Torsional Parameters Research Articles

Can preoperative complete blood count parameters be used in the diagnosis of patients with adnexal torsion: a case-control study

To determine whether there is a relationship between complete blood count parameters at adnexal torsion and to investigate the clinical utility of these parameters in preoperative diagnosis. The retrospective, case-control study was conducted at a tertiary care hospital in Turkey and comprised data of patients who underwent adnexal torsion surgery from 2007 to 2017. Medical records of healthy controls who underwent various gynaecological surgeries during the period were used as the control group. Demographic characteristics and preoperative complete blood count parameters were retrieved from the medical records, and factors influencing adnexal torsion diagnosis were evaluated. Data was analysed using SPSS 21. Of the 296 subjects, 73(24.7%) were adnexal torsion cases and 223(75.3%) were controls. Demographic characteristics did not differ between the groups (p>0.05). Leukocytosis was present in 38(52%) cases. Mean white blood cell, neutrophil, and platelet counts and neutrophil-to-lymphocyte and platelet-to-lymphocyte ratios were significantly higher, and mean platelet volume was significantly lower in the cases compared to controls (p<0.05). Logistic regression analysis identified an independent association between a low mean platelet volume and adnexal torsion (p<0.05). The optimal cutoff value was 10.35fL, with 77.4% sensitivity and 74.2% specificity. There was found to be a significant relationship between adnexal torsion and certain parameters of the complete blood count. Low mean platelet volume could be considered a useful additional tool for the preoperative diagnosis.

P971 The echocardiographic phenotype in patients with cardiac amyloidosis and heart failure with preserved ejection fraction

Abstract BACKGROUND New echocardiographic phenotypes of heart failure (HF) are focused on myocardial systolic involvement of the left ventricle (LV), either endocardial and/or transmural. PURPOSE. To study the pattern of myocardial involvement in patients (p) with HF with preserved left ventricular ejection fraction (pLVEF) and cardiac amyloidosis (CA). METHODS. Comparative study of 16 p with CA and HF with pLVEF, considering as cut point LVEF &amp;gt; 50%, in NYHA class ≥ II / IV, and a control group of 16 healthy people. Longitudinal Strain (LS) and Circumferential Strain (CS) were calculated using 2D speckle-tracking echocardiography, along with Mitral Annulus Plane Systolic Excursion (MAPSE) and Base-Apex distance (B-A). Also, the following indexes were calculated: Twist (apical rotation + basal rotation, º); Classic Torsion (TorC): (twist/B-A, º/cm); Torsion Index (Tor.I): (twist/MAPSE, º/cm) and Deformation Index (Def.I): (twist/LS, º). We suggest the introduction of these dynamic torsion indexes as Tor.I and Def.I that include twist per unit of longitudinal systolic shortening of the LV instead of using TorC which is the normalisation of twist to the end-diastolic longitudinal diameter of the LV. RESULTS There were no differences of age between the groups (68.2 ± 11.5 vs 63.7 ± 2.8 years, p = 0.14). Global values of LS and CS were lower in p with CA indicating endocardial and transmural deterioration during systole, while TorC and Twist of the LV remained conserved in p with CA. However, there is an increase of dynamic torsion parameters such as Tor.I and Def.I that show an increased Twist per unit of longitudinal shortening of the LV in the CA group (Table). CONCLUSIONS In p with CA and HF with pLVEF, the impairment of LS and CS indicates endocardial and transmural systolic dysfunction. In these conditions, LVEF would be preserved at the expense of a greater dynamic torsion of the LV. Table LS (%) CS (%) Twist (º) TorC (º/cm) Tor.I (º/cm) Def.I (º/%) CA pLVEF (n = 16) -11.7 ± 4.2 17.2 ± 4.8 19.8 ± 8.3 2.5 ± 1.1 27.7 ± 13.5 -1.8 ± 0.9 Control Group (n = 15) -20.6 ± 2.5 22.7 ± 4.9 21.7 ± 6.1 2.7 ± 0.8 16.4 ± 4.7 -1.0 ± 0.3 p &amp;lt; 0.001 &amp;lt; 0.01 0.46 0.46 &amp;lt; 0.01 &amp;lt; 0.01 Dynamic Torsion Indexes and Classic Torion Parameters in pLVEF CA patients vs Control group.

P308 Changes in the echocardiographic phenotype during the evolution of cardiac amyloidosis from preserved to reduced left ventricle ejection fraction

Abstract Introduction Cardiomyopaties like Cardiac Amyloidosis (CA), are an important cause of Heart Failure (HF). They can cause endocardial or transmural involvement. It is possible to characterize the kind of affectation thanks to different phenotypes identified by 2D speckle tracking echocardiography. Purpose: To study the pattern of myocardial involvement in patients (p) affected by CA and HF. Methods: Comparative study of 30 p with CA and HF, in NYHA class ≥II/IV, of which 16 had preseved left ventricle ejection fraction (pLVEF) and 14 had reduced LVEF (rLVEF), considering as cut point a LVEF &amp;gt; 50%. There was a control group (CG) of 16 healthy subjects. Twist, radial strain (RS), circunferential strain (CS) and longitudinal strain (LS) were determined using 2D speckle-tracking echocardiography, along with mitral annulus plane systolic excursion (MAPSE) and basal-apex distance (B-A). The following indexes were calculated: Twist (apical rotation + basal rotation, °); Torsion (twist/B-A, °/cm); Torsion Index (TorI: twist/MAPSE, °/cm), and Deformation Index (DefI:twist/LS,°). The last indexes are dynamic parameters that allow for a more realistic assessment of LV torsion, since they include longitudinal shortening measures such as MAPSE and LS, describing in a more complete and physiological way the global LV systolic movement. Results There were differences of age between the three gropus, being older the p with rLVEF and younger the ones in the CG (63,7 ± 2,8; 68,2 ± 11,5; y 73,9 ± 12,9 years respectively). LS and CS were lower in rLVEF group when compared with pLVEF group, as well as in pLVEF group compared with the CG. The p with pLVEF showed increased values of the dynamic torsion parameters (DefI and TorI), indicating a compensatory increase of LV twist that disappears in p with rLVEF. Twist and Torsion are significantly lower only in the rLVEF group (see table). Conclusions In both CA groups, LS and CS deterioration indicates endocardial and transmural involvement. The loss of compensation given by the increased LV twist, reflected by DefI and TorI, marks the transition to the deterioration of LVEF. Results Table LVEF (%) LS (%) CS (%) TWIST (°) Torsion (°/cm) TorI (°/cm) DefI (°/%) Control Group (n = 15) 68.2 ± 6.3 -20.6 ± 2.5 -22.7 ± 4.9 21.7 ± 6.1 2.7± 0.8 16.4 ± 4.7 -1.0 ± 0.3 CA pLVEF (n = 16) 60,6 ± 5.4* -11.7 ± 4.2* -17.2 ± 4.8* 19.8 ± 8.3 2.5± 1.1 27.7 ±13.5* -1.8 ± 0.9* CA rLVEF (n = 14) 37.2 ± 8.8** -8.7 ± 3.2** -13.0 ± 3.4** 8.3 ± 5.6** 1.0 ± 1.7** 13.4 ± 9.6** -1.0 ± 0.7** *:p value &amp;lt;0,01 between CG and pLVEF group; **:p value &amp;lt;0,01 between pLVEF and rLVEF

Mathcal{N} -extended D = 4 supergravity, unconventional SUSY and graphene

We derive a 2+1 dimensional model with unconventional supersymmetry at the boundary of an AdS4 mathcal{N} -extended supergravity, generalizing previous results. The (unconventional) extended supersymmetry of the boundary model is instrumental in describing, within a top-down approach, the electronic properties of graphene-like 2D materials at the two Dirac points, K and K′. The two valleys correspond to the two independent sectors of the OSp(p|2) × OSp(q|2) boundary model in the p = q case, which are related by a parity transformation. The Semenoff and Haldane-type masses entering the corresponding Dirac equations are identified with the torsion parameters of the substrate in the model.

Low-redshift constraints on homogeneous and isotropic universes with torsion

One of the possible extensions of Einstein's General Theory of Relativity consists in allowing for the presence of spacetime torsion. The form of the underlying torsion tensor can be chosen such that the homogeneity and isotropy of Friedmann-Lemaitre-Robertson-Walker universes is preserved, and it has been recently suggested that such universes may undergo accelerating phases. We use recent low-redshift data, coming from Type Ia Supernova and Hubble parameter measurements, to phenomenologically constrain this class of models under the so-called steady-state torsion assumption of a constant fractional contribution of torsion to the volume expansion. We start by considering models without a cosmological constant (where torsion itself would be expected to yield the current acceleration of the universe) finding, in agreement with other recent works, that these are strongly disfavoured by the data. We then treat these models as one-parameter extensions of $\Lambda$CDM, constraining the relative contribution of torsion to the level of a few percent in appropriate units. Finally, we briefly discuss how these constraints may be improved by forthcoming low-redshift data and check the robustness of our results by studying an alternative to the steady-state torsion parametrization.

Cosmological dark sector from a mimetic–metric–torsion perspective

We generalize the basic theory of mimetic gravity by extending its purview to the general metric-compatible geometries that admit torsion, in addition to curvature. This essentially implies reinstating the mimetic principle of isolating the conformal degree of freedom of gravity in presence of torsion, by parametrizing both the physical metric and torsion in terms of the scalar ‘mimetic’ field and the metric and torsion of a fiducial space. We assert the requisite torsion parametrization from an inspection of the fiducial space Cartan transformation which, together with the conformal transformation of the fiducial metric, preserves the physical metric and torsion. In formulating the scalar–tensor equivalent Lagrangian, we consider an explicit contact coupling of the mimetic field with torsion, so that the former can manifest itself geometrically as the source of a torsion mode, and most importantly, give rise to a viable ‘dark universe’ picture from a mimicry of an evolving dust-like cosmological fluid with a nonzero pressure. A further consideration of higher derivatives of the mimetic field in the Lagrangian leads to physical bounds on the mimetic–torsion coupling strength, which we determine explicitly.

Frequency domain approach for probabilistic flutter analysis using stochastic finite elements

In this work, a stochastic finite element method based on first order perturbation approach is developed for the probabilistic flutter analysis of aircraft wing in frequency domain. Here, both bending and torsional stiffness parameters of the wing are treated as Gaussian random fields and represented by a truncated Karhunen–Loeve expansion. The aerodynamic load on the wing is modeled using Theodorsen’s unsteady aerodynamics based strip theory. In this approach, Theodorsen’s function, which is a complex function of reduced frequency, is also treated as a random field. The applicability of the present method is demonstrated by studying the probabilistic flutter of cantilever wing with stiffness uncertainties. The present method is also validated by comparing results with Monte Carlo simulation (MCS). From the analysis, it is observed that torsional stiffness uncertainty has significant effect on the damping ratio and frequency of the flutter mode as compared to bending stiffness uncertainty. The probability density functions of damping ratio and frequency using perturbation technique and MCS are also discussed at various free stream velocities due to stiffness uncertainties. Furthermore, the flutter probability of the cantilever wing is studied by defining implicit limit state function in conditional sense on flow velocity for the flutter mode. Both perturbation and MCS are considered to study the flutter probability of the wing. From the cumulative distribution functions of flutter velocity, it is noticed that the presence of uncertainty in torsional rigidity lowers the predicted flutter velocity in comparison to uncertainty in bending rigidity.

Development and Validation of the Quantum Mechanical Bespoke Protein Force Field.

Molecular mechanics force field parameters for macromolecules, such as proteins, are traditionally fit to reproduce experimental properties of small molecules, and thus, they neglect system-specific polarization. In this paper, we introduce a complete protein force field that is designed to be compatible with the quantum mechanical bespoke (QUBE) force field by deriving nonbonded parameters directly from the electron density of the specific protein under study. The main backbone and sidechain protein torsional parameters are rederived in this work by fitting to quantum mechanical dihedral scans for compatibility with QUBE nonbonded parameters. Software is provided for the preparation of QUBE input files. The accuracy of the new force field, and the derived torsional parameters, is tested by comparing the conformational preferences of a range of peptides and proteins with experimental measurements. Accurate backbone and sidechain conformations are obtained in molecular dynamics simulations of dipeptides, with NMR J coupling errors comparable to the widely used OPLS force field. In simulations of five folded proteins, the secondary structure is generally retained, and the NMR J coupling errors are similar to standard transferable force fields, although some loss of the experimental structure is observed in certain regions of the proteins. With several avenues for further development, the use of system-specific nonbonded force field parameters is a promising approach for next-generation simulations of biological molecules.

Torsional Energy Barriers of Biaryls Could Be Predicted by Electron Richness/Deficiency of Aromatic Rings; Advancement of Molecular Mechanics toward Atom-Type Independence.

Biaryl molecules are ubiquitous pharmacophores found in natural products and pharmaceuticals. In spite of this, existing molecular mechanics force fields are unable to accurately reproduce their torsional energy profiles, except for a few well-parametrized cases. This effectively limits the ability of structure-based drug design methods to correctly identify hits involving biaryls with confidence (e.g., during virtual screening, employing docking and/or molecular dynamics simulations). Continuing in our endeavor to quantify organic chemistry principles, we showed that the torsional energy profile of biaryl compounds could be computed on-the-fly based on the electron richness/deficiency of the aromatic rings. This method, called H-TEQ 4.0, was developed using a set of 131 biaryls. It was subsequently validated on a separate set of 100 diverse biaryls, including multisubstituted, bicyclic and tricyclic druglike molecules, and produced an average root-mean-square error (RMSE) of 0.95 kcal·mol-1. For comparison, GAFF2 produced an RMSE of 3.88 kcal·mol-1, owing to problems associated with the transferability of torsion parameters. The success of H-TEQ 4.0 provided further evidence that force fields could transition to become atom-type independent, providing that the correct chemical principles are used. Overall, this method solved the problem of transferability of biaryl torsion parameters, while simultaneously improving the overall accuracy of the force field.

Cooperative Effects of Cytosine Methylation on DNA Structure and Dynamics.

The behavior of the structural parameters of DNA considering different levels of methylation in CpG islands is studied by means of full-atom molecular dynamics simulations and electronic circular dichroism, both in an artificial model system and in a gene promoter sequence. It is demonstrated that methylation although intrinsically brings quite local perturbations may, if its level is high enough, induce cooperative effects that strongly modify the DNA backbone torsional parameters altering the helicity as compared to the nonmethylated case. Because methylation of the CpG island is correlated with the regulation of gene expression, understanding the structural modifications induced in DNA is crucial to characterize all the fine equilibria into play in epigenetics phenomena.

Structural Parameter Optimization Design of Torsion Beam Semi-Independent Suspension Based on Multi-Island Genetic Algorithm

In order to reduce the variation of suspension parameters during wheel runout, andimprove the handling stability of the whole vehicle, a method for optimal design of Torsional beamsuspension structural parameters based on Multi-island genetic algorithm is proposed. Study on theMacpherson Front suspension of a car, based on the Euler's four-element method of multi-bodydynamics and the spatial analytic geometric transformation formula, the mathematical model ofTorsional beam suspension is derived in this paper, the reliability of the mathematical model isverified by the simulation analysis of the corresponding Adams model. On this basis, the degree ofsuspension performance affected by structure parameters is obtained by Sensitivity analysis. Finally,the optimization of suspension performance is realized by modifying the parameters by usingMulti-island genetic algorithm, which plays an important role in the stability and safety of thewhole vehicle.

A Bayesian approach for identification of ice Ih, ice Ic, high density, and low density liquid water with a torsional order parameter.

An order parameter is proposed to classify the local structures of liquid and solid water. The order parameter, which is calculated from the O-O-O-O dihedral angles, can distinguish ice Ih, ice Ic, high density, and low density liquid water. Three coloring schemes are proposed to visualize each of the coexisting phases in a system using the order parameter on the basis of Bayesian decision theory. The schemes are applied to a molecular dynamics trajectory in which ice nucleation occurs following spontaneous liquid-liquid separation in the deeply supercooled region as a demonstration.

Mie 16–6 force field predicts viscosity with faster-than-exponential pressure dependence for 2,2,4-trimethylhexane

In response to the 10th Industrial Fluid Properties Simulation Challenge, we report viscosity (η) estimates obtained with equilibrium molecular dynamics for 2,2,4-trimethylhexane at 293 K and over a range of pressures (P) from 0.1 MPa to 1000 MPa. The Mie Potentials for Phase Equilibria (MiPPE) force field is utilized in this study, as a previous study demonstrated that it provides reliable estimates of η with respect to P. Whereas most studies report only the uncertainties associated with random fluctuations in the simulation output and subsequent data analysis, we investigate the effect of uncertainties arising from the force field non-bonded and torsional parameters. The pressure-viscosity coefficient as a function of pressure is reported for several different empirical models, namely, McEwen-Paluch, Roelands, Roelands-Modified, and Barus. Although the uncertainties increase substantially with increasing pressure, cross-validation model selection provides quantitative evidence supporting faster-than-exponential, a.k.a. super-Arrhenius, behavior with an apparent inflection point in a log10(η)-P plot around 200 MPa. Near-quantitative agreement between simulation results and new experimental data is achieved for P≤600 MPa, followed by significant over prediction at higher pressures.

Thermodynamics of Helix formation in small peptides of varying lengthin vacuo, implicit solvent and explicit solvent: Comparison between AMBER force fields

Helix formation is of great significance in protein folding. The helix-forming tendencies of amino acids are accumulated along the sequence to determine the helix-forming tendency of peptides. Computer simulation can be used to model this process in atomic details and give structural insights. In the current work, we employ equilibrate-state free energy simulation to systematically study the folding/unfolding thermodynamics of a series of mutated peptides. Two AMBER force fields including AMBER99SB and AMBER14SB are compared. The new 14SB force field uses refitted torsion parameters compared with 99SB and they share the same atomic charge scheme. We find that in vacuo the helix formation is mutation dependent, which reflects the different helix propensities of different amino acids. In general, there are helix formers, helix indifferent groups and helix breakers. The helical structure becomes more favored when the length of the sequence becomes longer, which arises from the formation of additional backbone hydrogen bonds in the lengthened sequence. Therefore, the helix indifferent groups and helix breakers will become helix formers in long sequences. Also, protonation-dependent helix formation is observed for ionizable groups. In 14SB, the helical structures are more stable than in 99SB and differences can be observed in their grouping schemes, especially in the helix indifferent group. In solvents, all mutations are helix indifferent due to protein–solvent interactions. The decrease in the number of backbone hydrogen bonds is the same with the increase in the number of protein–water hydrogen bonds. The 14SB in explicit solvent is able to capture the free energy minima in the helical state while 14SB in implicit solvent, 99SB in explicit solvent and 99SB in implicit solvent cannot. The helix propensities calculated under 14SB agree with the corresponding experimental values, while the 99SB results obviously deviate from the references. Hence, implicit solvent models are unable to correctly describe the thermodynamics even for the simple helix formation in isolated peptides. Well-developed force fields and explicit solvents are needed to correctly describe the protein dynamics. Aside from the free energy, differences in conformational ensemble under different force fields in different solvent models are observed. The numbers of hydrogen bonds formed under different force fields agree and they are mostly determined by the solvent model.

Interaction and molecular dynamics simulation study of Osimertinib (AstraZeneca 9291) anticancer drug with the EGFR kinase domain in native protein and mutated L844V and C797S.

Targeted therapy is a novel, promising approach to anticancer treatment that endeavors to overcome drug resistance to traditional chemotherapies. Patients with the L858R mutation in epidermal growth factor receptor (EGFR) respond to the first generation tyrosine kinase inhibitors (TKIs); however, after one year of treatment, they may become resistant. The T790M mutation is the most probable cause for drug resistance. Third generation drugs, including Osimertinib (AZD9291), are more effective against T790M and other sensitive mutations. Osimertinib is effective against the L844V mutation, has conditional effectiveness for the L718Q mutation, and is ineffective for the Cys797Ser (C797S) mutation. Cells that have both the T790M and C797 mutations are more resistant to third generation drugs. Although research has shown that Osimertinib is an effective treatment for EGFR L844V cells, this has not been shown for cells that have the C797S mutation. This molecular mechanism has not been well-studied. In the present study, we used the GROMACS software for molecular dynamics simulation to identify interactions between Osimertinib and the kinase part of EGFR in L844V and C797S mutants. We evaluated native EGFR protein and the L844V and C797S mutations' docking and binding energy, kI, intermolecular, internal, and torsional energy parameters. Osimertinib was effective for the EGFR L844V mutation, but not for EGFR C797S. All simulations were validated by root-mean-square deviation (RMSD), root-mean square fluctuation (RMSF), and radius of gyration (ROG). According to our computational simulation, the results supported the experimental models and, therefore, could confirm and predict the molecular mechanism of drug efficacy.

Weighted sparse representation based on failure dynamics simulation for planetary gearbox fault diagnosis

The most common and effective way of rotating machinery diagnostics is to extract fault impact features from the vibration signals and to carry out further processing. As for planetary gear sets, because of the simultaneous mesh of multiple gears and the effect of the carrier rotation, the fault features are submerged in the strong harmonic signals and other noise. Due to the lack of prior information on the faults, the conventional fault diagnostic methods often fail to achieve satisfactory results. To address this problem, we give the prior information of a chipped planetary gear set by dynamics simulation, and utilize the information in the time domain to improve the diagnosis performance. Firstly, a pure torsional lumped parameter model is used to simulate the system vibration response with different degrees of failure. Through statistical analysis, the margin factor, the most sensitive indicator, is selected as prior information to reflect the local gear fault among several indexes. Finally, a weighted sparse representation method based on the prior information provided above is proposed to extract the impact features. Moreover, it is found that the extracted components have a strong–weak cyclic impact feature in the chipped planetary gear sets. The features and effectiveness of the method are verified by an experiment on a planetary gearbox test rig. To validate the superiority of the proposed method, comparisons are made among several state-of-the-art feature extraction methods.

Piles Subjected to Torsional Cyclic Load: Numerical Analysis

Pile foundations supporting large structures (such as high-rise buildings, oil drilling platforms, bridges etc.) are often subjected to eccentric lateral load (in addition to the vertical loads) due to the action of wind, waves, high speed traffic and ship impacts etc. The eccentric lateral load, which is usually cyclic (repetitive) in nature, induces torsion in the pile foundation. This paper presents a numerical model based on boundary element approach to study the performance of a single pile subjected to the torsional cyclic load. The model is initially validated by comparing it with the experimental data available from the literature. Thereafter, the model has been utilised to conduct a parametric study to understand the influence of the torsional cyclic loading parameters on the axial pile capacity. The results indicated that the model is able to capture the degradation in the axial pile capacity due to the torsional cyclic loading with a reasonable accuracy. Moreover, the parametric study showed that the frequency, amplitude and number of cycles play a significant role in the torsional cyclic response of the pile. The present study is essential for the development of design guidelines for pile foundations subjected to torsional cyclic load.

Identification of torsional receptances

Identification of torsional receptances of shaft structures has been a challenge. This paper presents a method for measuring or estimating high-quality torsional receptances using two different methods based on the Receptance Decoupling Technique. In both methods, a T-block needs to be attached to facilitate the generation of torsion, and only the numerical receptance data of the T-block cast in a simple theoretical model and a few measured receptance data of the assembled system are required. Both methods are studied and assessed in numerical simulation, and the more robust method is further validated in experiments. The usage of rotational accelerometer is shown to significantly improve the quality of the estimation when the noise level is high. It is demonstrated that high-quality torsional receptances can be indirectly measured with high repeatability using the proposed method and thus can be used subsequently to identify torsional modal parameters, update finite element models, make structural modifications, or implement active torsional vibration control. Due to ubiquitous use of rotating machines, this novel method has significant applications.

QUBEKit: Automating the Derivation of Force Field Parameters from Quantum Mechanics.

Modern molecular mechanics force fields are widely used for modeling the dynamics and interactions of small organic molecules using libraries of transferable force field parameters. However, for molecules outside the training set, the parameters are potentially inaccurate and it may be preferable to derive molecule-specific parameters. Here we present an intuitive parameter derivation toolkit, QUBEKit (QUantum mechanical BEspoke Kit), which enables the automated generation of system-specific small molecule force field parameters directly from quantum mechanics. QUBEKit is written in python and combines bond, angle, torsion, charge, and Lennard-Jones parameter derivation methodologies alongside a method for deriving the positions and charges of off-center virtual sites from the partitioned quantum mechanical electron density. As a proof of concept, we have rederived a complete set of parameters for 109 small organic molecules and assessed the accuracy by comparing computed liquid properties with experiments. QUBEKit gives competitive results when compared to standard transferable force fields, with mean unsigned errors of 0.024 g/cm3, 0.79 kcal/mol, and 1.17 kcal/mol for the liquid density, heat of vaporization, and free energy of hydration, respectively. This indicates that the derived parameters are suitable for molecular modeling applications, including computer-aided drug design.

Study of Torsional Vibrations of Turbomachine Shafts: Part 2. Results of the First Phase Experimental Study of Shafting Torsional Vibrations of a T-175/210-12.75 Turbo Unit

The results of the experimental study of shafting torsional vibrations of a T-175/210-12.75 heating turbo unit at Omsk CHPP-5 are presented and discussed. The hardware and software used in the study were previously described. The technique implemented for controlling the torsional vibration parameters was detailed in the first part of this work. The results of the previous calculation study agree well with the experimental data on the torsional vibration control. The features of the discrete phase method used for the determination of the shafting torsional vibration parameters are considered. It was shown that the parameters of forced and natural vibrations should be registered using different approaches to the collection and processing of the measurement results. Errors made when processing the measurement results for forced torsional vibrations are described by citing specific examples. The data processing techniques used by different researchers are compared by citing the available test results. The consequences of incorrect averaging of time intervals between labels of a measuring disk made with the purpose of eliminating the pitch difference effect are shown, and it is demonstrated that the difference relations between intervals cannot be used for the subsequent calculation using the fast Fourier transform. The preliminary results in the determination of the shafting torsional vibration parameters in one measuring cross section are presented. It is shown that the shafting torsional vibration intensity depends on the operation modes of a turbo unit and is highly dependent on the change in the steam consumption in the low-pressure section (LPS). These research results are the first to prove that there is a dependence of shafting torsional vibrations of a T-175/210-12.75 heating turbine on the relative volume steam consumption in the LPS. The problems to be solved for further improvement of shafting torsional vibration control systems of turbo units are formulated.