Lobe Pumps Research Articles

An experimental and numerical study of a three-lobe pump for pumped hydro storage applications

Pumped hydro storage (PHS) plays an important role as a matured technology that accounts for the vast majority of global energy storage capacity, and its expansion is therefore desirable. The expansion of PHS in mid- and high-water heads is limited to topographic features, but there is an untapped potential in low-head applications. For most of the PHS applications, a Francis reversible pump-turbine (RPT) is regarded as the most common and cost-effective machine, but it is not a suitable option for water heads of less than 30m. In its place, positive displacement machines like lobe pumps could potentially work as RPT machines and unleash new possibilities for low-head pumped hydroelectric storage. In addition, unlike bladed pump-turbines, lobe pumps-turbines present a fish friendliness design, an important attribute to preserve the aquatic wildlife. This work will therefore present a three-lobe pump that could potentially be used in low-head PHS. An experimental model for a lobe machine will be presented, and its results will be used to validate the computational fluid dynamic simulations. Numerical investigations will address the characteristic curves regarding water-head, rotation speed and flow rate.

Влияние вязкости жидких пищевых продуктов на производительность кулачковых насосов (на примере перекачивания рыбного жира)

Lobe pumps do not damage the structure of a highly viscous substance. Therefore, the lobe pumps are increasingly used for pumping the liquid food products, despite the high cost. For selecting the rotary lobe pumps, the dependences of the productivity on the pressure drop are necessary. Some manufacturers of the lobe pumps post online the dependences of these characteristics on the rotor speed. There is considered a method developed for calculating the performance diagrams of lobe pumps (Q–P) subject to the influence of the viscosity of pumped liquid food products based on the results of the tests. For example, the characteristics of WEB RF-024, Pomac PLP 1-1.5 when pumping fish oil are considered. The analysis of the test results showed the need to take into account in the calculations the minimum speed 
 of rotation of the rotor n0, at which pumping of the liquid begins. It is stated that the minimum rotational speed n0 is 
 a nonlinear function of pressure drop. The volume of liquid pumped in one revolution does not depend on the pressure drop. The volume of liquid with high viscosity pumped in one revolution does not depend on the pressure drop. An in-crease in the temperature of fish oil leads to a decrease in the performance of the lobe pump.

Evaluating shear in perfusion rotary lobe pump using nanoparticle aggregates and computational fluid dynamics.

Perfusion cell culture technology has gained a lot of interest in recent years in the biopharmaceutical industry. One common application is N-1 perfusion which is used to intensify fed batch production processes and increase facility output. Upon running our perfusion process for the first time at manufacturing scale, unexpected cell damage was observed. Reducing the recirculation pump speed resulted in improvements in cell viability which implied the impact of pump shear stress on cell viability. In this study, we used polymethyl methacrylate (PMMA) nanoparticles to determine the shear stress inside two different sized rotary lobe pumps used in N-1 perfusion. The results were used to validate a computational fluid dynamics (CFD) model to predict the maximum shear under different operating conditions of the pump. The CFD model identified the radial and mesh clearance zones as regions that experience the maximum shear stress inside the pump. The model was then used to evaluate the impact of different geometry modifications in the pump lobes, and it predicted a 17% reduction in the maximum shear stress by increasing the mesh and radial clearances by 0.08mm and 0.13mm, respectively. The study indicates that CFD can be a useful tool to predict shear stress inside rotary pumps. The results can be used to optimize the pump operating conditions or even customize the pump geometry to save time and cost of process scaling to manufacturing without compromising the preset operating conditions or critical scale-up parameters.

Verder expands in South Korea with pump company acquisition

The Verder Group has bought JEC Ltd, a South Korean manufacturer of hygienic rotary lobe, centrifugal and twin-screw pumps and blending systems.

CFD simulation of a screw compressor including leakage flows and rotor heating

Computational Fluid Dynamics (CFD) simulations have promising potential to become an important part in the development process of positive displacement (PD) machines. CFD delivers deep insights into the flow and thermodynamic behaviour of PD machines. However, the numerical simulation of such machines is more complex compared to dynamic pumps like turbines or fans. The fluid transport in size-changing chambers with very small clearances between the rotors, and between rotors and casing, demands complex meshes that change with each time step. Additionally, the losses due to leakage flows and the heat transfer to the rotors need high-quality meshes so that automatic remeshing is almost impossible.In this paper, setup steps and results for the simulation of a dry screw compressor are shown. The rotating parts are meshed with TwinMesh, a special hexahedral meshing program for gear pumps, gerotors, lobe pumps and screw compressors. In particular, these meshes include axial and radial clearances between housing and rotors, and beside the fluid volume the rotor solids are also meshed.The CFD simulation accounts for gas flow with compressibility and turbulence effects, heat transfer between gas and rotors, and leakage flows through the clearances. We show time- resolved results for torques, forces, interlobe pressure, mass flow, and heat flow between gas and rotors, as well as time- and space-resolved results for pressure, velocity, temperature etc. for different discharge ports and working points of the screw compressor. These results are also used as thermal loads for deformation simulations of the rotors.

A new curve for application to the rotor profile of rotary lobe pumps

This paper proposes a new type of curve, an elliptical roulette, which it initially applies to rotary lobe pumps. Once the new rotor profile has been mathematically modeled using the principle of gearing, equations can be derived to assess the presence or absence of undercutting in the tooth profile. The effect of the new profile properties on pumping performance is evaluated using a specially developed three-dimensional fluid analysis model. The proposed curve is tested using six novel rotor profiles based on the elliptical axial ratio parameter λ (a shorter axis divided by a larger axis). These six new cases and a traditional case are analyzed under the same volume and clearance conditions and their differences compared. The results show that a smaller elliptical axial ratio design produces better flow characteristics. In particular, an elliptical axial ratio smaller than 0.6 not only achieves high discharge efficiency but allows vibration and noise to be controlled by the flow rate fluctuation coefficient, which approximates the traditional indicator. The proposed curve can thus serve as a useful reference for pump or rotary fluid machine design.

A newly developed rotor profile for lobe pumps: Generation and numerical performance assessment

This study develops a new lobe pump rotor profile that significantly improves pump performance. Rotor profiles including two traditional designs and two new designs consist of three segments that are generated by circular or/and epicycloidal curves. This study evaluates the performance of four profiles via volume calculation and flow field analysis, considering to the number of lobes. Results demonstrate that the shapes of rotor surfaces affect pump performance remarkably. An epicycloidal profile provides a much advantage than a circular profile. The new rotor profile with three segments was generated by the curves in order of epicycloidal-circular-epicycloidal (ECE profile) obtained performance of 55% higher than the traditional profiles and the order of circular-epicycloid-circular (CEC profile). The analysis in this study also proves that a multi-lobe design of three or four lobes does not increase pump performance, but provides a more stable output and higher capacity than a two-lobe pump.

Rheological Properties of Manure/Biomass Mixtures and Pumping Strategies to Improve Ingestate Formulation: A Review

Abstract. Research in anaerobic digestion of agricultural by-products has been introducing new and changing heavier fibrous energy-rich feedstocks that, when co-digested with manure, allow the enhancement of the biogas potential per m 3 of volatile solids but also induce significant changes in ingestate rheological properties (in comparison with raw manure). Doubts about the adequate level of amalgamation achievable by these mixtures inevitably arise. Because of the relationship between the total solids content and ingestate apparent viscosity, optimal mixing is not achieved only as consequence of the action of fermenter paddles and other stirring devices, but pumping devices also act positively on the way biomasses and manures are mixed. At up to 8% to 10% total solids, the high shear rates provided by centrifugal pumps (better if equipped with rotating knives) cause the manure-biomass mixture to behave like a Newtonian fluid. When the total solids percentage of the mixture exceeds this threshold, other pumping systems (lobe pumps as well as screw pumps) can provide adequate pressure to drive the mixture to the fermenter; however, in this case, further conditioning devices need to be considered to act positively on the anaerobic influent condition to improve its microbial degradation.

Factors Impacting on Performance of Lobe Pumps: A Numerical Evaluation

AbstractThe aim of current research is to investigate numerically the fluid dynamics of lobe pumps and typical factors which could impact on performance of the pump including profile of rotor surface, number of lobes, gap size between rotor and casing, and clearance between two rotors,etc. The circular and epicycloidal curves are used to generate profiles for rotor surface, while the complex flow phenomena inside the pump are simulated by dynamic mesh technique. With wide range of investigated speed from 1000 to 5000rpm, the study produces significant information on flow pattern, velocity and pressure fields. The advantage of epicycloidal pumps over circular ones has been demonstrated via characteristic curve which performs pressure head versus rotational speed. Meanwhile the analysis has proved that multilobes, three and four lobes, do not increase performance of the pump but provide more stable output and higher capacity compared with two-lobe pumps. The results confirm great impact of gap size between rotor and casing wall on the pump efficiency. Decrease of the gap from 1.25mm down to 0.5mm produces about 425% increasing of pressure head. In addition, it has been also proved that the clearance between two rotors could be varied from 0.12mm to 0.15mm without much effect on performance of the pump.

Rotary lobe pumps run like clockwork

As a result of its consistency, oil is a medium that places demanding requirements on pumping technology. Suitable pumps must also reliably convey highly viscous materials and provide a high capacity in very limited spaces, such as tankers, as Paul Krampe, head of development at rotary lobe pump specialist Vogelsang explains.

Modeling shear‐induced CHO cell damage in a rotary positive displacement pump

Rotary lobe pumps are commonly used in the biotechnology industry for a variety of purposes. Shear damage to animal cells within the rotary lobe pump can adversely affect the product yield or purity during, for example, cell concentration via cross-flow filtration. In this research, CHO cells grown in 20-L bioreactors were fed to a rotary lobe pump in both single pass and recycle experiments were conducted at different RPMs and "slip" conditions. The results indicate that the slip flow rate more severely impacts the viability of the CHO cells than the pump RPM. A novel mathematical modeling approach is presented that predicts shear rates in all of the positive displacement pump's slip regions, and then predicts cell death vs. operating conditions. This model accounts for the complex flow situation that results from changes to RPM, backpressure and pump geometry (i.e., clearances).

Feedback Control with Hybrid Pump for Realistic Human Blood Pressure Reconstruction

Abstract Human blood pressure simulation is of particular interest for artificial blood vessel evaluation in regenerative medicine, and for endovascular surgery simulation to become more realistic. Conventional pumps do not offer a solution for the flow quality requirements; therefore we propose a hybrid pump that combines the best properties of lobe and piston pumps. Feedback control was applied to the hybrid pump, the system was tested using three different waveforms as reference. One of the waveforms is a polynomial approximation of pressure variation inside a coronary artery; when used a realistic human blood pressure simulation was produced. A scaffold for blood vessel regeneration was evaluated with the simulated human blood pressure.

Injection housing – optimising rotary lobe pumps for liquids with high solids content

Today, rotary lobe pumps are used increasingly for pumping liquids with solid particles and during the last 20 years they have gained market share among positive displacement pumps. Manufacturer Hugo Vogelsang Maschinenbau GmbH attributes the pump's success to a well thought out design and wear-resistant materials, enabling them to handle aggressive media more efficiently.

Rotary lobe pumps – a piece of history

One of the earliest examples of rotary lobe pump evolution has recently been returned to its birthplace in Eastbourne, UK to be has restored to its original condition and displayed in Alfa Laval's pump museum. This prompted the company's product support manager, Tony Marshall, to investigate how technology has evolved since this pump was first built and sold over 50 years ago.

Fast modeling of conjugate gear tooth profiles using discrete presentation by involute segments

This paper introduces the method of the discretization of the gear tooth flank in involute segments for the determination of conjugate gear tooth profiles. Instead of following a point-to-point analytical approach to the problem of determining the path of contact and the geometry of the generating rack and the mating wheel, the actual tooth flank is considered to be composed of infinitesimal local involutes and therefore a closed solution can be achieved. Due to its simplicity, the method is faster than the standard theory of gearing and this is particularly useful in problems requiring iterative calculations of the tooth geometry such as gear optimization. The method is implemented on modified involute as well as loboid gears used in lobe pumps and it is verified against existing theories.

Cadbury factory in South Africa uses Rotorflo lobe pumps

Cadbury factory in South Africa uses Rotorflo lobe pumps

Gap leakage behaviour of helical vane rotary lobe pumps

Double-shaft, rotary lobe pumps are often used for conveying slurries in liquid manure, biogas and sewage plants. Mechanical wear enlarges the gaps and decreases the effective flow rate. In this contribution, Meno Turk of Leibniz-Institute for Agricultural Engineering and Burkhard Verhulsdonk of pump manufacturer Hugo Vogelsang Maschinenbau discuss a study in which the effects of wear on the pumping behaviour of helical rotary lobe pumps were systematically analysed, its influences evaluated and new technical solutions for wear compensation were developed.

Effect of lobe pumping on human albumin: development of a lobe pump simulator using smoothed particle hydrodynamics1

Using SPH (smoothed particle hydrodynamics), the motion of a lobe pump under load was simulated in order to predict the level of shear stress experienced by a protein solution. By varying the gap size between the lobes and pump housing, variations in pump efficiency and shear stress were determined. The simulations indicated that pump shear was dependent on gap size, with shear stress levels (0-40 Pa) correlating with those estimated in previous albumin-pumping studies. As gap size increased, the number of fluid particles experiencing low shear (<10 Pa) increased, whereas those experiencing high shear (>20 Pa) showed a decreasing trend. The pump efficiency, however, decreased with gap size, requiring more lobe revolutions to pass a unit volume. Taken together, these observations indicate that lobe pumps operated with increased gaps between the rotors and the housing result in larger number of particles within the fluid experiencing shear stresses. Moreover, the simulations indicate that it is best to use larger lobe pumps operated at high efficiency to transfer protein-containing solutions.

Effect of lobe pumping on human albumin: investigating the underlying mechanisms of aggregate formation1

A common problem in the manufacture of liquid protein therapeutics is the tendency for aggregation and particle formation on extended storage. One aspect of processing that might contribute to particle formation is pumping. In the present study, we demonstrate that lobe pumps can promote aggregation in albumin preparations. This is accentuated where the clearance between the pump housing and lobes is increased. Under these conditions, the pump efficiency decreases, resulting in increased exposure of the protein to the pump environment. Depending on the inherent physicochemical stability of the protein, this can lead to aggregate formation, which can influence the long-term stability characteristics of the product.

Rotary lobe pumps from Boerger

Rotary lobe pumps from Boerger