Conference Agenda

A semi-empirical modeling approach for predicting the flow rate, input power, and discharge temperature of scroll compressors has been developed. Using a dataset comprised of five scroll compressors that were tested with multiple refrigerants, the prediction accuracy of the modeling approach is evaluated. The generalizability of the modeling approach to predict compressor performance of alternative refrigerants is demonstrated. Further refinement of the modeling approach accounting for fluid properties of specific refrigerants is investigated.

In scroll compressors, the gas compression pressure induces an overturning moment, tilting the attitude of the orbiting scroll. As a result, the conventional “wedge oil film force” is generated in the thrust-slide bearing due to its orbiting motion, as is well known. This study presents a new understanding of another highly effective lubrication mechanism for the thrust slide bearing, due to the motion denoted as “precession rolling” without self-rotation of the thrust plate. The tilt direction of the thrust plate rotates as the scroll orbits, resulting in the precession of the thrust plate axis without self-rotation, inducing precession rolling of the thrust plate against the fixed plate. The focus of the present study is on the possible induction of extremely high oil film pressure due to precession-rolling. This precession-rolling-induced rolling pressure can occur in addition to the conventional wedge oil film pressure that effectively supports the very large thrust load on the orbiting scroll. This oil film force due to precession-rolling is analyzed using a theoretical analysis of the oil film pressure between scroll wraps. As a result, the oil film force due to precession-rolling is found to be far larger than the conventional wedge-induced oil film force, indicating that the precession-rolling-induced pressure is an extremely important factor in the lubrication of the thrust-slide bearing in fully loaded, large capacity scroll compressors.

Durability, NVH, sealing and tribological (friction, wear) aspects of scroll compressor design have been receiving increased attention during development, owing to their growing prevalence in some residential, commercial and automotive HVAC applications. These have been historically addressed either by testing, or more recently, through multi-dimensional CAE (3D FEA and CFD). Both approaches are time-consuming and expensive. As typically applied, detailed 3D analyses are one-off, performed “manually”, involve multiple CAE tools and models used by various experts. Their use in a design optimization process is cumbersome. This paper presents a more practical and automated workflow that integrates such detailed analyses with performance simulation of scroll compressors within a single CAE tool.  The methodology combines a flexible-body, multi-body dynamic analysis of moving parts of the scroll compressor, including details of contacts and sealing, along with models of oil film hydrodynamics of journal and thrust bearings, with an established and proven thermodynamic simulation of the gas compression process using fast 1D-flow techniques. The workflow is significantly faster than that of the existing methods, is much richer in the breadth of its predictions, and at the same time its automated nature means fewer manual steps and reduced requirement for expertise. The paper describes the methodology used in the workflow and presents an array of predictions.

Scroll technology has been progressively developing since the invention of the scroll compressor in 1905. A scroll pump incorporates a scroll pair consisting of an orbiting scroll part and a stationary scroll part. For a conventional oil-free scroll pump, a tip seal is required to prevent leakage from the axial gap and reduce friction. Over time, the tip seal will wear out which requires maintenance and replacement. Conventional oil-free scroll pumps experienced issues such as low energy efficiency, short maintenance intervals, unstable vacuum pressure, and high internal leakage rates. Scroll Laboratories, Inc. (Scroll Labs) addressed these shortcomings by developing innovative oil-free “floating scroll” compressors and vacuum pumps. The “floating scroll” well balances separating forces within the scrolls both radially and axially, reducing forces on contacting surfaces to essentially zero and minimizing wear. It makes direct contact with the scroll pairs possible and eliminates the tip seal. This new architecture enables the scroll to run at high speed maintains good sealing between compression chambers and self-compensates for the wear caused by scroll contact It enables the miniaturization of scroll pumps, by eliminating the tip seal and gas ballast valve. Without these two components, the improvement in efficiency and extended life of the scroll compressor and vacuum pump becomes a reality. Besides gases, the floating scroll compressors and vacuum pumps can handle solid particles and liquid without ballast valves. No damage to scrolls or water hammer happens during compression. It is the best solution for the applications in which 2-phase fluids exist. Here are the examples:

• Hydrogen recirculation compressors for fuel cells.
• Vacuum pumps for freeze drying process.
• Compressors and vacuum pumps for the PV TOPCon process.
• Vacuum pumps for rotary evaporators.
• Vacuum pumps for PECVD process.
• Compressors for CO2 refrigeration.

Today, Scroll Labs’ products serve a vast array of industries including spectrometry, medical devices, lyophilization, aerospace, postharvest, and gas detection.