Investigation of the influence of an adjustable air split inside a gas turbine combustion chamber on the flexibility of micro gas turbine operation

Kurzfassung

In previous studies a hybrid energy system, consisting of a high temperature storage and a micro gas turbine, was researched. The coupling of these systems offers many different advantages, but also poses some challenges for the gas turbine combustion. Therefore, the influence of this thermal storage integration on the gas turbine combustion was investigated. It was concluded, that a stable combustion below the legal emission thresholds could not be achieved for the whole operating range. Therefore, this paper starts with atmospheric tests, showcasing that an adjustment of the air split inside the combustion chamber enables the combustor to optimize its combustion properties. The air split is directly linked to the local air number of the primary combustion zone, which therefore allows the combustor to adapt to the respective boundary conditions, leading to an enhanced flame stability and optimized exhaust gas emissions. Hence, this paper introduces further experimental and numerical investigations of an orifice, which allows for this adaptation of the air split. It will be shown, that the orifice enables an adjustment of the local air number of up to 47.5 %, allowing for a strong emission reduction, depending on the operating point. The potential of this adaptation will be demonstrated in gas turbine tests mimicking the varying inlet conditions of the hybrid energy system, different low part load points and a fuel variation with a biogas surrogate. The feasibility of this orifice, which increases the resilience towards the boundary conditions of the combustor, boosting its operational flexibility, while enabling emission levels far below the legal thresholds will be successful shown.