Harold Sun - Academia.edu (original) (raw)
Papers by Harold Sun
Journal of Turbomachinery, 2019
A passive shock wave control method, using a grooved surface instead of the original smooth surfa... more A passive shock wave control method, using a grooved surface instead of the original smooth surface of a gas turbine nozzle vane to alter a single shock wave into a multiple shock wave structure, is investigated in this paper, so as to gain insight into the flow characteristics of a multiple shock wave system and its variations with various grooved surface geometry parameters. With the combination of numerical and experimental approaches, the shock wave structure and the flow behavior in a linear turbine nozzle channel with different grooved surface configurations were compared and analyzed in details. The numerical and experimental results indicate that the multiple shock wave structure induced by the grooved surface is beneficial for mitigating the intensity of the shock wave, reducing the potential excitation force of the shock wave and decreasing the shock wave loss as well. It was also found that the benefits are related to the geometry of the grooved surface, such as groove wi...
2016 IEEE 55th Conference on Decision and Control (CDC), 2016
Methanol as a low carbon alternative fuel for automobile application has been studied for the pas... more Methanol as a low carbon alternative fuel for automobile application has been studied for the past few decades. There are a few technical barriers that have prevented the methanol-fueled vehicle from gaining market penetration. These technical barriers include: cold start difficulty, highly toxic aldehyde emission out of methanol fuel combustion that could be considerably higher than spark ignited (SI) gasoline engines, corrosion, lubricity and material compatibility issues of methanol fuel system components were also concerns for mass production of methanol-fueled vehicles. Tremendous efforts have been made over the past three decades to address these technical challenges. Many investigations have demonstrated brake thermal efficiency advantage of methanol fueled SI engines over conventional gasoline engines for passenger car application, as well as China V emission compliance even after regulated useful lifetime as part of methanol fueled vehicle pilot projects in China. Many stud...
International Journal of Engine Research, 2018
Ever since the energy crises in 1970s, the methanol, among other alternative fuels, has been stud... more Ever since the energy crises in 1970s, the methanol, among other alternative fuels, has been studied for automotive application. The methanol has been widely used for auto racing due to its superior anti-knock characteristics. However, aldehyde is a highly toxic pollutant and aldehyde emission out of alcohol fuel combustion could be considerably higher than spark-ignited gasoline engines. The corrosion and durability of methanol fuel components were also concerns for mass production of methanol-fueled vehicles. The authors have worked with an automotive manufacturer in China to investigate the brake thermal and emission improvement potentials of a methanol-fueled, spark-ignited engine over the original gasoline engine on a passenger car application and to demonstrate the performance and China V emission compliance over its useful life of 160,000 km. The study found that the methanol-fueled engine has 4%–6% brake thermal advantage over the original gasoline engine, and a three-way ox...
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2018
Effects of nozzle endwall clearances on variable nozzle turbocharger turbine performances have be... more Effects of nozzle endwall clearances on variable nozzle turbocharger turbine performances have been widely studied, but improving the variable nozzle turbocharger efficiency utilizing an optimal distribution of nozzle endwall clearances between the hub and the shroud sides has not drawn wide attention. Meanwhile, with the various distributions, shock wave variations that are closely related to turbine reliability are rarely reported. To fill the gap, this research performed three-dimensional numerical simulations on a variable nozzle turbocharger turbine to analyze the effects of various nozzle endwall clearance distributions on both turbine performance and shock wave. The results showed that there is an optimal distribution of the nozzle endwall clearance that can improve turbine efficiency and shift nozzle trailing edge shock wave. Performed on a linear turbine nozzle and with detailed validations, both experimental measurements and numerical simulations provide evidence that supports the numerical analyses conducted on a variable nozzle turbocharger turbine.
Aerospace Science and Technology, 2019
A shock wave mostly occurs around a compression corner in supersonic flow and, when the corner is... more A shock wave mostly occurs around a compression corner in supersonic flow and, when the corner is followed with another, two shock waves normally generate and, between them, an intersection is possible because of the increased shock angle of the downstream shock. A grooved-surface can generate multiple-shockwave structure in a local supersonic flow field as well. Different from the shockwave structure resulted from the compression corners, its structure may be approximately parallel or divergent when an additional expansion process occurs between two adjacent shock waves. This paper focuses exclusively on the shockwave structures based on both experimental and numerical methods. The physical mechanism for the generation of the approximately parallel and divergent shockwave structures is understood and then the approximately parallel shock wave structure is proved to belong to the same family with the divergent one. In addition, the relationship of the total oblique shock loss with the groove number is analyzed theoretically and numerically in entropy.
Advances in Mechanical Engineering, 2014
The clearance flow between the nozzle and endwall in a variable geometry turbine (VGT) has been n... more The clearance flow between the nozzle and endwall in a variable geometry turbine (VGT) has been numerically investigated to understand the clearance effect on the VGT performance and internal flow. It was found that the flow rate through turbine increases but the turbine efficiency decreases with height of clearance. Detailed flow field analyses indicated that most of the efficiency loss resulting from the leakage flow occurs at the upstream of the rotor area, that is, in the nozzle endwall clearance and between the nozzle vanes. There are two main mechanisms associated with this efficiency loss. One is due to the formation of the local vortex flow structure between the clearance flow and the main flow. The other is due to the impact of the clearance flow on the main flow after the nozzle throat. This impact reduces the span of shockwave with increased shockwave magnitude by changing the trajectory of the main flow.
SAE International Journal of Engines, 2013
• To support industry efforts of clean and efficient internal combustion engine development for p... more • To support industry efforts of clean and efficient internal combustion engine development for passenger and commercial applications • This program focuses on turbocharger improvement for medium and light duty diesel applications, from complete system optimization percepective to enable commercialization of advanced diesel combustion technologies, such as HCCI/LTC. • Improve combined turbocharger efficiency up to 10% or fuel economy by 3% on FTP cycle at Tier II Bin 5 emission level. (Task 3. Control and Actuation System Design and Development) 5. Actuation system design.
2016 American Control Conference (ACC), 2016
International Journal of Engine Research, 2021
Ceramic Catalytic Turbine (CCT) Technology is expected to become an important means to reduce veh... more Ceramic Catalytic Turbine (CCT) Technology is expected to become an important means to reduce vehicle emissions, especially during engine warm-up. In this paper, catalytic reaction was numerically simulated in 3D for a CCT on a gasoline engine during the warm-up period. The results showed that turbulence in the turbine promotes catalytic activity; CCT starts to significantly affect exhaust pollution since turbine inlet temperature of 550 K; the conversion efficiency of harmful gas in exhaust rises sharply when turbine inlet reaches 575–625 K; when the inlet temperature is about 720 K, the conversion efficiencies of C3H6, CO, and NO reach 23.7%, 21.1%, and 15.5%, respectively. Meanwhile the gas temperature is increased by about 30 K at turbine outlet. In addition, during the process of numerical modeling and calculation, it is found that minor change in boundary layer thickness has a negligible impact on the simulation. However, an extremely thin boundary layer will cause computation...
Volume 8: Microturbines, Turbochargers and Small Turbomachines; Steam Turbines, 2016
One of critical concerns in a variable geometry turbine (VGT) design program is shock wave genera... more One of critical concerns in a variable geometry turbine (VGT) design program is shock wave generated from nozzle exit at small open conditions with high inlet pressure condition, which may potentially lead to forced response of turbine wheel, even high-cycle fatigue issues and damage of inducer or exducer. Though modern turbine design programs have been well developed, it is difficult to eliminate the shock wave and all the resonant crossings that may occur within the wide operating range of a VGT turbine for automotive applications. This paper presents an option to mitigate intensity of the shock wave induced excitation using grooves on nozzle vane surface before the shock wave. Two kinds of turbines in which nozzle vanes with and without grooves were numerically simulated to obtain a three-dimensional flow field inside the turbine. The predicted performances from steady simulations were compared with test data to validate computational mesh and the unsteady simulation results were...
SAE Technical Paper Series, 2021
Journal of Mechanical Science and Technology, 2020
In this work, the influence of thickness and solidity of guide vane on the unsteady flow of a rad... more In this work, the influence of thickness and solidity of guide vane on the unsteady flow of a radial inflow turbine with variable nozzle has been numerically studied. Three vanes with the thickness changes from 0.3 to 0.1 and the solidity changes from 1.43 to 2.86, were chosen for this study. By investigating the unsteady flow field, it is found that the vane with low thickness and high solidity (vane B) can reduce shock by 75 % compared to the vane with high thickness and low solidity (base model); meanwhile, it can also mitigate the nozzle endwall leakage flow thus improves the flow uniformity of rotor inlet. As the intensity of shock and nozzle leakage flow were mitigated, the aerodynamic loading fluctuation of rotor blade can be weakened effectively, which will lead to improved rotor blades forced response. However, at small opening, vane B shows about 0.5 % lower efficiency than the base model; at large open condition, the efficiency degradation of vane B is up to 1.4 %. Therefore, there is a trade-off between the efficiency and forced response when choosing the nozzle vane solidity and thickness.
Journal of Turbomachinery, 2019
A passive shock wave control method, using a grooved surface instead of the original smooth surfa... more A passive shock wave control method, using a grooved surface instead of the original smooth surface of a gas turbine nozzle vane to alter a single shock wave into a multiple shock wave structure, is investigated in this paper, so as to gain insight into the flow characteristics of a multiple shock wave system and its variations with various grooved surface geometry parameters. With the combination of numerical and experimental approaches, the shock wave structure and the flow behavior in a linear turbine nozzle channel with different grooved surface configurations were compared and analyzed in details. The numerical and experimental results indicate that the multiple shock wave structure induced by the grooved surface is beneficial for mitigating the intensity of the shock wave, reducing the potential excitation force of the shock wave and decreasing the shock wave loss as well. It was also found that the benefits are related to the geometry of the grooved surface, such as groove wi...
2016 IEEE 55th Conference on Decision and Control (CDC), 2016
Methanol as a low carbon alternative fuel for automobile application has been studied for the pas... more Methanol as a low carbon alternative fuel for automobile application has been studied for the past few decades. There are a few technical barriers that have prevented the methanol-fueled vehicle from gaining market penetration. These technical barriers include: cold start difficulty, highly toxic aldehyde emission out of methanol fuel combustion that could be considerably higher than spark ignited (SI) gasoline engines, corrosion, lubricity and material compatibility issues of methanol fuel system components were also concerns for mass production of methanol-fueled vehicles. Tremendous efforts have been made over the past three decades to address these technical challenges. Many investigations have demonstrated brake thermal efficiency advantage of methanol fueled SI engines over conventional gasoline engines for passenger car application, as well as China V emission compliance even after regulated useful lifetime as part of methanol fueled vehicle pilot projects in China. Many stud...
International Journal of Engine Research, 2018
Ever since the energy crises in 1970s, the methanol, among other alternative fuels, has been stud... more Ever since the energy crises in 1970s, the methanol, among other alternative fuels, has been studied for automotive application. The methanol has been widely used for auto racing due to its superior anti-knock characteristics. However, aldehyde is a highly toxic pollutant and aldehyde emission out of alcohol fuel combustion could be considerably higher than spark-ignited gasoline engines. The corrosion and durability of methanol fuel components were also concerns for mass production of methanol-fueled vehicles. The authors have worked with an automotive manufacturer in China to investigate the brake thermal and emission improvement potentials of a methanol-fueled, spark-ignited engine over the original gasoline engine on a passenger car application and to demonstrate the performance and China V emission compliance over its useful life of 160,000 km. The study found that the methanol-fueled engine has 4%–6% brake thermal advantage over the original gasoline engine, and a three-way ox...
Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2018
Effects of nozzle endwall clearances on variable nozzle turbocharger turbine performances have be... more Effects of nozzle endwall clearances on variable nozzle turbocharger turbine performances have been widely studied, but improving the variable nozzle turbocharger efficiency utilizing an optimal distribution of nozzle endwall clearances between the hub and the shroud sides has not drawn wide attention. Meanwhile, with the various distributions, shock wave variations that are closely related to turbine reliability are rarely reported. To fill the gap, this research performed three-dimensional numerical simulations on a variable nozzle turbocharger turbine to analyze the effects of various nozzle endwall clearance distributions on both turbine performance and shock wave. The results showed that there is an optimal distribution of the nozzle endwall clearance that can improve turbine efficiency and shift nozzle trailing edge shock wave. Performed on a linear turbine nozzle and with detailed validations, both experimental measurements and numerical simulations provide evidence that supports the numerical analyses conducted on a variable nozzle turbocharger turbine.
Aerospace Science and Technology, 2019
A shock wave mostly occurs around a compression corner in supersonic flow and, when the corner is... more A shock wave mostly occurs around a compression corner in supersonic flow and, when the corner is followed with another, two shock waves normally generate and, between them, an intersection is possible because of the increased shock angle of the downstream shock. A grooved-surface can generate multiple-shockwave structure in a local supersonic flow field as well. Different from the shockwave structure resulted from the compression corners, its structure may be approximately parallel or divergent when an additional expansion process occurs between two adjacent shock waves. This paper focuses exclusively on the shockwave structures based on both experimental and numerical methods. The physical mechanism for the generation of the approximately parallel and divergent shockwave structures is understood and then the approximately parallel shock wave structure is proved to belong to the same family with the divergent one. In addition, the relationship of the total oblique shock loss with the groove number is analyzed theoretically and numerically in entropy.
Advances in Mechanical Engineering, 2014
The clearance flow between the nozzle and endwall in a variable geometry turbine (VGT) has been n... more The clearance flow between the nozzle and endwall in a variable geometry turbine (VGT) has been numerically investigated to understand the clearance effect on the VGT performance and internal flow. It was found that the flow rate through turbine increases but the turbine efficiency decreases with height of clearance. Detailed flow field analyses indicated that most of the efficiency loss resulting from the leakage flow occurs at the upstream of the rotor area, that is, in the nozzle endwall clearance and between the nozzle vanes. There are two main mechanisms associated with this efficiency loss. One is due to the formation of the local vortex flow structure between the clearance flow and the main flow. The other is due to the impact of the clearance flow on the main flow after the nozzle throat. This impact reduces the span of shockwave with increased shockwave magnitude by changing the trajectory of the main flow.
SAE International Journal of Engines, 2013
• To support industry efforts of clean and efficient internal combustion engine development for p... more • To support industry efforts of clean and efficient internal combustion engine development for passenger and commercial applications • This program focuses on turbocharger improvement for medium and light duty diesel applications, from complete system optimization percepective to enable commercialization of advanced diesel combustion technologies, such as HCCI/LTC. • Improve combined turbocharger efficiency up to 10% or fuel economy by 3% on FTP cycle at Tier II Bin 5 emission level. (Task 3. Control and Actuation System Design and Development) 5. Actuation system design.
2016 American Control Conference (ACC), 2016
International Journal of Engine Research, 2021
Ceramic Catalytic Turbine (CCT) Technology is expected to become an important means to reduce veh... more Ceramic Catalytic Turbine (CCT) Technology is expected to become an important means to reduce vehicle emissions, especially during engine warm-up. In this paper, catalytic reaction was numerically simulated in 3D for a CCT on a gasoline engine during the warm-up period. The results showed that turbulence in the turbine promotes catalytic activity; CCT starts to significantly affect exhaust pollution since turbine inlet temperature of 550 K; the conversion efficiency of harmful gas in exhaust rises sharply when turbine inlet reaches 575–625 K; when the inlet temperature is about 720 K, the conversion efficiencies of C3H6, CO, and NO reach 23.7%, 21.1%, and 15.5%, respectively. Meanwhile the gas temperature is increased by about 30 K at turbine outlet. In addition, during the process of numerical modeling and calculation, it is found that minor change in boundary layer thickness has a negligible impact on the simulation. However, an extremely thin boundary layer will cause computation...
Volume 8: Microturbines, Turbochargers and Small Turbomachines; Steam Turbines, 2016
One of critical concerns in a variable geometry turbine (VGT) design program is shock wave genera... more One of critical concerns in a variable geometry turbine (VGT) design program is shock wave generated from nozzle exit at small open conditions with high inlet pressure condition, which may potentially lead to forced response of turbine wheel, even high-cycle fatigue issues and damage of inducer or exducer. Though modern turbine design programs have been well developed, it is difficult to eliminate the shock wave and all the resonant crossings that may occur within the wide operating range of a VGT turbine for automotive applications. This paper presents an option to mitigate intensity of the shock wave induced excitation using grooves on nozzle vane surface before the shock wave. Two kinds of turbines in which nozzle vanes with and without grooves were numerically simulated to obtain a three-dimensional flow field inside the turbine. The predicted performances from steady simulations were compared with test data to validate computational mesh and the unsteady simulation results were...
SAE Technical Paper Series, 2021
Journal of Mechanical Science and Technology, 2020
In this work, the influence of thickness and solidity of guide vane on the unsteady flow of a rad... more In this work, the influence of thickness and solidity of guide vane on the unsteady flow of a radial inflow turbine with variable nozzle has been numerically studied. Three vanes with the thickness changes from 0.3 to 0.1 and the solidity changes from 1.43 to 2.86, were chosen for this study. By investigating the unsteady flow field, it is found that the vane with low thickness and high solidity (vane B) can reduce shock by 75 % compared to the vane with high thickness and low solidity (base model); meanwhile, it can also mitigate the nozzle endwall leakage flow thus improves the flow uniformity of rotor inlet. As the intensity of shock and nozzle leakage flow were mitigated, the aerodynamic loading fluctuation of rotor blade can be weakened effectively, which will lead to improved rotor blades forced response. However, at small opening, vane B shows about 0.5 % lower efficiency than the base model; at large open condition, the efficiency degradation of vane B is up to 1.4 %. Therefore, there is a trade-off between the efficiency and forced response when choosing the nozzle vane solidity and thickness.