Polyoxymethylene Dimethyl Ethers Research Articles

NaNbO3 Nanocubes: Perovskite Catalysts for Methanol Polymerization

Polyoxymethylene dimethyl ethers (PODEs) are a class of oxygenated fuels with promising applications in energy production and emission reduction. They are often utilized as a diesel fuel additive or substitute, which reduces the formation of harmful emissions such as polycyclic aromatic hydrocarbons (PAH), soot, nitrogen oxides (NOx), and carbon monoxide (CO). The oxidative polymerization of methanol presents a promising route for the formation of PODEs. NaNbO3, a type of perovskite oxide, was synthesized with a well-defined nanocubic structure through solvothermal synthesis using a Nb2O5 precursor. The catalytic potential of both the NaNbO3 nanocubes and the well-studied Nb2O5 precursor was assessed for the oxidative polymerization of methanol into PODEs. NaNbO­3 demonstrated catalytic performance comparable to Nb2O5 as both catalysts produced formaldehyde and dimethyl ether, which are precursors to PODE. Powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy, and Brunauer-Emmett-Teller (BET) surface area confirmed the crystalline nature and desired cubic morphology of the NaNbO3 nanocubes. Additionally, Nb2O5 precursors with an orthorhombic, as opposed to a monoclinic or hexagonal crystal system were determined to produce NaNbO3 nanocubes successfully. Effective shape control of the NaNbO3 nanocubes makes this catalyst an intriguing material to understand and apply in heterogenous catalysis.

Effects of ammonia energy ratio and PODE injection timing on combustion and emissions in a PODE/ammonia RCCI engine

The application of ammonia as an alternative carbon-free fuel has attracted increasing attention. In this paper, the effects and mechanisms of ammonia energy ratio (AER) and polyoxymethylene dimethyl ethers (PODE) injection timing on the combustion and emissions characteristics of a PODE/ammonia RCCI engine are investigated by both experimental and numerical methods. Results show that increasing AER from 10% to 40% leads to the delayed low temperature heat release (LTHR) due to reduced OH radical generated by PODE and the competition between PODE and ammonia for OH radical consumption. The larger AER increases the indicated thermal efficiency (ITE) by lowering combustion temperature and reducing heat transfer losses at the cost of higher hydrocarbon (HC), carbon monoxide (CO), and unburned NH3 emissions. The reduction of fuel-based nitrogen oxide (NOx) emissions with a larger AER is attributed to the enhanced in-cylinder thermal denitrification reactions. The delayed start of injection (SOI) from −60 °CA ATDC to −45 °CA ATDC leads to the higher peak in-cylinder pressure and temperature, resulting in the larger heat transfer losses and lower ITE. The impact of retarding SOI on NOx is insignificant under the combined effect of more thermal NO formation, less fuel-based NO generation, and weakened denitrification reactions. Additionally, nitrous oxide (N2O) shows dominant effects on the total greenhouse gas (GHG) emissions, and increasing AER or advancing injection timing produces more GHG. Under low loads and low AERs, although the introduction of ammonia helps to improve ITE, more researches are required to further reduce exhaust emissions.

Kinetic and Thermodynamic Requirements for Polyoxymethylene Dimethyl Ether Synthesis Catalyzed by Ion-Exchange Resin

Kinetic and Thermodynamic Requirements for Polyoxymethylene Dimethyl Ether Synthesis Catalyzed by Ion-Exchange Resin

An efficient data-driven approach for modeling and optimization of reactivity-controlled compression ignition engine fueled with polyoxymethylene dimethyl ethers and hydrogen

This paper presents an efficient data-driven approach for optimizing the utilization of PODEn and hydrogen in reactivity-controlled compression ignition (RCCI) engines. A novel high dimensional model representation (HDMR) technique is adopted to construct a highly accurate surrogate model for the RCCI engine based on the dataset generated by a detailed CFD model that has been calibrated against experimental data. The HDMR model is then coupled with Non-dominated Sorting Genetic Algorithm III (NSGA III), a multi-objective genetic algorithm, to search for the optimal operating conditions where the RCCI engine fueled by PODEn and H2 achieves the highest combustion performance. Results suggest that the constructed HDMR model is highly accurate, being able to predict the engine performance within milliseconds. The coupled HDMR-NSGA III approach successfully identifies the optimal engine operating condition, which significantly improves the combustion performance and reduces pollutant emissions compared with the base condition.

Investigation on combustion and emission characteristics of diesel polyoxymethylene dimethyl ethers blend fuels with exhaust gas recirculation and double injection strategy

As a kind of renewable and high oxygen content fuel, polyoxymethylene dimethyl ether (PODE) can be added in diesel to realize energy saving and emissions reduction. To evaluate the combustion and emission characteristics of a diesel engine fueled with diesel and diesel/PODE mixtures, exhaust gas recirculation (EGR) and main-pilot injection strategies with various injection timings were applied. PODE was blended with diesel by volume to form mixtures which were marked as D100 (pure diesel), D90P10 (90% diesel + 10% PODE), and D80P20 (80% diesel + 20% PODE). The results showed that the ignition delay (ID) and combustion duration (CD) of D80P20 were the shortest because of the highest cetane number (CN) and high oxygen content of PODE, indicating more concentrated heat release. At low and medium loads, D80P20 achieved the highest peak heat release ratio (PHRR) and peak combustion temperature (PCT) among the three fuels, and it was 14.3% and 3.6% higher than those of D100. PODE blending with diesel can significantly reduce particulate matter (PM) and D80P20 has the lowest PM emissions at all loads. Compared with D100, both PM and nitrogen oxide (NOx) emissions of PODE blends decreased simultaneously with 20% EGR at all loads. With the increase of pilot-main interval, the ID and CD of all test fuels increased, while the NOx and PM emissions decreased. The conclusions of the present research provide a state of the application in light-duty engines fueled with diesel/PODE blends in future work.

The influence of molecular structure on the oxidation reactivity of long-chain ethers: Experimental observation and theoretical analysis

Long-chain ethers have been proposed as promising biofuels for advanced combustion methods, yet their low-temperature oxidation (LTO) characteristics remain poorly understood. In this study, the LTO reactivities of n-heptane and five long-chain ethers with different structures, including dibutyl ether (DBE), diethylene glycol dimethyl ether (DGM), polyoxymethylene dimethyl ethers (PODE), 1,2-dimethoxyethane (1,2-DME), and dipropyleneglycol dimethyl ether (DPGDE) are investigated using a cooperative fuel research (CFR) engine, which is closer to the actual internal combustion engine operating environment. Products formed from LTO of ethers and n-heptane are investigated over a wide range of compress ratios (CRs), and their relationship to the global oxidation reactivity is suggested based on the quantum chemistry calculation. The presence of oxygen atoms in long-chain ethers significantly enhances oxidation reactivity, with the global oxidation reactivity ranking as follows: DGM > DPGDE > 1,2-DME > DBE > PODE > n-heptane. The key intermediate species generated during the LTO of n-heptane include aldehydes, ketones, and cyclic ethers, while oxygen atoms in ethers facilitate the formation of acids. The species pathway analysis and quantum chemistry calculations reveal that (1,5) and (1,6) H-transfers of alkylperoxy radical (ROȮ) are critical chain-propagation channels, playing pivotal roles in the LTO process. The impact of oxygen on oxidation reactivity can be attributed to two primary factors: accelerating the H-abstraction of ȮH and H-transfer of ROȮ by weakening the neighboring C-H bonds, and enhancing the branching ratio of H-transfer of ROȮ. The arrangement of two oxygen atoms between every two carbon atoms (–OCH2CH2O–) is optimal for oxidation reactivity, while the arrangement of oxygen and carbon (–OCH2OCH2–) weakens the oxidation activity due to fewer available hydrogens for H-transfer. The methyl group in branching-chain, exhibit reduced oxidation reactivity due to the strength of C-H bonds. Additionally, for ethers with the same structure, a longer carbon chain allows for more available hydrogens, resulting in stronger oxidation reactivity.

Experimental study for the effect of spark ignition on methanol/PODE dual fuel combustion under medium and low loads

Methanol/high reactivity fuel (HRF) dual fuel combustion cannot further extend methanol energy ratio (MER) at medium and low loads. Polyoxymethylene dimethyl ether (PODE) as a biofuel with high cetane number is well suited for HRF. This paper explored the effect of spark ignition (SI) on energy conversion and MER extension for methanol/PODE under medium and low loads. The results show that SI triggers the exothermic processes of SI and dual fuel spark-assisted compression ignition (D-SACI). SI raised MER from 30 %, 40 %, 46 % to 40 %, 60 %, 90 % for brake mean effective pressure (BMEP) of 0.2, 0.4, 0.6 MPa, respectively. SI and D-SACI combustion can partially or completely replace premixed compression ignition (CI). Diffusion combustion and one or more exothermic processes of SI, D-SACI and premixed CI make up two-stage or three-stage exotherm. D-SACI is easily triggered when spark timing approaches PODE injection timing, otherwise, SI exotherm is easily triggered; at BMEP of 0.6 MPa, the exothermic energy of premixed CI is gradually converted into the exothermic energy of D-SACI and SI as MER increases. By optimizing, maximum brake thermal efficiency for BMEP of 0.4 and 0.6 MPa are 37.75 % and 42.82 %, respectively, corresponding to the MER of 50 % and 80 %, respectively.

Optical engine investigation of ammonia combustion enhancement with polyoxymethylene dimethyl ethers (PODE₃) as pilot fuel

Ammonia, gaining attention as a carbon-free fuel amid declining fossil fuel reserves, faces challenges like combustion instability and misfiring in its application in internal combustion engines. In this study, polyoxymethylene dimethyl ethers (PODE3), a clean, renewable, and electrically synthesized fuel with high cetane number and oxygen content, is evaluated as a pilot fuel for ammonia in dual-fuel engines. The study, performed in a dual-fuel optical engine, investigates the use of PODE₃ compared to diesel as direct injection fuels for ammonia combustion, focusing on the impact of PODE3 injection timing and dwell (the interval between dual-stage injections) on the ignition characteristics of ammonia. The results demonstrate that, compared to diesel, using PODE3 enhances ammonia combustion in dual-fuel engines. This is evident from increased in-cylinder pressure, higher apparent heat release rate (AHRR), advanced combustion phases, and improved indicated mean effective pressure (IMEP), enhancing overall stability. PODE3 also effectively minimizes soot generation, evidenced by a 71.5 % reduction in spatially integrated natural luminosity (SINL), accompanied by a 16.9 % increase in peak flame area. Adjusting PODE3 injection timing is crucial; initial retardation improves combustion performance, marked by higher in-cylinder pressure and AHRR, as well as expanded flame area. However, over-delaying injection timing reduces these gains. The optimal performance is achieved under the SOI-25 condition, balancing combustion and flame development, though some areas remain unburnt. In a dual-stage injection strategy using PODE3, where the second injection timing remains fixed at −25 °CA ATDC, the critical adjustment of advancing the first injection timing to −35 °CA ATDC markedly enhances combustion performance compared to a single injection condition. This setting reduces ignition delays, increases peak in-cylinder pressures, and improves stability, which collectively contribute to a significant 20.4 % increase in the peak flame area, particularly between adjacent fuel jets. Expanding upon this, advancing the first injection timing further to −45 °CA ATDC leads to a decrease in peak in-cylinder pressure and AHRR, accompanied by a notable 40.3 % reduction in the peak flame area. This research affirms the advantages of PODE3 over diesel in ammonia-powered dual-fuel engines, markedly enhancing combustion performance and environmental sustainability, where the injection strategy of PODE3 emerges as a crucial element.

Combustion and emission of diesel/PODE/gasoline blended fuel in a diesel engine that meet the China VI emission standards

The present study examined the impact of blending polyoxymethylene dimethyl ethers (PODE) and gasoline with diesel on combustion and emission characteristics in an engine compliant with China VI emission standards. The effects on cylinder pressure, combustion duration, and emissions (CO, THC, PN, and NOx) by blending 20 % PODE into diesel and adjusting the gasoline content (0 %, 5 %, and 10 %) were analyzed. The results showed that the cylinder pressures and the combustion duration were reduced with the addition of PODE, compared to the cases of the pure diesel. Moreover, it was found that PODE contributed to reducing the emissions of CO, THC, and PN, and but increasing NOx emissions. Compared to the cases of PODE and diesel blended fuel, the effect of the addition of gasoline on the cylinder pressures and combustion duration presented a minor increasing tendency, and the lower proportion of gasoline blending was found to effectively curb NOx formation. Specifically, blending 5 % gasoline with a 20 % PODE and diesel mixtures resulted in a 4.01 % reduction in NOx emissions. Based on the results of the present study, it can be concluded that 5 % gasoline and 20 % PODE blend in diesel can enhance combustion efficiency and heat release rate and also can achieve a balanced reduction in NOx emissions. The present study provides valuable insights for the development of energy-saving and emission reduction technologies for diesel engines, highlighting the potential of optimized fuel blends to improve combustion and emissions control.

LES and RANS Spray Combustion Analysis of OME3-5 and n-Dodecane

Clean-burning oxygenated and synthetic fuels derived from renewable power, so-called e-fuels, are a promising pathway to decarbonize compression–ignition engines. Polyoxymethylene dimethyl ethers (PODEs or OMEs) are one candidate of such fuels with good prospects. Their lack of carbon-to-carbon bonds and high concentration of chemically bound oxygen effectively negate the emergence of polycyclic aromatic hydrocarbons (PAHs) and even their precursors like acetylene (C2H2), enabling soot-free combustion without the soot-NOx trade-off common for diesel engines. The differences in the spray combustion process for OMEs and diesel-like reference fuels like n-dodecane and their potential implications on engine applications include discrepancies in the observed ignition delay, the stabilized flame lift-off location, and significant deviations in high-temperature flame morphology. For CFD simulations, the accurate modeling and prediction of these differences between OMEs and n-dodecane proved challenging. This study investigates the spray combustion process of an OME3 − 5 mixture and n-dodecane with advanced optical diagnostics, Reynolds-Averaged Navier–Stokes (RANS), and Large-Eddy Simulations (LESs) within a constant-volume vessel. Cool-flame and high-temperature combustion were measured simultaneously via high-speed (50 kHz) imaging with formaldehyde (CH2O) planar laser-induced fluorescence (PLIF) representing the former and line-of-sight OH* chemiluminescence the latter. Both RANS and LES simulations accurately describe the cool-flame development process with the formation of CH2O. However, CH2O consumption and the onset of high-temperature reactions, signaled by the rise of OH* levels, show significant deviations between RANS, LES, and experiments as well as between n-dodecane and OME. A focus is set on the quality of the simulated results compared to the experimentally observed spatial distribution of OH*, especially in OME fuel-rich regions. The influence of the turbulence modeling is investigated for the two distinct ambient temperatures of 900 K and 1200 K within the Engine Combustion Network Spray A setup. The capabilities and limitations of the RANS simulations are demonstrated with the initial cool-flame propagation and periodic oscillations of CH2O formation/consumption during the quasi-steady combustion period captured by the LES.

Potential Analysis of Defossilized Operation of a Heavy-Duty Dual-Fuel Engine Utilizing Dimethyl Carbonate/Methyl Formate as Primary and Poly Oxymethylene Dimethyl Ether as Pilot Fuel

<div>This study demonstrates the defossilized operation of a heavy-duty port-fuel-injected dual-fuel engine and highlights its potential benefits with minimal retrofitting effort. The investigation focuses on the optical characterization of the in-cylinder processes, ranging from mixture formation, ignition, and combustion, on a fully optically accessible single-cylinder research engine. The article revisits selected operating conditions in a thermodynamic configuration combined with Fourier transform infrared spectroscopy.</div> <div>One approach is to quickly diminish fossil fuel use by retrofitting present engines with decarbonized or defossilized alternatives. As both fuels are oxygenated, a considerable change in the overall ignition limits, air–fuel equivalence ratio, burning rate, and resistance against undesired pre-ignition or knocking is expected, with dire need of characterization.</div> <div>Two simultaneous high-speed recording channels granted cycle-resolved access to the natural flame luminosity, which was recorded in red/green/blue and OH chemiluminescence.</div> <div>Selected conditions were investigated in more detail with the simultaneous application of planar laser-induced fluorescence of OH and HCHO and recording natural flame luminescence in a cycle-averaged manner.</div> <div>Poly oxymethylene dimethyl ether was used as pilot fuel, building on prior investigations. The mixture of 65 vol% Dimethyl Carbonate and 35 vol% Methyl Formate with prior verification on a passenger-car-sized engine substitutes synthetic natural gas in this study.</div> <div>Thermodynamically, the increased compression ratio up to 17.6 resulted in feasible operation and increased indicated efficiency. On the lower compression ratio of 15.48, a more comprehensive range of applicable air–fuel equivalence ratios and increased degrees of freedom regarding the pilot’s total energy share are observed compared to the base configuration with natural gas and EN590 as pilot fuel.</div> <div>The air–fuel equivalence ratio sweep from λ = 1.0–2.0 revealed predominantly premixed and high-temperature heat release via OH*. The temporal and spatial evolution shifts while leaning out the mixture with increasing gradients on the radial distribution and decouples for lean mixtures from the initial spray trajectory.</div>

A Comparative Experimental Analysis of Natural Gas Dual Fuel Combustion Ignited by Diesel and Poly OxyMethylene Dimethyl Ether

A Comparative Experimental Analysis of Natural Gas Dual Fuel Combustion Ignited by Diesel and Poly OxyMethylene Dimethyl Ether

Combined experimental and kinetic modeling study on the low-temperature oxidation of OME3/n-heptane blends

Experimental and kinetic studies on the blending of ethers or diesters with larger alkanes at low temperatures are enormously scarce. In this paper, the low-temperature oxidation (LTO) kinetics model of polyoxymethylene dimethyl ether 3 (OME3)/n-heptane (500 K–950 K) was established by using the jet-stirred reactor (JSR) to conduct the LTO experiments of OME3/n-heptane with different blending ratios. GC/MS was used to detect and quantify 17 kinds of stable products in the LTO process of OME3/n-heptane. The detailed OME3/n-heptane kinetic model was fully verified experimentally. The interaction mechanism of OME3/n-heptane was discussed based on the experiments and corresponding chemical kinetic analysis. Results show that the oxidative decomposition processes of OME3 and n-heptane were significantly different, the LTO and NTC process of OME3 were significantly weaker than those of n-heptane, but the high-temperature reactivity of OME3 was much stronger. In addition, n-heptane significantly promoted the intermediate species CH3OCHO and COCOC*O of OME3, mainly because n-heptane significantly prolonged the LTO of OME3 in the fuel blends. And the NTC process of the fuel blends was mainly dominated by OME3, while the LTO process was more influenced by n-heptane, which resulted in the weakened NTC of n-heptane and the significantly enhanced LTO process of OME3.

Effects of polyoxymethylene dimethyl ethers (PODEn) on soot characteristics in isooctane inverse diffusion flames

Polyoxymethylene dimethyl ethers (PODEn, n = 1–3) such as dimethoxymethane (DMM) and PODE3 are considered highly promising alternative fuels due to their lack of C–C bonds and significant oxygen contents. Particularly, PODE3-blends with diesel have been proven to substantially reduce soot emissions and fuel consumption rates under optimized engine conditions, although the impact on soot nanostructure properties remains unclear. This study explored the effects of DMM and PODE3 on soot characteristics in isooctane (i-octane) inverse diffusion flames, focusing on soot morphology, soot nanostructure, soot nanocrystallite, and soot spectral features. To compare soot particles behavior, DMM and PODE3 blended as the isooctane substitute (by 20% and 40% volumetric fractions) were examined with various diagnostic techniques, including high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS).The results showed that DMM and PODE3 contributed to a reduction in sooting tendency from i-octane flames, whereas the average soot mass decreased significantly as the PODE3 ratio increased, consistent with a higher oxygen concentration. Therefore, 20% PODE3/i-octane exhibited growing disorganized arrangements of soot particles with shorter fringes, smaller crystallite sizes, and a relatively lower degree of graphitization than 20% and 40% DMM additions. However, XPS analysis indicated that soot produced from PODE3/i-octane mixtures had less oxygen atoms because PODE3 has multiple –CH2O- chain groups that can convert oxygen into carbon monoxide with little soot production. Moreover, HRTEM, XRD, and Raman spectra analyses of 40% PODE3-doped flames confirmed an exceptional correlation with turbostratic soot structure, as manifested by the shortest fringe length, longest fringe tortuosity, more amorphous soot with the smallest crystallite dimensions, and least degree of graphitization.

Numerical Study of Premixed PODE3-4/CH4 Flames at Engine-Relevant Conditions

Polyoxymethylene dimethyl ether (PODEn, n ≥ 1) is a promising alternative fuel to diesel with higher reactivity and low soot formation tendency. In this study, PODE3-4 is used as a pilot ignition fuel for methane (CH4) and the combustion characteristics of PODE3-4/CH4 mixtures are investigated numerically using an updated PODE3-4 mechanism. The ignition delay time (IDT) and laminar burning velocity (LBV) of PODE3-4/CH4 blends were calculated at high temperature and high pressure relevant to engine conditions. It is discovered that addition of a small amount of PODE3-4 has a dramatic promotive effect on IDT and LBV of CH4, whereas such a promoting effect decays at higher PODE3-4 addition. Kinetic analysis was performed to gain more insight into the reaction process of PODE3-4/CH4 mixtures at different conditions. In general, the promoting effect originates from the high reactivity of PODE3-4 at low temperatures and it is further confirmed in simulations using a perfectly stirred reactor (PSR) model. The addition of PODE3-4 significantly extends the extinction limit of CH4 from a residence time of ~0.5 ms to that of ~0.08 ms, indicating that the flame stability is enhanced as well by PODE3-4 addition. It is also found that NO formation is reduced in lean or rich flames; moreover, NO formation is inhibited by too short a residence time.

CO2 solubility and absorption rate analysis of a mixed poly(oxymethylene) dimethyl ethers (PODE3–5) solution

Efficient and economical carbon capture is critical to counteract the diverse problems of global warming. In this work, the solubility of carbon dioxide (CO2) in different poly(oxymethylene) dimethyl ethers (PODE) solutions was experimentally investigated at temperatures from 278.15 to 308.15 K and pressures up to 1.2 MPa. The Henry's law constants of CO2 in the PODE system were determined and compared with other types of physical absorbents, which revealed PODE3–5 has great CO2 absorption ability in terms of molar and mass fraction. Meanwhile, the initial absorption rate of the physical absorption process of PODE3–5 was calculated and compared with commercially available absorbents using a gas absorption rate relationship. It was shown that the absorption rate of PODE3–5 in the CO2 absorption process is faster than that of other commercial absorbents. The CO2 solubility data of PODE3–5 were also correlated using the Jou-Mather model and the perturbed-chain statistical association fluid theory (PC-SAFT) equation of state model, and the recycling performance of the PODE3–5 absorbent was tested.

A conceptual model of polyoxymethylene dimethyl ether 3 (PODE3) spray combustion under compression ignition engine-like conditions

As one of the most popular synthetic fuels (E-fuels), Polyoxymethylene dimethyl ethers(PODEX) have garnered significant attention among researchers in the compression ignition engine field. This work aims to provide an exhaustive analysis of the combustion characteristics of PODE3, which typically constitutes the primary component of PODEX. This research seeks to deepen our understanding of the flame structure of PODE3, particularly in relation to ambient temperature variation, and unravel the underlying mechanisms driving the observed trends. To achieve this aim, a range of optical techniques was employed within a high-temperature high-pressure combustion vessel to quantify various general combustion parameters and assess OH* chemiluminescence, formaldehyde, and soot distribution. Two additional reference fuels, pure n-dodecane and a blend of 50 % vol n-dodecane and 50 % vol PODE3 were also tested. Additionally, some analysis from chemical kinetics and 1D spray model calculations were used to substantiate the experimental observations. The findings reveal that the flame structure of PODE3 differs significantly from traditional diffusion flames associated with diesel-like sprays. The flame lift-off length (LOL) of PODE3 aligns closely with that of n-dodecane, and maintains the two-lobe structure under high-temperature conditions. In contrast, under low ambient temperatures, the LOL of PODE3 significantly extends, accompanied by a concentration of OH* radicals at the spray center. The notable sensitivity of PODE3 flames to temperature variation is related to the chemical kinetics of formaldehyde and CO. As a result of the analysis, conceptual models of PODE3 flames under varying temperatures were proposed in the end.

Numerical study of novel OME1−6 combustion mechanism and spray combustion at changed ambient environments

For a climate-neutral future mobility, the so-called e-fuels can play an essential part. Especially, oxygenated e-fuels containing oxygen in their chemical formula have the additional potential to burn with significantly lower soot levels. In particular, polyoxymethylene dimethyl ethers or oxymethylene ethers (PODEs or OMEs) do not contain carbon-carbon bonds, prohibiting the production of soot precursors like acetylene (C2H2). These properties make OMEs a highly interesting candidate for future climate-neutral compression-ignition engines. However, to fully leverage their potential, the auto-ignition process, flame propagation, and mixing regimes of the combustion need to be understood. To achieve this, efficient oxidation mechanisms suitable for computational fluid dynamics (CFD) calculations must be developed and validated. The present work aims to highlight the improvements made by developing an adapted oxidation mechanism for OME1−6 and introducing it into a validated spray combustion CFD model for OMEs. The simulations were conducted for single- and multi-injection patterns, changing ambient temperatures, and oxygen contents. The results were validated against high-pressure and high-temperature constant-pressure chamber experiments. OH*-chemiluminescence measurements accomplished the characterization of the auto-ignition process. Both experiments and simulations were conducted for two different injectors. Significant improvements concerning the prediction of the ignition delay time were accomplished while also retaining an excellent agreement for the flame lift-off length. The spatial zones of high-temperature reaction activity were also affected by the adaption of the reaction kinetics. They showed a greater tendency to form OH* radicals within the center of the spray in accordance with the experiments.

Direct Oxidation of Methanol to Polyoxymethylene Dimethyl Ethers over FeMo@HZSM-5 Core–Shell Catalyst

Direct Oxidation of Methanol to Polyoxymethylene Dimethyl Ethers over FeMo@HZSM-5 Core–Shell Catalyst

Correction: Numerical assessment of polyoxymethylene dimethyl ether (OME3) injection timing in compression ignition engine

Correction: Numerical assessment of polyoxymethylene dimethyl ether (OME3) injection timing in compression ignition engine