Steady-state and stability analysis of a four-lobe journal bearing with non-newtonian lubricant considering slip
Amar Murthy Ambarkar, Raghunandana K.Purpose
The fundamental goal of this research is to develop a modified Reynolds equation capable of capturing both wall-slip phenomena and the non-linear properties of non-Newtonian fluids. This is accomplished by developing a single mathematical model that predicts the operational performance of a four-lobe journal bearing. The paper explores the steady-state features and stability behavior of these bearings using Navier’s slip-length model and the power-law model.
Design/methodology/approach
The steady-state pressure is estimated using the modified Reynolds equation with suitable boundary conditions, yielding pressure at all nodes, and the Gauss-Seidel method ensures convergence. These values are then utilized to compute the pressure in each lobe of the four-lobe bearing. The load-carrying capacity is approximated using Simpson’s rule. A non-linear transient analysis is performed to determine the journal stability, and the mass parameter is calculated using equations of motion. The flow process depicted summarizes the overall method.
Findings
The four-lobe bearing’s whirl ratio decreases as eccentricity ratios rise and n falls. At an eccentricity ratio of 0.8, the whirl ratio is lowest for n = 0.75. The power law index levels where this variation is observed range from 0.25 to 0.75. It is also clear that to run the four-lobe bearing with the least amount of spinning, the bearing needs to have a larger eccentricity ratio and a higher power law index, n.
Practical implications
The proposed model is an effective tool for optimizing bearing design, allowing engineers to alter crucial factors during the design process. Its practical applications include improving the performance of steam turbines, medium-to-small turbochargers, heavy-duty vehicle engines, generators, crankshafts and connecting rods. The updated model enables these components to operate at higher rotational speeds, with greater weights, and under harsher operating circumstances.
Originality/value
A theoretical analysis is provided in this part to assess the effect of wall slip and non-Newtonian lubricant on the stability of journal bearings. The current study exclusively analyzes cylindrical whirls. Furthermore, the study’s goal is to evaluate the influence of non-Newtonian lubricants on bearing stability in the laminar flow regime exclusively. A non-linear transient study of a rigid rotor supported on a journal bearing operating in a non-Newtonian lubricant with wall slip and under steady unidirectional force is performed. The non-linear time transient approach is utilized to replicate the journal center trajectory and hence determine the speed-dependent stability value.
Peer review
The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2026-0115/