In many industrial applications, from power generation to aviation, turbomachinery is essential. A crucial choice to be made during the design phase is whether to go with an axial or radial configuration. This decision significantly influences the performance, efficiency, and reliability of the turbomachine.
The primary distinction between axial and radial turbines lies in the way fluid flows through the components (compressor and turbine). These two types of turbine configurations are illustrated in Figure 1.
However, it is also important to remember that both axial and radial turbomachinery configurations have advantages and disadvantages, and they can be applied to various types of machines.
A heat pump serves as an alternative to gas or electric boilers, relying on the production of heat. Unlike boilers, a heat pump doesn’t generate heat but extracts energy from the air, water, or ground.
Heat pumps and electric boilers both draw power from the mains electricity supply, yet heat pumps exhibit higher efficiency. This efficiency is contingent upon the conversion efficiency, measured by the Coefficient of Performance (COP), of a specific heat pump. The COP represents the ratio of heat energy received to the electricity consumed, particularly in the operation of the pump’s compressor unit. Notably, a heat pump consumes 3-6 times less electricity than an electric boiler with the same output.
Even in challenging conditions, such as an outside air temperature of -25°C, heat pumps excel in providing heating. Simultaneously, they achieve a high COP – generating 2-5 kW of heat or cold (depending on the type of heat pump) per 1 kW of electricity. This starkly contrasts the lower efficiency of gas and electric boilers.
Heat Pump Use Potential
The economic (rising energy costs) and environmental (effects of climate change) aspects of heat pumps should also be noted when discussing heat pumps. Heat pumps make it possible to utilize renewable heat resources such as geothermal, solar thermal energy and recovered heat from the urban environment. In addition, heat pumps maximize the decarbonization potential of renewable electricity sources (such as wind and solar) by converting them into renewable heat. In combination with thermal storage and electric boilers, heat pumps provide flexibility and security to the building life-support system, offering daily, weekly, and seasonal flexibility. Read More
For many years, one of the primary analysis techniques has been undamped critical speed analysis, and this technique is still performed today for the preliminary estimation of critical speeds and mode shape characteristics. First, let’s take a look at what this kind of analysis technique is and what it involves.
Critical speeds and their associated mode shapes are most influenced by the support (bearing and pedestal structure) stiffness magnitudes, the support locations, and the rotor’s mass and stiffness properties. Based on this, the following definition can be given. A critical speed map is a graph representing the effect of rotor support stiffness on the critical speed of the rotor. A general view of the critical speed map is shown in Figures 1-2.
With this definition in hand, the next question would be what is critical speed? Critical speed is the rotational speed that corresponds with a structure’s resonance frequency (or frequencies). A critical speed appears when the natural frequency is equal to the excitation frequency. The excitation may come from unbalance that is synchronous with the rotational velocity or from any asynchronous excitation. Read More
Hydrodynamic plain bearings play a crucial role in the overall reliability, vibration, and performance of rotary bearing systems. High-performance rotating machines operate at high speeds and subject bearings to significant static and dynamic loads. Consequently, bearing modeling must accurately simulate physical effects. However, the increasing complexity and demanding applications of bearings pose challenges for engineers striving to develop reliable designs.
One critical aspect of bearing design is optimizing the bearing clearance to prevent metal-to-metal contact, especially under heavy loading. This optimization is closely linked to the selection of the minimum oil film thickness (MOFT), which becomes a limiting factor during the process. Another limitation to consider is the maximum allowable level of bearing loading (eccentricity).
The variable parameters that can be considered in the optimization process are as follows:
Authors note: While I have the utmost respect for die-hard Star Wars fans, I must confess that growing up, Episode I was my favorite. Perhaps it was the allure of Darth Maul’s dual lightsaber, the adrenaline-pumping Podracing on Tatooine, or Natalie Portman (no elaboration needed) that captivated my young mind. Although May 4th has already passed this year, my love of Episode I combined with my upcoming presentation at JANNAF had me thinking that perhaps it’s time to revisit the engineering behind Podracers.
In a previous blog post, we explored the possibilities of redesigning Anakin’s Podracer. Back then, we discovered that the movie’s turbine and compressor design fell far below the mark. However, poor Ani didn’t have access to the advanced AxSTREAM® software platform for designing turbomachinery systems and components, nor did he possess the financial means to acquire top-of-the-line hardware (let’s be honest, Watto’s junkshop hardly exuded luxury).
Today, we revisit the exhilarating world of Podracing, determined to avoid the disastrous fate that befell Ben Quadinaros’ craft.
Now, many factors could have contributed to that unfortunate incident. For example, frustration-induced control slamming is never advisable… However, the most plausible explanation is a failure at one of the subsystem interfaces. Why do I think so? Simply because this is a common issue with modern systems, including vehicles. Everyone involved means well and possesses the necessary technical prowess to perform their individual tasks. However, problems often arise when these meticulously designed parts and subsystems attempt to interface seamlessly. This is precisely where a coupled digital engineering solution comes into play! Close your eyes (then reopen them to keep reading) and imagine a place where all critical propulsion and auxiliary components can be modeled together, accommodating any desired conditions (including those we cannot run with physical hardware on a test bench).
Rolling element bearings are essential components in a vast range of rotating mechanical systems, providing rotational support and a wide range of methods for friction control. The performance of these bearings is crucial to the overall functionality of the machine. Therefore, predicting the dynamic behavior of rolling bearings accurately is vital to ensure their reliable operation. Figure 1 shows a general view of angular contact ball bearings.
Dynamic parameter calculation is the process of determining the bearing’s dynamic response under specific operating conditions, including load, speed, and lubrication. The calculation of these parameters is crucial for designing and selecting bearings and predicting their operating life. The main dynamic parameters are:
Radial and axial stiffness, which is the ability of a bearing to resist deformation when subjected to radial and axial loads. This parameter is essential in ensuring that the bearing maintains its shape and does not deform excessively under the applied load.
Damping, which is the ability of a bearing to absorb energy and dissipate it in the form of heat. This parameter is crucial in ensuring that the bearing does not overheat, leading to premature failure.
Moreover, bearing stiffness and damping are used for the rotor dynamic calculations of the machine supported by rolling element bearings for the accurate prediction of the rotor response under static and dynamic loads, taking into account the correct bearing characteristics. Read More
Now that we understand what a nuclear reactor is, why it is used, and how it works (covered in part 1), let’s take a deeper dive into the different types of nuclear reactors, their benefits and limitations, and strategies to design and model nuclear reactor cycles using AxSTREAM System Simulation.
Types of most commonly used nuclear reactors:
There are several types of nuclear power reactors available worldwide. Based on their design, they use uranium with different concentrations as fuel, moderators to delay the fission process, and coolants for heat transfer. However, the most commonly used nuclear reactors are pressurized water reactors (PWRs) and boiling water reactors (BWRs). PWRs dominate the global nuclear fleet with 301 units comprising 66% of all nuclear power plants in operation , followed by BWRs at 16% with 72 units, and all other types of reactors accounting for the remaining 18%.
Pressurized water reactors (PWRs):
PWRs were designed and implemented commercially sooner than BWRs due to the earlier notion that pressurized liquid water would be much safer to handle than steam in the reactor core and would add to the stability of the core during operation. That is why the first commercial reactor in Shippingport was a PWR. Figure 4 shows a schematic design of a typical PWR plant.
A PWR plant consists of two separate light water (coolant) loops, primary (nuclear part) and secondary (conventional portion) as shown in Figure 4. PWRs use ordinary water as both coolant and moderator. The PWR primary loop works at an average pressure of 15 to 16 MPa, with the help of a set of pressurizers, so the water does not boil even at a temperature of 320 to 350 ℃ in the reactor. The heat from the primary water (nuclear part) transfers to the secondary water (conventional part) in the steam generator (Figure 4). There, secondary water converts into steam which drives the turbine to generate electricity. The core water cycles back to the reactor to reheat, repeating the process. Read More
There is no doubt that energy has been driving and will drive the technological progress of human civilization. It is a vital component for economic development and growth, and thus our modern way of life. Researchers project that the world energy demand will almost double by 2040 (based on energy usage), which must be met by utilizing energy sources other than fossil fuels such as coal and oil. Fossil fuel power generation contributes to significant greenhouse gas emissions into the atmosphere and influences the climate change trend. Although several research and development programs (for example, carbon sequestration and ultra-supercritical steam turbine programs) have been initiated to make fossil power generation much cleaner, more is needed to fend off the bigger problem. Therefore, many countries worldwide have recognized the importance of clean (i.e., emission-free) nuclear energy, and there are proven technologies that are more than ready for deployment. Nuclear power can solve the energy trilemma of supplying clean and affordable base-load power.
The use of nuclear energy for power generation varies widely in different parts of the world. About 454 nuclear power reactors currently supply more than 10% of the world’s electricity, operating at a high capacity factor of 81% (world average). Thirty-one countries use nuclear power plants, with 70% of the world’s nuclear electricity generated in five countries – the USA, France, China, Russia, and South Korea. As such, many other countries have tremendous opportunities for nuclear energy growth. Today the average age of the operational power reactors stands at 30 years, with over 60% of all nuclear power plants having operated for more than 31 years. Hence, nuclear power reactors are an essential energy source that has been providing electricity to millions of people worldwide. Despite the controversy surrounding nuclear power due to the risk of radiation exposure, nuclear reactors have proven to be a reliable, efficient, and emission-free source of electricity generation. Nuclear reactors have been built for the primary purpose of electricity production, although they are used for other applications such as desalination, radioisotope production, rocket propulsion, and much more. A view inside the Olkiluoto 2 nuclear reactor vessel is shown in Figure 2. Read More
Hydrogen fuel and renewable energy are becoming increasingly relevant in the gas turbine industry as the world shifts towards decarbonization. Hydrogen fuel, in particular, is seen as a promising alternative to traditional fossil fuels due to its clean-burning properties. As a result, many gas turbine manufacturers are exploring ways to modify existing engines to run on hydrogen or hydrogen mixtures. Additionally, the use of renewable energy sources such as wind and solar power to generate hydrogen fuel is gaining traction, providing a sustainable solution for the gas turbine industry. These developments are crucial in reducing carbon emissions and meeting climate goals, making hydrogen and renewable energy an essential focus for the future of the gas turbine industry.
In light of these developments, one of the key methods to achieve decarbonization is to use a mixed renewable gas (e.g., green hydrogen, biogas, syngas) or pure hydrogen (in the future) as a fuel for stationary gas turbine engines (GTE) that generate electricity.
The main advantage of this method is that companies need not design and manufacture fundamentally new engines for hydrogen combustion. Instead, modifying the existing GTE fleet is sufficient. Another benefit of introducing hydrogen gas turbine technology is the possibility of using idle or underutilized equipment, thereby providing a new lifecycle. Read More
The open Brayton cycle is commonly used in gas turbine engines for power generation, aircraft propulsion, and industrial processes. The Brayton cycle, named after American engineer George Brayton, who proposed it in 1872, converts fuel energy into mechanical work. The Brayton cycle became widely used in practical applications following the development of the gas turbine in the 1930s. Gas turbines were used extensively during World War II, and their efficiency and reliability improved significantly.
The Brayton cycle has numerous advantages for energy applications. For one, engineers can design it compactly, making it a strong fit for tight enclosures. With gas turbines being a common engine driver, the Brayton cycle is popular in modern applications. Since Brayton cycle engines are particularly efficient in gas turbine engines, they are useful for power generation, aircraft and marine propulsion, industrial processes, and more.
Additionally, Brayton cycle motors produce few emissions thanks to their efficient exhaust gas treatment systems, making them a greener choice than other fossil fuel systems. Coupled with their high efficiency from the isentropic compression and expansion processes that minimize energy loss, engineers continue to develop Brayton thermodynamic cycle systems to this day.
There are two main types of a Brayton cycle: open and closed. In an open Brayton cycle, the working fluid is continuously supplied to and exhausted from the system, and the process operates in an open loop. On the other hand, in a closed Brayton cycle, the working fluid is contained within the system and circulates in a closed loop. The schematics of a simple open-cycle gas turbine utilizing an internal-combustion process and a simple closed-cycle gas turbine using heat transfer processes are both shown in figure 1.
An ideal Brayton cycle consists of the following four processes:
Isentropic compression: air is compressed to high pressure and temperature via an isentropic process that is adiabatic and reversible.
Constant pressure heat addition: high-pressure air is fed into a combustion chamber where fuel is added and ignited.
Isentropic expansion: high-temperature gases from the combustion chamber expand in the turbine in an isentropic process, producing mechanical work.
Constant pressure heat rejection: the exhaust gases are expelled into the atmosphere.