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Title: Thermally Stratified Compression Ignition: A new advanced low temperature combustion mode with load flexibility

Abstract

We introduce a new advanced combustion mode, called Thermally Stratified Compression Ignition (TSCI), which uses direct water injection to control both the average temperature and the temperature distribution prior to ignition, thereby providing cycle-to-cycle control over the start and rate of heat release in Low Temperature Combustion (LTC). Experiments were conducted to fundamentally understand the effects of water injection on heat release in LTC. Our results show that water injection retards the start of combustion due to the latent heat of vaporization of the injected water. Furthermore, for start of water injection timings between 20 and 70 degrees before top dead center, combustion is significantly elongated compared to without water injection. The 10–90% burn duration with 6.6 and 9.0 mg of water per cycle was 77% and 146% longer than without water injection, respectively. Forced thermal stratification result from a direct water injection which reduces the heat release rate by local evaporative cooling. Finally, the load limits with and without water injection were determined experimentally. Without water injection, the load range was 2.3–3.6 bar gross IMEP. By using water injection to control heat release, the load range in TSCI was 2.3–8.4 bar gross IMEP, which is a range expansion ofmore » over 350%. These results demonstrate that direct water injection can provide significant improvements to both controllability and the range of operability of LTC, thereby resolving the major challenges associated with HCCI.« less

Authors:
 [1];  [2];  [2];  [2]
  1. Stony Brook Univ., NY (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Fuels, Engines and Emissions Research Center (FEERC); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). National Transportation Research Center (NTRC)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1342679
Alternate Identifier(s):
OSTI ID: 1413332
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Applied Energy
Additional Journal Information:
Journal Volume: 189; Journal Issue: C; Journal ID: ISSN 0306-2619
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 42 ENGINEERING; 20 FOSSIL-FUELED POWER PLANTS; Low temperature combustion; Advanced combustion; HCCI; Heat release; Thermal stratification

Citation Formats

Lawler, Benjamin, Splitter, Derek, Szybist, James, and Kaul, Brian. Thermally Stratified Compression Ignition: A new advanced low temperature combustion mode with load flexibility. United States: N. p., 2017. Web. doi:10.1016/j.apenergy.2016.11.034.
Lawler, Benjamin, Splitter, Derek, Szybist, James, & Kaul, Brian. Thermally Stratified Compression Ignition: A new advanced low temperature combustion mode with load flexibility. United States. doi:10.1016/j.apenergy.2016.11.034.
Lawler, Benjamin, Splitter, Derek, Szybist, James, and Kaul, Brian. Wed . "Thermally Stratified Compression Ignition: A new advanced low temperature combustion mode with load flexibility". United States. doi:10.1016/j.apenergy.2016.11.034. https://www.osti.gov/servlets/purl/1342679.
@article{osti_1342679,
title = {Thermally Stratified Compression Ignition: A new advanced low temperature combustion mode with load flexibility},
author = {Lawler, Benjamin and Splitter, Derek and Szybist, James and Kaul, Brian},
abstractNote = {We introduce a new advanced combustion mode, called Thermally Stratified Compression Ignition (TSCI), which uses direct water injection to control both the average temperature and the temperature distribution prior to ignition, thereby providing cycle-to-cycle control over the start and rate of heat release in Low Temperature Combustion (LTC). Experiments were conducted to fundamentally understand the effects of water injection on heat release in LTC. Our results show that water injection retards the start of combustion due to the latent heat of vaporization of the injected water. Furthermore, for start of water injection timings between 20 and 70 degrees before top dead center, combustion is significantly elongated compared to without water injection. The 10–90% burn duration with 6.6 and 9.0 mg of water per cycle was 77% and 146% longer than without water injection, respectively. Forced thermal stratification result from a direct water injection which reduces the heat release rate by local evaporative cooling. Finally, the load limits with and without water injection were determined experimentally. Without water injection, the load range was 2.3–3.6 bar gross IMEP. By using water injection to control heat release, the load range in TSCI was 2.3–8.4 bar gross IMEP, which is a range expansion of over 350%. These results demonstrate that direct water injection can provide significant improvements to both controllability and the range of operability of LTC, thereby resolving the major challenges associated with HCCI.},
doi = {10.1016/j.apenergy.2016.11.034},
journal = {Applied Energy},
number = C,
volume = 189,
place = {United States},
year = {Wed Mar 01 00:00:00 EST 2017},
month = {Wed Mar 01 00:00:00 EST 2017}
}

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  • Our work explores the volatility of particles produced from two diesel low temperature combustion (LTC) modes proposed for high-efficiency compression ignition engines. It also explores mechanisms of particulate formation and growth upon dilution in the near-tailpipe environment. Moreover, the number distribution of exhaust particles from low- and mid-load dual-fuel reactivity controlled compression ignition (RCCI) and single-fuel premixed charge compression ignition (PPCI) modes were experimentally studied over a gradient of dilution temperature. Particle volatility of select particle diameters was investigated using volatility tandem differential mobility analysis (V-TDMA). Evaporation rates for exhaust particles were compared with V-TDMA results for candidate pure n-alkanesmore » to identify species with similar volatility characteristics. The results show that LTC particles are mostly comprised of material with volatility similar to engine oil alkanes. V-TDMA results were used as inputs to an aerosol condensation and evaporation model to support the finding that smaller particles in the distribution are comprised of lower volatility material than large particles under primary dilution conditions. Although the results show that saturation levels are high enough to drive condensation of alkanes onto existing particles under the dilution conditions investigated, they are not high We conclude that observed particles from LTC operation must grow from low concentrations of highly non-volatile compounds present in the exhaust.« less
  • Gasoline Compression Ignition (GCI) has been shown as one of the advanced combustion concepts that could potentially provide a pathway to achieve cleaner and more efficient combustion engines. Fuel and air in GCI are not fully premixed as compared to homogeneous charge compression ignition (HCCI) which is a completely kinetic-controlled combustion system. Therefore, the combustion phasing can be controlled by the time of injection, usually post injection in a multiple-injection scheme, to mitigate combustion noise. Gasoline fuels ignite more difficult than Diesel. The autoignition quality of gasoline can be indicated by research octane number (RON). Fuels with high octane tendmore » to have more resistance to auto-ignition, hence more time for fuel-air mixing. In this study, three fuels, namely, Aromatic, Alkylate, and E30, with similar RON value of 98 but different hydrocarbon compositions were tested in a multi-cylinder engine under GCI combustion mode. Considerations of EGR, start of injection (SOI), and boost were investigated to study the sensitivity of dilution, local stratification, and reactivity of the charge, respectively, for each fuel. Combustion phasing was kept constant during the experiments to the changes in ignition and combustion process before and after 50% of the fuel mass is burned. Emission characteristics at different levels of EGR and lambda were revealed for all fuels with E30 having the lowest filter smoke number (FSN) and was also most sensitive to the change in dilution. Reasonably low combustion noise (< 90 dB) and stable combustion (COVIMEP < 3%) were maintained during the experiments. The second part of this paper contains visualization of the combustion process obtained from endoscope imaging for each fuel at selected conditions. Soot radiation signal from GCI combustion were strong during late injection, and also more intense at low EGR conditions. Furthermore, soot/temperature profiles indicated only the high-temperature combustion period, while cylinder pressure-based heat release rate (HRR) showed a two-stage combustion phenomenon.« less