In situmeasurement of hydrocarbon fuel concentration near a spark plug in an engine cylinder using the 3.392  m infrared laser absorption method: application to an actual engine

Abstract

An infrared absorption method with a 3.392 µm He–Ne laser was used to determine the hydrocarbon fuel concentration near the spark plug in a spark-ignition engine. Iso-octane was used for the fuel. The pressure and temperature dependence of the molar absorption coefficient was clarified. The molar absorption coefficients of a multi-component fuel such as gasoline were estimated by using the coefficient of each component and considering the mass balance. A sensor was developed and installed in a spark plug, which was substituted in place of an ordinary spark plug in a spark-ignition engine. Light can pass from the sensor through the engine cylinder to measure the fuel concentration. The effects of liquid droplets inside the engine cylinder, mechanical vibrations and other gases such as H2O and CO2 on the measurement accuracy were considered. Four main conclusions were drawn from this study. First, the pressure and temperature effects on the molar absorption coefficient of liquid fuel vapour were determined independently in advance using a constant-volume vessel. The pressure and temperature dependence of the molar absorption coefficient was determined under engine firing conditions. Second, the molar absorption coefficients of a multi-component hydrocarbon fuel such as gasoline were estimated by considering the molar fraction of each component. Third, in situ measurements of the hydrocarbon fuel concentration in an actual engine were obtained using the spark plug sensor and the molar absorption coefficient of iso-octane. The concentration near the spark plug just before ignition was almost in agreement with the mean value that was obtained from the measurement of the flow rate made with a burette, which represented the mean value averaged over many cycles. And fourth, no liquid droplets were observed at near-idling conditions. The effects of other gases, such as CO, CO2 and H2O, can be neglected.

High‐Temperature Study of 2‐Methyl Furan and 2‐Methyl Tetrahydrofuran Combustion

“…In the measurement of the absorbance, common mode rejection is used to minimize uncertainty related to laser stability and noise. The cross sections, as observed in previous work on a number of hydrocarbons , can decrease as the shock pressures and temperature increase. In previous studies, it was observed that the cross sections of cyclohexane, naphthene, and aromatic hydrocarbons decreased with increasing temperature and pressure.…”

Infrared laser-absorption sensing for combustion gases

“…Several researchers have developed single-ended probes for studying IC-engines via IR-LAS [248,249,42,250,241,242]. Hall and Koenig [248] were the first to implement IR fibers into a spark-plug probe (similar to that shown in Figure 19) for delivering and receiving IR light.…”

“…A similar configuration and diagnostic technique was more recently used by Cundy et al [250]. Tomita et al [249] used a similar probe design, but used two sapphire rods cleaved at 45 • to direct light in and out of the engine and used a HeNe near 3.39 μm to monitor fuel absorption. More recently, Rieker et al [42] integrated a fiber-coupled WMS-2f /1f -based TD-LAS sensor into a spark plug and demonstrated crankangle resolved measurements of temperature and H 2 O concentration in motored and fired tests.…”

“…As discussed in Section 6.4, several researchers have developed LAS sensors integrated into spark plugs [248,249,42,250,241]. Since these sensors have already been discussed, this section will focus on non-intrusive line-of-sight sensors for measurements of gas properties in IC-engine systems.…”

A study of mixture formation processes in direct injection stratified charge gasoline engines by quantitative laser-induced fluorescence imaging and the infrared absorption method

“…These two wavelengths were selected so as not to the IR absorbing sensor. interfere with absorption bands of carbon dioxide and water based on the HITRAN database [25]. The light of 1.30 mm wavelength is used to sense the existence of fuel droplets and contamination of the sapphire rod surfaces.…”