The Woodruff School

SUMMARY

With limitations of traditional power cycles on their operating temperature ranges and max efficiencies, the research community has shifted attention to usage of supercritical fluids as the main working fluid of power cycles. Among the supercritical fluids, supercritical carbon dioxide (sCO2) is considered as the most promising candidate for its relatively low critical point, low cost, and availability. The main merit of using sCO2 as the working fluid of a power cycle is its high density near the fluid’s critical point, which reduces the required compression power, both decreasing the volume of turbomachinery and leading to increased overall cycle efficiency. However, non-linear property variations and mixing of different supercritical regimes in close proximity to the critical point poses great risks for cycles taking the full advantage of these benefits.
The non-linear property variations close to the critical point provide a challenge in developing a multiphysics model, which can serve as a backbone for simulating more advanced geometries of sCO2 power cycle processes. To understand the physical phenomena of property variations and mixing of supercritical fluids at differing conditions, a high-pressure test chamber and supporting closed-loop cycle facilities are constructed. Experiments are conducted under two different regimes of supercritical fluids at varying degrees of proximity to the critical point to investigate characteristics of the transition in regimes within the supercritical conditions and the impact of property variations on the turbulent flow characteristic. To tackle these objectives, laser Raman scattering and Schlieren techniques are applied to visualize the flow mean quantities and record the density fields, correlating the results to the proximity of the test conditions and determining the turbulence nature of the flow. Further, the experimental results will also provide distinct baseline conditions for validating LES models.

https://teams.microsoft.com/l/meetup-join/19%3ameeting_YzczMjA0YTEtYTdmZi00OGE5LTg1NDYtMGM5ZjgzNmI5Nzdi%40thread.v2/0?context=%7b%22Tid%22%3a%22482198bb-ae7b-4b25-8b7a-6d7f32faa083%22%2c%22Oid%22%3a%227c37b61b-fe97-4035-ba3b-264fc9736fe4%22%7d

SUBJECT:	Ph.D. Proposal Presentation

BY:	Chang Hyeon Lim

TIME:	Wednesday, December 8, 2021, 10:00 a.m.

PLACE:	Virtual, Virtual

TITLE:	Experimental investigation of supercritical CO2 flow turbulent mixing near critical point

COMMITTEE:	Dr. Devesh Ranjan, Chair (ME) Dr. Peter Loutzenhiser (ME) Dr. Satish Kumar (ME) Dr. Joseph Oefelein (AE) Dr. Adam Steinberg (AE)

SUMMARY With limitations of traditional power cycles on their operating temperature ranges and max efficiencies, the research community has shifted attention to usage of supercritical fluids as the main working fluid of power cycles. Among the supercritical fluids, supercritical carbon dioxide (sCO2) is considered as the most promising candidate for its relatively low critical point, low cost, and availability. The main merit of using sCO2 as the working fluid of a power cycle is its high density near the fluid’s critical point, which reduces the required compression power, both decreasing the volume of turbomachinery and leading to increased overall cycle efficiency. However, non-linear property variations and mixing of different supercritical regimes in close proximity to the critical point poses great risks for cycles taking the full advantage of these benefits. The non-linear property variations close to the critical point provide a challenge in developing a multiphysics model, which can serve as a backbone for simulating more advanced geometries of sCO2 power cycle processes. To understand the physical phenomena of property variations and mixing of supercritical fluids at differing conditions, a high-pressure test chamber and supporting closed-loop cycle facilities are constructed. Experiments are conducted under two different regimes of supercritical fluids at varying degrees of proximity to the critical point to investigate characteristics of the transition in regimes within the supercritical conditions and the impact of property variations on the turbulent flow characteristic. To tackle these objectives, laser Raman scattering and Schlieren techniques are applied to visualize the flow mean quantities and record the density fields, correlating the results to the proximity of the test conditions and determining the turbulence nature of the flow. Further, the experimental results will also provide distinct baseline conditions for validating LES models. https://teams.microsoft.com/l/meetup-join/19%3ameeting_YzczMjA0YTEtYTdmZi00OGE5LTg1NDYtMGM5ZjgzNmI5Nzdi%40thread.v2/0?context=%7b%22Tid%22%3a%22482198bb-ae7b-4b25-8b7a-6d7f32faa083%22%2c%22Oid%22%3a%227c37b61b-fe97-4035-ba3b-264fc9736fe4%22%7d