Effects of iso-octane/ethanol blend ratios on the observance of negative temperature coefficient behavior within the Ignition Quality Tester

Abstract

An ignition delay study investigating the reduction in low temperature heat release (LTHR) and negative temperature coefficient (NTC) region with increasing ethanol concentration in binary blends of ethanol/isooctane was conducted in the Ignition Quality Tester (IQT). The IQT is advantageous for studying multi-component fuels such as iso-octane/ethanol which are difficult to study at lower temperatures covering the NTC region in traditional systems (e.g., shock tubes, rapid compression machines, etc.). The high octane numbers and concomitant long ignition delay times of ethanol and isooctane are ideal for study in the IQT allowing the system to reach a quasi-homogeneous mixture;allowing the effect of fuel chemistry on ignition delay to be investigated with minimal impact from the fuel spray due to the relatively long ignition times. NTC behavior from iso-octane/ethanol blends was observed for the first time using an IQT. Temperature sweeps of iso-octane/ethanol volumetric blends (100/0, 90/10, 80/20, 50/50, and 0/100) were conducted from 623 -993 K at 0.5, 1.0 and 1.5 MPa and global equivalence ratios ranging from 0.7 to 1.0. Ignition of the iso-octane/ethanol blends in the IQT was also modeled using a 0-D homogeneous batch reactor model. Significant observations include: 1) NTC behavior was observed for ethanol/iso-octane fuel blends up to 20% ethanol. 2) Ethanol produced shorter ignition delay times than iso-octane in the high temperature region. 3) The initial increase in ethanol from 0% to 10% had a lesser impact on ignition delay than increasing ethanol from 10% to 20%. 4)The 0-D model predicts that at 0.5 and 1.0 MPa ethanol produces the shortest ignition time in the high-temperature regime, as seen experimentally.

Performance of lignin derived compounds as octane boosters

“…Analysis of the pressure traces for these compunds confirms the absence of low temperature heat release (Fig. 10), therefore the use of the conventional ASTM D6890 definition for start of ignition (i.e., a fixed 138 kPa above the chamber pressure recovery point) is valid [66].…”

“…The left vertical line, which is the upper limit of the DCN temperature requirement, fits for the RON indication. Bogin et al also found that the ID at higher temperature was more representative of MON conditions [66]. However, more experiments are needed to study this topic further.…”

“…The mass of fuel injected was then held constant for each temperature sweep, and consequently the equivalence ratio of the combustion events decreased as the combustion chamber cooled. Other studies comparing constant mass to constant equivalence ratio temperature sweeps have shown that the effects of this change in equivalence ratio on ID measurements are small [64][65][66].…”

An Experimental and Numerical Study of N-Dodecane/Butanol Blends for Compression Ignition Engines

“…In addition, thermo-physical properties (density, viscosity, surface tension) also show good agreement for n-dodecane as surrogate for diesel fuels. Therefore, n-dodecane can better represent the diesel fuel as a surrogate [27][28][29][30][31][32][33][34][35], and will be adopted here as a representative fuel to describe diesel combustion. As for the reliable reaction mechanisms for butanol, the mechanism by Wang et al [36] is based on nheptane/butanol/PAH mechanism and has been used by Chen et al [37] in studying in-cylinder combustion for butanol/diesel blends.…”

Combustion Characteristics of n-heptane Through Temperature Variation Measurements Using Ignition Quality Tester

“…Bogin et al [62] respectively. The N T C region was observed at 1 and 1.5 M P a from 0% to 20% ethanol while it was not observed at low pressure (0.5 M P a) and ethanol concentration higher than 50% because the IDs became very long (> 700 ms).…”