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Both experimental and numerical studies were presented on the flow field characteristics in the process of gaseous jet impinging on liquid–water column. The effects of the impinging process on the working performance of rocket engine were also analyzed. The experimental results showed that the liquid–water had better flame and smoke dissipation effect in the process of gaseous jet impinging on liquid–water column. However, the interaction between the gaseous jet and the liquid–water column resulted in two pressure oscillations with large amplitude appearing in the combustion chamber of the rocket engine with instantaneous pressure increased by 17.73% and 17.93%, respectively. To analyze the phenomena, a new computational method was proposed by coupling the governing equations of the MIXTURE model with the phase change equations of water and the combustion equation of propellant. Numerical simulations were carried out on the generation of gas, the accelerate gas flow, and the mutual interaction between gaseous jet and liquid–water column. Numerical simulations showed that a cavity would be formed in the liquid–water column when gaseous jet impinged on the liquid–water column. The development speed of the cavity increased obviously after each pressure oscillation. In the initial stage of impingement, the gaseous jet was blocked due to the inertia effect of high-density water, and a large amount of gas gathered in the area between the nozzle throat and the gas–liquid interface. The shock wave was formed in the nozzle expansion section. Under the dual action of the reverse pressure wave and the continuously ejected high-temperature gas upstream, the shock wave moved repeatedly in the nozzle expansion section, which led to the flow of gas in the combustion chamber being blocked, released, re-blocked, and re-released. This was also the main reason for the pressure oscillations in the combustion chamber.

In order to study the influence of inert gas injection to gas explosion in the process of fire zone sealing, tunnel fire model was established by COMSOL software, and numerical simulation is carried out to study change laws of flow field and concentration field in the process of fire zone sealing. Through comparing the distribution law of flow field and concentration field whether the inert gas injection and different flows, obtained the influence of inert gas injection to gas explosion in the process of fire zone sealing. As the decrease of entrance average wind speed, the maximum wind speed in the centre vertical section of tunnel gradually reduces. when the entrance average wind speed is 1m/s, counter current layer is produced near the fire resource, length and thickness of counter current layer and maximum current speed rises with the declining of the entrance average wind speed, and swirl will be formed when the entrance average wind speed is less than 0.01m/s. In the process of fire zone sealing, the maximum gas concentration in the fire area and on the side of leeward goes up with the declining of the entrance average wind speed, the nitrogen concentration will gradually increase with the declining of entrance average wind speed.

The dynamic behaviors of water contained in calcium–silicate–hydrate (C–S–H) gel with different water content values from 10% to 30% (by weight), are studied by using an empirical diffusion model (EDM) to analyze the experimental data of quasi-elastic neutron scattering (QENS) spectra at measured temperatures ranging from 230 K to 280 K. In the study, the experimental QENS spectra with the whole Q-range are considered. Several important parameters including the bound/immobile water elastic coefficient A, the bound water index BWI, the Lorentzian with a half-width at half-maximum (HWHM) Γ 1(Q) and Γ 2(Q), the self-diffusion coefficients D t1 and D t2 of water molecules, the average residence times τ 01 and τ 02, and the proton mean squared displacement (MSD) 〈u 2〉 are obtained. The results show that the QENS spectra can be fitted very well not only for small Q (≤ 1 A−1) but also for large Q. The bound/immobile water fraction in a C–S–H gel sample can be shown by the fitted BWI. The distinction between bound/immobile and mobile water, which includes confined water and ultra-confined water, can be seen by the fitted MSD. All the MSD tend to be the smallest value below 0.25 A2 (the MSD of bound/immobile water) as the Q increases to 1.9 A−1, no matter what the temperature and water content are. Furthermore, by the abrupt changes of the fitted values of D t1, τ 01, and Γ 1(Q), a crossover temperature at 250 K, namely the liquid-to-crystal-like transition temperature, can be identified for confined water in large gel pores (LGPs) and/or small gel pores (SGPs) contained in the C–S–H gel sample with 30% water content.

The relaxation dynamics of liquids is one of the fundamental problems in liquid physics, and it is also one of the key issues to understand the glass transition mechanism. It will undoubtedly provide enlightenment on understanding and calculating the relaxation dynamics if the molecular orientation flipping images and relevant microparameters of liquids are studied. In this paper, we first give five microparameters to describe the individual molecular string (MS) relaxation based on the dynamical Hamiltonian of the MS model, and then simulate the images of individual MS ensemble, and at the same time calculate the parameters of the equilibrium state. The results show that the main molecular orientation flipping image in liquids (including supercooled liquid) is similar to the random walk. In addition, two pairs of the parameters are equal, and one can be ignored compared with the other. This conclusion will effectively reduce the difficulties in calculating the individual MS relaxation based on the single-molecule orientation flipping rate of the general Glauber type, and the computer simulation time of interaction MS relaxation. Moreover, the conclusion is of reference significance for solving and simulating the multi-state MS model.

Opto-thermionic refrigeration is an environment-friendly method. To improve the opto-thermionic refrigeration efficiency, a system with a perovskite oxide multilayer of p-BaTiO3/BaTiO3/SrTiO3/BaTiO3/n-BaTiO3 is proposed based on the model of opto-thermionic refrigeration. Because the Auger coefficient of SrTiO3 is two orders smaller than that of GaAs, the calculated refrigeration power of the p-BaTiO3/BaTiO3/SrTiO3/BaTiO3/n-BaTiO3 system is much higher than that of the p-AlGaAs/AlGaAs/GaAs/AlGaAs/n-AlGaAs system. A refrigeration power of as high as 39 Wc m −2 is obtained numerically in the p-BaTiO3/BaTiO3/SrTiO3/BaTiO3/n-BaTiO3 system, which suggests a potential application of the oxide structures in opto-thermionic refrigeration. (Some figures in this article are in colour only in the electronic version)