Experimental study of steam turbine control valves

2004 ◽  
Vol 218 (5) ◽  
pp. 493-507 ◽  
Author(s):  
D Zhang ◽  
A Engeda ◽  
J R Hardin ◽  
R H Aungier
Keyword(s):  
Experimental Study ◽  
Steam Turbine ◽  
Basic Mechanism ◽  
Experimental Investigations ◽  
Unstable Flow ◽  
Structure Interaction ◽  
Root Cause ◽  
Noise Vibration ◽  
The 1960S ◽  
Complicated Nature

Because of the converging-diverging configuration of the valve passage, venturi valves have been widely used in large turbines to regulate inlet flow as turbine governing valves for about half a century. From the 1960s, a number of valve failure incidents have been reported. Improvement to current designs was strongly demanded but, owing to the complicated nature of the fluid-structure interaction mechanisms, the basic mechanism causing valve failure is still far from being fully understood. Experimental investigations on a half-scale valve were performed here. The study confirmed that asymmetric unstable flow is the root cause of valve problems, such as noise, vibration and failure.

Performance Study and Instability Analysis of Steam Turbine Control Valve

2012 ◽  
Author(s):  
Abraham Engeda
Keyword(s):  
Steam Turbine ◽  
Control Valve ◽  
Basic Mechanism ◽  
Experimental Investigations ◽  
Primary Control ◽  
Steam Turbines ◽  
Performance Study ◽  
Unstable Flow ◽  
Flow Noise ◽  
Valve Assembly

Industrial steam turbines represent one of the largest fractions of prime movers. Regardless of the steam-turbine application being considered, speed and/or load control will be required. Speed control is the primary control loop for all turbine applications, industrial as well as utility. The inlet of industrial steam turbine is usually controlled by a single valve, or a series of valves (multi-valve assembly) working in concert. As a turbine governing valve, the venturi valve, has been widely used in steam turbines to regulate inlet flow in the last 40 years. But as turbine output power become larger, a number of valve failure incidences started to be reported and improving the valve designs became a high priority. But despite numerous investigations to eliminate valve failure, the attempts were not fully successful due to the complicated nature of the fluid-structure interaction mechanisms, and the basic mechanism causing valve vibration and failure is still far from being fully understood. Steam control valves are required to operate under wide ranges of valve openings and pressure ratios. As a continuation of previous valve designs, a newly designed valve with two different seat configurations has been investigated experimentally and studied. This paper reports the results of one of the newly designed valves with a short seat configuration. This paper presents detailed experimental investigations to clarify the mechanisms of valve instability caused by unsteady flows around the valve. A result of the asymmetric unstable flow, noise and vibration characteristics of the valve together with an overall performance assessment of the valve is presented.

Skin-skin contact: The normal-force dependence of the coefficient of friction between a bare finger and artificial skin changes randomly

2021 ◽  
Author(s):  
Koki Inoue ◽  
Shogo Okamoto ◽  
Yasuhiro Akiyama ◽  
Yoji Yamada
Keyword(s):  
Experimental Study ◽  
Coefficient Of Friction ◽  
Normal Force ◽  
Skin Surface ◽  
Artificial Skin ◽  
Skin Changes ◽  
Root Cause ◽  
Skin Contact ◽  
The Coefficient Of Friction ◽  
Frictional Forces

Abstract This study investigates the dependence of the coefficients of friction on the normal force produced by sliding a bare finger over different artificial skins with seven levels of hardness. The coefficient of friction was modeled as a power function of the normal force. An experimental study that involved sliding a finger over artificial skin surfaces was carried out under two conditions: the fingertip being wiped by a dry cloth or a cloth soaked in ethanol. Although the exponential term was assumed to be nearly constant for identical tribological conditions, we observed that the exponent varied randomly and could be negative, zero, or positive. This probabilistic behavior has not been explicitly analyzed in previous studies on human fingertips. The probability density function of the exponent depended on the moisture content of the finger. The exponent was either nearly zero or positive when the finger sliding on the skin surface was wiped with an alcohol-soaked cloth and dried. These findings play an important role in analyzing the frictional forces produced during skin–skin contact in terms of determining the root cause behind the random variations in the dependence of the coefficient of friction on the normal force.

scholarly journals Test Rig for Applied Experimental Investigations of the Thermal Contact Resistance at the Blade-Rotor-Connection in a Steam Turbine

2019 ◽  
Vol 141 (2) ◽  
Author(s):  
Dennis Toebben ◽  
Xavier E. R. de Graaf ◽  
Piotr Luczynski ◽  
Manfred Wirsum ◽  
Wolfgang F. D. Mohr ◽  
...  
Keyword(s):  
Contact Resistance ◽  
Steam Turbine ◽  
Contact Pressure ◽  
Rotational Speed ◽  
Thermal Contact Resistance ◽  
Thermal Stresses ◽  
Thermal Contact ◽  
Experimental Investigations ◽  
Molybdenum Steel ◽  
Bottle Neck

Recent studies have shown that in a prewarming, respectively, warm-keeping operation of a steam turbine, the blades and vanes transport most of the heat to the thick-walled casing and rotor. Thereby, a thermal bottle-neck arises at the connection between the blade root and the rotor. The thermal contact resistance (TCR) at these interfaces affects the temperature distribution and thus the thermal stresses in the rotor. The present paper introduces an experimental setup, which is designed to quantify the TCR at the blade-rotor-connection of a steam turbine. An uncertainty analysis is presented, which proves that the average measurement uncertainties are less than one percent. The experiments especially focus on the investigation of the contact pressure, which is a function of the rotational speed. Therefore, the results of several steady-state measurements under atmospheric and evacuated atmosphere using a high temperature-resistant chromium-molybdenum steel are presented. For the evaluation of the TCR, a numerical model of the specimen is developed in addition to a simplified 1D approach. The results show a significantly increasing TCR with decreasing contact pressure, respectively, rotational speed.

Experimental Study on Compressive Strength of Recycled Aggregate Concrete

2008 ◽  
Vol 385-387 ◽  
pp. 381-384 ◽  
Author(s):  
Wei Wang ◽  
Hua Ling ◽  
Xiao Ni Wang ◽  
Tian Xia ◽  
Da Zhi Wang ◽  
...  
Keyword(s):  
Experimental Study ◽  
Compressive Strength ◽  
Coarse Aggregate ◽  
Recycled Aggregate Concrete ◽  
Time Dependent ◽  
Recycled Aggregate ◽  
Experimental Investigations ◽  
Aggregate Concrete ◽  
Cement Ratio ◽  
Practical Engineering

With the increase in the use of recycled aggregate concrete (RAC), it is necessary to clearly understand its behavior and characteristics. In this paper, experimental study on compressive strength of RAC with same water/cement ratio is conducted. Firstly, influence of recycled coarse aggregate contents on cube compressive strength of RAC is studied. Secondly, experiment on time-dependent strength developing process of RAC is conducted with different solidification ages. Finally, based on above experimental investigations, empirical formula for compress strengths of RAC with different ages is presented. The result of this paper is helpful to theoretical analysis and practical engineering design of RAC structures.

The influence of background turbulence on Ahmed-body wake bistability

2021 ◽  
Vol 926 ◽  
Author(s):  
D. Burton ◽  
S. Wang ◽  
D. Tudball Smith ◽  
H. N. Scott ◽  
T. N. Crouch ◽  
...  
Keyword(s):  
Experimental Study ◽  
Turbulence Intensity ◽  
Free Stream ◽  
Wind Tunnels ◽  
Experimental Investigations ◽  
Switching Rate ◽  
Free Stream Turbulence ◽  
Background Turbulence ◽  
Ahmed Body

The discovery of wake bistability has generated an upsurge in experimental investigations into the wakes of simplified vehicle geometries. Particular focus has centred on the probabilistic switching between two asymmetrical bistable wake states of a square-back Ahmed body; however, the majority of this research has been undertaken in wind tunnels with turbulence intensities of less than $1\,\%$ , considerably lower than typical atmospheric levels. To better simulate bistability under on-road conditions, in which turbulence intensities can easily reach levels of $10\,\%$ or more, this experimental study investigates the effects of free-stream turbulence on the bistability characteristics of the square-back Ahmed body. Through passive generation and quantification of the free-stream turbulent conditions, a monotonic correlation was found between the switching rate and free-stream turbulence intensity.

scholarly journals FP-TES: Fluidization Based Particle Thermal Energy Storage, Part II: Experimental Investigations

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4302
Author(s):  
Verena Sulzgruber ◽  
David Wünsch ◽  
Heimo Walter ◽  
Markus Haider
Keyword(s):  
Experimental Study ◽  
Energy Storage ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Bulk Material ◽  
Storage System ◽  
Co2 Reduction ◽  
Cold Test ◽  
Experimental Investigations ◽  
Mathematical Correlation

In recent years, the fight against global warming and therefore CO2 reduction have become the most important issue for humanity. As a result, volatile sources of energy—like wind and solar power—are penetrating the electrical grid and therefore an increased demand on storage capacities is required. At the TU Wien Institute for Energy Systems and Thermodynamics, a Fluidization Based Particle Thermal Energy Storage (FP-TES) working with bulk material as a sensible storage material is developed. In this paper, the concept and an experimental study of the cold test rig is presented. By means of various pressure measurements, a novel concept of particle transport based on advanced fluidization technology without any mechanical transport devices is investigated. Moreover, a mathematical correlation between the pressure gradients and the particle mass flow is found. Overall, the experimental study provides a full proof of concept and functionality of the novel energy storage system.

Experimental study on the repeatability of positioning of linear axes of machine tools

2019 ◽  
Vol 234 (4) ◽  
pp. 739-751
Author(s):  
Guangming Sun ◽  
Gaiyun He ◽  
Dawei Zhang ◽  
Bohui Ding
Keyword(s):  
Experimental Study ◽  
Machine Tools ◽  
Computer Numerical Control ◽  
Numerical Control ◽  
Experimental Investigations ◽  
Single Factor ◽  
Factors Affecting ◽  
Assembly Method ◽  
Orthogonal Experiments ◽  
Control Machine

This study presents experimental investigations on the mechanisms of the repeatability of positioning of linear axes of computer numerical control machine tools. First, the factors affecting the repeatability of positioning of linear axes are obtained based on orthogonal experiments. Second, the mechanism of each factor affecting the repeatability of positioning is studied based on single-factor experiments. Finally, an assembly method to improve the repeatability of positioning of linear axes is proposed. The method can provide designers and workers with informative guidelines for improving the repeatability of positioning in design and assembly processes.

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