Analyzing Thermal Power Generation Efficiency

Figure 1 - Thermal Power Plant Layout
Figure 1 – Thermal Power Plant Layout

Steam turbine power generating plants, also known as Thermal Power stations, are the most conventional type of electricity production today. Most of today’s electricity power is generated though this technology. Naturally, as implied by its name, a thermal power station uses steam power as its prime mover to convert energy in coal, or other fossil fuel, by heating water to steam and utilizing Rankine cycle principles to generate heat and electricity.

The basic theory of thermal power generation is pretty straight forward: in a simple thermodynamic cycle, saturated liquid water is heated to steam. The working fluid will then pass through a steam turbine, where its energy is converted to mechanical work to run the generator and produce the electricity. Then fluid will be condensed to be recycled back in the heater. Just as simple as that, electricity power is generated from the cycle based on Rankine cycle principle.

The utilization of thermal power station comes with the advantage of economical initial and generation cost, easy maintenance and simple cycle operation in practice. That being said, there are also couple major drawbacks associated to the technology, primarily, low overall efficiency –due to the nature of Rankine cycle’s characteristic of thermal efficiency and environmental issues.

There are many scientific reasoning behind thermal power generation’s low efficiency. It is important to know the reasons why to engage in a better technology. These are the primary reasons:

  • During the combustion of carbon, effective conversion more or less is found to be 90%, this happen primarily due to limitation of heat transfer where some heat are lost into the atmosphere. Coal also contains moisture that vaporizes and take the latent heat from combustions.
  • The thermodynamic step, working on Rankine cycle principle, is where 50% (or more) efficiency is consumed. When the steam is condensed for re-use, latent heat of condensation is lost in the cooling water, which decreases the energy input by a very significant magnitude. Losses can also happen in the blades and other components. The Rankine cycle efficiency is determined by the maximum temperature of steam that can be transferred through the turbine, which means the efficiency is also constrained by the temperature associated with the cycle. Two other main factors that affect the thermal efficiency of power plants are the pressure of steam entering the turbine and the pressure in the condenser. That being said, a cycle with supercritical pressure and high temperature usually results to a higher efficiency.
  • During a conversion of mechanical to electrical, some efficiency loss happens in the generator and transformer. A small percentage of energy generated will then be used for internal consumption.

Knowing the causes of low efficiency leads us to the next question: What are the steps to optimize our thermal power plant efficiency?

  • Since thermal efficiency depends on temperature and pressure, it can be improved by using high pressure and temperature steam, though obviously it will be limited based on the boundary conditions of the operating system. A lower pressure can also be set in the condenser.
  • Improvement could also be implemented by the application of reheating steam technology between turbine stages.
  • Waste heat recovery optimization, capture excess heat for reuse, and install insulation to reduce any losses.
  • Upgrading major systems/components of thermodynamic cycles and renewing materials to reduce natural losses in efficiency due to age.
  • Improve efficiency monitoring system to enable instant detection of losses as well as analyzing efficiency based on real data.

These are just some ways that could be utilized to optimize power generation efficiency, indeed each of the steps come with their own specific obstacles of implementation, but there are infinite ways that can be explored to advance the technology.

Learn more about maximizing your power plant productivity through our webinars and explore our tools to help with your efficiency optimization for power generation and component design!

Sources:
http://www.learnengineering.org/2013/01/thermal-power-plant-working.html

Design Considerations in Turbochargers (Part 1 – Incidence)

A turbocharger (TC) has to provide a required pressure ratio for efficient combustion and operation of an internal combustion engine (ICE). The turbocharger consists of a turbine and a compressor sides on the same shaft. The turbine utilizes the energy of exhaust gases while the compressor forces the air into the engine. The compressor with a wide operating range is a strict requirement in the automotive industry because the unit has to operate across all of the ICE regimes.

Even though any compressor has a design point, the ability to operate at low and high mass flows is critical for TC compressors. To satisfy the operating range requirement, a designer tries increasing mass flow at choke and decreasing mass flow at surge. This is quite a challenge. For smaller mass flow rates, the impeller outlet and diffuser should be optimized. The choice of a vaneless diffuser is always justified by increased flow range at the cost of efficiency.

To increase the right-most mass flow limit, a designer optimizes the compressor inlet. The common practice is to design blades with large inlet metal angles. Increase in inlet angles open larger area for the flow to pass. This, in turn, leads to large incidence angles at design point. Therefore, many TC compressors are designed with large positive incidence in the design point. The incidence angle increases for every speedline going toward the surge line. Incidence distribution on a TC compressor map is shown in the figure below. It is equal to +12 deg (with respect to tangent) in the design point.

Fig. 1 Incidence on the TC compressor map
Fig. 1 Incidence on the TC compressor map

Glossary:

Blog - incidenceDesign point: An operating condition where a compressor reaches maximum efficiency

Compressor Map: Pressure versus mass flow characteristic at different rotational speeds and isoefficiency contours

Speedline: Dependence of pressure on mass flow rate for a given shaft speed

Surge: Left-most point on a compressor map for a given shaft speed

Choke: Right-most point on a compressor map for a given shaft speed

Incidence: The difference between inlet flow and metal angles. If an incidence is small, the flow has less resistance to enter the impeller.

Source: http://www.turbobygarrett.com/turbobygarrett/compressor_maps

Beyond the Clouds in No Time

We can all agree that airplanes are cool, and rockets are awesome, but when combined, the result is even better! Besides getting engineers to jump up and down for this revolutionary concept, Reaction Engines Ltd applied it to an actual SABRE engine concept.

SABRE stands for Synergistic Air-Breathing Rocket Engine and one typically does not associate “Air-Breathing” with “Rocket.” which makes this engine a one of a kind to reach new heights (literally). Let’s dig into the geeky technical specs of the engine while going through some quick history of this revolutionary single stage to orbit propulsion system.

SABRE Engine
Source: Reaction Engines

SABRE is an evolution of Alan Bond’s series of liquid air cycle engine (LACE) and LACE-like designs that started in the early/mid-1980s under the HOTOL project. Upon termination of HOTOL funding, Bond formed Reaction Engines Ltd. SABRE is currently being developed for hypersonic flights and runs on a combined cycle; the precooled jet engine configuration is used in the air-breathing phase of the flight until air becomes scarce and speed critical. From this moment on the engine switches to its close cycle rocket mode to bring the Skylon airplane to orbit (2 engines are mounted on the aerospace plane).

The air-breathing mode (below Mach ~5 and about 25 km altitude which is about 20% of the orbital velocity and altitude, respectively) works almost like a regular jet with one major difference being the apparition of a new component, first discussed in 1955; the air precooler which is placed behind the translating axisymmetric shock inlet cone that slows the air to subsonic speeds inside the air-breathing engine using 2 shock reflections. The precooler is “capable of cooling incoming air (without liquefying it, from around 1000°C) to −150°C (−238°F), to provide liquid oxygen (LOX) for mixing with hydrogen to provide jet thrust during atmospheric flight before switching to tanked LOX when in space.” This precooler also allows a considerable reduction of the thermal constraints of the engine which then requires “weaker” and much lighter materials that are a necessity when reaching orbital velocities and altitudes. With compressors working more efficiently with a colder fluid, and the incoming air already highly compressed from the flight speed and shock waves, the fed pressure in the combustion chamber is around 140 atm. When in rocket mode, the inlet cone is closed and liquid oxygen and liquid hydrogen are burned from on-board fuel tanks for the remaining 80% of velocity and climb required to reach orbit.

Source: Reaction Engines

On a very recent note, feasibility studies conducted by the U.S. Air Force Research Laboratory were successfully passed in 2015.

Although the application of the SABRE engine is destined for orbital use, its cousin (Scimitar) has been designed for the environmental-friendly A2 hypersonic (top speed higher than Mach 5) passenger jet for 300 rushed passengers (about 3 times more than the Concorde) under the LAPCAT (Long-Term Advanced Propulsion Concepts and Technologies) study founded by the European Union.

When dealing with such high speeds, noise becomes a real constraint and flying above inhabited areas is restricted, which is why specific aerial routes are designed. According to Alan Bond, the A2 design could fly subsonically from Brussels International Airport into the North Atlantic, reaching Mach 5 across the North Pole and over the Pacific to Australia in about 4.6 hours, with a price tag similar to what you would pay for business class these days. This speed would heat the body of the craft so that windows are not an option because the appropriate thickness would represent a considerable weight. It is therefore thanks to flat panel displays showing images that you would be able to enjoy the scenery.

Blog - plane 2
Source: www.salon-de-l-aviation.com

 

When one talks about high-velocity flight it is difficult not to think of the French Concorde that operated between 1976 and 2003 and could travel at Mach 2.04 (limited by thermal constraints due to the material used) using the Scramjet technology; scramjet standing for “supersonic combustion ramjet”. This allowed a New York City to Paris flight in less than 3.5 hours instead of 8 hours with a conventional jet.

Blog -220px-Concorde_Ramp
Source: http://www.concordesst.com/powerplant.html

The principle of this technology is to compress air with shock waves under the body of the aircraft before injecting the fuel (the Concorde’s intake ramp system can be seen on the figure on the right).

Due to the high inefficiency of this technology at low speeds, afterburners are used from take-off until reaching the upper transonic regime.

Keeping in mind that the heating of the Concorde’s body due to friction could make it expand by as much as close to a foot, it becomes easy to understand one of the reasons why high altitudes (scarcer air and therefore lesser aerodynamic resistance) are chosen for such high flight velocities; the Concorde cruising altitude was around 56,000 ft and would be decreased when sun radiation levels were becoming too high. On a side note you can keep an eye out at Charles de Gaulle airport in Paris (France) for a Concorde displayed outside.

Oh and did I forget to mention that the turbomachinery parts on the SABRE engine are currently being designed in the AxSTREAM suite??

SoftInWay Case Study

Attend the Turbo/Pump Symposia 2015 in Houston, Texas

Next month, the 44th Turbomachinery & 31st Pump Symposia will take place at the George R. Brown Convention Center in Houston Texas. The exhibition opens on Monday, September 14th, until Thursday, the 17th. The symposia are hosted in order to inspire knowledge exchange among industry professionals, along with professional development, technology transfer, and networking.

SoftInWay will be attending the symposia and exhibiting in booth #2637. Here’s what we are looking forward to the most:

  • Training courses led by top industry experts
  • Lectures, tutorial, case studies, discussion groups, and short courses
  • Exhibits including full-sized equipment and the latest industry innovations
  • Networking and knowledge exchange with fellow turbomachinery and pump professionals

We are also excited to show attendees what we have developed in the last year. Here at SoftInWay, we are constantly building our industry knowledge and software capabilities. We’ll be offering extensive software demonstrations in our booth. Be sure to stop by (and ask about our portable phone chargers)!

Need a free pass to attend the exhibition? You can get yours here. We’ll see you there.

New Release: AxCYCLE v. 4.0

We have just released the newest version of AxCYCLE, our software tool for thermodynamic cycle design and analysis. AxCYCLE 4.0 has some brand new features that will inevitably aid you in designing optimal Gas, Steam, Combined, Turbocharger, Supercritical CO2, Organic Rankine, and Waste Heat Recovery Cycles.

Take a look at the latest updates and additions:

Turbine Efficiency Calculation
In previous versions of AxCYCLE, efficiency was an input parameter that needed to be changed manually for each off-design condition. The Calculated Efficiency option will automatically recalculate the efficiency for off-design conditions.

blog - axcycle 4.0

New Components
Several new components were added to the AxCYCLE library for more sophisticated and customizable cycles.

Bearing: Used to simulate mechanical energy losses in bearings. The estimated mechanical losses are assigned as a power value and are accounted for in the total energy balance

Gearbox: Used to simulate the mechanical energy transfer between two shafts considering mechanical energy losses in the gearbox. These losses are measured using a gearbox efficiency value.

End Seal: Used to simulate seal leakage. The value of the leakage depends on the difference between the upstream and downstream pressure.

Steam Cycle Builder
AxCYCLE’s new wizard for the creation of basic steam cycles. It can be used for steam cycles with regenerative heating, optional moisture separators, and re-heaters. The Builder creates a cycle diagram with the correct fixed conditions and initial values, meaning the generated cycle is ready for calculation! It does all of the work for you!

Learn more about AxSTREAM and AxCYCLE on our website, or email us at info@softinway.com to find out exactly how we can help with your next turbomachinery project.

Plan Your Turbomachinery Training for the Rest of 2015

The sun is starting to shine and the weather is warming up. The schools are closed, the beaches are open, and everyone is itching to get to their vacation. But summer will be over before we know it! Don’t wait too long to begin planning for the final months of 2015. Take a look at our fall and winter courses that are now open for registration. Early sign-ups qualify for discounted prices! Here’s what’s available for the rest of the year:

Classroom Courses:

Centrifugal Compressor Design
September 15-19 | Zug, Switzerland (Register)
October 5-9 | Boston, MA, USA (Register)

Axial & Centrifugal Pumps Design
September 22-26 | Bangalore, KA, India (Register)
December 14-18 | Boston, MA, USA (Register)

Stream & Gas Turbine Design
September 22-26 | Boston, MA, USA (Register)
November 23-27 | Zug, Switzerland (Register)

Turbocharger Design & Performance Matching
October 12-16 | Bangalore, KA, India (Register)

Axial Compressor Design
November 23-27 | Bangalore, KA, India (Register)

Online Courses (click the dates to register!):

AxCYCLE for Organic Rankine Cycle Design
July 9-10, September 3-4, November 12-13

Waste Heat Recovery Design (Last of the year!)
July 13-30

AxCYCLE for Steam & Combined Cycle Design
July 28-29, September 10-11, November 4-5

AxCYCLE for Supercritical CO2 Cycle Design
August 4-5, October 27-28

Axial Turbine Design (Last of the year!)
August 10-20

Axial Compressor Design
September 21-October 1

Turbocharger Design
November 30-December 17

Also don’t forget about our monthly webinars! Keep an eye out for email invitations to our live presentations and demonstrations of the industry’s latest trends and developments. You can find all of our recorded webinars in our learning portal – SoftInWay Turbomachinery University. Your free registration gives you access to all recordings!

Turbo Expo 2015 – What We’re Excited For

In a few weeks, SoftInWay will be on its way to Montreal, Canada for ASME’s Turbo Expo! We are looking forward to a busy and exciting conference.

What we’re most excited for:

1. Montreal AfterWork: Professional Networking Event
This event is being held for professionals involved in Energy, Technology, Finance, and Startups to meet and network in a casual and enjoyable environment. All Turbo Expo attendees and local Montreal professionals are welcome to come by, have a drink, and chat about the latest developments in their field!

Date/Time: 6:30-9:00pm | Tuesday, June 16, 2015
Location: Santos Tapas Bar | 191 Rue St Paul W, Montreal, QC, H2Y1Z5 Canada
Attire: Business Casual
Registration: www.zurichafterwork.com/rsvp/

2.  SoftInWay Stage Presentations

Continue reading “Turbo Expo 2015 – What We’re Excited For”

Demystifying “Pushbutton” Approaches for CFD & FEA Turbomachine Design

Demystifying “Pushbutton” Approaches for CFD & FEA Design, Analysis, Redesign, & Optimization of Turbomachines

centrifugalcompressordesignAlthough there is not just one way to design a turbomachine there sure is one way not to do it; blindly.

A misconception that I commonly see when teaching engineers about fundamentals of turbomachines, as well as when leading design workshops, is that some engineers (mostly the younger generations) envision themselves plugging numbers, pushing buttons and getting results immediately without any real brain power behind their actions.

Nowadays, software packages are an integral part of an engineer’s toolkit, but in the same way that a mechanic would not (or should not) use a screwdriver as a hammer, each software has its own applications and ways to use it.

Continue reading “Demystifying “Pushbutton” Approaches for CFD & FEA Turbomachine Design”

Innovation in Aerospace: Aircraft Compressor Design

Aerospace - croppedOur next webinar is on Thursday, April 30th! Are you an engineer involved in the Aerospace Industry and its latest development, a manager interested in improving the performance of your aircraft engines, or a student interested in the future of aerospace and the current climate of the industry? You should attend! During the webinar we will be taking a close look at the most recent trends and developments of compressors in aircraft engines with a focus on the key factors for the successful development of aircraft engines.

Key factors for successful development of aircraft engines include technological viability, performance, and re-usability. As one of the industry’s most high-technology products, aircraft engines require innovation in manufacturing and especially in design. They also face the need for continuous development in its technical capabilities in terms of achieving not only higher efficiencies and reliability but also safety and environmental legislations.

Continue reading “Innovation in Aerospace: Aircraft Compressor Design”

Is CFD Evolving Fast Enough for the Technologic World?

It is common knowledge that CFD analyses are more of a “see you tomorrow” affair than an “I’ll grab a coffee and I’ll be back”.

Although the fairly recent developments in electronics allow for more computing power while being more affordable, it can still take a significant amount of time to run a good CFD case.

AxCFD
The AxCFD module in SoftInWay’s AxSTREAM

One of the main advantages of running CFD is that there is no need to have an actual, manufactured prototype in order to run an experiment. Prototypes have been known to be mainly restricted to companies/individuals that had manufacturing capabilities and quite a lot of money on their hands. However, with recent advancements like 3D printing, this prototyping is not only possible but is also relatively fast (and getting faster everyday with new techniques being developed).

It comes to a point where it is worth evaluating, qualitatively, each method, however different they actually are.

Although CFD is an extremely common practice in modern day engineering and is immensely useful, it tends to sometimes completely replace actual prototyping and this can create some issues… Indeed, CFD is neither an exact science nor it is always “cheap” (some complex problems can easily cost several thousand dollars in computing costs) but either way it sure has its perks. These two arguments are unfortunately largely part of a general misconception of CFD that decision makers and the younger generation of engineers are often victims of. When managers are given the choice between purchasing a software that can supposedly simulate any physical problem (CFD case) and a machine that can physically build components (manufacturing case) the upfront cost strongly leads these decision makers to adopt the first option.

However, CFD does not always suffice.  Results of CFD analyses are influenced by numerical and modeling errors, unknown boundary conditions or geometry and more. Refining your mesh is becoming easier and ultimately leads to reduced numerical errors while, at the same time, increasing your calculation time. Modeling errors can come from misuse or inaccuracy of certain models when trying to simulate real, complex physics like turbulence. And so on to the point that different codes and even different engineers can find some minor discrepancies in the final results of the same case.

This means that less experienced engineers tend to over-trust their results, thinking of CFD as the universal answer to every physical problem. To place (smartly) more confidence in CFD results the codes should be calibrated and corrected based on experimental results that do require prototyping at some point unless a product is wrongly put on the market without proper physical testing – which can happen, unfortunately. Comparing both an original and an optimized geometry in CFD is perfectly possible and realistic but as for any solver a baseline should be created. One cannot simply say he has improved the efficiency of a machine by 2% if the original machine was not analyzed beforehand.

Calibration of the CFD models is based on available data from experiments and this data is often very limited compared to the results that CFD can provide. While a physical test would provide values like power as well as some pressures and temperatures in most cases, CFD analyses can go way beyond this by providing parameters distributions, flow recirculation areas, representation of the boundary layer appearing on the surfaces, etc. that allow getting a good understanding of what is happening to the flow within the machine, which is something that definitely cannot be appreciated in most experimental runs. Beside the mentioned disadvantages that 3D printing has, an important one that is shared with CFD is that the time needed to build a geometry strongly depends on its size. However, CFD can deal with the repetition of an element in a row fairly accurately while the entire wheel has to be manufactured to be analyzed. This sort of restrains rapid prototyping to smaller machines, at the moment.

For these reasons and despite all these “warnings”, CFD remains and will remain an essential engineering tool that provides a good comparison of cases rather than a truly accurate representation of the reality we live in. As a conclusion, CFD still continues to evolve with the recent technological developments and should be supplemented with experimental testing instead of substituting it.