Published Online:May 2026
Product Name:The IUP Journal of Mechanical Engineering
Product Type:Article
Product Code:IJME020526
DOI:10.71329/IUPJMECH/2026.19.2.25-36
Author Name:Rahul Basu
Availability:YES
Subject/Domain:Engineering
Download Format:PDF
Pages:25-36
The paper presents a comprehensive dynamic stability analysis of a coupled twospool rotor system, modeled after modern aero-engines such as Rolls-Royce RB211. It evaluates the influence of intershaft stiffness (KIS) and intershaft damping (CIS) on critical speeds, whirl behavior, and stability margins of low-pressure (LP) and high-pressure (HP) rotors, which are dynamically linked via an intershaft bearing. The methodology employs a reduced-order mass-stiffness-damping model, incorporating gyroscopic effects and Eigenvalue analysis to derive natural frequencies, damping ratios, and stability characteristics. Simulations use a discrete matrix approach, validated against RB211 operational data, and generate Campbell diagrams and damping ratio plots to assess system response. The results indicate that increasing KIS from 2.5 MN/m to 10 MN/m raises the first critical speed by approximately 25% (from 3,800 rpm to 4,750 rpm), while CIS enhancement from 500 Ns/m to 10,000 Ns/m improves stability margins up to 30% by suppressing subsynchronous instabilities. These findings highlight the pivotal role of intershaft dynamics in optimizing aero-engine rotor performance, offering insights for design enhancements in multi-spool architectures.
Multi-spool aero-engine configurations, such as the Rolls-Royce RB211 and Trent families, rely on dynamically coupled low-pressure (LP) and high-pressure (HP) rotor systems to achieve enhanced performance and efficiency.