scholarly journals INFLUENCE OF GAP FORM IN NON-CONTACT SEAL OF HIGH-SPEED TURBOMACHINE UPON ITS PARAMETERS

2016 ◽  
Vol 2016 (4) ◽  
pp. 39-45
Author(s):  
Андрей Иванов ◽  
Andrey Ivanov
Keyword(s):  
Dynamic Characteristics ◽  
Carrying Capacity ◽  
High Speed ◽  
Liquid Propellant ◽  
Contact Seal ◽  
Definition Of ◽  
Rotor Bearings ◽  
Turbomachine Rotor ◽  
Sealing Elements ◽  
Turbo Pump

Consolidation is one of the most significant elements in any turbomachine defining both economy and capacity for work of a unit. In high-speed pumps and turbines which belong turbo-pump units (TPU) of liquid-propellant engines (LPE) to, one uses mainly non-contact seals and in the first place groove seals. A radial seal gap its value and a form is a basic factor defining parameters and characteristics of sealing. In the paper there is shown the influence of geometrical characteristics of a non-contact seal gap in a high-speed turbomachine upon its characteristics. The influ-ence of the form of a sealing gap upon carrying capacity in it is analyzed that is particularly significant at the definition of seal influence upon critical frequencies of rotor rotation. The mutual misalignments in rotor and stator elements of a seal result in rotor stability reduction, the occurrence of additional radial loads upon bearings. Deviations in a surface form and deformations of sealing elements result in the pressure redistribution in a seal gap that, in its turn, changes forces character affecting a rotor from the side of a seal and, hence, its dynamic characteristics. The analysis of the influence upon carrying capacity in a seal gap of such factors as ellipse, obliquity, barreling, saddling is carried out. The results shown in the paper allow defining the tolerances influence upon manufacturing and deformations of sealing elements upon dynamic characteristics of a high-speed turbomachine rotor at the stage of designing a “rotor-bearings-seals” system.

scholarly journals Emission Modes in Electrospray Thrusters Operating with High Conductivity Ionic Liquids

Aerospace ◽  
2020 ◽  
Vol 7 (10) ◽  
pp. 141
Author(s):  
Nolan M. Uchizono ◽  
Adam L. Collins ◽  
Anirudh Thuppul ◽  
Peter L. Wright ◽  
Daniel Q. Eckhardt ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Steady State ◽  
High Speed ◽  
Liquid Propellant ◽  
Long Distance ◽  
Flow Rates ◽  
Extraction Voltage ◽  
Wide Range ◽  
Emission Behavior ◽  
Definition Of

Electrospray thruster life and mission performance are strongly influenced by grid impingement, the extent of which can be correlated with emission modes that occur at steady-state extraction voltages, and thruster command transients. Most notably, we experimentally observed skewed cone-jet emission during steady-state electrospray thruster operation, which leads to the definition of an additional grid impingement mechanism that we termed “tilted emission”. Long distance microscopy was used in conjunction with high speed videography to observe the emission site of an electrospray thruster operating with an ionic liquid propellant (EMI-Im). During steady-state thruster operation, no unsteady electrohydrodynamic emission modes were observed, though the conical meniscus exhibited steady off-axis tilt of up to 15°. Cone tilt angle was independent over a wide range of flow rates but proved strongly dependent on extraction voltage. For the geometry and propellant used, the optimal extraction voltage was near 1.6 kV. A second experiment characterized transient emission behavior by observing startup and shutdown of the thruster via flow or voltage. Three of the four possible startup and shutdown procedures transition to quiescence within ∼475 μs, with no observed unsteady modes. However, during voltage-induced thruster startup, unsteady electrohydrodynamic modes were observed.

A modified damping model of vector form intrinsic finite element method for high-speed spiral bevel gear dynamic characteristics analysis

2021 ◽  
pp. 030932472110188
Author(s):  
Xiangying Hou ◽  
Yuzhe Zhang ◽  
Hong Zhang ◽  
Jian Zhang ◽  
Zhengminqing Li ◽  
...  
Keyword(s):  
Finite Element ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Numerical Solutions ◽  
Bevel Gear ◽  
Spiral Bevel Gear ◽  
Vector Form ◽  
Good Efficiency ◽  
Spiral Bevel ◽  
Damping Model

The vector form intrinsic finite element (VFIFE) method is springing up as a new numerical method in strong non-linear structural analysis for its good convergence, but has been constricted in static or transient analysis. To overwhelm its disadvantages, a new damping model was proposed: the value of damping force is proportional to relative velocity instead of absolute velocity, which could avoid inaccuracy in high-speed dynamic analysis. The accuracy and efficiency of the proposed method proved under low speed; dynamic characteristics and vibration rules have been verified under high speed. Simulation results showed that the modified VFIFE method could obtain numerical solutions with good efficiency and accuracy. Based on this modified method, high-speed vibration rules of spiral bevel gear pair under different loads have been concluded. The proposed method also provides a new way to solve high-speed rotor system dynamic problems.

Dynamic characteristics of a drill in the drilling process

2003 ◽  
Vol 217 (2) ◽  
pp. 161-167 ◽  
Author(s):  
B W Huang
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Thrust Force ◽  
Time Dependent ◽  
Drilling Process ◽  
Improve Quality ◽  
Vibration Model ◽  
High Speed Drilling ◽  
Spinning Speed ◽  
Twisted Beam

The dynamic characteristics of high-speed drilling were investigated in this study. To improve quality and produce a higher production rate, the dynamic characteristics of the drilling process need to be studied. A pre-twisted beam is used to simulate the drill. The moving Winkler-type elastic foundation is used to approximate the drilling process. A time-dependent vibration model for drilling is presented. The spinning speed, pre-twisted angle and thrust force effects of the drill are considered. The numerical analysis indicates that the natural frequency is suddenly reduced as the drill moves into a workpiece.

scholarly journals Analysis of the dynamic characteristics of downsized aerostatic thrust bearings with different pressure equalizing grooves at high or ultra-high speed

2021 ◽  
Vol 13 (5) ◽  
pp. 168781402110180
Author(s):  
Ruzhong Yan ◽  
Haojie Zhang
Keyword(s):  
Dynamic Characteristics ◽  
High Speed ◽  
Rotation Speed ◽  
Dynamic Stiffness ◽  
Simulation Method ◽  
Perturbation Amplitude ◽  
Thrust Bearings ◽  
Supply Pressure ◽  
Ultra High Speed ◽  
Air Film

This study adopts the DMT(dynamic mesh technology) and UDF(user defined functions) co-simulation method to study the dynamic characteristics of aerostatic thrust bearings with equalizing grooves and compare with the bearing without equalizing groove under high speed or ultra high speed for the first time. The effects of air film thicness, supply pressure, rotation speed, perturbation amplitude, perturbation frequency, and cross section of the groove on performance characteristics of aerostatic thrust bearing are thoroughly investigated. The results show that the dynamic stiffiness and damping coefficient of the bearing with triangular or trapezoidal groove have obvious advantages by comparing with that of the bearing without groove or with rectangular groove for the most range of air film thickness, supply pressure, rotation speed, perturbation amplitude, especially in the case of high frequency, which may be due to the superposition of secondary throttling effect and air compressible effect. While the growth range of dynamic stiffness decreases in the case of high or ultra-high rotation speed, which may be because the Bernoulli effect started to appear. The perturbation amplitude only has little influence on the dynamic characteristic when it is small, but with the increase of perturbation amplitude, the influence becomes more obvious and complex, especially for downsized aerostatic bearing.

Development of High-Speed Response Electromagnetic Linear Actuator Using for Pneumatic Control Valve

2014 ◽  
Vol 532 ◽  
pp. 41-45 ◽  
Author(s):  
Myung Jin Chung
Keyword(s):  
Optimal Design ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Design Method ◽  
Control Valve ◽  
Design Parameters ◽  
Linear Actuator ◽  
Analytic Model ◽  
Electromagnetic Linear Actuator ◽  
Quadratic Programming Method

Analytic model of electromagnetic linear actuator in the function of electric and geometric parameters is proposed and the effects of the design parameters on the dynamic characteristics are analyzed. To improve the dynamic characteristics, optimal design is conducted by applying sequential quadratic programming method to the analytic model. This optimal design method aims to minimize the response time and maximize force efficiency. By this procedure, electromagnetic linear actuator having high-speed characteristics is developed.

Switchmode Hydraulic Power Supply Theory

2005 ◽  
Author(s):  
Jianwei Cao ◽  
Linyi Gu ◽  
Feng Wang ◽  
Minxiu Qiu
Keyword(s):  
Flow Rate ◽  
Dynamic Characteristics ◽  
Power Supply ◽  
Power Loss ◽  
High Speed ◽  
Hydraulic Pressure ◽  
Hydraulic Systems ◽  
Hydraulic Pump ◽  
Hydraulic Power ◽  
Supply Pressure

Switchmode hydraulic power supply is a new kind of energy-saving pressure converting system, which is originally proposed by the authors. It is mainly applied in multiple-actuator hydraulic systems, and installed between hydraulic pump and actuators (one switchmode hydraulic power supply for one actuator). It can provide pressure or flow rate that is adapted to the consumption of each actuator in the system by boosting or bucking the pressure, with low power loss, and conveniently, through high-speed switch valves, just like a hydraulic pressure transformer. There are two basic types of switchmode hydraulic power supply: pressure boost and pressure buck. Their structures and working principles are introduced. The dynamic characteristics of two typical types of switchmode hydraulic power supply, the pressure boost type and the pressure buck type, were analyzed through simulations and experiments. The performances were evaluated, and improvements on the efficiency of switchmode hydraulic power supply were proposed.

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