Abstract
Gun barrels are subjected to time-varying high-intensity heat flux under multiple firing, which may damage the material and limit the overall performance of the gun. In order to monitor the thermal state of a gun barrel, an inverse method coupling the finite difference method with the sequential function specification method was developed to estimate the unknown time-varying heat flux imposed on the inner wall of a gun barrel. A two-layer hollow cylindrical tube was assumed with the convection heat transfer boundary condition on the outer wall of the tube. A direct heat transfer model was developed, and was used to estimate the temporal distribution of boundary heat flux in approximately real time based on the measured transient temperature at some positions on the outer wall of the gun barrel. Numerical tests were performed to verify the effectiveness and reliability of this method by investigating the influence of temperature measurement noises and future time step selection. The results show that the proposed method has high precision and efficiency in extracting the time-varying heat flux under one-shot and three-shot firing conditions. When there is a measurement noise, this method has good anti-illness characteristics and can achieve better results by appropriately selecting the value of a future time step.
Highlights
In engineering, some thermal equipment with a hollow-cylindrical shape experiences extremely severe thermal shock
Fast changing heat flux wave can cause degradation of estimation accuracy. The reason for this is that, a larger value of r can smooth the inversion result, it creates deterministic error and is likely to cause some information of rapid heat flux changes to be lost
When the measurement noise is large, the inversion results might be improved by adjusting the value of a future time step r and step size ∆τ
Summary
Some thermal equipment with a hollow-cylindrical shape experiences extremely severe thermal shock. Corrosion effects and thermal stress induced by transient high-intensity heat flux may damage the material and limit the overall performance of a thermal system. In cylindrical gun barrels, the high temperature occurring at the commencement of rifling is the primary cause of gun barrel erosion. The large heat input from multiple firing can cause damage to the gun material, especially the very thin chrome layer that coats on the inner wall of the gun barrel, e.g., melting, cracking, erosion, and wear. A large temperature gradient may exist between the inner and outer walls of the gun barrel, generating great thermal stress [3,4], which may cause damage to the Energies 2018, 11, 3332; doi:10.3390/en11123332 www.mdpi.com/journal/energies
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