- 1、本文档共5页,可阅读全部内容。
- 2、有哪些信誉好的足球投注网站(book118)网站文档一经付费(服务费),不意味着购买了该文档的版权,仅供个人/单位学习、研究之用,不得用于商业用途,未经授权,严禁复制、发行、汇编、翻译或者网络传播等,侵权必究。
- 3、本站所有内容均由合作方或网友上传,本站不对文档的完整性、权威性及其观点立场正确性做任何保证或承诺!文档内容仅供研究参考,付费前请自行鉴别。如您付费,意味着您自己接受本站规则且自行承担风险,本站不退款、不进行额外附加服务;查看《如何避免下载的几个坑》。如果您已付费下载过本站文档,您可以点击 这里二次下载。
- 4、如文档侵犯商业秘密、侵犯著作权、侵犯人身权等,请点击“版权申诉”(推荐),也可以打举报电话:400-050-0827(电话支持时间:9:00-18:30)。
查看更多
critical speed
1-5
Technical Bulletin
TBN017.0/1998
CRITICAL SPEED OF SHAFTS
All rotating shaft, even in the absence of
external laod, deflect during rotation.
The combined weight of a shaft and
wheel can cause deflection that will
create resonant vibration at certain
speeds, known as Critical Speed.
The magnitude of deflection depends
upon the followings :-
(a) stiffness of the shaft and it’s support
(b) total mass of shaft and attached parts
(c) unbalance of the mass with respect
to the axis of rotation
(d) the amount of damping in the
system
Therefore, the calculation of critical
speed for fan shaft is necessary.
Critical Speed Equation (Nc)
There are two method used to calculate
critical speed, Rayleigh-Ritz and
Dunkerley Equation. Both the Rayleigh-
Ritz and Dunkerley equation are an
approximations to the first natural
frequency of vibration, which is assumed
to be nearly equal to the critical speed of
rotation.
In general, the Rayleigh-Ritz equation
overestimates and the Dunkerley
equation underestimates the natural
frequency.
The equation illustrated below is the
Rayleigh-Ritz equation, good practice
suggests that the maximum operation
speed should not exceed 75% of the
critical speed.
st
g30
Nc,speedCritical
δπ
=
where :
g = gravity acceleration (9.81 m/s2)
δst = total maximum static deflection
Critical speed depend upon the
magnitude or location of the load or
load carried by the shaft, the length of
the shaft, its diameter and the kind of
bearing support.
Total Maximum Static Deflection (δst)
The maximum static deflection, δst, is
obtained by adding both the maximum
static deflection of the rotating shaft and
the load.
(1) Maximum static deflection on shaft
(δstI)
1.1)
EI384
wL5
Ist
3
=δ
2-5
1.2)
EI8
wL
Ist
3
=δ
(2) Maximum static deflection on load
only (δst2)
2.1 )
EI48
WL
2st
3
=δ
2.2 )
您可能关注的文档
- Chapter3-Switch_Tchnology_Fundamentals.ppt
- Chapter5复习.pdf
- Chapters 19,23 Confidence Intervals.ppt
- CHARACTERISTICS OF ORGANIC GEOCHEMISTRY OF SEDIMENTS IN THE NORTHERN PART OF THE SOUTH HUAN.pdf
- Characterization and corrosion studies of fluoride conversion coating on degradable Mg implants.pdf
- CHARACTERIZATION OF IRON COMPLEXES SUPPORTED ON POLYMER AND THEIR CATALYTIC ACTIVITY IN BUT.pdf
- Characterization and properties of catalase immobilized onto controlled pore glass and its applicati.pdf
- Characterization of protomodular varieties of universal algebras.pdf
- Characterizing integers among rational numbers with a universal-existential formula.pdf
- Charge Exchange Spectra of Hydrogenic and He-like Iron.pdf
文档评论(0)