Mixtures Of Dimethyl Ether Research Articles

Experimental validation of RE170 / R600 (Dimethyl Ether / Butane) mixture as a superior refrigerant compared to R600a (Isobutane)

Isobutane (R600a) is the most used refrigerant for low-capacity refrigeration systems, as it combines excellent environmental properties and offers good energy performance. A real possibility to increase the efficiency of these systems is using new refrigerant mixtures offering energy improvements (being compatible with existing systems). This work, from an experimental perspective, proposes mixtures of dimethyl ether and butane (RE170/R600) as potential drop-in refrigerants of R600a systems. For a given operating condition, the energy performance of RE170/R600 mixtures with maximum proportion of 27.5 % of RE170 has been tested using a water-to-water single-stage compression cycle, measuring COP increments from 10.1 to 17.6 % in relation to R600a. Then, the blend RE170/R600 (15/85 %), considered as the potential drop-in fluid of R600a, has been tested in a wide range of operating conditions, concluding that it offers the same cooling capacity than R600a but with COP increments from 12.6 % to 17.6 %.

Environmental-friendly extraction of di(2-ethylhexyl) phthalate from poly(vinyl chloride) using liquefied dimethyl ether

Poly(vinyl chloride) (PVC) is one of the most widely used plastics. However, a major challenge in recycling PVC is that there is no economical method to separate and remove its toxic phthalate plasticizers. This research made a breakthrough by extracting PVC with liquefied dimethyl ether (DME) and successfully separating the plasticizer components. Nearly all (97.1 %) of the di(2-ethylhexyl) phthalate plasticizer was extracted within 30 min by passing liquefied DME (285 g) through PVC at 25 °C. The compatibility of PVC with organic solvents, including liquefied DME, was derived theoretically from their Hansen solubility parameters (HSP), and actual dissolution experiments were conducted to determine the optimal PVC solvents. A liquefied DME mixture was used to dissolve PVC, and the extract was diluted with ethanol to precipitate the dissolved PVC. We demonstrated that liquefied DME is a promising method for producing high quality recycled products and that the process retains the fundamental properties of plasticizers and PVC without inducing degradation or depolymerization. Because of its low boiling point, DME can be easily separated from the solute after extraction, allowing for efficient reuse of the solvent, extracted plasticizer, and PVC. DME does not require heat and produces little harmful wastewater, which significantly reduces the energy consumption of the plasticizer additive separation process.

LateSearching for the most energy-efficient composition of a mixture of dimethyl ether and carbon dioxide as an air conditioning system refrigerantr

BACKGROUND: Carbon dioxide can be an alternative refrigerant for vapor compression refrigeration systems, particularly air conditioning systems (ACSs). However, its use suffers from the increased pressure in the refrigeration circuit. To solve this, for its reduction, a mixture of CO2 with a substance that has significantly lower pressures under the same conditions can be developed, for example, dimethyl ether (DME), which has zero GWP and ODP, is inexpensive and readily available. The study of DME, in particular, was conducted by the Department E4 “Refrigeration and Cryogenic Engineering, Air Conditioning and Life Support Systems” of N.E. Bauman Moscow State Technical University. DME is moderately toxic and flammable.
 AIM: This study aims to investigate the possible use of a mixture of DME and carbon dioxide for energy-efficient application in ACSs using commercially available compressors for R410A.
 METHODS: Comparative calculation analysis of the characteristics of a simple one-stage vapor compression cycle was performed using R410A and a mixture of DME and CO2 using the calculation packages Mathcad 15, Aspen HYSYS v. 10, SOLKANE8, and REFPROP.
 RESULTS: 1. The cycle on pure DME is the most effective in terms of the coefficient of performance: ε = 5.63 at an ambient air temperature of 26°C, ε = 3.07 at 40°C. 2. It is necessary to consider the influence of temperature glides, the average value of which ranges from 10°C to 30°C depending on the concentration of components. 3. At DME/CO2 ratios of 40/60% and 60/40% (in mole fraction), the discharge pressure corresponds to the discharge pressure in the R410A cycle, with 39.62 bar at an ambient temperature of 26°C and 37 bar at 40°C, respectively.
 CONCLUSIONS: An environmentally friendly mixture of DME and CO2 with low GWP and zero ODP is developed. An increase in the percentage of DME in the mixture increases the coefficient of performance and reduces the pressure range, and at the same time, significant temperature glides arise, which affects the installation efficiency, namely, the transition to a cycle with a receiver tank, i.e., with a recuperative heat exchanger between the fluorinated refrigerant flow leaving the evaporator and the fluorinated refrigerant flow leaving the condenser. The developed mixture is less efficient than the R410A refrigerant in terms of the coefficient of performance and discharge pressure. However, it is possible to further consider a mixture of DME and CO2 with concentrations of 40% and 60%, respectively, as a replacement for the R410 refrigerant because there is a correspondence of discharge pressures for serial compressors (about 40 bar); however, it is necessary to keep in mind the flammability risk of the mixture.

Elucidating the low temperature chemistry of o-xylene enhanced by the reaction pool of dimethyl ether

The branched aromatic hydrocarbon with short side chains, such as o-xylene, has weak low temperature oxidation reactivity, while it could proceed low temperature chain recycling reactions by blending a fuel component with higher oxidation reactivity. However, the study of low temperature oxidation kinetics of o-xylene is very scarce. Therefore, this work investigated the low temperature oxidation process of o-xylene in an atmospheric jet stirred reactor by adding a biofuel with higher low temperature oxidation reactivity, i.e. dimethyl ether (DME). A series of characteristic low temperature intermediates, such as phenyl hydroperoxides and ketohydroperoxide from the oxidation of o-xylene, were detected by using the synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). The chemical structures of representative low temperature intermediates were determined by comparing the ionization thresholds from measured photoionization efficiency curves with calculated ionization energies. A kinetic model for o-xylene and DME mixture was developed and verified by literature and present experimental data. Rate of production (ROP) and sensitivity analyses were performed, which indicate that the low temperature oxidation chemistry of o-xylene, such as the negative temperature coefficient behavior, is enhanced by the reaction pool of DME. According to the classical low temperature oxidation mechanism of n-alkanes, the low temperature reactions of o-xylene were proposed. In particular, phenyl hydroperoxides and ketohydroperoxides were revealed to be key indicators for the occurrence of first and second O2 addition reactions during the oxidation of o-xylene, respectively. In addition, the sensitivity analysis uncovers the interaction kinetics between the reaction pools of o-xylene and DME, as well as their effects on fuel consumption and products formation. In summary, present evidence elucidates the low temperature chemistry of a representative branched aromatic, which could contribute to the development of future engines and control of combustion pollutants.

Feasibility on equivalence ratio measurement via OH*, CH*, and C2* chemiluminescence and study of soot emissions in co-flow non-premixed DME/C1–C2 hydrocarbon flames

The effects of dimethyl ether (DME) addition to methane and ethylene fuels on the combustion characteristics of heat release, soot emissions, and flame temperature were investigated experimentally and numerically in a non-premixed laminar flame configuration. The flame-heat release soot-volume fraction was measured experimentally using CH*, OH*, and C2* chemiluminescence and planar two-color soot pyrometry, respectively. The CH*, OH*, and C2* were used to locate flame-heat release regions as well as to investigate the soot signal’s effect on their measurements. The ratios of the chemiluminescence pairs (OH*/CH* and OH*/C2*) were studied for the feasibility of map local equivalence ratios. Numerical calculations across a full range of DME mixing ratios were performed through 1D laminar flame simulations implemented with a detailed mechanism to provide an indication of the flame structures and profiles of key species including OH*, OH, CH*, CH, CH3, C3H3, C2H2, heat release rate (HRR), and flame temperature. An existing developed soot model was used in a 2D computational study to investigate its validity for modeling soot for DME (oxygenated fuel)/C2H4/N2 flames. Parametric studies have been carried out on some key parameters in the soot model to find optimum values that can be used in future studies. Although soot radiation intensities increased at a small amount (25%vol) of DME addition in the DME/methane flames, the soot pyrometry results showed a reduced soot volume fraction with an increased DME mixture ratio in both DME/methane and DME/ethylene flames studied, agreeing with the key conclusion of 1D numerical results. The flame HRR decreases with the increasing addition of DME to methane and ethylene flames and correlates with the trend of OH* and CH* profiles. The 1D simulation showed a non-monotonic correlation between OH*/CH* ratios and equivalence ratios, implying a limited use of OH*/CH* for the equivalence ratio measurement in non-premixed flames with DME additions.

Investigation of Substitution Energy for Engines Recovered from Synthetic Fuels Enhanced by Dimethyl Ether

Climate change and the depletion of fossil fuel reserves, it is important to utilize alternative fuels, which can help ease its impact on the environment. Besides, waste disposal is an important aspect to take into account, especially given the versatility and financial feasibility of synthetic polymers. The research in the article refers to the investigation of the synthetic fuel’s effectiveness, which is produced using waste synthetic polymer, and, due to the mixture of dimethyl ether in diesel engines, serves as an addition to this fuel. The performance and emission characteristics of biodiesel derived from synthetic rubber through the pyrolysis process are examined in this study. Furthermore, dimethyl ether is introduced as an additive at two different volume concentrations, specifically 25% and 50%, with the aim of improving the engine characteristics. The impact of these additives on the overall biodiesel performance and emissions is thoroughly investigated to provide insights into the potential benefits of utilizing synthetic rubber-derived biodiesel in combination with dimethyl ether in engine applications.

Accelerated ignition-shock coupling and deflagration to detonation transition by ozone kinetic enhancement of dimethyl ether mixture

This study aims to understand the effect of kinetic enhancement by ozone addition on the Deflagration to Detonation Transition (DDT) and ignition-shock coupling in a microchannel using dimethyl ether (DME). Simultaneous high-speed chemiluminescence and shadowgraph imaging are carried out to analyze the flame front propagation, shock wave structures, autoignition, and ignition-shock coupling during the DDT process. The experimental results show that for all cases, with and without ozone kinetic enhancement, autoignition and DDT always occur in a reactivity gradient region with oblique shock cluster between the flame front and the flame acceleration-induced precursor shock. The observed DDT occurs via the Zeldovich hot spot gradient mechanism through the following stages: (1) Oblique shock cluster formation and acoustic compression between the flame front and the precursor shock, (2) autoignition initiation in the oblique shock cluster region, (3) spontaneous ignition wave propagation, and (4) ignition-shock coupling. It is found that autoignition location, oblique shock strength, induction zone length, ignition-shock coupling, and DDT onset flame velocity are very different from ozone kinetic enhancement. As the ozone addition is higher, the autoignition is advanced and the ignition location moves farther ahead of the flame front at a lower flame front propagation speed and weaker oblique shock clusters. Two different ignition-shock coupling modes are identified depending on ozone concentration. Without ozone kinetic enhancement, DDT occurs via ignition wave coupling with the precursor shock. However, ozone addition can accelerate the autoignition and initiate a direct ignition-shock coupling for DDT without interaction with the precursor shock. The present results show that kinetic enhancement in autoignition using an ignition enhancer such as ozone or plasma is critical and effective in accelerating and controlling DDT.

Study on the effect of dimethyl ether and diesel-castor biodiesel blends on emission and combustion characteristics

The biodiesel from Castor was, investigated with a water-cooled four-stroke diesel engine of model CT 110 with B0, B5, and B10 without and with dimethyl ether (DME) of 2 % and with a fixed load of (80 %) to study the combustion and emission. The biodiesel was made by alkaline transesterification with NaOH as a catalyst. Using established test protocols, the fuels' characteristics, including their viscosity, surface tension, heating value, flash point, and elemental makeup, were measured. Experimental research is used to determine how the pressure and heat release rate affect the performance characteristics of both reference fuel and the blends. The combustion studies are conducted with engine speeds of 1800, 2400, and 3000 rpm and emissions were analyzed with engine speeds starting from 1600 rpm to 3000 rpm with exhaust gas analyzer Gunt, CT159.02 digital analyzer. From the combustion analysis when the blend ratio increases the cylinder pressure (CP) and heat release rate (HRR) also increase due to oxygen molecules in the biodiesel. The addition of DME to biodiesel blends reduces carbon monoxide (CO) emissions relative to neat diesel and biodiesel blends. With the increase of diesel castor biodiesel blends, nitrogen oxide (NOX) emissions decreased as a result of the reduction in the HRR. The effect of castor diesel biodiesel blend on the NOX emissions shows, that when the blend ratio increased the NOX emissions also increased. When DME is added to a higher blend ratio of castor biodiesel, the engine is operated only at higher engine speed. Specifically, for B10 NOX emission was detected after engine speed of 2500 rpm. When the engine ran with DME for blends of castor biodiesel the engine was not operated at low engine speed. The increase of diesel castor biodiesel blends in the case of DME mixture unburned hydrocarbon (UHC) emissions increased. The finding of this research work was as the biodiesel blend increased the cylinder pressure and heat release rate also increased. So, using sustainable biodiesel-diesel blends made from castor oil with DME additive it is advisable to operate diesel engines for better emission regulation.

Phase behaviour and physical properties of dimethyl ether (DME)/flue gas/water/heavy oil systems under reservoir conditions

The application of a mixture of dimethyl ether (DME) and flue gas (i.e., CO2 + N2) is a promising method to recover heavy oil; however, the phase behaviour and physical properties of DME/flue gas/water/heavy oil systems are not well quantified. In this study, theoretical and experimental techniques are developed to determine phase behaviour and physical properties of the aforementioned systems at pressures ranging from 2 MPa to 20 MPa and temperatures spanning from 352.15 K to 433.15 K. Experimentally, eight constant composition expansion (CCE) tests are carried out to obtain new experimental data for the DME/flue gas/water/heavy oil systems for the first time. Theoretically, a thermodynamic model that incorporates the Peng-Robinson equation of state (PR EOS), a modified α function, the Péneloux volume-translation strategy, and the Huron-Vidal (HV) mixing rule has been modified to reproduce the measured phase equilibria data. The tuned binary interaction parameters (BIPs) are utilized in conjunction with the thermodynamic model to accurately predict saturation pressure (Psat) and swelling factors (SFs) with a root-mean-squared relative error (RMSRE) of 3.32% and 0.57%, respectively. Furthermore, the newly proposed model demonstrates its high accuracy in forecasting the oleic/vapor (LV) two-phase boundaries for N2/heavy oil systems and DME/CO2/heavy oil systems with an RMSRE of 1.93% and 2.77%, respectively. Similarly, the accuracies of the predicted aqueous/oleic/vapor (ALV) three-phase boundaries for N2/water/heavy oil systems and DME/flue gas/water/heavy oil systems are 2.85% and 3.47%, respectively. Water is found to increase the phase boundaries for DME/CO2/heavy oil systems but decrease those of N2/heavy oil systems and DME/flue gas/heavy oil systems. Additionally, as the concentration of N2 and/or CO2 in the mixture is increased, its Psat is increased.

Harnessing dimethyl ether and methyl formate fuels for direct electrochemical energy conversion

In this work, the oxidation of a mixture of dimethyl ether (DME) and methyl formate (MF) was studied in both an aqueous electrochemical cell and a vapor-fed polymer electrolyte membrane fuel cell (PEMFC) utilizing a multi-metallic alloy catalyst, Pt3Pd3Sn2/C, discovered earlier by us. The current obtained during the bulk oxidation of a DME-saturated 1 M MF was higher than the summation of the currents provided by the two fuels separately, suggesting the cooperative effect of mixing these fuels. A significant increase in the anodic charge was realized during oxidative stripping of a pre-adsorbed DME + MF mixture as compared to DME or MF individually. This is ascribed to greater utilization of specific catalytic sites on account of the relatively lower adsorption energy of the dual- molecules than of the sum of the individual molecules as confirmed by the density functional theory (DFT) calculations. Fuel cell polarization was also conducted using a Pt3Pd3Sn2/C (anode) and Pt/C (cathode) catalysts-coated membrane (CCM). The enhanced surface coverage and active site utilization resulted in providing a higher peak power density by the DME + MF mixture-fed fuel cell (123 mW cm−2 at 0. 45 V) than with DME (84 mW cm−2 at 0.35 V) or MF (28 mW cm−2 at 0.2 V) at the same total anode hydrocarbon flow rate, temperature, and ambient pressure.

Phase Behavior and Physical Properties of Dimethyl Ether/CO2/Water/Heavy Oil Systems under Reservoir Conditions

Summary In this paper, techniques have been developed to quantify phase behavior and physical properties including phase boundaries, swelling factors (SFs), and phase volumes for reservoir fluids containing polar components from both experimental and theoretical aspects. Experimentally, a total of seven pressure-volume-temperature (PVT) experiments, including one set of dimethyl ether (DME)/heavy oil system, one set of DME/water/heavy oil system, three sets of DME/CO2/heavy oil systems, and two sets of DME/CO2/water/heavy oil systems, have been carried out to measure saturation pressures, phase volumes, and SFs by using a versatile PVT setup. Theoretically, the modified Peng-Robinson equation of state (PR EOS) incorporated with the Huron-Vidal (HV) mixing rule and the Péneloux volume-translation strategy is used as the thermodynamic model to perform phase equilibrium calculations. Once validated with the measured phase compositions of DME/water mixtures collected from the literature, the theoretical model developed in this work is used to reproduce the experimental measurements for the aforementioned reservoir fluids. It is observed that the saturation pressures of DME/CO2/water/heavy oil mixtures are higher than those of DME/CO2/heavy oil mixtures at the same temperature and same molar ratio of solvents and heavy oil, owing to the fact that more water molecules can be evaporated into the vapor phase. The binary interaction parameters (BIPs) between DME/heavy oil and CO2/DME pair, which are obtained by matching the measured saturation pressures of DME/CO2/heavy oil mixtures, work well for DME/CO2/heavy oil mixtures in the absence and presence of water. In addition, the swelling effect of heavy oil can be enhanced by adding the DME and CO2 mixtures compared with only DME or CO2. The new model developed in this work is capable of accurately reproducing the experimentally measured multiphase boundaries, SFs, and phase volumes with root-mean-squared relative errors (RMSREs) of 4.68, 0.71, and 9.35%, respectively, indicating that it can accurately provide fundamental data for simulating, designing, and optimizing the hybrid steam-solvent recovery processes for heavy oil reservoirs.

Thermodynamics of solvent-driven water extraction from hypersaline brines using dimethyl ether

Solvent-driven water extraction (SDWE) has promising applications in hypersaline brine desalination, including zero-liquid discharge processing for industrial wastewaters, and resource recovery, such as the extraction of lithium and rare earth elements from solution mining leachates. In this study, we develop a computational thermodynamic framework to analyze the liquid–liquid extraction of water from hypersaline brines using dimethyl ether (DME), an aprotic solvent that is partially miscible with water. The high volatility of DME enables its rapid separation from water–DME mixtures after water absorption, while its low polarity minimizes the organic-phase solubility of electrolytes, such as sodium chloride (NaCl). We first build a thermodynamic model based on the LIQUAC excess Gibbs free energy model for water–DME–NaCl mixtures. Maximum likelihood estimators for water–DME–NaCl interaction parameters are calculated through the nonlinear regression of fluid phase equilibrium and osmotic coefficient data using metaheuristic global optimization techniques. A multistage counter-current liquid–liquid separator (LLS) model is then developed to explore the water recovery and brine concentration ratios achievable as a function of feed molality and DME to feed water flow rate ratio. For a saline feed with a molality of 2.0molkg−1 (over three times the salinity of seawater) our analysis demonstrates that a one-stage LLS can achieve a water recovery ratio of 0.51 with an initial DME to saline feed molar flow rate ratio of 4.0, rising to 0.63 with a second equilibrium stage. We conclude by quantifying the amount of DME required to reach zero-liquid discharge brine salinities and analyzing the impact of staging and temperature on separation performance. Our thermodynamic model enables the rapid evaluation of SDWE systems for emerging hypersaline brine desalination and valorization applications.

Filtration Efficiency and Regeneration Behavior in a Catalytic Diesel Particulate Filter with the Use of Diesel/Polyoxymethylene Dimethyl Ether Mixture

Polyoxymethylene dimethyl ether (PODEn) is a promising diesel additive, especially in particulate matter reduction. However, how PODEn addition affects the filtration efficiency and regeneration process of a catalytic diesel particulate filter (cDPF) is still unknown. Therefore, this experimental work investigated the size-dependent particulate number removal efficiency under various engine loads and exhaust gas recirculation (EGR) ratios when fueling with diesel (D100) and diesel/PODEn mixture (P10). In addition, the regeneration behavior of the cDPF was studied by determining the breakeven temperatures (BETs) for both tested fuels. The results showed that the cDPF had lower removal efficiencies in nucleation mode particles but higher filtration efficiencies in accumulation mode particles. In addition, the overall filtration efficiency for P10 particles was higher than that for D100 particles. Positioning the upstream cDPF, increasing the EGR ratio slightly decreased the number concentration of nucleation mode particles but greatly increased that of accumulation mode particles. However, increasing the EGR ratio decreased the removal efficiency of nanoparticles, and this effect was more apparent for the P10 case. Under the same period of soot loading, the pressure drop of P10 fuel was significantly lower than that of diesel fuel. In addition, a significantly lower BET was observed for the P10 fuel, in comparison with D100 fuel. In conclusion, adopting cDPF is beneficial for fueling with P10 in terms of the overall filtration efficiency in the particulate number and the lower input energy requirement for active regeneration. However, with the addition of EGR, the lower filtration efficiencies of nanoparticles should be concerned, especially fueling with diesel/PODEn mixture.

A mixture of carbon dioxide and dimethyl ether as a refrigerant for ground air conditioning system

BACKGROUND: The selection of refrigerants for modern air conditioning systems (ACS) in ground facilities is a multidisciplinary task. Particularly, meeting the required energy efficiency of the refrigeration cycle as well as ensuring ecological safety of production, operation, and utilization of the refrigeration system. Herein, the working pressure levels of the refrigeration cycle considerably affect the availability, cost, and safety of the refrigeration equipment. The fire safety of the working substance is also important.
 AIM: To investigate the feasibility of a mixture of dimethyl ether and carbon dioxide as refrigerant for energy efficient and safe application of ACS in ground facilities.
 METHODS: Comparative analysis of a simple one-stage vapor–compression cycle using traditional working substances (R22 and R410A) and the proposed working substance, which is in the form of a mixture of dimethyl ether and carbon dioxide, using packages, such as Mathcad, HYSYS, CoolPack, and REFPROP, was performed.
 Results: An ecofriendly mixture of dimethyl ether and carbon dioxide with low global warming potential and zero ozone depletion potential was proposed as refrigerant. Increasing the percentage of dimethyl ether in the blend reduces the temperature glide in the gas cooler, a property of CO2, and pressures at which the blend operates. The mixture has limited operational properties due to the flammability of dimethyl ether, but its environmental performance makes the material of some practical interest.
 CONCLUSION: Fire safety of the proposed working substance was calculated. The concentration of dimethyl ether in the mixture at which it becomes flammable and unsafe for ACS was determined to be 8.3%.
 With an increase in the dimethyl ether content in the mixture with CO2 from 4% to 8%, the refrigeration coefficient of the cycle increases from 2.53 to 2.88, but it is 1.57 times less than that of R410A.
 The difference in operating pressures between the used non-ecological refrigerants and proposed mixture was determined. Results indicate that the mixture of dimethyl ether and carbon dioxide is currently inapplicable to mass production compressors, which use R410A as refrigerant. The condensation pressure of the most effective and nonflammable mixture of dimethyl ether and CO2 (with dimethyl ether concentration of 8%) is 101 bar against 30 bar for R410A.
 Therefore, we intend to evaluate test mixtures of dimethyl ether with other substances in the future.

Influence of LPG and DME Composition on Spark Ignition Engine Performance

This article presents a detailed analysis of the potential of dimethyl ether (DME) fuel applications in SI engines. This paper presents the tests results completed on an 1.6-dm3 Opel Astra engine fueled by gaseous fuel as a mixture of LPG and DME. Dimethyl ether is a fuel with properties similar to liquid LPG fuel. In addition, DME is very well miscible with LPG, hence the possibility of creating a mixture with any DME divisions. The assessment of the possibility of using DME as a component of the mixture was carried out with the use of a chassis dynamometer and equipment, enabling an analysis of the changes taking place inside the cylinder. The results of the analyses are the parameters of the thermodynamic processes describing changes in the engine cylinder.

PAH formation in the pyrolysis of benzene and dimethyl ether mixtures behind shock waves

In this work the laser-induced fluorescence (LIF) method was used to study the formation of polyaromatic hydrocarbons (PAHs) in the pyrolysis of benzene C6H6 and dimethyl ether C2H6O (DME) mixtures diluted with argon behind reflected shock waves within a temperature range of 1300–2000 K and pressures of 3.5–5.7 bar. To monitor the volume fraction of the condensed phase, laser extinction at a wavelength of 633 nm at the temperature range 1600–2500 K was measured. The LIF spectra of PAHs formed at varying temperatures and at different times relative to the onset of the pyrolysis process were recorded. It was found that the LIF spectra shift toward longer wavelengths with increasing temperature and reaction time. It has been shown that PAHs with four or more aromatic rings are the precursors of the appearance of the condensed phase. In mixtures with DME, greater amounts of small aromatics (consisting of one-two rings and fewer larger PAHs) were detected relative to benzene pyrolysis. Besides, the DME presence significantly reduced the optical density of the mixture at 633 nm, indicating a decrease in the soot yield. Modeling of PAHs and soot growth for the conditions of experiments using the modern sectional kinetic mechanism was carried out. The simulation results have demonstrated a change in PAH formation pathways that depend on fuel composition and temperature. The effect of DME on the growth of PAHs in benzene pyrolysis is both a decrease in temperature due to heat consumption during the decomposition of DME and the appearance of additional pathways for small PAHs formation and, at the same time, a decrease in the yield of heavier compounds consisting of four or more aromatic rings.

Effects of blending 2,5-dimethylfuran and dimethyl ether to toluene primary reference fuels: A chemical kinetic study

In the present work, renewable oxygenates 2,5-dimethylfuran (DMF) and dimethyl ether (DME) are considered as alternatives to fossil fuels for gasoline engines. The effects of blending DMF and DME on the combustion of gasoline surrogate are numerically studied. The gasoline surrogate is toluene primary reference fuel (TPRF) mixtures containing iso-octane, n-heptane, and toluene. Two skeletal mechanisms are proposed for the analysis: mechanism A with 504 species and 4212 reactions and mechanism B with 153 species and 740 reactions. These mechanisms are validated against a wide range of experimental data on ignition delay times and 1-D flames. The main findings of the present work are: 1) The ignition inhibiting effect of DMF dominates over the promoting effect of DME at 750 K and 25 bar when the total mole fraction of DMF and DME is less than 20 %. On the contrary, DME augments ignition with greater strength than the inhibition effect of DMF at 825 K and 25 bar. These observations are made for equimolar mixture of DMF and DME blended with TPRF in varying proportions. 2) The laminar burning velocity change stays within 10% of TPRF-air values for 50% TPRF/25%DMF/25%DME-air mixture for 0.6 ≤ φ ≤ 1. 6. 3) DME mitigates additional soot emission caused by DMF blending with TPRF. 4) For the first time in literature, it is shown that the laminar burning velocity and the maximum slope of OḢ mole fraction in the stoichiometric flames vary linearly with the research octane number (RON) for TPRF-air mixtures.

Ignition characteristics of premixed cool flames on a heated wall

This work examined the cool flame ignition and stabilization on heated walls with different surface reactivities. A premixed mixture of dimethyl ether (DME) and O2 was impinged on a heated wall and the wall temperature was linearly ramped to determine the cool flame ignition temperature. Numerical analyses identify a hysteresis phenomenon in the cool flame ignition and extinction processes, which appears to be primarily governed by the low-temperature reaction kinetics. The formation of HCHO during the cool flame ignition process was monitored using the planar laser-induced fluorescence (PLIF) technique synchronized with instantaneous wall temperature measurements. The data indicated that the HCHO concentration near the wall surface abruptly increased at the ignition of the premixed cool flame. The predicted hysteresis behaviors for cool flame ignition and extinction with a nonlinear folded S-curve and a smoothly stretched S-curve were successfully observed experimentally for the first time ever for lean mixtures. Moreover, the results show that compared with the ignition limits on an inert SiO2 surface, noticeable increases and decreases of the cool flame ignition temperature were observed on Fe and Pt surfaces, respectively. These findings suggest that significant wall chemical effects occur during the cool flame ignition process, based on interactions between the gas phase and surface reactions.

Pool boiling heat transfer coefficient of dimethyl ether and its azeotropic ternary mixtures

Dimethyl ether (DME) is a popular medium widely used in industrial applications. Being highly flammable substance, only recently it has again found commercial use as a primary working fluid in cooling and heating systems. Known as refrigerant RE170, it is now considered to be one of the potential natural refrigerants of the future due to minimal Global Warming Potential and zero Ozone Depletion Potential.Two novel azeotropic ternary mixtures of RE170/R1234yf/R152a were developed in order to improve cooling capacity and performance of a dimethyl ether refrigeration cycle. The mass ratios were purposefully selected to offer high cycle efficiency COP, high specific cooling capacity qe, small specific volume of vapour, reduced compressor power requirements, and the smallest possible temperature glide.The mixtures were subjected to experimental analysis in order to establish to what degree the added fluids (R1234yf and R152a) influence boiling and heat transfer performance. Boiling curves and heat transfer coefficients were determined experimentally and compared with the values obtained for pure RE170. Finally, several known heat transfer coefficient correlations (suitable for both hydrocarbons and synthetic refrigerants) were applied to the resulting data and evaluated for accuracy by evaluation of MAPE. The Cooper correlation was the most accurate for for ternary mixtures of dimethyl ether in the broadest range of temperatures, heat fluxes, and compositions (MAPE between 3.5-19.8). In order to improve the accuracy even further, the original Cooper correlation was modified with the acentric factor and the molecular mass power factor was optimised for modern chloride-less refrigerants. Resulting equation, when applied to ternary mixtures, returns errors below 5% in the entire range of experimental data.

Extraction of lipids from New Zealand fern fronds using near-critical dimethyl ether and dimethyl ether–water–ethanol mixtures

Dimethyl ether (DME), under near-critical conditions, can be used to extract lipids containing valuable fatty acids from wet biomass. In this work, DME, and a mixture of DME with a water–ethanol co-solvent, are used to extract fronds of the fern Cyathea dealbata, and the fatty acid composition of the extract was compared with the fern total lipids obtained by chloroform–methanol extraction. Extraction was carried out by circulating DME through a packed bed of milled undried fern material at pressure of 4.0 MPa, temperature of 58 °C, flow rate of 13.6 kg per kg undried fern material per hour, for 60 min followed by extraction using DME with addition of 5 wt% of a 70% ethanol in water co-solvent mixture until 572 g of co-solvent had been introduced. The total combined yield of DME and DME–ethanol–water extracts was 6.3 wt% of the fronds with the recovery of 88–93% of the major fatty acids (18:3n-3, 16:0, 18:2n-6, 18:1n-9). The remaining residue contained<7% of the fern total lipids. The extracts were slightly enriched in eicosapentaenoic acid (EPA, 95% recovery), while a significant portion of arachidonic acid (ARA, 19%) remained in the residue. The DME and DME–ethanol–water extracts contained 6.9 and 6.1 mg/g of ARA, and 13.4 and 14.2 mg/g of EPA, respectively.