Experimental Study of an Exhaust Ejector With Entraining Diffuser

2005 ◽  
Author(s):  
Qi Chen ◽  
A. M. Birk
Keyword(s):  
Gas Turbine ◽  
Exhaust System ◽  
Industrial Applications ◽  
Area Ratio ◽  
Pressure Recovery ◽  
Entrainment Ratio ◽  
Wide Range ◽  
Inlet Swirl ◽  
Air Ejector ◽  
Velocity Pressure

Air-air ejectors are used in a wide range of industrial applications. In gas turbine installations, ejectors are typically used for entraining ventilation air or cooling of exhaust ducting. In some gas turbine applications, the exhaust system must be cooled to limit temperatures inside the structure or to manage heat signatures. The ducts are usually cooled by ejectors with film or effusion cooled diffusers. Entraining diffusers typically have poor pressure recovery and as a result, the ejector performance is affected. This paper presents experimental results on the performance of an air-air ejector with an entraining diffuser. The effects of inlet swirl, and primary nozzle area ratio on the diffuser pressure recovery and ejector pumping were studied. The ejector experiments were carried out on a cold flow wind tunnel that can provide primary air flow rates up to 2.2 kg/s at ambient temperature. Velocity, pressure and temperature measurements were taken in the annulus upstream of the primary nozzle, at the nozzle exit, at the diffuser inlet, on the diffuser walls, and at the diffuser exit. The results show that swirl strongly improves flow non-uniformity at the diffuser exit. The peak pumping performance and the strongest diffuser gap flows was observed with 20° of swirl in the primary nozzle flow. At the no swirl condition, the nozzle area ratio slightly affected the overall entrainment ratio. However, the large nozzle area ratio resulted in the best pumping when swirl was applied.

Effect of Prediffuser Angle on the Static Pressure Recovery in Flow Through Casing-Liner Annulus of a Gas Turbine Combustor at Various Swirl Levels

2015 ◽  
Vol 8 (1) ◽  
Author(s):  
Prakash Ghose ◽  
Amitava Datta ◽  
Achintya Mukhopadhyay
Keyword(s):  
Gas Turbine ◽  
Static Pressure ◽  
Numerical Study ◽  
Pressure Recovery ◽  
Gas Turbine Combustor ◽  
Pressure Losses ◽  
Pressure Distributions ◽  
Inlet Swirl ◽  
Flow Through ◽  
The Ideal

A numerical study has been performed in an axisymmetric diffuser followed by a casing-liner annulus of a typical gas turbine combustor to analyze the flow structure and pressure recovery in the geometry. Static pressure recovery in a gas turbine combustor is important to ensure high pressure of air around the liner. However, the irreversible pressure losses reduce the static pressure recovery from the ideal value. The presence of swirl in the flow from compressor and prediffuser geometry before the dump diffuser influences the flow pattern significantly. In this study, flow structures are numerically predicted with different prediffuser angles and inlet swirl levels for different dump gaps. Streamline distributions and pressure plots on the casing and liner walls are analyzed. Static pressure recovery coefficients are obtained from the pressure distributions across the combustor. The effect of dump gap on the static pressure recovery has also been evaluated. It is observed that the best static pressure recovery can be obtained at optimum values of inlet swirl level and prediffuser angle. Dump gap is found to have significant influence on the static pressure recovery only at small prediffuser angle.

Experimental and CFD Study of an Exhaust Ejector With Round Entraining Diffuser

2007 ◽  
Author(s):  
Qi Chen ◽  
A. M. Birk
Keyword(s):  
Computational Study ◽  
Flow Temperature ◽  
Primary Flow ◽  
Flow Rates ◽  
Wall Functions ◽  
Experimental Configuration ◽  
Swirl Angle ◽  
Inlet Swirl ◽  
Air Ejector ◽  
Velocity Pressure

This paper presents experimental and CFD data for the performance of a round straight air-air ejector with a 4-ring entraining diffuser. The effects of inlet swirl angle and flow temperature on the ejector pumping, back pressure, wall pressure distribution, and diffuser pressure recovery were studied. The ejector experiments were carried out on a hot flow wind tunnel that can provide primary flow rates up to 2.2 kg/s at ambient temperature and 1.8 kg/s at 500°C. Velocity, pressure and temperature measurements were taken in the annulus upstream of the primary nozzle, on the mixing tube and diffuser walls, and at the mixing tube and diffuser ring exits. A parallel computational study was conducted along with the experimental study. A commercial CFD solver, Fluent 6.216, was used for simulation. The Realizable k-ε turbulence model and non-equilibrium wall functions were implemented on the cases. The CFD inlet boundary conditions were chosen to replicate the experimental configuration.

A Sensitivity Study of Gas Turbine Exhaust Diffuser-Collector Performance at Various Inlet Swirl Angles and Strut Stagger Angles

2017 ◽  
Author(s):  
Michal P. Siorek ◽  
Stephen Guillot ◽  
Song Xue ◽  
Wing F. Ng
Keyword(s):  
Gas Turbine ◽  
Flow Direction ◽  
Flow Behavior ◽  
Exhaust System ◽  
Sensitivity Study ◽  
Inlet Swirl ◽  
Inlet Conditions ◽  
Gas Turbine Exhaust ◽  
The Impact ◽  
Turbine Exhaust

This paper describes studies completed using a quarter-scaled rig to assess the impact of turbine exit swirl angle and strut stagger on a turbine exhaust system consisting of an integral diffuser-collector. Advanced testing methods were applied to ascertain exhaust performance for a range of inlet conditions aerodynamically matched to flow exiting an industrial gas turbine. Flow visualization techniques along with complementary Computational Fluid Dynamics (CFD) predictions were used to study flow behavior along the diffuser endwalls. Complimentary CFD analysis was also completed with the aim to ascertain the performance prediction capability of modern day analytical tools for design phase and off-design analysis. The K-Epsilon model adequately captured the relevant flow features within both the diffuser and collector, and the model accurately predicted the recovery at design conditions. At off-design conditions, the recovery predictions were found to be pessimistic. The integral diffuser-collector exhaust accommodated a significant amount of inlet swirl without a degradation in performance, so long as the inlet flow direction did not significantly deviate from the strut stagger angle. Strut incidence at the hub was directly correlated with reduction in overall performance, whereas the diffuser-collector performance was not significantly impacted by strut incidence at the shroud.

Factors Affecting the Performance of the Supersonic Parallel Diffuser

1966 ◽  
Vol 8 (1) ◽  
pp. 62-69 ◽  
Author(s):  
B. W. Martin
Keyword(s):  
Static Pressure ◽  
Pressure Ratio ◽  
Area Ratio ◽  
Stagnation Pressure ◽  
Pressure Recovery ◽  
Cross Sectional ◽  
Factors Affecting ◽  
Single Shock ◽  
Wide Range

Following the work of Baker and Martin (1), this paper provides further information about static pressure recovery in axi-symmetric supersonic parallel diffusers of fixed length and the same upstream generating nozzle when the diffuser cross-sectional area is varied over a wide range. Correlations based on these and associated experiments by Martin and Baker (2) indicate an area ratio for maximum possible static pressure recovery. At breakdown of the single shock, the diffuser stagnation pressure ratio corresponds to that for normal shock pressure recovery, while the outlet Mach number becomes independent of area ratio as the latter increases. The factors which influence the development and stability of the single shock regime are considered in some detail, from which the role of the boundary layer is shown to be predominant.

A Sensitivity Study of Gas Turbine Exhaust Diffuser-Collector Performance at Various Inlet Swirl Angles and Strut Stagger Angles

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Michal P. Siorek ◽  
Stephen Guillot ◽  
Song Xue ◽  
Wing F. Ng
Keyword(s):  
Gas Turbine ◽  
Flow Direction ◽  
Flow Behavior ◽  
Exhaust System ◽  
Sensitivity Study ◽  
Inlet Swirl ◽  
Inlet Conditions ◽  
Gas Turbine Exhaust ◽  
The Impact ◽  
Turbine Exhaust

This paper describes studies completed using a quarter-scaled rig to assess the impact of turbine exit swirl angle and strut stagger on a turbine exhaust system consisting of an integral diffuser-collector. Advanced testing methods were applied to ascertain exhaust performance for a range of inlet conditions aerodynamically matched to flow exiting an industrial gas turbine. Flow visualization techniques along with complementary computational fluid dynamics (CFD) predictions were used to study flow behavior along the diffuser end walls. Complimentary CFD analysis was also completed with the aim to ascertain the performance prediction capability of modern day analytical tools for design phase and off-design analysis. The K-Epsilon model adequately captured the relevant flow features within both the diffuser and collector, and the model accurately predicted the recovery at design conditions. At off-design conditions, the recovery predictions were found to be pessimistic. The integral diffuser-collector exhaust accommodated a significant amount of inlet swirl without degradation in performance, so long as the inlet flow direction did not significantly deviate from the strut stagger angle. Strut incidence at the hub was directly correlated with reduction in overall performance, whereas the diffuser-collector performance was not significantly impacted by strut incidence at the shroud.

scholarly journals A User Programmable General Purpose Microprocessor Control System

1980 ◽  
Author(s):  
D. E. Mann
Keyword(s):  
Real Time ◽  
Gas Turbine ◽  
Diesel Engines ◽  
Industrial Applications ◽  
General Purpose ◽  
Real Time System ◽  
Authority Control ◽  
Wide Range ◽  
Structure And Design ◽  
Hardware Structure

This paper describes the hardware structure and design of a general-purpose microprocessor based controller intended for the full authority control of gas turbine and diesel engines in ground based vehicle and industrial applications. Particular attention is paid to the digital processor and how it’s design was influenced by the user requirements of a general purpose, real-time system. The system is currently being manufactured in production form. An accompanying paper describes the supporting software and user program facilities (Ref 1). Such systems based on the use of microprocessors must not only provide general purpose hardware, but also software structured so that a wide range of control algorithms may be programmed and performed within strict limits of real-time. This paper describes the development of the Type C4E87 General Purpose Controller (REF Fig. 1) with particular reference to its hardware structure and design within a system intended primarily for application as a full authority control of gas turbine and diesel engines etc.

Strut Losses in a Diverging Annular Diffuser With Swirling Flow

2006 ◽  
Author(s):  
G. K. Feldcamp ◽  
A. M. Birk
Keyword(s):  
Total Pressure ◽  
Swirling Flow ◽  
Pressure Recovery ◽  
Swirl Number ◽  
Pressure Losses ◽  
Swirl Angle ◽  
Wide Range ◽  
Annular Diffuser ◽  
Inlet Swirl ◽  
The Ideal

An experimental investigation into the overall influence of struts spanning a double divergent annular diffuser followed by a straight cored annular diffuser has been undertaken in order to determine the performance of various strut configurations over a wide range of inlet swirl conditions. Two strut profiles have been investigated in four and eight strut configurations. Results have shown that the presence of struts under no swirl conditions have a relatively small effect on the overall total pressure loss. Increasing the inlet swirl angle to 20° has shown that the struts are able to assist in recovery of the swirling flow such that the pressure recovery nearly approaches that without struts, despite increased total pressure losses. Performance at 40° swirl is highly dependent on strut profile; the higher thickness-to-chord ratio strut configurations show minimal decrease in pressure recovery compared to 20° swirl, while the lower thickness-to-chord ratio configurations experiences a significant decrease as the result of significant flow separation from the struts. The exit swirl number has been shown to correlate strongly with the strut profile shape, while the number of struts had only a secondary influence. The exit velocity profiles show significant distortions at 40° swirl, and as a result the ideal pressure recovery calculated from the inlet and exit profiles change with strut configuration at 40° swirl.

Hub Extension in an Axial Gas Turbine Diffuser

2012 ◽  
Author(s):  
A. Hirschmann ◽  
S. Volkmer ◽  
M. Casey ◽  
M. Montgomery
Keyword(s):  
Mach Number ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Pressure Loss ◽  
Pressure Profile ◽  
Turbine Rotor ◽  
Area Ratio ◽  
Pressure Recovery ◽  
Sudden Expansion ◽  
Inlet Section

Diffusers downstream of axial gas turbines typically support a hub carrying the turbine rotor bearing. The blunt end of the hub is one of the main causes of loss production. However, a long hub can theoretically reduce the losses and improve the pressure recovery of the diffuser and thus the overall performance of the gas turbine. At the end of the hub the flow experiences a sudden expansion, which can be described by the Borda Carnot equation for incompressible fluid. The pressure loss at the end of the hub depends on the dynamic head and the area ratio of the expansion. With a long hub the blunt end moves further downstream into the diffuser and therefore the flow velocity and the area ratio of the step are reduced, resulting in a lower pressure loss. Two different casing geometries, each with a short and a long hub configuration are examined experimentally and numerically using CFD (Computational Fluid Dynamics). The geometrical configurations lead to a separation at the casing for a uniform total pressure profile at the inlet which shows the highly loaded state of the diffuser configuration. Experiments have been conducted at a high subsonic inlet Mach number comparable to real turbine exit flows and a low Mach number representing incompressible flow. It is shown that in some cases the long hub has a benefit to pressure recovery. However, the Mach number at the inlet of the diffuser influences the intensity of this effect. A high inlet Mach number increases the losses in the inlet section of the diffuser and at the struts supporting the hub and hence decreases the diffuser performance. Consequently the performance depending on the particular diffuser design can be decreased with an extended hub configuration.

A Versatile Design of a Controlled Swirl Distortion Generator for Testing Gas Turbine Engines

2008 ◽  
Author(s):  
Yogi Sheoran ◽  
Bruce Bouldin
Keyword(s):  
Gas Turbine ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Delta Wings ◽  
Turbine Engine ◽  
System Sensitivity ◽  
Swirl Generator ◽  
Wide Range ◽  
Inlet Swirl ◽  
Area Of Concern

Inlet swirl distortion has recently become a major area of concern in the gas turbine engine community. Gas turbine engines are being installed in embedded installations that are downstream of increasingly complicated inlet systems, such as those used in Unmanned Aerial Vehicles (UAVs). These inlet systems can produce complex swirl patterns in addition to total pressure distortion. The effect of swirl distortion on engine or compressor performance and operability must be evaluated. The gas turbine community is developing methodologies to measure and characterize swirl distortion. There is a strong need to develop a mechanism for generating prescribed swirl distortion intensities and patterns for testing compression system sensitivity to swirl distortion. Several devices such as delta wings or complex turning vanes have been proposed and used to generate swirl distortion with limited success. This paper presents a versatile swirl distortion generator design that produces a wide range of swirl distortion patterns of a prescribed strength, including bulk swirl, 1/rev, and 2/rev patterns. It also creates different paired swirl patterns, varying from equal and opposite “twin swirls” to offset swirl pairs. This paper describes the design of the swirl generator. Computational Fluid Dynamics (CFD) results are presented along with some test data which illustrate how the swirl generator functions and how altering the swirl generator configuration can produce different swirl distortion patterns.

Substituent Effects on the Thermal Decomposition of Phosphate Esters on Ferrous Surfaces

2019 ◽  
Author(s):  
James Ewen ◽  
Carlos Ayestaran Latorre ◽  
Arash Khajeh ◽  
Joshua Moore ◽  
Joseph Remias ◽  
...  
Keyword(s):  
Thermal Decomposition ◽  
Film Formation ◽  
Substituent Effects ◽  
Vapour Phase ◽  
Industrial Applications ◽  
Phosphate Esters ◽  
Antiwear Additives ◽  
Formation Mechanisms ◽  
Phosphate Ester ◽  
Wide Range

<p>Phosphate esters have a wide range of industrial applications, for example in tribology where they are used as vapour phase lubricants and antiwear additives. To rationally design phosphate esters with improved tribological performance, an atomic-level understanding of their film formation mechanisms is required. One important aspect is the thermal decomposition of phosphate esters on steel surfaces, since this initiates film formation. In this study, ReaxFF molecular dynamics simulations are used to study the thermal decomposition of phosphate esters with different substituents on several ferrous surfaces. On Fe<sub>3</sub>O<sub>4</sub>(001) and α-Fe(110), chemisorption interactions between the phosphate esters and the surfaces occur even at room temperature, and the number of molecule-surface bonds increases as the temperature is increased from 300 to 1000 K. Conversely, on hydroxylated, amorphous Fe<sub>3</sub>O<sub>4</sub>, most of the molecules are physisorbed, even at high temperature. Thermal decomposition rates were much higher on Fe<sub>3</sub>O<sub>4</sub>(001) and particularly α-Fe(110) compared to hydroxylated, amorphous Fe<sub>3</sub>O<sub>4</sub>. This suggests that water passivates ferrous surfaces and inhibits phosphate ester chemisorption, decomposition, and ultimately film formation. On Fe<sub>3</sub>O<sub>4</sub>(001), thermal decomposition proceeds mainly through C-O cleavage (to form surface alkyl and aryl groups) and C-H cleavage (to form surface hydroxyls). The onset temperature for C-O cleavage on Fe<sub>3</sub>O<sub>4</sub>(001) increases in the order: tertiary alkyl < secondary alkyl < primary linear alkyl ≈ primary branched alkyl < aryl. This order is in agreement with experimental observations for the thermal stability of antiwear additives with similar substituents. The results highlight surface and substituent effects on the thermal decomposition of phosphate esters which should be helpful for the design of new molecules with improved performance.</p>

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