- The smoke-generation model has been activated for case 492 of the PHOENICS library, which represents a (rather simple) three-dimensional gas-turbine-like combustor, which is fed by a rich-fuel-air vapour mixture, and by primary-, secondary- and dilution-air streams.
- The graphical convergence monitor for the 40-fluid run
shown here
gives proof of a satisfactorily converging calculation;

and computer times are seen to be small.### The results

The table shows how the number of fluids influences the predicted rate of smoke production and the computer time.

number smoke seconds 1 0.74 100 10 2.38 139 20 2.28 217 30 2.31 267 40 2.26 485 50 2.27 599 Note that:

- On this occasion MFM predicts more smoke production than the conventional single-fluid model; and
- the 10-fluid model provides a good approximation.

The following figures show the computed PDFs for a location in the middle of the outlet plane of the combustor, for 10 fluids, 40 fluids, 50 fluids.

The shapes are all similar; and the root-mean-square and population-average values do not differ much.

The following contour plots show various aspects of the 50-fluid calculation:

- The
**very different**smoke distributions on an axial plane according to:

(a) the single-fluid (no fluctuations) model and

(b) the multi-fluid modelThe flow is from right to left.

- The somewhat different distributions of population-average temperature
according to:

(a) the single-fluid model

and

(b) the multi-fluid modelThe highest temperature encountered is (understandably) greater for the single-fluid than for the multi-fluid model.

- The concentrations of fluids: fluid 1, (pure air) fluid 6, (fuel-lean) , and fluid 11 (approximately stoichiometric).

- Obviously, a large amount of valuable insight into combustor behaviour
can be derived from such studies.
- The author commends them to the attention of designers.