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In order to solve the problem where the traditional intelligent inspection robot only has a single inspection function, we studied the use of a dry powder (including an ultra-fine dry powder) as a fire-extinguishing medium for the first time. In fire-extinguishing robots, the spray pressure is difficult to control, and there are several other issues. For integrated inspection, an intelligent, nitrogen-driven fire-extinguishing robot using a dry powder in a pressure-controlled spray was developed. On this basis, in order to investigate nitrogen-driven dry powder particle spraying as a gas–solid two-phase mechanism, as well as the flow characteristics and the influence of relevant parameters on the spraying effect, a nitrogen-driven dry powder particle spraying system was established as part of a gas–solid two-phase computational fluid dynamics model. The flow field of the spraying system and the particle motion characteristics were analyzed to explore the micro-mechanisms of the influence of different driving pressures, pipe diameters, and nozzle configurations on the spraying of the dry powder. In order to investigate the macroscopic effect of dry powder spraying where the gas–solid two-phase micro-mechanisms could not be revealed, an experimental platform was set up, and the experiments verified the accuracy of the numerical simulation results. We also investigated the dry powder spraying effect under different driving pressures, pipe diameters, nozzle configurations, and loading ratios. Finally, an orthogonal test was designed based on the results of the single-factor experiments to find the best combination of parameters required to achieve the optimal spraying effect. The research results can provide a theoretical and technical reference for the design and development of nitrogen-driven dry powder spraying systems. [ABSTRACT FROM AUTHOR]

To explore the influence of different wax components and the shear effect exerted by the pump and pipe wall in the process of crude oil pipeline transportation on the microbehavior of wax aggregation in crude oil at low temperatures, molecular dynamics models of binary and multivariate systems of crude oil with different wax components are established in this paper. The simulation results are compared with the existing experimental results and the NIST database to verify the rationality and accuracy of the models. By using the established binary model to simulate four crude oil systems containing different wax components, it can be found that the longer the wax molecular chain, the more easily the wax molecules aggregate. The influence of temperature on the aggregation process of wax molecules with different chain lengths is also studied. The lower the temperature, the greater the difference in wax molecular aggregation degree caused by the difference in molecular chain length. Nonequilibrium molecular dynamics is used to simulate the shear process of a multivariate system of crude oil, and the micromechanisms of the shear effect on the aggregation process of wax molecules are studied. Shearing can destroy the stable structure of crude oil, resulting in the orientation and conformational transformation of wax molecules, and obtaining the region of wax molecules sensitive to temperature and shear effects, the temperatures of which are below the wax precipitation point and the shear rate of which is lower than the maximum shear rate to prevent the molecular structure from being destroyed. At the same time, the sensitivity of wax components with different chain lengths to the shear effect is studied. The research results provide theoretical guidance for ensuring the safe and economic operation of waxy crude oil production. [ABSTRACT FROM AUTHOR]

Based on the technological requirements related to waxy crude oil pipeline transportation, both unavoidable and avoidable destroyed exergy are defined. Considering the changing characteristics of flow pattern and flow regime over the course of the oil transportation process, a method of dividing station oil pipelines into transportation intervals is suggested according to characteristic temperatures, such as the wax precipitation point and abnormal point. The critical transition temperature and the specific heat capacity of waxy crude oil are calculated, and an unavoidable destroyed exergy formula is derived. Then, taking the Daqing oil pipeline as an example, unavoidable destroyed exergy in various transportation intervals are calculated during the actual processes. Furthermore, the influential rules under various design and operation parameters are further analyzed. The maximum and minimum unavoidable destroyed exergy are 381.128 kJ/s and 30.259 kJ/s. When the design parameters are simulated, and the maximum unavoidable destroyed exergy is 625 kJ/s at the diameter about 250 mm. With the increase of insulation layer thickness, the unavoidable destroyed exergy decreases continuously, and the minimum unavoidable destroyed exergy is 22 kJ/s at 30 mm. And the burial depth has little effect on the unavoidable destroyed exergy. When the operation parameters are simulated, the destroyed exergy increases, but it is less affected by the outlet pressure. The increase amplitude of unavoidable destroyed exergy will not exceed 2% after the throughput rises to 80 m3/h. When the outlet temperature increases until 65 °C, the loss increase range will not exceed 4%. Thus, this study provides a theoretical basis for the safe and economical transportation of waxy crude oil. [ABSTRACT FROM AUTHOR]