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Critical speed

About: Critical speed is a research topic. Over the lifetime, 2764 publications have been published within this topic receiving 31365 citations.


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Journal ArticleDOI
TL;DR: In this article, a method for calculating critical speeds, unbalance response and damped natural frequencies of long rotors on a flexible foundation is described, and the shaft and the foundation are separately and coupled at the bearings through impedance matching.
Abstract: A method is described for calculating critical speeds, unbalance response and damped natural frequencies of long rotors on a flexible foundation. The shaft and the foundation are calculated separately and coupled at the bearings through impedance matching. Included in the analysis is also a method for representing the shaft response by an expansion in its free-free modes.

13 citations

Journal ArticleDOI
TL;DR: In this article, the effect of fluid viscosity on the developing process of the instability in an over-hung flexible rotor partially filled with fluid, the dynamical behavior of the rotor system while the instability occurs, and the unstable region of rotational speeds were investigated.
Abstract: The effect of fluid viscosity on the developing process of the instability in an over-hung flexible rotor partially filled with fluid, the dynamical behavior of the rotor system while the instability occurs, the unstable region of rotational speeds, and the whirl frequency of the rotor system in the unstable region of rotational speeds, are experimentally investigated in this paper. It is shown that when the rotational speed is just over the reduced first critical speed of the fluid-filled rotor system that is less than the first critical speed of empty rotor system, the unstable motion occurs. The rotor system in the unstable speed region does not whirl at either a constant rotational speed or the first critical speed of the empty rotor system, the whirl frequency of the rotor system in the unstable speed region, dominated by the fluid-filled ratio and weakly depending on the viscosity of fluid, linearly increases with the rotational speed. There exists a hysteresis range of rotational speeds at the upper bound of the unstable speed region, which is not caused by the rotor transient motion when passing through the unstable speed region. As the fluid viscosity increases, both the unstable speed region and the hysteresis region narrow. The influence of the fluid viscosity on the unstable speed region of a rotor filled with a high viscosity fluid must be considered. DOI: 10.1115/1.2166857

13 citations

Journal ArticleDOI
TL;DR: A predictive method valid up to the critical speed for determining the six degree-offreedom trajectories of stores released from single, TER, or MER configurations mounted on realistic aircraft is presented.
Abstract: This paper presents a predictive method valid up to the critical speed for determining the six degree-offreedom trajectories of stores released from single, TER, or MER configurations mounted on realistic aircraft. A computer program has been developed to calculate the aerodynamic forces and the trajectory. The paper also presents comparisons with data selected from an extensive wind-tunnel test program designed to test the theory through systematic measurements. Generally, the method predicts accurately the experimentally measured flowfields, store loadings, and six-degree-of-freedom trajectories.

13 citations

Journal ArticleDOI
TL;DR: In this article, the authors describe the analytical basis and the method of application for direct propagation of conical sections and trunnions for a transfer matrix analysis of a rotor model.
Abstract: The transfer matrix method for rotordynamic analysis (alternately hnown as the HlI1P or LMP method) has enjoyed wide popularity due to its flexibility and ease of application. A number of computer programs are generally available which use tfl,is method in various forms to perform undamped critical speed, unbalance response, damped critical speed and stability analyses. For all of these analyses, the assembly of the transfer matrices from the rotor model is essentially the same. In all cases, the rotor model must be composed entirely of cylindrical beam elements. There are two situations when this limitation is not desirable. The first situation is when the rotor being modelled has one or more sections whose cross sections vary continually i'IJ the axial direction. The most common of these sections is the conical section. Pres­ ently, a conical section must be modelled as a series of "steps" of cylindrical sections. This adversely affects both the simplicity and accuracy of the rotor model. The second situation when current transfer matrix techniques are not accurate is when the rotor being modelled has one or more sections that do not behave as beam elements. The most common example is a trunnion which behaves as a plate. This paper describes the analytical basis and the method of application for direct reprffSentation of conical sections and trunnions for a transfer matrix analysis. Analytical results are cur­ rently being generated to demonstrate the need for and advantages of these modelling procedures.

13 citations

Journal ArticleDOI
TL;DR: In this article, a closed-form solution for rigid-body motions of two-dimensional traveling, sagged cables with a nonlinear geometrical constraint is developed, which shows that the rigid body motions are always stable even if the translation speed is over the critical speed.

13 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20241
202343
2022120
202182
202092
2019102