A jet-stirred chamber for turbulent combustion experiments

A new type of jet-stirred chamber (JSC) incorporating multiple impinging turbulent jets is proposed as an apparatus for the study of turbulent premixed flames. ANSYS-FLUENT computations using a RANS - Reynolds Stress Model were used to simulate the flows inside the JSC and identify an optimal configuration of inlet jets and outlet ports providing the most nearly ideal flow, i.e. homogeneous and isotropic with large turbulence intensity compared to the mean velocity. A configuration of 8 jets, each surrounded by a concentric annular outlet, at the corners of an imaginary cube circumscribed by a spherical chamber, produced by far the most nearly optimal flow characteristics. The performance of this configuration, called Concentric Inlet And Outlet (CIAO), was compared quantitatively to two popular fan-stirred chamber (FSC) designs and the CIAO JSC was found to provide far more nearly ideal flow properties. The robustness of the CIAO design was demonstrated by intentionally misaligning the jets or mismatching their flow velocities. A comparison of simulated turbulent flames in CIAO and an FSC showed that CIAO enabled far more nearly spherical expanding flames with nearly the same inferred turbulent burning velocity (ST) regardless of the flame radius rf and the value of the mean progress variable (c¯) used to define the flame location, whereas in the FSC the flame was not nearly as spherical and there was considerable variation of ST depending on rf and c¯.