Combustion Characteristics Of Fuels Research Articles

Assessing combustion characteristics of alternative fuels in a CI engine by use of a wavelet-based analysis of engine vibration signals

In the current work, a wavelet-based approach for assessing combustion performance of alternative fuels in compression-ignition engines, indicated that changes in cylinder pressure amplitude were reflected by commensurate changes in a proposed parameter, with a maximum of a 9% variation. The proposed parameter, the wavelet transform coefficient maximum amplitude (WMA), successfully accomplished this for various engine conditions. The wavelet transform coefficient standard deviation (WSD), a second proposed parameter, was able to track changes in the rates of pressure rise associated with changes in load conditions and fuel type, with a maximum variation in the parameter of 7%. The approach was assessed by testing six fuels in a test engine unit. Thermodynamic property data and vibration signal data were recorded for each of the fuels tested, at six loading conditions. Subsequently, combustion performance was evaluated using traditional thermodynamic parameters and using the WMA and WSD via a MATLAB based algorithm. Thus, it was surmised that the proposed approach can form the basis for a vibration-based assessment of alternative fuel combustion performance in reciprocating engines.

Combustion of liquid hydrocarbon fuels sprayed into gas generation chamber with superheated steam as low emission technology for energy production

Experimental and numerical studies were conducted to scientifically validate the Steam Injection Method with Gas Generation chamber (SIMGG) as a low-emission combustion technology for energy production in low and medium power boilers using different types of fuels. For the first time, a fully functional prototype of a burner implementing SIMGG was tested under the conditions of a standard low-power boiler installation, and combustion characteristics of fuels with various physical properties (diesel fuel and a mixture of used automotive oils) were obtained under different operating parameters. The results of the studies show that using SIMGG reduces carbon monoxide (CO) and nitrogen oxides (NOx) emissions by up to half or more under closed-combustion conditions for various fuels. The lowest total emissions of CO and NOx are achieved at an air excess coefficient of 1.2 and a steam-to-fuel ratio of greater than 0.66.

Ignition and Combustion Characteristics of Alternative Fuel under High-Temperature and High-Pressure Conditions

Ignition and Combustion Characteristics of Alternative Fuel under High-Temperature and High-Pressure Conditions

Study on the combustion characteristics and reaction mechanism of aluminum/alcohol-based nanofluid fuel

Enhancing the volumetric energy density of fuels is a crucial approach in the exploration of efficient energy sources. As a commonly used high-energy additive, Aluminum nanoparticles (Al NPs) holds broad application prospects. This study delves into the effects of Al NPs on the combustion characteristics of methanol and ethanol fuels through in-depth analysis of single droplet combustion and spray combustion experiments involving alcohol-based nanofluid fuels. The experiments revealed that adding Al NPs significantly enhances fuel combustion efficiency, shortening both the combustion life and ignition delay time. Spray combustion tests demonstrated that adding 2 wt% Al NPs increased the maximum and average flame propagation speeds of ethanol fuel spray by 48.93 % and 47.94 %, respectively, while the maximum explosion pressure rose from 0.66MPa to 0.83MPa, with a reduced time to reach peak explosion pressure by 106ms. Based on the SEM and XRD characterization results of the combustion residues and the analysis of flame morphology, a physical model of the alcohol-based nanofluid fuel spray combustion flame was established. Numerical simulations of the gas-phase kinetics model showed that the generation rates of radicals such as H, O, and OH were significantly increased with the addition of Al NPs, intensifying the combustion reaction. The findings provide a theoretical basis for future fuel design and combustion performance optimization.

Combustion characteristics of sustainable aviation fuels in a scaled-down afterburner test rig

Combustion characteristics of sustainable aviation fuels in a scaled-down afterburner test rig

Properties and combustion characteristics of bioslurry fuels from agricultural waste pyrolysis

ABSTRACT The current research investigates the combustion characteristics of bioslurry fuel derived from the products of agricultural waste pyrolysis. The bioslurry fuel was prepared by mixing biochar and pyrolysis oil. The combustion characteristics of a suspended single droplet of the bioslurry were analysed. The results indicate that an increase in pyrolysis temperature (400–600°C) lead to higher concentrations of fixed carbon (56–60%), increased ash content (16–18%), and higher calorific values (25–32 MJkg−1). As the pyrolysis temperature rises, the biochar surface becomes more porous, lower volatile matter content and particle size. As biochar content increases, the bioslurry’s density, viscosity, and caloric value increase but stability index decreases. Higher biochar content in the bioslurry increases the ignition delay and burnout time while reducing the burning rate. The bioslurry fuel contained 30% biochar achieved a calorific value of 28 MJkg−1 and a viscosity of 600 cP, comparative to conventional fossil fuels. Highlights Up to 30% BC can be added to pyrolysis oil to produce SF. Pyrolysis temperature increased FC, ash, and calorific value of biochar. Biochar surface appears more porous with increasing pyrolysis temperature. Biochar content affects bioslurry combustion characteristics.

Investigating the effect of fuel properties and environmental parameters on low-octane gasoline-like fuel spray combustion and emissions using machine learning-global sensitivity analysis method

The gasoline compression ignition mode is an advanced combustion mode that achieves high efficiency with low emissions. This study constructs a global sensitivity analysis (GSA) by coupling machine learning (ML) algorithms and conducts a comprehensive investigation into the statistical correlations between research octane number (RON), fuel sensitivity (S), three initial ambient parameters, and the spray combustion characteristics of gasoline-like fuels. Eighty sets of CFD numerical simulation data were used for training the machine learning model. Results show liquid length (LL) is most sensitive to changes in ambient pressure while ambient temperature significantly influences vapor penetration length (VPL). Regarding combustion behaviors, ignition delay (ID) and flame lift-off length (LOL) show the highest sensitivity to ambient temperature. The occurrence of distinct ignition points in the domain also advances from 1.75 ms to 0.42 ms as the ambient temperature rises from 1000K to 1200K. Additionally, the ambient temperature has higher-order interaction effects with ambient pressure on LOL. The production of NOx in the field is also more closely correlated with ambient temperature, with higher temperatures promoting its generation. Furthermore, ambient temperature exhibits a positive interaction effect with both ambient pressure and oxygen concentration on NOx emissions.

Expansion ignition limit of hydrocarbon fuels based on the controllable free radical relay combustion under extreme conditions

Controllable hydrocarbon fuel combustion and combustion path adjustment are effective but difficult approaches to achieve reliable ignition under extreme conditions. However, the effective mechanism to control the combustion characteristics of hydrocarbon fuels is still unclear. In this study, the fuel (Fuel 6) based on free radical relay combustion (FRRC) significantly expands the ambient temperature-based ignition limits of pure fuel and shows a weak temperature correlation with ignition delay time. In addition, Fuel 6 still has a 100 % ignition probability at 50 kPa (the corresponding ignition limit flight altitude increased from 0.9 km above sea level to 5.4 km). Gaussian simulations show the thermodynamic feasibility of FRRC and prove the relay effect. According to kinetic analysis, the combustion reactions can be adjusted based on FRRC and exhibit three types of oxidation reactions, of which the reaction activation energies are all lower than those of the oxidation reactions of pure fuel. Furthermore, the results of in-situ Fourier transform infrared spectroscopy are consistent with the kinetic analysis based on thermogravimetric and differential thermogravimetric studies. The investigation of the combustion control mechanism under extreme conditions helps to broaden the ignition limit of the aviation engine combustor and to significantly improve the accurate control level of ignition under extreme conditions, providing theoretical support for solving the ignition problems of advanced aviation engines under extreme conditions.

Exploring the first-stage ignition and model optimization in the comprehensive study of n-dodecane oxidation

n-Dodecane is commonly employed as a surrogate for investigating the combustion characteristics of jet and diesel fuels. Enhancing comprehension of its combustion behavior and developing accurate chemical kinetics models for simulating combustion is of paramount importance in engine development. This study focuses on a detailed exploration of n-dodecane oxidation kinetics under low-temperature conditions and presents a novel dataset concerning the first-stage ignition delay time. A broad spectrum of experimental conditions is investigated, encompassing a range of temperature (600 ∼ 1350 K), pressure (5 ∼ 20 atm), equivalence ratios (0.5 ∼ 1.0), and dilution gases (N2 and Ar). Additionally, combustion experiments in a pure oxygen environment are performed, contributing valuable data to existing research. To enhance the precision of the chemical reaction kinetics model of n-dodecane, this study integrates updated rate coefficients obtained from the latest theoretical calculations for specific reaction classes. The improved rate rule provides a more accurate reference for the construction of the chemical reaction kinetics model of long straight alkane. The resulting improved model excels in accurately predicting both the first-stage ignition delay time and the total ignition delay time under a wide range of operational conditions. Additionally, the model performance is rigorously evaluated through a comprehensive assessment against a diverse array of datasets gathered from various literature references. The results show that, in contrast to the previously proposed model, this enhanced model provides highly reliable predictions over a broad range of parameters.

Investigation on spray combustion modeling for performance analysis of future low- and zero-carbon DI engine

Global warming issues and fossil fuel depletion crisis have forced transportation industry to seek clean engine fuels both liquid and gaseous. Dual-fuel mode with high-pressure direct injection (HPDI) has been recognized as mainstream method in developing flexible-fuel internal combustion engines (ICEs). But flexible-fuels’ physicochemical properties and spray combustion characteristics under HPDI have changed a lot. Unfortunately, there is currently no universal model for predicting spray combustion behaviors and analyzing performance of flexible-fuel ICEs. Therefore, this paper aims to develop a novel spray combustion model and provide optimal injection and combustion strategies for performance improvement of low- and zero-carbon HPDI ICEs. Based on balance of momentum change and vortex ring drag force, the jet spray effective injection velocity is obtained. Then the jet spray penetration under varying injection rate is solved. Finally, the developed model is established and validated experimentally, with the spray combustion characteristics of various fuels investigated. The results show that the developed model has a good accuracy and robustness for flexible-fuels’ characteristic analysis. Meanwhile, multiple-injection could increase the combustion efficiency (CE) over 10.27 % than single-injection, and CE increases with dwell time. Moreover, CE of H2 in nitrogen-oxygen (N2–O2) atmosphere is 10.15 % higher than that in argon-oxygen (Ar–O2) atmosphere.

Combustion Characteristics of Vat-Photopolymerized Fuels with a Spiral Star Port for Hybrid Propulsion.

Despite hybrid rocket motors offering distinct advantages over solid or liquid rocket motors, their low regression rate and insufficient combustion efficiency remain significantly unimproved. This study focuses on the effects of the helix lead on the regression rate distribution and combustion efficiency of vat-polymerized fuel grains with a spiral star port for a hybrid rocket. Both experimental and numerical investigations were conducted to study the combustion characteristics and regression rate distribution of three-dimensional (3D) print grains. Spiral star grains with varying helix leads of 60, 90, and 120 mm were fabricated using light-curing 3D printing technology. A 3D simulation model was developed to obtain the temperature distribution, species mass distribution, and combustion efficiency. Furthermore, firing tests were performed on a two-dimensional radial hybrid combustion test stand to measure the regression rate. Digital image processing of computed tomography images was used to determine the regression rate. Simulation results indicated that the spiral star grain port helps to improve the combustion efficiency compared with those seen with round tube and straight star port grains. With an increase in the axial distance, the flame zone gradually shrinks, and the smaller the helix lead, the faster the shrinkage. At a mass flow rate of 1.50 g/s for oxygen, the regression rate of the spiral star grains is significantly higher than that of the straight star grain and the conventional round tubular grains, and the regression rate gradually increases with a decrease in the helix lead. This finding is expected to solve the problem of the low regression rate of solid fuels with spiral star pore-shaped grains prepared by the light-curing 3D printing method.

Combustion characteristics of water-oil emulsion droplets with special additives

Relevance. Fuel oil application in power plants is characterized by increased values of underburning and anthropogenic emissions. One way to reduce anthropogenic emissions is the use of oil-water emulsions. Also, additional specialized additives are used to reduce anthropogenic emissions and improve fuel combustion characteristics. Aim. To determine the optimal fuel oil additive to reduce anthropogenic emissions and ignition delay times. Methods. The following additives: ION-M, Rosneft R503V3, Rosneft R502V1 (relative mass concentration 0.5%) were added to the water-oil fuel. The physicochemical properties of fuel oil M-100, as well as the elemental composition of CHNSO, were determined. The rheological characteristics of water-oil fuel compositions were established. Using high-speed photography, the droplet ignition delay times were determined. Using the gas analyzer, it was possible to prevent anthropogenic emissions. Results and conclusions. The results of the study showed that the additive based on a special combination of positively and negatively charged ions (ION M) reduces ignition delay times by 20–60%, when the gas temperature varies in the range from 700 to 900 °C. The addition of the additive based on fatty vegetable acids (P502B3) reduced the ignition delay times by 7–10%, when the temperature changed in the range from 700 to 900 °C relative to water-oil fuel. It was found that when using the P502B1 additive in water-oil fuel, it was possible to reduce the ignition delay times by 15–50%. It was determined that in the presence of combustion catalysts, water binds with heavy hydrocarbons and thus the release of volatile substances occurs faster, i. e. the supplied heat is not wasted on heating water into droplets, but evenly affects the entire volume of fuel. The results of the study of anthropogenic emissions showed that the use of additives when burning water-oil fuel reduces the concentrations of CO, CO2, NO, SO2 by 8, 6, 10 and 13%, respectively, compared to fuel oil.

Research on Dual Fuel Combustion Characteristics of PFI Natural Gas +DI Gasoline in Large Cylinder Diameter Engine

A 3D simulation model of a single cylinder of a natural gas engine was established. PFI natural gas DI gasoline was used to control the time matching between injection and ignition, so that gasoline could form a small active stratified area near the spark plug. The combustion characteristics under different matching conditions were studied, and finally compared with pure natural gas. It is found that gasoline can be used in large cylinder diameter natural gas engine in a small range, which can accelerate the combustion of natural gas fuel, shorten the time used by CA0-CA5 by 77.6%, shorten the time used by CA5-CA90 by 26.5%, and increase the indicated thermal efficiency of natural gas engine by 1.4%.

Large Eddy Simulations of n-heptane and n-dodecane binary blends in swirling multi-component spray flames

Well-understanding and mastering Sustainable Aviation Fuels (SAF) mixture composition as well as the potential of their initial component concentrations’ impact on flames is clearly of critical importance in today’s effort and energy transition. In this study, the focus lies on conducting Large Eddy Simulations (LES) to comprehend the impact of species concentration changes in well-controlled multi-component fuel blends on flame structures. The SICCA-spray rig from the EM2C laboratory operated with three blends of n-dodecane and n-heptane in varying proportions, is specifically addressed and investigated in light of the available data. To conduct these simulations, the dynamically thickened flame model and an evaporation multi-component sub-model are coupled with a reduced chemistry mechanism for n-heptane and n-dodecane binary blends. Across all investigated blends, the simulated swirling spray flame predictions align well with the experimental measurements confirming the suitability of the proposed modeling. For this configuration, the alterations in species concentration do not appear to significantly impact the overall flame structures and characteristics when observed from an average perspective. However, localized differences are identified, revealing notable composition effects. The simulation outcomes indicate that the early consumption of n-heptane contributes to stabilizing the flame, whereas the vaporization of n-dodecane is the primary factor responsible for combustion occurring further downstream. These effects are closely tied to the evaporation properties of each fuel compound and their concentration proportions within the blend, as expected. This insight highlights the intricate relationship between fuel properties, their concentrations within blends, and the resulting combustion behavior, shedding light on the complexities of multi-component fuel combustion characteristics.

Emission and Combustion Characteristics of Different Diesel Fuels Produced in Kurdistan-Region - Iraq

Emission and Combustion Characteristics of Different Diesel Fuels Produced in Kurdistan-Region - Iraq

Study of Hedge Ignition and Flame Propagation Characteristics of Unsymmetrical Dimethylhydrazine and Its Metamorphosed Mixtures in a Nitrogen Tetroxide Atmosphere

Unsymmetrical dimethylhydrazine (UDMH) is a common liquid propellant widely used in rocket engines and other applications. The safety of UDMH in service is affected by its slow oxidation during long-term storage to form impurities such as dimethylamine (DMA) and formaldehyde dimethylhydrazone (FDH). How these impurities affect combustion performance is not known, and in order to assess these effects, the present experiments investigated the combustion characteristics of self-igniting fuels and carried out ignition delay time measurements and flame propagation velocity measurements of pure UDMH and its denatured mixtures in a nitrogen tetroxide (NTO) atmosphere. This experiment was carried out to measure the delay time of hedge ignition of pure UDMH and qualitative analysis of its flame propagation properties under vacuum conditions at room temperature (T = 293 K). Ignition delay time measurements and flame propagation characterization were performed under the same experimental conditions for UDMH mixed with 1%, 5% and 10% FDH, UDMH mixed with 1%, 5% and 10% H2O, UDMH mixed with 1%, 5% and 10% DMA, as well as for UDMH mixed with the same proportions of the three substances (1%, 5% and 10%). The flame propagation characteristics were analyzed. The results showed that the incorporation of DMA, H2O and FDH in different proportions could inhibit the combustion of UDMH to varying degrees and prolong its ignition delay time. It is worth noting that the introduction of FDH had the least effect on it, and the least effect was observed at a concentration of 1%. In contrast, the effect of DMA on UDMH is more obvious, and the addition of H2O has the largest increase in the ignition delay time of UDMH. In the flame propagation experiment, the flame of the experimental group adding H2O can no longer fill the whole experimental window, while the other experimental groups can still make the window full of flame. Combined with the measurements of the ignition delay time, it can be seen that the moisture content has the greatest effect on the combustion characteristics.

The Use of Arak Bali as a Fuel Influence on Fire Characteristics of Combustion

Analyze the characteristics of gas fuel from arak Bali, like shape and flame speed. Test characteristics such as methanol and ethanol content material gas from arak Bali, after it tested the gas fuel combustion characteristics of arak Bali such as the shape and speed of flame. Testing characteristics such as the content of methane and ethanol gas from arak Bali performed in the forensic laboratory while testing the ignition characteristics of the shape and speed of fuel from evaporating arak Bali done using a helle-shaw cell combustion chamber model. Air mixture ratio variations with gas fuel from arak Bali is 24/1, 25/1, 26/1, 27/1, 28/1, 29/1, 30/1 and 31/1. The observed effect is the shape and speed of the premixed flame propagation in the helle-shaw cell combustion chamber model. The results of the study, the moisture content of the basic ingredients of gas fuel arak Bali consisting of 40% methanol and 60% ethanol. Gas fuel from arak Bali has a stoichiometry air-fuel ratio of 30/1. Getting closer to the stoichiometry air-fuel ratio, flame color changes from reddish color faded to red, reddish blue, blue and bright blue last. The maximum speed of propagation of fire occurring in stoichiometry air-fuel ratio is 328.33 cm/sec.

Transient Performance of Gas-Engine-Based Power System on Ships: An Overview of Modeling, Optimization, and Applications

Liquefied natural gas (LNG) is widely regarded as the midterm solution toward zero-carbon transportation at sea. However, further applications of gas engines are challenging due to their weak dynamic load performance. Therefore, the comprehension of and improvements in the dynamic performance of gas-engine-based power systems are necessary and urgent. A detailed review of research on mechanisms, modeling, and optimization is indispensable to summarize current studies and solutions. Developments in engine air-path systems and power system load control have been summarized and compared. Mechanism studies and modeling methods for engine dynamic performance were investigated and concluded considering the trade-off between precision and simulation cost. Beyond existing studies, this review provides insights into the challenges and potential pathways for future applications in decarbonization and energy diversification. For further utilization of clean fuels, like ammonia and hydrogen, the need for advanced air–fuel ratio control becomes apparent. These measures should be grounded in a deep understanding of current gas engines and the combustion characteristics of new fuels. Additionally, the inherent low inertia feature of electric power systems, and consequently the weak dynamic performance when adopting renewable energies, must be considered and studied to ensure system reliability and safety during transient conditions.

Optical engine experiments on combustion and emission performance of n-dodecane/ammonia dual fuels

Ammonia is regarded as a promising carbon-free fuel, but it suffers from poor ignition and combustion as well as heavy emissions. High-reactivity fuels are often adopted as ignition boosters to solve these issues. In this work, the combustion and emission characteristics of n-dodecane and ammonia dual fuels were studied in an optical engine, with emphasis on the role of n-dodecane addition and injection timing. Simultaneous pressure acquisition, high-speed photography, and FT-IR spectroscopy were adopted for measurements. The results demonstrate the significance of ammonia energy ratio and n-dodecane injection timing in improving engine performance. Specifically, engine combustion is suppressed as ammonia energy ratio is raised, manifesting decreased peak pressure, postponed combustion phasing, and enlarged cyclic variations. Visualizations show that such changes are closely related to the evolutions of flame initiation and development. Meanwhile, there are always unburned regions which become pronounced at higher ammonia energy ratios, answering for the massive emissions of NH3 and NOx. Furthermore, with the advance of n-dodecane injection timing, engine performance is first improved and then suppressed, featuring nonmonotonic variations in in-cylinder pressure and combustion evolutions. Particularly, ignition delay and late-stage combustion duration are largely prolonged, which is associated with the weakness of fuel stratification and combustion mode transition. The advance of n-dodecane injection timing facilitates unburned NH3 reduction while increasing NOx and N2O emissions. High thermal efficiency while reduced pollution emissions can be achieved under suitable injection timing conditions. This work can provide useful insights into the combustion control of diesel and ammonia dual-fuel engines.

Influence of the Composition and Particle Sizes of the Fuel Mixture of Coal and Biomass on the Ignition and Combustion Characteristics

The work determines the characteristics of the processes of thermal decomposition and combustion when heating coal, cedar needles, and their mixtures with different fuel particle sizes. Based on the results of thermal analysis, the following characteristics were determined: the temperature at which the coke residue ignition occurs, the temperature at which the combustion process is completed, and the combustion index. An analysis was carried out of the interaction between the fuel mixture components on the characteristics of their combustion for compositions (50% coal and 50% biomass) with a particle size of 100–200 μm and 300–400 μm. The combustion kinetic parameters of individual solid fuels and their mixtures containing 50% coal and 50% biomass are compared. The activation energy for coal combustion was 60.3 kJ mol−1, for biomass 24.6 kJ mol−1, and for mixture 42.5 kJ mol−1. The co-combustion of coal and biomass has a positive effect on the main combustion characteristics of solid fuels. Fuels with particle sizes of 100–200, 200–300, and 300–400 μm were studied at temperatures of 500–800 °C under heating conditions in a heated airflow. Using a hardware-software complex for high-speed video recording of fast processes, the ignition delay times were determined, the values of which for the considered fuels vary in the range from 0.01 to 0.20 s. Adding 50 wt% biomass with particle sizes of 100–200, 200–300, and 300–400 μm to coal reduces the ignition delay times of mixtures by 55, 41, and 27%, respectively. The results obtained can become the basis for the conversion and design of modern power plants operating on solid fuel mixtures to co-combust coal with biomass.