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排序方式: 共有298条查询结果,搜索用时 343 毫秒
291.
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
292.
The dynamic behavior of the engine organs in severe conditions is complicated to identify. In this paper, the dynamic behavior of the crankshaft of the diesel engine Deutz F8L413 direct injection-type air cooled in the severe operating conditions is investigated in a 3D global model. The maximum operating characteristics of the engine are experimentally measured on a bench test equipped with a hydraulic brake. The most stressed areas of the crankshaft are determined by numerical simulations. In addition, an analysis of the fatigue behavior of the crankshaft is carried out by using two fatigues criteria. The efficiency of the model is demonstrated by comparing between the numerical results and the experimental data obtained with the natural modes of vibration test. 相似文献
293.
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
294.
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
295.
L. Bouillaut O. François P. Aknin R. Donat S. Bondeux S. Dubois 《Recherche - Transports - Sécurité》2011,27(4):241-257
This article deals with a generic approach called VirMaLab (virtual maintenance laboratory) for reliabilitybased maintenance modeling for complex systems (with multi-components and multi-states). Based on the probabilistic graphical models formalism (also known as Bayesian networks), this stochastic approach takes into account both the degradation process of the considered system (an original semi-Markovian model is proposed) and maintenance strategies (from diagnosis factors to all kinds of maintenance actions). For complete decision support tools, cost parameters should also be considered (maintenance actions, unavailability of the system, running, etc.). In this article, two applications of this approach to rail maintenance are introduced. The first one focuses on the optimization of the compromise refurbishment/repairing of central part of the RER A line. The second one focuses on the comparison and evaluation of various maintenance strategies in the modernization of the command control systems of Paris metro lines. 相似文献
296.
The wave transmission, reflection, and energy dissipation of the double vertical wall with permeable lower part (horizontal slots) were experimentally and theoretically studied under normal regular waves. The effect of different wave and structural parameters on the hydrodynamic characteristics was investigated e.g. the wave length, the upper part drafts, the lower part porosities, and the space between the double walls. Also, the theoretical model based on an EigenFunction Expansion Method was developed to study the hydrodynamic breakwater performance. In order to examine the validity of the theoretical model, the theoretical results were compared with the present experimental results. Comparison between experiments and predictions showed that theoretical model provides a good estimate to the wave transmission, reflection, and energy dissipation coefficients when the friction factor f = 3. The hydrodynamic efficiency of the proposed breakwater is strongly affected by changing the following: (1) The two upper part drafts together, (2) The upper part draft of the first barrier, (3) The two lower part porosities together, (4) The lower part porosity of the first barrier. 相似文献
297.
The latching control represents an attractive alternative to increase the power absorption of wave energy converters (WECs) by tuning the phase of oscillator ve... 相似文献
298.
[Objective] This paper carries out an experimental study of a multi-function dirllship model with moonpool structure in towing tank, aiming at analyzing the effects of the moonpool structure on the ship resistance in open and closure condition.[Methods]Taking a dirllship as the research object, the ship motion response in regular and irregular waves is investigated. The resistance of the ship in hydrostatic water and waves is measured with tension sensors, and the acceleration characteristics of the bow, midship and stern are analyzed by acceleration sensors.[Results]The results indicate that hull resistance under light load conditions is greater when open moonpool, while hydrostatic water resistance with closed moonpool is greater under design load conditions. The closed moonpool in regular waves reduces stern acceleration by 58.2%, bow resistance by 46.7% and heave response by 41.8%. The peak of resistance at the bow in irregular waves is about ten times higher than that at the stern, and the peak of resistance occurs more often when the moonpool is open at the same time.[Conclusions]The experimental study shows that the difference in load conditions changes the waterplane area and affects the hull resistance in hyrostatic water. In contrast, the closure of the moonpool not only reduces acceleration and resistance, but also improves surge and heave. As such, this paper can provide references for the structural design of drillships with moonpools. © 2023 Journal of Nanjing Agricultural University. All rights reserved. 相似文献