外文翻譯--降低家用電冰箱的旋轉噪聲（英文）

1、IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 28, NO. 2, MARCHJAPRIL 1992 287 Fan Noise Reduction of Household Refrigerator Akira Takushima, Yoshihara Shinobu, Shozo Tanaka, Masaki Eguchi, and Kenji Matsukj Abstract-

2、This paper describes the method of reducing the fan noise, especially the impeller noise, of a household refrigera- tor. The fan in the tested refrigerator is a propeller fan, and the fan unit consists of an impeller

3、, which has four blades, a rear board, which covers the evaporator, and a front board, which has a number of openings. The flow through the openings freezes food in the freezer. By measuring the internal flow with a

4、laser Doppler velocimeter, it was made clear that the How through the impeller was not symmetrical to the axis. The unsymmetrical flow seems to be caused by the restrictions of flow passages, and it might produce the

5、impeller noise. Al- though some methods of preventing the How from unsymmetry had been investigated, they were found to be hard to apply to this case because of the difficulties in design change. The search for the s

6、ound source by the sound intensity method indicated that the noise was radiated through the openings of the front board. The guiders were installed on the rear board in the fan unit to guide the How away from the open

7、ings. As a result, the impeller noise was reduced, whereas the flow was kept almost the same. INTRODUCTION ECENTLY, sound comfort has become important, in R addition to thermal comfort, in residential houses. Theref

8、ore, reduction in noise from a refrigerator is neces- sary. The noise sources of a household refrigerator are a compressor and a fan. The noise reduction from a compres- sor has been studied by many companies and inst

9、itutions. However, research on fan noise has hardly been done. The methods of reducing fan noise, especially impeller noise, of a household refrigerator are studied in this paper. The tested refrigerator in this pape

10、r has the specifications as shown in Table I. Fig. 1 shows the cross section of the tested household refrigerator. The air, which is cooled by the evapolator behind the freezer part, is sent by the fan unit into the

11、freezer part and the refrigerating part. The passages are arranged so that the air through the evaporator may come back to the evaporator. Fig. 2 shows the front view and the cross section of the fan unit. The fan us

12、ed in the refrigerator is a propeller fan, and the fan unit consists of an impeller, which has four blades and whose diameter is 90 mm, the rear board, which is called the “evaporator cover,” which covers the evapora-

13、 tor, and the front board, which is called the “fan louver” and has a number of openings. The impeller is installed at the center of the orifice (100-mm in diameter), which is located Paper MID 91-7, approved by the A

14、ppliance Industry Committee of the IEEE Industry Applications Society for presentation at the 1990 41st Interna- tional Appliance Technology Conference, Columbus, OH, May 15- 16. Manuscript released for publication Ap

15、ril 17, 1991. The authors are with the Energy Conversion Laboratory, Sharp Corpora- tion, Nara, Japan. IEEE Log Number 9104067. Freezer Door Fan Louver Evapolator Cover Fig. 1. Cross section of refrigerator TABLE I

16、 SPECIFICATIONS OF REFRIGERATOR f r e e z e r Part 73 L R e f r i q e r a t i n q P a r t 122 L Size I Width 590 mm I Depth 600 mm Height 1785 m nat the upper part of the evaporator cover. The fan louver has

17、 some openings that are shown by the solid lines in Fig. 2. Some part of the flow, which comes through the impeller, freezes food in the freezer part through the openings. The opening, which is shown by the dotted lin

18、es in Fig. 2, is located on the evaporator cover, and the flow through the opening is guided to the refrigerating part. Ribs are installed on the evaporator cover in order to guide the flow to all openings efficientl

19、y. The motor of the fan is supplied fixed voltage so that the impeller rotates at 3000 r/min throughout the experiments. MEASUREMENT OF VELOCITY AND NOISE The test fan unit was made to measure the flow field. It has

20、 the same shape as the fan unit, and the fan louver was made of a clear acrylic board. The laser Doppler velocimeter (LDV) was used for flow measurement. The specifications of the LDV are shown in Table 11, and the a

21、pparatus is shown in Fig. 3. Aerosol, which was used as seeding particles for the LDV measure- ment, was generated by a conventional ultrasonic atomizer. Laser beams were irradiated in the direction perpendicular to

22、the fan louver. The measured planes were located at a distance of 6, 12, 18 and 24 mm back from the fan louver. The noise of the refrigerator was measured in a soundproof room. The size of the room is 2.7 m wide x 3.0

23、 m deep x 2.2 m high, and the level of the background noise is 18.2 dB(A). The compressor of the refrigerator was stopped 0093-9994/92$03.00 0 1992 IEEE TAKUSHIMA et al.: FAN NOISE REDUCTION OF HOUSEHOLD REFRIGERATOR

24、 289 g 5 0 8- D 10 0 f 30 a L 2 20 h I0 m a D $ 0 “ -10 0 100 200 300 400 500 600 700 800 900 l k Frequency Hz Noise frequency spectrum of fan unit. Fig. 6. FLOW IN THE FAN UNIT The impeller noise is flu

25、id noise that is caused by the pressure fluctuation that occurs when a blade crosses air. One of the causes of larger impeller noise from the propeller fan is that the flow is not symmetrical to the rotational axis of

26、 the impeller. Another is that the impeller sucks the fluid, includ- ing vortices, from the back of the impeller. The flow in the fan unit was measured by LDV to get the causes of the impeller noise. Fig. 7 is the ve

27、locity vector diagram of the internal flow. Although there are flows that move circularly or radially around the impeller, the flow center is not the impeller center and is toward the opening on the evaporator cover.

28、 Fig. 8 shows the radial velocity around the impeller on the orifice. The angle in the figure is defined as the counterclock- wise angle on the plane parallel to the fan louver where angle 0“ starts at the X axis. If

29、 the flow is closer to the evaporator cover the divergence of the radial velocity will be larger. On the same circle, there exist the suction region, where the velocity is negative, and the discharge region, where the

30、 velocity is positive. Although the divergence near the fan louver (6 mm) is smaller, it is confirmed in the figure that the flow into and through the impeller is not parallel to the axis. Fig. 9 shows the contour of

31、 the turbulence energy that indicates the amount of the flow fluctuation, which is thought to occur when the blade of the impeller passes the air. Therefore, the large region of the turbulence energy is the region of

32、 the discharge from the impeller. The image of the 3-D flow obtained from these figures shows that the suction flow of the impeller has already turned to the direction of the opening on the evaporator cover. It is not

33、 symmetrical to the rotational axis, and it goes to the opening on the evaporator cover while it moves rotatively. The flow moves less rota- tively and more radially, whereas the flow goes near the fan louver. INFLUE

34、NCE OF THE OPENING ON THE EVAPORATOR COVER One of the causes of the unsymmetrical flow is the variety of the air resistance at the discharge. The air through the impeller flows to the opening made on the evaporator

35、cover and is connected to the refrigerating part. It is probably because the part near the opening has less resistance. There- fore, experiments were made under conditions where the .... ( 4 (b) Fig. 7. Internal flo

36、w of fan unit: (a) 6 mm from fan louver; (b) 12 mm from fan louver; (c) 18 mm from fan louver; (d) 24 mm from fan louver. 5 , 1 I I I I J 0 45 90 135 180 225 270 515 360 -2 I R n p l r ( “ 1 Fig. 8. Ra

37、dial velocity on orifice. (b) (d) Fig. 9. Turbulence energy in fan unit (m2/s2): (a) 6 mm from fan louver; (b) 12 mm from louver; (c) 18 mm from fan louver; (d) 24 m m from fan louver. opening on the evaporator cov

38、er was closed for the flow resistance to become uniform. Fig. 10 shows the flow in the fan unit. Although this case is a little more effective than the cases of Figs. 7 and 8, the dissymmetry was not improved complet

39、ely. THE EFFECT OF SUCTION FLOW The fan unit has a shroud above the motor as shown in Fig. 2 , and it is installed in the refrigerator as shown in Fig. 1. It seems that suction flow into the impeller does not come