Dilution Percentage Research Articles

Effects of Dilution on Laminar Burning Velocity of Premixed Methane/Air Flames

Effects of dilution on premixed methane/air combustion are investigated through experiments and numerical simulations on laminar burning velocities. Experiments are carried out at atmospheric pressure and 393 K; computed results are obtained using the GRI mechanism and the Premix code of the Chemkin package. Laminar burning velocities are determined for several diluents (nitrogen, carbon dioxide, vapor water, a mixture of the three previous gases representative of exhaust gases, helium, and argon) and for different dilution percentages. The equivalence ratio is kept constant equal to stoichiometric. Excellent agreements between experimental data and computed results are obtained. Because heat capacity seems to possess the predominant effect on the laminar flame, an explicit correlation between the heat capacity of the diluent and the laminar burning velocity is proposed.

Dilution Effect during Laser Cladding of Inconel 617 with Ni-Al Powders

In this study, continuous wave CO2 laser with 1.7 and 2 kW were used to deposit clad layers of premixed powders of either Ni-10 wt% Al or Ni-30 wt% Al onto inconel 617 substrate. Different cladding traverse speeds in the range 1 to 35 mm/s were used for premixed clad powder of Ni-10 wt% Al and 1.65 to 11.2 mm/s for premixed clad powder of Ni-30 wt% Al. Two powder feeding rates were used, 10 and 8.9 gm/min for premixed clad powders of Ni-10 wt% Al and Ni-30 wt% Al respectively. The other laser independent variables were selected to be constant. The results showed that different percentages of area dilution were found ranging from 3.7 to 78.3% for premixed clad powder of Ni-10 wt% Al and 6.9 to 41 % for premixed clad powder of Ni-30 wt% Al depending on the laser cladding independent variables used. Furthermore, dilution was affected mainly by cladding traverse speeds.

Tribological Effects of Mineral-Oil Lubricant Contamination with Biofuels: A Pin-on-Disk Tribometry and Wear Study

Use of biodiesel produces engine oil dilution because of unburned biodiesel impinging on cold walls of the combustion chamber, being scrapped to the oil pan, and leading to changes of oil friction, wear and lubricity properties. In this paper, mixtures of SAE 15W-40 oil, which were contaminated by known percentages of the biodiesels from canola oil, peanut oil, soybean oil, and chicken fat, were tested in a pin-on-disk tribometer. A contact was employed of AISI 1018 steel disk and AISI 316 stainless-steel ball for pin material, and friction force and specific wear were measured. Wear on the disk surfaces showed that any degree of mineral-oil dilution by the tested biodiesels reduces the wear protection of engine oil even at small mixture percentages. However, these reductions were not substantially different than those observed for same percentages of dilution of mineral oil by fossil diesel. The tested mixture of oil contaminated with animal fat feedstock (e.g., chicken fat) biodiesel showed the best wear behavior as compared to those for the other tested mixtures (of mineral oil with vegetable feedstock biodiesel dilutions). Obtained results are discussed as baseline for further studies in a renewable energy multidisciplinary approach on biofuels and biolubes.

Esterification Synthesis of Ethyl Oleate in Solvent-Free System Catalyzed by Lipase Membrane from Fermentation Broth

In this study, the immobilized lipase was prepared by fabric membrane adsorption in fermentation broth. The lipase immobilization method in fermentation broth was optimized on broth activity units and pH adjustments. The viscose fermentation broth can be used with a certain percentage of dilution based on the original broth activity units. The fermentation broth can be processed directly without pH adjustment. In addition, the oleic acid ethyl ester production in solvent-free system catalyzed by the immobilized lipase was optimized. The molar ratio of ethanol to oil acid, the enzyme amount, the molecular amount, and the temperature were 1:1, 12% (w/w), 9% (w/w)(based the total amount of reaction mixture), and 30°C, respectively. Finally, the optimal condition afforded at least 19 reuse numbers with esterification rate above 80% under stepwise addition of ethanol. Due to simple lipase immobilization preparation, acceptable esterification result during long-time batch reactions and lower cost; the whole process was suitable for industrial ethyl oleate production.

Optimization of electrical submersible pump artificial lift system for extraheavy oils through an analysis of bottom dilution scheme

This study presents the analysis of the variables that have the greatest impact on energy requirements for an artificial lift system applied to extra heavy crude oils, considering an uncertainty behavior analysis through their sensitivity in the vertical flow modeling implemented for a Chichimene Field well. The selected variables are the viscosity and fluid density, the required artificial lift system pressure differential, well depth, the flow rate of produced fluids and the dilution percentage. The oil produced in this field has a density of 7,8 API, and the well studied features a water cut of about 10% and produces a total of 2400 BOD. For this flow naphtha dilution rates were defined using up to 20% by volume. The ranges of energy required for the lifting system for different scenarios raised by the analysis variables were also determined. For these conditions a variation of the energy required 20% for a fluid flow incremental of 50 BFOD was obtained, as established from the flow capacity of the well and the pressure required for sustaining a pressure head of 100 psi and 400 psi. Bottom dilution scheme establishes a change in artificial lift system energy requirement, of up to 25% for a 15% of diluter, whereas the relationship between the volumes produced and the system arrays gives an energy efficiency of 40%.

Experimental study on CO 2 capture conditions of a fluidized bed limestone decomposition reactor

In this study, the decomposition conditions of limestone particles (0.25–0.50 mm) for CO 2 capture in a steam dilution atmosphere (20–100% steam in CO 2) were investigated by using a continuously operating fluidized bed reactor. The results show that the decomposition conversion of limestone increased with the steam dilution percentage in the CO 2 supply gas. At a bed temperature of 920 °C, the conversions were 72% without steam dilution and 98% with 60% steam dilution. The conversion was 99% with 100% steam dilution at 850 °C of the bed temperature. Steam dilution can decrease not only the decomposition temperature of limestone, but also the residence time required for nearly complete decomposition of CaCO 3. The hydration and carbonation reactivities of the CaO produced were also tested and the results show that both the reactivities increased with the steam dilution percentage for decomposing limestone.

Computed extinction limits and flame structures of H2/O2 counterflow diffusion flames with CO2 dilution

A narrowband radiation model is coupled to the OPPDIF program, which uses detailed chemical kinetics and thermal and transport properties to enable the study of one-dimensional counterflow H2/O2 diffusion flames with CO2 as dilution gas over the entire range of flammable strain rates. The effects of carbon dioxide dilution, ambient pressure and inlet temperature of opposed jets on the extinction limits and flame structures are compared and discussed. The extinction limits are presented using maximum flame temperature and strain rate as coordinates. Both high-stretch blowoff and the low-stretch quenching limits are computed. When the CO2 dilution percentage is higher, the flame is thinner and flame temperature is lower. The combustible range of strain rates is decreased with increasing CO2 percentage due to the effects of CO2 dilution, which is categorized as dilute effect, chemical effect and radiation effect. In addition, the flame temperature of low-stretch diffusion flame with radiation loss is substantially lower than that computed with the non-radiation model. This large temperature drop results from the combined effect of flame radiation and chemical kinetics. The extinction limits and flame temperature are increasing with increasing atmospheric pressure and temperature, but the flame thickness is decreased with the pressure. At higher pressure and temperature, the extinction limits are extended more on the high-stretch blowoff limits, indicating the influence of the ambient pressure and temperature on the chemical reaction.

Application of Response Surface Methodolody to Prediction of Dilution in Plasma Transferred Arc Hardfacing of Stainless Steel on Carbon Steel

The application of response surface methodology was highlighted to predict and optimize the percentage of dilution of iron-based hardfaced surface produced by the PTA (plasma transferred arc welding) process. The experiments were conducted based on five-factor five-level central composite rotatable design with full replication technique and a mathematical model was developed using response surface methodology. Furthermore, the response surface methodology was also used to optimize the process parameters that yielded the lowest percentage of dilution.

Predicting the dilution of plasma transferred arc hardfacing of stellite on carbon steel using response surface methodology

Control of dilution is important in hardfacing, where low dilution is typically desirable. At present, most fabrication industries use shielded metal are welding, gas metal arc welding, gas tungsten arc welding and submerged are welding processes for hardfacing purposes. In these processes, the percentage of the dilution level is higher, ranging between 10% and 30%. In Plasma Transferred Arc (PTA) hardfacing, a solidified metallurgical bond between the deposit and the substrate is obtained with minimum dilution (less than 10%). This paper highlights the application of response surface methodology to predict and optimize the percentage of the dilution of a cobalt-based hardfaced surface produced by the PTA process. Experiments were conducted based on a fully replicable five-factor, five-level central composite rotatable design and a mathematical model was developed using response surface methodology. Furthermore, the response surface methodology was used to optimize the process parameters that yield the lowest percentage of dilution.

Understanding the Parameters Controlling Plasma Transferred Arc Hardfacing Using Response Surface Methodology

Control of dilution is important in hardfacing, where typically low dilution is desirable. At present, majority of the fabrication industries use shielded metal arc welding (SMAW), gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), and submerged arc welding (SAW) processes for hardfacing purposes. In these processes, the percentage of dilution level is higher, ranging between 10–30%. In plasma transferred arc (PTA) hardfacing, a solidified metallurgical bond between deposit and substrate is obtained with minimum dilution (less than 10%). This article highlights the application of response surface methodology (RSM) to predict and optimize the percentage of dilution of nickel based hardfaced surface produced by PTA process. The experiments were conducted based on five-factor, five levels central composite rotatable design with full replications technique and mathematical model was developed using RSM. Further, the RSM is used to optimize the process parameters that yield the lowest percentage of dilution.

Effect of initial crystallized silicon layer on the properties of microcrystalline silicon grown by internal inductively coupled plasma-type plasma enhanced chemical vapor deposition

Using an internal inductively coupled plasma (ICP)-type-plasma enhanced vapor deposition system, microcrystalline silicon thin films were deposited as a function of H 2/SiH 4 gas ratio at 180 °C. Especially, the effects of deposition with/without an initial thin silicon layer formed with a very high hydrogen percentage on the microstructure of the deposited silicon thin film were investigated. The deposited silicon thin film showed higher crystallization percentage at the higher hydrogen percentage in H 2/SiH 4 due to the high ratio of H/SiH in the plasma. At the same gas mixture of H 2/SiH 4, the deposition of silicon thin film after the formation of an initial silicon layer with a high hydrogen percentage on the glass substrate increased the crystallization percentage from 3 to 14%. The initial silicon layer deposited with a high hydrogen percentage showed a nanocrystalline grain structure; therefore, the nanocrystalline structure in the initial silicon layer appeared to act as a nucleation site for the growth of microcrystalline silicon thin films. Using the internal ICP-PECVD, the microcrystalline silicon having about 87% of crystallization could be deposited on the glass substrate at 180 °C with the 90% of hydrogen dilution percentage and with the thin initial silicon layer.

Analysis and simulation of a‐Si:H/a‐SiC:H PINIP structures for color image detection

AbstractIt is presented in this paper a study on the photo‐electronic properties of multilayer a‐Si:H/a‐SiC:H p–i–n–i–p structures. This study is aimed to give an insight into the internal electrical characteristics of such a structure in thermal equilibrium, under applied bias and under different illumination condition. Taking advantage of this insight it is possible to establish a relation among the electrical behavior of the structure, the structure geometry (i.e. thickness of the light absorbing intrinsic layers and of the internal n‐layer) and the composition of the layers (i.e. optical bandgap controlled through percentage of carbon dilution in the a‐Si1–x Cx:H layers).Showing an optical gain for low incident light power con‐ trollable by means of externally applied bias or structure composition, these structures are quite attractive for photo‐sensing device applications, like color sensors and large area color image detector.An analysis based on numerical ASCA simulations is presented for describing the behavior of different configurations of the device and compared with experimental measurements (spectral response and current–voltage characteristic). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Limestone Calcination with CO 2 Capture (II): Decomposition in CO 2/Steam and CO 2/N 2 Atmospheres

Decomposition of limestone particles (0.25−0.5 mm) in a steam dilution atmosphere (20−100% steam in CO 2) was investigated by using a continuously operating fluidized bed reactor for CO 2 capture. The decomposition conversion of limestone increased as the steam dilution percentage in the CO 2 supply gas increased. At a bed temperature of 1193 K, the conversions were 72% without dilution (100% CO 2) and 98% with 60% steam dilution. The decomposition conversions obtained with steam dilution and N 2 dilution differed significantly, and this result is explained in terms of the difference between the heat transfer to particle in steam and N 2 dilution atmosphere. The reactivities of the CaO produced from limestone decomposition with steam dilution and without dilution (100% CO 2) were tested by means of hydration and carbonation reactions. In the hydration test, the time required for complete conversion [CaO → Ca(OH) 2] of the CaO produced by steam dilution was approximately half that required for the CaO prod...

Degree of conversion of resin blends in relation to ethanol content and hydrophilicity

Objectives To evaluate the degree of conversion of five experimental adhesive systems in relation to their hydrophilicity. The resin blends ranged from hydrophobic to hydrophilic and were tested as neat bonding agents, or solvated with increasing percentages of ethanol. The hypothesis tested was that extent of polymerization of resin blends is affected by resin hydrophilicity, solvent concentrations or time of polymerization. Methods Five light-curing versions of neat experimental resin blends were submitted to investigation: (1) 70% E-BisADM, 28.75% TEGDMA; (2) 70% BisGMA, 28.7% TEGDMA; (3) 70% BisGMA, 28.7% HEMA; (4) 40% BisGMA, 30% TCDM, and 28.75% TEGDMA; (5) 40% BisGMA, 30% BisMP, and 28.75% HEMA. All blends included 1% EDMAB and 0.25% CQ. Ethanol in different weight percentages (A: 0%, B: 30%, C: 50%, D: 70% and E: 90%) was added to these resin blends simulating different formulation of adhesives. A differential scanning calorimeter was used to measure the degree of conversion of resin blends as a function of resin hydrophilicity, solvent concentration and time of curing. Data were analyzed with three-way ANOVA and Tukey's post hoc test. Results Exotherms showed that degree of conversion was influenced by the hydrophilicity of the blends resin ( p < .05), percentage of ethanol dilution ( p < .05) and time of curing ( p < .05). 30% ethanol dilution increased degree of conversion compared to neat compounds irrespective to resin type and curing time, showing the highest degree of conversion values of the study design. Significance This study supports the hypothesis that high ethanol percentages (>50 mass%) may compromise extent of polymerization kinetics of dental adhesives.

Selection of welding process for hardfacing on carbon steels based on quantitative and qualitative factors

Weld hardfacing techniques are employed mainly to extend or improve the service life of engineering components either by rebuilding or by fabricating in such a way as to produce a composite wall section to combat wear, erosion, corrosion, etc. In this paper, an attempt has been made to determine the best welding process to hardface boiler grade steels based on quantitative factors (by measuring percentage of dilution) and qualitative factors (using the analytic hierarchy process [AHP]). Five different welding processes including shielded metal arc welding (SMAW), gas metal arc welding (GMAW), gas tungsten arc welding (GTAW), submerged arc welding (SAW), and plasma transferred arc welding (PTAW) have been compared. Based on the quantitative and qualitative factors, the PTAW process is found to be the best method to hardface boiler grade steels.

Influence of hydrogen partial pressure on growth and properties of nanocrystalline SiC by magnetron sputtering

Hydrogenated nanocrystalline silicon carbide (nc-SiC:H) thin films were prepared by reactive magnetron sputtering. Deposition was achieved in a plasma of argon (Ar) and an hydrogen (H 2 ) gas mixture with various H 2 dilution percentages (10–80% H 2 ) at a fixed substrate temperature of 500 °C. In order to describe the local bonding and the relative proportion of the different complexes formed during growth, the films were investigated by means of Fourier Transform Infrared absorption and Raman spectroscopy. Other structural features were analyzed by AFM measurements, electron diffraction and high resolution transmission electron microscopy observations. Optical and electrical properties of the films were also characterized. This study shows that hydrogen dilution plays an important role on the microstructure of the films as well as on their properties. The highest refractive index was obtained for a 60% ratio of hydrogen in the plasma and the highest dark conductivity found was 2.03 × 10 −4 Ω −1 cm −1 . A close relationship between the Si-H bond content and the conductivity is confirmed.

Investigation of Gas Phase Species and Deposition of SiO2 Films from HMDSO/O2 Plasmas

AbstractSummary: SiOxCyHz films are deposited by radio frequency plasma enhanced chemical vapor deposition (PECVD) using a mixture of HMDSO and oxygen as source gases. The gas phase species produced in HMDSO and HMDSO/O2 plasmas are investigated by optical emission spectroscopy (OES) and mass spectrometry (MS). These data reveal that oxygen dilution causes strong dissociation of the HMDSO monomer. The film composition was investigated with X‐ray photoelectron spectroscopy (XPS) and Fourier‐transform infrared (FT‐IR) spectroscopy. Low O2 dilution (≤50%) results in the deposition of polymer‐like SiOxCyHz films while higher O2 dilution (≥80%) results in the deposition of inorganic SiO2‐like films. Surface energy measurements show that the SiO2 films have higher surface energy than the polymer‐like SiOxCyHz films. Deposition rates are measured with variable angle spectroscopic ellipsometry and are strongly dependent on the percentage of O2 dilution in the feed mixture.Si 2p high‐resolution XPS spectra of films deposited in 50 W HMDSO/O2 plasmas with different gas ratios in the feed.magnified imageSi 2p high‐resolution XPS spectra of films deposited in 50 W HMDSO/O2 plasmas with different gas ratios in the feed.

Nanocrystalline silicon thin films deposited by high-frequency sputtering at low temperature

Abstract Intrinsic and n-type hydrogenated nanocrystalline silicon thin films (nc-Si:H) were deposited at a temperature as low as 95 °C by high-frequency (HF) sputtering, with hydrogen dilution percentage varying from 31% to 73%. In order to study the properties of the films prepared by this method, the samples were examined by infrared absorption spectroscopy (IR), X-ray diffraction (XRD), SEM, spectroscopic ellipsometry (SE), laser Raman spectrometry and atomic force microscopy (AFM). XRD measurements showed that this film has a new microstructure, which is different from the films deposited by other methods. In addition, an n-type nc-Si:H/p-type c-Si heterojunction solar cell, which has an open circuit voltage (Voc) of 370 MV and a short-circuit current intensity (Jsc) of 6.5 mA/cm2, was produced on the nanocrystalline silicon thin film. After 10 h light exposure under AM1.5 (100 MW/cm2) light intensity at room temperature, radiation degradation has not been found for the device.

Effect of the hydrogen dilution on the short-range and intermediate-range-order in radiofrequency magnetron sputtered hydrogenated amorphous silicon films

Raman spectroscopy experiments correlated with infrared absorption, optical transmission and photothermal deflection spectroscopy ones are used to investigate in detail the short-range-order (SRO) and intermediate-range-order (IRO) in hydrogenated amorphous silicon (a-Si:H) films elaborated at high rates (~15 A/s) by radiofrequency magnetron sputtering with various hydrogen dilution percentage (5 to 20%), leading to different hydrogen-related microstructure and content. The analysis of the transverse optic (TO)- and transverse acoustic (TA)-like modes of the Raman spectra indicates that both, the SRO and IRO are more strongly dependent on the nature of hydrogen bonding configurations, namely the relative proportion of polyhydride Si-H 2 and (Si-H 2 ) n complexes and/or clustered monohydride (Si-H) n groups incorporated in the films, rather than on the total bonded hydrogen content. The increase observed in the line width of the TO- and TA-like modes are well correlated with that of the disorder parameter E 0 , also called Urbach edge parameter, which is related to the exponential absorption from the valence band tails states distribution. Moreover, the analysis of the optical transmission data clearly evidences that the dispersion energy E d and the static refractive index n 0 are also maximum for films having the lowest value of E 0 , suggesting that they exhibit the highest mean coordination number and compactness respectively, consistent with better SRO and IRO.

Effect of small nitrogen dilution on the microstructure of hydrogenated silicon thin films deposited by magnetron radiofrequency sputtering

The effects of the nitrogen dilution and pressure on the structural and optical properties of hydrogenated microcrystalline silicon films deposited at 250 °C by the radiofrequency magnetron sputtering method have been studied in the (0–1%) range of nitrogen dilution percentage in the gas phase mixture (Ar 70%–H2 30%, total pressure 5 Pa). A combination of mass spectrometry, Raman spectroscopy, infrared absorption, UV–visible transmission and photothermal deflection spectroscopies has been used to characterize the films. Mass spectrometry revealed that the SiH2/SiH ratio decreased when increasing the nitrogen partial pressure. This change has been found to be related to the microstructural transition from microcrystalline to amorphous by Raman spectroscopy, while infrared spectroscopy showed an increase of SiN bonds. The structural change has been explained in terms of reaction of SiH2 crystallization precursors with nitrogen. The very small nitrogen partial pressure leads to an important nitrogen enrichment of the films, which causes the decrease of absorption coefficient and refractive index and the increase of the optical gap. This suggests that the films turned into an amorphous hydrogenated silicon nitride alloy.