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During design development phases, automotive components undergo a strict validation process aiming to demonstrate requested levels of performance and durability. In some cases, specific developments encounter a major blocking point : decoupling systems responsible for optimal acoustic performances. On the one hand, damping rubbers need to be soft to comply with noise, vibration & harshness criteria. However, softness would provoke such high amplitudes during vibration endurance tests that components would suffer from failures. On the other hand, stiffer rubbers, designed for durability purposes, would fail to meet noise compliance. The rubber design development goes through a double-faced dilemma : design with acceptable trade-off between NVH and durability, and efficient ways to develop compliant designs. This paper illustrates two case studies where different methodologies are applied to validate decoupling systems from both acoustic and reliability perspectives.

HVAC systems are of critical importance in ensuring passengers’ thermal comfort inside the car cabin as well as safety requirements for defogging functions. These systems involve various components and subcomponents such as blowers, thermal exchangers or actuators, with a wide range of well-known technologies and also new ones on recently introduced innovative products. Currently, within established electrification trends worldwide, the HVAC system is becoming the most important embedded system that can induce major contribution of noise and vibration. These NVH issues can emerge through different transfer paths inside the car cabin possibly causing significant discomfort to passengers. During developments, the NVH issues are mastered and contained by both suppliers according to internal requirements and OEMs according to specifications.

Automotive thermal systems are of major importance in ensuring optimum operating of thermal engines and in preserving battery capacities. These systems involve various components with a wide range of technologies, designs and subcomponents as HVACs, compressors or fan systems. Currently, as thermal engine noises are reduced and electrification trends are continuously increasing, thermal systems can be a major source of noise and vibration. These NVH issues can emerge inside the car cabin inducing significant discomfort to passengers and can also emerge outside the car causing major disturbances to passersby. During development stages, NVH issues are mastered and contained by suppliers according to internal specifications in addition to complying with OEM requirements. However, NVH issues may not be well detected when using regular NVH metrics.

The Heating Ventilation and Air Conditioning system (HVAC) is a compact and complex system designed to provide thermal comfort inside the car cabin. The system is composed of various components: fan, flaps, thermal exchangers, filters and specific turned ducts allowing thermal conditioning and airflow distribution to car cabin areas. Nowadays, as thermal engine noises are reduced and electrified car sales are increasing, the HVAC could be a major noise source inside the car cabin that could induce significant discomfort to passengers. HVAC noise issues are well known and solved. Many of them are related to the fans’ electrical motor, such as ticking and harmonic noises. The remaining noises are mainly aeroacoustic linked to the fan and interactions between HVAC components and airflow. HVAC behavior also consists of transfer paths and acoustic transparency responsible of emerging noises.

In the framework of noise reduction of HVAC (Heating, Ventilating and Air Conditioning) systems designed for cars, the present study deals with the numerical prediction of aeroacoustics phenomena encountered inside such devices for industrial purposes, i.e. with a reasonable CPU time. It is then proposed in this paper to assess the validity of the chaining, via Lighthill-Curle analogy, of a DES (Detached Eddy Simulation) resulting from the CFD code OpenFOAM (ESI Group) versus a RANS-LES (Large Eddy Simulation) and a BEM calculation resulting from the Vibro/Aeroacoustics software VA One (ESI Group) on an academic case of air passing through a rectangular diaphragm at a low Mach number. The BEM code being parallelized, the performances of DMP (Distributed Memory Processing) solution will also be assessed.

The noise radiated inside the car cabin depends on many sources such as the embedded equipments like the Heating, Ventilation and Air Conditioning (HVAC) module. An HVAC is a compact and complex system composed of several elements: blower, flaps, thermal exchangers, ducts… Air provided by an HVAC is blown by a blower passing through different components and then distributed to car cabin areas. Interactions between airflow and the HVAC fixed components generate noises that emerge in the car cabin. CEVAS project, managed by the automotive equipment manufacturer Valeo, is aiming to develop a prediction tool which will provide HVAC noise spectrum and sound quality data. The tool is based, in particular, on aeroacoustic characterization of individual elements and associations of elements.

Passengers' thermal comfort inside a car cabin is mainly provided by the Heating, Ventilation and Air Conditioning (HVAC) module. Air provided by HVAC is blown via a blower, passing through different components: flaps, thermal exchangers, ducts… and then distributed to car cabin areas. Interaction between airflow and HVAC components generates noises that emerge in car cabin. Due to this fact, noise is naturally created and its level is linked to flow rate. Valeo is aiming, though CEVAS project, to develop a prediction tool which will provide HVAC spectrum and sound quality data. This tool will be based, in particular, on aeroacoustic measurements using 2N-ports model and Particle Image Velocimetry methods to provide characteristics of HVAC components.