A three-dimensional direct simulation of an immersed solid particle approaching another particle, or a flat wall, is conducted to investigate the mechanics of hydrodynamic impact of immersed particles. The simulation ...
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A three-dimensional direct simulation of an immersed solid particle approaching another particle, or a flat wall, is conducted to investigate the mechanics of hydrodynamic impact of immersed particles. The simulation method is based on a modified immersed boundary method using a fixed grid system. When the particle separation distance becomes smaller than grid spacing, to account for the hydrodynamic resistance effect of liquid layer between particles near contact, a microlayer model is developed to allow determination of the pressure profile within the micro-layer without neglecting the inertial force of the layer flow. The pressure force is then taken into account in equation of particle motion. Comparisons of the simulation results with the experimental results reported in the literature are shown to substantiate the model presented in this study. The simulations reveal the complex three-dimensional flow field of the liquid and the motion of the approaching particle. The fluid pressure in the gap caused by the unsteady motion of the particle is significantly increased when the separation distance of particles is less than about one-tenth diameters of particle. Therefore the velocity of approaching particle starts to decrease due to the hydrodynamic resistance force at this position.
A new vibrating tube densimeter was developed with a precision of better than ±0.5 kg/m3. Using this apparatus, the saturation liquid density of dimethyl ether was measured from 233.15 K to 320.15 K, and the max ...
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A new vibrating tube densimeter was developed with a precision of better than ±0.5 kg/m3. Using this apparatus, the saturation liquid density of dimethyl ether was measured from 233.15 K to 320.15 K, and the max relative expanded uncertainty was 0.34%(coverage factor k = 2). The experimental data of this work were correlated as a polynomial function of the temperature with the published data of our previous work. The average and maximum relative deviation were 0.13% and 0.37%, respectively.
Prediction of dryout point is experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annular with narrow gap is bilaterally heated by AC ...
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Prediction of dryout point is experimentally investigated with deionized water upflowing through narrow annular channel with 1.0 mm and 1.5 mm gap respectively. The annular with narrow gap is bilaterally heated by AC current power supply. The experimental conditions covered a range of pressure from 0.8 to 3.5 MPa, mass flux from 26.6 to 68.8 kg/m2 s and wall heat flux from 5.0 to 50.0 kW/m2. The location of dryout is obtained by observing a sudden rise in surface temperature, Kutateladze correlations is cited, however proved to be not a proper one for annuli gap and modified to predict the location of dryout. Considering in detail the effects of the geometry of annuli, pressure, mass flux and heat flux on dryout, an empirical correction is finally developed to predict dryout point in narrow annular gap under low flow condition which has a good agreement with experimental data.
A stabilized diesel/methanol blend was developed and the combustion characteristics and heat release analysis of this blend was carried out in a compression ignition engine. The study showed that the increase in the m...
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A stabilized diesel/methanol blend was developed and the combustion characteristics and heat release analysis of this blend was carried out in a compression ignition engine. The study showed that the increase in the methanol mass fraction will result in an increase in the heat release rate in the premixed burning phase and shorten the combustion duration of the diffusive burning phase. Ignition delay increases with the increase in the methanol mass fraction and the behaviour is more obvious at low engine load and high engine speed. The rapid-burn duration varies little with the methanol mass fraction and the total combustion duration decreases with the increase in the methanol mass fraction. At a low engine speed, the centre of heat release curve tends to be close to the top dead centre (TDC), with an increase in the methanol mass fraction at all engine loads and fuel delivery advance angles, the maximum rate of pressure rise and the maximum rate of heat release increase with the increase in the methanol mass fraction. At a high engine speed, the centre of the heat release curve closes to TDC at high engine load and will depart from TDC at low engine load. The maximum rate of pressure rise and heat release gives an increasing trend with the increase of methanol mass fraction at high engine loads. The maximum cylinder pressure increases with the increase of the methanol mass fraction. The presence of oxygen reduces the peak pressure, but the reduction was found to be insensitive to the proportion of oxygen within the 6-11 per cent range of testing.
A stabilized diesel-methanol blend was realized and a study on the performance and emissions of the diesel-methanol blend was carried out in a compression ignition engine. The study showed that the engine thermal effi...
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A stabilized diesel-methanol blend was realized and a study on the performance and emissions of the diesel-methanol blend was carried out in a compression ignition engine. The study showed that the engine thermal efficiency increases and the diesel equivalent b.s.f.c. decreases with increase in the oxygen mass fraction (or methanol mass fraction) of the diesel-methanol blends due to an increased fraction of premixed combustion phase, oxygen enrichment and improvement in the diffusive combustion phase. Further increase in the fuel delivery advance angle will achieve a better engine thermal efficiency when the diesel engine is operated using the diesel-methanol fuel blends. A marked reduction in the exhaust CO and smoke can be achieved when operating with the diesel-methanol blend. There is not a large variation in the exhaust hydrocarbon with the addition of methanol in diesel fuel. NOx increases with increase in the mass of methanol added;methanol addition to diesel fuel was found to have a strong influence on the NOx concentration at high engine loads rather than at low engine loads, and a flat NOx-smoke trade-off curve exists when operating with the diesel-methanol fuel blends.
The liquid phase turbulent structure of an air-water bubbly horizontal flow in a circular pipe has been investigated experimentally. Three-dimensional measurements were implemented with two "X" type probes o...
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The liquid phase turbulent structure of an air-water bubbly horizontal flow in a circular pipe has been investigated experimentally. Three-dimensional measurements were implemented with two "X" type probes oriented in different planes, and local liquid-phase velocities and turbulent stresses were simultaneously obtained. Systematic measurements were conducted covering a range of local void fraction from 0 to 11.7%. The important experiment results and parametric trends are summarized and discussed.
The liquid phase turbulent structure of an air-water bubbly horizontal flow in a circular pipe has been investigated experimentally. Three-dimensional measurements were implemented with two "X" type probes o...
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The liquid phase turbulent structure of an air-water bubbly horizontal flow in a circular pipe has been investigated experimentally. Three-dimensional measurements were implemented with two "X" type probes oriented in different planes, and local liquid-phase velocities and turbulent stresses were simultaneously obtained. Systematic measurements were conducted covering a range of local void fraction from 0 to 11.7%. The important experiment results and parametric trends are summarized and discussed.
The heat transfer process of ice formation on the outside of coil pipe in the ice storage tank with glycol solution as the second refrigerant was studied in this paper analytically and experimentally. A model was deve...
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The heat transfer process of ice formation on the outside of coil pipe in the ice storage tank with glycol solution as the second refrigerant was studied in this paper analytically and experimentally. A model was developed for the charging process and the conduction shape factor was applied. Also, the result obtained from the model was compared with the experimental data, both data were in agreement. The simple model is useful for the operation, design and optimization of the ice storage tank.
In this paper,the least-squares method is used to solve the Inverse Heat Conduction Problem(IHCP)to determine the space-wise variation of the unknown boundary condition on the inner surface of a helically coiled tube ...
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In this paper,the least-squares method is used to solve the Inverse Heat Conduction Problem(IHCP)to determine the space-wise variation of the unknown boundary condition on the inner surface of a helically coiled tube with fluid flow inside,electrical heating and insulation *** sensitivity coefficient is analyzed to give a rational distribution of the thermocouples. The results demonstrate that the method effectively extracts information about the unknown boundary condition for the heat conduction problem from the experimental measurements. The results also show that the least-squares method converges very quickly.
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