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251.
Hyun Park Nam Hyun An Nicholas Hutchins Kwing-So Choi Ho Hwan Chun Inwon Lee 《Journal of Marine Science and Technology》2011,16(4):390-401
An experimental assessment has been made of the drag reducing efficiency of the outer-layer vertical blades, which were first
devised by Hutchins and Choi (Proceedings of ASME FEDSM’02 2002 ASME Fluids Engineering Division Summer Meeting, Montreal)
and Hutchins (An investigation of larger-scale coherent structures in fully developed turbulent boundary layers, Hutchins
N (2003), PhD thesis, University of Nottingham). The reported drag reduction efficiency, which was as much as 30%, was quantified
only in terms of the reduction in the local skin-friction coefficient. The assessment of the drag reducing efficiency did
not take the side effects of the inclusion of the blades into considerations. Those effects are the increase in the wetted
surface area and the flow disturbances due to the presence of the blades. In the present study, a series of drag force measurements
in towing tank has been performed toward the assessments of the total drag reduction efficiency of the outer-layer vertical
blades. It was found that for the case of h 4.0 × z 4.0 (h/δ = 1.04), the outer-layer vertical blades array achieved about 9.6% drag reduction without considering the increase in the
wetted surface area. A proper scaling method to give collapsed plot of drag reduction efficiency C
F/C
F0 was attempted, but the correlation remained limited. Of the two scaling methods, the outer scaling is found to be relevant
one. 相似文献
252.
We analyzed the lubrication characteristics of a design-selected spiral groove liquid seal for the critical component, the
carrier, of a rotary vane-type fuel pump developed for external installation on fuel tanks for liquid phase LPG (liquefied
petroleum gas) injection (LPLi) vehicles, with the aim of fundamentally improving lubrication performance and so protecting
the carrier from early frictional wear damage at its suction face. The main reason for selecting a spiral groove pattern was
because the viscosity of liquid LPG is very low, comparable to that of air, and current commercial dry gas seals adopting
spiral grooves have been successfully employed in completely noncontacting applications. Utilizing the Galerkin finite element
lubrication analysis method, a detailed lubrication characteristic analysis of the seal was performed, and lubrication performance
optimization was performed by systematic parameter analyses of the design variables. Compared to the initial reference design,
the final optimized spiral groove seal design had a groove depth increased by 66.7% and an equilibrium seal clearance increased
by 65.3%. Our model also predicted that under a condition of equilibrium between the closing force of the pumping pressure
and the seal opening force, the optimally designed carrier spiral groove liquid seal was capable of maintaining a stable lubricating
film with sufficient axial stiffness and thereby demonstrated successful noncontact operation; in addition, leakage through
the seal was minimal. 相似文献
253.
D. -H. Shin B. -H. Lee J. -B. Jeong H. -S. Song H. -J. Kim 《International Journal of Automotive Technology》2011,12(1):125-130
Hybrid electric vehicles (HEV) utilize electric power and a mechanical engine for propulsion; therefore, the performance of
HEVs is directly influenced by the characteristics of the energy storage system (ESS). The ESS for an HEV generally requires
high power performance, long cycle life, reliability and cost effectiveness; thus, a hybrid energy storage system (HESS) that
combines different types of storage devices has been considered to fulfill both performance and cost requirements. To improve
the operating efficiency and cycle life of a HESS, an advanced dynamic control regime in which pertinent storage devices in
the HESS can be selectively operated based on their status is presented. Verification tests were performed to confirm the
degree of improvement in energy efficiency. In this paper, an advanced HESS with a battery management system (BMS) that includes
an optimal switching control function based on the estimated state of charge (SOC) is presented and verified. 相似文献
254.
S. J. Kang M. F. Kader Y. D. Jun K. B. Lee 《International Journal of Automotive Technology》2011,12(1):39-44
Adequate visibility through the automobile windshield is of paramount practical significance, most often at very low temperatures
when ice tends to form on the windshield screen. But the numerical simulation of the defrost process is a challenging task
because phase change is involved. In this study numerical solution was computed by a finite volume computational fluid dynamics
(CFD) program and experimental investigations were performed to validate the numerical results. It was found that the airflow
produced by the defrost nozzle is highly nonuniform in nature and does not cover the whole windshield area. The nonuniformity
also severely affected the heating temperature pattern on the windshield. The windshield temperature reached a maximum in
the vicinity of the defroster nozzle in the lower part of the windshield and ranged from 9∼31°C over a period of 30 min, which
caused the frost to melt on the windshield. The melting time was under 10 minutes, which satisfied the NHTSA standard. The
numerical predictions were in close agreement with the experimental results. Thus, CFD can be a very useful design tool for
an automobile HVAC system. 相似文献
255.
C. -H. Lee J. -M. Lee M. -S. Choi C. -K. Kim E. -B. Koh 《International Journal of Automotive Technology》2011,12(2):193-198
Since the invention of automobiles, the need to know the braking performance of vehicles has been acknowledged. However, because
there are numerous design variables as well as nonlinearities in the braking system, it is difficult to predict the performance
accurately. In this paper, a computational program is developed to estimate the braking performance numerically. This synthetic
braking performance program accounts for pedal force, pedal travel and deceleration of braking parts, such as master cylinder,
booster, valve, brake pad, rotor, and hoses. To improve the accuracy of program, a semi-empirical model of a braking system
is introduced by using the empirical test data of pad compression, hose expansion and the friction coefficient between the
pad and rotor. The accuracy of the estimation is evaluated by comparing it to the actual vehicle test results. The developed
program is easy for the brake system engineers to manipulate and it can be used in the development of new vehicles by incorporating
the graphical presentations. 相似文献
256.
J. K. Kim Y. J. Kim W. H. Yang Y. C. Park K.-H. Lee 《International Journal of Automotive Technology》2011,12(3):375-381
This study proposes a structural design method for an outer tie rod installed in a passenger car. The weight of the outer
tie rod is optimized by using the aluminum alloy Al6082M, which is developed as a steel-substitute material, and applying
structural optimization techniques. The high strength aluminum with improved mechanical properties was developed to reduce
the weight of the outer tie rod. The newly developed aluminum alloy Al6082M is applied as the material of the outer tie rod.
The static strength due to inertia force, durability and buckling performances are considered in the structural design of
the outer tie rod. At the proto design stage of a new outer tie rod, it is cost-effective to utilize FE (finite element) analysis
to predict each of these performances. In addition, the current trend in the structural design of automobile parts is to use
optimization techniques to reduce the weights of the parts. First, for an arbitrary base design, the static strength, the
life cycle and the buckling load are calculated to check whether the design satisfies its criteria. Then, the critical performance
is selected so as to include its loading condition only in the optimization process. In this study, the metamodel based optimization
process using kriging is adopted to obtain the minimum weight satisfying the critical design requirement. Then, the feasibility
of the determined optimum shape is investigated against the other performances. Finally, the optimum design of outer tie rod
is modified by considering forging efficiency. The performances of the final design are investigated through simulation and
experiment. 相似文献
257.
M. H. Lee H. M. Lee K. S. Lee S. K. Ha J. I. Bae J. H. Park H. G. Park H. J. Choi H. H. Chun 《International Journal of Automotive Technology》2011,12(5):733-744
In this paper, a hardware-in-the-loop simulation (HILS) system was developed before the development of an electric power steering
(EPS) system in a vehicle. This study was focused on the establishment of the HILS system. Driving conditions are simulated
with the HILS system. The actual steering input parameters are confirmed on the monitor while driving the HILS system. The
steering forces observed in the simulation with the developed HILS system are similar to those in real vehicle tests. The
developed HILS system can be applied in the development of various types of EPS systems. 相似文献
258.
An experiment was conducted to characterize the effects of SOF on EGR cooler fouling. A removable singletube test rig combined with a soot generator was developed to represent an EGR cooler and diesel exhaust gas. The use of a soot generator, which controlled the size and concentration of soot particles, enabled independent variables to be completely controlled. Either n-dodecane or diesel lube oil as substitute SOFs were vaporized and injected into the test rig to evaluate their effects on the growth of PM deposits and the degradation performance of the EGR cooler. Coolant temperature, which seemed to be associated with SOF content, was chosen as an independent variable, and PM deposit mass per unit area and the effectiveness drop versus time increased as the coolant temperature decreased. The PM deposit mass per unit area and effectiveness drop had maximum values at a coolant temperature of 40°C for every n-dodecane injection rate. For substitute SOFs tested in this experiment, the deposit mass increased when either n-dodecane or diesel lube oil was injected, but the effect of lube oil was more significant. Diesel lube oil seemed to have a stronger effect on the reduction of thermal conductivity by filling pores in the deposits. When diesel lube oil was injected, the deposit mass per unit area increased 127% compared to dry soot without injection. The effectiveness drop after 10 hours increased only 12.5%. 相似文献
259.
This paper presents a system to identify road and non-road regions from monocular color images of paved and unpaved roads. Despite being a single object, the road in these images is subject to large changes in appearance due to environmental effects and track materials. This condition has challenged the practical application of road identification. The proposed system combines random forest with color correlogram to overcome such conditions and offers a classifier for road and non-road regions in traffic images. As a color feature, the color correlogram depicts the spatial correlation of color changes in an image. Using random forest, road identification is formulated as a learning paradigm. The combined effects of color correlograms and random forest create a robust system capable of identifying roads even in variable situations in real time. This combination is more effective than other combinations, such as a color histogram plus random forest, a color correlogram plus neural network, or a color histogram plus neural network. 相似文献
260.
In lean-DeNOX catalysis reactions, hydrogen is a good reducing agent in PGM catalysts as well as an effective promoter in
selective catalytic reduction reactions over base metal oxide catalysts. However, such a lean-DeNOX system, which uses hydrogen,
requires an on-board fuel reforming system applicable to internal combustion engines. In this study, catalytic partial oxidation
(CPOx) performance was tested in a laboratory for various reactants and hydrocarbon conditions. Volume concentrations of 5–10%
oxygen and 0-5% water vapor were used to simulate diesel exhaust, and n-C12H26 was used as the feedstock for the reforming reaction. In the CPOx of n-C12H26, the highest hydrogen selectivity was 64% and was achieved at 100,000 h-1 GHSV. Additionally, the C/O ratio was less than
unity in the absence of water vapor. However, as the water concentration was increased to 2.5 and 5.0 vol. % in the n-C12H26 CPOx reactions, the maximum hydrogen selectivity was increased from 64% in the absence of water to 70% and 75%, respectively.
This effect is a consequence of the water-gas shift reaction over the catalyst bed. Regarding oxygen concentration effects,
hydrogen selectivity slightly increased with increasing oxygen concentration from 10% to 15%. It was also found that the CPOx
reaction of n-C12H26 can be ignited at temperatures below 300 C. Accordingly, it can be concluded that CPOx is a useful and feasible device for
promoting diesel DeNOx catalysis in terms of hydrogen productivity and reaction initiation. 相似文献