Fuel Communications最新文献

There is much current interest in improving the efficiency gas turbines used in aircraft engines and thereby reducing their carbon emissions. The perforated combustor liners in gas turbine silencers absorb the sound associated with thermo-acoustic instabilities and thereby reduce them. A semi-empirical model has been developed to predict the absorption of perforated liners in the absence of bias flow as a function of frequency in terms of liner characteristic such as orifice diameter, thickness, spacing, orientation and perforation ratio and liner configuration which requires an additional model for the impedance of the cavity behind the liner. The expression used for impedance includes a cavity factor which corrects for the change in combustor liner diameter. Predictions of energy absorption coefficient spectrum are compared with data from measurements on several configurations of full-scale liners. It is found that predictions using the standard tangent term in the cavity impedance do not agree with data at frequencies below 500 Hz as well as predictions that use a cosine term instead. The resulting model, which is validated by the data comparisons, should be useful in optimising liner characteristics for manufacture.

KOH-modified metakaolin (KMK) was synthesized, characterized and utilized as a heterogeneous catalyst for biodiesel production from allamanda seed oil (ASO) for the first time. The effect of variables (temperature, time and catalyst concentration) affecting biodiesel production process was optimized using Box-Behnken design of response surface methodology. The biodiesel produced was consequently characterized to determine its fuel properties. Optimization results showed that maximum biodiesel yield of 90.67$\pm$0.14%. was achieved at fixed methanol/ASO molar ratio of 5:1 and at the optimum conditions of 52.5 °C reaction temperature, 180 min reaction time and 0.5 wt.% catalyst concentration. The properties of the produced biodiesel were comparable to the ASTM D6751 and EN 14214 specifications, thus indicating the suitability of the ASO biodiesel as a possible alternative to petroleum diesel.

Electromobility is the future main system for Swedish road transport that encourage sustainable urban transportation. However, emission impacts of applying electric vehicles (EVs) are currently controversial. This study evaluates and compares internal combustion engine vehicles (ICEVs) refer to both petrol and diesel-based engines and BEVs, focusing on environmental and energy impacts. The entire life cycle of vehicles production, fuel production and fuel use are considered and life cycle emissions impacts due to various electricity generation alternatives will be studied. LCA of BEV is also conducted under different recycling scenarios to determine what extent CO₂ can be further reduced owing to car and battery recycling. The results show that BEVs charged by natural-gas, and renewable electricity produce less emissions of CO₂, SO₂, PM, VOCs, NO_X and Sb than ICEVs but higher PO₄ emissions and need more energy. The largest fraction of CO₂ emissions for BEVs charged via renewable electricity is due to vehicle production (61-78% of BEV's life cycle CO₂ emissions). CO₂ emissions regarding to vehicle production for BEVs is 14.6 ton (60.8 gCO₂/km) which is 132% and 123% of that for petrol and diesel ICEVs, respectively. Human toxicity and eutrophication impacts highlight as potentially important categories for transition from ICEVs to BEVs due to high toxicity and PO₄ emissions in BEV production. By applying high scenario for car and battery recycling, CO₂ emissions in BEVs lifespan charged by renewable electricity can be reduced 50% (83 gCO₂/km); total PO₄ emissions can be also decreased 56% with production of 79 mgPO₄/km.

Coking coal is still on the list of critical raw materials in many countries since it is the main element integrated into the blast furnace. While the energy consumption and steelmaking efficiency in the furnace depends on the coke quality, understanding and modeling coking indexes based on their coal parent properties would be a substantial approach for the steelmaking industry. As an innovative approach, this short comminucation has been considered explainable artificial intelligence (XAI) for modeling coal coking indexes (Free Swelling index “FSI” and maximum fluidity “Log (MF)”). XAIs can convert black-box models into human basis systems and develop a significant learning performance and estimation accuracy. SHapley Additive exPlanations (SHAP), as one of the most recently developed XAI models in combination with eXtreme gradient boosting (XGBoost), were used to model coal samples from Illinois, USA. For the first time, FSI and Log (MF) treat as ordinal variables for modeling. Modeling outcomes relieved that SHAP-XGBoost could accurately show interdependency between features, demonstrate the magnitude of their multi relationships, rank them based on their importance, and predict the coking index quite accurately compared with conventional machine learning methods (random forest and support vector regression). These significant results would be opened a new window by applying XAI tools for controlling and modeling complex systems in the energy and fuel sectors.

Laminar flame speed (LFS) is a key physicochemical property of a premixed fuel/oxidizer mixture, and is critical in the description of complex combustion phenomena. Accurate experimental measurements of LFSs for various fuels have been performed to develop and validate detailed kinetic mechanisms, which in turn are used to predict LFSs under various combustion conditions. However, such procedure is inefficient, especially in large-scale turbulent combustion modeling studies. Based on previous experimental studies of LFSs for various fuels, this work aims to develop a data-driven machine learning (ML) model for the prediction of LFSs of hydrocarbon and oxygenated fuels. Descriptors computed from semi-empirical quantum chemistry methods are used as input in ML models due to the simplicity and computational-efficiency. Pearson correlation analysis is used to select important features, and 5 descriptors are screened as the input features for ML model development. The accuracies and interpretabilities of existing 16 ML algorithms in the prediction of LFSs are compared through systematically evaluated the errors based on the differences between experimental data and model prediction. These ML models include regression trees, support vector machine regression, gaussian process regression, and ensemble trees. An efficient ML model for predicting LFSs of hydrocarbon and oxygenated fuels based on gaussian process regression algorithm is proposed, which exhibits good accuracy in predicting of LFSs for variable pressure, temperature, and equivalence ratio. The dependency of LFSs on the descriptors are also analysed. The developed ML model is fast enough for integration into large-scale computational fluid dynamics for combustion studies.

Using an in-house 0D plasma chemical solver, this paper investigates the species involved in plasma-assisted reforming of both pure ammonia and stoichiometric ammonia-air mixtures. A nanosecond repetitively pulsed plasma is simulated for dielectric barrier discharge conditions, with reduced electric fields of 180 and 360 Td, energies per pulse of 0.5 and 1 mJ/cm³, and pulse repetition frequencies up to 500 kHz. To show the effect of reforming on combustion performance, the reformates are fed into a neutral species combustion chemistry solver to calculate the ignition delay time at gas-turbine relevant conditions. For a reformed stoichiometric mixture, it is possible to achieve a reduction of two orders of magnitude in ignition delay time. This reduction, however, comes at the cost of lost enthalpy, as ammonia reacts with oxygen to create water. Path flux and sensitivity analyses were performed, and it as found that the two most crucial species in the reformate were H₂ and NH₂. The presence of NH₂ in high concentration also resulted in lower concentrations of NO after ignition, compared to the unreformed mixture. When reforming pure ammonia, the same number of pulses and energy as in the stoichiometric case reduce ignition by one order of magnitude. A higher reduction is possible with more pulses, unlike the stoichiometric reforming case in which ignition is reached during the reforming process, and with no loss of enthalpy due to oxidation. At 200 kHz, a reduction of two orders of magnitude is possible after 1500 pulses. These results support the feasibility of plasma-assisted reforming for the improvement of ammonia combustion characteristics at relevant conditions.

The work investigates the suitability of a multi-component hydrocarbon fuel, namely HCF-1, as a potential fuel-cum-coolant for space vehicles under supercritical environments. The effects of reactor temperature, space-time, and initiator loading on fuel conversion, coke deposition, heat sink capacity, and gas selectivity are examined. The obtained value of fuel conversion, coke deposition rate, and chemical heat sink at 680 °C and 55 bar pressure are 10.3 wt.%, 7 mg/min, and 805 kJ/kg, respectively. The increase of fuel space-time from 2.8 s to 8.5 s increased the endothermicity by about 1.8-times. A decreasing trend in the olefin-to-alkane ratio with temperature and space-time is observed. The microscopic analysis confirmed the presence of both spherical-shaped (amorphous) and ribbon-like (filamentous) structures in the coke deposits. The estimated value of the apparent activation energy of the HCF-1 cracking reaction is 125 kJ/mole. Tributylamine (TBA) is recognized as a potential initiator to improve the cracking characteristics of the HCF-1. The fuel conversion and endothermicity increased by 58% and 18%, respectively, in the presence of 10,000 ppm of TBA at 650 °C. From the investigation, it can be said that the HCF-1 has a good potential to act as an endothermic fuel.

In view of reducing greenhouse gas emissions the transition from fossils fuels to sustainable energy carriers is a prerequisite to keep global warming within tolerable limits. Since IC engines will continue to play a role in global energy strategies during a transitional phase, especially for large engine applications difficult to electrify, the use of ammonia as substitute fuel may be an approach for decarbonization. However, its utilization needs research since ignition concepts and combustion properties still pose considerable challenges in view of reliable and efficient operation. A new "optical engine" test facility ("Flex-OeCoS") has been successfully adapted enabling dodecane pilot fuel ignited premixed ammonia dual-fuel combustion investigations. It features IC engine relevant operation conditions such as pressures, temperatures, and flow (turbulence) conditions as well as adjustable mixture charge composition and pilot fuel injection settings. In parallel, thermodynamic heat release analysis in terms of ignition and combustion characteristics was performed. Simultaneously applied high-speed Schlieren/OH* chemiluminescence measurements supported the examination of the combustion process. Initially premixed ammonia dual fuel combustion has been compared to a representative methane combustion process in terms of different gas properties (lower heating value, air-fuel ratio) which illustrates its lower reactivity affecting heat release and flame propagation. Moreover, ignition delay, combustion transition, and turbulent flame propagation as well as heat release characteristics have been investigated for premixed ammonia dual-fuel combustion within variation of air-fuel equivalence ratio, start of pilot fuel injection, and pressure/temperature operation conditions. The results illustrate strong dependency on air-fuel equivalence ratio (energy content) and temperature conditions in terms of ignition delay, dual-fuel combustion transition, and corresponding heat release. The optical investigations confirm the thermodynamic analysis and promote assessment of pilot fuel evaporation, ignition, combustion transition, and flame propagation. Conclusions give extended insight into the thermo-chemical processes of ammonia pilot fuel ignited dual-fuel combustion. The acquired data may also support further development of numerical CRFD methods.

Biofouling of gasoline can occur during fuel storage caused by bacteria and fungi that form a biofilm at a fuel/water interface and that produce organic acids and sulfides. Fuel additives are applied to gasoline to prevent biofouling but are relatively expensive, are not always effective against biofilms, and do not contribute to the combustibility of gasoline. Bio-isobutanol is an approved, certified advanced biofuel and is added up to 16% (v/v) in gasoline blends “iBut16”; n-butanol blends are currently under review. Microorganisms are inhibited by n-butanol or isobutanol when the aqueous concentration reaches >2-3% (w/v). We determined that n-butanol partitions into the aqueous phase of a model gasoline/water system reaching concentrations of 42 g/L and up to 48 g/L from gasoline blends at 10% and 24% (v/v), respectively. Likewise, isobutanol blended in gasoline at 10% and 24% (v/v) partitioned into an aqueous phase at 45 g/L and 53 g/L, respectively. Several bacterial and fungal strains that originate from fuel storage tanks, or are known to be solvent tolerant, were evaluated for their potential growth in a range of n- and isobutanol concentrations. Growth rates for all strains tested were reduced by 40–100% relative to untreated controls in n- and isobutanol concentrations of 1.5 and 2.0% (v/v). No observable growth occurred for any of the microorganisms in solvent concentrations at 3.0% (v/v). T amphiphilic and chaotropic properties of n- or isobutanol help them inhibit microbial growth and could serve as effective biocides during fuel storage as well as being valuable fuel additives.

This study investigates the physicochemical behavior of Wheat Straw and Groundnut Stalk biomass and its impact on the thermal behavior during torrefaction process. The torrefaction was experimentally investigated by thermogravimetric analysis (TGA) at five isothermal heating rates of 20, 30, 40 and 50 °C/min. Results revealed that during the torrefaction process, significant fraction of hemicellulose and volatile content reduces that improves the high heating value. The results indicated that torrefaction treatment improved the fuel properties with elevated torrefaction temperature, including the lower volatile content, higher carbon content, and higher heating value. Kinetic parameter analysis indicated that the Ozawa–Flynn–Wall and Starink model were significant in calculating the activation energy, and the average activation energy was 240 kJ/mol and 238 kJ/mol (Wheat Stalk and torrified wheat Stalk) 127 kJ/mol and 129 kJ/mol (Groundnut Stalk and torrified Groundnut Stalk). An excellent linear relationship between lnA and E_α was observed, indicating that the compensation effect existed between the E_α and lnA during torrification. These results provide important basic data support for the thermochemical conversion of cornstalk to energy and chemicals.