Lukasz Halon

Exploring Effective and Efficient Use of CO2 for Drilling of Novel CFRP Fibre Stack Materials

Supervised by: Dr Andrew Nowakowski, Dr Ellis Taylor, Dr Emma Warren, Steve Grey, Andy Boffin 

Sponsored by: Kennametal 

I'm doing an EngD because I see it as a great combination of academic research and practical industry application. I’m looking forward to not only advancing current manufacturing knowledge, but also applying it directly to solve a real-world problem. Being able to work on a project from start to finish will give me ample opportunities to develop further as an engineer, and I’m confident that it will be a rewarding challenge.

My research aim is to optimise the design of supercritical CO2 delivery channels for Kennametal's tooling. Current Kennametal customers request 0.2mm delivery holes, a size that is both challenging to manufacture and typically based on anecdotal "rules of thumb" rather than concrete engineering principles.

Using Computational Fluid Dynamics (CFD) models, I am investigating the flow behaviour of supercritical CO2 to find an ideal channel design. This new design must balance important factors like minimizing CO2 usage, ensuring sufficient back pressure for coolant delivery, and preventing ice crystal formation in the delivery channel.

The ultimate goal is to provide a scientifically validated recommendation for the optimal channel size and geometry. The anticipated outcome is an improved design that either justifies the current coolant channel manufacturing challenges or, ideally, proves a larger, easier-to-manufacture channel is more effective.

I find my research exciting because it focuses on a novel and unconventional approach to drilling: CO2 cooling. While emulsion coolants are still the industry standard, CO2's superior heat removal capacity makes it the perfect choice to investigate for drilling hard-to-cut materials like those found in the aerospace industry.

What sets my project apart is using CO2 in its supercritical state. Supercritical CO2 can dissolve oil lubricants, delivering them directly to the cutting zone, therefore not only providing improved cooling, but also lubrication. This could benefit the the aerospace industry in a number of ways, including reduced machining time, lower tool wear and improved quality of drilled holes. Ultimately, it’s exciting to be working on a promising and novel technology with real application to industry. 

Supercritical CO2 (scCO2) cooling can provide significant benefits to the industry by reducing tool wear, machining time, and improving part quality. Additionally, the cleanliness of CO2 could transform the manufacturing industry.

Traditional emulsion coolants are prone to bacterial growth and require machined parts and chips to be cleaned. Traditional coolant tanks require frequent monitoring and processing, costing time, money and energy. Additionally, the fine coolant droplets created during machining pose a health risk to machine operators.

Unlike emulsion coolant, CO2 evaporates into the atmosphere after use, removing the need for storage, cleaning and processing. The CO2 used for cooling is usually captured as a by-product from other industrial processes making its use more carbon neutral. 

CO2 can not only reduce energy consumption and cost, but also prevent contamination of the product which is vital when machining carbon fibre. My research into more efficient use of scCO2 will hopefully encourage its use and maximise its benefits.