The Role of Turbomachinery in Modern Hypersonic Cycles

In the coming age of hypersonics, a variety of engine types and cycles are being innovated and worked on. Yet turbomachinery remains unique in its ability to use a single airbreathing engine cycle to carry an aircraft from static conditions to high speeds. One of the largest limitations of turbomachinery at hypersonic speeds (Mach 5+) is the stagnation temperature, or the amount of heat in the air as it is brought to a standstill. While material improvements for turbomachinery are made over time which increases the effective range of temperatures steadily (Figure 1), this steady rate means that the ability of these materials to allow use at stagnation temperatures of more than 1600K remains unlikely any time soon.

Figure 1 Material Improvements Over Time
Figure 1 Material Improvements Over Time

This is the limiting point for traditional turbojet cycles, as Mach 5+ speeds result in temperatures far exceeding these limitations, even for the compressor. However, improvements in cryogenic storage of liquid hydrogen has allowed the concept of precooling, using the extremely low liquid temperature of hydrogen to cool the air enough to push this Mach number range, as well as improve compressor efficiency. To drive the turbine, the exhaust gas and combustion chamber can used, heating the hydrogen and reducing the nozzle temperature for given combustion properties. This has the added effect of separating the turbine inlet temperature from the combustion temperature, reducing limitations on combustion temperatures.  This type of cycle can reduce the inlet temperatures underneath material limits. Read More

Optimization of the Closed Supercritical CO2 Brayton Cycle with the Detailed Simulation of Heat Exchangers

Recently scientists and engineers have turned their attention again to carbon dioxide as a working fluid to increase the efficiency of the Brayton cycle. But why has this become such a focus all of a sudden?

The first reason is the economical benefit. The higher the efficiency of the cycle is, the less fuel must be burned to obtain the same power generation. Additionally, the smaller the amount of fuel burned, the fewer emission. Therefore, the increase in efficiency also positively affects the environmental situation. Also, by lowering the temperature of the discharged gases, it is possible to install additional equipment to clean exhaust gases further reducing pollution.

So how does all of this come together? Figure 1 demonstrates a Supercritical CO2 power cycle with heating by flue gases modeled in AxCYCLE™. This installation is designed to utilize waste heat after some kind of technological process. The thermal potential of the exhaust gases is quite high (temperature 800° C). Therefore, at the exit from the technological installation, a Supercritical CO2 cycle was added to generate electrical energy. It should be noted: if the thermal potential of waste gases is much lower, HRSG can be used. More information on HRSG here: http://blog.softinway.com/en/introduction-to-heat-recovery-steam-generated-hrsg-technology/

Any cycle of a power turbine installation should consist of at least 4 elements : 2 elements for changing the pressure of the working fluid (turbine and compressor) and 2 elements for changing the temperature of the body (heater and cooler). The cycle demonstrated in Figure 1 has an additional regenerator, which makes it possible to use a part of the heat of the stream after the turbine (which should be removed in the cooler) to heat the stream after the compressor. Thus, part of the heat is returned to the cycle. This increases the efficiency of the cycle, but it requires the introduction of an additional heat exchanger.

The heat exchangers used in the sCO2 cycle are of three basic types: heaters, recuperators, and coolers. Typical closed Brayton cycles using sCO2 as the working fluid require a high degree of heat recuperation.

Supercritical CO2 Power Cycle with Heating by Flue Gases
Figure 1 – Supercritical CO2 Power Cycle with Heating by Flue Gases

Having examined this scheme and examined the process in detail, we can draw the following conclusions about the advantages of this cycle which is demonstrated in Figure 2: Read More

Improving Efficiency, One Rocket at a Time (An Excerpt from Exceptional People Magazine)

The following is an excerpt from  Exceptional People Magazine, conducted by Monica Davis and focused on profiling SoftInWay’s CEO, Dr. Leonid Moroz.   The article appeared in the September/October 2019 issue. A link to the full interview can be found here

Turbomachinery design is critical in industries like aerospace, oil and gas, defense, and clean technology. Dr. Leonid Moroz’s company, SoftInWay Inc., also helps some of the world’s largest manufacturers of turbines, turbochargers, pumps, and fans. But Moroz is happy to explain that his company’s innovations also impact the car you drive, the vacuum cleaner you use, the air conditioning in which you work, and the electricity needed to power your mobile phone.

Leonid Moroz
Dr. Leonid Moroz, CEO of SoftInWay

A lover of music and athletics as a child, Moroz knew early on that engineering held promise as a lifelong career. So he started his career as a Group Leader at TurboAtom. TurboAtom, while a state-owned entity, is one of the world’s top thermal, nuclear, and hydropower plant turbine construction companies. It’s a company that operates at the level of companies like General Electric and Siemens.

Moroz designed both gas and steam turbines during his eight years at TurboAtom. While he was there, he also earned his Ph.D. in Turbomachinery from the Kharkiv Polytechnic Institute in Ukraine.

When he founded global aerospace engineering leader SoftInWay, Inc. in 1999, he intended to assist turbomachinery manufacturers needing his expertise. What evolved from that intent has revolutionized engineering design and allowed improved efficiencies for multiple system types: Its flagship software, AxSTREAM.

AxSTREAM helps engineers develop efficient turbomachinery flow path design, redesign, analysis, and optimization. Under Moroz’ direction, AxSTREAM itself has also evolved into a design platform supporting rapid development of a new generation of liquid rocket engines.

Still a relatively small company, SoftInWay supports over 400 companies worldwide and works closely with universities, research laboratories, and government organizations. The company takes its educational responsibilities seriously, continually offering webinars, training sessions, educational blogs, and online workshops on topics like When To Upgrade Your Pump, The Pros and Cons of Wind Energy, and Radial Outflow Turbine Design.

Moroz loves to talk about his work, his company, its innovations, and his team. He’s proud to have had the same group of engineers for 30 years, so SoftInWay feels more like a family than a workplace. As the company has become a leading global R&D engineering company, it has expanded to encompass locations in Boston, Massachusetts; Zug, Switzerland; Ukraine; and India.

Yes, Moroz’ specialty is indeed a bit technical for people who aren’t in turbomachinery engineering design. But Moroz and his team clearly enjoy what they’re doing because it benefits society and makes life easier and more comfortable in myriad ways.

Next time you switch on that ShopVac or Hoover, be sure to thank Dr. Leonid Moroz.

Monica: We often take for granted how engineering plays a huge role in our daily lives. How much of the world depends on the kind of technology and engineering capabilities you produce?

Dr. Moroz: Quite substantially. For example, society produces a lot of waste and heat. If you have options, it utilizes waste and heat to produce power, or it is thrown away. We’ve helped companies to utilize this energy and to produce power to heat or cool our houses, to prepare food, and to help our businesses survive.

Image from a SoftInWay Classroom Course

Another example again would be launchers design. Launchers are important for turbomachinery. A significant part of space development depends on turbomachinery inside those launchers.

It’s important to understand two directions where people can utilize turbomachinery with power consumption and power generation. Power generation is when you produce power, so we need to be more efficient, but the second part, when we get this power, we need to cool our houses, we need to cool our cars, and so on, and again, it’s turbomachinery.

You can be sure that you utilize turbomachinery to develop an air conditioning system that is efficient and is quite substantially in large buildings.

Power consumption for air conditioning is like 30 or 40 percent of the overall power consumption. Can you imagine if you were to decrease this by 10 to 20 percent? It would be a considerable saving…Read the full interview here

 

Digital Engineering Modern Turbomachinery Design Platforms

Automatic Turbocharger Compressor Design 

In the age of green energy and increased efforts to minimize our carbon footprint,  the design of a turbocharger plays an important role in reducing engine fuel consumption and emissions while increasing the performance.  When developing an engine with a turbocharger, the general approach is to select a turbocharger design from a product list. The primary issue with this approach is that it does not cover 100% of the requirements of engine characteristics, i.e. it has non-optimal construction for the engine being developed. The operational characteristics of an engine directly depends on the interactions between the system components. This non-optimal construction will always lead to a decrease in the engine’s performance. In addition, the iteration process of turbocharger selection is time and resource consuming.

That is why the most optimal way to develop an engine with turbocharging is to design a turbocharger from scratch; wherein the operational points of compressor needed to satisfy the engine’s optimal operation are known, i.e. compressor map (Figure 1). But how do we quickly get a compressor map? Even at the preliminary design level, the design of turbocharger flow path requires dozens of hours for high-level engineers. And what about less experienced engineers?

Figure 1 Compressor Map Generated in AxSTREAM
Figure 1 Compressor Map Generated in AxSTREAM®

Incorporating a digital engineering approach with a turbomachinery design platform such as  AxSTREAM® allows designers to find the compressor design with all the required constraints which correspond to the specified compressor map needed. The design process is presented in Figure 2. Read More

New Series on Rotordynamics: Preface

Welcome to our latest blog series on rotor dynamics! In this series we’ll be covering fundamentals and a general overview of the engineering discipline that is rotor dynamics, including some basic definitions, why it’s important, the different calculations, and the overall objectives and purposes for these calculations.

Axial Compressor Rotor

In the months ahead, you can expect to learn more about: Read More

Industrial Refrigerator Modeling

Refrigerators are an integral part of everyday life to the point where it is almost impossible to image our day without them. As in our everyday life, refrigeration units are also widely used for industrial purposes, not only as stationary units but also for transporting cold goods over long distances. In this blog, we will focus on the simulation and modeling of such an industrial refrigeration unit.

Picture 1 - Industrial Refrigerator
Industrial Refrigerator

Like any stationary refrigeration unit, a unit used for cooled transportation includes an intermediate heat exchanger, a pump, an evaporator, a compressor, a condenser, and a throttle. The most common refrigeration scheme uses three heat fluids in the industrial refrigeration cycle. There is Water, which is used for heat removal from Refrigerant- R134A and Propylene glycol 55%. These other fluids are used as intermediate fluids between the refrigerator chamber and refrigerant loop. The working principle of all fridge systems are based on the phase transition process that occurs during the refrigerator cycle shown in Figure 1. The propylene glycol is pumped into the evaporator from the heat exchanger, in which it cools and transfers heat to the refrigerant. In the evaporator, the refrigerant boils and gasifies during the heat transfer process and takes heat from the refrigerator. The gaseous refrigerant enters the condenser due to the compressor working, where its phase transition occurs to the liquid state and cycle repeats.
Read More

Considerations when Designing Turbomachinery with sCO2 as a Working Fluid

Supercritical CO2 (sCO2) power cycles offer higher efficiency for power generation than conventional steam Rankine cycles and gas Brayton cycles over a wide range of applications, including waste heat recovery, concentrated solar power, nuclear, and fossil energy. sCO2 cycles operate at high pressures throughout the cycle, resulting in a working fluid with a higher density, which will lead to smaller equipment sizes, smaller carbon footprint, and therefore lower cost. However, the combinations of pressure, temperature, and density in sCO2 power cycles are outside the experience of many designers. Challenges in designing sCO2 cycles include turbomachinery aerodynamic and structural design, bearings, seals, thermal management and rotordynamics. According to the report from Sandia National Lab, compressors operating near critical point and turbines have received only TRL (technical readiness level) 4 and 5 out of 9. This blog discusses the impact on turbomachinery design.

Radial or Axial

The selection of radial or axial for turbomachinery is typically performed based on the operating conditions (adiabatic head H and inlet volumetric flow Q). Non-dimensional turbomachinery parameters of specific speed Ns and specific diameter Ds can be selected from NsDs charts to estimate size, speed, and type of turbomachinery. Turbomachinery types for a sCO2 recompression cycle with scales ranging from 100 kW to over 300 MW have been studied and concluded that systems below 10 MW will likely feature only radial turbines and compressors with a single-stage or low stage counts. Such recompression cycle can be simulated in AxCYCLE™ tool which is shown in Figure 1. As size increases, the most efficient configuration for the turbine and recompressor transitions from radial to axial at approximately 30 MW and 100 MW, respectively. Suitable types of turbomachinery and its components for different power range can be reviewed in Figure 2. A radial configuration for the main compressor was expected at all scales due to its lower volume flow and wider range to facilitate variation in gas properties due to operation near the critical point.

Recompression Cycle simulated in AxCYCLE
Figure 1 – Recompression Cycle Simulated in AxCYCLE

Read More

When to Upgrade Your Pump

The typical life cycle cost of an industrial pump depends on its maintenance and energy consumption. Hence, it is necessary to keep track of the pump performance and do periodic maintenance to achieve performance level close to the performance predicted by the manufacturer. There are many instances in which maintenance becomes very costly to achieve the required performance. This is the point when owners must decide about whether to upgrading the system. Figure 1 shows the life cycle cost of typical industrial pumps.

Figure 1 Life Cycle Cost of Typical Industrial Pump
Figure 1 Life Cycle Cost of Typical Industrial Pump

In recent years, there have been many innovations in implementing newer materials as well as improvements in hydraulics. Improving pump designs is an ongoing process with designers looking for increasing performance by a few percentage points. The goal of the present pump manufacturers is to offer higher efficiency and reliability, but replacing an older pumps with newer pumps can mean higher costs. The focus for replacing the internals of the pumps with improved design has gained prominence since many of the components, like the casing and rotor, of the existing pumps can be reused. So instead of replacing the entire pump, it can be upgraded or retrofitted. When it comes to an upgrade, the first thing that should be considered is the return on investment which includes the initial investment, operating costs, and the reduction in energy consumption due to the improved pump performance.

Read More

Introduction to Heat Recovery Steam Generated (HRSG) Technology

The acronym HRSG (Heat Recovery Steam Generated) is in different sources describing the operation of cogeneration and heating plants, but what does it mean? Heat Recovery Steam Generated (HRSG) technology is a recycling steam generator which uses the heat of exhaust from a gas turbine to generate steam for a steam turbine generating electricity.

The simplest scheme of a Combined Cycle Gas Turbine (CCGT) is presented in Figure 1.

The simplest scheme of CCGT
Figure 1: The simplest scheme of CCGT.

In Figure 1, the exhaust flue gases temperature on the outlet of the turbine is equal to 551.709 ℃. This is a too high a temperature to release the gasses into the environment. The excess heat is able to be disposed of while receiving additional electric power which is approximately equivalent to 30% of the capacity of a gas turbine.

To reach the maximum economical and eco-friendly criteria possible for the installation, many pieces of equipment are used including: a waste heat boiler (HRSG); turbines with a selection for a deaerator (Turbine With Extraction, Deaerator); feed and condensate pumps (PUMP2, PUMP); a condenser (Condenser); and a generator (Generator 2). Exhaust gases entering into the HRSG transfer heat to water which is supplied by the condensate pump from the steam turbine condenser to the deaerator and further by the feed pump to the HRSG. Here boiling of water and overheating of the steam occurs. Moving further, the steam enters the turbine where it performs useful work.

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7.2 Optimal Design of the Axial Turbines Flow Paths Taking into Consideration the Mode of Operation

Previous chapter Full book

Key Symbols
Indexes and Other Signs
Abbreviations

For demonstration of opportunities of the developed complex of the methods, algorithms and mathematical models for solving the problems of optimal design of the turbine units taking into account their mode of operation [38, 40–42] the results of optimization research of turbine expander flow path and of gas turbine unit GTU GT-750-6M low pressure turbine flow path are presented below.

7.2.1 Optimization of Rendering Turbine Expander Unit (RTEU) Flow Path of 4 MW Capacity With Rotary Nozzle Blades

In gas pipelines, natural gas is transported under the pressure 35–75 atmospheres. Before serving the natural gas to the consumer its pressure must be lowered to the level of pressures local supply systems. At the moment gas distribution stations widely are using technologies of utilization of natural gas let-down pressure before serving the consumer. To extract energy from compressed gas the special rendering turbine expander units (RTEU) are used in which the potential overpressure energy is converted into mechanical work of a rotor rotation of a turbine, which serves as generator drive.

Seasonal unevenness of natural gas consumption, usually caused by environmental temperature, leads to a deeply no projected RTEU operation modes and adversely affect their performance and service life. For example, the gas flow through the flow path of the RTEU during the year may vary in ranges from 0.25–0.35 to 1.05–1.25 from the rated value. The foregoing attests to the relevance and necessity of taking into account the factor variability of operation loads during the selection of the basic geometric parameters of the RTEU FP.

This section provides results of optimization of 4-stage flow path of existing design of RTEU taking into account real operation modes of it, using the developed algorithm [40].

Operating conditions of the considered RTEU are characterized by significant monthly uneven mass flow rate of the working fluid through the flow path of the unit with fixed heat drop and rotor speeds:

7.02

The mass flow rate of natural gas, depending on the operating mode, changed in the range from 4.94 to 20.66 kg/s (the mass flow rate at the design mode is Gnom = 16.66 kg/s).

At present several ways to regulate the mass flow through the RTEU FP are known. The changing of the walk-through sections of nozzle cascade (NC), thanks to the use of rotary nozzle blades, is the most effective.

It is known that the implementation of the rotary nozzle blades can significantly extend the range of workloads of the turbine installation and improve performance indicators of FP. However, to get the maximum effect from the rotation of the nozzle blades, there is a need to further address the challenge of defining optimal angles α1e for each stage, depending on the
operating mode of the RTEU FP. Read More