Pingjian Ming’s research while affiliated with Sun Yat-sen University and other places

An improved droplet breakup model coupled with the effect of turbulence flow within the nozzle was implemented into the general transport equation analysis code to describe the flame lift-off length and predict the soot distribution. This model was first validated by the non-evaporating and evaporating spray experimental data. The computational results demonstrate that the breakup model is capable of predicted spray penetration and liquid length with reasonable accuracy. The inclusion of turbulence enhanced the breakup model, increased the droplet breakup rate, decreased spray penetration for about 6–12% compared to the results of Kelvin-Helmholtz Rayleigh-Taylor (KH-RT) breakup model. Then, the model was applied to investigate the influence of ambient density, temperature, oxygen concentration and injection pressure on the flame lift-off length under typical diesel combustion conditions. The predictions showed good agreement with the experimental data. The result also indicated that the turbulence inside the nozzle strengthen the rate of breakup, resulting in more smaller droplets, leading to high evaporation rate and smaller vapour penetration lengths, thus decreases the lift-off length about 8%. Finally, the model was used to explore the soot distribution. The overall trend of soot with the variations in injection pressure was well reproduced by the breakup model. It was found that the droplet with faster velocity under high injection pressure, this could lead to larger lift-off length, which will play a significant role for the fuel–air mixing process and thus cause a decrease in soot in the fuel jet. Results further indicated that the turbulence term can decrease the soot mass about 5–9% by improved the droplet breakup process.

Aerodynamic noise characteristics of a marine diesel engine compressor which has high flow rate and high pressure ratio were analyzed through bench experiment. The aerodynamic noise test was conducted on a selfcirculation test bench under multi operating conditions and various characteristic changes after noise control. The test results show that the compressor aerodynamic noise is mainly composed of the blade passing frequency(BPF)noise and buzz saw noise. Less TCN noise appears at low speed region. The sound pressure level of the compressor aerodynamic noise increases gradually with the increase of rotating speed and also with the increase of pressure ratio at the same speed. Furthermore, the aerodynamic noise presents an irregular propagation state after the reflection at compressor inlet, rather than spherical wave propulsion. Based on the above analyses, an intake silencer was designed and used for controlling the aerodynamic noise. The influence of the silencer on aerodynamic noise characteristics was tested and analyzed in comparison of inlet open test results. The test results show that after installing the silencer, the aerodynamic noise is significantly reduced and the BPF noise is clearly controlled in a wide range. In addition, the aerodynamic noise distribution of the compressor becomes more uniform. © 2018, Editorial Office of the Transaction of CSICE. All right reserved.

A new hybrid breakupmodel was developed for spray atomization under diesel engine relevant conditions, characterizing high injection pressure and high backpressure. Most of primary breakup theory considers only one factor on primary breakup process, while with the development of test equipment, more experimental data are provided to prove that many factors have influence on primary breakup. The current breakup models were reviewed and the predictions simulated with the new hybrid breakup model were compared with the experimental measurements. Results were calculated using the Taylor analogy breakup (TAB), cascade atomization and drop breakup (CAB), and Kelvin Helmholtz Rayleigh Taylor b(KHT-RT) reakup model. Results showed that the TAB model significantly underpredicts the diameter of the droplet which further influences droplet evaporation. Although the CAB model predicts the similar results with experimentthe maximum relative error is close to 20%. The KH-RT model slightly overestimates the droplet diameter and leads to large differences with experimental data under the condition of evaporation.

Based on a general IC engine working process simulation model, a program for solving three dimensional unstructured radiative heat transfer in internal combustion engines was developed by using a scattering medium radiative heat transfer model. Under the assumption that the combustion products were made up of isotropic scattering media, a numerical method of spatial isotropic scattering medium radiative heat transfer was studied based on theunstructured finite volume method (UFVM), which was verfied by the typical geometric bodies-a semicircle enclosure with a circular hole and a rhombic enclosure. All results obtained by the presented FVM were consistent with the exact solutions given in the literatures. Then the radiative heat transfer in TBD620 diesel engines was studied by numerical method. It is shown that the radiation has less impact on the average pressure and temperature. For isotropic scattering media, the scattering albedo has less influence on the average pressure and temperature, but can change the spatial distribution of the medium temperature in cylinder. © 2016, Chinese Society for Internal Combustion Engines(CSICE). All right reserved.

A finite-volume method (FVM) is used to address combined heat transfer, natural convection, and volumetric radiation with an isotropic scattering medium, in a tilted shallow enclosure. Numerical simulations are performed in the in-house fluid flow software GTEA. All the results obtained by the present FVM agree very well with the numerical solutions in the references. The effects of various influencing parameters such as the Planck number (0.0001 ≤ Pl ≤ 10), the scattering albedo (0 ≤ ω ≤ 1), the inclination angle (−60° ≤ α ≤ 90°), and aspect ratio (1 ≤ AR ≤ 5) on flow and heat transfer have been numerically studied. For a constant Pl number, flow is slightly intensified at the midplane as the Ra number increases from 106 to 5 × 106. As the scattering albedo increases, the effect of radiation heat transfer decreases on both slanted and horizontal enclosures. In positive tilt angles, the influence of α on heat transfer is quite remarkable. The highest Nurad appears at α = 30° (ω = 1)and 0° (ω = 0, 0.5), whereas Nurad is maximum at α = − 15° (ω = 1) and −45° (ω = 0, 0.5). At α = −15°, the maximum and minimum values of Nurad are presented for ω = 0, AR = 1 and ω = 1, AR = 5.

The finite-volume method (FVM) for radiation heat transfer with a nonscattering medium is extended to an isotropic scattering medium, and this method is implemented in the fluid flow solver GTEA on hybrid grids. For comparison and validation, three test cases, a semicircle enclosure with a hole, a rhombic enclosure, and a square cavity, are chosen. All the results obtained by the present FVM agree very well with the numerical solutions in the references. Furthermore, the effects of the extinction coefficient and scattering albedo on the flow and temperature distribution are studied numerically in the cavity based on present approach. As the extinction coefficient increases from 0.2 to 5, the temperature gradient adjacent to the hot and cold walls gradually decreases at Ra = 105, however, the temperature profiles become similar at Ra = 106. For Ra = 105, 106, the scattering albedo affects the structures of the isotherm and streamline to some extent. As the scattering albedo increases, the convection heat transfer in the middle region of the hot wall increases, but the radiation heat transfer and the total radiation heat transfer along the hot wall decrease.

Thermal and curing reaction coupling has great inuence on composites molding process. An algorithm of solving complicated structure composites curing process with coupled anisotropic transient thermal and curing reaction kinetics formulation based on unstructured gird finite volume method is presented. The spatial item of heat diffusion equation of anisotropic composites is discretized by unstructured grid finite volume method, and time item is discretized by Euler implicit scheme. Curing kinetics equation is calculated by Euler explicit scheme, and obtained the heat source of the energy equation through the curing reaction rate which subjected to temperature distribution and corresponding manufacturing process plans, thus realizing the two-way coupling of thermal and curing reaction. Finally, this method is verified correctness and reliability through several classical examples for which prior results and experimental data are available in the literature, at the same time, it shows that the method presented can deal with the numerical simulation of the coupled thermal and curing reaction kinetics of composites molding process with complicated structure.

A direct numerical method for the anisotropic diffusion equation is presented and the balance-point method and adaptive method are also derived. All these methods are formulated and implemented in the in-house fluid flow solver GTEA. Two test cases, an isotropic problem and an anisotropic problem with exact solution on a skewed mesh, are chosen for comparison and validation. The error and computation time are illustrated. It is concluded that the direct method has the least computation time among all the diffusion problems and that all the methods meet the precision requirement in engineering computation even on skewed meshes.

The numerical simulation of combined natural convection and radiation heat transfer with a participating medium in a square cavity was performed with the in-house software GTEA (General Transport Equation Analysis). The results obtained by the present method are good consistent with the solutions of the literature. Further, the Effects of Planck number and scattering albedo on the temperature distribution and velocity are studied numerically in the square cavity. It is found that the Effect of radiation heat transfer increases with the decrease of Planck number. Taking into consideration the influence of isotropic scattering medium, the temperature of the central part of the square cavity becomes larger for smaller values of ω. Next to the insulated wall, the horizontal velocity changes significantly.

Turbocharger is an important part of the turbocharged diesel engine. Due to the increase of mass flow rate and pressure ratio, aerodynamic noise of turbocharger has become more apparent. And turbocharger noise becomes one of the major noise sources of the main engine system of the ship. In the paper, the aerodynamic noise is predicted by using Computational fluid mechanics (CFD) and indirect boundary element method (IBEM) based on Lighthill acoustic analogy theory. Unsteady viscous flow in the centrifugal Compressor is simulated with finite volume method using the single stator and rotor blade passages and the characteristic of compressor is agreed well with the experimental value. The flow field characteristics and frequency spectrum of the fluctuating pressure are analyzed which agree well with the theoretical value. Dipole is the main noise source in compressor and the datum of pressure fluctuation at rotor blade are extracted. The boundary element model of the volute is established and the scattering effect on sound propagation is taken into account. Using indirect boundary element method, radiation noise field at compressor entrance at the blade passing frequency and its harmonics are predicted. The results can provide a useful reference to low noise design and structure optimization of centrifugal compressor.