SIW bandpass filters in modified box‐section scheme with bypass/constant/frequency‐dependent coupling in diagonal cross‐coupling path

This paper examines stability of the flexible single mass rotor, acted on by motion induced forces due to aero-dynamic cross-coupling and supported most generally by oil film tilting pad bearings which are in turn mounted on flexible, damped supports. Plotted results include the frequency dependent spring and damping coefficients for the 4-pad tilting pad bearing, damping coefficients for the 360-deg squeeze bearing and stability plots of rotor-bearing systems including aerodynamic cross-coupling, the 4-pad tilting pad bearing and the 150-deg partial arc bearing with various support arrangements.

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Numerical Investigations on the Leakage and Rotordynamic Characteristics of Pocket Damper Seals—Part I: Effects of Pressure Ratio, Rotational Speed, and Inlet Preswirl

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.4028373 ◽

2014 ◽

Vol 137 (3) ◽

Cited By ~ 6

Author(s):

Zhigang Li ◽

Jun Li ◽

Zhenping Feng

Keyword(s):

Rotational Speed ◽

Pressure Ratio ◽

Cross Coupling ◽

Inlet Pressure ◽

Frequency Dependent ◽

Rotordynamic Coefficients ◽

Outlet Pressure ◽

Swirl Velocity ◽

Coupling Stiffness ◽

Orbit Model

Effects of pressure ratio, rotational speed and inlet preswirl on the leakage and rotordynamic characteristics of a eight-bladed fully partitioned pocket damper seal (FPDS) were numerically investigated using proposed three-dimensional (3D) transient computational fluid dynamics (CFD) methods based on the multifrequency elliptical whirling orbit model. The accuracy and availability of the multifrequency elliptical whirling orbit model and the transient CFD numerical methods were demonstrated with the experimental data of frequency-dependent rotordynamic coefficients of the FPDS at two rotational speeds with high preswirl conditions. The frequency-dependent rotordynamic coefficients of the FPDS at three pressure ratios (three inlet pressures and three outlet pressures), three rotational speeds, three inlet preswirls were computed. The numerical results show that changes in outlet pressure have only weak effects on most rotordynamic coefficients. The direct damping and effective damping slightly increase in magnitude with decreasing outlet pressure at the frequency range of 20–200 Hz. The effect of inlet pressure is most prominent, and increasing inlet pressure for the FPDS results in a significant increase in the magnitudes of all rotordynamic coefficients. The magnitudes of the seal response force and effective damping are proportional to pressure drop through the seal. Increasing rotational speed and increasing inlet preswirl velocity both result in a significant decrease in the effective damping term due to the obvious increase in the magnitude of the destabilizing cross-coupling stiffness with increasing rotational speed or increasing preswirl velocity. The crossover frequency of effective damping significantly increases and the peak magnitude of effective damping decreases with increasing rotational speed or increasing preswirl velocity. The destabilizing cross-coupling stiffness is mainly caused by the circumferential swirl velocity generating from high rotational speed and inlet preswirl. Reducing swirl velocity (such as swirl brake) can greatly enhance the stabilizing capacity of the FPDS.

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Two- and Four-Pole Multilayer SIW Filter with High Selectivity and Higher-Order Mode Suppression

Frequenz ◽

10.1515/freq-2018-0214 ◽

2019 ◽

Vol 73 (5-6) ◽

pp. 209-217 ◽

Cited By ~ 1

Author(s):

Dinghong Jia ◽

Quanyuan Feng ◽

Qianyin Xiang

Keyword(s):

High Selectivity ◽

Filter Design ◽

Design Method ◽

Single Layer ◽

Cross Coupling ◽

Bandpass Filters ◽

Coupling Scheme ◽

Transmission Zeros ◽

Compact Size ◽

Spurious Mode

Abstract This letter presents an approach to design two-pole source-load coupling and four-pole cross-coupling substrate integrated waveguide (SIW) bandpass filters based on multilayer process. Utilizing the field distribution, the vertical magnetic and electric coupling of fundamental mode is designed by suppressing the first spurious mode. Then, source-load and cross-coupling schemes are realized with controllable features in two-pole and four-pole filters, respectively. The harmonic passband produced by TE102 mode can be suppressed by proper coupling technique enabling the connection with TE102 mode in two- and four-pole filter designs, respectively. Three transmission zeros, which are derived from source-load coupling, are introduced around the passband of two-pole filter to improve its selectivity. In the four-pole filter design, a six-order cross-coupling scheme including source and load produces four transmission zeros around the passband, leading to a sharp selectivity. In addition, another transmission zero is generated at the adjacent location of the passband to improve the out-of-band rejection. Compared with conventional horizontally coupled filters made of single layer, the proposed filters show a compact size. To demonstrate the proposed design method, a two-pole and a four-pole double-layered SIW bandpass filters are fabricated and measured. Measured results show that the proposed filters exhibit high selectivity and good out-of-band rejection, as well as a good agreement between simulated and measured results.

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Numerical Investigations on the Leakage and Rotordynamic Characteristics of Pocket Damper Seals: Part I — Effects of Pressure Ratio, Rotational Speed and Inlet Preswirl

Volume 5C: Heat Transfer ◽

10.1115/gt2014-25300 ◽

2014 ◽

Author(s):

Zhigang Li ◽

Jun Li ◽

Zhenping Feng

Keyword(s):

Rotational Speed ◽

Pressure Ratio ◽

Cross Coupling ◽

Inlet Pressure ◽

Frequency Dependent ◽

Rotordynamic Coefficients ◽

Outlet Pressure ◽

Swirl Velocity ◽

Coupling Stiffness ◽

Orbit Model

Effects of pressure ratio, rotational speed and inlet preswirl on the leakage and rotordynamic characteristics of a eight-bladed fully-partitioned pocket damper seal (FPDS) were numerically investigated using proposed 3D transient CFD methods based on the multi-frequency elliptical whirling orbit model. The accuracy and availability of the multi-frequency elliptical whirling orbit model and the transient CFD numerical methods were demonstrated with the experimental data of frequency-dependent rotordynamic coefficients of the FPDS at two rotational speeds with high preswirl conditions. The frequency-dependent rotordynamic coefficients of the FPDS at three pressure ratios (three inlet pressures and three outlet pressures), three rotational speeds, three inlet preswirls were computed. The numerical results show that changes in outlet pressure have only weak effects on most rotordynamic coefficients. The direct damping and effective damping slightly increase in magnitude with decreasing outlet pressure at the frequency range of 20–200Hz. The effect of inlet pressure is most prominent, and increasing inlet pressure for the FPDS results in a significant increase in the magnitudes of all rotordynamic coefficients. The magnitudes of the seal response force and effective damping are proportional to pressure drop through the seal. Increasing rotational speed and increasing inlet preswirl velocity both result in a significant decrease in the effective damping term due to the obvious increase in the magnitude of the destabilizing cross-coupling stiffness with increasing rotational speed or increasing preswirl velocity. The crossover frequency of effective damping significantly increases and the peak magnitude of effective damping decreases with increasing rotational speed or increasing preswirl velocity. The destabilizing cross-coupling stiffness is mainly caused by the circumferential swirl velocity generating from high rotational speed and inlet preswirl. Reducing swirl velocity (such as swirl brake) can greatly enhance the stabilizing capacity of the FPDS.

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Direct synthesis of tubular bandpass filters with frequency-dependent inductors

1998 IEEE MTT-S International Microwave Symposium Digest (Cat. No.98CH36192) ◽

10.1109/mwsym.1998.689395 ◽

2002 ◽

Cited By ~ 4

Author(s):

Qiang Huang ◽

Ji-Fuh Liang ◽

Dawei Zhang ◽

Guo-Chun Liang

Keyword(s):

Direct Synthesis ◽

Bandpass Filters ◽

Frequency Dependent

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Planar three-resonator bandpass filters with cross coupling

Journal of Communications Technology and Electronics ◽

10.1134/s1064226917020127 ◽

2017 ◽

Vol 62 (2) ◽

pp. 185-193 ◽

Cited By ~ 6

Author(s):

A. V. Zakharov ◽

M. E. Il’chenko ◽

I. V. Trubarov

Keyword(s):

Cross Coupling ◽

Bandpass Filters

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Quasi-Reflectionless Microstrip Bandpass Filters With Improved Passband Flatness and Out-of-band Rejection

10.36227/techrxiv.12276524 ◽

2020 ◽

Author(s):

Xiaohu Wu ◽

Yingsong Li ◽

Xiaoguang Liu

Keyword(s):

Impedance Matching ◽

Cross Coupling ◽

Bandpass Filters ◽

Output Analysis ◽

Design Concepts ◽

Frequency Responses ◽

Transmission Zeros ◽

Prior Art ◽

Coupled Lines ◽

Stopband Attenuation

High-order quasi-reflectionless bandpass filters with improved passband flatness and good impedance matching both in-band and out-of-band are proposed in this work. The proposed design consists of conventional coupled-lines bandpass sections loaded with the presented absorptive stubs at the input and output. Analysis shows that the absorptive stub is equivalent to a 2-pole bandstop filter. Compared to the prior art, the higher-order nature of the presented absorptive stub enables a flatter passband and better out-of-band rejection. The overall filter stopband attenuation can be readily improved by increasing the number of coupled-lines sections without altering the passband responses. Furthermore, cross-coupling between the two absorptive stubs can be used to improve the out-of-band rejection by introducing two transmission zeros without affecting the absorption characteristics. The proposed design concepts are experimentally validated by the design and fabrication of a set of 2.4-GHz 1-, 2-, and 3-pole microstrip quasi-reflectionless bandpass filters. Measured frequency responses of these filters closely match those of the simulation.

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