Liquid Rocket Propulsion with SoftInWay

Preliminary Design of Fuel Turbine

Operation of most liquid-propellant rocket engines, first introduced by Robert Goddard in 1926- is simple. Initially, a fuel and an oxidizer are pumped into a combustion chamber, where they burn to create hot gases of high pressure and high speed. Next, the gases are further accelerated through a nozzle before leaving the engine. Nowadays, liquid propellant propulsion systems still form the back-bone of the majority of space rockets allowing humanity to expand its presence into space. However, one of the big problems in a liquid-propellant rocket engine is cooling the combustion chamber and nozzle, so the cryogenic liquids are first circulated around the super-heated parts to bring the temperature down.

Rotordynamics analysis
Rotordynamics Analysis

Because of the high pressure in the combustion chamber needed to accelerate the hot gas mixture, a feed system is essential to pressurise and to transport the propellant from the propellant tank(s) to the thrust chamber. In today’s rocket engines, propellant pressurization is accomplished by either (turbo)-pumps or by a high pressure gas that is released into the propellant tank(s), thereby forcing the propellants out of the tank(s). In space engineering, especially for high total impulse, short duration launcher missions, the choice is almost exclusively for pump-fed systems.

To design such systems, a highly sophisticated and complete tool is required. SoftInWay has developed AxSTREAM, the most integrated engineering platform in the market, for turbomachinery design, analysis and optimization. The long experience in the field along with the use of AxSTREAM allow SoftInWay to support its customers in the space industry. Below, you can catch a glimpse at AxSTREAM’s capabilities through a demonstration project of the RL10-A3-3 fed system. The RL10-A3-3 rocket engine is a regeneratively cooled, turbopump fed engine with a single chamber and a rated thrust of 15,000 lb at an altitude of 200,000 ft., and a nominal specific impulse of 444 sec. Propellants are liquid oxygen and liquid hydrogen injected at a nominal oxidizer-to-fuel ratio of 5:1 [1]. The design focused creating new rotating parts of the RL10-A3-3 feed system as presented in Figures 1 and 2, including full scope of rotordynamics analysis.

New Rotating Parts for RL10-A3-3 Feed System

Contact us for an AxSTREAM demonstration and attend one of our training courses to get a trial with AxSTREAM and become SoftInWay’s next success story.

References

[1]https://pslhistory.grc.nasa.gov/PSL_Assets/History/C%20Rockets/Design%20Report%20for%20RL-10-A-3-3.pdf

The Future of Nuclear Power Plants

With the blast of the French nuclear power plant a few weeks ago, safety of nuclear power plant designs has fallen under more scrutiny. Although according to sources the blast took place in the turbine hall and no nuclear leak was found, this event has brought more attention to improved design and operation standards.

Following the incident earlier this month Toshiba, a Japanese multinational company, announced the resignation of its chairman following a $6.3 billion loss in their nuclear sector –also withdrawing from the nuclear business. The two back to back events have highlighted the main two problems of nuclear power: high cost and environmental/safety concerns. Said to be a green technology, nuclear power raises concerns with potential nuclear meltdown and risk of safety from toxic waste, accompanying the fact that building a new plant cost around $5,000.00 per kilowatt of capacity with around 6 years of lead time. Each dollar invested on a nuclear power plant has about 2-10 less carbon savings and is 20-40 times slower compared to other alternatives. Yes, evidently nuclear power is found to be very reliable, enabling consistent baseload energy production at any time of day and night. Though, it has been questioned whether this reliability is worth the high cost of nuclear production, in fact all nuclear plants are still operating with 100% subsidized.

Transatomic power, a company started by two MIT PhD candidates, came up with a new approach to safer and cheaper nuclear reactors. Utilizing molten salt reactors, which has not really been used commercially and so far is only existed in paper, the technology is promised to cut initial cost and increase safety. Today’s conventional nuclear reactor is cooled by water, due to the high operating temperature, failure to do so will open the risk of radiation leak as well as hydrogen explosion. The high boiling point of salt helps solve some of the problems associated with the technology. The new design also incorporates ways of producing faster neutrons, enabling the reactor to burn most waste materials, thus keep waste to minimum. The ability of this smaller unit to be made in a factory (and not onsite) as well as cost reduction on the safety side makes this attractive economically as well. That being said, this generation 4 nuclear reactor is still in design and development will take years and high capital cost.

References:

https://www.nytimes.com/2017/02/14/business/toshiba-chairman-nuclear-loss.html?_r=0

http://fortune.com/2017/02/16/toshiba-nuclear-power-plants/

Turbomachinery Rotor Dynamics – Latest Modelling & Simulation CAE for Design and Analysis, using SoftInWay’s Integrated Tool

The Rotor-Dynamic System of a typical turbomachine consists of rotors, bearings and support structures. The aim of the designer undertaking analysis is to understand the dynamics of the rotating component and its implication. Today the industry practices and specifications rely heavily on the accuracy of rotor-dynamic simulated predictions to progressively reduce empirical iterations and save valuable time (as repeated direct measurements are always not feasible). Be it a centrifugal pump or compressor, steam or gas turbine, motor or generator, the lateral rotor-dynamic behavior is the most critical aspect in determining the reliability and operability. Such analytical predictions are often tackled using computer models and accuracy in representing the physical system is of paramount importance.  Prior to analysis it is necessary to create a detailed model, and hence element such as cylindrical, conical , inner bore fillet/chamfer, groove/jut, disk / blade root and shroud, copy/mirror option, bearing element and position definition are built. Stations (rather than nodes) having six DOF (degrees of freedom) are used to model rotor-dynamic systems. Typically for lateral critical analysis each station has four DOF, two each translational and rotational (angular). Decoupled analysis followed by coupled lateral, torsional and axial vibration makes prediction realistic and comprehensive. The mathematical model has four essential components, i.e. rotating shafts with distributed mass and elasticity, disks, bearing and inevitable synchronous imbalance excitation. Components such as impellers, wheels, collars, balance rings, couplings – short axial length and large diameter either keyed or integral on shaft are best modelled as lumped mass. Bearings, dampers, seals, supports, and fluid-induced forces can be simulated with their respective characteristics. Bearing forces are linearized using dynamic stiffness and damping coefficients and together with foundation complete the bearing model. The governing equation of motion for MDOF system require  determination of roots (Eigenvalue) and Eigen Vectors. Lateral analyses – such as static deflection and bearing loads, critical speed analysis, critical speed map, unbalance response analysis, whirl speed and stability analysis, torsional modal and time transient analyses are then performed.Aashish blog 1 image

Indeed rotor-dynamic modelling with practical experience and engineering judgement improves accuracy.  Its ability to model complexities such as flexible supports, foundation, rotor seal interaction, and instabilities while making the CAE model comprehensive, user friendly, and fully integrated with other well proven and mature suites for flow path and  blade design makes SofInWay’s software platform unique.

Integrated Approach within AxSTREAM® Platform

Suited to meet the diverse needs of designers, analysts and users of turbomachinery, SoftInWay’s webinar in collaboration with Test Devices Inc scheduled on Mar 2, 2017, 10 AM EST helps you to understand HOW rather than why. It will  cover rotor and bearing types, principles of an integrated approach to rotor-dynamics system design and simulation, purpose and procedures for rotor-dynamic and structural analysis. The software demonstration will include modelling features, import/export options, lateral and torsional capabilities, bearing analyses and modelling capabilities, and case studies. It will also briefly highlight fundamentals such as characteristic influence of shaft rotational on natural frequencies in comparison to classical natural frequencies and modes in structures, gyroscopic effects, rigid vs flexible rotors, free and forced vibration as applicable to turbomachine rotors, impact of bearing characteristics and concept of cross coupling, modes, Campbell diagram, stead and transient response, instabilities, condition monitoring, testing, evaluation and acceptance criteria (log dec and margins) and much more. Testing methods covered by Tech Devices Inc. highlight testing procedures and methods for design validation and building confidence that the design exceeds expectations.

 

The Challenges for Turbomachinery Startups

Globalization, increase in defense expenditure by different countries, economic development and growth of air traffic has all resulted in the need for various turbomachinery components. The turbomachinery industry as a whole has seen extensive growth over the last few years and is poised to grow further in the next few decades. The development of Turbomachinery components namely turbines, compressors, pumps, turbopumps, turbochargers are a niche field with the technology limited to just a handful of major players. The recent interest in Un-manned aerial vehicles for military and defense applications, the environmental concerns and rising fuel cost has paved the way for development of small gas turbines and turbomachinery for waste heat recovery systems. Since the market is large and capital cost is not very high due to the equipment size, there is greater interest among technologist and entrepreneurs to step into the business of turbomachinery.photographer-and-plater_1160-733

However, turbomachinery design is still a niche field and require technical expertise, which is again limited. Naturally to get into the league of turbomachinery developers and to compete with established players many startups look at the short cuts which usually is copying of designs from existing players, scaling competitors’ products etc. Though this can help them in getting a product into the market sooner with lower cost on design, this is quite dangerous to the industry as copying designs, scaling etc. results in poor products with performance not being competitive which will lead to the premature killing of the product as a whole. For any startups in turbomachinery, they need to have state of the art product, which can compete with existing players who are well established in the industry.

Developing a new product requires not only huge investments but also time to develop prototype, test, collect feedback etc. This is a major challenge which every turbomachinery startups face, however existing players are blessed with the extensive test and operational data available with them, which is generated over the years. To overcome this challenge the best alternative for turbomachinery startup is to connect with a design house like SoftInWay Inc. who can collaborate and support in developing the product from concept to manufacturing. SoftInWay Inc. in the last decade has helped many companies to develop state of the art turbomachinery through the engineering consultancy, training and technology transfer.

If you would like to know how SoftInWay Inc. can partner with you to realize your dreams, please contact info@softinway.com / India@softinway.com / Switzerland@softinway.com / Ukraine@softinway.com

Double Flash System Application in Geothermal Power

Geothermal power market has been showing sustainable growth globally, with many installations in developing countries. As people turn to renewable sources while demand for energy is experiencing rapid growth, geothermal is found to be a reliable energy source and current development is calculated to increase global capacity by over 25%. Geothermal power plants can usually be divided into several types of cycles, including binary, flash, double flash and more. Flash power plants are found to be the most common forms of geothermal power plant and specifically, we are going to talk about the double flash cycle.

A flash system produces high pressure dry steam to move the turbine, generating electricity after going through a flash separator. A double flash system uses two flashes separating systems in order to generate more steam from the geothermal liquid and increase cycle output. The cycle starts with high temperature fluid extracted from a geothermal source to a high pressure separator (HPS) for flashing. The HPS produces a saturated steam that enters the high pressure turbine and the remaining brine is directed into a secondary low pressure separator (LPS). Reducing the flashing pressure increases the mixture quality in the LPS, which results in higher steam production. Low pressure saturated steam is mixed with the steam flow exhausted from the high pressure turbine and the resulting steam flow is directed to the low pressure turbine and produces more electricity. Steam that is exhausted from the low pressure turbine will then be compressed and injected back to the ground. In a flash system, separator pressure has a significant effect on the amount of power generated from the system – and the flashing pressures also influence double flash cycle significantly. In order to optimize one design, the value of parameters versus cost of operations should be taken into account.

A double flash system is able to achieve better energy utilization than a single flash cycle, which means that the application has a higher efficiency. At the same geofluid conditions, double flash systems are able to give you a higher capacity. That being said, since this is a more complex system the application of such technology would not be economically feasible for some applications.

References:

http://www.doiserbia.nb.rs/img/doi/0354-9836/2016%20OnLine-First/0354-98361600074L.pdf

https://www.geothermal-energy.org/pdf/IGAstandard/SGW/2013/Pambudi.pdf

https://www.geothermal-energy.org/pdf/IGAstandard/WGC/2010/2612.pdf

The Feasibility of Bringing Back Coal

Power generation and energy sectors happen to be very politically volatile. With our new leader in the USA taking control, we are expecting a shift in technology trends. The topic of bringing more coal fired power plants back to the equation has been brought up quite often, coming after Trump’s skeptical statement regarding global warming and climate-change. To follow that statement, Donald Trump pledged to lift restriction on US agencies funding new coal plants in other parts of the world. In addition, Australia’s minister also has been arguing regarding adding new coal power plants into the mix. As world’s largest coal exporter, it should economically make sense for Australia to forego with the plan.

There are three major categories that typically determine whether a technology would be suitable to be implemented: cost to public, reliability of supply and environmental impact. The old coal power generator is found to be less reliable as well as less environmentally friendly. Consequently, a new technology must be used to provide “cleaner” energy from coal. Southern Company has become one of the first private sectors using new technology to produce energy from coal.  The technology is said to be generating electricity while at the same time capturing carbon dioxide from coal. Maybe if this technology is implemented, we will come back to coal.Power Plant

That being said, what is clean coal technology? Coal is currently known to be the biggest enemy to environment, however clean coal seeks to reduce emission. Before burning the coal, some technology purifies the coal to remove unwanted minerals. Then control the burning to minimize the harsh emission, installing wet scrubbers or desulfurization systems, electrostatic precipitators and Low NOx burners among many other processes.

There are two main problems with clean coal: unproven and expensive. Operating cost for Southern company quadrupled to about $1 billion from the original estimate according to a report. Not only that, the initial cost of investment of this power plant is also two times over budget. Not to say that the same case would be applied to other clean coal power plant, but at the time being, installation of this technology is expensive. Until this could be studied further, seems like cost would be hovering well above standard normal. Another downside is that coal plants are inflexible. While they do give a very constant supply of power, they can’t easily increase or decrease supply –and when they do, it’s economically unreliable. This doesn’t eliminate the chances of coal making a comeback in the future, however, for the time being coming back to coal seems unreasonable since the renewables seems to be making a very positive growth towards the future.

References: 

https://www.theguardian.com/commentisfree/2017/jan/24/no-new-coal-is-not-feasible-on-price-reliability-or-emissions

http://www.bloombergquint.com/technology/2017/01/27/after-2-6-billion-writedown-clean-coal-giant-set-for-opening

Surge Conditions of Centrifugal and Axial Compressors

Centrifugal and axial compressors must operate within certain parameters dictated by both the constraints of the given application as well as a number of mechanical factors.  In general, integrated control systems allow compressors to navigate dynamically within their stable operating range.   Typical operating ranges for compressors are represented on a plot of volumetric flow rate versus compression ratio.  Compressors have a wide number of applications, from household vacuum cleaners to large 500 MW gas turbine units.  Compression ratios found in refrigeration applications are typically around 10:1, while in air conditioners they are usually between 3:1 and 4:1.  Of course, multiple compressors can be arranged in series to increase the ratio dramatically to upwards of 40:1 in gas turbine engines.  While compressors in different applications range dramatically in their pressure ratios, similar incidents require engineers to carefully evaluate what is the proper operating range for the particular compressor design.

Dan Post 10
Figure 1- Typical Performance Map Limits – Compressor Ratio (Rc) vs. Volumetric Flow Rate (Qs)

For intensive applications of centrifugal and axial compressors, the phenomenon of surge resides as one of the limiting boundary conditions for the operation of the turbomachine. Essentially, surge is regarded as the phenomena when the energy contained in the gas being compressed exceeds the energy imparted by the rotating blades of the compressor. As a result of the energetic gas overcoming the backpressure, a rapid flow reversal will occur as the gas expands back through the compressor. Once this gas expands back through to the suction of the compressor, the operation of the compressor returns back to normal. However, if preventative measures are not taken by the appropriate controls system or any implemented mechanical interruptions, the compressor will return to a state of surge. This cyclic event is referred to as surge cycling and can result in serious damage to the rotor seals, rotor bearings, driver mechanisms, and overall cycle operation.

Because of surge and other phenomena such as stall, engineers must embed proper control systems that effectively handle different off-design conditions seen in particular compressor arrangements. Depending on the application, certain compressors will rarely operate away from their design point, and such control systems are not necessary. However, in advanced applications such as large gas turbine unit compressors, controls systems allow the compressor to navigate within a range between the choke, stall, minimum speed, and maximum speed limits. The chart seen in Figure 1 describes the operating range of a compressor using a Rc—Qs map. In many cases, an antisurge valve (ASV) working in conjunction with an antisurge PI controller will action open or closed based on varying transient conditions seen on the compressor. For design purposes, it is vital to understand compressor limits in order to properly develop or outsource a compressor based on the performance metrics needed for the application.

A Primer on Compressor Design

As technology has evolved, so has the refrigeration industry. What were once holes in the ground filled with ice and snow have transformed into the modern high-efficiency compression machinery we have become so familiar with today. However, as common as these devices have become, the design process remains a challenge. This is where a combination of scientific knowledge, experience and creative initiative comes into play. While there are, of course, several variations in terms of the application of each design step, the guidelines presented here could be applied not only to refrigeration compressors, but also to compressors used in many other processes and industries.

There are a number of steps to consider throughout the compressor design process, and each step has to relate back to the original design concept. Experience has shown that having a starting concept and an end goal in mind is imperative. Namely, before you can begin the process, you need to know where you are starting and where you want to end up. With this in mind, before we can even get started with preliminary design, blade profiling and analysis of computational fluid dynamics (CFD), it is important to take out a piece of paper and start brainstorming. Consideration of the different refrigeration technologies (cycles), is always a great place to start, so we can ensure we will design the best compressor for the application. The cycle will directly impact the rest of the compressor design decisions, so this is not a step that can be bypassed. This article’s discussion begins with cyclic compression.

Cycle design and optimization 

Cyclic refrigeration units are used for reducing and maintaining the temperature of a body below the general temperature of its surroundings. In a refrigerator, heat is pumped from a low-temperature heat source to high-temperature surroundings. According to the second law of thermodynamics, this process can only be performed with some aid of external work. The vapor-compression refrigeration cycle (which is a type of cyclic refrigeration) is used in most household refrigerators, as well as in many large industrial systems. The advantages of choosing this route are that the technology is mature, the costs are relatively low and the process has the capacity to be driven directly with electrical or mechanical energy.

For initial consideration of the compressor, we must perform calculations to determine the operating conditions and system function, the type of working fluids and the system size and requirements, as well as the economic analysis of the whole cycle. By completing these steps prior to beginning the preliminary design, we are establishing boundary conditions, performance requirements and geometric constraints for the compressor before committing to a design that may or may not be realistic.

FIGURE 1. While there are numerous compressor types frequently used in the process industries, centrifugal compressors are among the most ubiquitous
FIGURE 1. While there are numerous compressor types frequently used in the process industries, centrifugal compressors are among the most ubiquitous

Next, we must determine the type of compressor we want to use for the refrigeration cycle. For the purposes of this article, we will focus on the centrifugal configuration (Figure 1). However, many other options exist, including reciprocating, scroll, helical and rotary compressors.

To elaborate on the output from cycle calculations, we also need to know several specific data points for the proposed compressor, including the required pressure ratio, discharge pressure, volumetric flowrate of the refrigerant, application requirements and the assumed required economics. At this stage, the procedure feels much more like science than art.

Next, the designers need to decide whether they want to design a compressor using an existing similar design (requiring them to scale up or down and optimize the design) or to start from scratch with something completely new. For the purposes of this article, let’s focus on a new design. Now that these decisions have been made, let’s revisit that piece of paper from the brainstorming session and launch into the design process to make the project a reality.

*  This is an excerpt from an article written by Valentine Moroz, SoftInWay’s COO, which appeared in Chemical Engineering Magazine. To read the rest of the article, please follow the link

Computational Fluid Dynamics in Turbomachinery Design

The evolution of turbomachinery technology can be traced back several centuries and has resulted in the high efficiency turbomachines of today. Since the 1940s, turbomachinery development has been led mainly by gas turbine and aeroengine development, and the growth in power within the past 60 years has been dramatic. The development of numerical methods and the increasing computing capacity helped establish a strong design capability in the industry.

The first numerical methods related to turbomachinery were developed years before the use of digital computations. In 1951 Wu [1] introduced the blade-to-blade (S1) and hub-to-tip (S2) stream surfaces, which dominated the field until the 1980s when computer resources made it possible to account for 3D methods. The axisymmetric S2 calculations, also called “throughflow calculation” became the backbone of turbomachinery design, while the S1 calculation remains the basis for defining the detailed blade shape.

Fully 3D methods replaced the stream surface calculations by a single calculation for the whole blade row. This removed the modelling assumptions of the quasi three-dimensional approach but required far greater computer power and so was not usable as a routine design tool until the late 1980s. For similar reasons, early methods had to use coarser grids that introduced larger numerical errors than in the Q3D approach. Such limitations are now overcome with the rapid growth of computer technology.

Nowadays, the design of advanced turbomachinery components [2] is facing more demanding requirements. Higher performance must be achieved within shorter design cycles and at lower cost. Ambitious objectives in the reduction of weight, complexity and manufacturing cost lead to fewer compressor and turbine stages, and therefore to increased stage loading. For designers, this new situation implies the capability to control the very complex flow phenomena occurring in highly loaded stages, on the whole operating range of the engine, early in the design process. In addition to aerodynamic performance, the aggressive design of advanced, fully 3D blades also requires an early focus on all the aspects related to engine mechanical limitations such as blade flutter, forced response and thermal constraint.

The increased requirements on 3D CFD modelling lead to parallel processing of the flow phenomena. The majority of commercial CFD tools demands additional cost for parallel computing, which increase the total cost of the design process. With AxCFD, the users have the opportunity to use parallel calculation without the need to pay extra! AxCFD along with all design modules is fully integrated in the AxSTREAM Software Suite, the most complete engineering platform on the market. Try it now and enjoy the comfort of designing turbomachines from scratch to complete 3D CAD in a couple of hours.

References:

[1] Wu, C. H. A general through flow theory of fluid flow with subsonic or supersonic velocities in turbomachines of arbitrary hub and casing shapes. NACA paper TN2302, 1951
[2] H. Joubert, H. Quiniou, “Turbomachinery designed used intensive CFD”, Snecma http://www.icas.org/ICAS_ARCHIVE/ICAS2000/PAPERS/ICA6104.PDF 

The Future of Combined Cycle

In modern days, power generation planners are faced with the challenge of pushing out the most energy from fuel while at the same time minimizing cost and emission.However, finite fuel also generates mass concerns regarding the reserve left to be used in nature. Consequently, people are continuously looking for an economical and highly efficient solution.

To this date, combined cycle gas turbine applications are found to be the best solution to the problem. The application is known to be highly efficient, have favorable energy conversion rates, comparatively lower start up time compared to conventional steam cycles and able to squeeze more power from the same amount of fuel.

countriesOver the past decade, the use of combined cycles has taken over most of the power generation industry. Triggered in the 1990s by the higher costs and environmental concerns of coal power plants, people starting to look for an alternative to cover demands in energy. At the time natural gas seems to be the most logical substitute.

With the increase of renewable energy application, the demand for combined cycles also increases and helps offset the fluctuations of renewable technology. Combined cycle power plants are also found to emit significantly fewer greenhouse gasses compared to most traditional power plants. With this in mind, the use of combined cycle power plants has substantially reduced the amount of emission.

Due to all of the advantages of CCGT mentioned above and more–not to mention the low installed cost, fuel flexibility, flexible duty cycle, and short installation cycle,  investors find combined cycle implementation to be attractive. According to Black & Veatch, natural gas-fired generation is projected to add 348,000MW to U.S grid, where most (if not all) of it will be supplied by a combined cycle generation.

Interested in optimizing your combined cycle plant? AxCYCLE  should do the trick!

 

Reference:

http://www.power-eng.com/articles/2014/02/a-report-on-combined-cycle-projects-in-north-america.html

https://powergen.gepower.com/content/dam/gepower-pgdp/global/en_US/documents/technical/ger/ger-4206-combined-cycle-development-evolution-future.pdf