Testing and Validation of Reciprocating Positive Displacement Pump for Benchtop Pulsating Flow Model of Cerebrospinal Fluid Production and Other Physiologic Systems

Background: The flow of physiologic fluids through organs and organs systems is an integral component of their function. The complex fluid dynamics in many organ systems are still not completely understood, and in-vivo measurements of flow rates and pressure provide a testament to the complexity of each flow system. Variability in in-vivo measurements and the lack of control over flow characteristics leave a lot to be desired for testing and evaluation of current modes of treatments as well as future innovations. In-vitro models are particularly ideal for studying neurological conditions such as hydrocephalus due to their complex pathophysiology and interactions with therapeutic measures. The following aims to present the reciprocating positive displacement pump, capable of inducing pulsating flow of a defined volume at a controlled beat rate and amplitude. While the other fluidic applications of the pump are currently under investigation, this study was focused on simulating the pulsating cerebrospinal fluid production across profiles with varying parameters. Methods: Pumps were manufactured using 3D printed and injection molded parts. The pumps were powered by an Arduino-based board and proprietary software that controls the linear motion of the pumps to achieve the specified output rate at the desired pulsation rate and amplitude. A range of 0.01 to 0.7 was tested to evaluate the versatility of the pumps. The accuracy and precision of the pumps’ output were evaluated by obtaining a total of 150 one-minute weight measurements of degassed deionized water per output rate across 15 pump channels. In addition, nine experiments were performed to evaluate the pumps’ control over pulsation rate and amplitude. Results: volumetric analysis of a total of 1200 readings determined that the pumps achieved the target output volume rate with a mean absolute error of -0.001034283 across the specified domain. It was also determined that the pumps can maintain pulsatile flow at a user-specified beat rate and amplitude. Conclusion: The validation of this reciprocating positive displacement pump system allows for the future validation of novel designs to components used to treat hydrocephalus and other physiologic models involving pulsatile flow. Based on the promising results of these experiments at simulating pulsatile CSF flow, a benchtop model of human CSF production and distribution could be achieved through the incorporation of a chamber system and a compliance component

Perancangan Pompa Air Positive Displacement yang Digerakkan Oleh Turbin Angin Sudu Jamak

Di beberapa daerah di Indonesia seperti Kabupaten Sumbawa, masih memiliki wilayah terpencil yang jauh dari jaringan listrik nasional, jaringan irigasi pertanian dan perusahaan daerah air minum, tetapi memiliki kelebihan yaitu tersedianya sumber air tanah (air sumur) dengan kedalaman sumur antara 3 m sampai 9 m. Namun untuk mengangkat air sumur dibutuhkan suatu sistem pemompaan, seperti pompa berpenggerak motor bakar, motor listrik atau memanfaatkan sumber energi terbarukan seperti turbin angin sudu jamak yang di gerakkan secara mekanik. Sudu dihubungkan dengan poros dan mekanisme engkol ditempatkan di ujung poros. Ketika sudu berputar secara otomatis mekanisme engkol juga akan berputar. Karena pengaturan eksentrik poros, gerakan putaran mekanisme engkol diubah menjadi gerakan linier yang diteruskan ke batang piston pompa, sehingga proses pemompaan akan berlangsung secara terus menerus sesuai dengan ketersediaan dan kecepatan angin. Memanfaatkan turbin angin sebagai penggerak pompa air bisa dilakukan karena letak geografis Kabupaten Sumbawa yang memiliki garis pantai cukup panjang dengan kecepatan angin di atas 2,3 m/detik. Pada penelitian ini telah dirancang pompa air model piston (pompa air positive displacement) dengan penggerak turbin angin sudu jamak, diameter silinder pompa 50,80 mm, panjang langkah pompa 127 mm, ketinggian (head) pemompaan 9 m pada kecepatan angin 2,8 m/detik. Dari hasil perancangan diketahui aliran air rata-rata efektif yaitu 7,8 m3/hari dan torsi untuk memulai pemompaan yaitu 11,21 Nm.

Optimizing Bottom Hole Assembly Design Criteria to Improve Mechanical Performance in Slim Hole Drilling Environment

After analyzing the historical data of neighboring wells adjacent to the drilling site, 11 bit trips were required due to the low mechanical performance of the bottom hole assembly elements. This observation is based on maximum circulation hours and low helical bucking values that make it uneconomic to drill the sections with a positive displacement motor drive system. A redesign the bottom hole assembly was proposed to achieve an improved mechanical performance which allowed the section to be drilled with a single assembly. With a focus on increasing the mechanical limitations of the downhole elements, the use of 4 ¾" equipment is considered instead of the 3 ½" standard equipment used in this hole size. One of the biggest challenges was modifying the 4 ¾" positive displacement motor (PDM) to fit into the 5 ½" hole given that the mud motor has a maximum unmodified diameter of 5 ½". Using the force analysis module of a State-of-the-art BHA modelling software suite, multiple iterations were performed to simulate and validate an alternative PDM design and accompanying directional assembly. This new design featured modifications to an existing 4 ¾" PDM deploying a long gauge bit in combination with a fit for purpose measurement while drilling system. After numerous runs using this assembly design, it was found that there was no additional or unexpected wear of the modified Mud Motor components or associated elements of the downhole equipment. These observations act to validate the pre-job engineering force analysis. With the improved mechanical specifications of the 4 ¾" Bottom Hole Assembly (BHA) components, circulating hours were increased from 100 hours to 250+ hours in a stepwise process. This enabled drilling of the entire 5 ½" section with a single BHA, comparing favorably to the legacy approach with an average of eleven bit runs. The modified 4 ¾" PDM coupled with long gauge bit technology enabled a reduction in the oriented to rotate drilling ratio and an associated increase in the overall rate of penetration (ROP). It can be concluded that the substitution of 4 ¾" drilling equipment for 3 ½" in the 5 ½" hole section, increased the drilling efficiency between 30-50% according to field data obtained in Ukraine. The modified 4 ¾" PDM combined with long gauge bit technology has the potential to improve 5 ½" hole drilling performance in other locations. Following a structured planning process using State-of-the-art BHA modelling software suite enabling the evaluation of the significant forces that act in the drilling assembly and so significantly reducing the risks associated with exceeding the original design limits of the assembly. By improving the mechanical performance of the drilling assembly in a 5 ½" hole, new territory for drilling engineers and design engineers is now available to increase the drilling performance in slim wellbores.

An Analysis of the Effects Causing an Asymmetric Behavior of the Lateral Lubricating Films of External Spur Gear Machines

The torque efficiency and flow efficiency of positive displacement machines for fluid power applications are determined by the behavior of their internal lubricating interfaces. This aspect has motivated the development of tribological simulation tools for the analysis of these interfaces. The level of details these tools can provide allows explaining some counterintuitive aspects that occur in these interfaces. This paper focuses on a significant example, which is the high asymmetric behavior of the lubricating films occurring in pressure compensated external gear pumps. These units are often designed with a symmetric axial balancing compensation system. Notwithstanding, there are differences between the lateral gaps that can be explained only considering the mutual effects of the pressure development in the film and the material deformation. To study this problem, this paper utilizes the tool Multics-HYGESim developed by the authors’ research team. Two analyses are performed: the first one imposing axial symmetry in the behavior of the gap, which is the common assumption discussed in literature; the second one (referred to as “full configuration”), which holds the asymmetric behavior of the gap. An experimental set-up is used to validate the modeling assumptions based on the measurements of the drain leakage and volumetric efficiency. The main paper findings are on the uneven distribution of these leakages, which indicates an asymmetric behavior of the gap films in the unit.

Meaningful and Physically Consistent Efficiency Definition for Positive Displacement Pumps - Continuation of the Critical Review of ISO 4391 and ISO 4409

ISO 4391:1984 gives the common efficiency definition for positive displacement machines. ISO 4409:2019 uses this efficiency definition to specify the procedure for efficiency measurements. If the machine conditions do not correspond with an incompressible flow due to operation at high pressure levels, the compressibility of the fluid and the dead volume of a pump must be taken into account. On this point, ISO 4391:1984 is physically inconsistent. Achten et. al. address this issue in their paper at FPMC 2019 presenting a critical review of ISO 4409:2007. They introduce new definitions of the overall efficiency as well as the mechanical-hydraulic efficiency. At the same time, they question the validity of the volumetric efficiency definition. Li and Barkei continue on this issue in their paper at FPMC 2020 and give a new efficiency definition based on the introduction of a new quantity Φ which describes the volume specific enthalpy of the conveyed fluid. The motivation of this paper is to contribute to the ongoing and fruitful discussion. Our approach starts with the most general efficiency definition, namely the isentropic efficiency. Subsequently, we make assumptions concerning the fluid properties with respect to the compressibility of the conveyed fluid. On the basis of the ideal cycle of a positive displacement pump and the p-v diagram, we derive physically consistent and more meaningful representations of the overall, the mechanical-hydraulic and the volumetric efficiency that address the inconsistency of ISO 4391:1984. Furthermore, we compare our findings with the existing results of Achten et. al. and Li and Barkei.

A Novel Positive Displacement Axial Piston Machine With Bent Cylinder Sleeves

In this paper, an investigation of a novel positive displacement axial piston machine using a bent cylinder sleeve configuration is presented. The proposed design eliminates the side moments on the piston/cylinder interface, therefore, reduces the frictional loss and improves the total energy efficiency. A multi-physics elastohydrodynamic lubrication model was used to aid the design of the piston/cylinder and the cylinder block/port block interface. Then, a lumped parameter model was used to optimize the port block geometry. Groove geometry was chosen primarily to reduce flow ripple, tilting moment, and cavitation risk. To improve the housing stiffness, the lumped parameter model was combined with a finite element analysis. This ensured safety for the testing. In the end, steady-state experiments were performed on the prototype based on the ISO4409 normative. The unit’s speed was set to 500 rpm, then increased by 500 rpm until it reached 3000 rpm. The supply pressure was set to 20 bar. The outlet pressure was set to 70 bar at first, then increased by 50 bar until it reached 220 bar. The results show a remarkable volumetric efficiency with a peak of 99.5%. It is however noted that due to some of the issues with the initial iteration of the current design, there is a reduction in mechanical efficiency. The causes and possible future solutions to these issues are discussed in the manuscript.

Continuous Improvement: Rotary Steerable System with Electromagnetic Telemetry as Approach to Reduce Well Time

One of the main challenges from operating companies is the continuous reduction of well construction time. During drilling, considerable time is spent on static measurements to determine the wellbore location and to verify that the actual well path matches the planned one. The electromagnetic telemetry system (EMT) allows the taking of static directional survey measurements during connections, when the drill string is in slips. Transmitting commands to the rotary steerable system (RSS) through the EMT does not cause the drilling process to stop, which also reduces well construction time. The work describes well drilling experience with the use of the electromagnetic channel for communication with the rotary steerable system and the positive displacement downhole motor not only in horizontal section but in all well sections, starting from the top hole. Combined use of the complete logging while drilling tools (LWD) with this type of the telemetry system is a valuable finding. The article describes BHA, operational principles of this type of the telemetry system, and problems which may arise during operation.