Impact of Passive Tip-Injection on the Performance of Partially Shrouded Turbines: Basic Concept and Preliminary Results

In terms of efficiency improvement many methods for reducing the blade tip-leakage mass flow rate have been proposed. Some of these methods are based on increasing the flow resistance with aid of geometrical modifications of the blade tip (squealers, winglets, shrouded blades, etc.) whereas other methods take advantage of aerodynamical resistance with passive tip-injection as an example. The objective of this paper is a combination of both methods in order to achieve higher reduction in tip-leakage mass flow rate. In the first part of this work necessary characteristic parameters of modern low pressure turbine blades in aircraft gas turbines are estimated. These parameters are taken into consideration to calculate the range of physical quantities influencing tip-leakage flow. Subsequently a two dimensional flow model is obtained with the so called discharge coefficient as the ratio of the actual tip gap mass flow rate to its highest possible value. The investigations are based on dimensionless calculations. In the end the results obtained from dimensionless 2D CFD-simulations are presented and compared with the analytical results. This leads to conclusions regarding the impact of various parameters on the effectiveness of the passive tip-injection.

On the Impact of Passive Tip-Injection on the Downstream Flow Field of a Shrouded LP-Turbine: CFD and Experimental Results

Volume 2B: Turbomachinery ◽

10.1115/gt2016-56196 ◽

2016 ◽

Author(s):

Pouya Ghaffari ◽

Reinhard Willinger

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Tip Leakage ◽

Air Turbine ◽

Tip Injection ◽

Lp Turbine ◽

Downstream Flow ◽

The Impact ◽

Discharge Behaviour

Using shrouded blades with fins is a common method to reduce the leakage mass flow rate through the clearance between rotor and stator. A variety of methods have been developed improving the discharge behaviour of this sealing application. The leakage mass flow rate and its interaction with the main flow resulting in mixing losses and deviations in turning is also an important issue and has to be taken into consideration. The objective of this paper is to present a method aiming at reduction of tip-leakage mass flow rate and its high angular momentum by means of passive tip-injection. The results include analytical study followed by CFD calculations for compressible flow in a rotational frame of reference as well as experimental data. An uncooled low pressure air turbine with shrouded blades is considered for the CFD and the measurements. Three passive tip-injection configurations are investigated numerically out of which one configuration is also examined experimentally in the framework of this study.

Effect of Active Modulation of Through-Casing Coolant Injection on Turbine Efficiency

Volume 2A: Turbomachinery ◽

10.1115/gt2017-64705 ◽

2017 ◽

Author(s):

Brian M. T. Tang ◽

Marko Bacic ◽

Peter T. Ireland

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Total Pressure ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Tip Leakage ◽

Turbine Efficiency ◽

Coolant Injection ◽

Cooling Air

This paper presents a computational investigation into the impact of cooling air injected through the stationary over-tip turbine casing on overall turbine efficiency. The high work axial flow turbine is representative of the high pressure turbine of a civil aviation turbofan engine. The effect of active modulation of the cooling air is assessed, as well as that of the injection locations. The influence of the through-casing coolant injection on the turbine blade over-tip leakage flow and the associated secondary flow features are examined. Transient (unsteady) sliding mesh simulations of a one turbine stage rotor-stator domain are performed using periodic boundary conditions. Cooling air configurations with a constant total pressure air supply, constant mass flow rate and actively controlled total pressure supply are assessed for a single geometric arrangement of cooling holes. The effects of both the mass flow rate of cooling air and the location of its injection relative to the turbine rotor blade are examined. The results show that all of the assessed cooling configurations provided a benefit to turbine row efficiency of between 0.2 and 0.4 percentage points. The passive and constant mass flow rate configurations reduced the over-tip leakage flow, but did so in an inefficient manner, with decreasing efficiency observed with increasing injection mass flow rate beyond 0.6% of the mainstream flow, despite the over-tip leakage mass flow rate continuing to reduce. By contrast, the active total pressure controlled injection provided a more efficient manner of controlling this leakage flow, as it permitted a redistribution of cooling air, allowing it to be applied in the regions close to the suction side of the blade tip which more directly reduced over-tip leakage flow rates and hence improved efficiency. Cooling air injected close to the pressure side of the rotor blade was less effective at controlling the leakage flow, and was associated with increased aerodynamic loss in the passage vortex.

Stall Inception and Development Process Due to Tip Leakage Flow in Axial Compressor Rotor Blades Row

Journal of Mechanics ◽

10.1017/jmech.2014.4 ◽

2014 ◽

Vol 30 (3) ◽

pp. 307-313 ◽

Author(s):

R. Taghavi-Zenou ◽

S. Abbasi ◽

S. Eslami

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Axial Compressor ◽

Leading Edge ◽

Rotor Blades ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Tip Leakage ◽

Compressor Rotor

ABSTRACTThis paper deals with tip leakage flow structure in subsonic axial compressor rotor blades row under different operating conditions. Analyses are based on flow simulation utilizing computational fluid dynamic technique. Three different circumstances at near stall condition are considered in this respect. Tip leakage flow frequency spectrum was studied through surveying instantaneous static pressure signals imposed on blades surfaces. Results at the highest flow rate, close to the stall condition, showed that the tip vortex flow fluctuates with a frequency close to the blade passing frequency. In addition, pressure signals remained unchanged with time. Moreover, equal pressure fluctuations at different passages guaranteed no peripheral disturbances. Tip leakage flow frequency decreased with reduction of the mass flow rate and its structure was changing with time. Spillage of the tip leakage flow from the blade leading edge occurred without any backflow in the trailing edge region. Consequently, various flow structures were observed within every passage between two adjacent blades. Further decrease in the mass flow rate provided conditions where the spilled flow ahead of the blade leading edge together with trailing edge backflow caused spike stall to occur. This latter phenomenon was accompanied by lower frequencies and higher amplitudes of the pressure signals. Further revolution of the rotor blade row caused the spike stall to eventuate to larger stall cells, which may be led to fully developed rotating stall.

Unsteady Interaction Between Annulus and Turbine Rim Seal Flows

Volume 8: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2012-69089 ◽

2012 ◽

Cited By ~ 3

Author(s):

Martin Chilla ◽

Howard Hodson ◽

David Newman

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Gas Turbines ◽

Measurement Data ◽

Design Flow ◽

Flow Conditions ◽

Disc Space ◽

Flow Interaction ◽

In core gas turbines relatively cold air is purged through the hub gap between stator and rotor in order to seal the disc space against flow ingestion from the main annulus. Although the sealing mass flow rate is commonly very small compared to the main annulus mass flow rate, it can have significant effects on the development of the passage endwall flows and on the overall loss generation. In this paper, the interaction between annulus and rim sealing flows is investigated using numerical simulations of a generic high-pressure turbine. At first, the numerical approach is validated by comparing the results of calculations to measurement data at the design flow conditions. Following that, results from steady and unsteady calculations are used to describe in detail the aerodynamics in overlap-type rim seals and their effects on the blade passage flow. It is found that the flow interaction at the rim seal interface is strongly influenced by the velocity deficit of the rim sealing flow relative to the annulus flow as well as by the circumferentially non-uniform pressure field imposed by the rotor blades. At typical sealing flow conditions, the flow interaction is found to be naturally unsteady, with periodical vortex shedding into the rotor passage. Finally, the influence of the specific rim seal shape on the flow unsteadiness at the rim seal interface is investigated and the impact on turbine performance is assessed.

Impact of Passive Tip-Injection on Tip-Leakage Flow in Axial Low Pressure Turbine Stage

Volume 2A: Turbomachinery ◽

10.1115/gt2015-42226 ◽

2015 ◽

Author(s):

Pouya Ghaffari ◽

Reinhard Willinger ◽

Sabine Bauinger ◽

Andreas Marn

Keyword(s):

Aerodynamic Resistance ◽

Low Pressure ◽

Leakage Flow ◽

Turbine Stage ◽

Tip Leakage Flow ◽

Tip Leakage ◽

Low Pressure Turbine ◽

Blade Tip ◽

Tip Injection ◽

In addition to geometrical modifications of the blade tip for reducing tip-leakage mass flow rate the method of passive tip-injection serves as an aerodynamic resistance towards the tip-leakage flow. The impact of this method has been investigated thoroughly at unshrouded blades in linear cascades. Furthermore combinations of shrouded blades with passive tip-injection have been investigated analytically as well as via numerical simulations for incompressible flow in linear cascades. The objective of this paper is to consider a real uncooled low pressure turbine stage with shrouded blades and to investigate the effect of passive tip-injection on various operational characteristics. CFD calculations have been carried out in a rotational frame taking into consideration compressible flow and serve for evaluating the method of passive tip-injection in the given turbine stage. Experimental data obtained from the machine without tip-injection serve as boundary conditions for the CFD calculations.

Volume 8: Industrial and Cogeneration; Manufacturing Materials and Metallurgy; Marine; Microturbines, Turbochargers, and Small Turbomachines ◽

Theoretical and Experimental Investigation of a 34 Watt Radial-Inflow Steam Turbine With Partial-Admission

10.1115/gt2020-15804 ◽

2020 ◽

Author(s):

Patrick H. Wagner ◽

Jan Van herle ◽

Jürg Schiffmann

Keyword(s):

Steam Turbine ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Pressure Ratio ◽

Turbine Blades ◽

Tip Clearance ◽

Experimental Results ◽

Partial Admission ◽

Blade Tip

Abstract A micro steam turbine with a tip diameter of 15 mm was designed and experimentally characterized. At the nominal mass flow rate and total-to-total pressure ratio of 2.3 kg h−1 and 2, respectively, the turbine yields a power of 34 W and a total-to-static isentropic efficiency of 37%. The steam turbine is conceived as a radial-inflow, low-reaction (15%), and partial admission (21%) machine. Since the steam mass flow rate is limited by the heat provided of the system (solid oxide fuel cell), a low-reaction and high-power-density design is preferred. The partial-admission design allows for reduced losses: The turbine rotor and stator blades are prismatic, have a radial chord length of 1 mm and a height of 0.59 mm. Since the relative rotor blade tip clearance (0.24) is high, the blade tip leakage losses are significant. Considering a fixed steam supply, this design allows to increase the blade height, and thus reducing the losses. The steam turbine drives a fan, which operates at low Mach numbers. The rotor is supported on dynamic steam-lubricated bearings; the nominal rotational speed is 175 krpm. A numerical simulation of the steam turbine is in good agreement with the experimental results. Furthermore, a novel test rig setup, featuring extremely-thin thermocouples (ϕ0.15 mm) is investigated for an operation with ambient and hot air at 220 °C. Conventional zero and one-dimensional pre-design models correlate well to the experimental results, despite the small size of the turbine blades.

Conjugate Heat Transfer Analysis on Generic Rim Seal Configurations in Rotor-Stator System

Volume 5B: Heat Transfer ◽

10.1115/gt2018-75228 ◽

2018 ◽

Author(s):

Xingyun Jia ◽

Liguo Wang ◽

Qun Zheng ◽

Hai Zhang ◽

Yuting Jiang

Keyword(s):

Heat Transfer ◽

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Conjugate Heat Transfer ◽

Heat Transfer Analysis ◽

Minimum Mass ◽

Aerodynamic Efficiency ◽

Axial Clearance ◽

Performance of generic rim seal configurations, axial-clearance rim seal (ACS), radial-clearance rim seal (RCS), radial-axial clearance rim seal (RACS) are compared under realistic working conditions. Conjugate heat transfer analysis on rim seal is performed in this paper to understand the impact of ingestion on disc temperature. Results show that seal effectiveness and cooling effectiveness of RACS are the best when compared with ACS and RCS, the minimum mass flow rate for seal of RACS is 75% of that of RCS, and 34.6% of ACS. Authors compare the disc temperature distribution between different generic rim seal configurations where the RACS seems to be favorable in terms of low disc temperature. In addition, RACS has higher air-cooled aerodynamic efficiency, minimizing the mainstream performance penalty when compared with ACS and RCS. Corresponding to the respective minimum mass flow rate for seal, the air-cooled aerodynamic efficiency of RACS is 23.71% higher than that of ACS, and 12.79% higher than the RCS.

Performance investigation of a volute porous tongue of a turbocharger turbine

Engineering review ◽

10.30765/er.40.1.08 ◽

2020 ◽

Vol 40 (1) ◽

pp. 59-66

Author(s):

Abderrahmane Chachoua ◽

Mohamed Kamal Hamidou ◽

Mohammed Hamel

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Gas Turbines ◽

Stokes Equations ◽

Navier Stokes ◽

Recirculation Flow ◽

Recirculating Flow ◽

Show Evidence ◽

The Right

The design for better performance of the spiral housing volute used commonly in radial and mixed inflow gas turbines is of prime importance as it affects the machine stage at both design and off design conditions. The tongue of the scroll divides the flow into two streams, and represents a severe source of disturbances, in terms of thermodynamic parameter uniformity, maximum kinetic energy, the right angle of attack to the rotor and minimum losses. Besides, the volute suffers an undesirable effect due to the recirculating mass flow rate in near bottom vicinity of the tongue. The present project is an attempt to design a tongue fitted with cylindrical holes traversing normal to the stream wise direction, where on account of the large pressure difference between the top and the bottom sides of the tongue will force the recirculating flow to go through the rotor inlet. This possibility with its limitations has not yet been explored. A numerical simulation is performed which might provide our suitable objectives. To achieve this goal the ANSYS code is used to build the geometry, generate the mesh, and to simulate the flow by solving numerically the averaged Navier Stokes equations. Apparently, the numerical results show evidence of favorable impact in using porous tongue. The realization of a contact between the main and recirculation flow by drilled holes on the tongue surface leads to a flow field uniformity, a reduction in the magnitude of the loss coefficient, and a 20 % reduction in the recirculating mass flow rate.

Design and Testing of a Can Combustor for a Small Gas Turbine Application

ASME 2013 Gas Turbine India Conference ◽

10.1115/gtindia2013-3691 ◽

2013 ◽

Author(s):

K. V. L. Narayana Rao ◽

N. Ravi Kumar ◽

G. Ramesha ◽

M. Devathathan

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Gas Turbines ◽

Pressure Loss ◽

High Energy ◽

Experimental Results ◽

High Mass ◽

Test Facility ◽

Design Requirements

Can type combustors are robust, with ease of design, manufacturing and testing. They are extensively used in industrial gas turbines and aero engines. This paper is mainly based on the work carried out in designing and testing a can type combustion chamber which is operated using JET-A1 fuel. Based on the design requirements, the combustor is designed, fabricated and tested. The experimental results are analysed and compared with the design requirements. The basic dimensions of the combustor, like casing diameter, liner diameter, liner length and liner hole distribution are estimated through a proprietary developed code. An axial flow air swirler with 8 vanes and vane angle of 45 degree is designed to create a re-circulation zone for stabilizing the flame. The Monarch 4.0 GPH fuel nozzle with a cone angle of 80 degree is used. The igniter used is a high energy igniter with ignition energy of 2J and 60 sparks per minute. The combustor is modelled, meshed and analysed using the commercially available ansys-cfx code. The geometry of the combustor is modified iteratively based on the CFD results to meet the design requirements such as pressure loss and pattern factor. The combustor is fabricated using Ni-75 sheet of 1 mm thickness. A small combustor test facility is established. The combustor rig is tested for 50 Hours. The experimental results showed a blow-out phenomenon while the mass flow rate through the combustor is increased beyond a limit. Further through CFD analysis one of the cause for early blow out is identified to be a high mass flow rate through the swirler. The swirler area is partially blocked and many configurations are analysed. The optimum configuration is selected based on the flame position in the primary zone. The change in swirler area is implemented in the test model and further testing is carried out. The experimental results showed that the blow-out limit of the combustor is increased to a good extent. Hence the effect of swirler flow rate on recirculation zone length and flame blow out is also studied and presented. The experimental results showed that the pressure loss and pattern factor are in agreement with the design requirements.

Flow Field in the Tip Gap of a Planar Cascade of Turbine Blades

Journal of Turbomachinery ◽

10.1115/1.3262266 ◽

1989 ◽

Vol 111 (3) ◽

pp. 276-283 ◽

Cited By ~ 21

Author(s):

M. Yaras ◽

Yingkang Zhu ◽

S. A. Sjolander

Keyword(s):

Mass Flow Rate ◽

Mass Flow ◽

Flow Rate ◽

Pressure Difference ◽

Good Accuracy ◽

Flow Direction ◽

Turbine Blades ◽

Rate Distribution ◽

Velocity Magnitude ◽

The Relationship

Measurements are presented for the flow in the tip gap of a planar cascade of turbine blades. Three clearances of from 2.0 to 3.2 percent of the blade chord were considered. Detailed surveys of the velocity magnitude, flow direction, and total pressure within the gap were supplemented by blade surface and endwall static pressure measurements. The results help to clarify the relationship between the leakage mass flow rate distribution and the driving pressure differences. It was found that even for the present relatively large clearances, fluid near the endwall experiences a pressure difference that is comparable with the blade pressure difference. It is also shown that a simple model can predict with good accuracy the mass flow rate distribution and the magnitude and direction of the velocity vectors within the gap.