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VGV optimization for performance

Ling, Sara LU and Sönne, Ted LU (2014) MVK920 20141
Department of Energy Sciences
Abstract
Today’s market for gas turbines is very competitive and it is important to constantly improve the performance of the engines. It is commonly known that gas turbines have better performance at low ambient temperatures than at high ambient temperatures. One way to counteract the negative influence of a high ambient temperature is to use variable compressor guide vanes. The aim of this thesis is to evaluate the potential of using another way to control these variable guide vanes to enhance the performance of gas turbines at high ambient temperatures. This is done by modelling and calculations complemented with interviews and discussions with employees at Siemens Industrial Turbomachinery.
This master thesis consists of several studies that... (More)
Today’s market for gas turbines is very competitive and it is important to constantly improve the performance of the engines. It is commonly known that gas turbines have better performance at low ambient temperatures than at high ambient temperatures. One way to counteract the negative influence of a high ambient temperature is to use variable compressor guide vanes. The aim of this thesis is to evaluate the potential of using another way to control these variable guide vanes to enhance the performance of gas turbines at high ambient temperatures. This is done by modelling and calculations complemented with interviews and discussions with employees at Siemens Industrial Turbomachinery.
This master thesis consists of several studies that together form a foundation to build an improved control algorithm from. In the first study of this thesis the compressor turbine performance at different physical shaft-speeds is evaluated. The second study shows how the gas turbines react when the ambient temperature is varied. In the third study the variable guide vanes are altered to find the most suitable way to control them. The fourth study studies the most promising positions, from the third study, with consideration to the effects from the secondary air system. The fifth study shows how the engine would react to a more opened position of the variable guide vanes when running at part load. In the final study of this thesis, separate controlling of the inlet guide vane and the first stator is evaluated to see if it could increase the performance for SGT-700. In this thesis the effects on surge margin and engine lifespan, as the variable guide vane positions are altered, are also evaluated.
Based on the results in this master thesis SGT-700 is concluded to be running at optimal variable guide vane settings at the tested ambient temperatures. The test of using separate actuators for the inlet guide vane and stator 1 did not result in any improved performance.
The results show that SGT-750 could gain from a more opened position at high ambient temperatures when running on full load. The most promising case at 30°C is an opening of the inlet guide vane of 2.5° relative to today’s existing position. This results in an increase in shaft power of 0.5% and an increase in thermal efficiency of 0.1%. The most promising case at 45°C is an opening of the inlet guide vane of 4° relative to today’s existing position. This results in an increase in shaft power of nearly 2.9% and an increase in thermal efficiency of 1.1%.
At part load the results show that SGT-750 will benefit from running at a more opened position as long as the aerodynamic shaft-speed is low. As the aerodynamic shaft-speed is increased, the part load performance does no longer benefit from running at a more opened position of the variable guide vanes.
Using these new variable guide vane positions will lead to a decreased surge margin but the decrease in surge margin is considered acceptable. The proposed changes will lead to lower physical shaft-speeds thus lowering the centrifugal stresses. The lowered stresses are positive but will not result in longer service intervals.
Based on the results in this master thesis the recommendation is that further time and resources are devoted to find an improved control algorithm for SGT-750. The biggest potential of improvement is found for engines running at full load at high ambient temperatures. It is also recommended that further investigation is done into the possibility to use a more opened position at part load. (Less)
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author
Ling, Sara LU and Sönne, Ted LU
supervisor
organization
course
MVK920 20141
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Twin-shaft, Tropical matched, Performance, Gas turbine, Ambient temperature, Variable guide vane, Siemens
report number
ISRN LUTMDN/TMHP-14/5317-SE
ISSN
0282-1990
language
English
id
4465257
date added to LUP
2014-06-17 11:15:46
date last changed
2014-06-17 11:15:46
@misc{4465257,
  abstract     = {Today’s market for gas turbines is very competitive and it is important to constantly improve the performance of the engines. It is commonly known that gas turbines have better performance at low ambient temperatures than at high ambient temperatures. One way to counteract the negative influence of a high ambient temperature is to use variable compressor guide vanes. The aim of this thesis is to evaluate the potential of using another way to control these variable guide vanes to enhance the performance of gas turbines at high ambient temperatures. This is done by modelling and calculations complemented with interviews and discussions with employees at Siemens Industrial Turbomachinery.
This master thesis consists of several studies that together form a foundation to build an improved control algorithm from. In the first study of this thesis the compressor turbine performance at different physical shaft-speeds is evaluated. The second study shows how the gas turbines react when the ambient temperature is varied. In the third study the variable guide vanes are altered to find the most suitable way to control them. The fourth study studies the most promising positions, from the third study, with consideration to the effects from the secondary air system. The fifth study shows how the engine would react to a more opened position of the variable guide vanes when running at part load. In the final study of this thesis, separate controlling of the inlet guide vane and the first stator is evaluated to see if it could increase the performance for SGT-700. In this thesis the effects on surge margin and engine lifespan, as the variable guide vane positions are altered, are also evaluated.
Based on the results in this master thesis SGT-700 is concluded to be running at optimal variable guide vane settings at the tested ambient temperatures. The test of using separate actuators for the inlet guide vane and stator 1 did not result in any improved performance.
The results show that SGT-750 could gain from a more opened position at high ambient temperatures when running on full load. The most promising case at 30°C is an opening of the inlet guide vane of 2.5° relative to today’s existing position. This results in an increase in shaft power of 0.5% and an increase in thermal efficiency of 0.1%. The most promising case at 45°C is an opening of the inlet guide vane of 4° relative to today’s existing position. This results in an increase in shaft power of nearly 2.9% and an increase in thermal efficiency of 1.1%.
At part load the results show that SGT-750 will benefit from running at a more opened position as long as the aerodynamic shaft-speed is low. As the aerodynamic shaft-speed is increased, the part load performance does no longer benefit from running at a more opened position of the variable guide vanes.
Using these new variable guide vane positions will lead to a decreased surge margin but the decrease in surge margin is considered acceptable. The proposed changes will lead to lower physical shaft-speeds thus lowering the centrifugal stresses. The lowered stresses are positive but will not result in longer service intervals.
Based on the results in this master thesis the recommendation is that further time and resources are devoted to find an improved control algorithm for SGT-750. The biggest potential of improvement is found for engines running at full load at high ambient temperatures. It is also recommended that further investigation is done into the possibility to use a more opened position at part load.},
  author       = {Ling, Sara and Sönne, Ted},
  issn         = {0282-1990},
  keyword      = {Twin-shaft,Tropical matched,Performance,Gas turbine,Ambient temperature,Variable guide vane,Siemens},
  language     = {eng},
  note         = {Student Paper},
  title        = {VGV optimization for performance},
  year         = {2014},
}