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431.
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
432.
Sahbi Khanfir Kazuhiko Hasegawa Vishwanath Nagarajan Kouichi Shouji Seung Keon Lee 《Journal of Marine Science and Technology》2011,16(4):472-490
With a recent increase in ship capacity and propulsion performance, a wide-beam ship fitted with a twin-rudder system has
been adopted in many cases. However, to improve ship manoeuvring, it is still necessary to have a better understanding of
rudder-hull interactions in twin-rudder ships. Captive model tests (oblique towing and circular motion test) as well as free-running
tests with a single-propeller twin-rudder ship and a twin-propeller twin-rudder ship are carried out. The effect of drift
angle on the rudder forces and some peculiar phenomena concerning rudder normal force for twin-rudder ships are evaluated.
A method for estimating the hull-rudder interaction coefficients based on free-running experimental results is proposed. 相似文献
433.
J. H. Jeong D. W. Jung O. T. Lim Y. D. Pyo Y. J. Lee 《International Journal of Automotive Technology》2014,15(6):861-869
This work experimentally investigates how the dwell time between pilot injection and main injection influences combustion and emissions characteristics (NOx, CO, THC and smoke) in a single-cylinder DI diesel engine. The experiments were conducted using two fuel injection systems according to the fuel type, diesel or dimethyl ether (DME), due to the different fuel characteristics. The injection strategy is accomplished by varying the dwell time (10°CA, 16°CA and 22°CA) between injections at five main injection timings (?4°CA aTDC, ?2°CA aTDC, 0°CA aTDC, 2°CA aTDC and 4°CA aTDC). Results from pilot-main injection conditions are compared with those shown in single injection conditions to better demonstrate the potential of pilot injection. It was found that pilot injection is highly effective for lowering heat-release rates with smooth pressure traces regardless of the fuel type. Pilot injection also offers high potential to maintain or increase the BMEP; even the combustion-timing is retarded to suppress the NOx emission formation. Overall, NOx emission formation was suppressed more by the combustion phasing retard effect, and not the pilot injection effect considered in this study. Comparison of the emissions for different fuel types shows that CO and HC emissions have low values below 100 ppm for DME operation in both single injection and pilot-main injection. However, NOx emission is slightly higher in the earlier main injection timings (?4°CA aTDC, ?2°CA aTDC) than diesel injections. Pilot injection was found to be more effective with DME for reducing the amount of NOx emission with combustion retardation, which indicates a level of NOx emission similar to that of diesel. Although the diesel pilot-main injection conditions show higher smoke emission than single-injection condition, DME has little smoke emission regardless of injection strategy. 相似文献
434.
Hot judder simulation of a ventilated disc and design of an improved disc using sensitivity analysis
J. H. Park T. W. Park J. H. Lee M. H. Cho 《International Journal of Automotive Technology》2014,15(1):1-6
In a disc brake system, thermal expansion of the material is caused by friction energy that is generated by the sliding contact between a disc and pad during braking. This phenomenon, thermo-elastic instability, can lead to hot spots on the disc surface and a hot judder phenomenon. Transient finite element analysis has been used to simulate this phenomenon. Three dimensional finite element models of a disc, pad, and cylinder were created. Each part was connected by a joint. Contact condition was applied to the disc and pad with a friction coefficient (μ) of 0.4. A convective heat transfer coefficient was set as 40 W/m2K. Using a commercial program SAMCEF, the simulation of the thermo-mechanically coupled system was performed. In order to find the sensitive parameters of brake judder, sensitivity analysis was carried out with consideration for disc design parameters. As a result, the hot spot phenomenon was confirmed and hot judder was predicted. Moreover, the more sensitive parameters of the hot judder phenomenon were presented. Finally, an improved disc model and an analysis technique were verified by comparison to dynamo test results. 相似文献
435.
From MY2010 US-NCAP, the 5th percentile female Hybrid III dummy has been used for the safety evaluation of the right front passenger position in the frontal impact test. In Korea, the Ministry of Land, Infrastructure and Transport (MLIT) decided to evaluate the safety of the 5th percentile female dummy in the frontal impact test from 2013 KNCAP. In this paper, using the frontal NCAP data for the 5 vehicles available from the NHTSA test database, the safety of the 5th percentile female dummy were examined. Using the evaluation and rating method by the KNCAP, 5 vehicles received 5 stars. Using the evaluation and rating method by the US-NCAP, only one vehicle received 5 stars and the remaining 4 vehicles received 4 stars. In the US-NCAP, the Nij was the most influential factor for the star rating. In the KNCAP, the evaluation and rating method for the 5th percentile female Hybrid III dummy is less stringent than the method of the US-NCAP. The evaluation and rating method is proposed to increase the stringency of the star rating for the female dummy in the KNCAP. 相似文献
436.
J. H. Kwak H. S. Kim J. H. Lee S. H. Lee 《International Journal of Automotive Technology》2014,15(4):543-551
We designed and applied a mobile emission laboratory for on-road measurements of exhaust particles emitted from conventional diesel, compressed natural gas (CNG), liquefied petroleum gas (LPG), and dimethyl ether (DME)-fueled vehicles. Fuel type and vehicle driving conditions significantly affected the particle size distribution and the number concentrations of the nucleation mode. For all buses, the size distributions of particles in the exhaust under idling conditions had larger mode diameters than at constant speed conditions of 50 km/h or 80 km/h. The nucleation mode (< 50 nm) fraction of diesel, CNG, LPG, and DME at a constant speed of 50 km/h was 53%, 63%, 79%, and 99%, respectively, indicating that the DME-fueled bus emitted the most nanoparticles. As the vehicle speed increased from 50 km/h to 80 km/h, the nucleation mode fraction of diesel, CNG, LPG, and DME changed to 43%, 99%, 99%, and 99%, representing a significant increase in the number concentrations of nanoparticles in the CNG and LPG-fueled vehicles. The particle size distributions in the exhaust of diesel, CNG, LPG, and DME-fueled vehicles were not affected by increase in the chasing distance. 相似文献
437.
S. C. Ko K. C. Oh C. K. Seo C. B. Lee 《International Journal of Automotive Technology》2014,15(3):347-352
Several NOx reduction technologies under development in recent years have now been commercialized, including selective catalytic reduction (SCR) with NH3 or hydrocarbons, and Lean NOx Trap. The aim of the present study is to investigate characteristics on NOx adsorption according to the oxygen concentration, de-NOx performance according to lean/rich injection cycle and toxic intermediates at LNT downstram for lean-burn gasoline engine. Under oxygen of 6%, NOx storage capacity was the highest, showed the highest NOx conversion of 98%. The reason for this phenomena is because the excited oxygen atoms at high oxygen concentration increased oxidizing power of NO. Under low temperature of 205°C, LNT catalyst showed the least NOx conversion of 14% because its activity became lower, while the generation rate of toxic HNCO was highest as CO which is generated during the rich condition, reacts with NOx stored on Ba site. 相似文献
438.
Understanding the process of activity scheduling is a critical pre-requisite to an understanding of changes in travel behavior. To examine this process, a computerized survey instrument was developed to collect household activity scheduling data. The instrument is unique in that it records the evolution of activity schedules from intentions to final outcomes for a weekly period. This paper summarizes an investigation of the structure of activity/travel patterns based on data collected from a pilot study of the instrument. The term “structure” refers to the sequence by which various activities enter one’s daily activity scheduling process. Results of the empirical analyses show that activities of shorter duration were more likely to be opportunistically inserted in a schedule already anchored by their longer duration counterparts. Additionally, analysis of travel patterns reveals that many trip-chains were formed opportunistically. Travel time required to reach an activity was positively related to the scheduling horizon for the activity, with more distant stops being planned earlier than closer locations. 相似文献
439.
K. -B. Kim K. -W. Choi K. -H. Lee 《International Journal of Automotive Technology》2012,13(3):401-407
A relatively new approach for improving fuel economy and automotive engine performance involves the use of automotive combined
cycle generation technologies. The combined cycle generation, a process widely used in existing power plants, has become a
viable option for automotive applications due to advances in materials science, nanotechnology, and MEMS (Mico-Electro Mechanical
Systems) devices. The waste heat generated from automotive engine exhaust and coolant is a feasible heat source for a combined
cycle generation system, which is basically a Rankine cycle in the context of this study. However, there are still numerous
technical issues that need to be solved before the technology can be implemented in automobiles. A simulation was performed
to examine the amount of waste energy that could be recovered through the use of a combined cycle system. A simulation model
of the Rankine cycle was developed using Cycle-Tempo software. The simulation model was ultimately used to evaluate the rate
of waste heat recovery and the consequential increase in the overall thermal efficiency of the engine with the combined cycle
generation system under typical engine operating conditions. The most effective automotive combined cycle system recovered
68% of the waste heat from the exhaust and coolant, resulting in a 6% improvement in engine efficiency. The results are expected
to be beneficial for evaluating the feasibility of combined cycle generation systems in automotive applications. 相似文献
440.
The brake and steering systems in vehicles are the most effective actuators that directly affect the vehicle dynamics. In general, the brake system affects the longitudinal dynamics and the steering system affects the lateral dynamics; however, their effects are coupled when the vehicle is braking on a non-homogenous surface, such as a split-mu road. The yaw moment compensation of the steering control on a split-mu road is one of the basic functions of integrated or coordinated chassis control systems and has been demonstrated by several chassis suppliers. However, the disturbance yaw moment is generally compensated for using the yaw rate feedback or using wheel brake pressure measurement. Access to the wheel brake pressure through physical sensors is not cost effective; therefore, we modeled the hydraulic brake system to avoid using physical sensors and to estimate the brake pressure. The steering angle controller was designed to mitigate the non-symmetric braking force effect and to stabilize the yaw rate dynamics of the vehicle. An H-infinity design synthesis was used to take the system model and the estimation errors into account, and the designed controller was evaluated using vehicle tests. 相似文献