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Researchers : Dooseung Kim, Sanghyuk Nam, Hakseon Lee
Motivation & Objectives
- Nuclear power plants have played an important role in power generation even though many risks are involved with them.
- Due to the risks, many countries are planning to enforce policies of decommissioning nuclear power plants and the laser cutting process rose a way to dismantle the facilities remotely.
- For the laser cutting tools, the behavior of assist gas is highly related to their performances.
- To develop the remote-dismantling process of nuclear power plants, we have to model the operation circumstances of the process and build numerical analysis techniques to evaluate the results accurately in both qualitative and quantitative perspectives.
- The objectives are
: Model operating circumstances of laser cutting process and build strategies for numerical analysis.
: Analyze the flow fields after the assist gas ejected out of the nozzle tip.
: Identify the design parameters and find the optimal shape of the supersonic jet nozzle which maximizes thrust.
Designing a nozzle
<Simulation configuration>
< Parameters of the simple-LAVAL nozzle >
- There are 7 design parameters of the simplified-LAVAL nozzle
: Diameters(D) of inlet, outlet and throat
: Angles(theta) of inlet and outlet
: Lengths(L) of inlet and outlet
: Using constraints, the parameters are reduced from seven to three.
- There is an optimal shape of the supersonic nozzle which maximizes thrust about 2~3 times than the base case.
- For the optimal case, the force in x-direction gets 2.5 times larger than the base case.
Flow fields
- The contours of average (gauge) pressure(P), density(rho) and Mach number(Ma) field near the material wall.
Evaluation of under-water laser cutting with supersonic assist gas
Evaluate cutting performance with temperature and wall shear stress at cutting area
<Domain - Air cutting>
<Domain - Underwater cutting>
<Absolute Pressure - Air>
<Absolute Pressure - Underwater>
<Mach number - Air>
<Mach number - Underwater>
<Temperature Contours>
(a) Carbon steel Underwater cutting, (b) Carbon steel Air cutting, (c) Stainless steel Underwater cutting, (d) Stainless steel Air cutting
Evaluation of laser cutting with combustion gas as assist gas
To supply thermal energy to the cutting area
<H2+Air combustion from aerospike nozzle>
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