Development of a CFD solver for simulating the cavitating nitrogen flow inside a cutting tool in cryogenic turning

Turning is one of the most common processes in manufacturing field. Many efforts has been done in order to improve the cooling techniques. Titanium alloys, mainly because of their poor thermal conductivity, need to be cut at relatively low cutting speeds, with obvious negative consequences on the profitability of machining. Cryogenic cooling, normally with liquid nitrogen, proved promising results for this issue. Cooling with LN2 has many advantages such as cheap refrigeration, omitting issues related to environmental contamination of conventional coolants, and prevention of potential oxidation on the finished surface by removing O2. The present document focuses on CFD analysis of the cavitating coolant from the reservoir till the beginning of a spray jet through a cutting tool in MUSP Organization. Modeling the cavitating cryogenic flows have been concern of different industries. However, there are no specific commercial software for the cryogenic fluids. Besides, the cryogenic cavitating flow necessitates additional modifications on the existing solvers of the common fluids according to the condition that are comprehensively discussed within this study; Slight temperature changes affect and the thermodynamics of the fluid. Therefore, corresponding physics demand special equations related to the so called “thermodynamic effects” which are discussed and introduced within the present thesis. Afterwards, a new OpenFOAM code is developed and introduced. So far, the published articles considered two approaches for the effect of temperature changes to the saturation pressure and the other thermodynamic effects. They either estimated the thermodynamic properties changes proportional to slight temperature difference of their study scale, or they adjoined a thermodynamic property calculator software to their main code. On the other hand, in the present study, Schnerr-Sauer mass transfer correlation based on critical radius cavitation algorithm is utilized in a pimple algorithm calculating the thermodynamic properties in the range of 65 to 125K for the nitrogen flow. Considering that the different industrial usage of this substance is about 80-100K, this code can be widely used in larger scales than this project. Moreover, unlike the previous corresponding papers, compressibility of the non-saturated phases are well considered in VOF analysis. Besides, some crucial thermo-properties of the fluid like specific heat capacity are updated with the temperature changes and applied for the later equations. Moreover, instead of solving the time-consuming full energy equation, the simplified non-cavitating version of temperature distributing formula is applied before each pimple iteration and the latent heat of cavitation is updated by the nominal temperature drop model. On the other hand, this free solver attached to the open source frame work, OpenFOAM, can easily be mounted on a USB and run on any machine without any legal expense or additional software. This combination of formula in the mentioned algorithm is done for the first time. The request of this study is originated for a lathe machine of Titanium alloys in Piacenza of the same organization.