Effects of Cavity Purge Flow on Intermediate Turbine Duct Flowfield

2018 ◽  
Author(s):  
Jun Liu ◽  
Qiang Du ◽  
Guang Liu ◽  
Pei Wang ◽  
Hongrui Liu ◽  
...  
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Design Criterion ◽  
Operating Conditions ◽  
Duct Flow ◽  
Intermediate Turbine Duct ◽  
Low Pressure Turbine ◽  
Cavity Structure ◽  
Flow Mechanisms ◽  
Purge Flow

To increase the power output without adding additional stages, ultra-high bypass ratio engine, which has larger diameter low pressure turbine, attracts more and more attention because of its huge advantage. This tendency will lead to aggressive (high diffusion) intermediate turbine duct design. Much work has been done to investigate flow mechanisms in this kind of duct as well as its design criterion with numerical and experimental methods. Usually intermediate turbine duct simplified from real engine structure was adopted with upstream and downstream blades. However, cavity purge mass flow exists to disturb the duct flow field in real engine to change its performance. Naturally, the wall vortex pairs would develop in different ways. In addition to that, purge flow rate changes at different engine representative operating conditions. This paper deals with the influence of turbine purge flow on the aerodynamic performance of an aggressive intermediate turbine duct. The objective is to reveal the physical mechanism of purge flow ejected from the wheel-space and its effects on the duct flow field. Ten cases with and without cavity are simulated simultaneously. On one hand, the influence of cavity structure without purge flow on the flow field inside duct could be discussed. On the other hand, the effect of purge flow rate on flow field could be analyzed to investigate the mechanisms at different engine operating conditions. According to this paper, cavity structure is beneficial for pressure loss. And the influence concentrates near hub and duct inlet.

Design of an Intermediate Turbine Duct Downstream of a High Pressure Turbine

2016 ◽  
Author(s):  
Chaoshan Hou ◽  
Hu Wu
Keyword(s):  
High Pressure ◽  
Three Dimensional ◽  
Low Pressure ◽  
Aerodynamic Load ◽  
Duct Flow ◽  
Original Design ◽  
High Pressure Turbine ◽  
Intermediate Turbine Duct ◽  
Low Pressure Turbine ◽  
Inlet Conditions

The flow leaving the high pressure turbine should be guided to the low pressure turbine by an annular diffuser, which is called as the intermediate turbine duct. Flow separation, which would result in secondary flow and cause great flow loss, is easily induced by the negative pressure gradient inside the duct. And such non-uniform flow field would also affect the inlet conditions of the low pressure turbine, resulting in efficiency reduction of low pressure turbine. Highly efficient intermediate turbine duct cannot be designed without considering the effects of the rotating row of the high pressure turbine. A typical turbine model is simulated by commercial computational fluid dynamics method. This model is used to validate the accuracy and reliability of the selected numerical method by comparing the numerical results with the experimental results. An intermediate turbine duct with eight struts has been designed initially downstream of an existing high pressure turbine. On the basis of the original design, the main purpose of this paper is to reduce the net aerodynamic load on the strut surface and thus minimize the overall duct loss. Full three-dimensional inverse method is applied to the redesign of the struts. It is revealed that the duct with new struts after inverse design has an improved performance as compared with the original one.

Automotive Hydraulic Valve Fluid Field Estimator Based on Non-Dimensional Artificial Neural Network (NDANN)

2003 ◽  
Author(s):  
M. Cao ◽  
K. W. Wang ◽  
L. DeVries ◽  
Y. Fujii ◽  
W. E. Tobler ◽  
...  
Keyword(s):  
Neural Network ◽  
Control System ◽  
Flow Field ◽  
Flow Rate ◽  
Field Model ◽  
Operating Conditions ◽  
Asymmetric Flow ◽  
Fluid Force ◽  
Fluid Field ◽  
Hydraulic Valve

A conventional automatic transmission (AT) hydraulic control system includes many spool-type valves that have highly asymmetric flow geometry. An accurate analysis of their flow fields typically requires a time-consuming computational fluid dynamics (CFD) technique. A simplified flow field model that is based on a lumped geometry is computationally efficient. However, it often fails to account for asymmetric flow characteristics, leading to an inaccurate analysis. In this work, a new hydraulic valve fluid field model is developed based on a non-dimensional neural network (NDANN) to provide an accurate and numerically efficient tool in AT control system design applications. A “grow-and-trim” procedure is proposed to identify critical non-dimensional inputs and optimize the network architecture. A hydraulic valve testing bench is designed and built to provide data for neural network model development. NDANN-based fluid force and flow rate estimator are established based on the experimental data. The NDANN models provide more accurate predictions of flow force and flow rates under broad operating conditions compared with conventional lumped flow field models. The NDANN fluid field estimator also exhibits input-output scalability. This capability allows the NDANN model to estimate the fluid force and flow rate even when the design geometry parameters are outside the range of the training data.

Flashing Flow Mechanisms of HFC-134a and HFC-410a Through Short-Tube Orifices

2011 ◽  
Author(s):  
Kitti Nilpueng ◽  
Somchai Wongwises
Keyword(s):  
Temperature Distribution ◽  
Pressure Distribution ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Operating Conditions ◽  
Evaporator Temperature ◽  
Hfc 134A ◽  
Flow Mechanisms ◽  
Short Tube

In this study, the flow mechanisms of HFC-134a and HFC-410A, including flow pattern, pressure distribution, temperature distribution, and mass flow rate inside short-tube orifice are presented and compared under the same working temperature. The test runs are performed at condenser temperature ranging between 35 and 45°C, evaporator temperature ranging between 2 and 12°C, and degree of subcooling ranging between 1 and 12 °C. The results show that the temperature distribution along the short-tube orifice obtained from HFC-410A is slightly higher than that obtained from HFC-134a. On the other hand, the pressure distribution between both refrigerants shows the large difference. It is also found that the tendency of mass flow rate obtained from HFC-134a almost coincides with those obtained HFC-410A as the operating conditions and short-tube orifice size are varied. However, the average mass flow rate of HFC-134a is slightly lower than that of HFC-410A.

scholarly journals Investigation of the Flow Field in the Vicinity of an Axial Flow Fan During Low Flow Rates

2014 ◽  
Author(s):  
Francois G. Louw ◽  
Theodor W. von Backström ◽  
Sybrand J. van der Spuy
Keyword(s):  
Flow Field ◽  
Numerical Simulations ◽  
Flow Rate ◽  
Axial Flow ◽  
Operating Conditions ◽  
Design Flow ◽  
Low Flow ◽  
Axial Flow Fan ◽  
Free Vortex ◽  
Flow Rates

Large axial flow fans are used in forced draft air cooled heat exchangers (ACHEs). Previous studies have shown that adverse operating conditions cause certain sectors of the fan, or the fan as a whole to operate at very low flow rates, thereby reducing the cooling effectiveness of the ACHE. The present study is directed towards the experimental and numerical analyses of the flow in the vicinity of an axial flow fan during low flow rates. This is done to obtain the global flow structure up and downstream of the fan. A near-free-vortex fan, designed for specific application in ACHEs, is used for the investigation. Experimental fan testing was conducted in a British Standard 848, type A fan test facility, to obtain the fan characteristic. Both steady-state and time-dependent numerical simulations were performed, depending on the operating condition of the fan, using the Realizable k-ε turbulence model. Good agreement is found between the numerically and experimentally obtained fan characteristic data. Using data from the numerical simulations, the time and circumferentially averaged flow field is presented. At the design flow rate the downstream fan jet mainly moves in the axial and tangential direction, as expected for a free-vortex design criteria, with a small amount of radial flow that can be observed. As the flow rate through the fan is decreased, it is evident that the down-stream fan jet gradually shifts more diagonally outwards, and the region where reverse flow occur between the fan jet and the fan rotational axis increases. At very low flow rates the flow close to the tip reverses through the fan, producing a small recirculation zone as well as swirl at certain locations upstream of the fan.

Velocity Measurements Downstream of the Impellers in a Multistage Centrifugal Blower

1994 ◽  
Author(s):  
G. L. Amulfi ◽  
D. Micheli ◽  
P. Pinamonti
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Flow Rate ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Field Analysis ◽  
Test Plant ◽  
Hot Wire ◽  
Centrifugal Blower ◽  
Ensemble Averaging

The paper presents the results of an experimental investigation on a four-stage centrifugal blower, having the aim of obtaining an accurate description of the flow field behind the impellers in several operative conditions and for different geometrical configurations. Actually, the test plant allows to change the turbomachinery characteristics assembling one, two, three or four stages and three different types of diffusers. In this first research step, the blower has been tested in the four-stage vaneless diffuser configuration. The unsteady flow field behind the impellers and in the diffusers has been measured by means of a hot-wire anemometer. A Phase Locked Ensemble Averaging Technique has been utilised to obtain the relative flow field from the instantaneous signals of the stationary hot-wire probes. Several detailed measurements sets have been performed using both single and crossed hot-wire probe, to obtain the velocity vectors and turbulence trends, just behind the blower impellers and in several radial positions of the vaneless diffusers. These measurements have been done at different flow rate conditions, covering unsteady flow rate phenomena (rotating stall) too. The results obtained allowed to get a detailed flow field analysis in the multistage centrifugal blower, in relation to the geometrical configuration and to the differing operating conditions.

Computational Investigation of the Flow Field Inside an Submersible Tubular Pump

2011 ◽  
Author(s):  
Yan Jin ◽  
Chao Liu ◽  
Jiren Zhou ◽  
Fangping Tang
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Optimization Design ◽  
High Efficiency ◽  
Simple Algorithm ◽  
Operating Conditions ◽  
Rotating Speed ◽  
Pumping System ◽  
Wide Range ◽  
Engineering Costs

Submersible tubular pump is particularly suitable for ultra-low head (net head less than 2 m) pumping station which can reduce the excavation depth, lower engine room height, simplify hydraulic structure, and save civil engineering costs. Submersible tubular pump with smaller motor unit can reduce the flow resistance. The flow field inside the submersible tubular pump is simulated in a commercial computation fluid dynamics (CFD) code FLUENT. The RNG k-ε turbulent model and SIMPLE algorithm are applied to analyze the full passage of a submersible tubular pump, the performance of pump such as head, shaft power and efficiency are predicted based on the calculation of different operating conditions. The simulations are carried out over a wide range of operating points, from 0.8 of the reference mass flow rate at the best efficiency point (BEP) to the 1.28 of the BEP flow rate at the same rotating speed. For verifying the accuracy and reliability of the calculation results, a model test is conducted. The comparison of simulation results and the experiment data show that the calculation performances are agree with the experiment results in the high efficiency area and large discharge condition, but in the condition of low discharge, it exists deviations between the two results. Compare with the numerical simulation and experiment, which can provide more evidences for the hydraulic performance prediction and optimization design of submersible tubular pump pumping system.

The Aerodynamic Interaction of Tip Leakage and Mainstream Flows in a Fully-Ducted Axial Fan

2004 ◽  
Author(s):  
Alessandro Corsini ◽  
Franco Rispoli ◽  
Geoff Sheard ◽  
Iain Kinghorn
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Tip Clearance ◽  
Vortical Flow ◽  
Aerodynamic Noise ◽  
Axial Fan ◽  
Noise Emission ◽  
Flow Mechanisms ◽  
Flow Effects

The three dimensional structures of the blade tip vortical flow field is herein discussed for an axial fan in a fully-ducted configuration. The investigation has been carried-out using an accurate in-house developed multi-level parallel finite element RANS solver, with the adoption of a non-isotropic two-equation turbulence closure. Due to the fully-ducted configuration the fan has a complex vortical flow field near the rotor tip. The tip clearance flows have been detected for operating conditions near peak efficiency and near stall, with multiple vortex formations being identified in both cases. The nature of the flow mechanisms in the fan tip region is correlated to the specific blade design features that promote reduced aerodynamic noise. It was found that the blade lean at the higher radii attenuates the sensitivity to leakage flow effects. Consequently, the rotor operates efficiently and with nearly unchanged noise emission approaching its throttling limit. The rotor loss behaviour, within the passage and downstream of it, is also discussed at both near design and part-load conditions.

Velocity Measurements Downstream of the Impellers in a Multistage Centrifugal Blower

1995 ◽  
Vol 117 (4) ◽  
pp. 593-601 ◽  
Author(s):  
G. L. Arnulfi ◽  
D. Micheli ◽  
P. Pinamonti
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Flow Rate ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Field Analysis ◽  
Test Plant ◽  
Hot Wire ◽  
Centrifugal Blower ◽  
Detailed Measurement

The paper presents the results of an experimental investigation on a four-stage centrifugal blower, having the aim of obtaining an accurate description of the flow field behind the impellers in several operative conditions and for different geometric configurations. Actually, the test plant allows one to change the turbomachinery characteristics assembling one, two, three, or four stages and three different types of diffuser. In this first research step, the blower has been tested in the four-stage vaneless diffuser configuration. The unsteady flow field behind the impellers and in the diffusers has been measured by means of a hot-wire anemometer. A phase-locked ensemble-averaging technique has been utilized to obtain the relative flow field from the instantaneous signals of the stationary hot-wire probes. Several detailed measurement sets have been performed using both single and crossed hot-wire probes, to obtain the velocity vectors and turbulence trends, just behind the blower impellers and in several radial positions of the vaneless diffusers. These measurements have been done at different flow rate conditions, covering unsteady flow rate phenomena (rotating stall) also. The results obtained allowed us to get a detailed flow field analysis in the multistage centrifugal blower, in relation to the geometric configuration and to the differing operating conditions.

Effects of Suction and Injection Purge-Flow on the Secondary Flow Structures of a High-Work Turbine

2008 ◽  
Author(s):  
P. Schuepbach ◽  
R. S. Abhari ◽  
M. G. Rose ◽  
T. Germain ◽  
I. Raab ◽  
...  
Keyword(s):  
Experimental Study ◽  
High Pressure ◽  
Flow Field ◽  
Secondary Flow ◽  
Flow Structures ◽  
Turbine Efficiency ◽  
Flow Mechanisms ◽  
Purge Flow ◽  
High Work ◽  
Secondary Flow Field

In high-pressure turbines, a small amount of air is ejected at the hub rim seal, to cool and prevent the ingestion of hot gases into the cavity between the stator and the disk. This paper presents an experimental study of the flow mechanisms that are associated with injection through the hub rim seal at the rotor inlet. Two different injection rates are investigated: nominal sucking of −0.1% of the main massflow and nominal blowing of 0.9%. This investigation is executed on a one-and-1/2-stage axial turbine. The results shown here come from unsteady and steady measurements, which have been acquired upstream and downstream of the rotor. The paper gives a detailed analysis of the changing secondary flow field as well as unsteady interactions associated with the injection. The injection of fluid causes a very different and generally more unsteady flow field at the rotor exit near the hub. The injection causes the turbine efficiency to deteriorate by about 0.6%.

Effects of Suction and Injection Purge-Flow on the Secondary Flow Structures of a High-Work Turbine

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
P. Schuepbach ◽  
R. S. Abhari ◽  
M. G. Rose ◽  
T. Germain ◽  
I. Raab ◽  
...  
Keyword(s):  
Experimental Study ◽  
High Pressure ◽  
Flow Field ◽  
Secondary Flow ◽  
Flow Structures ◽  
Turbine Efficiency ◽  
Flow Mechanisms ◽  
Purge Flow ◽  
High Work ◽  
Secondary Flow Field

In high-pressure turbines, a small amount of air is ejected at the hub rim seal to cool and prevent the ingestion of hot gases into the cavity between the stator and the disk. This paper presents an experimental study of the flow mechanisms that are associated with injection through the hub rim seal at the rotor inlet. Two different injection rates are investigated: nominal sucking of −0.14% of the main massflow and nominal blowing of 0.9%. This investigation is executed on a one-and-1/2-stage axial turbine. The results shown here come from unsteady and steady measurements, which have been acquired upstream and downstream of the rotor. The paper gives a detailed analysis of the changing secondary flow field, as well as unsteady interactions associated with the injection. The injection of fluid causes a very different and generally more unsteady flow field at the rotor exit near the hub. The injection causes the turbine efficiency to deteriorate by about 0.6%.

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