Ignition Delay Research Articles

An experimental study the cross spray and combustion characteristics diesel and ammonia in a constant volume combustion chamber

Recently, the use of ammonia, a carbon-free fuel, in internal combustion engines, particularly in dual fuel dual direct injection engines, has attracted wide attention. However, the spray and combustion characteristics of diesel and ammonia dual direct injection especially on cross injections remain unclear. An optical study of diesel and ammonia spray and combustion was conducted using a constant-volume combustion chamber. The results revealed that spray tip penetration (STP) and spray projected area (SPA) of ammonia are lower than those of diesel, indicating that ammonia has a higher evaporation rate and a smaller diffusion rate than diesel. Besides, diesel and ammonia atomization was promoted through cross injection and collisions. As the cross injection interval increased, the liquid-phase STP of the collision spray increased, and its liquid-phase SPA decreased, while its vapor-phase SPA increased, promoting the diffusion and evaporation rates of the collision spray. In addition, increasing the interval of diesel and ammonia injection can shorten the ignition delay, and increase the flame lift-off length, leading to a more intense combustion process and less soot emissions. Therefore, the combustion and emission characteristics can be effectively improved by adjusting the injection timing of the two fuels reasonably.

Exploration on the combustion chemistry of p-xylene: A comprehensive study over wide conditions and comparison among C8H10 isomers

Pyrolysis and oxidation of p-xylene over wide conditions were studied in this work in order to provide a comprehensive insight into the combustion chemistry of p-xylene. Concerning this goal, the pyrolysis of p-xylene was investigated in a flow reactor at pressures from 0.04 to 1 atm over the temperature range of 1000–1600 K. Key radicals, isomers and PAH products including three xylyl isomers, benzyl, xylylene isomers, styrene, benzene, fulvene, indene, naphthalene and phenanthrene, were identified and quantified using synchrotron vacuum ultraviolet photoionization mass spectrometry. The oxidation of p-xylene was studied in a jet-stirred reactor at 10 atm, 800–1300 K and equivalence ratios of 0.5–2.0 with a residence time of 0.5 s. Oxidation products were quantified by using gas chromatography combined with mass spectrometry and Fourier transform infrared spectrometry. A kinetic model for p-xylene combustion over wide conditions was developed based on our previously proposed p-xylene oxidation model and validated against the new experimental measurements in this work and literature reported experimental data, including flow reactor oxidation, laminar premixed flame, ignition delay time and laminar burning velocity. In the flow reactor pyrolysis, p-xylene mainly undergoes unimolecular decomposition to yield p-xylyl, which mainly suffers the H-loss reaction to form p-xylylene and isomerization reaction to form o-xylyl. The resonantly stabilized fulvenallenyl and benzyl radicals play an important role in the formation of bicyclic and tricyclic PAHs including indene, naphthalene, and phenanthrene. In the JSR oxidation, p-xylene is predominantly consumed via H-abstraction by oxygenated radicals such as OH, O, and HO2 forming p-xylyl, which can be oxidized by HO2 and eventually converted to p-methylbenzaldehyde. As the most abundantly produced oxygenated aromatics, further consumption of p-methylbenzaldehyde results in the formation of other observed oxygenated aromatics such as cresol, benzofuran, and benzaldehyde. The combustion chemistry of three C8H10 isomers, i.e., p-xylene, o-xylene, and ethylbenzene, were also compared in terms of pyrolysis and oxidation fuel reactivity, and PAHs formation and growth, showing remarkable fuel isomeric effects.

Combustion Behavior of Fuel Droplets with Metallic, Non-Metallic and Organo-Metallic Boron Additives

ABSTRACT There is considerable interest in the utilization of fuels derived from boron materials, with their high calorific value, in various applications ranging from propellants to pyrotechnics. Conversely, their impact on the combustion behavior of conventional hydrocarbon fuels remains largely unclear. In this study, ignition, combustion, micro-explosion and simultaneous atomization behaviors of gasoline-based alternative fuels containing metallic (28–35 µm MgB2), nonmetallic (1 µm amorphous boron, 10 µm AlB12 with 86–88% and 95–97% purity) and organo-metallic boron derivatives (triethyl borate (TEB) containing C2H5 groups and trimethyl borate (TMB) containing CH3 groups) were investigated. The experiments were carried out at droplet scale and recorded using a high-speed camera and a thermal camera. The findings revealed a systematic reduction in ignition delay for each gasoline fuel enriched with boron derivatives. 2.5%AlB12/G and pure TMB droplets were the fastest extincting fuel droplets (0.9678 s and 1.245 s, respectively). The highest maximum flame temperature was recorded as 626 K and 610 K for pure TMB and 80%TEB/G, respectively. Droplet diameter regression analyses showed that the diameters of fuel droplets containing predominantly metallic and nonmetallic boron derivatives decreased in accordance with the d 2 -law. This study demonstrated that cost-effective and easily producible amorphous boron and organometallic boron derivatives are promising energy carriers for hydrocarbon fuels.

Chemical kinetic study of gasoline surrogate with ammonia on combustion: Iso-octane modeling

To facilitate the transition towards a carbon–neutral society, it is necessary to undertake comprehensive research on the utilization of ammonia in gasoline engine applications. In the present work, a new chemical kinetic mechanism for iso-octane/ammonia (iC8H18/NH3) was proposed and widely validated with the experiment data of ignition delay time (IDT) and laminar burning velocity (SL). The iC8H18 model of Cai [Combust. Flame, 162, 2015] and NH3 model of Zhang [Combust. Flame, 234, 2021] was chosen as the based model, and they connected through the chemical coupling between the iC8H18 and the NH2 chemistry. In addition, the influence of C-N interaction on the prediction ability of iC8H18/NH3 model was also analyzed and found that the H-abstraction reaction between NH2 and iC8H18 is the key reaction affecting the IDT and SL of mixture. Present work was also focused on the chemistry kinetic of iC8H18/NH3 mixture. The reaction pathway analysis shows that the addition of NH3 slightly enhanced the H-abstraction reaction of iC8H18 in tertiary site (cC8H17) and slightly inhibited the H-abstraction reaction of primary site (aC8H17, bC8H17, and dC8H17). In the end, the mole fraction of NO in iC8H18/NH3 flames is analyzed. The results show that NH3 addition increased the concentration of NO, but with the gradual increase of equivalence ratio, the increasing trend of NO concentration gradually decreases. A higher equivalence ratio can be selected to effectively control the increase of NOx concentration. Through the analysis of NO formation and reduction reaction pathway, it was found that NH3 addition increases the mole fraction of NH2 radical, the NO formation pathway was stronger than NO reduction pathway due to the sufficient OH radical, and finally leading to the increase of NO concentration. However, with the increase of equivalence ratio, the concentration of NH2 radical exceeds OH, and the number of OH is insufficient in satisfying the NH3-related NO reaction pathway, resulting in a decrease of the influence of NH3 addition on NO concentration.

Analysis of the influence of the type of heat transfer on the dynamics of the ignition processes of wood biomass particles under complex heating conditions

The article presents the results of theoretical and experimental studies of the processes of wood particles ignition under heating conditions typical for furnace devices operating using the circulating fluidized bed technology. The characteristics and conditions of ignition processes under radiation, radiation-convective and radiation-convective-microwave heating are compared. According to the results of the experiments, it was found that the use of microwave energy to accelerate the ignition of wood biomass particles is most effective at moderate temperatures of the combustion medium (at Tg≤870 K). Such conditions, as a rule, are formed in furnace devices that operate using boiling and circulating layer technologies. Based on the results of the analysis of the regularities established in the experiments, a mathematical model of the processes of ignition of a particle of wood biomass under conditions of complex radiation-convective-microwave heating has been developed. Using the method of quasi-stationary "thermal" approximation developed by the authors, an approximate analytical solution of the essentially nonlinear problem of ignition of wood biomass particles under conditions of complex heating is obtained. A comparative analysis of the theoretical and experimental values of the ignition delay time showed their good agreement. The results of the performed studies illustrate the possibility of a sufficiently significant reduction in the ignition delay times of wood biomass particles when using microwave radiation in addition to "conventional" sources of heating fuel particles in the furnace space in the temperature range at which the minimum concentration of anthropogenic nitrogen oxides in fuel combustion products is ensured.

Enhanced ignition and combustion performance of boron-based energetic materials through surface modification and titanium dioxides coating

The present study focuses on the removal of ineffective hydroxyl surface (B–OH) of the shell of pristine boron (B) particles, followed by its modification using a low-cost, eco-friendly, and non-hazardous ethylene glycol (EG). Subsequently, very small-sized titanium dioxide (TiO2) particles are coated onto the boron surface by adding titanium tetraisopropoxide (TTIP) precursors at room temperature. Characterization techniques were employed to investigate the structure and morphology of these materials. FTIR, XPS, and TEM analysis reveal that EG effectively removes ineffective boron hydroxyl surfaces and modifies the surface through passivation by its surface functionalities. Furthermore, EG assists in the coating very small-sized TiO2 particles on the boron surface. Thermal stability tests show that the modified boron surface and TiO2-coated boron surface exhibit earlier oxidation of the core boron compared to pristine boron. This enhanced capability for earlier oxidation of core boron was further investigated in the shock tube and bomb calorimeter for measurement of ignition delay time and heat of combustion. The findings demonstrate that room temperature synthesized TiO2-coated B particles (ignition delay time of ∼181 μs and heat of combustion of ∼17.3 kJ/g) outperform pristine B particles (ignition delay time of ∼284 μs and heat of combustion of ∼13.2 kJ/g). This improvement is attributed to the removal of ineffective boron hydroxyl surfaces, surface modification, uniform coating with very small TiO2 particles, the catalytic effect of TiO2 on oxygen diffusion, and effective oxidation of core boron. This study suggests that efficient energetic material can be achieved at room temperature with no potential harm to the environment.

Kinetic study of ignition process of ammonia/n‐heptane fuel blends under engine conditions

AbstractPilot‐ignited ammonia‐fueled engines have drawn more and more attention for low carbon emissions compared to traditional diesel engines. The ignition processes of NH3/NC7H16 mixtures under compression ignition engine‐like conditions are numerically investigated. By comparing the ignition delay times (IDTs) calculated by six ammonia mechanisms with experimental data, the Glarborg mechanism is selected. Then, the Glarborg mechanism and the Zhang detailed n‐heptane mechanism are merged into a new mechanism, which is adopted in the present study. Results show that the negative temperature coefficient behavior of the IDTs is only observed as the ammonia mass fraction is 70%. Only temperature has a significant effect on IDTs at all research conditions, and the effect of ammonia mass fraction is significant when the temperature is lower than 1000 K. However, the effects of equivalence ratio and pressure are small, especially at high temperatures, high equivalence ratios, and high pressures. Interestingly, the IDTs are categorized into three regions by temperature and ammonia mass fraction. The sensitivity analysis indicates that the sensitivity coefficients of most reactions associated with ammonia decrease with a decrease in ammonia mass fraction, whereas only R4210 is sensitive to ammonia mass fraction for n‐heptane‐related reactions. Rates of production and consumption (ROP) analyses indicate that the ammonia mass fraction mainly affects the ROPs of NC7H16, NH3, and NNH at low and medium temperatures, whereas the ammonia mass fraction affects the ROP of H2NO before the temperature of 2000 K. The ROPs of NC7H16, NH3, and NNH significantly increase with increasing temperature, whereas the ROP of H2NO slightly increases with increasing temperature. The increase of temperature in the early and middle stages is mainly contributed by the oxidation of n‐heptane, while the increase of temperature in the middle and late stages is mainly contributed by the oxidation of ammonia.

Influence of the type of woody biomass on energy and environmental characteristics of the thermal preparation processes and ignition of bio-water-coal fuel particles

The article presents the results of studies of ignition and combustion processes of droplets (during the initial period of heating), and then particles (after drying the surface layer) of bio-water-coal fuel (Bio-WCF) under conditions corresponding to typical furnace spaces of boiler units of thermal power plants (TPPs). The ignition delay times for Bio-WCF droplets of typical (for modern spray devices) sizes (diameter d=3 mm) have been established. The component compositions of the combustion products of significantly inhomogeneous bio-water-coal suspensions have also been established in a wide range of variations in the temperature of the oxidizing medium. A large-scale analysis of the influence of the type and concentration of woody biomass in a bio-water-coal suspension on energy (ignition delay time of WCF) and environmental (intensity of formation of anthropogenic combustion products of fuel) characteristics was carried out. It is shown that the addition of woody biomass to the water-coal suspension leads to a significant acceleration (by 10–20%) of the ignition process. An analysis of the component composition of combustion products showed that the introduction of wood biomass into the composition of water-coal fuel leads to a decrease in the intensity of the formation of anthropogenic combustion products. It has been established that an increase in the concentration of the vegetable component of the fuel leads to a significant sequestration of sulfur and nitrogen oxides.

Exploring the Impact of CO2 Atmosphere on Propane Moderate or Intense Low-Oxygen Dilution Combustion: A Numerical Simulation Study

Abstract Moderate or intense low-oxygen dilution (MILD) combustion is a promising combustion technology widely recognized by the international combustion community. In this study, numerical simulation was used to investigate the effects of CO2 atmosphere on MILD combustion of propane in a 20-KW furnace.The results show that the O2/CO2 atmosphere leads to a lower average temperature in the furnace, better temperature uniformity, and more uniform distribution of OH and CH2O compared to MILD combustion in the N2/O2 atmosphere. Propane MILD combustion is established well under the physical and chemical effects of CO2. An analytical approach is proposed to describe the physical and chemical effects of CO2 on MILD combustion. The physical effect of CO2 shortens the ignition delay time and advances the pyrolysis and ignition of propane, which causes a high-temperature zone in the front furnace and reduces the temperature uniformity in MILD combustion. However, the chemical effect of CO2 dominates the establishment of the MILD combustion by increasing the ignition delay time and reducing burning rates, with the help of the physical effects of CO2 by intensifying the entrainment in the furnace. Thus, the overall effects of CO2 lead to enhanced temperature uniformity by enlarging the area and evening the temperature of both the ignition zone and combustion zone. These findings provide valuable insights into the physical and chemical mechanisms of CO2 in MILD combustion and have important implications for optimizing combustion processes for improved efficiency and reduced emissions.

Experimental investigation on the combustion characteristics of ultra-lean premixed hydrogen/air using turbulent jet ignition

Amid growing environmental concerns, hydrogen (H2) is emerging as a prospective alternative fuel for driving internal combustion engines. Employing lean combustion technology in tandem with turbulent jet ignition (TJI) has the potential to enhance combustion rates while mitigating NOx emissions. Therefore, an experiment was developed to investigate the combustion characteristics of ultra-lean premixed H2/air by TJI. An active pre-chamber (PC) with an additional H2 supply was selected. Moreover, the effect of nozzle structures and equivalence ratio was discussed. The results show that with a nozzle diameter of 3 mm and an elevation of ΦPC to 1.4, the lean flammability limit is extended to an equivalence ratio of 0.13, with a consistently stabilized ignition delay within 4 ms. Increasing the nozzle number also extends the lean flammability limit, but it incurs higher energy losses. Additionally, two ignition mechanisms exist in TJI: flame ignition and combined ignition. The transition from flame ignition to combined ignition commonly occurs when the equivalence ratio of the main chamber drops below 0.3. This transition typically results in higher peak pressures and burnt fuel ratio, lower combustion duration, and longer ignition delay.

Understanding the Nonlinear Reactivity Promoting Effect of n-Heptane Addition on the Binary Mixture From Low to Intermediate Temperature: A Case of Methane/n-Heptane Mixtures

Abstract To understand the effect of n-heptane (NC7H16) addition on the auto-ignition of methane (CH4) at low to intermediate temperatures, the ignition delay times (IDTs) of stoichiometric CH4/NC7H16 blends with varying NC7H16 concentrations were measured at temperatures from 600 to 1000 K, pressures of 20 and 40 bar. Detailed chemical kinetic mechanisms were validated against the newly measured IDTs. Adding NC7H16 in the binary mixture shows a nonlinear promoting effect on the IDTs: micro-addition of NC7H16 can significantly reduce the IDTs of the binary mixture when the NC7H16 is lower than 20%. However, the decrease of the IDTs becomes much slower when further increasing the NC7H16 addition. Affected by the negative temperature coefficient (NTC) behavior of NC7H16, this nonlinear effect is particularly notable at around 795 K, the low boundary of the NTC region. To reveal the nonlinear reactivity-promoting effect of NC7H16 addition on the binary mixture, reaction flux, ignition sensitivity, rate of production of the key radicals along heat production analyses were conducted. Apart from contributing more O˙H production through the low-temperature chain-branching reaction pathways of NC7H16, adding NC7H16 also promotes the pre-ignition heat release of the binary mixture. The heat release raises the system temperature and further promotes the mixture ignition, enhancing the nonlinear effect at low temperatures.

Enhancing biodiesel stability and performance: synthesis and extraction of macauba biodiesel for sustainable engine applications

The demand for sustainable fuels has driven research on biodiesel blends’ combustion characteristics and emissions. The study evaluates the performance of macauba and soybean biodiesel blends by analyzing torque, power, and fuel consumption indicators. The effects of leaf extract additives on engine performance are also assessed. Comparing macauba and soybean blends show similar load, brake power, and engine speed trends on response variables. However, slight variations in coefficients and significance levels indicate unique combustion and emission profiles for each blend. Understanding these distinctions is crucial for optimizing engine performance and emission control strategies. Parameters analyzed include brake-specific fuel consumption (BSFC), brake thermal efficiency (BTE), exhaust gas temperature (EGT), carbon monoxide (CO) emissions, hydrocarbon (HC) emissions, oxides of nitrogen (NOx) emissions, smoke opacity, cylinder pressure, heat release rate, and ignition delay. Blends 80% Soy Methyl and 20% Macauba Methyl Biodiesel (BSM20) demonstrates 5–10% superior fuel efficiency, 8–12% higher energy conversion capability, 3–5% lower exhaust temperatures, 10–15% reduced emissions, and 5–8% enhanced efficiency versus other blends and Diesel. It also shows 10–20% lower hydrocarbon and CO emissions, 15–25% reduced NOx, 20–30% lower particulate matter, and more efficient energy release during combustion. Optimizing heat release rate and ignition delay is crucial; BSM20 shows a 10–15% shorter ignition delay. Understanding blend distinctions is key for optimizing performance and emissions. BSM20 blend demonstrates superior fuel efficiency, energy conversion capability, lower exhaust gas temperatures, reduced emissions, and enhanced engine efficiency compared to other blends and Diesel. It also shows lower hydrocarbon, CO, and NOx emissions, reduced particulate matter emissions, and more efficient energy release during combustion. Optimizing heat release rate and ignition delay is crucial for cleaner combustion and improved engine performance.

Experimental and modeling study of ignition delay times of n-C5H12 and C3H6 under O2/CO2 atmospheres

The combustion chemistry kinetics of fossil fuels under O2/CO2 atmospheres and high pressures attract the attention of researchers, since the pressurized oxy-fuel combustion (POC) is seen as a promising technology for capturing CO2 from thermal power industry and exhaust gas recirculation (EGR) is a promising technology to reduce NOx emissions. N-C5H12 is a representative fuel as gasoline components, and C3H6 is an important intermediate product in the oxidation of n-C5H12. In this study, the ignition delay times of n-C5H12 and C3H6 diluted in CO2 are measured at pressures of 1 and 10 atm under O2/CO2 atmospheres at three equivalence ratios (0.5, 1.0, and 2.0) in a shock tube, respectively. A detailed model named as Oxymech3.0 is developed based on the last version, Oxymech2.0 Plus. The model is evaluated with the experimental results in this work, as well as the ignition delay times of n-C5H12 and C3H6 in conventional atmospheres, the laminar flame speeds of n-C5H12 and C3H6, and the species profiles of n-C5H12. The evaluation results of Oxymech3.0 model are compared with several existing models and show the updating reactions in this work improve the prediction of the n-C5H12 and C3H6 IDTs in O2/CO2 atmospheres. The effects of reactions with CO2 for n-C5H12 and C3H6 are very faint. The chemical effects of CO2 mainly caused by the chaperon effects of CO2 for both n-C5H12 and C3H6. For n-C5H12, the chaperon effects are sourced from the third-body collision reactions 2CH3 (+M) ⇔ C2H6 (+M) (R2652), CH3 + H (+M) ⇔ CH4 (+M) (R2637), and C2H2 + H (+M) ⇔ C2H3 (+M) (R2714) at low pressures, while those from the pressure-dependent reactions H + O2 (+M) ⇔ HO2 (+M) (R2562) and H2O2 (+M) ⇔ 2OH (+M) (R2571) enhance at high pressure. For C3H6, the chaperon effects of CO2 are caused by C3H5-A + CH3 (+M) ⇔ C4H8-1 (+M) (R1456) at low pressure and by H + O2 (+M) ⇔ HO2 (+M) (R2562) when the pressure is higher.

BYCFoam: An Improved Solver for Rotating Detonation Engines Based on OpenFOAM

A rotating detonation engine (RDE) is a highly promising detonation-based propulsion system and has been widely researched in recent decades. In this study, BYCFoam, the latest gaseous version of the BYRFoam family, is developed specifically for RDE simulations. It is based on the standard compressible flow solver rhoCentralFoam in OpenFOAM and incorporates several enhancements: improved reconstruction variables and flux schemes; detailed chemistry and transport properties; the utilization of an adaptive mesh refinement (AMR) and dynamic load balancing (DLB). A series of comprehensive numerical tests are conducted, including the shock-tube problem, shock-wave diffraction, homogeneous ignition delay, premixed flame, planar detonation, detonation cellular structure and rotating detonation combustor (RDC). The results demonstrate that BYCFoam can accurately and efficiently simulate the deflagration and detonation processes. This solver enhances the capability of the BYRFoam family for the in-depth exploration of RDE in future research.

Engine behavior analysis on a conventional diesel engine combustion mode powered by low viscous cedarwood oil/waste cooking oil biodiesel/diesel fuel mixture – An experimental study

Binary biofuel is the best alternative source that completely replaces petroleum-based fuel. In this study, we have experimented with the waste cooking oil and cedarwood oil as biofuel in a DI CI engine for various proportions and related its combustion, emission, and performance characteristics to those of base diesel. This study aims to eliminate the utilization of fossil fuel in a diesel engine by introducing green binary fuel (low viscous fuel resulting from the blending of cedarwood oil with WCO biodiesel) successfully. The objective of the study is to convert cedarwood – WCO into green binary fuel and investigate its performance, emission, and combustion properties. The transesterification process is utilized for the enhancement of WCO as biodiesel. It occasioned a reduction in brake thermal efficiency as the addition of waste cooking oil in the blend increased. At the same time, the maximum value of BTE of 27.8% was attained for B10C90 (10% transesterified waste cooking oil and 90% cedarwood oil in volume), whereas it was 28.1% for diesel at maximum load conditions. The BSEC was 15.4 MJ/kW-hr for B10C90 and 12.8 MJ/kWhr for diesel. The emission characteristics, CO, HC, NOx, CO2, and smoke for B10C90 were 17.93 g/kWhr, 0.55 g/kWhr., 20.09 g/kWhr, 2210.9 g/kWhr, and 25.55%. Combustion features such as NHRR, burn duration, MPRR, combustion efficiency, Ignition delay, and coefficient of variance for B10C90 were 53.74 bar, 29.38 CAD, 4.71 bar/CAD, 99.7%, 7.01 CAD, and 4.73% respectively. It showed that B10C90 had comparable performance (BTE) and combustion values to mineral diesel with better emission characteristics.

Alternative Methods for Biodiesel Cetane Number Valuation: A Technical Note.

Biodiesel is an environmentally beneficial and clean energy source that may replace fossil fuels, which are detrimental to the environment and cannot be replenished. Therefore, the physicochemical parameters of biodiesel must be determined in order to verify its quality. The cetane number is a crucial dimensionless fuel property that gauges the fuel ignition quality in power diesel engines. A higher cetane number results in a shorter ignition delay time, and vice versa. Biodiesel's cetane number may fluctuate due to a variety of fatty acid compositions, including variations in carbon chain length and the degree of unsaturation. The cetane number generally increases with increasing saturation and chain length, while it decreases as chain length is reduced and degrees of unsaturation and branching increase. This is the main reason for why alkanes possess a higher cetane number than alkenes and aromatics. The standard protocols for evaluating the cetane number of biodiesel are ASTM D613 and ISO 5165 test techniques using a monocylindrical cetane engine. However, adhering to these conventional procedures is quite challenging and time-consuming, and the cetane number test result may also be affected by the presence of certain gases and fumes. As a result, many researchers are bothered with cetane number valuation, and occasionally they skip it due to a lack of other options. Consequently, the aim of this paper is to present a set of more straightforward and relevant alternative techniques that can be applied to predict the cetane number of biodiesel when engine-based measurement is not practical. The three techniques with their designed pictographic outlooks conferred in this article include color indicator titration, aniline point, and fatty acid composition-based methods. The reported values of these procedures meet the minimum cut point of the biodiesel cetane number required by ASTM D6751 (≥47) and exhibit minimal variation from the typical standard methods. Nevertheless, the above-mentioned techniques are not applicable to other alternative biofuels except biodiesel products because they have a direct implication on the characteristics of the fatty acid profiles of different oil precursors, such as carbon chain length, degree of saturation or unsaturation, and aromaticity, which make up monoalkyl esters.

Effect of Alumina and Bio‐Based Calcium Oxide Nanoadditives on Reduction of Emissions and Performance Improvement in a Common Rail Direct Injection Diesel Engine Fueled with B20 Blend of Waste Cooking Oil Biodiesel

This experimental study investigates the performance, combustion, and emission characteristics of a common rail direct injection diesel engine running on used cooking biodiesel prepared through transesterification. The nanoparticles calcium oxide (CaO) and alumina (Al2O3) are mixed with the B20 blend using an ultrasonicator to create a homogeneous mixture. The following five fuel series are used in the study: a B20 blend with three different nanoparticle ppms are blended to form Al2O3CaO 90 ppm, Al2O3 + CaO 60 ppm, and Al2O3 + CaO 30 ppm. The enhanced surface area to volume ratio of nanoparticles enhances the degree of mixing and chemical reactivity during combustion. Also, the characteristics of diesel engines result in reduced specific fuel consumption. The test fuel B20 + 90 ppm (90 ppm nanoparticles dispersion) results 9% and 11% increase in brake thermal efficiency compared to diesel and B20, respectively. The presence of nanoparticles in biodiesel has initiated the combustion slightly earlier due to its improved ignition qualities that permit catalytic combustion and a shorter ignition delay. In comparison to diesel and B20, the Al2O3CaO90 ppm fuel blend lowers NOx emissions by 18% and 21%, carbon monoxide emissions by 40% and 43%, hydrocarbon emissions by 35% and 40%, and smoke emissions by 24% and 29%, respectively.

Use of Artificial Neural Network to Develop Surrogates for Hydrotreated Vegetable Oil with Experimental Validation in Ignition Quality Tester

<div>This article presents surrogate mixtures that simulate the physical and chemical properties in the auto-ignition of hydrotreated vegetable oil (HVO). Experimental investigation was conducted in the Ignition Quality Tester (IQT) to validate the auto-ignition properties with respect to those of the target fuel. The surrogate development approach is assisted by artificial neural network (ANN) embedded in MATLAB optimization function. Aspen HYSYS is used to calculate the key physical and chemical properties of hundreds of mixtures of representative components, mainly alkanes—the dominant components of HVO, to train the learning algorithm. Binary and ternary mixtures are developed and validated in the IQT. The target properties include the derived cetane number (DCN), density, viscosity, surface tension, molecular weight, and volatility represented by the distillation curve. The developed surrogates match the target fuel in terms of ignition delay and DCN within 6% error range. This investigation will be of value to developing high-fidelity models to investigate HVO combustion and spray behavior. This will be beneficial to researchers advancing the design and development of compression ignition engines to efficiently operate on renewable fuels such as HVO.</div>

Investigation of the combustion process in a dual-fuel engine

Modeling of in-cylinder processes occurring in a dual-fuel engine is necessary to obtain the ignition delay period as a function of the angle of rotation of the crankshaft and the subsequent calculation of its effective and environmental indicators. There is a need to identify the theoretical dependence of the fuel combustion process on the parameters that determine the operating modes of a dual-fuel engine, which leads to the need to create a mathematical model that allows the most accurate description of the combustion process, taking into account the maximum possible number of factors. The paper considers the optimization of the parameters of the workflow and the prediction of the performance of the projected and existing dual-fuel engines.

Ignition Delay and Reaction Time Measurements of Hydrogen–Air Mixtures at High Temperatures

Induction and reaction times of hydrogen–air mixtures (ϕ = 0.5–2) have been measured behind reflected shock waves at temperatures of 1000–1600 K, pressures of 0.1, 0.3, 0.6 MPa in the domain of the extended second explosion limit. The measurements were performed in the shock tube with a completely transparent test section of 0.5 m long, which provides pressure, ion current, OH and high-speed chemiluminescence observations. The experimental induction time plots demonstrate a clear increasing of the global activation energy from high- to low temperature post-shock conditions. This trend is strongly pronounced at higher post-shock pressures. For a high-temperature range of T > 1200 K, induction time measurements show an activation energy for the global reaction rate of hydrogen oxidation of 64–83 kJ/mole. Detected reaction times exhibit a big scatter and a weak temperature dependence. The minimum reaction time value was nearly 2 µs. Obtained induction time data were compared with calculations carried out in accordance with the known kinetic mechanisms. For current and former shock-tube experiments within a pressure range of 0.1–2 MPa, critical temperatures required for strong (1000–1100 K), transient and weak auto-ignition modes behind reflected shock waves were identified by means of the pressure and ion-probe measurements in stoichiometric hydrogen-air mixture. The transfer from the strong volumetric self-ignition near the reflecting wall to the hot spot ignition (transient) was established and visualized below <1200 K with a post-shock temperature decreasing.