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In 2022, the aviation industry was responsible for 2.5% of global carbon dioxide emissions and 3.5% of global warming, highlighting the need for sustainable practices. A viable approach to achieving cleaner aviation is switching to renewable and sustainable aviation fuels. Another step is to leverage simulations in lieu of real-world testing during the aircraft design cycle. Simulations are crucial for improving aircraft design, especially in today's highly competitive market landscape with shorter time-to-market. They present an opportunity to make aviation more eco-friendly and optimize the performance design. For instance, when contemplating biofuel use for an aircraft, it is preferable to simulate the reactions and the involved physics before testing the fuel inside the combustion chamber of a real airplane. Simulation technology ought to play a significant role as we continue to work towards a cleaner and greener aviation industry.
Organizations such as Clean Sky and Clean Aviation are investing millions of dollars to develop cleaner aviation technology by 2031. The Federal Aviation Administration (FAA) has launched the Continuous Lower Energy, Emissions, and Noise (CLEEN) program, which comprises various phases aimed at decreasing aircraft fuel consumption, noise pollution, NOx emissions, and integrating sustainable aviation fuel (SAF) (without changing the existing fuel nozzle). The FAA has allocated approximately $600 million from 2010 to 2025 for this program, and Tier I firms from the aviation industry are actively participating in it.
Honeywell’s CLEEN III program is maturing advanced propulsion engine technologies for improved fuel burn, reduced emissions, and noise.
During the gas turbine engine simulation process, a multi-tiered approach is employed. Individual engine components are first simulated to determine performance and other critical parameters. Following this, a simulation is carried out for the entire engine. However, interactions among the different stages are expected when they are put together. Single-stage designs cannot account for these interactions, and multiple stages require minor adjustments to the metal angles, stagger angles, unguided turnings, etc., to account for changes in inlet conditions. Simulation can help account for these interactions and make design adjustments easier.
For instance, a thermal simulation can predict the temperature profile in a turbine cooling flow, which is crucial for predicting blade life and optimizing efficiency. Designers can use these simulation results to create a realistic temperature profile that matches the literature data. Additionally, simulations allow for testing multiple scenarios, thereby enabling the identification of the ideal design for a given application.
Typically, design enhancements are targeted toward achieving 90% or higher compressor efficiencies. However, such outcomes cannot be solely attained through hardware testing. Hence, simulation-based optimization is recommended not just at the component level but for the whole system, which would be for the entire gas turbine. A mere 1% increase in efficiency can directly lead to a 1% reduction in fuel consumption, especially for engines with high-pressure compressors and low-pressure turbines.
There are multiple certifications that an airplane must undergo before it is considered fit for flying. One such test is the bird strike test. This test entails launching a bird weighing around 1.8kg to 3.65 kg into a running engine at a specific velocity. The cost of this test can be significant, with larger engines costing around 43 million dollars and smaller engines around 3 million dollars. In the event of a failed test, assembling parts and entering the rig can take up to a year. This is particularly problematic as full-size engine prototypes must be tested, and the manufacturing process is restricted to producing only two to three parts at a time. If the bird strike test fails, all parts must be redesigned from the ground up, with additional pressure, to get it right the first time and prevent the need to repeat the process.
Damaged engine blades of an aircraft. (Image Source: https://training.egyptair.com/News/BirdStrike-Event)
The image displayed above depicts engine blade damage caused by a bird strike. Preventing bird ingestion into the engine core is crucial, as it can result in irreparable harm to the compressor's rotating components and blades.
Compressors of a gas turbine are commonly constructed from titanium, which is often alloyed with nickel and steel. The lifetime pollution of titanium is 10 kg of CO2 per kg of titanium; for nickel, it is roughly 13 kg of CO2 per kg of nickel. In contrast, steel is relatively environmentally friendly, producing only 1.85 kg of CO2 per kg of steel.
Consider the GE CF6-80C1 engine, which weighs around 4000 kg and has a turbine weight of one-third, a compressor weight of another one-third, and the rest of the weight is from the other accessories. If this engine were to fail a test, it would produce a significant amount of carbon, around 33,000 kg. To avoid such failures, we need to ensure our simulations are effective. Cadence Fidelity CFD tools are pioneers in making simulations easy and are a go-to solution for shifting left in the design cycle.
Simulation is a valuable tool for enhancing aircraft design in today's competitive market. It allows for the exploration of different options from a sustainability perspective while minimizing resource wastage. Additionally, simulation can predict the temperature profile of any component or entire system, thereby providing flexibility to optimize the interactions of the different components within the system for maximum efficiency. Through the testing of multiple scenarios, simulations enable the identification of the ideal design for a given application, which helps to reduce testing, making the process more efficient and cost-effective. Cadence CFD tools make simulations easier and allow shifting left in the design cycle. By embracing the power of CFD - Computational Fluid Dynamics - we can create a cleaner, more sustainable aviation industry.
To learn more about the Role of Simulation In Making Aviation Cleaner, watch the recorded video of the presentation delivered by Dr. Shraman Goswami from Honeywell at CadenceCONNECT CFD Silicon Valley, April 2023.