ISO/TS 31657-2:2020

Overview

ISO/TS 31657-2:2020 - Plain bearings - Hydrodynamic plain journal bearings under steady‑state conditions - Part 2 provides dimensionless characteristic functions and tabulated data for the calculation of multi‑lobed journal bearings (selected two‑, three‑ and four‑lobe designs). The Technical Specification gives the functions and curves required for operationally safe design under steady‑state (stationary) operating conditions, and is intended to be used together with ISO/TS 31657‑1 (symbols, presumptions and calculation examples).

Key topics

• Characteristic values for multi‑lobed bearings (two‑, three‑ and four‑lobe), listed in tables and plotted as curves for design use.
• Parameters and boundary conditions: relative lubrication pocket width (b = 0.8), gap ratios h in the operating range (approx. 0.02 ≤ h ≤ 1), and selected geometrical parameters (angular spans Ω, pocket centerlines φ, bearing width ratio B).
• Static characteristic values provided dimensionlessly, including:
  • Sommerfeld number (So),
  • Relative eccentricity (ε) and attitude angle (β),
  • Maximum lubricant film pressure parameter (pS⋅max),
  • Minimum relative film thickness (hmin),
  • Friction force parameter (f),
  • Lubricant flow rate parameters (Q^3, Qp, Q^2),
  • Non‑dimensional maximum lubricant temperature rise (ΔT).
• Dynamic characteristic values: non‑dimensional film stiffness coefficients (c_ik) and damping coefficients (d_ik) for use in rotordynamic analyses.
• Document structure: tabulated characteristic values (Tables 1–43) for different geometries; Annex A includes characteristic curves for selected four‑lobe bearings (example Ω = 70°, φ = 315°).

Applications and users

ISO/TS 31657‑2:2020 is practical for anyone involved in the design, analysis or maintenance of rotating equipment using hydrodynamic plain journal bearings:

• Bearing designers and mechanical engineers calculating load capacity, film thickness and friction for multi‑lobed plain bearings.
• Rotordynamics and vibration engineers using stiffness and damping coefficients in stability and critical speed analyses.
• OEMs of turbines, generators, compressors, pumps and large rotary machines specifying multi‑lobed journal bearings for improved performance and safety.
• Tribologists, maintenance engineers and simulation software developers who implement bearing models and want standardized characteristic functions. Using the tables and functions helps ensure consistent, operationally safe design and facilitates comparison between multi‑lobe geometries.

Related standards

• ISO/TS 31657‑1 - (referenced) explains symbols, presumptions, boundary conditions and includes calculation examples essential to applying Part 2.
• Produced by ISO/TC 123 (Plain bearings); consult national standards bodies or ISO for the complete ISO/TS 31657 series.

Keywords: ISO/TS 31657-2:2020, plain bearings, hydrodynamic plain journal bearings, multi-lobed journal bearings, Sommerfeld number, film stiffness, damping, characteristic values, steady-state design.