Turbine Test Facility Research Articles

Effect of correlated precision errors on uncertainty of a subsonic venturi calibration

An uncertainty analysis performed in conjunction with the calibration of a subsonic venturi for use in a turbine test facility produced some unanticipated results that may have a significant impact in a variety of test situations. Precision uncertainty estimates using the preferred propagation techniques in the applicable American National Standards Institute/American Society of Mechanical Engineers standards were an order of magnitude larger than precision uncertainty estimates calculated directly from a sample of results (discharge coefficient) obtained at the same experimental set point. The differences were attributable to the effect of correlated precision errors, which previously have been considered negligible. An analysis explaining this phenomenon is presented. The article is not meant to document the venturi calibration, but rather to give a real example of results where correlated precision terms are important. The significance of the correlated precision terms could apply to many test situations.

The Installation, Testing, and Lessons Learned of the TF40B Gas Turbine Test Facility

The TF40B Gas Turbine Test Facility is the only dedicated Landing Craft, Air Cushion main propulsion engine test complex available to the U.S. Navy. This facility, located at the Naval Surface Warfare Center, Carderock Division (NSWCCD) in Philadelphia, PA, began operation in August, 1992. Since then, the test engine has logged approximately 230 starts and 350 operating hours. This paper will present the installation, testing, and lessons learned of the TF40B test facility. The installation section will discuss the modifications made to the existing test facility to accept the TF40B engine. The test section will include the Foreign Object Damage (FOD) screen evaluation, both on-line and crank wash detergent fluid evaluations, cold weather fuel testing, engine vent line testing and Aerojet 5 oil evaluation. The lessons learned section will include problems related to the electric starter, waterbrake, inlet and exhaust systems, data acquisition system, instrumentation control panel, and the test cell equipment arrangement.

Impact of Rotor–Stator Interaction on Turbine Blade Film Cooling

The goal of this study is to quantify the impact of rotor–stator interaction on surface heat transfer of film cooled turbine blades. In Section I, a steady-state injection model of the film cooling is incorporated into a two-dimensional, thin shear layer, multiblade row CFD code. This injection model accounts for the penetration and spreading of the coolant jet, as well as the entrainment of the boundary layer fluid by the coolant. The code is validated, in the steady state, by comparing its predictions to data from a blade tested in linear cascade. In Section II, time-resolved film cooled turbine rotor heat transfer measurements are compared with numerical predictions. Data were taken on a fully film cooled blade in a transonic, high pressure ratio, single-stage turbine in a short duration turbine test facility, which simulates full-engine nondimensional conditions. Film cooled heat flux on the pressure surface is predicted to be as much as a factor of two higher in the time average of the unsteady calculations compared to the steady-state case. Time-resolved film cooled heat transfer comparison of data to prediction at two spanwise positions is used to validate the numerical code. The unsteady stator–rotor interaction results in the pulsation of the coolant injection flow out of the film holes with large-scale fluctuations. The combination of pulsating coolant flow and the interaction of the coolant with this unsteady external flow is shown to lower the local pressure side adiabatic film effectiveness by as much as 64 percent when compared to the steady-state case.

An Experimental Study of Film Cooling in a Rotating Transonic Turbine

Time-resolved measurements of heat transfer on a fully cooled transonic turbine stage have been taken in a short duration turbine test facility, which simulates full engine nondimensional conditions. The time average of this data is compared to uncooled rotor data and cooled linear cascade measurements made on the same profile. The film cooling reduces the time-averaged heat transfer compared to the uncooled rotor on the blade suction surface by as much as 60 percent, but has relatively little effect on the pressure surface. The suction surface rotor heat transfer is lower than that measured in the cascade. The results are similar over the central 3/4 of the span, implying that the flow here is mainly two dimensional. The film cooling is shown to be much less effective at high blowing ratios than at low ones. Time-resolved measurements reveal that the cooling, when effective, both reduced the dc level of heat transfer and changed the shape of the unsteady waveform. Unsteady blowing is shown to be a principal driver of film cooling fluctuations, and a linear model is shown to do a good job in predicting the unsteady heat transfer. The unsteadiness results in a 12 percent decrease in heat transfer on the suction surface and a 5 percent increase on the pressure surface.

Comparison of Time-Resolved Turbine Rotor Blade Heat Transfer Measurements and Numerical Calculations

Time-resolved turbine rotor blade heat transfer data are compared with ab initio numerical calculations. The data were taken on a transonic, 4-to-1 pressure ratio, uncooled, single-stage turbine in a short-duration turbine test facility. The data consist of the time history of the heat transfer distribution about the rotor chord at midspan. The numerical calculation is a time accurate, two-dimensional, thin shear layer, multiblade row code known as UNSFLO. UNSFLO uses Ni’s Lax-Wendroff algorithm, conservative boundary conditions, and a time tilting algorithm to facilitate the calculation of the flow in multiple blade rows of arbitrary pitch ratio with relatively little computer time. The version used for this work had a simple algebraic Baldwin-Lomax turbulence model. The code is shown to do a good job of predicting the quantitative time history of the heat flux distribution. The wake/boundary layer and transonic interaction regions for suction and pressure surfaces are identified and the shortcomings of the current algebraic turbulence modeling in the code are discussed. The influence of hardware manufacturing tolerance on rotor heat transfer variation is discussed. A physical reasoning explaining the discrepancies between the unsteady measurement and the calculations for both the suction and pressure surfaces are given, which may be of use in improving future calculations and design procedures.

Study on Verification of Law of Vibration Similarity by Scale-Model Steam Turbine.

Rotating blades of steam turbines are the essential machine parts to convert fluid force to mechanical force, and high reliability in operation, especially for vibratory strength, is the most important requirement. The vibratory characteristics and strength can be examined basically by laboratory element tests at the design stage. However, an actual loading test in a test turbine facility is the most assured and integrated method to verify the blade reliability. Due to restrictions on the quantity of steam supplied to the test turbine, the actual loading test is usually carried out using a scale-model turbine instead of a full-scale model turbine. Generally mechanical and aerodynamic laws of similarity are applied to the scale-model turbine. In the case of vibratory characteristics, however, there are related factors, such as damping, for which applicability of similarity laws is uncertain ; hence it should be confirmed whether the scale-model turbine test is effective in evaluating the vibratory strength of the rotating blades. Both full-scale model turbine tests and scale-model turbine tests were carried out under the same operating conditions in the same test turbine facility in order to investigate the vibration similarity. This paper shows the effectiveness of the actual loading test using the scale-model turbine as a verification test of blade reliability for vibratory strength.

The Aerodynamic and Mechanical Performance of a High-Pressure Turbine Stage in a Transient Wind Tunnel

A new transient facility for the study of time mean and unsteady aerodynamics and heat transfer in a high-pressure turbine has been commissioned and results are available. A detailed study has been made of aspects of the performance and behavior relevant to turbine mechanical design, and an understanding of the variation of the turbine operating point during the test, crucial to the process of valid data acquisition, has been obtained. In this this paper the outline concept and mode of operation of the turbine test facility are given, and the key aerodynamic and mechanical aspects of the facility’s performance are presented in detail. The variations of the those parameters used to define the turbine operating point during facility operation are examined, and the accuracy with which the turbine’s design point was achieved calculated. Aspects of the mechanical performance presented include the results of a finite element stress analysis of the loads in the turbine under operating conditions, and the performance of the rotor bearing system under these arduous load conditions. Both of these aspects present more information than has been available hitherto. Finally, the future work program and possible plans for further facility improvement are given.

Design of an air-cooled metallic high-temperature radial turbine

Recent trends in small advanced gas turbine engines call for higher turbine inlet temperatures. Advances in radial turbine technology have opened the way for a cooled metallic radial turbine capable of withstanding turbine inlet temperatures of 2500 F while meeting the challenge of high efficiency in this small flow size range. In response to this need, a small air-cooled radial turbine has been designed utilizing internal blade coolant passages. The coolant flow passage design is uniquely tailored to simultaneously meet rotor cooling needs and rotor fabrication constraints. The rotor flow-path design seeks to realize improved aerodynamic blade loading characteristics and high efficiency while satisfying rotor life requirements. An up-scaled version of the final engine rotor is currently under fabrication and, after instrumentation, will be tested in the warm turbine test facility at the NASA Lewis Research Center.

Temperature and Pressure Measurement Techniques for an Advanced Turbine Test Facility

A high pressure (4 × 106 N/m2), high-temperature (2400 K) turbine test facility is being constructed at the NASA Lewis Research Center for use in turbine cooling research. Several recently developed temperature and pressure measuring techniques will be used in this facility. This paper will briefly describe these measurement techniques, their status, previous applications and some results. Noncontact surface temperature measurements will be made by optical methods. Radiation pyrometry principles combined with photoelectric scanning will be used for rotating components and infrared photography for stationary components. Contact (direct) temperature and pressure measurements on rotating components will be handled with an 80-channel rotary data package which mounts on and rotates with the turbine shaft at speeds up to 17,500 rpm. The data channels are time-division multiplexed and converted to digital words in the data package. A rotary transformer couples power and digital data to and from the shaft.

Turbine Blade Vibration Due to Nozzle Wakes

Turbine blade vibrations due to resonance with the nozzle passing frequency have been measured and discussed with primary emphasis on the relationships between the resonant stresses and the stage flow parameters. Vibratory stresses were measured in a full admission, single-stage, impulse steam turbine test facility. The blading was shrouded into 6-blade groups, designed to bring the out-of-phase tangential modes into resonance. Some comparisons are made between measured and predicted frequencies and mode shapes. The variation of stresses, with such parameters as stage torque, velocity ratio, and mass flow, was studied by testing at eleven different operating conditions. It was found that stresses increased with torque, but less than proportionately so. It was found that stresses varied with velocity ratio in a complicated fashion, reaching a maximum and then a minimum as velocity ratio is increased. These empirical results are interpreted qualitatively in the light of available theory. It is concluded that the apparent dependence on velocity ratio may also reflect a dependence on Mach number and a dependence on the number of wakes in simultaneous engagement with a given blade. The same rotor blading was tested with two sets of nozzle (stator) blades of different sizes, and some data were also obtained at various values of axial spacing between rotating and stationary blades. The interrelationship between the effects of relative sizes and spacing between the two blade rows is discussed.