Research

Research Interest

• Fuel spray modeling
• Injector nozzle flow modeling
• Two phase flow modelling
• Combustion modelling of different fuels
• Injection strategies
• Optimization of Engine performance and emissions
• Fuel spray visualization
• Injection rate measurement
• Image processing
• Micro reactor modelling
• Air Conditioning and Mechanical Ventilation (ACMV)
• Indoor Air Quality (IAQ)

Internal Nozzle flow

The fuel injection system in diesel engines has a consequential effect on the fuel consumption, combustion process and formation of emissions. Cavitation and turbulence inside a diesel injector plays a critical role in primary spray breakup and development processes. Thus understanding the phenomenon of cavitation is significant in capturing the injection process with accuracy. The two-phase mixture model by Schnerr and Sauer was adopted along with k-ε turbulence model in Fluent CFD package to solve the governing equations numerically.

Flash boiling simulations were performed using Converge CFD employing Homogeneous Relaxation Model (HRM) coupled with the Volume of Fluid (VOF) approach. Simulations considered the effect of turbulence, cavitation, flash-boiling, compressibility and non-condensable gases under transient needle lift. To model turbulence, the RNG k-ε model was used. The simulation is capable of capturing the ROI accurately with upstream pressure boundary condition and transient needle lift profile.

Experimental spray investigation

The analysis of spray images is done in two stages, (i) processing of spray images using custom code written in Matlab and (ii) quantifying spray characteristics using ImageJ code. The sequence of steps involved in image processing is shown in Fig. The spray visualization equipment designed and developed for this purpose is shown below.

Rate of injection

The rate of injection was measured using the mmentum flux method. In complement to injection rate, this method can be used to characterize teh hydraulic coefficients like discharge coefficient, area coefficient and velocity coefficient. The key advantage of this method over other methods is that the hole-to-hole variation can be measured.

Fuel Spray Modeling

A new hybrid spray model was implemented by coupling the cavitation induced spray sub model to KHRT spray model. This new model was implemented into KIVA4 CFD code. The new spray model was extensively validated against the experimental data of non-vaporizing and vaporizing spray obtained from constant volume combustion chamber (CVCC) available in literature as well with in-house experimental data.

Converge CFD code has also been employed to model the diesel and gasoline injector sprays.

Engine Modelling

The Engine simulations were done using multi-dimensional CFD code KIVA-4 coupled with CHEMKIN-II code to solve chemical kinetics. The KIVA and CHEMKIN codes are coupled in order to solve the detailed chemical reaction mechanism of different fuels. At each time step, the KIVA code gives the species concentrations and their thermodynamic properties calculated at each cell of the computational domain to the CHEMKIN code. In return the CHEMKIN code gives back the newly calculated species values to the KIVA code after solving the reactions.

Micro reactor modelling

A novel energy efficient heterogeneous gaseous T-junction micro reactor was designed which uses inlet flow pulsations. By feeding the same amount of reactant and same pumping power/parasitic loads, the new design was able to run two micro reactors and could achieve almost the same level of performance as that of a steady flow micro reactor with an expense of one micro reactor.

Indoor air quality (IAQ)

A hybrid air treatment system incorporating a cooling system is introduced for tropical climates. The air treatment system (ATS) comprises an ozone-based oxidation process and an air scrubbing device. The air purification process has been experimentally investigated. Experimental results demonstrated the feasibility of the proposed ATS to provide improved indoor air quality. The reduced outdoor air intake facilitates a higher chilled water supply temperature resulting in an improved chiller performance and reduction of cooling load. The energy consumption performance of the proposed hybrid ATS air-conditioning system has been evaluated for an office building experiencing tropical climatic conditions. The cooling load on a design day has demonstrated that the reduction of outdoor air intake enabled marked energy savings potential in terms of the cooling demand. By analysing the building performance based on tropical climatic data, an annual energy consumption saving of up to 64.6 kW h/m2 can be achieved via the hybrid ATS air-conditioning system.