Measurement of Fuel Concentration in the Vicinity of the Combustion Chamber Surface by Infrared Laser Absorption Method

Abstract

The concentration of unburned fuel in the quenching layer on the single surface of a combustion chamber is measured by the infrared laser absorption method. The combustion chamber is divided into two compartments by a partition that has two holes covered with fine-meshed stainless gauze. After a propane-air mixture is ignited by a spark plug, a flame develops and quenches at the quenching block on the partition in the upper compartment. The mixture in the lower compartment remains unburned, but both compartments are at the same pressure. Two laser beams are introduced into the chamber; one is used to measure the fuel concentration near the quenching block (quenching wall) in the upper compartment and the other is used to measure the mixture concentration in the lower compartment. The fuel concentration near the surface of the quenching wall is obtained by analyzing the intensities of the two laser beams. A quenching layer is observed immediately after the flame reaches the quenching wall that is so thin that the thickness of the preheat zone of the flame overlaps each other and the fuel concentration in the quenching layer is very low. A little fuel then diffuses into the burned gas, but almost all the fuel stays near the quenching plate surface. The quantity of fuel remaining in the quenching layer at the time of flame extinction was lowest with an equivalence ratio of about 1.2, which is inconsistent with the characteristics exhibited by the quenching layer thickness.

Keywords

• unburned hydrocarbon
• quenching layer
• spark ignition engine
• infrared laser
• absorption method