Effects of operating conditions and the reed rigidity on the opening delay of a discharge reed valve in compressors

Abstract

On the opening delay of a discharge reed valve for compressors caused by the oil film in the clearance between the reed and the valve seat, effects of design conditions on the opening delay are analyzed through the experiment and the numerical simulation. Investigated are three kinds of conditions, the time rate of the bore pressure (compression speed), the oil viscosity, and the thickness of the reed. The experiment shows that the over-compression by the delay increases with increasing each of three condition values. The simulation reproduces qualitatively the effect of the bore pressure rate on the delay. The smaller bore pressure rate makes, under a certain bore pressure, the larger film thickness or the larger cavitation bubble diameter that results in the oil film rupture and the valve opening under the smaller bore pressure. The simulation also reproduces qualitatively the effect of the reed thickness. The larger reed thickness with the larger bending rigidity leads to the smaller reed deformation, the smaller oil film thickness, and the longer delay. On the oil film viscosity, the simulation fails in reproducing the change in the delay. The fail is due to the change in the oil film thickness of the simulation being smaller than that of the experiment. The experiment and simulation results indicate that, on all three conditions, the change in the increase of the oil film thickness leads to the change in the valve opening time and thereby the over-compression.

Oil flow at discharge valve in a scroll compressor

“…Such an organized breakup pattern is suggestive of an onset of instabilities at the film interface and questions the validity of a set film thickness value for rupture in valve stiction models. 5,6 Such patterns of breakup are suggested from Pizarro-Recabarren et al 7 and Resch and Scheidl 8 and their experimental observations. In the work of these aforementioned authors, 7,8 cavitation sites were visualized in the oil film during the opening process of a reed valve when a pressure pulse is generated at the discharge orifice.…”

“…[5][6][7][8] In order to reduce the OCR of such systems by keeping the oil inside the compressor, separation strategies need to be ideally integrated into the discharge plenum of the compressor. Obtaining a good liquid separation requires knowledge of the liquid flow characteristics.…”

“…Another important aspect of the presence of oil is the change in the opening characteristics of reed valves due to stiction effect, several authors have dedicated time to this problem and the most recent advances are very significant in the directions of fully understanding of how the stiction effect can be modeled and how does the oil film break up. [5][6][7][8] In order to reduce the OCR of such systems by keeping the oil inside the compressor, separation strategies need to be ideally integrated into the discharge plenum of the compressor. Obtaining a good liquid separation requires knowledge of the liquid flow characteristics.…”

Investigation on the Suction Reed Valve Motion with Sticky Force in a Refrigerator Compressor

“…It was pointed out that typically for the discharge systems of domestic refrigeration compressors, viscous effects were the dominant component in the oil stiction force under dynamic conditions [15]. Yoshizumi et al developed a coupling simulation algorithm, which including models of the oil film cavitation to obtain the two-dimensional oil film pressure distribution by numerically solving the Reynolds' equation through the numerical method [16]. Brown et al measured the stiction force in a test rig where the parameters of the seat geometry, the oil viscosity, and the rate of application of lift on the valve disc could be controlled [17].…”

Design and development of the u-vane compressor

“…15 Pressure transducers blocked by rotor at (a) 0°, (b) 70° and (c) 300° The comparisons between predicted and measured variations of instantaneous pressure in the working chamber at various operational conditions are presented in Figures 8.16 to 8.18. The effective force area coefficient ( , 39) with a constant value of 0.2 is employed in the prediction model.Moreover, the value of valve damping ratio (ξ ) is kept at a constant of 0.5 to account for the viscous damping effect as a result of the oil stiction on the valve[139,241].…”