Laminar Flame Characteristics of C1–C5 Primary Alcohol-Isooctane Blends at Elevated Temperature

Abstract

Abstract:The laminar combustion characteristics of blends of isooctane and C1-C5 primary alcohols (i.e., methanol, ethanol, n-propanol, n-butanol and n-pentanol) were investigated using the spherical expanding flame methodology in a constant volume chamber at various equivalence ratios and volume fractions of alcohol. The stretch effect was removed using the nonlinear methodology. The results indicate that the laminar flame speeds of alcohol-isooctane blends increase monotonously with the increasing volume fraction of alcohol. Among the five alcohols, the addition of methanol is identified to be the most effective in enhancing laminar flame speed. The addition of ethanol results in an approximately equivalent laminar flame speed enhancement rate as those of n-propanol, n-butanol and n-pentanol at ratios of 0.8 and 1.5, and a higher rate at 1.0 and 1.2. An empirical correlation is provided to describe the laminar flame speed variation with the volume fraction of alcohol. Meanwhile, the laminar flame speed increases with the mass content of oxygen in the fuel blends. At the equivalence ratio of 0.8 and fixed oxygen content, similar laminar flame speeds are observed with different alcohols blended into isooctane. Nevertheless, with the increase of equivalence ratio, heavier alcohol-isooctane blends tend to exhibit higher values. Markstein lengths of alcohol-isooctane blends decrease with the addition of alcohol into isooctane at 0.8, 1.0 and 1.2, however they increase at 1.5. This is consistent with the behavior deduced from the Schlieren images.

Effects of Swirl Number and Central Rod on Flow in Lean Premixed Swirl Combustor

“…The location of the peak values of OH in case with the central rod is more upstream because of the higher flash back. Higher mass fractions of CH 3 corresponds to the slower flame propagation as observed by Li et al [59]. At high swirl numbers, the mass fraction increases contributing to the lower flame speed.…”

A Study of the Impact of Methanol, Ethanol and the Miller Cycle on a Gasoline Engine

“…Iliev [21] described an increase for all blends up to M50 due to increased cylinder temperature. The dominant factor for M5 and M15 was therefore the flame propagation speed as power and temperature output was reduced for both, which for methanol is 63 cm/s compared to 52 cm/s for gasoline [27], causing increased levels of NO x , as suggested by Larfeldt [28]. M100 ultimately caused a 99% reduction in NOx ouput at rated speed due to reduced combustion temperatures.…”

Higher Alcohol and Ether Biofuels for Compression-Ignition Engine Application: A Review with Emphasis on Combustion Kinetics

“…To provide further model validation data and to unravel the flame propagation characteristics of higher alcohols, the laminar burning velocities of higher alcohols have been measured by various studies. The first studies on n -pentanol and n -hexanol laminar burning velocities include those of Togbé et al , Later, a series of articles was published by Li et al, ,,, where they reported laminar burning velocities for all higher n -alcohols from n -pentanol up to n -octanol, supplemented by blend data of the respective C 6 –C 8 alcohols with methanol and additional data for n -pentanol/iso-octane blends . Comparisons with other pentanol isomers revealed that n -pentanol has the highest burning velocities among the isomers. , On the other hand, comparing the higher n -alcohols of different chain lengths shows that these exhibit comparable burning velocities, as depicted in Figure .…”

“…The first studies on n-pentanol and n-hexanol laminar burning velocities include those of Togbéet al 140,141 Later, a series of articles was published by Li et al, 133,135,151,157 where they reported laminar burning velocities for all higher n-alcohols from n-pentanol up to noctanol, supplemented by blend data of the respective C 6 −C 8 alcohols with methanol 157 and additional data for n-pentanol/ iso-octane blends. 151 Comparisons with other pentanol isomers revealed that n-pentanol has the highest burning velocities among the isomers. 133,135 On the other hand, comparing the higher n-alcohols of different chain lengths shows that these exhibit comparable burning velocities, as depicted in Figure 5.…”