Due to substantial use of gas turbines and their highly dynamic behavior, they have a profound impact on electrical grid. Although the control philosophies of various turbines are almost the same, there are some nuances in governor systems. As long as these details affect system response in extremely dynamic phenomena such as load rejection, they should be included in models. In this paper, the governor system is subjected to careful scrutiny; tasks of controllers are classified schematically and some special features such as back-tracing and feed-forward are discussed. The turbine is also modeled and a function is developed to calculate turbine exhaust gas temperature. The proposed governor-turbine model is validated by test results and a comparative analysis shows that the back-tracing method prevents wind-up phenomenon and the feed-forward method improves stability and response time.

The energy management strategy of a hybrid-electric aircraft is coupled with the design of the propulsion system itself. A new design space exploration methodology based on Set-Based Design is introduced to analyse the effects of different strategies on the fuel consumption, ${\mathrm{NO}}_{\mathrm{x}}$ and take-off mass. Probabilities are used to evaluate and discard areas of the design space not capable of satisfying the constraints and requirements, saving computational time corresponding to an average of 75%. The study is carried on a 50-seater regional turboprop with a parallel hybrid-electric architecture. The strategies are modelled as piecewise linear functions of the degree of hybridisation and are applied to different mission phases to explore how the strategy complexity and the number of hybridised segments can influence the behaviour of the system. The results indicate that the complexity of the parametrisation does not affect the trade-off between fuel consumption and ${\mathrm{NO}}_{\mathrm{x}}$ emissions. On the contrary, a significant trade-off is identified on which phases are hybridised. That is, the least fuel consumption is obtained only by hybridising the longest mission phase, while less ${\mathrm{NO}}_{\mathrm{x}}$ emissions are generated if more phases are hybridised. Finally, the maximum take-off mass was investigated as a parameter, and the impact to the trade-off between the objectives was analysed. Three energy management strategies were suggested from these findings, which achieved a reduction to the fuel consumption of up to 10% and a reduction to ${\mathrm{NO}}_{\mathrm{x}}$ emissions of up to 15%.

One of the main areas of research for the More Electric Aircraft (MEA) is mounting a generator on the low-pressure shaft in addition to the starter/generator mounted on the high-pressure shaft. Given that there are electrical machines on both the low-and high-pressure shafts, there is an “electrical bridge” to establish power exchange between the shafts. Potential improvements in the engine performance in terms of fuel consumption, engine stability and compatible thrust with flight mission at various flight scenarios under such transfer, have been studied and discussed in the literature. To prove the concept and demonstrate the practicality of power transfer, an engine emulator has been constructed. The emulator will replicate basic behavior of the engine by using similarity analysis to allow for conducting tests in a scaled environment without the need for an actual physical engine. A unique time-scaling technique is implemented to synchronize the time of the engine model and the test rig for transient studies. This enables scalable flexible engine emulation at different power generation ratings. A new criterion composed of shaft inertia, time and speed scaling factors, is also introduced to assess the validity of shaft inertia emulation. The experimental results are reported to demonstrate and further discuss the feasibility of electric power transfer between the engine shafts.

Multiple-spool gas turbines are usually utilized for power supply in aircrafts, ships, and terrestrial electric utility plants. As a result, having a reliable model of them can aid with the control design process and stability analysis. Since several interconnected components are coupled both thermodynamically and through shafts, these engines cannot be modeled linearly as single shaft gas turbines. In this paper, intercomponent volume method (ICV) has been implemented for turbine modeling. A switched feedback control system incorporating bump-less transfer and antiwindup functionality is employed as governor for the engine. Validation with test results from a three spool gas turbine highlights high accuracy of turbine-governor model in various maneuvers. Results show that over-speed after load rejection is considerable due to the fact that in this arrangement, the power turbine (PT) is not coupled with the compressor which acts like a damper for single shaft gas turbines. To address this problem, bleed valves (mainly before combustion chamber) are used to arrest the over-speed by 20%. In addition, a switch is employed into the governor system to rapidly shift fuel to permissible minimum flow.