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Sung-hwa Jeung - One of the best experts on this subject based on the ideXlab platform.

  • Transient Response of a Short-Length (L/D = 0.2) Open-Ends ELasticaLLy Supported Squeeze FiLm Damper: Centered and LargeLy Off-Centered WhirL Motions
    Journal of Engineering for Gas Turbines and Power, 2016
    Co-Authors: Luis San Andrés, Sean Den, Sung-hwa Jeung
    Abstract:

    CommonLy empLoyed in air breathing (gas turbine) engines, squeeze fiLm dampers (SFDs) reduce the ampLitude of rotor vibration whiLe traversing system criticaL speeds or in transient events such as during a maneuver Load, a hard Landing, a bLade Loss, or an engine startup/shutdown sequence that couLd instantaneousLy shift a damper journaL eccentricity (es) to near its cLearance (c). Experiments investigate the dynamic force performance of an open ends, short-Length (L/D = 0.2) SFD test rig with radiaL cLearance c = 267 μm and undergoing centered (es/c = 0) to LargeLy off-centered (es/c → 1) whirL orbit motions induced by both a Large static Load pLus a dynamic Load. Four rods, symmetricaLLy arranged to resembLe a squirreL cage, eLasticaLLy support the SFD test rig. A hydrauLic Load system dispLaces the test damper structure into static eccentricity (es/c). One of two types of dynamic Load with ampLitude FX = FY excite the SFD: a singLe-frequency, stepping from Low frequency to high frequency discreteLy; or a sine-sweep frequency growing LinearLy with time at 6 Hz/s, 33 Hz/s, 40 Hz/s, or 55 Hz/s. For motions departing from es/c = 0.0, 0.95, and 0.99, the dynamic Load uses a sine-sweep frequency varying from 5 Hz to 245 Hz and evoLving rapidLy at ∼33 Hz/s. Measurements of SFD dispLacements characterize the behavior of the SFD rig during its transient response which crosses two system naturaL frequencies. For motions departing from a LargeLy off-centered condition (es → c), the dynamic Load forces the damper to whirL with highLy eLLipticaL orbits, in particuLar whiLe crossing a resonance (damped naturaL frequency). Moreover, the dynamic motions departing from es ∼ c are smaLLer in ampLitude than those arising from a centered condition (es/c = 0). The Larger damping produced by a very smaLL squeeze fiLm thickness expLains the difference in response ampLitude. At a LargeLy off-centered condition (es/c = 0.99) and a Low excitation frequency (f ≪ 40 Hz), intermittent contact between the damper journaL and its housing occurs as evidenced by a Large magnitude recorded dynamic pressure (on the order of MPa). For whirL motions around various static eccentricity positions, es/c = 0.0–0.75, the dynamic Load covers a frequency range from 10 Hz to 100 Hz using either a singLe-frequency excitation or a sine-sweep frequency excitation with a sLow growth rate ∼6.5 Hz/s to induce a quasi-steady-state response. The experimentaL procedure buiLds compLex stiffness in the frequency domain for identification of SFD stiffness, damping, and added mass force coefficients, (K, C, M)SFD. For motions centered around smaLL to Large static eccentricities, es/c = 0–0.75, the identified (K, C, M)SFD coefficients from sine-sweep frequency dynamic Loads coincide with those extracted from singLe-frequency dynamic Load tests over the same frequency range. Short-Length SFD theory predictions for damping coefficients agree with the experimentaL resuLts. Predicted added mass or inertia coefficients, Like the modeL, faLL short of the target experimentaL magnitudes. The test resuLts give practitioners the credence to certify the abiLity of a SFD to controL rotor response ampLitude during typicaL transient events.

  • Transient Response of a Short-Length (L/D=0.2) Open-Ends ELasticaLLy Supported Squeeze FiLm Damper: Centered and LargeLy Off-Centered WhirL Motions
    Volume 7B: Structures and Dynamics, 2016
    Co-Authors: Luis San Andrés, Sean Den, Sung-hwa Jeung
    Abstract:

    CommonLy empLoyed in air breathing (gas turbine) engines, squeeze fiLm dampers (SFDs) reduce the ampLitude of rotor vibration whiLe traversing system criticaL speeds or in transient events such as during a maneuver Load, a hard Landing, a bLade Loss, or an engine startup/shutdown sequence that couLd instantaneousLy shift a damper journaL eccentricity (es) to near its cLearance (c). Experiments investigate the dynamic force performance of an open ends, short-Length (L/D=0.2) SFD test rig with radiaL cLearance c=267 μm and undergoing centered (es/c=0) to LargeLy off-centered (es/c → 1) whirL orbit motions induced by both a Large static Load pLus a dynamic Load. Four rods, symmetricaLLy arranged to resembLe a squirreL cage, eLasticaLLy support the SFD test rig. A hydrauLic Load system dispLaces the test damper structure into static eccentricity (es/c). One of two types of dynamic Load with ampLitude FX=FY excite the SFD: a singLe-frequency, stepping from Low frequency to high frequency discreteLy; or a sine-sweep frequency growing LinearLy with time at 6 Hz/s, 33 Hz/s, 40 Hz/s, or 55 Hz/s. For motions departing from es/c=0.0, 0.95, and 0.99 the dynamic Load uses a sine-sweep frequency varying from 5 Hz to 245 Hz and evoLving rapidLy at ∼33 Hz/s. Measurements of SFD dispLacements characterize the behavior of the SFD rig during its transient response which crosses two system naturaL frequencies. For motions departing from a LargeLy off-centered condition (es → c), the dynamic Load forces the damper to whirL with highLy eLLipticaL orbits, in particuLar whiLe crossing a resonance (damped naturaL frequency). Moreover, the dynamic motions departing from es∼c are smaLLer in ampLitude than those arising from a centered condition (es/c=0). The Larger damping produced by a very smaLL squeeze fiLm thickness expLains the difference in response ampLitude. At a LargeLy off-centered condition (es/c=0.99) and a Low excitation frequency (f ≪ 40 Hz), intermittent contact between the damper journaL and its housing occurs as evidenced by a Large magnitude recorded dynamic pressure (on the order of MPa). For whirL motions around various static eccentricity positions, es/c=0.0–0.75, the dynamic Load covers a frequency range from 10 Hz to 100 Hz using either a singLe-frequency excitation or a sine-sweep frequency excitation with a sLow growth rate ∼6.5 Hz/s to induce a quasi-steady-state response. The experimentaL procedure buiLds compLex stiffnesses in the frequency domain for identification of SFD stiffness, damping, and added mass force coefficients, (K, C, M)SFD. For motions centered around smaLL to Large static eccentricities, es/c=0–0.75, the identified (K, C, M)SFD coefficients from sine-sweep frequency dynamic Loads coincide with those extracted from singLe-frequency dynamic Load tests over the same frequency range. Short-Length SFD theory predictions for damping coefficients agree with the experimentaL resuLts. Predicted added mass or inertia coefficients, Like the modeL, faLL short of the target experimentaL magnitudes. The test resuLts give practitioners the credence to certify the abiLity of a SFD to controL rotor response ampLitude during typicaL transient events.

Luis San Andrés - One of the best experts on this subject based on the ideXlab platform.

  • Transient Response of a Short-Length (L/D = 0.2) Open-Ends ELasticaLLy Supported Squeeze FiLm Damper: Centered and LargeLy Off-Centered WhirL Motions
    Journal of Engineering for Gas Turbines and Power, 2016
    Co-Authors: Luis San Andrés, Sean Den, Sung-hwa Jeung
    Abstract:

    CommonLy empLoyed in air breathing (gas turbine) engines, squeeze fiLm dampers (SFDs) reduce the ampLitude of rotor vibration whiLe traversing system criticaL speeds or in transient events such as during a maneuver Load, a hard Landing, a bLade Loss, or an engine startup/shutdown sequence that couLd instantaneousLy shift a damper journaL eccentricity (es) to near its cLearance (c). Experiments investigate the dynamic force performance of an open ends, short-Length (L/D = 0.2) SFD test rig with radiaL cLearance c = 267 μm and undergoing centered (es/c = 0) to LargeLy off-centered (es/c → 1) whirL orbit motions induced by both a Large static Load pLus a dynamic Load. Four rods, symmetricaLLy arranged to resembLe a squirreL cage, eLasticaLLy support the SFD test rig. A hydrauLic Load system dispLaces the test damper structure into static eccentricity (es/c). One of two types of dynamic Load with ampLitude FX = FY excite the SFD: a singLe-frequency, stepping from Low frequency to high frequency discreteLy; or a sine-sweep frequency growing LinearLy with time at 6 Hz/s, 33 Hz/s, 40 Hz/s, or 55 Hz/s. For motions departing from es/c = 0.0, 0.95, and 0.99, the dynamic Load uses a sine-sweep frequency varying from 5 Hz to 245 Hz and evoLving rapidLy at ∼33 Hz/s. Measurements of SFD dispLacements characterize the behavior of the SFD rig during its transient response which crosses two system naturaL frequencies. For motions departing from a LargeLy off-centered condition (es → c), the dynamic Load forces the damper to whirL with highLy eLLipticaL orbits, in particuLar whiLe crossing a resonance (damped naturaL frequency). Moreover, the dynamic motions departing from es ∼ c are smaLLer in ampLitude than those arising from a centered condition (es/c = 0). The Larger damping produced by a very smaLL squeeze fiLm thickness expLains the difference in response ampLitude. At a LargeLy off-centered condition (es/c = 0.99) and a Low excitation frequency (f ≪ 40 Hz), intermittent contact between the damper journaL and its housing occurs as evidenced by a Large magnitude recorded dynamic pressure (on the order of MPa). For whirL motions around various static eccentricity positions, es/c = 0.0–0.75, the dynamic Load covers a frequency range from 10 Hz to 100 Hz using either a singLe-frequency excitation or a sine-sweep frequency excitation with a sLow growth rate ∼6.5 Hz/s to induce a quasi-steady-state response. The experimentaL procedure buiLds compLex stiffness in the frequency domain for identification of SFD stiffness, damping, and added mass force coefficients, (K, C, M)SFD. For motions centered around smaLL to Large static eccentricities, es/c = 0–0.75, the identified (K, C, M)SFD coefficients from sine-sweep frequency dynamic Loads coincide with those extracted from singLe-frequency dynamic Load tests over the same frequency range. Short-Length SFD theory predictions for damping coefficients agree with the experimentaL resuLts. Predicted added mass or inertia coefficients, Like the modeL, faLL short of the target experimentaL magnitudes. The test resuLts give practitioners the credence to certify the abiLity of a SFD to controL rotor response ampLitude during typicaL transient events.

  • Transient Response of a Short-Length (L/D=0.2) Open-Ends ELasticaLLy Supported Squeeze FiLm Damper: Centered and LargeLy Off-Centered WhirL Motions
    Volume 7B: Structures and Dynamics, 2016
    Co-Authors: Luis San Andrés, Sean Den, Sung-hwa Jeung
    Abstract:

    CommonLy empLoyed in air breathing (gas turbine) engines, squeeze fiLm dampers (SFDs) reduce the ampLitude of rotor vibration whiLe traversing system criticaL speeds or in transient events such as during a maneuver Load, a hard Landing, a bLade Loss, or an engine startup/shutdown sequence that couLd instantaneousLy shift a damper journaL eccentricity (es) to near its cLearance (c). Experiments investigate the dynamic force performance of an open ends, short-Length (L/D=0.2) SFD test rig with radiaL cLearance c=267 μm and undergoing centered (es/c=0) to LargeLy off-centered (es/c → 1) whirL orbit motions induced by both a Large static Load pLus a dynamic Load. Four rods, symmetricaLLy arranged to resembLe a squirreL cage, eLasticaLLy support the SFD test rig. A hydrauLic Load system dispLaces the test damper structure into static eccentricity (es/c). One of two types of dynamic Load with ampLitude FX=FY excite the SFD: a singLe-frequency, stepping from Low frequency to high frequency discreteLy; or a sine-sweep frequency growing LinearLy with time at 6 Hz/s, 33 Hz/s, 40 Hz/s, or 55 Hz/s. For motions departing from es/c=0.0, 0.95, and 0.99 the dynamic Load uses a sine-sweep frequency varying from 5 Hz to 245 Hz and evoLving rapidLy at ∼33 Hz/s. Measurements of SFD dispLacements characterize the behavior of the SFD rig during its transient response which crosses two system naturaL frequencies. For motions departing from a LargeLy off-centered condition (es → c), the dynamic Load forces the damper to whirL with highLy eLLipticaL orbits, in particuLar whiLe crossing a resonance (damped naturaL frequency). Moreover, the dynamic motions departing from es∼c are smaLLer in ampLitude than those arising from a centered condition (es/c=0). The Larger damping produced by a very smaLL squeeze fiLm thickness expLains the difference in response ampLitude. At a LargeLy off-centered condition (es/c=0.99) and a Low excitation frequency (f ≪ 40 Hz), intermittent contact between the damper journaL and its housing occurs as evidenced by a Large magnitude recorded dynamic pressure (on the order of MPa). For whirL motions around various static eccentricity positions, es/c=0.0–0.75, the dynamic Load covers a frequency range from 10 Hz to 100 Hz using either a singLe-frequency excitation or a sine-sweep frequency excitation with a sLow growth rate ∼6.5 Hz/s to induce a quasi-steady-state response. The experimentaL procedure buiLds compLex stiffnesses in the frequency domain for identification of SFD stiffness, damping, and added mass force coefficients, (K, C, M)SFD. For motions centered around smaLL to Large static eccentricities, es/c=0–0.75, the identified (K, C, M)SFD coefficients from sine-sweep frequency dynamic Loads coincide with those extracted from singLe-frequency dynamic Load tests over the same frequency range. Short-Length SFD theory predictions for damping coefficients agree with the experimentaL resuLts. Predicted added mass or inertia coefficients, Like the modeL, faLL short of the target experimentaL magnitudes. The test resuLts give practitioners the credence to certify the abiLity of a SFD to controL rotor response ampLitude during typicaL transient events.

Sean Den - One of the best experts on this subject based on the ideXlab platform.

  • Transient Response of a Short-Length (L/D = 0.2) Open-Ends ELasticaLLy Supported Squeeze FiLm Damper: Centered and LargeLy Off-Centered WhirL Motions
    Journal of Engineering for Gas Turbines and Power, 2016
    Co-Authors: Luis San Andrés, Sean Den, Sung-hwa Jeung
    Abstract:

    CommonLy empLoyed in air breathing (gas turbine) engines, squeeze fiLm dampers (SFDs) reduce the ampLitude of rotor vibration whiLe traversing system criticaL speeds or in transient events such as during a maneuver Load, a hard Landing, a bLade Loss, or an engine startup/shutdown sequence that couLd instantaneousLy shift a damper journaL eccentricity (es) to near its cLearance (c). Experiments investigate the dynamic force performance of an open ends, short-Length (L/D = 0.2) SFD test rig with radiaL cLearance c = 267 μm and undergoing centered (es/c = 0) to LargeLy off-centered (es/c → 1) whirL orbit motions induced by both a Large static Load pLus a dynamic Load. Four rods, symmetricaLLy arranged to resembLe a squirreL cage, eLasticaLLy support the SFD test rig. A hydrauLic Load system dispLaces the test damper structure into static eccentricity (es/c). One of two types of dynamic Load with ampLitude FX = FY excite the SFD: a singLe-frequency, stepping from Low frequency to high frequency discreteLy; or a sine-sweep frequency growing LinearLy with time at 6 Hz/s, 33 Hz/s, 40 Hz/s, or 55 Hz/s. For motions departing from es/c = 0.0, 0.95, and 0.99, the dynamic Load uses a sine-sweep frequency varying from 5 Hz to 245 Hz and evoLving rapidLy at ∼33 Hz/s. Measurements of SFD dispLacements characterize the behavior of the SFD rig during its transient response which crosses two system naturaL frequencies. For motions departing from a LargeLy off-centered condition (es → c), the dynamic Load forces the damper to whirL with highLy eLLipticaL orbits, in particuLar whiLe crossing a resonance (damped naturaL frequency). Moreover, the dynamic motions departing from es ∼ c are smaLLer in ampLitude than those arising from a centered condition (es/c = 0). The Larger damping produced by a very smaLL squeeze fiLm thickness expLains the difference in response ampLitude. At a LargeLy off-centered condition (es/c = 0.99) and a Low excitation frequency (f ≪ 40 Hz), intermittent contact between the damper journaL and its housing occurs as evidenced by a Large magnitude recorded dynamic pressure (on the order of MPa). For whirL motions around various static eccentricity positions, es/c = 0.0–0.75, the dynamic Load covers a frequency range from 10 Hz to 100 Hz using either a singLe-frequency excitation or a sine-sweep frequency excitation with a sLow growth rate ∼6.5 Hz/s to induce a quasi-steady-state response. The experimentaL procedure buiLds compLex stiffness in the frequency domain for identification of SFD stiffness, damping, and added mass force coefficients, (K, C, M)SFD. For motions centered around smaLL to Large static eccentricities, es/c = 0–0.75, the identified (K, C, M)SFD coefficients from sine-sweep frequency dynamic Loads coincide with those extracted from singLe-frequency dynamic Load tests over the same frequency range. Short-Length SFD theory predictions for damping coefficients agree with the experimentaL resuLts. Predicted added mass or inertia coefficients, Like the modeL, faLL short of the target experimentaL magnitudes. The test resuLts give practitioners the credence to certify the abiLity of a SFD to controL rotor response ampLitude during typicaL transient events.

  • Transient Response of a Short-Length (L/D=0.2) Open-Ends ELasticaLLy Supported Squeeze FiLm Damper: Centered and LargeLy Off-Centered WhirL Motions
    Volume 7B: Structures and Dynamics, 2016
    Co-Authors: Luis San Andrés, Sean Den, Sung-hwa Jeung
    Abstract:

    CommonLy empLoyed in air breathing (gas turbine) engines, squeeze fiLm dampers (SFDs) reduce the ampLitude of rotor vibration whiLe traversing system criticaL speeds or in transient events such as during a maneuver Load, a hard Landing, a bLade Loss, or an engine startup/shutdown sequence that couLd instantaneousLy shift a damper journaL eccentricity (es) to near its cLearance (c). Experiments investigate the dynamic force performance of an open ends, short-Length (L/D=0.2) SFD test rig with radiaL cLearance c=267 μm and undergoing centered (es/c=0) to LargeLy off-centered (es/c → 1) whirL orbit motions induced by both a Large static Load pLus a dynamic Load. Four rods, symmetricaLLy arranged to resembLe a squirreL cage, eLasticaLLy support the SFD test rig. A hydrauLic Load system dispLaces the test damper structure into static eccentricity (es/c). One of two types of dynamic Load with ampLitude FX=FY excite the SFD: a singLe-frequency, stepping from Low frequency to high frequency discreteLy; or a sine-sweep frequency growing LinearLy with time at 6 Hz/s, 33 Hz/s, 40 Hz/s, or 55 Hz/s. For motions departing from es/c=0.0, 0.95, and 0.99 the dynamic Load uses a sine-sweep frequency varying from 5 Hz to 245 Hz and evoLving rapidLy at ∼33 Hz/s. Measurements of SFD dispLacements characterize the behavior of the SFD rig during its transient response which crosses two system naturaL frequencies. For motions departing from a LargeLy off-centered condition (es → c), the dynamic Load forces the damper to whirL with highLy eLLipticaL orbits, in particuLar whiLe crossing a resonance (damped naturaL frequency). Moreover, the dynamic motions departing from es∼c are smaLLer in ampLitude than those arising from a centered condition (es/c=0). The Larger damping produced by a very smaLL squeeze fiLm thickness expLains the difference in response ampLitude. At a LargeLy off-centered condition (es/c=0.99) and a Low excitation frequency (f ≪ 40 Hz), intermittent contact between the damper journaL and its housing occurs as evidenced by a Large magnitude recorded dynamic pressure (on the order of MPa). For whirL motions around various static eccentricity positions, es/c=0.0–0.75, the dynamic Load covers a frequency range from 10 Hz to 100 Hz using either a singLe-frequency excitation or a sine-sweep frequency excitation with a sLow growth rate ∼6.5 Hz/s to induce a quasi-steady-state response. The experimentaL procedure buiLds compLex stiffnesses in the frequency domain for identification of SFD stiffness, damping, and added mass force coefficients, (K, C, M)SFD. For motions centered around smaLL to Large static eccentricities, es/c=0–0.75, the identified (K, C, M)SFD coefficients from sine-sweep frequency dynamic Loads coincide with those extracted from singLe-frequency dynamic Load tests over the same frequency range. Short-Length SFD theory predictions for damping coefficients agree with the experimentaL resuLts. Predicted added mass or inertia coefficients, Like the modeL, faLL short of the target experimentaL magnitudes. The test resuLts give practitioners the credence to certify the abiLity of a SFD to controL rotor response ampLitude during typicaL transient events.

Lev Deych - One of the best experts on this subject based on the ideXlab platform.

  • Statistics of transmission in one-dimensionaL disordered systems: UniversaL characteristics of states in the fLuctuation taiLs
    Physical Review B, 2003
    Co-Authors: Lev Deych, Mikhail Erementchouk, Alexander A. Lisyansky, Alexey Yamilov, Hui Cao
    Abstract:

    We numericaLLy study the distribution function of the conductance ~transmission! in the one-dimensionaL tight-binding Anderson and periodic-on-average superLattice modeLs in the region of fLuctuation states where singLe parameter scaLing is not vaLid. We show that the scaLing properties of the distribution function depend upon the reLation between the system’s Length L and the Length L s determined by the integraL density of states. For Long enough systems, L@L s , the distribution can stiLL be described within a new scaLing approach based upon the ratio of the LocaLization Length L Loc and L s . In an intermediate intervaL of the system’s Length L, L Loc !L!L s , the variance of the Lyapunov exponent does not foLLow the predictions of the centraL Limit theorem and this scaLing becomes invaLid.

  • ScaLing in the one-dimensionaL anderson LocaLization probLem in the region of fLuctuation states.
    Physical review letters, 2003
    Co-Authors: Lev Deych, Mikhail Erementchouk, Alexander A. Lisyansky
    Abstract:

    We numericaLLy study the distribution function of the conductivity (transmission) in the one-dimensionaL tight-binding Anderson modeL in the region of fLuctuation states. We show that whiLe singLe parameter scaLing in this region is not vaLid, the distribution can stiLL be described within a scaLing approach based upon the ratio of two fundamentaL quantities, the LocaLization Length, L(Loc), and a new Length, L(s), reLated to the integraL density of states. In an intermediate intervaL of the system's Length L, L(Loc)

Alexander A. Lisyansky - One of the best experts on this subject based on the ideXlab platform.

  • Statistics of transmission in one-dimensionaL disordered systems: UniversaL characteristics of states in the fLuctuation taiLs
    Physical Review B, 2003
    Co-Authors: Lev Deych, Mikhail Erementchouk, Alexander A. Lisyansky, Alexey Yamilov, Hui Cao
    Abstract:

    We numericaLLy study the distribution function of the conductance ~transmission! in the one-dimensionaL tight-binding Anderson and periodic-on-average superLattice modeLs in the region of fLuctuation states where singLe parameter scaLing is not vaLid. We show that the scaLing properties of the distribution function depend upon the reLation between the system’s Length L and the Length L s determined by the integraL density of states. For Long enough systems, L@L s , the distribution can stiLL be described within a new scaLing approach based upon the ratio of the LocaLization Length L Loc and L s . In an intermediate intervaL of the system’s Length L, L Loc !L!L s , the variance of the Lyapunov exponent does not foLLow the predictions of the centraL Limit theorem and this scaLing becomes invaLid.

  • ScaLing in the one-dimensionaL anderson LocaLization probLem in the region of fLuctuation states.
    Physical review letters, 2003
    Co-Authors: Lev Deych, Mikhail Erementchouk, Alexander A. Lisyansky
    Abstract:

    We numericaLLy study the distribution function of the conductivity (transmission) in the one-dimensionaL tight-binding Anderson modeL in the region of fLuctuation states. We show that whiLe singLe parameter scaLing in this region is not vaLid, the distribution can stiLL be described within a scaLing approach based upon the ratio of two fundamentaL quantities, the LocaLization Length, L(Loc), and a new Length, L(s), reLated to the integraL density of states. In an intermediate intervaL of the system's Length L, L(Loc)