Analysis of cyclic thermodynamic system combining ammonia gas turbine and transcritical carbon dioxide

Abstract

Ammonia has attracted significant research attention due to its high hydrogen content and lack of elemental carbon. Unfortunately, the thermal efficiency of ammonia gas turbines is relatively low. To address this problem, this paper proposes a cyclic system that combines an ammonia gas turbine with the T-CO2 power cycle. The cycle, based on comprehensive energy distribution and utilization, makes full use of the cooling capacity of liquid ammonia fuel to cool CO2 below the critical point and uses the waste heat of the ammonia gas turbine in stages. The paper begins by establishing and validating a thermodynamic model of the combined cycle. Numerical simulations show that, under the basic operating conditions, the energy efficiency of the combined cycle is 53.44%. Next, an analysis of the regenerator of the bottom cycle shows that it introduces a low heat source, which avoids a pinch point in the regenerator. Finally, the study investigates how different key parameters affect the performance of the combined cycle. A calculation indicates that changing the temperature and pressure of the ammonia turbine inlet increases the efficiency of the combined cycle by up to 32.75%. The maximum efficiency of the combined thermal cycle is 62.42%. For a gas turbine inlet pressure not exceeding 5 bar, a small pressure ratio improves the cycle efficiency.