Turbo Machines Research Articles

Design and performance evaluation of a reversible bladeless turbo machine

It is well known that bladeless or Tesla turbomachinery idea was proposed by Nikola Tesla over a century ago, and it has several distinct features, such as reversibility of operation, which includes expander and compressor operations obtained by reversing the rotational speed, provided that the statoric channels are purposely designed.The main objective of this paper is to design a reversible Tesla or bladeless machine with optimal design parameter choice that can operate both in compressor and expander modes. As a consequence of the high losses due to rotor and stator interactions, statorless (volute) configurations are investigated here, showing superior performance in both compressor and expander modes of operation. Numerical study has been conducted for both compressor and expander modes of this machine using air as working fluid. In compressor mode, numerical results have been validated with experimental data, while results for expander mode will be validated in the near future. The numerical results predict peak isentropic efficiencies of 57.5 % and 63.5 %, for the compressor and expander modes of operation excluding assembly losses, respectively, while rotor efficiency is quite high > 90 % at very low mass flow rates. Tests on Tesla machine prototype have shown an experimental isentropic efficiency of maximum 32.4 % when operating in compressor mode. The overall assembly efficiency is reduced, compared to numerical predictions, due to leakage and end wall losses. The CFD simulations could match the experimental results at high pressure ratio and low mass flow, with less than 2 % error on pressure ratio. Through the improvement of the sealing system and the reduction of losses (leakage and end wall friction), it is expected that overall prototype efficiency could improve by at least 10 percentage points.

Effect of scale factor on the dynamic response of frame foundations

Abstract In geotechnical engineering, a scale factor “n” is a numerical ratio that relates the physical properties of a physical model to those of a prototype. The effect of scale factor on the dynamic response of a frame foundation used for high-speed turbo machines is examined through numerical analyses to clarify the influence of scaling dimensions, frequency, static and dynamic loads, and scaled models’ material on the dynamic responses of the frame foundation. The static and dynamic analyses were conducted using Ansys Workbench software. The total number of analyses used to investigate the scale factor effect was 28. Both modal and harmonic analyses were performed to calculate the natural frequencies and displacement responses of the scaled and prototype models under the scaled dynamic loading. Five scale factors were used in this study for concrete models (1, 20, 25, 32, and 40), and two additional analyses on steel models of scale (1 and 20) were used to study the material scaling. The prototype results were first verified, and then the models were investigated after scaling the dynamic loads and dimensions. The results of this study revealed the importance of scaling the frequency when studying the high-speed turbo machine foundation models to reflect the correct responses of the prototype foundation.

Design and Optimization of Centrifugal Pump Impeller Blade

Centrifugal pumps exploit the transformation of rotating kinetic energy into hydrodynamic energy to move fluid. They are a subclass of dynamic axisymmetric work-absorbing turbo machines. In order to aid in pump design, this project uses computational fluid dynamics software to explore intricate internal flows in centrifugal pump impellers. Three distinct kinds of pump impellers were taken in this instance. Pump specs under consideration include speed and discharge. These parameters have been adjusted in order to conduct a comparison analysis of these pump impellers. The plane between blades is modeled in CFD software is used to perform the flow analysis in addition to CAD software. As a consequence, the pressure and velocity distributions were the basis for the valid results, and the computational results were used to compare the pumps' respective performances.

A novel prognostics solution for accurate identification of degradation patterns in turbo machines with variable observation window

The degradation of a system is a time bound phenomenon, which leads to the deterioration of turbomachinery, in terms of performance and reliability. If undetected and not acted upon in time, this could also lead to sudden system failure, resulting in unplanned unit downtime and maintenance. Unplanned downtime of a turbomachine leads to severe production loss for the end customer and consequent economic damages. Early detection of a degradation pattern would provide the customer with the opportunity to timely carry out corrective actions, preventing an unscheduled down time. The paper evaluates degradation identification methodology currently known from literature and finds them not accurate enough for general purpose application required by the solution. The paper discusses a novel methodology which can accurately detect degradation patterns of timeseries data. Critical features of this methodology are novel time-based correlation enabled regression model with variable observation window, autonomous training, and automatic adjusting capability to incorporate operating behavior change or physical system replacement. This leads to high accuracy, high generalization, and domain agnostic application capability. Moreover, particular focus is given to achieving high probability of detection and a low probability of false alarm. The paper demonstrates the performance achieved by the methodology when applied to the field of prognostics and diagnostics of IoT connected turbomachines through 50+ real application cases.

Numerical Investigations and Artificial Neural Network-Based Performance Prediction of a Centrifugal Fan Having Innovative Hub Geometry Designs

It is a well-known fact that air approaches the eye region of the rotating impeller of a centrifugal fan with shock-less entry conditions in an ideal scenario. The flow in this region is associated with induced swirl losses, leading to cumulative performance losses. Proper flow guidance in the vicinity of the eye region is essential to minimize possible flow losses. The flow guiding structure may be in the form of a projection or extrusion connected to the rotating impeller of the turbo machines and is generally named a hub. These attachments enhance the overall flow augmentation of the turbo machines in terms of static pressure improvement by reducing a significant amount of inlet turning losses. This article attempts to highlight the efficacy of hubs of various shapes and sizes on the pressure rise of the centrifugal fan using Computational Fluid Dynamics (CFD). Simulation results revealed that the optimized hub configuration yields about an 8.4% higher head coefficient and 8.6% higher relative theoretical efficiency than that obtained for the hub-less base configuration. This improvement in these paraments therefore also commemorates the global progress in energy efficiency as per the UN’s Sustainable Development Goals, SDG 7 in particular. Simultaneously, in the Artificial Neural Network (ANN), a Multi-Layer Perceptron (MLP) model is used to forecast the performance of a centrifugal fan with an optimized hub design. The results predicted by the ANN model are found to be in close agreement with the optimized hub shape’s numerical results.

A Static and Dynamic Analysis of A High-Speed Turbo Machine Foundation

A Static and Dynamic Analysis of A High-Speed Turbo Machine Foundation

Simulation study of crack parameters’ effects on the vibration characteristics of a bladed disk system

As a key component of the turbo machine rotor in harsh operating conditions, high cycle fatigue failure and even cracks are common in bladed disks. In this paper, modal analysis was carried out for a single cracked bladed disk system, the effects of crack depth, crack height and rotating speed on its vibration characteristics were studied by the method of both numerical simulation and orthogonal test, and the effects of crack distribution on the vibration characteristics of multi-crack bladed disk systems were also studied. Finally, some conclusions have been drawn, they provide a fundamental understanding of blade health monitoring and fault prediction, and are important to improve the reliability and safety of turbine operation.

Numerical investigation on the effects of HC geometry on the flow and heat transfer in the disk cavity system at the turbine vane root

In this study, we numerically investigate the flow and heat transfer in the sealing system at the vane root of a heavy-duty turbine with the aim of determining the optimal geometry of honeycomb cells within a certain parameter range. First, we analyze the impact of honeycomb cell geometry on flow in the sealing gaps, including flow rotation, energy dissipation in the teeth chamber and honeycomb cell, and frictional losses. Next, we examine the heat transfer capacity between the leakage flow and the surfaces of the rotor or stator, and establish the relationship between the stream function and the average heat transfer coefficient. Third, we compare the predicted core swirl ratio, the most important aerodynamic parameter in disk cavities, with those from equations in the literature. The decrease in core swirl ratio in the upstream disk cavity indicates that the use of different honeycomb cell geometries may lead to excessive axial thrust. Finally, we study the local and average heat transfer capacities on the turbine disk and introduce a correction factor (0.12–0.21) into the correlation to make it applicable to analogous turbine disks or rotor–stator cavities in other turbo machines with low radii honeycomb labyrinth seals. Based on our findings, we provide recommendations for the optimal honeycomb cell geometries for the two sealings for different targets. These results serve as a reference for designers of honeycomb labyrinth seals for gas turbines and other turbo machines.

Real-Time Detection of Faults in Rotating Blades Using Frequency Response Function Analysis

Turbo machines develop faults in the rotating blades during operation in undesirable conditions. Such faults in the rotating blades are fatigue cracks, mechanical looseness, imbalance, misalignment, etc. Therefore, it is crucial that the blade faults should be detected and diagnosed in order to minimize the severe damage of such machines. In this paper, vibration analysis of the rotating blades is conducted using an experimental laboratory setup in order to develop a methodology to detect faults in the rotating blades. The faults considered for the study include cracks and mechanical looseness for which dynamic responses are recorded using a laser vibrometer. Analysis has been carried out by comparing the frequency response function spectrums of the fault blade with those of the healthy blade related to the resonance frequency. The Internet of Things and wireless sensor networks are implemented to transmit the measured data to the cloud platform. A support vector machine algorithm is used for preparing the learning model in order to extract and classify the faults of the rotating blades. It can be clearly seen from the results that there is variation in the frequency response function spectrums of healthy and faulty conditions of the rotating blades.

Экспериментальное исследование работоспособности газодинамического подшипника

The question of the high-speed turbo machines operability is directly related to the processes occurring in the support structures – gas sliding bearings. The most common structure of such supports is the multi-petal bearing. One of the main research directions in this area is the development of a design ensuring the reliable operation of the bearing. The durability of gas bearings depends directly on the number of start-stop cycles, which is its key difference from liquid bearings. The start-up period of the turbo machine represents the most challenging mode of operation for the petal gas dynamic bearings. A critical feature of this mode is the insufficient formation of a gas layer at low rotational speeds. The load on the working surfaces of the support is assessed as nominal, equal to the rotor's weight. If the start-up mode of the turbo machine is successfully passed, then in future, during the acceleration, it will be operational. The research of the transitional mode during the start-up requires a complex approach, including both theoretical and experimental studies. This paper is a continuation of theoretical studies for multi-petal gas dynamic bearings with overlapping petals. The key parameters ensuring the operability of such supports include the shaft ascent speed at the start-up and the value of the force acting on the support. As part of the research, an experimental installation was developed to obtain values of shaft ascent speed depending on static load force. Series of experiments included different variations of initial loads, up to the critical value. The results of the experiments provide the values of permissible static loads and a range of shaft ascent speed values. This study facilitates further parametric investigations in the mathematical modeling of processes occurring in gas dynamic bearings.

A Review on Performance Characteristics of an Air Foil Thrust Bearing

The axial loads of high-speed rotating turbo machines are supported by self-acting hydrodynamic components known as air foil thrust bearings (AFTB). The load bearing capability of these bearings depends primarily on the foil structure and secondarily on the operating conditions. The present review enlightens on the tribological performance parameters of the said bearing in enhancing the load carrying capacity. Various design and fabrication methods including theoretical models are briefly summarised and comparisons of experimental results are presented in order to reveal the possible research gap that leads in optimising the gas lubricated foil thrust bearings (GFTB) for their better employment in typical applications.

Design Studies Using Corrosive and Non-Corrosive Materials to Improve on Reliability and Efficiency of an Impeller of a Centrifugal Pump

Design Studies using Corrosive and Non-corrosive Materials to Improve on Reliability and Efficiency of an Impeller of a Centrifugal Pump N. Idris*1, 3and I. U. Umaru2 1Department of Chemical EngineeringUniversity of MaiduguriBorno State, NigeriaEmail: idrismn@unimaid.edu.ng ABSTRACT The quest to improve on the reliability, operability, sustainability of centrifugal pumps in all facets of process operations, oil and gas industries across the globe have a pivoted role to play in the development of world energy technology and sustainability in numerous ways. This is because several operability challenges and malfunctioning of centrifugal pumps can usually results to unexpected shutdown of process operations and mostly in cases with faulty standbys.Centrifugal pump is a type of a turbo machine in which mechanical energy is converted into pressure energy by means of centrifugal force acting on the fluid. The impeller is the revolving component of the centrifugal pump that transmits energy from the electric motor that drives the pump to the fluid being pumped by acceleration of the fluid outwards from the centre of rotation.Several researches have been conducted using experiment and numerical simulations to design the centrifugal pump impellers. As a result of recent research, the performance of contemporary centrifugal pump impellers yielded positive results. However, for sustainability there is a need to design the impellers using corrosive and non-corrosive materials to improve on its reliability and efficiency of the pump.The aim and objective of the studies are: to analyze the pressure, head and efficiency of the designed centrifugal pump impeller, to improve on the efficiency and reliability of a centrifugal pump impeller by changing the blade angle and the use of corrosive and non-corrosive fluids, experimental measurements to analyze the pressure fluctuation performance of a centrifugal pump impeller using CFD. Keywords: Oil and gas, centrifugal pump, reliability, sustainability Correspondence about this article: Please for all correspondence on this article, kindly contact the principal author as stated above. Thank you.

Validation of a partitioned fluid-structure interaction simulation for turbo machine rotors

ABSTRACT A partitioned solution approach for the fluid-structure interaction (FSI) simulations of turbo machine rotors is presented. The in-house developed boundary element method solver panMARE is used for the fluid simulation, while the structural side is treated with the commercial finite element method solver ANSYS. The generic in-house multiphysics coupling library comana is used for the management of the implicit coupling procedure. As the first example, the KRISO container ship propeller is considered. The simulation is validated for open water test conditions assuming a rigid propeller based on the thrust and torque coefficients. Simulation results for a flexible propeller in open water are also presented. In the second example, the validation of the FSI simulation is conducted for a multilayered flexible submersible mixer based on thrust and torque coefficients and local strains. The results show a good agreement between the simulations and the experimental data for both examples.

Balancing Technique for Turbo Machinery Rotor

Balancing process carried out in the thermal power station is very complex and complicated. The complete unit is to be cooled down for balancing this takes nearly 10 to 15 days. After cooling the unit is disassembled and the rotor is taken out for which again 10 to 15 days are required for balancing and assembly. Rotor is placed on the balancing machines for balancing which is carried out by Engineers of the testing department. Balancing of a bulky rotor is difficult and it is carried out step by step. After balancing, complete rotor is to be placed in the turbo machine which is a most difficult task as it has to match the all alignment and other conditions properly. The complete process takes period of nearly one and half month for balancing the rotor, so balancing of the rotor is called to be the costly project in the thermal power station. After the balancing procedure is completed, while starting the complete unit various parameters are to be controlled such as steam inlet temperature, pressure, flow of the steam and rpm of the unit to avoid any type of danger. Loss of production of power during the shutdown period is major loss of any power station. Paper details the automatic thermal balancing of turbo machinery rotor using heating coils.

Simulation of Micro Contact Interactions in Sliding of Solid Particles along the Radial Blades of Turbo Machines

Simulation of Micro Contact Interactions in Sliding of Solid Particles along the Radial Blades of Turbo Machines

Numerical Analysis on the Effect of J-groove on Flows in Narrow Gaps between Rotating Disk and Casing

During operation and working of turbo machines, axial thrust balancing is important. To control and balance the axial thrust, a very simple method using shallow radial grooves mounted on the casing wall, called “J-groove”, was proposed, and studied experimentally[1]. This paper presents a numerical study of the effect of J-groove on the flow in the narrow gap along enclosed rotating disks based on open-source CFD software. It is seen that the difference in pressure between the hub and shroud tip is increased with the increasing number, depth, and length of J-groove. But in the case of increasing width of J-groove, the pressure loss along the radius decreases when the ratio of the groove width to the outer radius W is less than 0.2 and increases when W greater than 0.2.

Моделирование микроконтактных взаимодействий при скольжении твердых частиц вдоль радиальных лопастей турбомашин

Моделирование микроконтактных взаимодействий при скольжении твердых частиц вдоль радиальных лопастей турбомашин

Способ расчета динамических напряжений в лопатке переменного сечения турбомашины

The problem of assessing the dynamic stresses arising from vibrations of the blades of turbo machines is an urgent and significant problem affecting the overall reliability of the turbo machine. Its solution requires a mathematical study and a physical experiment to determine the intensity of the gas flow impact and the blade reaction.However, there is relatively little information in the scientific publications on this issue. The article considers a semi-empirical method for calculating dynamic stresses at the base of a variable cross-section blade at the first tone resonant vibrations. These vibrations can be considered as the most dangerous because of the maximum amplitude. To perform the calculation a real blade was replaced with a calculated one, composed of separate portions with a constant profile, and the contribution of each part to the stress in the base section was determined. An example of calculating the dynamic stress by the proposed method with a resonant vibration of the first tone of a constant-section blade is given. The calculation showed that the solution to a complex problem can be represented as a sum of solutions to simpler problems. The calculation method can be used in the design of turbine and compressor blades.

Study of pitting corrosion under actual operating conditions of a first stage compressor blade

In this study, pitting corrosion was investigated numerically and experimentally under actual operational conditions of a gas turbine compressor. First, the samples cut from a blade made of Custom 450 stainless steel were exposed to different corrosion times in a 3.5 wt% NaCl solution. After the creation of pits in the samples, the dimensions of the corrosion pits were measured using a 3D profilometer device. The stoichiometry equations governing the corrosion of the Custom 450 alloy in a chloride solution were extracted and applied to the models. The results of this simulation were validated by comparing the depth of the simulated pits and the experimental samples. Subsequently, simulation was conducted for 48 months on a compressor having pits. There is a good agreement between the simulation results and the results obtained from the Turbo machine laboratory of the Texas A&M University. In addition, pits grew under the influence of corrosion, joined together, and made an equivalent pit.

Nonlinear vibration of rotating cylindrical shell due to unilateral contact induced tip rubbing impact: Theoretical and experimental verification

This contribution addresses on the theoretical and experimental observations of nonlinear vibration performance of the aero engine drum undergoing repeated impact between the rotor and stator vane segment. By assuming the drum as a rotating thin-wall cylindrical shell, the governing equations of motion of rotating shell under tip rubbing force have been derived in frame of Lagrange equation and verified via the experiment. A fixed point rubbing force model between the clearance of elastic drum and stator vane segment is proposed based on the linear collision force relation. Particularly, an experimental scheme of rotating shell system with unilateral contact is established to simulate the rubbing process of rotating flexible drum and rigid segment. Finally, the influence of rotating speed is investigated in detail and several interesting phenomenon have been confirmed by both analysis and experiment. Overall, the present investigation may suggest an efficient guidance for design of rotating thin-wall shell structures in aero engine and turbo machines.