一汽汽车技术空调AcousticPart2.doc(NXPowerLite)

1、.ACOUSTIC A/C LOOP KNOW HOWPDT NVA20 000 Rev APROJECTApplication : VCC19/02/02MODIFICATIONS LIST1.1. DEFINITION / ABBREVIATION1.1.1. DefinitionCompressor noiseAir borne noise : Large bandVibration noise : Low frequency noise (200-800Hz)Pulsation rattle noise : Low frequency noise

2、 (200-1000Hz)Expansion valve noiseTrumpet noise : Peaks between 400 and 1000 HzEvaporator noiseInjection noise : High frequency noise (>2 kHz) during the transient period after have switched ON the Air Conditioning.Flow noise : High frequency noise (>1 kHz) during the stationary peri

3、od (A/C ON).Subjective evaluation (GMUTS)NoteSubjective ratingCommercial10Excellent : Not noticeable even by trained evaluators9Very good : Noticeable only by trained evaluators8Good : Noticeable only by critical customers7Satisfactory : Noticeable by all customers6Acceptable : Rated disturbing

4、 by some customersBORDELINE5Unsatisfactory : rated disturbing by all customersNon commercial4Poor : Rated as failure by all customers3Very poor : Complained as bad failure by all customers2Bad : Limited operation1Very bad : Non operational1.1.2. AbbreviationA/C : Air ConditioningHVAC : Heat Ventilat

5、ion Air Conditioning2. ACOUSTIC A/C LOOP KNOW HOW2.1. PULSATION RATTLE NOISE Cause : high pressure pulsation (that come from the compressor) inside the A/C lines.Solution : add a muffler as near as possible from the compressor. Size : 40 40mmSpecification : VDA specification appendix A4 : press

6、ure pulsation is limited.Explanation : the muffler generates waves reflection that allow to decrease the pressure pulsation level inside the A/C loop. So that, in this application, the evaporator doesnt radiate any noise.60 mm40 mmPrecaution : Muffler far from the compressor has low impact on the no

7、ise. The standard muffler size is 60 * 40 mmThis solution has been tested on the R50 vehicle (test report : ACDB.CS.01.117.R&D)Figure 1 : Third octave spectrum, R50 Base at idleR50 without muffler at idle and 45 °CFigure A1 :Series product without muffler Figure A2 : Muffler size and positi

8、onMoreover, this test has been confirmed by A/C loop noise tests on the Acoustic Confort Test Bench (test report : ACDB.BB.01.125.R&D) :2500rpm, 45°C, 40% HR, without muffler, 300mm from the evaporatorA/C OFFPulsation rattle noise + compressor noiseClutchA/C OFF40mm40mm2500rpm, 45°C, 4

9、0% HR, with muffler 40 40, 300mm from the evaporatorCompressor noiseThis test shows that add a muffler allows to reduce significantly the pulsation rattle noise (this A/C loop lines are accepted by the customer), that allows to have GMUTS=8 with muffler vs. 5 without muffler.2.2. ;Management : VCCType : Acoustic recommendationsPage 4/12VCC.PRO