On the Hardness Change of 18-8 Austenitic Steel during Thermal Fatigue under Conditions of Transient Temperature Gradient

Conical friction surface is a novel configuration for friction plate in transmission. Numerical FEA models for transient heat transfer and distribution of conically grooved friction plate have been established to investigate the thermal behavior of the conical surface with different configurations. The finite element method is used to obtain the numerical solution, the temperature test data of conical surface are obtained by the friction test rig. In order to study and compare the temperature behavior of conically grooved friction plate, several three-dimensional transient temperature models are established. The heat generated on the friction interface during the continuous sliding process is calculated. Two different pressure conditions were defined to evaluate the influence of different load conditions on temperature rise and the effects of conical configuration parameters on surface temperature distribution are investigated. The results show that the radial temperature gradient on conical friction surface is obvious. The uniform pressure condition could be used when evaluating the temperature rise of conically grooved friction plate. The increase of the cone height could improve the radial temperature gradient of the conically grooved friction plate.

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Qualitative phenomenological investigation of the transient temperature gradient during gas turbine's hot section component cooling

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/0954410019879319 ◽

2019 ◽

Vol 234 (3) ◽

pp. 709-715

Author(s):

AM Tahsini

Keyword(s):

Temperature Gradient ◽

Life Expectancy ◽

Transient Behavior ◽

Temperature Gradients ◽

Transient Temperature ◽

Qualitative Model ◽

Time Rate ◽

Two Phase ◽

Qualitative Phenomenological ◽

Different Time Scales

In this study, the temporal variation of temperature gradient in the gas turbine hot section components in the transient process is raised, and according to its impact on life expectancy computations, the accuracy of the usual methods is investigated qualitatively. It is worth noting that in such two-phase problems, existing different time-scales prevent some common simplifications that are usually used for unsteady investigations like a quasi-steady assumption, and so there is no choice but to conduct coupled transient studies despite their high time-consuming manner. Hence, the phenomenological and qualitative model is introduced to analyze the cooling problem and show the transient behavior. The results show that during unsteady operations, if the time rate of changes is high, some considerable overshoots (more than 30%) of temperature gradients in hot sections may be ignored in common quasi-steady predictions, which must be predicted only by using the unsteady and coupled simulations.

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An Accurate and Simple Approach to Allow for the Transient Temperature Gradient in a Vaporizing Droplet

Volume 1: Symposia, Parts A and B ◽

10.1115/fedsm2012-72047 ◽

2012 ◽

Author(s):

Alexander Snegirev ◽

Victor Talalov

Keyword(s):

Temperature Gradient ◽

Life Time ◽

Droplet Evaporation ◽

Transient Temperature ◽

Internal Temperature ◽

Ambient Temperatures ◽

Wide Range ◽

Order Polynomial ◽

Volatile Liquid ◽

Evaporation Dynamics

The purpose of this work is to analyze the importance of considering internal temperature gradient in modeling droplet evaporation, and to demonstrate performance of simplified methods in which the temperature gradient is approximately taken into account. Based on three characteristic time scales, two dimensionless criteria have been identified which determine magnitude of the internal temperature gradient and its effect on the evaporation dynamics. Numerical values of these criteria in a wide range of ambient temperatures show that the effect of the internal temperature gradient is more pronounced in more volatile liquid at higher ambient temperatures. Although droplet life time predictions are not sensitive to the internal temperature gradient, its effect might be strong at the initial stages of droplet evaporation, and this substantiates the need in robust and computationally inexpensive methods to take it into account. Two simple and yet accurate approaches (quasi-steady higher order polynomial approximation and the integral balance method) have been favourably tested and recommended for use in CFD spray modeling.

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Development and application of a temperature gradient detector for manned underwater robot

International Journal of Advanced Robotic Systems ◽

10.1177/1729881420916963 ◽

2020 ◽

Vol 17 (4) ◽

pp. 172988142091696

Author(s):

Dewei Li ◽

Ye Li ◽

Zhongjun Ding ◽

Xiangxin Wang ◽

Baohua Liu

Keyword(s):

Temperature Gradient ◽

Deep Sea ◽

Stability Limit ◽

In Situ Measurement ◽

Transient Temperature ◽

Underwater Robot ◽

Scientific Application ◽

Deep Sea Sediment ◽

Operation Conditions

Manned underwater robot is an important platform to carry various sensors and working tools to finish the in situ measurement and sampling in the deep sea. Due to its limited loading capacity, the device it will be carried, usually, requires to be able to dive to its working depth with a small volume and weight. According to the application requirements of deep-sea sediment temperature gradient in situ measurement observed, a detector system that can obtain data in situ is designed, which mainly includes a titanium alloy electronic cabin and a temperature probe. A comprehensive design analysis method is used to compare and analyze the ultimate static pressure, stability limit load, bending moment load, and transient temperature field on the underwater operation conditions. Optimal dimensions and filled media in the probe are decided. Finally, the pressure resistance test is finished in the lab, and scientific application is conducted on Jiaolong’s 127th dive in the Northwest Indian Ocean, which successfully sampling the temperature gradient data of deep-sea sediments in the Daxi hydrothermal area. The method introduced in this article can effectively improve the safety and reliability of deep-sea structure and greatly reduce costs throughout the design cycle.

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Thermal Behavior of Multidisk Friction Pairs in Hydroviscous Drive Considering Inertia Item

Journal of Tribology ◽

10.1115/1.4028062 ◽

2014 ◽

Vol 136 (4) ◽

Cited By ~ 7

Author(s):

Fangwei Xie ◽

Jianzhong Cui ◽

Gang Sheng ◽

Cuntang Wang ◽

Xianjun Zhang

Keyword(s):

Surface Roughness ◽

Temperature Distribution ◽

Temperature Gradient ◽

Outer Radius ◽

Transient Temperature ◽

Unsteady Temperature ◽

Temperature Correlation ◽

Average Temperature ◽

Soft Start ◽

Lubricant Viscosity

Considering the influence of the inertia item on temperature distribution of multidisk friction pairs in hydroviscous drive (HVD), transient temperature models are derived with the aim of revealing the effect of engagement pressure, lubricant viscosity, viscosity–temperature correlation, surface roughness and the ratio of inner and outer radius of disks on temperature distribution. The results indicate that unsteady temperature gradient can be avoided by matching the suitable materials for multidisk friction pairs. The average temperature for the case of neglecting the inertia item is lower than that of the case of including the inertia item. It is shown that during the soft-start, the temperature along the radial direction achieves its peak value near the outlet and keeps decreasing along the axial direction; while after the engaging process, the temperature distribution tends to be uniform. It is also shown that the decrease of engagement pressure, surface roughness and the ratio of inner and outer radius of disks can reduce temperature gradient effectively as well as the increase of lubricant viscosity. The average temperature for the case of including the viscosity–temperature correlation is much higher than that for other cases.

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Finite Element Analysis on Directional Solidification of Al-Ni-Co Alloys

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.472-475.494 ◽

2012 ◽

Vol 472-475 ◽

pp. 494-498

Author(s):

Shi Long Tian ◽

Zhi Li Yang

Keyword(s):

Finite Element ◽

Temperature Gradient ◽

Directional Solidification ◽

Molten Steel ◽

Solidification Front ◽

Solidification Rate ◽

Temperature Fields ◽

Transient Temperature ◽

Element Analysis ◽

Co Alloys

Transient temperature fields of directional solidification of Al-Ni-Co alloys were studied by employing finite element method. Temperature gradient at solidification front and solidification rate was analyzed under different pouring temperature of molten steel. The results show that with different initial pouring temperatures of molten steel, individual ratio of temperature gradient at solidification front to solidification rate soars up in the initial stage of solidification, then varies within 2000-6000°C•s•cm-2, and finally plunges down and goes together when the solidification thickness reaches 5-6cm. Simulation result is consistent with the production reality. Numerical simulation results can provide an available reference for process optimization of directional solidification of Al-Ni-Co alloys.

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