Analysis of Vibro-Acoustic Propagation Generated by an Automotive Refrigeration System

Transcription

1 Analyi of Vibro-Acoutic Propagation Generated by an Automotive Refrigeration Sytem Copyright SAE International Rodrigo Santo, João ulo Sabioni PSA Peugeot Citroën do Brail Automóvei Ltda. Céar Abrahão, Alexandre Ramo LMS, A Siemen Buine Abtract Air conditioning ytem are being increaingly applied in the Brazilian automotive indutry becoming indipenable rather than an optional item for car buyer, who are contantly eeking out more comfort. Converely, the application of thee ytem in motor vehicle involve the ue of compreor which operate at high preure, making them important ource of vibration and unwanted noie in the cabin of the vehicle, thu cauing vibratory dicomfort and noie annoyance. Depite the major technological development in automotive air conditioning ytem, there i till a hortage of engineering reearch conducted in the field of vibration and noie originated in thee particular ytem. The preent tudy i aimed at invetigating and characterizing experimentally the vibration and acoutic propagation in the interior of a vehicle, generated by the compreor of the air conditioning ytem. In order to allow correlation between noie and vibration, meaurement were taken over time uing the acquiition ytem LMS SCADAS, in two condition: increaing rotation in the engine and tabilized rotation at the highet noie level. The data collected wa proceed and analyzed uing different methodologie in time and frequency domain uing the LMS oftware Tet.Lab v.a. The reult how that the noie emitted by the air conditioning ytem i related to the operating rotational peed of the compreor and the and H harmonic are the mot emiive inide the cabin. Moreover, the reult indicate that the vibration propagation happen primarily via the condener. Therefore, a quieter ytem can be produced by a cloe cooperation between car vehicle and compreor. Introduction Noie and vibration play important role in paenger comfort and influence a client' perception of vehicle overall quality. Thu, in deigning a vehicle, the effect of noie and vibration hould be limited in compliance with the appropriate legilation and kept under level accepted by cutomer. ge of 7 The noie of a vehicle i produced mainly by: (A) Structure vibration which are caued by direct tranmiion from the engine, effort reulting of road urface excitation and aerodynamic, which caue the urface of the vehicle to vibrate and produce noie. (B) Direct radiation from variou individual ource of noie uch a gae intake and exhaut, the engine itelf, the tranmiion ytem, the ventilation and air conditioning ytem, the wheel, and acceory belt. Many of thee ource radiate noie through opening on the vehicle tructure. Table how the primary ource of noie, along with the importance of their contribution in the car interior and exterior []. Table: Noie ource and contribution in the vehicle []. Source Engine vibration Engine and tranmiion aerial noie Exhaut ytem Admiion ytem Fan Vibration due to road urface excitation Tire noie due to road urface excitation Internal noie level Main ource of noie in low frequencie Main ource of high-frequency noie Unimportant Unimportant Perceptible Main ource of low-frequency noie Inignificant External noie level Unimportant Main ource of highfrequency noie Main ource of lowfrequency noie Main ource of lowfrequency noie followed by exhaut ytem Significant in the low and medium frequency band Inignificant Significant The intenity of noie in the interior of vehicle ha been decreaing ignificantly over the year due to the reduction of

2 noie level from the engine, tire and aerodynamic. The noie level of the engine can be reduced by uing better exhaut ytem and muffler. Yauda [3] preented a muffler with a noie attenuation behavior imilar to the Helmholtz reonator, capable of reducing both low and medium frequency noie imultaneouly. The dynamic characteritic of the tire i a crucial factor in noie generation inide the vehicle, due to effort exerted by the track. Thu, in recent year the acoutic of the tire air chamber ha become one of the main ubject of tudie and of great concern to the indutry. Moliani [6] propoed an efficient model for invetigating the mechanim of phyical coupling between the acoutic cavity and tire tructure. The reult how that the model capture the key mechanim of the encloed air acoutic effect over tire dynamic. Sytem that ue belt, when poorly deigned, can lead to unwanted noie that ubtantially increae of the vehicle warranty cot. Sheng [] introduced an experimental characterization and analyi of friction and vibro-acoutic behavior of automotive rubber belt in wet condition. The tudy demontrated that extreme overload condition can lead to exceive lippage on the interface between pulley and acceory belt, generating noie. A a reult of the technological advance in engine, in regard to the lowering of noie level, the contribution made by the mot important noie ource in the vehicle interior ha been changing. Conequently, large number of econdary noie ource previouly camouflaged, became noticeable to paenger and may have a ignificant impact on their well being. One uch ource i the heating, ventilating and air conditioning ytem, HVAC, reponible for the heating, ventilation, purification and air cooling in the cabin. Thi ytem can operate at different temperature and air flow etting, which are automatically or manually et by the uer according to the thermal condition inide the cabin. In hot weather condition, the HVAC aembly operate at high ventilation peed with the air conditioning compreor on. In thee condition, the HVAC noie impact on paenger acoutic comfort i very ignificant and ha been recognized a a ource of diatifaction amongt car buyer. paenger. However, there i till a hortage of engineering work in the field of vibration and noie from HVAC ytem related to the air conditioning compreor. Thu, the objective of thi work i to invetigate and experimentally characterize vibration and ound propagation into the interior of a vehicle, originated in the air conditioning compreor. The vehicle ued in thi tudy wa a hatchback with a ixcylinder wobble plate compreor. HVAC Sytem The HVAC ytem conit of five main component: evaporator, compreor, condener, receiverdryer/accumulator and the expanion device, a hown in Figure. The mot important component i the compreor. It increae the preure of the refrigerant and promote the circulation of the fluid in the ytem. The high preure, then overheated refrigerant i led from the compreor to the condener where it i liquefied upon heat exchange with the external environment. The cycle i completed in the evaporator, in which the evaporation of the refrigerant take place, aborbing heat from the inide of the vehicle cabin. An eential component of an air conditioning aembly i the expanion device. Thi component regulate the paage of refrigerant to the evaporator. Expanion valve and orifice tube are the mot commonly ued regulatory device. To enure the overheating of the refrigerant after the evaporator, the HVAC ytem ue an accumulator or receiver-dryer, capable of retaining particle [8]. Leite [] uing pychoacoutic technique demontrated that the annoyance caued by HVAC noie can be decribed by the tatic model of Zwicker and a maximum acceptable level can be determined. Mavuri [] preented a comparative meaurement of noie level of variou HVAC ytem inide the cabin of vehicle of different make and model. Tet were conducted with the engine off, at idle (vehicle tationary) and ome meaurement were taken in a moving car with the HVAC ytem operating in different mode. Thi tudy can be a valuable tool for the indutry. One of the HVAC ytem major component i the compreor. When actuated it i reponible for producing a preure differential in the refrigerant ga, generating ga flow and cauing the refrigerant to circle through the cooling circuit. Compreor operate at high preure peak and are therefore important ource of unwanted noie and vibration inide the cabin, provoking acoutic and vibration dicomfort to ge of 7 Figure : Baic component of HVAC ytem [7]. Variable-diplacement compreor have been the mot ued currently, due to it continuou operation, ability to provide uperior thermal comfort inide the car and leer fuel conumption [9]. Thi type of compreor i manufactured from a plate et at a kewed angle to the axi of the compreor, and piton poitioned axially and parallel to the power axi. Currently there are two model: wobble plate and wah plate. The difference between them i in the way the dic and the piton are interconnected. In the cae of the wobble plate model, Figure, the plate and the piton are connected by a rod, while in the wah plate model the connection i made directly.

3 Figure : Wobble plate model compreor [9]. Order tracking In the preent tudy, the methodology ued to identify the main excitation frequencie of the air conditioning ytem wa the harmonic analyi, obtained by calculating the H i order, of the ytem: Where i=,,...,n i a multiple of the rotation frequency of the engine. In order to viualize the order, a colormap wa ued, howing the ditribution of energy level of the ytem over the frequency pectrum. In the tudied ytem, the peed ratio between the compreor and the engine i of.. The engine peed wa meaured via the CAN central monitoring of the vehicle. Thi allowed the calculation of the harmonic of the compreor. Experimental aembly For the date recording, the acquiition module LMS SCADAS Mobile, model SCM, wa ued a hown in Figure 3. Data were proceed and analyzed uing the LMS oftware Tet.Lab v.a. () Figure : Cooling circuit and data aement point Two microphone, Brüel & Kjaer model 89-A-, were intalled in poition cloe to the ear of the driver and front paenger of the vehicle, to record the level of the cabin interior noie. A preure enor wa intalled between the compreor and pipe to record the dicharge preure of the compreor. Data acquiition procedure Meaurement were performed in air conditioning et to maximum cooling, the firt tage of ventilation and external aeration. Vibratory acquiition were performed at a bandwidth of,8. For the acoutic acquiition a bandwidth of,6 wa ued. Tet were carried out under two condition: weep up mode, in the,-, rpm range, and tabilized rotation at the highet noie level,, rpm. In all tet condition, the noie level wa meaured over ninety econd, being the firt thirty econd the air conditioning witched off, the next thirty econd with air conditioning on and the final thirty econd off. Reult Vehicle cabin noie Figure 3: Data acquiition module LMS SCADAS Mobile. Triaxial accelerometer, Brüel & Kjaer model 6, were intalled on the compreor, high preure pipeline attached to the body, condener and expanion valve, point,, 3 and a hown in Figure. Figure how the colormap of the internal noie level of the vehicle in the weep up mode, from, to, rpm, with the air conditioner turned off. Reult indicate that the level of internal noie i mainly due to the econd and fourth harmonic of the engine, H and H. ge 3 of 7

4 m/ rpm XSI ::IS_DYN_CMM_8::REGIME_MOTEUR (CH36) db(b) rpm XSI ::IS_DYN_CMM_8::REGIME_MOTEUR (CH36) AVDD (CH) Figure : Noie meaured in weep up mode,, to, rpm, air conditioning witched off, front paenger eat. Figure 6 how the colormap of the noie level for when the air conditioning i turned on. In thi condition, it can be clearly noticed that between, and, rpm, the harmonic originated in the compreor become evident, conequently increaing the noie level inide the vehicle AVDD (CH) Figure 6: Noie meaured in weep up mode,, to, rpm, air conditioning witched on, paenger eat. Since the noie level due to compreor operation i between, to, rpm, the following vibro-acoutic analyze were performed from meaurement in the tabilized engine peed at around, rpm AVDD (CH) Figure 7: Noie meaured inide the cabin, front paenger eat Figure 7 how the noie level in the paenger ide for the air conditioning on and off condition, at tabilized engine peed. It i oberved that the harmonic from the compreor i the mot emiive, around 8, thu being i the mot important contributor to the noie level inide the cabin. Vibration due to compreor dicharge preure pulation Figure 8 how the pulation of the dicharge preure of the compreor. It can be oberved that when the compreor i actuated, between econd thirty to ixty, the and H harmonic are the one with the highet amplitude. Thu, pulation of dicharge preure i a ource of noie correlated to the internal noie DPP (CH) Figure 8: Compreor preure dicharge pulation Compreor, pipe and mount vibration The figure 9,, and how the reult of the harmonic of the four meaured point in the direction of the highet vibration level CompScrew :+Z (CH3) Figure 9: Compreor colormap, Z axi. H e-3 e-3 e-3 e-3 e-3 ge of 7

5 m/ m/ m/ (Peak) m/ Pendard:+Y (CH7) Figure : High preure pipeline attachment colormap, Y axi Conden:+X (CH7) Figure : Condener colormap, X axi TXV:+Z (CH) Figure : Expanion valve colormap, Z axi. Figure 3 how the vibration level due to the harmonic, on the four point aeed, on air conditioning turned off and on condition. It can be oberved that the compreor i the one with the highet level of vibration, thi being the main ource of vibration of the air conditioning ytem. Furthermore, it can be een that the condener i an important path of vibration tranmiion to the body, ince it preent high vibration amplitude. The expanion valve and the attachment point of the high-preure pipe in the body vibrate at lower ge of 7 e-3 e-3 e-3 e-3 e-3 e-3 e-3 e-3 e-3 e-3 e-3 e-3 e-3 e-3 e-3 According to the reult, the harmonic preent the highet vibration level at all point evaluated. Therefore, it i evident that the noie inide the cabin, due to compreor operation i cloely related to the vibration of the cooling ytem. level. The level of internal cabin noie i increae in about when the air conditioning i turned on. e-3 e-3 HP pipeline attachment e-3 e Figure 3: Noie and vibration level in the harmonic from the compreor in each aement point. Concluion The internal noie in the vehicle cabin when the air conditioning i turned off in the weep up mode, in the,-, rpm range, i mainly due to the harmonic H and H emanated by the engine. When air conditioning i turned on, it can be clearly oberved the emergence of, the main harmonic of a ix piton compreor, which reache it highet noie level between, and, rpm. Therefore, the compreor contribute to the level of noie inide the vehicle. Vibration reult how that the harmonic, cloe to 8, preent the highet vibration level at all point evaluated. Therefore, it i evident that the noie inide the cabin, due to compreor operation i cloely correlated with the vibration of the cooling ytem. Furthermore, it wa determined that the compreor preent the highet level of vibration, followed by the condener which i an important path for vibration tranmitted to the body. The expanion valve and the attachment point of the high-preure pipe vibrate at lower level. However, thee component hould alo be taken into account in vehicle vibratory comfort deign. The dicharge preure of the compreor and it vibration are the oberved noie ource and therefore, item that need to be improved to achieve acceptable noie level inide the cabin. Additionally, from the viewpoint of throughput, iolation on the fixing point of the pipe and condener hould be improved in order to reduce body overall vibration. Reference Condener Expanion valve Compreor Cabin noie [] Priede T., 97 J. Sound and Vibration 6-73, Origin of Automotive Vehicle Noie. [] Sheng G., Lee J. H., Narravula V., Song D.,,Tribology International 8, Experimental characterization and analyi of wet belt friction and the vibro-acoutic behavior. 6 3

6 [3] Yauda T., Wuc C., Nakagawa N., Nagamura K., 3, Applied Acoutic 9 7, Studie on an automobile muffler with the acoutic characteritic of low-pa filter and Helmholtz reonator. [] Mavuri, S, Watkin, S, Wang, X, St Hill, S and Weymouth, D., 8, SAE World Congre, Detroit, United State, An invetigation of vehicle HVAC cabin noie. [] Leite R.P., ul S., Gerge S.N.Y., 9, Applied Acoutic 636 6, A ound quality-baed invetigation of the HVAC ytem noie of an automobile model. [6] Moliani L.R., Burdio R.A., Tihla D., 3, International Journal of Solid and Structure 38, A coupled tire tructure/acoutic cavity model. [7] Minton Automotive, Air Conditioning. Available online at: < ept.. Contact Information Rodrigo Borge Santo MSME, Univeridade Etadual ulita UNESP, Ilha Solteira/SP, Brazil rbanto@hotmail.com João ulo Sabioni do Nacimento BSME, Univeridade Federal Fluminene - UFF jpaulo.abioni@gmail.com Céar Abrahão Pereira Melo BSME, Univeridade Federal de Uberlândia - UFU cearabrahao@gmail.com Alexandre Carlo Rodrigue Ramo BSME, Univeridade de São ulo EESC/USP alexandre.ramo@up.br [8] Santo, E., Dimenionamento e avaliação do ciclo de refrigeração de itema de climatização automotivo,, 9p., Trabalho final de curo (Metrado Profiionalizante em Engenharia Automotiva)- Ecola Politécnica da Univeridade de São ulo, São ulo,. [9] Tian, C., Xu, H., Zhang, L. and Li, X., 9, Applied Thermal Engineering 8-83, Experimental invetigation on the characteritic of variable diplacement wah plate compreor. [] Tian, C., Li, X. and Yang X.,, Applied Energy 8 -, Numerical analyi of evaporator froting in automotive air-conditioning ytem with a variable-diplacement compreor. ge 6 of 7

7 ge 7 of 7 All right reerved. No part of thi publication may be reproduced, tored in a retrieval ytem, or tranmitted, in any form or by any mean, electronic, mechanical, photocopying, recording, or otherwie, without the prior written permiion of SAE. ISSN 8-79 Copyright SAE International. Poition and opinion advanced in thi paper are thoe of the author() and not necearily thoe of SAE. The author olely reponible for the content of the paper.