The advent of digital computers and the availability of ever cheaper and faster micro processors have brought a tremendous amount of control system applications to the automotive industry in the last two decades. From engine and transmission systems, to virtually all chassis subsystems (brakes, suspensions, and steering), some level of computer control is present. Control systems theory is also being applied to comfort systems such as climate control and safety systems such as cruise control or collision mitigation systems.
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 as blowers, thermal exchangers, actuators… with a wide range of well-known technologies and also new ones on newly introduced 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 standards and OEMs according to specifications compliance. However, OEMs specifications are mainly consisting of overall noise levels and improvements over the years consisting of reduction of these specified levels.
This paper describes idle vibration reduction methods using a Stellantis vehicle as a case study. The causes of idle vibration are investigated using the NVH source, path, and receiver method. The torque transfer path into a vehicle has shown to be very important in determining vehicle idle vibration response. New electronic control enablers that affect idle vibration are tested and discussed, including Neutral Idle Control (NIC), Transfer-case Idle Control (TIC,®), and Switchable Engine Mounts (SEM). The Design For Six Sigma (DFSS) analysis method is used to arrive at an optimized result for vehicle idle vibration. In addition, Stellantis has developed a new idle vibration control enabler known as Transfer-case Idle Control (TIC), which was awarded by the US patent Office and will be applied on future vehicles. This paper also discusses the results confirming TIC’s capability of reducing idle vibration on all-wheel drive vehicles.
HVAC system design plays an important role in the acoustic comfort of passenger vehicles and becomes prominent in electric vehicles. In the case of buses, cabin volume is larger than in cars, thus HVAC system required inside buses are bigger in size, and to meet comfort requirement numerous blowers are used for airflow delivery. Due to multiple blowers rotating inside the mixing unit and large delivery of air inside of the large HVAC system airborne noise is produced during its operations. One way to evaluate this airborne noise with CFD methods would be using the traditional sliding mesh approach around all the blowers to resolve the flow and turbulence, which is computationally very expensive. However, ability to predict noise inside the bus cabin with lesser turnaround time is important to accommodate quick design changes at early product development stage.
An Inline 4-cylinder engine is equipped with second-order balance shafts. When the engine is running under a low load acceleration condition, the gear system of the balance shaft generated whine noise. In this paper, an analysis method for reducing the whine noise is presented. First, a flexible multi-body dynamic model of the engine is established, which includes shaft and casing deformation, micro-modification of the balance shaft gears. Taking the measured cylinder pressure as the input, the influence of the micro-modification of the gears’ tooth surface at the balance shaft on the meshed noise was calculated and analyzed. The torsional vibration at the crankshaft nose was measured during no-load conditions, and the measured data was compared with the estimated data, which validate the established multi-flexible body dynamic model of the engine. Secondly, a quasi-static model of the balance shaft gear transmission was established.
Current trends of advanced automotive engines focus on downsizing, better fuel efficiency, and lower emissions, which lead to several advancements in turbocharger designs and technology. More recent trends in electric and hybrid powertrains have further brought additional sources into the NVH balance. With vehicle environments becoming quieter, this has posed a great challenge in controlling undesirable noise from boosting systems. Boosting systems provide oxygen through boosted air pressure, to ICE or fuel cell systems, to improve their efficiency and limit their CO2 and pollutant emissions. Boosting systems are also key elements in current and new electrical and hybrid powertrains. During real driving conditions, the rotational speed of boosting systems (turbomachines and compressors) varies greatly, which makes them produce different noise signatures that can be unpleasant for the end users.
This paper describes a simulation methodology developed for gear rattle severity evaluation and drivetrain architecture optimization . The noise generated by gear rattle is one of the main contributors towards customer's overall NVH perception. This study adopts a model-based design approach towards gear rattle phenomenon to simulate the tendency of gear rattle in neutral and drive conditions . Gear rattle simulation model for Tractor driveline developed in 1-D environment and correlated with test data acquired on tractor drivelines for multiple field applications. This analytical physics-based model includes engine torsional signature, clutch damper torsional characteristic and dynamics of traction and PTO driveline. This dynamic simulation model helps to understand and predict the gear rattle severity of various drivetrain architecture early in the product development cycle and assess & Optimize driveline NVH performance.
Highly compression ratio is effective as one means of improving the thermal efficiency of an internal combustion engine. On the other hand, rapidly rise at combustion pressure to occur because of this high compression ratio causes a highly impulse force. The impulse force gives rise to a vibration and noise by spreading in an engine. Therefore, it can be said that reducing the vibration of combustion, which increases as the compression ratio increases, is same technology with improving thermal efficiency. Regarding the function of reducing combustion vibration, we are conducting model-based research on technology to reduce vibration by applying a granular damper to the piston. To reducing the vibration of combustion efficiently, we attempt to suppress the vibration directly with the piston, which is the source of the vibration. In this way, the damping effect is maximized within the minimized countermeasure range.
Conventional silencers have extensively been used to attenuate airborne pressure pulsations in the breathing system of internal combustion engines, typically at low frequencies as dictated by the crankshaft speed. With the introduction of turbocharger compressors, however, particularly those with the ported shroud recirculating casing treatment, high-frequency tones on the order of 10 kHz have become a significant contributor to noise in the induction system. The elevated frequencies promote multi-dimensional wave propagation, rendering traditional silencing design methods invalid, as well as the standard techniques to assess silencer performance. The present study features a novel high-frequency silencer designed to target blade-pass frequency (BPF) noise at the inlet of turbocharger compressors. The concept uses an acoustic straightener to promote planar wave propagation across arrays of quarter-wave resonators, achieving a broadband attenuation.
The charge air cooler, which is placed between the compressor and the engine intake manifold, is an important component in a turbocharged engine. Air, already hot and under high pressure from the compressor, passes through many small fin tubes in the core of the charge air cooler which decreases the temperature of the air before it enters the engine cylinder. This process increases both engine power and efficiency. To improve the predictive accuracy of engine performance and intake noise using a 1-D GT-power model, it is essential for the charge air cooler model to capture all the parameters of the component, whether it is temperature change, pressure drop or the acoustical wave behavior. Although there may be flow-induced high frequency noise content present from the compressor, low frequency engine intake order noise is more dominant of the overall intake noise level for a turbocharged engine.
Vehicle weight reduction is important to improve the fuel mileage of ICE vehicles and to extend the range of electric vehicles. Glass fiber reinforced (GFR) Composite(Polyamide) brackets provide significant weight reductions at a competitive part price. Traditionally, metal brackets are designed to surpass a target natural frequency and static stiffness. Composite brackets are inherently less stiff and have lower natural frequencies. However, they also have higher material damping than metal brackets, and good isolation performance can be achieved. The key to integrating the Composite brackets into the vehicle design is to perform adequate analysis to ensure that the noise and vibration performance at the vehicle level meets expectations. In this paper, case studies are presented for three different vehicles - engine roll restrictor bracket (for ICE vehicle), rear differential bracket (for ICE), and rear (electric) motor mount bracket.