High Temperature HCCI Critical Compression Ratio of the C1-C4 Alcohol Fuels
- 6 April 2021
- journal article
- research article
- Published by SAE International in SAE International Journal of Advances and Current Practices in Mobility
- Vol. 3 (4), 1495-1507
- https://doi.org/10.4271/2021-01-0511
Abstract
In this work, a high temperature (HT) homogeneous charge compression ignition (HCCI) critical compression ratio (cCR) was defined as the compression ratio which resulted in HCCI combustion with a crank angle location of 50% fuel burned (CA50) of 3.0 degrees after top dead center (aTDC) while operating at an equivalence ratio of 0.33 (λ = 3), an intake pressure of 1.0 bar (naturally aspirated), an intake temperature of 473 K (200°C), and an engine speed of 600 rpm. Using a Cooperative Fuel Research engine, the HT HCCI cCR of seven alcohol fuels were experimentally determined and found to be ordered as follows (ordered from least reactive to most reactive): isopropanol > sec-butanol > methanol ≈ ethanol ≈ n-propanol ≈ isobutanol > n-butanol. The HT HCCI cCR for the alcohol fuels correlated well with experimental HCCI data from a modern gasoline direct injection (GDI) engine architecture with a pent-roof head and a rebreathe valvetrain. The HT HCCI cCR was also correlated with available cetane number (CN), motor octane number (MON), and research octane number (RON) values found in the literature. The coefficient of determination (R2) for these correlations was 0.02, 0.95, and 0.69, respectively. When the RON values were modified to account for the high cooling potential of the alcohol fuels, the R2 increased from 0.69 to 0.96. When a wider array of other fuels were considered, including pure components of different fuel classes, pure-component fuel blends, and gasoline fuel blends, the critical compression ratio no longer correlated well with MON or HOV-modified RON. It was concluded that when fuels of a similar fuel class are considered, such as neat C1-C4 alcohols, MON or an HOV-modified RON may be sufficient to compare the HCCI reactivity of the fuels at MON-like cylinder conditions. However, due to the complex nature of the octane number tests, the HCCI ignition propensity is not well predicted by the standard octane numbers when fuels of varying chemical characteristics and combustion chemistry attributes are considered. Therefore, a metric for characterizing gasoline-like fuels under compression ignition conditions is required, such as an HCCI test method on the CFR octane rating engine.Keywords
This publication has 38 references indexed in Scilit:
- Achieving Stable Engine Operation of Gasoline Compression Ignition Using 87 AKI Gasoline Down to IdleSAE International Journal of Advances and Current Practices in Mobility, 2015
- Alcohol combustion chemistryProgress in Energy and Combustion Science, 2014
- Autoignition of ethanol in a rapid compression machineCombustion and Flame, 2014
- Fundamental phenomena affecting low temperature combustion and HCCI engines, high load limits and strategies for extending these limitsProgress in Energy and Combustion Science, 2013
- Assessment of Residual Mass Estimation Methods for Cylinder Pressure Heat Release Analysis of HCCI Engines With Negative Valve OverlapPublished by ASME International ,2011
- Comparative High Temperature Shock Tube Ignition of C1−C4 Primary AlcoholsEnergy & Fuels, 2010
- Trends and challenges in the microbial production of lignocellulosic bioalcohol fuelsApplied Microbiology and Biotechnology, 2010
- A Shock Tube Study ofn- andiso-Propanol IgnitionEnergy & Fuels, 2009
- Influence of Fuel and Operating Conditions on Combustion Characteristics of a Homogeneous Charge Compression Ignition EngineEnergy & Fuels, 2009
- Expanding metabolism for biosynthesis of nonnatural alcoholsProceedings of the National Academy of Sciences of the United States of America, 2008