Executive Summary : | Liquid film evaporation on hot surfaces is widely seen in engineering applications and processes. Fuel film formation in engine manifolds of Port fuel injection (PFI) engines, film formation and sooting in gasoline direct injection (GDI) and diesel engines, dry out of flow in tubes of nuclear reactors, rapid spray cooling of hot ingots for surface hardening, cooling of high-power electronics and other systems are some examples of the same. In spite of the engineering importance of this topic, it was not possible since recently to accurately measure the film thickness of dynamic and evaporating films. The theoretical models are thus not well validated or tuned with experimental data and thus not reliable for use in practical applications. Recent developments in micro-fabrication techniques have made it possible to manufacture accurate optical devices for measurement of film thickness down to a value less than 5 micron starting from a value of around 100 micron. The advancement in thermal imaging technique has on the other hand made it possible to measure temperature distribution with high resolution and at a reasonable sampling frequency. A combination of these two can give a wealth of data to accurately measure the thermo-fluid-dynamics of an evaporating liquid film. This proposal aims to develop a simple experimental setup and make measurement of film thickness along with the temperature distribution of static and dynamic films on a heated surface. The project will be executed in three phases. In the first phase, measurement of gently deposited film on a hot surface will be conducted. Measurements will include measurement of film thickness, temperature distribution of films of water, single component fuels and multi-component fuel surrogate of gasoline. In the second phase, the measurement of the film thickness of a drop impacting on a surface will be performed. The third phase will involve measurement of a film formed by an impacting drop onto a hot surface.
The combined measurement of film thickness and surface temperature of an evaporating film can give very good guidance to the modelling approach for film evaporation. Hence, this will be valuable for the research community working on modelling of processes which involve film evaporation in practical devices like engines, spray cooling in different applications, etc. It will also help design engineers of automotive wet components where estimates on time required for evaporation of thin films are often necessary. On the other hand, the measurements will also enable a better understanding of the thermo-fluid-dynamics involved in film evaporation process. |