Low Temperature Combustion with Thermo-Chemical Recuperation

Posada, Francisco; Bedick, Clint; Clark, Nigel N.; Kozlov, Aleksandr; Linck, Martin; Boulanov, Dmitri; Pratapas, John

doi:10.4271/2007-01-4074

Cited by 10 publications

(7 citation statements)

References 29 publications

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“…More recently Vernon et al [21] used simulations to explore different energy recovery strategies for fuel reforming operation and concluded that a significant portion of the process heat required for reforming can be provided by the exhaust gases. Posada et al [31] were one the first to suggest the use of fuel reforming as a technique to simultaneously recover exhaust energy and help control the heat release rates of LTC; however, no attempt was made to quantify the efficiency benefits of having both strategies in place. In more quantitative analyses, Shudo et al [32] combined methanol reforming to produce DME and syngas in order to help control homogeneous charge compression ignition (HCCI) combustion.…”

Section: Homogeneous Charge Compression Ignition (Hcci) Partially Prmentioning

confidence: 99%

High efficiency dual-fuel combustion through thermochemical recovery and diesel reforming

Chuahy

Kokjohn

2017

Applied Energy

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A computational system optimization was conducted to explore the potential benefits of diesel reforming in dual-fuel combustion strategies. A comprehensive CFD model, validated against syngas (50/50 /CO by mole) metal engine experiments, was used to simulate the engine combustion process. The engine CFD solver was coupled with an equilibrium solver for the reformer process and three different reforming processes were investigated: Partial oxidation, steam reforming, and autothermal reforming. A system level approach was used to evaluate the impact of thermochemical recovery of exhaust energy and reformer losses. A design of experiments of simulations was conducted to explore the combustion system design space and a genetic algorithm was used to search the resulting response surface and find the optimal operating conditions. It was found that fuel reforming can increase engine net indicated efficiencies by as much as 9% due to a shorter combustion duration and reduction in heat transfer losses. The partial oxidation reforming system resulted in the lowest system efficiencies at 44% due to its exothermic nature, while steam reforming and autothermal reforming were able to achieve over 48% system efficiency, an improvement in global efficiency of 8% compared to a diesel baseline due to exhaust heat recovery.

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Section: Homogeneous Charge Compression Ignition (Hcci) Partially Prmentioning

confidence: 99%

High efficiency dual-fuel combustion through thermochemical recovery and diesel reforming

Chuahy

Kokjohn

2017

Applied Energy

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“…The chemical kinetic code that describes the combustion of n-heptane in air was taken from the Lawrence Livermore National Laboratory [42]. Heat transfer to the walls was calculated using the Woschni's correlation, with a constant wall temperature of 420 K. The thermodynamic fundamentals of this model were previously described by the authors in reference [43]. This oversimplified model does not account for the boundary layer mass, with lower temperature than the cylinder core.…”

Section: Model Analysis and Resultsmentioning

confidence: 99%

“…A constant wall temperature of 420 K was used for all cases in this simulation. The thermodynamic fundamentals of this model were previously described by the authors [43].…”

Section: Single-zone Modeling Descriptionmentioning

confidence: 99%

Low Temperature Combustion with Thermo-Chemical Recuperation to Maximize In-Use Engine Efficiency

Clark¹,

Posada²,

Bedick³

et al. 2009

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“…The reaction rates had to be modified to account for IC engines conditions. The first HCCI model developed for this project was based on this kind of auto-ignition mechanism for n-heptane (Posada et al 2007).…”

Section: Global Reaction Mechanismmentioning

confidence: 99%

“…Heat transfer to the walls was calculated using the correlation for convection proposed by Chang et al (2004), which is a modification of the traditional Woschni's correlation for SI engines, while considering the combustion features of the HCCI engine; a constant wall temperature of 420 K was used for all cases in this simulation. The thermodynamic fundamentals of this model were previously described by the author (Posada et al 2007) and described below.…”

Section: Single-zone Modeling Descriptionmentioning

confidence: 99%

Enabling HCCI combustion of n-heptane through thermo-chemical recuperation

Sanchez¹

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Enabling HCCI Combustion of n-Heptane through Thermo-Chemical Recuperation Francisco Posada Sanchez Concerns over air quality, environmental regulatory requirements and the need for reducing fuel consumption on conventional internal combustion engines (ICE) have motivated the development of alternative combustion processes for ICE. One alternative, homogeneous charge compression ignition (HCCI), has shown benefits of high efficiency with low NO x emissions, but suffers load range limitations and control issues. An increase in equivalence ratio at constant speed changes the combustion timing relative to top dead center (TDC), and also increases the pressure rise rate. The opposite occurs if the equivalence ratio is reduced, delaying the combustion timing with respect to TDC and reducing the peak pressure. Excessive heat release associated with richer mixtures drives the engine to ringing conditions, which sets the upper limit for HCCI operation. This thesis aims to investigate numerically the HCCI process under dual fuel operation. The secondary fuel stream bears different autoignition characteristics to regulate combustion timing and heat release at specific operational conditions. The secondary fuel stream is produced onboard as a reformed product of the primary fuel. The reforming process, which requires additional steam, takes advantage of the exhaust gases to convey the fuel reforming reactions, process that is called thermo-chemical recuperation (TCR). This thesis contributes to understanding the effects of different system conditions on the integrated HCCI-TCR system operational range and emissions of nitrogen oxides (NO X), and carbon monoxide (CO). Using n-heptane as the main fuel for HCCI combustion and fuel reforming, two different HCCI models are developed and validated. The single-zone model allows for studying the effect of the secondary fuel on combustion timing. A more complex model, the multi-zone model, allows for studying the effect of secondary fuel on overall engine performance and emissions. Both models operate under engine steady state assumptions (constant speed-load conditions). The combustion models were linked through a cycle simulation code to predict gas exchange processes, in particular the exhaust gas process which defines reforming conditions in the TCR. A model to predict the secondary fuel stream composition on the steam-fuel reformer, under steady state conditions, is developed and validated. Using n-heptane and steam as reactants, the model is able to predict the reformed gas (RG) concentration at the reformer outlet as a function of reforming temperature and relative initial molar fractions of n-heptane and water. The model results are compared against experimental work on steam reforming of n-heptane. RG composition obtained is used to substitute n-heptane at the intake, which alters the HCCI combustion history and performance. Changes in combustion history concurrently affect the exhaust conditions, therefore affecting fuel reforming conditions. This interrelation between the...

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Low Temperature Combustion with Thermo-Chemical Recuperation

Cited by 10 publications

References 29 publications

High efficiency dual-fuel combustion through thermochemical recovery and diesel reforming

High efficiency dual-fuel combustion through thermochemical recovery and diesel reforming

Low Temperature Combustion with Thermo-Chemical Recuperation to Maximize In-Use Engine Efficiency

Enabling HCCI combustion of n-heptane through thermo-chemical recuperation

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