Gas for Power

Gas turbines are one of the most widely-used power generating technologies, getting their name by the production of hot gas during fuel combustion, rather than the fuel itself. Today, the industry is clearly driven by the need of fast and demand-oriented power generation, thus additional effort is put in extremely short installation times, low investment costs and an enormously growing volatility in the electrical distribution in order to achieve higher levels of reliability in the power grid [2].

The majority of land based gas turbines can be assigned in two groups [3]: (1) heavy frame engines and (2) aeroderivative engines. The first ones are characterized by lower pressure ratios that do not exceed 20 and tend to be physically large. By pressure ratio, we define the ratio of the compressor discharge pressure and the inlet air pressure. On the other hand, aeroderivative engines are derived from jet engines, as the name implies, and operate at very high compression ratios that usually exceed 30. In comparison to heavy frame engines, aeroderivative engines tend to be very compact and are useful where smaller power outputs are needed. Gas turbine image

Nowadays, The increase of energy demand along with the growth of transportation market led to requirements for machines of highest efficiency (i.e. minimal fuel consumption), ability to operate in some certain range of conditions, and weight restrictions. In addition, to maintain competitiveness, it is essential to decrease the amount of time needed to complete the design cycle [4]. Most of machine’s geometrical properties are selected during preliminary design phase and remain almost unchangeable throughout next design phases, predefining its layout significantly. Therefore, the preliminary design task is the basis and the effort must be put in developing complete engineering tools to cover this task taking into account all possible aspects of a successful gas turbine design. In particular, a key advancement to the future of turbine technology is the turbine cooling of components in gas turbine engines to achieve higher turbine inlet temperatures, as increased inlet temperatures lead to better performance and higher lifespan of the turbine [5].

SoftInWay has extensive experience with gas turbine design and optimization. From our flagship software platform AxSTREAM® to AxCYCLE™ , designed for the thermodynamic simulation and heat balance calculations of heat production and electric energy cycles, to our extensive engineering consultant services, you can rest assured that all your project needs will be met by our engineering experts. The use of gas turbines for generating electricity dates back to 1939, where a simple-cycle gas turbine was designed and constructed by A. B. Brown Boveri in Baden, Switzerland, and installed in the municipal power station in Neuchâtel, Switzerland [6]. Today, SoftInWay Switzerland GmbH is located not far from Baden and allows the support of our European clients by offering consulting services, software and training for all engineers tastes. Visit our website and find out how you can take advantage of SoftInWay turbomachinery expertise.

References

[1]http://www.wartsila.com/energy/learning-center/technical-comparisons/gas-turbine-for-power-generation-introduction

[2]https://library.e.abb.com/public/ccb152e5e798b1cdc1257c5f004d64c1/DEABB%201733%2012%20en_Gas%20Turbine%20Power%20Plants.pdf

[3]https://energy.gov/fe/how-gas-turbine-power-plants-work

[4]http://softinway.com/wp-content/uploads/2013/10/Integrated-Environment-for-Gas-Turbine-Preliminary-Design.pdf

[5]Joel Bretheim and Erik Bardy, “A Review of Power-Generating Turbomachines”, Grove City College, Grove City, Pennsylvania 16127

[6]https://www.asme.org/about-asme/who-we-are/engineering-history/landmarks/135-neuchatel-gas-turbine

Steam for Power

Turbine technology being central to energy-producing industry, research and development efforts is directed towards cost-savings (increased efficiency, reliability, and component lifespan), sustainability (alternative fuels, lower emissions), and cost-competitiveness (particularly for the emerging technologies) [1]. This blog post is the first in a series of three that will focus on steam, gas and hydraulic turbines for power generation.

Going back to the Archimides era we will find the idea of using the steam as a way to produce work. However, it was not until the industrial revolution when the first reciprocating engines and turbines developed to take advantage of steam power. Since the first impulse turbine development by Carl Gustaf de Laval in 1883 and the first reaction type turbine by Charles Parsons one year later, the development of turbines have sky-rocketed, leading to a power output increase of more 6 orders of magnitude[2].

Steam turbines can be intended for either radial- or axial-flow, but the modern ones are mainly axial-flow units, particularly in large power plant applications, and they are generally large in size. The rotors are usually multistage arrangements designed to handle high pressures in the first stages and lower pressures in the later stages [3]. The two major axial-flow turbine stage configurations are impulse and reaction. The distinction is based upon relative pressure drop across the stage, where one stage consists of one row of stationary blades/nozzles, and one row of rotating blades. In the impulse turbine design (pressure drop occurs across stationary blades), the magnitude of the relative velocity of the steam remains unchanged, but the absolute velocity exiting the rotor is greatly reduced. The reaction design velocity triangle differs from the impulse design in that there is increase in relative velocity which corresponds to a pressure drop across the rotating blades and a loss of enthalpy.

steam turbine

As the steam flows over the rotor blades, depending on pressure or velocity absorbance we get a pressure compounding (each nozzle row coupled with one moving blade row) or a velocity compounding (one nozzle row direct steam to multiple moving blade rows) impulse turbine. There are also intermediary designs that incorporate both pressure and velocity compounding.

High computing capacity and continuous development of CFD have now allowed researchers to gain new insight into steam turbine problems. Reliability is of critical importance in steam power generation [2], and so current research surrounding steam turbines is focused around a few fundamental areas. However, as stated in “Full Steam Ahead” [4] advances in steam turbine R&D tend to favour larger-scale machines, which means that on the lower end (3 MW to 10 MW), a lot of manufacturers are using old technology.

The challenge for OEMs is to explore existing opportunities to use the latest design methods and technology to develop competitive machines. Find more about SoftInWay and AxSTREAM platform, and take advantage of working with a leading R&D player on the turbomachinery field.

References
[1] Joel Bretheim and Erik Bardy, “A Review of Power-Generating Turbomachines”, Grove City College, Grove City, Pennsylvania 16127
[2] McCloskey, T.H., 2003, Handbook of Turbomachinery, 2nd ed., Logan Jr., E., Ed., and Roy, R., Ed., Marcel Dekker, Inc., New York, NY, Chap. 8
[3]Logan Jr., E., 1981, Turbomachinery: Basic Theory and Applications, Marcel Dekker, Inc., New York, NY
[4] Valentine Moroz, “Full Steam Ahead”, November/December 2016, Turbomachinery International, p.31

 

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

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

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