High Temperature Heat Release Research Articles

Excellent thermal stability of tavorite LixFeSO4F used as a cathode material for lithium ion batteries

Tavorite LiFeSO4F shows excellent thermal stability with a high exothermic temperature and minimal heat release.

A Research of Fuel Chemical Composition on Maximum Pressure Rise Rate of HCCI Engine

The n-heptane and toluene blended fuel exhibits the dual phase high temperature heat release (DP-HTHR) HCCI combustion and it has the potential to achieve the high load HCCI operation. Three topics were investigated in this paper. The first topic was the possibility of DP-HTHR combustion with the blends of the refinery-based gasolines. Three prototype fuels (GAS2, GAS3, and GAS4 fuels) were evaluated. The second topic was the relation between HCCI knocking and heat release phasing. The combustion parameters, which determined the maximum pressure rise rate, were statistically investigated. Finally, the combustion images of DP-HTHR were recorded with a high speed camera, and the combustion process of DP-HTHR was investigated by the video images and heat release analysis data.

Numerical study of EGR effects on reducing the pressure rise rate of HCCI engine combustion

The effects of the inert components of exhaust gas recirculation (EGR) gas on reducing the pressure rise rate of homogeneous charge compression ignition engine combustion were investigated numerically by utilizing the CHEMKIN II package and its SENKIN code, as well as Curran’s dimethyl ether reaction scheme. Calculations were conducted under constant volume combustion and engine combustion (one compression and one expansion only, respectively) conditions. Results show that with constant fuel amount and initial temperature and pressure, as EGR ratio increases, combustion timings are retarded and the duration of thermal ignition preparation extends non-linearly; peak values of pressure, pressure rising rate (PRR), and temperature decrease; and peak values of heat release rate in both low temperature heat release (LTHR) and high temperature heat release decrease. Moreover, maximum PRR decreases as CA50 is retarded. With constant fuel amount, mixtures with different EGR ratios can obtain the same CA50 by adjusting the initial temperature. Under the same CA50, as EGR ratio increases, the LTHR timing is advanced and the duration of thermal ignition preparation is extended. Maximum PRR is almost constant with the fixed CA50 despite the change in EGR ratio, indicating that the influence of EGR dilution on chemical reaction rate is offset by other factors. Further investigation on the mechanism of this phenomenon is needed.

Oxidation of 1-butanol and a mixture of n-heptane/1-butanol in a motored engine

The oxidation of neat 1-butanol and a mixture of n-heptane and 1-butanol was studied in a modified CFR engine at an equivalence ratio of 0.25 and an intake temperature of 120 °C. The engine compression ratio was gradually increased from the lowest point to the point where significant high temperature heat release was observed. Heat release analyses showed that no noticeable low temperature heat release behavior was observed from the oxidation of neat 1-butanol while the n-heptane/1-butanol mixture exhibited pronounced cool flame behavior. Species concentration profiles were obtained via GC–MS and GC-FID/TCD. Quantitative analyses of the reaction products from the oxidation of neat 1-butanol indicate that 1-butanol is consumed mainly through H-atom abstraction. Among the H-atom abstraction reactions, it is observed that the H-atom abstraction from the α-carbon of 1-butanol is particularly favored. The investigation on the oxidation of the mixture of n-heptane/1-butanol showed that the oxidation of 1-butanol is facilitated at low temperatures through the radical pool generated from the oxidation of n-heptane.

Experimental study of the autoignition of C 8H 16O 2 ethyl and methyl esters in a motored engine

Autoignition of two biodiesel surrogates, methyl heptanoate and ethyl hexanoate, was studied in a motored CFR engine at an equivalence ratio of 0.25 and an intake temperature of 155 °C. The engine compression ratio was gradually increased from the lowest point (4.43) to the point where significant high temperature heat release (HTHR) occurred. Within the test range of this work, both of the two esters exhibited evident cool flame behavior. At the same compression ratio, methyl heptanoate was observed to have both an earlier onset and a higher magnitude of low temperature heat release (LTHR) than ethyl hexanoate, indicating that methyl heptanoate is more reactive in the low temperature region than ethyl hexanoate. GC–MS analyses of the reaction intermediates from the oxidation of the two esters showed that the alkyl chain of fatty acid esters experiences the typical paraffin-like low temperature oxidation sequence. Based on the observations from GC–MS analyses, major low temperature oxidation pathways of ethyl hexanoate are proposed in this work. Also, it is observed that the abstraction of H-atoms on the α-carbon of the ester carbonyl group plays an important role in the oxidation of fatty acid esters. In addition, the identification of hexanoic acid among the reaction intermediates from low temperature oxidation of ethyl hexanaoate together with the observation of more fuel carbon being converted to C 2H 4 during ethyl hexanoate oxidation than during methyl heptanoate oxidation provide evidence for the existence of the six-centered unimolecular elimination reaction during low temperature oxidation of ethyl esters.

Realization of Dual Phase High Temperature Heat Release Combustion of Base Gasoline Blends from Oil Refineries and a Study of HCCI Combustion Processes

Realization of Dual Phase High Temperature Heat Release Combustion of Base Gasoline Blends from Oil Refineries and a Study of HCCI Combustion Processes

Premixed ignition behavior of C 9 fatty acid esters: A motored engine study

An experimental study on the premixed ignition behavior of C 9 fatty acid esters has been conducted in a motored CFR engine. For each test fuel, the engine compression ratio was gradually increased from the lowest point (4.43) to the point where significant high temperature heat release (HTHR) was observed. The engine exhaust was sampled and analyzed through GC-FID/TCD and GC-MS. Combustion analysis showed that the four C 9 fatty acid esters tested in this study exhibited evidently different ignition behavior. The magnitude of low temperature heat release (LTHR) follows the order, ethyl nonanoate > methyl nonanoate ≫ methyl 2-nonenoate > methyl 3-nonenoate. The lower oxidation reactivity for the unsaturated fatty acid esters in the low temperature regime can be explained by the reduced amount of six- or seven-membered transition state rings formed during the oxidation of the unsaturated esters due to the presence of a double bond in the aliphatic chain of the esters. The inhibition effect of the double bond on the low temperature oxidation reactivity of fatty acid esters becomes more pronounced as the double bond moves toward the central position of the aliphatic chain. GC-MS analysis of exhaust condensate collected under the engine conditions where only LTHR occurred showed that the alkyl chain of the saturated fatty acid esters participated in typical paraffin-like low temperature oxidation sequences. In contrast, for unsaturated fatty acid esters, the autoignition can undergo olefin ignition pathways. For all test compounds, the ester functional group remains largely intact during the early stage of oxidation.

A Study of High Temperature Heat Release Personalities of Hydrocarbons in HCCI Combustion

A Study of High Temperature Heat Release Personalities of Hydrocarbons in HCCI Combustion

Spectroscopic and chemical-kinetic analysis of the phases of HCCI autoignition and combustion for single- and two-stage ignition fuels

The temporal phases of autoignition and combustion in an HCCI engine have been investigated in both an all-metal engine and a matching optical engine. Gasoline, a primary reference fuel mixture (PRF80), and several representative real-fuel constituents were examined. Only PRF80, which is a two-stage ignition fuel, exhibited a “cool-flame” low-temperature heat-release (LTHR) phase. For all fuels, slow exothermic reactions occurring at intermediate temperatures raised the charge temperature to the hot-ignition point. In addition to the amount of LTHR, differences in this intermediate-temperature heat-release (ITHR) phase affect the fuel ignition quality. Chemiluminescence images of iso-octane show a weak and uniform light emission during this phase. This is followed by the main high-temperature heat-release (HTHR) phase. Finally, a “burnout” phase was observed, with very weak uniform emission and near-zero heat-release rate (HRR). To better understand these combustion phases, chemiluminescence spectroscopy and chemical-kinetic analysis were applied for the single-stage ignition fuel, iso-octane, and the two-stage fuel, PRF80. For both fuels, the spectrum obtained during the ITHR phase was dominated by formaldehyde chemiluminescence. This was similar to the LTHR spectrum of PRF80, but the emission intensity and the temperature were much higher, indicating differences between the ITHR and LTHR phases. Chemical-kinetic modeling clarified the differences and similarities between the LTHR and ITHR phases and the cause of the enhanced ITHR with PRF80. The HTHR spectra for both fuels were dominated by a broad CO continuum with some contribution from bands of HCO, CH, and OH. The modeling showed that the CO + O → CO 2 + h ν reaction responsible for the CO continuum emission tracks the HTHR well, explaining the strong correlation observed experimentally between the total chemiluminescence and HRR during the HTHR phase. It also showed that the CO continuum does not contribute to the ITHR and LTHR chemiluminescence. Bands of H 2O and O 2 in the red and IR regions were also detected during the HTHR, which the data indicated were most likely due to thermal excitation. The very weak light emission in the “burnout” phase also appeared to be thermal emission from H 2O and O 2.

Dual Phase High Temperature Heat Release Combustion

Dual Phase High Temperature Heat Release Combustion

2322 二段階高温酸化反応燃焼によるHCCIエンジンの運転性能改善に関する研究(S27-2 エンジンの点火・燃焼の新展開(2),21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

2322 二段階高温酸化反応燃焼によるHCCIエンジンの運転性能改善に関する研究(S27-2 エンジンの点火・燃焼の新展開(2),21世紀地球環境革命の機械工学:人・マイクロナノ・エネルギー・環境)

DE2-2: A Theoretical Investigation on the Effects of Mixing on Low-Temperature Diesel Combustion and Emissions(DE: Diesel Engine Combustion,General Session Papers)

Low-temperature diesel combustion in conjunction with high levels of EGR is being paid much attention and investigated due to its ultra-low NO_x and soot emissions. The compound combustion as a new low temperature combustion technology has been proposed previously by authors, which combined Premixed Charge Compression Ignition (PCCI) and Lean Diffusion Combustion (LDC), where fuel and air are premixed to a lean equivalence ratio less than 2 before the onset of high-temperature heat release. The compound combustion is mainly dominated by the oxygen concentration and mixing. In order to have an insight into the effects of mixing on low temperature diesel combustion, a quantitative "φ(equivalence ratio)-T(temperature)" map for CO formation has been created by performing the zero dimensional calculations using a detailed chemistry of n-heptane in this study. Then a two-zone combustion model accounting for both heat loss and mass transferred between the two zones is developed to explore the lean diffusion combustion process for different EGR levels as well as mixing rates on the CO-φ-T map. The results show that at lean diffusion combustion phase, when the mixing rate is too high, NO_x emissions increase, and when the mixing rate is too low, CO emissions increase. As the EGR rate increases, mixing rate at the phase must properly increase so as to reduce CO emissions, achieving high efficiency and low NO_x emissions simultaneously.

Premixed ignition behavior of alternative diesel fuel-relevant compounds in a motored engine experiment

A motored engine study using premixed charges of fuel and air at a wide range of diesel-relevant equivalence ratios was performed to investigate autoignition differences among surrogates for conventional diesel fuel, gas-to-liquid (GTL) diesel fuel, and biodiesel, as well as, n-heptane. Experiments were performed by delivering a premixed charge of vaporized fuel and air and increasing the compression ratio in a stepwise manner to increase the extent of reaction while monitoring the exhaust composition via Fourier transform infrared (FTIR) spectrometry and collecting condensable exhaust gas for subsequent gas chromatography/mass spectrometry (GC/MS) analysis. Each fuel demonstrated a two-stage ignition process, with a low-temperature heat release (LTHR) event followed by the main combustion, or high-temperature heat release (HTHR). Among the three diesel-relevant fuels, the magnitude of LTHR was highest for GTL diesel, followed by methyl decanoate, and conventional diesel fuel last. FTIR analysis of the exhaust for n-heptane, the conventional diesel surrogate, and the GTL diesel surrogate revealed that LTHR produces high concentrations of aldehydes and CO while producing only negligible amounts of CO 2. Methyl decanoate differed from the other two-stage ignition fuels only in that there were significant amounts of CO 2 produced during LTHR; this was the result of decarboxylation of the ester group, not the result of oxidation. GC/MS analysis of LTHR exhaust condensate for n-heptane revealed high concentrations of 2,5-heptanedione, a di-ketone that can be closely tied to species in existing autoignition models for n-heptane. GC/MS analysis of the LTHR condensate for conventional diesel fuel and GTL diesel fuel revealed a series of high molecular weight aldehydes and ketones, which were expected, as well as a series of organic acids, which are not commonly reported as products of combustion. The GC/MS analysis of the methyl decanoate exhaust condensate revealed that the aliphatic chain acts similarly to n-paraffins during LTHR, while the ester group remains intact. Thus, although the FTIR data revealed that decarboxylation occurs at significant levels for methyl decanoate, it was concluded that this occurs after the aliphatic chain has been largely consumed by other LTHR reactions.

Effect of High-Octane Oxygenated Fuels on n-Heptane-Fueled HCCI Combustion

The effect of the addition of high-octane oxygenated fuel including methyl tertiary butyl ether (MTBE), ethanol, and methanol on combustion phasing and combustion rate of homogeneous charge compression ignition (HCCI) combustion fueled with n-heptane as base fuel was comparatively investigated. In this paper, n-heptane was blended with MTBE, ethanol, and methanol from 10 vol % to 60 vol % at 10 vol % increments, respectively. Three kinds of blended fuels were injected into intake air, and their premixed HCCI combustions were studied comparatively. The results show that the HCCI combustion fueled with high-octane oxygenated fuel/n-heptane blended fuels is delayed in the combustion phasing and suppressed in combustion rate in contrast to that with pure n-heptane. Given the higher fuel/air equivalence ratio, the combustion phasing of blended fuels is progressively delayed with the increasing proportion of MTBE, ethanol, or methanol, so that the high-temperature heat release (HTHR) can occur near top-dead cen...