Methanol-air Mixtures Research Articles

Computational investigation of a methanol compression ignition engine assisted by a glow plug

This work explores the feasibility of pure methanol combustion in a light-duty diesel engine assisted by a glow plug (GP). The simulations represented a mild engine load with an indicated mean effective pressure of 7 bar. An extensive computational study was conducted, and the successful operation of the pure methanol compression ignition engine was demonstrated. The effects of the GP position, spray umbrella angle, the relative angle (RA) between the glow plug and jet trajectory, and the injection strategy on the engine performance were evaluated. The autoignition of methanol-air mixture was found to primarily occur at an equivalence ratio between 0.2 and 0.4. However, an even richer mixture accompanied the lower temperature due to intense heat absorption of evaporation, significantly prolonging the ignition delay. Therefore, to improve the ignition and combustion heat release processes, RA was optimized to adequately control the mixture distribution around the GP. At each position of the GP, the optimum RA differed due to the complex flow and air-fuel mixing within the combustion chamber, which became smaller (from 12.5° to 5°) when the GP was moved anticlockwise from the intake port to the exhaust port regions. Furthermore, a split injection strategy was proposed to ensure the successful ignition of the methanol jets. The engine performance exhibited a high sensitivity to the pilot and main injection timings. A small pilot mass fraction of no higher than 20% was recommended to mitigate fuel jet-GP interaction and fuel impingement in the squish region.

Laminar flame speed measurement and combustion mechanism optimization of methanol–air mixtures

AbstractLaminar flame speeds of methanol/air mixtures at 338–398 K are measured by the heat flux method, extending the range of equivalence ratio up to 2.1. And a new optimized methanol mechanism with 94 reactions is proposed by using the particle swarm algorithm, adjusting 20 Arrhenius pre‐exponential factors in their uncertainty domains. The optimized model is compared with eight methanol combustion mechanisms and experimental data published in recent years, covering a wide range of initial temperatures (298–1537 K), pressures (0.04–50 atm) and equivalence ratios (0.5–2.1). The results show that the optimized mechanism not only improves the accuracy of ignition delay time with rapid compression machine at low temperature but also moderately improve the description of laminar flame speed in lean and stoichiometric conditions. Meanwhile, the optimized model significantly enhances the prediction accuracy of CH3 and CH2O radical, and perfectly captures the evolution trend of HCO radical in laminar flat flame. Overall, the optimized mechanism provides the best overall description of the currently available measurements, leading to more accurate and comprehensive prediction of ignition delay time, laminar flame speed and species concentration.

Laser ignition and flame propagation of methanol-air mixture in a constant volume combustion chamber

ABSTRACT The combustion performance of laser-ignited methanol-air mixture in a constant volume combustion chamber was investigated using the Schlieren photography technique. The experimentation was conducted at 5, 7, 9, and 11 MPa fuel injection pressure and 363 K initial chamber temperature using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser of 1064 nm wavelength. The gasoline direct injection (GDI) system was used for injecting the fuel at different pressures inside the chamber. The laser beam is focused into the chamber using a 150 mm focal length lens, and laser energy of 200 mJ was used for all experimentation. The Schlieren system was used for capturing flame propagation of methanol-air mixture for different equivalence ratios. The pressure-time history for equivalence ratio (ϕ) of 0.8, 0.9, and 1.0 was plotted and analyzed at different chamber filling pressures. Flame propagation was found faster for ϕ of 1.0 due to higher laminar velocity than 0.8 and 0.9. Flame visualization showed that the flame attains the ellipsoid shape during the early stage of ignition. It generates two lobes in the vertical direction and then again expands in a horizontal direction toward the ignition source. For all equivalence ratios, the flame propagation toward the incoming laser source (X-) was observed faster compared to the flame propagation in the direction and perpendicular to the laser beam direction. For all equivalence ratios, higher laminar flame speed was observed at 5 MPa injection pressure; however, it decreases as the injection pressure increases. At ϕ of 1.0 and 11 MPa injection pressure, the maximum peak pressure of 0.67 MPa and combustion duration of 19.3 ms were noted. At 9 MPa injection pressure and ϕ of 1.0, the peak pressure and combustion duration was found as 0.61 MPa and 19.4 ms, respectively. At ϕ of 0.8, the peak pressure and combustion duration were observed 0.27 MPa with 34.6 ms duration and 0.47 MPa with 36.9 ms duration at 5 MPa and 11 MPa injection pressures, respectively.

On the Mechanism of Promoting the Autoignition of Rich Methanol–Air Mixtures by Small Additions of Hydrogen Peroxide

On the Mechanism of Promoting the Autoignition of Rich Methanol–Air Mixtures by Small Additions of Hydrogen Peroxide

The effect of structural parameters of pre-chamber with turbulent jet ignition system on combustion characteristics of methanol-air pre-mixture

Pre-chamber turbulent jet ignition technology is an effective way to optimize the methanol-air mixture combustion process. A literature survey of structures of currently used pre-chambers of turbulent jet ignition systems was conducted, and three levels of four key structural factors were extracted from them, and nine pre-chambers were redesigned using the Taguchi experimental design method. The test showed that there are four typical pre-chamber ignition modes in the methanol-air mixture, namely, jet flame ignition, jet ignition, jet wake ignition, and dual-jet ignition. Compared with a spark plug, these ignition modes can increase the peak heat release rate by 15.78%, 123.51%, 136.96%, and 235.19%, respectively. When the mixture concentration in the pre-chamber is stoichiometric, the lean-burn limit for jet ignition and jet wake ignition is similar to that for spark ignition. By contrast, jet flame ignition can significantly extend the lean-burn limit. Among all the pre-chamber structural parameters, the total cross-sectional area of ​​the nozzles influenced the pre-chamber combustion performance and lean-burn limit performance the most, and the weight of the influence was always greater than 80%. The effects of the transition angle in the pre-chamber, the throat diameter, and the number of nozzles on its performance are discussed in this paper.

Large-eddy simulation of diesel pilot spray ignition in lean methane-air and methanol-air mixtures at different ambient temperatures

In dual-fuel compression-ignition engines, replacing common fuels such as methane with renewable and widely available fuels such as methanol is desirable. However, a fine-grained understanding of diesel/methanol ignition compared to diesel/methane is lacking. Here, large-eddy simulation (LES) coupled with finite rate chemistry is utilized to study diesel spray-assisted ignition of methane and methanol. A diesel surrogate fuel ( n-dodecane) spray is injected into ambient methane-air or methanol-air mixtures at a fixed lean equivalence ratio [Formula: see text] = 0.5 at various ambient temperatures ([Formula: see text] = 900, 950, 1000 K). The main objectives are to (1) compare the ignition characteristics of diesel/methanol with diesel/methane at different [Formula: see text], (2) explore the relative importance of low-temperature chemistry (LTC) to high-temperature chemistry (HTC), and (3) identify the key differences between oxidation reactions of n-dodecane with methane or methanol. Results from homogeneous reactor calculations as well as 3 + 3 LES are reported. For both DF configurations, increasing [Formula: see text] leads to earlier first- and second-stage ignition. Methanol/ n-dodecane mixture is observed to have a longer ignition delay time (IDT) compared to methane/ n-dodecane, for example ≈ three times longer IDT at [Formula: see text] = 950 K. While the ignition response of methane to [Formula: see text] is systematic and robust, the [Formula: see text] window for n-dodecane/methanol ignition is very narrow and for the investigated conditions, only at 950 K robust ignition is observed. For methanol at [Formula: see text] = 1000 K, the lean ambient mixture autoignites before spray ignition while at [Formula: see text] = 900 K full ignition is not observed after 3 ms, although the first-stage ignition is reported. For methanol, LTC is considerably weaker than for methane and in fully igniting cases, heat release map analysis demonstrates the dominant contribution of HTC to total heat release rate for methanol. Reaction sensitivity analysis shows that stronger consumption of OH radicals by methanol compared to methane leads to the further delay in the spray ignition of n-dodecane/methanol. Finally, a simple and novel approach is developed to estimate IDT in reacting LES using zero-dimensional IDT calculations weighted by residence time from non-reacting LES data.

Study of combustion, performance and emissions characteristics of oxygenated constituents and methanol fumigation in the inlet manifold of a diesel engine

To understand the aspect of methanol fumigation on diesel engine characterization, various percentages of methanol were injected from the inlet manifold, while the blend of Pine and Eucalyptus oil in diesel(P10E10D80) was injected from the main injector and used as a new source of biofuel. The cetane number and viscosity of the oil blend were found to have lower values than fossil diesel. The study envisages vaporization of oil blend and its induction into the diesel engine while P10E10D80 was used for the facilitation of ignition to the methanol-air mixture. The Sauter Mean Diameter of P10E10D80 was found to be lower than conventional diesel and thus was supposed to be more suitable for the evaporation of methanol and hence, by methanol fumigation studies. The study revealed that at 20% to 100% load, the use of methanol could replace 39% to 56% of P10E10D80, respectively, and subsequently improve the Brake Specific Energy Consumption(BSEC ;17%), brake thermal efficiency (BTE; 2.56%), Exhaust Gas Temperature(EGT;8.92%), Carbon Monoxide (CO;42%), Oxide of Nitrogen(NOx ;3.57%), Besides, the combustion of fumigated methanol was found to exhibiting 11.54% higher in-cylinder pressure and higher Heat Release Rate (HRR;22%) 39% at full load.

A preliminary numerical study on the use of methanol as a Mono-Fuel for a large bore marine engine

To use methanol as a mono-fuel in large bore marine engines, a distributed jets ignition combustion mode was applied on a 320 mm-bored engine, in which pre-chamber initiated jets were employed to ignite the in-cylinder lean mixtures and to enhance the flame propagation. A preliminary numerical study was carried out to investigate the effects of in-cylinder excess air ratio and ignition timing on combustion characteristics and performances of the engine. Conditions with excess air ratios ranged from 2.0 to 2.8 and ignition timings ranged from −8°CA ATDC to the top dead center were calculated. The numerical results show that, under the distributed jets ignition combustion mode, the in-cylinder lean methanol-air mixtures could be reliably ignited and the heat release rates showed a firstly slow and then rapid trend, resulting in high thermal efficiencies and low NOx emissions, which could meet for the IMO Tier III emission regulations without aftertreatment. Moreover, with the increase of the in-cylinder excess air ratio and the delaying of the ignition timing, the in-cylinder pressure, the peak pressure rising rate, the ringing intensity and the NOx emissions were continuously decreased. As the in-cylinder mixture becoming leaner, the combustion efficiency firstly kept constant and then rapidly dropped when the excess air ratio increased to 2.4, resulting in a peak value of the indicated thermal efficiency (49.2%) at this excess air ratio. According to the numerical results, a combustion control strategy was proposed: when the brake mean effective pressure was below 1.8 MPa, the in-cylinder excess air ratio was controlled at 2.4 and coupled with an earlier ignition timing to obtain high thermal efficiency, and when the brake mean effective pressure was higher than 1.8 MPa, the in-cylinder excess air ratio was controlled at 2.1 and coupled with a later ignition timing, thereby to achieve high power density.

Examining Thermal Management Strategies for a Microcombustion Power Device

Microcombustion attracts interest with its promise of energy dense power generation for electronics. Yet, challenges remain to develop this technology further. Thermal management of heat losses is a known hurdle. Simultaneously, non-uniformities in heat release within the reaction regions also affect the device performance. Therefore a combination of thermal management strategies are necessary for further performance enhancements. Here, a bench top platinum nanoparticle based microcombustion reactor, coupled with thermoelectric generators is used. Methanol-air mixtures achieve room temperature ignition within a catalytic cartridge. In the current study, the reactor design is modified to incorporate two traditional thermal management strategies. By limiting enthalpic losses through the exhaust and reactor sides, using multi-pass preheating channels and heat recirculation, expected improvements are achieved. The combined strategies doubled the power output to 1.01 W when compared to the previous design. Furthermore, a preliminary study of catalyst distribution is presented to mitigate non-uniform catalytic activity within the substrate. To do this, tailored distribution of catalyst particles was investigated. This investigation shows a proof-of-concept to achieve localized control, thus management, over heat generation within substrates. By optimizing heat generation, a highly refined combustion-based portable power devices can be envisioned.

Impact of dilution on laminar burning characteristics of premixed methane-dissociated methanol-air mixtures

A constant volume combustion vessel is employed to investigate the impact of different diluents and diluent gas fractions on the methane-dissociated methanol-diluent-air premixed flames at 0.3 MPa and 343 K. The diluent gas causes the adiabatic flame temperature and thermal diffusivity to decrease, which is the main reason for the decreased laminar burning velocity, and carbon dioxide exhibits a stronger inhibitory effect than nitrogen. With increasing diluent gas fraction, the diffusive-thermal instability is enhanced while the hydrodynamic instability is inhibited, these two factors are the main reason for the insensitivity of the flame instability to the diluent gas fraction. Further, flame instability is not sensitive to the diluent gas type. R38 is the dominant chain branching reaction, while R35 and R52 are the dominant chain termination reactions in the combustion process. With the increase in the diluent gas fraction, the rates of the dominant chain termination reactions shows greater inhibition of laminar burning velocity, a larger decrease in the chain branching reaction rate, and a smaller decrease in the chain termination reaction rate will significantly reduce the free radical concentration. The maximum reaction rate reduction when diluted by carbon dioxide is greater than when diluted by nitrogen.

Numerical study of cold-start performances of a medium compression ratio direct-injection twin-spark plug synchronous ignition engine fueled with methanol

The cold-start mixture preparation, combustion and emissions behaviors of a medium compression ratio direct-injection twin-spark plug synchronous ignition engine fueled with methanol were numerically simulated. Simulation results display that the methanol injection timing, ignition timing and the global equivalence ratio had an important influence on the concentration distribution of methanol-air mixture, the flow velocity, and the density of the flame surface during cold start. Ignition delay period reached the shortest at injection timing 70°CA BTDC. Ignition delay period for injection timing 130°CA BTDC and 50°CA BTDC increased 209% and 45.5% compared to injection timing 70°CA BTDC, respectively. Ignition delay period reached the shortest at ignition timing 21°CA BTDC. Ignition delay period of twin-spark plug was shorter than that of single-spark plug at the same equivalence ratio. There existed the maximum in-cylinder pressure, maximum heat release rate, maximum in-cylinder temperature, lowest unburned methanol and soot emissions, and highest NOX emissions at injection timing 70°CA BTDC. The maximum in-cylinder pressure, maximum heat release rate, and maximum in-cylinder temperature gradually increased with the advance of ignition timing. Injection timing 70°CA BTDC, ignition timing 21°CA BTDC, and equivalence ratio 0.9 could obtain the best cold start performance compromise using twin-spark plug ignition mode. At equivalence ratio 1.0, twin-spark plug ignition had better combustion performances, lower unburned methanol and soot emissions, and higher NOX emissions compared with single-spark plug ignition. Twin-spark plug synchronous ignition had more advantageous to cold starting ignition compared with single-spark plug ignition for a medium compression ratio direct-injection spark-ignition methanol engine.

Effects of ambient methanol on pollutants formation in dual-fuel spray combustion at varying ambient temperatures: A large-eddy simulation

Large-eddy simulation with a finite-rate chemistry model is carried out to investigate the formation of soot and nitrogen oxides (NOx) in the dual-fuel spray combustion. Liquid n-heptane is injected into a constant volume chamber, filled with a premixed methanol–air mixture with an equivalence ratio (ϕm) of 0.3. Three dual-fuel cases are simulated under initial temperatures of 900, 950 and 1000 K. Three single-fuel cases, with the same configurations, but with pure air being used as ambient gas composition are also simulated and used as baselines for comparison purposes. The paper aims to identify the main mechanisms of soot and NOx reduction in dual-fuel spray combustion under conditions relevant to internal combustion engines. The numerical model is validated using the Engine Combustion Network n-heptane fuel experimental data. It is found that soot emission has a strong non-linear dependence on ambient temperature in dual-fuel combustion. At high temperatures, soot emission is enhanced whereas at lower temperatures, it is suppressed. For the presently studied cases, the results show that the enhanced mixing is the primary reason for soot reduction in the 900 and 950 K cases, whereas the onset auto-ignition in ambient methanol/air mixture, which leads to a shortened lift-off length of the n-heptane spray flame and reduced ambient oxygen concentration, is the mechanism behind the enhanced soot emission in the 1000 K case. The methanol dilution effects of oxygen concentration and heat capacity on ignition delay time and the maximum flame temperature are minor in the current dual-fuel configurations. Regarding NOx emission in dual-fuel combustion, it is found that the effect of methanol on NOx formation also depends on the ambient temperatures. The NOx formation rate in the dual-fuel case is lower than that of the single-fuel case at 900 K. However, an opposite trend of NOx formation rate is observed in the 1000 K cases. The main reason for the increased NOx emission is the larger high temperature region resulted from the interaction of the spray flame and the ambient mixture ignition.

Numerical study on electron energy distribution characteristics and evolution of active particles of methanol-air mixture by non-equilibrium plasma

The extent of combustion enhancement by non-equilibrium plasma strongly depends on the electric field and electron number density. The electron energy distribution characteristics and evolution of active particles of methanol-air mixture by non-equilibrium plasma were numerical simulated. As an introductory work in this field, this study only partially cited other people’s data for comparative verification under without experimental validation data. The results showed that the electron energy distribution is mainly affected by field intensity. The electron energy distribution is increased with the increase of mean electron energy. The field intensity directly affects the formation and development of radicals in methanol-air plasma discharge. The generation of radicals in plasma discharge mainly occurs in the electron collision reaction with the electron energy of 3–10 eV. The concentration of excited states matter is higher than that of ionized states matter. The concentration of O radical is higher than the concentration of H and CH2OH, and then the concentration of H and CH2OH is much than that of OH and CH3. Considering the demand of radical concentration and economics of the peak pulse voltage, the field intensity of 220 Td - 400 Td is selected as a reasonable range for generating radicals.

Combustion Chemistry of Rich Methanol–Air Mixtures

Chain branching and heat release processes and their influence on the burning velocity of premixed rich and near-stoichiometric methanol–air flames were studied by numerical simulation and sensitivity analysis. The phenomenon of superadiabatic temperatures in these flames due to the kinetic mechanism of methanol combustion was first detected. Comparison of the simulation results of the structure of methanol and formaldehyde flames shows that the formation of water in superequilibrium concentrations in flames does not necessarily lead to superadiabatic temperatures, as believed earlier. It was first found that decreasing the dilution of the CH3OH/O2/N2combustible mixture with nitrogen at a constant equivalence ratio enhances the superadiabatic temperature effect. According to simulation results, in a rich near-limit methanol flame, the role of the chain branching reactions H + O2 = O + OH and O + H2 = H + OH is negligible due to their low rate. At relatively low temperatures, branching occurs mainly in reactions involving HO2and H2O2peroxide compounds, whose concentration is orders of magnitude higher than the concentration of the main chain carriers H, O, and OH. From the sensitivity analysis, it follows that the burning velocity of methanol flames is positively influenced mainly by the reactions of formation of chain carriers and is negatively influenced by the reactions of consumption of chain carriers. reactions having a major contribution to heat release but are not involved in the formation and consumption of radicals have small sensitivity coefficients.

Numerical modeling of plasma-assisted combustion effects on firing and intermediates in the combustion process of methanol–air mixtures

The effects of plasma-assisted ignition and combustion on the ignition-delay time (Tid) and intermediates in methanol combustion were simulated numerically through a chemical-kinetics mechanism of methanol oxidation. Plasma-assisted ignition can considerably shorten the Tid. Plasma-assisted ignition is more conducive to a low temperature and the lean combustion of a methanol-air mixture. According to the shortest Tid, the active particle order is: O < CH3O < 220 Td < H < OH < CH2OH < CH3 < autoignition. The concentration of O atoms in active particles affects the Tid shortening. Plasma-assisted combustion can significantly shorten the time for the system temperature to reach a maximum. The concentrations of the reactants CH3OH and O2 decrease sharply for autoignition after the ignition-delay period, and the products CO, CO2 and H2O increase rapidly. In plasma-assisted combustion, the addition of active particles significantly increases the rate of chemical reaction of consumption of O2, promotes the rapid redox reaction of methanol–air mixtures, oxidizes methanol fuel to CO2 and H2O more rapidly, and accelerates combustion. The sensitivity coefficients of temperature and Tid for plasma-assisted combustion are lower than those for autoignition.

Analysis of an idealized counter-current microchannel-based reactor to produce hydrogen-rich syngas from methanol

In an effort to investigate the suitability of the concept of portable hydrogen production, we examine numerically the combustion of a very rich methanol-air mixture in a micro-gap assembly consisting of multiple counter-current channels of finite length separated by thin solid conducting walls. Within the mathematical framework of the narrow-channel approximation, the problem can be formulated as a one-dimensional model for a single channel with an extra term representing heat transfer from the hot stream products to the fresh reactants in adjacent channels. We show that the heat recirculation enables superadiabatic temperatures inside the reactor and promotes the oxidation of methanol far beyond the conventional rich limit of flammability. The result is a feasible thermal partial oxidation that produces hydrogen without the need for a catalyst. The paper presents an analysis of the model burner performance with detailed gas-phase kinetics in stationary regimes in terms of operating variables such as the equivalence ratio and the gas inflow velocity, and in terms of physical parameters such as the length of the reformer and the conductivity of the wall material. The idealized microreactor predicts maximum hydrogen yield of the order of 60% at equivalence ratios between 3 and 6.

Experimental and kinetic investigation on the effects of hydrogen additive on laminar premixed methanol–air flames

The effects of hydrogen addition on laminar premixed methanol–air flames were studied both experimentally and numerically. To achieve this, a constant volume chamber (CVC) and the premix code in CHEMKIN were used. During the experiments, the equivalence ratios (ϕ) and hydrogen mole fractions (Xh) were set to 0.6 to 1.8 and 0%–100%, respectively. In addition, initial environmental conditions were set to 375 K and 1 atm. The results indicate that the laminar flame speed (LFS) and burning velocity (LBV) both increase when more hydrogen is added into the methanol–air mixtures. For premixed methanol–air flames, the Markstein length (Lb) decreases monotonically with an increase in the equivalence ratio; however, when the hydrogen fraction is greater than 40%, an increasing trend in the Markstein length is presented as the mixtures move toward the fuel-rich side. The variation in Markstein length is non-monotonic with the hydrogen fraction. A kinetics analysis indicates that methanol is mainly consumed by the dehydrogenation reaction caused from the impact of the active free radicals (OH and H). Reactions involving active free radicals and light intermediate species have the highest sensitivity and contribute the most to the propagation of a laminar flame. Therefore, the promotion effect of hydrogen additive is due to an enhancement in the radical pooling of H, OH, and O. The chain branching reaction R5 (O2 + H = O + OH) is essential for the geometric growth of free radicals. In addition, the amount of formaldehyde decreases owing to the hydrogen blending.

Explosion characteristics of cyclic hydrocarbon-air mixtures at elevated temperature and pressures

Explosion characteristics of cyclic hydrocarbon (cyclohexane, cyclohexene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, benzene)-air mixtures were experimentally investigated in a closed vessel at the temperature of 403 K and pressures of 0.1 and 0.5 MPa. These fuels own different degrees of unsaturation. The crucial explosion parameters were determined, including explosion pressure, rate of pressure rise, explosion index as well as explosion delay. Results indicate that the peak explosion pressure and maximum rate of pressure rise all increase with the rise of initial pressure, demonstrating the high explosion risk at elevated pressure. Except benzene-air mixture, the more unsaturated cyclic hydrocarbon-air mixture has higher values of peak explosion pressure, maximum rate of pressure rise as well as explosion index, and lower values of explosion delay and burn period. Therefore, cyclohexadiene-air mixtures propagate the fastest and show the greatest potential explosion hazard. Cyclohexane-air mixture propagates the slowest and shows the smallest explosion potential as well. This is mainly caused by the different heat release of the cyclic fuel flames. The peak explosion pressure and maximum rate of pressure of benzene-air mixture are between those of cyclohexadiene- and cyclohexane-air mixtures at the lean to slightly rich conditions, while present the lowest values at the extremely rich conditions. This is attributed to the high tendency of soot formation in benzene flame and thus enhanced heat radiation to the vessel wall. Such heat loss also contributes the extended explosion delay and burn period of benzene-air mixture. Furthermore, the explosion index could be correlated with the explosion delay and burn period in exponential expression. This exponential relationship was found to be feasible for methanol-air mixture as well.

Ignition delay time and H2O measurements during methanol oxidation behind reflected shock waves

To improve detailed chemical kinetics models, the oxidation of methanol was investigated behind reflected shock waves in shock tubes. Ignition delay times of methanol–air mixtures, with Ar as diluent, were studied between 940 and 1540 K in a heated shock tube, for pressures up to 14.9 atm and for equivalence ratios of 0.5, 1.0, and 2.0. Water profiles were measured by utilizing a laser absorption technique in the 1350-to-1600-K temperature range, at an average pressure of 1.3 atm and for similar equivalence ratios. The present study shows the ignition delay times of methanol to be in very good agreement with results from the literature (Fieweger et al., 1997), whereas the other conditions have never been investigated before. The ignition delay time data are also in good agreement with modern detailed kinetics mechanisms such as the AramcoMech 3.0 model. The water time-history profiles were modeled using well-known literature mechanisms. Discrepancies were observed between these kinetics mechanisms, and poor predictions were observed for the lower temperatures investigated. Sensitivity and rate-of-production analyses were performed using 3 literature mechanisms (namely, AramcoMech 3.0, Princeton, and JetSurfII). Discrepancies were found among the models when predicting important reactions dominating the oxidation of methanol as well as the rate-of-production of H2O.

Platinum nanoparticle catalysis of methanol for thermoelectric power generation

Catalytic combustion of hydrocarbon and oxygenated fuels has the potential to provide an alternative power source for portable electronic devices. Our previous studies have demonstrated sustained catalytic combustion for a variety of fuels using multi-channel cordierite substrates. In particular, methanol-air mixtures catalyzed by platinum nanoparticles yielded room-temperature self-ignition and stable combustion. The present work explores a stacked-reactor design of a microcombustion-thermoelectric coupled device that marries thermal management strategies with catalytic combustion. Synthesized platinum nanoparticles (dp∼ 8 nm) were deposited on rectangular cordierite substrate cartridges with 800 μm wide channels. A custom-designed copper-aluminum reactor was used to host the catalytic cartridges. A near-stoichiometric mixture of methanol-air at 8000 mL/min air flow rate produced 62 °C temperature difference across thermoelectric generators. Material analysis demonstrated a non-uniform restructuring of catalyst material across the substrate. A parametric study of catalyst loading and air flow mapped the optimal operational range of the device. While a relatively low power output of 490 mW was measured, a theoretical power potential of 1400 mW was estimated. The results confirm the unique advantages of multi-channel catalytic cartridges and guide future developments in the application of nanocatalytic microcombustion for portable power sources.