High-output diesel engine heat transfer: Part 1 - comparison between piston heat flux and global energy balance

Abstract

High-output diesel engine heat transfer measurements are presented in this paper, which is the first of a two-part series of papers. Local piston heat transfer, based on fast-response piston surface temperature data, is compared to global engine heat transfer based on thermodynamic data. A single-cylinder research engine was operated at multiple conditions, including very high-output cases – 30 bar IMEPg and 250 bar in-cylinder pressure. A wireless telemetry system was used to acquire fast-response piston surface temperature data, from which heat flux was calculated. An interpolation and averaging procedure was developed and a method to recover the steady-state portion of the heat flux based on the in-cylinder thermodynamic state was applied. The local measurements were spatially integrated to find total heat transfer, which was found to agree well with the global thermodynamic measurements. A delayed onset of the rise of spatially averaged heat flux was observed for later start of injection timings. The dataset is internally consistent, for example, the local measurements match the global values, which makes it well suited for heat transfer correlation development; this development is pursued in the second part of this paper.

High-output diesel engine heat transfer: Part 2 – instantaneous spatially averaged heat transfer correlation

“…Figure 1 shows 〈 Nu 〉 as a function of Re for engine operating conditions 1, 2, 3, and 5 from Gingrich et al 1 Operating condition 4 and the intake manifold temperature (IMT) sweep for condition 3 were not used in the heat transfer correlation development due to excessive thermocouple failures. These two additional data sets were later used for correlation validation, with the knowledge that the uncertainty in the data was higher.…”

“…The calculation of the instantaneous Nusselt and Reynolds numbers from the experimental data in part 1 of this paper is explained next. Spatially averaged heat flux, _ q 00 h i, were calculated for a range of operating conditions in part 1 of this paper, 1 and used to estimate an instantaneous, spatially averaged heat transfer coefficient:…”

“…Spatially averaged heat flux, 〈 q · ″ 〉 , were calculated for a range of operating conditions in part 1 of this paper, 1 and used to estimate an instantaneous, spatially averaged heat transfer coefficient:…”

“…which was calculated for θ in the range the constants were optimized (−40 to 100° ATDC) and is also averaged across the 19 unique SOI/operating condition combinations (see Gingrich et al 1 ).…”

“…In this paper (part two in a series) a new instantaneous spatially averaged heat transfer correlation is developed using the local heat flux data presented in part one. 1 A significant amount of literature exists on the topic of engine heat transfer. Detailed reviews of engine heat transfer up until the late 1980’s were given by Borman and Nishiwaki 2 and Heywood.…”