Method and measuring apparatus for determining physical properties of gas

A method for determining physical properties and/or quantities relevant to combustion of gas or gas mixtures, the method comprising:

• the gas or gas mixture flows under pressure through a critical nozzle and past a microthermal sensor into a gas reservoir, with the same mass flow being applied to the critical nozzle and the microthermal sensor;
• measuring a pressure increase in the gas reservoir as a function of time;
• determining a first gas property factor (Γ*), dependent on a first group of physical properties of the gas or gas mixture, by reference to the measured values of the pressure increase;
• determining a second gas property factor (Γ), dependent on a second group of physical properties of the gas or gas mixture, from the flow signal of the microthermal sensor, with the second gas property factor containing, or depends on the heat capacity (cp) of the gas or gas mixture;
• determining a thermal conductivity (λ) of the gas or gas mixture using the microthermal sensor;
• and
• determining a physical property or quantity relevant to combustion from the first and/or second gas property factor (Γ*,Γ) and the thermal conductivity (λ) through correlation.

A method to use a gas reservoir and a critical nozzle for determining physical properties and/or quantities relevant to combustion of gas or gas mixtures, the method comprises:

• flowing the gas or gas mixture under pressure from the gas reservoir through the critical nozzle;
• measuring a pressure drop in the gas reservoir as a function of time;
• determining a gas property factor (Γ*), dependent on a physical property of the gas or gas mixture, based on the measured values of the pressure drop;
• and
• determining a desired physical property or quantity relevant to combustion based on the gas property factor (Γ*) through correlation.

A method to determine a physical property and/or a quantity relevant to a combustion gas or gas mixture using a gas reservoir and a microthermal sensor, calibrated for a specific calibration gas or gas mixture, the method comprises:

• flowing the gas or gas mixture under pressure from the gas reservoir past the microthermal sensor;
• determining a flow rate (vx) of the gas or gas mixture using the microthermal sensor;
• determining a summed-up volume flow (vx·A) based on the flow rate (vx);
• comparing the summed up volume flow to a gas volume released from the gas reservoir;
• determining a gas property factor (S/v′x), dependent on the physical properties of the gas or gas mixture, based on the comparison, wherein the quantity (v′x) represents a flow rate based on the released gas volume, and wherein the gas property factor comprises, for example, the heat capacity (cp) of the gas or gas mixture or is dependent on the same;
• and
• a desired physical property or quantity relevant to combustion is determined on the basis of the gas property factor through correlation.

A method to determine a physical property of combustion comprising:

• flowing a gas from a reservoir through a critical nozzle and a microthermal sensor wherein the mass flow of the gas through the critical nozzle is the same mass flow through the microthermal sensor;
• measuring a pressure drop in the reservoir as the gas flows through the critical nozzle;
• determining a first gas property factor based on the measured pressure drop;
• determining a second gas property factor based on a flow signal generated by the microthermal sensor;
• determining a thermal conductivity of the gas using the microthermal sensor, and
• determining a physical property of the combustion based on a correlation of the thermal conductivity and at least one of the first and second gas property factors.