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排序方式: 共有907条查询结果,搜索用时 187 毫秒
871.
Reliability-based topology optimization based on bidirectional evolutionary structural optimization using multi-objective sensitivity numbers 总被引:1,自引:0,他引:1
K. -H. Cho J. -Y. Park S. -P. Ryu J. -Y. Park S. -Y. Han 《International Journal of Automotive Technology》2011,12(6):849-856
Reliability-based topology optimization (RBTO) is used to obtain an optimal topology satisfying given constraints, as well
as to consider uncertainties in design variables. In this study, RBTO was applied to obtain an optimal topology for the inner
reinforcement of a vehicle’s hood based on bidirectional evolutionary structural optimization (BESO). A multi-objective topology
optimization technique was implemented to obtain the optimal topology for two models with different curvatures while simultaneously
considering the static stiffness of bending, torsion, and natural frequency. A performance measure approach (PMA) with probabilistic
constraints formulated in terms of the reliability index was employed to evaluate the probabilistic constraints. The optimal
topology obtained by RBTO was evaluated and compared to that obtained by deterministic topology optimization (DTO). A more
suitable topology was obtained through RBTO than DTO even though the final volume obtained by RBTO was generally slightly
greater than that obtained by DTO. The multiobjective optimization technique based on BESO can be applied very effectively
with topology optimization for a vehicle’s hood reinforcement. 相似文献
872.
The drag reduction of a pickup truck by a rear flap add-on was examined through CFD simulations and wind tunnel experiments.
When installed at the rear edge of the roof, the flap increased the cabin back surface pressure coefficient, causing the downwash
of the bed flow to be inclined on the tailgate. Thus, the attachment of the bed flow to the tailgate was eliminated; consequently,
the drag coefficient was reduced with increasing flap length and downward angle despite the enlarged reverse flow in the wake.
However, the drag coefficient did not decrease any further after a specific downward angle was reached because the bed flow
increased the drag force at the tailgate and the flap lowered the pressure field above the flap. To maximize the drag reduction
effect, the rear downward flap should be designed to have an optimum downward angle. 相似文献
873.
Design and use of an eddy current retarder in an automobile 总被引:1,自引:0,他引:1
In this study, the structure and working principles of an eddy current retarder acting as an auxiliary brake set is introduced
in detail. Based on the principle of energy conservation, a mathematical model was developed to design a retarder whose nominal
brake torque is 1, 900 N·m. According to the characteristics of the eddy current retarder, an exclusive test bed was developed
and used for brake performance measurements. The main technical parameters, such as the brake characteristics, temperature
characteristics and power consumption, were measured with the test bed. The test data show that the brake torque of the eddy
current retarder obviously decreased in the continuous braking stage and that there is a certain amount of brake torque in
the normal driving state because of the remnant magnetism of the rotor plate. The mathematical model could be used to design
an eddy current retarder. The exclusive test bed could be used for optimization of an eddy current retarder as well as for
R&D of a series of products. 相似文献
874.
C. L. Myung J. Kim S. Kwon K. Choi A. Ko S. Park 《International Journal of Automotive Technology》2011,12(3):331-337
This study was conducted for the experimental comparison of particulate emission characteristics between the European and
World-Harmonized test cycles for a heavy-duty diesel engine as part of the UN/ECE PMP ILCE of the Korea Particulate Measurement
Program. To verify the particulate mass and particle number concentrations from various operating modes, ETC/ESC and WHTC/WHSC,
were evaluated. Both will be enacted in Euro VI emission legislation. The real-time particle emissions from a Mercedes OM501
heavy-duty golden engine with a catalyst based uncoated golden DPF were measured with CPC and DMS during daily test protocol.
Real-time particle formation of the transient cycles ETC and WHTC were strongly correlated with engine operating conditions
and after-treatment device temperature. The higher particle number concentration during the ESC #7 to #10 mode was ascribed
to passive DPF regeneration and the thermal release of low volatile particles at high exhaust temperature conditions. The
detailed average particle number concentration equipped for golden DPF reached approximately 4.783E+11 #/kWh (weighted WHTC),
6.087E+10 #/kWh (WHSC), 4.596E+10 #/kWh (ETC), and 3.389E+12 #/kWh (ESC). Particle masses ranged from 0.0011 g/kWh (WHSC)
to 0.0031 g/kWh (ESC). The particle number concentration and mass reduction of DPF reached about 99%, except for an ESC with
a reduction of 95%. 相似文献
875.
W. K. Park S. D. Mun H. K. Lee G. E. Yang 《International Journal of Automotive Technology》2011,12(5):705-712
Compressed air can be used as an energy source for brake systems in medium-heavy and heavy-duty commercial vehicles. The moisture
in compressed air, which is due to high temperature and humidity, can be eliminated by using an air dryer. In this paper,
drying performance data for a cartridge were obtained and used to develop a drying performance program, to predict the moisture
and relative humidity in the air tanks of vehicles. The on-load time, off-load time, air flow, duty cycle, humidity and dew
point temperature were calculated according to air consumption. The validity of the program was verified, and it was shown
to be able to predict humidity changes in the air tank. The air tank capacity was increased from 100 to 130 to reduce the
duty cycle. Therefore, the regeneration rate decreased from 18% to 15%, but the dew point depression temperature (ΔT) remained
above 30°C. The duty cycle decreased from 50% to 43%, and the total operation time and power consumption of the air compressor
were reduced. In conclusion, fuel savings were obtained by changing the parameters to optimize the system. 相似文献
876.
J. -G. Ih C. -Y. Choi T. -K. Kim S. -H. Jang H. -J. Kim 《International Journal of Automotive Technology》2011,12(4):617-630
At the idle engine speed, the exhaust discharge noise is influenced by resonances in the whole system, which is composed of
connecting pipes and silencers. This pipe resonance radiates a high level of low frequency discharge noise, which is dominated
by the low order harmonics of the engine firing frequency. This low frequency noise deteriorates the vehicle’s interior noise
level and quality. The following study attempted to optimize the layout of an exhaust system to minimize low frequency noise
by changing the position of silencers and the lengths of inlet and outlet pipes in each silencer. After modeling the exhaust
system using four-pole parameters, the acoustical performance of the system was evaluated using the system insertion loss.
In the optimization, the virtual attenuation coefficient, which corresponds to the amount of attenuation coefficient required
for the silencers, was calculated to find a minimum value for the layout. The simulated annealing method, which is also known
as finding an optimal, was employed in searching for the optimized exhaust layout. Test examples of two cases, for two and
six design variables, were used. When the number of design variables was two, the positions of the center and rear silencers
were considered. When the number of design variables was six, the positions of the two silencers and the lengths of the inlet
and outlet pipes were considered. Three typical layouts for the exhaust system of each case were designed, including the given
system and an optimal system. By comparing the predicted and measured discharge noise level, it was confirmed that the optimized
exhaust layout has a higher noise reduction than the other layout designs. 相似文献
877.
A. J. Torregrosa J. Galindo C. Guardiola O. Varnier 《International Journal of Automotive Technology》2011,12(3):359-367
This paper presents a methodology for diesel engine intake line analysis that combines specific element tests and modeling.
The purpose of this methodology is to determine the impact of intake lines, or newly designed intake elements, on the volumetric
efficiency of internal combustion engines while avoiding expensive on-engine tests. For this research, the intake system is
divided into several elements which are individually characterized using flow and impulse test rigs. Next, individual systems
are modeled using a one-dimensional code. Finally, these component models are coordinated to provide an evaluation of the
volumetric efficiency. Intake lines coming from two turbocharged diesel engines are used to illustrate the method. The model
is validated by comparing the model results with the actual system performance evaluated in engine test cells. Discussions
of the feasibility of the technique and on the impact of element model inaccuracies on the overall system model are provided. 相似文献
878.
Idle stability directly affects a vehicle’s NVH (Noise, Vibration and Harshness) and is closely related to driver satisfaction.
The present study proposes a method of measuring an engine’s idle roughness, which is useful in quantifying the idle stability.
Engine brake torque was measured directly using a torque sensor, which can be installed without modification of the engine’s
mounting structure. In addition, angular acceleration was measured at the same position as the torque measurement, to compare
dynamic characteristics of the angular acceleration with the torque variation. Both torque and angular acceleration oscillate
between positive and negative values. In this study, torque data were divided into several regions, and each region starts
from the point where the torque data changes its sign from negative to positive. The root mean square values of both torque
and angular acceleration were calculated for each region. This calculation showed a very good correlation between the torques
and the angular accelerations. The idle stability was evaluated with the standard deviation of the measured torque, and the
cycle-to-cycle variation is a more dominant factor in the idle stability than is the cylinder-to-cylinder variation. Because
it is easier to measure the angular acceleration than to measure the torque, the variations of angular accelerations are usually
compared between engines. However, the present study showed that the moment of inertia of an engine and the angular acceleration
should be considered together when comparing the idle stability between engines. 相似文献
879.
G. H. Lee W. C. Choi S. I. Kim S. O. Kwon J. P. Hong 《International Journal of Automotive Technology》2011,12(2):291-297
This paper identifies a control method used to reduce torque ripple of a permanent magnet synchronous motor (PMSM) for an
electric power steering (EPS) system. NVH (Noise Vibration Harshness) is important for safe and convenient driving. Vibration
caused by motor torque is a problem in column type EPS systems. Maintaining a very low torque ripple is one solution that
allows for smoother steering. Theoretically, it is possible to design and drive the motor without torque ripple. However,
in reality, a PMSM system torque ripple is caused by the motor itself (saturation in the iron core and EMF distortion) and
the imperfect driver. This paper analyzes torque ripple of a PMSM system, and an advanced PMSM control method for the column
typed EPS system is presented. Results of the analysis indicate that the compensation current is needed in order to minimize
torque ripple when a PMSM is driven. 相似文献
880.
B. Suh A. Frank Y. J. Chung E. Y. Lee Y. H. Chang S. B. Han 《International Journal of Automotive Technology》2011,12(1):131-139
This research concerns the design of a powertrain system for a plug-in parallel diesel hybrid electric bus equipped with a
continuously variable transmission (CVT) and presents a new design paradigm for the plug-in hybrid electric bus (HEB). The
criteria and method for selecting and sizing powertrain components equipped in the plug-in HEB are presented. The plug-in
HEB is designed to overcome the vulnerable limitations of driving range and performance of a purely electric vehicle (EV),
and it is also designed to improve the fuel economy and exhaust emissions of conventional buses and conventional HEBs. Optimization
of the control strategy for the complicated and interconnected propulsion system in the plug-in parallel HEB is one of the
most significant factors for achieving higher fuel economy and lower exhaust emissions in the hybrid electric vehicle (HEV).
In this research, the proposed control strategy was simulated to prove its validity using the ADVISOR (advanced vehicle simulator)
analysis simulation tool. 相似文献