LUBRICATION OF THE DOXFORD DIRECT DRIVE DIESEL ENGINE

Abstract

After preliminary adjustments, the first engine was put on a 1,000 hr. non‐stop day and night run. During this first prolonged test there was heavy wear of the piston rings and cylinder liners, which circumstances became known and was given wide publicity. Apart from being worn, the piston rings were covered with a black sludge and there was considerable accumulation of this around the scavenge ports and in the entablature. This was traced to a defective spraying of fuel from the injectors, the test having been carried out on a high viscosity fuel and the cause was due to the injection pressure falling to about 4,800 lb/sq. in. at the end of injection. This first P type engine was rated at 10,000 h.p., i.e. 1,666 h.p. per cylinder, which was the highest output that had been obtained from a Doxford cylinder up to that time and therefore the quantity of fuel per injection was higher than ever before and this plug of oil taken from the accumulator bottles lowered the pressure by over 2,500 lb/sq. in., i.e. from 7,500 lb/sq. in. at the beginning of injection to about 4,800 lb/sq. in. at the end of injection. To overcome this, each set of three bottles was joined together by a relatively large diameter pipe and thus the volume of fuel available for each injection was increased threefold. With this arrangement the injection pressure fell by only 400 lb/sq. in. from the beginning to the end of injection and this completely eliminated the sludge, so that the difficulty with broken piston rings and worn liners was largely removed.