The Thermal Load and Ablation Mechanism of Piston Subjected to Detonation

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Jian Gao ◽  
Anren Yao ◽  
Chunde Yao
Keyword(s):  
Surface Layer ◽  
Thermal Ablation ◽  
Thermal Load ◽  
Heat Dissipation ◽  
The Finite Element Method ◽  
Reciprocating Engine ◽  
Ablation Mechanism ◽  
Transient Thermal ◽  
Short Time ◽  
Heat Released

Abstract The piston in reciprocating engine would be badly ablated under severe knock. However, the mechanism of the detonation-induced thermal ablation of piston is still unclear. A detonation bomb device (DBD) was used to measure the thermal load of piston under detonation. A test specimen mounted on the detonation bomb acts as a piston to bear the detonation load. Transient thermal numerical analysis was performed using the finite element method. Temperature of the specimen and in-cylinder pressure were collected synchronously. A method for estimating wall heat flux under detonation was proposed. Results showed that the heat received by the specimen accounts for about 20.9% of the total heat released by the mixture in this research. Under continuous detonations, the heat of the surface layer could not be conducted to the interior in a short time, leading to a rapid rise in surface temperature. The overall temperature rise of the specimen limits the heat dissipation of the specimen surface layer, resulting in the specimen being ablated by the over-temperature and over-pressure. Piston thermal ablation by detonation is verified and reappeared in the detonation bomb. The thermal load of the piston is largest under theoretical equivalent ratio.

Transient Thermal Load Effects on Coatings Bonded to Cylindrical Substrates and Containing Circumferential Cracks

1988 ◽  
Vol 110 (1) ◽  
pp. 35-40 ◽  
Author(s):  
K. Kokini ◽  
T. R. Hornack
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Thermal Load ◽  
Edge Crack ◽  
Ceramic Coatings ◽  
The Finite Element Method ◽  
Intensity Factors ◽  
Transfer Rates ◽  
Load Effects ◽  
Transient Thermal

The effect of a transient thermal load on a coating which is bonded to a cylindrical substrate is analyzed using fracture mechanics by considering the presence of a circumferential edge crack normal to the inner boundary of the coating. The solution is obtained using the finite element method and is compared to the exact solution of the problem. The analysis is then used to show that smaller heat transfer rates at the boundary result in smaller stress intensity factors. For three different materials combinations, including two ceramic coatings on metal, the nondimensional stress intensity factor has a similar magnitude for short crack lengths, but varies appreciably as the crack length becomes longer. It is also determined that inner coatings result in smaller or comparable stress intensity factors than thicker ones.

Materials Science A Simulation Model for Transient Thermal Analysis of Restored Teeth

1983 ◽  
Vol 62 (6) ◽  
pp. 756-759 ◽  
Author(s):  
J.H.P. De Vree ◽  
Th.A.M. Spierings ◽  
A.J.M. Plasschaert
Keyword(s):  
Material Properties ◽  
Thermal Load ◽  
Materials Science ◽  
Parameter Variation ◽  
Thermal Processes ◽  
The Finite Element Method ◽  
Cavity Design ◽  
Transient Thermal ◽  
Simple Parameter ◽  
Good Agreement

A theoretical model was developed to analyze the influence of various cement bases on temperature distribution and heat flow in restored teeth. A physical model of a molar was developed to simulate different thermal processes by simple parameter variation. The time-dependent temperature field was calculated using the finite element method (FEM). The values for material properties and thermal load were chosen from the dental literature. The results are in good agreement with clinical experimental research as published by Trowbridge et al. 1 It is concluded that the model is a valid tool for further research with regard to the influence of restorative materials and cavity design on the thermal behavior of restored teeth.

scholarly journals Thermal Analysis of Heat Distribution in Busbars during Rated Current Flow in Low-Voltage Industrial Switchgear

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2427
Author(s):  
Michał Szulborski ◽  
Sebastian Łapczyński ◽  
Łukasz Kolimas
Keyword(s):  
Structural Changes ◽  
Heat Dissipation ◽  
Current Flow ◽  
Low Voltage ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Coupled Analysis ◽  
Precise Representation ◽  
Transient Thermal ◽  
Halogen Free

The manuscript presents advanced coupled analysis: Maxwell 3D, Transient Thermal and Fluent CFD, at the time of a rated current occurring on the main busbars in the low-voltage switchgear. The simulations were procured in order to aid the design process of such enclosures. The analysis presented the rated current flow in the switchgear busbars, which allowed determining their temperature values. The main assumption of the simulation was measurements of temperature rise during rated current conditions. Simulating such conditions is a valuable asset in order to design better solutions for energy distribution gear. The simulation model was a precise representation of the actual prototype of the switchgear. Simulations results were validated by experimental research. The heat dissipation in busbars and switchgear housing through air convection was presented. The temperature distribution for the insulators in the rail bridge made of fireproof material was considered: halogen-free polyester. The results obtained during the simulation allowed for a detailed analysis of switchgear design and proper conclusions in practical and theoretical aspects. That helped in introducing structural changes in the prepared prototype of the switchgear at the design and construction stages. Deep analysis of the simulation results allowed for the development concerning the final prototype of the switchgear, which could be subjected to the full type tests. Additionally, short-circuit current simulations were procured and presented.

Electric Field Distribution Analysis of ±1000kV DC Wall Bushing during Polarity Reversal

2012 ◽  
Vol 229-231 ◽  
pp. 807-810
Author(s):  
Li Zhang ◽  
Qing Min Li ◽  
Li Na Zhang ◽  
Yu Di Cong
Keyword(s):  
Electric Field ◽  
Field Distribution ◽  
Potential Distribution ◽  
Electric Field Distribution ◽  
Polarity Reversal ◽  
Distribution Analysis ◽  
The Finite Element Method ◽  
Insulation System ◽  
The Moment ◽  
Short Time

±1000kV DC wall bushing under planning is a complex insulation system which bears the effects imposed by different working conditions. The electric field distribution is concentrated at the bushing outlet terminal, which might result in breakdown discharge especially when short-time abrupt conditions such as polarity reversal occur. In this paper, the finite element method is utilized to analyze electric field distribution and potential distribution of wall bushing during polarity reversal. Electric field distribution and potential distribution at the moment of polarity reversal are obtained, which provides value reference for the study of polarity reversal process.

The Micro-Temperatures of the Peaks and Valleys of Sliding Rough Surfaces

2018 ◽  
Vol 883 ◽  
pp. 53-62 ◽  
Author(s):  
Shin Yuh Chern ◽  
Jeng Haur Horng ◽  
Cheng Han Tsai ◽  
Hung Jung Tsai
Keyword(s):  
Thermal Conductivity ◽  
Temperature Rise ◽  
Rough Surfaces ◽  
Chemical Processes ◽  
The Finite Element Method ◽  
Precision Control ◽  
Sliding Speed ◽  
Surface Failure ◽  
Contact Surfaces ◽  
Transient Thermal

The surface micro-temperature of sliding, rough bodies is an important factor affecting contact properties, such as chemical reactions of automatic injectors for medicine and chemical processes and surface failure of micro-and macro-devices. In this work, the Finite Element Method is used to analyze the micro-temperature of the peaks and valleys of multiplying asperity sliding contact surfaces. The affecting parameters include pressure, roughness, sliding speed, Peclet number, and thermal conductivity of rough surfaces. Analysis results showed that the effects of the studied parameters are different to those of peak and valley temperatures. While pressure increased, the increasing rate of the temperature rise parameter of valleys was larger than those of peaks. The temperature rise of peaks increased as roughness increased. On the contrary, the temperature rise of valleys decreased as roughness increased. Sliding speed and thermal conductivity played the most important roles in affecting the maximum micro-temperature rise. The temperature rise difference between peaks and valleys was almost proportional to thermal conductivity, and was inversely proportional to sliding speed for all cases. This transient thermal analysis enables precision control of interface micro-temperature for micro-moving devices.

The Transient Thermal Stress and Deflection of a Brake

2005 ◽  
Author(s):  
Yuan Mao Huang ◽  
Shih-Han Chen
Keyword(s):  
Thermal Stress ◽  
Thermal Gradient ◽  
Transient Temperature ◽  
Outer Diameter ◽  
The Finite Element Method ◽  
Dimensional Model ◽  
Uniform Temperature ◽  
Principal Stresses ◽  
Disk Brake ◽  
Transient Thermal

This study utilizes the finite element method with a two-dimensional model of a disk brake and investigates its distributions of the transient temperature, thermal gradient, heat flux, thermal stress and deflection due to friction. A specified initial uniform temperature of the disk is used to simulate heat transfer of the disk. Since the temperature of the disk brake inboard is higher than that of the disk brake outboard, the deflection of the disk brake inboard is larger than those at other locations. The maximum deflection of 0.4 mm occurs at the outer diameter of the disk inboard. The disk expands radial outward and bends from the disk brake inboard toward the disk brake outboard. The coning angle between the disk outboard surface and the original vertical disk outboard surface is 0.39°, which is comparable with the existing datum of 0.35°. The principal stresses at the lower mounting location are 184 MPa and 236 MPa. The calculated safety factor is 1.27 based on the modified Mohr theory used for brittle materials, and this disk brake is reliable.

Exploration of Enhanced Heat Dissipation Design for Brake Disc of High Speed Train

2010 ◽  
Author(s):  
Zhizhuang Yu ◽  
Yong Wang
Keyword(s):  
Thermal Load ◽  
High Speed ◽  
Gas Flow ◽  
Heat Dissipation ◽  
Brake Disc ◽  
Frictional Surface ◽  
Brake Shoe ◽  
Remarkable Effect ◽  
Gas Channel ◽  
Heat Transfer Theory

The function of the brake disc is to provide the ultimate guarantee of the safety of high speed trains. A braking unit includes two discs and two brake shoes. Braking performance depends on the pressure of the brake shoe and the friction between the disc and the shoe. When a train is braked, the brake disc endures a thermal load, which may affect the mechanical properties of the disc. If the thermal load exceeds the strength limit of the material, it could impact the safe running of the train. Therefore, the thermal load should be reduced as much as possible. Now the frictional surface of disc is plane and heat congregates easily in the surface area. The purpose of this paper is to explore a design for enhanced heat dissipation. A gas channel was used on the frictional surface to achieve the effect of heat dissipation. This design was analyzed by means of tribology and heat transfer theory. The distribution of gas flow was also researched. The temperature and stress field of the disc were simulated and analyzed. By the analysis it can be seen that the gas channel on the frictional surface of disc has a remarkable effect on heat dissipation in the brake disc.

The Finite Element Analysis of Asphalt Pavement with Function Layer under Temperature-Load Action

2012 ◽  
Vol 468-471 ◽  
pp. 2413-2416 ◽  
Author(s):  
Chuang Du ◽  
Yan Yan Li ◽  
Rong Guo ◽  
Shi Bin Ma
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Surface Layer ◽  
Asphalt Pavement ◽  
The Finite Element Method ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Temperature Load ◽  
Load Action ◽  
Reflection Crack

In order to study the performance of asphalt pavement with function layer under temperature-load coupling action, the thickness of surface layer, the module of surface layer and was analyzed to abtain their influence on the function layer stress using the finite element method. The results clearly indicated that it is very effective to prevent the reflection crack by increasing the thickness of asphalt surface layer and it is not obvious to reduce the reflection crack through enhancing the module of asphalt surface layer.

System-Level Transient Thermal Analysis for Performance Optimization of High Power Microelectronics

2003 ◽  
Author(s):  
Victor Adrian Chiriac ◽  
Tien-Yu Tom Lee ◽  
H. S. Chen
Keyword(s):  
Thermal Performance ◽  
Performance Optimization ◽  
Numerical Study ◽  
Optimal Operation ◽  
System Level ◽  
Main Concern ◽  
Efficient Operation ◽  
Normal Test ◽  
Transient Thermal ◽  
Short Time

The increasing trend in power levels and densities leads to the need of design thermal optimization, at either module or system level. A numerical study using finite-volume software was conducted to model the transient thermal behavior of a system including a package dissipating large amounts of power over short time durations. The system is evaluated by choosing the appropriate heat sink for the efficient operation of the device under 100W of constant powering, also to enhance the thermal performance of the enclosure/box containing the test stack-up. The intent of the study is to provide a meaningful understanding and prediction of the high transient powering scenarios. The study focuses on several powering and system design scenarios, identifying the main issues encountered during a normal device operation. The power source dissipates 100W for 2 seconds then is cooled for another 2 seconds. This thermal cycle is likely to occur several times during a normal test-up, and it is the main concern of the manufacturers not to exceed a limit temperature during the device testing operation. The transient trend is further extrapolated analytically to extract the steady state peak temperature values, in order to maintain the device peak temperatures below 120°C. The benefit of the study is related to the possibility to extract the maximum/minimum temperatures for a real test involving a large number of heating-cooling cycles, yet maintaining the initial and peak temperatures within a certain range, for the optimal operation of the device. The flow and heat transfer fields are thoroughly investigated. By using a combination of numerical and analytical study, the thermal performance of the device undergoing infinity of periodic thermal cycles is further predicted.

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