A generalized solution of elasto-aerodynamic lubrication for aerodynamic compliant foil bearings

2020

Applied Sciences

Aerodynamic journal microbearings with microtribological phenomena significantly influence the operating stability of microfluidic devices. The modified Reynolds equations including different rarefaction models are derived and are solved by the partial derivative method and relaxation iteration algorithm. The effects of Knudsen number and bearing parameters on the static and dynamic characteristics of microbearings are investigated in detail. The results show that the rarefaction effect plays a crucial role in the ultra-thin gas film lubrication. The maximum film pressure of Fukui–Kaneko (FK) model is lowest and the result in Boltzmann model is largest in small Knudsen number regions. As the Knudsen number increases further, the curve of FK model is coincident with that of the Boltzmann model in the transition regime. The direct stiffness coefficients of Boltzmann model increase with the increase of eccentricity ratio and aspect ratio, whereas the effect of Knudsen number on the damping coefficients yields a relatively complicated trend.

Section: Governing Equations For Ultra-thin Gas Film Lubricationmentioning

confidence: 99%

“…Letting PH = S, (PH) 2 = S 2 = Π [32], the governing Equation (6) can be transformed into the elliptic partial differential equation form -…”

Section: Governing Equations For Ultra-thin Gas Film Lubricationmentioning

confidence: 99%

Research on Static and Dynamic Characteristics of Gas-lubricated Microbearings for Microfluidic Devices

2020

Applied Sciences

“…[13] into Eq. [12],δ 0 j can be obtained: [14] When the journal and the pads perturb with the same frequency , the dimensionless dynamic gas-film forces of the full tilting-pad bearing can be written as…”

Section: The Equivalent Dynamic Coefficientsmentioning

confidence: 99%

“…[14], [17], and [19], the dimensionless equivalent dynamic stiffness and damping coefficients can be expressed as 2 [21]…”

Section: The Equivalent Dynamic Coefficientsmentioning

confidence: 99%

Limits of Dynamic Coefficients of Self-Acting Tilting-Pad Gas Bearings

2009

Tribology Transactions

Many previously published articles have studied the effects of perturbation frequency on the dynamic coefficients of gas bearing, but they all do not give the rounded definition of dynamic coefficients in the whole frequency range. In this article, the dynamic stiffness and damping coefficients of tilting-pad bearings are calculated by the partial derivative method and the limits of dynamic coefficients are obtained by using the limit theory. Furthermore, the equivalent dynamic coefficients of tilting-pad bearings are also calculated, which makes it possible to denote the dynamic characteristics of the tilting-pad bearing with eight dynamic coefficients. In the article, the dynamic coefficients of the bearing are investigated in the whole frequency range. The numerical results indicate that the changing trends of dynamic coefficients with perturbation frequency are well in agreement with their limits. With the increase of perturbation frequency, the dynamic stiffness coefficients are all close to their corresponding limits, and the limits of all dynamic damping coefficients are equal to zero. Moreover, the cross-coupling terms of dynamic coefficients of the tilting-pad gas bearing are close to zero, which further reveals the main reason that the performance of the tilting-pad bearings is better than the generic fixed-pad bearings.

“…Heshmat and Ku investigated the effect of the excitation frequency and dynamic amplitude on the dynamic stiffness and damping coefficients of foil air bearing by using the two excitation tests method and indicated the frequency dependency of these dynamic coefficients [8]. In terms of theoretical study, Yu et al used partial derivative method to calculate the linear dynamic coefficients of foil air bearing and studied the effects of the eccentricity and perturbation frequency of journal on these coefficients [9]. This paper describes a multifunctional test rig for testing the performance of foil air bearings.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation on the performance of aerodynamic compliant foil air bearings

Deyi

2008 IEEE International Conference on Automation and Logistics

et al. 2008

Compliant foil air bearings have been successfully applied to a wide range of high-speed rotating machinery. It is very important to investigate the performance of this type of bearings. This paper describes an experimental identification into the static and dynamic performance of compliant foil air bearing. A multifunctional test rig is built and the test apparatus are introduced in detailed. The association of the bearing load capacity with the rotating speed and bearing eccentricity are studied by experimental measure. The dynamic stiffness and damping coefficients are calculated based on the experimental measures for a wide range of excitation frequency. The effect of the excitation frequency on these dynamic coefficients is also examined. The results are compared to those presented in published papers.