Generation of Turbulence in a RCEM towards Engine Relevant Conditions for Premixed Combustion Based on CFD and PIV Investigations

Kammermann, Thomas; Koch, Jann; Wright, Yuri M.; Soltic, Patrik; Boulouchos, Konstantinos

doi:10.4271/2017-24-0043

Cited by 12 publications

(13 citation statements)

References 42 publications

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“…An optically accessible RCEM with cylinder bore of 84mm, flat piston and maximal stroke of 249mm was used to compress methane/air charge and achieve engine-like conditions. A detailed description of the machine is available in [14].…”

Section: The Rapid Compression-expansion Machine (Rcem)mentioning

confidence: 99%

Effect of methane on pilot-fuel auto-ignition in dual-fuel engines

Srna

Bolla²,

Wright³

et al. 2019

Proceedings of the Combustion Institute

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The ignition behavior of n-dodecane micro-pilot spray in a lean-premixed methane/air charge was investigated in an optically accessible Rapid Compression-Expansion Machine at dual-fuel engine-like pressure/temperature conditions. The pilot fuel was admitted using a coaxial single-hole 100µm injector mounted on the cylinder periphery. Optical diagnostics include combined high-speed CH 2 O-PLIF (10kHz) and Schlieren (80kHz) imaging for detection of the firststage ignition, and simultaneous high-speed OH* chemiluminescence (40kHz) imaging for high-temperature ignition. The aim of this study is to enhance the fundamental understanding of the interaction of methane with the auto-ignition process of short pilot-fuel injections. Addition of methane into the air charge considerably prolongs ignition delay of the pilot spray with an increasing effect at lower temperatures and with higher methane/air equivalence ratios. The temporal separation of the first CH 2 O detection and high-temperature ignition was found almost constant regardless of methane content. This was interpreted as methane mostly deferring the cool-flame reactivity. In order to understand the underlying mechanisms of this interaction, experimental investigations were complemented with 1D-flamelet simulations using detailed chemistry, confirming the chemical influence of methane deferring the reactivity in the pilot-fuel lean mixtures. This shifts the onset of first-stage reactivity towards the fuel-richer conditions. Consequently, the onset of the turbulent cool-flame is delayed, leading to an overall increased high-temperature ignition delay. Overall, the study reveals a complex interplay between entrainment, low-T and high-T chemistry and micro-mixing for dual-fuel autoignition processes for which the governing processes were identified.

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Section: The Rapid Compression-expansion Machine (Rcem)mentioning

confidence: 99%

Effect of methane on pilot-fuel auto-ignition in dual-fuel engines

Srna

Bolla²,

Wright³

et al. 2019

Proceedings of the Combustion Institute

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“…The RCEM is a generic free-floating piston test rig (bore: 84 mm, variable stroke: 120 -249 mm) with optical accessibility through piston and cylinder head windows. A brief description of the machine and its operation principle is provided here, while further descriptions are available in [20,32,33].…”

Section: Rapid Compression-expansion Machinementioning

confidence: 99%

“…The homogeneity of the mixture temperature in this RCEM has been investigated in previous studies [20], reporting temperature homogeneity better that 3 K before compression. PIV investigations of the RCEM flow field reported quiescent conditions throughout the cycle [33].…”

Section: Rapid Compression-expansion Machinementioning

confidence: 99%

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Optical Investigation of Sooting Propensity of n-Dodecane Pilot/Lean-Premixed Methane Dual-Fuel Combustion in a Rapid Compression-Expansion Machine

Srna¹,

Bruneaux²,

Rotz³

et al. 2018

SAE Int. J. Engines

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The sooting propensity of dual-fuel combustion with n-dodecane pilot injection in a lean-premixed methane-air charge has been investigated using an optically accessible Rapid Compression-Expansion Machine to achieve engine relevant pressure and temperature conditions at start of pilot injection. A Diesel injector with a 100 µm single-hole coaxial nozzle, mounted at the cylinder periphery, has been employed to admit the pilot fuel.The aim of this study was to enhance the fundamental understanding of soot formation and oxidation processes of n-dodecane in presence of methane in the air charge by parametric variation of methane equivalence ratio, charge temperature and pilot fuel injection duration. The influence of methane on ignition delay and flame extent of the pilot fuel jet has been determined by simultaneous OH* chemiluminescence and Schlieren imaging. The sooting behavior of the flame has been characterized using the 2D-DBI imaging methodology. The apparent soot black-body temperature has been measured 1D-resolved along the injector axis by applying an imaging spectrograph.Addition of methane into the air charge considerably prolongs the ignition delay with an increasing effect under less reactive conditions and with higher methane equivalence ratios. Therefore, the influence of methane on the formation of soot is two-fold: in case of short pilot injection, the presence of methane was found to decrease the soot formation due to the leaner pilot fuel mixture at time of ignition. For longer pilot fuel injections, methane enhances the soot production by decreasing oxygen availability and introducing additional carbon. In all cases, methane strongly defers the oxidation of soot due to the lower availability of oxygen.

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“…Due to the long filling process, however, almost no flow and turbulence is present in the cylinder at the start of compression. Options to create a flow field and turbulence at TDC (top dead center) position exist, but its effects are quite limited [24,25]. True RCMs (rapid compression machines), which do not exist in the involved research institutes, differ from RCEMs by locking the piston at the end the compression stroke.…”

Section: Introductionmentioning

confidence: 99%

The Flex-OeCoS—a Novel Optically Accessible Test Rig for the Investigation of Advanced Combustion Processes under Engine-Like Conditions

et al. 2020

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A new test rig has been designed, built and commissioned, and is now jointly pursued to facilitate experimental investigations into advanced combustion processes (i.e., dual fuel, multi-mode) under turbulent conditions at high, engine-like temperature and pressure levels. Based on a standard diesel engine block, it offers much improved optical access to the in-cylinder processes due to its separated and rotated arrangement of the compression volume and combustion chamber, respectively. A fully variable pneumatic valve train and the appropriate preconditioning of the intake air allows it to represent a wide range of engine-like in-cylinder conditions regarding pressures, temperatures and turbulence levels. The modular design of the test rig facilitates easy optimizations of the combustion chamber/cylinder head design regarding different experimental requirements. The name of the new test rig, Flex-OeCoS, denotes its Flexibility regarding Optical engine Combustion diagnostics and/or the development of corresponding Sensing devices and applications. Measurements regarding in-cylinder gas pressures, temperatures and the flow field under typical operating conditions are presented to complete the description and assessment of the new test rig.

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Generation of Turbulence in a RCEM towards Engine Relevant Conditions for Premixed Combustion Based on CFD and PIV Investigations

Cited by 12 publications

References 42 publications

Effect of methane on pilot-fuel auto-ignition in dual-fuel engines

Effect of methane on pilot-fuel auto-ignition in dual-fuel engines

Optical Investigation of Sooting Propensity of n-Dodecane Pilot/Lean-Premixed Methane Dual-Fuel Combustion in a Rapid Compression-Expansion Machine

The Flex-OeCoS—a Novel Optically Accessible Test Rig for the Investigation of Advanced Combustion Processes under Engine-Like Conditions

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