Approach To The Numeric Geometry Analysis of Positive Displacement Compressors, Its Application To A Single Screw Compressor Simulation And Verification By Experiment
Thermodynamic models to simulate positive displacement compressors are well known for a few decades already and can describe the compressor performance quite well. One of the most complex part of the simulation process however is the positive displacement compressor geometry simulation. In the current context, under geometry simulation, values of working compressor volumes, as well as cross-sections of port openings, at different shaft (rotor) angles are considered. In the current paper, as an example, the Greene formula approach was applied to a geometry simulation of a single screw compressor. Working chamber geometry was defined by “cutting “ it with the gate rotor blade; flute volume was computed using Greene formula; suction and discharge ports were intersected with this volume so that port opening contours were defined and their respective cross sectional areas were calculated. The results of this geometry simulation were applied for a thermodynamic model of a single screw compressor. Experimental investigation of a single screw working process using pressure transducers has been conducted. Geometry simulation data was applied to calculate compression work from experimental pressure traces. Pressure-volume diagrams obtained experimentally were compared to the simulated ones. Also, indicator work obtained from simulation and experiment, was compared to the power input to the shaft, and demonstrated good correlation.
Simulation of expansion process in positive displacement expander
The CO2 is gaining popularity as natural refrigerant for multiple applications. However, low critical temperature of CO2 has negative impact on cycle efficiency during operation at transcritical conditions.
On the profile design of a scroll compressor
The scroll configuration plays a very important role in the design of a scroll compressor. Therefore, in the present paper, a general design process for the profile of a scroll compressor is proposed. The design process is developed based on geometric as well as kinematic considerations. It is general enough that not only a perfect meshing profile (PMP) but other profiles can be designed and constructed. The latter includes meshes with clearance and meshes with interference. A correction angle is introduced such that the discharge angle of the compressor can be varied from a negative value to a positive value, which in turn results in different shapes of scroll profile. The geometric boundary conditions for all profiles are maintained continuous up to the first order. Easier manufacture and better performance of scroll compressors may be predicted based on this condition. Computer simulations are provided to show the applicability and versatility of the proposed design process. (Keyworfls: scroll compressor; perfect meshing profile (PMP); clearance; interference)