A Tomographic Method for the Reconstruction of Local Probability Density Functions

A method of obtaining the probability density function (PDF) of local properties from path integrated measurements is described. The approach uses a discrete probability function (DPF) method to infer the PDF of the local extinction coefficient from measurements of the PDFs of the path integrated transmittance. The local PDFs obtained using the method are compared with those obtained from direct intrusive measurements in propylene/air and ethylene/air diffusion flames. The results of this comparison are good

A Small Angle Scattering Sensor System for the Characterization of Combustion Generated Particulate

One of the critical issues for the US space program is fire safety of the space station and future launch vehicles. A detailed understanding of the scattering signatures of particulate is essential for the development of a false alarm free fire detection system. This paper describes advanced optical instrumentation developed and applied for fire detection. The system is being designed to determine four important physical properties of disperse fractal aggregates and particulates including size distribution, number density, refractive indices, and fractal dimension. Combustion generated particulate are the primary detection target; however, in order to discriminate from other particulate, non-combustion generated particles should also be characterized. The angular scattering signature is measured and analyzed using two photon optical laser scattering. The Rayleigh-Debye-Gans (R-D-G) scattering theory for disperse fractal aggregates is utilized. The system consists of a pulsed laser module, detection module and data acquisition system and software to analyze the signals. The theory and applications are described

Adoption of AI-empowered industrial robots in auto component manufacturing companies

The usage of AI-empowered Industrial Robots (InRos) is booming in the Auto Component Manufacturing Companies (ACMCs) across the globe. Based on a model leveraging the Technology, Organisation, and Environment (TOE) framework, this work examines the adoption of InRos in ACMCs in the context of an emerging economy. This research scrutinises the adoption intention and potential use of InRos in ACMCs through a survey of 460 senior managers and owners of ACMCs in India. The findings indicate that perceived compatibility, external pressure, perceived benefits and support from vendors are critical predictors of InRos adoption intention. Interestingly, the study also reveals that IT infrastructure and government support do not influence InRos adoption intention. Furthermore, the analysis suggests that perceived cost issues negatively moderate the relationship between the adoption intention and potential use of InRos in ACMCs. This study offers a theoretical contribution as it deploys the traditional TOE framework and discovers counter-intuitively that IT resources are not a major driver of technology adoption: as such, it suggests that a more comprehensive framework than the traditional RBV should be adopted. The work provides managerial recommendations for managers, shedding light on the antecedents of adoption intention and potential use of InRos at ACMCs in a country where the adoption of InRos is in a nascent stage

Scalar properties in the overfire region of sooting turbulent diffusion flames

The scalar structure of the overfire (fuel-lean) region of sooting turbulent diffusion flames was investigated, considering ethylene and acetylene burning in air. Measurements and predictions are reported of the mean concentrations of major gas species and mean soot volume fractions. Predictions were based on the conserved-scalar formalism in conjunction with the laminar flamelet approximation. The comparison between predictions and measurements was encouraging, suggesting that state relationships for major gas species, found in laminar diffusion flames, were preserved in the overfire region of the turbulent flames. Measurements also indicated nearly constant soot generation efficiencies from point to point in the overfire region for sufficiently long characteristic residence times to yield nearly universal soot volume fraction state relationships at the same conditions. However, effects attributed to finite-rate chemistry were observed at shorter characteristic residence times, causing spatial variations of soot generation efficiencies in the overfire region, with associated loss of universal soot volume fraction state relationships.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27157/1/0000152.pd

Stochastic aspects of turbulent combustion processes

Methods of using stochastic simulations to treat nonlinear interactions in turbulent combustion processes are described -- emphasizing the use of statistical time-series techniques to analyze the turbulence--radiation interactions of nonpremixed flames. Three aspects of the problem are considered, as follows: the statistics of scalar properties in turbulent flames, the formulation of algorithms to stimulate flame radiation based on flame statistics, and evaluation of the methodology using recent measurements for nonluminous flames. It is shown that the process becomes tractable through the laminar flamelet approximation whereby all scalar properties are taken to be solely functions of a conserved scalar like the mixture fraction. Thus, the simulations are designed to generate realizations of mixtures fractions along radiations path with the radiation properties of each realization found using a narrow-bond radiation model. An autoregressive process that reproduces probability density functions and spatial and temporal correlations of mixture fraction was found to yield reasonably good predictions of the statistical properties of spectral radiation intensities measured for turbulent carbon monoxide and hydrogen jet flames burning in still air. Although the approach appears to be promising, additional development is needed in order to treat some of the unique statistical features of turbulence that are not encountered during conventional use of statistical time-series techniques.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29477/1/0000563.pd

Temperature / soot volume fraction correlations in the fuel-rich region of buoyant turbulent diffusion flames

Instantaneous soot volume fractions and temperatures were measured in the fuel-rich (underfire) region of turbulent nonpremixed acetylene, propylene, ethylene, and propane flames burning in still air. Large-scale, highly buoyant, pool-like flames were considered, having characteristic residence times greater than 250 ms and burner exit Richardson numbers greater than 18. Measurements were made using an optical probe than involved laser extinction for soot volume fractions and two-wavelength pyrometry for temperatures. Strong correlations were found between soot volume fractions and temperatures for each fuel-relatively independent burner operating conditions and position in the underfire region. This behavior is supportive of the existence of nearly universal relationships between soot volume and mixture fractions in the underfire region of turbulent nonpremixed flames having large characteristic residence times. Underfire soot is largely confined to a narrow range of mixture fractions (yielding a soot spike) and temperatures. The latter observation supports approximations of constant-temperature soot layers that have been proposed in teh past for estimates of continuum radiation from soot-containing diffusion flames.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28441/1/0000228.pd

Soot volume fractions in the overfire region of turbulent diffusion flames

Overfire soot volume fractions and mixture fractions, flame heights, and characteristic flame residence times, were measured for turbulent acetylene, propylene, ethylene and propane diffusion flames burning in still air. Test conditions ranged from highly buoyant pool-like flames to buoyant jet flames, using three burners (with exit diameters of 5, 50, and 234 mm) and a wide range of fuel flow rates. Soot generation efficiencies (the percentage of fuel carbon converted to soot and emitted from the flame) were uniform throughout the overfire region for a given flame condition. Soot generation efficiencies increased with increasing flame residence times but tended to approach asymptotic values for residence times roughly ten times longer than residence times at the normal smoke point. Within the asymptotic region, soot volume fractions are directly related to mixing levels, analogous to the laminar flamelet concept for nonpremixed flames, which offers substantial simplifications for analysis of the continuum radiation properties of the overfire region.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28438/1/0000225.pd

Generalized state relationships for scalar properties in nonpremixed hydrocarbon/air flames

Generalized state-relationship correlations giving the mass fractions of major gas species (N2, O2, fuel, CO2, H2O, CO, and H2) and temperature as functions of local fuel-equivalence ratios were studied for hydrocarbon---air diffusion flames. The data base included existing measurements in laminar methane, propane, n-heptane, acetylene, and ethylene flames burning in air (or N2/O2 mixtures) with burner configurations involving porous cylinders in crossflow, coflowing round jet flames, and flat-laminar diffusion flames. Reasonably good generalized state-relationship correlations were found for major gas species over the available data base, which included molar fuel H/C ratios in the range 1-4 and fuel-equivalence ratios in the range 10-2-102. Typical of state relationships for particular fuels, the generalized state relationships approximated thermodynamic equilibrium for fuel-lean conditions and departed from equilibrium in a relatively universal manner for near-stoichiometric and fuel-rich conditions. Temperature state-relationship correlations were also reasonably good, over the more limited available data base, in view of uncertainties concerning radiative heat losses from the test flames and thermocouples. The results should be useful for estimating the scalar properties and the infrared gas-band radiation properties of laminar and turbulent hydrocarbon/air diffusion flames--the latter in conjunction with the laminar flamelet concept.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28328/1/0000087.pd