Analysis of Low and High Temperature Heat Release in Dual-Fuel RCCI Engine and its Relationship with Particle Emissions

This study presents the influence of low-temperature heat release (LTHR) and high-temperature heat release (HTHR) on the combustion and particle number characteristics of the RCCI engine. The study investigates the relationship between the amount of LTHR, HTHR, and particle number emission characteristics. In this study, gasoline and methanol are used as low reactivity fuel (LRF), and diesel is used as a high reactivity fuel (HRF). The LRF is injected into the intake manifold using a port-fuel injection (PFI) strategy, and HRF is directly injected into the cylinder using a direct injection strategy. A particle sizer is used to measure particle emission in size ranging from 5 to 1000 nm. Firstly, the LTHR and HTHR are analyzed for different diesel injection timing (SOI) for RCCI operation. Later, the variation of particle emissions with LTHR and HTHR is characterized. Additionally, empirical correlations are developed to understand the relation between the LTHR and HTHR with particle emission. Two-staged auto-ignition of charge has been observed in RCCI combustion. Results depict that LTHR varies with diesel injection timing and the phasing of HTHR depends on the amount and location of LTHR. Results also showed that HTHR and LTHR significantly influence the formation of particle number concentration in RCCI combustion. The developed empirical correlation depicts a good correlation between diesel SOI and the ratio of HTHR to LTHR to estimate total particle number concentration.

Tight oil reservoir production characteristics developed by CO2 huff ‘n’ puff under well pattern conditions

Tight oil reservoirs have poor physical properties, and the problems including rapid oil rate decline and low oil recovery degree are quite common after volume fracturing. To obtain a general understanding of tight oil reservoir production improvement by CO2 huff ‘n’ puff, the high-pressure physical properties of typical tight oil samples are measured. Combining the typical reservoir parameters, the production characteristics of the tight oil reservoir developed by the CO2 huff ‘n’ puff are numerically studied on the basis of highly fitted experimental results. The results show that: (1) during the natural depletion stage, the oil production rate decreases rapidly and the oil recovery degree is low because of the decrease in oil displacement energy and the increase in fluid seepage resistance. (2) CO2 huff ‘n’ puff can improve the development effect of tight oil reservoirs by supplementing reservoir energy and improving oil mobility, but the development effect gradually worsens with increasing cycle number. (3) The earlier the CO2 injection timing is, the better the development effect of the tight reservoir is, but the less sufficient natural energy utilization is. When carrying out CO2 stimulation, full use should be made of the natural energy, and the appropriate injection timing should be determined by comprehensively considering the formation-saturation pressure difference and oil production rate. The research results are helpful for strengthening the understanding of the production characteristics of tight oil reservoirs developed by CO2 huff ‘n’ puff.

Experimental investigation of particle number reduction in turbocharged GDI engines

Introduction (problem statement and relevance). Now it is difficult to imagine the automotive industry without constant improvement of the power plant. This is due to the constant tightening of environmental standards, so in environmental standards Euro 6 there is a limit of the countable concentration of particulate matters. To meet the Euro 6 environmental standard, vehicle manufacturers use catalytic converters, and gasoline particle filters (GPF). These methods of reducing the emissions of the exhaust gas are quite common, but they also have a limitation on the service life. The use of only catalytic converters and GPF may not be sufficient to meet the Euro 7 standards in the future. So, there is a need to reduce emissions with exhaust gases by improving the combustion process.The purpose of work is to investigate the combustion process of a turbocharged gasoline direct injection engine to reduce particulate matter by increasing the injection pressure and optimizing the injection timing. Methodology and research methods. The studies are of an experimental nature, the reliability of the data is confirmed by the use of modern measuring equipment and post processing of the measured data. Scientific novelty and results. The fuel injection parameters, which have a significant influence on the particulate matter formation and oxidation are defined.Practical significance. The recommendations to reduce particulate matter formation and to meet the requirements of the future Euro standards are given.

PM and NOX emissions amelioration from the combustion of diesel/ethanol-methanol blends applying exhaust gas recirculation (EGR)

The fuel injection timings, equivalence ratio (Ø) and exhaust gas recirculation are considered the most important parameters can effect on combustion process and lower exhaust emissions concentrations. The influence of 15% EGR technology and operating parameters (Ø and injection timing) on NOX emissions and particulate matter (PM) using oxygenated fuel (ethanol and methanol) blends were investigated in this experimental study. The results showed that the NOX emissions concentrations with increasing the equivalence ratio (Ø) and applied EGR for all fuels studied. Besides, the E10 and M10 decreased the PM concentrations compared to the diesel fuel under various equivalence ratios (Ø). The applied EGR increased the PM concentrations, but when combination of oxygenated fuels and EGR leading to the decrease in the PM formation. The NOX emissions concentrations decreased from the combined effect of EGR and oxygenated fuels by 16.8%, 22.91% and 29.5% from the combustion of diesel, M10 and E10, respectively, under various injection timings. It is indicated that NOX emissions decreased with retarded injection timings, while the PM decreased under advanced injection timings.

A Study the Effect of Biodiesel Blends and the Injection Timing on Performance and Emissions of Common Rail Diesel Engines

This paper presents a study on the effect of the ratio of biodiesel and injection timing on the performance of diesel engines and their emissions. The research engine is a cylinder engine AVL-5402, simulated by software AVL-Boost. The simulated fuel includes fossil diesel and biodiesel blended with a replacement rate from 0% to 50%, with a simulation mode of 2200 (rev/min), at a rate of a 25%, 50% and 75% load. In this speed range, the engine has the lowest fuel consumption. The parameters to be evaluated are power, fuel consumption and emissions, based on the proportions of blended biodiesel. The results show that there is a relationship between the proportion of blended biodiesel, injection timing and the parameters of the engine. Specifically, the ratio of the biodiesel blend increases, injection timing tends to move closer to the top dead center (TDC), the tendency reduce engine power, fuel consumption increases, the emissions of CO and soot reduces, while NOx increases.

Numerical investigation on the impact of multiple injection strategies and spray included angles on combustion and emissions in a marine diesel engine

The computational fluid dynamical software AVL-FIRE code was used for investigating the impact of multiply injection strategies and spray included angles on combustion and emissions in a marine diesel engine. The fuel injection parameters of spray included angle and pilot injection timing with pilot-main injection, as well as post injection ratio and post injection duration angle with pilot-main-post injection, were all investigated and optimized. The results indicate that retarding pilot injection timing with pilot-main injection declines high temperature region, resulting in a notable reduction in NOx emissions. Since fuel evaporation and burn are hampered by long spray penetration due to low temperature and pressure with pilot injection, a suitable spray included angle are used to offer more efficient air-fuel mixing process. A wider spray included angle simultaneously reduces soot emission and indicated specific fuel consumption (ISFC). Post injection fuel exerts impact on combustion process by causing a great disturbance to flow field during post combustion. Increasing post injection ratio from 4% to 10% at a small post injection duration angle great emission performance is achieved by simultaneous reduction in NOx and soot emissions while only using a slight consumption of ISFC. To summarize, the defeat of traditional NOx-soot trade-off occurs as both NOx and soot emissions are decreased with optimized multiple injection strategy and spray included angle. Particularly, there are respectively four cases with pilot-main injection and two cases with pilot-main-post injection, that achieve simultaneous reduction in NOx emissions, soot emission, and ISFC, compared to the prototype.