Purdue University Purdue e-pubs International Compressor Engineering Conference School of Mechanical Engineering 2004 Noise and Vibration Reduction in Compressors for Commercial Applications Marcio Silveira Embraco Follow this and additional works at: https://docs.lib.purdue.edu/icec Silveira, Marcio, "Noise and Vibration Reduction in Compressors for Commercial Applications" (2004). International Compressor Engineering Conference. Paper 1662. https://docs.lib.purdue.edu/icec/1662 This document has been made available through Purdue e-pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu for additional 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.html
C065, Page 1 NOISE AND VIBRATION REDUCTION IN COMPRESSORS FOR COMMERCIAL APPLICATIONS Márcio Silveira Embraco Empresa Brasileira de Compressores SA Joinville, Santa Catarina, Brazil Phone 0055 47 4412082, Fax 0055 47 4412730, Marcio_Silveira@embraco.com.br ABSTRACT One of the main sources of noise in commercial refrigeration systems is the compressor, whether due to the level of noise directly radiated, or due to the interaction with the system. This interaction with the system also occurs as a result of gas pulsation and vibration levels that excite the components connecting the compressor to the system. This work presents studies carried out on reciprocating commercial compressors in the attempt to identify, quantify and to determine the generating sources of the noise, the ways of transmission and the influence of the final irradiator in the total noise and the vibration of the compressor through sensibility analysis of the product and process. The results show how important it is for the design engineer to choose the right components when defining new components for the development of quieter products or to modify existing products for the purpose of making them quieter. 1. INTRODUCTION The sound power level of a refrigeration system is basically formed by sound sources, energy propagation paths and irradiation of several parts and components, with these excitation, transmission, and radiation features playing an important role in refrigerator noise reduction. The J compressor family is basically used in commercial application as cold store, air conditioning, refrigerating chamber, etc. As it is a very old design, this compressor presents a sound power and vibration level above the limits defined for the final customer. The need to reduce noise limits for this kind of application has become more and more urgent over recent years. Considering the noise limits, it is possible to verify that the J compressor has high total noise and the predominance of noise peaks at low and high frequency which can be observed through subjective analysis. The noise problem was supported based on the Six Sigma approach. The job was divided into three steps to accurately characterize all noise problem solving phases: Identify predominant source through an analysis of main sources of compressor noise generation; Characterization of the main paths of vibratory energy transmission; Irradiation energy reduction through the redesign of the shell, this being the cause of irradiation. The analyses were conducted considering the total noise and 1/3 octave band to enable sound quality improvements impact strongly on customer perception. The main objective of this work was to reduce 5.0 db the total noise level of J compressor on average. Reduction of vibration and noise levels in low frequency is also considered very important for improving the sound quality of the refrigeration system for the final customers. In order to reach the noise reduction goal an analysis was conducted consisting primarily of an investigation into the main paths of vibratory energy flow in the compressor and the identification of the main points requiring modification. A detailed study of the main points responsible for the noise enabled a guided approach, which only concentrated on modifications to the parts affecting the final result. This approach starts with a road map defining each step in the noise analysis and the understanding of the sound power level in the system.
C065, Page 2 2. ROAD MAP What is the noise generator in a commercial compressor? Sources Transmission paths Irradiator Compression System Mechanism Motor Shell Discharge Suction Suspension What are the more important components to noise? Vibration Level Sound Power Level Pulsation Level Brainstorming Sensibility analysis Failure Tree Product Map Noise Characterization Process Analysis Simulation Experimental DOE FMEA Optimization RSD Results Conclusion Figure 1: Road Map simplified
C065, Page 3 3. NOISE CHARACTERIZATION The noise diagram in a commercial compressor can be divided as shown in figure 2 below. It is possible to observe that the vibratory energy transmission in the final process will be perceptible by the customer as high noise level. COMPRESSION SYSTEM DISCHARGE DISCHARGE LINE SUCTION KIT MOTOR CAVITY SHELL SUSPENSION COMPRESSOR NOISE LEVEL Structural Connections Air-borne Irradiation REFRIGERATION SYSTEM SOUND POWER LEVEL Figure 2: Energy vibratory flow of compressor Sources Paths Irradiator 4. NOISE CONTRIBUTION The sensibility analysis enables the contribution of each system to the frequency band to be identified and, consequently, the total noise of compressor. Figure 3 shows the contribution in the frequency spectrum of the 5 most important components in the compressor.
C065, Page 4 Noise Spectrum Distribution 100% 90% SWL [db] 80% 70% 60% 50% 40% 30% 20% 10% 0% 100 200 400 800 1600 3150 6300 Total Mechanism Discharge Shell Suspension Suction Frequency [Hz] Figure 3: Noise contribution of the components in the compressor 5. DEVELOPMENT With the contributions defined, the new J compressor project was defined with the follow options: A - New Shell B - New Muffler Figure 4: Shell Modal analysis Simulation C - New Suspension Figure 5: Muffler Modal analysis Simulation D- Discharge Modified [db/1.00u m/s²] 1/3 Octave Synthesis(Ac fundo) Working : normal com pressao acc tubo com amorteciment0 : Input : FFT Analyzer 150 145 140 135 130 125 120 115 110 105 Figure 6: Spring Response Simulation 100 200 500 1k 2k 5k 10k [Hz] Figure 7: Discharge Damping
C065, Page 5 This proposed J compressor received a new name - NJ In figures 8 and 9 it is possible observe all the proposed modifications and to comp are them with the old one. Shell Discharge Suction Muffler Suspension Figure 8: NJ compressor Figure 9: Current J compressor
C065, Page 6 6. RESULTS 6.1 Compressor Noise The noise results of some models are shown in the table below. The frequency spectrum is shown in figure 10 for model NJ2192GK. Refrigerant Table 1: NJ vs. J noise comparison Sound Power Level [dba] NJ Current J D Reduction R404 65.0 71.0 6.0 R22 61.5 67.0 5.5 R134a 59.0 65.0 6.0 J2192GK NJ2192GK Sound Power Level SWL [dba] 100 160 250 400 630 1000 1600 2500 4000 6300 10000 Frequency [Hz] Figure 10: Noise Comparison NJ vs. Current J compressor 6.2 System Noise Figure 11 presents the noise impact in a refrigeration system when the NJ compressor is applied in the refrigeration system. sys. J2192GK sys. NJ2192GK Fan noise Noise Refrigeration System with NJ x J Subjective analysis Compressor noise SWL[dBA] 100 160 250 400 630 1000 1600 2500 4000 6300 10000 Frequency [Hz] Figure 11: Noise Comparison in the Refrigeration System
C065, Page 7 6.3 Compressor Vibration The vibration levels present a reduction of more than 30% as shown in the table below: Model Table 2: NJ vs. J vibration comparison Vibration Level NJ Current J D Reduction R404 3.20 6.73 6.0 R22 3.40 5.45 5.5 R134a 3.90 6.00 6.0 7 6 5 4 3 2 1 0 R404 R22 R134a J NJ Figure 12: Vibration Comp arison NJ vs. Current J compressor 6.4 Jury Analysis The jury analysis system comparing the same system with current J and NJ is shown in figure 13: Jury analysis - Sound quality Jury analysis - Subjective loudness 8 8 7 7 6 6 5 5 4 4 3 2 1 0 system 1 more enjoyable system 2 more enjoyable the same 3 2 1 0 more quiet system 1 more quiet system 2 the same Figure 13: Jury Analysis Comparison NJ x Current J in a system
C065, Page 8 7. CONCLUSIONS With the proposed modification a significant total noise reduction was gained in the NJ compressor as well as a reduction in the frequency bands, improving the sound quality, which could be perceived by the final customer. The vibration reduction was considerably higher than 30% helping reduce the sound impact in the refrigeration system. The main object was reached considering the total noise reduction in the compressor and the gain to the customer when using the compressor in the refrigeration system. REFERENCES Silveira, M., 2003, Compressor J Total Noise Reduction, Engineering Report., Embraco. Lenzi, A., 2002, Acoustics and Vibration, Mechanical Engineering Department, UFSC, Werkema, M. C., 2000, 6 Sigma: Black Belt Training, FDG