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Sunday, July 12, 2020 | History

3 edition of Turbine blade-tip clearance excitation forces found in the catalog.

Turbine blade-tip clearance excitation forces

Manuel Martinez-Sanchez

Turbine blade-tip clearance excitation forces

final report on Contract number NAS8-35018

by Manuel Martinez-Sanchez

  • 376 Want to read
  • 33 Currently reading

Published by Massachusetts Institute of Technology, National Aeronautics and Space Administration, National Technical Information Service, distributor in Cambridge, Mass, [Washington, DC, Springfield, Va .
Written in English

    Subjects:
  • Turbines -- Blades.,
  • Turbomachines -- Blades.,
  • Aerodynamic forces.,
  • Blade tips.,
  • Flow distribution.,
  • Force distribution.,
  • Self excitation.,
  • Turbine blades.,
  • Vibration.

  • Edition Notes

    Other titlesTurbine blade tip clearance excitation forces.
    Statementsubmitted by M. Martinez-Sanchez and Edward M. Greitzer to NASA, George C. Marshall Space Flight Center, Alabama.
    SeriesNASA contractor report -- NASA CR-171534.
    ContributionsGreitzer, Edward M., George C. Marshall Space Flight Center., Massachusetts Institute of Technology.
    The Physical Object
    FormatMicroform
    Paginationv, 91 p.
    Number of Pages91
    ID Numbers
    Open LibraryOL15415419M

    t Figure 1. Impulse turbine geometry; G1, G2– mass flow rates of the main flow in the blade-to-blade passage of the stator and rotor, GT, GR – flow rates of leakages at the rotor blade tip and stator root, GW, GW0 – windage flow rates at the rotor disc, GH – flow rate at the rotor disc discharge holes measurements on large-scale turbines, e.g.[1] or [2]. The cross-forces are found to increase substantially when the gap is reduced from to % of blade height, probably due to viscous blade-tip effects. The forces also increase when the hub gap between stator and rotor decreases. The force coefficient decreased with operating flow coefficient.

    Capacitive blade tip clearance measurements for a micro gas turbine Abstract: The efficiency of a gas turbine has an inverse relationship with the clearance between the rotor blades and the casing. Recent efforts in miniaturization of micro gas turbine engines have created new challenge in tip clearance by: 6. ing mechanisms. One of these is the variation of the blade tip forces due to nonuniform blade tip clearance. Alford (1) was the first to model this aerody- namic force on the blade. By assuming uniform upstream and downstream flow fields, he was able to argue that the variaticn of the blade tip force .

    The active clearance control (ACC) of aero-engine turbine tip clearance is evaluated in a lapse-rate take-off transient, along with the comparative and quantitative analysis. The results show that the resultant active tip clearance control system has favorable steady-state and dynamic performance and benefits of increased efficiency, reduced. EXPERIMENTAL INVESTIGATION OF ROTORDYNAMIC INSTABILITIES CAUSED BY ROTOR BLADE-TIP EXCITATION FORCES by Douglas H. Loose B.S. Mechanical Engineering, 8m Mean or concentric turbine blade-tip clearance Angle between X-axis and Fl-axis at t = 0 "1 Local efficiency.


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Turbine blade-tip clearance excitation forces by Manuel Martinez-Sanchez Download PDF EPUB FB2

To investigate the tip clearance excitation forces in an unshrouded turbine. The numerical method. The results of an effort to assess the existing knowledge and plan the required experimentation in the area of turbine blade tip excitation forces is summarized.

The work was carried out in three phases. The first was a literature search and evaluation, which served to highlight the state of the art and to expose the need for an articulated theoretical experimental effort to provide not only Author: M.

Martinez-Sanchez, E. Greitzer. Turbine blade-tip clearance excitation forces. By E. Greitzer and M. Martinez-Sanchez. In the third phase a preliminary design of a turbine test facility that would be used to measure both the excitation forces themselves and the flow patterns responsible for them were conducted and do so over a realistic range of dimensionless parametersAuthor: E.

Greitzer and M. Martinez-Sanchez. Because blade-tip clearances affect turbine efficiency and excitation forces affect rotor stability, report proves useful to researchers and designers of advanced turbomachinery. The larger one is a closed, 2 atm pressurized Freon flow loop in which is installed a replica of the SSME first stage hydrogen turbine, which can be driven by the flow, and which generates about 14 KW of power into a load-absorbing DC : M.

Martinez-Sanchez and B. Jaroux. the Excitation Forces in Axial Turbines with Shrouded Blades resistance of the blade tip clearance can be increased geometrically Turbine blade-tip clearance excitation forces book winglets, squealers and This thesis investigates the in uence of passive tip-injection on the tip excitation in shrouded axial turbine stages.

Therefore an analytical model for the tip-leakage mass ow and. Application of Blade-Tip Sensors to Blade-Vibration Monitoring in Gas Turbines The acquired waveform makes it possible to ob tain, after processing the curve by electronic circuits, a number of parameters that can be used for non-contact measurements of blade vibration and momentary tip clearance.

Turbine tip clearance can generally be defined as the distance between the turbine blade tip and the turbine shroud or turbine containment structure, as shown in Figure 1.

High pressure turbine (HPT) tip clearance is typically designed with two main objectives, maintain a steady-state clearance and minimize pinch points during operation. Blade tip clearance measurement of the turbine engines based on a multi-mode fiber coupled laser ranging system Review of Scientific Instruments, Vol.

85, No. 11 Study on the theory, method and model for mechanical dynamic assembly reliability optimizationCited by: Effect of blade tip clearance.

(A) For an open centrifugal impeller, the efficiency loss is only one-third of a point for each percent of tip clearance ratio at the impeller outer diameter. (B) For an axial compressor blade, the efficiency loss is about two percentage points for each percent of tip clearance ratio.

Clearance-excitation force of shrouded turbine rotor Ob viously, the case ¯ ϕ = in the figures cor- responds to the Alford force in references [ 9 – 13 ]. Turbine blade-tip clearance excitation forces: final report on Contract number NAS Author: Manuel Martinez-Sanchez ; Edward M Greitzer ; George C.

Marshall Space Flight Center. Tanaka, in 10th International Conference on Vibrations in Rotating Machinery, Case study No. This report describes a sudden change and increase in synchronous vibration amplitude of a stacked rotor for high temperature ( deg.

C) high-speed (10, rpm) blade testing machine. (Phenomena observed) The amplitude kept increasing with increasing shaft speed after it increased. The performance of the engine can be significantly improved by minimizing the leak flows through the gap between the blade tip and the casing of the compressor or the turbine.

Therefore, this distance, known as tip clearance (TC), plays a major role in the aerodynamic efficiency of axial compressors and turbines. turbine engines.

Significance of the Problem Control of blade-tip clearance in the compressor and turbine sections of gas turbine engines can improve efficiency, minimize leakage flow, and shorten engine development time. Tip clearance varies throughout different operating conditions (e.g., start-up, idle, full power, shut-down) because.

The purpose of this paper is to numerically investigate the effect of blade tip clearance and its structure on the turbine aerodynamic performance and excitation force on blades.

Measurement of Turbine Blade-Tip Rotordynamic Excitation Forces This paper presents results of a program to investigate the magnitude, origin, and parametric variations of destabilizing forces that arise in high power turbines due to blade-tip leakage by: Large turbines are periodically torn down, inspected, and rebuilt.

Turbine blade clearance to the case is one of the most critical measurements. Too close and the blades could expand and the turbine could be destroyed, too far away and efficiency is lost and power is sacrificed. This makes it vital to know the actual blade tip clearance.

Forces on Large Steam Turbine Blades. RWE npower: Mechanical and Electrical Engineering. Power Industry. INTRODUCTION. RWE npower is a leading integrated UK energy company and is part of the RWE Group, one of Europe's leading utilities. We own and operate a diverse portfolio of power plant, including gas-fired combined cycle gas turbine, oil.

Gas Turbine Laboratory, Massachusetts Institut oef Technology, Cambridge, MA Measurement of Turbine Blade-Tip Rotordynamic Excitation Forces This paper presents results of a program to investigate the magnitude, origin, and parametric variations of destabilizing forces that arise in high power turbines due to blade-tip leakage effects.

The blade tip clearance was varied from 50 to µm. The experiment results proved that the sensor can accurately measure the blade tip clearances with a temporal resolution of 10 µm.

The capability of accurately measuring the tip clearances at high temperatures (~ K) and high turbine rotation speeds (~30 rpm), along with its Cited by: 8.Numerical Investigations on the Blade Tip Clearance Excitation Forces in an Unshrouded Turbine.

by Abstract. The purpose of this study was to investigate the characteristics of the blade tip excitation forces represented as the rotordynamic coefficients (stiffness and damping coefficients) in an unshrouded turbine using the three.Garcia et al.

17,18 tried to overcome several traditional shortcomings of capacitive, inductive, and discharging probes in measuring the blade tip timing and clearance in turbines.

Consequently, they proposed a probe based on a trifurcated bundle of optical fibers mounted on the turbine Cited by: 4.