Static test results are presented for smooth annular seals with a length-to-diameter ratio of 0.50, radius R = 51.00 mm, at the nominal radial clearance C r = 0.2032 mm. Tests were conducted for angular shaft speeds; ω = 2, 4, 6, 8 krpm, axial pressure drops; Δ P = 2.1, 4.13, 6.21, 8.27 bars, and eccentricity ratios ϵ 0 = e 0 / C r = 0.00, 0.27, 0.53, 0.8 where e 0 is the static eccentricity. Three pre-swirl inserts were used to target zero, medium, and high (0., 0.4, and 0.8) pre-swirl ratios for a set of pre-determined operating conditions with ISO VG 2 oil at 46.1°C. Pitot tubes measured the circumferential velocity at separate upstream and downstream seal locations and were used to calculate pre-swirl ratio, PSR = v inlet / R ω, and outlet-swirl ratio, OSR = v outlet / R ω. For all tested pre-swirl inserts, PSR tended to converge to 0.4∼0.5 as ω increased. PSR and OSR were poorly correlated. Volumetric leakage rate Q ˙ versus pressure differential Δ P was measured. The measured vector Reynolds number Re , combining the axial and circumferential Reynolds numbers ranged from ∼1000 to ∼3500. Based on Zirkelback and San Andrés 1996 publication, almost all of the flow regime is predicted to lie in the transition regime, with fewer points in the turbulent regime. Generally, the seals’ static centering properties were obtained by applying a static load F s and measuring the resulting displacement vector e 0 . At many low-speed, low-Δ P test conditions, the seal would not remain in the desired centered or near-centered position and had to be forced into place with a centering force F s . The authors believe that the observed de-centering effects resulted from test operations in the transition flow regime where the friction factor λ does not drop with increasing Δ P and increasing Re . A positive centering Lomakin effect requires that λ drop with increasing axial Reynolds number. The seals had positive centering effects over a large portion of the predicted transition flow regime, supporting the view that the shift from transition-to-turbulent flow regularly occurred at lower Re values than the R e = 3000 boundary used by Zirkleback and San Andrés.

A team led by General Electric Research (GER) and Southwest Research Institute (SwRI) was tasked to design, build and test an advanced 4MW CO2 compressor that would operate near the liquid-vapor dome for Carbon Dioxide (CO2). The US Department of Energy (DoE) Solar Technologies Office (SETO) funded program was targeted towards a Concentrated Solar Power (CSP) plant where optimum power cycle efficiency can be obtained when operated close to the liquid-vapor dome where CO2 is a supercritical fluid (sCO2) as compression power is reduced in the main compressor. However, the CSP cycle and other related supercritical CO2 cycles (fossil, nuclear, waste heat recovery) have considerable compression challenges both mechanically and aerodynamically when operating with a high density fluid that exceeds 70% the density of water. The subject of this paper is highlighting the challenge in determining compressor performance using industry standard measurements. This application is the highest density industrial-scale centrifugal compressor in the world at 720 kg/m 3 . This paper will investigate the uncertainty when measuring compressor efficiency using ASME PTC-10 instrumentation and the effect of the strong CO2 property variation when operating as a supercritical fluid, near the fluid-vapor dome. Prior work in this area by Wahl will be summarized and compared with the current compressor test program uncertainty. It will be shown that Wahl predicted high uncertainty as well although, the current testing program is even closer to the liquid-vapor dome than the test program under Wahl. The uncertainty analysis has shown that traditional PTC-10 temperature measurements lead to high levels of uncertainty for sCO2 compression near the liquid-vapor dome. The uncertainty is driven by the large changes in thermodynamic properties of sCO2. These property changes are affected by the measured pressure and temperature; however, temperature measurement error is the primary contributor to uncertainty. Because of this, looking at alternate sCO2 property measurements was investigated. Higher quality localized pressure calibration, improving flow measurement accuracy, and measuring density in addition to temperature all significantly improved efficiency uncertainty. The authors confirmed the most significant measurement change is to measure pressure and density through either a densitometer or a Coriolis flow meter which provides a density measurement in conjunction with flow rate accuracy.

Advancements in core compressor technologies are necessary for next generation, high Overall Pressure Ratio (OPR) turbofan engines. High pressure compressors (HPCs) for future engines are being designed with exit corrected mass flow rates less than 2.25 kg/s (5 lbm/s). In order to accurately measure the performance of these advanced designs, high accuracy measurements are needed in test facilities. The W7 High Speed Multistage Axial Compressor Facility at NASA Glenn Research Center has been used to acquire data for advanced compressor designs. This facility utilizes an advanced differential pressure flow meter called a V-Cone. The facility has historically tested components with physical mass flow rates in the range of 27 to 45 kg/s (60 to 100 lbm/s). As such, when the V-Cone was calibrated prior to installation, the calibrations focused on higher mass flow rates, and uncertainties in that regime range from 0.5% to 0.85%. However, for low mass flow rates under 9 kg/s (20 lbm/s), expected in tests of advanced high OPR HPCs rear stages, the uncertainties of the V-Cone exceed 2.5%. To address this, using a method similar to that utilized by the National Institute of Standards and Technology, an array of Critical Flow Venturi Nozzles (CFVs) was installed in the W7 test section and used to calibrate the V-Cone in 0.5 kg/s (1 lbm/s) increments up to 10.5 kg/s (23 lbm/s). This effort details the measurements and uncertainties associated with this calibration which resulted in a final uncertainty of the V-Cone measurements under 1%.

The experimental set-up for a hole-pattern seal is modeled using CFD and results compared with measured test data and bulk flow model (ISOTSEAL) predictions. The inlet swirl boundary condition for prior CFD analyses of this test case have either been assumed or based on pitot-tube measurements. In this paper, the validity of each is investigated by including radial inlet nozzles with the inlet plenum in the model geometry. A transient mesh deformation technique with multiple frequency journal excitations is used to determine frequency dependent rotordynamic coefficients. This multi-frequency excitation method is validated against single frequency sinusoidal journal excitation. An empirical limit on the number of frequencies that can be packed in a multi-frequency excitation signal to provide a reasonable estimate of rotordynamic coefficients is provided. Rotordynamic coefficients estimated using CFD compare well with measured rotordynamic coefficients. For the given test data, the ISOTSEAL bulk flow model does not provide good correlation for cross-coupled stiffness if the measured swirl ratio at the inlet of the seal is used in the prediction. However, improvement in correlation for cross-coupled stiffness is obtained if the swirl ratio found from CFD analysis is used in the bulk flow model, indicating that pitot-tube measurements of swirl may not be accurate.

In order to understand the details of the mechanism of the occurrence of wetness loss between blade rows, the blades of an HP nuclear turbine were modeled in an atmospheric subsonic wind tunnel, and a flow field with wet loss was analyzed in its totality using a three-hole Pitot tube and Phase Doppler Particle Analyzer (PDPA) system. In the secondary flow loss region and the end wall loss region, a significant increase in pressure loss was confirmed under wet conditions. Analysis by measurement and the Eulerian-Lagrangian coupled solver showed that these loss increases can occur due to the agitation of water droplets and water films in the passage vortex or corner vortex. Finally, this report contains a breakdown of profile loss, thermodynamic loss and acceleration loss of the wet air flow through the sub-sonic blade row.

Understanding the amount of air that enters a gas turbine is important for calculating their performance and efficiency. Flow meters are almost never used to measure that flow in production engines. Typical flow meters are impractical because the air flow into the compressor is very large, up to 1400 lbs/s (635 kg/s) or 1,000,000 ft 3 /min (28,300 m 3 /min), and typically an intentional pressure drop is involved in the measurement. This pressure drop negatively impacts the performance of the engine. If inlet air mass flow were known accurately without negatively impacting the engine performance, then engines could be run more efficiently. Currently, inlet mass flow is typically inferred, rather than measured. This leads to increased safety margins which require engines to be run more conservatively, i.e., at lower power. This paper describes a novel, inexpensive, and accurate air mass flow measurement system with negligible impact on engine performance.

This study carries out parametric investigations on aerodynamic loss of various types of LP turbine airfoils characterized with different flow deceleration rates (DR) on their suction surfaces under the realistic flow conditions such as wake inflow and freestream turbulence. The Reynolds number examined in this study ranges from 57,000 to 170,000. As for the freestream turbulence, two levels of the turbulence are used, i.e., about 1.2% and 3.5%. Stagnation pressure distributions downstream of each of the airfoil cascades are measured by use of a Pitot tube, while steady-state and unsteady boundary-layers are measured over the rear part of suction surface and pressure side near the trailing edge using a single hot-wire probe. The measured boundary-layer data are used to estimate the cascade loss along with RANS (Reynolds-Averaged Navier-Stokes) simulations by taking advantage of the momentum-theory based Denton’s method. First, relationships between the cascade loss for each flow condition and DR are examined. The estimated loss values are then compared with the measured cascade loss to check the validity of the loss estimation method, which is a derivative of Denton’s method, under the realistic flow conditions.

Previous investigations performed at the von Karman Institute for Fluid Dynamics (VKI) have shown an influence of the gas-to-wall temperature ratio on the bypass transition development along the VKI LS89 blade suction side. In the present work, the influence of this quantity on the flow field downstream of this highly-loaded nozzle guide vane is studied through the evaluation of the aerodynamic losses. The investigation is organized in three sections with different combinations of exit Mach numbers and freestream turbulence intensity (FSTI) while T gas /T wall is varied between 1.1 and 1.3 for all the tests. The Isentropic Compression Tube facility (CT-2) at VKI allowed the determination of the total pressure loss across the cascade by means of a Pitot tube in the upstream region and a downstream three-hole needle probe. The latter is traversed in the pitch-wise direction by a pneumatic traversing system. Finally, the cascade aerodynamic efficiency is quantified by means of the kinetic energy loss coefficient ζ and the total pressure drop profile distortions in the wake region.

Test results are presented for a smooth-rotor/circumferentially-grooved, annular pump seal. The seal’s geometry and operating conditions are representative of electrical submersible pumps (ESPs) as used for oil recovery; however, most ESPs use grooved rotors instead of grooved stators. Test results include static and rotordynamic data at speeds ω of 2, 4, 6 krpm, axial pressure drops Δ P of 2.1, 4.1, 6.2, 8.3 bars. The grooved seal has a length-to-diameter ratio L/D of 0.5 and a minimum radial clearance C r of 203 μm. It employs 15 circumferential grooves with a length G l , and depth G d of 1.52 mm, which are equally-spaced by a land length of 1.52 mm. Tests are conducted for eccentricity ratios ϵ 0 of 0.00, 0.27, 0.53, 0.80. Three different inlet-fluid prerotation inserts are used upstream of the test seals to create a range of inlet preswirl ratios. Pitot tubes are used to measure the circumferential velocity at one location immediately upstream of the test seal and one downstream location near the seal exit. The test fluid is ISOVG2 oil @ 46 °C. Test results for the grooved seal are compared to test results for a smooth annular seal with the same L , D , and minimum C r . The grooved-seal’s leakage rate Q̇, ranges from a low 15.64 LPM at ω = 6 krpm, and Δ P = 2 bar, to a high 56.36 LPM at ω = 2 krpm, and Δ P = 8 bar. When compared to the smooth seal, the grooved seal provides a 20% Q̇ reduction at ω = 2 krpm, and a 6% reduction at ω = 6 krpm. The grooved seal’s rotordynamic coefficients are generally not sensitive to changes in ϵ 0 . The smooth seal’s stiffness and damping coefficients are not very sensitive to changes in ϵ 0 in moving from ϵ 0 = 0 to 0.5, but typically increase dramatically in magnitude in moving from ϵ 0 = 0.5 to 0.8. From a rotordynamic viewpoint, the major difference between the two seals concerns the direct stiffness coefficients, with the grooved seal having near zero to negative values and the smooth seal having larger positive values, particularly at increased ϵ 0 values. The grooved seal generally produces lower-magnitude cross-coupled stiffness and direct damping coefficient values than the smooth seal.

The design of a low reaction turbine blade profiles was carried out to improve the steam flow efficiency. The blade profiles geometry design for both the stationary and moving blades and reprofiling of them are done using Vista ATBlade, according to the aerodynamic analysis results from the cascade analysis code MISES. The original stator profile is aft-loaded, and the new one present in this paper is highly-aft-loaded (HAL) to depress the development of secondary flow further, while maintaining even lower profile loss and wider incidence angle tolerance. The newly designed moving blade is more robust compared with the original one, thus it has larger aspect ratio under the same blade section average stress level, and with better incidence tolerant capability as well. The planar cascade air tests were first carried out to verify the stator profile loss improvement, with a decrease of energy loss coefficient of almost 0.8% obtained under the Reynolds number of about 1e6. Then the annular cascade air tests with fully 360 degrees stator blades installed were conducted to validate the reduction of endwall loss and the profile loss as well, and to measure the mass flow capability (real mass flow/ideal mass flow). Finally, two three-stage tests for the original blades and the new one were developed to verify the improvement under real multi-stages flow conditions. All the stages for both tests are designed with the hub reaction of about 15%, without interstage swirl, in the design condition. The flow probes at upstream of first stage stator and downstream of last stage moving blade, the hydraulic dynamometer and the flowmeter are used to test the overall efficiency. Three traverse planes are located at the upstream, middle and downstream of the second stage to measure the flow properties using five hole pneumatic probes. The test results showed a increase of overall efficiency of about 1.5%. The CFD simulations showed very good agreement of mass flow capability with the tests, for both the stator annular and multi-stage tests. The application of the newly designed blade profiles in SanHe subcritical reheat 300MW steam turbine (16.7MPa/537°C/537°C) retrofit gives the final proof of the efficiency improvement. The measured efficiency showed remarkable performance, with an increase of efficiency of 1.5%–2.2% for both the HP and IP cylinder.

A series of high pressure turbine nozzle guide vanes has been designed for progressively increasing blade loading and reduction in blade solidity without additional loss penalty. Early members of the series achieved this by changes to the suction surface contour, but for the latest design the pressure surface contour was extensively modified to reduce the velocities on this surface substantially. Cascade testing revealed that this vane had a higher loss than its predecessor, and this appears to be largely due to a long region of boundary layer growth on the suction surface and possibly also an unsteady separation. These tests demonstrated the value of a flattened pitot tube held against the blade surface in determining the boundary layer state. By using a pitot probe of only modest frequency response (of order 100 Hz) it was possible to observe significant qualitiative differences in the raw signals from laminar, transitional and turbulent boundary layers, which have previously been observed only with much higher frequency instruments. The test results include a comparison of boundary layer measurements on the same cascade test section in two different high-speed wind tunnels. This comparison suggests that freestream turbulence can have a large effect on boundary layer development and growth.

Using five-hole pitot tubes, detailed flow measurements were made before, within and after a low-speed three-dimensional turbine stator blade row to obtain quantitative information on the aerodynamic loss mechanism. Qualitative flow visualization tests and endwall static pressure measurements were also made. An analysis of the tests revealed that many vortical flows promote loss generation. Within a large part of the cascade, a major loss process could be explained simply as the migration of boundary layer low energy fluids from surrounding walls (endwalls and blade surfaces) to the blade suction surface near the trailing edge. On the other hand, complexity exists after the cascade and in the vortical flows near the trailing edge. The strong trailing shedding vortices affect upstream flow fields within the cascade. Detailed flow surveys within the cascade under the effects of blade tip leakage flows are also included.

The Machinery and Engine Technology (MET) Program of the National Research Council of Canada (NRCC) has established a program for the evaluation of sensors to measure gas turbine engine performance accurately. The precise measurement of fuel flow is an essential part of steady-state gas turbine performance assessment. Prompted by an international engine testing and information exchange program, and a mandate to improve all aspects of gas turbine performance evaluation, the MET Laboratory has critically examined two types of fuel flowmeters, Coriolis and turbine. The two flowmeter types are different in that the Coriolis flowmeter measures mass flow directly, while the turbine flowmeter measures volumetric flow, which must be converted to mass flow for conventional performance analysis. The direct measurement of mass flow, using a Coriolis flowmeter, has many advantages in field testing of gas turbines, because it reduces the risk of errors resulting from the conversion process. Turbine flowmeters, on the other hand, have been regarded as an industry standard because they are compact, rugged, reliable, and relatively inexpensive. This paper describes the project objectives, the experimental installation, and the results of the comparison of the Coriolis and turbine type flowmeters in steady-state performance testing. Discussed are variations between the two types of flowmeters due to fuel characteristics, fuel handling equipment, acoustic and vibration interference and installation effects. Also included in this paper are estimations of measurement uncertainties for both types of flowmeters. Results indicate that the agreement between Coriolis and turbine type flowmeters is good over the entire steady-state operating range of a typical gas turbine engine. In some cases the repeatability of the Coriolis flowmeter is better than the manufacturers specification. Even a significant variation in fuel density (10%), and viscosity (300%), did not appear to compromise the ability of the Coriolis flowmeter to match the performance of the turbine flowmeter.

Detailed traverse measurements of three dimensional flows and the associated losses inside a turbine rotor passage were carried out in the rotating frame of reference by using small five hole Pitot tubes. Strong secondary flows including passage vortices, a leakage vortex and various separation vortices were found to occur in the passage, and they are significantly influenced by the rotor speed, variation of which corresponds to different test incidences and blade loadings. Loss generation process in the rotor is described in relation to the migration of low energy fluids which are driven by the various vortices and their interaction at different rotor incidences.

To know the internal flows and the loss generation mechanisms in turbine blade passages, three–dimensional flows in a linear turbine cascade were measured in detail using a five–hole Pitot tube. Flow visualization tests were also carried out with oil smoke to see the unsteady behavior of the internal flows. The flow visualization tests show generation of various vortices occurring inside the cascade passage, which were hardly detectable with steady flow measurement. Many of the vortices behave unsteadily. The evolution of two legs of the leading edge horseshoe vortex was clearly visualized as a combined vortex system. Low energy fluids inside the boundary layer on the blade suction surface were seen to circulate very slowly and were fairly unstable. Rotational directions of the low energy fluids depend on the interaction with the surrounding vortex system. Many separated and strong reverse flows were also seen near the blade trailing edge.

Conditions in the internal-air system of a high-pressure turbine stage are modelled using a rig comprising an outer pre-swirl chamber separated by a seal from an inner rotor-stator system. Pre-swirl nozzles in the stator supply the “blade-cooling” air, which leaves the system via holes in the rotor, and disc-cooling air enters at the centre of the system and leaves through clearances in the peripheral seals. The experimental rig is instrumented with thermocouples, fluxmeters, pitot tubes and pressure taps enabling temperatures, heat fluxes, velocities and pressures to be measured at a number of radial locations. For rotational Reynolds numbers of Re ϕ ≃ 1.2 × 10 6 , the swirl ratio and the ratios of disc-cooling and blade-cooling flow rates are chosen to be representative of those found inside gas turbines. Measured radial distributions of velocity, temperature and Nusselt number are compared with computations obtained from an axisymmetric elliptic solver, featuring a low-Reynolds-number k-ε turbulence model. For the inner rotor-stator system, the computed core temperatures and velocities are in good agreement with measured values, but the Nusselt numbers are underpredicted. For the outer pre-swirl chamber, it was possible to make comparisons between the measured and computed values for cooling-air temperatures but not for the Nusselt numbers. As expected, the temperature of the blade-cooling air decreases as the swirl ratio increases, but the computed air temperatures are significantly lower than the measured ones. Overall, the results give valuable insight into some of the heat transfer characteristics of this complex system.

The present study addresses two aspects of the horseshoe vortex, namely its significance in the secondary flow in a turbine blade passage and the possibility of reducing its strength by an active flow mechanism, i.e the transverse injection of coolant air through a slot in a cylinder-endwall junction. The study reports on the results of two experiments in low speed wind tunnels, which employed a calibrated five-hole Pitot tube to measure the velocity vectors and the resulting secondary flowfields. The first aspect was studied in a 90° square cross section bend duct. The two horseshoe vortex legs were simulated by two half-Delta wing vortex generators. The results showed that the horseshoe vortices influence two regions of the secondary flowfield, i.e one near the passage entrance, where the pressure side leg forces a three dimensional separation of the endwall boundary layer, and the other is in the exit plane, where the coupling of the horseshoe with the passage vortex redistributes the flow with total pressure losses, without affecting the total loss, and increases the secondary kinetic energy by about 20%. For the second aspect, a rectangular bluff body, with a cylindrical leading edge, was positioned over the tunnel endwall and the transverse air injection was implemented through a thin slot, covering the 180° arc in the leading edge-endwall junction. The results showed that, for an average injection velocity equal to 35% that of the mainstream, the size and strength of the horseshoe vortex leg were reduced by nearly 60%. On the other hand, for stronger injection rates the vortex size and strength were increased.

Dimensional analysis has been used in experimental fluid mechanics for over a hundred years. Controllable and uncontrollable variables in an experiment can be efficiently organized into nondimensional groups or parameters. Such nondimensional parameters are used for geometric scaling, and for developing dynamic similitude in experimental processes. Commonly used nondimensional parameters in fluid mechanics include Reynold’s No., Mach No., Froude No., Weber No., Strouhal No., etc. Most modern text books and technical papers discuss the use of Buckingham Pi Theorem for developing the nondimensionalization process. An often ignored and somewhat older technique is the Rayleigh Method. Both the Pi Theorem and the Rayleigh Method are founded on the Principle of Dimensional Homogeneity, and require some experience in the grouping of physical variables. The present paper uses the Rayleigh method to develop two new nondimensional parameters. A discussion is presented about the use of the parameters in the application of turbine flowmeter calibration and test data analysis. It is shown that data analysis for turbine flowmeters is considerably simplified by the use of the new parameters.

In this report the diffusor geometry for a Pitot-Tube Jet pump (PTJ pump) is optimized, using 3D, steady CFD methods (software: ANSYS Fluent) as well as mesh morphing (software: Sculptor). The design point is Q = 16 m 3 / h . A complex optimization loop is set up, which takes geometric constraints, as well as manufacturing limits into account. The optimization is multi-objective and best practice guidelines are derived for future diffusor designs with respect to the reduction of total pressure losses and the diffusor displacement in the fluid of the rotor cavity. Both, advantages and disadvantages, are listed and evaluated.

The main topic of the paper is the discussion of the operational behavior of the solid oxide fuel cell (SOFC)/micro gas turbine (MGT) hybrid power plant test rig with the pressure vessels of the SOFC emulator. In the first part a brief introduction to the test rig and its components is given. In the arrangement of the test rig the MGT is connected via an interface to the tubing system. Here, the preheated air after the recuperator can be led either to the emulator or via a bypass tube directly to the MGT. Furthermore, there is a direct connection between the compressor outlet and emulator for the startup and shutdown procedure. The facility is equipped with detailed instrumentation, including mass flow meters, thermocouples and pressure probes. In the second part of the paper the characterization of the hybrid power plant test rig is shown. To analyze the thermodynamic and fluid dynamic impact of the coupling elements various studies were carried out. Hereby, the influence of the coupling elements on the operational behavior, system stability and system performance of the micro gas turbine is shown for stationary load points, as well as during transient maneuvers like startup, load-change and shutdown. To avoid critical operating conditions limitations were defined and emergency maneuvers were developed and tested. Out of these investigations an operating concept for the hybrid power plant test rig can be derived.