Analysis of the effect of syngas substitution of diesel on the Heat Release Rate and combustion behaviour of Diesel-Syngas dual fuel engine

The Heat Release Rate (HRR) model of ICEs is known to be most sensitive to the ratio of specific heats, gamma, which is known to be depended on temperature and the excess air ratio, lambda. The HRR of ICEs cannot be measured directly. As such, accurate HRR models, as well as accurate expressions of gamma and lambda are required to model the HRR behaviour of ICEs mathematically. In this work, an improved HRR model based on gamma(T, lambda) was used to investigate the effect of syngas substitution of diesel at constant energy on the Heat Release Rate (HRR) behaviour and the combustion phasing in a 5.7 kW engine out and 4.3 kW generator output, single cylinder, dual fuel, Reactivity Controlled Compression Ignition (RCCI) mode CI engine. An improved global excess air ratio, lambda(g) was used in the HRR analysis of the dual fuel engine. The engine was run on 10, 25, and 45% syngas substitution (by energy) and at 1, 2, 3, and 4 kW loads (generator output) for each syngas substitution. The improved dual fuel engine HRR model was validated by comparing the measured fuel consumption by energy (input energy) per (thermody-namic) cycle to the predicted fuel consumption by energy per cycle for the tested conditions. The values of the fuel consumption predicted by the Leeds HRR model were also compared to the predictions of the HRR models that were based on gamma(T). The overall average error in the predictions of the fuel input energy by the Leeds HRR model was 2.41% with a standard deviation of 1.65. The overall average errors in the other models ranged from 6.26 to 8.29%. The SoC, MFB50, PP, and PHRR occurred later for the diesel-syngas dual fuels compared to baseline diesel due to increased ignition delay as the fraction of syngas was increased. The current work showed that the use of diesel-syngas dual fuel in diesel engines in Nigeria (a developing country) can potentially reduce CO2 emissions by up to -0.26 million tonnes.