Efficiency Carbon Dioxide Research Articles

Crossover Management for Practical High Efficiency Carbon Dioxide Reduction

CO2 reduction is an important step in carbon capture, utilization, and storage (CCUS). The utilization of a membrane electrode assembly (MEA) with a gas diffusion electrode (GDE) realizes high current density CO2 reduction. However, most of the developed CO2 reduction catalysts suffer from low Faradaic efficiency when using a proton exchange membrane MEA, due to low local pH surrounding catalysts. Alternatively, with an anion exchange membrane MEA, CO2 reduction suffers from low conversion efficiency due to carbonate-bicarbonate crossover through the membrane to the anode. For continuously-running CO2 electrolyzers, the crossover of acids and cations results in low reduction efficiency and flooding of the GDE. We have designed and characterized an asymmetric membrane that prohibits carbonate-bicarbonate crossover, yet can maintain a high local pH surrounding the catalyst. The resulting MEA can achieve high Faradaic efficiency toward CO2 reduction using developed catalysts with near-zero CO2 crossover. When using oxygen evolution in the anode, we further developed an ion-blockage strategy to diminish the crossover of acids or cations during long-term operation, maintaining a relatively stable and suitable environment for CO2 reduction on GDE. The crossover management of carbonate, bicarbonate, protons and cations can lead to a long lifetime high-efficiency CO2 electrolyzer.

A critical review on synthesis and application aspect of venturing the thermophysical properties of hybrid nanofluid for enhanced heat transfer processes

Recently, nanofluids (NFs) have gathered significant attention among researchers due to their varied properties, which can be made per the requirements. NFs, created by infusing nanoparticles into a base-fluid, enhance their fundamental properties. A hybrid nanofluid (HNF) is a nanofluid (NF) containing different types of nanoparticles, and it is being studied for its customizable properties. Recently, researchers delved into the applications regarding HNFs, particularly in cases relating to heat transfer (HT). This study analyzes HNFs’ preparation methods and thermophysical properties, giving more importance to their applications in HT, including heat-exchange, solar thermal, and cooling systems. Considering stability, the two-step synthesis method is preferred over the single-step method. Multiple research efforts have led to the development of a fluid that possesses superior HT capabilities compared to the base-fluid. However, while bettering HT, an increase in volume concentration (VC) also raised challenges such as increased viscosity and pressure drop, particularly in porous media, necessitating additional pumping power. The use of turbulators and other configurations, along with HNF in systems like parabolic trough solar collectors (PTSCs), enhances solar thermal systems (STSs) by improving their HT capabilities. An advantageous use of EG-based multiwalled carbon nanotubes (MWCNTs) NF in solar collectors (SCs) is their ability to increase thermal efficiency and decrease carbon dioxide emissions, making them an attractive choice for use in SCs. Researchers face significant challenges in determining the ideal composition and concentration of nanoparticles in HNFs to attain optimal HT without causing excessive viscosity that could impede practical usability. Specifically, this study examines the distinctive thermophysical characteristics of HNFs that substantially improve their efficacy in HT applications.

Association of Sarcopenia and Oxygen Uptake Efficiency Slope in Male Patients With Heart Failure.

Sarcopenia, the loss of muscle mass and function, is a common comorbidity in patients with heart failure (HF). The skeletal muscle modulates the respiratory response during exercise. However, whether ventilatory behavior is affected by sarcopenia is still unknown. We enrolled 169 male patients with HF. Muscle strength was measured by a handgrip dynamometer. Body composition was measured with dual-energy X-ray absorptiometry. Sarcopenia was defined by handgrip strength <27 kg and appendicular lean mass divided by height squared (ALM/height 2 ) <7.0 kg/m 2 . Oxygen uptake efficiency slope (OUES), ventilation (VE), oxygen uptake (VO 2 ), and carbon dioxide output (VCO 2 ) were measured by a cardiopulmonary exercise test. Sarcopenia was identified in 29 patients (17%). At the first ventilatory threshold, VE/VO 2 (36.9±5.9 vs 32.7±6.5; P =.003) and VE/VCO 2 (39.8±7.2 vs 35.3±6.9; P =.004) were higher in patients with sarcopenia compared to those without sarcopenia. At the exercise peak, compared to patients without sarcopenia, patients with sarcopenia had lower OUES (1186±295 vs 1634±564; P <.001), relative VO 2 (16.2±5.0 vs 19.5±6.5 mL/kg/min; P =.01), and VE (47.3±10.1 vs 63.0±18.2L/min; P <.0001), while VE/VCO 2 (42.9±8.9 vs 38.7±8.4; P =.025) was increased. OUES was positively correlated with ALM/height 2 ( r =0.36; P <.0001) and handgrip strength ( r =0.31; P <.001). Hemoglobin (OR=1.149; 95% CI, 0.842-1.570; P =.038), ALM/height 2 (OR=2.166; 95% CI, 1.338-3.504; P =.002), and VO 2peak (OR=1.377; 95% CI, 1.218-1.557; P <.001) were independently associated with OUES adjusted by cofounders. Our results suggest that sarcopenia is related to impaired ventilatory response during exercise in patients with HF.

Improvement of Strength and Oxidation Resistance at High Temperature in AISI 4140 Steel by Micro-Alloying Chromium and Tungsten for Automotive Engine Applications

Increasing the operating temperature and pressure of an automotive engine and reducing its weight can improve fuel efficiency and lower carbon dioxide emissions. These can be achieved by changing the engine piston material from conventional aluminum alloy to high-strength heat- resistant steel. American Iron and Steel Institute 4140 modified steels (AISI 4140 Mod.s), which have improved strength, oxidation resistance, and wear resistance at high temperature were developed by adjusting the AISI 4140 alloy compositions and optimizing the heat treatment process for automotive engine applications. In this study, the effects of modifying alloy compositions on the microstructure, mechanical properties (both at room and high temperatures), and oxidation of AISI 4140 Mod.s were investigated. Effective grain refinement occurred due to the influence of high-temperature stable carbide forming elements such as Mo, and V. The bainite structure changed to martensite structure under the influence Cr and Ni. As the Cr and W contents increased, the oxidation resistance was improved, and the oxide layer thickness decreased after 10 hours exposure at 500°C. The AISI 4140 Mod. exhibited a 35% improvement in room temperature strength, 70% improvement in high-temperature strength, and 40% improvement in high-temperature oxidation resistance compared to conventional AISI 4140.

Hydrogen production system with near-zero carbon dioxide emissions enabled by complementary utilization of natural gas and electricity

The complementary utilization of different energy sources is a promising strategy for consuming excess electricity and improving system efficiency. In this study, complementary utilization of electricity and natural gas is proposed for a hydrogen production system based on chemical recuperation. The system uses electrolysis technology to convert excess electricity generated from intermittent and fluctuating renewable energy into green hydrogen. It also utilizes the by-product oxygen for oxy-fuel combustion to achieve near-zero carbon dioxide emissions after subsequent compression, transportation, and storage. The system uses natural gas for steam methane reforming to generate hydrogen. A portion of flue gas generated by the combustor is introduced into the reformer, replacing high-temperature steam for reforming with methane. In addition, the waste heat from the flue gas is introduced into the electrolysis cell to save electricity. Energy and exergy analyses of the proposed and reference systems were performed. The results revealed that the energy and exergy efficiencies of the proposed system are 81.20% and 73.29% at near-zero carbon dioxide emission, representing an improvement of 7.09 and 6.41 percentage points, respectively, compared to the reference system. It also appeared that 98.68% in situ oxygen consumption was achieved. The hydrogen mass flow generated by the proposed system is 33.83 kg/h, which is 8.78% higher than the 30.88 kg/h of the reference system. This study introduces a promising method for developing a hydrogen production system with high efficiency and near-zero carbon dioxide emissions.

Long term co-application of biochar and fertilizer could increase soybean yield under continuous cropping: insights from photosynthetic physiology.

Photosynthesis is the key to crop yield. The effect of biochar on photosynthetic physiology and soybean yield under continuous cropping is unclear. We conducted a long-term field experiment to investigate the effects of co-application of biochar and fertilizer (BCAF) on these parameters. Five treatments were established: F2 (fertilizer), B1F1 (3 t hm-2 biochar plus fertilizer), B1F2 (3 t hm-2 biochar plus reduced fertilizer), B2F1 (6 t hm-2 biochar plus fertilizer), and B2F2 (6 t hm-2 biochar plus reduced fertilizer). BCAF increased chlorophyll and leaf area, enhancing soybean photosynthesis. The net photosynthetic rate (Pn ), transpiration rate (Tr ), stomatal conductance (Gs ), water use efficiency (WUE) and intercellular carbon dioxide (CO2 ) concentration (Ci ) were enhanced by BCAF. In addition, BCAF improved soybean photosystem II (PSII) photosynthetic performance, driving force, potential photochemical efficiency (Fv /F0 ), and quantum yield of electron transfer (φE0 ). Furthermore, BCAF enhanced the accumulation of photosynthetic products, such as soluble proteins, soluble sugars and sucrose content, resulting in higher leaf dry weight. Consequently, BCAF increased the soybean yield, with the highest increase of 41.54% in B2F1. The correlation analysis revealed positive relationships between soybean yield and chlorophyll, leaf area, maximal quantum yield of PSII (Fv /Fm ), electron transport flux per cross-section at t = 0 (ET0 /CS0 ), trapped energy flux per cross-section at t = 0 (TR0 /CS0 ), composite blade driving force (DFTotal ), and leaf dry weight. We demonstrated that long-term BCAF enhances soybean photosynthesis under continuous planting, reduces fertilizer use and increases yield. This study reveals a novel way and theory to sustainably increase soybean productivity. © 2023 Society of Chemical Industry.

Effect of Alkali and Alkaline Earth Metallic Species on Gas Evolution and Energy Efficiency Evolution in Pyrolysis and CO2-Assisted Gasification

Abstract In this study, the same moles of alkali and alkaline earth metallic species were introduced into pine wood to investigate their effects on biomass pyrolysis and carbon dioxide-assisted gasification. First, thermogravimetric analysis was conducted to examine the pyrolytic behavior of pine wood loaded with alkali and alkaline earth metallic species. A semi-batch fixed bed platform was used to quantify gaseous product parameters, including gas mass flowrate, gas yield, recovered energy, energy efficiency, and net carbon dioxide consumption. Thermogravimetric results indicated that the loading of alkali and alkaline earth metallic species promoted the thermal decomposition of pine wood at low temperatures, but an inhibitory effect was observed at high temperatures. In terms of pyrolysis, adding alkaline earth metals increased syngas yields, and recovered energy, as well as energy efficiency, whereas alkali metals had the opposite effect. For the gasification, the loading of alkali metals showed a stronger catalytic than the pine wood loaded with alkaline earth metals. Based on the evolution of carbon monoxide, the effects of alkali and alkaline earth metallic species on enhancing the biochar's gasification reactivity were in the sequence of sodium &amp;gt; potassium &amp;gt; calcium &amp;gt; magnesium. In addition, the addition of alkali metals exhibited a stronger capacity for carbon dioxide consumption, which contributed to the management of the greenhouse gas. Considering only energy efficiency, adding alkaline earth metals in biomass pyrolysis is an optimal choice due to the higher overall energy efficiency obtained in less time.

Performance optimization of solid oxide electrolysis cell for syngas production by high temperature co-electrolysis via differential evolution algorithm with practical constraints

Co-electrolysis of water and carbon dioxide using solid oxide electrolysis cell combined with the catalytic reactor to produce renewable synthesis fuel is considered as a promising strategy for carbon dioxide utilization. However, in order to achieve a target product with a remarkable system-level efficiency, a certain proportion of carbon monoxide and hydrogen from solid oxide electrolysis cell must be sent to the catalytic reactor directly, which imposes practical constraints on the solid oxide electrolysis cell performance. Take this constraint into consideration, we proposed a performance design methodology that enables a rapid and effective optimization of the solid oxide electrolysis cell operating conditions. Firstly, a physical model is developed by integrating chemical equilibrium, electrochemistry, and energy conservation involved in the solid oxide electrolysis cell. Secondly, a physical model is utilized to generate a dataset for the development of neural network model and optimization algorithm. This approach allows for the efficient determination of optimal conditions while considering practical constraints. In the case study, under the constraint that the desired fuel is a long carbon chain fuel with a carbon dioxide conversion rate ranging from 80 % to 90 %, the highest efficiency achieved by the solid oxide electrolysis cell is optimized to 66.75 %. Moreover, this approach is extended to other two target fuels (dimethyl ether and methane) under different carbon dioxide conversion rate, and the optimal performance is designed. According to the results, there is a trade-off between high efficiency and high carbon dioxide conversion rate, as the low carbon dioxide conversion rate often leads to higher efficiency. This method allows for flexible design of operating conditions to meet different fuel requirements and guide practical applications.

Establishment and effectiveness evaluation of pre-test probability model of coronary heart disease combined with cardiopulmonary exercise test indexes

To establish a pre-test probability model of coronary heart disease (CHD) combined with cardiopulmonary exercise test (CPET) indexes and to compare the clinical effectiveness with Duke clinical score (DCS) and updated Diamond-Forrester model (UDFM), thus further explore the predictive value. 342 cases were used to establish the prediction model equation and another 80 cases were used to verify the effectiveness. The patients were divided into CHD group (n = 157) and non-CHD group (n = 185) according to coronary artery stenosis degree >50% or not. Combining DCS and UDFM as reference models with CPET indexes, a multivariate logistic regression model was established. The area under the ROC curve of the three models were calculated to compare the predictive effectiveness. There were significant differences in gender, chest pain type, myocardial infarction history, hypertension history, smoking, pathological Q wave and ST-T change between two groups (P < 0.01), as well as age, LVEF, heart rate at anaerobic domain, peak oxygen uptake in kilograms of body weight, percentage of peak oxygen uptake to the predicted value, the oxygen uptake efficiency slope and carbon dioxide ventilation equivalent slope (P < 0.05). Multivariate analysis showed gender, age, chest pain type, myocardial infarction history, hypertension history, smoking, pathological Q wave, ST-T change, and peak oxygen pulse were independent risk factors of CHD. The pre-test probability model of CHD combined with CPET indexes has good distinguish and calibrate ability, its prediction accuracy is slightly better than DCS and UDFM, which still needs to be verified externally in more samples.

Techno-Economic Analysis of Electrochemical Refineries Using Solid Oxide Cells for Oxidative Coupling of Methane

With the shift away from fossil resources, there is a need for alternative pathways to carbon-based commodities such as ethylene. The electrochemical oxidative coupling of methane (OCM) enables the synthesis of higher hydrocarbons from simple organic molecules i.e., methane and has the potential to replace conventional ethylene production in the future. However, current solid oxide OCM cell development is still in an early stage and more comprehensive system-level analyses are needed to better understand operating conditions and economics to guide research and development. For this purpose, process models and new integration strategies for the electrochemical OCM process were developed. The integration of the electrochemical OCM unit into the plant revealed to be challenging based on current solid oxide cell designs and will be discussed as part of this presentation. The performance of the OCM plant is benchmarked against current state-of-the-art ethane steam cracker plants. In this context, key performance metrics are efficiency, direct and indirect carbon dioxide emissions, power consumption, plant cost and cost of ethylene. Of particular interest are aspects of hydrogen co-production and carbon dioxide utilization as well as the impact of carbon dioxide emission factors from the grid, which have shown to be of particular importance for electrochemical processes. Moreover, critical aspects of heat integration will be discussed including fuel pre-heating, carbon deposition and thermal cell management. The analysis will provide new insights into economic cost driving factors and the impact of cell cost, current density, overpotentials and Faraday efficiency upon the cost of ethylene. Based upon this information, performance targets will be recommended that will allow electrochemical OCM to become economically competitive in a free market environment.

Gas turbine-based system taking advantage of LNG regasification process for multigeneration purposes; Techno-economic-environmental analysis and machine learning optimization

It is viable for engineers to determine how thermodynamic systems can benefit from heat recovery in order to improve efficiency, reduce costs, and lower carbon dioxide emissions. The authors of the study propose a new energy system that incorporates various cycles and units, including gas turbines, Rankine and two organic Rankine cycles, an absorption refrigeration unit, a proton exchange membrane (PEM) electrolyzer, and a liquefied natural gas (LNG) unit. The hydrogen produced is stored and transferred for use as fuel. The system was modeled and optimized using MATLAB programming software, with a parametric study and sensitivity analysis conducted before employing a genetic algorithm optimization to find the most suitable performance conditions. Modifying the compressor's pressure ratio within the range of 6–18 caused a shift in the cooling load, ranging from 45 to 36 MW. Nonetheless, these adjustments in pressure ratio yielded a reduction of 0.4 Cent/kWh in levelized cost of electricity (LCOE) and 0.15 $/kg in levelized cost of hydrogen (LCOH). In the base design mode, the total cost rate is 5715.3 $/h, the exergy efficiency is 39.03%, and the normalized CO2 emissions are 335.89 kg/GJ. However, the optimization results showed a reduced total cost rate of 1884.50 $/h, along with an improved exergy efficiency from 39.03% to 40.32% and a decrease in annual CO2 emissions from 211,000 metric tons to 175,000 metric tons. The implementation of artificial neural networks (ANN) has significantly decreased the time required for optimization from 47 h to just 16 min.

Performance analysis of multistage high‐temperature heat pump cycle

AbstractHigh‐temperature heat pumps (HTHPs) that can supply heat at temperatures at and above 200°C have the potential to increase energy efficiency and decrease carbon dioxide (CO2) emissions in industrial processes. In this study, three reversed Rankine cycles using water vapor (R‐718) as the working medium, with different intercooling strategies, were proposed and their performance has been investigated. The thermodynamic performance was estimated under different operating conditions, and the optimal pressure ratio (PR) between compression stages was found to be where both compressors had the same PR. The thermodynamic efficiency, φ, and exergy efficiency, ηexergy, were also analyzed at the optimum PR. The cycles that employed an intercooler between the first and second compression stages (IC cycles) showed higher φ and ηexergy values compared with the spray‐injection cycle. Among the IC cycles, the IC‐in cycle, with an inward flow direction of heat sink to the IC, demonstrated higher efficiency and deliverable temperature, Tsink out, than the spray‐injection and IC‐out cycles. To assess the practical impact of the HTHP cycles on industrial CO2 reduction, the PR for each stage was limited to 2.5. Theoretically, the IC‐in cycle could achieve a coefficient of performance of 5.86 with a Tsink out of 200°C or higher when Tevap and Tcond were at 90°C and 150°C, respectively. Additionally, the study demonstrated that the proposed HTHP system has the potential to reduce CO2 emissions by 8.1% in 2030 for industrial heat supply at temperature up to 200°C, by replacing existing industrial fossil boilers with high‐efficiency HTHP.

Flowable capacitive cathode for efficiency carbon dioxide reduction in photoelectrochemical cell

ABSTRACT Photoelectrochemical (PEC) Cell reduction carbon dioxide (CO2) is a promising avenue for converting CO2 into valuable products. In this work, a flowable electrode with a rotating impeller collector was proposed to enhance the efficiency of the carbon dioxide reduction reaction (CO2RR) in a photoelectrochemical system. Titanium carbide (Ti3C2), with its capacitive properties, serves as a catalyst and is fluidized in the cathode chamber. The frequent contact between the Ti3C2 catalysts and the rotating impeller collector extends the catalytic reaction throughout the catholyte and enhances the efficiency of CO2RR. The feasibility of the design was verified through suspension characterization, CO2 diffusion concentration measurement, capacitance characterization, and experimental factor analysis. The PEC with a flow electrode exhibits CO and CH4 production rates of 1.64 μmol g−1h −1and 9.62 μmol g−1h−1, respectively, which are 3.5 and 7.2 times higher than those of the fixed cathode. The Faradaic efficiency for CH4 reaches 92.4%. Moreover, the collision probability of the flow electrode is 17.7%, which is significantly higher than that of the conventional bubbling fluidized electrode. In addition, the capacitive properties of Ti3C2 particles favor the continuous CO2RR under open circuit conditions, which was verified by an EDS test of Na+. Finally, the operational mechanism of the PEC system is described.

Simulation and multi-aspect analysis of a novel waste heat recovery process for a power plant producing electricity, heating, desalinated water, liquefied carbon dioxide, and natural gas

This paper presents a novel multigeneration framework based on fossil fuels, which offers several advantages such as high thermodynamic efficiency, low electricity and liquid carbon dioxide (CO2) production costs, and significantly reduced pollutant emissions. The simulation was carried out using the Aspen HYSYS software. The thermodynamic analysis revealed that the process achieves a total exergy efficiency of 86 % and an energy efficiency of 31.36 %. The integrated system yields various products, including 597.6 kmol/h of liquid CO2, 3484 kmol/h of desalinated water, 17,600 kmol/h of natural gas for the trunk line, and 41742.1 kW of power. The analyses further demonstrated that the total exergy destruction in the process amounts to 118071 kW, with contributions from the HPGU, NHPGU, MNPGU, and CSLU units of 30.1 %, 22.23 %, 30.36 %, and 17.29 %, respectively. Regarding environmental impact, the analysis revealed that the indirect emissions from the process are negligible. When the CO2 recovery rate exceeds 99 %, the direct emission amounts to 153.72 kg/h, and the pollution intensity of the proposed scheme is 3.68 gCO2/kWhel, which is lower than that of other technologies. Additionally, the economic analysis indicated that the production costs of CO2 and electricity in the proposed process are 0.075 $/kgCO2 and 0.048 $/kWh, respectively.

Lightweight Design and Structural Analysis of a Wheel Rim Using Finite Element Method and Its Effect on Fuel Economy and Carbon Dioxide Emission

Wheel rims made of metal alloy considerably impact the vehicle’s overall weight. Consequently, employing alloys in the design of wheels results in higher fuel efficiency and lower carbon dioxide emissions. Weight reduction of vehicles also leads to better acceleration. Lightweight automotive design has been increasingly popular in recent years as a means of conserving energy and protecting the environment. The rim is an essential feature of the vehicle since it bears a substantial portion of its overall weight. A vehicle’s weight can be greatly reduced by using a lightweight rim. However, the impact of a lightweight rim on improved fuel economy and reduced carbon dioxide emissions has not been widely explored. In this study, a wheel rim has been designed, and a finite element model has been developed considering radial load, where tire pressure has also been considered. A practical experiment with identical parameters had also been carried out. The values of equivalent stress, strain, and deformation for a metal and an alloy which is steel and cast aluminum alloy (A356.0), respectively, have been compared. In terms of structural stability, steel and cast aluminum alloy have shown fairly similar results based on equivalent stress and deformation. However, the use of cast aluminum alloy has greatly decreased the rim’s weight as a result of its low density and high specific strength. Additionally, the aluminum alloy rim has shown superior fuel efficiency and lower carbon dioxide emissions. According to the findings, cast aluminum alloy rims are more feasible when building a vehicle wheel rim since they minimize the wheel’s and vehicle’s weight while maintaining structural strength. It leads to less fuel consumption, which can save fuel costs and is important for energy conservation.

Synergistic realization of high efficiency solar desalination and carbon dioxide reduction

Synergistic realization of high efficiency solar desalination and carbon dioxide reduction

Disproportionate exercise-induced pulmonary hypertension in relation to cardiac output in heart failure with preserved ejection fraction: a non-invasive echocardiographic study.

Pulmonary hypertension (PH) and pulmonary vascular remodelling are common in patients with heart failure with preserved ejection fraction (HFpEF). Many patients with HFpEF demonstrate an abnormal pulmonary haemodynamic response to exercise that is not identifiable at rest. This can be estimated non-invasively by the mean pulmonary artery pressure-cardiac output relationship (mPAP/CO slope). We sought to characterize the pathophysiology of disproportionate exercise-induced PH in relation to CO (DEi-PH) and its prognostic impact in patients with HFpEF. A total of 345 patients (166 HFpEF and 179 controls) underwent ergometry exercise stress echocardiography with simultaneous expired gas analysis. DEi-PH was defined as the mPAP/CO slope >5.2 mmHg/L/min (median value). At rest, there were no differences in right ventricular (RV) function and severity of PH between HFpEF patients with and without DEi-PH. Compared with controls (n=179) and HFpEF without DEi-PH (n=83), HFpEF with DEi-PH (n=83) demonstrated worse exercise capacity (lower peak oxygen consumption), depressed RV systolic function, impaired RV-pulmonary artery coupling, limitation in CO augmentation, more right-sided congestion, and worse ventilatory efficiency (higher minute ventilation vs. carbon dioxide volume) during peak exercise. Kaplan-Meier analyses showed that HFpEF patients with DEi-PH had higher rates of composite outcomes of all-cause mortality or heart failure events than those without (log-rank p=0.0002). Patients with HFpEF and DEi-PH demonstrated distinct pathophysiologic features that become apparent only during exercise. These data suggest that DEi-PH is a pathophysiologic phenotype of HFpEF and reinforce the importance of exercise stress echocardiography for detailed characterization of HFpEF.

Effects of Supplementary Irrigation on Soil Respiration of Millet Farmland in a Semi-Arid Region in China

Carbon dioxide (CO2) is recognized as key part of evaluating the soil environment, and the soil respiration rate is an effective indicator of CO2 emission. To explore the influence and coupling mechanism of irrigation on the soil respiration of millet farmland in the Northern Shanxi Province in China, conventional rainfed (CK) and supplementary irrigation (W1) at the late jointing stage were conducted. The soil respiration rate and carbon emission flux in millet farmland under different treatments were observed. The relationship between soil respiration rate and soil physical–chemical properties and the crop growth index was further analyzed. The result showed that the soil respiration rate and carbon emission flux of W1 were higher than those of CK treatment. The comparison of the linear regression correlation between soil respiration rate and soil physical–chemical properties revealed that the major regulating factors of the soil respiration rate were soil moisture (&lt;10.6%) followed by soil pH, soil moisture (&gt;10.6%), soil temperature, and finally soil organic matter content. There are uncertainties regarding the soil moisture content variation range in soil respiration. Moreover, supplementary irrigation promoted the growth indexes, yield, and irrigation water use efficiency in millet farmland. Further research with less irrigation treatment is necessary for exploring an optimization model of water use efficiency and low carbon dioxide emissions in millet fields, which would be helpful to realize agricultural water utilization and a “carbon peak” in the sense of farmland.

Potential of ozone addition on dethrottling of a gasoline/ethanol blend-fueled direct injection spark ignition engine in part load

Several efforts are required to improve engine efficiency and decrease global carbon dioxide (CO2) emissions and local pollutant products. In countries like Brazil, with a four-decade long experience with ethanol, the use of fossil fuels, although widespread, is being put under intense scrutiny. Governmental programs like ROTA 2030 stimulate engine research and development focused on environment-friendly fuels such as bioethanol-gasoline blends. Brazilian gasoline has about a quarter of ethanol, reducing the carbon footprint while maintaining suitable energy density. Regardless of the fuel, the load control method in part load operation of spark ignition engine causes a considerable penalty in fuel conversion efficiency. For these reasons, ozone addition was tested as an ignition enhancer that would allow higher de-throttling to reduce part-load pumping losses. The residual gas was used to dilute the mixture due to the possibility of keeping the three-way catalyst working properly with the stoichiometric mixture. An experimental investigation on efficiency, emissions and combustion related parameters was carried out in a downsized 1.0 l turbocharged direct-injected engine. Experimental tests were performed at 3 bar of indicated mean effective pressure (IMEP), 1500 rpm and stoichiometric air-fuel ratio. Spark timing (ST) was adjusted to achieve maximum indicated efficiency and the fuel used was Brazilian gasoline. Different ozone concentrations were used as a mixture with the intake air to overcome unstable engine operation by enhancing ignition. The results showed that it is possible to increase the gas exchange efficiency with ozone addition by promoting de-throttling operation with residual gases. Furthermore, the ozone addition exhibits the potential to promote autoignition of the end gas with spark assistance, even with a low compression ratio and residual gas fraction higher than 30%. However, the combustion efficiency is impaired by the higher residual gas fraction in some operation points that leave room for improvements.

Energy loss and comprehensive performance analysis of a novel high-efficiency hybrid cycle hydrogen-gasoline rotary engine under off-design conditions

The rotary engine is a potential power device for unmanned aerial vehicle. In this paper, a novel X-type hydrogen-gasoline rotary engine using high efficiency hybrid cycles (HEHCs) is proposed to realize the high efficiency and low carbon dioxide emission. Firstly, the zero-dimensional single-zone models are established for the X-type rotary engine using theoretical (ideal cycle and ideal working fluid of air), ideal (ideal cycle and real working fluid) and real (real cycle and real working fluid) HEHCs. The type I and II losses are introduced to indicate the energy losses from theoretical HEHC to ideal HEHC and from ideal HEHC to real HEHC, respectively. Furthermore, the effects of hydrogen doping fraction of gasoline-hydrogen hybrid fuel, ignition angle and rotational speed on type I and II losses are studied. Finally, the variation trends of cycle efficiency, indicated power, indicated fuel cost and indicated carbon dioxide emission (ICDE) are revealed under different operation conditions. The results show that the increasing hydrogen doping fraction rises the type I and II losses, while the increasing ignition angle or rotational speed declines the above losses. The maximum cycle efficiencies of real HEHC with pure gasoline and hydrogen doping fraction of 0.3 are 42.6% and 41.5% at the optimal ignition angles of 330° and 345°, respectively. The cycle efficiency of real HEHC is increased by 1.3% at the rotational speed of 9000 rpm with the increase of hydrogen doping fraction of 0.3. The indicated fuel cost and ICDE for the hydrogen doping fraction of 0.3 is 19.2% higher and 28.2% lower than that for pure gasoline under optimal ignition angles, respectively. The increasing hydrogen doping fraction reduces the effect of rotational speed on the cycle efficiency, indicated fuel cost and ICDE.