This paper presents numerical simulation of underwater shock wave propagation nearby complex rigid wall. The Ghost Fluid Method (GFM) for the treatment of complex rigid wall is developed. The theoretical analysis on the GFM-based algorithm and relevant numerical tests demonstrate that the GFM-based algorithm is first-order accurate as applied to complex rigid wall. A large number of challenging numerical tests show that the GFM-based algorithm is robust and quite simple in various practical problems. The numerical results on shock wave propagation in the vicinity of rigid wall are verified by comparing to exact solution and the results by body-fitted-grid method.
An
analysis was conducted on the relationship between the calorific
value of different types of coal and the theoretical air requirement.
It was found that the theoretical air volume required for generating
the same amount of heat during combustion is the same for different
types of coal. The concept of the air/coal ratio was improved by proposing
the concept of the air/carbon ratio, which refers to the ratio of
the mass of air to the mass of carbon during complete combustion;
the ratio is approximately 11.5 kg/kg (mass ratio), being roughly
constant for different types of coal, unlike the air/coal ratio showing
a significant change with coal types. The total air flow rate in a
boiler changed with load demand, and the influence of different fuel
types can be neglected at the same load level. On this basis, an air
flow rate control strategy for coal-fired utility boilers was proposed
and implemented in the boiler in which the air flow rate required
to the furnace is a function of the unit load. Experiments conducted
in a 300 MWe coal-fired utility boiler confirm that the use of the
control strategy of the air flow rate for the combustion optimization
improves the stability of the main steam pressure and mitigates the
fluctuations of the coal flow. These results provide a foundation
for the implementation of a new strategy of air/coal decoupling and
independent control of boiler combustion.
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