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

Part Two: A Company Snapshot of 2019 – Looking Back and Looking Forward

Part 1

Software Upgrades:

2019 was a year of innovation and exploration for our engineering team as we worked with our customers to develop capabilities both in and outside the realm of turbomachinery. Our dedicated structural and rotor dynamics engineers worked with some of our AxSTREAM RotorDynamics customers to continually develop capabilities to perform torsional forced response analyses in reciprocating compressors. On the thermal-fluid modeling front, our engineers added capabilities to AxSTREAM NET, enabling it to be used for multiphase flows in heat exchangers, rocket engine nozzles, and refrigeration systems, as well as continued development of capabilities for analyzing secondary flows and leakages from turbomachinery flowpaths.

 

Rocket Nozzle Modeling in AxSTREAM NET
Rocket Nozzle Modeling in AxSTREAM NET (left) and CAD Model (right)

Perhaps one of the biggest buzzwords of the last decade (and for years to come!), SoftInWay’s engineers underwent a project to further streamline the turbomachinery design process leveraging Artificial intelligence (AI). While AxSTREAM ION™ had already made it possible to automate processes in AxSTREAM and enable interaction with external CAD/CAM programs and other commercial/in-house codes, AxSTREAM.AI™ takes it one step further. By utilizing machine learning to iterate designs continually and training the program to recognize feasible and infeasible designs, AxSTREAM.AI™ is able to develop components in just several hours, as opposed to month-long or year-long projects. Read More

A Company Snapshot of 2019 – Looking Back and Looking Forward

Part 2

In what feels like the blink of an eye, 2019 has come to a close (well, almost). In the last decade, we have seen technology make leaps and bounds with advancements in everything from electric vehicles and propulsion, to artificial intelligence, to the microsatellite industry, and supercritical carbon dioxide (sCO2) power cycles. We’ve even seen the rise of the elusive and mysterious impossible burger. For engineers working in the field of technology as well as the SoftInWay team, it has been an exciting year full of new developments and growth; and we’d love to share a recap of our year with you, our readers!

So what has SoftInWay been up too this year?

Liquid Propulsion Systems Seminar:

Earlier in the year, we hosted a liquid rocket engine design/development seminar in Huntsville Alabama, AKA Rocket City USA. We had a good turnout from companies in the area that included Teledyne Brown, ATA Engineering, as well as other businesses large and small that call the Rocket City home. This event allowed us to show off our latest software development in the aerospace industry, AxSTREAM.SPACE, and how quickly and simply an engineer can design a turbopump for a liquid rocket engine as well as design/optimize the cooling channels in the engine’s nozzle, and perform the rotordynamics analyses for the turbopump.

Turbo Expo:

Read More

Thermal Management in Automotive Electric Propulsion Systems

There is a growing interest in electric and hybrid-electric vehicles propulsion system due to environmental concerns. Efforts are directed towards developing an improved propulsion system for electric and hybrid-electric vehicles (HEVs) for various applications in the automotive industry. The government authorities consider electric vehicles one of several current drive technologies that can be used to achieve the long-term sustainability goals of reducing emissions. Therefore, it is no longer a question of whether vehicles with electric technologies will prevail, but when will they become a part of everyday life on our streets. Electric vehicles (EVs) fall into two main categories: vehicles where an electric motor replaces an internal combustion engine (full-electric) and vehicles which feature an internal combustion engine (ICE) assisted by an electric motor (hybrid-electric or HEVs). All electric vehicles contain large, complex, rechargeable batteries, sometimes called traction batteries, to provide all or a portion of the vehicle’s propelling power.

EVs propulsion system offers several advantages compared to the conventional propulsion systems (petrol or diesel engines). EVs not only help reduce the environmental emissions but also help reduce the external noise, vibration, operating cost, fuel consumption while increasing safety levels, performance and efficiency of the overall propulsion system. However, there are many reasons why EVs and HEVs currently represent such a low share of today’s automotive market. For EVs, the most important factor is their shorter driving range, the lack of recharging infrastructure and recharging time, limited battery life, and a higher initial cost. Though HEVs feature a growing driving range, performance and comfort equivalent or better than internal combustion engine vehicles, their initial cost is higher and the lack of recharging infrastructure is a great barrier for their diffusion. Therefore, industry, government, and academia must strive to overcome the huge barriers that block EVs widespread use: battery energy and power density, battery weight and price, and battery recharging infrastructure. All major manufacturers in the automotive industry are working to overcome all these limitations in the near future.

Common Types of Electric Vehicles
Classification of EVs according to the types and combination of energy converters used
Figure 1. Classification of EVs according to the types and combination of energy converters used (electric motor & ICE). SOURCE:[3]
A more universal EVs classifications is carried out based on either the energy converter types used to propel the vehicles or the vehicles power and function [4]. When referring to the energy converter types, by far the most used EVs classification, two big classes are distinguished, as shown in Figure 1, namely: battery electric vehicles (BEVs), also named pure or full-electric vehicle, and hybrid-electric vehicles (HEVs). BEVs use batteries to store the energy that will be transformed into mechanical power by electric motors only, i.e., ICE is not present. In HEVs, propulsion is the result of the combined actions of electric motor and ICE. The different manners in which the hybridization can occur give rise to different architectures such as: series hybrid, parallel hybrid, and series-parallel hybrid. All these different EVs architectures are shown in Figure 2.

Architectures of different EVs and HEVs
Figure 2. Architectures of different EVs and HEVs. SOURCE:[3]
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