Pump Performance Improvement Using AxSTREAM ION

As pumps have numerous uses, they constitute a significant part of energy consuming equipment.  Therefore, pump efficiency plays a significant role in energy savings and operating cost. The design of a centrifugal pump is more challenging to reduce overall cost of the pump and increasing demand for higher performance.

Redesign Pump with Smooth Beta and Theta Distributions
Figure 1. Centrifugal Pump in AxSTREAM

There are two traditional approaches to design a pump for new requirements. One approach is to redesign or modify an existing impeller of centrifugal pump for increasing flow rate/head and efficiency. The modification will also involve selection of different geometric parameters and then optimizing them with the goal of performance improvement in terms of efficiency, increase the head, reduce cross flow and secondary incidence flows. The other approach is to design a pump from the preliminary stage to meet the desired design objectives. Most of the time, the designer knows what they need to achieve (performance target) but the challenge is in how to achieve this target within the given constraints (geometry, cost, manufacturability etc.).
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Series on Micro Gas Turbines And How They Can Make the World Greener

If you’re familiar with turbomachinery, then you probably know the pivotal role they play in our lives. If you’re not, no biggie! Have a look at this blog where I discuss a world without turbomachinery. But where do microturbines fit in? I can’t speak for anyone else, but my mind immediately jumps to turbochargers in small-displacement car engines. There is, however, a whole slew of information, history, and applications for microturbines beyond being a component in your car.

The best place to start, is to establish just what a microturbine is and isn’t. Granted the prefix in the word is a dead giveaway, but just how small is a micro gas turbine?  In terms of power output, a micro gas turbine puts out between 25 and 500 kW. The size of these machines varies; some systems can be the size of a refrigerator, while others can fit on your desk. For reference, some of these machines are smaller than your average corgi!

Micro Gas Turbine and Corgi
Figure 1: A micro gas turbine with a pencil for scale (left) and your average corgi (right). Not very aerodynamic, but awfully cute. Source

In terms of components, microturbines typically consist of a compressor, combustor, turbine, alternator, generator, and in most machines, a recuperator. While incorporating a recuperator into a microturbine system comes with its own set of challenges, the benefits are often well worth it as efficiency when recuperated hovers around 25-30% (with a waste heat recovery/cogeneration system, efficiency levels can reach up to 85% though).

Figure 3: A commercial airliner's turbofan engine the common image that is conjured when one thinks of turbines in transportation
Figure 3: A commercial airliner’s turbofan engine; the common image that is conjured when one thinks of turbines in transportation.
History

When and how did the concept of micro gas turbines come about? After the advent of the jet engine in World War II and the prominence of turbochargers being used on piston-driven propeller planes during the war, companies started to see where else gas turbine technology could be utilized. Starting in the 1950’s automotive companies attempted to offer scaled down gas turbines for use in personal cars, and you can read our blog covering that more in-depth here. You can probably guess by the number of gas turbine-powered cars on the road today, that it wasn’t very successful.

Fast forward to the 1970s, companies started to take an interest in micro turbines for stationary power generation on a small, portable scale. Allison developed microturbine-powered generators for the military that showed substantially lower fuel consumption in initial testing. In the 80’s, GRI supported the AES program where they attempted to develop a 50kW turbine for aviation applications, using a heat recovery system to improve efficiency through a cogeneration system. More recently, companies like Capstone have worked with GRI on new projects to introduce microturbines to different industries where they could be useful, using the latest advancements in technology to ensure higher efficiencies and reliability of designs past. To discuss the current state of affairs for microturbines however, it might be good to list some of their present advantages and drawbacks, and then explore where in the world they could be most useful.

Micro Turbine Compressor
Figure 4: A micro turbine compressor model.

 

Advantages and Disadvantages of Microturbines

As with just about any other type of technology, microturbines have their own set of advantages and disadvantages as a result of their design that are seen in their different applications.

Advantages: 

  • – Lower emissions
  • – Lower noise level than comparable reciprocating engines
  • – Fewer moving parts with results in less maintenance needs
  • – Lower vibration levels
  • – Ligherweight, compact systems
  • – Diverse fuel selection (jet fuel, kerosene, diesel, natural gas)

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Disadvantages:

  • – Very low efficiency without recuperator/waste heat recovery system
  • – High work requires high speeds (30-120 krpm) for small diameters
  • – Poor throttle response
  • – Expensive materials required for manufacturing
  • – More sensitive to adverse operating conditions

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A Micro Gas Turbine
Figure 5: A Microturbine
Potential Transportation Industry Applications

There are a number of different industries which microturbines can be found both in and outside of the transportation. Throughout the upcoming months, we’ll be taking a closer look at:

  • – The Aviation Industry
  • – The Automotive Industry
  • – The Marine Industry
  • – The Rail Industry

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Each of these industries has at least one application where micro gas turbine technology has the potential to conserve fuel and lower emissions without compromising power. In the next entry, we’ll look at the current state of the aerospace industry and where/how micro gas turbines can improve upon existing technology.

If you want to learn more about designing a micro gas turbine, or about the tools our engineers and thousands of others around the world rely on for their turbomachinery designs, reach out to us at info@softinway.com

Basic Definitions and Fundamental Concepts of Rotating Equipment Vibrations

Hello and welcome or welcome back to the January 2020 edition of our Rotor Dynamics Blog series! Here are the other entries in the series for those who are just joining us:

  1. Series Preface
  2. What is Rotor Dynamics? And Where is it Found?
  3. Why is Rotor Dynamics so Important?
  4. What API Standards Govern Rotor Dynamics Analysis?

In our previous blogs we established that rotor dynamics is a branch of applied mechanics in mechanical engineering and is concerned with the behavior of all rotating equipment, but let’s have a closer look at some of the factors that affect the behavior of rotating equipment.

Here’s a non-exhaustive list of the different static and dynamic forces and phenomena that can act on a rotor train:

  • – Unbalance
  • – Gravity
  • – Bearing reaction
  • – Inertia
  • – Seals
  • – Fluid-rotor interaction
  • – Impeller aerodynamic loadings
  • – Misaligned couplings and bearings
  • – Rubbing between rotating and stationary components

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Rotor Train Schematic
Rotor Train Schematic

As you can see there’s no shortage of different forces and factors which must be considered to ensure the smooth operation of your turbomachinery and other rotating equipment. While some of these factors are very familiar such as gravity, some factors like rotor unbalance have numerous causes. Here’s another (non-exhaustive) list of different factors that can cause rotor unbalance: Read More

Oxygen Life Support Systems in a Spacecraft

Introduction

Looking into the very near future, tourists traveling into space no longer seems like some fantastic science fiction. The Blue Origin and the Mojave Aerospace Ventures companies are ready to operate their respective manned suborbital spacecrafts in the coming year[1]. While, The Boeing Company and the SpaceX are finishing the certification of their crewed spacecrafts to deliver people at the Low Earth Orbit. This is only the tip of the iceberg in the great competition.

The next ambitious goal of the space industry is to create space hotels (see Figure 1). For example, NASA already has announced opening the ISS for tourists. These objects are long term human habitations and as such have specific requirements for oxygen life support systems (OLSS). If these requirements are not met, people can die. Small variations in the chemical composition of a mixture of the gases all influenced by, pressure, temperature, a humidity and etc.[2]  can have disastrous effects. The work of some of these partial system can be analyzed and optimized using AxSTREAM NET™.

Figure 1 - The art image of the Aurora Space Hotel
Figure 1 – Art Image of the Aurora Space Hotel[3]
Types of life support system of a spacecrafts

The type and complexity of OLSS depends on the duration of the tourists staying in the artificial environment. For example, let’s consider the oxygen life support systems. A hypothetical manned spacecraft has an internal volume 15 m3 (530 ft3) and can carry six space tourists. The amount of the oxygen for the metabolism of one person is 0.830 kg/day[4] (Figure 2). The atmosphere should consists of 19.5 to 23.5 % of an oxygen[5]. Also, the amount of the reserve oxygen should be 0.035 kg (0.077 pounds) per human/hour. If our six space tourists start their journey with the environment gas in the craft at 23.5 % of the oxygen , it will take 3.5 hours to reach critical level. It’s enough time for a suborbital flight, and the oxygen life support system would only be needed as a reserve source. Read More

What API Standards Govern Rotor Dynamics Analysis?

Hello and welcome to this December edition of the Intro to Rotor Dynamics Blog; and if you’re re-reading this, welcome back! Here are the other entries in this series if you want to retrace our steps thus far:

Series Preface

What is Rotor Dynamics? And Where is it Found?

Why is Rotor Dynamics so Important?

So now that we’ve covered the basic definition of rotor dynamics and established the consequences of inaccurate/incomplete analyses, let’s look at what standards govern rotor dynamics.

In general, there are several different codes and standards that rotor dynamics engineers look to in order to make machines compliant. The standard they look at for compliance depends on the location of the company, as well as the kind of machine, what industry the company/machines are present in, and what the machine’s application is.  With so many different applications, there are many different places to consult in order to make a compliant machine.

So, what are the governing bodies on rotor dynamics and vibration analyses as well as the balancing of rotating machines? Well, there are several

  • – First, you have the American Petroleum Institute, commonly known as API.
  • – Next, there’s the International Organization for Standardization, known as ISO.
  • – There’s also ANSI, the American National Standards Institute.
  • – Lastly, each company may have internal rules and standards, with their own calculations and tests that are more stringent than the requirements put forth by the other governing bodies.

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So where would you find the rules relating to rotor dynamics in the API’s and the ISO’s long lists of standards and regulations? I’m glad you asked.

Governing Bodies for Rotordynamics

API Standards

Read More

Choosing the Right Turbomachinery Component

Traditionally the engineering process starts with Front End Engineering Design (FEED) which is essentially the conceptual design to realize the feasibility of the project and to get an estimate of the investments required. This step is also a precursor to defining the scope for Engineering Procurement and Construction Activities (EPC). Choosing the right EPC consultant is crucial as this shapes the final selection of the equipment in the plant including turbomachinery.

Large thermal power machine

Choosing the right component for the right application is not an easy task. Too many times, one ends up choosing a component that is not the best choice by far. This is quite true when we look at component selections in the process industries compared to those in a power plant where the operating conditions are more or less constant. This improper selection of components is due to multiple reasons such as: insufficient research and studies; limitation of time, resources, budget etc. Read More

Thermal Management in Aerospace Electric Propulsion Systems

The growing interest towards electric propulsion system for various applications in aerospace industry is driven first by the ambitious carbon emissions and external noise reduction targets. An electric propulsion (EP) system not only helps reduce the carbon emissions and external noise, but also helps reduce operating cost, fuel consumption and increases safety levels, performance and efficiency of the overall propulsion system. However, the introduction of electric propulsion system leads engineers to account for certain key challenges such as electric energy storage capabilities, electric system weight, heat generated by the electric components, safety, and reliability, etc. The available electric power capacity on board may be one of the major limitations of EP, when compared with a conventional propulsion system. This may be the reason electric propulsion is not the default propulsion system. Now, let’s consider how electric propulsion is used in the aerospace industry. Following the hybridization or complete electrification strategy of the electric drive pursued on terrestrial vehicles, the aerospace industry is giving great attention to the application of electrical technology and power electronics for aircrafts.

Figure 1 Aircraft Electric Propulsion Architectures
Figure 1. Aircraft Electric Propulsion Architectures. SOURCE: [1]
Electric Propulsion in aircrafts may be able to reduce carbon emissions, but only if new technologies attain the specific power, weight, and reliability required for a successful flight. Six different aircraft electric propulsion architectures are shown in Figure 1, above, one is all-electric, three are hybrid electric, and two are turbo-electric.  These architectures, rely on different electric technologies (batteries, motors, generators, etc.).

Read More

Why is Rotor Dynamics so Important?

[:en]Welcome back for the 3rd installment of our introduction to rotor dynamics! If this is your first time having a look at this series, hello! Feel free to have a look at the previous installments if you want to play catch-up or get a refresher.

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Otherwise, let’s get into a question I’m sure a few of you have been asking. Why is rotor dynamics analysis so important?

Steam Turbine View and Train Lateral Model
Steam Turbine View and Train Lateral Model in AxSTREAM RotorDynamics

Let’s start with a basic premise. As we’ve previously established, rotor dynamics is the behavior of rotating equipment and the analyses of said behavior. Rotating equipment tends to be very expensive to design, develop, and manufacture, so from a financial standpoint, it is prudent to ensure that the behavior of the equipment as it operates does not jeopardize itself or any other. A machine like an aero engine cost hundreds of thousands or even millions of dollars for a team to design, analyze and refine the flowpath, therefore, an analysis which costs a fraction of that money and also ensures the rotor-train is properly supported is a prudent use of time and engineering resources. Read More

Unsteady Flow Simulation in Hydraulic Systems

[:en]An unsteady flow is one where the parameters change with respect to time. In general, any liquid flow is unsteady. But if a hydraulic system is working at constant boundary conditions, then the parameters of the fluid flow change slowly; thus this flow is considered steady. At the same time, if the parameters of the fluid flow oscillate over time relative to some constant value, then it called quasi-steady flow 1.

In practice, most fluid flows are steady or quasi-steady. Examples of the three flows are presented in Figure 1. Steady flow is presented by a simple pipe. The quasi-steady flow is represented by a sharpened edge channel. The unsteady flow is presented by an outflow from a reservoir.

Figure 1 - Different Types of Fluid Flow
Figure 1 – Different Types of Fluid Flow
Different Cases of Unsteady Flow

During operations, hydraulic systems act for long intervals at steady conditions which are called operating modes. Change between two different operating modes occurs over a short time interval (called a transient mode). If any hydraulic system works more than 95% of the time at these operating modes though, why is the unsteady flow is so important? Because the loads depend on time intervals. If the load is less, then the maximum system pressure is higher. Read More

An Introduction to Thermal Management in Electric Propulsion Systems

Reduction in CO2 emissions is driving the development of different electric, turbo-electric and hybrid electric propulsion systems for various applications and industries including space, aviation, automotive and marine. Electric propulsion (EP) is not a new concept, having been studied in parallel with chemical propulsion for many years. EP is a generic name encompassing all the ways of accelerating a propellant using electric power by different possible electric and/or magnetic means. The simplest way to achieve electric propulsion is to replace the heat generated by combustion in conventional chemical engines with electrical heating.

Electric propulsion systems offer several advantages compared to other conventional propulsion systems. It not only helps reduce the environmental emissions but also helps reduce fuel consumption and increases safety levels. Electric propulsion has become a cost effective and sound engineering solutions for many applications. Electric propulsion engines are also more efficient than others. It is proven to be one of the most energy saving technologies as we can use more renewable sources of energy (due to the versatility of electricity generation) instead of non-renewable sources of energy like gasoline. The major limitation of electric propulsion, when compared with conventional propulsion is limited by the available electric power capacity on board, this may be the reason, it is not the default propulsion system.

Electric Propulsion Architectures
Figure 1. Electric Propulsion Architectures. SOURCE: [4]
Generally, electric propulsion architectures vary depending on the application. Figure 1, above, shows the EP architectures for an aviation application. These architectures rely on different electric technologies (batteries, motors, generators, and so on). Typical aircrafts use gas turbine engines as the source of propulsion power, but all electric aircraft systems use batteries as the only source of propulsion power as shown in Figure 1 on the right. The hybrid systems use gas turbine engines for propulsion and to charge batteries which also provide energy for propulsion and accessories during one or more phases of flight as shown in Figure 1 on the left. Read More