Mary Balbo
Professor Leslie Wolcott
ENC 1102
21 February 2013
Annotated Bibliography
Conversation
The purpose of a diffuser is to increase the static pressure going into the gas turbine (also
known as static pressure recovery) by reducing the velocity of the air flowing through the midframe diffuser. Increasing the static pressure recovery causes an increase in the efficiency of the
entire gas turbine. However the current problem in today’s studies is the pressure losses due to
ineffective diffusers. I will research the different methods used to increase the static pressure
recovery in mid-frame diffusers.
Abdalla, H. A., et al. "Turbulence in wide-angle conical diffusers with swirling flow."
Alexandria Engineering Journal 44.4 (2005): 501-516.
In this article, researchers H. A. Abdalla and A. A. Abd El-Hamid discuss the “turbulence
quantities for swirling diffuser flows” (pg.1). This experiment is an investigation to determine
the turbulent characteristics of this kind of diffuser. With swirling flow, the turbulence peak
moves in toward the centerline of the diffuser rather than against the wall which therefore
decreases the near-wall separation.
This article closely relates to my research because it is fundamental information that
needs to be understood in this field. There are many graphs to represent the data and
mathematical formulas are presented which assists in the understanding of the article.
Mary Balbo
Professor Leslie Wolcott
ENC 1102
21 February 2013
Jenkins, L., S. Althoff Gorton, and S. Anders. "Flow control device evaluation for an internal
flow with an adverse pressure gradient." AIAA paper 266 (2002): 2002.
In this paper, researcher Luther Jenkins from NASA Langley Research Center discusses
the effect of more than one device being used to control the air flow. In this experiment Jenkins
uses micro vortex generators, micro bumps and piezoelectric synthetic jets to control the flow.
Vortex generators proved to be extremely effective in controlling the flow and the synthetic jets
proved effective only when they have sufficient velocity output.
This article is relevant to my research because it gives a new approach to diffuser wall
attachment. Jenkins also goes into great detail such as the test conditions along with the
experimental design. However all the images and graphs are compiled at the end of the paper
which makes it difficult to understand the paper as you are reading it.
Juhasz, A. "Performance of an asymmetric short annular diffuser with a nondiverging inner wall
using suction." (1974). Print
In this NASA Technical Note, researcher Albert Juhasz analyzes the effects of suction
used to prevent separation. In this experiment a gap was placed in the diffuser in order to create
inner wall suction. There were also suction slots in the outer wall. By creating inner and outer
wall suction, the separation from the walls is reduced. Results show that suction can efficiently
be used to control inlet airflow.
Mary Balbo
Professor Leslie Wolcott
ENC 1102
21 February 2013
This article is relevant to my research because this is a new technique used to try and
increase the efficiency of the gas turbine. This article specifically focusses on the control of the
air flowing through the diffuser. Focusing on controlling the flow allows researchers to better
control the pressure. This article goes into very specific design details as well as specific
procedures. Also, the results are clearly laid out in a list. However most of the diagrams are
place at the end instead of throughout the paper where they are mentioned. This poorly affects
my understanding and visualization of the experiment.
Kibicho, K., Sayers, A.T. “Measurements of Velocity Profiles and Static Pressure Recovery in a
Wide-Angled Diffuser.” R & D Journal 24.2 (2008):16-22. Print
In this R&D Journal article, K. Kibicho, a researcher from the Jomo Kenyata University
of Agriculture Technology in Kenya, South Africa, introduces and analyzes stall in a standard
wide-angle diffuser. The purpose of this experiment is to examine the behaviors of the air
flowing through the diffuser. Results show that the air being pumped through the diffuser is only
attaching to one wall instead of both. By having one wall undergo stall, the static pressure
recovery is significantly decreased (pages16-21).
This article shows the primary and most difficult problem with wide-angled diffusers and
provides a base line in my research. By understanding the base line problem and why the
problem is occurring, researchers can then have a better understanding of what to do in order to
fix that problem (page 16). Throughout this article there are numerous diagrams and charts.
Mary Balbo
Professor Leslie Wolcott
ENC 1102
21 February 2013
These diagrams and charts assist in explaining the methods and results and assist in supporting
the author’s claims. Also, because this article is simply showing what happens in a diffuser
without altering anything to improve the efficiency, the claims made in this paper seem to be
basic and unbiased (pages 16-21).
**Lord, Wesley K., Douglas G. MacMartin, and T. G. Tillman. "Flow control opportunities in
gas turbine engines." AIAA paper 2234 (2000): 19-22.
In this AIAA paper, researcher W. K. Lord from the United Technologies Research
Center states that “recent advances in flow control have the potential for significant impact on
the design and performance of modern gas-turbine engines” (pg.1). Throughout this paper Lord
discusses the many opportunities to reduce separation in the turbine. These opportunities include
simple technologies that could be more usefully that some people may believe. These
technologies include fans and compressors to add energy and better the pressure ratios. Also a
nozzle (reversed diffuser) is used to provide minimum pressure losses.
This paper relates to my research because Lord is focusing on many aspects including
flow control and separation. One thing that I noticed is that W. K. Lord mentions technologies
that people would not normally use in a gas turbine. These technologies may be ones that the
company has previously researched. However, Lord covers his bases by including why these
technologies may not be as useful due to issues that he encountered.
Mary Balbo
Professor Leslie Wolcott
ENC 1102
21 February 2013
McCormick, D. C. "Boundary layer separation control with directed synthetic jets." AIAA paper
519 (2000): 2000.
In this article, researcher D. C. McCormick from the United Technologies Research
Center introduces a new technology to assist in controlling the separation from the diffuser wall.
This new technology is a directed synthetic jet that “converts acoustic oscillations into mean
fluid motions” (pg. 1). This allows for slow moving air to be sucked from the wall to be blown
back into the diffuser to force attachment to the diffuser wall. It has been concluded that the jet is
very effective.
This article is relative to my research because it introduces and new and effective concept
to reduce separation from the diffuser wall. This article is full of pictures and graphs which
makes it easy to understand. However, this article seems to be one sided with no negative
comments in the conclusion.
Pietrasch, Roman Z., and Joerg R. Seume. "Interaction between struts and swirl flow in gas
turbine exhaust diffusers." Journal of Thermal Science 14.4 (2005): 314-320.
In this article, researchers Roman Pietrasch and Joerg Seume from the University of
Hannover, discuss swirl angles and how they affect the separation from the struts on the wall.
The researchers explain that diffuser efficiency decreases with large swirl angles. The
experiment tests different swirl angles against different strut configurations within the diffuser.
The experiment showed that a diffuser without struts produced a higher pressure recovery.
Mary Balbo
Professor Leslie Wolcott
ENC 1102
21 February 2013
This article is relevant to my research because it introduced a new technique to try to
increase the pressure recovery. Although the struts had a negative impact on the diffuser
performance the article is still somewhat insightful. However, the researchers broadly stated their
conclusions and did not explain why the struts failed.
Şahin, B., and A. J. Ward-Smith. "Flow control by perforated plates using a blanking technique
in wide-angle diffusers employed in practical electrostatic precipitator systems." Journal
of Wind Engineering and Industrial Aerodynamics 37.3 (1991): 269-284.
In this journal article, researchers B. Sahin and A. J. Ward-Smith, introduce a new
technique to try and reduce separation. In this experiment, perforated plates are placed against
the diffuser wall to draw air through them and force the air to fill the entire area. By doing this,
velocity profiles can be controlled. In the first test series, there was significant separation. In the
second test series a blanking technique was used. This technique decreased the separation.
This article is closely related to my research because it introduces a new and reasonable
technique to control the air flow and reduce separation. There were very few diagrams which
made it a bit difficult to understand. However, the authors were from different countries which
allows to different perspectives to tie into one paper. This allows for an understanding paper.
Mary Balbo
Professor Leslie Wolcott
ENC 1102
21 February 2013
Sieker, Olaf, and Joerg R. Seume. "Influence of rotating wakes on separation in turbine exhaust
diffusers." Journal of Thermal Science 17.1 (2008): 42-49.
In these proceedings, Olaf Sieker and Joerg Seume, German Researchers from Leibniz
University discuss the effects of the rotating wakes of the blade on the flow through the diffuser.
The diffuser is investigated by placing swirl generators at the inlet of the diffuser. Normal
conditions are then compared to the condition of a diffuser with generators.
This article is closely related to my research because I am concerned with the cause for
separation from the diffuser wall and this paper identifies and investigates one issue. Olaf and
Seume produce detailed results from a controlled study without a generator and results with
different sized generators. The researchers admit that the generators produce an increase in
pressure recovery but still have some issues. The researchers also give a reason to why the issues
are occurring which makes this article insightful.
Sinha, P. K., A. K. Das, and B. Majumdar. "Numerical Investigation of flow through Annular
Diffusing Duct."
In this article, researcher P. K. Sinha introduces the investigation of flow through an
annular diffuser. In this experiment, Sinha test multiple diffuser area ratios to see which one
resulted in better static pressure recovery. These diffusers are used in high-speed aircrafts so it is
important to achieve high pressure recovery. The experiment resulted in an area ratio that
Mary Balbo
Professor Leslie Wolcott
ENC 1102
21 February 2013
increased the static pressure recovery and the experiment results closely matched the predicted
results.
This article is related to my research because this is a fundamental experiment that
introduces a new diffuser design. The article is very short and sweet and goes into great detail.
However, there are very few diagrams and graphs to interpret the data presented in the article.
This makes the article difficult to understand.
WALKE, A. Duncan, Paul A. Denman, and James J. McGuirk. "Experimental and computational
study of hybrid diffusers for gas turbine combustors." Journal of engineering for gas
turbines and power 126.4 (2004): 717-725.
In this journal article, A. Duncan Walker, a researcher from the Department of
Aeronautical and Automotive Engineering at Loughborough University, tests and analyzes a
diffuser with a different design. The design for the hybrid diffuser allows the slow moving air
along the walls of the diffuser to escape through holes at the inlet of the diffuser. The escaping
air allows for better pressure recovery while acting as a cooling component for the turbine disk
and blades. Therefore, by increasing the pressure recovery and recycling air from the diffuser,
the gas turbine becomes more efficient (pages 717-724)
This article is relevant to my research due to its methods to attempt to increase the static
pressure recovery. In addition, this article is also focused on the big picture (increasing the
efficiency of the gas turbine) by recycling the air removed from the diffuser. The author and
Mary Balbo
Professor Leslie Wolcott
ENC 1102
21 February 2013
researcher, A. Duncan Walker, seems to cover all his tracks and seems to be relatively unbiased.
Walker admits that even though this experiment resulted in an increase in static pressure
recovery, there is still a better design to be tested that may result in even better outcomes (pages
721-724).
Ward-Smith, A. J., et al. "Flow regimes in wide-angle screened diffusers." International Journal
of Mechanical Sciences 33.1 (1991): 41-54.
In this article, researcher A. J. Ward-Smith, introduces a technique that commonly used
today. This experiment tests the use of screens and perforated plates. The screens are placed at
the inlet of the diffuser to control the inlet air flow. The perforated plates are used to control the
velocity inside the diffuser. The results conclude that the placement and porosity of the screens
allows for flow separation to be avoided.
This article closely relates to my research because it introduces another technique used to
reduce separation in the diffuser. There are many diagrams and graphs and the terminology is
fairly simple, therefore this article is easy to understand.