Ethanol Flow Rate Research Articles

Quantification of gas-assisted evaporation in minichannels with negative wall superheats

The present study quantifies the gas-assisted evaporation of ethanol in two parallel minichannels with negative wall superheats using helium as the auxiliary gas. At the exit of minichannels, an innovative gas–liquid separation and vapor condensation device is designed to measure the ethanol evaporated. The experimental results demonstrate that both the gas-assisted evaporation and mixing effects are significant mechanisms responsible for the significant enhancement of heat transfer with the introduction of helium gas in ethanol flow. For the present study, the maximum heat transfer enhancement of 275% is demonstrated under the condition of ethanol flow rate of 0.028 m/s, helium flow rate of 0.833 m/s, and wall superheat of −3.2 °C. Under such a condition, the gas-assisted evaporation contributes about 40% of total heat transfer rate. Flow visualization and exit quality measurement reveal that the phase change mechanism is dominated by convective evaporation in the region with negative wall superheat, while it is dominated by convective boiling under the conditions with positive wall superheat. The evaporation efficiency increases with decrease in ethanol flow rate, increases in helium flow rate and wall superheat. An empirical correlation for the evaporation efficiency is, thus, developed.

Study of ω-6 linoleic and ω-3 α-linolenic acids of hemp (Cannabis sativa) seed oil extracted by supercritical CO2 extraction: CCD optimization

In the present study, supercritical CO2 extraction of ω-6 linoleic and ω-3 α-linolenic fatty acids from hemp seed oil is successfully optimized through central composite design (CCD) considering five parameters (temperature, pressure, CO2 flow rate, particle size and co-solvent (ethanol) flow rate (mass % of CO2 flow rate)). Two statistical quadratic models are developed, exhibiting a good prediction of ω-6 linoleic and ω-3 α-linolenic acids concentrations with negligible error. All model parameters are found significant for P < 0.05. Interaction and quadratic terms of temperature are observed to be significant in comparison to linear term, which is found insignificant for P > 0.1. Statistical analysis suggests optimized parameters as temperature, 76 °C; pressure, 300 bar; CO2 flow rate, 13 g min−1; particle size, 0.43 mm and co-solvent flow rate as 8% of CO2 flow rate; which are experimentally verified. Moreover, effects of input parameters on the optimum ratio of ω-6 linoleic and ω-3 α-linolenic acids are investigated and found to be in the range from 2.11 to 3.17. UV spectroscopy estimates chlorophyll a, b and carotene content in hemp oil as (84.0 to 293.9) μg g−1, (46.4 to 216.4) μg g−1 and (4.3 to 66.6) μg g−1, respectively.

Supercritical CO2 extraction of chlorogenic acid from sunflower (Helianthus annuus) seed kernels: modeling and optimization by response surface methodology

In this research, supercritical CO2 extraction of chlorogenic acid (CGA) from sunflower seed kernels was investigated by ethanol as co-solvent. The effects of operating conditions including temperature (40–80 °C), pressure (10–30 MPa), CO2 flow rate (0.6–1.8 ml/min) and dynamic extraction time (40–120 min) was investigated on the chlorogenic acid (CGA) extraction recovery. The flow rate of ethanol and static extraction time were kept constant at 5 vol. % of CO2 flow rate and 25 min, respectively. The quantification of extracted samples was performed by high performance liquid chromatography (HPLC). Minitab 17 software was used to create the response surface design for the modeling and optimization of extraction recovery. Experimental data were fitted by a second order polynomial and the coefficient of determination was obtained to be 96.75%. Optimum recovery of CGA (52.08%) was obtained at 17.9 MPa, 40.0 °C, 104.6 min and 1.6 ml/min.

Parametric study on direct ethanol fuel cell (DEFC) performance and fuel crossover

A parametric study was carried out to investigate the effect of fuel concentration (0.5 M–3.0 M), operating temperature (ambient temperature to 85 °C), flow rate of ethanol (0.5–5.0 mL min−1) and air (100–600 mL min−1) on the direct ethanol fuel cell (DEFC) performance. The operations were conducted in three operational modes, namely, passive, semi passive, and active modes, and power generation were measured. Ethanol crossover was indicated by the carbon dioxide (CO2) concentration present at the cathode outlet and measured by using a CO2 analyzer. Results indicated that DEFC performance increased with the increase of ethanol concentration, and ethanol and oxidant flow rate increased with temperature until DEFC reaches the optimum conditions, i.e., concentration and flow rate. Meanwhile, the DEFC performance significantly and proportionally increased with operation temperature and reached values of up to 8.70 mW cm−2 and 85 °C at stable conditions. Furthermore, fuel crossover, that is, ethanol flux, increased in proportion to the ethanol concentration, i.e., 3.71 × 10−4 g m−2 s−1 and 8.79 × 10−4 g m−2 s−1 for 0.5 M and 3.0 M ethanol concentration, respectively. At different modes of operation, the active DEFC system exhibited the highest performance, followed by the semi passive and passive DEFC system. These results indicated that optimizing ethanol, oxidant flow rate and temperature would enhance the mass transport in anodes and cathodes, and hence improve the electrochemical reactions and DEFC performance.

Spinning Approach for Cellulose Fiber Yarn Using a Deep Eutectic Solvent and an Inclined Channel.

We developed a spinning approach for a dope produced by treating softwood pulp with a deep eutectic solvent (DES). The DES enables formation of a sufficiently viscous spinnable gel-like suspension of fibers, which solidifies upon the removal of the DES. This solidification, however, requires a longer time compared to most conventional wet spinning processes. Consequently, the continuity of the spinning process has been constrained in previous work. Moreover, the ability to draw the incipient yarn to increase orientation has been limited. Here we present a continuous spinning approach where the fiber yarn properties and processability can be improved using an inclined channel. A combination of an air gap and an inclined ethanol stream transports and draws the incipient fiber yarn during spinning. The influence of syringe tip diameter, angle of the channel, ethanol flow rate, and twisting were studied experimentally. The improvements in the spinning process resulted in an increase in load bearing capability and ability to reduce the linear density of the fiber yarn.

Synthesis of Amorphous Carbon Film in Ethanol Inverse Diffusion Flames.

Recently, carbon nanomaterials have attracted significant attention due to their remarkable physical and chemical properties. The preparation methods and applications of the carbon nanomaterials have developed rapidly. In this study, the flame synthesis of amorphous carbon film grown on copper foil in an ethanol inverse diffusion flame was presented. The effects of ethanol flow rate, the copper foil location in flame and growth time were investigated in detail. The growth status of the synthetic amorphous carbon film was analyzed by an optical microscope and HRTEM (high resolution transmission electron microscope). Raman spectroscopy and XRD (X-ray diffraction) were used to characterize the structure of the carbon film. The roughness of the carbon film was determined by AFM (atomic force microscopy). As the ethanol flow rate increased and the copper foil moved upwards in the flame, the area of the synthetic amorphous carbon film increased. The roughness of carbon films with the growth time of 30 s and 2 min were smaller. In addition, the synthetic amorphous carbon film exhibited a certain degree of flexibility and visual transparency. Through the study, a reference could be provided to find the optimum condition for the flame synthesis of satisfactory amorphous carbon film. For these experiments, when the ethanol flow rate reached 2 mL/min, the copper foil was located on the top of the flame and the growth time was 2 min, an amorphous carbon film with higher quality could be obtained.

A novel combustion system for liquid fuel evaporating and burning

To utilize sustainable biofuel, the current study proposes a novel combustion technique that directly burns liquid ethanol without a spray system. Two swirling air flows are induced by tangentially injected the gas from two concentric tubes at different stages. The liquid ethanol is fed by a liquid tank at the center. At the beginning methane flame assists in preheating the system to vaporize liquid ethanol and ignite the vapor. Thereafter methane is switched off, and liquid ethanol can be continuously vaporized through self-burning released heat. The heat and mass transfer processes are examined to illustrate such self-sustained burning–heating–evaporating system. The ethanol flow rate is gradually increased to provide different heat output. The flame structures, temperature distributions and pollutant emissions are carefully examined. The results show that the ethanol can be steadily burned to provide heat output between 0.7 and 2.5 kW. Generally a blue flame is obtained, and the NOx and CO concentrations are ultralow. By increasing ethanol flow rate to exceed 8 mL/min, an unsteady, sooting flame is observed owing to incomplete evaporation and poor mixing. A parametric study is conducted to evaluate the influences of liquid tank position, flow rate and tip structure on the combustion characteristics. Additionally, an optimal operation condition is proposed. The current study provides a promising method to burn low-boiling liquid fuel in a clean, efficient and compact way.

Isothermal crystallization of glycine in semi-continuous mode by anti-solvent addition

This article focuses on the isothermal semi-continuous crystallization of glycine aqueous solution by adding an anti-solvent, ethanol. The effect of the ethanol concentration on solubility and the impact of the ethanol flow rate on the metastable zone width and on the size distribution of the crystals were investigated. The study showed that increasing the ethanol concentration in the medium decreases solubility for the studied temperatures and that increasing the ethanol flow rate causes a widening of the metastable zone without inducing any noticeable effect on the crystals’ size distribution. In addition, nucleation kinetic models were determined for two temperatures (30 and 56 °C).

(Invited) Digital-Coded Isotope Labeling on Individual Single-Walled Carbon Nanotubes Grown on Crystal Quartz

Single-walled carbon nanotubes (SWNTs) are promising building blocks for next-generation high-performance electronics, e.g. field-effect transistors (FET). For the application, many properties, such as chirality, orientation, density and length, have to be well controlled. Despite significant progresses in controlling the SWNT chirality and density in recent years, further breakthroughs are desirable to make the SWNT-based electronics reality. Detailed understanding on the growth process of individual SWNTs with a practical form (quality, length, and alignment) will accelerate the development of application-oriented growth. In this study, we developed an isotope labeling technique with digital coding for the ex situ monitoring of individual and long (>100 μm) SWNTs. Owing to the nature of ex situ measurement, an enormous number of SWNTs can be characterized on a single substrate. In addition, digital-coding of the isotope labels enables identification of time evolution of SWNT growth with high accuracy. Horizontally aligned configuration were used for the tracing of individual SWNTs and for the breakdown of SWNT quantity into population and length [1]. Aligned SWNTs were grown on r-cut quartz substrates from iron catalysts patterned in stripes with 300-μm separation. Normal 12C ethanol was used for most parts of the growth, but pure 13C ethanol was periodically mixed in various ratios (33, 67, 100 %) to embed digital-coded isotope labels in SWNTs. For the standard growth, 5-sccm ethanol was introduced together with 50-sccm Ar/H2 buffer gas into the reactor with total pressure of ~1.5 kPa. After the growth, position of each isotope label and the SWNT properties were identified by Raman mapping. The sequence of the isotope labels clearly indicated that all the SWNTs that we observed grew in the root growth mode [2], where the catalysts stayed at the original position and SWNTs pushed forward. We obtained the time evolution of SWNT lengths, and found that the SWNTs started to grow after certain lengths of incubation time. For most cases, growth rate was constant until the abrupt termination of the growth. This suggests that the catalytic activity of metal particles did not gradually change with time under the current growth condition. Two different SWNTs with the same chirality (radial breathing mode (RBM) frequency of 190 cm-1 with 532 nm excitation laser) had different growth rates (~8 and ~15 μm/min), indicating the dependence of the growth rate on catalyst sizes or some other properties. For the extraction of intrinsic chirality dependence of the growth rate, we focused on spontaneously formed intramolecular junctions. For example, an intramolecular junction changed the RBM frequencies of an SWNT from 139 to 144 cm-1. Interestingly, the growth rate changed from ~10 to ~8 μm/min along with the chirality change. Since the growth behavior can be traced along individual SWNTs, the dependence on growth conditions, such as temperature and pressure of carbon feedstocks, was also investigated by changing the conditions during the growth. First, ethanol flow rate, which is nearly proportional to the partial pressure, was increased from 3 to 9 sccm in 2 sccm steps every four minutes. Most SWNTs grew faster as the flow rate increased; however, some SWNTs stopped growing for one or two minutes when the flow rate was suddenly increased. We also observed temperature-dependent growth rate, which provides insights into the growth dynamics of individual SWNTs. Part of this work was supported by JSPS KAKENHI Grant Numbers JP25107002, JP15H05760, JP17K06187 and JP17K14601. K.O. was financially supported by a JSPS Fellowship (JP15J07857).

Effects of process parameters on peanut skins extract and CO2 diffusivity by supercritical fluid extraction

Peanut skins (Arachis hypogea) are an agricultural waste product which has received much attention because they contain high nutritional values and can be potentially utilized in difference industries. At present, only a few studies have been conducted to study the effects of parameters on the peanut skins oil extraction. Therefore, this study aimed to determine the best extraction condition in order to obtain the highest extract yield using supercritical carbon dioxide (SC-CO2) with co-solvent Ethanol as compared to Soxhlet extraction method. Diffusivity of carbon dioxide in supercritical fluid extraction was determined using Crank model. The mean particle size used in this study was 425 µm. The supercritical carbon dioxide was performed at temperature (40 – 70 °C), flow rate of co-solvent ethanol (0 - 7.5% Vethanol/Vtotal), and extraction pressure (10 – 30 MPa) were used in this studies. The results showed that the percentage of oil yields and effective diffusivity increase as the pressure, rate of co-solvent, and temperature increased.

Characterization of phospholipids extracted from Atlantic salmon by-product using supercritical CO2 with ethanol as co-solvent

Abstract Marine (PLs) are rich in omega-3 polyunsaturated fatty acids (ω-3 PUFAs), and the good emulsifying property of PLs makes them suitable for use in the food, pharmaceutical, and cosmetic industries. This research was attempted to evaluate Atlantic salmon frame bone (SFB) PLs extracted by using supercritical carbon dioxide (SC-CO2) with ethanol as co-solvent extraction and organic solvent (ethanol) extraction. SC-CO2 with ethanol as co-solvent extraction was performed at 45 °C and different pressures (22.5–30.0 MPa) while maintaining a CO2 flow rate of 27 g/min and a co-solvent ethanol flow rate of 3 mL/min for 2.5 h. Extracted PLs were analyzed for a wide range of physico-chemical properties such as yield, PL purity, astaxanthin content, major PL groups, fatty acid composition, acid value (AV), peroxide value (POV), free fatty acid (FFA) value, and p-anisidine value (PAV). Thin layer chromatography was performed for qualitative analysis of different PL groups, and quantitative analysis was performed by high performance liquid chromatography with evaporative light scattering detection. The maximum PL yield of the SC-CO2 with ethanol as co-solvent extraction was 6.9 ± 0.3% of de-oiled SFB at 45 °C and 27.5 MPa, with 80.4 ± 1.6% purity. Among the four major groups of PLs identified, phosphatidylcholine was most common PL extracted, and the content varied from 79.6 ± 0.4% to 86.5 ± 0.3% for different extraction conditions. The stability parameters such as AV, POV, FFA value, and PAV of the SC-CO2 with ethanol as co-solvent extracted PLs were lower than those for organic solvent (ethanol) extracted PLs. SFB PLs showed significant thermal stability and contained substantial amounts of ω-3 PUFAs. PLs obtained by SC-CO2 with ethanol as co-solvent extraction showed better emulsion and free-radical scavenging properties than those of organic solvent (ethanol) extracted PLs. This research may be helpful in the SC-CO2 extraction of phospholipids from marine sources for researchers and food/pharmaceutical industries.

Mathematical modeling of supercritical CO2 extraction of valuable compounds from Eucheuma Cottonii and Gracilaria Sp

Extraction by using supercritical CO2 has been extensively developed to extract materials that are easily decomposed at high temperatures. Therefore, in this study extraction of valuable compounds (such as: carotenoids and fatty acids) from macroalgae of Eucheuma cottonii and Gracilaria sp was carried out experimentally with supercritical CO2 and mathematical model of Broken and Intact Cells (BIC) and Chrastil model. The result with BIC model is compared with the experimental result that has been done. Extraction was conducted at various pressures of 15, 20, and 25 MPa, temperature of 40, 60, and 80 ºC, CO2 flow rate of 6 mL/min, and ethanol concentrations for cosolvent of 5 %, 7.5%, and 10% CO2 flow rate. The content of extract was analyzed by using a Spectrophotometer UV - Vis and HPLC. The total yield of extract on Eucheuma cottonii was about 0.01623-0.03752 gr extract/gr sample at operating conditions 15 MPa pressure, temperature 60 ºC, and ethanol flow rate of 10%. The total yield of the extract on Gracilaria sp was 0.1982-0.4237 gr extract/gr samples, at operating conditions 15 MPa pressure, 60 ºC temperature, and ethanol flow rate 7.5% CO2 flow rate. The solubility of Eucheuma cottonii are greater than Gracilaria Sp with constant of Chrastil k, a, and b that are: 2,52; 0,911; and-27,66 at operating conditions. Broken and Intact Cells model could also describe well for extraction yield. The best fitting parameters in BIC model depends on condition at extraction process, such as : 0.45 – 0.46 for f, 0.5 - 0.75 for Xc, and 0.15 - 0.4 for K value..

Gas-assisted evaporation and boiling in minichannels

This study experimentally explores the heat transfer characteristics of gas-assisted evaporation and boiling in single or two parallel minichannels under both non-boiling and boiling conditions. The liquid working fluid used is ethanol and the inert gas is helium. Compared to the pure ethanol flow in a minichannel under both non-boiling and boiling conditions, the heat transfer enhancement (HTE) caused by the adjunction of helium is examined. The maximal HTE owing to an inert gas is located at the wall superheat (ΔTsat) of −10°C (i.e., non-boiling region) in the single minichannel in which the annular flow occurring in most parts of the channel; however, for the boiling region, the HTE is insignificant in the single minichannel, as the flow patterns observed for the studied cases are approximately the same. For the two parallel minichannels, the differences in the mean (effective) wall heat flux between the cases with and without helium become much more evident than those in a single minichannel. Under boiling conditions, primarily an annular flow, accompanied with bubble nucleation at the wall downstream, occurs for the studied cases when helium flow is present; however, extensive bubble nucleation occurs and bubbly flow prevails for the case without helium flow. Owing to the difference in flow pattern, the heat transfer performances for the cases with and without helium are significantly different in the parallel minichannels under this boiling condition. In addition, the HTE significantly increases with an increase in the helium flow rate at a given wall superheat. The maximal HTE, which also occurred at about ΔTsat=−10°C, is 206% obtained under the conditions of the lowest ethanol flow rate and the highest helium flow rate in the parallel minichannels.

Taguchi analysis of parameters for small-diameter single wall carbon nanotube growth

Small diameter single wall carbon nanotubes are desirable for various physical and electrical properties of carbon nanotubes. Here, we report the sensitivities of parameters and the optimal conditions for small diameter carbon nanotube growth by chemical vapor deposition (CVD). These results were obtained using the Taguchi method, which is commonly used to find the optimal parameters of various processes. The possible parameter ranges given by the experimental equipment and laboratory conditions, we attempted several times to determine the proper ranges, using photoluminescence (PL) imaging to determine the exact positions of suspended carbon nanotubes on the quartz substrates after synthesis. The diameters of the carbon nanotubes were then determined from the radial breathing modes (RBM) using Raman spectroscopy with a 785nm wavelength laser. Among the 4 major parameters listed above, we concluded that the temperature was the most significant parameter in determining carbon nanotube diameter, hydrogen flow rate was the second most significant, the ethanol and argon gas flow rate was the third, and finally time was the least significant factor.

A 1D+1D Model of Direct Ethanol Fuel Cells Based on an Optimized Kinetic Mechanism for Ethanol Electro-Oxidation Involving Free and Adsorbed Intermediate Species

A 1D+1D model for liquid-feed direct ethanol fuel cells with detailed ethanol electro-oxidation kinetics is presented. One-dimensional convective transport along the flow channels is coupled to a one-dimensional description for species transport across the MEA accounting for the effect of the electrochemical reactions and the mixed potential due to ethanol and acetaldehyde crossover. The model, validated against previous experimental data, provides the variation of the concentrations of the free species and the output and parasitic current densities along the flow channels. The downstream evolution of ethanol and acetaldehyde affects the anode reaction rates and the ethanol and acetaldehyde crossover fluxes, which in turn impacts on the cathode reaction rates. Polarization curves obtained at different positions along the flow channels show the effect of ethanol consumption and acetaldehyde upstream production and downstream consumption. Power density, parasitic current, fuel utilization and product selectivity curves are presented and discussed for different ethanol feed concentrations and flow rates.

Effects of electric field intensity and frequency of AC electric field on the small-scale ethanol diffusion flame behaviors

The Alternating Current (AC) electric field was applied on the small-scale flame in order to promote the characteristics or control the combustion. The effect of AC electric field on the small-scale ethanol diffusion flame behaviors was studied experimentally and numerically. The inner diameter of the burner nozzle was 0.9mm and the flame was established at room temperature and atmospheric pressure. Different electric field intensities and frequencies of AC electric field were generated by two parallel plate electrodes which were respectively placed above and below the flame. Numerical results combined with experimental observations were used to analyze the small ethanol diffusion flame characteristics under the electric field. The results show that flame behaviors are significantly influenced by the applied AC electric field. The body forces acting on charged particles in the electric field are considered under the AC electric field. The charged particles are accelerated in the applied electric field and transfer the momentum to the neutral particles. At a certain flow rate of ethanol, the flame temperature and flow velocity increase with the increasing of electric field intensity and AC frequency. The diffusion effect is strengthened by the electric field and the mass fraction distribution of the component has a tendency of inward contraction, which is consistent with the tendency of flame becoming shorter. It also can be concluded that the applied AC electric field promotes the mixing of fuel and oxidizer, thus enhances the combustion process. The reaction rate in the flame becomes faster and reaction position is closer to the fuel side. The combined effects of diffusion and reaction enhancements affect the flame behaviors.

Study on direct-contact phase-change liquid immersion cooling dense-array solar cells under high concentration ratios

A new cooling method by directly immersing the solar cells into phase-change liquid was put forward to cool dense-array solar cells in high concentrating photovoltaic system. A self-running system was built to study the feasibility of temperature control and the effect of bubbles generated by ethanol phase change under concentration ratio ranged between 219.8× and 398.4×. The results show that the cooling system is self-regulating without consuming extra energy and ethanol flow rate reaches up to 180.6kg/(s·m2) under 398.4×. The temperature of solar cells distributes in the range between 87.3°C and 88.5°C, the surface heat transfer coefficient of electric heating plate is up to 23.49kW/(m2·K) under 398.4×. The bubble effect on electrical performance of triple-junction solar cells is reported and the results show that Isc and Pmax decline 10.2% and 7.3%, respectively. A model based on bubble images illustrates that light loss at the interface between ethanol and bubble is the main reason to cut down the electrical performance.

Ethanol to 1,3‐Butadiene Conversion by using ZrZn‐Containing MgO/SiO2 Systems Prepared by Co‐precipitation and Effect of Catalyst Acidity Modification

AbstractThe conversion of ethanol to 1,3‐butadiene (1,3‐BD) has been investigated over ZrO2‐ and ZnO‐containing magnesia silica oxides prepared by a co‐precipitation method at different Mg‐to‐Si molar ratios. The effect of reaction temperature and ethanol flow rate was investigated. The catalyst acidity was modified through the addition of alkali metals (Na, K and Li) to the final materials. Catalysts were characterised by nitrogen physisorption analysis, X‐ray diffraction, scanning electron microscopy with energy dispersive X‐ray, temperature‐programmed desorption of ammonia, infrared spectroscopy and 29Si/(7Li) NMR spectroscopy. The catalytic results showed that the controlled reduction of catalyst acidity allows ethanol dehydration to be suppressed, whilst increasing 1,3‐BD selectivity. The best catalytic performance achieved 72 mol % for the combined 1,3‐BD and acetaldehyde selectivity.

Performance of a hydrogen-enriched ethanol engine at unthrottled and lean conditions

Concerning the throttling loss under part load conditions, it is feasible to further improve the engine thermal efficiency through operating the engine under the unthrottled condition and controlling its load by changing the excess air ratio. However, the narrow flammability of ethanol may lead the ethanol engine to encounter high cyclic variations under unthrottled and lean conditions. The addition of hydrogen is potentially helpful for solving this problem. In this test, the engine was run under an speed of 1400rpm and unthrottled conditions. The hydrogen volume fractions in the intake were respectively kept at 0% and 3%. For a given hydrogen blending level, the ethanol flow rate was reduced to enable the engine to run under lean conditions. The results showed that the engine efficiency was improved with the blending of hydrogen. The highest thermal efficiency was improved by 6.07% after blending 3% hydrogen to the intake air. The addition of hydrogen could increase the engine torque output at lean conditions. Both cooling and exhaust losses were decreased after the hydrogen enrichment while adopting the lean combustion strategy. The hydrogen addition contributed to the extended lean burn limit and decreased cyclic variation under lean conditions. HC and CO emissions were decreased whereas NOx emissions were increased after the blending of hydrogen.

Effects of direct-current electric fields on flame shape and combustion characteristics of ethanol in small scale

The aim of this work is to investigate the effects of direct-current electric fields on the behavior of the small-scale diffusion ethanol flame. The flow rate of liquid ethanol, the flame temperatures, and the flame shapes were measured. The results showed that the stable working ranges of a small-scale combustor became narrower under the direct-current electric field. The main reason was that the evaporation velocity of liquid ethanol limited by great heat loss effect cannot keep up with the increasing of combustion velocity by the ionic wind effect. The movements of those charged particles in flame enhanced the combustion process, resulting in higher flame temperatures under positive or negative direct-current electric field. The flame heights decreased with increasing applied voltages, due to the ionic wind effect increasing the flame temperature and the diffusivity. The flame voltage–current characteristic was also examined. Three regions can be divided: the subsaturation region, the saturation region, and the supersaturation region. Finally, the ratios of electric active power to actual burning thermal power of ethanol flame were calculated. It can be inferred that using the external direct-current electric field with little power consumption to control combustion and flame is a feasible method.