Dimethyl Ether Addition Research Articles

A shock tube study of the ignition delay time of DME/ammonia mixtures: Effect of fuel blending from high temperatures to the NTC regime

An experimental and chemical kinetic investigation has been conducted to understand the effect of dimethyl ether (DME) blending on the ignition delay time of ammonia (NH3) from high temperatures to the negative temperature coefficient (NTC) regime in a shock tube with the DME fractions of 0 %, 5 %, 25 %, 50 %, and 100 %, temperatures of 690–1810 K, pressures of 1.2 and 10 atm, and equivalence ratio of 1.0. Four representative literature chemical kinetic models were validated against our measurements, however none of the above models can provide reasonable predictions of the experimental data in the NTC regime. A chemical kinetic model was developed in this study, the model was also been validated by the ignition delay times, laminar flame speeds and specie profiles data of DME/ammonia mixtures in the literature. Experimental results show that the ignition delay times of NH3 can be obviously shorten by 5 % DME addition in both high temperature and the NTC region. Chemical kinetic analyses reveal that the addition of 5 % DME can rapidly generate OH radical through the reaction pathway of HO2 → H2O2 → OH at 1250 K. At 800 K, the blended DME can be rapidly consumed via the reaction pathway of R → RO2 → QOOH → OOQOOH to promote the production of OH radical in the early stage, thus lead to the reduced ignition delay time of DME/NH3 mixture.

Experimental and kinetic modeling investigation on the co-pyrolysis of benzene, acetylene, and dimethyl ether: Insights into the fuel component interactions

The addition of dimethyl ether (DME) to hydrocarbons is proposed to be a feasible strategy to reduce carbon dioxide emissions in engines. In order to unravel the interaction between hydrocarbons and oxygenated fuels, the co-pyrolysis of benzene, acetylene, and dimethyl ether (DME) is investigated in a flow reactor at 880–1250 K and 1 atm using gas chromatography in this work. Additionally, pyrolysis of pure benzene and co-pyrolysis of benzene and acetylene are also performed. It is observed that the pyrolysis of pure hydrocarbon components and co-pyrolysis of benzene and acetylene can hardly happen in the investigated temperature region, while the addition of DME to the pyrolysis of benzene and acetylene significantly accelerate their decompositions and enhance the formation of key aromatics, such as toluene and indene, showing remarkable synergistic effects on pyrolysis reactivity and aromatics growth. A kinetic model describing the combustion of the three components is developed and used to perform numerical investigation on fuel decomposition and PAH formation. Modeling analysis shows that the addition of DME can effectively activate the pyrolysis system through fast C-O bond dissociation reactions, thereby reducing the decomposition temperatures of benzene and acetylene. The phenyl radical produced from the H-abstraction of benzene can react with acetylene to produce phenylacetylene, while phenylacetylene can further combine with another phenyl radical to form b-phenyl-a-styryl radical which can readily convert to phenanthrene. The addition of DME also generates abundant methyl radical, which further reacts with benzene or other aromatics to form large aromatics such as toluene and methylated PAHs.

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.

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.

Simulation of the harmful emissions formation in the exhaust gases of marine diesel of multi-fuel systems

Currently, the world community is increasingly struggling with harmful effects on the environment, the biosphere and the atmosphere in various fields of industry. One of the pollutants is marine transport. The main type of environmental pollution from marine power plants is harmful emissions of CO, CO2, NO sulfur compounds and other components contained in diesel exhaust gases. The main regulatory document determining the compliance of marine power plants with international environmental requirements is the international convention MARPOL 73/78, developed by the International Maritime Organization (IMO). One of the ways to solve this problem is the use of additional components for fuels on ships, such as water, hydrogen, natural gas, biodiesel, dimethyl ether, ethyl alcohol, etc. In order to pre-calculate the effectiveness of any of the methods for reducing harmful emissions, a simulation of combustion processes in a marine diesel engine when running on diesel fuel with and without the addition of dimethyl ether is carried out. In this study, the AVL Fire program, which is included in the AVL software package and allows you to get visual results on the formation of combustion products in the diesel cylinder, the distribution of temperature flows, soot formation, etc., is used. The 3NVD24 marine diesel engine, which is equipped with the necessary measuring complex for conducting practical research with the possibility of experimental confirmation of the computer modeling results, is used as a prototype for the analysis. Based on the model calculations, various factors of the harmful compounds formation during combustion are analyzed.

Experimental study on the explosion characteristics of NH3/DME/air mixtures

Co-firing ammonia (NH3) fuel with dimethyl ether (DME) is a promising approach of achieving clean combustion. However, the fundamental explosion characteristics of NH3/DME blends have not been well understood. This paper presents an experimental study of the explosion characteristics of NH3/DME blends using a spherical constant-volume combustion chamber. The effects of equivalence ratio (ϕ = 0.7–1.5), initial pressure (Pu = 0.05–0.5 MPa), and DME fraction (XDME = 0–100%) on the explosions were examined. The results show that peak explosion pressure Pmax, maximum pressure rise rate (dP/dt)max, and deflagration index KG, vary non-monotonically with equivalence ratio, and reach peak values at around ϕ = 1.1–1.2. DME addition has a positive effect on explosion intensity. Both (dP/dt)max and KG show a linear increase trend with increasing DME, while the growth rate of Pmax decreases with DME fraction. The relatively higher increase in Pmax between 0 %DME and 20 %DME is mainly due to greater heat release. Pmax increases with increasing initial pressure, and this is because of the increase in mixture mass promoting the heat release, and the enhanced possibility of effective collision between molecules of gas mixtures. The influence of initial pressure on (dP/dt)max and KG depends on the equivalence ratio. Both (dP/dt)max and KG show a linear increase with increasing initial pressure at ϕ = 1.0 and 1.5, whereas they are insensitive to initial pressure at ϕ = 0.7. This is because the decrease in laminar burning velocity leads to a significant increase in explosion time at ϕ = 0.7 compared to ϕ = 1.0 and 1.5. In addition, the actual explosion pressure is closely associated with non-negligible heat loss during flame propagation, and the heat loss decreases with the addition of DME, but increases with increasing initial pressure.

A molecular investigation on the effects of OMEX addition on soot inception of diesel pyrolysis

This study aimed at revealing the atomic-level chemical pathways involved in the soot inception inhibition of diesel pyrolysis with oxymethylene dimethyl ether (OMEX) addition. Using the reactive force field parameters in molecular dynamics simulation, the results effectively identified the specific pathways of OME3 pyrolysis and soot inception, via the analysis of the conversion of three main species: CH2O, CH3O, and CH3, generated from the initial decomposition of OME3. It has been found that CH2O molecule would be converted to CO through continuous dehydrogenation, and the carbon atoms convertered into CO would not participate in forming soot precursors, thus reducing soot formation. The oxidizing groups (mainly OH) are primarily produced from the CH3O radicals. These oxidizing species would react with small gaseous soot precursors to form stable oxides, thus inhibiting soot formation. However, this influence is relatively small under conditions where no oxygen is involved. The CH3 radicals would participate in the formation of soot precursors. In this study, it was observed that the addition of OME3 did not reduce the number of main gaseous precursors of polycyclic aromatic hydrocarbons such as C2H2, C2H3, and C3H3 during diesel-OME3 co-pyrolysis, because there were reactions between CH3 radicals and C1 and C2 species to form C2 and C3 hydrocarbon products. Based on the simulation results, the process from diesel decomposition to incipient soot production under the effects of OME3 is panoramically demonstrated. It is also found that the chain length increase of OMEX with a fixed molar fraction does not influence soot inhibition noticeably. Increasing the proportion of OMEX added to diesel helps reduce soot as carbon atoms involved in the formation of soot precursors are reduced, and more oxidizing species would be produced to slow the formation of gaseous soot precursors.

Effect of dimethyl ether on ignition characteristics of ammonia and chemical kinetics

The contribution of dimethyl ether(DME) to the ignition delay times(IDTs) of ammonia(NH3) was investigated behind reflected shock waves. The experiments were performed at a pressure of 0.14/1.0 MPa, temperature range of 1150–1950 K, equivalence ratio of 0.5/1.0/2.0, and NH3/DME mixing ratios of 100/0, 95/5, 90/10, and 70/30. It was observed that the addition of DME decreased the IDTs and promoted the reactivity of NH3. With the increase of DME, the effect of the equivalence ratio on the IDTs of NH3 decreased. Under higher temperature and pressure conditions, the promoting effect of DME on the ignition of NH3 was weakened. An updated mechanism is proposed to reveal the promoting effect of DME on the ignition of NH3. Mechanisms from the literature were compared against the measurements, and the updated kinetic mechanism was validated with experimental data. Good agreement between measurements and simulations were shown. Chemical kinetic analyses were performed to interpret the interactions between DME and NH3 during fuel ignition. The numerical analysis indicated that the promotion effect of DME is primarily due to an increase of the rate of production and concentration of the radical pool, especially the OH radical pool. The large number of OH radicals generated by the reaction HO2 + CH3 = OH + CH3O during the early oxidation of DME is key to the NH3 consumption and early initiation of the chain reaction.

Special features of soot formation in a standard premixed ethylene/air flame diluted with DME

This paper presents the experimental and calculated results of the investigation of soot formation in a standard premixed ethylene/air flame with the addition of 15–100% dimethyl ether. The soot volume fraction was measured using the laser light extinction method at a wavelength of 520 nm. The flame temperature versus height above the burner was measured using standard Pt-Rh thermocouples. It was experimentally shown that the addition of 15% dimethyl ether to ethylene/air flame resulted in a 20% increase of soot volume fraction. The further replacement of ethylene by 60% dimethyl ether decreased the soot volume fraction at 5 fold relatively to a pure ethylene/air flame. Kinetic modeling of soot volume fraction growth with height above the burner was carried out based on the kinetic mechanisms developed by CREСK group (http://creckmodeling.chem.polimi.it/). The calculations were carried out using open software package OpenSMOKE ++, which includes the modeling of gas-dynamic processes in the premixed laminar flame reactor. Good agreement between the experimental and calculated data was obtained. The analysis of kinetic mechanism used in this study allowed determining the peculiarity of kinetic pathways of benzene formation, which is proposed as an initial substance for soot precursor. It was found, that increase of soot concentration at 15% dimethyl ether addition to the ethylene/air flame is caused by intensification of channel of benzene formation via C3H3 recombination, which additionally produced from C3H4-p (propyne). In turn, the increase of C3H4-p concentration occurred due to reactions of acetylene with CH3 radical formed during DME decomposition. These results obtained in a standard ethylene/air flame could be used for development and validation of various kinetic mechanisms of soot formation.

On the sudden reversal of soot formation by oxygen addition in DME flames

Dimethyl ether (DME) is a non-toxic and renewable fuel known for its soot emissions reduction tendencies. In laminar co-flow DME diffusion flames, adding oxygen to the fuel stream increases the sooting tendency until a critical point is reached, at which point the trend suddenly reverses. This work unravels the mechanisms behind this reversal process, and characterizes their contribution to controlling soot production. A series of experimental measurements using diffuse-light line-of-sight attenuation and two-colour pyrometry were performed to measure soot volume fraction and soot temperature considering a fixed mass flow rate of DME and variable addition of oxygen. Soot volume fraction increases from 0.095 ppm in the pure DME flame to 0.32 ppm when the added oxygen concentration reaches 33%. When the oxygen concentration is slightly increased to 35%, soot volume fraction is reduced by 60%. To explain the reasons behind the reversal, a series of numerical simulations were performed, which successfully demonstrated the same trend. Results show that the chemical effects of adding oxygen to the fuel stream are exceedingly more important than the thermal and dilution effects. It was found that the reversal occurred when nearly all DME disassociated before exiting the fuel tube, indicating a sudden transition from a partially premixed DME flame, to one which primarily burns C1 fuel fragments. An analysis of soot formation and oxidation rates showed that near the reversal, soot inception is the least affected process; furthermore, soot precursor availability is not significantly affected in magnitude, rather they appear further upstream. It is concluded that the favourable conditions for rapid DME decomposition into soot precursors enhances soot inception while depleting the necessary species for further soot mass growth, dramatically reducing soot concentration.

Combustion characteristics of biodiesel with different dimethyl ether blending strategies

In this study, the effects of adding dimethyl ether (DME) on biodiesel (BD) combustion were studied through counterflow flame modeling. DME was added through two blending strategies, i.e., air-side and fuel-side blending, and methyl decanoate (MD) was used as the surrogate for BD. The profiles of the flame temperature, primarily species, and heat release rates (HRRs) after DME addition into MD were analyzed to explore the kinetic differences between pre-blending and post-blending combustion modes of BD and DME in engines. Results show that the air-side and the fuel-side additions of DME can slightly increase the peak temperature and widen the reaction zones of the flames. MD presents two distinct oxidation zones, while DME is primarily oxidized within an identified flame region with a higher temperature than MD. DME premixing on the fuel side can prompt MD dehydrogenation through enhancing H and OH formation. The flames enriched by air-side DME premixing present significant hybrid heat-release structure that depends on the fuel-side air entrainment as well. The heat-release characteristics of the non-premixed reaction zone (NPZ) of the counterflow flames with air-side DME additions suggest that the increased temperature is the main factor leading to the change of heat-release reaction routes of the flames.

Experimental and kinetic modeling study of the laminar burning velocity of NH3/DME/air premixed flames

Ammonia (NH3) as a carbon-free fuel and a high-density hydrogen carrier has received significant attention. Co-firing NH3 with dimethyl ether (DME) is a promising option for overcoming the low reactivity of NH3. This paper presents an experimental and kinetic modeling study of the laminar burning velocity of NH3/DME/air mixtures. Experiments were conducted for the full range of DME fraction at 0.1 MPa, 298 K, and equivalence ratios (ϕ) from 0.7 to 1.5 using a spherical constant-volume combustion chamber. The influence of pressure was examined for 20% - 80%DME at 298 K and ϕ = 0.7 - 1.4 by considering different initial pressures (0.1, 0.3, and 0.5 MPa). A small size reaction mechanism for NH3/DME/air mixtures was developed and validated against experiments. This mechanism performs well in predicting the laminar burning velocity of NH3/air, DME/air, and NH3/DME/air flames as well as the ignition delay time of NH3, DME, and NH3/DME oxidation. Detailed kinetic analyses using the mechanism helped us understand the observed effects of DME addition and initial pressure on the laminar burning velocity. The linear increase of laminar burning velocity with increasing DME fraction is mainly attributed to the enhancement of both thermal effect and chemical kinetics effect, while the negative influence of initial pressure is because of the decrease of chemical kinetics effect. In addition, it was found that the main reaction pathways based on N-atom shift with DME addition, whereas those based on C-atom vary little. Furthermore, pressure power exponent β as a function of equivalence ratio shows different behaviors for different DME fractions due to the competition between NH2 and CH3 chain-termination reactions for the rich flames. The present work provides experimental measurements of the laminar burning velocity at various conditions and insights into the chemical kinetics for NH3/DME/air mixtures.

The microscopic pore crude oil production characteristics and influencing factors by DME-assisted CO2 injection in shale oil reservoirs

CO2 injection into shale oil reservoirs can effectively enhance recovery while simultaneously realizing geological storage. However, shale oil recovery by CO2 injection remains low. In this paper, classification and evaluation standards for shale oil reservoirs were established. Based on this, comparative experiments between pure CO2 flooding and dimethyl ether (DME)-assisted CO2 flooding were conducted, supplemented by nuclear magnetic resonance testing. The microscopic production characteristics of shale oil under different injection methods were analyzed. The effects of injection pressure, gas injection volume, and DME concentration on oil recovery were studied, and the potential of DME-assisted CO2 flooding was explored. The results show three types of shale samples: I, II, and III, with their corresponding physical properties, pore-throat structures, and percolation capacities decreasing in the same order. With the addition of DME, the CO2 solubility increased, while the produced oil viscosity significantly decreased. DME-assisted CO2 flooding has higher recovery compare with CO2 flooding. The increase is more significant as pressure increases. The increase in ultimate recovery was the largest for type III samples. In addition, regardless of whether pure CO2 flooding or DME-assisted CO2 flooding was applied, a higher injection pressure and injection volume mean higher recovery. The increase by DME-assisted CO2 flooding is much greater than that by pure CO2 flooding. During the miscible stage, the recovery is greater than that during the immiscible stage. The recovery increased with increasing DME molar concentration and then slowed down; therefore, the recommended molar concentration of DME in the mixed gas is 20 mol%. The research results provide new methods and ideas for enhancing shale oil recovery and realizing geological storage by CO2 injection.

Temperature dependence of ethanol and dimethyl ether chemical mixing effects on soot and gas products in ethylene pyrolysis

The present work aims to understand the temperature dependence of the fuel chemical mixing effects on soot and gas product formation in ethylene pyrolysis in a laminar flow reactor. The chemical and dilution effects of ethanol and dimethyl ether addition were studied experimentally by gas chromatography measurements and computationally using a detailed soot model coupled with PAHs chemistry. The chemical effects of ethanol and dimethyl ether mixing increased the production of CO, H2, and CH4, but the dilution effects decreased the production of H2, CH4, and C2H2. The chemical mixing effects inhibited the formation of C2H2 except for the case in which 50% ethanol was mixed with 50% ethylene at 1273 K. Ethanol and dimethyl ether mixing inhibited soot production, but the fuel mixing effects on soot reduction decreased with increasing temperature. The temperature dependence of the fuel mixing effects on soot production was dominated by the chemical effects rather than the dilution effects. Kinetic analysis of the soot formation process indicated that the methyl radical (CH3) from ethanol and dimethyl ether decomposition combined with C2 species (C2H2, C2H4) from ethylene pyrolysis to generate plenty of C3 species (C3H4–P, C3H6, C3H5-A, C3H4-A, C3H3), which further converted into benzene (C6H6) and polycyclic aromatic hydrocarbons (C10H8, C14H10, and C16H10). The reaction rate of the above C1+C2→C3→C6→PAHs pathway increased noticeably with increasing pyrolysis temperature, which strengthened the chemical effects of ethanol and dimethyl ether mixing on soot surface growth rate contributed by PAHs and therefore soot yield under high-temperature conditions.

Temperature dependence of chemical effects of ethanol and dimethyl ether mixing on benzene and PAHs formation in ethylene counter-flow diffusion flames

The present work investigates the chemical, thermal, and dilution effects of ethanol and dimethyl ether mixing (10%/20%) on aromatics formation in ethylene counter-flow diffusion flames (CDFs) under different thermal conditions (Tmax≈1729/2000/2063 K). The fuel mixing effects were studied experimentally by gas chromatography measurements and computationally using two detailed chemical reaction mechanisms. The effects of ethanol and DME mixing on benzene and PAHs formation was found to be temperature-dependent in ethylene CDFs. Ethanol and dimethyl ether blending promoted benzene formation in high-temperature flames (2000 K and 2063 K) in comparison to low-temperature flames (1729 K). A slight reduction of benzene concentration was found after dimethyl ether addition under low-temperature conditions. The total effects of ethanol and dimethyl ether mixing on typical PAHs (C10H8, C14H10, C16H10) in low-temperature ethylene flames were also weaker than those in high-temperature flames. The temperature dependence of the total fuel mixing effects was dominated by chemical effects, while dilution and thermal effects were not significantly affected by the temperature. Pathway analysis showed that the temperature dependence of chemical mixing effects on benzene and PAHs formation originated from the C4+C2→C6→PAHs and C3+C3→C6→PAHs pathways.

Experimental study on explosion behavior of propane-dimethyl ether blends

The explosion characteristics of propane-dimethyl ether blends were investigated using a 20-L spherical explosion vessel. The effects of dimethyl ether (DME) addition and equivalence ratio were explored. The results indicated the maximum pressure and maximum pressure rising rate increased with the addition of dimethyl ether and reached maximum value under the equivalence ratio of 1.2. The time to reach maximum explosion pressure showed the opposite effect. The effect of initial temperature and pressure on explosion characteristics of propane with 30% dimethyl ether blending ratio was studied under the equivalence ratio of 1.0. The results indicated that elevated initial pressure increased the maximum explosion pressure and the maximum pressure rising rate, but had little effect on the time to reach maximum explosion pressure. Increasing the initial temperature reduced the maximum explosion pressure and the time to reach maximum explosion pressure. The maximum pressure rising rate was approximately 38 MPa s−1 when the initial temperature was raised from 30 to 120 °C. CHEMKIN software and the theoretical model calculated the maximum explosion pressure to compare with experimental results.

Study of combustion and NO chemical reaction mechanism in ammonia blended with DME

Ammonia (NH3) has been supposed to be the potential alternative energy source towards carbon neutrality. However, it has several unfavorable combustion characteristics, such as the slow combustion rate, poor combustion stability, high ignition energy and so on. As a renewable fuel, dimethyl ether (DME) is also considered to be a favorable carbon–neutral fuel, which can improve the combustion process of ammonia. To investigate the combustion and emission mechanism for the NH3/DME dual-fuel combustion, a detailed chemical reaction mechanism with 221 species and 1597 reactions was developed based on the previous relevant work. The laminar burning velocity (LBV) and ignition delay time (IDT) of ammonia, DME and NH3/DME combustion under a wide range of initial conditions were validated in 0-D and 1-D models. The process of NO formation and reduction reaction was also studied under the laminar burning combustion and ignition model, and it was found that fuel NOx still dominates the total NOx production in NH3/DME combustion, and the DME addition in ammonia up to 50% promotes the NO formation reaction, producing more NO. In order to analyze the effect of DME addition on NO formation mechanism, the analyses of chemical reaction pathway, sensitivity analysis on NO, typical active radical evolution behaviors and rate of production (ROP) were conducted in detail. In comparison with D50 (50%NH3/50%DME), D25(75%NH3/25%DME) with higher ammonia content generates more NH and NH2 radicals, and therefore, promoting the NO reduction reaction. Lower DME content in D25 also generates less H/O/OH active radicals, which inhibits the generation of NO. It is reduced by 9% approximately in total at equivalence ratio of 0.7. In addition, CH3 generated from DME could also partly promote the conversion of HNO and NO2 to NO, slightly increasing the NO production.

Effects of air-side dimethyl ether premixing on combustion characteristics of nonpremixed biodiesel/air counterflow flames

Counterflow flame modeling was conducted to investigate the effects of air-side dimethyl ether premixing on the combustion of biodiesel/air non-premixed flames, using the detailed kinetic mechanisms of bio-diesel and dimethyl ether. Methyl decanoate was adopted as the bio-diesel surrogate component. Comparative analyses focused on heat release, methyl decanoate oxidation, and the soot precursor, i.e. benzene production in the flames. The complex triple-flame structures were observed in the flames with air-side addition of dimethyl ether. Due to the interactions in the hybrid reaction zones, the flames with air-side premixing had higher peak temperatures, broadened flame thickness, and greater production of the integrated OH radical, consequently resulting in more robust flame power. The reactions related to self-pyrolysis and H-abstraction are the top main routes for methyl decanoate oxidation. The thermal effect induced by the higher flame temperature enhanced the radial leakage of MD and other intermediates and lowered the benzene production rate. The non-premixed reaction zone was the most active region for benzene production. The air-side premixing could exert its chemical effect on benzene formation within this zone by changing propargyl and phenyl chemistry.

Study on deflagration process of LPG/DME blended combustible gas cloud in open space

In order to reveal the deflagration characteristics and evolution law of LPG (liquefied petroleum gas)/DME (dimethyl ether) blended gas cloud under normal temperature and pressure in open space under different equivalence ratios and DME contents (0%、30%、50%、70%、100%), experiments and numerical simulations were conducted to study the deflagration overpressure, flame speed, gas velocity and their interactions, and the sensitivity analysis of key elementary reactions of LPG/DME blended gas was carried out. The results showed that the addition of DME can elevate the deflagration intensity of LPG, and in the same equivalent ratio the more of DME was blended into LPG, the greater the peak overpressure was, and so as to the maximum flame speed and the peak gas velocity. What's more, within certain limits the peak overpressure generated by gas deflagration showed a linear increase with the increase of the maximum flame speed. During the gas cloud deflagration, the flame speed went through three stages, including flame formation, acceleration and attenuation, and the DME blended ratio (λ) showed significant effect on the flame acceleration process. Then, the formation mechanism of overpressure and the state field distribution during gas cloud deflagration were proposed. The chemical reaction rate has a decisive effect on the flame speed, and the maximum flame speed restricts the peak overpressure and the peak gas velocity. Finally, the effect of promoting reaction is dominant after the addition of DME according to the sensitivity analysis.

Қоспалы отынның негізгі қасиеттері (дизель отыны + диметил эфирі) және диметил эфирі қоспасының дизельдік қозғалтқыш жұмысының көрсеткіштеріне әсерін теориялық бағалау

In the work, there was carried out a physical and chemical analysis of alternative fuels, from which there was selected dimethyl alcohol. A number of theoretical calculations were carried out to evaluate the main properties of the mixed fuel and the effect of the addition of dimethyl ether on the performance of the diesel engine. For a more complete assessment of the effect of mixed fuel on engine performance, there were used regression modeling methods. The regression coefficients were calculated on a PC using the MATLAB application software package. Theoretical calculations and mathematical modeling have shown that the addition of 30% dimethyl ether to diesel fuel is the most effective part of the mixture to reduce the environmental performance of diesel engines.