Rate Of Rise Research Articles

Decadal Trends in Surface Elevation and Tree Growth in Coastal Wetlands of Moreton Bay, Queensland, Australia

Coastal wetlands surrounding urban environments provide many important ecosystem services including protection from coastal erosion, soil carbon sequestration and habitat for marine and terrestrial fauna. Their persistence with sea-level rise depends upon their capacity to increase their soil surface elevation at a rate comparable to the rate of sea-level rise. Both sediment and organic matter from plant growth contribute to gains in soil surface elevation, but the importance of these components varies among sites and with variation in climate over long time scales, for which monitoring is seldom available. Here, we analysed variation in surface elevation, surface accretion and mangrove tree growth over 15 years in Moreton Bay, Queensland, Australia, a period that spans variation in the El Niño/La Niña (ENSO) cycle, which strongly influences rainfall and sea level in the region. Piecewise structural equation models were used to assess the effects of biotic (tree growth, plant cover and bioturbation by invertebrates) and environmental factors on annual surface elevation increments throughout this period. Our model for mangroves identified that surface accretion and tree growth were both positively influenced by rainfall, but surface elevation was not, and thus, higher levels of compaction of the soil profile in high rainfall/high sea level years were inferred. In contrast, our saltmarsh model found that rainfall positively influenced surface accretion and elevation gains. Declines in surface elevation in the mangroves were influenced by the species composition of the mangrove, with higher levels of elevation loss occurring in mangrove forests dominated by Avicennia marina compared to those with a higher proportion of Rhizophora stylosa. Decadal-scale variation in ENSO affected mangrove tree growth, but surface elevation trends were more strongly influenced by variation in environmental conditions than by tree growth, although effects of biotic factors (mangrove species composition and bioturbation) on surface elevation trends were observed. Further research into tipping points with extreme ENSO events (either La Niña with high rainfall and high sea level or El Niño with low rainfall and low sea levels) will help clarify the future of mangrove and saltmarsh distribution within Moreton Bay.

Conversion of a Small-Size Passenger Car to Hydrogen Fueling: 0D/1D Simulation of EGR and Related Flow Limitations

Hydrogen is seen as a prime choice for complete replacement of gasoline so as to achieve zero-emissions energy and mobility. Combining the use of this alternative fuel with a circular economy approach for giving new life to the existing fleet of passenger cars ensures further benefits in terms of cost competitiveness. Transforming spark ignition (SI) engines to H2 power requires relatively minor changes and limited added components. Within this framework, the conversion of a small-size passenger car to hydrogen fueling was evaluated based on 0D/1D simulation. One of the methods to improve efficiency is to apply exhaust gas recirculation (EGR), which also lowers NOx emissions. Therefore, the previous version of the quasi-dimensional model was modified to include EGR and its effects on combustion. A dedicated laminar flame speed model was implemented for the specific properties of hydrogen, and a purpose-built sub-routine was implemented to correctly model the effects of residual gas at the start of combustion. Simulations were performed in several operating points representative of urban and highway driving. One of the main conclusions was that high-pressure recirculation was severely limited by the minimum flow requirements of the compressor. Low-pressure EGR ensured wider applicability and significant improvement of efficiency, especially during partial-load operation specific to urban use. Another benefit of recirculation was that pressure rise rates were predicted to be more contained and closer to the values expected for gasoline fueling. This was possible due to the high tolerance of H2 to the presence of residual gas.

Features of arterial pressure dynamics according to results of blood pressure monitoring in elderly patients

All over the world, special attention is paid to cardiovascular diseases in patients. According to epidemiological studies, a large contribution to mortality from them is high blood pressure, effective normalization of blood pressure will lead to an increase in life expectancy. The purpose of the study: to study the features of the daily blood pressure profile in elderly patients with hypertension. It was revealed that hypertension in elderly patients is more severe and has significantly higher rates of rise in systolic and diastolic pressure during the day and night hours, high variability, and insufficient (non-dipper) night-time decrease in blood pressure.Therefore, sick groups have a high risk of developing target organ damage, which is a predictor of the development of cardiovascular complications.

Investigating the influence of varying split injection profiles on stability of diesel engine operated under partially premixed mode with methanol

The present study explores the prospects of operational stability of dual fuel operation comprehensively, considering that; methanol and diesel are of two different kinds which exhibit different combustion processes. To this effect, investigating the stability of engine operation under such condition becomes important. In this investigation, the harshness of the operation and the non-repeatability of the combustion cycles are examined, which have been identified as the major stability indicator in many studies. Such stability indices are characterized in this study through a comprehensive set of parameters, including of maximum pressure rise rate (ROPRmax) and coefficient of variation of indicated mean effective pressure (COVIMEP); and of peak pressure (COVPP) and crank angle of 50% mass fraction burn (COVCA50). The experimental investigation is carried out under a split injection strategy by varying injection timings as well as injection mass percentages at predefined methanol injection durations. It is shown that the partially premixed mode under the split injection strategy exhibits significant potential in reducing the harshness of operation indicated by lower peak pressure rise and increasing the repeatability of the combustion cycles implied by the substantially lower scores of the considered parameters for mapping stability.

Machine Learning-Based Modeling and Predictive Control of Combustion Phasing and Load in a Dual-Fuel Low-Temperature Combustion Engine

<div>Reactivity-controlled compression ignition (RCCI) engine is an innovative dual-fuel strategy, which uses two fuels with different reactivity and physical properties to achieve low-temperature combustion, resulting in reduced emissions of oxides of nitrogen (NO<sub>x</sub>), particulate matter, and improved fuel efficiency at part-load engine operating conditions compared to conventional diesel engines. However, RCCI operation at high loads poses challenges due to the premixed nature of RCCI combustion. Furthermore, precise controls of indicated mean effective pressure (IMEP) and CA50 combustion phasing (crank angle corresponding to 50% of cumulative heat release) are crucial for drivability, fuel conversion efficiency, and combustion stability of an RCCI engine. Real-time manipulation of fuel injection timing and premix ratio (PR) can maintain optimal combustion conditions to track the desired load and combustion phasing while keeping maximum pressure rise rate (MPRR) within acceptable limits.</div> <div>In this study, a model-based controller was developed to track CA50 and IMEP accurately while limiting MPRR below a specified threshold in an RCCI engine. The research workflow involved development of an imitative dynamic RCCI engine model using a data-driven approach, which provided reliable measured state feedback during closed-loop simulations. The model exhibited high prediction accuracy, with an <i>R</i><sup>2</sup> score exceeding 0.91 for all the features of interest. A linear parameter-varying state space (LPV-SS) model based on least squares support vector machines (LS-SVM) was developed and integrated into the model predictive controller (MPC). The controller parameters were optimized using genetic algorithm and closed-loop simulations were performed to assess the MPC’s performance. The results demonstrated the controller’s effectiveness in tracking CA50 and IMEP, with mean average errors (MAE) of 0.89 crank angle degree (CAD) and 46 kPa and Mean absolute percentage error (MAPE) of 9.7% and 7.1%, respectively, while effectively limiting MPRR below of 10 bar/CAD. This comprehensive evaluation showcased the efficacy of the model-based control approach in tracking CA50 and IMEP while constraining MPRR in the dual-fuel engine.</div>

Ubiquitous acceleration in Greenland Ice Sheet calving from 1985 to 2022.

Nearly every glacier in Greenland has thinned or retreated over the past few decades1-4, leading to glacier acceleration, increased rates of sea-level rise and climate impacts around the globe5-9. To understand how calving-front retreat has affected the ice-mass balance of Greenland, we combine 236,328 manually derived and AI-derived observations of glacier terminus positions collected from 1985 to 2022 and generate a 120-m-resolution mask defining the ice-sheet extent every month for nearly four decades. Here we show that, since 1985, the Greenland Ice Sheet (GrIS) has lost 5,091 ± 72 km2 of area, corresponding to 1,034 ± 120 Gt of ice lost to retreat. Our results indicate that, by neglecting calving-front retreat, current consensus estimates of ice-sheet mass balance4,9 have underestimated recent mass loss from Greenland by as much as 20%. The mass loss we report has had minimal direct impact on global sea level but is sufficient to affect ocean circulation and the distribution of heat energy around the globe10-12. On seasonal timescales, Greenland loses 193 ± 25 km2 (63 ± 6 Gt) of ice to retreat each year from a maximum extent in May to a minimum between September and October. We find that multidecadal retreat is highly correlated with the magnitude of seasonal advance and retreat of each glacier, meaning that terminus-position variability on seasonal timescales can serve as an indicator of glacier sensitivity to longer-term climate change.

Experimental Study of Energy Design Optimization for Underwater Electrical Shockwave for Fracturing Applications

Underwater electrical shockwave can be used as a waterless, chemical-free, and environmentally friendly fracturing technique. A detailed experimental study was performed to develop a correlation between the optimum energy required to generate a shockwave that could be used in fracturing rock samples with the wire weight and diameter as independent factors. In addition, the effect of the water volume on the Underwater Electrical Wire Explosion (UEWE) was investigated to quantify the effect of the wellbore fluid volume in the fracturing process. The effect of increasing the discharge energy on the current waveform rising rate, peak amplitude, and fracturing geometry was investigated. A baseline for implementing the shockwave fracturing method on cement and limestone samples was defined to be used in future work. The results show that the water volume has a significant effect on the results of the experiment. A correlation was developed that defined the optimum minimum energy required to burn a certain wire weight with consideration to the wire diameter. Using the optimum required energy or higher will increases the current peak amplitude with the same current waveform rise rate, which leads to higher energy deposition into the wire and prevents the premature breakdown of the wire. The generated shockwave was used to successfully fracture cement and limestone cubic samples.

Responses of Coastal Wetlands to Rising Sea-Level Revisited: The Importance of Organic Production

A network of 15 Surface Elevation Tables (SETs) at North Inlet estuary, South Carolina, has been monitored on annual or monthly time scales beginning from 1990 to 1996 and continuing through 2022. Of 73 time series in control plots, 12 had elevation gains equal to or exceeding the local rate of sea-level rise (SLR, 0.34 cm/year). Rising marsh elevation in North Inlet is dominated by organic production and, we hypothesize, is proportional to net ecosystem production. The rate of elevation gain was 0.47 cm/year in plots experimentally fertilized for 10 years with N&P compared to nearby control plots that have gained 0.1 cm/year in 26 years. The excess gains and losses of elevation in fertilized plots were accounted for by changes in belowground biomass and turnover. This is supported by bioassay experiments in marsh organs where at age 2 the belowground biomass of fertilized S. alterniflora plants was increasing by 1,994 g m−2 year−1, which added a growth premium of 2.4 cm/year to elevation gain. This was contrasted with the net belowground growth of 746 g m−2 year−1 in controls, which can add 0.89 cm/year to elevation. Root biomass density was greater in the fertilized bioassay treatments than in controls, plateauing at about 1,374 g m−2 and 472 g m−2, respectively. Growth of belowground biomass was dominated by rhizomes, which grew to 3,648 g m−2 in the fertilized treatments after 3 years and 1,439 g m−2 in the control treatments after 5 years. Depositional wetlands are limited by an exogenous supply of mineral sediment, whereas marshes like North Inlet could be classified as autonomous because they depend on in situ organic production to maintain elevation. Autonomous wetlands are more vulnerable to SLR because their elevation gains are constrained ultimately by photosynthetic efficiency.

Effect of gas crossover on the cold start process of proton exchange membrane fuel cells

This study develops a transient three-dimensional model to investigate the effect of reactant gas crossover through the membrane on the cold start process of PEM fuel cells. Key operating and structure parameters such as current density, anode/cathode inlet pressure, and membrane thickness are explored. The results reveal that gas crossover enhances ice formation rate and cell temperature rise due to additional hydrogen–oxygen side reactions, increasing both heat and water generations. The dominance of the ice formation rate over the temperature rise rate by gas crossover adds complexity to successful cold starts. Notably, the influence of gas crossover is more pronounced at a lower current density. As the operating current density increases from 0.04 A cm−2 to 0.12 A cm−2, the contribution of gas crossover to the temperature rise rate and ice formation rate decrease from 31.6 % to 11.3 % and from 54.5 % to 16.8 %, respectively. The increase of anode inlet pressure accelerates ice formation and temperature rise, whereas cathode inlet pressure has minimal effect. A thicker membrane mitigates gas crossover and is beneficial to cold start success, especially under a wet initial condition. This study emphasizes the significant role of gas crossover in the PEM fuel cell cold start process, highlighting the imperative consideration of gas crossover in both cold start models and strategy developments.

Study of deployment of Pre-Insertion resistor to disconnector for mitigating overvoltage on 525 kV current transformers

Because of the incidence of voltage pulse trains generated from intrinsic arcs existing during the operation of adjacent disconnectors, several failures in 550 kV class current transformers have been reported across the Brazilian integrated power grid. Based on previous correlated research, the authors present in this article computational results of their proposition in adopting the pre-insertion resistor-fitted disconnector type for addressing this issue, which is already indicated to be adopted in power substations with 800 kV or higher although for different reasons. With this aim, ATP modeling has been developed for analyzing a study case of a section of a bay of a 550 kV power substation. The obtained results indicate not only the drastic reduction in the overvoltage amplitude, in about 18 times less for the value of the Severity Factor, as well as in the significant reduction in both to one-third in the rate of the overvoltage rise and in the maximum amplitude of the current train pulses, which show this proposal to be technically promising. Yet, a study of the influence of the value of the pre-insertion resistor and the respectively adopted configuration is presented, based on what is commercially available in view of making this proposal to be economically viable.

Application of microencapsulated fibrous carrier inhibitors in suppressing flake aluminum dust explosion: Performance and mechanism

Flake aluminum powder (FAl), due to its larger specific surface area and higher reactivity, posing a potential threat to the process safety of involved enterprises. To mitigate the explosion caused during the production of FAl, a green composite inhibitor, Sep@CS@PA-Na, was successfully prepared in the aqueous phase using microencapsulation technology with sepiolite (Sep), chitosan (CS), and sodium phytate (PA-Na) as raw materials. The suppression of FAl explosions in a vertical combustion duct system by inhibitors with different inerting ratios (α) was investigated. The results showed that after adding Sep@CS@PA-Na with an α of 0.75, the maximum flame propagation velocity (Vmax), the average flame velocity (Vavg), and the velocity of the flame reaching the pipeline top (Vtop) decreased by 79.6%, 75.1%, and 86.2%, respectively, and the reduction of the maximum flame front pressure (Pmax) and the maximum flame pressure rise rate ((dP/dt)max) were 90.4% and 89.8%, respectively, and the peak temperature (Tp) dropped to 505°C. Combined with TG-DSC and explosion product analysis, Sep@CS@PA-Na possessed both gas-phase reaction and surface reaction suppression functions, which were mainly reflected in the dilution effect, quenching effect, and barrier effect. This work will provide technical support for the emergency prevention and control of energetic metal dust explosions.

Investigation of marginally explosible dusts

“Marginally explosible dusts (MEDs)” are a group of combustible dusts that are distinguished by relatively low volume-normalized maximum rate of pressure rise (KSt) and maximum explosion pressure (Pmax) values. Earlier studies have suggested that dusts with KSt values less than 45 bar m/s in the laboratory-scale 20-L chamber would not explode in the 1-m3 chamber and therefore not on an industrial scale. Conversely, for some metallic dusts, significantly higher KSt values are generated in the 1-m3 chamber. Industries that handle MEDs continue to search for answers to the questions “are they explosible or not?” and “should we protect or not protect against potential explosions of these dusts?“. To answer these questions, four well-characterized materials namely, carbon black, oat grain flour, urea, and zinc were tested in the current study. These materials were selected because they exhibit different combustion behaviors and also cover a range of industries. Five ignition energies (i.e., 0.5, 1, 2.5, 5, and 10 kJ) were used in the 20-L chamber tests. The results show a clear case of overdriving (as a result of the high ignition energy density in the 20-L chamber) with respect to urea and carbon black dusts. Nevertheless, the urea dust is non-explosible. The data also suggests that the choice of test chamber to generate suitable explosion data is strongly dictated by the combustion path of MEDs. However, there are exceptions. The study also establishes the importance of both chemico-physical and thermal analyses to understanding the explosion behavior of MEDs. With reference to urea dust, a new definition for MEDs has been suggested as dusts having Pmax < 3.0 bar(g), KSt < 20 bar m/s (in the 20-L chamber), MEC >1000 g/m3, MIE >1000 mJ, and MIT >600 °C. This work provides guidelines to industries that handle MEDs on the explosibility classification of these dusts, thus addressing the existing difficulty, and informing industry on the safety strategies required when handling this group of dusts.

Numerical investigation on turbulent flame jet characteristics of a pre-chamber fueled with CH4/O2 and CH4/NH3/O2 mixture under different initial pressures

Ammonia is a very potential carbon-free alternative fuel with extremely low reactivity. The application of ammonia in internal combustion engines faces the risks of ignition failure, low burning rate, and poor combustion stability. Pre-chamber turbulent jet ignition (TJI), which can provide much more ignition energy, is a promising method to ignite ammonia fuel. However, the transient propagation process of pre-chamber jet flame has not been fully investigated yet. In this paper, the propagation characteristic of methane jet flame was numerically studied based on a constant volume combustion system. The supersonic jet flame propagation and Mach disk phenomenon were further analyzed with numerical methods. And the propagation characteristic of methane/ammonia mixed jet flame was investigated. According to the results, the formation and propagation process of methane jet flame has different characteristics at different stages. In High-speed development stage (Stage II) and Low-speed oscillation development stage (Stage III), the penetration distance of flame jet tip is almost proportional to the penetration time. However, the penetration speed of the two stages is significantly different. The change trend of the jet velocity at the outlet of orifice hole can also be divided into four stages: slow increasing, rapid increasing, gradual decreasing, and periodic oscillation. The periodic oscillation of the jet tip velocity and the jet velocity at the outlet of orifice hole is caused by the effect of forward and reverse shock waves. The calculation results of CH4/NH3/O2 mixture jet flame show that the addition of ammonia has significant effects on the flame propagation process in PC, the thermodynamic state of PC, and the propagation characteristics of jet flame. With the increase of ammonia proportion, the maximum pressure of PC gradually decreases and the pressure rise rate slows down. Meanwhile, the two-stage (the high-speed development stage and the low-speed development stage) characteristic of jet propagation process gradually disappears. And the addition of ammonia is more likely to destroy the two-stage characteristic under low initial pressure.

Study on the prediction of high-speed rotary lip seal wear in aero-engine based on heat-fluid-solid coupling

PurposeThis paper aims to investigate the effect of frictional heat on the wear of high-speed rotary lip seals in engines.Design/methodology/approachIn this research paper, the authors focus on the high-speed rotating lip seal of aircraft engines. Using the hybrid lubrication theory, a thermal-fluid-solid coupled numerical simulation model is established to investigate the influence of parameters such as contact pressure distribution, temperature rise and leakage rate on the sealing performance under different operating conditions. By incorporating the Rhee wear theory and combining simulation results with experimental data, a method for predicting the wear of the rotating seal lip profile is proposed. Experimental validation is conducted using a high-speed rotating test rig.FindingsThe results indicate that as the speed increases, the rise in frictional heat leads to a decrease in the sealing performance of the lip seal contact region. The experimental results show a similar trend to the numerical simulation results, and considering the effect of frictional heat, the predicted wear of the lip seal profile aligns more closely with the actual wear curve. This highlights the importance of considering the influence of frictional heat in the analysis of rotating seal mechanisms.Originality/valueThis study provides a reference for the prediction of wear profiles of engine high-speed rotary lip seals.

Investigating the impact of n-heptane (C7H16) and nanoparticles (TiO2) on diesel-microalgae biodiesel blend in CI diesel engines.

Recent global challenges encompass profound environmental pollution and the depletion of finite fuel resources. In this study, the biodiesel used in the mixture was derived from Azolla pinnata microalgae oil through a trans-esterification reaction chosen for its high oil concentration. During the initial phase of the experiment, varying volumes of biodiesel (5%, 10%, and 15%) and n-heptane (5%, 10%, and 15%) were introduced to diesel to form a ternary fuel blend. The experimental outcome shows that an n-heptane and biodiesel mixture of 10% by volume would produce the best results. Next, experiments were carried out by incorporating 10, 40, and 80ppm titanium oxide (TiO2) nanoparticles (NPs) in a recommended ternary fuel blend. The experimental investigation showed that D80A10H10TNP40 (diesel 80% + biodiesel 10% + n-heptane 10% + TiO2 40ppm) caused a 7.21% increase in brake thermal efficiency (BTE) with a decrease in brake specific fuel consumption (BSFC) and brake specific energy consumption (BSEC) by 9.58% and 10%, respectively, compared to (diesel 80% + biodiesel 20%) D80A20. D80A10H10TNP40 exhibits lower emissions, with a significant reduction of 11.29% and 20.96% in carbon monoxide (CO) and unburnt hydrocarbons (UBHC), respectively. Nitrogen oxide (NOX) and smoke emissions were reduced by 3.3% and 11.13%, respectively, compared to D80A10H10. Furthermore, D80A10H10TNP40 demonstrated enhanced combustion properties, comprising a significant rise of 4.39% in-cylinder pressure (CP), 35.29% in heat release rate (HRR), and 25.05% in the rate of pressure rise (RPR). The findings of this investigation indicate that D80A10H10TNP40 exhibits enhanced efficiency, emission, and combustion properties compared to the D80A20 fuel.

Prediction model of buoyancy-driven flow rate in inclined tunnels with a localized buoyancy source: Emphasis on stratification effects

In inclined narrow and long spaces such as tunnels, the buoyancy-driven flow pattern and the resulting ventilation flow rate are different from those in enclosure-type buildings, because of their large length-to-width aspect ratios. In this paper, the buoyancy-driven flow rate induced by a localized heat source in inclined tunnels was investigated. Theoretical analysis and three series of experiments including non-isothermal or isothermal buoyancy sources, i.e., large-scale fire tests, brine-water tests and helium-air tests were performed. Two typical buoyant flow patterns were identified in the experiments, which are stratified and well-mixed patterns, respectively. Both the stratification pattern and the longitudinal decay rate of temperature rise were proved to be correlated with a dimensionless factor, η=B01/3ΔLsina/(g0′1/2H3/2), which is composed of characteristic parameters referring to both buoyancy source and geometrical configuration. The flow stratification results in stack effect attenuation and consequently ventilation flow rate reduction. A model for predicting the buoyancy-driven flow rate in such spaces was proposed, with special emphasis on the effects of stratification pattern. The predictions were validated with the experimental data, and the necessity for accounting for the stack effect attenuation caused by stratification was proved. The prediction model possesses an explicit expression and can thus provide a convenient tool for design calculations.

Machine learning approaches for identification of heat release shapes in a low temperature combustion engine for control applications

This paper presents the application of machine learning classification algorithms to identify and classify different heat release rate (HRR) shapes to control the combustion for an optimal multi-mode low-temperature combustion (LTC) engine operation. Low-temperature combustion engine produces low nitrogen oxides (NOx) and soot emissions and offers high thermal efficiency. But high in-cylinder pressure rise rates limit the operating range of the LTC engine. Therefore, it is imperative to control combustion in the LTC engine for safe operation. To this end, the HRR traces for over six hundred engine operating conditions are classified using supervised (i.e., Decision Tree, K-Nearest Neighbors (KNN), and Support Vector Machines (SVM)) and unsupervised (i.e., Kmeans clustering) machine learning approaches to segregate different combustion regimes based on HRR shape. Kmeans clustering was not successful in classifying the HRR shapes. Among different supervised machine learning techniques, SVM has proved to be the best method, having an overall classifier prediction accuracy of 92.4% for identifying the distinct shapes using normalized HRR data. In addition, three classifiers have been trained based on the combustion parameters and control inputs. These classifiers are then used as scheduling variables to develop predictive models. A model predictive control (MPC) framework is developed to control multi-mode LTC engine on cycle-to-cycle basis. The MPC framework achieved the simultaneous reference tracking of combustion phasing (CA50) and indicated mean effective pressure (IMEP) while constraining maximum pressure rise rate (MPRR) below 8 bar/CAD.

Changing climate yet healthy forest stand of Tsuga dumosa in temperate zone of central Nepal

Nepal Himalaya is experiencing a faster rate of temperature rise than the global average, and the temperature has altered the growth patterns and distribution of mountain trees. A dendrochronological study was conducted for Tsuga dumosa (D.Don) Eichler to analyze growth-climate relationship from the temperate forest of central Nepal. We developed 116 year-long tree ring width chronology spanning from 1905 to 2020 CE. The study area showed a significant increase in atmospheric temperature and a decrease in rainfall during the past 42 years. It is found that the spring season (March–May) climate is sensitive to the radial growth of T. dumosa. Ring width indices showed a substantial positive correlation with the minimum temperature of January, March, and June of the growth year. Conversely, a negative correlation was observed with the maximum temperature of the previous year's months (July, September, and November), March, and September of the current year, and rainfall during June and November. Basal Area Increment (BAI) trend is positive, indicating the forest is healthy despite the decline in the years 1942, 1978, and 1998. We conclude that the warming of the spring season (March–May), previous year's late growing season and moisture supply (precipitation) during June are critical to the radial growth of Tsuga dumosa in the region. However, responses from multiple species and their exposure to different climate regimes would ideally be required to make predictions on the growth climate relationships of forest trees.

Thermal Storage Performance of a Shell and Tube Phase Change Heat Storage Unit with Different Thermophysical Parameters of the Phase Change Material

The thermal storage performance of shell and tube phase change heat storage units is greatly influenced by the thermophysical parameters of the phase change material (PCM). Therefore, we use numerical simulations to examine how the thermal storage capability of shell and tube phase change heat storage units is affected by thermophysical parameters such as specific heat capacity, thermal conductivity, and latent heat of phase change. The findings indicate that while the rate of temperature increase and the rate of the PCM melting both slow down as specific heat capacity increases, the overall heat storage increases. Within the specified range of parameters, the average rate of heat storage increases by approximately 4% for every 50% increase in specific heat capacity. The PCM’s rate of temperature rise slows down and its overall heat storage capacity rises throughout the middle stage of the phase change heat storage process as the latent heat of phase change grows. The average heat storage rate increases by approximately 6% and 22% for every 50% increase in latent heat and thermal conductivity, respectively. Notably, when the thermal conductivity is enhanced by a factor of 1.5, the average heat storage rate experiences an almost 50% increase. The thermal conductivity of the PCM has a negligible impact on total heat storage. The choice and use of the PCM in shell and tube phase change heat storage heat exchangers has a theoretical and empirical foundation thanks to this work.

Experimental and numerical investigation of methane combustion in a HCCI engine under enriched oxygen conditions

The challenge in the energy transition lies in the intermittent nature of renewable energy, requiring the development of effective storage methods. E-fuels are considered a promising solution, with potential applications to Homogeneous Charge Compression Ignition (HCCI) engines known for their high thermal efficiency and low nitrogen oxide emissions. However, HCCI engines face limitations such as low power density and a narrow operating range. To overcome these issues, oxygen-enriched combustion is proposed, aiming at enhancing the mixture reactivity and expanding the operating range by decreasing the intake temperature. As the potential of the expansion of the operating range has never been investigated, we performed an experimental campaign using a methane-fuelled HCCI engine at variable oxygen fractions in the oxidizer. To further elucidate the effects of oxy-fuel combustion, we also performed a kinetic analysis of the reactions driving the combustion behaviour. It has been experimentally found that increasing the oxygen content in the mixture, up to 90%, has a significant potential to decrease the needed intake temperature (up to 70 °C) of the charge to keep the Maximum Pressure Rise Rate (MPRR) below the safety threshold of 8 bar/CAD. Despite the notable IMEP increase achieved, operating the engine at high oxygen content presents significant technical challenges. Therefore, to make HCCI engines competitive with other combustion modes, it is essential to combine oxygen enrichment with additional power density enhancement techniques. The kinetic analysis has highlighted that the mixture is less sensitive to intake temperature changes at higher oxygen percentages (above 50%) and that the rates of the main reactions involved in methane and OH consumption are highly enhanced by oxygen addition.