A liquid fuel combustor based on the FLOX ® gas turbine burner concept has been developed for application in a Micro Gas Turbine (MGT) Range Extender (REX) for next generation cars. The characterization of this combustor was performed at the High Pressure Optical Test rig (HIPOT) at DLR Stuttgart. Spray characteristics were measured using droplet mie scattering and phase Doppler interferometry in flames of a stable burner operation point (BOP) at a pressure, preheat temperature, global lambda (G), and jet velocity of 3.5 bars, 300 °C, 1.45 and 120 m/s respectively. The experimental results showed long flames with deep penetration of the spray into the combustion chamber. A comprehensive data set of the spray characteristic with well-defined boundary condition was made available for CFD simulations. The CFD simulation of the two-phase flow was performed by coupling the DLR liquid phase simulation code SPRAYSIM with the commercial CFD-code ANSYS CFX-16.1. The comparison of axial and radial velocity profiles between simulation and experiment clearly showed that the turbulence model used in the numerical simulation was unable to predict the measured turbulence appropriately. The calculated and measured spray behavior in the combustion chamber showed satisfying agreement. The observed differences were mainly due to the simple 1-step global combustion model, which predicted an early onset of the heat release. The simulation showed that even though a large portion of the evaporation happened already inside the nozzle, the remaining spray droplets penetrate deep into the combustion chamber.

Abstract-In India, more than 300 million people use Devanagari script for documentation. In Devanagari script, Marathi and Hindi are mainly used as primary language of Maharashtra state and national language of India respectively. As compared with English script, Devanagari script is reach of morphemes. Thus the lemmatization of Devanagari script is quite complex than that of English script. There is lack of resources for Devanagari script such as WordNet, ontology representation, parsing the keywords and their part of speech. Thus the overall task of information retrieval becomes complex and time consuming. Devanagari script document always carries suffixes which may cause problem in accurate information retrieval. We propose a method of extracting root words from Devanagari script document which can be used for information retrieval, text summarization, text categorization, ontology building etc. An attempt is made to design the Morphological Analyzer for Devanagari script. We have designed CORPUS containing more than 3000 possible stop words and suffixes for Marathi language. Morphological Analyzer can acts as a preliminary stage for developing any information retrieval application in Devanagari script. We have conducted the experiments on randomly selected Marathi documents and we found the accuracy of designed morphological analyzer is up to 96%.

Thermoacoustic stability analysis is an essential part of the engine development process. Typically, thermoacoustic stability is determined by hybrid approaches. These approaches require information on the flame dynamic response. The combined approach of advanced System identification (SI) and Large Eddy Simulation (LES) is an efficient strategy to compute the flame dynamic response to flow perturbation in terms of the Finite Impulse Response (FIR). The identified FIR is uncertain due in part to the aleatoric uncertainties caused by applying SI on systems with combustion noise and partly due to epistemic uncertainties caused by lack of knowledge of operating or boundary conditions. Carrying out traditional uncertainty quantification techniques, such as Monte Carlo, in the framework of LES/SI would be computationally prohibitive. As a result, the present paper proposes a methodology to build a surrogate model in the presence of both aleatoric and epistemic uncertainties. Specifically, we propose a univariate Gaussian Process (GP) surrogate model, where the final trained GP takes into account the uncertainty of SI and the uncertainty in the combustor back plate temperature, which is known to have considerable impact on the flame dynamics. The GP model is trained on the FIRs obtained from the LES/SI of turbulent premixed swirled combustor at different combustor back plate temperatures. Due to the change in the combustor back plate temperature the flame topology changes, which in turn influences the FIR. The trained GP model is successful in interpolating the FIR with confidence intervals covering the "true" FIR from LES/SI.

A theoretical investigation of the effect of gas velocity oscillations on droplet number density and evaporation rate is presented. Oscillations in gas velocity cause a number density wave, i.e. an inhomogeneous, unsteady variation of droplet concentration. The number density wave, as it propagates downstream at the mean flow speed, causes modulation of the local evaporation rate, creating a vapour wave with corresponding oscillations in equivalence ratio. The present work devises an analytical formulation of these processes. Firstly, the response of a population of droplets to oscillations in the gas velocity is modelled in terms of a number density wave. Secondly, the formulation is extended to incorporate droplet evaporation, such that an analytical expression for the evaporation rate modulation is obtained. Subsequently, the droplet 1D convection-diffusion transport equation with the calculated evaporation source term is solved using an appropriate Green’s function to determine the resulting equivalence ratio perturbations. The dynamic response of equivalence ratio fluctuations to velocity oscillations is finally characterized in terms of a frequency-dependent transfer function. The aforementioned analytical approach relies on a number of simplifying approximations, nevertheless it was validated with good agreement against 1D Euler-Lagrange CFD simulations.

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