A numerical model was developed to simulate the condensation flow of the n-octane/n-nonane in three dimension throttle. With this model the condensation properties of n-octane/n-nonane in throttle were investigated, i...
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A numerical model was developed to simulate the condensation flow of the n-octane/n-nonane in three dimension throttle. With this model the condensation properties of n-octane/n-nonane in throttle were investigated, it was found that the maximum supersaturation ratio of n-octane/n-nonane vapor in the homogeneous condensation process was very high, in comparison n-nonane was harder to condense. The influence of inlet supersaturation ratio, total pressure and total temperature on the condensation of n-nonanein in throttling flow process was analyzed. From the results, the direct influences of inlet parameters were found on the wilson point location, average droplet radius and liquid phase mass fraction.
In the present study, the effects of injection timing and spark timing on combustion characteristics and particle emission were investigated. The particulate number concentration and size distribution were measured us...
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In the present study, the effects of injection timing and spark timing on combustion characteristics and particle emission were investigated. The particulate number concentration and size distribution were measured using an electrical low-pressure impactor. The combustion parameters were calculated from the cylinder pressure data. The results indicate that the combustion versus the injection timing is primarily dependent on the mixing quality of the air-fuel mixture. The particulate number concentration increases as the fuel injection is advanced but the particle size distribution is not affected significantly with different injection timings. This is probably related to the in-cylinder combustion. The initial combustion duration increases as the spark timing is advanced and the fastest rapid combustion duration is obtained at the maximum brake torque spark timing. As the fuel injection timing and spark timing are advanced, the particle number levels are increased but the particle size distribution shows few variations. Most of the particulates are in the nanoparticle size range. The amounts of nitrogen oxide and hydrocarbon emissions increase with advanced fuel injection timing and spark timing, and the carbon monoxide concentration experiences small variations under all operation conditions.
The effects of the inert components of exhaust gas recirculation (EGR) gas on reducing the pressure rise rate of homogeneous charge compression ignition engine combustion were investigated numerically by utilizing the...
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The effects of the inert components of exhaust gas recirculation (EGR) gas on reducing the pressure rise rate of homogeneous charge compression ignition engine combustion were investigated numerically by utilizing the CHEMKIN II package and its SENKIN code, as well as Curran's dimethyl ether reaction scheme. Calculations were conducted under constant volume combustion and engine combustion (one compression and one expansion only, respectively) conditions. Results show that with constant fuel amount and initial temperature and pressure, as EGR ratio increases, combustion timings are retarded and the duration of thermal ignition preparation extends non-linearly; peak values of pressure, pressure rising rate (PRR), and temperature decrease; and peak values of heat release rate in both low temperature heat release (LTHR) and high temperature heat release decrease. Moreover, maximum PRR decreases as CA50 is retarded. With constant fuel amount, mixtures with different EGR ratios can obtain the same CA50 by adjusting the initial temperature. Under the same CA50, as EGR ratio increases, the LTHR timing is advanced and the duration of thermal ignition preparation is extended. Maximum PRR is almost constant with the fixed CA50 despite the change in EGR ratio, indicating that the influence of EGR dilution on chemical reaction rate is offset by other factors. Further investigation on the mechanism of this phenomenon is needed.
Detailed Laser-Doppler Velocimeter (LDV) measurements have been carried out in a turbulent rectangular channel flow with smooth and rough surfaces at different Reynolds numbers. The measured distributions of turbulenc...
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ISBN:
(纸本)9781617829130
Detailed Laser-Doppler Velocimeter (LDV) measurements have been carried out in a turbulent rectangular channel flow with smooth and rough surfaces at different Reynolds numbers. The measured distributions of turbulence statistics across the half channel height at different wall conditions, including mean velocity, turbulence intensity, skewness factor, flatness factor and Reynolds shear stress are all reported and compared. The turbulent statistical quantities on different surfaces exhibit significant differences in both the inner and the outer region, which suggests that the roughness element has an important role on turbulent flow structure extending into the whole layer. There is a significant increase in the streamwise turbulence intensity and a slight increase in the normal turbulence intensity and the Reynolds shear stress over the rough surface. The profiles of the streamwise skewness factor become flatter over the rough walls, while the flatness factor distributions are nearly the same for different surfaces.
Cold stimuli evoke more rapid transient pain sensations in human teeth than hot ***, the underlying mechanism remains *** has been reported that hot stimuli cause an inward flow (toward the tooth pulp chamber) of the ...
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Cold stimuli evoke more rapid transient pain sensations in human teeth than hot ***, the underlying mechanism remains *** has been reported that hot stimuli cause an inward flow (toward the tooth pulp chamber) of the dentinal fluid in dentinal microtubules while cold stimuli cause flow in a reverse *** study attempts to quantify tooth pain sensation by coupling a computational fluid dynamics (CFD) model, which describes the fluid mechanics in dentinal microtubules, with a modified Hodgkin-Huxley (H-H) model, which describes the neural discharge behavior.
This paper describes an experimental study on the catalytic combustion of ventilation air methane in a vertical reactor. The mixture of natural gas and compressed air was used in the experiments, and the combustion pr...
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In order to show the effects of different diameter combinations on crude oil temperature when a crude oil pipeline and a products pipeline are laid in one trench, four typical diameter combinations are selected to con...
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In order to show the effects of different diameter combinations on crude oil temperature when a crude oil pipeline and a products pipeline are laid in one trench, four typical diameter combinations are selected to conduct numerical simulation. After a series of calculations, the minimum mean temperature difference and the maximum temperature difference of the crude oil along the pipelines are obtained. In real pipeline constructions, the effects of other diameter combinations on crude oil temperature can be predicted by the method of linear interpolation to calculate results of the four diameter combinations obtained in this study.
In this paper,we propose a novel probe to identify phases in any two-phase flows where one phase is conductive and the other *** can further obtain many parameters such as void fraction,bubble velocity,and interfacial...
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In this paper,we propose a novel probe to identify phases in any two-phase flows where one phase is conductive and the other *** can further obtain many parameters such as void fraction,bubble velocity,and interfacial area *** with the traditional probe,the novel probe has unique advantages that it is less dependent on water conductance or distance between the electrodes,and that the amplitude is bigger between high and low *** analyses showed that the measurement error became higher when water conductance decreases or distance increases,which is consistent with the theoretical *** results showed that the output signal kept constant with salt content of 0-5% and electrode distance of 0-30 mm in tap *** level difference was up to 6.4 V,resulting in identifying two phases *** traces of phase identification were completely consistent with the flow structures.
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