What Turbomachinery does to Avert Climate Change (Part 1 of 2)

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.

  1. 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.

Figure 1 Simple Rankine cycle schematics
Figure 1 Simple Rankine cycle schematics

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.

Figure 2 Recuperated Rankine cycle
Figure 2 Recuperated Rankine cycle

 

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.

 

 

 

  1. Operation at optimal conditions (design point for overall cycle and each component)
Figure 3 Comparison of efficiency and power rating for axial and radial configurations of turbines
Figure 3 Comparison of efficiency and power rating for axial and radial configurations of turbines

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.

Figure 4 Performance map of a centrifugal compressor showing its efficiency as a function of the mass flow rate for different rotation speeds
Figure 4 Performance map of a centrifugal compressor showing its efficiency as a function of the mass flow rate for different rotation speeds

In our next post, we will continue the discussion of the turbomachinery industry as it relates to climate change. Stay tuned!

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.

Gas Turbine Technology in Aircraft Propulsion

It is very interesting to take a look at how gas turbine technology has made its way into aircraft propulsion and improved over time. When the idea of a turbojet was introduced by Frank Whittle and others in the 1920s, no one could have guessed that it would change the future of air propulsion. The Committee on Gas Turbines from the National Academy of Sciences reported (1940): “In its present state … the gas turbine engine could hardly be considered a feasible application to airplanes mainly because of the difficulty in complying with stringent weight requirements imposed by aeronautics” [1]. This puts into perspective the immense advancement that gas turbine development has made to be an integrated part of aircraft propulsion today.

genx-1b engine
GEnx-1B engine (first run, 2006) for the Boeing 787 Dreamliner, from Airline Reporter [3].
Rolls-royce avon engine
Rolls-Royce Avon Engine (first run, 1946), from Wikipedia [2].
 

 

 

 

 

 

 

A quick look at the engine characteristics reveals the great advancement in design and manufacturing of jet engines from the early turbojets to the most advanced turbofans today. For instance, General Electric’s J31, with an overall pressure ratio of 3.8:1 and maximum thrust of 1,650 lbf, was one of the first manufactured jet engines in the United States [2]. Nowadays, Rolls-Royce Trent 1000 has achieved a maximum thrust of 78,000 lbf with an overall pressure ratio of more than 50:1 [4]. Without a doubt, gas turbine technology has made a huge impact on aircraft propulsion and there will be more to come in future.

Trent 1000 engine, from Rolls-Royce [4].
Trent 1000 engine, from Rolls-Royce [4].
[1] www.MIT.edu
[2] www.Wikipedia.org
[3] www.AirlineReporter.com
[4] www.Rolls-Royce.com

 

 

Mini and Micro Gas Turbines

Mini and Micro gas turbines are becoming increasingly relevant among today’s research of power production technologies. These turbines are smaller, lighter, less-polluting, and less expensive than traditional power generation units. Gas turbines have high-grade waste heat, low maintenance costs, and low vibration levels. The micro versions of these turbines play a key role in micro combined heat and power (CHP) and micro power generation. Continue reading “Mini and Micro Gas Turbines”

Come home. Book your ticket for the Turbo & Pump Symposia

The 43rd Turbomachinery and 30th Pump Symposia are quickly approaching. The 3-day event will begin on September 22nd in Houston, Texas at the George R. Brown Convention Center. The Symposia are organized in order to promote professional development, technology transfer, peer networking and information exchange among industry professionals. The event serves as a premier training and networking opportunity for professionals in both the turbomachinery and pump industries.

2013 Symposia
Source: Texas A&M Engineering Experiment Station

In ancient Greece, a symposium was a drinking party. Hosted by Socrates and philosophers alike, they were used to celebrate and discuss matters most vital to the universe. The “symposium” was a source of pride for the ancient aristocrats. Continue reading “Come home. Book your ticket for the Turbo & Pump Symposia”

3 Categories and Sources of Vibrations

In view of the large number of blades in any turbine machine, the existence of unavoidable sources of vibration excitation and the serious consequences of the failure of just one blade, an intimate knowledge and understanding of the vibration characteristics of the blades in their operating environment is essential.

Vibration excitation can arise from a variety of sources but principally involves the following categories: Continue reading “3 Categories and Sources of Vibrations”

Carryover Losses – Steam and Gas Turbines

losses
Losses

A number of loss prediction methods exist in turbomachines. Concerning axial turbines, there are at least seven methods just for cascade losses! But there are also loss models developed to predict individual loss components such as secondary, seal and tip clearance losses and more. Continue reading “Carryover Losses – Steam and Gas Turbines”