Content uploaded by Christian Richter
Author content
All content in this area was uploaded by Christian Richter on Oct 17, 2017
Content may be subject to copyright.
A preview of the PDF is not available
Dem Bechernicken auf der Spur - Investigation of the bucket tilting in bucket elevators
Abstract and Figures
In der Fördertechnik stellen Becherwerke ein wichtiges Element zur Vertikalförderung von Schüttgütern dar. Aufgrund der immer größer werdenden Massenströme greift man zunehmend auf Becherwerke mit hohen Geschwindigkeiten zurück. Das dynamische Verhalten des Gesamtsystems spielt bei der Auslegung und Konstruktion neuer Förderanlagen eine funktionsentscheidende Rolle. Der Beitrag stellt eine neuartige Simulationsmethode zur Kopplung von Maschinenmodellen (Mehrkörpersimulation, MKS) mit Stoffmodellen (Diskrete Elemente Methode, DEM) vor. Anhand eines vereinfachten Mehrkörpermodells eines Becherwerkes konnte das Nicken einzelner Becher bei unterschiedlichen Gurtsteifigkeiten und Gurtge-schwindigkeiten simuliert und mit Messwerten des realen Becherwerkes verglichen werden.
In bulk material handling systems the bucket elevator represents an important element for the vertical transport of bulk materials. Due to increasing mass flow rates, the application of high speed bucket elevators is becoming more and more common. The dynamic behaviour of the entire system is an essential factor in the design and construction of such conveyors. This article presents a new simulation method for coupling machine models (multi-body simulation, MBD) with material models (discrete element method, DEM). Based on a simplified multi-body model of a bucket, the tilting of individual buckets is simulated at different belt stiffnesses and belt speeds. The simulation results are compared with experimentally measured values of a real bucket elevator.
Figures - uploaded by Christian Richter
Author content
All figure content in this area was uploaded by Christian Richter
Content may be subject to copyright.
... The latest research group has employed numerical methods to address both the design and operation of bucket elevators. Specifically, they utilized the discrete element method (DEM) to tackle discharge profiles in bucket elevator operations, recognizing its significance as a key characteristic in bulk material handling [17][18][19][20]. Their findings consistently highlight the effectiveness of DEM simulations in optimizing machine parameters for bucket elevators. ...
... Applying the response surface methodology [29] to create polynomial equations, the final predictive models for transport mass (Mpp) and mass flow rate discharge (MRpp) for polypropylene are shown in Eqs. (19) and (20), while the final predictive models for transport mass (Msb) and mass flow rate discharge (MRsb) for soybean particles are detailed in Eqs. Tables 9 and 10 further validate these findings by employing backward elimination to enhance model accuracy, achieving R-Sq (prediction) values exceeding 90%. ...
... Fig. 6a shows that the discharge profiles of polypropylene particles resemble centrifugal discharge profiles, while Fig. 6b illustrates that the discharge profiles of soybean particles resemble mixed discharge profiles. These observations align with the theoretical distance of poles related to the discharge velocity of particles as described in Eq. (20) [18,28]. By considering the discharge profiles according to the distance of poles, as shown in Fig. 6, the classification algorithm is as follows: for gravity discharge, l p ≥ r 2 ; for centrifugal discharge, l p ≤ r 1 ; and for mixed discharge, r 1 ≤ l p ≤ r 2 . ...
This research introduces a novel approach to enhancing bucket elevator design and operation through the integration of discrete element method (DEM) simulation, design of experiments (DOE), and metaheuristic optimization algorithms. Specifically, the study employs the firefly algorithm (FA), a metaheuristic optimization technique, to optimize bucket elevator parameters for maximizing transport mass and mass flow rate discharge of granular materials under specified working conditions. The experimental methodology involves several key steps: screening experiments to identify significant factors affecting bucket elevator operation, central composite design (CCD) experiments to further explore these factors, and response surface methodology (RSM) to create predictive models for transport mass and mass flow rate discharge. The FA algorithm is then applied to optimize these models, and the results are validated through simulation and empirical experiments. The study validates the optimized parameters through simulation and empirical experiments, comparing results with DEM simulation. The outcomes demonstrate the effectiveness of the FA algorithm in identifying optimal bucket parameters, showcasing less than 10% and 15% deviation for transport mass and mass flow rate discharge, respectively, between predicted and actual values. Overall, this research provides insights into the critical factors influencing bucket elevator operation and offers a systematic methodology for optimizing bucket parameters, contributing to more efficient material handling in various industrial applications.
Industrial suppliers of technologies for parcel handling in bulk mode often use the discrete element method (in short: ”DEM”) to analyse the operation and throughput of unloading equipment. In addition to analysing the material flow of the parcels, a system can be virtually commissioned by emulating the controls of the conveyor equipment. For emulation, the real-time capability of the models is relevant, which can be achieved with several physics engines available today and a comparably high time step. In comparison to the so-called ”Smooth DEM”, which has smaller time steps, the so-called ”Non-smooth DEM” is considered to represent the material flow of parcels in bulk mode less accurately. For the investigation of this hypothesis, a bulk handling test plant for the handling of 100 loads (mainly DHL Packsets ”XS” and ”S”) was designed, built and operated to compare the experimantal results with DEM simulation based on the validation criteria of mass flow, bulk profile and impact load. For the Smooth DEM simulation of this bulk handling test, the so-called ”multi-sphere approximation” was not used, because modeling the parcel surface is only possible with many particles, which lead to high CPU computing times unsuitable for industrial application. In addition, the most relevant parcel properties for bulk feeding, being friction (calibration with the inclined plane test) and – depending on the used DEM software – also rebound (calibration with the free fall test) rely on the number and size of particles in contact, impeding calibration of uniform static friction and restitution coefficients. Instead, the so-called ”superquadric approximation” was used, allowing significantly shorter CPU computing times because each parcel is modeled with only one particle at a time, whose shape is set with the so-called ”blockiness”. This parameter was analyzed in detail during the calibration of the parameters of the DEM contact model in order to find the best compromise between shape approximation and CPU computing time. The hypothesis that the Smooth DEM can predict the mass flow of parcels in bulk mode more accurately than the Non-smooth DEM was verified by comparing Smooth DEM and Non-smooth DEM simulation of the bulk handling test with the experimental results. The shock resulting on a sensor box made of Plexiglas® and equipped with a data logger could be simulated by calibrating the elastic moduli of particles and contact surfaces within the standard deviation of the experimental impact with the Smooth DEM being based on a soft particle approach. These observations were made with the superquadrics’ blockiness value of n = 5, which was the result of calibrating the parameters of the DEM contact model. With this relatively low blockiness, the 30-second bulk handling test could be simulated in about five hours, while the less accurate simulation result of the Non-smooth DEM is produced in real time. This work is valuable for users who want to simulate the handling of parcels in bulk mode not only quickly but also accurately.
Der Schöpfwiderstand ist bei der Schüttgutförderung mit Becherwerken neben dem Hubwiderstand des Schüttguts eine für den Energiebedarf der Gesamtanlage entscheidende Größe. Der Schöpfwiderstand wird von der Becherform und Becherteilung, der Beschickungsart, der Zugmittelgeschwindigkeit sowie der Kohäsivität des Schüttguts beeinflusst. Eine Ursache für die Abhängigkeit des Schöpfwiderstandes von der Zugmittelgeschwindigkeit und der Kohäsivität des Schüttgutes liegt im Effekt des sogenannten Bechernickens. Als Bechernicken wird die Drehbewegung der Becher um ihren Befestigungspunkt am Zugmittel definiert. Das Bechernicken tritt beim Übergang der Becher von der kreisförmigen in die geradlinige Bewegung aufgrund der ruckartigen Verringerung der Becheraußenkantengeschwindigkeit auf. Bei hohen Becherfüllungsgraden kann aufgrund dessen bereits gefördertes Gut aus dem Becher geschleudert werden. Zum Erreichen des notwendigen Massenstroms muss mehr Gut geschöpft und gehoben werden. Dies hat einen schlechteren Wirkungsgrad der Förderanlage zur Folge. Eine weitere Einflussgröße auf die Effektivität des Fördervorgangs schnelllaufender Becherwerke ist das laterale Schwingen der Becher im freien Becherstrang. Beim Auflaufen der Becher auf die Umlenktrommeln erfahren die Becher und das Schüttgut aufgrund dynamischer Kräfte eine theoretisch unendlich große Beschleunigung auf die Bahnkurve der Antriebs- bzw. Spanntrommel. Dies ist jedoch physikalisch unmöglich. Der Becher führt daher zunächst eine Drehbewegung entgegen der Bahnkurve durch, um anschließend auf den Umlenkradius der Trommel einzuschwenken. Dieses Pendeln der Becher überträgt sich im nachfolgenden Becherstrang in Form einer gedämpften Schwingung. Bereits gefördertes Gut kann bei hohen Becherfüllungsgraden aus den Bechern in Richtung des Becherwerkfußes zurückfallen. Dieses Gut muss anschließend erneut geschöpft und gehoben werden. Weiterhin wird die Becher- Gurt-Verbindung, der Becherrücken und der Gurt durch die Biegewechsel belastet. Zur Analyse des Bewegungsverhaltens schnelllaufender Becherwerke wird in dieser Arbeit eine Simulationsmethode zur Berechnung des Bewegungsverhaltens von Maschinenmodellen im Kontakt mit Schüttgütern implementiert. Dabei werden die bekannten Methoden der Diskrete Elemente (DEM) Simulation und der Mehrkörpersimulation (MKS) auf Programmebene gekoppelt. Die Simulationsergebnisse der gekoppelten DEM-MK-Simulation werden anhand eines analytisch lösbaren Beispiels verifiziert. Zum Nachweis, dass die entwickelte Methode geeignet ist, das Bewegungsverhalten realer Förderanlagen und Maschinen im Kontakt mit Schüttgut abzubilden, wird ein vereinfachtes Mehrkörpersimulationsmodell des Versuchsbecherwerkes verwendet. Die Simulationsergebnisse des vereinfachten Versuchsstandes werden mit den experimentell ermittelten Ergebnissen verglichen. Die gekoppelte DEM-MK-Simulationsmethode wird in dieser Arbeit zur Ermittlung des Schöpfwiderstandes und der Schöpfarbeit eines Senkrechtbecherwerkes angewendet. Es wird der Einfluss der Beschickungsrichtung und der Kohäsivität des Schüttguts analysiert. Der Einfluss der Bechernickens auf das Entleerungsverhalten des Versuchsbecherwerkes wird für unterschiedliche Vorspannungen experimentell untersucht und den Simulationsergebnissen gekoppelter DEM-MK-Simulationen gegenüber gestellt. Abschließend wird die Methode der gekoppelten DEM-MK-Simulation für die Entwicklung einer neuen Umlenkgeometrie am Becherwerkfuß angewendet, welche den negativen Einfluss des Bechernickens auf den Schöpfwiderstand reduzieren kann.
Mistracking of the conveyor belt is one of the crucial operating problems of a belt conveyor. Reasons and counter-actions are known, however, the cause of mistracking and the effect on the belt can only be predicted based on empirical experience. A satisfying simulation method did not exist so far, because of the huge size of a belt conveyor and its nonlinear deformation with a high number of contact problems. This paper will give a short overview about the main causes and the possible counter-actions of belt mistracking. Furthermore a simplified mathematical approach will be presented for the numerical simulation of the belt's sideways movement. This approach is validated with measurements on a flat belt test rig. Therefore, a test system was developed, which allows the definition of a mistracking factor caused by one skewed idler. The validated model was extended for the simulation of a troughed belt conveyor. With this simulation a prediction could be given about the type, number and the position of the possible skewed idlers to reduce the mistracking of the belt.
The numerical effort of DEM simulations forces generally an idealisation of DEM models which makes the calibration process the key for realistic simulation results. The angle of repose test has become a standard test for the calibration of DEM parameters which is extensively discussed in literature. Different methods of the determination of the angle of repose test are described. One of the most used test method - especially for non-cohesive material - is the pull-up test of a cylinder which is filled with bulk material. If industrial problems should be analysed with DEM, the idealisation often includes the scale-up of the particle sizes. To neglect problems like arching, the size of the pull-up cylinder also needs to be scaled. The paper will present results of extensive experimental tests and simulations which show how this scale-up of particles and test rig influences the resulting angle of repose. It will be explained how the scale-up will influence the selection of the most important DEM parameters such as particle-particle friction and rolling friction. Furthermore, it will be shown how the basic pull-up test can also be used for the characterisation of cohesive materials.
Bucket elevators outwardly appear to be simple devices. However having a bucket bolted to a flexible belt creates difficulties at the interface of the belt, bucket and head pulley. At the point where a bucket's connection line becomes tangent to the pulley, the tip of the bucket must undergo a very rapid acceleration phase; theoretically infinite. In reality, as the point of tangency is reached, the tip of the bucket lags behind its theoretical position before accelerating and overshooting its nominally correct position. The motion of an empty bucket is a decaying damped oscillation. When the bucket is transporting bulk material then more complex motion occurs. This paper presents preliminary results of an investigation utilising Discrete Element modelling tools to better understand the impact of the transition point on the discharge pattern from the bucket. We anticipate that this will lead to a better understanding of structural fatigue of the belt carcass and provide a better understanding of the interacting mechanisms at work in bucket elevator systems.
Einsatz der Diskrete Elemente Methode in der Schüttguttechnik: Becher-und Kratzerförderer
- A Katterfeld
- T Gröger
[KAT07] Katterfeld, A.; Gröger, T.: Einsatz der Diskrete
Elemente Methode in der Schüttguttechnik:
Becher-und Kratzerförderer, In: Schüttgut.-:
Vogel Trans Tech Publications, Bd. 13.2007, 4
André Katterfeld, Lehrstuhlleiter Fördertechnik an der Otto-von-Guericke
- Univ.-Prof
- Dr
- Ing
Univ.-Prof. Dr.-Ing. André Katterfeld, Lehrstuhlleiter
Fördertechnik an der Otto-von-Guericke-Universität
Magdeburg.
Wissenschaftlicher Mitarbeiter am Lehrstuhl Fördertechnik an der Otto-von-Guericke
- .-Ing. Christian Dipl
- Richter
Dipl.-Ing. Christian Richter, Wissenschaftlicher
Mitarbeiter am Lehrstuhl Fördertechnik an der Otto-von-Guericke-Universität Magdeburg.
Wissenschaftlicher Mitarbeiter am Lehrstuhl Fördertechnik an der Otto-von-Guericke
- M Sc
- Thomas Rößler
M. Sc. Thomas Rößler, Wissenschaftlicher Mitarbeiter
am Lehrstuhl Fördertechnik an der Otto-von-Guericke-Universität Magdeburg.