Simultaneous Design for Turbocharger Compressors and Turbine Wheels

AxSTREAM Blade Profiling
Figure 1- AxSTREAM 3D Blade Profiler for Radial Designs

Increasing regulation for reducing emissions has forced the automotive industry to accept different technologies over the years in order to stay ahead of the market. In an industry that is so accustomed to internal combustion engines, new solutions such as electric motors and turbocharger systems have allowed experts in other industries to cultivate an influence in the automotive market. Specifically in the realm of turbomachinery, increased development has gone into designing turbochargers in order to minimize the effect and size of internal combustion engines. Design challenges are inherent in the fact that an engine is a positive displacement device whereas the turbocharger falls under aerodynamic turbomachinery. The two separate machine types have distinctly different flow characteristics, and the proper sizing of a turbocharger for its parent engine requires proper modeling of the engineering system as a whole.

In general, initial turbocharger sizing becomes a matter of obtaining the necessary boundary conditions required for a preliminary design. A thermodynamic cycle analysis of an ICE-Turbocharger system will allow the designer to obtain an initial idea of the bounds

Axmap for turbocharger
Figure 2 – Simultaneous Turbine (color) and Compressor (dotted) Maps – Power vs. MFR (left) & Pressure Ratio vs. MFR (right)

necessary for the compressor and turbine design. Given the engine information, necessary inlet conditions of the compressor such as temperature and pressure, efficiencies required, and heat transfer of the system, the user can then obtain the boundary conditions for the turbocharger compressor and turbine wheels.

From this point, the process becomes an exercise in turbomachinery design and analysis. With SoftInWay’s turbomachinery design and analysis platform, a boundary condition realization of the system eventually manifests into a full 3D design of the turbine/compressor wheel. Once the engineer designs both the turbine and compressor wheels, they will be left with two discrete physical systems. However, these two designs must eventually coincide into a harmonious system that accurately represents the “turbocharger”. In order to facilitate this representation, the user can overlay the different compressor and turbine maps based on a number of varying parameters. Given the Power and Pressure Ratio curves for a number of varying shaft speeds and temperatures, an off-design performance of the turbocharger system can be analyzed via AxSTREAM’s matching module (Figure 2). Another simultaneous analysis of the turbine and compressor wheels must be made on the component that connects them, the rotor. Rotor design, rotor dynamics, and bearings analysis are crucial to a legitimate turbocharger design and will be a topic of a next week’s blog post. If you would like to learn more about turbocharger design and analysis methods, please follow this link

References:
http://www.automotive-iq.com/engine/articles/high-boost-and-two-stage-turbo-power-systems

Steam Heat & Mass Balance Considerations in Refineries

Optimizing the heat and mass flow i.e. steam balance in a plant that has several levels of steam pressures is not a simple task due to the vast array of equipment such as turbines, heat exchanges, steam auxiliaries and accessories used. The steam balance of a refinery plant is further complicated because of use of steam for chemical processes and compression. Depending on processor licensor, technologies and many other traditional factors, it is not uncommon to see steam pressure levels defined in refineries as simply HP & LP or HP,MP & LP or as complex as VHP, HHP, HP, MP and LP.

The traditional approach to designing a steam system is to install steam generators able to generate steam at the maximum pressure and temperature with enough redundancy in capacity as required by the process. Modern steam generators tend to be inclined towards higher pressure steam rather than lower pressure steam – saturated high pressure steam has higher temperature meaning  less exchange surface in heat exchangers and reboilers, high density of high pressure steam requires less bore in the steam mains. Consequently, the usage of high pressure steam represents less capital expenditure. The resultant philosophy is to generate steam at the highest possible temperature and pressure, expand steam from a higher pressure to a lower pressure level through the most efficient means possible and use process at the lowest economically attractive pressure and temperature.

Concepts drawn from CHP namely topping and bottoming cycle have been implemented in refineries. In the topping cycle, fuel is used in a prime mover such as a gas turbine or reciprocating engine that generates electricity or mechanical power. The hot exhaust is then used to provide process heat, hot water, or space heating/cooling for the site. In a bottoming cycle, which is also referred to as Waste Heat to Power (WHP), fuel is first used to provide thermal input to a furnace or other high temperature industrial processes. A portion of the rejected heat is then recovered and used for power production, typically in a waste heat boiler/steam turbine system. To be effective, a bottoming cycle must have a source of waste heat that is of sufficiently high temperature (around 300 Deg C) for the system to be both thermodynamically and economically feasible.

A refinery with such steam pressure requirements at the design phase, in its life cycle however may operate under two distinct scenarios- excess or deficit steam. In the excess situation, equipment is shut or steam is vented off, and in deficit situation steam balance is made up by letting down from an immediate higher level.Blog 3

An optimal way to design and operate the steam balance system involves “what if” analysis and requires inputs from multiple sources such as process engineers, OEMs, equipment vendors, piping designers etc.  With the current trend in crude prices and need to maintain gross refining margins, an all possible mean need to be adopted for ensuring reduced costs. Though estimates vary, some figures indicate up to 130 Gigawatts (GW) of untapped potential at existing industrial and commercial facilities. To identify area of improvement in steam balance and optimize, a simplistic approach is an analysis using pressure and temperatures. A more detailed analysis requires estimation of enthalpy, entropy, exergy and anergy. Such an approach would consist of:

  1. Reconcile heat and mass balance for the steam system and achievement of LHS=RHS account (missing steam).
  2. Estimation of the performance of the existing cycle equipment from an efficiency and economic perspective.
  3. Ascertain inefficiencies in the steam system and opportunities for improvement and optimization by accurate simulation, modelling and scenario comparison.
  4. Assessment of the technical and economic feasibility of installing a rerate/upgrade/replacement


AxCYCLE™ is one such unique tool for design, analysis and optimization of thermodynamic systems (simulation, heat and mass balance calculation of heat producing and electric energy cycles) typically used for any heat and electric energy cycles including aircraft propulsion. Using AxCYCLE™ Economics – an extension to AxCYCLE™ it is possible to estimate capital/running investment calculation (CAPEX and OPEX) , fuel type selection, comparing different scenarios and return on investment.

Aircraft Engines: A Need for Increased Performance and Safety

Turbine engine of airplaneThe necessity for a robust aircraft engine design is strongly associated with not only flight performance, but also to passengers’ safety. The fatigue on the blade of CFM56 engine did not prove to be fatal in last August’s incident. None of the 99 passengers was hurt, but parts of the engine broke apart damaging the fuselage, wing and tail, and forcing the Boeing Co. 737-700 to an emergency landing. However, that was not the case in July 6, 1996, when the left power plant on a Boeing MD-88 broke apart while accelerating for take-off and the shrapnel was propelled into the fuselage killing a mother and a child seated in the Delta Air Lines Inc. aircraft [1]. A few years earlier, in January 8, 1989, a CFM56-3 blade failure proved to be fatal for 47 out of 118 passengers of the British Midlands Airways (BMA) Ltd Flight 92 departed from London Heathrow Airport en route to Belfast International Airport. Based on Federal Aviation Administration’s accident overview [2] post-accident investigation determined that the fan blade failed due to an aero-elastic vibratory instability caused by a coupled torsional-flexural transient non-synchronous oscillation which occurs under particular operating conditions. An animation describing this process is available at the following link: (Fan Blade Failure).

The last example [3] of this not so cheerful post took place on July 29, 2006, when a plane chartered for skydiving experienced jet engine failure and crashed. Tragically, there were no survivors. The failure was attributed to aftermarket replacement parts. The aircraft was originally equipped with Pratt & Whitney jet engines, specifically made with pack-aluminide coated turbine blades to prevent oxidation of the base metal. However, during the plane’s lifetime, the turbine blades were replaced with different blades that had a different coating and base metal. As a result of the replaced turbine blade not meeting specification, it corroded, cracked and caused engine failure.

As it can be observed, there are several reason why an engine can fail varying from inspection mistakes, manufacturing processes and design strategies. Nowadays, engine failures are far below the leading causes of accidents and death. Nevertheless, they are ranked fourth in the decade from 2006 through 2015 with 165 fatalities, according to Boeing statistics [4]. When it comes to blade fatigue regular inspections and maintenance play the most important role. However, the design process is equally important to ensure an efficient and powerful design. The design of the machine under specific flight conditions, taking into account aero-structure interaction, as well as vibration and Rotor dynamics analysis is essential to get a streamlined solution. AxSTREAM allows the user to investigate a variety of design points and further analyse the best solution that meets the constraints and operating conditions requirements. Moreover, AxSTREAM NET can now be used to estimate leakages and cooling or bleed air flow parameters for different fluid path sections while taking into account heat exchange of cooling flow with metal surfaces.

References:

[1] https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR9801.pdf

[2] http://lessonslearned.faa.gov/ll_main.cfm?TabID=2&LLID=62&LLTypeID=2#null

[3] http://www.robsonforensic.com/articles/aircraft-engine-materials-expert

[4] http://www.dallasnews.com/business/airlines/2016/09/12/investigators-cracked-engine-blade-broke-southwest-airlines-flight-last-month

Rotating Equipment Specialist in the Oil and Gas Industry – A Turbomachinery Professional

Turbomachinery is a core subject in many engineering curriculums. However, many graduates joining the oil and gas industry are designated as rotating equipment engineers. Though turbomachinery and rotating equipment are used synonymously, all turbomachinery are rotating equipment but not vice versa. Turbinis in Latin implies spin or whirl, and a natural question that arises is – what are the factors that differentiate turbomachinery?  In a general sense the term, “rotating” covers  the majority equipment used in the industry be it in the upstream, mid-stream or the downstream segment. Yet top rotating equipment specialist in the industry are seen spending their prime time or often being associated with certain unique and specific types of critical rotating machines – the turbomachines.Oil and Gas

In a classical sense, turbomachines are devices in which energy is added into or taken out from a continuously flowing fluid by the dynamic action of one or more moving blade rows. By this definition propellers, wind turbines and unshrouded fans are also turbomachines but they require a separate treatment. The subject of fluid mechanics, aerodynamics, thermodynamics and material mechanics of turbomachinery when limited to machines enclosed by a closely fitting casing or shroud through which a measurable quantity of fluid passing in unit time makes the practical linkage to rotating equipment – those which absorb power to increase the fluid pressure or head (fans, compressors and pumps) and those that produce power by expanding fluid to a lower pressure or head (hydraulic, steam and gas turbines). Further classification into axial, radial and mixed type (based on flow contour), and impulse & reaction (based on principle of energy transfer) is common. It is the large range of service requirement that leads to different type of pump (or compressor) and turbine in service.

From the oil and gas industry perspective, standards namely API governs the specifications of design, material and systems requirements of rotating equipment. In line with such standards, equipment under the purview of APIs SOME (Sub Committee on Mechanical Equipment) are considered to quantify rotating machine. Falling under the turbomachinery group are centrifugal pumps (API 610), general and special purpose steam turbines (API 611 & 612), gas turbines (API 616) , axial and centrifugal compressors and expander- compressors (API 617), special purpose fans (API 673) and integrally geared compressors (API 672).

It is understandable that universities and academic institutions will continue their focus on turbomachinery as a fundamental subject of the curriculum, with increased emphasis on training and use of CAE tools. Basics remaining the same, the special nature of application of turbomachinery in the industry makes job of a rotating equipment engineer a challenge. At a conceptual level four important facets of rotating equipment (turbomachines) that an engineer in the oil and gas industry need to comprehend are as follows: Kinematic, energetics and thermodynamics of performance– fluid-aero thermal design and analysis; integrity of rotor, bearings, seals, casing and structure – mechanical design and analysis; the complete hardware – metallurgy, material mechanics and manufacturing and finally the associated systems. As the oil and gas industry entrusts its specialist rotating equipment engineers with a demanding level of reliability and availability of turbomachines, new ways are required to enhance competence. The practical experience of rotating equipment engineers coupled with exposure to design principles and use of CAE and simulation tools is one such way to help them add more value to their business.  AxSTREAM® is an advanced  software suite that covers many aspects of various critical rotating equipment for the oil and gas industry on a single platform.

For an overview of AxSTREAM for design, analysis, retrofitting, and so on, visit our past webinars recording http://learn.softinway.com/Webinar .

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.

 

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

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.

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