Abstract: In measuring the mass flow rate of the inlet air entering an internal combustion engine or other combustion device, or of the exhaust gas discharged therefrom, a constant metered flow of helium or other inert tracer gas is introduced through a temperature-controlled critical flow orifice into the air intake of the engine or device, and the exhaust gas is continuously sampled and the sample analyzed by means of a mass spectrometer. From the measurement of the concentration of the tracer gas in the exhaust gas sample provided by the mass spectrometer, the required mass flow rate is derived and displayed. The mass spectrometer may be employed to measure in sequence the concentrations of other constituents of the exhaust gas sample as well as that of the tracer gas, and from these measurements other parameters related to the mass flow rate of intake air may be derived by means of a microprocessor, and displayed.

Abstract: An internal combustion engine of reciprocating-piston type with injection of liquid or gaseous hydrocarbon fuel, provided with catalytic means for initiating the combustion of the air/fuel charge in the combustion chamber of the or each cylinder. The major part of the combustion chamber of each cylinder is afforded by a recess formed in the piston crown, and a catalytic element of mesh, grid, perforated or sintered or other construction, is carried by the piston in a position at least partly overlying the said recess, the fuel being injected into the said recess to contact and pass through the catalytic element, being ignited by its contact with the catalytic element.