Precision flow testing can play an important role in optimizing gas turbine performance. It can determine the performance and expected lifespan of individual components vital to maintaining a reliable and profitable gas turbine.
By combining this information with performance and emissions data, it is possible to suggest improvements to individual components that will benefit overall turbine operation.
Due to the complex nature of individual components and the need for strict tolerances, a small anomaly can develop into a more serious issue that can affect the service life of combustion and hot-gas-path parts. This can result in increased repairs to components, de-rating of the machine, or even taking the gas turbine offline.
Data for each component’s flow test is collected, recorded and reviewed. It is then used to assess the component’s condition and useful life.
Figure 1: Inspection of 501 FD2 dual fuel support housing in Sulzer’s 450 kV, 5-axis digital imaging X-ray booth
Optimizing combustion flows
Vacuum flow testing replicates the direction of flow that occurs on combustion components while in operation. It helps to verify and adjust the flow rate through combustion liners to ensure temperature uniformity (Figure 1).
Fuel enters and mixes with air in the primary mixing zone of the combustion liner. Supplied air is directed through mixing, dilution and the louver features of the liners. The position, size and effective flow area of these features affect the fuel to-air ratio, flame temperature, flame profile, and ultimately the performance and emissions of the turbine.
The effective flow area of combustion liners may change following a repair. This may result from the removal of thermal barrier coatings and base material, for example.
Therefore, the effective flow area needs to be carefully tested after new barrier coatings are reapplied.
Flow testing of first-stage nozzle vane segments should also be considered (Figure 2).
Figure 2: Flow test of 501 DF42 fuel nozzles with steam injection on high-flow test bench 20
The first-stage nozzle consumes a significant portion of air supplied to the compressor discharge case. Turbines that underperform can be affected by the oversupply of cooling air to the first-stage nozzle vane segments. This simultaneously reduces the required air flow for combustion within the liners, limiting the output performance of a turbine. Gas turbines operate in environments where small particles can be ingested and deposited on components. The fouling or blockage of fuel nozzles, for example, can significantly affect turbine performance.
It can also lead to physical damage of the machine. Therefore, blades and buckets should be tested to check that cooling passages are not blocked (Figure 3).
Evaluating uniformity in sets of component flow data can help pinpoint parts that have issues. By comparing data from tests performed when parts are received to those performed after refurbishment, it is possible to identify problems.
Trending this information over time can help develop more informed maintenance schedules and estimates of useful component life.
Liquid flow testing monitors the flow rate of liquid-fuel and water-injection circuits of the fuel nozzles. Liquid flow testing also allows for the visual monitoring of spray patterns, which can indicate component wear or internal blockages. Liquid circuits need to maintain their spray patterns in order to achieve the correct flame profile and temperature distribution. Wear or internal debris may cause combustor burnout. If this occurs, the flame can impinge upon the combustion liner or basket wall and cause component damage.
Figure 3: Flow test of 7001 1st stage bucket on high-flow test bench
Assessing liquid flows
Fuel nozzle flow rates need to match those required by the manufacturer’s design specifications in order to achieve the expected output. These criteria may vary from one turbine to another, even if the turbines are of the same model type. An evaluation of flow data should be performed and made available for inventory spares or sets of fuel nozzles. Large operators minimize downtime during outages by using inventory spares.
Spare fuel nozzles, for example, should be clearly identified with a reference that identifies the turbine they originated from and specific flow data. Large organizations that operate multiple turbines in different locations with an inventory pool of spare parts, may have performance issues after swapping out for an inventory set.
For example, fuel nozzles designed for a turbine at sea level will have different specifications than the same model at another elevation. Without a comparison of flow rates, unknowingly swapping these fuel nozzles can reduce performance and may even affect start-up.
It is wise, then, to carefully review flow data from parts being removed from the turbine as well as those scheduled for installation to ensure there are no major differences.
Even when minimal differences are present, this analysis can determine the need for other actions, including changes to fuel valve settings, operational control adjustments or scheduling the turbine for tuning. Ultimately, flow testing aims to remove anomalies from a system, minimizing variation and delivering a more efficient machine. Minimizing temperature spread and vibration reduces wear to components, lowering repair and maintenance costs.
With the amount of software in today’s cars in the dimension of millions of lines of code, updating vehicle software today is a cumbersome business. Now Continental has created the necessary technology and infrastructure to enable secure software updates over the air, doing away with the need to visit the garage for every update.
With significance for software for the user experience of car buyers updates having dramatically increased over the past decade or so, automotive manufacturers are feverishly working on solutions to establish similar mechanisms for their vehicles. So far, only Tesla dares to update the software of its cars automatically. All others look jealously over the fence, frightened by the prospect of a terrible glitch or, even worse, a cyber attack against the transmission path. Also, updating a vehicle’s software is somewhat more complex than updating a smartphone’s operating system: Up to 100 computers are involved, and since they are all connected, the activities of most of them can have side effects on others. Plus, the number of possible variants and options in a car is much bigger than in a smartphone. And last but not least, no one can afford a failed software update – in a car such a situation would have far more serious consequences than with a smartphone.
Therefore, despite intensive R&D activities by companies like RedBend Software or Harman, the roll-out of solutions for software updates over the air for cars seemed to got stuck for quite a while. Now it seems like Continental has made the grade: The automotive supplier has developed the necessary solutions at the hardware level in the car and established a reseller relationship with Texas-based company Carnegie Technology which offers a software update platform. Continental will integrate this software into its automotive telematics solutions. The software will run on the next generation of Continental’s telematics module along with a supporting cloud-based component for analysis and diagnosis functions.
During the ride, this technology aggregates the bandwidths of available transmission paths and the seamless handover between mobile radio cells as well as between different wireless technologies such as WiFi, LTE, 3G and satellite connections. As a supplement to the terrestrial networks Continental together with satellite communications provider Inmarsat is currently developing wireless update techniques for satellite-based software updates. This will enable worldwide updates for vehicles and makes car vendors widely independent from mobile radio operators. For the update process, the Continental platform establishes a two-way satellite data connection.
Carnegie’s software solution is constantly monitoring and assessing the quality of the available network connections options. It then selects the connection that promises the fastest, most reliable and most cost-effective connection. Through its VehicleLink function, it can also use smartphones, laptops or similar devices integrated into the car and the bandwidth they can contribute. To reduce communications cost, the system also has access to external WiFi cells. The Carnegie solution also makes sure the downloads are resumed after interruptions, for instance if a car has passed through a tunnel. Likewise, this solution also manages voice calls to and from the vehicle and allows a broad range of priority options.
At the device level, Continental’s in-car networking modules can be either integrated into a smart antenna module or be used as an independent telematics unit. They are complemented by gateway units that in turn are connected to the vehicle’s internal data buses, providing the infrastructure for the OTA updates.
The solutions will be introduced to the public at the international automotive exhibition in September in Frankfurt Germany.
GERMANY: A new nanocoating developed for heat exchangers with anti-adhesive, anti-corrosive and anti-microbial properties could find ready acceptance in the air conditioning industry.
The Saarbrücken-based Leibniz Institute for New Materials is demonstrating the possibilities for the new coating at this year’s Hannover Messe which takes place in April.
The coating is aimed initially at the food industry where heat exchangers are used extensively by companies such as milk and juice processors. In order to ensure there is no risk to consumers, heat exchangers in these areas have to be free from microbes and must be cleaned at regular intervals using aggressive chemicals. These increase the sensitivity for corrosion, especially if mild steel is used as heat exchanger material.
According to Carsten Becker-Willinger, head of Nanomers at the Leibniz Institute for New Materials, the paint developed could also be used in other contexts, including air conditioning and water purification plants.
The developers achieve the anti-adhesive characteristics in the new coating by introducing hydrophobic compounds that are similar to common Teflon. These inhibit the formation of any undesired biofilm and allow residues to be transported out more easily before they clog up the channels of the heat exchangers. The coating also acts as a diffusion barrier, inhibiting corrosion by corrosive substances or aggressive cleaning agents. Colloidal copper is also used in the coating to prevent microbes, bacteria or fungus from adhering to surfaces.
“In addition, we can keep the paint chemically stable. Otherwise it would not withstand the aggressive chemicals that are required for cleaning,” explained Carsten Becker-Willinger.
The coating could also be adapted for special mechanical loads where, due to mechanical vibrations, the individual heat exchanger plates could be subjected to a certain amount of abrasion at points of contact.
The paint can be applied using standard methods such as spraying or immersion and subsequent hardening. It can be used on stainless steel, steel, titanium or aluminium.
The Leibniz Institute for New Materials is a leading center for materials research, conducting research into nanocomposite technology, interface materials, and bio interfaces.
Voith’s range of digital steam turbine controllers has been extended with the new TurCon DTc. This compact model can be set up quickly and easily to perform all standard control functions on mechanical driven machines and generators. The new controller is “pre-engineered” and suitable for steam turbines of all power classes.
Fast, simple and cost-effective system integration with the best possible reliability, process quality, productivity and safety are the typical customer specifications for modern steam turbine controllers. Decision-makers of OEMs or engineering contractors and modernizers looking to minimize costs prefer to use controllers that dispense with elaborate installation processes and offer a high degree of flexibility. Operators of steam turbines expect a reliable product that uses proven control algorithms to ensure high process quality and productivity.Because the controller is “pre-engineered” the customer only has to set the selected parameters, which keeps installation work to a minimum. There is no need to buy additional special software; data can be displayed at any time via the control panel or via the connected control system.
The TurCon DTc consists of two rugged assemblies, an intuitive 7″ TFT-LCD touchscreen control panel with integrated CPU and a remote I/O unit. The controller can be integrated into existing Industry 4.0 environments via a standardized Ethernet interface with Modbus TCP or OPC. An optional control panel or PC can be connected via the LAN interface, for example as part of a commissioning process or remote monitoring scenario.
The option of simultaneously controlling a maximum of 4 HP and 2 LP control valves is another special feature of the TurCon DTc. This means that there is no need to adjust the valves mechanically using a camshaft or via a separate valve coordinator (split range).
Other key elements ensuring reliability and availability include the three frequency inputs with a 2-out-of-3 voting for the speed sensors. The fault-tolerant speed measuring equipment offers high reliability and availability. An integrated simulation mode allows commissioning personnel to check whether the parameter settings are actually correct and improve them if necessary prior to hot commissioning. This minimizes the risk of damage due to incorrect parameters.
The TurCon DTc archives the last 1,000 status, warning and alarm messages with a time stamp, allowing process flows and malfunctions to be easily identified and traced. As a result, fast, targeted optimizations are possible.
Voith Digital Solutions bundles Voith’s long standing automation and IT expertise with the know-how in the fields of water power, paper machines and drive engineering.
Changes in ambient temperature have an impact on fullload power and heat rate of a gas turbine, but also on part-load performance and optimum power turbine speed. Manufacturers typically provide performance maps that describe these relationships for ISO conditions.
The excerpts are taken from a paper “Gas turbine performance” presented by Rainer Kurz of Solar Turbines and Klaus Brun of Southwest Research Institute at the 2015 Middle East Turbomachinery Symposium.
The performance curves are the result of the interaction between the various rotating components and the control system. This is particularly true for DLN engines. If the ambient temperature changes, the engine is subject to the following effects:
The air density changes. Increased ambient temperature lowers the density of the inlet air, thus reducing the mass flow through the turbine, and therefore reduces the power output (which is proportional to the mass flow) even further. At constant speed, where the volume flow remains approximately constant, the mass flow will increase with decreasing temperature and will decrease with increasing temperature.
The pressure ratio of the compressor at constant speed gets smaller with increasing temperature. This can be determined from a Mollier diagram, showing that the higher the inlet temperature is, the more work (or head)is required to achieve a certain pressure rise. The increased work has to be provided by the gas generator turbine, and is thus lost for the power turbine, as can be seen in the enthalpy-entropy diagram. At the same time NGgcorr (ie the machine Mach number) at constant speed is reduced at higher ambient temperature. As explained previously, the inlet Mach number of the engine compressor will increase for a given speed, if the ambient temperature is reduced. The gas generator Mach number will increase for reduced firing temperature at constant gas generator speed.
The Enthalpy-Entropy Diagram describes the Brayton cycle for a two-shaft gas turbine. Because the head produced by the compressor is proportional to the speed squared, it will not change if the speed remains the same. However, the pressure ratio produced, and thus the discharge pressure, will be lower than before. Looking at the combustion process, with a higher compressor discharge temperature and considering that the firing temperature is limited, we see that less heat input is possible, ie., less fuel will be consumed .The expansion process has less pressure ratio available or a larger part of the available expansion work is being used up in the gas generator turbine, leaving less work available for the power turbine.
On two-shaft engines, a reduction in gas generator speed occurs at high ambient temperatures. This is due to the fact that the equilibrium condition between the power requirement of the compressor (which increases at high ambient temperatures if the pressure ratio must be maintained) and the power production by the gas generator turbine (which is not directly influenced by the ambient temperature as long as compressor discharge pressure and firing temperature remain) will be satisfied at a lower speed. The lower speed often leads to a reduction of turbine efficiency: The inlet volumetric flow into the gas generator turbine is determined by the first stage turbine nozzle, and the Q3/NGG ratio (i.e., the operating point of the gas generator turbine) therefore moves away from the optimum.
Variable compressor guide vanes allow keeping the gas generator speed constant at higher ambient temperatures, thus avoiding efficiency penalties. In a single-shaft, constant speed gas turbine one would see a constant head (because the head stays roughly constant for a constant compressor speed), and thus a reduced pressure ratio. Because the flow capacity of the turbine section determines the pressure-flow-firing temperature relationship, equilibrium will be found at a lower flow, and a lower pressure ratio, thus a reduced power output.
The compressor discharge temperature at constant speed increases with increasing temperature. Thus, the amount of heat that can be added to the gas at a given maximum firing temperature is reduced.
The relevant Reynolds number changes: At full load, single-shaft engines will run a temperature topping at all ambient temperatures, while two-shaft engines will run either at temperature topping (at ambient temperatures higher than the match temperature) or at speed topping (at ambient temperatures lower than the match temperature). At speed topping, the engine will not reach its full firing temperature, while at temperature topping, the engine will not reach its maximum speed. The net effect of higher ambient temperatures is an increase in heat rate and a reduction in power. The impact of ambient temperature is usually less pronounced for the heat rate than for the power output, because changes in the ambient temperature impact less the component efficiencies than the overall cycle output.
By TMI Staff & Contributors
IESG Engineering have a service generating performance models of equipment (gas turbines, generators, boilers, HRSGs, SCRs and other equipment) based on different percentage loads and seasons, minimizing downtime and maximizing performance.
Over the last 200 years an ever-increasing proportion of our energy has come from non-renewable sources such as oil and coal. While demand for energy rises these resources are running out and scientists are exploring the potential of renewable sources of energy for the future.
Renewable and non-renewable energy resources All life on earth is sustained by energy from the sun. Plants and animals can store energy and some of this energy remains with them when they die. It is the remains of these ancient animals and plants that make up fossil fuels. Fossil fuels are non-renewable because they will run out one day. Burning fossil fuels generates greenhouse gases and relying on them for energy generation is unsustainable. Hence the need to find more renewable, sustainable ways of generating energy. Renewable or infinite energy resources are sources of power that quickly replenish themselves and can be used again and again. Some resources can be thought of as both renewable and non-renewable.
Wood can be used for fuel and is renewable if trees are replanted.
Biomass, which is material from living things, can be renewable if plants are replanted.
Non-renewable energy resources
Watch below table in a Wide Screen mode for a mobile option.
Type of fuel
Where it is from
Disadvantag Coal (fossil fuel)
Oil (fossil fuel)
Natural gas (fossil fuel)
How long will fossil fuels last? Estimates from international organizations suggest that if the world’s demand for
energy from fossil fuels continues at the present rate that oil and gas reserves may run out within some of our lifetimes. Coal is expected to last longer. Estimated length of time left for fossil fuels