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881.
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
882.
Y. S. Pyoun H. T. Kim Y. C. Lee A. Gafurov H. Kim D. H. Jung 《International Journal of Automotive Technology》2008,9(1):61-70
Surface topology, cone angle and the forces acting on the cone of the clutch type limited slip differential (LSD) are major
design parameters for the bias ratio and the noise condition. Therefore much research has been dedicated to these developments
but the results have been used to submit patents. A new cone type limited slip differential for sport utility vehicles and
recreational vehicles, which has a very simple structure and easy compliance with the vehicle performance, has been developed
by the axiomatic approach and the ultrasonic nano crystal surface modification (UNSM) technology. The design criteria and
optimal value of the design parameters are determined by the axiomatic approach utilizing CAE tools. Test methodologies in
a test rig and in a vehicle were also developed. Test results showed good performance of bias ratio and noise level but durability
is still under testing. This study is an extension of F2006P266, FISITA 2006. 相似文献
883.
T. H. Hwang K. Park S. -J. Heo S. H. Lee J. C. Lee 《International Journal of Automotive Technology》2008,9(1):17-27
The performance of most electronic chassis control systems in the past has been optimized individually. Recently, a great
research effort has been dedicated to the integration of chassis control systems in an effort to improve the vehicle performance.
This involves orchestration of individual control modules so that they can jointly contribute to the enhancement of their
control effect. In this research, two integrated control logics for AFS (Active Front Steering) and ESP (Electronic Stability
Program) have been developed. Of the two logics, one uses a supervisor that rules over the individual modules. The other logic
uses a CL (Characteristic Locus) method, which is a frequency-domain multivariable control technique. The two logics have
been tested under various driving conditions to investigate their control effects. The results indicate that the proposed
integrated control logics can yield vehicle performance that is superior to that of the individual control modules without
any integration scheme. 相似文献
884.
Lean burn is an effective way to improve spark ignition engine fuel economy. In this paper, the combustion and emission characteristics
of a lean burn natural gas fuelled spark ignition engine were investigated at various throttle positions, fuel injection timings,
spark timings and air fuel ratios. The results show that ignition timings, the combustion duration, the coefficient of variation
(COV) of the indicated mean effective pressure (IMEP) and engine-out emissions are dependent on the overall air fuel ratio,
spark timings, throttle positions and fuel injection timings. With the increase of the air fuel ratio, the ignition delays
and combustion duration increases. Fuel injection timings affect ignition timings, combustion duration, IMEP, and the COV
of the IMEP. Late fuel injection timings can decrease the COV of the IMEP. Moreover, the change in the fuel injection timings
reduces the engine-out CO, total hydrocarbon (THC) emissions. Lean burn can significantly reduce NOx emissions, but it results
in high cyclic variations. 相似文献
885.
A modified CVT ratio map is proposed to obtain the improved fuel economy for a metal belt CVT. Since the CVT system loss,
which occupies most of the drivetrain loss, depends on the engine speed, input torque, primary and secondary actuator pressure,
a modified CVT ratio map is produced to realize the highest engine-CVT overall efficiency through the consideration of CVT
system loss. The modified CVT ratio map is constructed with respect to the demanded vehicle power and present vehicle speed
based on the steady state CVT system loss. Using the modified CVT ratio map, performance simulations are carried out using
the dynamic models of the CVT powertrain. The simulation results indicate that the modified CVT ratio control provides improved
engine-CVT overall system efficiency, and improves the fuel economy of the federal urban driving schedule by 4.9 percent. 相似文献
886.
This research applies R-Markov Average Reward Technique based reinforcement learning (RL) algorithm, namely RMART, for vehicular signal control problem leveraging information sharing among signal controllers in connected vehicle environment. We implemented the algorithm in a network of 18 signalized intersections and compare the performance of RMART with fixed, adaptive, and variants of the RL schemes. Results show significant improvement in system performance for RMART algorithm with information sharing over both traditional fixed signal timing plans and real time adaptive control schemes. The comparison with reinforcement learning algorithms including Q learning and SARSA indicate that RMART performs better at higher congestion levels. Further, a multi-reward structure is proposed that dynamically adjusts the reward function with varying congestion states at the intersection. Finally, the results from test networks show significant reduction in emissions (CO, CO2, NOx, VOC, PM10) when RL algorithms are implemented compared to fixed signal timings and adaptive schemes. 相似文献
887.
Meng Wang Elmar Beeh Andreas Höfer Horst Friedrich 《International Journal of Automotive Technology》2018,19(6):969-979
Function integration is the way used commonly to achieve the lightweight design system. To realize the design successfully by combing two systems multifaceted issues in need to be considered. The potential functional conflicts between the existing systems are the major unfavorable factors limiting the design. In order to complete the better design, the functional and physical relationships in the systems should be figured out. This paper proposes the approach, by which the function integration process is expressed using the axiomatic design. In the design process, the mutual relationships of design parameters in the systems are investigated by means of design matrices. The design concepts are compared and evaluated by the method combining the axiomatic design and design structure matrix. 相似文献
888.
As the problem of full transit vehicles is encountered daily by passengers in most of the big cities, previous research evaluated the consequence of overcrowding in terms of on‐board crowding and passengers not being able to board with full vehicles. The impact of overcrowding in the real world is, however, not necessarily proportional to these numbers. This paper attempts to specify the critical lines and stations of a network by considering the number of passengers failing to board and attempting to evaluate its impact on service quality and safety risks. The hypothesis is that larger stations with wider platforms can often cope better with overcrowding than smaller stations. Therefore a station size dependent satisfaction function is proposed, which takes values from 0 to 1. The method is applied to London's underground network with a number of scenarios which show critical stations in the network if delays occur. 相似文献
889.
在对德国大众汽车公司生产的高尔夫A3型轿车行李箱盖的使用材料性能进行实验研究的基础上。建立了三维数学模型,利用I-deas工程软件对其有限元计算,并通过实验对结果进行验证,最后提出了高尔夫A3车行李箱盖的优化方案. 相似文献
890.
Does scale heterogeneity across individuals matter? An empirical assessment of alternative logit models 总被引:2,自引:0,他引:2
There is growing interest in establishing a mechanism to account for scale heterogeneity across individuals (essentially the
variance of a variance term or the standard deviation of utility over different choice situations), in addition to the more
commonly identified taste heterogeneity in mixed logit models. A number of authors have recently proposed a model that recognizes
the relationship between scale and taste heterogeneity, and investigated the behavioural implications of accounting for scale
heterogeneity in contrast to a term in the utility function, itself. In this paper we present a general model that extends
the mixed logit model to explicitly account for scale heterogeneity in the presence of preference heterogeneity, and compare
it with models that assume only scale heterogeneity (referred to as the scale heterogeneous multinomial logit model) and only
preference heterogeneity. Our empirical assessment suggests that accommodating scale heterogeneity in the absence of accounting
for preference heterogeneity may be of limited empirical interest, resulting in a statistically inferior model, despite it
being an improvement over the standard MNL model. Scale heterogeneity in the presence of preference heterogeneity does garner
favour, with the generalized mixed logit model an improvement over the standard mixed logit model. The evidence herein suggests,
however, that compared to a failure to account for preference heterogeneity that is consequential, failure to account for
scale heterogeneity may not be of such great empirical consequence in respect of behavioural outputs such as direct elasticities
and willingness to pay. However additional studies are required to establish the extent to which this evidence is transferable
to a body of studies. 相似文献