Sustainable biodiesel from flex-mix feedstock and its combustion in a VCR-CRDI engine with variable exhaust gas recirculation and injection pressure

Abstract

Biodiesel produced from single feedstocks has many challenges due to variations in the oil properties. Flex-mix approach is a long-term solution for turning mixed feedstock into high-quality biodiesels. In this investigation, a premixed used cooking oil and animal fat (pig fat) mixture (from 20-80%) was transesterified to produce flex-mix methyl ester (FMME). The FMME fuel characteristics were tested and compared to biodiesel standards. Generally, biodiesel emits higher oxides of nitrogen (NOx) gas due to the presence of high unsaturation compounds and oxygen. The present study aimed to address this issue by adopting the flex-mix approach in combination with fuel injection strategies (400, 500 and 600 bar), exhaust gas recirculation (EGR-10%, 20% and 30%) and variable compression ratio (CR 17.5:1, 20:1 and 22:1). At a CR of 22 and injection pressure (Pinj) 600 bar, the FMME fuel without EGR shows a minimum reduction in brake thermal efficiency (BTE) of 0.15 % when compared to diesel. Nitric oxide (NO) gas emissions decreased by nearly 50% for all Pinj and EGR, but they rose when the CR was increased to 20 and 22. Smoke and hydrocarbon (HC) emissions also increased with exhaust gas proportion. The engine performance with FMME fuel was found to be equivalent to fossil diesel fuel. According to the findings, the flex-mix approach could be a long-term alternative to producing renewable fuel for off-road diesel engines application.

Biodiesel Blends for Eco-Friendly CRDI-VCR Engines: Enhancing Exhaust Emissions and Engine Performance to Minimize Pollutant Emissions

“…The smoke opacity percentage for stationary and CRDI diesel engines was observed to be lower, as shown in Figure 9. For stationary engine mode (Figure 9a), it was observed that smoke emission increased with increased engine load due to augmented fuel quantity per stroke (Sharma et al 2022a) but decreased at higher loads due to better combustion effiency. Smoke emissions for KOME blends were found to be 2-5% higher than diesel fuel at low engine loads (0-5 Nm) due to low Tcyl and then decreased about 3-7% at higher loads (10-25 Nm) as compared to diesel fuel due to increased Tcyl, which improved fuel combustion.…”

“…Utilization of biodiesel is a way to diminish reliance on fossil fuel and the downside environmental impacts of fossil fuel combustion, while at the same time improving rural employment (Kumar and Paul 2023;Tutak et al 2023). The Indian government encouraged the role that developing biofuel, particularly from non-edible oil feedstocks on marginal or degraded soils, might play in establishing a thriving new rural sector (Sharma et al 2022a;2022b). Wang et al (2013), investigated fuel preparation from Waste cooking oil (WCO).…”

“…In stationary diesel engine mode (Figure 9a), the formation of CO emissions increased at low load (0-5 Nm) and decreased at medium load (10-15 Nm), then increased at higher load (20-25 Nm), as shown in Figure 9a. Higher CO at low and higher loads is due to incomplete combustion (Sharma et al 2022a;Nagaraja et al 2015). CO is higher at low loads due to insufficient temperature for CO oxidation to CO2, whereas CO increases at high loads due to the difficulty of oxygen (rich fuel mixture) for CO oxidation to CO2.…”

“…Biodiesel exhibited lower hydrocarbon (HC) emissions than diesel due to higher oxygen molecules and cetane numbers, which complete the combustion process and reduce HC emissions (Sharma et al 2022a;Jindal et al 2010). Figure 9(a) shows the formation of HC emissions produced by stationary diesel engines.…”

“…Transportation plays a vital part in any economy. Many developed countries, are focussing on vehicle electrification to convert all Internal combustion (IC) engine vehicles into electric vehicles (Sharma et al 2022a).…”