A positive displacement rotary compressor is introduced:RCC(Rotary Cylinder Compressor). For implementing suction and exhaust process, the compressor\u27s cylinder and shaft revolve around their own axes while the piston reciprocates relative to the cylinder and shaft. Compared with rotary piston compressor, the RCC has the advantages of high volumetric efficiency and small torque ripple

Du, Zhongcheng

Hu, Yusheng

Xu, Jia

English

Purdue E-Pubs

Purdue UniversityPurdue e-PubsInternational Compressor Engineering Conference School of Mechanical Engineering2018Study of Novel Rotary Cylinder CompressorYusheng HuGree Electric Appliances,Inc. of Zhuhai, China, People's Republic of;State Key Laboratory of Air-conditioning Equipment andSystem Energy Conservation, China, huyusheng001@163.comJia XuGree Electric Appliances,Inc. of Zhuhai, China, People's Republic of;State Key Laboratory of Air-conditioning Equipment andSystem Energy Conservation, China, jidianyihao@163.comZhongcheng DuGree Electric Appliances,Inc. of Zhuhai, China, People's Republic of;State Key Laboratory of Air-conditioning Equipment andSystem Energy Conservation, China, zhongch_du@163.comZhongcheng DuGree Electric Appliances,Inc. of Zhuhai, China, People's Republic of;State Key Laboratory of Air-conditioning Equipment andSystem Energy Conservation, China, zhongch_du@163.comFollow this and additional works at: https://docs.lib.purdue.edu/icecThis document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu foradditional information.Complete proceedings may be acquired in print and on CD-ROM directly from the Ray W. Herrick Laboratories at https://engineering.purdue.edu/Herrick/Events/orderlit.htmlHu, Yusheng; Xu, Jia; Du, Zhongcheng; and Du, Zhongcheng, "Study of Novel Rotary Cylinder Compressor" (2018). InternationalCompressor Engineering Conference. Paper 2602.https://docs.lib.purdue.edu/icec/2602  1423, Page 1  24th  International Compressor Engineering Conference at Purdue, July 9-12, 2018 Study of Novel Rotary Cylinder Compressor Yusheng Hu1, Jia Xu1, Zhongcheng Du1*, Sen Yang2, Liping Ren1 1State Key Laboratory of Air-conditioning Equipment and System Energy Conservation,  ZhuHai, Guangdong 519070, China Phone: +86-756-8974645, Fax: +86-756-8668386 E-mail: zhongch_du@163.com 2Chinese National Engineering Research Center of Green Refrigeration Equipment,  ZhuHai, Guangdong 519070, China  ABSTRACT A positive displacement Rotary Compressor is introduced: RCC (Rotary Cylinder Compressor). For implementing suction and exhaust process, the compressor's cylinder and shaft revolve around their own axes while the piston reciprocates relative to the cylinder and shaft respectively. Compared with Rotary Compressor, the RCC has the advantages of high volumetric efficiency and small torque ripple.  1. INTRODUCTION  Rotary Compressor has the advantages of simple structure, easy production, small size, light weight, few wearing part, and high reliability (Sekigami  et al, 1987, Sekigami et al, 1987). It has been widely used in the field of air conditioning.  However, there are some defects of the Rotary Compressors (Matsuzaka et al, 1982, Lee et al, 1988). The sealings about roller-cylinder and slider-roller are linear, which results in worse sealing effect and larger leakage than face sealing. The Rotary Compressor has the clearance volume, which results in finite pressure ratio. The slider bears large bending moment and belongs to the cantilever support structure, which results in wear easily. In order to reduce the vibration caused by eccentricity of the shaft, balance structure needs to be set up. These shortcomings limit further improvement of the performance of Rotary Compressor.  For the current defects of Rotary Compressor, GREE(R) has proposed a new type of compressor: Rotary Rotary Cylinder Compressor. This article mainly introduces the structure and operation principle of Rotary Cylinder Compressor, and makes a qualitative analysis of volumetric efficiency and mechanical efficiency.  2. STRUCTURE OF ROTARY CYLINDER COMPRESSOR  The Rotary Cylinder Compressor body mainly contains seven parts: main bearing, shaft, cylinder, piston, cylinder sleeve, spacing board, and sub bearing as shown in Figure 1.  The center of shaft is different from the center of cylinder. The distance between two different axes e is the eccentricity of compressor. The piston stroke L is twice the eccentric amount L=2·e. The compressor displacement formula is as follows.  V 2 L S 4e S      (1)   1423, Page 2  24th  International Compressor Engineering Conference at Purdue, July 9-12, 2018                   (a) Structure decomposition diagram                   (b) Side sectional view of pump body     (c) Cross sectional view of pump body Figure 1: Schematic diagram of pump body of Rotary Cylinder Compressor  3. OPERATION PRINCIPLE OF ROTARY CYLINDER COMPRESSOR  3.1 Suction and exhaust process During operation of the compressor, motor drives the shaft to rotate, shaft drives the piston to rotate, and piston drives the cylinder to rotate. The cylinder and shaft rotate around their respective axes. The piston reciprocates relative to shaft and cylinder simultaneously. Two different reciprocating motions are perpendicular to each other. As the cylinder always rotates, the compressor is named Rotary Cylinder Compressor (RCC).  The piston reciprocates relative to cylinder so that the volume of cavity formed by piston, cylinder and cylinder sleeve changes periodically. The cylinder performs a circular motion relative to the cylinder sleeve so that former volume cavity periodically links with suction port and discharge port. Under the joint action of the above two relative movements, RCC completes the suction, compression and exhaust processes, as shown in Figure 2.   1423, Page 3  24th  International Compressor Engineering Conference at Purdue, July 9-12, 2018  Figure 2: Schematic diagram of suction and exhaust process  3.2 Torque characteristics The relationships about chamber volume, pressure with rotation are as follows.   θV e S ( cos1 )θ     (2)  nθnsθ sP V P V    (3)  sθ ddsssdP 0P &θn n2 2P P P θ 21 cosθ 1 cosθn2P P θ 21 cosθP &                    (4)  According to the above formulas, the relationship between torque and angle can be obtained:    θ θ' 'T F e P S e S e sin 0P P θ θ                (5)  RCC has the structural feature of a single-cylinder with double-compression chamber: the suction, compression and exhaust processes are completed within 2π. Suction process completes within the first π while compression and exhaust processes complete within the last π. Two volume chambers are independent of each other. And there is a phase difference of π among two volume chambers. The former features make the torque cycle π. Figure 3 shows the variation of torque with rotation angle of RCC and single-cylinder rotary cylinder at the same displacement. From the figure, torque cycle of RCC is π while the Rotary Compressor’s is 2π. With the same displacement, the average moment of two kinds of compressors is equal. But the maximum torque of RCC is 12% smaller than that of the single-cylinder Rotary Compressor. In general, the smaller the torque fluctuation is, the more stable the operation is. In other words, RCC runs more smoothly than Rotary Compressor in the same displacement condition.   1423, Page 4  24th  International Compressor Engineering Conference at Purdue, July 9-12, 2018   Figure 3: Comparison of torque curves  4. EFFICIENCY ANALYSIS  4.1   Volumetric efficiency 4.1.1   Leaking channel and sealing RCC has two leaking channels: cylinder-cylinder-sleeve, cylinder-piston. Both leaking passages are face sealings. The Rotary Compressor has five leaking channels: roller-cylinder, roller-slide, roller-main-bearing, roller-sub-bearing, slide-slide-slot. The first two are linear sealings. Because the effect of linear sealing is less than face sealing, the leakage of these two leaking channels is relatively large in the total leakage. RCC is superior to the Rotary Compressor in terms of the sealing effect or the number of leaking channels.  Table 1: Sealing comparison of RCC and Rotary Compressor  Rotary Compressor RCC Distribution Sealing Distribution Sealing slider/roller linear sealing cylinder/ cylinder sleeve face sealing roller/cylinder linear sealing cylinder/piston face sealing roller/main bearing face sealing / / slider/slider slot face sealing / / roller/sub bearing face sealing / /      （a）Schematic diagram of linear sealing of Rotary Compressor   1423, Page 5  24th  International Compressor Engineering Conference at Purdue, July 9-12, 2018  （b）Schematic diagram of face sealing of RCC Figure 4: Comparison of seal forms  4.1.2 Clearance volume After the exhaust process, there is still some space where high-pressure gas exists. This part of the space is clearance volume. During operation of the compressor, high-pressure gas in the clearance volume expands to the suction chamber. This part of the gas will be used by next compression cycle. The above process will reduce the actual suction volume of compressor and volume efficiency. As the volume of cavity is changing, this part of the gas is recompressed. Repeated compression process will increase the indicator work of compressor.  The clearance volume of Rotary Compressor mainly comes from the vent hole and the exhaust oblique incision. Suction chamber of RCC is separated from the compression chamber. Suction and exhaust processes are independent of each other. At the end of the exhaust process, the high pressure gas of exhaust port is closed in the vent hole, but it can’t enter suction chamber. Of course, there's no more expansion. From this point of view, RCC has no clearance volume as shown in Figure 5.            (a) Rotary Compressor                                                                            (b)  RCC  Figure 5: Comparison of the clearance volume  In summary, RCC has less leaking channels and no clearance volume compared to Rotary Compressor. All these features are beneficial to increase cooling capacity and reduce indicated power of compressor. Finally, the performance of RCC is excellent. 4.2 Mechanical efficiency In addition to volumetric efficiency, mechanical efficiency also greatly influences the efficiency of compressor's   1423, Page 6  24th  International Compressor Engineering Conference at Purdue, July 9-12, 2018 pump body. Under a certain working condition, Table 2 shows the mechanical power consumption of RCC and Rotary Compressor at 30 Hz. Figure 6 shows the variation of the mechanical power consumption with the compressor frequency under the former conditions. Below 40 Hz, the power dissipation of RCC is less than the Rotary Compressor. The lower the frequency is, the greater the advantage is. At 15 Hz, it is only 48.79% of the Rotary Compressor. But over 40 Hz, the trend of power consumption with frequency is opposite. At this time, RCC is larger than the Rotary Compressor. The higher the frequency is, the greater the difference is.  Table 2: Compressor operating parameters  Refrigerant R410A Condensation Temperature(℃) 40 Evaporation Temperature(℃) 20 Swept Volume(cc) 9.6   Figure 6: Mechanical power consumption with frequency  As shown in Table 2, the pump body of Rotary Compressor has total eleven friction pairs. Eight of them are rotating friction pairs, and the rests are reciprocating friction pairs. However the pump body of RCC has total nine friction pairs as shown in Figure 7. Seven of them are rotating friction pairs, and the rests are the reciprocating friction pairs. From the contrast results, the number of friction pairs of RCC is less than Rotary Compressor’s.  Figure 7: Distribution of friction pair of pump body of RCC  1423, Page 7  24th  International Compressor Engineering Conference at Purdue, July 9-12, 2018 Table 3: Analysis of Movement Characteristics of RCC and Rotary Compressor  Movement Characteristic RCC Rotary Compressor rotating movement cylinder/cylinder sleeve shaft/roller cylinder/spacing board shaft/main bearing shaft/main bearing shaft/sub bearing cylinder/spacing board thrust face shaft/sub bearing roller/slider cylinder bearing roller/sub bearing thrust face roller/main bearing / roller/cylinder reciprocating movement shaft/piston slider/slider slot piston/cylinder slider/sub bearing / slider/main bearing  5. CONCLUSION AND NEXT STEPS  This paper introduces a new structure of compressor (RCC), which has the characteristics of high volume efficiency, smooth operation, high mechanical efficiency at low and medium frequency. Follow-up work will focus on reducing power consumption at high frequency. RCC is essentially a piston compressor. However, there is no suction valve plate, which means that the suction resistance is less than piston compressor (Miu et al, 1987).  RCC is simpler and the operation is more stable as a result of no crank linkage mechanism. All these indicate that RCC has a wide range of application prospects.  NOMENCLATURE  V compressor displacement cc L piston stroke mm e eccentricity of compressor mm S cross section area of piston mm^2 Pθ pressure of compression pocket MPa Ps  suction pressure MPa Pd discharge pressure MPa Vθ chamber volume cc Vs max chamber volume cc T torque of RCC N ·mm F△ resultant force of the piston top N e' arm of force mm  REFERENCES  Sekigami K(1987). Compact rotary compressor for refrigerators and dihumidifiers. Hitachi Review, 36(3), 169-176.  Serizawa Y(1987). Inverter controlled rotary compressors. Hitachi Review, 36(3), 177-184.  Matsuzaka T, Nagatomo S (1982). Rolling piston type rotary compressor.  Proc of the 1982 ICECP.West lafayeette: Purdue University (149-158). USA.   Lee J, Min T S (1988).  Performance analysis of rolling piston type rotary compressor. Proc of the 1986. ICECP.West lafayeette: Purdue University (154-162). USA.  Daoping Miu, Zhengye Wu (2001). Refrigeration compressor, China Machine Press.  

Study of Novel Rotary Cylinder Compressor

https://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=3601&amp;context=icec

Study of Novel Rotary Cylinder Compressor

Abstract

Similar works

Full text

Available Versions

Purdue E-Pubs