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[Objective] Carbon capture, utilization and storage(CCUS) is an indispensable technology for achieving carbon neutrality,and CO2 pipeline transmission is a significant component of this technology. In the process of supercritical CO2 pipeline transmission,unintentional pipeline leakage or venting operations may cause localized low temperatures in the trunk pipelines and vent piping due to the strong throttling effect caused by CO2, resulting in dry ice that blocks the pipeline and makes it brittle. [Methods] In the study, the OLGA software was utilized to develop a high-pressure CO2 pipeline relief model. The simulation results obtained from the model were then compared against foreign experimental data. The comparative analysis indicated that the OLGA software provided relatively accurate calculations for pressure drop and tended to be more conservative in calculating temperature drop. These findings supported the software's suitability for performing calculations related to the design of CO2 pipelines. Building upon this foundation, a long-distance high-pressure CO2 pipeline venting model was established to simulate and analyze the effects of different valve openings, initial temperatures, and initial pressures on temperature decrease, phase state changes, and venting duration during the CO2 pipeline venting process. [Results] It was revealed that reducing the vent valve opening effectively prevented excessively low temperatures within the pipeline during venting. Under the venting simulation conditions selected for this study, 13.5% valve opening effectively prevented dry ice formation, and the valve opening below 4.5% could maintain the pipeline temperature at higher than-30 ℃. The venting process of the high-pressure CO2 pipeline exhibited low convective heat transfer intensity and significant temperature drops, predominantly observed away from the relief port. The initial temperature had a substantial impact on the temperature in the pipeline during venting. More specifically, a lower initial temperature resulted in a decrease in the temperature in the pipeline during venting, increasing the likelihood of dry ice formation. [Conclusion] Therefore, in engineering practice, it is crucial to focus on fuid temperature in sections far from the relief port along the trunk pipelines and automatically reduce the vent valve opening in response to temperature drops, aiming to slow down the temperature drop rate during the venting process. Special attention should be paid to protecting CO2 pipelines, especially when operating under low-temperature dense phase conditions.

[Objective] Settlement is a common geological hazard encountered around buried pipelines. Such hazards have the potential to cause pipeline failure and damage, particularly in severe cases. Hence, studying pipe-soil interactions during continuous settlement is crucial to ensure the safety of buried pipelines facing settlement hazards. [Methods] This study explored the law governing pipe-soil interactions within different stratum settlement ranges and amounts, by conducting a continuous settlement experiment on a buried steel pipeline, using a specifically designed experimental system. The evolution process of pipe-soil interactions in the continuous settlement process was meticulously analyzed through numerical simulation. Furthermore, the numerical simulation results were subjected to a multivariate nonlinear fitting process, taking into account various parameters such as settlement, pipeline characteristics, and soil properties. [Results] As the stratum settlement increased,the steel pipeline and surrounding soil progressed from simultaneous settlement to separate settlement. The pipeline exhibited mechanical response in four stages: increase, unloading, fluctuation, and stabilization. As the stratum settlement range expanded, a greater amount of settlement took place before the pipeline was fully separated from the soil beneath it. With low settlement rates, the pipeline experienced significant increases in both maximum stress and settlement as the settlement rate grew. However, once the settlement rate surpassed 2×10-5 m/s,the maximum stress and settlement of the pipeline remained nearly unchanged, while the corresponding stratum settlement exhibited notable increases. Moreover, the fitting process yielded a maximum Von Mises stress prediction model for buried steel pipelines exposed to continuous settlement, achieving a calculation error dominantly within 10%. [Conclusion] The mechanical response of pipelines exhibits distinct variations across different settlement stages. Furthermore, any alterations in stratum settlement, settlement range, and settlement rate during the settlement process significantly influence the mechanical response of pipelines. In addition, the prediction model for the maximum Von Mises stress in buried steel pipelines exposed to continuous settlement is demonstrated effective. This model serves as a crucial basis for assessing the safety of buried pipelines under continuous settlement-induced disasters.

[Objective] Pressure regulation systems, serving as one of the vital links between long-distance pipelines and urban gas pipeline networks, play a significant role in the successful implementation of the “Hydrogen Society” Program. However, the contrasting physical properties of hydrogen and natural gas impose challenges to the effectiveness of process control in pressure regulation. [Methods] This study employed a combined approach involving decompression and pressure regulation experiments conducted on pure hydrogen and hydrogen-enriched compressed natural gas(HCNG), along with dynamic simulations of pressure regulation. By establishing a foundation for assessing the pressure stabilization effect of the decompression and pressure regulation system, considering factors such as pressure stabilization accuracy, response time, and fitness function, a sensitivity analysis was performed to investigate the influence of various parameters, including hydrogen blending ratios, flow fluctuation cycles, downstream flow change ranges, pipeline transmission pressures, as well as proportional, integral, and derivative parameters(PID). [Results] The following results were obtained:(1) With more frequent disturbances, gas flow rates increased, leading to larger system fluctuation ranges. Consequently, achieving pressure stabilization became more challenging for the decompression and pressure regulation system. This finding highlighted the importance of restraining the movement of pure hydrogen and HCNG at high flow rates in transmission pipelines.(2) The flow rate of the pressure regulation system carried sinusoidal fluctuations. Setting the pressure stabilization accuracy at ±1.5% and the proportional and integral parameters within the range of 1 to 2, the decompression and pressure regulation experiments showed that the decompression and pressure regulation of pure hydrogen and HCNG could be substantially achieved within the required pressure range of urban gas pipelines.(3) Pure hydrogen exhibited greater instantaneous fluctuations compared to natural gas when flowing through pipelines at identical rates of transmission.As a consequence, the response time and adaptability function of the control system gradually increased with higher hydrogen blending ratios. Moreover, the instantaneous pressure fluctuation of pure hydrogen reached 1.15 times that of pure methane, resulting in a response time and adaptability function of the control system that increased to 1.13 and 2.68 times those of pure methane, respectively. Under the same proportional and integral parameters, it was more challenging to maintain the pressure stabilization for the hydrogen-containing gas. Hence, decreasing the integral parameter or increasing the proportional parameter proportionally to the hydrogen blending ratio is recommended, to attain the same or even better pressure stabilization effect as observed in natural gas scenarios. [Conclusion] The research findings provide theoretical insights to guide the pressure regulation practices of pipelines carrying pure hydrogen and HCNG.

Small-scale devices of liquefied natural gas (LNG) have been widely applied in the natural gas industries, especially for stranded gas production. As the key equipment of LNG plants, the performance of the spiral wound heat exchanger (SWHE) influences operating costs, reliability and safety of the whole system. In order to obtain the accurate two-phase tube-side heat transfer model for small-scale LNG SWHE and analyze its thermal performance, an experimental device of dual mixed refrigeration (DMR) is constructed. A multi-phase multi- -stream calculation code for SWHE is developed to solve the energy balance equations among tube-side feed gas, tube-side refrigerant and shell-side refrigerant, based on experimental results and thermal property calculation. The results show that the homogeneous flow model can be applied to two-phase tube-side heat transfer calculation of feed gas and Bell and Ghaly’s model and Shah’s model can be both applied to the mixed refrigerant. The relative errors between the results of the experiment and program are all within the range of ±12%.

In order to effectively alleviate the congestion of power exchange stations, the game theory was used to discuss the spatial characteristics of electric vehicle power exchange demand, analyze the decision making and game process of electric vehicle users specifically. Moreover, on the basis of the research, the specific way of setting the price of the exchange station was proposed and the game mathematical model was constructed.

Influenced by policies, resources and environmental factors, the development of electric vehicles has been in an upsurge in these years. Compared with conventional vehicles, electric buses better meet the needs of environmental protection and contribute more to environmental well-being. The State Grid Liaoning Electric Power Supply Company, to promote the use of electric buses, has built many charging and swapping stations in Dalian, which has significant impact on the application of electric buses. To meet the needs of increasing electric buses, this paper mainly discusses the design schemes of the charging and swapping stations of Youyi Street in Dalian, and finally chooses the scheme of “entering the station for swapping-decentralized charging” through comparison in the design.

Currently, with the rapid development of small towns in China, residents’ heating demand has been increasing, which exposes the heating problems of the small towns. Especially in the heating season, the energy consumption of buildings accounting for a decent proportion and the increase in pollution emissions can seriously affect the lives of residents. To alleviate these problems and promote clean heating, it is necessary to investigate the resources situation of small towns and design targeted heating lines for load areas. Therefore, this article used data analysis, described the population, construction area and industrial structure of small towns in the northern region, summarized the current development trend of small towns in China. Besides, taking the small towns in Inner Mongolia Autonomous Region as an example, this paper tried to understand the heating problems of small towns, including low energy efficiency of thermal energy and poor thermal insulation of buildings. Based on the supply and demand side of small towns and the differences in the endowment characteristics in various regions, this paper also proposed different clean heating technology paths.

In face of increasingly severe environmental problems, green and low-carbon power supply has become an important trend of current development. At present, the smart grid which will respond to the demand has improved the interaction between current users and the grid. In addition, electric heating and solar power generation and other renewable power generation methods are promoted in north China. Electric heating is a flexible and regulatable load; when it reaches a certain scale, it is bound to become an objective demand response resource in power grid operation, so it is of great practical significance to explore the evaluation of the regulation capacity of electric heating load.

The marine area is the main direction of the development of oil and gas resources in the world. The pipeline transportation technology of natural gas hydrate slurry plays an important role in the exploitation of marine oil and gas and the exploitation of marine gas hydrate resources. In order to study the influence of pipe inclination on pipeline transportation, population balance model based on hydrate particle aggregation dynamics was coupled with the Eulerian–Eulerian two-fluid multiphase flow model to simulate the flow behaviors of hydrate slurry flow in pipes with different inclination angles. In the study, three variables of inclination, flow rate and initial particle size were considered. The results show that tilted pipes are beneficial to hydrate slurry transport rather than harmful. Meanwhile, higher flow rates and lower initial particle sizes are beneficial for promoting the flow safety of hydrate slurry transport. However, the flow pressure drop of the hydrate slurry increases with the increase of the flow rate and the decrease of the initial particle size, which is not conducive to the economics of mining. The research results in this paper can provide reference for the research of hydrate slurry flow safety and parameter guidance for hydrate solid fluidized mining.

On the basis of Space-Wise Least Square method, three numerical methods including Cholesky decomposition, pre-conditioned conjugate gradient and Open Multi-Processing parallel algorithm are applied into the determination of gravity field with satellite gravity gradiometry data. The results show that, Cholesky decomposition method has been unable to meet the requirements of computation efficiency when the computer hardware is limited. Pre-conditioned conjugate gradient method can improve the computation efficiency of huge matrix inversion, but it also brings a certain loss of precision. The application of Open Multi-Processing parallel algorithm could achieve a good compromise between accuracy and computation efficiency. Key words: satellite gravity gradiometry; Cholesky decomposition; pre-conditioned conjugate gradient; open multi-processing parallel algorithm; data processing