Hydrogen-rich Fuels Research Articles

Phosphorus in the burnt gas from fuel-rich hydrogenoxygen flames

Green bands, attributed to HPO by Lam Thanh My and Peyron, are emitted from the burnt gas of fuel-rich flames containing a trace of trimethyl phosphate, but not from lean flames. Their intensity is proportional to [ phosphorus]0·1±0·1 [ H] 2[ H 2O ]0·5±0·5 [ H 2 ]0·1±0·5 exp{− (5±5) κcal/RT} where [phosphorus] represents the addition of trimethyl phosphate. The dependence on [H] 2 is good to the nearest integral power. The uncertainty by the factor { [H 2O] [H 2] } 0·5 reflects the small change in this quantity in most of the experiments. An interpretation is offered which is consistent with the identification of the emitter as HPO: that the flame intensity is proportional to [H] [PO], and that the phosphorus is present mostly as P 2 molecules which are equilibrated according to: P+O-= P+ PO P+ OH= PO+ H The flame result can also be interpreted by an intensity proportional to [H] [P] with the same equilibria among P 2, PO and P. On either interpretation, the phosphorus must be considered to be mainly present as P 2 molecules.

Burning velocity and reaction rates in constant temperature non-adiabatic flames

Flames with different fuel/oxygen ratios can be burnt at constant final temperatures on cooled porous burners, the constant temperature being maintained by changing burning velocity so that more heat is abstracted from the flames of greater calorific value. It is not obvious whether the required change of burning velocity is also associated with a change in the rate of fuel consumption, and this question has been investigated. In some lean hydrogen or hydrocarbon flames, the rate of fuel consumption has been found to be almost constant in constant temperature flames despite large changes in burning velocity with mixture ratio; and for such flames, the change in burning velocity is accounted for merely by the necessary change in heat abstraction. In fuel-rich hydrogen flames, however, the increased burning velocity of progressively richer mixtures is also associated with a faster reaction rate. In the course of the work, it was noted that the maximum rate of fuel consumption did not occur at a constant fraction of the final temperature or of the temperature rise, and this casts doubt on an assumption sometimes made to deduce ‘activation energies’ of flame reactions.

Condition of Freshly Burnt Gases

PROF. DAVID refers to his experiments with Parkinson on the rate of emission of radiation from explosions. In this paper I find no mention of any drying process for the gases, or of any attempt to remove adsorbed moisture from the explosion vessel. I therefore assume that the gases were far from dry, and these experiments can scarcely be compared with those of Garner and colleagues to which I referred. They appear to me to support my statement that the concept of vibrationally activated molecules could not explain afterburning or latent energy of long duration in hydrogen-rich fuels. Also I may perhaps be permitted to quote Prof. David's own words relating to some earlier work on coal-gas–air explosions1, that the “rate of emission of radiation is a maximum about 1/40 sec. before the attainment of maximum temperature”. This effect is also very well shown in the curves of David and Parkinson to which Prof. David refers, Curve A in Fig. 2 showing a difference of about 0.03 sec. and Curve B in Fig. 3 of more than 0.05 sec., although for mixtures rich in hydrogen the effect is not observed.