Measuring a flow of gas through a combustion engine

Claim 1

A method of measuring the flow rate of gas at a given point in a combustion engine, which comprises introducing a constant metered flow of an inert gas, referred to as a tracer gas, into the inlet gas entering the intake of the combustion engine during the operation of the engine, simultaneously withdrawing a continuous sample flow of the exhaust gas from the engine exhaust system and supplying a constant-rate flow of the sample gas to a mass spectrometer for analysis, and operating the mass spectrometer to provide a measurement of the volumetric proportion of the tracer gas in the exhaust gas sample, and utilizing the said measurement to derive an indication of the transient value of the said flow rate of gas in the engine, oxidizing all residual CO and unburned hydrocarbons by reacting the exhaust gas sample catalytically with oxygen, prior to its supply to the mass spectrometer, and in which the mass spectrometer is adjusted to measure also the concentration of at least one more other component of the exhaust gas sample and to compare each such measurement with the measurement of that of the tracer gas, and in which the measurements provided by the mass spectrometer are utilized to derive an indication of one or more other parameters related to the transient mass flow rate of the exhaust gas leaving the engine, and, wherein, the mass spectrometer is of the quadrupole type, having an electrostatic ion separator comprising four parallel electrode rods, and including the step of adjusting the voltages applied to the four electrode rods in sequence to cause the spectrometer to provide a corresponding sequence of measurements of the concentrations of different constituents of the gas sample, and in which the resultant measurements are fed to a microprocessor programmed to give output readings in terms of the said other parameters, and, further, including the steps of selecting the said other parameters from the group comprising the inlet gas mass flow rate, the fuel mass flow rate, the sum of the inlet gas and fuel mass flow rates, and the ratio of the inlet gas mass flow rate to the fuel mass flow rate, and in which the mass spectrometer measures sequentially the concentrations of CO 2 , N 2 and O 2 as well as that of the tracer gas in the exhaust gas sample.

Claim 2

A method of measuring the flow rate of gas at a given point in a combustion engine, which comprises introducing a constant metered flow of an inert gas, referred to as a tracer gas, into the inlet gas entering the intake of the combustion engine during the operation of the engine, simultaneously withdrawing a continuous sample flow of the exhaust gas from the engine exhaust system and supplying a constant-rate flow of the sample gas to a mass spectrometer for analysis, and operating the mass spectrometer to provide a measurement of the volumetric proportion of the tracer gas in the exhaust gas sample, and utilizing the said measurement to derive an indication of the transient value of the said flow rate of gas in the engine, oxidizing all residual CO and unburned hydrocarbons by reacting the exhaust gas sample catalytically with oxygen, prior to its supply to the mass spectrometer, and in which the mass spectrometer is adjusted to measure also the concentration of at least one more other component of the exhaust gas sample and to compare each such measurement with the measurement of that of the tracer gas, and in which the measurements provided by the mass spectrometer are utilized to derive an indication of one or more other parameters related to the transient mass flow rate of the exhaust gas leaving the engine, and, wherein, the mass spectrometer is of the quadrupole type, having an electrostatic ion separator comprising four parallel electrode rods, and including the step of adjusting the voltages applied to the four electrode rods in sequence to cause the spectrometer to provide a corresponding sequence of measurements of the concentrations of different constituents of the gas sample, and in which the resultant measurements are fed to a microprocessor programmed to give output readings in terms of the said other parameters, and, further, including the steps of selecting the said other parameters from the group comprising the inlet gas mass flow rate, the fuel mass flow rate, the sum of the inlet gas and fuel mass flow rates, and the ratio of the inlet gas mass flow rate to the fuel mass flow rate, and in which the mass spectrometer measures sequentially the concentrations of CO 2 , N 2 and O 2 as well as that of the tracer gas in the exhaust gas sample.