10. Combustion and Reacting Flows

High-pressure turbulent/laminar burning velocities (ST/SL) of ammonia/hydrogen/air mixtures are important to all zero-carbon-emission internal combustion engines for achieving a future net-zero-carbon society. This work measures high-pressure SL and ST for centrally-ignited, outwardly-propagating premixed NH3/H2/air flames in a large dual-chamber, constant-pressure, fan-stirred cruciform burner capable of generating near-isotropic turbulence. At first, values of SL at p=1,3,5 atm are measured at three equivalence ratios (=0.8,1.0,1.2), each  with various blending hydrogen volume percentages (=0-50%). As expected, SL increases with increasing . At =45% and =1, SL~p-0.40 where SL0.34 m/s at 1 atm, closely matching SL0.37 m/s of the stoichiometric CH4/air flame. For simplicity, NH3/H2/air mixtures (=0.8,1.0,1.2) at =45% are selected to investigate the effects of pressure (p=1,3,5 atm) and r.m.s. turbulence fluctuation velocity (u=0-2.8 m/s) on ST. All values of ST are measured within a range of effective flame radii R=25-45 mm at a mean progress variable c ̅0.5. Six general correlations, proposed by (1) Kobayashi et al. (1998), (2) Bradley et al. (2005), (3) Chaudhuri et al. (2012), (4) Shy et al. (2019), (5) Wang et al. (2020), and (6) Lhuillier et al. (2021), are used to fit present NH3/H2/air ST/SL results together with our previous ST/SL data of CH4/air flames at =0.8 and 0.9 and at T298 and 423 K. It is found that these very scattering data of various mixtures under different conditions can be all merged into single curves by using the aforesaid six general correlations. Specifically, (1) ST,c̅=0.5/SL = 2.72[(u/SL)(p/p0)Le-1]0.41, (2) ST,c̅=0.5/u = 0.71(KLe)-0.3, (3) ST,c̅=0.5/SL = 0.31 (ReT,flameLe-1)0.5, (4) ST,c̅=0.5/u = 0.30(Da Le-1)0.5, (5) ST,c̅=0.5/SL-1 = 0.21(ReT,flameLe-2)0.54, and (6) (ST,c̅=0.5/SL)Da-1=0.11(KaLe-1)0.95 with coefficients of determination R2  0.90 in the (1), (3), (5), and (6), indicating very good self-similarity fittings, where Le, K, ReT,flame, Da, and Ka are Lewis number, Karlovitz factor, turbulent flame Reynolds number, turbulent Damköhler number, and Karlovitz number, respectively.