Investigation of Biodiesel–Diesel Fuel Blends on Combustion Characteristics in a Light-Duty Diesel Engine Using OpenFOAM

Abstract

This paper reports the differences in combustion characteristics of fossil diesel and the methyl esters of coconut (CME), palm (PME), and soy (SME) over a range of engine conditions. The studies are conducted at a constant engine speed of 2000 rpm, and at engine load values of 0.5 kW (low), 1.5 kW (medium), and 2.5 kW (high). The investigated fuels are CME, PME, and SME at 0% diesel mixture (B100), 50% diesel mixture (B50), and fossil diesel (B0). Here, the OpenFOAM open-source computational fluid dynamics code is utilized to simulate the in-cylinder events. An in-house model for thermophysical and transport properties is employed, along with a mechanism comprising 113 species and 399 reactions with integrated NO x kinetics. Good levels of accuracy are achieved in the prediction of the ignition delay (ID) period, peak pressures, pressure traces, and heat-release rate profiles for all the test fuels. Biodiesel fuels are found to produce larger fuel droplet sizes, longer spray penetration, and lower vaporization rates compared to those of fossil diesel. In terms of the combustion behavior, the ID period decreases as the engine load is increased for neat CME, PME, and SME. However, the ID period increases as the load is raised for the B50 mixtures of CME, PME, and SME. All neat biodiesels and their blends except neat SME produce shorter ID periods than fossil diesel. Changing the fuel type from diesel to biodiesel alter the physical and chemical delay and, hence, the overall ID period. As a result, variations in the combustion behavior between the fuels are recorded.

Graphite Oxide Nanoparticle as a Diesel Fuel Additive for Cleaner Emissions and Lower Fuel Consumption

“…Similar works conducted by other researchers have also adopted the D 2 law based on these assumptions. ,, The burn-rate constant, k , was calculated using D 2 = D o 2 – kt , where D is the droplet diameter, D o is the initial droplet diameter, and t is the duration taken between D o and D . The higher magnitude of the burn-rate constant is attributed to the higher combustion rate between air and fuel vapor within diffusion-controlled combustion, as illustrated in Figure .…”

“…ID indicates how fast a fuel droplet is ignited upon heating. Generally, shorter ID corresponds to higher cetane number in the diesel fuel and lower NO x due to lower flame temperature. − In this study, ID of a droplet is defined as the time interval between the start of heating and the start of ignition. In order to precisely determine the start of droplet ignition, a classical thermal definition of ignition conditions was adopted .…”

“…On the basis of the findings (shortened ID for the dosed fuels) from the single droplet experiment, we can deduce that a lower amount of fuel is burned in the premixed combustion, thus resulting in lower flame temperature. Consequently, the NO x formation is reduced in diesel engines. − …”

Experimental Investigation on the Effect of Ignition Enhancers in the Blends of Sapota Biodiesel/Diesel Blends on a CRDi Engine

“…Whereas the net combustion period shortened the premixed heat release proportion and the highest cylinder pressure increased. Harun Mohamed Ismail et al stated that, related to diesel fuel, biodiesel burns at a lower rate under the mixing-controlled combustion (MCC) or peak premixed combustion (PMC) phase. But the MCC and PMC phases are similar in the periods of combustion, compared to diesel, and the burn speed is high for biodiesel.…”

Improving combustion characteristics of diesel and biodiesel droplets by graphite oxide addition for diesel engine applications

“…Second, the linear burning was identified as a quasilinear decrement of a droplet observed on the A / A o curve. During this burning stage, all the droplets undergo diffusion‐controlled combustion wherein the burn rate is controlled by the rate of mixing between fuel vapor and air . The linear burn rate of the droplet was calculated using the D 2 law, given by where, k is the burn‐rate constant, D is the droplet diameter, D o is the initial droplet diameter, and t is the duration between D o and D . Other studies have also used the D 2 law equation to calculate the droplet burn rate from their droplet‐combustion experiment …”