Optimizing Ariane Turbopump Design with Fidelity CFD

Space exploration has always been a frontier driven by precision and innovation. Among the critical components of space launchers are turbopumps, which ensure the seamless and efficient flow of propellants to rocket engines, enabling the incredible thrust necessary to escape the Earth's gravity. However, designing turbopumps comes with unique challenges. From mitigating cavitation to handling dangerous rotation speeds and pressure rises, these components must be flawlessly engineered to operate under extreme conditions. Currently, computational fluid dynamics (CFD) tools are significantly advancing turbomachinery design and validation processes. This blog examines the role of advanced CFD technologies, such as Fidelity CFD, utilized by ArianeGroup for the Vinci hydrogen turbopump within the Ariane 6 space launcher, pushing boundaries in turbomachinery design and performance.

The Ariane Program and Ariane 6’s Versatility

The Ariane program, launched in the 1970s, has revolutionized European space exploration by ensuring independent access to space. Managed by ArianeGroup, it has successfully launched thousands of satellites and missions over five decades. Ariane 6 aims to build on this legacy with enhanced efficiency and cost-effectiveness, featuring mission flexibility, reduced production costs, and advanced technologies to stay competitive in global markets.

 A standout element of Ariane 6 is the Vinci Engine, a next-generation cryogenic engine developed through collaboration with European partners under the European Space Agency (ESA) program. This innovative engine, which operates on liquid hydrogen (LH₂) and liquid oxygen (LOx), can function at two thrust conditions—130kN and 180kN—and is re-ignitable, making it suitable for complex missions requiring multiple orbital insertions.

Additionally, the Vinci hydrogen turbopump (TPH) exemplifies cutting-edge engineering, operating at a rotation speed of around 90,000 rpm and achieving a pressure rise of up to 60 bar while generating roughly 3,600 kW of power. Its design includes an inducer for efficient low-pressure flow handling, two centrifugal stages for propellant compression, and a subsonic axial turbine for power generation. The development of the turbopump has utilized extensive testing and advanced CFD modeling, significantly reducing the need for costly physical testing.

Evolution of Ariane Turbopump Design with Fidelity CFD

ArianeGroup forged a decades-long partnership with NUMECA, now part of Cadence, to optimize various stages of turbomachinery design through CFD. This collaboration has enabled cost-effective design iterations and ensured models meet the extreme requirements of rocket propulsion systems.

Here’s how Fidelity CFD tools transformed Vinci turbopump development in three different stages:

Stage 1: Vinci TPH Development

The steady performance of Vinci TPH hydraulic components was assessed using Fidelity CFD tools, eliminating the need for initial water or similitude tests. However, in the year 2000, evaluating the net positive suction pressure (NPSP), which examines the capacity to operate under low inlet pressure, proved unfeasible. Consequently, a water test campaign was conducted to analyze the NPSP and cavitation dynamics. The flow of the Vinci TPH inducer was initially assessed with the Fine Turbo solver, now known as Fidelity Flow for turbomachinery.

Stage 2: Cavitation Modeling

Over the following years, new features were added to the Fidelity CFD tools to refine the assessment of NPSP and cavitation dynamics. These new features allowed the analysis of both steady and unsteady performance, along with thermal effects, which was not possible during the early stages of Vinci TPH development. In the second phase, Fidelity CFD was employed to evaluate NPSP in water.

Subsequent turbopump developments, like the TPX (Vulcain TPH new generation) from 2007 to 2010 and the Prometheus in 2022 (LOx/CH4), benefited from these advancements, eliminating the need for inducer water tests. These insights minimized the necessity for physical cavitation tests while enhancing design precision. With these advanced features in the Fidelity CFD tool, it gained widespread application for various flow types, including cavitating and supersonic/subsonic flows in turbines, effectively capturing unsteady behaviors.

Stage 3: Design Evolution

While some designs were validated early on in Vinci's development during the early 2000s, certain components required redesign for performance enhancement or due to advancements in manufacturing processes. Fidelity CFD tools facilitated early validation and redesign of components, averting costly mistakes and speeding up the development timeline. For example, they allowed for the smooth integration of design improvements based on unsteady loads into the Vinci engine without extensive prequalification, resulting in the Vinci TPH performing as expected during the flight model I (FM1).

Benefits of CFD in Turbomachinery

CFD offers unparalleled advantages for turbomachinery design, particularly for space exploration:

• Cost Reduction: Replacing or minimizing physical tests and reducing development iterations
• Enhanced Reliability: CFD ensures "right-first-time" performance, reducing the risk of failure during testing or missions
• Faster Qualification: Numerical simulations complement physical tests to expedite qualification stages for components and systems

Setting the Stage for Sustainable Space Exploration

Collaboration between Cadence and aerospace leaders like ArianeGroup demonstrates the potential for sustainable space exploration. CFD modeling increases the efficiency of the propulsion system and reduces the reliance on lengthy testing. It also fast-tracks the development of next-generation designs, such as the Prometheus turbopump.

Space mission requirements will inevitably become more complex. ArianeGroup’s hybrid engineering culture—blending computational accuracy with physical testing—serves as a blueprint for sustainable and efficient innovation.

Final Thoughts

The Ariane 6 space launcher, powered by the Vinci engine and refined through advanced CFD, represents the pinnacle of engineering collaboration, innovation, and sustainability in aerospace. Its design offers not just mission flexibility but also the confidence to meet the challenges of space exploration head-on.

For aerospace engineers, CFD analysts, and space enthusiasts, the partnership between ArianeGroup and Cadence Design Systems highlights how technology and expertise can combine to shape humanity’s future among the stars.

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