Abstract
The present article deals with the design of a micro turbogas turbine suitable for on board applications, e.g., as a power generator on hybrid transit bus, characterized by a simple constructive approach. Deriving the machine layout from an existing KJ-66 aircraft model engine, the authors propose a theoretical design of a compact, lightweight turbogas turbine, by investigating the technical possibility and limits of the proposed design. In particular, a different combustion chamber layout has been proposed, and fuel adduction channels for different swirler designs have been simulated via ANSYS Fluent in order to identify a satisfactory fuel spreading. As a result, the complete characterization of the design parameters and geometries has been performed, and a series of RANS simulations has been used in order to identify an optimal swirler configuration.
Highlights
Gas turbine technology proved to be essential in multiple applications throughout the last few decades, thanks to its unequaled power density and reliability
A comparison with similar machines, produced by Capstone, Ingersoll-Rand, Elliott Energy System, shows that micro TG are usually radial compressor-radial turbine machines; this design choice is better suited for high peripheral velocities, because the thin section at the tip rapidly grows moving towards the hub in radial turbines, increasing the resisting section and allowing higher rotational speed
The 5 swirlers elaborate approximately 20% of the compressed air flow, as usually this is the amount of primary air in which the fuel is injected, and the swirlers have been designed such that their inlet area is about 20% of the area of the inlet section of the chamber
Summary
Gas turbine technology proved to be essential in multiple applications throughout the last few decades, thanks to its unequaled power density and reliability. Some solutions have been widely used with good success in some major cities; in particular, New York has one of the world’s biggest hybrid bus fleets, counting 1677 units in 2013 The advantages of this solution for the environmental aspect of the problem are evident: hybrid vehicles allow noise and emission reduction, while operative cost is estimated to be generally lower, and fuel efficiency is increased. Battery capacity for a standard hybrid bus is around 150 kWh, and the purpose of the TG is not to fully recharge it in a few minutes but to constantly produce a lower amount of power, enough to keep the battery level relatively constant This approach is preferred for two reasons: firstly, high power implies higher weights, fuel consumption and costs, all of which must be limited in order to have a competitive product. The complete simulation of the combustion chamber was not possible due to limitations in computational resources, but the study of swirlers and fuel injection has been investigated via CFD simulations
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