Ramp Approach Parameter Correction Method for 3-axis Web Machining

Ambient conditions have a significant impact on the temperatures and pressures in the flow path and on the fuel flow of any gas turbine. Making observed data comparable requires a correction of the raw data to sea level Standard Day conditions. The most widely applied gas turbine parameter correction method is based on keeping some dimensionless Mach number similarity parameters invariant. These similarity parameters are composed of the quantity to be corrected multiplied by temperature to the power ‘a’ and pressure to the power ‘b’ with exponent ‘a’ being theoretically either 0, +0.5 or −0.5 and ‘b’ either 0 or 1.0. To improve the accuracy of this approach it is common practice to empirically adapt the temperature and pressure exponents ‘a’ and ‘b’ in such a way that the correction process leads to a better correlation of the data. Finding empirical exponents requires either many consistently measured data that cover a wide range of ambient temperatures and pressures or a computer model of the engine. A high fidelity model is especially well suited for creating optimally matched exponents and for exploring the phenomena that make these exponents deviate from their theoretical value. This paper discusses the questions that arise when creating empirical exponents with a thermodynamic model of the gas turbine. The gas turbine parameter correction method based on Mach number similarity parameters can get complex if effects like humidity, bleed air or power off-take, free power turbines, switching between various fuel types (Diesel and natural gas), water respectively steam injection, variable geometry or afterburners have to be considered. In such a case it might be simpler — and certainly more accurate — to use the thermodynamic model for the gas turbine parameter correction. Computing power required for running a model is nowadays of no relevance and the better consistency of the data available for engine performance monitoring can yield a significantly improved performance diagnostic capability.

Download Full-text

Parameter Equivalent Method of Stator Anisotropic Material Based on Modal Analysis

Energies ◽

10.3390/en12224257 ◽

2019 ◽

Vol 12 (22) ◽

pp. 4257 ◽

Cited By ~ 1

Author(s):

Zeyu Zhang ◽

Zhiyong Jiao ◽

Hongbing Xia ◽

Yuhan Yao

Keyword(s):

Finite Element ◽

Finite Element Model ◽

Anisotropic Material ◽

Element Model ◽

Correction Method ◽

Stator Core ◽

Modal Frequency ◽

Material Parameters ◽

The Relationship ◽

Parameter Correction

Accurate calculation of the vibration mode and natural frequency of a motor stator is the basis for reducing motor noise and vibration. However, the stator core and winding material parameters are difficult to determine, posing issues which result in modal calculation bias. To address the problem of calibrating the stator material parameters, we developed a parameter correction method based on modal frequency. First, the stator system was simplified to build a stator system finite element model. Secondly, the relationship between modal frequency and material parameters was analyzed by finite element software, the relationship between modal frequency and material parameters was derived, and the anisotropic material parameter correction method was summarized. Finally, a modal experiment was carried out by the hammering method, and the simulation and experimental errors were within 3%, which verified the accuracy of the finite element model. The proposed correction method of anisotropic material can quickly determine the stator material parameters, and the stator core and winding anisotropic material can ensure the accuracy of the modal analysis.

Download Full-text

Ortho-k lenses fitting in patients with “non-typical” corneas

The Eye ◽

10.33791/2222-4408-2020-1-22-29 ◽

2020 ◽

Vol 22 (129) ◽

pp. 22-29

Author(s):

Svetlana Kravchuk ◽

Olga Zhabina

Keyword(s):

Correction Method ◽

Diameter Ratio ◽

Corneal Curvature ◽

Individual Approach ◽

Fitting In ◽

Corneal Diameter ◽

Clinical Cases

We described two clinical cases of ortho-k lenses fitting in patients with “non-typical” corneal curvature/diameter ratio. The main goal was to acknowledge effective and safe use of this myopia correction method in patients with corneal diameter greater than 11 mm. Individual approach to each patient is the key to a successful and safe ortho-k lenses fitting.

Download Full-text