Soot Concentration Research Articles

Edge Effects on Simultaneous Reconstructions of Flame Temperature and Soot Volume Fraction Profiles by a CCD Camera.

In this paper, the influence of the edge effect on the simultaneous reconstruction of axisymmetric flame temperature and soot volume fraction profiles by a single CCD camera was investigated in detail. The reconstruction accuracy of the flame temperature profile and soot volume fraction was insensitive to the measurement error of the coefficient matrix. When the signal to ratio (SNR) of the measurement system for both the radiation intensity and coefficient matrix was as low as 46 dB, the reconstruction accuracy for both temperature and soot volume fraction was acceptable and was more influenced by the radiation intensity measurement error. The reconstruction of the flame temperature and soot volume fraction was greatly influenced by the edge effect. When the flame edge with weak radiation signals was ignored during the reconstruction, the relative reconstruction error for the temperature and soot volume fraction increased from the flame center to the edge, and reached an unacceptable value at the reconstruction boundary, especially for the soot volume fraction. The flame image boundary could be chosen as the unified reconstruction boundary to reconstruct the two-dimensional distribution of the temperature and soot volume fraction with satisfactory accuracy. The low soot volume fraction could influence the reconstruction accuracy for both the temperature and soot concentration in non-sooting regions. Moreover, there was no obvious regularity between the reconstruction accuracy of the temperature and soot volume fraction and the extension of the reconstruction boundary.

Optical properties of incipient soot

The exact knowledge of the optical properties of soot nanoparticles is fundamental for several aspects including the correct determination of the soot concentration in combustion environments using optical diagnostics and the correct estimation of the environmental impact of the emitted particles. Although extensive researches over the years have led to a substantial agreement on the optical properties of mature soot particles, the optical properties of the incipient soot nanoparticles are still uncertain. From the particle inception point to the formation of large and more mature soot particles, the evolution of the optical properties must account for variations due to the size and the physicochemical transformation of the investigated particles. This work aims to determine the refractive index and optical properties of inception particles formed in lightly sooting flames. A previous determination based on in-situ light absorption and scattering measurements is revisited taking advantage of particle size measurements by differential mobility analysis. The spectral dependencies of the optical properties are derived by the Kramers-Krӧnig analysis of the ex-situ VUV-NIR light absorption measurements. Results confirm the strong decrease in the absorptivity in the vis-NIR region of inception particles with unimodal size distribution and d63∼3 nm, and confirm a strong size dependency of soot optical properties. The thermal-optical analysis of the sampled particles shows that the particle mass absorption coefficient also correlates with organic carbon content.

Assessment of physical soot inception model in normal and inverse laminar diffusion flames

Despite the extensive studies, accurate and reliable modeling of the soot inception process, especially at high pressure conditions, amenable to multi-dimensional flame simulations remains a challenge. In this study, the physical inception model was comprehensively evaluated in the fully-resolved simulations of laminar normal diffusion flame (NDF) and inverse diffusion flame (IDF) at elevated pressures. The effects of inception models on polycyclic aromatic hydrocarbons (PAHs) and soot predictions were quantitatively analyzed, including the selection of soot precursors and collision efficiency models. The results show that the quantitative PAH predicted by different collision efficiency models can differ by an order of magnitude. Compared to the constant efficiency, the temperature-dependent collision efficiency was found to improve the quantitative PAH predictions and the prediction of the spatial soot distribution in NDF, with an increased level of soot on the flame centerline. The inclusion of small-sized PAH species (such as A2, A2R5, and A3) as soot precursors was also found to improve the quantitative prediction of soot volume fraction. The physical inception model performs well in NDF using the optimal parameters. Moreover, simultaneous measurements of PAH and soot were performed in IDF configuration for the evaluation of the physical inception model. Contrary to NDF, PAHs and soot are formed on the outer side of the flame and cannot be oxidized in IDF. The experiment observed that the PAHs concentration increased in the post-flame region, while the soot concentration remained unchanged. However, the opposite trend was obtained in simulations, that is, the PAHs concentration decreased while the soot concentration increased, because the physical inception model predicts the inception behavior in the post-flame area, resulting in persistent transformation of PAHs into soot particles. To improve the predictions in IDF, the radical effects in the inception process need to be considered in the model.

Soot Distribution Characteristics and Its Influence Factors in Burner-Type Regeneration Diesel Particulate Filter

The burner-type regeneration diesel particulate filter is one of the most widely used diesel particulate filters. Using AVL FIRE, a 3D model of a burner-type regeneration diesel particulate filter (DPF) was established, and simulation analyses were carried out. The effects of the exhaust parameters (temperature, exhaust mass flow rate, and soot load) and the structural parameters (channel density, inlet/outlet channel ratio, and the length–diameter ratio) on soot distribution (soot mass concentration and soot thickness) were analyzed. The results show that the soot distribution characteristics of regenerative DPF with a burner are as follows: the soot mass concentration first rapidly rises to the maximum value and then rapidly decreases to a low value, and the dust thickness gradually increases with the increase in location. With the increase in exhaust mass flow rate and soot load, soot mass concentration and soot thickness increase. With the increase in temperature, the mass concentration and thickness of the ash decreased. When the temperature exceeds 750 K, soot begins to regenerate. Among the exhaust parameters, the mass flow rate of the exhaust has the greatest influence on the soot distribution. The length–diameter ratio, the ratio of the inlet and the outlet channel, and channel density have little effect on the mass concentration of soot, and the soot mass concentration increases with the increase in channel density. In addition to the length–diameter ratio of 2.1, the soot thickness increases with the increase in the length–diameter ratio, and the rising rate is also accelerated. The thickness of soot decreased with the increase in channel density and the ratio of the inlet and the outlet channels. When the channel density is more than 250, the change in soot thickness is basically the same. When the ratio of the inlet and the outlet channels exceeds 1.3, the change in the soot thickness is basically the same. Among the structural parameters, channel density has the greatest influence on the soot distribution.

An examination of performance deterioration indicators of diesel engines on the plateau

This paper investigated the sensitivity of diesel engine performance to plateau environment. A three-dimensional computational fluid dynamics engine model validated against the experimental data was performed to provide analytical data from sea level to 5000 m at a constant engine speed and fuel injection strategy. The simulation results showed that the engine torque exhibited a nonlinear reduction with decreasing ambient pressure. Similarly, the fuel consumption increased non-linearly with altitude due to the combustion deterioration. However, the decline in the engine pressure-related parameters was smooth since flame extinction did not occur. As for nitrogen oxides emissions, high altitude operations steadily reduced the area of the thermal nitric oxide production zone, and therefore it decreased smoothly with altitude. In addition, soot emission levels rose with altitude mainly due to the reduced air utilization capacity, which boosted the soot formation while simultaneously undermined the percentage of soot oxidation. Soot concentrations suddenly increased when the engine was operated above ∼4000 m. This was due to the enhanced penetration of the diesel spray, which caused wall adhesion, adding another soot formation mechanism. As a result, soot is the appropriate indicator to find the maximum altitude that engine can tolerate without significant performance degradation.

Sooting transition diagnostics in counter-flow flames of C4 isomer fuels

Macroscopic transition processes of soot formation for 1-butene, isobutene, n-butane and isobutane counterflow diffusion flames from sooting-free to heavy-sooting were studied by varying fuel concentration (XF) in the fuel stream. A novel optical diagnostic algorithm was proposed to classify different sooting transition stages in flames. Effects of saturated/unsaturated bonds and linear/branched structures of fuel molecules on the sooting transition were investigated in details. Flame species were detected and quantified by on-line gas chromatography and also kinetic analysis was performed. KL factor was obtained by optical diagnostics to qualitatively compare soot concentrations. Results showed that XF required for 1-butene flame to reach the critical state of macroscopic sooting transition was the lowest, followed by isobutene, isobutane and n-butane flames. Fuels with higher sooting tendencies could achieve entire sooting transition process with a narrower range of XF. Linear butane was more difficult to achieve the sooting transition than branched butane, while linear 1-butene was easier to form soot than branched butene, reflecting the difference between isomeric structures acting on C4 alkenes and alkanes. These might be largely due to the close association of allyl (C3H5-A) with 1-butene. Higher C3 species content in isobutane flame made it have higher sooting tendency than n-butane.

Soot characteristics from diffusion flames coupled with plasma

The study of soot characteristics in plasma-flame interaction was necessary to improve combustion efficiency and reduce pollutant emissions. This work experimentally investigated effects of plasma on soot formation, evolution and characteristics in ethylene diffusion flames by both optical diagnostic and sampling methods. The optical diagnostic method was employed to capture the two-dimensional distribution of soot temperatures and concentrations. Moreover, the nanostructure, crystallite properties and oxidation reactivity of soot from diffusion flames with plasma addition were obtained using transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis and X-ray diffraction spectroscopy. The flame shapes and luminosity varied depending on the electrical parameters and oxygen concentration. It was found that the overall temperature increased somewhat with plasma activation, but remained roughly constant when the discharge frequency or applied voltage increased. The soot concentration immediately reduced with plasma on and then displayed different trends as the discharge frequency or applied voltage increased. The variation in soot concentration was caused by the combination of several parameters, including flame behavior, soot temperature and the effect of the electric field by energetic and chemically active species. The generated soot showed typical chain-like aggregates without plasma, but more film-like materials were presented with plasma acting on flames. The soot graphitization degree decreased notably with plasma generation resulting in higher oxidation reactivity because the shorter residence time and the plasma activation were simultaneously obtained, which both illustrated an inhibition effect of plasma on soot emissions. The disordered carbon content related to soot oxidation reactivity.

Soot production in high pressure inverse diffusion flames with enriched oxygen in the oxidizer stream

Catalyst degradation due to soot formation is one of the main issues in the autothermal reforming (ATR) process, which is widely regarded as the future technology for hydrogen production from natural gas. In this work, soot formation under conditions similar to ATR was systematically investigated, focusing specifically on the effects of pressure on soot formation in inverse diffusion flames (IDFs) under oxygen rich conditions. Methane was diluted with carbon dioxide; the oxygen content in the oxidizer stream varied from 55 to 70%-by-mol. Polycyclic aromatic hydrocarbon (PAH) and soot concentrations in the flames were measured by laser-induced fluorescence (LIF) and laser-induced incandescence (LII) respectively. Flame images showed that, as the pressure increased, the luminous region of the IDFs moved downward to mask the blue reaction region, and the flames became narrower. The degree of flame narrowing in the IDFs was milder than normal diffusion flames (NDFs). LIF measurements showed that increasing the pressure promoted PAH formation, which also subsequently promoted soot formation. Both PAH and soot formation increased linearly with pressure. The linear relationship was different from that of the NDFs. Flame simulations suggested that the promotion of soot formation with pressure was largely driven by PAH adsorption. Under the conditions of this study, lowering the oxygen content promotes soot formation in the IDFs. The results of this work contribute to the understanding of soot formation in IDFs at elevated pressures and the optimization of the ATR process.

Two-color pyrometry for backface temperature and emissivity measurement of burning materials

Two-color (2C) pyrometry has long been used for flame temperature and soot concentration studies and is now becoming more widely used to measure backface temperatures of burning materials. With the obvious advantage of being a contact-free method that requires only minimal optical access, 2C pyrometry combined with high-speed acquisition is a promising diagnostic tool to obtain exceptional temporal and spatial resolution of thermally degrading samples. However, its conceptual simplicity relies on a set of basic assumptions that when violated can result in large errors. In this work, we used an experimental configuration representative for fire resistance testing for aerospace and naval applications to analyze the impact of camera parameters and test setup on the accuracy of the surface temperature results obtained. Two types of fiber reinforced polymer composites and a steel plate are used to investigate material specific aspects that affect the measurements. An improved workflow for camera calibration is presented that takes into account the actual experimental setup. The temperature and emissivity mapping obtained through in-situ IR measurements is compared to data acquired through thermocouples and post-fire hemispherical directional reflectance measurements at room temperature. Excellent agreement is found for post-processed 2C pyrometry measurements and TC probe measurements with an uncertainty of 30 °C at 500 °C. In-situ emissivity mappings of burnt specimens are consistent with data from the literature for degraded composite samples and oxidized steel plates. Our results remind the importance of proper post-processing and demonstrate the potentials of 2C pyrometry for fire testing applications. We also present a detailed error budget and suggestions for calibration measurements to improve measurement accuracy.

Robust two-colour pyrometry uncertainty analysis to acquire spatially-resolved measurements

Two-colour pyrometry (2CP) has been used over several decades to study engine-relevant combustion processes, but results are generally regarded as qualitative or semi-quantitative. In many current 2CP systems, large measurement errors are introduced by parallax because the two measured wavelengths are not from the same line of sight. This work presents a spatially-resolved 2CP system with the objective of quantifying and reducing measurement uncertainty. An optical setup that eliminates parallax in 2CP is used together with pixel-by-pixel calibration of the camera sensor to increase measurement accuracy. Primary uncertainty terms are identified, and an error propagation analysis is performed to compute uncertainties in the final results of soot temperature, soot concentration parameter, KL, and soot mass. These methodologies are applied to investigate an auto-igniting fuel spray in a constant pressure flow rig at diesel-like conditions of high ambient pressure and temperature. Results show bias uncertainty of around 200 K (≈10%) for temperature and about 40%–60% for KL. High uncertainty was found to occur on the diffusion flame front where both optical thickness and soot concentrations are small. However, these uncertain measurement zones with relatively low soot concentrations contribute minimally to the total soot mass present in the reacting jet during the temporal evolution of the flame.

Effect of ash in biodiesel combustion particulate matter on the oxidation characteristics of carbon soot

This study investigates the effect of ash in biodiesel combustion particulate matter on the oxidation characteristics of carbon soot within a diesel particulate trap. Samples of pigment-U engineered carbon soot were mixed with different biodiesel ashes using an impregnation method. The samples were subjected to 24 h of heating at 120 °C and 2 h of heating at 350 °C before treatment. The oxidation activity, structural properties and the elemental species of the manufactured carbon soot were investigated using thermogravimetric analysis, specific surface area and pore analysis, Raman spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The oxidation characteristics of the carbon soot were investigated with different metal elements, masses and metal salt types. The results show that the doping of metal elements and metal salt types can increase the oxidation activity of the carbon soot, with Na elements and nitrate having the greatest effect on the oxidation activity. Doping with metal elements and metal salt species can make the structural orderliness and graphitization of the soot decrease, and the O and CO contents increase to different degrees. Sodium (Na) and nitrate have the greatest influence on the soot structural properties, with the numerical ratios and area ratios between peaks being the largest. Doping with Na results in an ID1/IG value of 1.44, and an AD3/AG value of 1.53. The CO content of soot doped with Na is the greatest, reaching 4.7%. The oxygen content of soot doped with Na carbonate is the largest, reaching 5.5%.

Thermal effect and oxygen-enriched effect of N2O decomposition on soot formation in ethylene diffusion flames

This study experimentally investigated the effect of nitrous oxide (N2O) decomposition on soot formation in N2O/ethylene diffusion flames. The effect of N2O decomposition on the soot formation mechanism was examined in three oxidation cases (Cases Case I–III). In Case I, N2O was used as the oxidant; in Case II, an oxygen-enriched N2/O2 mixture (67 % N2 + 33 % O2) was used as the oxidant; and in Case III, standard air (79 % N2 + 21 % O2) was used as the oxidant. A triple-port burner was used to generate diffusion flames with various R (ratio of the oxidizer flow velocity to the fuel flow velocity) values (R = 0–6). The soot concentration was measured through laser-induced incandescence, and the soot temperature was determined using two-color pyrometry. The measured soot temperatures increased significantly due to the thermal effect in the upstream position of the N2O/C2H4 flames. The oxygen-enrichment effect on soot formation increased gradually from 10 % to 60 % as R increased from 0.5 to 6. The integration of the soot concentration along the flame length revealed that the soot formation rate and soot oxidation rate might rebalance under the N2O decomposition effect.

Theory and practice of diagnostics of fire hazardous modes of operation of catalytic converters

Introduction. The wide-scale use of catalytic converters and particulate filters in automobile engines has aggravated the problem of their ignition and updated the research and methodological framework for the examination of causes of fire emergency modes (FEMs) of operation of fuel catalytic units (FCUs). The relationship between the FEMs of the FCU operation and failures of the fuel equipment, wear of the cylinder-piston group of engines and deviations in fuel compositions was confirmed. The goal was to develop a diagnostic method for fire hazardous modes of operation of FCUs of vehicles.Methodology. A model of oxidative catalysis underway in the FCU has been proven rational. The model is used to calculate the thermo-catalytic efficiency and heat generation in the active layer of the γ-Al2O3 platinum catalyst depending on the temperature of exhaust gases (EG), concentrations of CO, CH and soot. It has been found out that catalysis can theoretically develop in four limit domains: internal kinetic domain, internal diffusion domain, external diffusion domain, and external kinetic domain.Results and discussion. Experimental and computational studies have shown the probability of emergence of breakdown vehicles with a multiple excess of soot emissions and thermal stresses. A 10‑fold increase in CO, CH and soot in EG rises the thermal performance of the catalytic reaction from 17,282 to 491,907 kJ/h, creating a fire hazard in a KamAZ engine. To identify a FEM, the diagnostic method based on the «free acceleration» (FA) mode according to GOST 33997–2016 is proposed. The procedure is supplemented with maximum revolutions and restrictions (0.5 s) of the FA mode time. The latter is necessary for the guaranteed operation of the engine in the «full load mode». The method was applied in the course of the fire engineering studies on a Ford Mondeo car having a TDCi (Common Rail System) diesel engine and a catalytic particulate filter. Laboratory examination and analytical studies have found that the main reason for the operation of FCU in emergency (due to environmental and fire hazards) modes is the corrosion of precision parts of the fuel equipment accumulated during its long-term operation. Progressive corrosion is caused by excessive sulfur and moisture content in fuel and oil.Conclusions. It’s been proven that the emergency heating of a catalytic converter causes a sharp rise in the car combustion risk. The authors have proposed an original method for the diagnostics of fire-hazardous modes of operation of catalytic converters based on procedures set in GOST 33997–2016 (ТР ТС 018/2011).

Diffuse Back-Illumination Extinction Imaging Of Soot Formation From A Liquid Fuel Film

The transient combustion of a liquid iso-octane film, isolated from the often co-existing combustion of liquid sprays, was investigated within the nominally quiescent ambient of a constant volume chamber using a custom-made liquid fuel film generation system. Soot formation throughout the combustion process, from ignition to extinction, was visualized using high-speed diffuse back-illumination extinction imaging technique, providing temporally resolved spatial distribution of soot optical thickness (KL) in the chamber. The impact of ambient pressure and ambient oxygen content on soot formation was examined over a range of 2 – 5 bar (absolute) and 16 – 30% (in terms of molar fraction of oxygen), respectively. Regardless of the test conditions, the fuel film combustion entailed three stages, namely flame initiation, steady burning and flame extinction. While the ambient oxygen content was kept constant, the flame gradually became turbulent-like and the flame flickering less distinct as ambient pressure was increased. The total amount of soot generated within the chamber was found to first increase then decrease with the ambient pressure, due to the competing impacts of increasing pressure on promoting soot-formation reaction rate and enhancing mixing of fuel vapour with the entrained air. Increasing ambient oxygen content, on the other hand, consistently enhanced soot formation, which may be associated with its impact on boosting flame temperature and consequently liquid fuel evaporation rate. In addition, flame flickering remained distinct for ambient oxygen content above atmospheric level, while becoming substantially less observable for that below atmospheric level. Flickering frequency, for all test conditions with distinct flame flickering, had a value of approximately 10 Hz and gradually increased with time during the steady burning stage, suggesting the shrinkage of the fuel film diameter. Flickering of the flame resulted in fluctuations in the total amount of soot presented in the combustion chamber. The power of this fluctuation varied with time, and this temporal variation of fluctuation power also depended on experimental conditions, due to its dependency on the combined effects of soot concentration and volume of the flame.

Combustion and emission performance of isopropanol-butanol-ethanol (IBE) mixed with diesel fuel on marine diesel engine with nano YSZ thermal barrier coating

The effect of piston coating on the combustion and emission performance of IBE and diesel blended fuel was experimental studied. The experimental conditions were set to be a orthogonal matrix of three loads from low to high, coated and uncoated, IBE20 fuel and D100 fuel. The heat release rate, ignition delay periods and combustion duration were calculated by the cylinder pressure curves. The break thermal efficiency was calculated by the fuel consumption rate, and the concentration of soot, NOx and CO in the exhaust was collected. It was found that Nano-YSZ thermal barrier coating (TBC) can effectively reduce heat transfer loss, increase in-cylinder combustion temperature, and effectively solve the problems of high latent heat of vaporization and ignition delay of alcohol fuel. The experimental results showed that the Nano-YSZ coating could effectively reduce the brake specific fuel consumption, which was reduced by 5% when using pure diesel under 25% load, and was reduced by 7.3% for IBE20 fuel. Furthermore, TBC_IBE20 (IBE20 used in TBC Engine) exhibited the highest thermal efficiency under the three working conditions. Under all operating conditions, IBE20 had the potential to reduce soot emissions but increase NOx emissions, and thermal barrier coatings could amplify this potential.

Effects of Propanol on the Performance and Emissions of a Dual-Fuel Industrial Diesel Engine

The search for alternative fuels that can limit the use of traditional fossil fuels to power internal combustion engines is one of the main tasks faced by both the modern automotive industry and the modern energy industry. This paper presents experimental tests of a compression ignition engine, in which the conventional fuel, i.e., diesel, was partially replaced with propyl alcohol, i.e., a renewable biofuel. Studies on the co-combustion of diesel fuel with propanol were carried out, in which the energy share of alcohol varied from 0 to 65%. The research showed that an increase in the proportion of propanol, up to 30%, resulted in a significant increase in the rate of heat release and the rate of pressure increase in the cylinder of a compression-ignition engine. Increasing the alcohol content to 65% resulted in an increase in the ignition delay time and significantly shortened the duration of combustion. During the combustion of diesel fuel with a 50% propanol share, the engine was characterized by maximum efficiency, higher than diesel fuel combustion by 5.5%. The addition of propanol caused a slight deterioration of the combustion stability determined by the coefficient of variation for IMEP. The study of engine exhaust emissions has shown that the combustion of diesel fuel with a small proportion of propanol, up to 30%, causes an increase in nitrogen oxide emissions, while up to 50% contributes to a decrease in HC emissions. The increased share of alcohol contributed to a significant decrease in the emissions of both carbon monoxide and carbon dioxide, and caused a significant reduction in the concentration of soot in the exhaust of the compression-ignition engine.

Simulation Research of the n-Butanol Proportion Influence on HCCI Combustion of Free-Piston Diesel Engine Generators

For researching the influence of n-butanol proportion in diesel fuel on homogeneous charge compression ignition (HCCI) combustion of the free-piston diesel engine generator (FPDEG), a three-dimensional (3D) moving mesh computational fluid dynamics (CFD) simulation model of a FPDEG prototype was developed. A detailed chemical reaction mechanism of diesel fuel was selected as the HCCI combustion mechanism and coupled in the established HCCI combustion simulation model of the FPDEG prototype. The validity of the established HCCI combustion simulation model is proved by comparing the simulation and experimental pressure curves under the condition of pure diesel fuel. The simulation results of different n-butanol proportions in diesel fuel showed that as the n-butanol proportion increased from 0 to 60%, the maximum heat release rate decreased to 59.6 J/deg, the calculated indicated thermal efficiency augmented to 4.6%, the calculated indicated mean effective pressure increased to 0.057 MPa, and the final NOx and CO content decreased to 0.239 and 0.57 g/kg fuel, respectively, but the final soot content increased to 0.000562 g/kg fuel. Therefore, the n-butanol proportion of diesel fuel played a vital role in combustion and emission progress of the FPDEG.

Experimental study on the effect of post-injection parameters on performance of extra-high pressure common-rail diesel engine

The diesel engine combustion process is mainly controlled by the fuel injection characteristics, which will have a direct impact on the performance of the diesel engine, more flexible injection strategy is the development direction of high pressure common-rail system. In order to obtain the change law of the performance of extra-high pressure common-rail diesel engine under variable injection strategy, and improve the overall performance of diesel engine, the effect of different post-injection parameters on the performance of diesel engine was studied on a self-designed extra-high pressure common-rail diesel engine experiment bench, and the relevant results were discussed and analyzed. The results show that: with the rise of post-injection fuel quantity, NOx concentration and soot concentration decrease gradually, and with the rise of post-injection interval angle, NOx concentration decreases gradually, while soot concentration first decreases and then increases. Therefore, choosing post-injection fuel quantity and post-injection interval angle rationally can achieve lower NOx and soot emission at the same time. Meanwhile, with the rise of post-injection fuel quantity or post-injection interval angle, the fuel consumption rate presents an increasing trend.

Phase portrait and fractal analyses in nanobiophotonics: carbon nanoparticle aided intra-pigment energy transfer in leaves

The paper delineates the potential application of nonlinear time series analysis (TSA) in Nanobiophotonics to explore the soot-assisted intra-pigment energy transport mechanism in leaves. The soot nanofluid, containing nano carbon allotropes, prepared in different concentrations, is sprayed over Lablab purpureus (L.) sweet leaves. The chlorophyll extracted from the leaves after ten days is subjected to UV-Visible absorption and single beam thermal lens (TL) studies. The variation of the absorbance of signature peaks of chlorophyll pigments with the soot concentration reveals the role of soot in the intra-pigment energy transport, divulged through the time series TL signal. The TSA of the TL signals, the plotting of phase portraits, and the computation of sample entropy (S), fractal dimension (FD), and Hurst exponent for the pigment-soot systems unwrap the particle/molecular dynamics and the flow of energy within the system. The analysis by segmenting the variations of the TSA measures with soot concentration reveals that the values of S and FD of the system are high in the low and high concentration ranges, in agreement with the randomness reflected in the phase portrait. The middle region, where S and FD decrease, seems more energy-efficient for the photosystem through heat trap and energy exchange between the pigment-soot system. The study gives information about the critical concentration range suitable for increased photosynthesis in leaves and yield enhancement.

Evaluation of in-cylinder endoscopic two-colour soot pyrometry of diesel combustion

Flame temperature and soot concentration imaging was performed using endoscopic two-colour (2C) soot pyrometry to investigate the characteristics of in-cylinder diesel engine combustion processes and provide validation data for engine simulation and design. To appropriately interpret the 2C image results, this paper focuses on the uncertainty and challenges of the technique, the line-of-sight nature of the measurement and presents comparable information for validation exercises. A line-of-sight flame light intensity model was created to explore how the temperature T and soot concentration KL measured by the 2C technique can relate to non-uniform flame temperature and soot distributions. It was found that T and KL measured from the 2C technique were likely to relate differently to the actual distribution depending on where in the flame the measurement was taken and on assumptions made about the flame spatial structure. Assessment has been made of the range of the maximum and minimum flame temperatures (assumed to correspond to reaction zone temperature and flame centreline respectively) that are consistent with measured temperature T and soot concentration KL. The analysis of uncertainties, flame temperature and soot distribution along the line-of-sight, and image averaging allows for better quantitative comparison of 2C soot pyrometry images to CFD simulation, which increases confidence in simulation-driven engine development.