Due to technological advancements in the aerospace industry, air transportation has become the primary means of travelling. This begs the question of “what are the key factors that could push the industry to the next level and allow for higher performance, low cost and low carbon emission flights?”
For a low carbon aviation to be achieved, a lot of effort is currently put on the aircraft-propulsion integration. Low-pressure-ratio fans are one of the concepts that is being studied in this regard. The lower the pressure across the propulsive element the more the exhaust velocities will decrease and therefore the higher the propulsive efficiency will be. However, a constant level of thrust would require an increase of the fan area, which could lead to an increase of the total weight of the configuration and ultimately cancel the efficiency benefits of the concept. Read More
Nowadays the scientific community is strongly concerned about problems of efficiency increase and emissions reduction in power generation, ship, and vehicle drives such as internal combustion engines (ICE). A system utilizing waste heat recovery (WHR) is an effective solution for the aforementioned problems.
ORC (meaning organic Rankine cycle, not the scary monsters from Lord of the Rings) is one WHR solution which delivers additional power from the turbine/engine exhaust gas/steam energy. ORC systems operate on hydrocarbon-based fluids which effectively avoid the typical disadvantages associated with water-based steam turbine systems while bringing the advantage of better performance at part load and in non-continuous operation. ORC systems, capable of utilizing low temperature heat sources of 100-200°C, can be designed in compact and modular packages which require very little maintenance.
The design criteria of an ORC system and its components includes finding the maximum possible heat recovery from the available high and low temperature waste heat flows of a turbine or ICE to produce the maximum amount of additional power while decreasing the load on the turbine’s cooling system, under certain restrictions like geometry and cost.
The first step is to design the thermodynamic cycle configuration. Figure 1 is a flow diagram of a dual loop supercritical organic Rankine cycle (SORC) with separate turbines and given design parameters of the components, generated with AxCYCLE™ software, developed by SoftInWay. The cycle consists of 6 heat exchangers, 2 turbines (HPT and LPT), 2 pumps (HPP and LPP) and the condenser. Both turbines operate with the same backpressure – 1.3 bars. The flows of the working fluid (R245fa in this case) are mixed at the condenser inlet and split at its outlet. The temperature – entropy diagram for the presented cycle is shown on Figure 2. The process 1-2-3-4-5-1 corresponds to the high pressure loop operation and the process 10-20-30-40-10 is for the low pressure loop operation. All these can be easily manipulated and obtained with user-friendly interface of AxCYCLE™.
In terms of component design, ORC turbines can be of axial, radial inflow and radial outflow configurations. The type of turbine you should select depends on the application. To delve further into the topic, check out SoftInWay’s webinar on “Radial Inflow versus Outflow Turbines – Comparison, Advantages and Applicability” here – http://learn.softinway.com/Webinar/Watch/102 Read More
“That sun is trying to kill us” is something I hear every other day from my wife. Growing up and settling in the Midwest of the USA, she is used to the beating heat from our local star. I remember a particular summer when the consecutive number of days over 100F (~38C) was well over 60.
As you can imagine this post is about the sun. (By which, I mean the star closest to us, but similar principles would apply to other solar systems). The emphasis will be made on understanding what this energy is, and how we can harness it.
First, let’s discuss solar energy in general. As its name suggests, this type of energy comes from the sun. (Solaris means sun in Latin and is where our word solar comes from). So far, so good. Now, even though “radiation” gets a bad reputation, this is actually how the heat and energy from our star reaches us. The radiation is produced by nuclear reactions in our sun’s core. Two hydrogen atoms get fused together to form one helium atom. The chemical reaction releases heat and light. And all of this is occurring inside the sun 93 million miles away in space. The light and heat travel through space. Then some of that energy, in the form of radiation, reaches us here on Earth.
Now that we know what energy solar energy is and where it comes from, let’s briefly discuss the processes we currently have to capture this energy and what uses we can make of it.
There are primarily two types of sun power harnessing systems:
Concentrated Solar Power (also known as CSP)
Solar panels are typically photovoltaic (PV) which means that they will convert photon energy (photo) into electricity (voltaic). When you think of such technology the roof of houses and office buildings (PV panels – comprised of several PV cells) is usually the first example to come to mind. But, don’t forget the small solar cells used to power your calculator (PC cell), or the much larger installations on the side of the highway (PV arrays – comprised of multiple PV panels). After capturing this solar energy, you can either use it for your personal needs, or in some cases you can sell it back to the grid. Note: Amazon recently completed its 17th rooftop solar project by installing a 1.1 MW array on its Las Vegas fulfillment center (https://www.renewableenergyworld.com/articles/2018/05/amazon-s-onsite-solar-just-went-up-a-notch.html).Another way solar panels work for domestic application is to circulate a liquid through the panels to heat the home (air heating, water heating, and so on).
CSP use a different technology altogether. Fields of mirrors (that rotate with the sun) are used to concentrate the energy from the sun into what is called a “black body”. In heat transfer terms, this refers to something that has a high thermal coefficient (emissivity) and typically sits at the top of a tower. If you have ever used a magnifying glass to concentrate solar energy on some dry twigs to start a fire, you have seen how effective this approach can be.
The previous blog post of this series mentioned that both nuclear and solar sources were considered clean energies with solar being renewable while our sun still shines. What makes it clean exactly? I am glad you asked! (I know you did not, but let’s pretend you did.) To quote my last post, clean energies are defined as “energies that do not pollute the atmosphere when used.” With solar energy, the process of energy creation is indeed harmless to the surrounding. The environmental impact of the systems to manufacture items needed to capture the solar energy and recycling/disposing of waste products from that process may pollute. Some will argue that solar arrays can be a visual pollution, but that objective opinion does not make solar a “dirty” energy since gathering the energy neither produce pollutants nor emits carbon dioxide. Read More
We as human kind have always aimed at achieving something better, something bigger. This led to the research on gas turbines, which was mainly inspired due to the immediate requirement in the aerospace and power generation industry, to also look beyond the scope of aeronautics.
Today gas turbine technology is often used when dealing with aerospace and power generation industries, but believe it or not, gas turbine technology has been used in ground transportation too; notably locomotives.
The Early Applications
After the first world war, several countries had the expertise and the finances to invest in achieving the technological edge in the new post war era. The gas turbine technology was one such technological endeavor, and by the mid-20th century the gas turbine could be found in several applications. Birth of gas turbine locomotives can be credited to two distinct characteristics of these locomotives versus the contemporary diesel locomotives. First, there are fewer moving parts in a gas turbine, decreasing the need for lubrication. This can also potentially reduce the maintenance costs. Second, the power-to-weight ratio is much higher for such locomotives which makes a turbine of a given power output physically smaller than an equally powerful piston engine, allowing a locomotive to be powerful enough without being too bulky.
A pump is a hardware, which feeds energy to a fluid (e.g. Water) to flow through channels. Pumps are used, for example, to direct water out of the ground, to transport drinking or sewerage water over large distances in combined pipe networks or to discard water from polders. In any practical application, the pump needs to work with its best performance. It is also important to check that the flow rate and head of the pump are within the required specifications, which are normally presented as the Pump Characteristic curves. These plots play an important role in understanding the region in which the pump needs to be operated thus ensuring the life of the pump.
Pump Characteristic Curves
The performance of any type of pump can be shown graphically, which can be based on either the tests conducted by the manufacturer or the simulations done by the designer. These plots are presented as Pump Characteristic Curves. The hydraulic properties of any pump (e.g. Centrifugal Pump) can be described by the following characteristics.
Net Positive Suction Head (NPSH) Curve
The Q-H curve gives the relation between the volume flow rate and the pressure head, i.e. the lower the pump head, the higher the flow rate. Q-H curves are provided by the manufacturer of the pump and can normally be considered as simple quadratic curves. Read More
This might seem like a strange question, but we get ask this a lot. The question takes the form of: Can the sales side do a proper preliminary design and select the optimal machine (turbine/compressor/pump)? Is it possible for the design and application task to be integrated in a way allowing the application team the autonomy to make decisions without going back to the engineering team every time they get an inquiry? After realizing how large of a pain point this is for our clients, we decided to solve this problem for a major turbine manufacturer in Asia and in the process, provided a time-saving solution to maximize the returns for all the stakeholders.
The challenge came with the different competencies of the sales and design team. The sales/application teams are not necessarily experts in design while designers cannot double as application engineers to meet the sales requirements.
In our efforts to solve this issue, we worked with this turbine manufacturer. We listed all of their current processes, limitation, requirements, constraints, and etc. to explore the many possible ways to resolve this pain point. In the end, there were two solutions; (1) Develop custom selection software, or (2) Leverage the AxSTREAM® platform using AxSTREAM ION™.
Developing Custom Selection Software: Developing a custom selection software specific to the manufacturer where their application team can choose the optimal turbine based on expected customer needs. Developing such a custom system requires bringing together the expertise of different teams from turbomachinery (such as aero-thermal and structural) to software developer, testing, etc. Developing such a one-off system also takes considerable time at considerable cost. This approach could solve the current problem, but with rapidly changing technologies and market requirements, this is not a viable long-term solution.
Leverage the AxSTREAM® Platform using AxSTREAM ION™: We evaluated the limitation and possibilities of utilizing our turbomachinery design platform AxSTREAM® to meet the requirement of sales/application engineering team for today’s needs and in the future. We found the organization had a greater advantage using this existing platform rather than investing in the short-term solution of developing a custom selection software. Many of the building blocks required for customization are already available to use via an interface a non-technical sales person could easily use. This platform was utilized for meeting the requirement of this turbine manufacturer saving time and cost while resolving a large pain-point for the organization.
As turbomachinery engineers, it is not always easy to tell non-technical folks what we do. If we start with “I design turbines,” the first thing most people think of are those giant wind turbines, and we are stuck with the nickname “wind guy/gal”. What we do is far more complex than putting 3 blades on a stick and confusing bystanders with why the turbine is rotating on a seemingly windless day; and don’t even get me started on the claims that wind turbines are a non-visually pleasing ploy from the government to make use of our taxpayers money.
Okay, maybe I will get started on those topics, but not in this series. Today, I am introducing a new series of blog posts related to clean energies and how turbomachines tie in with this not-so-novel concept making a lot of noise nowadays.
Throughout this series, we will be discussing the different “clean” technologies in power generation which people have been using for hundreds of years, some more recent “hipster-y” applications, and look at what could make a difference in tomorrow’s world. These short posts will cover general and practical information, which students as well as seasoned engineers can use to better understand the topic at hand. Some articles/parts will be more technical than others, and no matter what your current level of proficiency, you will be able to pick out some useful takeaways. Read More
Bottoming cycles are generating a real interest in a world where resources are becoming scarcer and the environmental footprint of power plants is becoming more controlled. With this in mind, reduction of flue gas temperature, power generation boost, and even production of heat for cogeneration application is very attractive and it becomes necessary to quantify how much can really be extracted from a simple cycle to be converted to a combined configuration.
Supercritical CO2 is becoming an ideal working fluid primarily due to two factors. First, turbomachines are being designed to be significantly more compact. Second, the fluid operates at a high thermal efficiency in the cycles. These two factors create an increased interest in its various applications. Evaluating the option of combined gas and supercritical CO2 cycles for different gas turbine sizes, gas turbine exhaust gas temperatures and configurations of bottoming cycle type becomes an essential step toward creating guidelines for the question, “how much more can I get with what I have?” Read More
In every modern cleaning system there exists at least one pumping unit. With this in mind, understanding how it works and how to use it efficiently is critical to the successful operation and maintenance of that cleaning system. This blog will discuss centrifugal pumps in this context and take a look at important attributes to bear in mind when working with these systems.
In general, pumps are devices which impart energy to a flow of liquid. Although there are different types of pumps based on the flow direction, blade designs, and so on, centrifugal pumps are in the majority of those used in cleaning systems. Centrifugal pumps are simple, efficient, reliable, relatively inexpensive, and easily meet the needs of most cleaning system requirements including spraying, overflow sparging, filtration, turbulation and the basic function of moving liquids from one place to another using pressure.
A centrifugal pump uses a combination of angular velocity and centrifugal force to pump liquids. The below figure illustrates the working principle of the centrifugal pump.
The pump consists of a circular pump housing which is usually made up of metals, (stain steels etc.) solid plastic, or ceramics. The outlet extends tangentially from the diameter of the pump housing. Inside the pump housing there is a rotating component an “impeller” which rotates perpendicular to the central axis and is driven by a shaft secured to its center of rotation. The shaft, powered by an electric motor, enters the pump housing through a liquid tight seal which prevents leaking. Liquid entering the pump through the inlet is swirled in a circular motion and displaced from the rotation center of the impeller by centrifugal force. The combination of the swirling action (angular velocity) and centrifugal force (radial velocity) pushes the liquid out of the pump through the outlet.
Nowadays, transonic axial flow compressors are very common for aircraft engines in order to obtain maximum pressure ratios per single-stage, which will lead to engine weight and size reduction and therefore less operational costs. Although the performance of these compressors is already high, a further increment in efficiency can result in huge savings in fuel costs and determine a key factor for product success. Therefore, the manufacturers put a lot of effort towards this aspect, while trying to broaden the operating range of the compressors at the same time.
The creation of shocks, strong secondary flows and other phenomena increases the complexity of the flow field inside a transonic compressor and challenges the designers who need to face many negative flow characteristics such as, high energy losses, efficiency decrease, flow blockage, separation and many more. As the compressor operates from peak to near-stall, the blade loading increases and flow structures become stronger and unsteady. Despite the presence of such flow unsteadiness, the compressor can still operate in a stable mode. Rotating stall arises when the loading is further increased, i.e. at a condition of lower mass flow rate. There are several possible techniques to limit the negative effect of the flow features mentioned above. Here we will present only two. The first one is related to the blade shape generation, while the second one is linked to flow control techniques.