Combustion Analysis of a Diesel Engine during Warm up at Different Coolant and Lubricating Oil Temperatures

Abstract

A comprehensive analysis of combustion behaviour during cold, intermediately cold, warm and hot start stages of a diesel engine are presented. Experiments were conducted at 1500 rpm and 2000 rpm, and the discretisation of engine warm up into stages was facilitated by designing a custom drive cycle. Advanced injection timing, observed during the cold start period, led to longer ignition delay, shorter combustion duration, higher peak pressure and a higher peak apparent heat release rate (AHRR). The peak pressure was ~30% and 20% and the AHRR was ~2 to 5% and ±1% higher at 1500 rpm and 2000 rpm, respectively, during cold start, compared to the intermediate cold start. A retarded injection strategy during the intermediate cold start phase led to shorter ignition delay, longer combustion duration, lower peak pressure and lower peak AHRR. At 2000 rpm, an exceptional combustion behaviour led to a ~27% reduction in the AHRR at 25% load. Longer ignition delays and shorter combustion durations at 25% load were observed during the intermediately cold, warm and hot start segments. The mass fraction burned (MFB) was calculated using a single zone combustion model to analyse combustion parameters such as crank angle (CA) at 50% MFB, AHRR@CA50 and CA duration for 10–90% MFB.

Exergy and energy analysis during cold-start and warm-up engine operation

“…Regulations (EU Directive 2012/46/EU) define cold-start as the first five minutes from the engine start (after the engine has reached thermal equilibrium with the ambient environment) or until the coolant reaches 70 ℃. Within cold-start operation, the engine working condition is not optimal due to the sub-optimal temperature standard of the lubricating oil and engine block, which affect engine performance in addition to the exhaust emissions [9][10][11][12]. Roberts et al [5] reported that an engine cold-start operation consumes more fuel when compared to a warm engine.…”

“…A cause of inefficiency during cold operation has been attributed to incomplete combustion during the cold-start period due to low fuel and engine temperatures which can lead to higher friction and improper atomisation and evaporation of the fuel [13]. Compared to the hot-start, higher exhaust emissions, fuel consumption, and friction losses, in addition to lower engine power, mechanical efficiency and thermal efficiency during the cold-start period, have been reported in the literature [6,11,14].…”

Analysis of cold-start NO2 and NOx emissions, and the NO2/NOx ratio in a diesel engine powered with different diesel-biodiesel blends

“…These factors lead to higher friction losses, therefore more fuel is needed to maintain the output power. It has been frequently reported that cold-operation leads to higher fuel consumption [31,32] and lower engine power [33,34]. Subsequently, cold-operation leads to higher exhaust emission [35,36].…”

Models of Ignition Delay of Diesel Fuel Surrogates

“…Tests using a commercial 6-cylinder Cummins, Euro III, and turbocharged diesel engine coupled to a dynamometer to evaluate combustion behavior during the cold start, intermediate, and hot operating temperature stages, found that the advanced injection point during the cold start period resulted in a longer ignition delay, shorter combustion duration, maximum combustion chamber pressure, and peak apparent heat release rate of higher combustion than intermediate and hot operating temperature condition (12).…”