Alkali metal atoms show an intense natural fluorescence in the burned gas region of internal combustion engines. This fluorescence offers great opportunity for spectroscopic combustion analysis in internal combustion engines without the requirement of laser excitation or image intensifiers. To quantify this fluorescence intensity, spectroscopic and thermodynamic properties of the alkali metals lithium (Li), sodium (Na), potassium (K), rubidium (Rb) and cesium (Cs) and their oxidation products and ions were analyzed. Collisional energy transfer and reabsorption effects (including temperature- and pressure-dependent lineshapes) were calculated over the range of engine environments. Three compounds containing Li, Na and K, respectively, were selected as fuel additives for engine experiments. The experiments were conducted on an optical, single-cylinder, spark-ignited, direct-injection research engine, and the fluorescence of the three alkali components was recorded simultaneously using three complimentary metal-oxide semiconductor high-speed cameras. The two-component fluorescence intensity ratios (Na/K, Li/K and Na/Li) are shown to depend on temperature, pressure and equivalence ratio. However, the three-component ratio Na·Li/K2 is nearly independent of pressure and equivalence ratio in the tested range of operating conditions and can serve as a direct marker for burned gas temperature. Subsequently, equivalence ratio can be determined from any of the bicomponent fluorescence ratios.
DrakeMCFanslerTDPetersonKH. Stratified ignition processes in spray-guided SIDI engines. In: 9th Internationales Symposium für Verbrennungsdiagnostik [9th international symposium on internal combustion diagnostics], Baden-Baden, Germany, June 2010, pp.9–19. Mainz-Kastel: AVL Deutschland GmbH.
8.
ZengWIdicheriaCAFanslerTD. Conditional analysis of enhanced combustion luminosity imaging in a spray-guided gasoline engine with high residual fraction. SAE International 2011-01-1281, 2011.
9.
ReissingJKechJMMayerK. Optical investigations of a gasoline direct injection engine. SAE paper 1999-01-3688, 1999.
10.
BeckKWHeidenreichTBuschS. Spectroscopic measurements in small two-stroke SI engines. SAE paper 2009-32-0030/20097030, 2009.
11.
MosburgerMSickVDrakeMC. Quantitative high-speed burned gas temperature measurements in internal combustion engines using sodium and potassium fluorescence. Appl Phys B: Laser O2012; DOI 10.1007/s00340-012-5266-4.
CarabettaRKaskanW. Chemi-excitation of sodium in flames. Symp Combust Proc1967; 11(1): 321–333.
15.
TsuchiyaSKurataniK. Excitation and quenching of sodium atoms behind a shock wave. Combust Flame1964; 8: 299–310.
16.
CopleyGKibbleBPKrauseL. Experimental evidence for the absence of quenching of sodium resonance radiation by inert gas. Phys Rev1967; 163(1): 34–35.
17.
JenkinsDR. The determination of cross sections for the quenching of resonance radiation of metal atoms. I. Experimental method and results for sodium. P Roy Soc A: Math Phys1966; 293(1435): 493–511.
18.
WinansJG. Die Auslöschung der Natriumfluoreszenz durch Fremdgas. Z Phys1930; 60: 631–641.
19.
JenkinsDR. The determination of cross sections for the quenching of resonance radiation of metal atoms II. Results for potassium, rubidium and caesium. P Roy Soc A: Math Phys1968; 303(1475): 453–465.
20.
HooymayersHPLijnsePL. The relationship between the fluorescence yield and the underpopulation of doublet excited states. J Quant Spectrosc Ra1968; 9: 995–1009.
21.
LijnsePL. Electronic excitation transfer collisions in flames—VI. Interpretation of the temperature dependence of alkali-quenching by N2 and general conclusion about the energy transfer mechanism. J Quant Spectrosc Ra1974; 14: 1143–1155.
22.
GreigJR. The sodium D-line reversal method of temperature measurement in ionized flame gases. Brit J Appl Phys1965; 16: 957–964.
23.
LijnsePLVan der MaasC. Electronic excitation transfer collisions in flames. II. Temperature dependence of the quenching of Na (3P)-doublet by H2 and O2. J Quant Spectrosc Ra1972; 13: 741–746.
24.
LijnsePLZeegersPJTAlkemadeCTJ. Electronic-excitation transfer collisions in flames. V. Cross sections for quenching and doublet mixing of K(4P) doublet by N2, H2, O2 and H2. J Quant Spectrosc Ra1974; 14(10): 1079–1083.
25.
JenkinsDR. The determination of cross-section for the quenching of resonance radiation of metal atoms. IV. Results for lithium. P Roy Soc A: Math Phys1968; 306: 413–421.
26.
LijnsePLElsenaarRJ. The temperature dependence of the quenching of Na-D-doublet by N2 and H2O in flames of 1500–2500 K. J Quant Spectrosc Ra1971; 12: 1115–1128.
27.
LijnsePLZeegersPJTAlkemadeCTJ. Electronic-excitation transfer collisions in flames. III. Cross sections for quenching and doublet mixing of Rb (5P) doublet by N2, H2, O2 and H2O. J Quant Spectrosc Ra1973; 13(10): 1033–1045.
28.
LijnsePLZeegersPJTAlkemadeCTJ. Electronic-excitation transfer collisions in flames. IV. Cross sections for quenching and doublet mixing of Cs (6P) doublet by N2, H2, O2 and H2O. J Quant Spectrosc Ra1973; 13(12): 1301–1304.
29.
GlarborgPMarshallP. Mechanism and modelling of the formation of gaseous alkali sulfates. Combust Flame2004; 141: 22–39.
30.
KaskanWE. The reaction of alkali atoms in lean flames. Symp Combust Proc1965; 10(1): 41–46.
31.
BulewiczEMJamesCGSugdenTM. Photometric investigations of alkali metals in hydrogen flame gases. II. The study of excess concentrations of hydrogen atoms in burnt gas mixtures. P Roy Soc A: Math Phys1956; 235(1200): 89–106.
32.
JamesCGSugdenTM. Photometric investigation of alkali metals in hydrogen flame gases. I. A general survey of the use of resonance radiation in the measurement of atomic concentrations. P Roy Soc A: Math Phys1955; 227(1170): 312–329.
33.
HynesAJSteinbergMSchofieldK. The chemical kinetics and thermodynamics of sodium species in oxygen-rich hydrogen flames. J Chem Phys1983; 80(6): 2585–2597.
34.
GurvichLVBergmanGAGorokhovLN. Thermodynamic properties of alkali metal hydroxides. Part 1. Lithium and sodium hydroxides. J Phys Chem Ref Data1996; 25(4): 1211–1276.
35.
GurvichLVBergmanGAGorokhovLN. Thermodynamic properties of alkali metal hydroxides. Part II. Potassium, rubidium, and cesium hydroxides. J Phys Chem Ref Data1997; 26(4): 1031–1110.
36.
ChaseMW. NIST-JANAF thermochemical tables (J Phys Chem Ref Data monograph no. 9). 4th ed.1998. Woodbury, NY: American Institute of Physics for the National Institute of Standards and Technology.
HofmannFKohnH. Optical cross sections of resonance lines emitted by flames under conditions of partial thermal ionization. J Opt Soc Am1961; 51(5): 512–521.
39.
MosburgerM. Alkali metal spectroscopy for high-speed imaging of burned gas temperature, equivalence ratio and mass fraction burned in internal combustion engines. PhD Dissertation, University of Michigan, Ann Arbor, MI, 2013.
40.
DecJCoyEB. OH radical imaging in a DI diesel engine and the structure of the early diffusion flame. SAE paper 960831, 1996.
DahlanderPLindgrenR. Multi-hole injectors for DISI engines: nozzle hole configuration influence on spray formation. SAE paper 2008-01-0136, 2008.
43.
StachTSchlerferJVorbachM. New generation multi-hole fuel injector for direct-injection SI engines—optimization of spray characteristics by means of adapted injector layout and multiple injection. SAE paper 2007-01-1404, 2007.
