Lecture: Innovative gas turbine processes and their modelling

Learning Goals

Lecture

• Steady state (on and off-design) and transient modeling of gas turbine power plants and evaluation of their energetic performance.
• Introduction to transient and off-design operations in actual power plants based on actual examples of combined cycle power plants.
• Modeling and energetic evaluation of novel gas turbine processes and discussion of possible applications in energy generation.

Exercise

• Modelling of micro gas turbines for combined heat and power applications
• The exercise of the lecture will be structured like an actual research project. Student will learn how research projects are planned, structured, carried out and evaluated.
• Students accompanied by a researcher of the chair will carry out experiments in an actual micro gas turbine.
• Apply the modelling techniques learned in the lecture to model the micro gas turbine of the lab.
• Reflect on the results of the models based on their comparison to the experiments carried out in the lab.
• A final roll out presentation of the results during the experiments and the modelling tasks will be carried out in the form of an information marketplace. The students will learn how to present their results to their peers in a concise way.

 

Topics/Contents

Challenges of the energy sector in the 21st century – Relevance of gas turbines and their transient operation.

 

Variable renewable power generation has introduced new challenges in the operation of European electricity grids. On the one hand, the reduction of the system rotating inertia and sudden generation changes, due to market schedules, lead to significant frequency deviations. On the other hand, the uncertainty in weather forecasts and the inherent variability of wind and solar power systems increase the need for secondary and tertiary reserves. In particular, the demand for positive secondary reserve is expected to increase in the next 10 years in Germany by 40%, whereas the negative by 10 %. Tertiary reserve demand is expected to grow even stronger in Germany, namely by 70% and 90% respectively. Similar trends are expected on a European level.

In addition to the changes in network ancillary services, the presence of varying renewable generation puts further pressure on the existing fossil fuel units in terms of their operational flexibility. In fact, the residual load hourly ramps are expected to exceed in the next decade in many European countries 10% of the system load at the respective hour. This effect will further increase the overall probability of contingency events and makes measures for increased operational flexibility indispensable, if renewable generation continues to increase.

Gas turbines are expected to be the major provider of secondary and tertiary reserves for electric networks on a long term basis. The main reason is their very high operational flexibility and their ability to adapt in very versatile operational strategies and conditions. For this reason, the analysis and understanding of the transient, dynamic and off-design operation of gas turbines will be crucial for engineers in the coming years. Modeling and predicting their behavior is a major milestone for designing and operating future energy systems. At the same time the development of power plants based on innovative gas turbine cycles offers high potential in increasing their electrical efficiency while keeping their operational versatility.

In the course of this lecture, simulation tools for the modeling of gas turbine cycles both for their off-design and transient analysis are introduced in detail. Innovative gas turbine cycles are then presented and analyzed mostly in the context of energy systems with increased renewable generation. In parallel to these tasks an exercise will focus on the practical application of these models. Experiments will be carried out in a micro gas turbine installed in the chair of fluid dynamics. The generated data will be then used to validate and compare various models and discuss their strengths and shortcomings. 

Contents of the lecture are as follows.

• Introduction in gas turbines and their applications in the energy sector
• Introduction in micro gas turbines and distributed CHP (combined heat and power) plants
• Introduction in the transient operations of gas turbine power plants
• 0-D steady state modelling of gas turbines at design point
• 0-D off-design modelling of gas turbines and micro gas turbines
• 0-D transient modelling of industrial gas turbines and micro gas turbines
• Analysis of novel gas turbine cycles. Some examples of the cycles to be studied are the following:
  • Steam injected gas turbines
  • Humid air gas turbines
  • Maisotsenko cycle gas turbines
  • Integrated gasification combined cycle systems
  • Constant volume combustion gas turbines
  • Thermal solar gas turbines
  • Compressed air energy storage systems with gas turbines
• Methods to structure and carry out research projects
• Measurements in an actual micro gas turbine installed in the lab of the chair for fluid dynamics
• Applying the models to the micro gas turbine in the lab
• Verification of the models based on the results of the measurements and discussion

Teaching and learning methods

The lecture will focus on the models for industrial gas turbines and the study of innovative gas turbine processes. Apart from the typical frontal lectures, there will be several sessions where the active participation of the students will be necessary. An accompanying exercise will be structured as an actual research project. Its aim will be to apply all the models presented in the course of the lecture to micro gas turbines. The students will form groups of two to four persons, which will develop their own model of the micro gas turbine, based on the material presented in the lecture. Experiments will be subsequently carried out in an actual micro gas turbine that is installed in the laboratory of the chair. The generated data will be used to validate the models. A rollout of the results at the end of the semester and a report on the model and its validation will be the basis for the final grades of the students.

Desirable knowledge and skills for the participation in the lecture

Basic thermodynamics (Thermo I), basic energy systems theory, programming knowledge in matlab (or equivalent), basic turbomachinery theory, heat and mass transfer theory.

Description of the exam

Students will report on the work performed in the scope of the exercise in the form of a poster. A final poster rollout will take place at the end of semester. The poster must cover the following points:

• Description of the research question
• Description of the experimental facility
• Description of the actual experiments carried out
• Description of the modeling methodology used
• Presentation of the experimental and modelling results
• Discussion of the results and reflection on the comparison of experiments and models
• Conclusions

Moreover the students will give short presentation on a part of the relevant literature for the exercise approximately 5 weeks after the start of the semester.

The final grade will be a combination of the grades of the final poster (85%) and the grade of the interim presentation (15%).