Main Injection Timing Research Articles

Experimental, numerical and exergy analyses of a dual fuel combustion engine fuelled with syngas and biodiesel/diesel blends

This work investigates the effects of addition of syngas and biodiesel on a reactivity controlled compression ignition (RCCI) engine fuelled with diesel. Scanning electron microscopy (SEM) of exhaust particulate matter has been done to obtain particulate matter (PM) morphology. Energy and exergy analyses have been performed to observe energy and availability shares, and to provide directions for the energy recovery systems. Closed cycle combustion simulations have been performed to complement the experimental results and for an improved understanding of in-cylinder dynamics. Chemical and physical properties of three biodiesel samples have been analysed using elemental analysis, Fourier transform infrared spectroscopy and gas chromatography-mass spectrometry. Based on the initial study, used cooking oil based biodiesel blend (B20, 20% biodiesel) has been chosen in experiments. The optimal operating conditions for syngas/diesel and syngas/B20 in RCCI mode for different operating parameters have been investigated. Injection pressure, injection timing and pre-injection mass ratio have been modified to get improved combustion efficiency at mid-load. Syngas/diesel mode with an injection timing of 19° before top dead centre (bTDC) shows slightly higher brake thermal efficiency (BTE) with 22% and 77% lower oxides of nitrogen (NOx) and PM respectively as compared to conventional diesel combustion. In syngas/B20 mode, a maximum BTE of 24% has been observed for the case with a pre-injection at 50° bTDC with 30% mass fraction and 18° bTDC main injection timing. Syngas/diesel shows a reduction in primary soot particle count by about 67% and contains larger aggregates as compared to neat diesel.

Experimental Investigation on the High-frequency Pressure Oscillation Characteristics of a Combustion Process in a DI Diesel Engine

It is difficult to decompose the in-cylinder pressure of combustion of the direct injection (DI) diesel engine, a transient process associated with complicated oscillation components, because of its steep property. An adaptive cyclic average method based on time varying filter based empirical mode decomposition (TVF-EMD) is proposed to decompose the in-cylinder pressure signal, and the cyclic number is determined adaptively with protruding ratio of high-frequency oscillation. The proposed method is used to compare with the ensemble empirical mode decomposition and original TVF-EMD. The results indicate that the proposed method can overcome the drawbacks of these methods and extract high-frequency oscillations accurately and effectively. Three evaluation indexes, center frequency, normalized energy, and average center frequency are defined to analyze the frequency and energy characteristics of high-frequency oscillation quantitatively. The influence of speed, load, rail pressure, main injection timing, pilot injection interval, and pilot injection quantity are investigated systematically. The energy of high-frequency oscillation reaches the peak at medium-high speed, and increase with engine load and rail pressure. However, the relationship of high-frequency oscillation with fuel injection parameters are non-monotonic.

Artificial neural network approach on forecasting diesel engine characteristics fuelled with waste frying oil biodiesel

The present work investigates the influence of advanced injection strategy on a common rail direct injection assisted diesel engine characteristics fuelled with biodiesel and conventional diesel. Also, an artificial neural network is employed to forecast engine characteristics. Engine test is conducted under 100% load condition through an optimized nozzle opening pressure of 500 bar. Pre-injection timing is fixed permanently at 30 °CA bTDC, main injection timing varied from 15 °CA to 21 °CA bTDC and post-injection varied from 6 °CA bTDC to 6 °CA aTDC sequentially. However, the pre, main and post-injection quantities are changed respectively from 5% to 15%, 70% to 90%, and 5% to 15%. Minimum carbon monoxide, unburned hydrocarbon and smoke emission of 0.01% vol., 8 ppm and 1.59 FSN are achieved with pre-injection timing of 30 °CA, main injection timing of 21 °CA bTDC, and post injection timing of 6 °CA bTDC for B100-15%-70%-15%. Maximum brake thermal efficiency and nitric oxide emission of 34.3% and 1114 ppm are achieved in B100-5%-90%-5% at advanced injection timing and higher nozzle opening pressure. Artificial neural network models conform to experimental results having a lower root mean square error and correlation coefficient values in a range of 0.01 to 0.02 and 0.980 to 0.998 respectively. An artificial neural network is mostly preferred over other theoretical and empirical models to higher accuracy in predicting the output. Hence, multiple injection strategy fuelled biodiesel significantly decreased the emission and improved the performance compared to mechanical, single and split injection strategy.

Study of using diesel/high-ON biofuel blends as the pilot fuel with large proportion and split injection in the dual-fuel combustion

Dual-fuel combustion using diesel and high-octane number (ON) biofuel of n-butanol blends to ignite compressed natural gas (CNG) with pilot fuel split injection was investigated. 30% n-butanol/70% diesel (B30D70) and pure diesel (B0D100) as the pilot fuels were compared with the start of pre-injection (SOIp) timings swept from −30 (SOIp30) to −80 °CA ATDC (SOIp80) under the CNG substitution rates of 50% at low load and 65% at medium load. A fixed start of main-injection (SOIm) timing of −9 °CA ATDC in B0D100 and various SOIm timings in B30D70 to match CA50 of B0D100 were employed. The experimental results indicated that adding n-butanol in the pilot fuel can significantly reduce the PM emission at advanced SOIp timings even with large proportion of pilot fuel. At low load, B30D70 reveals higher indicated thermal efficiency (ITE) due to its shorter combustion duration compared to B0D100, and it also leads to lower NOx emissions resulted from the more homogeneous mixture. The CO and THC emissions tend to be slightly increased in B30D70 for the advanced SOIp timings. At medium load, B30D70 also obtains higher ITE but yields higher NOx emissions. Relatively low level of NOx emissions can be obtained at early SOIp timings, such as SOIp60, SOIp70 and SOIp80. The CO and THC emissions are similar for the two pilot fuels at these timings. For the comparisons of the two pilot fuels and injection strategies, it can be demonstrated that B30D70 is more favorable to the thermal efficiency and emissions with split injection at SOIp40 under low load condition and early SOIp timings under medium load condition.

커먼레일 디젤기관에서 함산소 연료와 파일럿 분사시기의 변화가 연소 및 배기특성에 미치는 영향

In this study, the effect of various pilot injection timings on combustion and emission characteristics were investigated in a common-rail direct injection (CRDI) diesle engine fueled with diesel-ethanol blends. The engine speed and engine load were controlled at constant 1500rpm and 70Nm, respectively. The tested fuels were DE0 (pure diesel fuel), DE5 (5 vol.% ethanol blended with 95 vol.% diesel oil), DE10 (10 vol.% ethanol blended with 90 vol.% diesel oil) and DE15 (15 vol.% ethanol blended with 85 vol.% diesel oil). The main injection timing was fixed at 0°CA TDC (top dead center), while various pilot injection timings including 25°CA BTDC (before top dead center), 20°CA BTDC and 10°CA BTDC were selected as the experimental variable. The experimental results showed that various pilot injection timings had little effect on the peak value of cylinder pressure, but had great influence on the start of combustion. The peak value of heat release rate (HHR) increased with the increase of ethanol content. However, the peak value of HRR reduced as the pilot injection is delayed. The diesel fuel containing 10% ethanol had a highest peak value of combustion pressure compared with the others, while the pilot injection timing occurred at 25°CA BTDC. On the other hand, the exhaust emissions of DE10 was also the lowest compared with the others. In addition, with the increase of ethanol content in diesel the PM and NOx emissions reduced.

저속 공회전시 커먼레일 디젤기관에서 디젤-팜오일 바이오디젤-에탄올 혼합연료의 연소 및 배기특성에 관한 연구

In this study, we investigated the effects of diesel-palm oil biodiesel-ethanol blends on combustion and emission characteristics in a 4-cylinder common rail direct injection (CRDI) diesel engine at low idling operations. The engine speed and engine load was 750 rpm and 40 Nm, while the main and pilot injection timing was respectively fixed at 2 °CA before top dead center (BTDC) and 20 °CA BTDC. The experimental results showed that the cylinder pressure increased with the increasing of palm oil biodiesel ratio from 20% to 100%. In addition, the peak value of cylinder pressure increased by 4.35% compared with pure diesel fuel when 5 vol.% ethanol oil added to diesel oil. Because the palm oil biodiesel and ethanol are the oxygenated fuel, the oxygen content played an important role in improving combustion. Based on the high oxygen content of biodiesel and ethanol, their mixing with diesel fuel effectively reduced PM emissions but increased NOx slightly, while CO and HC had no significant changes.

Improving PM-NOx trade-off with paraffinic fuels: A study towards diesel engine optimization with HVO

The current work investigates the impact of a paraffinic fuel on combustion and emissions of a diesel engine, examining alternative injection strategies for the full exploitation of the fuel characteristics. The paraffinic fuel used was the HVO (Hydrotreated Vegetable Oil) produced by Neste Oil with the brand name NEXBTL. The study was conducted on a light-duty turbocharged and aftercooled common-rail diesel engine, with both HVO and a conventional diesel fuel. Four steady-state operating points were examined, at low and medium engine speeds (1500 and 3000 rpm) and loads (35 and 100 Nm), typical of daily driving of a passenger car. The key contribution of the study is a comprehensive analysis of the phenomena influencing the crank angle resolved in-cylinder parameters, as well as interlinking the effects of different variations of injection pressure (default and 300 bar higher), pilot injection timing (default and ± 5°CA) and main injection timing (default and ± 2°CA) on gaseous emissions and particulate matter (PM). The findings have shown that at default engine settings the use of HVO results in up to 40% reduction of engine-out PM and HC emissions without appreciable changes in NOx emissions. The significant reduction of engine-out PM levels, facilitates the adoption of measures for NOx emissions limitation. The latter are reduced by up to 20% when the main injection timing is retarded (by 2° CA in the present study), while PM emissions are still kept well below the respective diesel fuel levels.

Investigation on pilot injection with low temperature combustion of Calophyllum inophyllum biodiesel fuel in common rail direct injection diesel engine

The present research work emphasises on the utilization of Calophyllum inophyllum biodiesel and preparation of 20% blend sample to explore the effects of variation of multiple injection strategies and amount of exhaust gas recirculation in a common-rail direct injection engine. In this aspects, the pilot injection quantity of B20 blend has been varied from 5 to 15% for the improvement of diesel engine characteristics. Among the tested results, an optimum pilot injection quantity has been identified and the same experimental work is extended for the addition of 10% and 20% exhaust gas recirculation under same operating conditions. The experimental study revealed that the increase in pilot injection rate from 5% to 15% at same operating conditions has shown higher brake thermal efficiency of 36.8% and the same improvement has not observed during exhaust gas recirculation addition. In terms of emissions point of view, the 15% pilot injection quantity of B20 fuel has resulted lowest hydrocarbon and carbon monoxide emissions when compared to diesel fuel by about 54.4% and 45.9% respectively. However, the implementation of 10% EGR rate at 15% pilot injection quantity reduced the oxides of nitrogen emission by 10.04%. On the other hand, the combustion characteristics are enhanced during increase in pilot injection rate and it decreased to lower level at higher concentration of EGR addition. Thus, the combined effect of 15% pilot injection rate and 10% EGR rate would be a best possible option for obtaining an improved performance and emission characteristics. Further, the study can be extended to vary the pilot injection, main and post injection timings with suitable EGR addition successful running of biodiesel blend.

Effects of fuel injection parameters on premixed charge compression ignition combustion and emission characteristics in a medium-duty compression ignition diesel engine

From the different power plants, the compression ignition diesel engines are considered the best alternative to be used in the transport sector due to its high efficiency. However, the current emission standards impose drastic reductions for the main pollutants, that is, NO x and soot, emitted by this type of engines. To accomplish with these restrictions, alternative combustion concepts as the premixed charge compression ignition are being investigated nowadays. The objective of this work is to evaluate the impact of different fuel injection strategies on the combustion performance and engine-out emissions of the premixed charge compression ignition combustion regime. For that, experimental measurements were carried out in a single-cylinder medium-duty compression ignition diesel engine at low-load operation. Different engine parameters as the injection pattern timing, main injection timing and main injection fuel quantity were sweep. The best injection strategy was determined by means of a methodology based on the evaluation of a merit function. The results suggest that the best injection strategy for the low-load premixed charge compression ignition operating condition investigated implies using a high injection pressure and a triple-injection event with a delayed main injection with almost 15% of the total fuel mass injected.

Assessment on the consequences of injection strategies on combustion process and particle size distributions in Euro VI medium-duty diesel engine

Although there are already several works where the influence of injection parameters on exhaust emissions, and specifically on particulate matter emissions, in diesel engines has been evaluated, the diversity in the results that can be found in the literature indicates the need to carry out new experiments that can provide more information about the influence of these parameters on modern diesel engines. This study intends to be placed within this scientific framework, hence a parametric study was carried out based on the independent modification of the main injection timing and the injection pressure with respect to the nominal conditions of a new Euro VI direct injection diesel engine. Four steady-state operation points of the engine map were chosen: 25% load and 950 r/min, 50% load and 1500 r/min, 75% load and 2000 r/min and 100% load and 2200 r/min, where in each of these operation points, the variations of the injection parameters in the study on the combustion process and its consequent impact on the particle size distribution, including an analysis of the geometric mean diameter values, were evaluated. The results showed that the different injection strategies adopted, despite not significantly affecting the engine efficiency, did cause a significant impact on particle number emissions. At the low load operation, the size distribution showed a bimodal structure, and as the main injection timing was delayed and the injection pressure was decreased, the nucleation-mode particle concentration decreased, while the accumulation-mode particle concentration increased. In addition, at medium load, the nucleation-mode particle emission decreased considerably while the accumulation-mode particle emission increased, and this increase was much greater with the main injection timing delay and the injection pressure reduction. Similar behavior was observed at high load, but with a much more prominent pattern.

Impact of injection settings on gaseous emissions and particle size distribution in the dual-mode dual-fuel concept

Reactivity controlled compression ignition concept has been highlighted among the low temperature combustion strategies. However, this combustion strategy presents some problems related to high levels of hydrocarbon and carbon monoxide emissions at low load and high-pressure rise rate at high load. Therefore, to diminish these limitations, the dual-mode dual-fuel concept has been presented as an excellent alternative. This concept uses two fuels of different reactivity and switches from a dual-fuel fully premixed strategy (based on the reactivity controlled compression ignition concept) during low load to a diffusive nature during high load operation. However, the success of dual-mode dual-fuel concept depends to a large extent on the low reactivity/high reactivity fuel ratio and the injection settings. In this study, parametric variations of injection pressure and injection timing were experimentally performed to analyze the effect over each combustion process that encompasses the dual-mode dual-fuel concept and its consequent impact on gaseous and particles emissions, including an analysis of particle size distribution. The experimental results confirm how the use of an adequate injection strategy is indispensable to obtain low exhaust emission and a balance between the different pollutants. In the fully premixed reactivity controlled compression ignition strategy, the particles concentrations were dominated by nucleation mode; however, the increase in injection pressure and the advance of the diesel main injection timing provided a simultaneous reduction of nitrogen oxide and solid particles (accumulation mode). During the highly premixed reactivity controlled compression ignition strategy, the accumulation-mode particles increased, and their concentrations were higher when the diesel main injection timing advanced and injection pressure decreased, as well as there was a slight increase in nitrogen oxide emissions. Finally, in the dual-fuel diffusion strategy, the concentrations of accumulation-mode particles were higher and there was a considerable increase of these particles with the advance of the diesel main injection timing and the reduction of the injection pressure, while the nitrogen oxide emissions decreased.

Investigation of intake pressure and fuel injection timing effect on performance characteristics of diesel engine

The low fuel consumption and efficient power usage in diesel engine has made diesel engine as the more appealing option in comparison with other type of engines. To raise the performance of DI (direct injection) diesel engine further, injection timing and intake pressure variation were studied under 2000 RPM (rotation per minute) engine rotation. This experiment used DI diesel engine with single cylinder. The length of stroke was set to 96.9 mm, the diameter of bore was set to 85 mm and the compression ratio of the engine was 16.3. The variations of main injection timing were set for 1° after TDC (top dead centre) as advanced injection timing, and 3° after TDC as retarded injection timing. Boost pressures for intake pressure were varied with 20 in increments and started from 0 KPa to 60 KPa. In-cylinder pressure characteristics and heat release rate were used to evaluate the engine performance. The experiment indicated, as the boost pressure raises, the heat release rate and in-cylinder pressure are increased. The main injection timing advancement from 3° after TDC to 1° after TDC causes increase to the peak of in-cylinder pressure after TDC in DI diesel engine. This phenomenon is due to the slower combustion in retarded injection timing. For heat release rate, the advancement of injection timing causes the differences between various intake pressures to be more apparent.

Effect of pilot quantity on combustion and emission characteristics of a single-cylinder diesel engine under fixed dwell condition: experimental and numerical study

Dwell and distribution of fuel quantity between two injection pulses are the most important parameters under pilot injection mode used in diesel engines. Most of the earlier studies have studied the effects of pilot fuel quantity (herein referred as pilot quantity) on diesel engine combustion at fixed pilot and main injection timings. Hence, results obtained represent the combined effects of dwell and pilot quantity. Aim of the present study is to investigate the sole effect of pilot quantity on combustion and emission characteristics of a diesel engine at a fixed dwell using experimental and simulation tools. Pilot injection timing was adjusted in order to maintain a constant dwell between pilot and main injection with varying pilot quantity, while main injection timing was maintained constant during the study. Numerical investigations were also performed using Converge 3-D computational fluid dynamics tool. When pilot quantity was increased from 15 to 45%, smoke emissions were reduced by 25%, while nitric oxide (NO) emission and fuel consumption were increased by 20.8% and 2.52%, respectively. Greater amount of fuel participating in pre-mixed combustion proportion in case of larger pilot quantity led to overall lesser smoke emissions compared to smaller pilot quantity case. Numerical results confirmed that prime source of soot emissions in case of pilot injection mode is the main injected fuel. Higher NO emission in case of larger pilot quantity is mainly attributed to the presence of greater and wider high-temperature region (HTR) compared to smaller pilot quantity case. Increased fuel consumption with increasing pilot quantity is mainly due to deteriorated space utilization.

Real-Time Simulation of Torque and Nitrogen Oxide Emissions in an 11.0 L Heavy-Duty Diesel Engine for Model-Based Combustion Control

A real-time combustion model was assessed and applied to simulate BMEP (Brake Mean Effective Pressure) and NOx (Nitrogen Oxide) emissions in an 11.0 L FPT Cursor 11 diesel engine for heavy-duty applications. The activity was carried out in the frame of the IMPERIUM H2020 EU Project. The developed model was used as a starting base to derive a model-based combustion controller, which is able to control indicated mean effective pressure and NOx emissions by acting on the injected fuel quantity and main injection timing. The combustion model was tested and assessed at steady-state conditions and in transient operation over several load ramps. The average root mean square error of the model is of the order of 110 ppm for the NOx simulation and of 0.3 bar for the BMEP simulation Moreover, a statistical robustness analysis was performed on the basis of the expected input parameter deviations, and a calibration sensitivity analysis was carried out, which showed that the accuracy is almost unaffected when reducing the calibration dataset by about 80%. The model was also tested on a rapid prototyping device and it was verified that it features real-time capability, since the computational time is of the order of 300–400 µs. Finally, the basic functionality of the model-based combustion controller was tested offline at steady-state conditions.

Simulation Study on Influence of Fuel Injection Strategy on Regeneration Performance of Catalytic Particle Filter

The influence rule of fuel injection strategy on regeneration performance of catalytic particle filter (CPF) will be studied in this paper, through using system dynamics, GT-POWER and AVL FIRE to build and match respectively the onedimensional complete machine model of D19 high pressure common rail diesel engine of variable geometry turbocharger (VGT) and the three-dimensional simulation model of CPF, which are based upon the 50% load working condition with 3000r/min. The study shows that with the delay of main injection timing, the regeneration rate of CPF gradually increase, simultaneously, residual volume of particulate matter (PM), pressure drop and NO2 of CPF at exit end decrease. At the earlier main injection timing, with increasing exhaust gas recirculation (EGR) rate, regeneration rate of CPF is decreasing and residual volume of PM is increasing dramatically. At the later main injection timing, with increasing EGR rate, PM residual volume shows trend of rise then descend. Adoption of post injection benefits for regeneration of CPF, with delay of post injection timing, pressure drop and PM residual volume of CPF both show trend of rise then descend, the post injection timing corresponding with the best efficiency of CPF regeneration will be forward lead with increasing of EGR rate. Appropriately enhancing amount of post injection will benefit for regeneration of CPF. And, the negative effect of CPF regeneration will be increased when using post injection and later timing to rise EGR rate.

Impact of split injection strategy on combustion, performance and emissions characteristics of biodiesel fuelled common rail direct injection assisted diesel engine

In this work, the effect of single and split injection strategy on combustion, performance and emissions characteristics of biodiesel was experimentally investigated on a common rail direct injection assisted diesel engine. In single injection strategy, Nozzle opening pressure and fuel injection timing was varied from 200 to 600 bar and 19°–27° CA bTDC respectively. Experimental results revealed that B100 had the maximum brake thermal efficiency of 35.74% at 500 bar and 25° CA bTDC. Engine exhaust emissions of unburned hydrocarbon and smoke were decreased, whereas nitric oxide emission increased in B100 fuel at higher nozzle opening pressure and advanced fuel injection timing. In split injection strategy, start of main injection timing and post injection timing was varied from 19° to 25° CA bTDC and −5° CA bTDC to 5° CA aTDC respectively. The results exhibited that the B100-90%-10% has the maximum brake thermal efficiency of 34.43%. Minimum unburned hydrocarbon and smoke emissions were obtained in B100-75%-25%. Maximum nitric oxide emission was obtained in B100-90%-10%. Thus, the experimental studies clearly states that advanced injection strategy reduces the exhaust emissions and improves the engine performance.

Parametric study of pilot–main injection strategies on the performance of a light-duty diesel engine fueled with diesel or a WCO biodiesel–diesel blend

Multiple injection strategies in diesel engines are known to reduce pollutant emissions directly in the combustion chamber, while biodiesel made from waste cooking oil (WCO) has been studied mainly using single injection. In the current study, they were combined to evaluate biodiesel’s potential based on a parametric study of the injection strategy. The main findings are that pilot injection increased the sensitivity of early main-injection timing by decreasing the main-injection ignition delay. Furthermore, for some injection strategies, the pressure wave in the injector’s feed pipe also impacted the resulting pollutant emissions. Thus, the optimum double-injection strategy, allowing decreased PM and NOx emissions, was obtained with a slightly retarded main-injection timing in comparison to the optimum single-injection strategy. Waste-cooking-oil biodiesel blended with diesel (20% to 80% proportion) has, however, shown higher PM emissions and lower NOx emissions compared to diesel when a single-injection or an optimal double-injection strategy is used.

Evaluation of a Hydrotreated Vegetable Oil (HVO) and Effects on Emissions of a Passenger Car Diesel Engine

In the coming years, the application of paraffinic biofuels, such as Hydrotreated Vegetable Oils (HVO), in the transportation sector is expected to increase. However, as the composition of HVO is different compared to conventional diesel, the engine optimized for conventional fuel cannot take full advantage of the HVO beneficial properties. Suitable adjustment of a number of engine parameters, if not complete engine re-calibration, will enable the full exploitation of such fuels’ potential for lower exhaust emissions and reduced fuel consumption. In the present work, the emission characteristics of HVO fuel in a light-duty Euro 5 diesel engine have been studied, under steady-state operation, as well as during the New European Driving Cycle (NEDC). The study was expanded to the investigation of exhaust emissions under modified Main Injection Timing (MIT) and EGR rate. The NEXBTL fuel, produced by Neste, was considered in the study and was compared with conventional market diesel. Emissions of nitric oxides (NOx), soot, carbon monoxide (CO), carbon dioxide (CO2) and hydrocarbons (HC) were studied. At default MIT and EGR settings the use of HVO resulted in a significant reduction of all regulated emissions. In addition, it was observed that the adjustment of MIT and EGR can enhance the exploitation of HVO potential for emissions reduction, highlighting the differences with the conventional diesel fuel.

Computational optimization of fuel supply, syngas composition, and intake conditions for a syngas/diesel RCCI engine

By utilizing the promising alternative fuel of syngas, and the syngas/diesel dual-fuel reactivity controlled compression ignition (RCCI) is a potential combustion strategy for internal combustion engines. However, the optimal operating parameters for syngas/diesel RCCI engines under wide operating conditions have not been investigated. In this study, the operating parameters include fuel supply, syngas composition, and intake conditions of a syngas/diesel RCCI engine were optimized under wide load by integrating the KIVA-3V code and the non-dominated sort genetic algorithm II (NSGA-II). The results indicated that nitrogen oxides (NOx) emissions can be controlled in considerably low levels, and the efficient combustion of the premixed syngas in the squish region can be realized with high premix ratio and early pilot injection of diesel. Equivalent indicated specific fuel consumption (EISFC) and ringing intensity (RI) are the major issues for the optimization at low and mid load, respectively. The double diesel injection strategy with the relatively late main injection timing is an effective way to both improve combustion efficiency at the low load and reduce RI at the mid load. For the double diesel injection, the ratio of pilot injection is controlled in a narrow range to provide sufficient high reactivity fuel in the piston bowl and to avoid the local high-temperature combustion region simultaneously. With the restrictions of EISFC and RI, the optimal H2 fraction in the syngas is 60–80%. Based on the optimal fuel supply and intake conditions, a syngas with 75% H2 and the diluent factor C of 0.8 is capable of realizing the high efficiency, moderate combustion, and low emissions for the RCCI engine at full load range.

Evaluation of Fuel Injection Strategies for Biodiesel-Fueled CRDI Engine Development and Particulate Studies

Fuel injection parameters such as fuel injection pressure (FIP) and start of main injection (SoMI) timings significantly affect the performance and emission characteristics of a common rail direct injection (CRDI) diesel engine. In this study, a state-of-the-art single cylinder research engine was used to investigate the effects of fuel injection parameters on combustion, performance, emission characteristics, and particulates and their morphology. The experiments were carried out at three FIPs (400, 700, and 1000 bar) and four SoMI timings (4 deg, 6 deg, 8 deg, and 10 deg bTDC) for biodiesel blends [B20 (20% v/v biodiesel and 80% v/v diesel) and B40 (40% v/v biodiesel and 60% v/v diesel)] compared to baseline mineral diesel. The experiments were performed at a constant engine speed (1500 rpm), without pilot injection and exhaust gas recirculation (EGR). The experimental results showed that FIP and SoMI timings affected the in-cylinder pressure and the heat release rate (HRR), significantly. At higher FIPs, the biodiesel blends resulted in slightly higher rate of pressure rise (RoPR) and combustion noise compared to baseline mineral diesel. All the test fuels showed relatively shorter combustion duration at higher FIPs and advanced SoMI timings. The biodiesel blends showed slightly higher NOx and smoke opacity compared to baseline mineral diesel. Lower particulate number concentration at higher FIPs was observed for all the test fuels. However, biodiesel blends showed emission of relatively higher number of particulates compared to baseline mineral diesel. Significantly lower trace metals in the particulates emitted from biodiesel blend fueled engine was an important finding of this study. The particulate morphology showed relatively smaller number of primary particles in particulate clusters from biodiesel exhaust, which resulted in relatively lower toxicity, rendering biodiesel to be more environmentally benign.