Second-law analysis of the reforming-controlled compression ignition

Eyal, Amnon; Tartakovsky, Leonid

doi:10.1016/j.apenergy.2020.114622

Cited by 27 publications

(17 citation statements)

References 48 publications

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“…Next, the discussion deals with a partial conversion of the high-potential carrier in the electrochemical engine, i.e., the bottoming Otto-cycle engine recovers waste heat and converts an unused part of the high-potential carrier to mechanical work. Figure 5 shows the efficiency and the optimal conversion of a high-potential carrier in the chemical engine as a function of T 1 /T L calculated using Equations (19) and (20). As seen, the optimal carrier conversion from the high to low potential in a chemical engine for maximum power is a linear function of the T 1 /T L ratio.…”

Section: Resultsmentioning

confidence: 99%

“…When a hybrid cycle involving a fuel cell and an ICE is considered, usage of fuel reforming in combination with waste heat recovery known as Thermochemical Recuperation (TCR) could be beneficial. Recently, utilization of fuel reforming through TCR in ICEs was proven to be energetically efficient [18][19][20]. Hence, a potential of its implementation in a hybrid Fuel-Cell-ICE cycle should be evaluated.…”

Section: Introductionmentioning

confidence: 99%

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Efficiency at Maximum Power of the Low-Dissipation Hybrid Electrochemical–Otto Cycle

Diskin

Tartakovsky

2020

Energies

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A novel analytical method was developed for analysis of efficiency at maximum power of a hybrid cycle combining electrochemical and Otto engines. The analysis is based on the low-dissipation model, which relates energy dissipation with energy transfer rate. Efficiency at maximum power of a hybrid engine operating between two reservoirs of chemical potentials is evaluated. The engine is composed of an electrochemical device that transforms chemical potential to electrical work of an Otto engine that uses the heat generated in the electrochemical device and its exhaust effluent for mechanical work production. The results show that efficiency at maximum power of the hybrid cycle is identical to the efficiency at maximum power of an electrochemical engine alone; however, the power is the product of the electrochemical engine power and the compression ratio of the Otto engine. Partial mass transition by the electrochemical device from the high to the low chemical potential is also examined. In the latter case, heat is generated both in the electrochemical device and the Otto engine, and the efficiency at maximum power is a function of the compression ratio. An analysis performed using the developed method shows, for the first time, that, in terms of a maximal power, at some conditions, Otto cycle can provide better performance that the hybrid cycle. On the other hand, an efficiency comparison at maximum power with the separate Otto-cycle and chemical engine results in some advantages of the hybrid cycle.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Efficiency at Maximum Power of the Low-Dissipation Hybrid Electrochemical–Otto Cycle

Diskin

Tartakovsky

2020

Energies

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“…Since a recent extensive review on fuel reforming in IC engines by Tartakovsky and Steintuch is available [8], only a few papers are mentioned here. Very recently Eyal and Tartakovsky analyzed the entropy production in HCCI engines with external reforming and found efficiencies improved by 7-9% [9]. In a dual-fuel approach with thermochemical recovery, Chuahy and Kokjohn improved the second-law efficiency by 20% [10].…”

Section: Introductionmentioning

confidence: 99%

Flexible energy conversion and storage via high-temperature gas-phase reactions: The piston engine as a polygeneration reactor

Atakan

Kaiser

Herzler

et al. 2020

Renewable and Sustainable Energy Reviews

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Piston engines are typically considered devices converting chemical energy into mechanical power via internal combustion. But more generally, their ability to provide high-pressure and high-temperature conditions for a limited time means they can be used as chemical reactors where reactions are initiated by compression heating and subsequently quenched by gas expansion. Thus, piston engines could be "polygeneration" reactors that can flexibly change from power generation to chemical synthesis, and even to chemical-energy storage. This may help mitigating one of the main challenges of future energy systemsaccommodating fluctuations in electricity supply and demand. Investments in devices for grid stabilization could be more economical if they have a second use.This paper presents a systematic approach to polygeneration9 in piston engines, combining thermodynamics, kinetics, numerical optimization, engineering, and thermo-economics. A focus is on the fuel-rich conversion of methane as a fuel that is considered important for the foreseeable future. Starting from thermodynamic theory and kinetic modeling, promising systems are selected. Mathematical optimization and an array of experimental kinetic investigations are used for model improvement and development. To evaluate technical feasibility, experiments are then performed in both a single-stroke rapid compression machine and a reciprocating engine. In both cases, chemical conversion is initiated by homogeneous-charge compression-ignition. A thermodynamic and thermo-economic assessment of the results is positive. Examples that illustrate how the piston engine can be used in polygeneration processes to convert methane to higher-value chemicals or to take up carbon dioxide are presented. Open issues for future research are addressed.

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“…Several strategies to overcome these challenges have been proposed in recent years. Reactivity controlled compression ignition (RCCI) [6] and reforming-controlled compression ignition (RefCCI) [7][8][9] are two methods aiming to give a solution to combustion controllability and some additional LTC problems by adapting the charge reactivity to the engine operation regime. This is achieved by using two different fuel types-reactive and nonreactive (for instance: diesel and gasoline, respectively) [8].…”

Section: Introductionmentioning

confidence: 99%

“…The main physical properties of DME, hydrogen, and some other fuels are listed in Table 1. To overcome the challenges of catalyst coking, to avoid the need for multiple reformers, and enable the use of a single primary fuel, the reforming-controlled compression ignition (RefCCI) approach was suggested and analyzed by the authors in [7] and [9]. The RefCCI method couples the benefits of the HP-TCR and the advanced combustion concept, the reactivity-controlled compression ignition (RCCI) developed by researchers from the University of Wisconsin [6].…”

Section: Introductionmentioning

confidence: 99%

Suitability of the Reforming-Controlled Compression Ignition Concept for UAV Applications

Eyal

Tartakovsky

2020

Drones

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Reforming-controlled compression ignition (RefCCI) is a novel approach combining two methods to improve the internal combustion engine’s efficiency and mitigate emissions: low-temperature combustion (LTC) and thermochemical recuperation (TCR). Frequently, the combustion controllability challenge is resolved by simultaneous injection into the cylinder of two fuel types, each on the other edge of the reactivity scale. By changing the low-to-high-reactivity fuel ratio, ignition timing and combustion phasing control can be achieved. The RefCCI principles, benefits, and possible challenges are described in previous publications. However, the suitability of the RefCCI approach for aerial, mainly unmanned aerial vehicle (UAV) platforms has not been studied yet. The main goal of this paper is to examine whether the RefCCI approach can be beneficial for UAV, especially HALE (high-altitude long-endurance) applications. The thermodynamic first-law and the second-law analysis is numerically performed to investigate the RefCCI approach suitability for UAV applications and to assess possible efficiency gains. A comparison with the conventional diesel engine and the previously developed technology of spark ignition (SI) engine with high-pressure TCR is performed in view of UAV peculiarities. The results indicate that the RefCCI system can be beneficial for UAV applications. The RefCCI higher efficiency compared to existing commercial engines compensates the lower heating value of the primary fuel, so the fuel consumption remains almost the same. By optimizing the compression pressure ratio, the RefCCI system efficiency can be improved.

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Second-law analysis of the reforming-controlled compression ignition

Cited by 27 publications

References 48 publications

Efficiency at Maximum Power of the Low-Dissipation Hybrid Electrochemical–Otto Cycle

Efficiency at Maximum Power of the Low-Dissipation Hybrid Electrochemical–Otto Cycle

Flexible energy conversion and storage via high-temperature gas-phase reactions: The piston engine as a polygeneration reactor

Suitability of the Reforming-Controlled Compression Ignition Concept for UAV Applications

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