To investigate surface movement and deformation characteristics due to continuous mining and continuous backfilling (CMCB)of coal under artificial lakes, laboratory and field coring mechanical tests were conducted on the CMCB area to verify the feasibility of the filling body. Based on the equivalent mining height probability integration method, the surface subsidence of the CMCB area was predicted. The height of the water-conducting fracture zone was analyzed using numerical simulation, and its results were compared with those of the probability integration method. The results show that the strength of the filling body is 5.063 MPa, which is higher than the designed strength of 2.0 MPa, ensuring safe mining.Owing to continuous mining and backfilling in the area, the maximum inclination value of the surface was 0.3 mm/m and the maximum horizontal deformation value of the surface was -0.2 mm/m, respectively, which is less than the range of grade Ⅰ damage to brick and concrete structures. The surrounding surface subsidence was gentle, and there was no safety hazard. The height of the water-conducting fracture zone was about 49.7 m, and the distance from the waterproof layer was about 160.3 m, indicating the safety of underwater coal mining. Results of the FLAC^3D numerical simulation and probability integration method were close, thereby verifying that the CMCB technology can effectively slow down surface movement and deformation.

The traditional maximum power point tracking (MPPT) algorithm is prone to fall into local optimization in the case of a multipeak photovoltaic array. The butterfly optimization algorithm has a strong global search capability and a relatively stable convergence process; however, it has not been widely used due to its low convergence accuracy. This paper proposes an MPPT algorithm that combines the improved butterfly optimization algorithm with the perturbation and observation method. The traditional butterfly optimization algorithm was optimized by introducing the chaotic mapping theory to improve the distribution of the initial butterfly population. Besides, the dynamic switching probability was used to optimize the switching strategy. Herein, first, the global search capability of the butterfly optimization algorithm was used to locate the range of the maximum power point, and then the small step size perturbation and disturbance observation method were used to accurately locate the maximum power point. This algorithm combines the advantages of the global optimization of the butterfly optimization algorithm and the precise optimization of the perturbation and observation method. Furthermore, Simulink simulation experiments were conducted, and the results were compared with the traditional butterfly optimization algorithm and particle swarm optimization algorithm. The results show that the improved algorithm can adapt to complex and changing light conditions and has certain advantages in both convergence accuracy and speed.

In this paper, we have used the observed data of annual total solar radiation from 1961 to 2016 in Jinan, Shandong Province, and compared and analyzed the fitting results of time series models AR(5) and ARIMA((1,2,4),1,0) via model identification and statistical tests. As per the residual test results, the sparse coefficient model ARIMA((1,2,4),1,0) can be used to predict the total annual surface solar radiation. The prediction results show that the overall interannual variation of surface solar radiation in Jinan from 2017 to 2025 follows an increasing trend and the utilization of solar energy resources can be further explored. Compared to the results of the multiple linear regression model, the time series sparse coefficient model has less error and higher prediction accuracy.

Currently, Shengli Oilfield has entered the period of ultrahigh water cut, thereby increasing the difficulty of exploitation and raising the cost of oil production. Energy conservation has become the main factor for controlling the cost of oil-production plants. The distributed energy system based on natural gas can be constructed by combining gas turbine or gas internal combustion engine for power generation and flue gas-driven heat pump for the recovery from sewage and heating crude oil. Energy-flow analysis and optimization can be achieved through pinch analysis of a traditional joint station and a joint station distributed energy system. Based on the energy-flow model of a gas internal combustion engine under variable working conditions, the combustion calculation of a gas internal combustion engine is performed via thermal simulation and the pinch analysis is conducted for a traditional joint station that heats crude oil via water jacket heating furnace. Based on the lithium bromide-absorption heat pump energy-flow model driven via flue-gas heat, the pinch point analysis is conducted for the distributed energy system of the joint station. A comparative analysis of the joint station distributed energy system and the traditional joint station is performed. The energy-saving potential of the joint station distributed energy system can reach 24%, contributing to the realization of the “carbon peaking and carbon neutrality” goal.

A combined cooling, heating, and power system based on solar hydrogen production and high-temperature proton-exchange membrane fuel cell is developed in this study. A mathematical model of the system is built using the Matlab software to analyze the operation conditions of the system under rated working condition. The key design parameters, such as the pressure swing adsorption separation rate, current density, and working temperature of the high-temperature proton-exchange membrane fuel cell are studied emphatically to explore their impact on exergy efficiency; primary energy efficiency; and the cooling, heating, power loads of the system. The results demonstrate that the combined cooling, heating, and power system can provide the power load of 236.68 kW, heating, and cooling loads of 1 180.30 kW, and 165.14 kW, respectively, during a 6 h hydrogen production period under the design flow rate of input methanol. The system can output power, heating, and cooling loads of 2.30 × 10⁷, 2.55 × 10⁷,and 1.43 × 10⁷ kJ every 24 h. The 24 h exergy and the primary energy efficiency of the system are 69.18% and 91.96% respectively. Further, it is observed that the largest exergy loss occurs in the burning room, heat exchanger 3, and solar reforming-reaction generator.

For the continuous decrease in the wellhead pressure of natural gas containing moisture and sulfur in gas fields with high quantities of sulfur, low-pressure gases are transported owing to the surplus pressure from high-pressure gas wells via ejectors. Herein, the Fluent software is used to numerically simulate temperature and pressure profiles for single- and two-phase flows of natural gas containing moisture and sulfur in an ejector. The ZahediⅠmodel is used to predict the formation area of natural gas hydrates in the ejector. The effect of the inlet temperature of the working fluid, sulfur content, and moisture content on the formation of natural gas hydrates is predicted and analyzed. With increasing inlet temperature of the working fluid, the generation area range of natural gas hydrates in the ejector decreases. When the sulfide content is high, the generation area range of natural gas hydrates is large. The working fluid contains water droplets. The generation area of natural gas hydrates in the ejector is smaller than that under a single-phase working medium. Based on these results, measures for reducing natural gas hydrates are proposed.

Currently, the leakage of drain pipeline values in power plants is detected automatically using the principle of heat transfer. However, existing studies have not yet analyzed the flow and heat transfer of the fluid in a pipeline during valve leakage. Furthermore, research on the arrangement of temperature measurement points and the accuracy requirements of temperature measurements is lacking. To address these shortcomings, this study uses a computational fluid dynamic simulation to investigate heat transfer and flow in pipelines when valve leakage occurs. In addition, the influence of different pipeline diameters and insulation materials on differences in the measured temperatures and the amount of leakage is analyzed. The findings of this study provide a reference for the real-time monitoring of dynamic changes in the flow near the valve and the diagnosis of leakage faults of drain valves on engineering sites.

In the process of deepwater drilling, early and accurate monitoring of gas invasion is crucial for drilling safety. Based on Hagdorn and Brown’s method, this study establishes a model for increasing gas velocity after gas invasion in deepwater drilling, optimizes the influence of well deviation angle on the division principle of gas-flow pattern and gas slippage velocity in deviated wells, and realizes the real-time calculation of the time when the gas reaches subsea wellhead in accordance with the gas-liquid flow law in the wellbore after gas invasion. The results can effectively reflect the flow law of wellbore annulus after the gas invasion in deepwater-deviated well drilling and are of great significance for gas-invasion monitoring and well control.

A novel method for measuring the mixing characteristics of dissimilar particles in dense gas-solid two-phase flow based on a capacitance probe was developed. In the mixing process, the variation in the micromixing ratio of dissimilar particles in a bubbling fluidized bed was studied. The influence of convection and diffusion on the mixing of particles at a series of locations in the bubbling fluidized bed and its micromechanism were analyzed. Results show that with increasing bed height, the influence of convective mixing on the mixing of particles first increases and then decreases. The mixing ratio near the wall fluctuates slightly with the mixing time and mainly shows diffusion mixing behavior. No considerable difference is observed in the time required for particles to reach mixing equilibrium at different bed heights, and the time required for particles to reach mixing equilibrium near the wall is approximately twice as long as that at the axial positions. However, the final micromixing indices are similar in the mixing equilibrium state.

In the passive improvement of heat transfer technology, the use of inserts in tubes is a very common and practical technique. Inserting a central inclined rod in a heat exchanger tube can realize multilongitudinal vortex flow, similar to the optimized flow field in the tube, and effectively improve the heat exchange performance of the heat exchanger tube while retaining a small increase in flow resistance. In this study, a heat exchanger tube with an inserted central inclined rod is examined based on the numerical simulation method. The influence of the number, pitch, and diameter of inclined rods on the heat transfer performance and resistance characteristics is investigated. Results show that the heat transfer tube with the inserted central inclined rod achieves considerably better heat transfer performance than the smooth tube. The Nusselt number of the heat transfer tube with the inserted central inclined rod increases within a certain range with an increasing number of inclined rods, and the pressure drop increases with the number of inclined rods. When the number of inclined rods is three, the comprehensive heat transfer performance of the heat transfer tube with the inserted central inclined rod is better. The Nusselt number and pressure drop decrease with increasing pitch of the inclined rod. When the pitch of the inclined rod is 20 mm, the comprehensive heat transfer performance of the heat transfer tube with the inserted central inclined rod is better. The Nusselt number and pressure drop increase with the inclined rod diameter. When the inclined rod diameter is 2.0 mm, the comprehensive heat transfer performance of the heat exchange tube with the inserted central inclined rod is better.

In this study, two production modes of oil-collecting pipeline transportation and oil-pulling single-well oil storage tanks are modeled and dynamic simulations are performed. Moreover, the heating load-variation rules and optimal heating parameters of the two modes are further explored. The distributed energy system schemes of crude oil transportation in single-well oil-collecting pipelines and oil-pulling oil storage tanks are designed, which involve a water jacket heating furnace, electric heat tracing, a solar heat-collecting device, a solar heat storage device, and an air source heat pump. Thermodynamic calculations of five types of heat sources are performed, and the objective function and constraint conditions for the two types of distributed energy systems are established to optimize the systems. Results show the required electric heat-tracing proportion of different modes, seasons, and times to achieve the rational use of the heat source and minimize investment and operational costs. Furthermore, economic analysis of several distributed heat sources is performed.

To improve the throttling loss of an electric water feed pump during the deep peak shaving operation of northeast coal-fired units, and the utilization rate of electric energy and coal consumption, a 600 MW electric water feed pump unit in power plant is taken as an example, using a frequency conversion scheme, under different working conditions (100%, 92%, 83%, 67%, 60%, 53%, and 50% rated loads), to analyze the power and frequency conversion conditions of single and double water feed pumps and identify the relationship between the flow rate, load, electrical efficiency, and active power of the motor. The test results show that the lower the flow, the more greater will be the improvements in the electrical efficiency and active power of the motor, up to 30% and 33%, respectively, subsequent to frequency conversion. Frequency conversion transformation is suitable for this unit, reducing the plant power consumption rate by 0.45%~0.87%, the power saving rate is 21%~33%. The variable frequency drive has a significant energy-saving effect on the deep peak shaving operation of the unit, providing a certain degree of reference for the transformation of the same type of unit.