Thermodynamic coupling mechanisms in precooled turbine-based combined cycle: From fuel properties to multi-objective performance characterization

The Precooled Turbine-Based Combined Cycle (PCTBCC) synergistically integrates precooled turbine engine with bypass ramjet, establishing itself as a pivotal hypersonic propulsion solution. This study systematically analyzes the thermodynamic parameters coupling mechanisms and optimizes the precooling strategy of PCTBCC, demonstrating a 33.6% improvement in specific impulse. Based on unified parametric benchmarks, the critical Mach numbers and propulsion performance of methane, hydrogen, ammonia, and methanol fuels are evaluated, which quantitatively elucidates the impact mechanisms of fuel thermophysical properties on propulsion performance. The results reveal that PCTBCC exhibits a 45.2% performance advantage over ramjets. Furthermore, this research establishes mapping relationships between fuel combinations’ thermophysical properties and propulsion performance/storage requirements, delineating the theoretical performance ceiling for multi-fuel PCTBCC. The results indicate that specific fuel combinations achieve a 25% reduction in storage volume compared to pure hydrogen while maintaining balanced performance parameters, including a critical Mach number of 4.03 and a specific impulse of 2191 s.