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.
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.
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.
Forced convection heat transfer of single-phase water in helical coils was experimentally studied. The testing section was constructed from a stainless steel round tube with an inner diameter of 10?mm, coil diameter o...
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Forced convection heat transfer of single-phase water in helical coils was experimentally studied. The testing section was constructed from a stainless steel round tube with an inner diameter of 10?mm, coil diameter of 300?mm, and pitch of 50?mm. The experiments were conducted over a wide Reynolds number range of 40000 to 500000. Both constant-property flows at normal pressure and variable-property flows at supercritical pressure were investigated. The contribution of secondary flow in the helical coil to heat transfer was gradually suppressed with increasing Reynolds number. Hence, heat transfer coefficients of the helical tube were close to those of the straight tube under the same flow conditions when the Reynolds number is large enough. Based on the experimental data, heat transfer correlations for both incompressible flows and supercritical fluid flows through helical coils were proposed.
The effect of primary air fraction f1, outer secondary air swirl strength and excess oxygen coefficient on the combustion characteristics of petroleum coke, Hejin lean coal and Shenmu soft coal are researched on a one...
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The effect of primary air fraction f1, outer secondary air swirl strength and excess oxygen coefficient on the combustion characteristics of petroleum coke, Hejin lean coal and Shenmu soft coal are researched on a one-dimensional furnace using a dual channel swirl burner. The results show that with the increase in primary air fraction f1, the NOx emission concentrations of both Hejin lean coal and petroleum coke increase, and the combustion worsens in the earlier stage, but the burn-out rate of Shenmu soft coal is improved. The NOx emission concentration obtains a minimum value with an increase in f1. The ignition and burn-out rate of petroleum coke and Shenmu soft coal are optimal when Ωdl is minimum and Ωdl=0.87, respectively. However, both the NOx emission concentration of petroleum coke and Shenmu soft coal are minimum when Ωdl=1.08. The increase in excess oxygen coefficient delays the ignition of petroleum coke, worsens the combustion condition and increases the NOx emission concentration, but it greatly decreases the NOx emission concentration of Shenmu soft coal.
A numerical simulation of the influence of different hydrogen fractions, excess air ratios and EGR mass fractions in a spark-ignition engine was conducted. Good agreement between the calculated and measured in-cylinde...
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A numerical simulation of the influence of different hydrogen fractions, excess air ratios and EGR mass fractions in a spark-ignition engine was conducted. Good agreement between the calculated and measured in-cylinder pressure traces as well as pollutant formation trends was obtained. The simulation results show that NO concentration has an exponential relationship with temperature and increases sharply as hydrogen is added. EGR introduction strongly influences the gas temperature and NO concentration in the cylinder. The difference in temperature will lead to even greater difference in NO concentration. Thus, EGR can effectively decrease NO concentration. NO concentration reaches its peak value at the excess air ratio of 1.1 regardless of EGR mass fraction. The study shows that natural gas-hydrogen blend combined with EGR can realize a stable combustion and low NO emission in a spark-ignition engine.
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.
Evaporation of multicomponent droplets has gained much attention nowadays because of their complex flow fields and various deposition *** we observe strong flows in evaporating sodium chloride saline droplets with sus...
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Evaporation of multicomponent droplets has gained much attention nowadays because of their complex flow fields and various deposition *** we observe strong flows in evaporating sodium chloride saline droplets with suspended alumina oxide *** evolution of flow pattern was studied by tracking the trajectories of particles and the velocity field was investigated with Particle Image Velocimetry *** non-uniform evaporation rate along the droplet surface leads to a concentration gradient which induces the convection *** the evaporation process before crystallization happens,evolution of the flow can be divided into two *** Regime I,a centrosymmetric convection recirculation is formed *** RegimeⅡ,the convection recirculation migrates to the droplet edge and evolves into several small *** the late evaporation stage,crystallization could induce strong convection *** is shown that the flow tends to become more chaotic with a lower salt concentration.
Based on the actual operation parameters and temperature-dependent material properties of a gas turbine unit,composite cooling blade model and corresponding reliable boundary conditions were *** thermal-fluid-solid co...
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Based on the actual operation parameters and temperature-dependent material properties of a gas turbine unit,composite cooling blade model and corresponding reliable boundary conditions were *** thermal-fluid-solid coupling simulations were then comprehensively conducted to analyze the transient flow and the temperature field of the blade under startup,shutdown,and variable loads *** with the obtained transient temperature data,the non-linear finite element method was exploited to examine the effect of these transient operations on the turbine blade thermal stress *** show that the temperature and pressure on the blade surface increase with the load level and vice *** the startup process progresses,the film cooling effectiveness and the heat convection of airflows inside the blade continuously grow;high-temperature areas on the pressure surface and along the trailing edge of the blade tip gradually *** high-temperature zones with the maximum of 1280 K are generated at the air inlet and outlet of the blade platform and the leading edge of the blade *** high thermal stresses detected on the higher temperature side of the temperature gradient are commonly generated in places with large temperature gradients and significant geometry *** the startup/shutdown process,the rate of increase/decrease of the thermal stress is positively correlated with the load variation rate.A slight variation rate of the load(1.52%/min)can lead to an apparent alteration(41%)to the thermal *** operations under action of the variable load,although thermal stress is less sensitive to the load variation,the rising or falling rate of the exerted load still needs to be carefully controlled due to the highly leveled thermal stresses.
Based on the first law of thermodynamics,and adopting the Peng-Robinson equation (P-R equation) as the basic equation for the properties of ammonia-water mixtures,a thermodynamic analysis on a single-stage distillatio...
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Based on the first law of thermodynamics,and adopting the Peng-Robinson equation (P-R equation) as the basic equation for the properties of ammonia-water mixtures,a thermodynamic analysis on a single-stage distillation Kalina cycle is presented.A program to calculate the thermodynamic properties of ammoniawater mixtures,and that for calculating the performance of Kalina cycles,were developed,with which the heatwork conversion particulars of Kalina cycles were theoretically *** influences on the cycle performance of key parameters,such as the pressure and temperature at the inlet of the turbine,the back pressure of the turbine,the concentration of the working solution,the concentration of the basic solution and the cycle multiplication ratio,were analyzed.
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