Gas Turbines - Science topic

Laith Mustafa If you have oxygen at 30 bar, it seems that the best approach would be to combust it with high pressure fuel in a small combustion chamber, then expand the hot gas through a turbine. This is not a conventional gas turbine approach and would need a purpose designed turbine based on the normal gas turbine's turbine stage.

Oxygen is of little benefit in conventional gas turbines because they work at very high excess air levels, so the oxygen would be "diluted".

Oxy-fuel combustors are used in steel-making, but are rare, as oxygen is usually expensive. Simply expanding the oxygen through an expander would generate a good cooling duty.

The differences between HVAC and gas turbine filter media mainly involve their applications, performance needs, and environmental conditions. HVAC filters, used in heating, ventilation, and air conditioning systems, enhance indoor air quality by removing dust, pollen, and mold. They are rated by the MERV scale, operate in controlled indoor environments, and require regular replacement. In contrast, gas turbine filters protect turbine engines from contaminants in power plants and industrial settings. They capture a wider range of particles, maintain low pressure drop, and withstand harsh outdoor conditions, requiring durable materials and robust construction. These filters need less frequent replacement but must follow strict maintenance schedules to ensure turbine efficiency and longevity.

According to the manufacturer, the net power output for an LM6000 operating at one atmosphere barometric pressure and 15°C ambient temperature is 42,406 kWe (kilowatts electric) with a net LHV heat rate of 8223 BTU/kWh, which means the thermal efficiency is 41.5% and the heat input is 102.2 MWt (megawatts thermal). The shaft power is 57,911 bhp or 43,183 kWm (kilowatt mechanical) and the generator efficiency is 98.2%. Note that HHV is a meaningless quantity in this case, as water in the exhaust is always in the vapor state. You can get curves from GE. The LM6000 is a real workhorse!

EES (Engineering Equation Solver) is sufficient to study of thermodynamic cycles. It is very easy and user friendly.

Martin Möser

Thanks Dear Moser

Yes, you are right. This image is belonging to the final stage of fatigue crack propogation. According to your comment. Is it true to say that

In low cycle fatigue we observe quasi cleavage palnes while for High cycle fatigue the group of striations is promoted in fracture area ?

The answer depends on the relative sizes of the generators and the application. So, in island mode the frequency control can be seriously affected by excess solar energy and peaks and troughs as clouds pass need more CCGT reserve for back-up etc.

It is difficult to answer this question without knowing your background and the use to which you intend to use the bleed air. It is better to fully understand the application as reputable suppliers will help you with your difficulties if any. Most internal parameters they like to keep to themselves but they will offer guidance. At some stage, to minimise the weight and cost of the topsides of an offshore platform, bleed air from the GT was considered to be used as compressed air supply. One of the difficulties faced was the demand variations of the GT shaft power and the compressed air needs. They do not always go in step and tripping the GT at a critical moment is not appreciated. Stephen.

Yes, several studies have been conducted on the use of ex-service gas turbine engines for electricity generation. For example, the U.S. Department of Energy's National Renewable Energy Laboratory has conducted a study on the feasibility of using retired gas turbine engines for distributed generation applications. Additionally, the University of Melbourne has conducted a study on the repurposing of retired military gas turbine engines for micro-grid electricity generation.

There are currently no commercial models of 2mw gas turbines using hydrogen and ammonia as fuel, however, such models have been constructed in laboratory settings. In recent years, scientists have been exploring the use of hydrogen and ammonia as fuel for small-scale gas turbine engines. In one study, a 2mw gas turbine was powered with a mixture of hydrogen and ammonia, with an overall efficiency of approximately 32%. The turbine was able to maintain a stable output with an electrical efficiency of up to 37%. This type of model could be used to power small-scale energy production in remote areas or to supplement existing systems.

Sorry outside of my field

Two reasons: larger volumetric flow rate and to avoid mechanical failure. Just because something is academically said to be "neither gas nor liquid" doesn't necessarily mean anything in a physical application. Also, you should appreciate that there is a theoretical difference between an open (e.g., turbine) and closed (e.g., cylinder and piston) system when calculating work. For a closed system W=∫pdV while for an open system W=∫Vdp In a boiler feed pump, such as you might find in a supercritical coal-fired power plant, p is quite large (4400 psia) but dV is small. The low pressure turbine is much larger than the high and intermediate pressure turbine in a modern steam power plant. The LP turbine provides about 45% of the total power, while the HP and IP combined provide about 55%. People think that because the pressure is large in the HP turbine that this should be doing most of the work, but it isn't. The LP turbine is much larger in size and the ∫Vdp is also large. While dp may be small across the LP turbine, V is huge. Dig deeper into the thermodynamics and you will understand the processes and machines better.

Are you asking about a HRSG (Heat Recovery Steam Generator), as is used in countless CCPP (Combined Cycle Power Plants) around the world? Most of those combustion turbines run on natural gas. If you want to know, ask one of the many manufacturers. Where ever you live, there is probably one of these plants nearby you might visit. https://en.wikipedia.org/wiki/Heat_recovery_steam_generator

Suggest the following paper:

No isentropic efficiencies are not the optimization parameters; there is not much control and also not wide range of this efficiency. It depends on the design of the compressor and turbine. Rather you should treat them as external parameters and concentrate on heat exchanger efficiency (regenerator efficiency), maximum cycle temperature, two or three stage compression with intercooling, reheating point, pressure ratio, etc.

1. When a Gas Turbine is connected to a Grid, grid frequency affects the flow and output but governor or controller maintains the power output at the set value. Small frequency fluctuations occur routinely and speed/power output controller regulates.

2. When GT is already generating its maximum you cannot increase the fuel flow and hence power.

3. As long GT is connected to grid, GT speed is dictated by grid only. GT's speed cannot change,

You are most welcome dear Bahare Ghasemi

Wish you the best always.

Hello George Marin,

I hope you are doing well.

you may find a good SCI journal as per your specific requirement through the Web of Science Master Journal List, through the below-given link:

Regards.

Dear

You can use PTC creo software

Dear Francesco

Thank you very much.

Regards

Hello everyone!

I have found an article where the authors have mentioned that the typical range of excess air in the industrial gas turbine cycle is 100-600 %.

Martínez, F. Rueda, et al. "Evaluation of the gas turbine inlet temperature with relation to the excess air." Energy and Power Engineering 3.04 (2011): 517.

URL: https://www.scirp.org/html/7382.html

Hope this would help the researchers who would come across this post.

Zulfiqar Ali Rhinoceros software is also another graceful alternative. Just model with the curve/surface tools and export it as .obj format. Then, you can extract the corresponding knot vector, control points, order of the basis, etc.

I am a little bit puzzled why you want to add a steam turbine in a small scale system? The smaller size, the lower efficiency and higher specific cost.

The heat losses and the by-pass losses over the turbine blades are proportionally higher, the smaller the turbine is. Since small turbines have more material (the weight of the material the turbine is made of) per capacity, the material is often of lower quality (lower temperature and pressure) and hence the turbine has lower efficiency.

Why not go for a gas engine with upto 40 % electric efficiency in scales down to 100 kW? Or a recuperative microturbine where some of the heat is used to pre-heat the combustion air.

i think the article attached will help you a lot to understand.

This is not an answer to your question. I need a favor, can you please send me the AxSTREAM Lite software package. I want to also use it for some analysis. Thank

Axial turbines take in gas parallel to the shaft axis. General applications include steam generators but usually axials perform better on liquid fluid flows like kaplan for low head generators

This publication contains very pertinent information for your research. I think it will be very useful to you.

Abstract

In the recent years, numerous studies have been done on Stirling cycle and Stirling engine which have been resulted in different output power and engine thermal efficiency analyses. Finite speed thermodynamic analysis is one of the most prominent ways which considers external irreversibilities. In the present study, output power and engine thermal efficiency are optimized and total pressure losses are minimized using NSGA algorithm and finite speed thermodynamic analysis. The results are successfully verified against experimental data.

The profiles are created mathematically.

Have a look on Deich et al. (1965) work. You will get your answer for turbomachinery.

This PDF is avaliable online.

Thank You all for your help. It looks like that both microphones and a dynamic pressure transducer will work for me. But my application is combustion that involves temperature, so with temperature in mind, I think I should go for a transducer that can sustain high temperature.

Also check https://www.modernpowersystems.com/features/featurewhen-things-go-wrong-identifying-combined-cycle-problem-areas/

Combustion equipment overview can be studied from this link...explained in a very good way

Refer to this chapter: title 2.5 Settling Chamber & Fig. 2 Design of settling chamber. Noorul Huda

Important variable power value

you can see in help section of MATLAB simulink. and better to make the same if you have mathematical equations.

Ahmad Hadizadeh I think, this article can help you.

Hi

It depends on different factors. you can compare the actual cycle with the Carnot cycle efficiency. You can write a suitable code in EES software to this purpose.

Well the pressure ratio of gas turbine may be in the range (4to 12) but there is an optimum pressure ratio which depend on maximum and minimum cycl tempersture

Hi dear Kourosh, I suggest the following resources:

https://www.witpress.com/Secure/elibrary/papers/9781853129568/9781853129568008FU1.pdf

I have tested gas turbines all over the world. This is perhaps the largest business area for my employer. I have dealt with similar issues of IR on several occasions. If the window is heating up, you have no choice but to move farther away. The results will not be meaningful and equipment damage will result. I always "calibrate" such measurements at multiple locations with one or more surface temperature probes, which I pre- and post-calibrate (at least with ice and boiling water). I have also calibrated film cooling with several solutions. On more than one occasion I had no equipment because it was all lost in shipping. I bought a variety of things at the bazaar and auto repair shops, took lots of measurements, including ice and boiling several liquids and also pressure in clear slack tubes filled with water. I have even used a sack of assorted coins to calibrate a precision balance. When it's all over, ship everything back to the laboratory and do it all over again to post-calibrate everything. Which cooling system are you interested in? Evaporative coolers? Foggers? Inlet chillers?

Dear Muhammad

Besides not being answer to your question, I do not know how to answer. We developed our own computer programs to deal with variable geometry compressors, turbines and propelling nozzles. These components are designed and their performances calculated using our own software. A set of compressor, turbine and propelling nozzles maps are synthesized (one each for different angles and interpolated for angles not covered in the maps). It is not difficult task, but takes time to develop, verify and certify every piece of software.

I think Ihtishamul Haq is working on Aspen plus, you can consult him.

Thanks

I would have distributed the amount of scrap in several parts and oxidized it in air for different lengths of time. For the vacuum melt I would have mixed a non-oxidized part of the scrap with a oxidized part (for example 1 to 1) and analyzed the melting result. If the carbon content is still too high, you have to make a mixture with a more oxidized part of scrapat the second melt or change the mixture not oxidized to oxidized to 1 to 2. You may have to make several melts with different compositions (part not oxidized + part oxidized) to get the correct carbon content.

Japan is working towards 1700 C TIT. See MHI https://www.mhi.co.jp/technology/review/pdf/e451/e451015.pdf

Ericsson is a thermodynamic closed cycle which consists of two isothermal processes and two constant pressure processes. Heat addition and rejection are at isothermal processes. This uses gas as a medium in practical application. The application is in hot air engines.

Dear Kourosh Vaferi

First of all, you need to determine that you are looking for a material for rotor blades or the stator ones.

I think the best material (the ideal one) is a material which can stand for the high temperatures with high thermal conductivity.

If the material can stand for high temperatures, there is no need for cooling. and when it has no cooling, high thermal conductivity results in uniform temperature distribution and lower thermal stresses.

The material should also have low coefficient of thermal expansion and high strength.

Dear Kourosh Vaferi

The corrosion on rotor blades is always worse for two reasons. First, the rotating blades of a rotor bear more mechanical stress than stators. Second, salt particles collide and adhere together more often with the rotating blades of a rotor. So pitting corrosion, crevice corrosion, and stress corrosion are commonly found on rotating blades.

Dear Venkitesh

you can write the combustion equation, and define the LHV.

Yazan Altarazi , I hope it will be useful :

Cheaper fuels can be used in gas turbines. In these, fuels of petroleum origin are used as a fuel.

Hello Kamal,

Please check the following URL. I think the NASA data set can be useful for your work.

[Turbofan Engine Degradation Simulation Data Set]:

https://ti.arc.nasa.gov/tech/dash/groups/pcoe/prognostic-data-repository/

hi Haris, the gas turbine are very sensitive to off-design condition. if you are modelling a gas turbine for electrical generation at constant rpm is the worst condition because the compressor efficiency is really affecetd at low loads. that the reason of the inlet guide vane at the inlet and the several blade wheel with variable geometry, because constant rpm in absence of that devices always produce the same air flow disregarding the load value. There are papers where you can find a comprehensive study about that . Look in internet the papers written by Rainier kurtz ( engineer in carter pillar)

dear collegue. realy I am not sure if i understood your question. the tempearture range of operation in gas turbine depende on what kind of cycle you are trying to simulate. is not the same a simple cycle than a regenerative cycle. At the same time the pressure ratio for the gar turbine engine is another important thing. generally when higher pressure ratio are used higher inlet temperature are provided. the upper limit for inlet temperature is decided by metal constrains and cooling system used in the blades. The outlet temperature of gas turbine before the regenerator (if used) at full load are ranging from 450-600 degree centigrade.

Yeah thanks!!

I remenber when I was a younger student of mechanical engineer i made the same question to my professor of "motor combustion engine" and he told me. the gas turbine are rotary machine with small gap between rotor tip and the stator which are responsible for its efficiency. unfortuantelly when you reduce the size of the turbine you cant reduce the gap, that is the reason for not use GT in cars.

I suggest you read this tutorial (link below). I hope that helps you.

Dear/Roh Dargahi

Referring to your question about data for validation related to geometry or any properties (pressure, Mach number,......) You should share one or two researchers from air craft company working with you in order to provide you with most of hidden measurements and some references related to your work.

Regards

You can find an example in this paper:

Urban Energy Hubs Economic Optimization and Environmental Comparison in Italy and Vietnam

Please take a look at these articles

Thanks for your answer, Dudley. Do you have any Idea how temperature distribution is measured within the combustor (both in liners and flame) rather than laser techniques. I am aware of using Thermal Sensitive Painting on the combustor liners to measure Temp but not for the flame itself!

isentropic efficiency varies with pressure ratio of turbine. so, if you want to study the effect of the pressure ration, it would be better to use polytropic efficiency.

Dear Kamal,

the adiabaticity of turbomachinery is an assumption justified by the fact that heat losses in such machines are negligible with respect to the enthalpy variation experienced by the fluid passing through them.

The load frequency control model of speed governor, turbine, etc is in my paper just published in Oct, 2018. Please check the paper to see if that will solve your problems

Dear Mohanned, The previous figure was from analysis done by Yale University I have attached an analysis with the citation. Generally natural gas with show a 40 to 60% reduction in greenhouse gases and much more in relation to other air contaminants and does not generate anywhere near the solid waste. The selection of cheap fossil fuel from coal tar sands or oil can end up very expensive when these externalities are calculated which are costs to human health and the environment which should not be considered expendable.

In Russia, engineers must choose blade loads based on normative documents. Failure to comply with the standard is punishable by law. For example, loads for blades for gas turbines must choose based on " РТМ 108.022.102-77 Турбины газовые стационарные. Расчет на прочность хвостовых соединений рабочих лопаток газовых турбин"

you can use fluent software to stimulate the gas turbine combustion

Mohmmad Bahreini I think you can use the tables of gasdynamic functions (fig.1) (russian: таблицы газодинамических функций). If you know pressure ratio before and after your valve you can find gasodynamic functions of mass flow rate q(L) by using tables of gasodynamic functions. After that you can calculate absoltely mass flow rate using this formula (fig.2). This formula taken from book " The theory of turbomashines " the autor: doctor of technical science Kirilov I.I. (russian: Кириллов И.И.Теория турбомашин. Л., "Машиностроение". 1972 г.) : G = f*sqrt(k/R*(2/(k+1))^((k+1)/(k-1))) * P*/sqrt(T*) *q(L)

,where

f - sectional area

k=1,4 (for air)

R=287 [J/(kg*K)] (for air)

P* - total pressure before valve

T*-total temperature before valve

q(L) - gasdynamic function of mass flow rate

1. Fuel consumption;

2. Shaft Power (given that there is a torque meter).

From these two parameters you can calculate GT Efficiency and Output Power. And these parameters reflect the technical state of all GT parts including axial compressor, combustor, turbine and others. So, if there are some deteriorations with axial compressor, for example, fouling, the GT (either aero or industrial) won't give a nominal power and efficiency.

thank you sir Saad EL-Sayed ,

i have readout this paper ,actually im doing work on CFD+CRN Validation of CH4 combustion.i need pre mixed combustion NOx emission data on which i can compare my simulations results .

You can find geometry in grabcad.com

In my country of Iraq despite the presence of high solar radiation, but the production of electricity through oil is cheaper than its production by solar cells

The Gas Turb software library contains several compressor maps that you can use. Generally, very few articles include actual compressor performance maps due to proprietary reasons. Have a look at one of our articles where we digitized one compressor map of GE LM2500 gas turbine with the title "A component map tuning method for performance prediction and diagnostics of gas turbine compressors". The source of the compressor map is "Klapproth, J., M. Miller, and D. Parker. "Aerodynamic development and performance of the cf6-6/lm2500 compressor." 4th International Symposium on Air Breathing Engines. 1979."

Hi Ali.

There are several articles related to engine performance simulation in MATLAB/Simulink environment. One of our recent articles involves the development of a two shaft gas turbine in simulink. Feel free to download our article from the following link: https://authors.elsevier.com/a/1XxRr4r6KuvuY6

Nox, Efficiency increasing via TIT and CPD, avoiding unavoidable off-design degrating, Realable a fast dynamic models, accurate, robust and fast controller respond, hot section material improving, flexibility in load and frequency control, and so on... It is depenedent on your research line.

Dear sir

Yes yoy can with air fuel ratio

Dear all,

I did a bit of research in my thesis work with component based weight modeling. This is the link to my conference paper ( ), where you can find few relations and related references to estimate individual gas turbine component weight contributions that might be useful to other people. I hope this may help somebody.

Kind regards,

Jacopo

Above linked paper can give you some ideas.