Generally speaking, main flow path of gas turbine is assumed to be perfect for standard 3D computation. But in real engine, the turbine annulus geometry is not completely smooth for the presence of the shroud and asso...Generally speaking, main flow path of gas turbine is assumed to be perfect for standard 3D computation. But in real engine, the turbine annulus geometry is not completely smooth for the presence of the shroud and associated cavity near the end wall. Besides, shroud leakage flow is one of the dominant sources of secondary flow in tur- bomachinery, which not only causes a deterioration of useful work but also a penalty on turbine efficiency. It has been found that neglect shroud leakage flow makes the computed velocity profiles and loss distribution signifi- cantly different to those measured. Even so, the influence of shroud leakage flow is seldom taken into considera- tion during the routine of turbine design due to insufficient understanding of its impact on end wall flows and tur- bine performance. In order to evaluate the impact of tip shroud geometry on turbine performance, a 3D computa- tional investigation for 1.5-stage turbine with shrouded blades was performed in this paper. The following ge- ometry parameters were varied respectively：展开更多
Horizontal axis tidal turbines have attracted more and more attentions nowadays, because of their convenience and low expense in construction and high efficiency in extracting tidal energy. The present study numerical...Horizontal axis tidal turbines have attracted more and more attentions nowadays, because of their convenience and low expense in construction and high efficiency in extracting tidal energy. The present study numerically investigates the flow motion and performance of a horizontal axis tidal turbine with a supporting vertical cylinder under steady current. In the numerical model, the continuous equation and incompressible Reynolds-averaged Navier-Stokes equations are solved, and the volume of fluid method is employed to track free surface motion. The RNG k-ε model is adopted to calculate turbulence transport while the fractional area/volume obstacle representation method is used to describe turbine characteristics and movement. The effects of installation elevation of tidal turbine and inlet velocity on the water elevation, and current velocity, rotating speed and resultant force on turbine are discussed. Based on the comparison of the numerical results, a better understanding of flow structure around horizontal axis tidal turbine and turbine performance is achieved.展开更多
Typically, crude oil production in Nigeria always accompanied by surface production of associated gas. With little associated gas recovery facilities in place, majority of associated gas is continuously flared with fe...Typically, crude oil production in Nigeria always accompanied by surface production of associated gas. With little associated gas recovery facilities in place, majority of associated gas is continuously flared with few portions re-injected into the reservoir for enhance oil recovery (EOR). In addition to environmental hazards, wasting substantial amount of produced associated gas is deemed detrimental to a country currently generating less than 54% of its electric power requirement. Onsite power generation as one of the many means of utilization of associated gas has been conceived. Conversely, the availability and performance of the gas turbine engine for onsite associated gas utilization requires evaluation owing to variations in associated natural gas composition globally and the dependency of associated gas production on reservoirs and oil production activities. This paper presents an analytical investigation of gas turbine engine inspired by GE LMS100 frame engine for onsite utilization of associated gas in Nigeria. Gas turbine performance results are presented and performance parameters are compared against typical commercial natural gas grade.展开更多
Impulse turbine, working as a typical self-rectifying turbine, is recently utilized for the oscillating water column（OWC） wave energy converters, which can rotate in the same direction under the bi-directional air f...Impulse turbine, working as a typical self-rectifying turbine, is recently utilized for the oscillating water column（OWC） wave energy converters, which can rotate in the same direction under the bi-directional air flows. A numerical model established in Fluent is validated by the corresponding experimental results. The flow fields, pressure distribution and dimensionless evaluating coefficients can be calculated and analyzed. Effects of the rotor solidity varying with the change of blade number are investigated and the suitable solidity value is recommended for different flow coefficients.展开更多
The classical momentum-blade element theory is improved by using the empirical formula while part of rotor blades enters into the turbulent wake state, and the performance of a horizontal-axis wind turbine (HAWT) at a...The classical momentum-blade element theory is improved by using the empirical formula while part of rotor blades enters into the turbulent wake state, and the performance of a horizontal-axis wind turbine (HAWT) at all speed ratios can be predicted. By using an improved version of the so-called secant method, the convergent solutions of the system of two-dimensional equations concerning the induced velocity factors a and a' are guaranteed. Besides, a solving method of multiple solutions for a and a' is proposed and discussed. The method provided in this paper can be used for computing the aerodynamic performance of HAWTs both ofrlow solidity and of high solidity. The calculated results coincide well with the experimental data.展开更多
This study is concerned with the numerical simulation of the flow through an open type cross-flow runner of a nano-hydraulic turbine driven by rapid and shallow stream. It employs the two-dimensional particle method, ...This study is concerned with the numerical simulation of the flow through an open type cross-flow runner of a nano-hydraulic turbine driven by rapid and shallow stream. It employs the two-dimensional particle method, which was used for the flow simulation of a small-scale hydraulic turbine of impulse-type in the prior study. The tip speed ratio 2, defined as the ratio of the runner tip speed to the water stream velocity upstream of the runner, ranges from 0.1 to 0.8. The simulated flow at 2 = 0.5 is confirmed to agree well with the experimentally visualized one. The effect of 2 on the flows inside the rotating cascade as well as around the runner is clarified. The turbine performance, calculated by using the simulated flow, is also highlighted to agree almost with the measurement. These demonstrate that the present simulation method is indeed applicable to the development of open type cross-flow runner of nano-hydraulic turbine utilizing rapid and shallow stream.展开更多
Online compressor wash for six GE LM2500PE engines at a Statoil North Sea offshore field is analyzed. Three engines are generator drivers whilst three engines are compressor drivers. Two of the compressor drive engine...Online compressor wash for six GE LM2500PE engines at a Statoil North Sea offshore field is analyzed. Three engines are generator drivers whilst three engines are compressor drivers. Two of the compressor drive engines are running at peak load （T5.4-control）, hence production rate is limited by the available power from these engines. All the six engines analyzed run continuously without redundancy, hence gas turbine uptime is critical for the field＇s production and economy. The performance and operational experience with on-line wash at different water-to-air ratios and engine loads, as well as economy potentials related to successful on-line wash are given. This work is based on long-term operation with on-line wash, where operational data are collected and performance analyzed, over a 4-5 year period. All engines are operated with four-month intervals between maintenance stops, where off-line crank-wash is performed as well as other necessary maintenance and repairs. On-line wash is performed daily between the maintenance stops at full load （i.e., normal operating load for the subject engine）. To keep the engine as clean as possible and reduce degradation between maintenance stops, both an effective on-line water wash system as well as effective air intake filter system, are critical factors. The overall target is to maintain high engine performance, and extend the interval between maintenance stops through effective on-line wash. It is of vital importance to understand the gas turbine performance deterioration. The trending of its deviation from the engine baseline facilitates load-independent monitoring of the gas turbine＇s condition. Engine response to water injection at different loads and water-to-air ratios, as well as engine response to compressor deterioration is documented and analyzed. Instrument resolution and repeatability are key factors required in order to obtain reliable performance analysis results. Offshore instrumentation on older installations is often limited to the necessary instruments for machine control/protection, and additional instruments for effective performance monitoring and analysis are often missing or, if installed, have less accuracy. As a result of these analyses, a set of monitoring parameters is proposed for effective diagnosis of compressor degradation. Avenues for further research and development are proposed in order to further increase the understanding of the deterioration mechanisms and the gas turbine performance and response.展开更多
In the present study, the performance of the NTNU Blind Test 1 wind turbine is analyzed in the computational fluid dynamics (CFD) simulations by using the CFD code FANS with structured overset grids. First, the numeri...In the present study, the performance of the NTNU Blind Test 1 wind turbine is analyzed in the computational fluid dynamics (CFD) simulations by using the CFD code FANS with structured overset grids. First, the numerical methods including the governing equations, the turbulence closure model, and the flow solver are introduced. In addition, the NTNU BT1 wind tunnel experiment is described. Then, structured overset grid blocks are generated in the computational domain with fully resolved wind turbine geometry, including the blades, hub, nacelle, and tower. Afterward, unsteady Reynolds averaged Navier-Stokes (RANS) simulations with the two-layer k - ε turbulence model are performed with an inlet velocity of 10 m/s and a tip-speed ratio (TSR) of 6. The overset-grid capability of FANS is leveraged to handle the rotation of the rotor. Finally, simulations are performed for a range of TSRs and a comparison is made among the present CFD results, other numerical results obtained from representative methods, and the experimental data. It is observed that the CFD-predicted thrust coefficients match the experimental measurement at low TSRs while under-predicting the values at high TSRs, and potential reasons for this deviation are discussed.展开更多
基金Financial support from the Innovation Foundation of BUAA for PhD Graduates(YWF-13-A01-014)
文摘Generally speaking, main flow path of gas turbine is assumed to be perfect for standard 3D computation. But in real engine, the turbine annulus geometry is not completely smooth for the presence of the shroud and associated cavity near the end wall. Besides, shroud leakage flow is one of the dominant sources of secondary flow in tur- bomachinery, which not only causes a deterioration of useful work but also a penalty on turbine efficiency. It has been found that neglect shroud leakage flow makes the computed velocity profiles and loss distribution signifi- cantly different to those measured. Even so, the influence of shroud leakage flow is seldom taken into considera- tion during the routine of turbine design due to insufficient understanding of its impact on end wall flows and tur- bine performance. In order to evaluate the impact of tip shroud geometry on turbine performance, a 3D computa- tional investigation for 1.5-stage turbine with shrouded blades was performed in this paper. The following ge- ometry parameters were varied respectively：
基金funded by by the National Science Fund for Distinguished Young Scholars(Grant No.51425901)the National Natural Science Foundation of China(Grant Nos.51479053 and 51137002)+4 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK2011026)the 111 Project(Grant No.B2012032)the Specialized Research Funding for the Doctoral Program of Higher Education(Grant No.20130094110014)the Marine Renewable Energy Research Project of State Oceanic Administration(Grant No.GHME2013GC03)the Fundamental Research Funds for the Central University(Hohai University,Grant Nos.2013B31614 and 2014B04114)
文摘Horizontal axis tidal turbines have attracted more and more attentions nowadays, because of their convenience and low expense in construction and high efficiency in extracting tidal energy. The present study numerically investigates the flow motion and performance of a horizontal axis tidal turbine with a supporting vertical cylinder under steady current. In the numerical model, the continuous equation and incompressible Reynolds-averaged Navier-Stokes equations are solved, and the volume of fluid method is employed to track free surface motion. The RNG k-ε model is adopted to calculate turbulence transport while the fractional area/volume obstacle representation method is used to describe turbine characteristics and movement. The effects of installation elevation of tidal turbine and inlet velocity on the water elevation, and current velocity, rotating speed and resultant force on turbine are discussed. Based on the comparison of the numerical results, a better understanding of flow structure around horizontal axis tidal turbine and turbine performance is achieved.
文摘Typically, crude oil production in Nigeria always accompanied by surface production of associated gas. With little associated gas recovery facilities in place, majority of associated gas is continuously flared with few portions re-injected into the reservoir for enhance oil recovery (EOR). In addition to environmental hazards, wasting substantial amount of produced associated gas is deemed detrimental to a country currently generating less than 54% of its electric power requirement. Onsite power generation as one of the many means of utilization of associated gas has been conceived. Conversely, the availability and performance of the gas turbine engine for onsite associated gas utilization requires evaluation owing to variations in associated natural gas composition globally and the dependency of associated gas production on reservoirs and oil production activities. This paper presents an analytical investigation of gas turbine engine inspired by GE LMS100 frame engine for onsite utilization of associated gas in Nigeria. Gas turbine performance results are presented and performance parameters are compared against typical commercial natural gas grade.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51279190 and 51311140259)the Shandong Province Natural Science Foundation for Distinguished Young Scholars(Grant No.JQ201314)
文摘Impulse turbine, working as a typical self-rectifying turbine, is recently utilized for the oscillating water column（OWC） wave energy converters, which can rotate in the same direction under the bi-directional air flows. A numerical model established in Fluent is validated by the corresponding experimental results. The flow fields, pressure distribution and dimensionless evaluating coefficients can be calculated and analyzed. Effects of the rotor solidity varying with the change of blade number are investigated and the suitable solidity value is recommended for different flow coefficients.
文摘The classical momentum-blade element theory is improved by using the empirical formula while part of rotor blades enters into the turbulent wake state, and the performance of a horizontal-axis wind turbine (HAWT) at all speed ratios can be predicted. By using an improved version of the so-called secant method, the convergent solutions of the system of two-dimensional equations concerning the induced velocity factors a and a' are guaranteed. Besides, a solving method of multiple solutions for a and a' is proposed and discussed. The method provided in this paper can be used for computing the aerodynamic performance of HAWTs both ofrlow solidity and of high solidity. The calculated results coincide well with the experimental data.
文摘This study is concerned with the numerical simulation of the flow through an open type cross-flow runner of a nano-hydraulic turbine driven by rapid and shallow stream. It employs the two-dimensional particle method, which was used for the flow simulation of a small-scale hydraulic turbine of impulse-type in the prior study. The tip speed ratio 2, defined as the ratio of the runner tip speed to the water stream velocity upstream of the runner, ranges from 0.1 to 0.8. The simulated flow at 2 = 0.5 is confirmed to agree well with the experimentally visualized one. The effect of 2 on the flows inside the rotating cascade as well as around the runner is clarified. The turbine performance, calculated by using the simulated flow, is also highlighted to agree almost with the measurement. These demonstrate that the present simulation method is indeed applicable to the development of open type cross-flow runner of nano-hydraulic turbine utilizing rapid and shallow stream.
文摘Online compressor wash for six GE LM2500PE engines at a Statoil North Sea offshore field is analyzed. Three engines are generator drivers whilst three engines are compressor drivers. Two of the compressor drive engines are running at peak load （T5.4-control）, hence production rate is limited by the available power from these engines. All the six engines analyzed run continuously without redundancy, hence gas turbine uptime is critical for the field＇s production and economy. The performance and operational experience with on-line wash at different water-to-air ratios and engine loads, as well as economy potentials related to successful on-line wash are given. This work is based on long-term operation with on-line wash, where operational data are collected and performance analyzed, over a 4-5 year period. All engines are operated with four-month intervals between maintenance stops, where off-line crank-wash is performed as well as other necessary maintenance and repairs. On-line wash is performed daily between the maintenance stops at full load （i.e., normal operating load for the subject engine）. To keep the engine as clean as possible and reduce degradation between maintenance stops, both an effective on-line water wash system as well as effective air intake filter system, are critical factors. The overall target is to maintain high engine performance, and extend the interval between maintenance stops through effective on-line wash. It is of vital importance to understand the gas turbine performance deterioration. The trending of its deviation from the engine baseline facilitates load-independent monitoring of the gas turbine＇s condition. Engine response to water injection at different loads and water-to-air ratios, as well as engine response to compressor deterioration is documented and analyzed. Instrument resolution and repeatability are key factors required in order to obtain reliable performance analysis results. Offshore instrumentation on older installations is often limited to the necessary instruments for machine control/protection, and additional instruments for effective performance monitoring and analysis are often missing or, if installed, have less accuracy. As a result of these analyses, a set of monitoring parameters is proposed for effective diagnosis of compressor degradation. Avenues for further research and development are proposed in order to further increase the understanding of the deterioration mechanisms and the gas turbine performance and response.
基金Project supported by the National Natural Science Foundation of China(Grant No.52131102).
文摘In the present study, the performance of the NTNU Blind Test 1 wind turbine is analyzed in the computational fluid dynamics (CFD) simulations by using the CFD code FANS with structured overset grids. First, the numerical methods including the governing equations, the turbulence closure model, and the flow solver are introduced. In addition, the NTNU BT1 wind tunnel experiment is described. Then, structured overset grid blocks are generated in the computational domain with fully resolved wind turbine geometry, including the blades, hub, nacelle, and tower. Afterward, unsteady Reynolds averaged Navier-Stokes (RANS) simulations with the two-layer k - ε turbulence model are performed with an inlet velocity of 10 m/s and a tip-speed ratio (TSR) of 6. The overset-grid capability of FANS is leveraged to handle the rotation of the rotor. Finally, simulations are performed for a range of TSRs and a comparison is made among the present CFD results, other numerical results obtained from representative methods, and the experimental data. It is observed that the CFD-predicted thrust coefficients match the experimental measurement at low TSRs while under-predicting the values at high TSRs, and potential reasons for this deviation are discussed.
