Isentropic compression means that when the pulse load acting on the surface of the object is slowly loaded, the compression wave inside the compressed object does not evolve into a shock wave with steep wavefront (see shock wave in solid) during the whole measurement time, and the compression process inside the mass is isentropic.
Entropy is a physical quantity representing the directionality of thermodynamic process. The most basic conclusion is that entropy will never decrease in any thermodynamic process. If the process is reversible, the entropy will remain unchanged, otherwise it will increase.
Isentropic is the process that the system changes from state 1 to state 2. If its entropy value is constant, it is called isentropic process, and the change it undergoes is called isentropic change.
Expand:
The isentropic compression technology refers to the compression process inside the material when the pulse load acting on the surface of the object is slowly loaded, and the compression wave in the compressed object does not evolve into a shock wave with steep wavefront during the whole measurement time (see shock wave in solid).
Main methods:
Magnetic field compression technology
It discharges from the capacitor bank to the coil, generating an initial strong magnetic field in the cylindrical cavity. When the system works, the high-grade explosive is detonated by the detonator to drive the cylindrical flyer to fly in the direction of the column axis. Because the flyer is made of good conductor, the initial magnetic field lines trapped in the cavity are not easy to leak into the flyer during the flight of the flyer to the column axis, so the magnetic field lines in the cavity will be continuously "compressed" with the inward movement of the flyer, thus enhancing the magnetic field strength in the cavity. In the above process, the magnetic field near the flyer is always compressed first, but because the disturbance of the electromagnetic field propagates at the speed of light, which is much faster than the speed of the flyer, it can be considered that the compressed magnetic field reaches equilibrium in the whole cavity "instantly". Because of the pressure? P is proportional to the square of magnetic induction intensity B (p=B/4π), so the change of magnetic induction intensity caused by flyer flight will make the central specimen under increasing pressure and be in an isentropic compression state.
Inclined wave generator
A compression wave shaper that can transform a shock wave with a steep wavefront into a scattered wavefront can weaken the influence of entropy increase caused by viscosity and heat conduction loss on the shock wave wavefront and realize the isentropic compression process (Figure 2). The equation of state of the materials used to manufacture the oblique wave generator shall satisfy the following conditions -2.