The combustion and emission characteristics of a turbo-charged, common rail diesel engine fuelled with diesel-biodiesel-DEE blends were investigated. The study repons that the brake-specific fuel consumption of diesel...
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The combustion and emission characteristics of a turbo-charged, common rail diesel engine fuelled with diesel-biodiesel-DEE blends were investigated. The study repons that the brake-specific fuel consumption of dieselbiodiesel-DEE blends increases with increase of oxygenated fuel fractions in the blends. Brake thermal efficiency shows little variation when operating on different dieselbiodiesel-DEE blends. At a low load, the NOx emission of the diesel-biodiesel-DEE blends exhibits little variation in comparison with the biodiesel fraction. The NOx emission slightly increases with increase in the biodiesel fraction in diesel-biodiesel-DEE blends at medium load. However,the NOx emission increases remarkably with increase of the biodiesel fraction at high load. Particle mass concentration decreases significantly with increase of the oxygenated-fuels fraction at all engine speeds and loads;particle number concentration decreases remarkably with increase of the oxygenated-fuels fraction. HC and CO emissions decrease with increasing oxygenated-fuels fraction in these blends.
In this paper,the effect ofcetane number (CN)improver on performance and emissions,including particulate number concentration and size distribution,of a turbocharged,common-rail diesel engine fueled with biodiesel-met...
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In this paper,the effect ofcetane number (CN)improver on performance and emissions,including particulate number concentration and size distribution,of a turbocharged,common-rail diesel engine fueled with biodiesel-methanol were *** volume fractions (0.3% and 0.6%) of CN improver were added to BM30 (30% of methanol in the biodiesel-methanol blend) in the *** results show that,compared with those of biodiesel-methanol blend,the peak value of cylinder pressure increases,the second peak of heat release rate decreases,the start of second heat release are advanced,and the fuel economy and thermal efficiency are improved when CN improver is added to biodiesel-methanol ***,CO and HC emissions decrease,NOx emission varies little and smoke emissions increase ***,exhaust particles of BM30 mainly distribute in nanosize ***,particle number concentration decreases and peak of size distribution profile shifts toward large size direction.
In the solar tower power plant, the receiver is one of the main components of efficient concentrating solar collector systems. In the design of the receiver, the heat flux distribution in the cavity should be consider...
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In the solar tower power plant, the receiver is one of the main components of efficient concentrating solar collector systems. In the design of the receiver, the heat flux distribution in the cavity should be considered first. In this study, a numerical simulation using the Monte Carlo Method has been conducted on the heat flux distribution in the cavity receiver, which consists of six lateral faces and floor and roof planes, with an aperture of 2.0m×2.0m on the front face. The mathematics and physical models of a single solar ray's launching,reflection, and absorption were proposed. By tracing every solar ray, the distribution of heat flux density in the cavity receiver was obtained. The numerical results show that the solar flux distribution on the absorbing panels is similar to that of CESA-I's. When the reradiation from walls was considered, the detailed heat flux distributions were issued, in which 49.10% of the total incident energy was absorbed by the central panels,47.02% by the side panels, and 3.88% was overflowed from the aperture. Regarding the peak heat flux, the value of up to 1196.406 kW/m2 was obtained in the center of absorbing panels. These results provide necessary data for the structure design of cavity receiver and the local thermal stress analysis for boiling and superheated panels.
Nucleate pool boiling on micro-pin-finned surface structure is proposed for efficiently cooling electronic compo- nents with high heat flux in microgravity, and was verified by experiments performed utilizing the drop...
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Nucleate pool boiling on micro-pin-finned surface structure is proposed for efficiently cooling electronic compo- nents with high heat flux in microgravity, and was verified by experiments performed utilizing the drop tower Beijing. Micro-pin-fins with tile dimensions of 50 × (30 μm2 (thickness × height) and the space of 50 μm were fabricated on the chip surface by the dry etching technique. FC-72 was used as the working fluid. Nucleate pool boiling of FC-72 on a smooth surface was also tested for comparison. Unlike much obvious deterioration of heat transfer of nucleate pool boiling on the smooth surface in microgravity, constant heater surface temperature of nucleate pool boiling for the micro-pin-finned surface was observed, even though a large coalesced bubble completely covered the surface under microgravity condition. The performance of high efficient heat transfer on micro-pin-finned surface is independent of the gravity, which stems from the sufficient supply of fresh liquid to the heater surface due to the capillary forces.
The structural and electronic properties of low index (100) and (111) ZrO2-CeO2 interfaces are analyzed on the basis of density functional theory calculations. The formation energy and relative stability of substituti...
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The structural and electronic properties of low index (100) and (111) ZrO2-CeO2 interfaces are analyzed on the basis of density functional theory calculations. The formation energy and relative stability of substitutional defects, oxygen vacancies, and vacancy-dopant complexes are investigated for the (100) orientation. By comparing these results with the ones obtained in bulk structures, we provide a possible explanation for the higher experimental ionic conductivity measured at the interface.
Cryogen spray cooling (CSC) in conjunction with laser therapy has been the clinical standard for hypervascular lesions. In order to optimize nozzle and enhance the cooling efficiency to improve the treatment of laser ...
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Cryogen spray cooling (CSC) in conjunction with laser therapy has been the clinical standard for hypervascular lesions. In order to optimize nozzle and enhance the cooling efficiency to improve the treatment of laser surgery, an experimental system of transient cryogen spray cooling is built and eight straight-tube nozzles with different diameter and length are designed. A thin film thermocouple is directly deposited on the cooling surface to measure the surface temperature during the cryogen spray cooling. An analytical expression based on Fourier's law and Duhamel's theorem is used to calculate surface heat flux from the temperature measurements. Based on the measurements and calculations, the effect of the eight straight-tube nozzles on the heat transfer dynamics of the cooling surface and the atomization characterics are comparatively studied. Additionally, the criterion to evaluate the cooling efficiency of different nozzles is proposed, and the variation of heat extraction from the cooling surface with different spray distances by different nozzles is given.
Experimental study of air natural convection in horizontally-positioned copper metallic foams with open cells was conducted. Temperature distributions on the heating surface were tested under different heating power f...
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ISBN:
(纸本)9781612847504
Experimental study of air natural convection in horizontally-positioned copper metallic foams with open cells was conducted. Temperature distributions on the heating surface were tested under different heating power for foam samples having different porosities and pore densities. The effects of porosity and pore density on the total thermal resistance of the foam sample were quantified. It is found that the porous surface can enhance the natural convection and reduce the thermal resistance by about 20% in comparison with a smooth surface. The surface area density and mass flow rate in natural convection are affected by porosity and pore density simultaneously. When the porosity is relative small (Ε = 90%), there exits a critical value of the Gr number (turning point) for two pore densities (10ppi and 40ppi). When the Gr number is less than this critical value, the foam with a higher pore density has the lower total thermal resistance, whereas when the Gr number exceeds the turning point value, the opposite holds. If the porosity is increased to Ε = 95%, the foam with a higher pore density has the lower thermal resistance in the whole experimental range. When the porosity and pore density is the same, the foam with smaller size has the higher thermal resistance in the whole experimental range. If the size is relatively small (10010050mm), for the two pore densities studied (20ppi and 80ppi), there exits a critical value of the Gr number (turning point). The foam with a lower porosity(Ε = 90%) has the lower thermal resistance and the decrease is more obvious for the case of *** the size is relatively big(10010080mm),there exists a critical value of the Gr number (turning point) only for the case of 10ppi. When the Gr number is less than this critical value, the foam with a higher porosity (Ε = 95%) has the higher total thermal resistance, the opposite holds. While for the other two pore densities (20ppi and 40ppi), there is no turning point. The foam with a highe
In this paper, 20%H2 (20% hydrogen in natural gas-hydrogen blends, by volume) is selected as the test fuel, and the ignition timing and EGR ratio are adjusted to optimize the performance, combustion, and emissions of ...
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