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Design of an optically accessible turbulent combustion system

In order to design the next generation of gas turbine combustors and rocket engines, understanding the flame structure at high-intensity turbulent flows is necessary. Many experimental studies have focused on flame structures at relatively low Reynolds and Damköhler numbers, which are useful but do not help to provide a deep understanding of flame behavior at gas turbine and rocket engine operating conditions. The current work is focused on the presentation of the design and development of a high-intensity (Tu = 15–30%) turbulent combustion system, which is operated at compressible flow regime from Mach numbers of 0.3 to 0.5, preheated temperatures up to 500 K, and premixed conditions in order to investigate the flame structure at high Reynolds and Damköhler numbers in the so-called thickened flame regime. The design of an optically accessible backward-facing step stabilized combustor was designed for a maximum operating pressure of 0.6 MPa. Turbulence generator grid was introduced with different blockage ratios from 54 to 67% to generate turbulence inside the combustor. Optical access was provided via quartz windows on three sides of the combustion chamber. Extensive finite element analysis was performed to verify the structural integrity of the combustor at rated conditions. In order to increase the inlet temperature of the air, a heating section is designed and presented in this paper. Separate cooling subsystem designs are also presented. A 10 kHz time-resolved particle image velocimetry system and a 3 kHz planer laser-induced fluorescence system are integrated with the system to diagnose the flow field and the flame, respectively. The combustor utilizes a UNS 316 stainless steel with a minimum wall thickness of 12.5 mm. Quartz windows were designed with a maximum thickness of 25.4 mm resulting in an overall factor of safety of 3.5.