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
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 . 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. Read More
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. 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. can have disastrous effects. The work of some of these partial system can be analyzed and optimized using AxSTREAM NET™.
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 (Figure 2). The atmosphere should consists of 19.5 to 23.5 % of an oxygen. 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
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:
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.
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.
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.
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
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.
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.).
[: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.
Otherwise, let’s get into a question I’m sure a few of you have been asking. Why is rotor dynamics analysis so important?
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
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.
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
In just about every corner of the globe, machines are used and needed for the modern world and its people to function in normal everyday life. But what if these machines were to just…disappear? How badly would it disrupt modern society? Our young protagonist is about to find himself in the midst of such a scenario as he comes to realize he’s taken residence in an apartment building located inside a little neighborhood known as…the twilight zone.
I open my eyes slowly and rejoin the world, in all of its silence. Hold on, it’s Thursday, the alarm was supposed to wake me up! I roll over to check the time, and the screen is just a blank, black façade. That’s odd. The alarm clock isn’t working. The fan isn’t on either. The power must be out. What could have happened to shut off the power? Read More
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.
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
Gas turbines have had a presence in many industries for more than a century. They are a unique technology for either producing an energy or propelling a vehicle and the efficiency of modern gas turbines is being improved continuously. One of them, a cooling system, has been described in earlier blogs. Another is the lubrication system of a gas turbine which we will cover in this blog. This system, similar to that of a piston engine or a steam turbine, provides lubrication to decrease mechanical losses and prevent of wear on friction surfaces. Another function is the removal of heat released during friction by high rotational part and transmitted from the hot part of a turbine. The basic units which need lubrication are the bearings supporting a shaft of a gas turbine 2.
Elements for lubrication
In a common case, gas turbine installation contains three main journal bearings used to support the gas turbine rotor 3. Additionally, thrust bearings are also maintained at the rotor-to-stator axial position 4. Click here for additional information about optimization of journal bearings. The bearing has important elements in its construction to prevent leakages from a lubrication system. The work, design and analysis of labyrinth seals is describe here.