•Oxygen ratio was used instead of the equivalence ratio.•Oxygen ratio decreases with engine load, but increases with engine speed.•IMEP, BMEP, friction power, CO2, HC, PM and PN decreased with ...oxygenated fuels.•BSFC, BTE and NOx increased with oxygenated fuels.•Accumulation mode count median diameter decreased with oxygenated fuels.
This study investigates the effect of oxygenated fuels on engine performance and exhaust emission under a custom cycle using a fully instrumented 6-cylinder turbocharged diesel engine with a common rail injection system. A range of oxygenated fuels based on waste cooking biodiesel with triacetin as an oxygenated additive were studied. The oxygen ratio was used instead of the equivalence ratio, or air to fuel ratio, to better explain the phenomena observed during combustion. It was found that the increased oxygen ratio was associated with an increase in the friction mean effective pressure, brake specific fuel consumption, CO, HC and PN. On the other hand, mechanical efficiency, brake thermal efficiency, CO2, NOx and PM decreased with oxygen ratio. Increasing the oxygen content of the fuel was associated with a decrease in indicated power, brake power, indicated mean effective pressure, brake mean effective pressure, friction power, blow-by, CO2, CO (at higher loads), HC, PM and PN. On the other hand, the brake specific fuel consumption, brake thermal efficiency and NOx increased by using the oxygenated fuels. Also, by increasing the oxygen content, the accumulation mode count median diameter moved toward the smaller particle sizes. In addition to the oxygen content of fuel, the other physical and chemical properties of the fuels were used to interpret the behavior of the engine.
•First and second law thermodynamic analysis of oxygenated fuels.•Engine and emission data analysis at 12 operating point.•Improvement in thermal efficiency by oxygenated fuels.•Maximum exergetic ...efficiency for Waste cooking biodiesel (B100).
This study uses the first and second laws of thermodynamics to investigate the effect of oxygenated fuels on the quality and quantity of energy in a turbo-charged, common-rail six-cylinder diesel engine. This work was performed using a range of fuel oxygen content based on diesel, waste cooking biodiesel, and a triacetin. The experimental engine performance and emission data was collected at 12 engine operating modes. Energy and exergy parameters were calculated, and results showed that the use of oxygenated fuels can improve the thermal efficiency leading to lower exhaust energy loss. Waste cooking biodiesel (B100) exhibited the lowest exhaust loss fraction and highest thermal efficiency (up to 6% higher than diesel). Considering the exergy analysis, lower exhaust temperatures obtained with oxygenated fuels resulted in lower exhaust exergy loss (down to 80%) and higher exergetic efficiency (up to 10%). Since the investigated fuels were oxygenated, this study used the oxygen ratio (OR) instead of the equivalence ratio to provide a better understanding of the concept. The OR has increased with decreasing engine load and increasing engine speed. Increasing the OR decreased the fuel exergy, exhaust exergy and destruction efficiency. With the use of B100, there was a very high exergy destruction (up to 55%), which was seen to decrease with the addition of triacetin (down to 29%).
•A diesel vehicle was driven at various levels of aggressiveness on public roads.•Instantaneous vehicle energy was determined taking road gradient into account.•Aggregate and instantaneous energy was ...shown to correlate well with NOX emissions.•With road gradient, the correlation remained regardless of driver aggressiveness.•Potential application in developing better emissions models.
This study explores the influence of different driving styles and road gradient profiles on NOX emissions in a diesel passenger vehicle on urban driving. Driving dynamics parameters were correlated with cumulative NOX emissions measured during on-road driving on urban roads. In this work, the vehicle was driven on two different urban routes, one with mostly hilly roads and the other with predominately flat roads to assess the effect of road gradient on NOX emissions. Each route was driven six times, the first drive on each route was driven very timidly, each subsequent drive systematically became more aggressive with the sixth drive being very aggressive. From the vehicle speed and road gradient data, the instantaneous vehicle energy was estimated and correlated against the instantaneous NOX emission. In order to investigate for monotonic relationships, Spearmans rank correlation coefficient was used to investigate potential correlations between NOX emissions and driving parameters. A strong positive correlation was observed between instantaneous NOX emissions and instantaneous vehicle energy irrespective of the driving behaviour. The correlation of driving dynamics parameters with NOX emissions also showed a similar trend indicating that driving aggressiveness and vehicle NOX emissions have a strong relationship. Also there is evidence that the influence of road gradient on NOX emissions decreases with an increase in driving aggressiveness.
Using wavelet and fractal theories, cycle-to-cycle variations (CCVs) in a common-rail compression ignition (CI) engine have been investigated at engine loads of 25% and 50%, biodiesel blend level was ...from 0% to 100%. Wavelet power spectrums and singularity spectra were calculated to identify the dominant oscillatory combustion modes and multifractal complexity. Reaction paths and component consumption sensitivity of n-heptane and methyl decanoate were studied to reveal the effect of biodiesel blend level on the combustion process of diesel fuel. Results reveal that the effect of biodiesel blend level on the CCVs is more significant at a low load, even when biodiesel blend level increases to 20%, the coefficients of variation decreases from 3.99% to 1.57%. The CCVs exhibit multiscale dynamics for all tested cases, and persistent high-frequency oscillations appear around a 16-cycle period persisting over the entire or several hundred of the engine cycles. As the biodiesel blend level increases, the periodic bands with the highest power were interrupted and combined with lower-frequency and high-frequency intermittent fluctuations. However, for the higher load, the dynamics of CCVs are mainly displayed in an intermittent fashion. The larger broadness of singularity spectra at higher engine loads suggests a higher degree of multifractality. For all of the tested cases, the dynamics of the CCVs behave like antipersistent walks. As a oxygenated fuel, biofuel substitution leads to increase of c7h15-1 concentration and radicals such as OH, O and H2O2, which are beneficial to decrease ignition delay and accelerate the chemical reaction rate of diesel fuel, and therefore inhibit the CCVs.
In the transportation sector, the share of biofuels such as biodiesel is increasing and it is known that such fuels significantly affect NOx emissions. In addition to NOx emission from diesel ...engines, which is a significant challenge to vehicle manufacturers in the most recent emissions regulation (Euro 6.2), this study investigates NO2 which is a toxic emission that is currently unregulated but is a focus to be regulated in the next regulation (Euro 7). This manuscript studies how the increasing share of biofuels affects the NO2, NOx, and NO2/NOx ratio during cold-start (in which the after-treatment systems are not well-effective and mostly happens in urban areas). Using a turbocharged cummins diesel engine (with common-rail system) fueled with diesel and biofuel derived from coconut (10 and 20% blending ratio), this study divides the engine warm-up period into 7 stages and investigates official cold- and hot-operation periods in addition to some intermediate stages that are not defined as cold in the regulation and also cannot be considered as hot-operation. Engine coolant, lubricating oil and exhaust temperatures, injection timing, cylinder pressure, and rate of heat release data were used to explain the observed trends. Results showed that cold-operation NOx, NO2, and NO2/NOx ratio were 31–60%, 1.14–2.42 times, and 3–8% higher than the hot-operation, respectively. In most stages, NO2 and the NO2/NOx ratio with diesel had the lowest value and they increased with an increase of biofuel in the blend. An injection strategy change significantly shifted the in-cylinder pressure and heat release diagrams, aligned with the sudden NOx drop during the engine warm-up. The adverse effect of cold-operation on NOx emissions increased with increasing biofuel share.
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•Cold-operation NOx was 31–60% higher than hot-operation with different fuels.•Cold-operation adverse effect on NOx was more with biofuel.•Cold-operation NO2 was 1.15–2.42 times higher than hot-operation with all fuels.•Cold-operation NO2/NOx was 3–8% higher than hot-operation with different fuels.•NO2/NOX ratio was 13–17% during cold-operation and 5–13% during hot-operation.
•A comprehensive study on engine performance and emissions with n-butanol-diesel blends was conducted.•n-Butanol blends indicated insignificant changes in engine performance.•Much lower UBHC ...emissions with increase in blow-by and NOx emissions were observed with n-butanol blends.•Substantial reductions in both PM and PN emissions were observed with n-butanol blends.
This paper presents a comprehensive study of a wide range of engine performance parameters, including: indicated torque (IT), indicated power (IP), indicated mean effective pressure (IMEP) and indicated specific fuel consumption (ISFC). Further, the combustion parameters measured include: start of injection timing, in-cylinder peak pressure, boost pressure and rate of maximum pressure rise. Resultant emission parameters investigated include: exhaust blow by, unburned hydrocarbon (UBHC), oxides of nitrogen (NOx), particulate matter (PM), particle number (PN) and particle size distribution (PSD). Normal butanol (n-butanol) was chosen to blend with a reference diesel fuel. The experiment was conducted using a 6-cylinder, turbocharged common rail diesel engine in accordance with the 13-Mode European Stationary Cycle (ESC). Considering limits of solubility of n-butanol in reference diesel, a maximum of 30% n-butanol was blended with 70% reference diesel. Three different butanol blends having 10% butanol with 90% reference diesel, 20% butanol with 80% reference diesel and 30% butanol with 70% reference diesel (the blending percentages were on a volume basis) were prepared. The engine experimental results show that without considerably deteriorating engine performance, most of the emissions were significantly reduced with the butanol blends compared to those of the reference diesel.
•A four-component reduced mechanism for diesel-NG fuels was proposed.•The detailed mechanisms were reduced using DRG, DRGEP and FSSA methods.•The effects of cross reactions of diesel components were ...examined.•Reduced mechanisms were validated by literatures and experiments.
In this paper, a four-component reduced mechanism (methane, n-dodecane, methylcyclohexane and toluene) with 150 species and 847 reactions was proposed for predicting the combustion characteristics and emissions from natural gas-diesel dual fuel engines. Equivalence ratio (ϕ) from 0.5 to 2.0, pressure (P) from 30 to 90 bar, temperature (T) from 500 to 1700 K and ϕ from 0.5 to 2.0, P from 1 to 10 bar, T from 298 to 550 K were set as the reaction conditions for two reaction models respectively. The detailed mechanisms were reduced using the directed relation graphs (DRG), directed relation graphs with error propagation (DRGEP) and full species sensitivity analysis (FSSA) methods. The validation of the reduced mechanism was performed based on the ignition delay and the laminar flame speed data available in the literature. Then the effects of cross-reactions on the oxidation of diesel were further studied, associated with the reaction flux, concentration and sensitivity analysis. Finally, the reduced mechanisms were verified at a reactivity controlled compression ignition (RCCI) combustion mode at 25% and 75% loads, the maximum validation error is 3.3%. It was found that the effects of cross-reactions on ignition were more pronounced in medium and low temperatures. Ignition was also enhanced by an increase in the equivalence ratio, but was not found to be sensitive to pressure. Under lower temperatures, adding cross-reactions can better reveal the formation of diesel intermediates. However, at higher temperatures, the addition of cross-reactions did not significantly increase the reaction speeds of the intermediate products.
•Diesel was blended with 1% and 5% waste lubricating oil.•During cold start, NOx emissions were higher than hot start.•During cold start, NOx increased as the engine warmed up.•NOx emissions had a ...direct correlation with maximum rate of pressure rise.•NOx emissions had an inverse correlation with maximum in-cylinder pressure.
NOx emissions from diesel engines are a concern from both environmental and health perspectives. Recently this attention has targeted cold-start emissions highlighting that emission after-treatment systems are not effective in this period. Using a 6-cylinder, turbocharged, common-rail diesel engine, the current research investigates NOx emissions during cold-start using different engine performance parameters. In addition, it studies the influence of waste lubricating oil on NOx emissions introducing it as a fuel additive (1 and 5% by volume). To interpret the NOx formation, this study evaluates different parameters: exhaust gas temperature, engine oil temperature, engine coolant temperature, start of injection/combustion, in-cylinder pressure, heat release rate, maximum in-cylinder pressure and maximum rate of pressure rise. This study clarified how cold-start NOx increases as the engine is warming up while in general cold-start NOx is higher than hot-start. Results showed that in comparison with warmed up condition, during cold-start NOx, maximum in-cylinder pressure and maximum rate of pressure rise were higher; while start of injection, start of combustion and ignition delay were lower. During cold-start increased engine temperature was associated with decreasing maximum rate of pressure rise and peak apparent heat release rate. During cold-start NOx increased with temperature and it dropped sharply due to the delayed start of injection. This study also showed that using waste lubricating oil decreased NOx and maximum rate of pressure rise; and increased maximum in-cylinder pressure. NOx had a direct correlation with the maximum rate of pressure rise; and an inverse correlation with the maximum in-cylinder pressure.
The disposal of waste rubber and scrap tyres is a significant issue globally; disposal into stockpiles and landfill poses a serious threat to the environment, in addition to creating ecological ...problems. Fuel production from tyre waste could form part of the solution to this global issue. Therefore, this paper studies the potential of fuels derived from waste tyres as alternatives to diesel. Production methods and the influence of reactor operating parameters (such as reactor temperature and catalyst type) on oil yield are outlined. These have a major effect on the performance and emission characteristics of diesel engines when using tyre derived fuels. In general, tyre derived fuels increase the brake specific fuel consumption and decrease the brake thermal efficiency. The majority of studies indicate that NOx emissions increase with waste tyre derived fuels; however, a few studies have reported the opposite trend. A similar increasing trend has been observed for CO and CO
emissions. Although most studies reported an increase in HC emission owing to lower cetane number and higher density, some studies have reported reduced HC emissions. It has been found that the higher aromatic content in such fuels can lead to increased particulate matter emissions.
•Custom test was designed to study the engine performance during cold-start.•Oxygenated fuels had higher indicated torque during hot-start transient modes.•Oxygenated fuels had lower indicated torque ...during cold-start transient modes.•Oxygenated fuels had higher max in-cylinder pressure at hot-start transient modes.•Oxygenated fuels had lower max in-cylinder pressure at cold-start transient modes.
Using a six-cylinder turbocharged common rail compression ignition engine, this study investigated the effect of oxygenated fuels on transient and steady-state performance. This paper considers the effect of oxygenated fuels on both cold- and hot-start operation. A range of fuel oxygen contents between 0% and 13.57% was derived from diesel, waste cooking biodiesel and two other blends, containing triacetin as a fuel additive. A custom test was designed to investigate engine performance parameters using acceleration, load increase and steady-state modes of operation. For each fuel, the cold-start test was conducted after an overnight engine-off time. In this study, different parameters related to engine performance were studied, such as engine coolant and lubricant temperatures and their rise rate, boost pressure, injected fuel, turbocharger lag, engine speed and torque, start of injection, maximum in-cylinder pressure, maximum rate of pressure rise, cyclic variability, FMEP, mechanical and thermal efficiencies, and BSFC. In comparison with hot-start, the cold-start results indicated a higher injected fuel, indicated torque, maximum in-cylinder pressure, maximum rate of pressure rise, FMEP, BSFC and CoV of IMEP, and a lower SOI, ME and BTE. During cold-start, using oxygenated fuels, instead of diesel, resulted in a lower rate of lubricant temperature rise and a higher BSFC, while decreasing the FMEP. Using oxygenated fuels, instead of diesel, during the idle and transient modes resulted in lower indicated torque and maximum in-cylinder pressure under cold-start whilst, under hot-start, it resulted in higher indicated torque and maximum in-cylinder pressure, because during hot-start, the fuel oxygen is significantly influential in torque build-up during turbocharger lag. While, during cold-start there are some other influential factors. In addition, oxygenated fuels—compared to diesel—experienced higher CoV of IMEP during cold-start while, during hot-start, they had lower values.
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