Satisfactory Combustion Research Articles

New Method for the Combustion of Samples for Radiocarbon Dating

COMBUSTION to carbon dioxide is part of the preparation of most samples for radiocarbon dating. The procedures so far adopted by dating laboratories for this process have followed the example set by Libby1, and are based on the classical technique of organic combustion analysis in which the sample is burned in a stream of oxygen in a tube furnace. Variations are chiefly in the design of the furnace and in methods of subsequent purification of the carbon dioxide. Satisfactory combustion is usually critically dependent on the rate of gas flow, and the process is time consuming, for it requires constant attention on the part of the operator over a period of 1–2 h for an average sample. Moreover, there are often difficulties in dealing with certain types of sample, particularly bone and antler where the presence of significant quantities of oxides of nitrogen and sulphur in the combustion products lead to problems in the subsequent purification of the carbon dioxide, especially when it is required for filling a proportional counter.

Analyses of High‐Speed Crankshaft Loads

In the design of an articulated connecting‐rod system for a radial engine, certain conflicting desiderata have to be fulfilled, which of necessity dictate recourse to compromise. Considerations of strength, weight, a small overall diameter, component interchangeability and satisfactory combustion in all cylinders, often mean irregular disposition of the wrist‐pin centres on the master rod and variations in the stroke of different cylinders; consequent on which small differences occur in compression ratio, leading to dissimilar combustion conditions between the cylinders.

Pulverised Fuel for Marine Boilers

ALTHOUGH use of pulverised fuel has made great progress in steam boilers on land, similar results have not been achieved in marine boilers for various reasons. One of these is the great size of the combustion chamber hitherto found necessary. The rate of combustion is determined by the rate at which air and fuel come into contact. With lump fuel this can be accelerated mechanically, but with powdered fuel actually moving with the air stream, it is difficult to secure relative motion between the two and probably diffusion is the limiting factor. Turbulence may promote mixing, but not necessarily accelerate diffusion. At the Fuel Research Station an attempt has been made to secure rapidity of combustion by the design of a ‘grid’ burner so constructed that the primary air and the fuel are fed in a number of thin layers with secondary air sandwiched in between them. The burner air is cooled by tertiary air introduced at the periphery. With this burner and the coal of volatile matter content down to 21 per cent, satisfactory and flexible combustion was attained with a compact flame. The satisfactory nature of the combustion is indicated by the low proportion of carbon—7 per cent—found in the ash leaving the furnace. The results of tests of this burner form the subject of Fuel Research Technical Paper No. 36, “Pulverised Fuel—the ‘Grid’ Burner” (H.M.S.O. 6d. net).

Dynamic Forces in Aircraft Engines

Having–honoured me with an invitation to deliver a lecture this Session, the Society intimated that the most acceptable subject would be “Heavy–Oil Engines for Aircrat.” Unfortunately difficulties intervened which prevented the Society's choice from being adopted, and the outcome has been the hurried preparation of this lecture upon a subject which may seem remote from that mentioned.As regards the broad title, this remoteness is more apparent than real, however, since the difficulties to be surmounted in evolving heavy–oil engines for aircraft relate quite as much to the mechanics of engine design as to problems of fuel injection and combustion. That this is so may be gathered from the paper Mr. Pye read before the British Association last summer, and from Mr. Chorlton's comments in the December issue of the Society's Journal. In Mr. Pye's paper, information is given which shows that much progress has been macfe in this country (and notably at the Royal Aircraft Establishment) in the direction of obtaining satisfactory combustion at high engine speeds with airless fuel injection.