Annular Honeycomb-Stator Turbulent Gas Seal Analysis Using a New Friction-Factor Model Based on Flat Plate Tests

Abstract

A new empirical friction-factor model for honeycomb surfaces based on flat plate test results has been developed as a function of Mach number and dimensionless pressure and honeycomb geometry variables. A rotordynamic analysis for centered, turbulent-annular-honeycomb-stator seals has been developed incorporating the new empirical friction-factor model for honeycomb-stator surfaces. The results of the new analysis in predicting the rotordynamic and leakage characteristics have been compared to: (a) Moody’s friction-factor model analysis, and (b) experimental data for short (L/D = 1/6, 25.4 mm long) seal. The comparisons show that the new honeycomb friction-factor model greatly improves the predictions of leakage and rotordynamic coefficients compared to Moody’s friction-factor model, especially, for direct and cross-coupled stiffness.

Bioinspired engineering of honeycomb structure – Using nature to inspire human innovation

“…Since the 1980s, honeycomb seals with hexahedral cellular structure have been frequently used as replacement for the conventional labyrinth seals to ensure a minimum gap loss and increased strength in turbomachinery [231,232]. Among all the geometrical parameters of honeycomb seal, the sealing clearance and honeycomb cell size are the most important factors in the design process [40,[233][234][235][236][237][238][239][240][241][242][243][244]. In particular, the Dresser-Clark company for the first time uses them as end seals for high-pressure centrifugal compressors [245].…”

The Acoustic Influence of Cell Depth on the Rotordynamic Characteristics of Smooth-Rotor/Honeycomb-Stator Annular Gas Seals

“…An implicit requirement in all of the analyses leading to the model of Eq. (I) is that the acoustic frequencies of the gas within an annular seal be substantially above the rotordynamic frequencies of interest This paper will use the two-control-volume model of Ha and Childs (1994) to demonstrate that this requirement is generally not met, and consequently, honeycomb seals can not be modeled adequately with frequency-independent stiffness, damping, and mass coefficients.…”

The Acoustic Influence of Cell Depth on the Rotordynamic Characteristics of Smooth-Rotor/Honeycomb-Stator Annular Gas Seals

“…Various improvements were attempted, starting with Elrod et al (1989Elrod et al ( , 1990 who developed an improved model for the inlet loss. Ha and Childs (1994) implemented friction-factor data from flat-plate measurements to improve the friction-factor model for honeycomb surfaces. In a response to a discussion of their paper, Ha and Childs expanded the model to allow radial transient flow into the honeycomb surface.…”

“…An implicit requirement in all of the analyses leading to the model of Eq. (I) is that the acoustic frequencies of the gas within an annular seal be substantially above the rotordynamic frequencies of interest This paper will use the two-control-volume model of Ha and Childs (1994) to demonstrate that this requirement is generally not met, and consequently, honeycomb seals can not be modeled adequately with frequency-independent stiffness, damping, and mass coefficients. The prior governing equations for plain and honeycomb gas seals (Nelson, 1985, and) employ a single control volume.…”

“…In essence, the honeycomb seal land acts as a porous surface. Hence, as indicated in the authors' response of Ha and Childs (1994), the use of an additional control volume (adjacent to the main flow control volume) which allows flow to only enter and exit in the radial direction can better describe the physical nature of the flow. Figure 1 shows the locations of the two control volumes in a honeycomb seal with the clearance exaggerated for clarity.…”