Laminar burning velocity and Markstein length of ammonia/hydrogen/air premixed flames at elevated pressures

Abstract

HydrogenEffects of pressure Laminar burning velocity Markstein length a b s t r a c t Ammonia shows promise not only as a hydrogen-energy carrier but also as a carbon-free fuel. However, combustion intensity of ammonia must be improved to enable its application to practical combustors. In order to achieve this, hydrogen-added ammonia/air flames were experimentally and numerically investigated at elevated pressures up to 0.5 MPa. The hydrogen ratio, which is defined as the hydrogen concentration in the fuel mixture, was varied from 0 to 1.0. The unstretched laminar burning velocity and Markstein length of spherically propagating laminar flames were experimentally evaluated. The results showed that, unstretched laminar burning velocity increases non-linearly with an increase in the hydrogen ratio. The Markstein length varies non-monotonically with an increase in the hydrogen ratio. The unstretched laminar burning velocity, and the Markstein length decrease with an increase in the initial mixture pressure. Although the decrease in the Markstein length is larger when the initial mixture pressure increases from 0.1 to 0.3 MPa, the values of Markstein lengths at 0.5 MPa are almost the same as those at 0.3 MPa.

An updated short chemical‐kinetic nitrogen mechanism for carbon‐free combustion applications

“…36,37 The results for normal atmospheric pressure, shown in Figure 4A, are seen to agree well with predictions of both the original mechanism (dashed curves) and the new mechanism (solid curves), practically all the way from pure ammonia fuel to pure hydrogen fuel under these conditions, although overpredictions for stoichiometric conditions may be seen for pure hydrogen. 36,37 The results for normal atmospheric pressure, shown in Figure 4A, are seen to agree well with predictions of both the original mechanism (dashed curves) and the new mechanism (solid curves), practically all the way from pure ammonia fuel to pure hydrogen fuel under these conditions, although overpredictions for stoichiometric conditions may be seen for pure hydrogen.…”

“…Equivalence-ratio dependence of laminar burning velocities of A, 40% NH 3 /60% H 2 , B, 50% NH 3 /50% H 2 , and C, 61.5% NH 3 /38.5% H 2 in air at a pressure of 1 atm, for mixtures initially at room temperature 5 FIGURE 4 Laminar burning velocities of NH 3 /H 2 /air mixtures in closed chambers initially at room temperature (298 K). 36,37 A, Initial pressure is 0.1 MPa. Open symbols are for an equivalence ratio of 0.6, and black symbols are for =1 (stoichiometric conditions); burner-stabilized measurements 38 are seen to agree.…”

“…Open symbols are for an equivalence ratio of 0.6, and black symbols are for =1 (stoichiometric conditions); burner-stabilized measurements 38 are seen to agree. B, For stiochiometric mixtures, 37 open symbols are for 0.1 MPa, and black symbols are for 0.5 MPa predictions and measurements with increasing hydrogen content, suggesting that the observed disagreements may be associated with the ammonia chemistry. The new mechanism is seen to afford noticeably improved agreement with experiment for stiochiometric and fuel-rich conditions.…”

Study on flame stability in oxygen-enriched ammonia/N₂/O₂ laminar diffusion flame

“…近年，欧米をはじめとする諸外国を中心にアンモニアを代替燃料とするための研究が行われている (Zamfirescu and Dincer, 2008, Takizawa et al, 2008, Ronny, 1988, Kumar and Meyer, 2013, Duynslaegher et al, 2009, Duynslaegher et al, 2010, Pfahl et al, 2000, Li et al, 2014, Hayakawa et al, 2015a, Hayakawa et al, 2015b, Ichikawa et al, 2015, 武石他, 2015, 武石他, 2016, 小林, 早川, 2016, 小池他, 2016, 武石他, 2017 (水谷, 矢野, 1978, Chung and Lee, 1991, Takahashi and Schmoll, 1990, 小谷他, 2004, Otakeyama et al, 2009 …”

Study on flame stability and flame height in oxygen-enriched ammonia/N₂/O₂ laminar diffusion flame

“…する諸外国を中心にアンモニアを代替燃料とするための研究が行われている , Duynslaegher et al, 2009, Duynslaegher et al, 2010, Hayakawa et al, 2015a, Hayakawa et al, 2015b, Ichikawa et al, 2015, 武石他, 2015, 武石他, 2016a, 小林, 早 川, 2016, 小池他, 2016, 武石他, 2016b …”