Stability of an Axial Thrust Self-Balancing System

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
Takashi Shimura ◽  
Satoshi Kawasaki ◽  
Masaharu Uchiumi ◽  
Toshiya Kimura ◽  
Mitsuaki Hayashi ◽  
...  
Keyword(s):  
Large Amplitude ◽  
High Speed ◽  
System Analysis ◽  
Axial Direction ◽  
Radial Pressure ◽  
Liquid Hydrogen ◽  
Axial Vibration ◽  
Axial Thrust ◽  
Balance System ◽  
Excited Vibration

Rocket pumps are characterized by high speed and high delivery pressure. Therefore, balancing of axial thrust acting on the rotor assembly is one of the most important factors. To realize complete axial thrust balancing, a balance piston-type axial-thrust self-balancing system is often used in rocket pumps. This axial thrust balance system acts dynamically as if it were a mass and spring system, although there is no mechanical spring. Sometimes, large amplitude axial vibration is observed in a liquid hydrogen turbopump. Too much vibration in the axial direction causes metal-to-metal rubbing, resulting in fatal accidents of rocket turbopumps. However, the cause of the vibration has not yet been clarified. In the present study, the self-balancing system was modeled by combining the mechanical structure and the fluid system in a calculation program of one-dimensional multidomain system analysis software. Stability of the system was investigated using this program and the possibility of existence of self-excited vibration was confirmed. Effects of geometry, fluids, viscous damping, radial pressure drop in the chamber, and orifice flow coefficients on the stability of the balance piston system were examined. As a result, it was concluded that large compressibility of liquid hydrogen was the cause of the large amplitude axial vibrations. With the results of analyses, methods to stabilize the system in order to suppress the axial vibration were suggested.

Stability of an Axial-Thrust Self-Balancing System

2012 ◽  
Author(s):  
Takashi Shimura ◽  
Satoshi Kawasaki ◽  
Masaharu Uchiumi ◽  
Toshiya Kimura ◽  
Mitsuaki Hayashi ◽  
...  
Keyword(s):  
High Speed ◽  
Rocket Engine ◽  
Axial Direction ◽  
Small Radius ◽  
Axial Vibration ◽  
Axial Thrust ◽  
Balance System ◽  
Delivery Pressure ◽  
Rotor Assembly ◽  
Outlet Orifice

Rocket pump is characterized by high speed and high delivery pressure. Therefore, balancing of axial thrust acting on the rotor assembly is one of the most important factors. To realize complete axial thrust balancing, a balance piston-type axial-thrust self-balancing system is often used in rocket pumps. Such a system is comprised of an inlet orifice (#1) located at the outlet part of the impeller, outlet orifice (#2) located at the small-radius position of the back shroud and a chamber between these two orifices. Those orifices made by edges of the casing and the impeller shroud look like rings. The rotor assembly is allowed to move axially less than 1 mm to control the clearances of the orifices. The rotor assembly moves toward the turbine part when unbalanced axial thrust is imposed on the rotor assembly in the direction from the inlet of the pump toward the turbine part. As a result, the clearance of the inlet orifice increases and that of the outlet orifice decreases. This results in an increase in the pressure in the chamber between the orifices and makes the axial thrust generated by the balance piston in the direction from the turbine part toward the inlet of the pump increase. In this way, unbalance axial thrust imposed on the rotor assembly can be compensated automatically. This axial thrust balance system acts dynamically as if it is a mass and spring system although there is no mechanical spring. Too much vibration in the axial direction causes metal to metal rubbing, resulting in the explosion of rocket turbopumps. Although large amplitude axial vibration has been observed in rocket engine turbopumps, the cause of the vibration has not yet been clarified. In the present study, the self-balancing system was modeled by combining the mechanical structure and the fluid system in a calculation program. Stability of the system was investigated using this program. Effects of geometry, fluids, etc., were examined and methods to stabilize the system in order to suppress the axial vibration were developed.

Rotation-induced axial oscillation of a composite nanoconvertor at low temperature

2020 ◽  
pp. 107754632093711
Author(s):  
Bo Song ◽  
Kun Cai ◽  
Jiao Shi ◽  
Qing-Hua Qin
Keyword(s):  
Molecular Dynamics ◽  
Low Temperature ◽  
Large Amplitude ◽  
Oscillation Amplitude ◽  
Axial Direction ◽  
Axial Vibration ◽  
Axial Oscillation ◽  
Axial Translation ◽  
Vibration Responses ◽  
Dynamics Simulations

We propose a model of a nanostructure which can transform an input rotation into an output oscillation. In the model, the rotor has two identical internally hydrogenated deformable parts. The mechanism is that the rotation-induced centrifugal force and van der Waals force drive the recoverable deformation of the hydrogenated deformable parts, which gives rise to the axial translation of the free end of the rotor. Once the two hydrogenated deformable parts deform periodically, the free end of the rotor oscillates periodically in the axial direction. Molecular dynamics simulations are conducted to reveal the dynamic response of the system at low temperature. Four main types of deformation and the first three orders of vibration responses of the hydrogenated deformable parts are analyzed. Synchronous breathing vibration of the two hydrogenated deformable parts produces ideal oscillation with large amplitude. Asynchronous axial vibration of the hydrogenated deformable parts reduces the oscillation amplitude or produces beat vibration. The way to control the amplitude of the axial oscillation/vibration is given.

scholarly journals The Influence of the Axial Rub Added in the Radial Rub on the Wear of the Seal Fins during the High Speed Rub of Labyrinth-Honeycomb Seal

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1997
Author(s):  
Bin Lu ◽  
Haijun Xuan ◽  
Xiaojian Ma ◽  
Fangjun Han ◽  
Weirong Hong ◽  
...  
Keyword(s):  
Wear Rate ◽  
High Speed ◽  
State Of The Art ◽  
Negative Influence ◽  
Axial Thrust ◽  
Cross Sectional ◽  
Honeycomb Seal ◽  
Aero Engine ◽  
Honeycomb Seals ◽  
Clearance Change

Labyrinth-honeycomb seals are a state-of-the-art sealing technology commonly used in aero-engine interstage seal. The undesirable severe rub between the seal fins and the honeycomb due to the clearance change may induce the cracking of the seal fins. A pervious study investigated the wear of the seal fins at different radial incursion rates. However, due to the axial thrust and mounting clearance, the axial rub between the seal fins and the honeycomb may occur. Hence, this paper focuses on the influence of the axial rub added in the radial rub on the wear of the seal fins. The rub tests results, including rubbing forces and temperature, wear rate, worn morphology, cross-sectional morphology and energy dispersive spectroscopy results, are presented and discussed. Overall, the participation of the axial rub leads to higher rubbing forces, temperature, and wear rate. The tribo-layer on the seal fin is thicker and the cracks are more obvious at high axial incursion rate. These phenomena indicate the axial rub has a negative influence on the wear of the seal fins and should be avoided.

Turbine Nozzle Endwall Phantom Cooling With Compound Angled Pressure Side Injection

2018 ◽  
Author(s):  
Kevin Liu ◽  
Hongzhou Xu ◽  
Michael Fox
Keyword(s):  
Film Cooling ◽  
High Speed ◽  
Axial Direction ◽  
Secondary Flows ◽  
Test Case ◽  
Pressure Side ◽  
Complex Flow ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Extended Area

Cooling of the turbine nozzle endwall is challenging due to its complex flow field involving strong secondary flows. Increasingly-effective cooling schemes are required to meet the higher turbine inlet temperatures required by today’s gas turbine applications. Therefore, in order to cool the endwall surface near the pressure side of the airfoil and the trailing edge extended area, the spent cooling air from the airfoil film cooling and pressure side discharge slots, referred to as “phantom cooling” is utilized. This paper studies the effect of compound angled pressure side injection on nozzle endwall surface. The measurements were conducted in a high speed linear cascade, which consists of three nozzle vanes and four flow passages. Two nozzle test models with a similar film cooling design were investigated, one with an axial pressure side film cooling row and trailing edge slots; the other with the same cooling features but with compound angled injection, aiming at the test endwall. Phantom cooling effectiveness on the endwall was measured using a Pressure Sensitive Paint (PSP) technique through the mass transfer analogy. Two-dimensional phantom cooling effectiveness distributions on the endwall surface are presented for four MFR (Mass Flow Ratio) values in each test case. Then the phantom cooling effectiveness distributions are pitchwise-averaged along the axial direction and comparisons were made to show the effect of the compound angled injection. The results indicated that the endwall phantom cooling effectiveness increases with the MFR significantly. A compound angle of the pressure side slots also enhanced the endwall phantom cooling significantly. For combined injections, the phantom cooling effectiveness is much higher than the pressure side slots injection only in the endwall downstream extended area.

Prototype Design of a High-Speed Viscous Air Spindle

2008 ◽  
Author(s):  
Guido M. J. Delhaes ◽  
Anton van Beek ◽  
Ron A. J. van Ostayen ◽  
Robert H. Munnig Schmidt
Keyword(s):  
High Speed ◽  
Load Capacity ◽  
Axial Direction ◽  
Cylindrical Part ◽  
Traction Forces ◽  
Micro Cutting ◽  
Tool Holder ◽  
Air Spindle ◽  
Prototype Design

In this paper an innovative air driven spindle for micro cutting applications is presented. The spindle uses a viscous traction concept which has the advantage that the viscous traction forces can act directly on the cylindrical part of the tool, which makes the tool-holder redundant. Furthermore, the tool can be actuated in the axial direction within the housing. In this paper the concept of the viscous turbine, a design of a prototype spindle along with the traction and load-capacity of the spindle are discussed.

Aerodynamics of a two-dimensional bluff body with the cross-section of a train

2020 ◽  
Vol 23 (12) ◽  
pp. 2679-2693 ◽  
Author(s):  
Huan Li ◽  
Xuhui He ◽  
Hanfeng Wang ◽  
Si Peng ◽  
Shuwei Zhou ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Large Amplitude ◽  
High Speed ◽  
Bluff Body ◽  
Mean Amplitude ◽  
Two Dimensional ◽  
Aerodynamic Forces ◽  
Moderate Reynolds Number ◽  
Amplitude Mode

Experiments on the aerodynamics of a two-dimensional bluff body simplified from a China high-speed train in crosswinds were carried out in a wind tunnel. Effects of wind angle of attack α varying in [−20°, 20°] were investigated at a moderate Reynolds number Re = 9.35 × 104 (based on the height of the model). Four typical behaviors of aerodynamics were identified. These behaviors are attributed to the flow structure around the upper and lower halves of the model changing from full to intermittent reattachment, and to full separation with a variation in α. An alternate transition phenomenon, characterized by an alteration between large- and small-amplitude aerodynamic fluctuations, was detected. The frequency of this alteration is about 1/10 of the predominant vortex shedding. In the intervals of the large-amplitude behavior, aerodynamic forces fluctuate periodically with a strong span-wise coherence, which are caused by the anti-symmetric vortex shedding along the stream-wise direction. On the contrary, the aerodynamic forces fluctuating at small amplitudes correspond to a weak span-wise coherence, which are ascribed to the symmetric vortex shedding from the upper and lower halves of the model. Generally, the mean amplitude of the large-amplitude mode is 3 times larger than that of the small one. Finally, the effects of Reynolds number were examined within Re = [9.35 × 104, 2.49 × 105]. Strong Reynolds number dependence was observed on the model with two rounded upper corners.

Dynamic behaviors of a high-speed turbocharger rotor on elliptical floating-ring bearings

2019 ◽  
Vol 233 (12) ◽  
pp. 1785-1799 ◽  
Author(s):  
Congcong Zhang ◽  
Yongliang Wang ◽  
Rixiu Men ◽  
Hong He ◽  
Wei Chen
Keyword(s):  
High Speed ◽  
Reynolds Equation ◽  
Low Cost ◽  
Dynamic Behaviors ◽  
Oil Whirl ◽  
Excited Vibration ◽  
Dynamic Performances ◽  
Simulation Results ◽  
Bearing Design ◽  
Run Up

Floating-ring bearings are commonly used in automotive turbocharger applications due to their low cost and their suitability under extreme rotation speeds. This type of bearings, however, can become a source of noise due to oil whirl-induced sub-synchronous vibrations. The scope of this paper is to examine whether the concept of a floating-ring bearing with an elliptical clearance might be a solution to suppress sub-synchronous vibrations. A very time-efficient approximate solution for the Reynolds equation to the geometry of elliptical bearings is presented. The nonlinear dynamic behaviors of a turbocharger rotor supported by two concepts of elliptical floating-ring bearings are systematically investigated using run-up simulations. For the first concept of elliptical floating-ring bearings i.e. the outer bearing of the floating-ring bearing changed in the form of elliptical pattern (see Figure 1(b) in the article), some studies have pointed out that its steady-state and dynamic performances are superior to plain cylindrical floating-ring bearings but, the nonlinear run-up simulation results shown that this type of elliptical floating-ring bearings is not conducive to reduce the self-excited vibration levels. However, for the second type of elliptical floating-ring bearings i.e. both the inner and outer films of the floating-ring bearing changed in the form of elliptical pattern (see Figure 1(c) in the article), it is shown that the sub-synchronous vibrations have been considerably suppressed. Hence, the second noncircular floating-ring bearing design is an attractive measure to suppress self-excited vibrations.[Figure: see text]

Asymmetric Arm Design on Delta Robot System

2014 ◽  
Author(s):  
Tsung-Liang Wu ◽  
Jih-Hsiang Yeh ◽  
Cheng-Chen Yang
Keyword(s):  
Energy Saving ◽  
High Speed ◽  
Kinematic Model ◽  
Industrial Applications ◽  
Critical Parameters ◽  
Robot System ◽  
System Cost ◽  
Excited Vibration ◽  
Pick And Place ◽  
Delta Robot

The Delta robot system is widely used in high speed (4 cycles/s at 25-200-25 mm) pick-and-place process in production line. Some industrial applications include photo-voltaic (PV), food process, and electronic assembly, and so on. The energy saving and system cost are two critical parameters for designing the next generation of pick-and-place system. To achieve these goals, a light-weight moving structure with sufficient strength to overcome the excited vibration will be one of the solutions. In this paper, an asymmetric arm design is proposed and fabricated to gain the benefit of strength-to-weight. The asymmetric arm is designed by reinforcing a specific direction and is validated the vibration suppression capability both by simulation and experiment. A position controller that is derived from the kinematic model of Delta robot is utilized to manipulate the robot under a forward-backward motion with a polynomial trajectory with 200 mm displacement. The residual vibration, then, was measured after the forward-backward motion to compare the settling performance between symmetric- and asymmetric-arms on the Delta robot system, respectively. The results conclude as following: (1) The asymmetric arms perform slightly worse (0.03 sec more in settling time) than symmetric arm but there is 15% weight reducing comparing to symmetric arm. (2) Both energy saving and system cost reducing would be achieved by utilizing actuators with lower power consumption and fabrication on carbon fiber arms with mass customization.

Effect of Mechanical Preloads on the Dynamic Performance of Gas Foil Bearings

2008 ◽  
Author(s):  
Tae Ho Kim ◽  
Luis San Andre´s
Keyword(s):  
Large Amplitude ◽  
High Speed ◽  
Low Cost ◽  
Dynamic Performance ◽  
Cycle Performance ◽  
High Power Density ◽  
Shaft Speed ◽  
Foil Bearings ◽  
Bearing Force ◽  
Good Agreement

Gas foil bearings (GFBs) enable efficient, reliable and maintenance free operation of high-power-density microturbomachinery (< 200 kW). High speed rotors supported on bump-type GFBs, however, are prone to show large-amplitude subsynchronous motions albeit reaching limit cycle performance. Presently, commercial GFBs are simply modified to introduce a mechanical preload that induces a hydrodynamic wedge to generate more load support and direct stiffnesses. Three metal shims inserted under the bump strip layers and in contact with the bearing housing create a multiple lobe clearance profile at a very low cost. Shaft speed coastdown measurements reveal the rotordynamic performance of a rotor supported on original GBFs and (modified) shimmed GFBs. The later GFBs determine a raise in the rotor-bearing system natural frequency, as expected, and also act to delay the onset speed of large-amplitude subsynchronous motions. Predictions of imbalance response implementing linearized bearing force coefficients are in good agreement with measured amplitudes of synchronous response for both GFB configurations, original and modified.

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