Optimizing an Automotive HVAC System for Enhancement of Acoustic Comfort 2021-28-0147

The Indian automotive industry is going through a rapid transformation phase. Regulatory emission norms such as, migration from BSIV to BSVI engine, increased adoption of μ-hybrid, full electric and autonomous cars are examples of such rapid transformation. The upgradation of internal combustion engines for compliance with new regulatory norms (e.g., from BSIV to BSVI) has caused a significant change in the automotive acoustic performance. As the powertrain system are being upgraded and getting quieter, the on-board Heating, Ventilation and Air-Conditioning system (HVAC) system emerges as one of the prominent noise sources which strongly influences overall refinement levels inside the cabin. This in turns is affecting overall feeling of passenger’s comfort. The HVAC system of an automobile is a compact and yet a complex system designed to provide thermal comfort inside the car cabin. It is also a source of acoustic annoyance due to humming, hissing, chattering, air rush and refrigerant whistling noises. In particular, the study of noise propagation in the refrigeration circuit, from evaporator outlet to AC compressor inlet is significant. The current work focusses on low frequency humming and chattering noise in the refrigerant circuit and it covers various aspects of uneven refrigerant flow. Refrigerant pressure pulsation, measured at piston pass frequency of AC compressor, propagates as an audible humming noise and refrigerant flow induced chattering noise in suction pipe. This paper examines transfer paths and acoustic transparency responsible for emerging noises and describes optimum design solutions to control the pressure pulsations in the refrigerant and hence noise.