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Title:Tribological studies of surface texturing for application in air-conditioning and refrigeration compressors
Author(s):Mishra, Surya P.
Advisor(s):Polycarpou, Andreas A.
Department / Program:Mechanical Sci & Engineering
Discipline:Mechanical Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Surface texturing
Compressor tribology
Environmentally friendly refrigerants
Abstract:Operating conditions such as load and speed of compressors are getting more aggressive to improve efficiency. Also, protection from beneficial surface layers, such as ferrous chlorides, on the critical interfaces is compromised as the refrigerants industry is moving from traditional (CFC/HFC) to environmentally friendly refrigerants. Thus, there is a need to have a closer look at the critical tribo-contacts and devise ways to make them more robust and wear-resistant. In this work, first of its kind studies were done to evaluate the possibility of using surface texturing for realistic gray cast iron compressor surfaces. Three types of micro-dimple patterns (40 μm diameter and 10 μm depth, 60 μm diameter and 7.5 μm depth, 60 μm diameter and 4 μm depth) with two area densities of 5% and 20% were created on the pin surfaces by the method of laser surface texturing. The results of the controlled tribological experiments with the texture patterns were compared against untextured surfaces under starved lubrication conditions. Under identical conditions of load, the untextured pins failed while all the textured pins operated successfully. In addition, the textured pins survived the entire duration of three hours in durability type studies highlighting their long term usefulness. Selected tests were also done at different sliding speeds, lubricant types and refrigerants and the usefulness of surface texturing at aggressive conditions was realized. For the wear and durability experiments, the beneficial effect of the micro-dimples could be attributed to the lubricant storage ability. A trade-off between the effect of the material pile-ups or bulges around the micro-dimples and the lubricant storage volume of the micro-dimples determined the difference in performance between the texture patterns. In addition, step loading scuffing experiments were done using the texture patterns and the scuffing resistance was found to primarily depend on the lubricant storage ability of the micro-dimples. Even though surface texturing was found to have a positive effect, such behavior needs to be evaluated under specific lubricants and refrigerants, to fully understand the complex phenomena driving the improved performance. Overall, the research work done in this thesis developed new information about the application of surface texturing for air-conditioning and refrigeration compressor applications. It was demonstrated successfully that texturing could be applied to compressor surfaces operating under realistic conditions such as starved lubrication and provide significant tribological benefits.
Issue Date:2011-08-25
Rights Information:Copyright 2011 Surya P. Mishra
Date Available in IDEALS:2011-08-25
Date Deposited:2011-08

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