BURA Collection:

Pressure-regulated pool boiling for lithium-ion batteries based on a thermo-lifetime-economic coupling framework

2026-08-20T02:00:56Z

Title: Pressure-regulated pool boiling for lithium-ion batteries based on a thermo-lifetime-economic coupling framework Authors: Wang, Xiang; Li, Liang; Tassou, Savvas A Abstract: Pool boiling cooling offers strong potential for lithium-ion battery thermal management due to its high-efficiency phase-change heat transfer. However, most existing studies are limited to atmospheric pressure, and the coupled effects of pressure on thermal behaviour, battery lifetime, and economic performance remain unclear. In this study, a thermo-lifetime-economic coupling model is developed and experimentally validated through pressure-controlled pool boiling cooling of a battery module over a pressure range of 20–100 kPa. The results show that pool boiling significantly outperforms natural air-cooling, reducing the maximum temperature from 88.8 °C to 45.6 °C (48.6%) and the temperature difference from 9.3 °C to 3.1 °C (66.7%) at 2.5C. Further pressure reduction enhances thermal performance by lowering the saturation temperature and promoting earlier nucleate boiling. When the pressure decreases from 100 kPa to 20 kPa, the maximum temperature and temperature difference are further reduced by 26.3% and 38.7%, respectively, leading to a lifetime improvement of up to 65.1%. However, this improvement is accompanied by a substantial increase in auxiliary power consumption, which rises by more than 14.6 times, resulting in a strong thermo-economic trade-off with diminishing returns at low pressures. Furthermore, system scale critically affects economic feasibility. Pressure reduction increases cost at small scales but becomes favourable beyond a critical scale due to the growing contribution of lifetime-related cost. These results show that pressure regulation can improve pool boiling battery cooling, but the operating pressure should balance thermal performance, lifetime, and energy consumption. Description: Data availability: Data will be made available on request.

Dynamic transient control of hydrogen direct-injection SI engines: effects of ramp duration on engine performance and abnormal combustion

2026-08-19T02:01:03Z

Title: Dynamic transient control of hydrogen direct-injection SI engines: effects of ramp duration on engine performance and abnormal combustion Authors: Zaman, Zayne; Mohamed, Mohamed; Wang, Xinyan; Zhao, Hua; Harrington, Anthony; Hall, Jonathan Abstract: Hydrogen internal combustion engines offer a route to near-zero carbon on-road transport while preserving existing engine manufacturing and calibration know-how. Translating that potential into real-world driving, however, depends on transient control; steady-state maps alone cannot guarantee either safe operation or low NOx emissions during load steps. This paper reports a controlled transient sweep on a 0.4 L single-cylinder direct-injection spark-ignition hydrogen research engine. Five ramp durations (1.38, 1.08, 0.84, 0.48 and 0.24 s) were evaluated at a constant engine speed of 2,000 rpm with a target relative air–fuel ratio of 2.75 under closed-loop feedback control. The measurements track injection pulse width, spark timing, boost, lambda, IMEP, peak in-cylinder pressure and the maximum pressure rise rate (𝘙_max) through each transient. As ramp duration is shortened, lambda excursions and air-path overshoot grow rapidly: at 0.24 s the in-cylinder pressure overshoot approaches the mechanical safety limit, IMEP overshoots the steady-state target by about 22 %, and 𝘙_max exceeds the 600 kPa/°CA calibrated threshold. With a ramp of 0.48 the most hazardous 𝘙_max peak at roughly 1,000 kPa/°CA is caused, demonstrating that fastest is not always most damaging. Only the 1.38 s baseline keeps all combustion-severity metrics inside their reliability envelope. A feed-forward fuelling term scaled by the rate of manifold pressure change dP/dt is proposed to close the transient lambda gap; with physical implementation and experimental validation proposed as a future optimisation step. The results identify pressure-gradient management as the binding constraint for transient calibration of lean DI hydrogen engines. Description: Data availability: Data will be made available on request.

Intelligent Monitoring of Machining Processes using Gaussian Process Regression and On-Machine Comparator Measurement

2026-08-15T09:42:18Z

Title: Intelligent Monitoring of Machining Processes using Gaussian Process Regression and On-Machine Comparator Measurement Authors: Papananias, Moschos; Noh, Yohan; Cheng, Kai Abstract: This paper presents an intelligent machining process monitoring approach with emphasis on On-Machine Comparator Measurement (OMCM) and the effect of remastering on dimensional accuracy. Comparator measurement applies the comparator principle by referencing each measurement to a calibrated master part. In this approach, a mastering procedure is first performed by measuring the calibrated master part to establish a reference. By directly comparing the test part with the master part under repeatability conditions, constant systematic errors in the measurement system are effectively cancelled when determining deviations from the master part. However, the accuracy of this method depends on the time interval between mastering and subsequent production measurements. An experimental study is conducted on a vertical milling centre using non-intrusive sensing. Gaussian Process Regression (GPR) is employed to model Coordinate Measuring Machine (CMM) measured diameter deviations and the associated uncertainty. OMCM is implemented, and the effect of remastering is discussed. The results demonstrate that measurement accuracy deteriorates when remastering is not performed prior to significant system drift, whereas timely remastering improves accuracy and reduces uncertainty, highlighting the critical role of remastering in maintaining measurement reliability with OMCM.

Molecular dynamics simulation of high slip flow of water confined between graphene nanochannels at experimentally accessible shear rates

2026-08-15T06:52:17Z

Title: Molecular dynamics simulation of high slip flow of water confined between graphene nanochannels at experimentally accessible shear rates Authors: Civello, Carmelo Riccardo; Maffioli, Luca; Smith, Edward R; Ewen, James P; Daivis, Peter J; Dini, Daniele; Todd, BD Abstract: The transient time correlation function (TTCF) method has emerged as a powerful methodology for accurately probing systems at low shear rates. In the present study, TTCF was used to evaluate the shear rate dependence of the slip length in a high-slip system consisting of water confined between graphene walls at experimentally accessible shear rates, for which classical nonequilibrium molecular dynamics (NEMD) is unfeasible. The corresponding Navier friction coefficient was computed for all shear rates spanning six orders of magnitude and compared with the equilibrium limit. We report for the first time NEMD results obtained at experimentally accessible shear rates using the TTCF approach for a system that has attracted significant interest over the past decades. The slip length calculated with TTCF is in good agreement with previous equilibrium molecular dynamics simulations and experiments. Our aim here is to highlight the extraordinary power of TTCF, particularly for high-slip (low effective shear rate) systems, and to verify that equilibrium methods directly match NEMD measurements at experimentally accessible shear rates. Description: Data Availability: The data that support the findings of this study are available within the article and its supplementary material: https://ndownloader.figstatic.com/files/65223213 .