Abstract:Oxidation of AISI 304L and 348 stainless steels was investigated in water at 1000-1350 °C by TGA, SEM, EDS, and Raman spectroscopy. Linear-Parabolic kinetics and multilayer oxide scales with voids were found for both alloys. Based on the experimental results, AISI 304L presented higher oxidation resistance and higher activation energy. Zircaloy-4 kinetic results were used for validation and performance comparison. In severe accidents conditions, stainless steel might lead to a faster hydrogen production compar… Show more
“…The bypass valve closes when the thermostat is open. Because the thermostat is constantly immersed in water [36], its components are made of stainless steel to prevent rust [37], except for the SMA spring. The SMA spring has a particular task in the thermostat to activate the control of the coolant flow direction based on the prescribed range of the engine operating temperature within a defined time.…”
Pollutants in exhaust gases and the high fuel consumption of internal combustion engines remain key issues in the automotive industry despite the emergence of electric vehicles. Engine overheating is a major cause of these problems. Traditionally, engine overheating was solved using electric pumps and cooling fans with electrically operated thermostats. This method can be applied using active cooling systems that are currently available on the market. However, the performance of this method is undermined by its delayed response time to activate the main valve of the thermostat and the dependence of the coolant flow direction control on the engine. This study proposes a novel active engine cooling system incorporating a shape memory alloy-based thermostat. After discussing the operating principles, the governing equations of motion were formulated and analyzed using COMSOL Multiphysics and MATLAB. The results show that the proposed method improved the response time required to change the coolant flow direction and led to a coolant temperature difference of 4.90 °C at 90 °C cooling conditions. This result indicates that the proposed system can be applied to existing internal combustion engines to enhance their performance in terms of reduced pollution and fuel consumption.
“…The bypass valve closes when the thermostat is open. Because the thermostat is constantly immersed in water [36], its components are made of stainless steel to prevent rust [37], except for the SMA spring. The SMA spring has a particular task in the thermostat to activate the control of the coolant flow direction based on the prescribed range of the engine operating temperature within a defined time.…”
Pollutants in exhaust gases and the high fuel consumption of internal combustion engines remain key issues in the automotive industry despite the emergence of electric vehicles. Engine overheating is a major cause of these problems. Traditionally, engine overheating was solved using electric pumps and cooling fans with electrically operated thermostats. This method can be applied using active cooling systems that are currently available on the market. However, the performance of this method is undermined by its delayed response time to activate the main valve of the thermostat and the dependence of the coolant flow direction control on the engine. This study proposes a novel active engine cooling system incorporating a shape memory alloy-based thermostat. After discussing the operating principles, the governing equations of motion were formulated and analyzed using COMSOL Multiphysics and MATLAB. The results show that the proposed method improved the response time required to change the coolant flow direction and led to a coolant temperature difference of 4.90 °C at 90 °C cooling conditions. This result indicates that the proposed system can be applied to existing internal combustion engines to enhance their performance in terms of reduced pollution and fuel consumption.
“…[9] The Nb-stabilized nuclear grade X6CrNiNb18-10, also designated AISI 347, is superior regarding intergranular stress corrosion cracking and therefor saw application in German Boiling Water Reactors (BWR). [2,7,10] Various studies [3,6,[11][12][13][14] dealt with the development of the oxide layer morphology and the thickness of SS in HTW. Some [3,11,[15][16][17][18] investigated the protective Cr-rich primary oxide layer.…”
The oxide layer development of X6CrNiNb18-10 (AISI 347) over exposure time in high temperature water has been investigated. While a parabolic development of Cr in the protective primary layer and Fe in the secondary layer can be observed, dimensions of the Ni layer remains constant. Ni requires the presence of a pronounced Fe-rich secondary layer before being able to reside on the outer secondary layer. With rising immersion time, the Ni element fraction surpasses the Cr element fraction in the secondary layer. The oxide growth of the secondary layer could be observed. After 480 h, almost the entire surface is covered by the outer oxide layer. In the metal matrix no depletion of Cr or Ni could be observed over time. However, an increased presence of Cr and Ni in the primary layer was at the expense of Fe content.
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