Characteristic Timescales for Lean Blowout of Alternative Jet Fuels

Peiffer, Erin; Heyne, Joshua S.; Colket, Meredith B.

doi:10.2514/6.2018-4914

Cited by 8 publications

(5 citation statements)

References 10 publications

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“…Chemical time scales (τ chem ) are influenced by the fuel and associated kinetics, and the evaporative time scales (τ evap ) are associated with the fuel's physical and distillate properties. Building on this theory, several recent studies have resolved the competing dynamic phenomena by illuminating the relative competition between chemical-physical, 45 chemical-evaporative, 34 and chemical-evaporative-physical-mixing 46 time scales.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Building on this theory, several recent studies have resolved the competing dynamic phenomena by illuminating the relative competition between chemical-physical, chemical-evaporative, and chemical-evaporative-physical-mixing time scales.…”

Section: Introductionmentioning

confidence: 99%

“…Recent work by Peiffer et al. , investigated four parameters to notionally quantify four key physical processes in the LBO limit: spray breakup, droplet evaporation, extinction, and autoignition. Two of these processes, spray breakup and droplet evaporation, were used to illuminate the holistic evaporation process and time scale ( τ evap ).…”

Section: Introductionmentioning

confidence: 99%

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Lean Blowoff in a Toroidal Jet-Stirred Reactor: Implications for Alternative Fuel Approval and Potential Mechanisms for Autoignition and Extinction

et al. 2020

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Sustainable aviation fuels (SAFs) have been identified as a method to reduce the aviation sector's environmental impact through carbon mitigation. Current certification processes of potential, viable SAFs require labor cost intensive assessments with investigation into combustor performance parameters related to fuel effects such as lean blowoff (LBO) where there exists the competition between multiphase physics and chemical kinetics of the fuel. Recent efforts show LBO effectively scales with the evaporative, mixing, and chemical time scales of a given combustor. Here, a toroidal jet-stirred reactor (TJSR), an experimental configuration meant to emulate perfectly stirred reactor (PSR) studies, is used to study the effects of fuel chemistry physical time scales on LBO while mitigating and minimizing the effects of evaporation mixing, respectively. For this investigation, six fuels/fuel mixtures spanning a range of derived cetane number (DCN) were evaluated in a lean premixed, prevaporized environment with engine relevant characteristics such as recirculation inlet temperature residence times (P = ∼1 atm, T = 460 K, τ = 5.5−6.5 ms). Gas phase emissions sampled within the reactor were measured with a Fourier transform infrared spectrometer to gain insight into relevant trends in species production for varying fuels as leaner conditions were approached. LBO in the TJSR was correlated with the parameters of the DCN and radical index, an indicator of OH production, signifying competition between the chemical processes of autoignition and extinction, respectively; these observations deviate from the established PSR theory for ignition extinction physics. However, the emergence of these correlations in the TJSR experiment support the importance of low temperature chemistry and flame robustness. A physical time scale approach to LBO is applied to the current experiment to elucidate the competition of autoignition and extinction phenomena. Knowledge of the physical LBO time scales and their relationship to chemical fuel properties suggest that the holistic LBO time scale may be viable as a preliminary screening metric for SAF certification.

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Section: ■ Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lean Blowoff in a Toroidal Jet-Stirred Reactor: Implications for Alternative Fuel Approval and Potential Mechanisms for Autoignition and Extinction

et al. 2020

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“…Recent random forest regression (RFR) results on LBO of SAFs in four combustor rigs showed that derived cetane number (DCN) is the most significant feature importance in both the Referee Rig and toroidal jet-stirred reactor at elevated temperatures, and the second most significant feature importance in the Sheffield rig [13,14]. These three rigs show the dominance of chemical timescales near LBO, where chemical timescales are a function of the fuel chemical properties and accompanying thermodynamic conditions.…”

Section: Introductionmentioning

confidence: 99%

“…No previous work has reported results of a comparable number of fuel properties, number of fuels, and the broader implication of their findings at once. Experimental results from testing such fuels can illustrate the maximum FOM sensitivity, aiding in the prescreening and formal evaluation of novel SAFs [10,13,20]. These tests, moreover, can be utilized to advance computational fluid dynamics modeling.…”

Section: Introductionmentioning

confidence: 99%

Orthogonal Reference Surrogate Fuels for Operability Testing

2020

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The approval and evaluation process for sustainable aviation fuels (SAF) via ASTM D4054 is both cost- and volume-intensive, namely due to engine operability testing under severe conditions. Engine operability tests of combustor under figures of merit (FOM) limit phenomena are the fuel effects on lean blowout, high-altitude relight, and cold-start ignition. One method to increase confidence and reduce volume in tiered testing is to use surrogate fuels for manipulation of properties. Key fuel performance properties (surface tension, viscosity, density) for cold-start ignition was determined prior to this study. Prior work regarding this FOM has not considered the combination of these properties. A surface tension blending rule was validated and incorporated into the jet fuel blend optimizer (JudO). A generalized surrogate calculator for N-dimensional surrogate components and features was developed. Jet fuel surrogates developed in this study were a mixture of conventional and sustainable aviation fuels instead of pure components. These surrogates suggested to be tested in this study could illuminate near worst-case effects for sustainable aviation fuel in a given configuration/rig. With those scenarios tested, we can further understand the influence on the key properties relative to cold-start ignition. This work and supporting experimental evidence could potentially lower the barrier for SAF approval processes.

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Experimental study on the impact of alternative jet fuel properties and derived cetane number on lean blowout limit

et al. 2022

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The impact of alternative aviation jet fuels and their properties on lean blowout (LBO) limits has recently raised several questions in the jet fuel area. There is a need for a detailed investigation of the impact of fuel properties on the LBO limit involving actual engine hardware. This study investigates the impact of a range of alternative aviation jet fuels with notable differences in physical and chemical properties and derived cetane number (DCN) on the LBO limit and their effects on key performance indicators. LBO performance results for ten different alternative fuels using a Rolls-Royce single-can Tay combustor are presented in this study. The study also assesses impact of different equivalence ratios and flow rates on LBO, with the aim of determining the impact of a certain range of operating conditions. The results are further analysed to determine the influence of fuel chemical and physical properties on the LBO limit. Finally, based on results in the above experiments, individual fuel properties are adjusted for subsequent experimental analysis of blended fuels. With this approach, 25 additional fuel blends are evaluated and presented, with an emphasis on varying the DCN. This study provides effective data and results to facilitate future fuel optimisation and reduce the risk of a negative performance of new fuels in gas turbines.

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Characteristic Timescales for Lean Blowout of Alternative Jet Fuels

Cited by 8 publications

References 10 publications

Lean Blowoff in a Toroidal Jet-Stirred Reactor: Implications for Alternative Fuel Approval and Potential Mechanisms for Autoignition and Extinction

Lean Blowoff in a Toroidal Jet-Stirred Reactor: Implications for Alternative Fuel Approval and Potential Mechanisms for Autoignition and Extinction

Orthogonal Reference Surrogate Fuels for Operability Testing

Experimental study on the impact of alternative jet fuel properties and derived cetane number on lean blowout limit

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