Laminar flame speeds of natural gas-carbon monoxide-air mixtures are calculated by CHEMKIN II with GRI Mech-3.0 over a large range of fuel compositions,equivalence ratios,and initial *** calculated results of natural ...
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Laminar flame speeds of natural gas-carbon monoxide-air mixtures are calculated by CHEMKIN II with GRI Mech-3.0 over a large range of fuel compositions,equivalence ratios,and initial *** calculated results of natural gas are compared with previous experimental results that show a good *** calculated laminar flame speeds of natural gas-carbon monoxide-air mixtures show a nonmonotonic increasing trend with volumetric fraction of carbon monoxide and an increasing trend with the increase of initial temperature of *** maximum laminar flame speed of certain fuel blend reaches its biggest value when there is 92%volumetric fraction of carbon monoxide in fuel at different initial *** stoichiometric natural gas-carbon monoxide-air mixtures are selected to study the detailed chemical structure of natural gas-carbon monoxide-air *** results show that at stoichiometric condition,the fuel blend with 80%volumetric fraction of carbon monoxide has the biggest laminar flame speed,and the C normalized total production rate of methane with 80%volumetric fraction of carbon monoxide is the largest of the five stoichiometric mixtures.
Laminar flame speeds of hydrogen/natural gas/air mixtures have been measured over a full range of fuel compositions(0-100%volumetric fraction of H_(2))and a wide range of equivalence ratio using Bunsen *** sensitivity...
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Laminar flame speeds of hydrogen/natural gas/air mixtures have been measured over a full range of fuel compositions(0-100%volumetric fraction of H_(2))and a wide range of equivalence ratio using Bunsen *** sensitivity scientific CCD camera is use to capture the image of laminar *** reaction zone area is employed to calculate the laminar flame *** initial temperature and pressure of fuel air mixtures are 293 K and 1 *** laminar flame speeds of hydrogen/air mixture and natural gas/air mixture reach their maximum values 2.933 and 0.374 m/s when equivalence ratios equal to 1.7 and 1.1,*** laminar flame speeds of hydrogen/natural gas/air mixtures rise with the increase of volumetric fraction of ***,the increase in laminar flame speed as the volumetric fraction of hydrogen increases presents an exponential increasing trend versus volumetric fraction of *** formulas to calculate the laminar flame speeds of hydrogen,natural gas,and hydrogen/natural gas mixtures are also *** these formulas,the laminar flame speed at different hydrogen fractions and equivalence ratios can be calculated.
Numerical oscillation can easily be found in dealing with the thermoacoustic convection problems for its steep gradient in consideration of which flux-correct transport algorithm (FCT) and timestep splitting technique...
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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, 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.
Investigations into the characteristics of hemodynamics will provide a better understanding of the pathology of cerebral aneurysms for *** this work,a steady state discontinuous-growth model of the cerebral aneurysms ...
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Investigations into the characteristics of hemodynamics will provide a better understanding of the pathology of cerebral aneurysms for *** this work,a steady state discontinuous-growth model of the cerebral aneurysms was *** the assumption of the fluid-structure interaction between the wall of blood vessel and blood,a fluid-structure coupling numerical simulation for this model was built using software ANSYS and *** simulation results showed that as the aneurysm volume increased,a blood flow vortex came forth,the vortex region became asymptotically larger,and eddy density became gradually stronger in *** the emergence of the vortex region,the blood flow in the vicinity of the downstream in the aneurysms volume turned into bifurcated flow,and the location of the flow bifurcated point was shifted with the aneurysm volume growing while directions of the shear stress applied to two sides of the bifurcated point were *** Von Mises stress distribution along the wall of aneurysm volume decreased in the prior period and increased gradually in the later *** maximum stress was in the neck of the volume and the minimum was on the distal end in the whole process of *** was shown that as the aneurysm increased the maximum deformation location of the aneurysm,vertical to the streamline,was transferred from the distal end of the aneurysm to its neck,then back to its distal end of the aneurysm again.
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