Jiaqiang E

Battery degradation is a non-negligible cost in battery energy storage (BESS) dispatch for industrial microgrids, yet most deep reinforcement learning (DRL) studies optimize only the procurement cost. This paper embeds a rainflow-calibrated cyclic aging cost into the reward of a degradation-aware soft actor-critic (DA-SAC) framework with an adjustable weight λ, making the cost–lifetime trade-off explicit. On one year of 15 min data from an industrial microgrid in Chongqing, the main evaluation is conducted in an offline simulation, and the typical days are validated by hardware-in-the-loop (HIL) real-time simulation on the Speedgoat real-time target with the policy on a Beckhoff edge controller. DA-SAC reduces the cyclic degradation cost by about 28% relative to MPC, but its operating cost cannot go below CNY 649.4/day, worse than a simple price threshold rule (641.8), a boundary we attribute to long-horizon credit assignment. Dynamic programming (DP) provides a strong baseline whose closed-loop lookup reaches cost parity with MPC under noisy forecasts (CNY 618.4 vs. 618.1/day), and deployment time SAC correction improves the coarse-grid DP from CNY 620.6 to 619.4/day, with greater forecast noise robustness (+3.5% vs. +4.55% for MPC under a three-fold noise increase). Degradation-aware DRL is therefore most valuable when combined with the exact opportunity cost of DP under a single main site and a fixed forecast noise level.

Background: As global environmental issues and the energy crisis continue to intensify, diesel–natural gas dual-fuel engines have been extensively studied due to their stable combustion, low emissions, abundant natural gas reserves, and relatively low cost. Methods: Based on a modified YCK15 six-cylinder heavy-duty diesel engine, the experiments and GT-SUITE v2016 simulation were used to study the effects of NG substitution rate (NGSR) and diesel injection timing (DIT) on the combustion characteristics, power and emission performance of a diesel–NG dual-fuel engine running at 1800 rpm, with NGSR ranging from 0 to 50% and DIT ranging from 5 °CA BTDC to 17 °CA BTDC under four engine load conditions: 100%, 75%, 50% and 25%. Significant Findings: The results showed that the NGSR and DIT have considerable impact on performance enhancement and emission reduction. As NGSR increased, cylinder pressure decreased under high load and increased under low load. Under four loads, the temperature inside the cylinder revealed a downward trend, and the power and indicated thermal efficiency (ITE) decreased slightly, with power and ITE declining by less than 5% and 2%, but the fuel economy and emissions were well improved. Compared to 50% NGSR and pure diesel condition, brake-specific fuel consumption (BSFC) decreased by 5.63%, 4.60%, 2.98%, and 1.83%, respectively, and NO_x emissions decreased by 32.68%, 36.41%, 37.90%, and 38.99%, respectively. As DIT increased, cylinder pressure and temperature both increased under all four load conditions, and the power and ITE improved significantly, but this caused an increase in NOx emissions. Compared to DIT of 17 °CA BTDC with 5 °CA BTDC, power increased by 8.29%, 9.76%, 13.38%, and 16.51%, respectively, and ITE increased by 7.69%, 8.77%, 11.46%, and 12.77%, respectively. The response surface was established and performance optimized using the design of experiments (DOE) module in GT-SUITE v2016. At an NGSR of 50% and 100% loads, the optimized power was 0.431% higher than the pure diesel mode, ITE was 0.396% higher, brake-specific fuel consumption was reduced by 7.397%, and NO_x emissions were reduced by 27.027%.

Before launch, cryogenic propellant tanks experience a pre-pressurization stage during which their thermodynamic behavior is sensitive to operating conditions and external disturbances. For liquid hydrogen (LH2) storage tanks, small-amplitude oscillations may modify interfacial transport and phase change, thereby influencing pressure evolution and mass distribution. In this study, a computational fluid dynamics (CFD) model that accounts for gas–liquid interfacial phase change and environmental heat leakage is developed to investigate the thermodynamic response of an LH2 tank subjected to slight external oscillation during pre-pressurization. The effects of oscillation amplitude, inlet gas temperature, mass flow rate, and initial ullage gas fraction on temperature distribution, pressure development, and phase mass variation are analyzed. The results indicate that increasing the oscillation amplitude from 0.006 m to 0.014 m delays the pressurization time from 4.72 s to 5.04 s, while higher inlet temperatures (e.g., 330 K vs. 280 K) shorten the time to reach the target pressure but weaken interfacial condensation, resulting in a slower recovery of liquid hydrogen mass. Raising the inlet mass flow rate from 0.20 kg/s to 0.40 kg/s reduces the time to reach the preset pressure by approximately 56%, and larger initial ullage gas fractions (ullage height from 1 m to 6 m) significantly prolong the pressurization time and produce a wider high-temperature region. These quantitative results clarify the coupled oscillation-thermodynamic effects and can support optimization of LH2 tank operation during pre-pressurization.

GT‐Power software was employed to model a methanol–diesel dual‐fuel engine operating at 1800 rpm for investigating the effects of the methanol air–fuel ratio (AFRm) in the intake port on engine combustion and emission performance. Eight AFRm values were selected for analysis: 15, 20, 25, 30, 35, 40, 45, and 50. Torque was used as the output signal to manage diesel injection mass by the controller. Research findings indicate that by maintaining constant engine torque and leveraging the complementary energy release of methanol and diesel fuel, fluctuations in brake power and efficiency caused by variations in AFRm remain below 2%. Increasing AFRm alters the composition of the methanol–air–diesel mixture, resulting in higher trapped AFR and induced AFR within the cylinder. The increased density of the combustion mixture elevates cylinder pressure and heat release rate, leading to higher temperatures throughout the system, particularly in the cylinder. A combination of elevated temperatures, increased oxygen content, and greater diesel injection results in 52.29% and 10.59% increases in NO _x and CO ₂ emissions, along with 6.51% and 15.87% decreases in CO and HC emissions. Second‐order regression equations were established for cylinder peak pressure, brake efficiency, BFSC, NO _x , CO, CO ₂ , and HC to demonstrate the influence of AFRm on these parameters visually. Confirmation test results indicate that the errors between simulated values and predicted values from the fitting curves remain within 1%. Due to the inherent limitations of one‐dimensional simulation and simplified chemical reaction mechanisms in GT‐Power, the predicted results may deviate from actual engine behaviour.

This study develops and validates a thermodynamic model for a supercritical carbon dioxide (CO₂) pneumatic launch system, evaluating its potential as an environmentally friendly and efficient energy conversion technology alternative to conventional working fluids such as compressed air and nitrogen. Utilizing real-gas thermophysical properties from the NIST database, the model incorporates mass and energy conservation principles to simulate the transient launch process. Under the assumption of a pre-attained initial state, comparative analyses demonstrate that supercritical CO₂ offers significantly higher specific internal energy, resulting in up to 20% greater payload capacity and improved exit velocities under identical initial conditions. A detailed parametric investigation examines the effects of key structural parameters—including the initial volume of the low-pressure chamber, launch tube diameter, valve diameter, and valve opening time—on launch performance, efficiency, and safety. Results indicate that while a smaller low-pressure chamber volume and larger launch tube diameter enhance launch efficiency and velocity, they must be balanced against structural safety limits to avoid excessive acceleration. Valve diameter expansion improves mass transfer and acceleration, yet diminishing returns are observed beyond 0.10 m. The study highlights supercritical CO₂ as a promising high-energy-density working fluid that eliminates toxic exhaust at the launch site. These findings provide practical guidelines for system design optimization, offering a technical pathway toward compact, low-emission pneumatic launch equipment, provided that the upstream energy for CO₂ conditioning is efficiently managed.

In order to effectively reveal the nonlinear characteristics of a dish concentrating solar thermal power system (DCSTPS) under pulsating wind-induced loads, a fluid simulation model of the DCSTPS was established, and the simulated pulsating winds were developed via the user-defined function (UDF) combined with the autoregressive (AR) model using MATLAB (R2015b). And based on the fluid simulation calculations of the DCSTPS, the time-range data of the relevant wind vibration coefficients under different working conditions were obtained. The research results show the following: (1) When the altitude angle α is 0° or 180° due to the azimuth angle β = 0°, the maximum values of their drag coefficient C_x, lateral force coefficient C_y, and lift coefficient C_z are similar, and the maximum of rolling moment coefficient C_Mx is significantly smaller than the values at the other two angles; the maximum of the pitch moment coefficient C_My and maximum of the azimuth moment coefficient C_Mz are significantly larger than the values of the other two angles. (2) The increase in altitude angle α leads to a reduction in the drag coefficient C_x, an increase in the lift force coefficient C_z, and an increase of the pitch moment C_Mx. Moreover, an improved phase space delay reconstruction method was developed to calculate the delay time, Lyapunov exponent, and Kolmogorov entropy of the DCSTPS, and the research results show that (1) the maximum Lyapunov exponent and Kolmogorov entropy of the DCSTPS are greater than zero under the action of pulsating wind; (2) the action of pulsating wind will cause increases in the maximum Lyapunov exponent and Kolmogorov entropy of the DCSTPS and will accelerate the divergence speed of the DCSTPS trajectory; and (3) the time for the DCSTPS to enter the chaotic state will be shortened, while the time of entering a chaotic state and degree of subsequent chaotic states will be significantly affected by relevant wind vibration coefficients but without regularity.

To avoid the problem of wind-induced resonance damage in a dish concentrating solar thermal power system (DCSTPS), a fluid dynamics model and a finite element analysis model of the DCSTPS were established separately. The wind load was mapped onto the surface of the concentrator of the DCSTPS using the sequential coupling method, and the static analysis and modal analysis of the DCSTPS were established based on the fluid–structure coupling (FSC) method and the validity of the established model was verified. Based on the results, it can be concluded that the upper edge of the dish solar concentrator (DSC) of the DCSTPS and the three cantilever beams near the Stirling generator are the most vulnerable to being damaged, the DCSTPS will not experience strong resonance phenomena, and effects of the FSC will decrease the natural frequencies of each order. The results of the safety grade catastrophe evaluation of the DCSTPS showed that the safety grade of the DCSTPS was 0.2586 and 0.2819 under case 1 (α = 30°, β = 90°) and case 2 (α = 60°, β = 90°), where it was found that the membership value of the moment load was low, resulting in the stress on the connection seat of the altitude angle and the steering device of the base approaching the allowable stress of the material.

With the rapid development of solar thermal power generation technology, the structural stability of the dish solar concentrator system under complex wind environments has become a critical limiting factor for its large-scale application. This study investigates the flow field distribution and structural response under fluctuating wind loads using computational fluid dynamics (CFD). A three-dimensional model was developed and simulated in ANSYS Fluent under varying wind angles and speed cycles. The results indicate that changes in the concentrator’s orientation significantly influence the airflow field, with the most adverse effects observed at low elevation angles (0°) and an azimuth angle of 60°. Short-period wind loads (T = 25 s) exacerbate transient impact effects of lift forces and overturning moments, markedly increasing structural fatigue risks. Long-period winds (T = 50 s) amplify cumulative drag forces and tilting moments (e.g., peak drag of −73.9 kN at β = 0°). Key parameters for wind-resistant design are identified, including critical angles and period-dependent load characteristics.