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This experimental study investigated the influence of different turbine guide vane parameters on the ignition limit and light-round processes in a triple-dome combustor. It was found that for the triple-dome combustor, the minimum fuel/air ratios at the ignition limit all show a trend of initial decrease followed by subsequent increase with the growth of incoming air mass flow rate. The ignition fuel/air ratio decreases with the increase in turbine blockage ratio, and the optimal scheme is achieved with a blockage ratio of 0.8. Under the condition where the incoming air mass flow rate is 0.089 kg/s, the light-round time decreases with the increase in fuel/air ratio, and the light-round time of the combustor without guide vanes is shorter than that of the other schemes. With the increase in incoming air mass flow rate, the light-round time of the schemes with guide vanes is shortened. Under the same incoming air mass flow rate and fuel/air ratio, the increase in the blockage ratio will lead to an increase in the light-round time of the triple-dome combustor. [ABSTRACT FROM AUTHOR]

During the warm months of the year in Catalonia, the marine air overcomes the coastal mountain range and reaches the eastern Ebro sub-basin. This phenomenon is called marinada and has recently been thoroughly characterized for the first time by , based on surface climatological data. However, the main physical mechanisms involved in its arrival and propagation remain to be discovered. This study aims to understand how the marinada is formed and how it interacts with the already developed atmospheric boundary layer. Surface and atmospheric observations are used in combination with the coupled surface–atmosphere model Meso-NH to reveal the mechanisms at play. It is shown that the marinada is generated by the advection of a cool marine air mass over the Catalan Pre-coastal Range by the action of the sea breeze and the upslope wind. This marine air mass then flows into the Ebro basin, creating what is known as the marinada. The characteristics and dynamics of the marinada allow it to be classified as a fall wind. It is also shown that the arrival, propagation and decay of the marinada is strongly dependent on the larger-scale weather situation: westerlies or thermal low. The current study provides a consistent framework for understanding the marinada, paving the way for better modeling and prediction of the phenomenon. [ABSTRACT FROM AUTHOR]

This research focuses on the analysis of vibration of a compression ignition engine (CIE), specifically examining potential failures in the Fuel Rail Pressure (FRP) and Mass Air Flow (MAF) sensors, which are critical to combustion control. In line with current trends in mechanical system condition monitoring, we are incorporating information from these sensors to monitor engine health. This research proposes a method to validate the correct functioning of these sensors by analysing vibration signals from the engine. The effectiveness of the proposal is confirmed using real data from a Common Rail Direct Injection (CRDi) engine. Simulations using a GT 508 pressure simulator mimic FRP sensor failures and an adjustable potentiometer manipulates the MAF sensor signal. Vibration data from the engine are processed in MATLAB using frequency domain techniques to investigate the vibration response. The results show that the proposal provides a basis for an efficient predictive maintenance strategy for the MEC engine. The early detection of FRP and MAF sensor problems through a vibration analysis improves engine performance and reliability, minimizing downtime and repair costs. This research contributes to the advancement of monitoring and diagnostic techniques in mechanical engines, thereby improving their efficiency and durability. [ABSTRACT FROM AUTHOR]

As a device for cooling charged air before it enters the cylinder, the intercooler is an indispensable part of the regular operation of a booster diesel engine. To solve the problem of the insufficient cooling performance of an intercooler for a high-power supercharged diesel engine, in this study, the flow field in the intercooler is simulated using the computational fluid dynamics (CFD) model of porous media, and the performance data measured using the steady flow test bench are used to provide boundary conditions for the calculation. The effects of the charged air mass flow rate and the tube bundle's transverse spacing on the heat dissipation performance of the intercooler are analyzed and compared. The calculation results show that, under the condition of satisfying the regular operation of the diesel engine, the heat transfer coefficient of the intercooler heat dissipation belt increases with the increase in air mass flow and the spacing of cooling pipes, and the heat transfer coefficient can be increased by up to 57%. Still, excessive spacing of the cooling water pipes increases pressure loss in the charged air. Finally, the transverse spacing of the tube bundle is set to 17 mm, ensuring the pressure drop in the charged air, and the heat dissipation performance of the intercooler is increased by 6.04%. This paper provides a feasible solution for further optimizing the heat dissipation performance of intercoolers. Finally, grey correlation theory is used to study the correlation between air mass flow, cooling water pipe spacing, and intercooler heat dissipation performance. The correlation values are 0.8464 and 0.8497, respectively, indicating a significant relationship between air mass flow, cooling water pipe spacing, and intercooler heat dissipation performance. [ABSTRACT FROM AUTHOR]

The air compressor holds paramount importance due to its significant energy consumption when compared to other Balance of Plant components of polymer electrolyte membrane (PEM) fuel cells. The air supply system, in turn, plays a critical role in ensuring the stable and efficient operation of the entire fuel cell system. To enhance system efficiency, the impact of varying the stoichiometric ratio of air and air pressure was observed. This investigation was carried out under real loading conditions, replicating the conditions experienced by the power module when fuel cells are in use within a forklift. The air compressor can be operated at different pressure and excess air ratios, which in turn influence both the fuel cell's performance and the overall efficiency of the power module system. Our research focused on assessing the performance of PEM fuel cells under different load cycles, adhering to the VDI60 requirements for forklift applications. This comprehensive examination encompassed the system's minimum and maximum load scenarios, with the primary goal of optimizing excess air and pressure ratio parameters, especially under dynamic load conditions. The results revealed that higher air pressures and lower excess air ratios were conducive to increasing system efficiency, shedding light on potential avenues for enhancing the performance of PEM fuel cell systems in forklift applications. [ABSTRACT FROM AUTHOR]

Methane (CH 4) was measured at El Arenosillo observatory, in an Atlantic coastal area located in Southwestern Europe, throughout a four-year period (September 2019–December 2023). Short-term trend, temporal variations and patterns were explored. A trend of 12.1 ± 1.1 nmol mol−1 year−1 was obtained based on daily averages. CH 4 exhibited its highest mole fraction in cold months and its lowest in summer, and a seasonally varying diurnal cycle was also observed, with peaks in the early morning (7:00–8:00 UTC) and minimum values at 18:00–19:00 UTC. Mitigation strategies should be implemented based on an understanding of CH 4 patterns. To achieve this, CH 4 variations under an atmosphere governed by two synoptic patterns were studied. The atmospheric dynamic was analysed with the wind fields from ERA5 data reanalysis and the air masses pathways with the back-trajectories computed with the HYSPLIT model. CH 4 horizontal distribution was explored with the TROPOMI observations. The CH 4 baseline was collected under the influence of Atlantic air, while a rise from 40 to 80 nmol mol−1 was found with continental airflows from the inland Guadalquivir Valley. CH 4 under sea-land breezes did not contribute to the increase of CH 4. However, XCH 4 from TROPOMI showed an accumulation in the marine area of the Gulf of Cadiz. Ongoing CH 4 observations will be used to identify potential changes in the trend, understand the contribution of transported CH 4 from areas such as the Western Mediterranean Basin, or assess its impact on surface ozone, among other objectives. • Methane (CH 4) was measured over a four-year period in Southwestern Europe. • The potential regional sources emitting CH 4 were identified. • A short-term trend of 12.1 ± 1.2 nmol mol−1 year−1 was obtained. • CH 4 is modulated by weather patterns with the baseline under Atlantic air. • Mesoscale processes led to the accumulation of XCH 4 in the marine area. [ABSTRACT FROM AUTHOR]

The focus of this study is to explore the thermodynamic characteristics of an intermediate heat-exchange cycle (IHEC) system in aero engines, employing experimental analysis. Using air, fuel, and intermediate working fluid (IWF) as working mediums, an IHEC system experimental platform incorporated two heat exchangers (HEX) was established. A theoretical analysis model for characteristics of the IHEC system was developed using the heat current method and a novel method for estimating the overall heat transfer coefficient (K). Deviations between experimental and simulation results for system equilibrium heat transfer rates and temperatures at each node of the IHEC system are within ±10%, and the maximum average relative deviation of the proposed method for estimating K is −7.93%. Detailed analyses have been conducted regarding the effects of fuel mass flow rate, IWF mass flow rate, air mass flow rate, and air inlet temperature on the system. Raising the fuel mass flow rate leads to reduced temperatures at each system node, while the system's equilibrium heat transfer rate initially increases and then stabilizes. Variations in IWF mass flow rate have complex impacts on the IHEC system, influenced by HEX design margins and heat transfer capacities. Tailored analyses are necessary based on specific circumstances. • A theoretical analysis model for system-level characteristics of the IHEC system was developed. • A two-stage heat exchanger combined IHEC system experimental platform was established. • Different parameter's effects on systematic thermodynamic performance have been conducted. • The accuracy of the mathematical model was verified by experiments. [ABSTRACT FROM AUTHOR]

A model for the approximation of cavitation-induced air release in three-dimensional flow simulations is proposed. A cavitating orifice flow is investigated. It is assumed that vapor vanishes in the proximity of the orifice, and bubbles further downstream consist essentially of air. The model is based on a homogeneous mixture assumption and comprises one main parameter, which needs to be adjusted to the experimentally measured degassing fraction. Experimental validation is based on transmission light images downstream of the orifice. In the proximity of the orifice, the inclusion of air release in the CFD simulation yields a better agreement to experimentally measured cavitation intensity than the consideration of pure vapor only. It is concluded that a considerably larger amount of air is released than is dissolved in the evaporated amount of liquid. The simulation results suggest that the released air mass corresponds to about 1% of the evaporated liquid mass. These observations may be a good basis for purposeful future experiments, which are indispensable for the development of a more predictive approach of cavitation-induced air release in 3D CFD methods. [Display omitted] • A compressible solver for cavitating flow is extended by air release. • Air release is modeled by a homogeneous mixture approach. • Inclusion of released air improves the match to shadowgraphy data. • Mass of released air equals about 1% of evaporated liquid mass. [ABSTRACT FROM AUTHOR]

Effusion cooling has been extensively employed in the liner thermal protection of modern combustors, however, its performance in swirling flow fields remains to be thoroughly investigated. This research aims to reveal insights into the effusion cooling characteristic across various swirl numbers (S N = 0∼1.21) and average blowing ratios (M ‾ = 1.2–8.9) based on experimental and numerical approaches. Furthermore, semi-empirical engineering function equations for the area-weighted average cooling efficiency were compiled. The results show that inhomogeneity of the near-wall flow obstructs local effusion outflow, especially in the countercurrent side of the impingement zone, resulting in incremental flow heat transfer and disability in forming a cooling film. The increment of S N from 0.49 to 1.21 recedes the undermost level of conjugate cooling efficiency by an average of about 0.13, progressively impairs the cooling of the leading edge, and begets an ante displacement of the poorest cooling position from 0.43 to 0.31 (ratio of flow wise direction coordinate distance to flame tube dome height). Higher cooling air volume effectively strengthens the coolant effluent capacity to offer a more uniform distribution of cold air under swirl flow, and the overall conjugate cooling efficiency is enhanced by about 0.34 when M ‾ increases from 1.2 to 8.9. • Analysis conjugate cooling efficiency of effusion cooling across a wide swirl number and average blowing ratio margin range. • Analysis the feature of the effusion outflow by summarizing the cooling air mass flow rate ratio of single perforation row. • Partition the wall of the flame tube based on dimensionless pressure in the streamwise direction. • Fit semi-empirical engineering function equations for the average conjugate cooling efficiency of diverse zoned liners. [ABSTRACT FROM AUTHOR]