scholarly journals Experimental Investigation of Inductive Sensor Characteristic for Blade Tip Clearance Measurement at High Temperature

Sensors ◽  
2019 ◽  
Vol 19 (17) ◽  
pp. 3694 ◽  
Author(s):  
Zhenxia Liu ◽  
Ziyu Zhao ◽  
Yaguo Lyu ◽  
Lingqiang Zhao
Keyword(s):  
Measurement Error ◽  
Temperature Effect ◽  
Engine Performance ◽  
High Sensitivity ◽  
Response Speed ◽  
Tip Clearance ◽  
Inductive Sensor ◽  
Contact Distance ◽  
Repeatability Error ◽  
Blade Tip

Turbine tip clearance of aero-engine is important to engine performance. Proper tip clearance can reduce the gas leakage over turbine blade tips and improve the engine efficiency of turbo machinery and reduce the fuel consumption. Therefore, accurate tip clearance measurement is essential. The inductive measurement method is one of the non-contact distance measurement methods, which has the characteristics of high sensitivity, fast response speed, and strong anti-interference ability. Based on the principle of inductive sensor measuring tip clearance, the ambient temperature change may cause the material electromagnetic performance change for the conductivity and permeability varies with temperature. In order to verify the temperature effect on the sensor performance, the repeated calibration experiments were carried out to obtain the sensor repeatability error of 5.4%. Then, the sensor was calibrated in the range of 0mm–4mm clearance at temperature from 600 °C to 1000 °C and obtained the measurement error of 4.6%. Results indicate when the temperature ranged from 600 °C to 1000 °C, clearance measurement error is smaller than the sensor repeatability error so the temperature effect on the sensor characteristics can be ignored. This conclusion makes the sensor promising for monitoring the blade tip clearances at various temperature environment.

scholarly journals Experimental Investigation of High Temperature-Resistant Inductive Sensor for Blade Tip Clearance Measurement

Sensors ◽  
2018 ◽  
Vol 19 (1) ◽  
pp. 61 ◽  
Author(s):  
Ziyu Zhao ◽  
Zhenxia Liu ◽  
Yaguo Lyu ◽  
Yajun Gao
Keyword(s):  
High Temperature ◽  
Engine Performance ◽  
Response Speed ◽  
Tip Clearance ◽  
Effect Of Temperature ◽  
Inductive Sensor ◽  
Sensing Range ◽  
Coil Inductance ◽  
Contact Distance ◽  
Planar Coil

Turbine tip clearance of aero-engine is important to engine performance. Proper control of rotor tip clearance contributes to engine efficiency improvement and fuel consumption reduction. Therefore, accurate tip clearance measurement is essential. The inductive measurement method is one of the non-contact distance measurement methods, which has the characteristics of high sensitivity, fast response speed and strong anti-interference ability. Based on the principle of inductive sensor measuring tip clearance, the ambient temperature change will cause the material electromagnetic performance change for the conductivity and permeability varies with temperature. The calibration experiment was conducted to obtain the sensor resolution and sensing range. The effect of temperature on sensor parameters was extracted from high temperature experiment data. Results show the resolution of planar coil made of platinum wire can be 10 μm and the maximum sensing range can reach 5 mm. At temperature from 500 ℃ to 1100 ℃, coil inductance almost does not change with temperature while coil resistance varies exponentially with temperature, that means the coil inductance variation can reflect the tip clearance change and resistance can indicate the measuring temperature.

Sensitivity Analysis and Experimental Validation of Transient Performance Predictions for a Short-Range Turbofan

2016 ◽  
Author(s):  
Maria V. Culmone ◽  
Nicolás Garcia-Rosa ◽  
Xavier Carbonneau
Keyword(s):  
Short Range ◽  
Engine Performance ◽  
Sensitivity Study ◽  
Simulation Software ◽  
Tip Clearance ◽  
Mass Storage ◽  
Transient Effects ◽  
Transient Model ◽  
Blade Tip ◽  
The Impact

Transient effects are important features of engine performance calculations. The aim of this paper is to analyze a new, fully transient model implemented using the PRopulsion Object Oriented Simulation Software (PROOSIS) for a civil, short range turbofan engine. A transient turbofan model, including the mechanical inertia effect has been developed in PROOSIS. Specific physical effects such as heat soakage, mass storage, blade tip clearance and combustion delay have been implemented in the relevant components of PROOSIS to obtain a fully transient model. Since a large number of components are concerned by all the transient effects, an influence study is presented to determine which are the most critical effects, and in which components. Inertia represents the relevant phenomenon, followed by thermal effects, combustion delay and finally mass storage. The comparison with experimental data will provide a first validation of the model. Finally a sensitivity study is reported to assess the impact of uncertain knowledge of key input parameters in the response time prediction accuracy.

scholarly journals Influence of Large Relative Tip Clearances for a Micro Radial Fan and Design Guidelines for Increased Efficiency

2020 ◽  
Author(s):  
Patrick H. Wagner ◽  
Jan Van herle ◽  
Lili Gu ◽  
Jürg Schiffmann
Keyword(s):  
Pressure Rise ◽  
Leading Edge ◽  
High Sensitivity ◽  
Design Guidelines ◽  
Tip Clearance ◽  
Small Scale ◽  
Blade Tip ◽  
Dynamics Simulations ◽  
Experimental Findings ◽  
Blade Tip Clearance

Abstract The blade tip clearance loss was studied experimentally and numerically for a micro radial fan with a tip diameter of 19.2mm. Its relative blade tip clearance, i.e., the clearance divided by the blade height of 1.82 mm, was adjusted with different shims. The fan characteristics were experimentally determined for an operation at the nominal rotational speed of 168 krpm with hot air (200 °C). The total-to-total pressure rise and efficiency increased from 49 mbar to 68 mbar and from 53% to 64%, respectively, by reducing the relative tip clearance from 7.7% to the design value of 2.2%. Single and full passage computational fluid dynamics simulations correlate well with these experimental findings. The widely-used Pfleiderer loss correlation with an empirical coefficient of 2.8 fits the numerical simulation and the experiments within +2 efficiency points. The high sensitivity to the tip clearance loss is a result of the design specific speed of 0.80, the highly-backward curved blades (17°), and possibly the low Reynolds number (1 × 105). The authors suggest three main measures to mitigate the blade tip clearance losses for small-scale fans: (1) utilization of high-precision surfaced-grooved gas-bearings to lower the blade tip clearance, (2) a mid-loaded blade design, and (3) an unloaded fan leading edge to reduce the blade tip clearance vortex in the fan passage.

Verification and Design of High Precision Eddy Current Sensor for Tip Clearance Measurement

2018 ◽  
Author(s):  
Ziyu Zhao ◽  
Zhenxia Liu ◽  
Yaguo Lyu ◽  
Xinxin Xu
Keyword(s):  
High Precision ◽  
Eddy Current ◽  
High Sensitivity ◽  
Response Speed ◽  
Measurement Range ◽  
Tip Clearance ◽  
Current Sensor ◽  
Eddy Current Sensor ◽  
Planar Coil ◽  
Sensor Coil

A high precision eddy current sensor for tip clearance measurement was proposed to assess the dynamic tip clearance measurement for aero-engine rotator. Based on the Lenz’s law, the eddy current sensor has high sensitivity, quick response speed and strong anti-interference capability, in addition, the simple geometry and easy installation are its main merits. The aim is to study the influence of planar coil structure parameters and excitation signal parameters on the sensor coil measurement, provide the basis for design of practical sensor in turbine tip clearance measurement. The dynamic calibration experiment verified the designed planar sensor coil, the results indicated the sensor resolution was 10μm and the measurement range was not less than 3mm. The dynamic experiment proved the measuring range, resolution, response speed of designed sensor can meet the requirement of turbine blade tip clearance measurement. The work provides experience in eddy current sensor design in different application, not only in turbine. And the future work will focus on the high temperature issues.

scholarly journals High-Precision Extraction Method for Blade Tip-Timing Signal with Eddy Current Sensor

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Ji-wang Zhang ◽  
Ke-qin Ding ◽  
Guang Chen
Keyword(s):  
Measurement Error ◽  
Eddy Current ◽  
Background Noise ◽  
High Speed ◽  
Ensemble Empirical Mode Decomposition ◽  
Tip Clearance ◽  
Mode Decomposition ◽  
Blade Tip ◽  
The Asymmetry ◽  
Blade Tip Clearance

Online monitoring of high-speed rotating blades has always been a hot topic. Of the various methods, the blade tip timing (BTT) technique, based on eddy current sensors, is considered to be the most promising. However, BTT signals are easily influenced by various factors, which means that the accurate extraction of BTT signals remains a challenge. To try to solve this problem, the causes of measurement error were analyzed. The three main reasons for the error were established: the variation in blade tip clearance, the interference of background noise, and the asymmetry of the blade tip shape. Further, pertinent improvement methods were proposed, and a compensation method was proposed for the errors caused by the variation of tip clearance. A new denoising and shaping algorithm based on ensemble empirical mode decomposition (EEMD) was introduced for the errors caused by background noise. Additionally, an optimal installation position of the sensor was also proposed for the errors caused by the asymmetry of the blade tip shape. Finally, simulations and experiments were used to demonstrate the improved methodology. The results show that the measurement error on vibration amplitude and vibration frequency using the proposed method is less than 2.89% and 0.17%, respectively, which is much lower than the traditional method (24.44% and 0.39%, respectively).

Effects of Turbine Tip Clearance on Gas Turbine Performance

2008 ◽  
Author(s):  
Cleverson Bringhenti ◽  
Joa˜o Roberto Barbosa
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Engine Performance ◽  
Outer Wall ◽  
Tip Clearance ◽  
Large Space ◽  
Steady State Condition ◽  
Turbine Engine ◽  
Wall Boundary Layer ◽  
Blade Tip

There are many different sources of loss in gas turbines. The turbine tip clearance loss is the focus of this work. In gas turbine components such as compressor and turbine the presence of rotating blades necessitates a small annular tip clearance between the rotor blade tip and the outer casing. This clearance, although mechanically necessary, may represent a source of large loss in a turbine. The gap height can be a fraction of a millimeter but can have a disproportionately high influence on the stage efficiency. A large space between the blades and the outer casing results in detrimental leakages, while contact between them can damage the blades. Therefore, the evaluation of the sources of the performance degradation independently presents useful information that can aid in the maintenance action. As part of the overall blade loss the turbine tip clearance loss arises because at the blade tip the gas does not follow the intended path and therefore does not contribute to the turbine power output and interacts with the outer wall boundary layer. Increasing turbine tip clearance causes performance deterioration of the gas turbine and therefore increases fuel consumption. The increase in turbine tip clearance may as a result of rubs during engine transients and the interaction between the blades and the outer casing. This work deals with the study of the influence of the turbine tip clearance on a gas turbine engine, using a turbine tip clearance model incorporated to an engine deck. Actual data of an existing engine were used to check the validity of the procedure. This paper refers to a single shaft turbojet engine under development, operating under steady state condition. Different compressor maps were used to study the influence of the curve shapes on the engine performance. Two cases were considered for the performance simulation: constant corrected speed and constant maximum cycle temperature.

The Effect of Local Casing Features and External Dummy Flanges on Casing Contraction for Thermal Control of Blade Tip Clearance

2019 ◽  
Author(s):  
Myeonggeun Choi ◽  
David R. H. Gillespie
Keyword(s):  
Engine Performance ◽  
Relative Sensitivity ◽  
Thermal Control ◽  
Tip Clearance ◽  
Axial Position ◽  
Design Parameters ◽  
Leakage Flows ◽  
External Cooling ◽  
Blade Tip ◽  
Tip Leakage Flows

Abstract Thermal closure of the engine casing is widely used to minimise undesirable blade tip leakage flows and thus improve jet engine performance. While this may be achieved using an external cooling scheme on the casing wall, the geometry of the casing itself may have considerable influence on the contraction. In this paper, key controllable design parameters such as the thickness of the casing, the extent (radial height) of the annular dummy flanges and their axial position have been examined to identify how the geometric features may be manipulated to obtain an optimised system for both contraction and weight. Finite element modelling has been used to simulate the contraction of a range of casing geometries using external cooling schemes, adapted previous work by the authors. The displacement-coolant exchange rate of each casing configuration is reported in mm / kg s−1. The results show the relative sensitivity of the contraction of the engine casing to the casing thickness, the radial height, and thickness profiling of the flanges, and also to the balance between jets impinging on the casing and towards the root of the flanges.

scholarly journals The Impact of Realistic Casing Geometries and Clearances on Fan Blade Tip Aerodynamics

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Alistair John ◽  
Ning Qin ◽  
Shahrokh Shahpar
Keyword(s):  
Engine Performance ◽  
Leading Edge ◽  
Tip Clearance ◽  
Blade Design ◽  
Engine Operation ◽  
Surface Method ◽  
Flow Features ◽  
Blade Tip ◽  
Fan Blade ◽  
The Impact

During engine operation, fan casing abradable liners are worn by the blade tip, resulting in the formation of trenches. This paper describes the influence of these trenches on the fan blade tip aerodynamics. A detailed understanding of the fan tip flow features for cropped and trenched clearances is first developed. A parametric model is then used to model trenches in the casing above the blade tip and varying blade tip positions. It is shown that increasing clearance via a trench reduces performance by less than increasing clearance through cropping the blade tip. A response surface method is then used to generate a model that can predict fan efficiency for a given set of clearance and trench parameters. This model can be used to influence fan blade design and understand engine performance degradation in service. It is shown that an efficiency benefit can be achieved by increasing the amount of tip rubbing, leading to a greater portion of the tip clearance sat within the trench. It is shown that the efficiency sensitivity to clearance is biased toward the leading edge (LE) for cropped tips and the trailing edge (TE) for trenches.

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