In this work, in-depth experimental and numerical analyses are carried out on a single-cylinder bio-methane heavy-duty spark ignition engine, mounting a passive pre-chamber, to investigate the flame kernel formation, the combustion process and the overall performance. In the first stage, an extensive experimental activity is performed on the examined engine. Measurements are carried out in several engine operating points, exploring lean mixture conditions up to the lean burn limit and recording global engine parameters, combustion indicators, in-cylinder pressure traces and emissions. A 0D/1D engine model, integrated with user-coded phenomenological sub-models of flame kernel, turbulent combustion and emissions, is developed and combustion is properly tuned referring to the experimental stoichiometric points. A physics-based correlation of flame kernel duration for air/bio-methane charge is identified to forecast the kernel formation time at the spark event, which is a challenging task in presence of diluted mixtures and variable in-cylinder thermodynamic conditions. Flame kernel formation time predicted by the correlation considers the dependencies on pressure, unburned temperature, equivalence ratio and residual gas content of the air/fuel mixture. The proposed numerical approach demonstrates that a reliable prediction of the kernel duration remarkably improves the simulation of burn rates and pressure traces in the main chamber, especially under high mixture dilutions. The 0D/1D model accounting for the kernel formation satisfactorily replicates the main engine performance, including net Indicated mean effective pressure and Indicated specific fuel consumption with maximum absolute errors of 1.8% and 4%, respectively; main gaseous emissions (nitrogen oxides, carbon monoxide and unburned hydrocarbons) are reproduced with an overall acceptable accuracy; greater errors are observed only at high load, with absolute experimental/numerical deviations of about 200 ppm for nitrogen oxides and slightly greater than 400 ppm for carbon monoxide and unburned hydrocarbons.
High-power pulsed lasers are increasingly important in defense, remote sensing, and advanced scientific applications, but their strong intermittency and high peak heat flux pose major challenges for compact and efficient thermal management. Existing studies have mainly focused on individual cooling or storage components, while the dynamic energy matching among heat collection, thermal storage, and active heat dissipation remains insufficiently understood. To address this gap, this study develops a numerical model of a coupled pulsed-laser thermal management system integrating two-phase heat collection, phase-change thermal storage, and vapor-compression refrigeration heat dissipation. The effects of refrigerant charge, ambient temperature, pulse duty cycle, phase change material thermal conductivity, and thermal storage capacity on the system dynamic performance are systematically evaluated to reveal the supply–demand matching mechanism. The results show that normalized refrigerant charge ranges of 0.24–0.77 for the pump-driven loop and 0.057–0.141 for the vapor-compression refrigeration cycle help stabilize the R134a phase distribution and cooling response. Increasing ambient temperature prolongs the pre-cooling and cold-storage durations. Within the investigated range, compared with fixed-speed operation at the maximum-load condition of 50 °C, operation at 40 °C reduces compressor power by approximately 48 %. The preferred phase change material thermal conductivity increases with pulse duty cycle, from approximately 0.5 W·m⁻1·K⁻1 at 1:10 to 1.0 W·m⁻1·K⁻1 at 1:3, because higher duty cycles require faster heat transfer and stronger thermal response. Overall, these findings reveal the mechanism of system-level supply–demand matching and provide a theoretical basis and engineering reference for energy-efficiency optimization and adaptive real-time control of airborne high-power pulsed-laser thermal management systems.
This study examines the application of large-scale phase change material (PCM) packed beds for compressor inlet air cooling to enhance gas turbine power generation during high-temperature periods. The proposed system employs encapsulated PCM installed in covered underground trenches to provide latent thermal energy storage and maintain an approximately constant inlet air temperature, without the use of water injection. Three PCMs—RT31, RT35hc, and lithium nitrate trihydrate—were evaluated, with lithium nitrate trihydrate demonstrating superior thermal performance and more compact system dimensions. The method was applied to a gas turbine with a rated capacity of 123.4 MW and average capacity of 85 MW. The average air mass flow for this turbine is 281.63 kg/s. The simulation results indicate that the system can increase annual electricity generation by more than 4,700 MWh. Compared with water-based cooling, the PCM system achieves comparable power enhancement while saving approximately 4,300 tons of water annually. Unlike conventional evaporative cooling systems, the proposed PCM packed-bed approach enables water-free compressor inlet air cooling, making it particularly suitable for humid climates where wet- and dry-bulb temperatures are close and for regions experiencing water scarcity.
With the development of photovoltaic technology, half-cell bifacial photovoltaic (BPV) panels have attracted more and more attention. However, half-cell BPV panels installed outdoors often suffer from partial shading caused by different obstacles. In this study, an outdoor experimental setup was constructed to evaluate the impact of front partial shading conditions (obstacle transmittances (τ = 0 %∼80 %), shading ratios (x = 0 %∼75 %) and different shading directions (horizontal and vertical)) on thermal and electrical performance of half-cell BPV panels. Results show that, τ and x ,manifested as the combined effect of τ and bypass diode operation/reverse bias, are identified as dominant factors for thermal performance, independent of shading direction. A certain τ between 20 % and 40 % reverses the changing trend of panel’s average temperature with x , as well as the relative magnitude between average temperature in shaded area and that un-shaded area. Temperature non-uniformity factor (ε) of panels peaks at x = 50 % under different τ and shading directions. For electrical performance, partial shading in horizontal and vertical directions exhibits different influence patterns. For vertical direction, electrical power (P) decreases with increasing x. While for horizontal direction, P initially decreases with the increase of x , then remains relatively stable (P at x = 25 % and x = 50 % is nearly identical), and finally decreases again. When the shading area is small (x = 25 %) and large (x = 75 %), the average instantaneous electrical power loss ratio (κave) difference in vertical and horizontal shading is small. While vertical shading causes greater κave than horizontal shading at x = 50 %. And with increasing τ, κave differences between two directions diminish. Findings clarify shading effect mechanisms and provide guidance for half-cell BPV panels’ performance evaluation.
To address the challenges of accurately predicting the dynamic behavior of proton exchange membrane (PEM) electrolyzers under fluctuating renewable energy inputs and the high cost of long-term experiments, this paper develops and validates a PEM dynamic model via the experimental and simulation combined approach to. A voltage model with current density and temperature as variables was established through static polarization curves and dynamic step/ramp load change experiments. The proposed model captures both electrical and thermal transient characteristics and is validated using a PEM electrolyzer experiment platform. The results agree well with the validation experiments, with a static mean absolute error (MAE) of 0.0033 V, a root mean square error (RMSE) of 0.004 V, and a maximum dynamic temperature deviation below 0.5 °C. Subsequently, the developed model was applied to dynamic system simulations under representative seasonal conditions as well as an extreme low‑irradiance scenario. Seasonal comparison shows that summer achieves the highest average hydrogen production efficiency of 74.7 %, along with an average specific energy consumption (SEC) of 4.115 kWh/Nm3 and an average cell voltage of 1.72 V. Although autumn delivers the highest daily hydrogen production of 52.74 mol, winter exhibits a comparatively higher average hydrogen production efficiency (73.4 %) than both spring and autumn despite generating the lowest daily hydrogen output (34.71 mol). Under an extreme low-irradiance condition, hydrogen output falls to 12.2 mol, while the system continues to operate stably without shutdown or failure, exhibiting strong environmental adaptability. This synergistic method (experiment, modeling, validation, simulation) offers a reliable and computationally efficient tool for long-term performance assessment and operational optimization of PEM electrolyzer systems integrated with variable renewable energy sources.
Distributed emergency power supplies are increasingly critical amid rising climate uncertainties and geopolitical instability. Combustion-driven thermoelectric generators (TEGs) offer a promising solid-state solution, yet their performance remains fundamentally constrained by hot-side thermal management. Existing systems struggle to simultaneously achieve high heat flux and uniform temperature distribution, which severely limits both power output and conversion efficiency. Previous studies have treated combustor design and heat collection as separate problems, overlooking their synergistic coupling. To bridge this gap, this study proposes and experimentally validates an integrated system that couples a super-adiabatic porous combustor with a multiple jet impinging heat collector. The core novelty lies in a synergistic positive feedback mechanism whereby the ultra-lean combustion capability of porous combustor generates high-velocity flue gas to drive effective jet impingement, while the resulting high electrical output powers the air blower against the system’s flow resistance, sustaining the ultra-lean operating condition. Under closed-loop water cooling, key parameters including equivalence ratio (0.35 ∼ 0.54), input power (2.57 ∼ 3.86 kW), and cooling intensity are systematically optimized. The system achieves a record high power output of 71.1 W, surpassing all previously reported independently operating combustion-driven TEGs, with a corresponding overall power generation efficiency of 1.84%. Crucially, the novel heat collector transforms the heat collection mechanism by extracting heat in situ from continuously cooling flue gas to isothermal flue gas impinging on the collector surface, fundamentally altering the wall temperature profile. This yields a hot-side temperature non-uniformity of only 16.8 K, which is merely 8.97% of the average operating temperature difference (187.2 K), substantially lower than previously reported values. The findings of this study provide a concrete prototype and a method for reducing hot-side temperature non-uniformity for the development of high-performance combustion-driven thermoelectric generators.
