| 1. |
- Båstedt, Peter, et al.
(författare)
-
Subcooled Flow Boiling in High Power Density Internal Combustion Engines I: Thermal Survey Measurement Campaign
- 2022
-
Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 16:1
-
Tidskriftsartikel (refereegranskat)abstract
- Nucleate boiling occurs inadvertently in the coolant jacket of high power density internal combustion engines, especially in vicinity of regions experiencing high thermal loads. Occurrence of boiling can be beneficial and be an efficient way to improve heat transfer locally near hot spots, but excessive boiling can be detrimental to structural integrity of the engine. While most of the efforts to understand boiling have been focused on experiments in simplified geometries, this article presents results from thermal survey measurement on a production engine. The purpose of the measurement campaign is to understand the intensity and extent of nucleate boiling occurring in different parts of the engine coolant jacket. This is achieved by sweeping across different input parameters, such as engine operating load point, cooling system operating pressure, coolant flow rate, and coolant inlet temperature. Different boiling regimes are encountered in different parts of the coolant jacket. A wide database of local solid temperatures measured at several critical locations is obtained and these results are interpreted in line with the underlying physics of subcooled flow boiling. The database not only helps to understand the boiling phenomenon occurring in engine coolant jacket, but is also used to calibrate a numerical boiling model.
|
|
| 2. |
- Vasudevan, Sudharsan, 1991
(författare)
-
Subcooled boiling flow in liquid-cooled internal combustion engines
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Road transport sector contributes significantly to emission of carbon dioxide and other greenhouse gases, which negatively impact the global climate. Efficient management of energy, irrespective of the type of propulsion, has the potential to minimize fuel consumption and to reduce emission of greenhouse gases. This makes thermal (energy) management an indispensable part of automotive propulsion research and development. Cooling plays an important role in protecting the components from failure due to extreme thermal loads. An efficient cooling strategy, such as precision cooling, removes the excess heat precisely from the parts experiencing critical temperatures, without over cooling the component. The thesis focuses primarily on numerical methodologies to explore the potential of local nucleate boiling for efficient cooling of internal combustion engines. Nucleate boiling is a heat transfer phenomenon involving a phase change process, where the liquid coolant vaporizes in the form of bubbles close to the heated surface. Occurrence of nucleate boiling, locally in the vicinity of hot spots, offers a significant potential for efficient precision cooling, but at the risk of encountering film boiling. Film boiling is encountered as a consequence of excessive boiling which leads to coalescence and agglomeration of vapor bubbles, resulting in formation of a thin vapor film, next to the heated surface. On account of the low thermal conductivity of the vapor, film boiling prevents cooling and could potentially lead to material failure. Therefore, tapping the potential of controlled local nucleate boiling is a preferable approach. In the current work, a new semi-mechanistic wall boiling model is proposed that not only estimates the occurrence of boiling, but also the boiling heat flux and the extent of boiling. It is vital to know the extent of boiling in order to avoid, with sufficient margin, the risk of encountering film boiling. The proposed model is validated with results from channel flow experiments available in the literature. Further, the model is implemented in real engine simulations in both single phase and multiphase Computational Fluid Dynamics (CFD) frameworks. The model performance is evaluated by comparing the results of the simulations with relevant measurements. The model estimates the wall boiling heat flux with reasonably good accuracy and indicates the occurrence of excessive boiling with sufficient margin for industrial applications.
|
|
| 3. |
- Vasudevan, Sudharsan, 1991, et al.
(författare)
-
Subcooled Flow Boiling in High Power Density Internal Combustion Engines II: Numerical Modeling
- 2022
-
Ingår i: SAE International Journal of Engines. - : SAE International. - 1946-3944 .- 1946-3936. ; 16:1
-
Tidskriftsartikel (refereegranskat)abstract
- Results from a thermal survey measurement campaign on a four-cylinder Volvo engine was presented in Part I of this article. The focus was predominantly on heat transfer in the engine coolant jacket. This part presents numerical modeling focused specifically on the coolant flow and associated heat transfer in the coolant jacket using computational fluid dynamics (CFD), as a part of a high-resolution complete engine 3D conjugate heat transfer (CHT) model. With local nucleate boiling being an indispensable phenomenon in high power density engines, a dedicated boiling model is essential and is to be used in conjunction with CFD while analyzing heat transfer in the coolant jacket. This article validates a new boiling model with data obtained from the extensive thermal survey measurements, presented in Part I. The new model includes a parameter, based on vapor bubble interactions, that serves as an indication of the transition from beneficial nucleate boiling to high-risk transition and film boiling regimes. This parameter might be used to assess the robustness of new engine designs. The advantages and limitations of the new boiling model are presented and are discussed in detail.
|
|
