Low Temperature Combustion
[Due to the increasing size of the archives, each topic page now contains only the prior 365 days of content. Access to older stories is now solely through the Monthly Archive pages or the site search function.]
Exploring gasoline-range naphtha as a low-soot, low-NOx alternative compression ignition fuel
October 08, 2013
Dr. Gautam Kalghatgi and his colleagues at Saudi Aramco and other organization such as FEV, RWTH Aachen University, and Shell Global Solutions, have been investigating the potential use of naphtha as an alternative compression-ignition (CI) fuel that offers a number of benefits, including efficient combustion; low soot and NOx emissions resulting in a less complicated aftertreatment system to meet modern emissions standards; and a fuel that is simpler to make than current gasoline or diesel fuels.
A number of papers from Kalghatgi and his colleagues—and now other groups, including Tsinghua University in China and the Eindhoven University of Technology—have been published recently, exploring different aspects of this approach. At the SAE/KSAE 2013 International Powertrains, Fuels & Lubricants Meeting in Korea later this month, Kalghatgi and his colleagues will present two more, one exploring the fuel economy potential of partially premixed compression ignition (PPCI) combustion using naphtha, the other exploring the use of larger size nozzle holes and higher compression ratio in a diesel engine for combustion of such a “gasoline-type” fuel.
New hybrid plasma-catalyst aftertreatment system feasible for low-temperature combustion engines
September 17, 2013
|Schematic diagram of the plasma−catalyst reactor. Credit: ACS, Kang et al. Click to enlarge.|
Researchers at the Korea Institute of Machinery and Materials (KIMM) have developed a new hybrid reactor for automotive exhaust aftertreatment that combines plasma and a honeycomb-structured monolith catalyst resulting in an enhanced synergistic effect of low-temperature catalytic activity.
As reported in a paper published in the ACS journal Environmental Science & Technology, the plasma−catalyst synergistic reaction is more effective at low temperatures; the hybrid reaction reduces the temperature required to achieve the same level of DRE (destruction and removal efficiency) for hydrocarbon (HC) pollutants when compared to the temperature of the reaction under the influence of the catalyst alone. As a result of their work, the authors suggest that the plasma−catalyst technology is feasible to control exhaust emissions from next-generation low-temperature combustion (LTC) diesel engines.
Researchers identify new pathways in low-temp oxidation of hydrocarbons; important to fuel combustion, atmospheric chemistry and biochemistry
September 05, 2013
|The diagram illustrates the newly-described reaction that transforms molecules of ketohydroperoxide into acids and carbonyl molecules, after going through intermediate stages. Credit: ACS, Jalan et al. Click to enlarge.|
Researchers at MIT, with colleagues at the University of Minnesota, have provided evidence and theoretical rate coefficients for new pathways in the low-temperature oxidation of hydrocarbons. Their paper is published in the Journal of the American Chemical Society.
The newly explained reaction—the basic outlines of which had been first hypothesized by Korcek and co-workers more than 30 years ago but the workings of which had never been understood in detail—is an important part of atmospheric reactions that lead to the formation of climate-affecting aerosols; biochemical reactions that may be important for human physiology; and combustion reactions in engines. The new study provides theoretical confirmation of Korcek’s hypothesis that ketohydroperoxide molecules (KHPs) are precursors to carboxylic acid formation.
Using ozone injection to control HCCI combustion
August 28, 2013
HCCI (homogeneous charge compression ignition) has been extensively studied in recent years due to its potential to maintain strong efficiency similar to compression ignition (CI) engines but also to produce very low emissions of NOx and particulate matter. Control of HCCI autoignition and combustion phasing is challenging, however. Unlike CI and spark ignition (SI) engines, HCCI cannot be easily controlled by external means (e.g., injectors or spark plugs), because the process is mainly governed by chemical kinetics.
Accordingly, many strategies have been studied to control combustion. Now, researchers in France have added to that body of work by showing that ozone seeding in the intake of an HCCI engine can control HCCI combustion.
Sandia team proposes models for partially premixed low-temperature direct-injection diesel combustion
August 14, 2013
|The Sandia team has proposed extensions to John Dec’s 1997 model for diesel combustion, represented above. Credit: Musculus et al.; Dec. Click to enlarge.|
A team at Sandia National Laboratories recently proposed conceptual models for a specific subset of low-temperature combustion regimes: low-load, single-injection, partially premixed compression ignition (PPCI LTC) conditions that are diluted by exhaust-gas recirculation (EGR) to oxygen concentrations in the range of 10–15%.
Their paper, which provides a detailed review and synthesis of various current experimental and modeling studies—and which extends Sandia scientist John Dec’s seminal 1997 model for diesel combustion—is published in the journal Progress in Energy and Combustion Science.
U Wisc. study explores effects of biodiesel-gasoline blend in diesel engine
August 01, 2013
One high-efficiency combustion concept under investigation is gasoline compression ignition (GCI)—the use of gasoline-like fuels to deliver very low NOx and PM emissions as well as high efficiency in a diesel compression ignition engine. (Earlier post.) A challenge to be overcome with this approach is the higher resistance to autoignition of gasoline fuels.
A team from the University of Wisconsin-Madison’s Engine Research Center now reports in a paper in the journal Fuel on the effects of biodiesel-gasoline blends compared to neat gasoline using a partially premixed, split-injection GCI combustion strategy.
UC Berkeley leading project investigating partial fuel stratification and microwave-assisted sparkplugs for LTC engines
July 01, 2013
|The LTC research project has three proposed components. Click to enlarge.|
The University of California Berkeley is partnering with MIT, Lawrence Berkeley, Lawrence Livermore and Sandia National Labs and Ricardo to investigate the the use of partial fuel stratification (PFS) in compression-ignition (CI) engines as well as the combination of PFS and microwave-assisted spark plug (µWASP) technology in spark-ignition (SI) engines to enable Low Temperature Combustion (LTC) engines to operate over the full load and speed range.
The 3-year, $1.65-million project is supported by the US Department of Energy (DOE) and National Science Foundation as part of their collaborative research program for advanced combustion engines. (Earlier post.) The project is being led by UC Berkeley professors Prof. Robert W. Dibble and Prof. Jyh-Yuan Chen as co-principal investigators, with Dr. Samveg Saxena of UC Berkeley and Lawrence Berkeley National Laboratory, and Prof. Wai Cheng (Co-PI), Massachusetts Institute of Technology (collaborating institution). One focus of the project will be centered on light- and heavy-duty vehicles running on gasoline/ethanol blends in order to improve engine efficiency and lower emissions.
Study finds moderate biofuel blends increase benefits of RCCI in light-duty engines
June 19, 2013
Preliminary results from a new study by a team from Oak Ridge National Laboratory (ORNL) and the University of Wisconsin suggest that the fuel properties of moderate biofuel blends such as E20 and B20 increase the benefits of the use of Reactivity Controlled Compression Ignition (RCCI). RCCI is a Low Temperature Combustion (LTC) strategy that uses in-cylinder blending of two different fuels to produce low NOxand PM while maintaining high thermal efficiency. (Earlier post.)
Previous studies on RCCI have used single-cylinder heavy-duty engines; in this study, Reed Hanson, Scott Curran and Robert Wagner (ORNL) and Rolf Reitz (U. of Wisconsin) investigated RCCI in a light-duty multi-cylinder engine over a wide number of operating points. Fuels in earlier studies were generally petroleum-based fuels such as diesel and gasoline, with some work done with high percentages of biofuels, such as E85.
U. Wisconsin team reports gross indicated thermal efficiency of RCCI operation near 60%
April 29, 2013
In a paper presented at the 2013 SAE World Congress, a team from the University of Wisconsin reported a gross indicated thermal efficiency of Reactivity Controlled Compression Ignition (RCCI) operation of near 60%, given optimized combustion management and thermodynamic conditions. That 60% gross engine efficiency provides a pathway to meet the DOE Super Truck 50% brake thermal efficiency (BTE) engine goal as well as a pathway for reaching 55% BTE, the researchers concluded.
The findings also showed that improvements to boosting system efficiencies for low exhaust temperatures and overall reductions in friction are required to capitalize on the high gross efficiences offered by RCCI.
Delphi advancing Gasoline Direct-Injection Compression-Ignition engine concept; new two-stage supercharger/turbocharger boost system
April 12, 2013
At SAE World Congress next week in Detroit, Delphi Automotive will present two technical papers describing its ongoing progress with the Gasoline Direct-Injection Compression-Ignition (GDCI) engine concept. (Earlier post.)
GDCI is an advanced low-temperature combustion concept that uses compression ignition under lean to near stoichiometric fueling conditions over the complete engine operating range. Previous studies of GDCI have shown good potential for very high efficiency, low NOx, and low PM over the full speed-load range. GDCI achieves low-temperature combustion using multiple-late injection (MLI), intake boost, and cooled EGR.
Tsinghua study compares two diesel-gasoline combustion modes; both deliver high efficiencies and low emissions
March 18, 2013
|The effects of gasoline ratio on indicated thermal efficiency of HCII and GDBF modes. Yu et al. Click to enlarge.|
Researchers at Tsinghua University have compared the combustion and emissions characteristics of two dual-fuel (diesel-gasoline) modes intended to integrate the advantages of both fuels to achieve high thermal efficiency and low emission targets. A paper on their results is published in the journal Fuel.
Gasoline Homogeneous Charge Induced Ignition (HCII) by diesel combines the port fuel injection of gasoline to form a homogeneous charge with the direct injection of diesel fuel as an ignition source. (E.g., RCCI, earlier post.) Gasoline/Diesel Blend Fuels (GDBFs) use a premixed blend of diesel and gasoline which is directly injected into the cylinder for combustion. (E.g., dieseline, earlier post.)