This nearly simultaneous appearance of LTHR is consistent with previous formaldehyde PLIF and chemical-kinetic modeling studies [49, 50].
This is expected to be a function of higher local fuel concentration (due to less mixing with the ambient gas than upstream regions ), and higher local temperatures due to greater local LTHR for the higher fuel concentration.
To further analyze and compare changes in measured IR intensity during the LTHR for these three CR SSE timings near the late-injection limit of CA50 control authority, the spatially averaged IR intensities within the bowl region for the four images at each acquisition time are shown in Figure 12.
With respect to the AHRR curves in Figure 10, the LTHR during the exposure duration rises from roughly half of its peak AHRR to nearly the peak AHRR value.
The temperature rise due to LTHR is complete, however, and the higher temperature should yield greater thermal emission, as long as the concentration of C-H emission sources is not excessively depleted by the LTHR reactions.
Single-Zone Engine and C-H Emission Model Results - LTHR
3-micron emission during and after LTHR, the single-zone engine simulation and associated C-H infrared emission model (Eqn.
Instead, the utility of this model is in identifying the relative changes in hydrocarbon content relative to the reaction progress during LTHR.
As can be seen, PRR in bar/deg decreases monotonically with increased speed; however, PRR in MPa/ms decreases at low speeds as the effect of LTHR disappears (see previous paragraph), but it increases over the rest of the speed sweep, albeit with an indication of fattening for speeds [greater than or equal to] 2100 rpm.
in] = 100 kPa, straight fuel shows significant LTHR and ITHR, as evident in Fig.
The weaker LTHR and ITHR at higher speeds is expected to reduce combustion stability, and therefore, allow less CA50 retard for controlling the RI to be [less than or equal to] 5 MW/[m.
The LTHR and ITHR are found to decrease with increased engine speed at both low and boosted [P.