Session: 23-04 Gas Lubricated Journals

Paper Number: 154169

Evaluating the Influence of Different Equations of State on Real Gas Effects in Herringbone Grooved Bearings 

The ideal gas model is a simplified approximation of real gas behavior and can be used under certain conditions where the assumptions of the ideal gas law are valid. It's commonly employed in situations where the gas behaves predictably in terms of pressure, volume, and temperature. The reasons for using ideal gas in the bearing models are its relatively simple implementation, reasonable calculation time, and good correspondence to the experimental results for certain gases and conditions. Some of the conditions when the ideal gas model can be used are comparatively low pressure, moderate to high temperature, and conditions that are far from critical gas temperature and pressure. Most gases can be modeled with the ideal gas model under normal atmospheric conditions (room temperature and pressure) with sufficient accuracy.

The developing industry pushes the requirements of the machine components to the limits, and bearings with optimal parameters and specific requirements such as using process gases as lubricants and operation at critical conditions can be met more often in modern applications. In certain high-performance applications, such as turbomachinery with gas-lubricated bearings, the behavior of gases deviates significantly from the ideal gas law, particularly at high pressures, low temperatures, or near the critical point of the gas. These deviations, known as real gas effects, can substantially impact bearing performance, influencing load capacity, damping, and dynamic stability. Failing to account for real gas behavior in such conditions can lead to inaccurate predictions of system performance, potentially compromising reliability and efficiency. Incorporating real gas models through appropriate equations of state is crucial for accurate simulation and design in these applications, ensuring better operational stability and optimization of bearing performance.

This means that engineers and scientists need to be in a constant search of new bearing options which brings the consideration of different gases as lubricants and critical conditions as operational ones as well as develop and apply real gas models to perform correct simulation of the bearing performance to the priority tasks.

The current paper considers several equations of state, in particular, the cubic ones, to substitute the ideal gas equation for modeling journal gas bearings. The comparison of the proposed real gas models is performed by the analysis of main bearing parameters including load-displacement characteristics, power losses, volume flow rates, as well as stiffness and damping coefficients. The calculation results are compared with the experimental data available in the published sources. The work aims to detect the influence of real gas effects on the accurate prediction of the bearing operational parameters.

In addition to the bearings’ performance investigation, the rotor dynamics response of the test rotor in bearings modeled with stiffness and damping coefficients calculated using different equations of state is performed to show the impact of real gas effects on the accurate prediction of the machine dynamics.

The results of the paper show the significant influence of real gas effects modeled by different equations of state on the calculation of bearing performance parameters and the rotor dynamics response, which together with the calculation time of bearing models including each equation of state allows finding the most optimal approach to the modeling of herringbone grooved gas journal bearings considering the real gas effects.

The novelty of the paper consists of the consideration of various gas models for the prediction of the bearing operation parameters and the rotor dynamics response, as well as mathematical models created to obtain an accurate solution to the problem. The theoretical background, considered models, calculated results, and conclusions regarding the optimal equation of state suitable for herringbone grooved gas journal bearings in certain conditions will be valuable for engineers and scientists who are involved in the process of design and investigation of machines implementing different types of bearings including herringbone gas groove bearings.

Presenting Author: Roman Kochurov SoftInWay, Inc.

Presenting Author Biography: Dr. Roman Kochurov has over 12 years of combined experience in mechanical engineering (thermo-structural, fatigue, lifetime prediction, root cause failure investigations), and rotor-bearing systems dynamics analyses including research work and simulation methodologies development.

He received his Master’s degree in Mechanical Engineering from National Technical University ‘Kharkiv Polytechnic Institute’ in 2008, and a Ph.D. degree from ‘A.N. Podgorny Institute for Mechanical Engineering Problems at the National Academy of Sciences of Ukraine in 2012, where worked as a research engineer till 2012. Since 2012 he has worked in the R&D Company Actual Mechanics’, Ukraine, in the position of Head of the Dynamics&Strength of Machines Department. In 2020 he joined SoftInWay Inc., Burlington, US, where performs his duties as dynamics and strength department manager and rotordynamics engineer.

Authors:

Roman Kochurov SoftInWay, Inc.
Volodymyr Martynenko SoftInWay Switzerland GmbH
Leonid Moroz SoftInWay, Inc.
Yuriy Govorushchenko SoftInWay Switzerland GmbH