In this work, the vapor pressure equation, saturated liquid density equation, saturated vapor density equation and Helmholtz equation of state for dimethyl ether are developed by genetic optimization algorithm combine...
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In this work, the vapor pressure equation, saturated liquid density equation, saturated vapor density equation and Helmholtz equation of state for dimethyl ether are developed by genetic optimization algorithm combined with a weighted least-square fit of selected experimental data based on extensive collection of DME's experimental data. The average absolute deviation of vapor pressure equation, saturated liquid density equation and saturated vapor density equation is 0.50%, 0.38% and 0.55%, respectively. The uncertainty in density of the equation of state ranges from 0.1% in the liquid to 1% near the critical point.
A local refinement method of unstructured grid generated by bubble packing method (BPM) is proposed. In the present method, different size bubbles are added to the real and artificial vertices of the domain and bubble...
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A local refinement method of unstructured grid generated by bubble packing method (BPM) is proposed. In the present method, different size bubbles are added to the real and artificial vertices of the domain and bubble information of these vertices is transferred to the inner nodes of the domain by the Shepard interpolation method. Moreover, a method to control the population of bubbles is presented to add bubbles in large gap between bubbles and remove bubbles to eliminate overlapping so that the generation of skinny triangles is avoided and the grid quality is clearly improved. Furthermore, the improved BPM is applied to generate unstructured grid with local refinement near boundary for square domain to simulate the lid-driven flow in a square cavity with Re=1 000. The numerical result agrees well with the benchmark solution, indicating that the improved BPM is effective to the computation of fluid flow and heat transfer.
An experimental study has been performed to investigate pool water instantaneous flash evaporation in a rectangle chamber. Some key parameters such as superheat, initial water temperature and water level have been stu...
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An experimental study has been performed to investigate pool water instantaneous flash evaporation in a rectangle chamber. Some key parameters such as superheat, initial water temperature and water level have been studied. The water level was at 40 mm, 60 mm, 100 mm, 150 mm. Initial conditions of the liquid varied from 36C to 88C temperature and 2.1C to 48C superheat. The experimental results showed that the initial water temperature, the superheat and the water level are the key parameters. The experimental results showed that the greater the superheat and the higher the initial water level approaches, the longer the flashing will persist. Under a constant superheat, the initial water temperature has little influence on duration of flashing. Experimental study allows us to correlate the flashing duration time with the superheat and the initial water level as well as the initial water temperature.
Based on the wavelet analysis theory of signal singularity detection, the critical heat flux (CHF) and minimum film boiling starting point (qmin) of boiling curves can be detected and analyzed by using the wavelet mul...
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Based on the wavelet analysis theory of signal singularity detection, the critical heat flux (CHF) and minimum film boiling starting point (qmin) of boiling curves can be detected and analyzed by using the wavelet multi-resolution analysis. To predict the CHF in engineering, empirical relations were obtained based on genetic algorithm. The results of wavelet detection and genetic algorithm prediction are consistent with experimental data very well.
An algorithm for bubble packing method based unstructured grid generation of a curved-edge polygon is developed to avoid bubble departure from a curved boundary during dynamic bubble movement. The curve boundary is ma...
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An algorithm for bubble packing method based unstructured grid generation of a curved-edge polygon is developed to avoid bubble departure from a curved boundary during dynamic bubble movement. The curve boundary is mapped into a straight line to allow bubble adding and moving. Then the bubble position is mapped into the curve boundary by the arc-length parameterization method. Combined with conventional methods, a new method to judge a point in a given curved-edge polygon is proposed. Local grid refinement is realized by adding different size bubbles to the real and artificial vertices and setting the bubble's radius by the weighted average method. Moreover, the SIMPLE algorithm on unstructured collocated grid systems is developed and applied to simulate the lid-driven flow in a polar cavity. The numerical simulation results agree well with the experimental data under different Reynolds numbers.
In present paper, the effect of velocity ratio on plane mixing layer is experimentally investigated with Particle Image Velocimetry (PIV). The velocity ratio between low- and high-speed side are 0.25, 0.33 and 0.50, r...
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In present paper, the effect of velocity ratio on plane mixing layer is experimentally investigated with Particle Image Velocimetry (PIV). The velocity ratio between low- and high-speed side are 0.25, 0.33 and 0.50, respectively. The Reynolds number based on the velocity difference of two streams and hydraulic diameter of the channel ranges from 15840~132000. The results indicate that the maximum mean Reynolds stress on the same cross section increases with Reynolds number increasing but decreases with velocity ratio increasing at the equal Reynolds number. The mean vorticity increases with Reynolds number increasing on the same cross-section and increases with the velocity ratio increasing at the equal Reynolds number. The maximum non-dimensional mean vorticity decreases according to an exponential law along the stream-wise direction, and the decreasing speed of maximum mean vorticity increases with the velocity ratio increasing.
The explosion limits of dimethyl ether, methane and different mixtures of dimethyl ether and methane were measured under the temperature ranging from room temperature to 80C and the pressure ranging from 0.1 to 0.3 MP...
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The explosion limits of dimethyl ether, methane and different mixtures of dimethyl ether and methane were measured under the temperature ranging from room temperature to 80C and the pressure ranging from 0.1 to 0.3 MPa. In addition, the effects of temperature and pressure on the explosion limit were analyzed, and the accuracies of some theoretical calculation models of explosion limit were tested with the experimental results.
Combustion characteristics of diluted hydrogen-air premixed combustion were studied in a constant volume bomb over wide ranges of diluent ratios and equivalence ratios using two kinds of diluent gases. A two-zone mode...
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Thermoacoustic phenomena are almost nonlinear, which features self-excited onset. In this paper, a closed-open Rijke tube with the heat source placed at the middle of the tube is modeled. Based on parallel computation...
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Thermoacoustic phenomena are almost nonlinear, which features self-excited onset. In this paper, a closed-open Rijke tube with the heat source placed at the middle of the tube is modeled. Based on parallel computation, onset of the Rijke tube is carried out numerically. Onset phenomena with various initial fields are observed. Oscillating frequency of the gas within limit cycle is obtained. The gas flow and heat transfer characteristics are studied. These numerical results agree well with those from previous numerical simulations. Such work is helpful for better understanding on the thermoacoustic phenomena, and offers a reference for the study of the thermoacoustic problems with mesoscopic methods such as the lattice Boltzmann method.
The thermoacoustic engine driven by concentrating solar collector is a novel power system with wide application prospect. We designed and built a solar powered thermoacoustic engine. In this study, the thermodynamic p...
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The thermoacoustic engine driven by concentrating solar collector is a novel power system with wide application prospect. We designed and built a solar powered thermoacoustic engine. In this study, the thermodynamic performance of the solar focusing collector was numerically studied by using the two-axis solar collector performance simulation program with Simulink. The thermodynamic performance of the solar powered thermoacoustic engine was numerically investigated by coupling the results of the solar collector simulation program with the results of Deltae which is a program to simulate the performance of a thermoacoustic engine. The simulation results provide reference data for experimental study.
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