How is reheat accomplished in a gas turbine?

Reheat in a gas turbine is accomplished by heating the gases between the high-pressure (HP) turbine and the low-pressure (LP) turbine. This process takes advantage of the gas that has just passed through the HP turbine, which has experienced a significant drop in temperature and pressure. By reheating this gas, the energy content is increased before it enters the LP turbine.

This reheating allows the turbine to extract more energy from the gas as it expands through the LP turbine, effectively increasing the overall efficiency and power output of the turbine cycle. The reheat step is critical as it optimizes the work done by the LP turbine, leading to improved thermal efficiency.

The other choices suggest alternative methods of heating or expanding the gases, but they do not align with the standard practice of reheating in gas turbines, which specifically occurs between the HP and LP turbines to maximize energy extraction efficiently.