Wide Range Of Rotational Speeds Research Articles

Numerical Simulation and Computational Flow Characterization Analyses of Centrifugal Pump Operating as Turbine

Using a pump in reverse mode as a hydraulic turbine remains an alternative for hydropower generation in meeting energy needs, especially for the provision of electricity to remote and rural settlements. The primary challenge with small hydroelectric systems is attributed to the high price of smaller size hydraulic turbines. A specific commercial pump model, with a flow rate of 12.5 m3/h, head 32 m, pressure side diameter of 50 mm, impeller out, and inlet diameters of 160 mm and 6 mm, respectively, was chosen for this research. This research aimed to investigate a pump’s flow characteristics as a turbine to help select a suitable pump to be used as a turbine for micro- or small hydropower construction. Numerical methodologies have been adopted to contribute to the thoughtful knowledge of pressure and velocity distribution in the pump turbine performance. In this study, the unsteady flow relations amongst the rotating impeller and stationary volute of the centrifugal pump made up four blades and four splitters. Intermittent simulation results of pressure and velocity flow characteristics were studied considering diverse impeller suction angles. The study was conducted by considering a wide range of rotational speeds starting from 750 rpm to 3250 rpm. From the results, it was found that PAT operation was improved when operated at low speeds compared to high-speed operation. Thus, speeds between 1500 rpm and 2000 rpm were suitable for PAT performance. This research helps to realize the unsteady flow physiognomies, which provide information for future research on PAT. This study makes useful facts available which could be helpful for the pump turbine development. Future studies should focus on cost analysis and emission generation in energy generation.

Compensating the performance of permanent magnet synchronous machines for fully electric vehicle using LPV control

The state-of-the-art robust H∞ linear parameter-varying controller is designed for wide speed operating range for non-linear mathematical model of permanent magnet synchronous machines (PMSM) in d-q reference frame for fully electric vehicle. This study propose polytopic approach using rotor speed as scheduling variable to reformulate mathematical model of PMSM into linear parameter varying (LPV) form. The weights were optimized for sensitivity and complementary sensitivity function. The simulation results illustrate fast tracking and enhanced performance of the proposed control technique over wide range of rotor speed. Moreover, as part of this work, the results of H∞ linear parameter varying controller is validated by comparing it with linear quadratic integrator and proportional integral derivative (PID) control techniques to show the effectiveness of the proposed control technique.

Silencer for high-frequency turbocharger compressor noise via an acoustic straightener

Decades of successful research and development on automotive silencers for engine breathing systems have brought about significant reductions in emitted engine noise. A majority of this research has pursued airborne noise at relatively low frequencies, which typically involve plane wave propagation. However, with the increasing demand for downsized turbocharged engines in passenger cars, high-frequency compressor noise has become a challenge in engine induction systems. Elevated frequencies promote multi-dimensional wave propagation rendering at times conventional silencer treatments ineffective due to the underlying assumption of one-dimensional wave propagation in their design. The present work focuses on developing a high-frequency silencer that targets tonal noise at the blade-pass frequency within the compressor inlet duct for a wide range of rotational speeds. The approach features a novel "acoustic straightener" that creates exclusive plane wave propagation near the silencing elements. An analytical treatment is combined with a three-dimensional acoustic finite element method to guide the early design process. The effects of mean flow and nonlinearities on acoustics are then captured by three-dimensional computational fluid dynamics simulations. The configuration developed by the current computational effort will set the stage for further refinement through future experiments.

Численное исследование течения в проточной части центробежного нагнетателя природного газа при различных положениях входного направляющего аппарата

The paper focuses on the problem of a possible expansion of the range of operating modes of a centrifugal natural gas compressor due to the rotation of the inlet guide vanes at different rotor speeds. The geometry of the flow path of the investigated object, obtained by three-dimensional scanning, is presented. On its basis, a numerical model is built and the influence of various factors of the formulation of the computational problem on the results of modeling the gas flow in the flow path of the compressor is analyzed. The calculations were performed using the k--ε and SST turbulence models for various parameters of the computational grid and conditions for averaging the flow parameters between the computational domains. The results obtained were compared with the nameplate and operational data. Recommendations on the formulation of the modeling problem are proposed, the results of the calculations are described, and the characteristics of the centrifugal compressor are plotted at different angles of the inlet guide vanes in a wide range of rotor speeds. The possible range of expansion of the operating modes of the investigated compressor is described, which can be provided by varying the position of the inlet guide vane

New FORTRAN meanline code for investigating the volute to rotor interspace effect on mixed flow turbine performance

Mixed flow turbines are widely used in several industrial applications covering turbomachinery, automotive engineering and electricity production. For decades, it is well known that mixed flow turbines are a seat of several loss phenomena such as the volute to rotor interspace loss, subject of this paper. Commonly, the meanline approach is the first step solution for building a preliminary design of such turbines and estimating subsequent losses. The accuracy of the code used in the meanline modeling is crucial for building an optimized turbine design with a minimized loss generation. This paper presents an improved validated meanline code, written in the newest object-oriented version of the FORTRAN language, for turbomachinery performance prediction. Unlike commercially available codes, the code allows the calculation of the rotor passage loss coefficient given the turbine expansion ratio without the need for additional test data. The standard deviation value between the code and test data is less than 10%, for all studied cases which ensure the validity of the developed model. Then, the developed code is exploited to investigate the effect of the volute to rotor interspace geometry on the loss generation and performance of a mixed flow turbine. Indeed, a performance distribution over a wide range of rotational speed and an energy loss breakdown are depicted and discussed showing a significant impact of the volute to rotor interspace. The results revealed an improvement in the turbine efficiency up to 2.9% with a volute to rotor interspace radii ratio of 0.59 at 80% of the design speed.

Magnetic Elastomer Sensor for Dynamic Torque and Speed Measurements

In this paper is proposed a dynamic torque, rotational speed, and shaft position sensor. It is built of magnetic elastomer coating directly applied over a rotating shaft. The sensor is used for precise measurements of changes in torque and speed, and it is usable at high rotational speeds, directly on the device shaft. The sensor is based on magnetic elastomer material deformation and the corresponding change in magnetic field amplitude and direction. The proposed sensor design is simple and can acquire reliable readings for a wide range of rotational speeds. Sensor design consists of the following: magnetic elastomer coating with nanoparticles, in which, elastomer is used for a sensing convertor; magneto-resistive linear field sensor; and microprocessor unit for calibration and control. Numerical and experimental test results are demonstrated and analyzed. Sensor implementation aims to meet magnetic mechatronic systems’ specific requirements.

Vibration of Rotating and Revolving Planet Rings with Discrete and Partially Distributed Stiffnesses

Vibration properties of high-speed rotating and revolving planet rings with discrete and partially distributed stiffnesses were studied. The governing equations were obtained by Hamilton’s principle based on a rotating frame on the ring. The governing equations were cast in matrix differential operators and discretized, using Galerkin’s method. The eigenvalue problem was dealt with state space matrix, and the natural frequencies and vibration modes were computed in a wide range of rotation speed. The properties of natural frequencies and vibration modes with rotation speed were studied for free planet rings and planet rings with discrete and partially distributed stiffnesses. The influences of several parameters on the vibration properties of planet rings were also investigated. Finally, the forced responses of planet rings resulted from the excitation of rotating and revolving movement were studied. The results show that the revolving movement not only affects the free vibration of planet rings but results in excitation to the rings. Partially distributed stiffness changes the vibration modes heavily compared to the free planet ring. Each vibration mode comprises several nodal diameter components instead of a single component for a free planet ring. The distribution area and the number of partially distributed stiffnesses mainly affect the high-order frequencies. The forced responses caused by revolving movement are nonlinear and vary with a quasi-period of rotating speed, and the responses in the regions supported by partially distributed stiffnesses are suppressed.

Modeling of rotating machinery: A novel frequency sweep system identification approach

In this study, the dynamic modeling of rotating machinery, which is a harmonic excitation system, is investigated based on a nonlinear autoregressive (NARX) model with external inputs. Generally, NARX model-based techniques require Gaussian (white) noise, and thus these methods are not suitable for rotating machinery. Although there have been some reports on the modeling of harmonic excitation systems, the existing methods cannot establish a single-input single-output (SISO) NARX model to represent the rotating machinery over a wide range of rotational speeds. An improved modeling method called the frequency sweep system identification approach is proposed in this study to solve this issue. A discrete-time Fourier transform (DTFT) is performed on the system input and output datasets over a wide speed range to obtain the resulting spectra, and the amplitudes corresponding to the rotational frequencies are extracted and spliced together to convert multiple time-domain signals into one input data set and one output data set composed of frequency-domain data. Then, the modeling process can be carried out using the orthogonal forward search algorithm. Moreover, the effect of the data sequence on the identification results is discussed theoretically. A key feature of the proposed method is that the model structure detection and coefficient calculation are conducted with spliced frequency-domain vectors. The feasibility of the proposed modeling approach is validated through numerical and experimental cases. This work is a supplement to existing modeling methods based on the NARX model and provides a modeling basis for the analysis and design of rotating machinery in combination with the NARX model.

Experimental research on tribological characteristics of TiAlN coated valve plate in electro-hydrostatic actuator pumps

Moving towards high power density, high dynamic responsibility, and high reliability, the electro-hydrostatic actuators (EHA) have put forward great demand on the piston pumps. As a typical pump control system, EHA pumps need to maintain high efficiency in a wide range of rotational speed and pressure to implement the function of position servo. High speed and wide speed range bring great challenge to the cylinder block/valve plate interface, which has to fulfill simultaneously a bearing and sealing function. Cermet coatings are beneficial to improve the friction and wear performance of the sliding surfaces. In this study, a dedicated frictional test apparatus of cylinder block/valve plate interface has been built which could accurately simulate the working conditions of EHA pumps in a wide operational condition. Equations of the friction coefficient are established based on the combination of experiments and friction theory. When pairing with the tin-bronze cylinder block, friction coefficients of TiAlN coated and nitrided valve plate are calculated by these equations. Additionally, the wear status of these two friction pairs are evaluated by a 3D measuring laser microscope. In the wide speed range of 500–10000 rpm, the decrease percentage of friction coefficient and the wear rate for TiAlN coated valve plate are 52.55%–64.9% and 12–14% of the nitrided one, respectively.

A new dynamic model for a rotating beam carrying extra partially distributed mass

In this paper, a new dynamic model for the vibration analysis of an inwardoriented rotating cantilever beam with extra distributed mass was presented. The derived differential equation of motion was solved using the meshless methods of generalizedMultiquadric Radial Basis Function (RBF) and the eigenfrequencies of the system were determined. The same problem was also modeled using the finite element method and the results were compared to validate the accuracy of the proposed model. Later, the effect of the partially distributed mass amount and location on the eigenfrequencies was studied for various beam lengths. The results showed that the eigenfrequency at a constant rotational speed mostly decreased unless the mass was located at the free end of the beam. The location of the mass had a greater effect on the first eigenfrequency compared to the second and third eigenfrequencies. A joint dimensionless eigenfrequency was found at a specific rotational speed regardless of the distributed mass. Nearly constant dimensionless eigenfrequencies could be obtained for a wide range of rotational speeds by adjusting the distributed mass.

Fault detection and diagnostic method of diesel engine by combining rule-based algorithm and BNs/BPNNs

The stable operation of diesel engine is critical to the normal production of the industry, and the prevention, monitoring, and identification of faults are of great significance. At present, the fault research on diesel engines still has some defects, such as only few types of faults diagnosis are identified, the accuracy of fault diagnosis is still low, and fault identification is located at a fixed speed. A novel fault detection and diagnostic method of diesel engine by combining rule-based algorithm and Bayesian networks (BNs) or Back Propagation neural networks (BPNNs) is proposed. The signals are processed by wavelet threshold denoising and ensemble empirical mode decomposition. The signal-sensitive feature values are extracted from the decomposed intrinsic mode function. Seven faults are roughly identified using rule-based algorithm and finely identified using BNs or BPNNs. Results show the proposed fault diagnosis method has a good diagnostic performance for a wide range of rotation speeds when the training data for BNs and BPNNs are from fixed speeds. In addition, the influences of the layers of decomposed signals, sensor noise and external excitation interference on the fault diagnostic performance are also researched.

Experimental characterisation of asynchronous partially contacting motion in a multiple-degree-of-freedom rotor system

Recent theory has predicted the onset of asynchronous bouncing motion at speeds beyond those of internal resonance in multi-degree-of-freedom rotating systems with intermittent contact. This paper provides the first attempt to experimentally validate the theory. Vibrations incorporating rotor-stator contact are recorded from a vertically ounted rotordynamics test rig comprising two rigid shaft-disk assemblies that are axially joined by a bellows coupling. The upper rotor has an elastic bearing whereas the lower one is free but has a snubber ring located on its lower shaft, with clearance about 2.5% of the entire system’s length. Nonlinear vibrations are excited by a small measured eccentricity of about 20% of the clearance. Measurements are taken by a wireless accelerometer and processed to produce an experimental bifurcation diagram, for small steps in the rotor speed, allowing the transients to decay. Evidence is found of bistability between quiescent and violent motion over a wide range of rotational speeds, including those representing both fundamental and internal resonances. The results are shown to qualitatively match numerical simulations from a differential equation model that incorporates rigid impacts.

Approaching the Ideal BLDC Motor: A Novel Electronic Speed Controller System for a Generator-Converted BLDC Motor with Field Weakening Feature

The concept of an ideal Brushless DC (BLDC) motor which has adjustable rotor magnetic field offers an opportunity for wider BLDC area of implementation as a very versatile electric powerhouse especially in variable load areas such as on electric vehicle or other people movers. Characterized by its high-efficiency level, low maintenance and long service duration, the lack of physical commutation brush like in regular DC motor dictates the requirement of an electronic control system to regulates its commutation.
 
 An electronic control system equipped with rotor field control capability in a collaboration with an ideal BLDC motor, is believed to offers wider implementation opportunity. Unlike a normal BLDC motor which has a standard power curved characterized with maximum power is only achievable in one specific speed, if properly controlled will have an adjustable maximum power in a wide range of rotational speed. 
 
 This study proposes a novel approach to an ideal BLDC implementation through novel electronic speed controller with rotor field control in addition to normal standard motor power control. As there is no such thing as an ideal BLDC motor at the current moment, an automotive generator which has an electromagnetic rotor is converted to become a BLDC motor as an effort to approach the ideal BLDC motor concept. Field weakening, the term used for adjusting rotor magnetic field in induction motor control, is adopted as the term for adjusting the BLDC rotor field in operation. Further, a novel an electronic control system is developed which special features to also control the rotor magnetic field.
 
 The converted generator has been found to able to function like an ideal BLDC motor, by adjusting the electromagnetic rotor in its operation. It has been found to be able to provides maximum motor power within a wide range of rotational speed. Through rotor field adjustment, the converted generator provides a real-time versatile capability of allocating its power to either the high torque at low motor speed or to a very high speed at minimum torque. 39% to 81% operational efficiency levels have been achieved during the experiment, rendering the performance level of the converted generator and controller way above brushed DC motor and in par with most of standard BLDC motor.
 
 The Field Weakening control has also been found to be useable for speed control. Further, a Proportional – Integral close-loop speed regulation has also been developed for both motor and rotor control and was found to be able to works subsequently with seamless transition between each other.

Immersion and Invariance Manifold Adaptive Control of the DC-Link Voltage in Flywheel Energy Storage System Discharge

In order to keep constant DC-link voltage of a flywheel energy storage system (FESS) discharge in a wide rotational speed range, the control structure of the FESS is comprised of an inner current loop and an outer DC-link voltage loop. Since the dynamic equation of the DC-link voltage in the FESS discharge is nonlinear, it is difficult for some controllers to make the DC-link voltage in discharge be constant as the rotational speed is varying in a large range. Considering the nonlinearity of the DC-link voltage in discharge and the fast discharge requirements of the FESS, an immersion and invariance manifold (I&IM) adaptive nonlinear controller for a constant DC-link voltage is proposed via methodology of immersed in the invariant manifold. The stability of the control algorithm and the influence of the parameter error on the stability are verified by the Lyapunov stability theory, and the influence of the parameters error on the steady state and transient characteristics of the closed-loop system is analyzed numerically. It is proved that the closed-loop system satisfies the global uniform asymptotic stability conditions at the equilibrium point, and the error of the model parameters does not affect the equilibrium point of the system. Finally, the effectiveness of the I&IM adaptive nonlinear controller were studied by simulation and experiment. The results show that the DC-link voltage in discharge remains stable when switching the system load in cases of different rotational speeds and loads.

A tri-stable energy harvester in rotational motion: Modeling, theoretical analyses and experiments

This paper originally investigates the performance of a tri-stable piezoelectric energy harvester (TPEH) in rotational motion, aiming to solve the challenging issue of power supply for wireless sensors. Based on the Lagrange equation, the related theoretical model with the consideration of the effect of rotational motion is originally derived to describe its dynamic response and energy harvesting performance. In addition, the perturbation method is used to theoretically describe the TPEH for the oscillations around both non-zero and zero stable equilibrium positions. The numerical simulations and case studies are carried out to investigate the influence of the Kc coefficient on the dynamic response of the TPEH. More importantly, the corresponding experiments under different constant rotational speeds are performed to validate the energy harvesting enhancement of the presented TPEH and the accuracy of its theoretical model. It is experimentally verified that the TPEH can efficiently harvest energy in the wide rotational speed range (240–440 rpm), and the proposed theoretical model is suitable for the TPEH. Overall, the energy harvesting enhancement of the TPEH in rotational motion are verified, and the accuracy of the presented theoretical model is also experimentally validated.

Results of bench tests of hydraulic dynamometer of type CFT-9.0 manufactured by Fuchino Co Ltd

Topical issues of creating test benches for power drive units are considered. The results of testing a hydraulic dynamometer with the aim of clarifying its characteristics are presented. When creating test benches, it is important to choose the right power damping system with its accurate measurement. For these purposes hydraulic dynamometers (HD) are used. The domestic industry has not yet mass-produced them, experimental development is underway. In this regard, it seems appropriate to use imported diesel engines, for example, Japanese-made, of type CFT-9.0 manufactured by Fuchino Co Ltd. This equipment has a commercial preference over other foreign manufacturers. This article discusses the principle of HD operation, its design features, the identified shortcomings and ways to address them, the results of tests of the gas engine on a special bench of JSC «NPO CKTI».The tests carried out made it possible to verify the operability of the acquired HD, to determine the dependence of the HD power on the rotation frequency, the dependence of the cooling water flow rate on the HD power and the dependence of the HD power on the steam flow rate to the steam turbine drive.The results obtained indicate that the HD of type CFT-9.0 manufactured by «Fuchino Co Ltd» can be recommended as a hydrodynamic power absorber with its high-precision measurement in a wide range of rotation speed, modes and power consumption up to 8.5 MW.

Synchronous Adaptive Resolver-to-Digital Converter for FPGA-Based High-Performance Control Loops

This paper deals with a gain scheduling synchronous demodulation scheme useful to obtain speed and position measurements from resolver position sensors. The proposed algorithm is devoted to a field-programmable gate array implementation in order to provide the elaborated information for very low latency control loops. The presented design allows getting accurate estimations in a wide range of rotational speeds without requiring costly off-the-shelf integrated circuits and leads to higher accuracy at low speed if compared to commercial solutions. To this purpose, the resolver excitation circuit has been simplified working directly with a square wave signal, and the resolver frequency behavior due to the nonsinusoidal excitation has been considered.

Magnetically Actuated Piezoelectric-Based Rotational Energy Harvester With Enhanced Output in Wide Range of Rotating Speeds

This paper reports the design, fabrication, and performance of a novel rotational energy harvester, utilizing multiple magnetic actuators and piezoelectric beams for the maximum performance in a wide range of rotational speeds. The harvester can be used in different rotational applications with low or high rotational speed and produce high output. Thin lead–zirconium–titanate (PZT) piezoelectric beams were fixed on the axis of a nonmoving wheel. One end of the beams was fixed to the center axis of the stationary wheel, while the other end hung free. Small magnets were bonded on each of the piezoelectric beams’ free ends and on a concentric wheel, fixed to a working shaft. As the working shaft drove the dynamic wheel, the magnets on the moving surface attracted the magnets on the piezoelectric beams, causing the beams to be plucked into vibration as the magnets passed by one another. The device was tested at six different rotational speeds from 180 to 500 r/min, with two different layouts, single and double plucking magnets. There will be potentials to increase up to six plucking magnets and four piezoelectric beams in this design for an increased performance. Voltage output versus time graphs were analyzed for each speed and setup. It was determined that increasing the number of plucking magnets and rotational speed was the most effective ways to increase the beam vibration and maximize the energy harvester’s performance. This is the most effective approach to increase the performance of the energy harvester in the applications that require lower speeds. The least effective case was the low speed, single magnet design, where the beam vibrated little and approximately half of the energy harvester’s time was idle time, minimizing the power harvested.

Annihilation of non-stationary vibration of a gas turbine rotor system under rub-impact effect using a nonlinear absorber

In this study, the effects of a smooth nonlinear energy sink (NES) on a continuously rotating system is investigated by considering its non-stationary motion and rub in disks positions. This rotary system is modeled based on a gas generation (GG) section of an industrial gas turbine. The contact between the rotor and stator is considered to be elastic with Coulomb-type frictional forces. It is considered that the NES's damping and stiffness are linear and cubic, respectively. The shaft is modeled using Rayleigh beam theory and the extended Hamilton principle is employed to obtain the equations of motion. In order to fully model the dynamics of the system, in the Galerkin method, the first three bending modes of the system are used. The genetic algorithm is used to obtain the optimized parameters of the NES and minimize the Root Mean Square (RMS) near to operating speed and the peak amplitudes of the rotor vibrations in the working range. It is demonstrated that the NES can considerably decrease the vibration level and possibility of rub phenomenon in the non-stationary motion of rotating system within a wide range of rotational speed and also can make the motion of the system smoother.

Selection of the oil-free bearing system for a 30 kW ORC microturbine

The article discusses results of the analyses of various bearing systems for the rotor of an ORC (Organic Rankine Cycle) microturbine with an electric power of 30 kW. It is impossible to choose the appropriate bearing system taking into account only basic parameters of the bearings. When designing a new power turbine, it is important to conduct the dynamic and strength analysis of the entire rotor-bearings-supporting structure system. The nominal rotational speed of the newly designed single-stage axial-flow turbine is 40,000 rpm. The turbine will be powered using the vapour of a low-boiling working medium. The chosen working medium cannot be used in combination with all materials that are commonly used for turbine constructions. An additional requirement was that the turbogenerator must be oil-free. The temperature of the working medium directed to the rotor blades could exceed a value of 200 °C. Three bearing systems were considered: bearings lubricated with a low-boiling fluid (in the liquid form), gas bearings lubricated with the vapour of a low-boiling medium and rolling bearings. Since the rotors used in those three systems have different geometries, their dynamic properties vary as well. The rotor dynamics analyses were carried out using computer programs belonging to the MESWIR environment, which had been developed at the Institute of Fluid-Flow Machinery of the Polish Academy of Sciences (IMP PAN) in Gdańsk. The computational model, based on the finite element method, was used to prepare graphs on which are presented vibration amplitudes as functions of the rotational speed. The computational model, based on the finite element method, served to perform calculations on the basis of which graphs presenting vibration amplitudes as functions of the rotational speed were prepared. Moreover, vibration trajectories of individual nodes of the computational model were shown. Besides analyses of the bearings themselves, calculations were also carried out to assess the dynamic properties of the rotors supported by those bearings in a wide range of rotational speeds. As a result of the conducted analyses, the concept of an innovative turbogenerator was created. Its rotor can operate at a very high rotational speed, and the bearings do not require oil lubrication.