Modeling of neural network of enclosed space vessel
Modeling is divided into two parts; Part 1 will measure the steady state flow and this comes from solving the conservation equations and gets output representing steady state flow at each point in a certain plane in the garage of the ship. These equations are solved using the CFD giving the steady state percentage of CO at different positions, different loads and different ventilation situations. All this is the static part but, in our case to make the model and control we have to work on the dynamic model because any change in the system will not happen at once so we have time delay based on the time constant of the system (?_d) and another delay time due to the flow of ventilator air to the sensor point (?_v).
So flow rate will be calculated from different sources, ventilation source and this will be a dynamic equation represented as a first order system based on the dimension of ship and ventilation flow rate.
Every car and bus will make a concentration of air flow at the sensor point. So the total flow at steady state will be the summation of all flow rate available.
Time at steady state to remove ( change) air condition at certain point tss = volume/Qx sec where x is the distance between the ventilator and the sensor and so Qx is the flow of air across the distance x and so the delay time( time from start of ventilation till the sensor senses variation in flow and it depends on the velocity) td= x/vx where vx is the velocity of air flow and ? = tss/4.
Static model of air flow is given by
?/(?x_i ) (?u_i ?)=?/(?x_i ) (Ã_(? ) ??/(?x_i ))+S_?
where (?) is the general variable for the general conservation form, (?) is the density, (ui) the velocity vector components, (??) is the effective exchange coefficient of (?) and (S?) the source rate per unit volume. For example (?) could be continuity of gas flow CO or pure air with the assumptions in the reference[7]. Then the conservation equation takes the following general form:
?/?t (?Y_i )+?(?v ?Y_i )=-?J_i+R_i+S_i
where
(Ri) is the net rate of production of species (i),
(Si) is the rate of creation by addition from the dispersed phase, and
(Yi) is the local mass fraction of each species, for ith number of species
v ?
?J_i
By solving these equations, using the CFD making finite elements and calculating flow distribution from cars and buses and ventilators and calculating the concentration of CO in different positions at different loads. All these calculations at steady state condition(i.e. number of cars are constant and the speed of the ventilator is constant too)
If the distance between the ventilator “V” and point “P” is “x”. The percentage of the airflow produced from the ventilator “V” will reach this point moving a distance “x”. and so there is a time constant of ventilation system at measuring point “?_v”and this is the dynamic delay. The same is done for the cars and buses and so Qt will be as shown
where
Kv, Kc, Kb: Constants of ventilator, cars and buses
?_v,?_c,?_b:Time constants ofventilator,cars and buses
Total flowrate(Q_t) at P_1=?_1.Q_v+?_(i=1)^(n_c)???_i.Q_c+?_(j=1)^(n_b)???_j.Q_b ??
where
?_1, ?_i, ?_j: Percentage of quantity of flow of ventilators, cars and buses
Q_v: Quantity of flow of ventilator
Q_c: Quantity of flow of car
Q_b: Quantity of flow of bus
n_c: Number of cars
n_b: Number of buses
??_c, ?_b