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The future of combustion: Clean Burning

Clean burning simulation

You don't need us to tell you that the planet is getting hotter. In our humble opinion, the greatest engineering challenge of our time is converting the systems that helped create the world as we know it into sustainable products. With Application Engineering for Combustion CFD, we help many customers across multiple industries simulate the burning of methane, propane, gasoline, diesel, and more. Of course, the goal is always to use simulation to design efficient combustion systems that minimize emissions and maximize performance. However, for these combustion systems, internal combustion engines, gas turbines and process burners, the heat is turned on to reduce their carbon footprint.


Sustainable fuels

Excellent design of combustion systems that burn fossil fuels can only get you so far. A major focus for engineers is now to adapt or design from scratch combustion systems that burn alternative fuels such as electronic fuels, hydrogen or ammonia.


Clean energy


The decarbonization of the automotive industry is what we imagine comes to most people's minds when considering the “cleaning” of combustion systems. There are many articles and columns discussing the long debate between internal combustion engines (ICEs) and battery-powered vehicles! We won't add anything here (except the fact that Simcenter STAR-CCM+ is the tool to design both). Ultimately, ICEs will be needed to advance industries where batteries are not viable and if they can function in a way that produces negligible CO₂ emissions, then they should be part of the mix in the future of transportation.


Clean energy

Fortunately, Simcenter STAR-CCM+ has been adding tools to ensure that simulation can be leveraged to design such systems. And so, over the past few years, Simcenter STAR-CCM+ has been continually improved to enable the analysis of new fuels and emissions.


Software improvements

Fuels proposed for use in In-Cylinder applications may have different fundamental reactive properties. An important example is Laminar Flame Speed ​​(LFS). In Simcenter STAR-CCM+ you can directly calculate the LFS for any fuel mixture and use it with Flamelet, ECFM and Complex Chemistry combustion models. Below we can see an example of an ICE using a mixture of Gasoline and Hydrogen as fuel, with the simulation being carried out using Simcenter STAR-CCM+ In-Cylinder Solution:



The methodology allows a quantitative prediction of gross emissions depending on the hydrogen fraction:


Exhaust emissions for different fuel mixtures at equal Qth.

Exhaust emissions for different fuel mixtures at equal Qth.


Naval applications


Of course, the shipping industry is not immune to the need to burn cleanly. Maritime transport is responsible for around 2.5% of all greenhouse gas emissions, but it is essential as 90% of all global goods are transported this way. While there may be use cases where electrification is a viable approach, for large operators, batteries (alone) may never be the solution. Engineers designing marine propulsion systems are having to rock the boat with the use of conventional fuel and explore other (decarbonized) fuels during the design process.


Ammonia and fuel cell engines can reduce carbon emissions

Ammonia and fuel cell engines can reduce carbon emissions


One of these options is the use of Ammonia. Ammonia can be burned without generating CO₂ and is relatively easy to store, making it a good candidate as a future fuel for the shipping industry. Once the logistics (distribution, availability) of ammonia are resolved, it could be the number one topic for the development of internal combustion engines in the near future. However, despite the potential, ammonia has its own challenges, such as the need for high ignition energy. For this reason, ammonia can be used in conjunction with small amounts of diesel to start the combustion process. Ultimately, this still provides much cleaner combustion than traditional use of fossil fuels.


Simcenter STAR-CCM+ can be used by designers to understand this process. In the example below, Ammonia and Diesel jets are studied at various injection times and angles.



Under certain conditions, for example insufficient or too strong interaction between the two fuel sprays, misfires may occur. Being able to accurately simulate this reduces the need for extensive testing and allows for a detailed understanding of how to design to avoid such a scenario.



Using the Complex Chemistry combustion model, excellent prediction of misfire occurrences as well as regular combustion can be predicted.


How green is your simulation?


Most industrial CFD simulations rely on High Performance Computing (HPC) and crunching the numbers requires energy that inevitably carries its own carbon footprint.


This article from the British Computing Society highlights the challenge and states that CO₂ emissions from HPC data centers are expected to grow by 2 to 9 times over the next 10 years.


Sustainable technology

The obvious course of action is to clear the energy that powers your CFD simulations, but of course this is probably not within your control and furthermore leaves us with nothing to do! With the latest versions of Simcenter STAR-CCM+, combustion engineers can now leverage GPU-native Flamelet combustion modeling. Leveraging GPU hardware allows engineers to run their simulations using significantly less power, reducing emissions and costs, as well as achieving faster responses (a rare win-win situation).


So let's take a combustion system, in this case a pressurized annular combustor, and add some hydrogen to the fuel to reduce the CO₂ emissions generated.



Great, but nothing in life is free, and we've talked in the past about how the simple act of adding hydrogen can disrupt the thermoacoustic stability of the combustion system. All is not lost as this system can be analyzed using high-fidelity LES combined with the Flamelet Generated Manifold combustion model to accurately predict thermoacoustic behavior. And even better, all of this can run natively on GPUs.


Simulation time comparison

The 50% reduction in computing time is evaluated here by comparing a 640-core CPU solution (commonly used CPUs with 32 cores per CPU node, 2.4-3.3 Ghz, 256 MB L3 cache) with a of GPU on 8 NVIDIA A100 cards.


The end result is a solution that is 50% faster and consumes 60% less energy, in addition to being 42% cheaper. Even more importantly, the frequencies of thermoacoustic instabilities generated due to hydrogen addition are also excellently predicted and can therefore be eliminated or mitigated:


 dBxHz graph

Predicted and measured thermoacoustic spectra for a pressurized annular burner with CH4/H2 flame


What we have here, folks, is a case of Simcenter STAR-CCM+-inspired carbon emissions creation : we save on emissions while designing to save on emissions!


 

Interested in designing cleaner, more efficient combustion systems to reduce your carbon footprint? Schedule a meeting with CAEXPERTS today and find out how we can help you meet application engineering challenges for combustion CFD. With our experience and the advanced tools of Simcenter STAR-CCM+, we can explore sustainable solutions for your projects, from simulating alternative fuels to optimizing marine propulsion systems. Don't waste time, get in touch now!



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