Vertical Pumps: What Are They, Where Are They Used and How To Design Them?

Introduction

Vertical pump designs are similar to conventional pumps, with some unique differences in their applications.  Pumps use centrifugal force to convert mechanical energy into kinetic energy and increase the pressure of the liquid. Vertical pumps move liquids in the vertical direction upwards through a pipe. All pumps pressurize liquids, which are mostly incompressible. Unlike compressible gases, it is impossible to compress liquids, therefore the volumetric flow rate can not be reduced. Therefore liquids are transported by pumping and the inlet volume flow rate is equal to the exit volume flow rate.

Vertical centrifugal pumps are simply designed machines, and have similarities to their horizontal counterparts. A casing called a volute contains an impeller mounted perpendicularly on an upright (vertical) rotating shaft. The electric drive motor uses its mechanical energy to turn the pump impeller with blades, and imparts kinetic energy to the liquid as it begins to rotate. These pumps can be single stage or multistage with several in-line stages mounted in series.

The centrifugal force through the impeller rotor causes the liquid and any particulates within the liquid to move radially outward, away from the impeller center of rotation at high tangential velocity. The swirling flow at the exit of the impeller is then channeled into a diffusion system which can be a volute or collector, which diffuses the high velocity flow and converts the velocity into high pressure. In vertical pumps, the high exit pressure enables the liquid to be pumped to high vertical locations. Thus the pump exit pressure force is utilized to lift the liquid to high levels, and usually at high residual pressure even at the pipe discharge.

Applications of Vertical Pumps

An “in line” vertical pump is illustrated in Figure 1 (Reference 1), where the flow enters horizontally and exits horizontally and can be mounted such that the center line of the inlet and discharge pipes are in line with each other.  This is a centrifugal pump with a tangential scroll at the inlet that redirects the flow by 90 degrees and distributes it circumferentially and in the axial direction into the impeller eye. The discharge is a simple volute that collects the tangential flow from the impeller exit, and redirects it into the radial direction.

in line Pump - Figure 1
An “in line” Vertical Pump. Source

Figure 2 shows a vertical pump that has a vertical intake that directs the flow straight into the eye of the pump rotor. At the impeller exit, the tangential flow is collected by a volute and diffused in an exit cone. An elbow after the exit cone redirects the flow into the vertical direction to lift the liquid to the desired altitude. (Reference 2). Read More

Back to Basics: What Makes a Good Pump?

Everyone is familiar with pumps, but how many people really think about how much depends on this ubiquitous invention? The scope of pump applications is wide: distribution and circulation of water in water supply and heat supply systems, irrigation in agriculture, in the oil industry, in fire extinguishing systems, etc.

A pump is a hydraulic machine designed to move fluid and impart energy to it. A schematic diagram of a simple pumping unit is presented below.

Figure 1 Pumping Unit Diagram
Figure 1: Pumping Unit Diagram
1 – intake valve; 2 – suction pipeline; 3 – vacuum gauge; 4 – pump; 5 – manometer; 6 – check valve; 7 – gate valve; 8 – pressure pipeline

Positive Displacement and Dynamic Pumps

According to the principle of operation, pumps can be divided into two main groups: positive displacement and dynamic. In positive displacement pumps, a certain volume of the pumped liquid is cut off and moved from the inlet to the pressure head, where additional energy is supplied to it. In pumps with dynamic action, the increase in energy occurs due to the interaction of the liquid with a rotating working body.

The most widely used pumps are centrifugal pumps which are of the dynamic type. The principle of centrifugal pumps uses a rotating impeller to create a vacuum in order to move the fluid. The impeller rotates within the housing and reduces pressure at the inlet. This motion then drives fluid to the outside of the pump’s housing, which increases the pressure.

These pumps benefit from a simple design and lower maintenance requirements and costs. This makes them suited to applications where the pump is used often or continuously run.

Figure 2 Centrifugal Pump
Figure 2a: Centrifugal Pump
Centrifugal Pump Designed using AxSTREAM
Figure 2b: Centrifugal Pump Designed using AxSTREAM

In most cases, the pumps are electrically driven, but if the pump is of high power and high speed, then these pumps are driven by steam turbines. Read More

Evolution of Reverse Engineering

Introduction

In today’s intensely competitive global market, product enterprises are constantly seeking new ways to shorten lead times for new product developments that meet all customer expectations. In general, product enterprise has invested in CAD/CAM, rapid prototyping, and a range of new technologies that provide business benefits. Nowadays, reverse engineering (RE) is considered one of the technologies that provide business benefits by shortening the product development cycle [1]. Figure 1, shows how reverse engineering can close the gap between what is “as designed” and what is “actually manufactured” [1].

Product Development
Figure 1. Product Development Cycle. SOURCE: : [1]
Reverse engineering (RE) is now recognized as an important factor in the product design process which highlights inverse methods, deduction and discovery in design. In mechanical engineering, RE has evolved from capturing technical product data, and initiating the manual redesign procedure while enabling efficient concurrency benchmarking into a more elaborated process based on advanced computational models and modern digitizing technologies [2]. Today the application of RE is used to produce 3D digital models of various mechanical worn or broken parts. The main steps in any reverse engineering procedure are: sensing the geometry of the existing object; creating a 3D model; and manufacturing by using an appropriate CAD/CAM system [2]. Read More

Modern Challenges in Aviation Propulsion Systems

Introduction

Aviation is coming into a new age of carbon free energy, similar to what is being explored with ground transportation. Currently, aviation transportation generates about 2.5% of the global CO2 emission [1]. Several countries have introduced targets to achieve net-zero emissions by 2050 [2].

Many aerospace teams have joined the great engineering challenge to change the future of aviation.  With this, a number of different types of aircraft with different types of propulsion systems have been proposed.

Hybrid Propulsion System

The first step to a carbon-free propulsion system is hybrid technology. This kind of power plant increases efficiency, decreases emission of greenhouse gases and uses a traditional engine to produce electricity and electric motors to drive the fans or propellers [3].

The chemical engines operate at optimal conditions at any mode of a route. On the other hand, the electric motor is able to work in generator mode, using the kinetic energy of the vehicle during deceleration.

Hybrid propulsion energy system
Figure 1 – Hybrid propulsion energy system

The hybrid aircraft is classified by several attributes. Using thrust devices, we will consider the two base types of propellers and fans. Read More

Considerations in Industrial Pump Selection

Pumps are machines that transfer liquids from suction to discharge by converting mechanical energy from a rotating impeller into what is known as head. The pressure applied to the liquid forces the fluid to flow at the required rate and to overcome frictional losses in piping, valves, fittings, and process equipment.

When it comes to pump selection, reliability and efficiency go hand-in-hand. Generally, a pump that has been selected and controlled properly for its normal operating points will operate near its best efficiency point (BEP) flow, with low forces exerted on the mechanical components and low vibration — all of which result in optimal reliability.

There are several factors like process fluid properties, end use requirements, environmental conditions, pump material, inlet conditions, and others which should be considered while selecting pumps for industrial applications. Selecting the right pump type and sizing it correctly are critical to the success of any pump application. Pumping applications include constant or variable flow rate requirements, serving single or networked loads, and consisting of open loops (nonreturn or liquid delivery) or closed loops (return systems).

Some crucial factors considered while pump selections include:

Fluid Properties: The pumping fluid properties can significantly affect the choice of pump. Key considerations include:

  • Acidity/alkalinity and chemical composition. Corrosive and acidic fluids can degrade pumps and should be considered when selecting pump materials.
  • Operating temperature: Pump materials and expansion, mechanical seal components, and packing materials need to be considered with pumped fluids that are hotter than 200°F.
  • Solids concentrations/particle sizes: When pumping abrasive liquids such as industrial slurries, selecting a pump that will not clog or fail prematurely depends on particle size, hardness, and the volumetric percentage of solids.
  • Specific gravity: It affects the energy required to lift and move the fluid and must be considered when determining pump power requirements.
  • Vapor pressure and Viscosity: Proper consideration of the fluid’s vapor pressure will help to minimize the risk of cavitation. High viscosity fluids result in reduced centrifugal pump performance and increased power requirements. It is particularly important to consider pump suction-side line losses when pumping viscous fluids.

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Materials of Construction: It is always required to check the compatibility of materials of construction with the process liquid or any other liquids the pump might encounter. The initial cost of these materials is normally the first consideration. The operational costs, replacement costs and longevity of service and repair costs will, however, determine the actual cost of the pump during its lifetime. Charts are available to check the chemical compatibility and identify the most appropriate materials of construction for the pump.

The impact of the impeller material on the life of a pump under cavitation conditions is shown in Figure 1. As an example, changing from mild steel (reliability factor of 1.0) to stainless steel (reliability factor of 4.0) would increase the impeller life from cavitation damage by a factor of four. Hard coatings, such as certain ceramics, can also increase the impeller life under cavitating conditions.

Material Cavitation Life Factors
Figure 1 Material Cavitation life factors

Pump Sizing and Performance Specifications: The desired pump discharge is needed to accurately size the piping system, determine friction head losses, construct a system curve, and select a pump and drive motor. Process requirements can be achieved by providing a constant flow rate, or by using a throttling valve or variable speed drives. Read More

When to Use 1D Vs. 3D Simulation

Today’s simulation and analysis (S&A) tools allow engineers to study and verify system/machine properties and visualize the aerodynamic, thermodynamic, structural, and other physical properties without having to build a physical prototype. We can perform cooling secondary flow systems analysis in a gas turbine; a detailed performance study for a supercritical CO2 turbine/compressor; predict cavitation for industry a water pump/rocket turbopump; and so many more. Products and machines are becoming more and more complex. Unfortunately, engineers only run a handful of designs through the S&A process, due to the cost associated with limited computer resources and the time required to run simulations and to create complex 3D models of designs. Furthermore, verification and certification of system designs are often done using actual hardware—a costly and time-consuming endeavor. Considering these aspects, 1D and 3D simulations are significantly important. However, engineers need to determine the trade-off between 1D and 3D simulation.

AxSTREAM and STAR-CCM
Figure 1 AxSTREAM Platform with Modules from 0D to 3D including seamless geometry import into STAR-CCM+

1D Simulation

Imagine what’s required to generate one 3D design for a gas turbine secondary cooling flow system, and multiply it by 1,000 design alternatives. Even if we were to only use conceptual CAD models, this project would require extraordinary computing power and data storage—not to mention simulation and design expertise.

And so, even with the movement to bring more cloud-based S&A tools to market, resources required for 3D modeling will still result in very few designs being extensively explored, thanks to their complexity. Detailed low-dimensional models of system behavior can provide valuable insights into system performance and function thus guiding the design process. Read More

Modeling and Analysis of a Submarine’s Diesel Engine Lubrication System

Even in today’s age of underwater nuclear power, the majority of the world’s submarines still use diesel engines as their main source of mechanical power, as they have done since the turn of the century. A diesel engine must operate at its optimum performance to ensure a long and reliable life of engine components and to achieve peak efficiency. To operate or keep running a diesel engine at its optimum performance, the correct lubrication is required. General motors V16-278A type engine is normally found on fleet type submarines and is shown in Figure 1. This engine has two banks of 8 cylinders, each arranged in a V-design with 40 degree between banks. It is rated at 1600 bhp at 750 rpm and equipped with mechanical or solid type injection and has a uniform valve and port system of scavenging[1].

Figure 1. GM V16-278A, Submarine Diesel Engine. SOURCE: [1]
Figure 1. GM V16-278A, Submarine Diesel Engine. SOURCE: [1]
Lubrication system failure is the most expensive and frequent cause of damage, followed by incorrect maintenance and poor fuel management. Improper lubrication oil management combined with abrasive particle contamination cause the majority of damage. Therefore, an efficient lubrication system is essential to minimize risk of engine damage.

The purpose of an efficient lubrication system in a submarine’s diesel engine is to:

  1. Prevent metal to metal contact between moving parts in the engine;
  2. Aid in engine cooling by removing heat generated due to friction;
  3. Form a seal between the piston rings and the cylinder walls; and
  4. Aid in keeping the inside of the engine free of any debris or impurities which are introduced during engine operation.

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All of these requirements should be met for an efficient lubrication system. To achieve this, the necessary amount of lubricant oil flow rate with appropriate pressure should circulate throughout the entire system, which includes each component such as bearings, gears,  piston cooling, and lubrication. If the required amount of flow rate does not flow or circulate properly to each corner of the system or rotating components, then cavitation will occur due to adverse pressure and excessive heat will be generated due to less mass flow rate. This will lead to major damage of engine components and reduced lifetime.
Read More

APPLICATION OF DIGITAL TWIN CONCEPT FOR SUPERCRITICAL CO2 OFF-DESIGN PERFORMANCE AND OPERATION ANALYSES

This is an excerpt from a technical paper, presented at the ASME Turbo Expo 2020 online conference and written by Leonid Moroz, Maksym Burlaka, Tishun Zhang, and Olga Altukhova. Follow the link at the end of the post to read the full study! 

Introduction

The attempts to simulate transient and steady-state sCO2 cycles off-design performance were performed by numerous authors [1], [2], [3], [4], and [5]. Some of them studied the dynamic behavior of regulators, some studied different control strategies or off-design behavior in different scenarios, which definitely has certain utility in the development of the reliable technology of sCO2 cycle simulation. Nevertheless, they used rather simplified models of components, especially turbomachinery and heat exchangers, which are of crucial importance to correctly simulate cycle performance.

The authors of this paper attempted to apply the digital twin concept to a simulation of off-design and part-load modes of the sCO2 bottoming cycle considering real machine characteristics and performance, which nobody tried to apply in this area.

On IGTC Japan 2015, SoftInWay Inc. has published a paper “Evaluation of Gas Turbine Exhaust Heat Recovery Utilizing Composite Supercritical CO2 Cycle”. The paper considered combinations of different bottoming sCO2 cycles for a specific middle power gas turbine. It mainly studied the advantages of different types of sCO2 cycles to increase the power production utilizing GTU waste heat.

The present paper is a further study based on that so the Cycle 2 [6] from that previous paper was selected as the sCO2 bottoming PGU layout in the present paper for subsequent analysis. The cycle is a combination of recompression cycle and simple cycle which offers 16.13 MW as output. GE LM6000-PH DLE gas turbine, was used as the heat source for bottoming PGU. According to GE official brochure [7], the GE LM6000 offers 40 MW to over 50 MW with up to 42% efficiency and 99% fleet reliability in a flexible, compact package design for utility, industrial and oil and gas applications. GE LM6000-PH DLE provides 53.26 MW output with exhaust temperature at 471 ℃ and exhaust flow at 138.8 kg/s. (This information came from GE products specification from 2015. It appears that GE continuously modifying the parameters of its turbines along with the naming of different modifications. Therefore, today’s parameters and configuration names might be slightly different comparing to 2015) Exhaust gas pressure was assumed to be 0.15 MPa. These parameters were taken to analyze the bottoming PGU and are presented below in TABLE 1.

SELECTED SET OF GE LM6000-PH DLE PARAMETERS
TABLE 1: SELECTED SET OF GE LM6000-PH DLE PARAMETERS

The digital twin (DT) concept is the developing technology that allows simulation of object behavior during its life cycle or in specified time due to changing ambient conditions, for example. The DT is applicable for performance tuning, digital machine building, healthcare, smart cities, etc [8] that allows decreasing the time and costs of development and optimize the object on the developing stage. GE has raised DT concepts for power plants to continually improves its ability to model and track the state of the plants [9].

In the context of this paper, DT is a simulation system comprised of physicist-based models organized in a special algorithmic structure that allows simulating the behavior of sCO2 PGU under alternating ambient conditions and grid demands.

The DT in this study was created utilizing AxSTREAM® Platform, which includes multiple software tools. The following software tools were utilized in this study: AxCYCLE™ was used to perform cycle thermodynamic calculation; solution generator in AxSTREAM® helped with finding possible machine geometry with given boundary conditions when performing preliminary design for compressors and turbines at design point; parameters and performance of turbomachinery including mass flow rate, pressure, power, efficiencies, etc. were calculated by Meanline/Streamline solver in AxSTREAM® for design and off-design conditions; AxSTREAM NET™ is a 1D system modeling solver and it was introduced here to simulate performance of heat exchangers (HEX) and pressure drop in the pipes involved in the cycle; AxSTREAM ION™ was used to integrate all modules and tools together in one simulation system. Read More

Initial Sizing of Centrifugal Fans

Centrifugal fans are a type of turbomachine equipment widely used in all kinds of modern and domestic life. Centrifugal fans were developed as highly efficient machines, and the design is still based on various empirical and semi empirical rules proposed by fan designers. Due to these various rules, there are different methodologies used to design impellers and other components.

Centrifugal fans consist of an impeller in a casing with a spirally shaped contour, shown in Figure 1 (left side). The air enters the impeller in an axial direction and is discharged at the impeller outer periphery. The air flow moves along the centrifugal direction (or radial direction). Centrifugal fans can generate relatively high pressures, as compared with axial flow fans. For axial flow fans, the pressure rise is small, about be few inches of water.

Radial Fan and Static Pressure
Figure 1 Radial Fan and Static Pressure, Shaft Power V/s Volume Flow Curves for Different
Types of Blades

Generally centrifugal fans have three types of blade: forward blade, backward blade and radial blade. The characteristic curve of these three kinds of centrifugal fans is shown on right side in Figure 1.

Sizing Using Cordier Diagram

Centrifugal fans (most turbomachines) can be classified based on specific speed (Ns) and specific diameters (Ds) as shown in Figure 2. Specific speed is a criterion at which a fan of unspecified diameter would run to give unit volume flow and pressure. The correlation for specific speed and specific diameter can be seen here:

Pump Formula

where, ‘N’ is rotational speed (RPM), ‘Q’ is flow rate (ft3/sec), ‘H’ is head (ft), ‘D’ is diameter (ft) Read More

The Top 5 Coolest Turbomachinery Inventions (According to Us!)

As the leading authority on turbomachinery design, redesign, analysis, and optimization, we work with a wide range of machines from small water pumps and blowers to massive steam turbines, jet engines, and liquid rocket engines. While all of these machines have a certain “cool factor” to them since, after all, we’ve proven they make the world go round; some machines take coolness to the next level. Today, we’re taking a look at 5 of the coolest specific turbomachinery inventions, according to us.

Number 5 – The Arabelle Turbines

Starting with number 5, we have a pair of steam turbines, each known as “Arabelle”. You may be asking yourself “So what, steam turbines are everywhere.” You would be right, but these two have a bit of a size advantage. In fact, they’re the largest steam turbines in the world.

Designed and built by General Electric in France, these turbines are, according to GE, “longer than an Airbus 380 and taller than the average man. A pair of them, each capable of producing 1770 megawatts, is now set to cross the English Channel to provide energy for generations” (1).

They’ll be installed in a new nuclear power plant known as Hinkley Point C in Somerset. Their 1.7 gigawatt output will be enough to power 6 million homes, which is 7% of the UK’s power consumption. (1) The output and sheer size of the turbines aren’t the only large number either, the project costs nearly 24 billion US dollars.

A CAD model of the Arabelle steam turbines, image courtesy of General Electric.
A CAD model of the Arabelle steam turbines, image courtesy of General Electric.

The sheer size and performance figures have earned GE a place on our list of top 5 cool turbomachines!

Number 4 – The Garrett 3571VA Variable Geometry Turbocharger

This is one only gearheads and diesel-fans may recognize, but even then, it’s an obscure one. This Garrett turbocharger was a game changer for diesel engines used in light and medium duty trucks, specifically the Navistar International VT365, also known as the Ford 6.0 Liter Powerstroke engine. Read More