Influence of Wetness on Efficiency of the Full Scale Size Low Pressure Turbines

2012 ◽  
Author(s):  
Tomohiko Tsukuda ◽  
Hiroyuki Kawagishi ◽  
Naoki Shibukawa ◽  
Tadayuki Hashidate ◽  
Koichi Goto ◽  
...  
Keyword(s):  
Load Condition ◽  
Low Pressure ◽  
Test Results ◽  
Absolute Value ◽  
Low Pressure Turbine ◽  
Scale Size ◽  
Low Load ◽  
Lp Turbine ◽  
Stage Efficiency ◽  
Load Conditions

Efficiencies of 60Hz full size test turbines were measured in various wet steam conditions to reveal the wetness impact on the performance. We changed the wetness and stage load conditions independently under the condition of constant steam mass flow rate in the low pressure turbine. The test results told that the stage efficiency decreases with the increasing of wetness as many studies showed, furthermore, the stage efficiency decreases more in smaller load conditions than in the design point. In addition, blade length effects were examined by comparing two types of LP turbine to be found that the longer case got more deficits at the same wetness. Some theoretical evaluations were tried and a combination of some simple loss models explained the tendencies above, qualitatively. The evaluation showed that absolute value of mechanical wet loss such as braking loss remained unchanged regardless of load conditions, so in low load condition, ratio of mechanical loss to stage load increased, resulting decrease of stage efficiency. It also showed that increasing wet loss at the longer blade was mainly because higher circumferential velocity caused larger mechanical wet loss such as braking loss.

Redesign of High-Lift LP-Turbine Airfoils for Low Speed Testing

2010 ◽  
Author(s):  
Michele Marconcini ◽  
Filippo Rubechini ◽  
Roberto Pacciani ◽  
Andrea Arnone ◽  
Francesco Bertini
Keyword(s):  
Separated Flow ◽  
Low Pressure ◽  
High Lift ◽  
Low Speed ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Flow Configurations ◽  
Artificial Neural Network Ann ◽  
Lp Turbine ◽  
Turbine Airfoils

Low pressure turbine airfoils of the present generation usually operate at subsonic conditions, with exit Mach numbers of about 0.6. To reduce the costs of experimental programs it can be convenient to carry out measurements in low speed tunnels in order to determine the cascades performance. Generally speaking, low speed tests are usually carried out on airfoils with modified shape, in order to compensate for the effects of compressibility. A scaling procedure for high-lift, low pressure turbine airfoils to be studied in low speed conditions is presented and discussed. The proposed procedure is based on the matching of a prescribed blade load distribution between the low speed airfoil and the actual one. Such a requirement is fulfilled via an Artificial Neural Network (ANN) methodology and a detailed parameterization of the airfoil. A RANS solver is used to guide the redesign process. The comparison between high and low speed profiles is carried out, over a wide range of Reynolds numbers, by using a novel three-equation, transition-sensitive, turbulence model. Such a model is based on the coupling of an additional transport equation for the so-called laminar kinetic energy (LKE) with the Wilcox k–ω model and it has proven to be effective for transitional, separated-flow configurations of high-lift cascade flows.

Application of the Rotating Water Table to Nozzle Wake Excitation in Low Pressure Turbines

1985 ◽  
Author(s):  
Shun Chen
Keyword(s):  
Water Table ◽  
Low Pressure ◽  
Test Facility ◽  
Test Results ◽  
Unsteady Forces ◽  
Low Pressure Turbine ◽  
Rotating Blade ◽  
Stator Vane ◽  
Two Dimensional Flow ◽  
Hydraulic Analogy

The hydraulic analogy was employed in a rotating water table for simulating the compressible two dimensional flow in a low pressure turbine stage. Both steady and unsteady forces were measured directly on a rotating blade in a blade row rotating concentrically with a row of stator vanes. With proper modeling of the simulation, it is shown that the rotating water table can yield results that agree favorably with the analytical predictions and turbine test results. Using this test facility, the effects of axial spacing between rotor and stator rows on the nozzle wake excitation have been investigated for two different stator vane profiles. The water table test results correlate qualitatively with the turbine test data. The cancellation of nozzle passing frequency excitation by off-setting nozzle pitch was demonstrated in the water table and the results compared with both the analytical predictions and the laboratory turbine test results.

Aerodynamic Numerical Investigation of Low-Pressure Steam Turbine Last Stage Under Low Load Conditions With Mode Decomposition Methods

2019 ◽  
Author(s):  
Ping Hu ◽  
Tong Lin ◽  
Rui Yang ◽  
Xiaocheng Zhu ◽  
Zhaohui Du
Keyword(s):  
Steam Turbine ◽  
Frequency Spectrum ◽  
Low Frequency ◽  
Low Pressure ◽  
Unsteady Pressure ◽  
Mode Decomposition ◽  
Low Load ◽  
Last Stage ◽  
Operating Points ◽  
Load Conditions

Abstract It is common that steam turbine works at different operating points, especially under low load conditions, to cater to complex and varied demands for power generation recently. Considering the long and thin shape of last stage moving blades (LSMBs) in a low-pressure (LP) steam turbine, there are many challenges to design a suitable case which balances global efficiency against sufficient structure strength when suffering excitations at low load operating points. In present work, the aim is to extract specific aerodynamic excitations and recognize their distribution and propagation features. Firstly, steady 3D computational fluid dynamics (CFD) calculations are simulated at 25GV and 17GV (25% and 17% of design mass flow conditions) and corresponding unsteady calculations are performed with enough rotor revolutions to obtain integrated flow periodicities. Unsteady pressure signals near tip region of LSMBs are monitored circumferentially in both static and rotating coordinates. The fast Fourier transformation (FFT) results of unsteady pressure signals show that there are broadband humps with small disturbance amplitudes in low frequency spectrum at 25GV, however, a sharp spike is shown in low frequency spectrum at 17GV. Further, circumferential mode decomposition (CMD) method has been applied to distinguish different fluctuations in frequency and the mode numbers and circumferential propagating pace of which have been obtained. Finally, dynamic mode decomposition (DMD) method has been performed to describe detailed mode shapes of featured flow perturbances both in static and rotating coordinate system. These analyses indicate that at 25GV, a band of unsteady responses with very low amplitude was noted which has some features similar to rotating instability (RI). However, distribution and propagation features of flow unsteadiness at 17GV are in good agreement with rotating stall (RS) in compressor.

Application of GE Low Load Package on an Existing District Heating Power Plant: A Case Study

2020 ◽  
Author(s):  
Antonio Mambro ◽  
Francesco Congiu ◽  
Francesco Piraccini
Keyword(s):  
Power Plant ◽  
Power Plants ◽  
District Heating ◽  
Low Pressure ◽  
Heating Power ◽  
Low Pressure Turbine ◽  
Low Load ◽  
Flow Through ◽  
Last Stage

Abstract The continuous increase of variable renewable energy and fuel cost requires steam turbine power plants to operate with high flexibility. Furthermore, the reduction in electricity price is forcing many existing and new district heating power plants to further optimize the heat production to maintain a sustainable business. This situation leads to low pressure steam turbines running at very low volume flow for an extended time. In this work, a case study of an existing 30 MWel district heating power plant located in Europe is presented. The customer request was the removal of the steam turbine last two stages along with the condenser to maximize steam delivery for district heating operations. However, based on the experience gained by GE on low load during the last years, the same heat production has been guaranteed without any significant impact on the existing unit, excluding any major modification of the plant layout such as last stage blading and condenser removal. Making use of the latest low flow modeling, the minimum cooling flow through the low-pressure turbine has been reduced by more than 90% compared to the existing unit. Optimization of the hood spray system and logic will reduce trailing edge erosion during low load operation leading to a significant extension in the last stage blade lifetime. These modifications, commercialized by GE as the Advanced Low Load Package (ALLP), provide a cheap, flexible and effective solution for the customer. With today’s knowledge, GE has the capability to guarantee low load operation minimizing the mass flow through the low-pressure turbine to the minimum required for safe operation. As a benefit to the customer, this option allows a gain in operational income of about 1.5 M€ per year.

Study of Flow Controlling on LP Turbine at Different Reynolds Number

2012 ◽  
Author(s):  
Muhammad Aqib Chishty ◽  
Hossein Raza Hamdani ◽  
Khalid Parvez ◽  
Muhammad Nafees Mumtaz Qadri
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Flow Separation ◽  
Separation Bubble ◽  
Low Pressure ◽  
Control Flow ◽  
Loss Coefficient ◽  
Shear Stresses ◽  
Low Pressure Turbine ◽  
Lp Turbine

Active and passive techniques have been used in the past, to control flow separation. Numerous studies were published on controlling and delaying the flow separation on low pressure turbine. In this study, a single dimple (i.e. passive device) is engraved on the suction side of LP turbine cascade T106A. The main aim of this research is to find out the optimum parameters of dimple i.e. diameter (D) and depth (h) which can produce strong enough vortex that can control the flow either in transition or fully turbulent phase. Furthermore, this optimal dimple is engraved to suppress the boundary layer separation at different Reynolds number (based on the chord length and inlet velocity). The dimple of different depth and diameter are used to find the optimal depth to diameter ratio. Computational results show that the optimal ratio of depth to diameter (h/D) for dimple is 0.0845 and depth to grid boundary layer (h/δ) is 0.5152. This optimized dimple efficiently reduces the normalized loss coefficient and it is found that the negative values of shear stresses found in uncontrolled case are being removed by the dimple. After that, dimple of optimized parameters are used to suppress the laminar separation bubble at different Re∼25000, 50000 and 91000. It was noticed that the dimple did not reduce the losses at Re∼25000. But at Re∼50000, it produced such a strong vortex that reduced the normalized loss coefficient to 25%, while 5% losses were reduced at Re∼91000. It can be concluded that the optimized dimple effectively controlled flow separation and reduced normalized loss coefficient from Re 25000 to 91000. As the losses are decreased, this will increase the low pressure turbine efficiency and reduce its fuel consumption.

Unsteady Flow Features and Vibration Stresses of an Actual Size Steam Turbine Last Stage in Various Low Load Conditions

2013 ◽  
Author(s):  
Naoki Shibukawa ◽  
Yoshifumi Iwasaki ◽  
Mitsunori Watanabe
Keyword(s):  
Steam Turbine ◽  
Pressure Fluctuation ◽  
Load Condition ◽  
Test Facility ◽  
Stress Increase ◽  
Unsteady Pressure ◽  
Low Load ◽  
Vibration Stress ◽  
Last Stage ◽  
Load Conditions

Experimental investigations with a six stage real scale low pressure steam turbine operated at a very low load conditions are presented in this paper. Although the tested 35 inch last stage blades are circumferentially coupled at both tip and mid span with an intention to reduce the vibration stress, still its increase was observed at extremely low load condition. The pressure fluctuations were measured by several silicon diaphragm sensors which were mounted on both inner and outer casings of the stator inlet, exit and blade exit position. The measurement of the vibration stress was performed by strain gauges on several blades. The power spectra of unsteady pressures were precisely investigated considering both their location and steam flow condition. And the results implied that huge reverse flow and re-circulation started in the same location as a blade-to-blade CFD predicted. In terms of the correlation between vibration stress and the flow feature, the pressure fluctuation around the blade tip produces dominant effects on the vibration stress. The unsteady pressure frequency were also investigated and compared with those of the blade resonance and rotational speed. Basic trends observed in the results are similar to what other researchers reported, and on top of that, the continuous trends of pressure fluctuation and blade vibration stress were systematically investigated. Even the wall pressure, not the pressure on blade surface, showed the effective fluctuations which excited the several nodes of natural frequencies of the last stage blade. A series of FFT of fluid force by a full annulus quasi-steady CFD simulation seems to predict dominant mode of the excitation which account for the behavior of vibration stresses. The mechanism of the rapid stress increase was examined by considering CFD results and measured unsteady pressure data together. As the test facility takes a responsibility as an independent power producer, the tests were conducted in real plant operations which include multi stage effects, inlet distortions, Reynolds Number effect and so on. The obtained data and the particular indicator of vibration stress increase can be used as a part of design tool validation with neither aerodynamic nor mechanical corrections.

A Computer Program for Simulating Transient Behavior in Steam Turbine Stage Pressure of AHWR

2006 ◽  
Author(s):  
Anu Dutta ◽  
I. Thangamani ◽  
G. Chakraborty ◽  
A. K. Ghosh ◽  
H. S. Kushwaha
Keyword(s):  
System Analysis ◽  
Mathematical Formulation ◽  
Load Condition ◽  
Low Pressure ◽  
Research Centre ◽  
Turbine Stage ◽  
Feed System ◽  
Part Load ◽  
Desalination Plant ◽  
Load Conditions

It is proposed to couple the Advanced Heavy water reactor (AHWR), which is being developed by Bhabha Atomic Research Centre, India, with a desalination plant. The objective of this coupling is to produce system make-up and domestic water. The proposed desalination plant needs about 1.9 kg/sec of steam and the minimum pressure requirement is 3 bars. The desalination plant can be fed with bled steam extracted from a suitable stage in low pressure turbine. As the turbine stage pressure changes with the load, it is essential to know the availability of bled steam at aforesaid pressure for various load condition. The objective of the present study is to identify a suitable extraction point so as to ensure availability of steam at desired condition for desalination plant, even at part load conditions. In order to fulfill the above objective a steam and feed system analysis code was developed which incorporates the mathematical formulation of different components of the steam and feed system such as, high pressure (HP) and low pressure (LP) turbines, re-heater, feed heaters etc. The dynamic equations are solved simultaneously to obtain the stage pressure at various load conditions. Based on the results obtained, the suitable extraction stage in LP turbine was selected. This enables to determine the lowest possible part load operation up to which availability of desalination plant could be ensured.

The Effects of Steady Injection on an Ultra High Lift Vane in a LP Turbine

2008 ◽  
Author(s):  
Thomas Schumann ◽  
Martin G. Rose ◽  
Stephan Staudacher ◽  
Jochen Gier ◽  
Th. Schro¨der
Keyword(s):  
Steady Flow ◽  
Flow Injection ◽  
Lift Coefficient ◽  
Suction Side ◽  
Low Pressure ◽  
Control Flow ◽  
Flow Area ◽  
High Lift ◽  
Low Pressure Turbine ◽  
Lp Turbine

The application of steady flow injection to control flow separation on the suction side of an ultra high lift low pressure turbine airfoil is presented. The blade lift coefficient of the ultra high lift airfoil at 1.46 Zweifel coefficient is considerably higher than those of conventional airfoils. Blade Reynolds numbers and blade dimensions are comparable to the first stages of aero engine low pressure turbines. The ultra high lift vane row is installed into a three stage low Mach number turbine test rig. Steady flow injection through suction side streamwise holes is investigated: with an angle to the surface of 45 deg. The pitch to diameter ratio is 10. The variation of the blowing ratio allows a closer study of the influence and effects occuing due to flow injection. Results show that steady flow injection can almost completely eliminate separation on the suction side. For four different blowing ratios blade pressure distribution and exit flow area traverse shows rising stage loading. A maximum of one percent change in flow exit angle was measured. The experimental results reveal that the injection jets only locally suppress the separation. This results in a spanwise variation in lift and trailing edge shed vortical structures.

Aerodynamic Design of a New Five Stage Low Pressure Turbine for the Rolls Royce Trent 500 Turbofan

2001 ◽  
Author(s):  
I. Ulizar ◽  
P. González
Keyword(s):  
Low Pressure ◽  
Previous Experience ◽  
Aerodynamic Design ◽  
Design Work ◽  
Cost Performance ◽  
Detailed Design ◽  
Low Pressure Turbine ◽  
Lp Turbine ◽  
The Moment ◽  
Turbine Design

Almost a decade ago, ITP (Industria de Turbo Propulsores, S.A.) started to participate in Low Pressure turbine design supported by Rolls-Royce. The Trent 500 LP turbine aerodynamic design is the most challenging and extensive design work carried out to the moment. The Trent 500 is part of the Rolls Royce Trent family. It has been designed to enter in service in the Airbus 340-600. This engine has very aggressive targets in terms of cost, performance, weight and noise. An optimization process was carried out during the preliminary and detailed design phases to accomplish these targets. This paper describes the most outstanding characteristics of the LP turbine, how the previous experience and Research and Technology results have been employed in this design and also some of the new advanced features, e.g. the introduction of spoon aerofoils.

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