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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.]

Caterpillar and Argonne’s VERIFI undertake cooperative virtual engine design, control project; first VERIFI CRADA

July 03, 2014

Low-temperature combustion regimes show great efficiency and emissions potential, but they present optimization and control challenges that must be addressed before they enter the engine mainstream.

Caterpillar Inc. has entered into a Cooperative Research and Development Agreement (CRADA) with Argonne National Laboratory and its recently formed Virtual Engine Research Institute and Fuels Initiative (VERIFI), where experts are developing new engine combustion models that incorporate accurate descriptions of two-phase flows, chemistry, transport phenomena and device geometries to provide predictive simulations of engine and fuel performance.

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A pathway to gasoline compressed ignition using naphtha fuels; higher efficiency, lower cost

May 02, 2014

A new study by Dr. Gautam Kalghatgi and his colleagues at Saudi Aramco provides further support a pathway for significant improvements in the efficiency of a gasoline engine (i.e., spark ignited, SI) by running it in compression ignition mode with naphtha fuels. (Earlier post.) This latest work, presented at SAE 2014 World Congress, shows that moving to higher compression ratios (CR) and lower fuel cetane numbers (DCN) from an SI base engine offers a better trade-off than increasing DCN with a lower CR. In other words, using only cetane to improve CI fuel consumption is less beneficial than relying on a low cetane fuel and higher compression ratio.

Past work done by Kalghatgi and his team, as well as by Prof. Bengt Johansson at Lund University and others, has demonstrated that using low-octane gasoline in diesel engines has the potential to achieve very high efficiency while reducing the cost of diesel engines by lowering injection pressures and requiring less expensive exhaust aftertreatment. Broadly, this approach is termed Gasoline Compression Ignition (GCI).

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Oak Ridge researchers pursuing in-cylinder reforming for control of advanced combustion

April 21, 2014

Researchers at Oak Ridge National Laboratory are pursuing investigations into the use of a non-catalytic in-cylinder reforming process—i.e., the conversion of liquid hydrocarbon fuel to a hydrogen- and CO-rich syngas—potentially for controlling combustion phasing in homogeneous charge compression ignition (HCCI) and other forms of advanced combustion.

When fuel is injected during negative valve overlap (NVO) in O2-deficient conditions, a portion of the fuel is reformed to products containing H2 and CO. In a paper presented at the recent SAE 2014 World Congress, the ORNL team and colleague from Sandia National Laboratories reported on the chemistry of an NVO in-cylinder reforming process as experimentally determined from a single-cylinder engine. The Oak Ridge team plans to pursue the in-cylinder reforming technique in a multi-cylinder configuration in which one of the engine cylinders would act as the reformer, “essentially breathing in reverse compared to the other cylinders (breathing in from the exhaust manifold and exhausting into the intake system).”

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Promising Delphi 1st-gen Gasoline Direct Injection Compression Ignition engine meeting ultra fuel efficient program targets

April 17, 2014

Researchers at Delphi Powertrain, in collaboration with colleagues at Hyundai Motor, the University of Wisconsin-Madison, and Wisconsin Engine Research Consultants (WERC), have developed a first-generation multi-cylinder Gasoline Direct Injection Compression Ignition (GDCI) engine, based on several years of extensive simulations and single-cylinder engine tests. (Earlier post, earlier post.)

In a presentation at the SAE 2014 High Efficiency IC Engine Symposium and then in a paper given at SAE 2014 World Congress, Mark Sellnau, Engineering Manager, Delphi Advanced Powertrain, reported that Brake Specific Fuel Consumption for the 1.8L GDCI engine was significantly better than advanced production spark-ignited gasoline engines, and comparable to very efficient hybrid vehicle engines at their best efficiency conditions (214 g/kWh). Compared to new diesel engines, the Delphi team found that BSFC for GDCI at light loads was comparable or better, and at high loads was about 5% higher.

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Brunel engineers optimizing CAI combustion in 2-stroke camless gasoline DI engine

February 10, 2014

Brunel
Operating range of 2-stroke CAI fueled with gasoline, E10 and E85. Zhang et al. (2013a) Click to enlarge.

Researchers at Brunel University in the UK, led by Professor Hua Zhao, Head of Mechanical Engineering and Director, Centre for Advanced Powertrain and Fuels (CAPF), are investigating optimizing the performance of controlled autoignition (CAI) combustion in a four-valve camless gasoline direct injection engine running in a two-stroke cycle. Most recently, this has entailed an exploration of boosting strategies, as described in a new paper published in the International Journal of Engine Research, as well as an exploration of the effects of ethanol blends.

Controlled autoignition (e.g., homogeneous charge compression ignition, HCCI) combustion processes offer the promise of simultaneously reducing fuel consumption and NOx emissions. Accordingly, the processes have been extensively researched over the last decade and adopted on prototype gasoline engines (e.g., GM’s ongoing work, earlier post).

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Nissan reveals Frontier Diesel Runner with 2.8L Cummins turbo diesel; leveraging ATLAS engine program

February 06, 2014

Frontier_Diesel_Runner_01
Nissan Frontier Diesel Runner Powered by Cummins. Click to enlarge.

At the Chicago Auto Show, Nissan debuted a concept diesel-powered mid-size pickup: the Frontier Diesel Runner Powered by Cummins. Based on a Frontier Desert Runner 4x2 model, was created to gauge the market reaction to a Nissan mid-size pickup with a diesel engine and plot a potential future direction for the Frontier.

The Frontier Diesel Runner arrives six months after the announcement of a partnership with Cummins Inc. to provide a 5.0-liter turbo diesel V8 in the next-generation Titan full-size pickup, which will arrive in calendar year 2015. (Earlier post.)

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Study finds butanol-gasoline blends effective to control soot from CI engines under Low Temperature Combustion

January 31, 2014

Butanol
(Left) Thermal efficiency and (right) soot from different gasoline-butanol blends at different EGR rates. Yang et al. Click to enlarge.

A study by a team at Tianjin University found that the addition of n-butanol to gasoline for use in a compression ignition engine (CI) under Low Temperature Combustion (LTC) conditions has a significant effect on soot reduction. The peak soot value of a 30% butanol blend (B30) was 85% lower than that of pure gasoline; the EGR rate that corresponds to the peak value of soot is also decreased with the higher n-butanol fraction. Their study is published in the journal Fuel.

Partially Premixed Combustion involving the injection of gasoline fuel into CI engines is being explored by other researchers as a means to reducing simultaneously NOxand soot emissions. High octane fuels such as gasoline are preferred for high-efficiency and clean combustion at high engine loads, the Tianjin researchers note.

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U Wisc.-Ford team develops more realistic multi-component surrogate diesel models for modeling of low temperature combustion

December 07, 2013

A team from the Engine Research Center at the University of Wisconsin-Madison, Ford Motor, and Ford Forschungszentrum Aachen have developed new multi-component surrogate models for three different diesel fuels, and then examined their fidelity in capturing the characteristics of a diesel engine operated under various conditions, including conventional and low-temperature combustion (LTC) modes.

Fuel and EGR effects were also explored in the two different combustion modes using the developed surrogate models. In a paper published in the ACS journal Energy & Fuels, they reported that the results showed that the combustion trends in conventional combustion are less affected by fuel or EGR changes, while LTC conditions exhibit a much higher sensitivity, thus demanding more realistic fuel models precisely to describe advanced combustion modes.

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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.

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New hybrid plasma-catalyst aftertreatment system feasible for low-temperature combustion engines

September 17, 2013

Master-1.img-001
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.

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Researchers identify new pathways in low-temp oxidation of hydrocarbons; important to fuel combustion, atmospheric chemistry and biochemistry

September 05, 2013

Jalan
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.

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Using ozone injection to control HCCI combustion

August 28, 2013

Hcci
In-cylinder pressure (on the left) and heat release rate (on the right) as a function of the CAD and ozone concentration injected in the intake of the engine for PRF40. The results show that ozone seeding improves combustion and advances phasing. The same trends were observed for the other fuels studied. Credit: ACS, Masurier et al. Click to enlarge.

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.

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Sandia team proposes models for partially premixed low-temperature direct-injection diesel combustion

August 14, 2013

DEC
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.

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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.

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