Where published:26th International Compressor Engineering Conference at Purdue
Year:2022
Gerotor pumps operate with two rotors, each rotating in the same direction about parallel but offset axes. Commercial applications for these machines include oil pumps, fuel pumps, and hydraulic power transmissions. It is also possible to use the gerotor configuration to achieve internal compression by specifying appropriate discharge port geometry, and the addition of helical twist to the rotors has been shown to achieve further benefits of reducing porting losses and power transfer between rotors. These internally-geared screw compressors have a number of potential advantages over conventional twin-screw configurations, including reduced leakage areas, co-directional thermal expansion, reduced rotor deflection, reduced viscous losses, and higher swept volume for a given machine envelope. Many of the loss mechanisms in these machines are similar in nature to conventional twin-screw machines but must be characterised due to the unique aspects of sealing line geometry and co-rotation (leading to much lower sliding velocities at contact points). Experimental testing is an essential step for model validation and appraisal of the potential benefits of this technology. This paper describes the test rig that is currently being developed to investigate the operation and performance of internally-geared machines (screw compressors), and how the geometry of a prototype machine has been specified
The geometry data discussed in this study can be used to provide the necessary input data for chamber modeling of the compression process using the SCORG software.
The paper describes the project made in the ‘Internally-Geared Screw Compressor’ research project. The key conclusions from the current study are as follows.
- Initial sizing and geometry selection of an internally geared machine can be performed on the basis of required volumetric flow, limiting speed for the fluid during filling, and limiting bearing speeds.
- Once the geometry of the rotor and porting are defined, thermodynamic analysis of the compression process can be performed using a chamber modeling approach.
- A small-scale prototype of the internally-geared compressor has been designed along with a test rig to investigate the operation of performance of oil-injected air compression.
- Experimental data from this test rig is intended to support the development of loss models for internally-geared machines, and provide data for validation of 1D and 3D numerical analysis.