Numerical calculation of fire flue gas filling in ship engine room with multilayer structure

Based on large eddy simulation, the filtered balance equations and the Smagorinsky subgrid-scale model of fire in ship engine room with multilayer structure were established.Second-order finite difference method was used to disperse spatial variables, explicit second-order predictor-corrector scheme method was used to disperse flow variables, and explicit second-order Runge-Kutta method was used to disperse time variables.Velocity field, temperature field, flue gas concentration and the height of flue gas layer were solved respectively, and the change laws of fire flue gas filling in ship engine rooms with multilayer structure and monolayer structure were analyzed.Analysis result shows that the spread speed and area of flue gas in multilayer structure are greater than those in monolayer structure.When ship engine room with monolayer structure is full of flue gas, filling time is 200 s, while the filling time of ship engine room with multilayer structure is 1 500 s.Under two structures, the temperatures of cold air layer and hot flue gas layer almost increase at first then decrease, the maximum temperatures at the tops of ship engine rooms are 170 ℃, 250 ℃ respectively, however, the maximum temperatures at the bottoms of ship engine rooms are 175 ℃, 100 ℃ respectively.