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This paper describes the application of CAE tools in the design optimization of a DCT and driveline system of a passenger vehicle, with emphasis on NVH performance. The multi-body dynamics simulation tools are employed for driveline system analysis. The MBD model consists of the engine, transmission, clutch, drive shafts, tires and vehicle. The wheel slip effects are considered in the calculation of shuffle frequencies. In the analysis of gear whine, the transmission housing, gears and shafts are modeled by detailed 3-D finite element models, so that the mesh stiffness of the gears and the housing support stiffness are described more accurately. The calculated velocity spectra of the housing are presented. The prediction of gear rattle in the transmission is carried out. The loose gear acceleration index and the averaged impact power of free gears are calculated to assess the rattle generation potential and the level of rattle severity.

A computational study was conducted in order to characterize the heat transfers in a sedan vehicle underbody and the exhaust system. A steady-state analysis with consideration for both the radiation and conjugate heat transfers was undertaken using the High-Reynolds formulation of the k-epsilon turbulence model with standard wall function and the DO model for the radiation heat transfer. All three mechanisms of heat transfer, i.e., convection, conduction, and radiation, were included in the analysis. The convective heat transfer due to turbulent fluid motion was modeled with the assumption of constant turbulent Prandtl number; and heat conduction was solved directly for both fluid and solid.

Empirical and theoretical studies are made between active-flow control and passive-flow control schemes in investigating the influences of gas flow, heat transfer, chemical reaction, oxygen concentration, and substrate properties. The exhaust active-flow control includes the parallel alternating flow, partial restricting flow, periodic flow reversal, and extended flow stagnation that are found to be especially effective to treat engine exhausts that are difficult to cope with conventional passive-flow converters [1, 2]. The tests are set up on a single cylinder Yanmar engine. Theoretical studies are performed with the one-dimensional transient modeling techniques to analyze the thermal behavior of the diesel after-treatment systems when active flow control schemes are applied.

Diesel fueling and exhaust flow strategies are investigated to control the substrate temperatures of diesel aftertreatment systems. The fueling control includes the common-rail post injection and the external supplemental fuel injection. The post injection pulses are further specified at the early, mid, or late stages of the engine expansion stroke. In comparison, the external fueling rates are moderated under various engine loads to evaluate the thermal impact. Additionally, the active-flow control schemes are implemented to improve the overall energy efficiency of the system. In parallel with the empirical work, the dynamic temperature characteristics of the exhaust system are simulated one-dimensionally with in-house and external codes. The dynamic thermal control, measurement, and modeling of this research intend to improve the performance of diesel particulate filters and diesel NOx absorbers.

Diesel Particulate Filters (DPF) are viable to reduce smoke from diesel engines. An oxidation process is usually required to remove the Particulate Matter (PM) loading from the DPF substrates. In cases when the engine exhaust temperature is insufficient to initiate a thermal regeneration, supplemental energy is commonly applied to raise the exhaust gas and/or the DPF substrate temperatures. A flow reversal (FR) mechanism that traps a high temperature region in the DPF substrate by periodically altering the gas flow directions has been identified to be capable of reducing the supplemental energy and thus to improve the overall thermal efficiency of the engine. However, extended operations with low exhaust temperature lowers the DPF boundary temperatures that defers the regeneration processes. Furthermore, the temperature fluctuations caused by the periodic FR operation also increase the thermal stress in the DPF.

One-dimensional transient modeling techniques are adapted to analyze the thermal behavior of lean-burn after-treatment systems when active flow control schemes are applied. The active control schemes include parallel alternating flow, partial restricting flow, and periodic flow reversal (FR) that are found to be especially effective to treat engine exhausts that are difficult to cope with conventional passive flow converters. To diesel particulate filters (DPF), lean NOx traps (LNT), and oxidation converters (OC), the combined use of active flow control schemes are identified to be capable of shifting the exhaust gas temperature, flow rate, and oxygen concentration to more favorable windows for the filtration, conversion, and regeneration processes. Comparison analyses are made between active flow control and passive flow control schemes in investigating the influences of gas flow, heat transfer, chemical reaction, oxygen concentration, and converter properties.

A vehicle’s NVH performance has a significant impact on the user experience of the driver and passengers. About one-third of the vehicle complaints are related to NVH performance. As the core component of the vehicle, the drivetrain’s NVH characteristics have a significant impact on vehicle comfort. How to reliably and stably reproduce the specific condition of the whole vehicle through the test method, and obtain the highly consistent objective data for analyzing and improving the NVH characteristics of the drivetrain is of great significance in engineering. For this purpose, China Automotive Technology Research Center Co., Ltd. (CATARC) designed and built a new type drivetrain NVH test facility, which consists of five dynamometers, and can carry horizontal/vertical, front/rear drive or four-wheel drive structures including powertrain, transmission, and rear axle, or even a whole vehicle.

As the commercial vehicle increases staggeringly in China, environmental pollution and excessively fuel consumption can't be neglected anymore. Vehicle thermal management has been adopted by many vehicle manufactures as an ideal alternative to reduce fuel consumption and exhaust emission by its cost-efficient and effective merit. In addition, the components in heavy duty commercial vehicle engine hood may suffer overheat harm. Hence investigating the thermal characteristics in engine hood can be an effective way to identify and dismiss the potential overheat harm. In terms of this, the paper has adopted CFD simulation method to obtain the comprehensive thermal flow field characteristics of engine hood in a heavy commercial vehicle. Then by analyzing the thermal flow field in engine hood, concerning optimization strategies were put forward to improve the thermal environment.

As the main power form of new energy vehicles, e-axle systems are has been widely used in passenger vehicles and commercial vehicles. A passenger car equipped with an e-axle, in constant speed and low torque conditions, there is a noticeable rattle noise, through experimental investigation and comparative analysis, it is confirmed that the connection spline of motor and reducer is the main influencing factor. Then, Through the qualitative analysis of simulation, it is found that both spline clearance and misalignment have an amplification effect on the motor speed, thereby stimulating the gear pair of the reducer to produce rattle. The amplification effect of spline clearance is stronger than that of spline misalignment.