The Influence of Injection pressure on Combustion and Emission Characteristics of a common-rail HSDI Diesel Engine

Abstract

The present work investigates the influence of fuel injection pressure on the combustion and emission characteristics of ultra-low diesel fuel for high speed direct injection ( HSDI) diesel engine at different fuel injection timings( -12,-9,-6,-3,0 )ATDC has been made . The fuel injection pressure were (800,1000,1200) bar and at high load ( 80Nm= 5BMAP) , low load ( 40Nm=2.5BMAP ) , With constant engine speed ( 1500rpm) . In-cylinder pressure was measured and analyzed using LABVIWE program .A calculation program specially written in MATLAB software was used to extract the apparent heat release rate, the ignition delay, combustion duration and specifies the amount of heat released during the premixed and diffusion combustion phases ( premixed burn fraction PMBF) and ( diffusion burn fraction DBF). The influence of injection pressure on the exhaust emissions such as carbon monoxide (CO), total hydrocarbons (THCs), nitric oxides (NOx), smoke number (SN) and fuel consumption were also investigated.A result referring to that when the injection pressure was increased, the ignition delay reduced. A shorter ignition delay at high injection pressure also advanced the combustion, and increased the in-cylinder pressure, heat release rate and their peaks respectively .The premixed burn fraction increased with fuel injection pressure increasing, and this caused a decrease in each of the exhaust SN, THC and CO emissions but the NOx emissions increased.