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Development of a model that allows performance and combustion characteristics for a supercharged diesel engine was the main objective sought by the present work. Thus, the developed model is used, to examine the impact of start combustion, combustion duration, compression ratio, and heat flux, as well as intake conditions such as pressure and temperature, on the combustion characteristics of the supercharged diesel. For this purpose, a one zone thermodynamic prediction model was adopted with Wiebe function for combustion sub-model. The heat transfer was correlated using Woschni correlation. A numerical simulation is developed considering the crankshaft angle as the independent variable. Validation of the computational code has been favorably evaluated using our experimental data. To give a more general aspect to the developed model, experimental data found in the literature, are also used for this purpose. The results show that the addition of a turbocharger increases low-speed airflow and hence fuel consumption. In addition, an increase in intake pressure contributes to the rise of the heat flux released during combustion, while an increase in intake temperature leads to a strong increase in combustion temperature. Moreover, an increase in the compression ratio leads in a remarkable increase in all parameters simultaneously. However, maximum combustion pressure limits must not be exceeded. This is because the pressure has an effect with the engine mechanical strength. [ABSTRACT FROM AUTHOR]

The major challenge in Homogeneous Charge Compression Ignition (HCCI) combustion is the difficulty to control auto-ignition timing. It has been shown that HCCI combustion is governed by chemical kinetics; therefore it is highly dependent on fuel/air mixture properties. Auto-ignition timing or Start of Combustion (SOC) is usually characterized by the crank angle where 5% of fuel is consumed. Understanding the effect of charge properties on SOC is essential to establish a model with the capability of predicting the auto-ignition timing. Despite the extensive work done on control-oriented modeling of HCCI ignition timing, there is still a need to improved real-time models with easily-measured inputs considering engine working conditions. The purpose of this paper is to introduce a real-time model for predicting HCCI auto-ignition timing. Thus a new correlation similar to Mean Value Method (MVM) equations has been introduced. This correlation named as Simple Algebraic Model (SAM) is based in the effects of inlet parameters on SOC. SAM has been employed to reduce runtime in control-oriented models such as Modified Knock Integral Model (MKIM). Results show the acceptable accuracy in prediction of SOC for control applications and noticeable increase in calculation speed in contrast with MKIM. [ABSTRACT FROM AUTHOR]

In this paper, a detailed multi-dimensional simulation based on fuel chemical reactions has been presented to investigate the effects of the most important parameters on performance and emission of a reactivity controlled compression ignition (RCCI) engine. The different characteristics of combustion phasing such as start of combustion, combustion duration, and 10%–90% of mass fraction burned (MFB) for iso-octane/n-heptane fuels have been studied. The effects of each important parameter such as amount of fuel delivered by varying fuels ratio, engine load and speed, injection timing, equivalence ratio, exhaust gas recirculation (EGR) application, boost pressure, injection pressure as well as combination of these different parameters and improved fuel octane number at higher compression ratios were evaluated to discover the most effective parameter on performance and emission of an RCCI engine. Distribution and coefficient of variation (COV) of equivalence ratio were examined in base cases to evaluate the influence of high reactivity fuel on distribution points. In addition, to acquiring a comprehensive perception, the results highlighted that by concurrently applying different parameters with diverse effects, new corridors to significantly abate nitrogen oxides (NO x ) pollutant can be achievable depending on the specific situations. Generally, the parameters that prolong the combustion duration demonstrated positive effects on combustion process leading to cleaner combustion with lower engine-out NO x . [ABSTRACT FROM AUTHOR]

• 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]

Optical visualization technique such as engine endoscopy is a very important tool for time resolved spatial combustion visualization and characterization. It provides valuable information about combustion in a production grade engine, which cannot be obtained by using any conventional techniques. In this study, engine endoscopy was done in a single-cylinder; constant speed compression ignition (CI) engine fuelled with diesel and biodiesel blends. A dedicated control circuit was developed to synchronize the camera with in-cylinder combustion events. Combustion images were captured at different engine loads to determine start of combustion (SoC), spatial soot distribution and spatial flame radiation temperatures. With increasing biodiesel content in the fuel, larger area of luminous flames in the combustion images was obtained for lower biodiesel blends (up to B20) however it became smaller for higher biodiesel blends (for B50 and higher). It was also found that the area of soot distribution decreased in later stages of combustion for all test fuels which indicates better oxidation of soot particles. Combustion images showed earlier SoC for biodiesel blends with increasing engine load, which was another important finding of these experiments. Rate of heat release (RoHR) was lower for biodiesel blends compared to mineral diesel. Higher blends of biodiesel showed lower flame radiation temperatures due to soot particles emission that caused lower soot particles volume fraction and higher oxygen content in fuel hence more NOx emission from biodiesel combustion. [ABSTRACT FROM AUTHOR]

Abstract: The start of combustion (SOC) in the combustion chamber has a considerable influence upon all performances of the engine. In this paper, cylinder pressure was investigated as a means for the closed-loop SOC control of a common-rail direct injection (CRDI) diesel engine. In order to detect the SOC, the crank angle position where the difference pressure became 10bar was selected as the pressure variable. Using this pressure variable as a feedback variable, an adaptive feedforward control was proposed. The feedforward controller consisted of the radial basis function network (RBFN) and the feedback error learning method, which was used for the training of the network. The proposed SOC control strategy showed a far better regulation performance than that of the linear feedback controller. A further extension of the strategy based on the individual cylinder pressure feedback, the individual cylinder SOC control strategy, effectively reduced cylinder-by-cylinder SOC variation in steady and transient engine operations. [Copyright &y& Elsevier]

A great deal of attention is being paid to the common-rail direct injection (CRDI) diesel engine as a promising technology for enhancing engine performance and satisfying stringent emission regulations. In a conventional CRDI diesel engine, the start of combustion (SOC) is controlled in an open-loop manner by adjusting the start of energizing (SOE) of an injector. The open-loop SOC control cannot compensate for unexpected variations in the injection delay and ignition delay resulting from cycle-by-cycle variation, cylinder-to-cylinder variation, production variation, and ageing. In this study, cylinder pressure was investigated as a means for controlling the SOC of a CRDI diesel engine. Various pressure variables were compared for the purpose of detecting the SOC of a CRDI diesel engine. The crank angle position at which the difference pressure becomes 10 bar (CADP10) was selected as the pressure variable for the detection of the SOC. The control performance was evaluated with engine-dynamometer experiments in steady and transient operating conditions. The experimental results showed that difference pressure managing can be effectively used for real-time detection of the SOC. Furthermore, the SOC detection technique enables the fuel control strategy to be transformed from an open-loop scheme to a closed-loop scheme. [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]

Reactivity controlled compression ignition (RCCI) strategy uses two different fuels with independent reactivates which impacts combustion characteristics such as gross work, start of combustion (SOC) and burn duration as well as engines emissions. Effects of hydrogen addition have been numerically investigated on a RCCI natural-gas/di-methyl ether engine. For this purpose, six different percentages of H 2 (i.e.0,10,20,30,40 and 50%) has been evaluated. In all case studies total-heating values was kept constant. Numerical results showed increase in total gross work with the increase of hydrogen and up-to 19.7% boost by adding 50% of hydrogen. In the direction of adding hydrogen there are ascend in cumulative heat release which is about 15.9% with 50% of hydrogen. According to DME decomposition process, more than 10% of it was decomposed to its products, specially CH 4 before SOC which affects fuel mixture Cetane number and in-cylinder heat release. Results showed advancement in combustion start about 5 CAD in 50% H 2 , it is about 7.8 CAD for CA50. Burn duration of using 50% H 2 decreased about 6 CAD, approximately. Released CO and UHC descended 5.5 and 9.7 gr/kWh, respectively in 30% H 2. Temperature and pressure also increased during hydrogen addition with 16.3 and 25.6% in 50% of hydrogen. • Six different percentages of hydrogen as additive were studied numerically. • Hydrogen addition causes higher engine performance according to IMEP. • In acceptable NOx emission UHC and CO descended 10 and 59 gr/kWh, respectively. • According to DME breaking up speed about 10% of it was broken up before SOC. • SOI is important in the engines with DME as fuel due to DME decomposing process. [ABSTRACT FROM AUTHOR]