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991.
D. Jung W. L. Wang A. Knafl T. J. Jacobs S. J. Hu D. N. Assanis 《International Journal of Automotive Technology》2008,9(1):9-15
The effects of the Abrasive Flow Machining (AFM) process on a direct injection (DI) Diesel engine fuel injector nozzle are
studied. Geometry characterization techniques were developed to measure the microscopic variations inside the nozzle before
and after the process. This paper also provides empirically-based correlations of the nozzle geometry changes due to the AFM
process. The resulting impact of the process on the engine performance and emissions are also assessed with a DI Diesel engine
test setup. This study shows that properly AFM-processed injectors can enhance engine performance and improve emissions due
to the improved quality of the nozzle characteristics. However, an extended process can also cause enlargement of the nozzle
hole as a side effect, which can adversely affect emissions. Emission measurements show the trade-off for the minimum levels
as the process proceeds. Since the enlargement of the hole during the AFM process is not avoidable and must be minimized,
strict control over the process is required. This control can be enforced by either limiting the AFM processing period, or
by properly preparing the initial hole diameter so as to accommodate the inevitable changes in the nozzle geometry. 相似文献
992.
In this paper, an experimental study on the wall-impinging spray of the slit-type GDI injector is presented. To examine the
effects of various factors on the development of a spray impinging on the wall, experiments were conducted at various injection
pressures, ambient pressures, wall distances from the injector tip, wall temperatures, and wall inclination angles. Behavior
of the impinging spray was visualized using a planar laser scattering method. It is shown that the spray path penetration
of the wall-impinging spray increases with increases in injection pressure, wall distance, wall temperature, or wall angle.
On the other hand, the spray path penetration of the wall-impinging spray decreases with increases in ambient pressure. The
predicted spray path penetration calculated by the empirical equation estimates the spray path penetration in all cases, and
the empirical equation is optimized for the total injection pressure. 相似文献
993.
Analysis of the transient atomization characteristics of diesel spray using time-resolved PDPA data 总被引:1,自引:0,他引:1
The transient atomization characteristics of a single-hole diesel spray were investigated to clarify the time-dependent droplet
formation process of the spray through time-resolved analysis of the droplet size data acquired by using a 2-D PDPA (phase
Doppler particle analyzer). Comparisons among the three single-hole diesel nozzles on the atomization characteristics were
made to confirm the effects of the hole-diameter. The hole diameter of the single-hole diesel nozzles varied with dn=0.22, 0.32 and 0.42 mm. The time-resolved diameter, SMD (Sauter mean diameter) and AMD (arithmetic mean diameter) of droplets
in diesel spray injected into still ambient air were measured. The SMD and AMD decreased with decreasing nozzle hole diameter.
The SMD distribution along the spray centerline steeply decreased with increasing axial distance before reaching a constant
value. In the time-dependent analysis of the SMD of the whole flow field, the SMD gradually increased with time after the
initiation of injection, reached a maximum value, and then decreased. 相似文献
994.
H. -M. Kim S. -K. Park K. -S. Choi H. -M. Wang D. -H. Lee D. -K. Lee Y. -S. Cha J. -S. Lee J. Lee 《International Journal of Automotive Technology》2008,9(2):149-153
An important goal in diesel engine research is the development of a means to reduce the emissions of nitrogen oxides (NOx).
The use of a cooled exhaust gas recirculation (EGR) system is one of the most effective techniques currently available for
reducing nitrogen oxides. Since PM (Particulate Matter) fouling reduces the efficiency of an EGR cooler, a tradeoff exists
between the amount of NOx and PM emissions, especially at high engine loads. In the present study, we performed engine dynamometer
experiments and numerical analyses to investigate how the internal shape of an EGR cooler affects the heat exchanger efficiency.
Heat exchanger efficiencies were examined for plain and spiral EGR coolers. The temperature and pressure distributions inside
these EGR coolers were obtained in three dimensions using the numerical package program FLUENT. 相似文献
995.
The sub-chamber type gasoline engine was suggested to be a type of clean engine, but the presence of residual gas in the sub-chamber
was a serious fault. In this experimental study, the CNG direct injection method was applied to scavenge residual gas from
the sub-chamber. The CVC (constant volume chamber) is divided into the sub-chamber and main-chamber and used as the main experimental
apparatus. Because each combustion chamber of the CVC has an injector, the injector can be used freely, at the same time or
individually. Therefore, the scavenging efficiency can be improved by changing injection times for the sub-chamber. The experimental
results demonstrated that when all the fuel was injected into the sub-chamber, the combustion duration was shortened by 30%
compared to that of injection into the main-chamber. Although residual gas was observed in the CVC, when the frequency of
injections into the sub-chamber increased, good combustion characteristics were obtained. 相似文献
996.
J. W. Lee Y. I. Jeong M. W. Jung K. O. Cha S. I. Kwon J. C. Kim S. Park 《International Journal of Automotive Technology》2008,9(4):397-403
In recent years, particle number emissions rather than particulate mass emissions in automotive engines have become the subject
with controversial discussions. Recent results from studies of health effects imply that it is possible that particulate mass
does not properly correlate with the variety of health effects attributed to engine exhaust. The concern is now focusing on
nano-sized particles emitted from I. C. engines. In this study, particulate mass and particle number concentration emitted
from light-duty vehicles were investigated for a better understanding of the characteristics of the engine PM from different
types of fuels, such as gasoline and diesel fuel. Engine nano-particle mass and size distributions of four test vehicles were
measured by a condensation particle counter system, which is recommended by the particle measurement program in Europe (PMP),
at the end of a dilution tunnel along a NEDC test mode on a chassis dynamometer. We found that particle number concentrations
of diesel passenger vehicles with DPF system are lower than gasoline passenger vehicles, but PM mass has some similar values.
However, in diesel vehicles with DPF system, PM mass and particle number concentrations were greatly influenced by PM regeneration.
Particle emissions in light-duty vehicles emitted about 90% at the ECE15 cycle in NEDC test mode, regardless of vehicle fuel
type. Particle emissions at the early cold condition of engine were highly emitted in the test mode. 相似文献
997.
J. -Y. Zhang J. -W. Kim K. -B. Lee Y. -B. Kim 《International Journal of Automotive Technology》2008,9(6):695-702
This paper investigates an active front steering control strategy based on quantitative feedback theory (QFT). By incorporating
feedback from a yaw rate sensor into the active steering system, the control system improves the dynamic response of the vehicle.
The steering response of a vehicle generally depends upon uncertain quantities like mass, velocity, and road conditions. Thus,
QFT is used to design a controller with robust performance. A multi-degree-of-freedom nonlinear model is co-simulated here
by MATLAB Simulink and ADAMS/CAR. The performance of the control system is evaluated under various emergency maneuvers and
road conditions. The result shows that the designed robust control system has good control performance and can efficiently
improve handing qualities and stability characteristics. 相似文献
998.
This study was performed to clarify criteria for cavitation inception and the relationship between flow conditions and cavitation
flow patterns of diesel and biodiesel fuels. The goal was to analyze the effects of injection conditions and fuel properties
on cavitating flow and disintegration phenomena of flow after fuel injection. To accomplish this goal, it was utilized a test
nozzle with a cylindrical cross-sectional orifice and a flow visualization system composed of a fuel supply system and an
image acquisition system. In order to analyze the rate of flow and injection pressure of the fuel, a flow rate meter and pressure
gauge were installed at the entrance of the nozzle. A long distance microscope device equipped with a digital camera and a
high resolution ICCD camera were used to acquire flow images of diesel and biodiesel, respectively. The effects of nozzle
geometry on the cavitating flow were also investigated. Lastly, a detailed comparison of the nozzle cavitation characteristics
of both fuel types was conducted under a variety of fuel injection parameters. The results of this analysis revealed that
nozzle cavitation flow could be divided into four regimes: turbulent flow, beginning of cavitation, growth of cavitation,
and hydraulic flip. The velocity coefficient of diesel fuel was greatly altered following an increase in flow rate, although
for biodiesel, the variation of the velocity coefficient relative to the rate of flow was mostly constant. The cavitation
number decreased gradually with an increase in the Reynolds number and Weber number, and the discharge coefficient was nearly
equal to one, regardless of cavitation number. Lastly, it could not observe cavitation growth in the tapered nozzle despite
an increase in fuel injection pressure. 相似文献
999.
H. S. Kook 《International Journal of Automotive Technology》2008,9(4):493-500
Flows over cavity openings are known to be highly structured and periodic due to the strong sound pressures emitted by the
cavities. This article is concerned with the measurement of flow fields over the sunroof opening of an SUV. Since the PIV
system used in the present work is not capable of taking phase-locked velocity fields during the measurement stage, phase-marked
PIV measurements are performed and the phase-locked velocity fields are retrieved during a post-processing stage. The new
PIV measurement method is shown to yield fairly accurate results with a proper choice of a phase-bandwidth. By using the phase-marked
PIV measurement method, the evolution of large-scale structures in shear flow over the sunroof opening as phase changes is
revealed. The detached shear layer is shown to fluctuate and then form a discrete large vortex convecting and impinging on
the rear roof edge of the SUV. The average convection velocity of the vortex is calculated to be 0.45 of the nominal free
stream flow velocity. Flow fields are compared for four different cases of deflector protrusion and a case without a deflector.
Installation of a deflector can significantly change the flow field. For a deflector that reduces the buffeting noise by more
than 10 dB, it is shown that turbulent fluctuations are initiated by the deflector but do not grow in amplitude as they convect
downstream. As the deflector protrusion is increased, the amount of flow under the deflector increases in general. The flow
exiting from the channel formed by the deflector and an A-frame is shown to increase the thickness of the shear layer near
the leading edge of the sunroof opening. 相似文献
1000.
J. N. Han N. J. Cho S. W. Chae Y. Choi 《International Journal of Automotive Technology》2008,9(5):633-640
A hybrid mesh generation algorithm using a modified plastering method for three-dimensional objects with variable thickness
is presented. The method starts with a quad-dominant surface mesh and generates layered elements with variable thickness by
using adaptive offsetting, resulting in hex-tet dominant mesh generation. Hexahedral and prismatic meshes are generated by
the inward offsetting of the initial boundary mesh. In order to generate a conforming mesh, pyramid elements are constructed
on top of hexahedral elements, and tetrahedral elements are generated for the remaining domain by using an advancing front
method. This method is applied to several different geometries, and the effectiveness of the proposed algorithm is demonstrated. 相似文献