Last week I described two ways which the turbomachinery industry addresses climate change. This week, I explain two more:
Waste Heat Recovery
Even though processes are becoming more and more efficient they are still mostly wasteful (Figure 1).
The excess energy from processes is eventually released into the environment but bringing down the temperature of the exhaust allows multiple things; direct reduction of the global warming potential as well as possibility to utilize this heat to boil a working fluid before running it through a turbine where it can generate some power without requiring burning additional fuel. A well-known example of such a system is the traditional gas-steam cycle that allows turning a 45% efficient gas turbine cycle into a 60% system by utilizing the gas turbine exhaust heat to boil some water in a secondary loop before passing the resulting steam through a different turbine. In the same manner waste heat recovery can be applied with different fluids (including the trending refrigerants like R134a & R245fa, steam and the state-of-the-art supercritical CO2 as shown on Figure 2) and a multitude of applications; internal combustion engines, steel production plants, marine transports, etc.
Selection of the best working fluid
Whether it’s deciding to design the main energy conversion cycle or its waste heat recovery system one of the critical parameters to pay close attention to is the working fluid selection; good selection of the fluid will often lead to make a compromise between cost/availability, thermodynamic performance (see Figure 3) and environmental friendliness. One must make sure that the performances of the designed cycle with the chosen fluid are high enough and the fluid cheap enough to make the concept financially viable without sacrificing pollution considerations which can prove devastating in case of leaks.
The working fluid selection is also performed so that in addition to the environmental footprint being reduced the physical footprint is minimized as well; this is done through the selection of high density fluids (helium, SCO2, etc.) which allows for a reduction in component size and therefore cost (as portrayed on Figure 4), – indirectly it also allows for less material being produced which also “saves trees”.
Most people complain about climate change, but few take measures to address it. In this article we will see some ways turbomachinery-oriented companies contribute to the well-being of the planet.
Selection and optimization of energy conversion technology (recuperation, proper selection of expander configuration, etc.)
Not all technologies are created equal; where you would use a steam turbine is not necessarily where you would want a gas turbine or an organic Rankine cycle (ORC) instead. Each one of them has its pros and its cons; ORC exist because they do not require as much energy as what is needed for steam cycles, gas turbines have a great power density and an outstanding start-up time (several minutes instead of hours) which makes them great candidates for punctual, unexpected peaks in power demand, etc.
Now, take the case of a gas, steam or ORC; they all include, in their most basic configuration, a compressing element (compressor or pump), an expander (usually a turbine), a cooling/condensing component and a heating component (boiler, combustion chamber, HRSG, etc.) as one can see on Figure 1 and each of these have an associated efficiency.
This means that their careful design and thorough optimization should be performed in order to maximize the overall performance of the full system. Whether it’s used for power generation or propulsion the result is the same; more power generated for the same amount of heat input (usually the combustion of fuel). However, before starting the full design of the different components the entire system needs to be optimized as well; correct positioning of extractions/inductions, appropriate cooling parameters, use of recuperation/regeneration (see Figure 6), and so on.
Only when the cycle boundary conditions (and therefore its configuration) are fixed the full design of the components can be performed although some preliminary studies should be undertaken to determine the feasibility of these designs and get an estimation of the components performances. Another goal of such feasibility studies is to determine such things as the estimated dimensions of the components, the configuration of the expander (axial, radial, axi-radial, counter-rotating, etc.) Finally some compromises always need to be done between efficiency improvement and cost of manufacturing, operation and maintenance.
Operation at optimal conditions (design point for overall cycle and each component)
Each energy conversion system whether it is for power generation, propulsion or any other application is designed for a set of operating conditions called a design point. This is where the system will typically be optimum for and where it will be running most of its “on” time. This is why ensuring that the design point (or design points) is accurately defined is critical since operation outside of these defined conditions will lead to additional losses that translate into a lesser power production for the same cost of input energy. Performance prediction of systems at off-design conditions is an essential part of any design task which allows restricting system operation to conditions of high components efficiency. If the pump/compressor is operated at a different mass flow rate its pressure ratio will be different and so will be the efficiency and therefore the amount of power generated by the expander, see Figure 4.
In our next post, we will continue the discussion of the turbomachinery industry as it relates to climate change. Stay tuned!
Last week, SoftInWay attended the Turbomachinery & Pump Symposia in Houston, Texas. The conference consisted of many fascinating displays and presentations. There was a lot to see and learn.
We noticed many new industry trends and patterns during our time in Texas, but some were more prevalent than others. One thing that caught our attention in particular: Utilities and Oil & Gas owners and operators want to do more with performance prediction independently of OEMs. This would cut out a middleman and allow owners and operators to cut time and costs within their projects.
Our tools provide modules needed to conduct performance prediction. Are you hoping to independently predict performance for your next project? We would love to talk to you. Send us an email to learn more about the capabilities of AxSTREAM and AxCYCLE.
Were you at the conference? Let us know what you noticed in the comments.
Our next webinar is on October 8th! Join us as we discuss Design of Waste Heat Recovery Systems Based on Supercritical ORC for Powerful Engines.
Waste heat recovery is a hot topic (pun intended) that SoftInWay embraced rapidly. Numerous projects have been successfully performed on both the thermodynamic and the turbomachinery components levels.
In this webinar, we will discuss the case of a powerful ICE that can now benefit from a 20% boost in power due to waste heat recovery using a supercritical organic Rankine cycle (SORC). Different configurations, levels of complexity and parameters are studied and compared for the thermodynamic cycle as well as different fluid. Moreover, to show you that SORC is the way to go the results obtained are compared to what would be obtained with a different type of WHR system; double-pressure water steam cycle.
The session will include:
Introduction to the powerful ICE considered and its waste heat sources
Working fluid and parameters selection for the waste heat recovery system (WHRS)
Comparison of different configurations of WHRS SORC
Preliminary design of the turbine(s)
Who should attend?
Engineers actively contributing to making their processes more efficient.
Engineers working in the mechanical, aerospace, automotive, marine, power generation industries who want to optimize their process equipment by utilizing untapped heat.
Engineering students looking for a comprehensive and state-of-the-art case study to optimize existing equipment allowing them to widen and deepen their understanding of waste heat recovery to meet the requirements of future employers.
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!
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.
Design 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.
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 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.
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.
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.
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??
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.
Join us for our next free webinar on September 3rd, 2015!
Rotor manufacturers seek design aspects which will lead to the maximum level of reliability. These aspects include support, which is most effectively provided by journal bearings, a vitally important component of a turbine. Without the journal bearing and rotor accurate analysis, it can be risk of catastrophic machine damage. Turbine components must be closely checked and kept stable for optimal and safe performance.
Our next webinar will highlight our emerging applications for turbomachines, compressors, and other mechanisms used with rotors and journal bearings. The interacting influence of bearings on the dynamic behavior (rotor dynamics) of machinery will be reviewed and illustrated by the construction of analytical models.
The session will include:
Brief introductions to Rotor and Journal Bearings construction and their roles in the turbomachinery industry.
Introduction to Rotor Dynamic and Journal Bearings analyses.
Program application presentation and description capabilities and properties.
Who should attend?
Engineers working in turbomachinery interested in calculating and optimizing machine rotor dynamics
Engineers interested in improving machine life and performance with optimal bearings
Engineering students interested in the future of turbomachinery design and optimization.
We hope you can attend! Register by following the link below.
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.
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 firstname.lastname@example.org to find out exactly how we can help with your next turbomachinery project.