Cooling Air Flow Characteristics in Gas Turbine Components

1982 ◽  
Vol 104 (2) ◽  
pp. 275-280 ◽  
Author(s):  
H. F. Jen ◽  
J. B. Sobanik
Keyword(s):  
Gas Turbine ◽  
Analytical Model ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Air Flow ◽  
Flow Characteristics ◽  
Calibration Procedure ◽  
Bench Test ◽  
Cooling Air Flow ◽  
Cooling Air

An analytical model for the prediction of cooling air flow characteristics (mass flow rate and internal pressure distribution) in gas turbine components is discussed. The model addresses a number of basic flow elements typical to gas turbine components such as orifices, frictional passages, labyrinth seals, etc. Static bench test measurements of the flow characteristics were in good agreement with the analysis. For the turbine blade, the concept of equivalent pressure ratio is introduced and shown to be useful for predicting (i) the cooling air flow rate through the rotor blade at engine conditions from the static rig and (ii) cooling air leakage rate at the rotor serration at engine conditions. This method shows excellent agreement with a detailed analytical model at various rotor speeds. A flow calibration procedure preserving flow similarity for blades and rotor assemblies is recommended.

scholarly journals Cooling Air Flow Characteristics in Gas Turbine Components

1981 ◽  
Author(s):  
H. F. Jen ◽  
J. B. Sobanik
Keyword(s):  
Gas Turbine ◽  
Analytical Model ◽  
Flow Rate ◽  
Pressure Ratio ◽  
Air Flow ◽  
Flow Characteristics ◽  
Calibration Procedure ◽  
Bench Test ◽  
Cooling Air Flow ◽  
Cooling Air

An analytical model for the prediction of cooling air flow characteristics (mass flow rate and internal pressure distribution) in gas turbine components is discussed. The model addresses a number of basic flow elements typical to gas turbine components such as orifices, frictional passages, labyrinth seals, etc. Static bench test measurements of the flow characteristics were in good agreement with the analysis. For the turbine blade, the concept of equivalent pressure ratio is introduced and shown to be useful for predicting (1) the cooling air flow rate through the rotor blade at engine conditions from the static rig and (2) cooling air leakage rate at the rotor serration at engine conditions. This method shows excellent agreement with a detailed analytical model at various rotor speeds. A flow calibration procedure preserving flow similarity for blades and rotor assemblies is recommended.

Hot gas ingestion in chute rim seal clearance of gas turbine

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Xingyun Jia ◽  
Huaiyu Dong ◽  
Yuzhou Ming ◽  
Yue Wu ◽  
Lidong He
Keyword(s):  
Air Flow ◽  
Interaction Mechanism ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Navier Stokes ◽  
Marginal Effect ◽  
Pressure Potential ◽  
Hot Gas ◽  
Cooling Air Flow ◽  
Cooling Air

Abstract The Reynolds-averaged Navier–Stokes (RANS) solver was used to calculate, using a test rig to verify the accuracy. The interaction mechanism between different sealed cooling air and gas ingestion at the rotor-stator cavity and chute rim clearance has been investigated. Several groups of representative sealed cooling air flow were selected to explore the cooling efficiency, flow characteristics, tangential and radial velocity ratios in the cavity and the pressure potential field characteristics of trailing edge. The conclusions are obtained: the sealed cooling air flow rate has a significant marginal effect on the sealing effect. The gas ingestion behavior under the small sealed cooling air flow belongs to the disc cavity intrusion, and the intrusion and outflow regions at the of rim clearance are obviously divided into the intrusion characteristic section and the outflow characteristic section. The ingestion behavior under large sealed cooling air flow belongs to clearance ingestion, and the intrusion flow is limited to the chute rim clearance position, which cannot be further penetrated into the cavity. At this time, the clearance area and the cavity area become independent, and the gas ingestion characteristics depend more on the internal flow of the clearance and the vortex structure formed.

Thermal Behavior of Radial Foil Bearings Supporting an Oil-Free Gas Turbine: Design of the Cooling Flow Passage and Modeling of the Thermal System

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
Donghyun Lee ◽  
Hyungsoo Lim ◽  
Bumseog Choi ◽  
Byungok Kim ◽  
Junyoung Park ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Gas Turbine ◽  
Air Flow ◽  
Successful Implementation ◽  
Flow Passage ◽  
Foil Bearings ◽  
Operation Speed ◽  
Bearing Sleeve ◽  
Cooling Air Flow ◽  
Cooling Air

Gas foil bearings (GFBs) have many noticeable advantages over the conventional rigid gas bearings, such as frictional damping of the compliance structure and tolerance to the rotor misalignment, so they have been successfully adopted as the key element that makes possible oil-free turbomachinery. As the adoption of the GFB increases, one of the critical elements for its successful implementation is thermal management. Even though heat generation inside the GFB is small due to the low viscosity of the lubricant, many researchers have reported that the system might fail without an appropriate cooling mechanism. The objective of the current research is to demonstrate the reliability of GFBs installed in the hot section of a micro-gas turbine (MGT). For the cooling of the GFBs, we designed a secondary flow passage and thermohydrodynamic (THD) analysis has been done for temperature prediction. In the analysis, the 3D THD model for the radial GFB extended to include the surrounding structure, such as the plenum, chamber, and the rotor in the solution domain by solving global mass and energy balance equations. In the MGT, the pressurized air discharged from the compressor wheel was used as the cooling air source, and it was injected into the plenum between two radial GFBs. We monitored the pressure and temperature of the cooling air along the secondary flow passage during the MGT operation. No thermal instability occurred up to the maximum operation speed of 43,000 rpm. The test results also showed that the pressure drop between the main reservoir and the plenum increases with an increasing operation speed, which indicated an increased cooling air flow into the plenum. The plenum and bearing sleeve temperature was maintained close to the cooling air source temperature for the entire speed due to a sufficient cooling air flow into the bearing. In addition, the direct injection of the cooling air from the main stream lowered the bearing sleeve temperature by 5–20 °C over the injection through the reservoirs. The predicted plenum and bearing sleeve temperatures with the developed THD model show good agreement with the test data.

Experimental Feasibility Study of Radial Injection Cooling of Three-Pad Air Foil Bearings

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Suman K. Shrestha ◽  
Daejong Kim ◽  
Young Cheol Kim
Keyword(s):  
Heat Exchange ◽  
Flow Rate ◽  
High Speed ◽  
Air Flow ◽  
Air Flow Rate ◽  
Design Factor ◽  
Cooling Performance ◽  
Radial Injection ◽  
Cooling Air Flow ◽  
Cooling Air

The foil bearing (FB) is one type of hydrodynamic bearing using air or another gas as a lubricant. When FBs are designed, installed, and operated properly, they are a very cost-effective and reliable solution for oil-free turbomachinery. Because there is no mechanical contact between the rotor and its bearings, quiet operation with very low friction is possible once the rotor lifts off the bearings. However, because of the high speed of operation, thermal management is a very important design factor to consider. The most widely accepted cooling method for FBs is axial flow cooling, which uses cooling air or gas passing through heat-exchange channels formed underneath the top foil. The advantage of axial cooling is that no hardware modification is necessary to implement it, because the elastic foundation structures of the FB serve as the heat-exchange channels. Its disadvantage is that an axial temperature gradient exists on the journal shaft and bearing. In this paper, the cooling characteristics of axial cooling are compared with those of multipoint radial injection, which uses high-speed injection of cooling air onto the shaft at multiple locations. Experiments were performed on a three-pad FB 49 mm in diameter and 37.5 mm in length, at speeds of 30,000 rpm and 40,000 rpm. Injection speeds were chosen to be higher than the journal surface speed, but the total cooling air flow rate was matched to that of the axial cooling cases. Experimental results show that radial injection cooling is comparable to axial cooling at 30,000 rpm, in terms of cooling performance. Tests at 40,000 rpm reveal that the axial cooling performance reaches saturation when the pressure drop across the bearing is larger than 1000 Pa, while the cooling performance of radial injection is proportional to the cooling air flow rate and does not become saturated. Overall, multipoint radial injection is better than axial cooling at high rotor speeds.

scholarly journals Off-Design Evaluation of a Multiple Expansion Reheating Gas Turbine in Cogeneration Applications

1991 ◽  
Author(s):  
Erio Benvenuti ◽  
Roberto Bettocchi ◽  
Giuseppe Cantore ◽  
Giorgio Negri Di Montenegro
Keyword(s):  
Gas Turbine ◽  
Air Flow ◽  
Thermal Power ◽  
Operational Flexibility ◽  
External Cooling ◽  
Heat Requirements ◽  
Cooling Air Flow ◽  
Performance Results ◽  
Air Control ◽  
Cooling Air

The multiple expansion reheating gas turbine proves to have a potential of good operational flexibility for the intrinsic capability of responding to variations in electric and thermal power demands without appreciable impact on efficiency. The present study deals with evaluation of the performance attainable in off-design operation, with power control obtained through changes in the first and second combustor firing temperatures and in the compressor intake air flow achieved by means of variable inlet guide vanes. Because of the important impact of the hot part cooling air flows on performance, the study includes also a hypothesis of controlling such flows in off-design operation through external means. The predicted off-design performance results superior in the hypothesis of external cooling air flow control, thus making such a system worthy of consideration for possible future developments of machines in this category. To evaluate the suitability of the multiple expansion reheating gas turbine in cogeneration applications, the electric efficiency and the electrical index have been taken into consideration. The capability of varying the reheating temperature represents an effective way of controlling the electrical index with good efficiencies in industrial cogeneration with strongly varying electric power and process heat requirements. With regard to the cooling air control through external means, implementation of such a more complex system seems to be avoidable at least when the gas turbine is intended specifically for application in cogeneration, because of its smaller impact on the overall efficiency of the system.

scholarly journals Model of thermal buoyancy in cavity-ventilated roof constructions

2021 ◽  
pp. 174425912098418
Author(s):  
Toivo Säwén ◽  
Martina Stockhaus ◽  
Carl-Eric Hagentoft ◽  
Nora Schjøth Bunkholt ◽  
Paula Wahlgren
Keyword(s):  
Analytical Model ◽  
Flow Rate ◽  
Numerical Study ◽  
Air Flow ◽  
Wind Pressure ◽  
Air Flow Rate ◽  
Test Set ◽  
Air Cavity ◽  
Thermal Buoyancy ◽  
The Impact

Timber roof constructions are commonly ventilated through an air cavity beneath the roof sheathing in order to remove heat and moisture from the construction. The driving forces for this ventilation are wind pressure and thermal buoyancy. The wind driven ventilation has been studied extensively, while models for predicting buoyant flow are less developed. In the present study, a novel analytical model is presented to predict the air flow caused by thermal buoyancy in a ventilated roof construction. The model provides means to calculate the cavity Rayleigh number for the roof construction, which is then correlated with the air flow rate. The model predictions are compared to the results of an experimental and a numerical study examining the effect of different cavity designs and inclinations on the air flow rate in a ventilated roof subjected to varying heat loads. Over 80 different test set-ups, the analytical model was found to replicate both experimental and numerical results within an acceptable margin. The effect of an increased total roof height, air cavity height and solar heat load for a given construction is an increased air flow rate through the air cavity. On average, the analytical model predicts a 3% higher air flow rate than found in the numerical study, and a 20% lower air flow rate than found in the experimental study, for comparable test set-ups. The model provided can be used to predict the air flow rate in cavities of varying design, and to quantify the impact of suggested roof design changes. The result can be used as a basis for estimating the moisture safety of a roof construction.

Characterisation of Static Strip Seal Flow

2007 ◽  
Author(s):  
Arash Farahani ◽  
Peter Childs
Keyword(s):  
Gas Flow ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Main Stream ◽  
Cfd Modelling ◽  
Height Range ◽  
And Performance ◽  
Nozzle Guide ◽  
The Cost ◽  
Cooling Air

Strip seals are used in gas turbine engines between two static elements or between components which do not move relative to each other, such as Nozzle Guide Vanes (NGVs). The key role of a strip seal between NGV segments is sealing between the flow through the main stream annulus and the internal air system, a further purpose is to limit the inter-segmental movements. In general the shape of the strip seal is a rectangular strip that fits into two slots in adjacent components. The minimum clearance required for static strip seals must be found by accounting for thermal expansion, misalignment, and application, to allow correct fitment of the strip seals. Any increase in leakage raises the cost due to an increase in the cooling air use, which is linked to specific fuel consumption, and it can also alter gas flow paths and performance. The narrow path within the seal assembly, especially the height has the most significant affect on leakage. The height range of the narrow path studied in this paper is 0.01–0.06 mm. The behaviour of the flow passing through the narrow path has been studied using CFD modelling and measurements in a bespoke rig. The CFD and experimental results show that normalized leakage flow increases with pressure ratio before reaching a maximum. The main aim of this paper is to provide new experimental data to verify the CFD modelling for static strip seals. The typical flow characteristics validated by CFD modelling and experiments can be used to predict the flow behaviour for future static strip seal designs.

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