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.
Large fraction of the low-pressure turbine cascade boundary layer is laminar flow due to low Reynolds number. High-lift low-pressure turbine blade leads to increase the adverse pressure gradient at rear of the turbine...
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Based on the 1-D & 2-D combined computational model, numerical optimizing analyses on the performance of the orifice type pulse tube refrigerator (OPTR) and double-inlet type pulse tube refrigerator (DPTR) were ca...
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Based on the 1-D & 2-D combined computational model, numerical optimizing analyses on the performance of the orifice type pulse tube refrigerator (OPTR) and double-inlet type pulse tube refrigerator (DPTR) were carried out. The evolvements process of the flow field in the OPTR and DPTR were examined. The results show that in the compressor expansion process the gas separation phenomenon occurs in the pulse tube, and in the compression process, there exists the gas aggregation phenomenon. The gas velocities in the separation and aggregation interfaces are zero, so the interface is called zero interface. In a period, the zero interface will move from one end of the pulse tube to the other end, which is called zero interface effect. The zero interface effect is an important factor for the performance enhancement of the PTR. The longer the time of the zero interface effect existing in a period, the better the PTR performance. Then based on the simulation results, the mechanism analysis for the existing of zero interface effect was performed. The results show that the introduction of the orifice valve leads to the formation of zero interface effect and the introduction of the double-inlet valve could augment the zero interface effect. For the OPTR, the time of the zero interface existing is about 1/6 period and for the DPTR the existing time of the zero interface is about 1/2 period.
Low-pressure premixed laminar flames of 1,3-butadiene/oxygen /argon and 1,3-butadiene+acetylene/oxygen/argon have been investigated with tunable synchrotron photoionization and molecular beam mass spectrometry. Flame ...
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