In comparison to large steam and gas turbines, the rotating equipment found in heat ventilation and air conditioning (HVAC) applications is often seen as more simplistic in design. However, sometimes a simpler model of a rotating machine does not mean a simpler approach can be used to accurately investigate its rotor dynamics behavior. For example, a large number of effects should be taken into account for single-stage compressors used in HVAC applications. Three important ones include:
High values of rotational speeds above the first critical speed;
Rigid rolling element bearing used in the design and therefore a relatively flexible foundation which should be modeled properly;
Aerodynamic cross-coupling adding additional destabilizing forces to the structure.
All these effects should be modeled properly when performing lateral rotor dynamics analyses of HVAC machines. And, in some cases, this simpler model can prove a much more challenging task than building the complex model of a steam turbine rotor.
Let’s consider a seemingly simple example of a high-speed single-shaft compressor for HVAC application (Figure 1). It consists of the compressor and motor rotors, the flexible coupling connecting them, the ball bearings connecting the rotors to the bearing housing joined with the compressor volute, and the structural support.
The compressor rotor is connected with the motor through a flexible coupling. Its lateral vibrations can be considered uncoupled from the motor rotor vibrations, and the lateral rotor dynamics model appears pretty straightforward (Figure 2).
However, additional factors are discovered if you include the mechanical properties of the supporting structure when considering the lateral rotor dynamics calculations. These factors are very important to an accurate model. Read More
Axial fans have become indispensable in everyday applications starting from ceiling fans to industrial applications and aerospace fans. The fan has become a part of every application where ventilation and cooling is required, like in a condenser, radiator, electronics, etc., and they are available in a wide range of sizes from few millimeters to several meters. Fans generate pressure to move air/gases against the resistance caused by ducts, dampers, or other components in a fan system. Axial-flow fans are better suited for low-resistance, high-flow applications and can have widely varied operating characteristics depending on blade width and shape, a number of blades, and tip speed.
The major types of axial flow fans are propeller, tube axial, and vane axial.
– Propellers usually run at low speeds and handle large volumes of gas at low pressure. Often used as exhaust fans these have an efficiency of around 50% or less.
– Tube-axial fans turn faster than propeller fans, enabling operation under high-pressures 2500 – 4000 Pa with an efficiency of up to 65%.
– Vane-axial fans have guide vanes that improve the efficiency and operate at pressures up to 5000 Pa. Efficiency is up to 85%.
Aerodynamic Design of an Axial Fan
The aerodynamic design of an axial fan depends on its applications. For example, axial fans for industrial cooling applications operate at low speeds and require simple profile shapes. When it comes to aircraft applications however, the fan must operate at very high speeds, and the aerodynamic design requirements become significantly different from more traditional fan designs. Read More
Due to concerns about air travel’s impact on climate change, research and development into electric aircraft has been ongoing for several years. Within the last decade several startups as well as larger corporations have been developing electric or hybrid electric aircraft (Ros, 2017). The ultimate goal is to Conduct long (>500 miles), full-electric commercial flights with large aircrafts capable of carrying 100’s of passengers, but this will require at least 5-10 more years of development. Luckily, smaller electric aircraft designed for short-range flights (<500 miles) with anywhere from 1-20 passengers have already been tested successfully utilizing electric batteries, a hybrid-electric system and even a hydrogen fuel cell. With these advances, emission-free air travel is closer than you think.
Examples of full-electric aircraft designs include the Airbus E-Fan 1.0 and E-Fan 1.1 (Airbus Group), shown in Figure 1. These two-person aircraft utilize two ducted, variable-pitch fans, shown in Figure 2. Each fan is powered by a 30-kW electric motor. The motors are powered by several lithium-ion battery packs stored in the wings. While the aircraft only provides an hour of flight time, the batteries can recharge in approximately one hour and can be easily be swapped in and out.
There are several reasons besides climate change why electric aircraft should be developed from a business perspective (Figure 3). Short and mid-range regional flights make up a significant portion of all flights around the world. The current flight range of electric aircraft is limited to these short and mid-range fights. Additionally, shorter flights spend relatively more time taking off and landing than cruising at high altitudes, which makes shorter trips less energy efficient. While short, regional flights are economically unattractive for large commercial aircraft, a smaller aircraft with less fuel consumption may provide a valuable alternative. Read More
As a special tribute this Veterans Day, we decided to have a look at some of the most notable engines that have been used to propel military vehicles throughout history.
Kicking off our list is the Pratt & Whitney 135 turbofan engine. The pride and joy of Pratt & Whitney’s military engine lineup, the 135 powers the US Military’s F35 Lightning II. Presently, two variants of the F135 are used in several different variants of the F35, although it should be noted that the F135 was developed specifically for the F35. The 3 engine variants are known as the F135-PW-100, the F135-PW-600, and the F135-PW-400, each for a different application of the F35. The 100 variant is used in the conventional take off and landing F35A, the 600 is used in the F135B for short take off and vertical landing F35B, and the 400 uses salt corrosion-resistant materials for the Naval variant F35C.
The F135 is capable of 28,000 lbf of thrust with the afterburner capability pushing thrust all the way to a whopping 43,000 lbf of thrust, making the Lightning II a supersonic STOVL aircraft suited to a wide variety of applications, as seen in the above illustrations. At the heart of the Pratt F135 are 3 fan stages, 6 compressor stages, and 3 turbine stages. In the STOVL variant, the F135-600 uses the same core components, but is also coupled to a drive shaft which connects the engine to the lift fans which were originally developed by Rolls-Royce, and give the Lightning the ability to hover, perform short distance takeoffs, and vertical landings.
The F35 by Pratt & Whitney and in turn the F35 Lightning II by Lockheed Martin represent the cutting edge in military aviation, and are the centerpieces of Pratt and Lockheed respectively. The Lightning variants and this line of turbofan engines will be in service with several branches of the US military and its allies around the world for the foreseeable future, with more iterations of the F135 to come. Read More
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.
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:
where, ‘N’ is rotational speed (RPM), ‘Q’ is flow rate (ft3/sec), ‘H’ is head (ft), ‘D’ is diameter (ft) Read More
Landspeeders belong to the “repulsorlift” transport class, like the podracers we looked at last year, and travel above a world’s surface (up to 2 meters) without contact (very useful on swampy lands like Dagobah). Landspeeders are the successors to the hanno speeder which was mainly used as a racing vehicle with many Tatooine natives still using them to race in the Boona Eve Classic today.
Landspeeders are found in both civilian and military applications but due to intergalactic ITAR regulations we will only cover the civil aspect here with a focus on the most famous of them all. If you want to know more about our experience working with military, defense and governmental organizations (whether you area part of the Empire, Rebels, Resistance or Separatists) feel free to contact us.
The Famous X-34
Luke Skywalker’s X-34, with its 6 selectable hover heights, features an engine consisting of 3 air-cooled thrust gas turbines able to reach a top speed of about 155 mph. The side engines are also used for steering although it is not obvious whether this steering is achieved by varying their thrust to be asymmetric or through vectoring of their exhaust. With the X-34 total length being 3.4 meters it helps us estimate the overall dimensions of its engines which are, each, roughly 80 cm long by 30 cm wide. Read More
Mechanical engineering is an ever-changing field, and we want to be there to help engineers stay ahead of the curve, even while they are flattening it. In that spirit, we wanted to share with you our different training options that are available now. Whether you are looking to brush up on the fundamentals, or evaluate a software platform, this is a great time to train and explore the latest and greatest in turbomachinery engineering.
Without further ado, let’s get into it!
Private Corporate Trainings Online
First and foremost, the best most comprehensive training you can get from SoftInWay is a private session with one of SoftInWay’s lead engineers and your team. Why is this the best training option? A couple of reasons:
Courses are entirely customizable: The scope of these private training courses is tailored to your specific needs. Are you looking to learn the fundamentals? Or perhaps you want to expand your team’s R&D capabilities when it comes to turbomachinery, rotor dynamics, and 1D thermal systems? Whatever the application, we’ll work with you to develop a course curriculum which brings the most value to you and your team.
One-on-one consultation with our expert engineers on individual projects and challenges. Our engineering expertise ranges from flowpath design on a turbomachine, to rotor dynamics, as well as secondary flows/multiphase flows, and other all-encompassing projects such as liquid rocket engine design.
ll registrants get a 1-month license of the relevant AxSTREAM modules. During the class, users will be familiarized with the ins and outs of AxSTREAM, and be able to make use of AxSTREAM’s capabilities for 1 month afterwards.
The class can be as long or as short as you need and scheduled around you and your team. 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.).
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
High bypass ratio (BPR) fans are of heightened interest in the area of civil air vehicle propulsion. It increases the air inhaling and improves both the thrust and the propulsive efficiency. The specific fuel consumption is also reduced in today’s turbofan engines.
The inlet fan designs and optimizations are very important as the fan can be subjected to different inlet conditions. As a matter of fact, a modern high bypass fan system provides over 85% of the engine’s net thrust. Hence, a well-designed bypass fan system is crucial for the overall propulsion characteristics of a turbofan engine. A tool which can perform both inverse tasks and direct tasks on bypass fan system is a necessity for turbofan design.
AxSTREAM ® Streamline Solver
The AxSTREAM® streamline solver is a throughflow solver, the specificity of the outcome one should expect from this solver is up the meridional flow field. Hence, when we develop the model, we shall take Acarer and Özkol’s work  as a reference example. Read More