Measurement of black carbon emissions from multiple engine and source types using laser-induced incandescence : sensitivity to laser fluence

A new regulatory standard for non-volatile particulate matter (nvPM) mass-based emissions from aircraft engines has been adopted by the International Civil Aviation Organisation. One of the instruments used for the regulatory nvPM mass emissions measurements in aircraft engine certification tests is the Artium Technologies LII 300, which is based on laser-induced incandescence. The LII 300 response has been shown in some cases to vary with the type of black carbon particle measured. Hence it is important to identify a suitable black carbon emission source for instrument calibration. In this study, the relationship between the nvPM emissions produced by different engine sources and the response of the LII 300 instrument utilising the auto-compensating laser-induced incandescence (AC-LII) method was investigated. Six different sources were used, including a turboshaft helicopter engine, a diesel generator, an intermediate pressure test rig of a single-sector combustor, an auxiliary power unit gas turbine engine, a medium-sized diesel engine, and a downsized turbocharged direct-injection gasoline engine. Optimum LII 300 laser fluence levels were determined for each source and operating condition evaluated. It was found that an optimised laser fluence can be valid for real-time measurements from a variety of sources, where the mass concentration was independent of laser fluence levels covering the typical operating ranges for the various sources. However, it is important to perform laser fluence sweeps to determine the optimum fluence range as differences were observed in the laser fluence required between sources and fuels. We discuss the measurement merits, variability, and best practices in the real-time quantification of nvPM mass concentration using the LII 300 instrument and compare that with other diagnostic techniques, namely absorption-based methods such as photoacoustic spectroscopy (using a photoacoustic extinctiometer, PAX, and a micro soot sensor, MSS) and thermal-optical analysis (TOA). Particle size distributions were also measured using a scanning mobility particle sizer (SMPS). Overall, the LII 300 provides robust and consistent results when compared with the other diagnostic techniques across multiple engine sources and fuels. The results from this study will inform the development of updated calibration protocols to ensure repeatable and reproducible measurements of nvPM mass emissions from aircraft engines using the LII 300

Study of the lineshape of the chi(c1) (3872) state

A study of the lineshape of the chi(c1) (3872) state is made using a data sample corresponding to an integrated luminosity of 3 fb(-1) collected in pp collisions at center-of-mass energies of 7 and 8 TeV with the LHCb detector. Candidate chi(c1)(3872) and psi(2S) mesons from b-hadron decays are selected in the J/psi pi(+)pi(-) decay mode. Describing the lineshape with a Breit-Wigner function, the mass splitting between the chi(c1 )(3872) and psi(2S) states, Delta m, and the width of the chi(c1 )(3872) state, Gamma(Bw), are determined to be (Delta m=185.598 +/- 0.067 +/- 0.068 Mev,)(Gamma BW=1.39 +/- 0.24 +/- 0.10 Mev,) where the first uncertainty is statistical and the second systematic. Using a Flatte-inspired model, the mode and full width at half maximum of the lineshape are determined to be (mode=3871.69+0.00+0.05 MeV.)(FWHM=0.22-0.04+0.13+0.07+0.11-0.06-0.13 MeV, ) An investigation of the analytic structure of the Flatte amplitude reveals a pole structure, which is compatible with a quasibound D-0(D) over bar*(0) state but a quasivirtual state is still allowed at the level of 2 standard deviations

Measurement of the CKM angle γγ in B±→DK±B^\pm\to D K^\pm and B±→Dπ±B^\pm \to D π^\pm decays with D→KS0h+h−D \to K_\mathrm S^0 h^+ h^-

A measurement of $CP$-violating observables is performed using the decays $B^\pm\to D K^\pm$ and $B^\pm\to D \pi^\pm$, where the $D$ meson is reconstructed in one of the self-conjugate three-body final states $K_{\mathrm S}\pi^+\pi^-$ and $K_{\mathrm S}K^+K^-$ (commonly denoted $K_{\mathrm S} h^+h^-$). The decays are analysed in bins of the $D$-decay phase space, leading to a measurement that is independent of the modelling of the $D$-decay amplitude. The observables are interpreted in terms of the CKM angle $\gamma$. Using a data sample corresponding to an integrated luminosity of $9\,\text{fb}^{-1}$ collected in proton-proton collisions at centre-of-mass energies of $7$, $8$, and $13\,\text{TeV}$ with the LHCb experiment, $\gamma$ is measured to be $\left(68.7^{+5.2}_{-5.1}\right)^\circ$. The hadronic parameters $r_B^{DK}$, $r_B^{D\pi}$, $\delta_B^{DK}$, and $\delta_B^{D\pi}$, which are the ratios and strong-phase differences of the suppressed and favoured $B^\pm$ decays, are also reported

Study of the doubly charmed tetraquark T+cc

Quantum chromodynamics, the theory of the strong force, describes interactions of coloured quarks and gluons and the formation of hadronic matter. Conventional hadronic matter consists of baryons and mesons made of three quarks and quark-antiquark pairs, respectively. Particles with an alternative quark content are known as exotic states. Here a study is reported of an exotic narrow state in the D0D0π+ mass spectrum just below the D*+D0 mass threshold produced in proton-proton collisions collected with the LHCb detector at the Large Hadron Collider. The state is consistent with the ground isoscalar T+cc tetraquark with a quark content of ccu⎯⎯⎯d⎯⎯⎯ and spin-parity quantum numbers JP = 1+. Study of the DD mass spectra disfavours interpretation of the resonance as the isovector state. The decay structure via intermediate off-shell D*+ mesons is consistent with the observed D0π+ mass distribution. To analyse the mass of the resonance and its coupling to the D*D system, a dedicated model is developed under the assumption of an isoscalar axial-vector T+cc state decaying to the D*D channel. Using this model, resonance parameters including the pole position, scattering length, effective range and compositeness are determined to reveal important information about the nature of the T+cc state. In addition, an unexpected dependence of the production rate on track multiplicity is observed

Numerical study of confined laminar CH4/air diffusion flames established in an inverted burner

Several experimental studies have demonstrated that confined laminar diffusion flames established in an inverted burner are very stable and emit soot when the global equivalence ratio exceeds a critical value. An inverted diffusion flame can be used as a stable source of soot particles for development and intercomparison of various particle sizing techniques. Unlike normal coflow diffusion flames fired upward, inverted diffusion flames fired downward experience a negative gravity, the resultant flow fields are very different, and the residence time is significantly prolonged. The different flow fields in normal and inverted diffusion flames mean that the flame structure and soot formation characteristics are significantly different. This study makes a first attempt to numerically investigate the flame properties and soot formation in confined laminar coflow CH4/air diffusion flames established in an inverted axisymmetric burner at atmospheric pressure. A fairly detailed reaction mechanism, GRI Mech 3.0, was used to model combustion chemistry. Soot formation was modeled using a semi-empirical, acetylene-based, two-equation soot model. Radiation heat transfer was calculated using the discrete-ordinates method and a wide-band non-gray gas model. Numerical calculations were conducted over a relatively narrow range of global equivalence ratio of 0.54-0.67 based on a recent experimental study. The heat transfer boundary condition was found to be important to the prediction of soot emission and the velocity distribution. Using measured temperature distribution along the quartz tube, the numerical model successfully predicted the emission of soot under the conditions investigated and revealed the flow, temperature, and species concentration distributions in the inverted coflow diffusion flames for the first time. However, the predicted primary soot particle diameters are significantly smaller than those reported in the literature based on TEM images analysis of sampled soot. The discrepancies between the numerical results and experimental data can be attributed to the deficiency of the simple soot model and the approximate treatment of the heat transfer boundary conditions at the quartz tube. Copyright \ua9 Crown.Peer reviewed: YesNRC publication: Ye

The effect of particle aggregation on the absorption and emission properties of mono- and polydisperse soot aggregates

This study concerns the effect of soot-particle aggregation on the soot temperature derived from the signal ratio in two-color laser-induced incandescence measurements. The emissivity of aggregated fractal soot particles was calculated using both the commonly used Rayleigh-Debye-Gans fractal-aggregate theory and the generalized Mie-solution method in conjunction with numerically generated fractal aggregates of specified fractal parameters typical of flame-generated soot. The effect of aggregation on soot temperature was first evaluated for monodisperse aggregates of different sizes and for a lognormally distributed aggregate ensemble at given signal ratios between the two wavelengths. Numerical calculations were also conducted to account for the effect of aggregation on both laser heating and thermal emission at the two wavelengths for determining the effective soot temperature of polydisperse soot aggregates. The results show that the effect of aggregation on laser energy absorption is important at low fluences. The effect of aggregation on soot emissivity is relatively unimportant in LII applications to typical laminar diffusion flames at atmospheric pressure, but it can become more important in flames at high pressures due to larger primary particles and wider aggregate distributions associated with enhanced soot loading. \ua9 2011 Her Majesty the Queen in Right of Canada.Peer reviewed: YesNRC publication: Ye

A numerical study of laminar methane/air triple flames in two-dimensional mixing layers

Triple flames formed in methane/air mixing layers with three different mixture fraction gradients were investigated by numerical simulation. The primitive variable method, in which the fully elliptic governing equations were solved with detailed chemistry and complex thermal and transport properties, was used. Radiation heat transfer from CO2, CO and H2O was calculated using the discrete-ordinates method coupled to a statistical narrow band correlated-K based wide band model. The results show that with the increase of the mixture fraction gradient, the combustion intensity in the diffusion flame branch of a triple flame is enhanced. In the near-stoichiometric mixture fraction region, the local burning flux of a triple flame is reduced when the mixture fraction gradient is increased. However, when the mixture fraction is significantly different from the stoichiometric value, the local burning flux increases as the mixture fraction gradient is increased. The correlation of the burning speed versus stretch rate established from conventional homogeneous premixed flames cannot completely explain the phenomena observed in triple flames. The interaction between the diffusion and premixed flame branches significantly affects the local burning velocity in regions where the mixture fraction is far from the stoichiometric value in a triple flame. This interaction is caused by both conduction heat transfer and radical exchange. Radiation has negligible effect on local burning properties in a triple flame.NRC publication: Ye

The effect of reformate gas enrichment on extinction limits and NOx formation in counterflow CH4/air premixed flames

The reformate gas enriched counterflow lean premixed CH4/air flames were studied by numerical simulation in this paper. The reformate gas was assumed to be the product of partial oxidation of methane by air, and it consists of H2, CO and N2. Detailed chemistry and complex thermal and transport properties were employed. The results indicate that the addition of the reformate gas enlarges the flammable region, and extends the lean flammability limit of counterflow CH4/air premixed combustion. When the reformate gas is added, the formation of NO is reduced in a near-stoichiometric flame, and increased in an ultra-lean flame at a constant equivalence ratio. The more significant advantage of the reformate gas enriched lean premixed combustion is that it greatly reduces the formation of NO by allowing a combustor to operate at leaner condition without any effect on flammable range. Further, the addition of the reformate gas decreases the formation of NO2 and N2O at a constant equivalence ratio.NRC publication: Ye

Evaluation of the laminar diffusion flamelet model in the calculation of an axisymmetric coflow laminar ethylene-air diffusion flame

A numerical study of an axisymmetric coflow laminar ethylene-air diffusion flame at atmospheric pressure was conducted using detailed chemistry and complex thermal and transport properties and two different methodologies: (1) the direct simulation method of solving the two-dimensional axisymmetric elliptic governing equations, and (2) the steady-state stretched diffusion flamelet model. Soot formation and radiative heat transfer were not taken into account in these calculations, both for simplicity and to avoid the complications associated with the issues of how to incorporate these chemical and physical processes into the flamelet model. The same reaction mechanism and thermal and transport properties were used in the 2D direct simulation and the generation of the flamelet library. The flamelet library was generated from the solutions of counterflow ethylene-air diffusion flames at a series of stretch rates. Results of the 2D direct simulation and the flamelet model are compared in physical space. Although the overall results of the flamelet model are qualitatively similar to those of the direct simulation, significant differences exist between the results of the two methods even for temperature and major species. The direct simulation method predicts that the peak concentrations of CO2 and H2O occur in different regions in the flame, while the flamelet model results show that the peak concentrations of CO2 and H 2O occur in the same region. The flamelet model predicts an overly rapid approach to the equilibrium structure in the downstream region, leading to significantly higher flame temperatures. The main reason for the failure of the flamelet model in the downstream region is due to the neglect of the effects of multidimensional convection and diffusion and the fundamental difference in the chemical structure between a coflow diffusion flame and a counterflow diffusion flame. The findings of this paper are highly relevant to understanding the flamelet model results in the calculations of multidimensional turbulent diffusion flames.NRC publication: Ye