#### 1.1 Mathematical Models and the Object Design Problem

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The methodology of a turbine optimal design as a complex multi-level engineering system should support the operation with diverse mathematical models, providing for each design problem communication between the neighboring subsystems levels.

One approach to turbine design with using of block-hierarchical representation consists in the transition from the original mathematical models for the subsystems and numerical methods of optimization to “all-purpose” mathematical model and general method of parameters optimization.

We will specify as original the mathematical model (OMM), which is a closed system of equations that describe the phenomena occurring in the designed object.

Regardless of the mathematical apparatus (algebraic, ordinary differential, integral, partial differential equations, etc.), OMM can be represented symbolically as follows:

where  X ⃗={x ⃗,u ⃗ };L(B ⃗,X ⃗) – the operator defining the model’s system of equations.

#### Aerospace Industry and Propulsion Advancements – A Teaser for the Farnborough International Airshow

[:en]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.

#### Organic Rankine Cycles: Low Temperature, High Efficiency

[:en]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

#### [:en]Optimization of Axial Turbine Flow Paths: Preface [:]

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The decades of the 1970s and 1980s of the last century were marked by the emergence and rapid development of a new scientific direction in turbine manufacturing – optimal design. A summary of the approaches, models, and optimization methods for axial turbine flow path is presented in the monographs [13–15 and 24].

It should be noted that work on the optimal design of the flow path of axial turbines and the results obtained not only have not lost their relevance, but are now widely developing. Evidence of this is the large number of publications on the topic and their steady growth. Optimization of the turbomachine flow path is a priority area of research and development of leading companies and universities.

Without the use of optimization, it is impossible nowadays to talk about progress made in the creation of high efficiency flow paths of turbomachines. It is worth noting that the widespread use in power engineering of modern achievements of hydro-aerodynamics, the theory of thermal processes, dynamics and strength of machines, materials science, and automatic control theory, is significantly expanding the range of tasks confronting the designer and greatly complicating them.

The proposed book comprehensively addresses the problem of turbomachine optimization, starting with the fundamentals of the optimization theory of the axial turbine flow paths, its development, and ending with specific examples of the optimal design of cylinder axial turbines. It should be noted that the mutual influence of designed objects of turbine
installations and the many design parameters of each object, which the product’s effectiveness depends on, is putting the task of multiparameter optimization on the agenda.

For turbines with extractions of working media for various needs, efficiency ceases to be the sole criterion of optimality. It is necessary to enable in the optimization process such important parameters as power supply. The task of optimal design of turbine has become multifaceted. It should also be stressed that often the turbo installation mode of operation is far from nominal. So taking into account the operating mode in the optimization can significantly improve the efficiency of the turbine.

In the book, along with the widely used methods of nonlinear programming, taking into account the complexity of the task and the many varied parameters, the use of the theory of planning the experiment coupled with the LP sequence to find the optimal solution is discussed. The first chapter of the book deals with general issues of the optimal design of complex technical systems and, in particular, the problem of optimization of turbomachines, using one of the approaches to the design of turbo installations – a block-hierarchical view of the design process. With this priority is given to flow path optimization of axial turbines. The task of object design and using mathematical models is formulated. A brief overview of optimization techniques, including the optimization method for turbines considering mode of operation is given.

#### Solar Energy – What is it and How is it Used?

[:en]“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:

1. Solar panels
2. 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.

#### Birth, Fall and Resurgence of Gas Turbine Technology for Trains

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.

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### Introduction

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.

1. Q-H Curve
2. Efficiency Curve
3. Net Positive Suction Head (NPSH) Curve

#### Q-H 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.

#### Can a sales team select the right turbomachinery for a client without bothering the engineering team?

[:en]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™.

1. 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.
2. 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.

#### Clean Energy

[:en]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.