Dirt Mitigation Techniques in Double-Walled Combustor Liners
Open Access
- Author:
- Fallon, Brandon
- Graduate Program:
- Mechanical Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 01, 2022
- Committee Members:
- Daniel Haworth, Professor in Charge/Director of Graduate Studies
Karen Ann Thole, Thesis Advisor/Co-Advisor
Robert Francis Kunz, Committee Member
Stephen P Lynch, Thesis Advisor/Co-Advisor - Keywords:
- Dirt Deposition
Film Cooling
Combustor
computational fluid dynamics
particle laden flow - Abstract:
- Within a gas turbine engine, combustion takes place in a combustor at temperatures that exceed the melting point of existing combustor materials. To prevent overheating and enhance the durability of the combustor, a double-walled cooling scheme is often included in designs. Gas turbines are often deployed in dusty or sandy environments where large quantities of fine particulate matter are ingested into the engine’s mainstream and coolant flows. Once in the coolant flow, particulates will deposit on and block the internal cooling passages resulting in reduced coolant flows and component life cycles. The research discussed in this thesis evaluated new double-walled combustor liner designs that incorporated pin-fin structures on the effusion plate surface to limit dirt deposition. The pin-fin structures consisted of elliptical and conical shapes as well as channels that resembled a swirl shape. Dirt was injected into the coolant flow using two injection modes, either slug or continuous feed, to evaluate the effects of dirt loading on deposition rates. The performance of each coupon was quantified by measuring the mass of dirt that was captured on the pin-fin effusion wall and by calculating the percent reduction in flow parameter. Computational fluid dynamics (CFD) was performed to determine correlations between internal flow field variables and experimental deposition patterns. Results of the study showed that conical pin-fins that were directly aligned with an impingement jet had the least dirt capture and lowest reduction in flow parameter. It was also found that slug feed tests resulted in more dirt capture than continuous feed tests, but the relative performance and deposition pattern for each design remained identical regardless of feed type. Evaluation of the internal flow field revealed that coupons with large near-wall velocities captured more dirt than coupons with small near-wall velocities. A complimentary slug feed study was performed on effusion plates with conical pin-fins that were aligned with impingement jets. The height, diameter, and half angle of each cone was altered to evaluate the effect that cone topography had on particle deposition. Several experiments were also conducted with larger diameter impingement jets to determine correlations between impingement parameters and deposition. Experimental results indicated that narrow cones with small diameters collected less dirt than wide flat cones. Increasing the impingement jet diameter also significantly reduced dirt capture. CFD evaluation revealed that dirt was likely to deposit when the flow direction suddenly reoriented and when components of the flow vectors were aligned with the surface. Lastly, it was found that the flow parameter scaled well with dirt capture such that low flow parameters resulted in less deposition.