The geological conditions of fault-controlled carbonate volatile oil reservoirs in Shunbei oilfield and the relationship between production wells are complex, and conventional methods have poor applicability in calculating dynamic reserves. Considering that the reservoir has the characteristics of fracture and cavity development, multi-phase seepage and inter-well interference, a volatile oil reservoir pseudo-pressure function was proposed and the functional relationship between saturation and pressure was given. The multi-phase flow material balance well group dynamics of the volatile oil reservoir material balance theory were established. The proposed method utilizes bottomhole flow pressure to calculate dynamic reserves, while there is no need for static pressure testing in the well group. The results show that the multiphase flow material balance equation describes the linear relationship between oil production rate and cumulative production. A partial correlation analysis was conducted on the main controlling factors of the well group’s dynamic reserves, and it was concluded that the main factors affecting the production dynamic characteristics are average oil production, production decline rate and formation energy. Quantitatively evaluate the impact of errors in important parameters of the formation and fluid on the calculation results of dynamic reserves. It is believed that the compression coefficient and porosity of the formation have a great influence on the accuracy of dynamic reserve calculations. The well group dynamic reserve calculation method was applied to a typical well group in the Shunbei oilfield, and the dynamic reserve decrease in the calculation results of a single well was compared to quantify the decrease in dynamic reserves in the Shunbei oilfield due to inter-well interference. The method can accurately calculate the dynamic reserves of well groups in the Shunbei fault-controlled volatile oil reservoirs.

The tight oil reservoirs in the eastern Ordos Basin are characterized by shallow burial, low pressure, small principal geostress, and low fracture pressure, which are significantly different from the general mid-deep tight oil reservoirs. Previously, the development of horizontal wells in this area through hydraulic fracturing was mainly based on field experience, and the design of the fracturing construction lacked a theoretical foundation, making the impact pattern of construction parameters unclear and the enhancement of production effect uncertain. Hence, research on the optimization of key parameters in fracturing construction is urgently needed. To maximize production efficiency, an integrated research method involving fracturing simulation and numerical reservoir simulation has been adopted. FrSmart has been used for fracturing simulation, Petrel for building geological reservoir models, and tNavigator for numerical simulation. Through the comprehensive application of various numerical simulation software, optimal cluster spacing, displacement, and single-segment fluid volume suitable for horizontal well fracturing in the reservoir were determined. By adjusting the conventional volume fracturing process parameters of well YCN-1 in the study area to a cluster spacing of 20 m, a displacement of 12 m³/min, and increasing the single-segment fluid volume to 1 000 m³, significant improvements in fracturing and production enhancement effects were achieved. Field test results show that the production of well YCN-1 after optimizing fracturing parameters is 29.98% and 50.27% higher than that of the unoptimized wells N-2 and N-3, respectively. Therefore, a method of critical significance for guiding the fracturing construction of shallow tight oil reservoirs, enhancing fracturing efficiency, and improving production effects has been proposed.

Proppant performance is very important to the hydraulic fracturing design of unconventional oil and gas reservoirs. Few scholars have studied the micro performance parameters of proppant in terms of particle size and shape. The effect of particle size and shape on proppant breakage rate and fracture conductivity in shale gas reservoir was quantitatively characterized through laboratory experiments. The results show that when the closing pressure is lower than 28 MPa, the same type of proppant with uniform particle size and high spherical degree is compared with the proppant with poor sorting, the crushing rate is reduced by 15% and the fracture conductivity is increased by 10%. When the closing pressure exceeds the compressive strength of the proppant, the well-separated proppant can maintain the fracture conductivity better as the flow channel is further blocked by the debris generated by the broken proppant. The experimental results provide a reference for in-situ fracturing design of shale formation, improving the quality control level of downhole materials and selecting proppant.

In order to study the effect of unsteady flight parameters on the aerodynamic characteristics of simulated butterflies, a flight dynamics model was established with the black-framed blue Morpho butterfly as the research object. Based on the flight principle, the relative coordinates of butterfly wings, body and ground during flight were established, and the kinematic equations of butterfly wings and body during flight were constructed. The aerodynamic characteristics of the simulated butterfly were verified based on the flight principle of the butterfly, and the effects of the change of flutter angle and pitch angle on the lift and drag of the simulated butterfly were studied under the natural environment flow field. The results show that there is a positive correlation between turning angle and lift force, but no correlation with drag. When the flutter angle is less than 120°, the lift is positively correlated, when the flutter angle is greater than 120°, the lift is negatively correlated, and the flutter angle is negatively correlated with the drag. A high pressure area begins to occur at the leading edge of the wings when the downward flapping occurs, and at the edge of the wings when the upward flapping occurs. The research results provide a reference for the control parameters and wing design of flapping wing aircraft, and provide a scientific basis for further optimization of bionic flapping wing flight.

The quality of internal plunge grinding process is affected by the grinding performance of different grinding wheels. In order to online monitor the grinding performance of different grinding wheels under the same experimental parameters during the internal grinding process. A particle swarm optimization-back propagation(PSO-BP) neural network-based grinding performance monitoring method for different grinding wheels was proposed. Firstly, the feature parameters of acoustic emission signal, power signal, vibration signal, displacement signal and current signal were extracted. Then, according to the eigenvalue data samples of each sensor and the global optimization function of BP neural network by particle swarm optimization algorithm, the PSO-BP online monitoring model was established by using PSO algorithm to optimize the initial weights and thresholds of BP neural network to accurately monitor the grinding performance of different grinding wheels. Finally, the BP neural network model and the PSO-BP model were analyzed and compared with the experimental data. The results show that the PSO-BP monitoring model has higher monitoring accuracy than the BP neural network model, with an average correct rate as high as 97.6%, and the validity of PSO-BP is verified through a large number of experiments, which is able to effectively monitor the grinding performance status of different grinding wheels.

In order to enhance the overall performance of the heat sink, a novel meshed microchannel heat sink structure was introduced, and its geometric parameters were optimized by performing a multi-objective optimization. The Box-Behnken design method was utilized to conduct response surface analysis on the design variables of channel width, fin thickness, and channel depth. The resulting temperature and pressure drop functions of the spider-shaped microchannel were then fitted as objective functions. The Pareto solution set was derived by applying a multi-objective particle swarm optimization algorithm, followed by utilizing the technique for order preference by similarity to an ideal solution(TOPSIS) method for selection from the Pareto solution set. It is concluded that the Pareto solution set is the optimal choice across various conditions. The multivariate statistical coefficients R² for temperature and pressure drop functions are 0.999 6 and 0.998 4, respectively, suggesting a high level of accuracy in the fitting function. The optimized structure not only reduces the average temperature by 3 K compared with the original design, but also decreases the pressure drop by 1 514 Pa. This significant improvement in comprehensive performance demonstrates that a well-designed channel structure can further enhance the heat sink performance of the microchannel.

For full-bridge LLC resonant converter, intermittent control strategy is an effective means to improve its light load efficiency. An improved intermittent control method was proposed to solve the problems of limited efficiency improvement and large output voltage ripple in light load state of converter by traditional intermittent control. This control method fixes the intermittent conduction time and makes the converter work at the resonant frequency during the intermittent conduction time, which further improves the light load efficiency of the converter and reduces the output voltage ripple. In order to verify the feasibility of the proposed method, a simulation model was built and the simulation waveforms of the traditional intermittent control strategy and the improved intermittent control strategy were compared and analyzed, and an experimental prototype with rated power of 100 W was made. The simulation and experimental results show that the output voltage ripple of the full-bridge LLC resonant converter with the improved intermittent control strategy can meet the engineering requirements, and compared with the traditional intermittent control strategy, the efficiency under light load is improved by up to 4.1%.

A large number of nonlinear components are used in the AC microgrid of photovoltaic grid-connected system which is equipped with a certain capacity of energy storage devices. When there is a large number of nonlinear loads in the microgrid system, the current waveform of the microgrid system is prone to distortion, resulting in harmonic pollution. In order to reduce the interference of grid-connected microgrid system on the receiving grid, based on the LCL grid-connected inverter structure, PI+ repeated control compound control strategy was adopted to realize the tracking and control of command current on the basis of meeting the tracking speed and accuracy, which can effectively suppress harmonic current and compensate reactive power. Based on the composite control, it is considered that when the photovoltaic output power and load power change, the multi-function grid-connected inverter under the composite control can still realize dual functions when the researched microgrid and the grid transmit different power in different modes. Finally, the simulation results show that the strategy realizes harmonic compensation and reactive power compensation, and transmits power to the grid at the same time.

Hydrogen, which produces only water during usage, is an excellent secondary energy source. However, its environmental impact should consider the primary energy sources used for hydrogen production, as well as transportation. The use of the grid can not absorb the abandoned photoelectrolysis water to produce green hydrogen and incorporate it into natural gas, and the use of natural gas pipeline network transportation can ensure the environmental protection and clean hydrogen energy. An optimal operation model considering the start-stop characteristics of proton exchange membrane (PEM) electrolytic cell was established. The model can obtain the optimal production plan when dealing with intermittent energy, hydrogen demand fluctuation and time-varying electricity price, and achieve the balance of time-varying electricity price, hydrogen production, photovoltaic output and operating cost. The production plan shows the load of electrolyzer in different periods, which verifies the correctness of the model. By changing the minimum load in the constraint condition, the results show that the proportion of standby and idle state decreases with the decrease of the minimum load, and the running cost also decreases slightly. When the critical value reaches 6.1%, the running cost no longer changes.

A low-carbon optimal operation model of an integrated energy system that takes demand response and double-layer power-to-gas conversion into account was proposed to increase system energy utilization and lower carbon emissions. Firstly, the optimization model of dual-layer electric-gas multi-energy complementary integrated energy system with high efficiency of hydrogen was established to study the advantages of hydrogen energy in many aspects. Secondly, the demand response model was modeled, which was divided into price type and alternative type according to the characteristics of flexible load. Thirdly, a stepped carbon trading mechanism was introduced to curb the carbon emissions of the system. Finally, taking Nanning Jiangnan industrial park as an example, the model was solved in CPLEX environment of MATLAB, and verified by scene comparison analysis. The results show that the model can fully mobilize the demand side to participate in the system optimization and achieve the effect of energy saving and emission reduction.