | * Resonance itself as the phase variations may be unstable (noisy phase). | ||
====One should choose==== | ====One should choose==== | ||