Kvazistik Muvozanatsizlikni Tushunish
Kvazi-statik muvozanatsizlik ning o'ziga xos va nisbatan kam uchraydigan turi hisoblanadi dinamik muvozanatsizlikni. Bu holat rotorning bosh inersiya o'qi valning aylanish o'qi bilan kesishganda, ammo not rotorning og'irlik markazida yuz beradi. Oddiy qilib aytganda, bu holat o'z ichiga ham statik muvozanatsizlik and juftlik muvozanatsizligi — with the special feature that the static and couple unbalance vectors lie in one and the same axial plane. That coplanar alignment is what gives it its name and its distinctive behaviour.
1. Ta'rif: Kvazistik Muvozanatsizlik Nima?
Tasavvur qilish uchun mukammal balanslangan rotorni ta'riflaydigan narsani eslang: uning bosh inersiya o'qi aylanish o'qi bilan ustma-ust tushadi. Turli xil unbalance ikkita o'qning bir-biridan qanday ajralishi mumkinligini turli yo'llar bilan tavsiflaydi. Kvazi-statik muvozanatsizlikda ikkita o'q cross — they intersect — but the crossing point is offset along the shaft from the centre of gravity rather than sitting on it. Geometrically this is a tilted-and-shifted axis whose static and couple ingredients lie in the same axial plane — it is precisely that coplanar combination which makes the two axes intersect at all.
Like every form of dynamic unbalance, it can only be fully measured while the rotor is spinning. Because the whole condition is equivalent to a single resultant unbalance acting in one specific axial plane, a single correction of the right magnitude in that samolyot can remove it — provided that plane is accessible on the machine; otherwise it is treated as an ordinary two-plane balancing job. A purely static check on knife-edges cannot reveal it, because the couple component only produces forces under rotation.
2. Boshqa Muvozanatsizlik Turlari bilan Munosabat
Kvazi-statik muvozanatsizlikni uchta standart toifaga nisbatan joylashtirib ko'rish foydali:
- Static unbalance: faqat og'irlik markazining val o'qidan siljishi. U bir xil fazadagi in phase ikkita podshipnikda.
- Moment muvozanatsizligi: faqat “silkinish” — qarama-qarshi uchlarida va qarama-qarshi tomonlarida teng og'ir nuqtalar mavjud. U 180 gradus faza siljishida podshipniklarda.
- Dinamik muvozanatsizlik: umumiy holat — bir-biriga nisbatan ixtiyoriy faza burchagida statik va juft muvozanatsizlikning kombinatsiyasi.
- Kvazi-statik muvozanatsizlik: a special case of dynamic unbalance in which the static and couple unbalance vectors lie in the same axial plane, so the tilted principal axis still crosses the shaft axis (at a point other than the centre of gravity).
Boshqacha aytganda, har qanday kvazi-statik rotor dinamik jihatdan muvozanatsiz, ammo faqat ma'lum bir geometrik tasodif “kvazi-statik” belgisiga loyiq bo'ladi.
3. Amaliy Misol: Konsol Rotori
Klassik darslik misoli — overhung rotor uning muvozanatsizligi mashinaning og'irlik markazidan uzoqda, bitta tekislikda joylashgan. Uzun valning uchiga, ikkala podshipnikdan tashqarida o'rnatilgan og'ir qanot to'plamiga ega yirik sanoat ventilyatorini tasavvur qiling.
Faraz qilaylik, ventilyator diskida bitta og'ir nuqta mavjud — disk o'zida sof statik muvozanatsizlik. Ushbu bir kuch ikkita podshipnikka nosimmetrik tarzda ta'sir etadi:
- Ventilyatorga yaqinroq podshipnik katta tebranish kuchini his qiladi.
- Ventilyatordan uzoqroqda joylashgan podshipnik ham kuch his qiladi, ammo massa tayanchlardan tashqarida “konsol” holatida bo'lgani uchun bu kuch yaqin podshipnik atrofidagi burilish harakati orqali ta'sir etadi.
Podshipniklardagi umumiy natija — bu tebranish (statik) va silkinish (juft) komponentlarini birlashtiradigan murakkab harakat. Ikkisi ham bitta jismoniy og'ir nuqtadan kelib chiqqanligi sababli, ular o'rtasida qat'iy nisbat mavjud — va aynan shu qat'iy nisbat kvazistatatik holatni keltirib chiqaradi. Shuning uchun ham tashqariga chiqib turuvchi rotorlar juda sezgir bo'ladi va deyarli har doim ikki tekislikda balanslashtirishni talab qiladi.
4. Correction
In principle, quasi-static unbalance can be removed by a single correction in the appropriate axial plane, because it is equivalent to one resultant unbalance acting in that plane. In practice that exact plane is often not accessible on the assembled machine, so in the field it is corrected just like any general dynamic unbalance. The balancing workflow is:
- Tebranishni o'lchash amplitude and phase at 1× running speed ikki podshipnik joylashuvida.
- Kerakli qiymatlarni hisoblash muvozanatlash og'irliklari va ularning burchak joylashuvi uchun tanlangan ikki tuzatish tekisligida, odatda influence-coefficient method with a trial weight.
- Og'irliklarni statik va juft komponentlarni bir vaqtda bekor qiladigan tarzda o'rnating.
Amaliyotda bu standart ikki tekislikda balanslashtirish ish hisoblanadi. Masalan, Balanset-1A kabi ko'chma ikki kanalli asbob har ikki podshipnikda amplituda va fazani o'lchaydi, rotorning ta'sir koeffitsientlarini aniqlaydi va har bir tekislik uchun massa va burchakni hisoblab chiqadi — so'ngra qoldiq nomuvozanat talab qilingan ISO 21940-11 sifat darajasiga muvofiqligini tekshiradi. Tahlilchi faza o'qishlaridan holatni kvazistatatik deb aniqlashi mumkin, ammo amaliy tuzatish har qanday dinamik balanslanmagan holat uchun qo'llaniladigan standart ikki tekislikli protseduradan iborat.
5. Farqni Ajratishning Ahamiyati
If the field routine is usually the same two-plane job, why name the condition at all? Because recognising a quasi-static pattern aids understanding — and it can even simplify the procedure, since a single correction in the right axial plane is sufficient when that plane is accessible. The phase relationship tells the engineer that a single overhung heavy spot — rather than two independent ones — is the likely physical cause, which guides where to look for the source: a damaged blade, accumulated product, or an assembly fault on the overhung disk. That insight is part of the broader value of careful phase interpretation in rotor dynamics.
