Impact of a Collector Box on the Pressure Recovery of an Exhaust Diffuser System

2011 ◽  
Author(s):  
Bryan C. Bernier ◽  
Mark Ricklick ◽  
J. S. Kapat
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Experimental Tests ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Computational Domain ◽  
Complex Flow ◽  
Local Pressure ◽  
3 Dimensional ◽  
Pressure Profiles

The effects of an industrial gas turbine’s Exhaust Collector Box (ECB) geometry on static pressure recovery and total pressure loss were investigated in this study. This study aims to further understand how exit boundary conditions affect the performance of a diffuser system. In this investigation, the exhaust diffuser remained constant through each test, with collector box geometries being varied. The same uniform velocity profile was maintained at the diffuser inlet for all geometries considered. The local pressure recovery through the diffuser with 4 axial ports at 4 circumferential locations was reported along with 14 locations in the accompanying ECB. A system performance analysis for each geometry was conducted using the total pressure loss from inlet to exit of the model. Velocity and total pressure profiles obtained with a hotwire anemometer and Kiel probe at the exit of the diffuser and at the exit of the ECB are also presented in this study. Three (3) different ECB geometries are investigated at a Reynolds number of 60,000. Results obtained from these experimental tests are used to validate the accuracy of a 3-dimensional RANS with realizable k-ε turbulence CFD model from the commercial software package Star-CCM+. The study confirms the existence of two strong counter-rotating helical vortices at the exit of the ECB which significantly affect the flow within the diffuser. Evidence of a strong recirculation zone within the ECB was found to force separation within the exhaust diffuser. Extending the length of the ECB proved to decrease the total pressure loss of the system by up to 19% experimentally. Additionally, the realizable k-ε turbulence was able to accurately represent the total pressure loss of the system within 5%. Despite the extremely complex flow field within the ECB, the computational domain reasonably represented the system in both magnitude and trends.

Numerically Optimizing an Annular Diffuser Using a Genetic Algorithm With Three Objectives

2012 ◽  
Author(s):  
David J. Cerantola ◽  
A. M. Birk
Keyword(s):  
Genetic Algorithm ◽  
Pressure Loss ◽  
Total Pressure ◽  
Exhaust System ◽  
Outer Wall ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Annular Diffuser ◽  
Inlet Conditions ◽  
Wall Profile

A genetic algorithm was implemented to determine preferential solutions of a short annular diffuser exhaust system of length 1.5Do (outer annulus diameters). Five free variables defined the centre body shape and two variables determined the outer wall profile. Diffuser performance was evaluated using three objectives—(i) diffuser pressure recovery, (ii) outlet velocity uniformity, and (iii) total pressure loss—that were calculated from steady state solutions obtained using the computational fluid dynamics software FLUENT 13.0 with the realizable k-ε turbulence model and enhanced wall treatment. Inlet conditions were ReDh = 8.5 × 104 and M = 0.23. After thirty-five generations, a paraboloid-shaped centre body with length 0.74Do and initial annular expansion of approximately 14° produced preferential solutions. A configuration with a converging outer wall above the centre body developed greater outlet flow uniformity and lower total pressure loss whereas a straight outer wall followed by the solid diffuser generated more static pressure recovery.

Flow Investigation Through a 30° Turn Diffusing Duct in Subsonic Flow Regime

2009 ◽  
Author(s):  
Prasanta K. Sinha ◽  
Biswajit Haldar ◽  
Amar N. Mullick ◽  
Bireswar Majumdar
Keyword(s):  
Axial Velocity ◽  
Pressure Loss ◽  
Total Pressure ◽  
High Speed ◽  
Static Pressure ◽  
Transverse Velocity ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Pressure Probe ◽  
Mean Velocity

Curved diffusers are an integral component of the gas turbine engines of high-speed aircraft. These facilitate effective operation of the combustor by reducing the total pressure loss. The performance characteristics of these diffusers depend on their geometry and the inlet conditions. In the present investigation the distribution of axial velocity, transverse velocity, mean velocity, static and total pressures are experimentally studied on a curved diffuser of 30° angle of turn with an area ratio of 1.27. The centreline length was chosen as three times of inlet diameter. The experimental results then were numerically validated with the help of Fluent, the commercial CFD software. The measurements of axial velocity, transverse velocity, mean velocity, static pressure and total pressure distribution were taken at Reynolds number 1.9 × 105 based on inlet diameter and mass average inlet velocity. The mean velocity and all the three components of mean velocity were measured with the help of a pre-calibrated five-hole pressure probe. The velocity distribution shows that the flow is symmetrical and uniform at the inlet and exit sections and high velocity cores are accumulated at the top concave surface due to the combined effect of velocity diffusion and centrifugal action. It also indicates the possible development of secondary motions between the concave and convex walls of the test diffuser. The mass average static pressure recovery and total pressure loss within the curved diffuser increases continuously from inlet to exit and they attained maximum values of 35% and 14% respectively. A comparison between the experimental and predicated results shows a good qualitative agreement between the two. Standard k-ε model in Fluent solver was chosen for validation. It has been observed that coefficient of pressure recovery Cpr for the computational investigation was obtained as 38% compared to the experimental investigation which was 35% and the coefficient of pressure loss is obtained as 13% in computation investigation compared to the 14% in experimental study, which indicates a very good qualitative matching.

Investigation on Performance of Compressor Cascade with Tubercle Leading Edge Blade

2020 ◽  
Vol 37 (3) ◽  
pp. 295-303 ◽  
Author(s):  
Tu Baofeng ◽  
Zhang Kai ◽  
Hu Jun
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Large Scale ◽  
Design Method ◽  
Leading Edge ◽  
Experimental Tests ◽  
Aerodynamic Performance ◽  
Total Pressure Loss ◽  
Compressor Cascade ◽  
Linear Compressor Cascade

AbstractIn order to improve compressor performance using a new design method, which originates from the fins on a humpback whale, experimental tests and numerical simulations were undertaken to investigate the influence of the tubercle leading edge on the aerodynamic performance of a linear compressor cascade with a NACA 65–010 airfoil. The results demonstrate that the tubercle leading edge can improve the aerodynamic performance of the cascade in the post-stall region by reducing total pressure loss, with a slight increase in total pressure loss in the pre-stall region. The tubercles on the leading edge of the blades cause the flow to migrate from the peak to the valley on the blade surface around the tubercle leading edge by the butterfly flow. The tubercle leading edge generates the vortices similar to those created by vortex generators, splitting the large-scale separation region into multiple smaller regions.

scholarly journals A Compact Diffuser System for Annular Combustors

1983 ◽  
Author(s):  
R. C. Adkins ◽  
J. O. Yost
Keyword(s):  
High Pressure ◽  
Mach Number ◽  
Pressure Loss ◽  
Total Pressure ◽  
Aerodynamic Performance ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Analytical Relationship ◽  
Exit Mach Number ◽  
Aerodynamic Simulation

Airflow tests have been conducted on an aerodynamic simulation of a combustor with pre-diffuser of compact configuration. The inlet Mach number throughout the tests was 0.35. The configuration was successful because of the attainment of a high pressure recovery, (Cp = 0.80), coupled with an exceptionally low total pressure loss (λ = 0.04). A useful analytical relationship is derived between the aerodynamic performance of combustor, compressor exit Mach number and diffuser performance.

scholarly journals Optimization Study of the Dump Diffuser in Gas Turbine to Reduce Pressure Loss

2018 ◽  
Vol 2018 ◽  
pp. 1-14
Author(s):  
Fei Xing ◽  
Hao Su ◽  
Shining Chan ◽  
Leilei Xu ◽  
Xinyi Yu
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Static Pressure ◽  
Vortex Method ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Test Model ◽  
Gap Ratio ◽  
Efficient Combustion ◽  
The Impact

As a key component-connecting compressor and the entrance of combustion chamber, the diffuser is able to increase the pressure and slow down the airflow in order to promote efficient combustion as well as avoid a large amount of pressure loss. In this paper, experimental investigation and numerical studies have been carried out to understand the effects of air bleeding from dump region and dump gap ratio on the total pressure loss and static pressure recovery of the dump diffusers. The ultimate objective is optimizing the dump diffuser design to get the maximum static pressure recovery and minimum total pressure loss. A simplified test model is used to study the effect of the air bleeding from the outer dump region and the dump gap ratio on the total pressure loss and static pressure recovery in the dump diffuser. The impact of the dump gap ratio in the performance of the dump diffusers has also been discussed. Nearly all the pressure raise occurs in the prediffuser, and most of the total pressure loss occurs in the dump region. For the recirculating area in the dump region, the controllable vortex can be introduced. Bleeding air from the outer dump region can improve the velocity distribution near the flame tube. The results show that when 0.4% of the air is bled from outer dump region, the performance of the dump diffuser is optimal. Hence, the controllable vortex method is effective for improving the performance of the dump diffuser.

The Influence of Inlet Conditions on the Performance of Annular Diffusers

1980 ◽  
Vol 102 (3) ◽  
pp. 357-363 ◽  
Author(s):  
S. J. Stevens ◽  
G. J. Williams
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Turbulence Structure ◽  
Mean Velocity ◽  
Flow Measurements ◽  
Outlet Flow ◽  
Inlet Conditions ◽  
Uniform Diameter

Low speed tests have been carried out to investigate the performance and mechanism of flow in two annular diffusers having center bodies of uniform diameter and conically diverging outer walls. In the first part of the investigation the diffusers were tested over a range of naturally developed inlet velocity profiles ranging from near-uniform to fully developed flow. Information is presented concerning the pressure recovery, total pressure loss, and characteristics of the outlet flow. Measurements have also been made of the mean velocity profile and turbulence structure at a number of stations along the length of the diffusers. The second part of the test program was devoted to studying the effects of increased inlet turbulence. The results show a marked improvement in the stability of the outlet flow and gains in pressure recovery, up to a maximum of 20 percent, with only small increases in total pressure loss.

Experimental Study of the Flow and Pressure Drop Performances in Advanced Combustor Distributor Diffuser

2013 ◽  
Author(s):  
H. X. Liang ◽  
J. Q. Suo ◽  
M. Li
Keyword(s):  
Flow Field ◽  
Pressure Loss ◽  
Total Pressure ◽  
High Performance ◽  
Area Ratio ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Flow Rates ◽  
Turbine Engine ◽  
Outlet Flow

Gas turbine engine uses diffuser system to decelerate the compressor exit flow velocity before it enters combustor, it is important to design the compact structure and high performance of the diffuser for gas turbine engine. The diffuser and combustor dome configurations are critical flow path parameters in the design of a low-pressure-loss, high-performance combustion system. With rising of the inlet Mach number of the combustor, dramatically increasing of the diffuser total pressure loss and flow separation. So a new distributor diffuser was designed. In this paper preliminary results from an experimental investigation into the aerodynamic performance on a rectangle combustor-diffuser system with seven distributor plates were presented. Measurements were taken in the diffuser section to assess the diffuser performance characteristics under various conditions, the appropriate outlet flow field can be attained by changing the plate area ratio and form. Tests were carried out to investigate the influence of distributor diffuser plate geometry. During these measurements for each parametric configuration, data were obtained at 24 different flow rates through the distributor diffuser, it gave the conclusion that the distributor diffuser area ratio could be more than traditional diffusers with shorter construction and higher pressure recovery performance, while the flow loss through it was not beyond the traditional limit. Overall static pressure recovery improves and overall total pressure loss reduces with increasing distributor diffuser area ratio, and the increased flow rates through the distributor diffuser gave rise to a higher total pressure loss. The total pressure loss fraction was less than 2.5% when Mach number changed from 0.3 to 0.38; if the area ratio was more than 2.1, the diffuser loss coefficient remained less than 0.3, pressure recovery coefficient more than 0.5 and area ratio up to 2.45. There exists an area ratio in 1.6∼2.0 which makes diffuser outlet flow field distribution more uniform; Baffle structure can adjust the flow field distribution of outlet diffuser. As a result, the distributor diffuser can be potentially satisfied with demands for high performance combustor.

scholarly journals Correlation between total pressure losses of highly loaded annular diffusers and integral stage design parameters

2018 ◽  
Vol 2 ◽  
pp. I9AB30 ◽  
Author(s):  
Dajan Mimic ◽  
Christoph Jätz ◽  
Florian Herbst
Keyword(s):  
Boundary Layer ◽  
Gas Turbines ◽  
Pressure Loss ◽  
Total Pressure ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Design Parameters ◽  
Pressure Losses ◽  
Tip Leakage ◽  
Highly Loaded

Diffusers convert kinetic flow energy into a rise in static pressure. This pressure recovery is the primary aerodynamic design objective for exhaust gas diffusers in power-generating steam and gas turbines. The total pressure loss is an equally important diffuser design parameter. It is strongly linked to the pressure recovery and the residual kinetic energy of the diffuser outlet flow. A reduction benefits the overall thermodynamic cycle, which requires the adjacent components of a diffuser to be included in the design process. This paper focuses on the total pressure losses in the boundary layer of a highly loaded annular diffuser. Due to its large opening angle the diffuser is susceptible to flow separation under uniform inlet conditions, which is a major source for total pressure losses. However, the unsteady tip leakage vortices of the upstream rotor, which are a source of losses, stabilise the boundary layer and prevent separation. Experiments and unsteady numerical simulation conducted show that the total pressure loss reduction caused by the delayed boundary layer separation exceed the vortex-induced losses by far. This flow interaction between the rotor and diffuser consequently decreases the overall total pressure losses. The intensity of the tip leakage vortex is linked to three rotor design parameters, namely work coefficient, flow coefficient and reduced blade-passing frequency. Based on these parameters, we propose a semi-empiric correlation to predict and evaluate the change in total pressure losses with regards to design operating conditions.

scholarly journals Impact of Wake Dispersion on Axial Compressor Performance

2017 ◽  
Author(s):  
Chunill Hah
Keyword(s):  
Boundary Layer ◽  
Pressure Loss ◽  
Total Pressure ◽  
Axial Compressor ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Efficiency Gain ◽  
Rotor Wake ◽  
Total Pressure Recovery ◽  
Stator Blade

Rotor wake dispersion in a low-speed, one and half stage axial compressor is investigated in detail with a Large Eddy Simulation (LES). The primary focus is to quantify the total pressure recovery due to wake stretching and the total pressure loss from the rotor wake interaction with the stator blade boundary layer. The relative magnitude of the aerodynamic loss due to these two effects is examined at several radial locations. The spacing between the rotor and the stator was varied from 29% to 112% of the rotor axial chord at the mid span to investigate the effects of rotor wake decay before entering the stator passage. The current analysis indicates that the efficiency through the compressor stage is increased about 0.5% when the spacing between the rotor and the stator is decreased from 112% to 29% of the rotor axial chord at mid-span. 22% of the efficiency gain from the narrower axial gap is due to the wake recovery and 63% is due to the stronger unsteady pressure field at the exit of the rotor due to stage interaction. Total pressure loss/recovery across the stator varies significantly in the radial direction for the current compressor, which has a much lower aspect ratio. The total pressure recovery due to wake stretching is larger than the total pressure loss due to the unsteady boundary layer development on the stator blade from 20% to 35% of the span from the hub for 29% spacing and from 35% to 55% of the span for 112% spacing. Above 50% of the span, rotor tip clearance flow affects wake dispersion and the overall wake recovery is less than expected.

scholarly journals Flow Behavior in a Dump Diffuser With Distorted Flow at the Inlet

1990 ◽  
Author(s):  
Shinji Honami ◽  
Tadashi Morioka
Keyword(s):  
Pressure Loss ◽  
Total Pressure ◽  
Flow Behavior ◽  
Total Pressure Loss ◽  
Pressure Recovery ◽  
Laser Doppler Velocimeter ◽  
Jet Stream ◽  
Cold Flow ◽  
Flow Experiments ◽  
Made In

The cold flow experiments are made in a two-dimensional dump diffuser. Behavior of an impinging jet over a flame dome head and its reattachment to the casing wall is presented, when a symmetric or distorted flow is provided at the diffuser inlet. A hot-wire anemometer and laser doppler velocimeter are used. Diffuser performances of the pressure recovery and total pressure loss on three types of pre-diffuser geometry and four cases of dump gap between pre-diffuser exit and flame dome head are tested. Both pre-diffuser geometry and dump gap are dominant parameters affecting pressure recovery and total pressure loss. A small dump gap causes insufficient pressure recovery in the pre-diffuser, resulting in a loss of total pressure in the diffuser. Distribution of the flow rate to the branched channels is relatively insensitive to the inlet velocity profile with distortion, as the shift of the jet stream occurs just upstream of the flame dome head.

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