Group uses both experimental and numerical tools to study a variety of problems related to sprays and multiphase flows. A detailed list of facilities available with this group is available in this page. You are encouraged to see the list of equipment and software available with group. Please contact us if you need to use to use these facilities.
Spray & atomization is an important aspect in several engineering applications, viz. liquid fuel combustion, bio-medical application, manufacturing processes, etc. In our group, we are investigating both primary and secondary breakup in sprays. Our work spans over both experimental and numerical investigation of sprays. We use high-fidelity computer modelling to simulate primary breakup of round jet and sheet-based atomizers. We have also used high speed videography and laser based investigations to characterize evaporating and non-evaporating sprays. We have two constant volume spray chambers; one for pulsed sprays and the other for continuous sprays. In-house VOF based CFD solvers have been developed to simulate primary breakup of sprays. Novel GPU based parallelization has been pursued to enhance the solver speeds. Some of our related work are given below.
VOF based two-phase CFD solver were developed to study primary breakup of sprays. Initially, a 2D in-house solver was developed that used PLIC based geometric reconstruction to track the liquid gas interface. Two different linear system solver algorithms were implemented: (a) multigrid method algorithm, (b) symmetric Gauss Siedel preconditioned conjugate gradient (SGSPCG) algorithm. GPU based parallelization was implemented to enhance the computational speed of the solver. Primary breakup of diesel like 2D jets and air blast atomizers were studied. Rayleigh-Taylor (RT) and Kelvin-Helmholtz (KH) instabilities were observed in these breakups. Moreover, pre-film atomization was also studied and it was found that the droplet size distribution after the primary breakup follows a log-normal distribution.
Characteristics of evaporating spray emanating from a Gasoline Direct Injection system was studied using high speed videography and laser based diagnostics. Sprays from iso-octane, ethanol and n-butanol were investigated. Both liquid and vapour penetration lengths were estimated using high speed video in conjunction with schlieren and shadowgraph techniques. In-house Matlab based code has been developed to estimate the penetration lengths. It was found that butanol has the longest penetration length when compared followed by ethanol and finally iso-octane showed the smallest penetration length. Likewise, PDPA measurements also showed that butanol sprays had the largest droplets. Thermo-physical properties like latent heat of evaporation, degree of superheat of fuel injection, etc. significantly affected the spray morphology. Lastly, fuel injected under hot injection condition can lead to flash evaporation. Flash evaporation leads to a rapid disintegration of the sprays and leads to much smaller droplet size distribution.
Experimental and numerical investigation of combustion process in SI and CI engine has been performed. Combustion characteristics of alternative fuels, especially butanol has been performed. Experimental studies include in-cylinder combustion visualization using a optically accessible engine. Numerical investigation consisted of developing combustion chemical kinetics and implementing a unsteady flamelet based combustion model.
Experimental in-cylinder combustion visualization was performed for a GDI engine. Spray plume morphology and subsequent combustion was studied. It was found that due to longer liquid penetration length of butanol, significant amount of piston head wetting was observed. This led to a yellow sooty flame. However, under hot engine condition, piston wetting significantly decreased due to flash evaporation. Crank resolved Spatially Integrated Natural flame Luminosity (SINL) analysis clearly showed that at elevated temperatures, the combustion shifts to a more pre-mixed combustion type. One of the important conclusions of this work was that a delayed injection strategy should be followed for butanol under high load condition and flash evaporation helps in improved combustion characteristics for hard to atomize fuels like butanol.
Unsteady flamelet based combustion model has been used to simulate in-cylinder combustion of CI engines. A 246 species and 1062 reaction combustion kinetic mechanism was developed to simulate the combustion of n-butanol/n-dodecane mixture. This mechanism was thoroughly validated based on ignition delay and speciation data. Subsequently, this mechanism was integrated with a 3D CFD solver using the unsteady flamelet model. Coupled Eulerian-Lagrangian approach was used to simulate turbulent combustion of n-butanol/n-dodecane blended sprays. In-cylinder combustion showed that at higher blend ratios, NOx emissions decrease. Significant decrease in soot emission was observed for all blend ratios.
A broad range of activities are covered in this head. Some of the work that is being pursued are sloshing of liquid in a partially filled tank, fluid mechanics in physical separation of minerals in hydro-cyclones, heat and mass transfer in cryogenic storage tanks, etc. Both experimental and numerical studies have been pursued to investigate these problems.
Sloshing of liquid in partially filled tanks generates forces that are of interest in both automotive, marine and aerospace industries. Liquid sloshing generates large forces on the tank walls, which in turn may result in large unbalance forces and noise. In the automotive industry, this noise is particularly considered as an irritant to passenger comfort. A multi-physics approach was taken to model splash noise under such conditions. Two-phase CFD modelling was used to generate transient pressure data which was then used to estimate wall vibration using FEM analysis. Finally, computational acoustics was used to simulate noise transmission to far field. Modelling capabilities were validated using high speed videography and dynamic pressure measurement.
Characteristics of evaporating spray emanating from a Gasoline Direct Injection system was studied using high speed videography and laser based diagnostics. Sprays from iso-octane, ethanol and n-butanol were investigated. Both liquid and vapour penetration lengths were estimated using high speed video in conjunction with schlieren and shadowgraph techniques. In-house Matlab based code has been developed to estimate the penetration lengths. It was found that butanol has the longest penetration length when compared followed by ethanol and finally iso-octane showed the smallest penetration length. Likewise, PDPA measurements also showed that butanol sprays had the largest droplets. Thermo-physical properties like latent heat of evaporation, degree of superheat of fuel injection, etc. significantly affected the spray morphology. Lastly, fuel injected under hot injection condition can lead to flash evaporation. Flash evaporation leads to a rapid disintegration of the sprays and leads to much smaller droplet size distribution
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