Design of HVAC system plays an important role in acoustic comfort for passengers. With automotive world moving towards electrical vehicles where powertrain noise is low, designing low noise HVAC system is becoming more important. For an automobile manufacturer, ability to predict the production vehicle cabin noise at the early design stage is important as it allows more freedom for design changes, which can be incorporated in the vehicle at lower cost. Although HVAC prototype and system level testing at early design stage is possible for noise estimation but flow field is not visible in test that makes difficult to improve design. CFD simulation can provide detailed information on flow field, noise source strength and location. But in such a simulation, accurate prediction has been a challenge due to the inability of CFD tools to model acoustic absorptive characteristics of interior walls of cabin.
The parameter setting has a great influence on the noise reduction performance of the road noise active control (RNC) system. This paper analyzes and optimizes the parameters of the RNC system. Firstly, the model of the RNC system is established based on the FxLMS algorithm. Based on this model, taking the maximum noise reduction as the evaluation index, the sensitivity analysis of convergence coefficient, filter order, and reference signal gain was carried out using the Sobol method with the data measured by a real vehicle on asphalt pavement at 40km/h. The results show that there is no significant interaction between the three parameters. Then, using the idea of orthogonal experiment, the simulation results of the control model are analyzed by taking the maximum noise reduction as the evaluation index. It is found that the convergence coefficient has the greatest effect on the maximum noise reduction, followed by the filter order, and the reference signal gain has the least effect.
With an increasing demand for hybrid and battery electric vehicles, it has become imperative to make the electrical switching process safe. In electric vehicles, this process is carried out by compact DC contactors which are designed to withstand years of use over millions of cycles. The quick disconnection is often enabled by an external magnetic field and pressurized hydrogen-nitrogen environment in the contactor. The disconnection process of these contactors leads to the formation of an arc which results from the breakdown of the gas inside the contactor chamber. The breakdown occurs in the inter-connection gap; however, the arc starts to move across the gap between the connectors due to the self-induced magnetic field. The interaction of arcs to the connector's body could lead to undesired metal vapours which could further decrease the creepage distance.
For cold gas Inflator, high refinement of ultimate load forecast is one key of Inflator development. At beginning, two methods based on implicit algorithm, Zero Curvature method and RIKS method were used for burst disk hydro-burst test ultimate pressure load calculation. After considering the effect of bursting disk stamping process, comparing with results of real test, the refinement of the two methods were above 97% both. Studying the corresponding relations between displacement and stress matrix of the center point of burst disk by RISK method. It was found that under ultimate load, the third principal stress vs. displacement curve of the central node shown extreme point, and load step of the point was corresponding the one of maximum pressure load. This shown that after reaching the ultimate load, the center of the bursting disc lost stability in the direction of thickness.
For cold gas Inflator, high refinement of ultimate pressure load forecast of inflator housing is one key of Inflator development. For inflator housing hydro-burst test ultimate load FEA calculation, arc-length method is utilized for obtaining high precision results. At beginning, the material parameters of inflator housing for simulation is correlated. The FEA material model adopts the stress-strain data from uniaxial tensile experiments. Considering the geometrical nonlinearity resulting from large deformation as well as material nonlinearity from plastic hardening, the whole tensile process from tensile deformation to failure of the specimen is stimulated by utilizing the arc-length method. Numerical results show that the arc-length method is appropriate to predict the entire deformation process, and the obtained key deformation stages, the distribution and inclined angle of the localized necking occurs also agrees with that of theoretical analysis.
With the improvement of vehicle comfort requirements of market users, NVH performance has been paid more and more attention. Especially the pure electric passenger vehicle is lack of combustion engine noise masking effect, it is more likely to cause the drivers attention for any abnormal noise. In the steering operation under the low speed acceleration of pure electric vehicles, the cabin interior noise derived from the road and the wind is relatively low, and there is not marketing effect of traditional internal combustion engine noise, any slight abnormal noise is more likely for the drivers and passengers feel unsafe and complain. However, there is lack of systematic analysis and research on the untypical NVH problem in the automotive industry. This paper systematically expounds the test and analysis process of abnormal noise.
Exhaust noise performance has been developed using vehicle. Recently, the demand on reducing vehicles and untact development is increasing. In this study, the method for developing exhasut noise using system models was researched. The exhaust noise can be estimated using engine sound source and exhaust system's transfer functions. We measured engine sound source strength and exhaust system's insertion loss in experimental approach. We drew the theoretical equation leading to tail pipe noise with 2 systems' inherent property and considering connection point conditions such as impedences. We compared the estimated noise with measured using several vehicles. We concluded this approach is helpful for qualitative evaluation for the developing vehicle's exhaust noise without making vehicles. After estimating exhaust noise, we can set the system's target to meet the vehicle's target.
Various techniques are constantly being devised to accelerate model generation leading to shorter product development cycle. This work proposes and implements a reduced synthetic gas bench (SGB) test protocol for a commercial Pt-Pd diesel oxidation catalyst (DOC) that can be used to develop global reaction kinetics. The kinetics thus developed were implemented in a 1D model to predict DOC emissions accurately over a wide operating window. Hydrocarbons (HCs) in the exhaust were categorized as Propylene (C3H6) representing partially oxidized hydrocarbons and n-Decane (C10H22) representing unburnt fuel. Test protocols were defined using the order of inhibition of the various species present in the exhaust, namely, CO, NOx (NO+NO2) and HC for the specific reaction under consideration. The oxidation reactions for CO and HCs were found to be inhibited competitively by CO and HCs; both the NOx species inhibited these reactions to the same extent.
Low frequency interior wind noise is typically dominated by underfloor flow noise. The source mechanisms are fluctuating surface pressure loading from both turbulence and acoustic field levels developed in the semi-reverberant cavity between floor and road. Previous studies have used computation fluid dynamics (CFD) to estimate the aero-acoustic loading applied to a vibro-acoustic model, which is then used to predict the transmitted interior wind noise. This paper reports a new perspective in two respects. First it uses sophisticated surface pressure microphone arrays to directly measure the underfloor aero-acoustic loading in the wind tunnel. Second, it considers two different underfloor aerodynamic configurations – with and without lightweight aero cover panels, which are installed primarily to reduce aerodynamic drag.
In the automotive industry, acoustic trim components are playing an essential role in the vehicle Noise, Vibration and Harshness (NVH). They act in three different ways: reducing the structure vibration, absorbing incident acoustic waves and reducing both the structure-borne and air-borne noise transmission. Mastering acoustic trims is key for interior acoustic comfort and a major differentiator in terms of customer appreciation. An elegant and efficient way to solve fully trimmed vehicle models numerically is the well documented and widely used Reduced Impedance Matrix (RIM) method. It solves the structure and cavity in modal coordinates, while the acoustic trim components are solved in physical coordinates where their complex damping behavior can be fully captured. This method is very accurate to compute structure and cavity results but couldn’t initially recover data such as pressure or displacement inside the acoustic trim parts.
The identification of vehicle noise is the basis for studying the acoustic characteristics of vehicles. In this paper, both excitation of noise sources and response of interior noise were identified. Firstly, a transfer path analysis (TPA) model was established to identify the excitation of noise sources, which includes vehicle main noise sources, such as engine, tire, exhaust pipe and muffler. Based on the operational signals and transfer function which were tested in the vehicle semi-anechoic room, the excitation of noise sources was identified using inverse matrix method. Identify result indicated that tires have higher excitation amplitude than engine in high frequency band. Therefore, the transfer path between the tire and the cabin, such as carpet and windshield, should be taken as the focus of acoustic performance improvement. By improving the acoustic material on the transfer path, the loss of sound in the transfer path will be increase.
Operating internal combustion (IC) engines in low heat rejection (LHR) mode by providing thermal barrier coating (TBC) to some of the engine components will improve thermal efficiency and reduce few tailpipe emissions. Yttria stabilized zirconia (YSZ) is a commonly used TBC material in IC engines due to its better thermal characteristics. On the other hand, running an engine with gaseous fuel on dual fuel operation gives better and efficient combustion. In this research work, an attempt was made to study the combined effects of running a compression ignition (CI) engine on dual fuel operation with low heat rejection (LHR) mode on its performance, and emissions were investigated. For this purpose, a 4.4 kW, four-stroke, naturally aspirated, single-cylinder, direct injection (DI) diesel engine was converted to run on dual fuel mode. Two pistons were used in this study; one was coated with a thermal barrier coating material and the other one was uncoated.
Robotic technology has begun to play an essential role in ground automotive applications. Utility trucks are among the first responders in extreme climate and severe weather conditions, comprised of two systems: a mobile platform and an articulated robotic morphing arm. The conventional industrial manipulators are mounted on stationary bases, while a mobile manipulator is dynamically coupled on a mobile platform. Such trucks with morphing manipulator can increase the possibility of road accidents in many ways and, additionally, create dangerous situations on the roads, and off-road conditions, while moving, and performing tasks. Large boom equipped trucks for reaching elevated heights can become unstable due to drastic variation of the boom equipment moment of inertia causing the extreme weight re-distribution among the wheels. The morphing capabilities of the utility trucks need to be investigated together with the vehicle-road forces in order to hold the truck safe on the roads.
As the key assembly of new energy vehicles, the noise and vibration, and harshness (NVH) performance of integrated electric drive system directly affects the driving quality of new energy vehicles. In this paper, the vibration noise characteristic test of 3in1 electric drive system is carried out in the semi-muffler chamber. In order to compare and analyze the difference between 2in1 and 3in1 electric drive system NVH performance, the PEU in the 3in1 system was removed and placed on the ground away from the platform, and vibration noise test was carried out. In order to analyze the difference of NVH performance between 2in1 status and 3in1 status, the PEU in the 3in1 system was removed and placed on the ground far away from the bench, and the NVH test was carried out. The microphone signal at 1m position and the vibration acceleration signal of the key structural surface of the system are measured experimentally.
The application of turbochargers in fuel vehicles brings high-frequency noise, which seriously affects the vehicle's ride comfort. The hiss noise of a turbocharged car is improved in this paper. Firstly, under different operating conditions and whether the air intake system is wrapped, the noise in the vehicle cabin and the driver's right ear is tested, and the noise sources and noise characteristics are identified. Then, the acoustic calculation model of the muffler is established, and the transmission loss(TL) of the original muffler behind the turbocharger(MBT) is calculated. The TL of the muffler is measured by the double-load impedance tube method. The finite element calculation model is verified by comparing the TL of muffler calculated with tested. Thirdly, the MBT is redesigned. The improved muffler significantly improves the performance of eliminating high-frequency noise, and its TL beyond 20 dB is expanded to the band of 1600 ~ 3500 Hz.
Idle sound quality for motorcycle is very important to the customers . People would like to have a strong individualized sound in idle, linear and smooth sound in the driving condition. Since the idle fluctuation noise is based on the engine firing sequence, the exhaust manifold structure and the idle frequency eight or six cylinders engine are really hard to get a real good fluctuated tailpipe sound in the idle condition compared to the two or three cylinders engines. However, some surrogate methodology can be applied on these engines. Based on the noise cancellation process in amplitude and phase in the exhaust duct system, engineers can manipulate the noise with several lower peaks, that the other higher peaks can be perceived by the masking effect in the time domain. In this scenario, people only feel the big noise fluctuation peaks, even the smaller peaks are still there in the background. In addition, waves can be further improved by the Hot-End structure.