Experimental Study of Ignition and Combustion Characteristics of a Diesel Pilot Spray in a Lean Premixed Methane/Air Charge using a Rapid Compression Expansion Machine
“…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].…”
“…Various aspects of dual-fuel combustion (Diesel pilot ignited) have been studied up to date in complete engines [5][6][7], single cylinder engines [8][9][10][11][12][13][14][15], optical engines [15][16][17][18] as well as rapid compression machines [19][20][21]. The approach of most of the engine experiments was to substitute part of the Diesel fuel (by reducing the injection duration) with premixed methane while monitoring the exhaust emissions and heat release rate.…”
Section: Introductionmentioning
confidence: 99%
“…Dual-fuel combustion experimental research in optically accessible test rigs mostly focused on the influence of methane on ignition Page 2 of 17 03/02/2018 delay [19][20][21], flame spreading rate [17,[19][20][21]23] and shape of the combustion front [17]. Only a few optical studies investigating incylinder dual-fuel combustion sooting propensity have been published up to date with the available data mostly limited to natural luminosity imaging [15,23] and two-color pyrometry [24].…”
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.
“…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].…”
“…Various aspects of dual-fuel combustion (Diesel pilot ignited) have been studied up to date in complete engines [5][6][7], single cylinder engines [8][9][10][11][12][13][14][15], optical engines [15][16][17][18] as well as rapid compression machines [19][20][21]. The approach of most of the engine experiments was to substitute part of the Diesel fuel (by reducing the injection duration) with premixed methane while monitoring the exhaust emissions and heat release rate.…”
Section: Introductionmentioning
confidence: 99%
“…Dual-fuel combustion experimental research in optically accessible test rigs mostly focused on the influence of methane on ignition Page 2 of 17 03/02/2018 delay [19][20][21], flame spreading rate [17,[19][20][21]23] and shape of the combustion front [17]. Only a few optical studies investigating incylinder dual-fuel combustion sooting propensity have been published up to date with the available data mostly limited to natural luminosity imaging [15,23] and two-color pyrometry [24].…”
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.
“…The wall temperature is measured by a total of six type K thermocouples, two located in the cylinder head and four in the liner. Very good temperature homogeneity has been observed [22], with a standard deviation of the gas temperature in the order of 3 K. It was found that the distribution of temperature is barely affected by the gas in-flow due to its slow speed. An initial gas temperature equal to the wall temperature is achieved due to the long duration of the intake process.…”
“…Finally, piston 4 contains the compressed air that drives the machine. Details on the operation principle of the RCEM can be found in [22]. The technical characteristics of the RCEM can be seen in Table 1.…”
ElsevierDesantes Fernández, JM.; García Oliver, JM.; Vera-Tudela-Fajardo, WM.; López Boulouchos, K. (2016). Study of the auto-ignition phenomenon of PRFs under HCCI conditions in a RCEM by means of spectroscopy. Applied Energy. 179:389-400.
AbstractAn investigation of the effects of contour conditions and fuel properties on the auto-ignition and combustion process under HCCI conditions is presented in this study. A parametric variation of initial temperature, intake pressure, compression ratio, oxygen concentration and equivalence ratio has been car-
ried out for Primary Reference Fuels in a Rapid Compression ExpansionMachine while applying spectroscopy. The results have also been contrasted with natural chemiluminescence measurements. Additionally, the experiments have been simulated in CHEMKIN and the results derived from the optical techniques have been compared with the results from the chemical kinetics of the process, validating the chemical kinetic mechanism and an additional sub-model of excited OH * . Two different scenarios can be seen according to the results from the spectrograph. For very lean or very low- * Corresponding author
N-dudecane pilot-ignited lean-premixcd nnlurnl-gas combustion has heen invcstigulecl in a rapid compression-expansion machine. The aim or this study was to characterize the combustion spectral footprint : identify the main sources or na(ural luminosity, characterize the lcmpoml brightness evolution, and providc guidance for the evaluation of nmural lum inosity imaging acquisitions. Nutural luminosity spectra in the range of 280-610 nm were acquired, 1 D-rcsolvcd along the injector ax is, using an imuging spectrograph and intensified high-specd camera. Four significant contributions to lhe noiura l luminosity wcre idcntificd: Soot, OH* and CH* chemilumincsçcnce, as well as overlapping hrnadbaml chemilum incscence of C02*, CHO* and Cli iO• s pecies. The CH* chemiluminescence could be only dctccted nt ign ition and during the pilot-fuel combustion period. Similarly, iniliul OH*. and broadhand luminosity wcrc also detected at ignition. 1-lowevcr. this lum ino~ity .idditionally incnmscd lale in the cycle, when methane. cnrichcd wilh diluted pilot-fuel, lbrms an extensive burnl zone with close-to-stoichiomctry conditions. For the ignition delay dctcction, imnging of broadband luminosity hus 10 be recomrnended si ncc m ignition il shows a highel' 1-Lsc-rate thun the OH* chemiluminescence. 1t was shown llrnt. aller ignition, in dual-fuel combusti on. the coupling hetween the nalurnl luminosity and heat release-ratc is too wcak to extract usefül in formatio n. The natural llame luminosily originales !rom the emission or sevcral spccies emittîng i1, a wide range of wavclcnglhs. In spnrk-Îgnited premixed-comhustion cngines. several studies investigaled the llume and spark•plasma spcclra [ 1]. Within the varîety of combustion concepts fenturing auto-ignition. the spectral footprînl of non•sooting Homogcm:ous-Chargc Compression• Ignition (HCC I) is must thoroughly investigateagc 1
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