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<p>This paper focuses on the numerical investigation of the effects of flight speed fluctuations on the intake system performance of the scramjet demonstrator developed in the Universidade Federal do Rio Grande do Norte (UFRN). A set of 2D-RANS simulations based on equations of continuity, momentum, and energy was used to model the airflow, with the turbulence evaluated by the k-kl-ω transition model. The airflow regime was modeled as stationary and the atmospheric air under the conditional hypothesis of calorically perfect gas or non-equilibrium gas (if applicable). Three different design and off-design flight conditions were studied at Mach numbers of 6.4, 6.8 (design speed), and 7.2, considering horizontal flight at an altitude of 30&#xa0;km. Several airflow phenomena are presented, such as flow fields of thermodynamic properties and velocity (Mach number), shock wave structures, and compression performance coefficients. The results showed an increase in pressure and temperature ratios with relative speed reduction at the isolator. The air mass admitted at the isolator was reduced for off-design speeds due to shock structures repositioning, significantly affecting the combustion performance, promoting air mass losses of about 8% at lower flight velocities. The shock/boundary layer interaction at high velocities provokes a separation region next to the cowl, causing air mass losses lower than 1% and accentuating local heating, above the melting limits of most engineering materials. Strong shock trains at the isolator were observed, presenting more intense wall pressure oscillations for higher flight velocities. However, the flow remained supersonic for all analyzed conditions obtaining effective stabilization, in this case, using an isolator 370&#xa0;mm long. High compression performance was obtained for coefficients of adiabatic compression efficiency, within a range from 83% (Mach 6.4) to 85% (Mach 7.2), and kinetic energy efficiency, with values approximately constant, about 93,1%. These results expose velocity fluctuation limits of 5% around the design condition to reduce the excessive air mass losses and local heating of the cowl, with a lower impact on compression performance.</p>

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Performance of the mixed compression intake system of a scramjet demonstrator at different off-design flight speeds

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年8月4日

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  • Ítalo Sabino Arrais Bezerra,
  • Sandi Itamar Schafer de Souza,
  • Paulo Gilberto de Paula Toro

摘要

This paper focuses on the numerical investigation of the effects of flight speed fluctuations on the intake system performance of the scramjet demonstrator developed in the Universidade Federal do Rio Grande do Norte (UFRN). A set of 2D-RANS simulations based on equations of continuity, momentum, and energy was used to model the airflow, with the turbulence evaluated by the k-kl-ω transition model. The airflow regime was modeled as stationary and the atmospheric air under the conditional hypothesis of calorically perfect gas or non-equilibrium gas (if applicable). Three different design and off-design flight conditions were studied at Mach numbers of 6.4, 6.8 (design speed), and 7.2, considering horizontal flight at an altitude of 30 km. Several airflow phenomena are presented, such as flow fields of thermodynamic properties and velocity (Mach number), shock wave structures, and compression performance coefficients. The results showed an increase in pressure and temperature ratios with relative speed reduction at the isolator. The air mass admitted at the isolator was reduced for off-design speeds due to shock structures repositioning, significantly affecting the combustion performance, promoting air mass losses of about 8% at lower flight velocities. The shock/boundary layer interaction at high velocities provokes a separation region next to the cowl, causing air mass losses lower than 1% and accentuating local heating, above the melting limits of most engineering materials. Strong shock trains at the isolator were observed, presenting more intense wall pressure oscillations for higher flight velocities. However, the flow remained supersonic for all analyzed conditions obtaining effective stabilization, in this case, using an isolator 370 mm long. High compression performance was obtained for coefficients of adiabatic compression efficiency, within a range from 83% (Mach 6.4) to 85% (Mach 7.2), and kinetic energy efficiency, with values approximately constant, about 93,1%. These results expose velocity fluctuation limits of 5% around the design condition to reduce the excessive air mass losses and local heating of the cowl, with a lower impact on compression performance.