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Predicting supercharging effect in suction line in inverter rotary compressor


Atsushi KUBOTA*1, Hirokatsu KOUSOKABE*1 and Tetsuya TADOKORO**2
*1 Research & Development Group, Hitachi, Ltd.
832-2 Horiguchi, Hitachinaka, Ibaraki 312-0034, Japan
E-mail: atsushi.kubota.fw[at]hitachi.com

**2 Global Pruduct Development, Hitachi - Johnson Controls Air Conditioning, Inc.
500 Tomita, Ohira-machi, Tochigi, Tochigi 329-4404, Japan

 


Abstract

This paper proposes a new method for predicting the supercharging effect to easily and precisely design the dimensions of the suction line in inverter rotary compressors, including two-stage ones. First, we obtained experimental data on the rotational speed characteristics of volumetric efficiency ηv and overall adiabatic efficiency ηad with three types of single-stage one-cylinder compressors using R22 and a two-stage two-cylinder one using R410A. We introduced a function for only increasing ηv with supercharging by approximating the phenomenon by simple acoustic theory and calculated the numerical constants of the function by fitting dimensionless experimental data. Second, we proposed a basic prediction equation for only the resonant rotational speed fn, which was adjusted for the effect of the crank angle where the suction process ended, by modeling the interaction between the constant acoustic wave in the suction pipe and the roller movement as a rectangular wave. Additionally, we introduced the damping factorβto express the effect of the scale of the suction chamber in relation to the constant acoustic wavelength in the suction pipe. We confirmed that 95% of the predicted values of increasingηv were within an accuracy of ±3% when the rotational speed ratio (f/fn) was 0.8 - 1.2 and all predicted values of fn were within an accuracy of -3 - +1%.

 

Keywords

Air Conditioning, Inverter, Refrigerant, Rotary Compressor, Supercharging

 

Figures


Fig. 1 Configuration of suction line in single-stage compressor


Fig. 2 Experimental apparatus and structure of two-stage compressor


Fig. 3 Experimental results of volumetric efficiency


Fig. 4 Dimensionless correlation between (f/fn) and (ηvv,0)



Fig. 5 Pressure fluctuation model around resonant rotational speed fn


Fig. 6 Comparison of measured and calculated fn


Fig. 7 Comparison of calculated scale effect on coordinates of (Rθs/L) versus β with experimental data

Last update: 11.9.2017