It is generally recognized that the dilution of crankcase-oil with water and unburned fuel tends to accelerate the wear of engine bearings, cylinders and pistons. The author traces the engineering development of a rectifying device and system designed to combat this problem. In this system, diluted oil that tends to work-up past the pistons, in company with the water vapor and unburned fuel that tend to work down into the crankcase, is drawn from the cylinder-walls and pistons by vacuum. This diluted oil is conducted into a still or rectifier where it is subjected to heat from the engine exhaust. The heating action is just sufficient to volatilize the fuel and water, the resulting vapor being returned to the intake-manifold and thence to the engine where it is burned. The lubricating oil that remains behind is conducted back into the crankcase. The system functions automatically. A float-actuated mechanism controls the flow of the diluted oil through the rectifier, and a thermostatically-controlled valve regulates the degree of heat to which the liquid is subjected.
Troubles encountered in the early stages of development of this device and the means employed to overcome them are described. Temperatures prevailing throughout the system when it is in operation are given. Data relating to the volume of oil handled by the device in ordinary service are presented.
Comparative tests to determine engine wear with and without the device are described. In one of these, dust was intentionally introduced into the intake-manifold to determine whether it was detrimental to engine life when dilution was and was not present. Based on these and other test results, the author expresses the opinion that an ordinary amount of dust is not harmful if the oil is maintained at somewhere near its initial viscosity by a rectifying device. Relative wear data are presented in curve form.
Crankcase-oil dilution is one of the main obstacles to be overcome before fuels of low volatility can be burned satisfactorily in automotive engines of the present day. The author states his belief that the use of a rectifying system to drive off the diluents from the lubricating oil and prevent their reaching the crankcase will assist in conserving the supply of petroleum fuels.