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381.
J. Lee S. Choi H. Kim D. Kim H. Choi K. Min 《International Journal of Automotive Technology》2013,14(4):551-558
Recent studies on dual-fuel combustion in compression-ignition (CI) engines, also known as diesel engines, fall into two categories. In the first category are studies focused on the addition of small amounts of gaseous fuel to CI engines. In these studies, gaseous fuel is regarded as a secondary fuel and diesel fuel is regarded as the main fuel for combustion. The objectives of these studies typically involve reducing particulate matter (PM) emissions by using gaseous fuel as a partial substitution for diesel fuel. However, the addition of gaseous fuel raises the combustion temperature, which increases emissions of nitrogen oxides (NOx). In the second category are studies focused on reactivity-controlled compression-ignition (RCCI) combustion. RCCI combustion can be implemented by early diesel injection with a large amount of low-reactivity fuel such as gasoline or gaseous fuel. Although RCCI combustion promises lower NOx and PM emissions and higher thermal efficiency than conventional diesel combustion, it requires a higher intake pressure (usually more than 1.7 bars) to maintain a lean fuel mixture. Therefore, in this study, practical applications of dual-fuel combustion with a low air-fuel ratio (AFR), which implies a low intake pressure, were systemically evaluated using propane in a diesel engine. The characteristics of dualfuel combustion for high and low AFRs were first evaluated. The proportion of propane used for four different operating conditions was then increased to decrease emissions and to identify the optimal condition for dual-fuel combustion. Although the four operating conditions differ, the AFR was maintained at 20 (? approximately equal to 0.72) and the 50% mass fraction burned (MFB 50) was also fixed. The results show that dual-fuel combustion can reduce NOx and PM emissions in comparison to conventional diesel combustion. 相似文献
382.
C. Jeong Y. Lee S. Choi D. Jung K. Lee 《International Journal of Automotive Technology》2013,14(1):123-132
Research and development involving intelligent vehicles of today is geared to safe, driver-friendly and sensitive vehicles that provide a driver with a pleasant and convenient driving environment while preventing him or her from possible risks of accident. In developing convenient and safe vehicles, research on drivers’ driving patterns, reactions and state characteristics depending on road conditions in actual field is essential in order to devise more driver-friendly intelligent vehicles. This paper describes how a driver-vehicle interaction (DVI) field database is built in order to obtain a driver’s input in normal road driving condition on highways, country roads, and city roads, and his or her state information, as well as data on the vehicle and traffic conditions. And the newly built database is compared with the RDCW FOT database established by UMTRI of the US for analysis to suggest that the driving tendencies of drivers in Korea and the road driving conditions are not the same as those in the US, reconfirming the need to establish a DVI field database, which will be used for the development of intelligent vehicles suitable for the Korean environment. The DVI data collected from actual driving in field are anticipated to be widely utilized as basic data for research on various intelligent driving safety systems, advanced driver assistance systems (ADAS) and human-vehicle interface (HVI) that are suitable for the driving environment in Korea. 相似文献
383.
Evaluation of automotive forward collision warning and collision avoidance algorithms 总被引:2,自引:0,他引:2
K. Lee H. Peng 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2005,43(10):735-751
Collision warning/collision avoidance (CW/CA) systems target a major crash type and their development is a major thrust of the Intelligent Vehicle Initiative. They are a natural extension of adaptive cruise control systems already available on many car models. Many CW/CA algorithms have recently been proposed but the existing literature mainly focuses on algorithm development. Evaluations of these algorithms have been usually based on subjective ratings. The main contribution of this paper is the utilization of a naturalistic driving data set for the evaluation of CW/CA algorithms. We first collect manual driving data from the ICCFOT project, then process the data by Kalman smoothing, and finally identify 'threatening' and 'safe' data sets according to vehicle brake inputs and vehicle range behavior. Five CW/CA algorithms published in the literature are evaluated against the identified data sets. The performance of these algorithms is determined through a performance metric commonly used in signal detection and information retrieval under unbalanced data population. 相似文献
384.
S. H. Jeong J. E. Lee S. U. Choi J. N. Oh K. H. Lee 《International Journal of Automotive Technology》2012,13(7):1133-1140
Recently, the advanced driver assistance system (ADAS), which helps mitigate car accidents, has been developed using environmental detection sensors, such as long and short range radar, lidar, wide dynamic range cameras, ultrasonic sensors and laser scanners. Among these detection sensors, radars can quickly provide drivers with reliable information about the velocity, distance and direction of a target obstacle, as well as information about the vehicle in changing weather conditions. In the adaptive cruise control system (ACCS), three radar sensors are usually needed because two short range radars are used to detect objects in the adjacent lane and one long range radar is used to detect objects in-path. In this paper, low-cost radar based on a single sensor, which can detect objects in both the adjacent lane and in-path, is proposed for use in the ACCS. Before designing the proposed radar, we analyzed the world-wide radar technology and market trends for ACCS. Based on this analysis, we designed a novel radar sensor for the ACCS using radar components, such as an antenna, transceiver module, transceiver control module and signal processing algorithm. Finally, target detection experiments were conducted. In the experimental results, the proposed single radar can successfully complete the detection required for the ACCS. In the conclusion, the perspective and issues in the future development of the ACCS radar are described. 相似文献
385.
S.?Lee Y.?Cho M.?Song H.?Kim J.?Park D.?BaikEmail author 《International Journal of Automotive Technology》2012,13(3):355-363
Particulate matter in diesel engine exhaust, particularly nano-particles, can cause serious human health problems including
diseases such as lung cancer. Because diesel nano-particle issues are of global concern, regulations on particulate matter
emissions specify that not only the weight of particulate matter emitted but also the concentration of nanoparticles must
be controlled. This study aimed to determine the effects on nano-particle and PM emissions from a diesel engine when applying
a urea-SCR system for NOx reduction. We found that PM weight increases by approximately 90% when urea is injected in ND-13 mode over the emission without
urea injection. Additionally, PM weight increases as the NH3/NOx mole ratio is increased at 250 °C. In SEM scans of the collected PM, spherical particles were observed during urea injection,
with sizes of approximately 200 nm to 1 μm. This study was designed to determine the conditions under which nano-particles
and PM are formed in a urea-SCR system and to relate these conditions to particle size and shape via a quantitative analysis
in ND-13 mode. 相似文献
386.
C. -J. Kim Y. J. Kang B. -H. Lee H. -J. Ahn 《International Journal of Automotive Technology》2012,13(3):451-458
Critical responses are frequently detected at the coupled torsional beam axle (CTBA) of a lightweight vehicle. However, the
freedom to modify the design of the axle shaft is limited because the suspension system must satisfy other vehicle requirements
such as steering performance. Conventional sensitivity analysis cannot provide practical information about the resonant behavior
because the analysis only identifies the contribution of the axle shaft to the behavior. This paper presents a novel sensitivity
analysis based on transmissibility ratios (TRs). The vehicle components other than the axle shaft that can be modified to
control the critical spectra are identified using acceleration responses. A multi-body vehicle model is constructed to simulate
the proposed design modifications, and the simulation results show that the vibration of the axle shaft is considerably reduced
by the modifications. Because the TRs on the CTBA are effectively minimized through the modified design strategy, the resonant
response from the axle shaft can be controlled efficiently. 相似文献
387.
S. J. Lee S. J. Jeong W. S. Kim C. B. Lee 《International Journal of Automotive Technology》2008,9(6):659-670
The use of a diesel particulate filter (DPF) in a diesel aftertreatment system has proven to be an effective and efficient
method for removing particulate matter (PM) in order to meet more stringent emission regulations without hurting engine performance.
One of the favorable PM regeneration technologies is the NO2-assisted regeneration method due to the capability of continuous regeneration of PM under a much lower temperature than that
of thermal regeneration. In the present study, the thermal behavior of the monolith during regeneration and the conversion
efficiency of NO2 from NO with an integrated exhaust system of a diesel oxidation catalyst (DOC) and DPF have been predicted by one-channel
numerical simulation. The simulation results of the DOC, DPF, and integrated DOC-DPF models are compared with experimental
data to verify the accuracy of the present model for the integrated DOC and DPF modeling. The effects of catalyst loading
inside the DOC and the volume ratio between the DOC and DPF on the pressure drop, the conversion efficiency, and the oxidation
rate of PM, have been numerically investigated. The results indicate that the case of the volume ratio of ‘DOC/DPF=1.5’ within
the same diameter of both monoliths produced close to the maximum conversion efficiency and oxidation rate of PM. Under the
engine operating condition of 175 kW at 2200 rpm, 100% load with a displacement of 8.1, approximately 55 g/ft3 of catalyst (Pt) loading inside the DOC with the active Pt surface of 5.3 m2/gpt was enough to maximize the conversion efficiency and oxidation rate of PM. 相似文献
388.
The objective of this work was to investigate the effects of injection conditions and swirl on D.I. diesel combustion using
a transparent engine system. The test engine is equipped with a common rail injection system to control injection conditions
and to obtain split injection characteristics. A combustion analysis and steady flow test were conducted to measure the heat
release rate due to cylinder pressure and the swirl ratio. In addition, spray and diffusion flame images were obtained using
a high speed camera. The LII & LIS methods were also used to obtain 2-D soot and droplet distributions. High injection pressure
was found to shorten ignition delay, as well as to enhance peak pressure. The results also revealed that the heat release
rate in the premixed combustion region was markedly reduced through the use of pilot injection, while the soot distribution
and the heat release rate in the diffusion combustion region were increased. The swirl effect was found to shorten ignition
delay at certain injection timings, and to enhance the heat release rate in all experimental conditions. 相似文献
389.
The need for the unmanned ground combat vehicle (UGCV), which is used for the surveillance, reconnaissance and targeting during
extremely dangerous condition on the battlefield, has steadily increased, and the transition from manned ground combat vehicles
to unmanned ground combat vehicles is expected to reduce the loss of lives during battle. The UGCV needs many types of capabilities
to achieve satisfactory performance. This paper focuses on the modeling and control of the power system of the UGCV, and proposes
the fuel cell hybrid system (FCHS) for the power system of the UGCV. The fuel cell hybrid system has many advantages in stealth
drive and the system efficiency. In addition, the FCHS is much quieter than the engine generator and generates much less heat.
The benefits of the FCHS are advantageous for use in Army operations, which require ‘silent watch’ capability and the ability
to operate without showing up on an enemy’s radar screen. The FCHS has a fuel cell and uses an energy storage system (ESS)
as a power source. The ESS (e.g., batteries or ultracapacitors) helps the fuel cell supply power to the electric drive system
and also recovers energy during deceleration. The ESS makes it possible to improve the efficiency and dynamic characteristic
of the power system. In this paper, the FCHS is composed of different combinations of component models. The component sizes
are chosen to satisfy performance requirements. In order to determine the power distribution between the fuel cell and the
ESS, a power management strategy based on the required power and the SOC (state of charge) of the ESS is proposed. Batteries
and ultracapacitor, components of the ESS, have different characteristics. Accordingly, varying the combination of ESS components
can change the performance of the power system. The performance of the FCHS with respect to different combinations of ESS
is analyzed using simulated results. 相似文献
390.
K. Y. Lee 《International Journal of Automotive Technology》2008,9(1):87-93
The microstructural changes and the tensile properties of TRIP-assisted steels resulting from different chemical compositions
were investigated by using SEM, TEM, XRD and UTM. As a result of microscopic observation, the morphology of retained austenite
could be characterized by two types: a granular type in steel containing higher Si and a film type in steel having higher
C. In the case of the steel containing higher C with a tensile strength of 860 MPa and a total elongation of 38%, the film
type retained austenite could be observed among the lath bainitic ferrites. Actually, the metastable retained austenite was
required for good formability, which means that the chemical composition plays a significant role in the microstructure and
tensile property of TRIP-assisted steel. With respect to the tensile property, each steel type that contained an suitable
amount of Si and Mn demonstrated a typical TRIP effect on a stress-strain curve while steel that contained a higher Mn content
exhibited similar behaviors, as demonstrated in the dual phase steels. 相似文献