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• Combustion analysis was conducted using Di-octyl Phthalate (DOP) blended with diesel. • During ambient start, DOP blends recorded higher pressure rise rate and peak AHRR. • Ignition delay increased and combustion duration decreased as DOP percentage increased. • Combustion parameters were influenced by fuel-bound oxygen and in-cylinder temperature. • In-cylinder temperature was higher using blended fuels during ambient operation. Presented in this article is a comprehensive analysis of combustion behaviour using Di-octyl Phthalate (DOP) – an oxygenated third-generation biofuel, blended with ultra-low sulphur diesel (D100) in proportions of 10 % (DOP10D90) and 20 % (DOP20D80) (%v/v). The experiments were conducted on a heavy-duty diesel engine during ambient, preheated and hot engine operation. A cold-engine custom-designed drive cycle, with frequent engine stop/start was used. D100 was found to warm up faster by 7 % during the first 120 s of ambient operation, compared to DOP blended fuels. The maximum rate of pressure rise was 18 % and 14 % higher using DOP10D90 and DOP20D80, respectively, compared to D100. Peak apparent heat release rates (AHRR) were 11 % and 7 % higher using DOP10D90 and DOP20D80 fuels, respectively, compared to D100 during the first 120 s of ambient operation. Oxygen bound to the fuel molecule caused an increase in the maximum rate of pressure rise and an increase in the peak AHRR during ambient operation. As the DOP quantity increased in the fuel blend, the ignition delay increased, while the combustion duration decreased. Neither of these parameters was affected by engine warm-up. The shortest combustion duration was observed using DOP20D80, leading to a faster burn rate during the premixed combustion stage during ambient start, compared to DOP10D90 and D100. [ABSTRACT FROM AUTHOR]

This paper presents a method that uses the coefficient of variation (COV) of pressure in a diesel engine combustion chamber to determine the crank angle degree (CAD) for which the heat release rate (HRR) reaches the maximum value. The COV was proposed for determining the point corresponding to the angle of start of combustion (SoC). Regression models were fit with these descriptors for the engine powered by diesel, biodiesel or a combination of both, operating under full- or part- load conditions. The uncertainty parameter in these models was determined. Good agreement between the experimental results and the literature data shows the validity of the analysis. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• Effect of water addition on natural gas HCCI combustion characteristics was studied. • Water addition controls the start of combustion under different loads. • Water addition reduces the ringing intensity and expands the operation range to run on high load condition. • Coordinated intake temperature and water addition is easier to realize controlled combustion. • Internal mechanism of important species was proposed. The coordinated control of combustion boundary conditions and fuel chemistry is the core academic idea of homogenous charge compression ignition (HCCI) combustion. Realizing controlled combustion is the current development goal of HCCI engine and adding additives to the cylinder cooperate with the change of boundary conditions is an effective way to achieve it. In the paper, using a multi-zone thermodynamic model coupled with a detailed chemical reaction mechanism (including 53 species and 325 reactions) to study. First, the rationality of the multi-zone model was verified for six different operating conditions. Then seven different mass fraction of water were added to the cylinder and examined its effect on natural gas (NG) HCCI combustion. The thermal, dilution and chemical effects of water on start of combustion (SOC) were carried out using artificial inert species method. It was determined that in-cylinder pressure and heat release rate (HRR) decreases, SOC retards with the increase of water addition at different loads and boundary conditions. Under high load which is knock and abnormal combustion, water addition controls SOC and reduces ringing intensity (RI) to normalize the combustion process. The results show that the sensitivity of combustion to water addition increases and the tolerance of engine to water decreases as the intake temperature (T in) reduces and excess air ratio (λ) rises. The thermal effect of water on SOC is greater than that its dilution and thermal effect. It is easier to achieve controlled combustion by changing T in than λ in NG HCCI engine with water to mitigate knock. In addition, the effect of water on important species in chamber was proposed to prove the above conclusion from internal mechanism. [ABSTRACT FROM AUTHOR]