COMPRESSOR

Abstract

A compressor, for use alone or as a component part of a turbocharger. The compressor comprises a compressor housing and a compressor wheel mounted in the compressor housing. An internal surface of the compressor housing defines an axial inlet. The axial inlet comprises an annular groove for reducing compressor noise.

Claims

1. A compressor comprising: a compressor housing; and a compressor wheel mounted in the compressor housing; wherein an internal surface of the compressor housing defines an axial inlet, the axial inlet comprising an annular groove for reducing compressor noise.

2. The compressor according to claim 1, wherein the groove has a depth that is less than the distance between the internal surface of the compressor housing defining the axial inlet and an external surface of the compressor housing opposing the internal surface.

3. The compressor according to claim 1, wherein the groove has a constant profile around its circumference.

4. The compressor according to claim 1, wherein the groove has a variable profile around its circumference.

5. The compressor according to claim 4, wherein the depth of the groove varies around its circumference.

6. The compressor according to claim 1, wherein the groove comprises an inlet, wherein the inlet is radially aligned with the internal surface of the compressor housing.

7. A compressor according to claim 6, wherein the groove has a rectangular profile.

8. A compressor according to claim 7, wherein the rectangular profile is defined by the groove inlet, a closed end surface, and axially opposing sidewalls.

9. A compressor according to claim 8, wherein the corner between the internal surface of the compressor housing and each sidewall of the groove is curved, and wherein the corner between each sidewall and the closed end surface is curved.

10. The compressor according to claim 1, wherein the dimensions of the groove are defined by the equation: $\mathrm{IL}=10\log \frac{{\left(\frac{s_B}{2S}\right)}^2+{\left(\mathrm{cotkL}\right)}^2}{{\left(\mathrm{cotkL}\right)}^2}$ wherein IL is the reduction in compressor noise, S.sub.b is the area of the groove inlet, S is a cross-sectional area of the axial inlet, L is the depth of the groove, k is a factor calculated by $k=\frac{\omega }{c}$  where ω is the frequency of the sound waves in the compressor in use and c is the acoustic speed of the sound waves in the compressor in use.

11. The compressor according to claim 10, wherein an average reduction in compressor noise is approximately 4 dB.

12. The compressor according to claim 1, wherein the compressor housing defines an inlet port to the axial inlet, and wherein the groove is located between the inlet port and the compressor wheel.

13. The compressor according to claim 1, wherein the compressor wheel comprises an inducer end, and wherein the groove is located between the inlet port and the inducer end of the compressor wheel.

14. The compressor according to claim 1, wherein the axial inlet comprises a nozzle portion and a duct portion, and wherein the groove is located in the duct portion.

15. The compressor according to claim 14, wherein the nozzle portion is between the inlet port and the duct portion.

16. The compressor according to claim 1, wherein the groove comprises a plurality of grooves in the axial inlet.

17. The compressor according to claim 1, wherein an axial length of the groove (h) is between around 5 mm and 45 mm.

18. The compressor according to claim 1, wherein a depth of the groove (L) is between around 5 mm and around 10 mm.

19. The compressor according to claim 1, wherein a diameter of the axial inlet (d.sub.i) is between 30 mm and 50 mm.

20. The compressor according to claim 1, wherein a ratio (h:L) of an axial length of the groove (h) to a depth of the groove (L) is between around 1:1 and around 5:1.

21. The compressor according to claim 1, wherein a ratio (di:h) of a diameter of the duct portion (d.sub.i) to the axial length of the groove (h) is between around 1:1 and around 5:1

22. The compressor according to claim 1, wherein a ratio (di:L) of a diameter of the duct portion (d.sub.i) to the depth of the groove (L) is between around 4:1 and around 25:1.

23. A turbocharger comprising: a turbine mounted on a first end of a shaft, and a compressor according to claim 1; wherein the compressor wheel is mounted on a second end of the shaft opposing the first end of the shaft.

24. A compressor housing defining an axial inlet and, wherein an internal surface of the axial inlet comprises an annular groove for reducing compressor noise.

Description

BRIEF DESCRIPTION OF FIGURES

[0023] The disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[0024] FIG. 1 is a section elevation of a known compressor;

[0025] FIG. 2 is a section elevation of a compressor according to the present disclosure;

[0026] FIG. 3 is a detail view of the groove, indicated at B in FIG. 2;

[0027] FIG. 4 is a section side elevation of the axial inlet along the line A-A in FIG. 2.

DETAILED DESCRIPTION

[0028] In reference to FIG. 2, there is a compressor, similar to that described above in relation to FIG. 1, the additional features of which will be described herein. Like features have been provided with like reference numerals, increased by 100.

[0029] The housing 118 has an inlet port 132. The axial inlet 122 is defined by a radially inner surface 128 of the housing 118 that extends axially inboard from the inlet port 132. The axial inlet 122 has a nozzle portion 122a and a duct portion 122b. The duct portion 122b is axially inboard of the nozzle portion 122a. The diameter of the radially inner surface 128 defining the nozzle portion 122a of the axial inlet 122 reduces linearly along its axial length axially inboard of the inlet port 132. The diameter of the radially inner surface 128 defining the duct portion 122b of the axial inlet 122 is substantially constant along its axial length. In other embodiments, the axial inlet 122 only has a duct portion, such that the radially inner surface 128 defining the axial inlet 122 has a constant diameter along its entire axial length.

[0030] The axial inlet 122 includes a groove 150. In use the groove 150 acts as a side branch resonator to attenuate sound in the compressor 110. The groove 150 disturbs the otherwise uniform airflow through the axial inlet 122 to create a portion of inlet air flow with a sound wave propagation path that is out of phase with the sound wave propagation path of the normal inlet air flow. Optimally, the groove 150 results in the sound wave propagation path of the disturbed air flow being out of phase with the sound wave propagation path of the normal air flow by half a wavelength. This provides the maximum reduction in amplitude of the superposed sound waves.

[0031] The groove 150 is located between inlet port 132 and an inducer end 139 of the impeller hub 138. The groove 150 is located in the duct portion 122b of the axial inlet 122. The groove 150 is generally annular and extends around the full circumference of the axial inlet 122. The groove 150 has a diameter greater than the diameter of the radially inner surface 128 of the housing 118 in the duct portion 122b of the axial inlet 122, and the groove 150 has a diameter less than the diameter of a radially outer surface 129 of the housing 118 opposing the radially inner surface 128. Therefore the groove 150 has a depth L that is less than a thickness of the housing 118 between the radially inner surface 128 and the radially outer surface 129 of the housing 118. The groove 150 has an axial length h less than the axial length of the axial inlet 122. The groove 150 has an axial length h less than the axial length of the duct portion 122b of the axial inlet 122. The axial length h of the groove 150 is less than the axial distance x between the point 145 at which the nozzle portion 122a connects to the duct portion 122b, and the inducer end 139 of the impeller hub 138. In other embodiments, the axial length of the groove 150 may be approximately the same as the axial distance x between the point 145 at which the nozzle portion connects to the duct portion, and the inducer end 139 of the impeller hub 138. In further embodiments, the groove 150 has an axial length that is any appropriate length up to around 140 mm. In further embodiments, the axial length of the groove 150 is around 5 mm to 45 mm, optionally greater than around 5 mm and less than around 15 mm, for example, around 10 mm, or greater than 30 mm and less than 45 mm, for example, around 42 mm, e.g. 41.65 mm.

[0032] As shown in FIG. 3 the groove 150 is rectangular in profile. The groove 150 has an inlet 150a, a closed end surface 150b and sidewalls 150c and 150d. Corners 152 of the groove 150, between the radially inner surface 128 of the housing 118 and the sidewalls 150c and 150d, and between the sidewalls 150c and 150d and the closed end surface 150b, are curved. The radius of the curved corners 152 is sized appropriately with regard to the dimensions of the groove 150, to provide optimal sound reduction. In the embodiment shown, the profile of the groove 150 is uniform around its circumference. Alternatively, in other embodiments, the groove 150 may vary in profile around the circumference. The groove 150 may vary in depth L, axial length h or shape around the circumference.

[0033] As shown in FIG. 2 there is a single groove 150 in the inlet passage. In other embodiments there may be a plurality of grooves in the inlet passage, for example there may be 2 grooves, 3 grooves, 4 grooves, or more. Each groove may have the same profile, or each groove may have a different profile.

[0034] The reduction in blade-pass noise in a compressor 110 with a groove 150 according to the present disclosure, compared to a compressor 10 without a groove and therefore not in accordance with the present disclosure, is the “insertion loss”. The insertion loss is calculated using the principles of a quarter-wave resonator. Normally, a quarter-wave resonator comprises a side duct connected to a main duct to form a t-shape, with air flow through the main duct. The insertion loss in a quarter-wave resonator is calculated by the quarter-wave equation:

[00003]$\mathrm{IL}=10\log \frac{{\left(\frac{s_B}{2S}\right)}^2+{\left(\mathrm{cotkL}\right)}^2}{{\left(\mathrm{cotkL}\right)}^2}$

[0035] The quarter-wave equation has been adapted to apply the variables to the geometry of a groove 150 in an axial inlet 122, rather than a side duct connected to a main duct. In reference to FIGS. 3 and 4, the variables are as follows: S.sub.b is the area of the groove inlet 150a, calculated by S.sub.b=πd.sub.ih where d.sub.i is the diameter of the duct portion 122b of the axial inlet 122 and h is the axial length of the groove 150; S is the cross-sectional area of the axial inlet 122, calculated by

[00004]$S={\pi \left(\frac{d_i}{2}\right)}^2;$

L is the depth of the groove 150, calculated by

[00005]$L=\frac{\left(d_g-d_i\right)}{2}$

where d.sub.g is the diameter of the closed end surface 150b of the groove 150; k is a factor calculated by

[00006]$k=\frac{\omega }{c}$

where ω is me frequency of the sound waves in the compressor 110 and c is the acoustic speed of the sound waves in the compressor 110; and IL is the insertion loss.

[0036] Typically, the compressor rotates at frequencies between approximately 80000 and 190000 rpm. The axial length of the groove h may be any appropriate value up to around 140 mm, such as around 5 mm to around 45 mm or around 10 mm to 35 mm. In further embodiments the axial length of the groove h is between around 5 mm and around 15 mm, for example, around 10 mm, or between around 30 mm and around 45 mm, for example, around 42 mm, e.g. around 41.65 mm. The depth of the groove L may be any appropriate value up to around 30 mm. In further embodiments the depth of the groove L is between around 5 mm and around 10 mm, for example, around 7 to 9 mm, e.g. around 7 mm or around 8.85 mm. The diameter of the duct portion d.sub.i may be any appropriate value up to around 180 mm. In further embodiments the diameter of the duct portion d.sub.i is between around 30 mm and around 50 mm, for example, around 40 to 45 mm, e.g. around 41.8 mm. The ratio (h:L) of the axial length of the groove h to the depth of the groove L is between around 1:1 and around 5:1. In further embodiments the ratio of the axial length of the groove h to the depth of the groove L is around 2:1 to 4:1, for example, around 1.5:1, e.g. around 1.43:1, or by way of a further example, around 4.7:1, e.g. around 4.71:1. The ratio (d.sub.i:h) of the diameter of the duct portion d.sub.i to the axial length of the groove h is between around 1:1 and around 5:1. In further embodiments the ratio of the diameter of the duct portion d.sub.i to the axial length of the groove his around 1:1 to around 2:1, e.g. around 1.27:1, or around 3:1 to around 4.5:1, e.g. around 4.18:1. The ratio (d.sub.i:L) of the diameter of the duct portion d.sub.i to the depth of the groove L is between around 4:1 and around 25:1. In further embodiments the ratio of the diameter of the duct portion d.sub.i to the depth of the groove L is around 5:1 to around 10:1, e.g. around 5.97:1, around 10:1 to around 15:1, or around 15:1 to 20:1, e.g. around 19.67:1.

[0037] The blade-pass noise can be reduced over 85% of the rotational frequencies of the compressor wheel. The average insertion loss is approximately 4 dB. Preferably the insertion loss is greater than 6 dB over 31% of the rotational frequencies of the compressor wheel. Preferably the insertion loss is 11 dB when the compressor wheel is rotating at a frequency of 140000 rpm.