Premixed Charge Compression Ignition Mode Research Articles

Impact of Biofuel Blending on Hydrocarbon Speciation and Particulate Matter from a Medium-Duty Multimode Combustion Strategy

The U.S. Department of Energy’s Co-Optima initiative simultaneous focused on diversifying fuel sources, improving efficiency, and reducing emissions through using novel combustion strategies and sustainable fuel blends. For medium-duty/heavy-duty diesel engines, research in this area has led to the development of a multimode strategy that uses premixed charge compression ignition (PCCI) at low loads and conventional diesel combustion (CDC) at mid–high loads. The aim of this study was to understand how emissions were impacted when using PCCI instead of CDC at low loads and switching to an oxygenated biofuel blend. It provides a detailed speciation of the hydrocarbon (HC) and particulate matter (PM) emissions from a multimode medium-duty engine operating at low loads in PCCI and CDC modes and high loads in CDC. The effect of the oxygenated biofuel blend on emissions was studied at all three mode–load conditions using #2 ULSD and a bio-derived fuel (25% hexyl hexanoate (HHN)) blended in #2 ULSD. The PCCI mode effectively decreased NOx, total HC, and PM/PN emissions, with a substantial decrease in larger particles (≥50 nm). A PM/PN reduction was observed at high loads with the 25% HHN fuel. While the total HC emissions were not impacted by fuel type, the detailed HC analysis exposed changes in the HC’s composition.

A quantitative study on the combustion and emission characteristics of an Ammonia-Diesel Dual-fuel (ADDF) engine

In order to resolve the global warming problem, Ammonia-Diesel Dual-Fuel (ADDF) combustion has been a feasible strategy for burning ammonia to reduce carbon emissions from internal combustion engines. In the research of this paper, an ADDF engine experimental platform was developed and established. Premixed-Charge Compression Ignition (PCCI) combustion and diesel-piloted combustion modes under different operating conditions were investigated to achieve the goals of high thermal efficiency and low emissions. Moreover, the influence of diesel injection strategy and intake pressure on combustion, gaseous and particle emissions were explored. The results indicate that high thermal efficiency can be obtained using PCCI mode with early injected diesel, which forms a homogeneous mixture with ammonia under the low load condition. Under medium and high load conditions, less diesel was injected early, and ignition was delivered by a pilot injection of diesel close to the top dead centre. Under all operating conditions, the gross indicated thermal efficiency (ITEg) exceeded 48%, and the maximum ITEg was 51.5%, which was comparable to the diesel-only mode. Meantime, the emission of ammonia, NO and N2O were normally below 6 g/kWh, 7 g/kWh, and 1 g/kWh, respectively. With increasing ammonia energy substitution ratio, the particle emission changed from accumulation-mode particles to nucleation-mode particles, but the mass of accumulation-mode particles dominated.

A comparative experimental study on emission characteristics and ammonia energy ratio of diesel generator operating in ammonia/diesel dual fuel mode by premixed and port injection

The extensive use of traditional fossil fuels has exacerbated crises such as environmental pollution, depletion of non renewable energy and global greenhouse effect. Ammonia (NH3) is considered a promising fuel to replace conventional fossil energy in internal combustion engines. A four-cylinder, four-stroke commercial diesel generator (HTD-20GF) was modified and two different ammonia fuel injection systems, premixed charge compression ignition (PCCI) combustion and gas phase port injection (GPPI), were developed. The exhaust emission characteristics, thermal efficiency and ammonia energy ratio of ammonia/diesel dual fuel (ADDF) generator in both PCCI and GPPI modes were studied. The experimental results showed that the overall NO emission in GPPI mode was lower than that in PCCI mode. From the experimental results, both PCCI and GPPI mode can reduce CO2 emission. The GPPI mode was significantly more effective than the PCCI mode in reducing the volume fraction of CO2 in the exhaust gas. Compared with all diesel mode, the HC content in the exhaust gas got worse at lower ammonia energy ratio in both modes, but the increase rate of HC emissions slightly improved as the ammonia energy ratio increased. However, PCCI and GPPI modes reduced the thermal efficiency of the generator, and ammonia had a more negative effect on the thermal efficiency of the ADDF generator in PCCI mode.The experimental results also tested the limiting ammonia energy ratio of this commercial generator at 1 kW. In summary, this study provides a new perspective on the different feeding methods of ammonia as a fuel, which may contribute to the selection of fuel injection methods for ammonia engines to decrease emissions.

Experimental studies on premixed charge and reactivity-controlled compression ignition combustion modes using gasoline/diesel fuel combination

Homogeneous charge compression ignition (HCCI) is a promising technology to reduce NOx and soot emissions in compression ignition (CI) engines. However, this technology lacks combustion control to circumvent the knocking and misfire limitations. Premixed charge compression ignition (PCCI) and reactivity-controlled compression ignition (RCCI) are techniques that use partial homogeneous charge to reduce NOx and soot emissions. Here, combustion is regulated either by controlling the injection timing or fuel reactivity. PCCI uses a part of fuel as premixed to form a partially homogeneous charge and the rest as direct-injected. RCCI, on the other hand, uses a low reactive fuel (LRF) for port injection to form a partially homogeneous charge and a high reactive fuel (HRF) for direct injection. In this work, we studied PCCI and RCCI modes using commercially available fuels like diesel and gasoline, and we compared the results with diesel baseline operation. Adding 40% (by weight) heated diesel port injection to normal diesel operation in PCCI mode at different loads showed a minimum reduction in NOx and smoke emissions by 15% and 6%, respectively, when compared with diesel baseline. This mode was found to be equally efficient with diesel baseline operation at low torque conditions. Similarly, adding 40% (by weight) of gasoline port injection to normal diesel operation in RCCI mode at different loads showed a minimum reduction in NOx and smoke emissions by 20% and 14%, respectively, when compared with diesel baseline. This mode was found to be equally efficient with diesel baseline operation at high torque conditions.

Combustion and emission behaviors of dual-fuel premixed charge compression ignition engine powered with n-pentanol and blend of diesel/waste tire oil included nanoparticles

The main aim of this study was to investigate the effect of n-pentanol percentage on the performance, combustion, and emission characteristics of a premixed charge compression ignition (PCCI) engine operated on dual-fuel mode. The primary fuel used in the engine was a blend of diesel fuel and pyrolytic oil, which was obtained from waste tires by the pyrolysis process. Moreover, CuO/ZnO (CZ) nanoparticles were added to the fuel blend to supply excessive oxygen for better combustion. In addition, n-pentanol is an ecologically innovative and cost-competitive compound used as a secondary fuel with high octane rating. For this experimental work, the fuel blend was prepared by adding 20% waste tire pyrolysis oil to 80% diesel fuel containing 50 ppm CZ nanoparticles, while n-pentanol was sprayed into the intake manifold with varying percentages, namely 10%, 20%, and 30%. As a result of the PCCI dual-fuel mode, PTO20CuZnO50P10 was found to be the best selection since it brought a significant decrement in emission parameters such as oxides of nitrogen (NOx), carbon monoxide (CO), hydrocarbon (HC), and smoke was 12%, 37%, 10%, and 23%, respectively, compared to the conventional diesel engine at peak load condition. However, it is recorded a reduction in brake thermal efficiency and an increase in specific fuel consumption under PCCI mode using PTO20CuZnO50P10 compared to the conventional diesel engine. In general, PTO20CuZnO50P10 was chosen as the best fuel for the PCCI mode of operation aiming to reduce pollutant emissions.

Experimental assessment on characteristics of premixed charge compression ignition engine fueled with multi-walled carbon nanotube-included Tamanu methyl ester

The premixed charge compression ignition (PCCI) engine is developed to develop combustion at low temperatures to enhance engine efficiency and decrease exhaust emissions. This study was performed to compare the performance and emission characteristics of the PCCI mode-based engine operated with induction of ethanol in the inlet manifold and direct injection of multi-walled carbon nanotube (MWCNT)-blended Tamanu methyl ester (TME) at various proportions such as 10, 40, 70, and 100 ppm in comparison with the conventional CI engine fueled with diesel and TME. It was found that adding 100 ppm of MWCNT could provide significant improvements in the performance and emission characteristics of the PCCI engine because of its superior atomization, catalytic behavior, and high surface-to-volume ratio. As a result of comparison with conventional CI engine, brake thermal efficiency and brake-specific fuel consumption of PCCI engine running on MWCNT-blended TME was reduced by 4.12% and increased by 4.28%, respectively. Besides, emissions of hydrocarbon, carbon monoxide, nitrogen oxide, and smoke were reduced by 3.3%, 3.27%, 75%, and 45%, respectively. For combustion analysis, the CI engine has a higher in-cylinder pressure and heat release rate than the PCCI mode, which could be due to the PCCI mode's lower combustion and lean charge mixture. ICP and HRR of PCCI engines running on MWCNT-blended TME were reduced by 7.5% and 3.8%, respectively. In general, this current study reveals a significant reduction in pollutant emissions and an increase in engine performance by using a combined strategy between MWCNT-blended TME and low-temperature combustion mode like PCCI, which was previously unexplored.

Novel strategies to extend the operating load range of a premixed charge compression ignited light-duty diesel engine

Low-temperature combustion (LTC) is an alternative combustion mode to conventional diesel combustion (CDC) that offers a simultaneous reduction in oxides of nitrogen (NOx) and particulate matter (PM) emissions while retaining higher thermal efficiency. Premixed charge compression ignition (PCCI) is a promising LTC strategy that utilizes the early direct injection of diesel and exhaust gas recirculation (EGR) to reduce NOx and PM emissions simultaneously. A limited operating load range and high unburned hydrocarbon (HC) and carbon monoxide (CO) emissions are the significant shortcomings to be addressed to realize PCCI as a commercially viable option. The present work aims to address these limitations based on experimental investigations carried out in a production light-duty diesel engine. An existing mechanical fuel injection system is replaced with a flexible common rail direct injection (CRDI) system to implement PCCI in the test engine. Based on initial parametric investigations, it was found that a combination of early direct injection, lower injection pressures, and EGR was deemed necessary to achieve PCCI mode in the test engine. However, the achievable load range was limited to 40% of the rated load, along with high HC and CO emissions. Novel approaches are attempted to address these limitations, including replacing diesel with diesel-gasoline blends with 30% gasoline by volume and utilizing a dual charge dilution strategy with water vapour induction and EGR. The start of fuel injection (SOI) sweeps from 30 to 70 deg. CA bTDC were performed to find optimal timing at each load condition to maximize the thermal efficiency within a stable combustion regime between a misfire and knocking. For loads above 40%, EGR in the range of 14% to 26.5% was used to bring the combustion within knock limits. By combining the proposed novel strategies, the engine operating load range could be extended from 40% to 80% of the rated load in PCCI. The NOx and soot emissions were significantly reduced up to 98.5% and 99.1%, respectively, compared to CDC. The engine brake thermal efficiency is increased by up to 1.6%. However, there was a significant penalty regarding HC and CO emissions.

Effect of oxy hydrogen gas addition on combustion, performance, and emissions of premixed charge compression ignition engine

Premixed Charge Compression Ignition (PCCI) is one of the well-known ways to achieve low NOx and Soot emissions in Internal Combustion engines. However, this strategy has shown limited scope to bring down the Carbon Monoxide (CO) and Hydrocarbons (HC) emissions. To overcome this drawback, a novel attempt had been made to use oxy hydrogen gas as fuel additive in the PCCI engine. The conventional CI engine was converted into PCCI engine by Port Fuel Injection of diesel fuel and preheating of air. The comparison was made between Conventional Diesel Combustion (CDC) and PCCI mode with and without use of oxy hydrogen gas. Due to accelerated chemical reactions, Indicated Mean Effective Pressure and Indicated Thermal Efficiency improved. Due to the addition of the oxy hydrogen gas the average reduction in CO emission was 26.19% at 25% load and 18.88% at 50% load. In the case of HC, the average emission reduction was 19.27% at 25% load and 23.74% at 50% load. NOx emissions were within the range of 10 ppm even after the addition of oxy hydrogen gas. The oxy hydrogen gas addition resulted in almost negligible Smoke and oxides of nitrogen emissions even without the use of exhaust gas recirculation.

An experimental study on the effect of injection pressure on diesel PCCI engine

The aim of this work was to analyze the effects of injection pressure and exhaust gas recirculation (EGR) on combustion, performance, and emissions characteristics of diesel premixed charge compression ignition (PCCI) mode. In this work, the injection pressure of diesel was varied from 500 bar to 1000 bar. The optimum injection pressure in diesel PCCI mode was identified based on the engine performance and emissions. The thermal efficiency was improved and smoke emission was drastically reduced as increasing injection pressure. However, injection pressure was not significantly influence the amount of NO, HC and CO emissions. The diesel PCCI mode was possible until a brake mean effective pressure (BMEP) of 2 bar since there was a vigorous knocking at higher BMEPs. Addition of EGR retarded the combustion process, suppressed the knocking, increased the thermal efficiency and extended the operating range to higher BMEPs of 3 and 4 bar.

Effects of Two Pilot Injection on Combustion and Emissions in a PCCI Diesel Engine

The effects of two pilot injections on combustion and emissions were evaluated in a single−cylinder turbocharged diesel engine, which operated in premixed charge compression ignition (PCCI) modes with multiple injections and heavy exhaust gas recirculation under the low load by experiments and simulation. It was revealed that with the delay of the start of the first pilot injection (SOI−P1) or the advance of the start of second pilot injection (SOI−P2), respectively, the pressure, heat release rate (HRR), and temperature peak were all increased. Analysis of the combustion process indicates that, during the two pilot injection periods, the ignition timing was mainly determined by the SOI−P2 while the first released heat peak was influenced by SOI−P1. With the delay of SOI−P1 or the advance of SOI−P2, nitrogen oxide (NOx) generation increased significantly while soot generation varied a little. In addition, increasing Q1 and decreasing the second pilot injection quantity (Q2) can manipulate the NOx and soot at a low level. The advance in SOI−P2 of 5 °CA couple with increasing Q1 and reducing Q2 was proposed, which can mitigate the compromise between emissions and thermal efficiency under the low load in the present PCCI mode.

Experimental studies to improve the performance, emission and combustion characteristics of wheat germ oil fuelled CI engine using bioethanol injection in PCCI mode

Bioethanol is gaining momentum to be the best suitable replacement fuel for internal combustion engines; since it can be produced from biomass and lesser NOx emissions due its increased latent heat of vaporization. It has high flame speed which helps to complete the combustion quickly in premixed charge compression ignition (PCCI) mode. The focus of this work is to inject bioethanol in the inlet port with varying energy share; subsequently wheat germ oil is injected directly inside the combustion chamber. Experiments were conducted with various injection timing and duration for bioethanol to optimize for PCCI operation. The brake thermal efficiency of the wheat germ oil is lower than the diesel. The operation of bioethanol with wheat germ oil in PCCI mode improves the combustion behaviour and the significant improvement is seen with the emission and performance characteristics. Brake thermal efficiency increase to the maximum of 29.14% with 30% bioethanol energy share which is very closure to the diesel value of 29.78%. NO emission reduces from 813 ppm to 756 ppm with 30% energy share at maximum load. Smoke emission increases from 65% opacity with diesel to 78% opacity with wheat germ oil at maximum load. Addition of bioethanol decreases the smoke emission; it decreases from 78% opacity to 67% opacity with 30% bioethanol share. Addition of diesel improves the cylinder pressure from 62.4 bar to 67.6 bar at maximum load. Ignition delay and combustion duration are reduced with bioethanol addition due to higher flame speed which in turn increases the heat release rate.

Evaluation of comparative engine combustion, performance and emission characteristics of low temperature combustion (PCCI and RCCI) modes

In this study, a comparative investigation of engine combustion, performance and emission characteristics of low temperature combustion modes namely premixed charge compression ignition (PCCI) and reactivity controlled compression ignition (RCCI) with conventional compression ignition (CI) combustion mode was performed. Experiments were performed in a single cylinder research engine at constant engine speed (1500 rpm) and at four different engine loads (1, 2, 3 and 4 bar brake mean effective pressure (BMEP)). Baseline CI and PCCI mode combustion experiments were performed using mineral diesel as test fuel; while mineral diesel-methanol fuel pair was used as high-reactivity fuel (HRF) and low-reactivity fuel (LRF) respectively in RCCI mode combustion. Results showed that RCCI mode combustion was relatively more stable compared to baseline CI and PCCI combustion modes. At higher engine loads, RCCI mode combustion exhibited relatively lower knocking and combustion noise than other combustion modes. Performance characteristics showed that brake thermal efficiency (BTE) of RCCI mode combustion was comparable to baseline CI mode combustion, however, at higher engine loads, RCCI mode combustion resulted in relatively higher BTE compared to both baseline CI and PCCI combustion modes. Significantly lower EGT of RCCI mode combustion compared to baseline CI as well as PCCI combustion modes was another important finding of this study. Emission results showed that RCCI mode combustion emitted relatively lower oxides of nitrogen (NOx), but significantly higher hydrocarbons (HC) compared to baseline CI and PCCI combustion modes. A NOx-BTE trade-off analysis was also carried out, which demonstrated the suitability of RCCI mode combustion at all engine loads. Finally, a parametric analysis was carried out to compare the critical parameters of baseline CI, PCCI, and RCCI combustion modes at low and high engine loads, which exhibited improved engine performance and emission characteristics of low temperature combustion (LTC) modes, especially the RCCI mode combustion.

Split Injection Strategies for Biodiesel-Fueled Premixed Charge Compression Ignition Combustion Engine—Part II: Particulate Studies

Abstract In this study, experiments were performed in a single-cylinder research engine to investigate the particulate matter (PM) characteristics of the engine operated in premixed charge compression ignition (PCCI) mode combustion vis-a-vis baseline compression ignition (CI) mode combustion using three test fuels, namely, B20 (20% v/v biodiesel blended with mineral diesel), B40 (40% v/v/ biodiesel blended with mineral diesel), and baseline mineral diesel. The experiments were carried out at constant fuel injection pressure (FIP) (700 bar), constant engine speed (1500 rpm), and constant fuel energy input (0.7 kg/h diesel equivalent). PM characteristics of PCCI mode combustion were evaluated using two different fuel injection strategies, namely, single pilot injection (SPI) (35 deg before top dead center (bTDC)) and double pilot injection (DPI) (35 deg and 45 deg bTDC) at four different start of main injection (SoMI) timings. Results showed that both PCCI mode combustion strategies emitted significantly lower PM compared to baseline CI mode combustion strategy. However, the blending of biodiesel resulted in relatively higher PM emissions from both CI and PCCI combustion modes. Chemical characterization of PM showed that PCCI mode combustion emitted relatively lower trace metals compared to baseline CI mode combustion, which reduced further for B20. For detailed investigations of particulate structure, morphological characterization was done using transmission electron microscopy (TEM), which showed that PM emitted by B20-fueled PCCI mode combustion posed potentially lower health risk compared to baseline mineral diesel-fueled CI mode combustion.

Split Injection Strategies for Biodiesel-Fueled Premixed Charge Compression Ignition Combustion Engine—Part I: Combustion, Performance, and Emission Studies

Abstract In this study, a single-cylinder research engine was used to investigate the comparative combustion, performance, and emissions characteristics of the engine in a premixed charge compression ignition (PCCI) mode combustion vis-a-vis baseline compression ignition (CI) mode combustion using three test fuels, namely, B20 (20% v/v biodiesel blended with mineral diesel), B40 (40% v/v biodiesel blended with mineral diesel), and mineral diesel. For both combustion modes, experiments were performed at constant fuel injection pressure (FIP, 700 bar), engine speed (1500 rpm), and fuel energy input (0.7 kg/h diesel equivalent). PCCI mode combustion experiments were performed at four different start of main injection (SoMI) timings using two different pilot fuel injection strategies, namely, single pilot injection (SPI, 35 deg before top dead center (bTDC)) and double pilot injection (DPI, 35 deg, and 45 deg bTDC). Results showed that advancing SoMI timing for both CI and PCCI combustion modes resulted in knocking; however, the DPI strategy resulted in relatively lesser knocking compared with the SPI strategy. The performance of PCCI mode combustion was relatively inferior compared with baseline CI mode combustion; however, biodiesel blends slightly improved the performance of PCCI mode combustion. Overall, this study shows that the PCCI mode combustion operating load range can be improved by using the DPI strategy.

Experimental Study of Premixed-Charge Compression Ignition Mode in Low Load Fueled With Butanol Isomers and Diesel Binary Fuels in a Common-Rail Diesel Engine

Abstract Low NOx and particulate matter (PM) emissions are simultaneously attempted to implement via an experimental study on diesel/butanol isomers binary fuels in premixed-charge compression ignition (PCCI) mode. N-butanol, iso-butanol, sec-butanol, and tert-butanol were blended with diesel in a certain volume ratio of 0.24:0.76, denoted as N24, I24, S24, and T24, respectively. The indicated thermal efficiency (ITE) of binary fuels in PCCI mode decreases slightly than that in direction injection (DI) mode. T24 obtains higher ITE than the other three test fuels with 50% exhaust gas recirculation (EGR). NOx formation is certainly inhibited more than 60% in PCCI mode, especially when the EGR rate is 50%. PCCI mode produces more CO, HC, and carbonyl emissions than DI mode to varying degrees; under these circumstances, T24 tends to have the lowest emissions among four test fuels, reflecting the potential of tert-butanol as a diesel alternative fuel. Butanol isomers have a vital contribution on particulate matter emissions inhibition for both PM total number and total mass. Tert-butanol tends to form accumulation mode particle, and n-butanol tends to form nucleation mode mainly caused by molecular structure diversity of isomers. The geometric mean diameter of diesel/butanol isomers increases in PCCI mode compared with that in DI mode.

Experimental studies on the key parameters controlling the combustion and emission in premixed charge compression ignition concept based on diesel surrogates

Compared with the traditional diesel combustion mode, the premixed charge compression ignition mode only changes the fuel injection strategy combined with a certain ratio of exhaust gas recirculation, which needs little change to the overall engine. Studies on the effects of the cetane number and volatility of the diesel fuels are critical to the combustion, emissions and load range expansion of the premixed charge compression ignition mode. Based on the multi-component surrogate fuels, this paper controlled the cetane number and the volatility of diesel surrogates by changing the components and their proportions combined with the adjustment of fuel injection parameters to study the factors that affect the combustion and emissions of the premixed charge compression ignition mode. The cetane number of fuels played a decisive role in the combustion phase under the same injection strategy. The decrease of cetane number of the direct injected fuels led to the increase of CO and HC emissions. Low cetane fuels helped to inhibit premature combustion of pilot injected fuel. The decrease in fuel cetane number could suppress the emissions of accumulated particles. Changing the volatility of the fuel had limited effects on the combustion phase and combustion speed. High volatility fuel could effectively reduce the CO and HC emissions in the premixed charge compression ignition mode although it cannot fundamentally solve the high CO and HC emission problems caused by the premixed strategy. Increasing the volatility of the fuel could reduce the concentration of accumulated particles. Under the premise of ensuring that the NOx emissions were lower than 200 ppm via adjusting the injection parameters, increasing fuel volatility may decrease the indicated fuel consumption as low as 178 g/kWh.

Experimental analysis of PCCI in a diesel engine with different fuel blends

PurposeMore stringent emission standards are being promulgated all over the world for regulating and decreasing the levels of emission more so caused from on-road vehicles and engines and for improving the air quality problems.Design/methodology/approachIn this study, an attempt has been made to experimentally analyze the performance and emission characteristics of the premixed charge compression ignition (PCCI) mode assisted by a pilot injector.FindingsThe results indicate that brake thermal efficiency marginally decreases, and specific fuel consumption increases in all PCCI modes, and HC, CO emissions are higher in the case PCCI modes and oxides of nitrogen and soot levels are considerably reduced in the case of diesel PCCI-biodiesel and petrol PCCI-biodiesel modes.Research limitations/implicationsAs obtaining very lean homogenous mixture is hard, it becomes difficult to sustain PCCI mode over the operating range of varying speeds and loads to effectively control the PCCI combustion over the operating range.Social implicationsBeing a responsible human being, we all have the responsibility in keeping this world cleaner, free from all sort of pollution. In this regard, the concept of waste recycling and energy recovery plays a vital role in the development of any economy. This has led to resource conservation and pollution reduction.Originality/valueThe present work Jatropha oil methyl ester (JOME) was chosen as fuels for PCCI mode. Investigations were carried out with blends of JOME with diesel in PCCI combustion mode to evaluate the performance, combustion and emission characteristics of these fuels.

Novel fuel injection strategies for PCCI operation of a heavy-duty turbocharged diesel engine

Towards the objective of achieving benefits of the Premixed Charge Compression Ignition (PCCI) mode in a multi-cylinder, turbocharged, common-rail, direct-injection, heavy-duty diesel engine, simulations were first conducted to assess improvement in in-cylinder charge homogeneity by several strategies. These strategies include multiple injections, Port Fuel Injection (PFI), and combination of PFI and Early Direct Injection (EDI). The maximum Uniformity Index (UI) achieved by EDI was 0.78. The PFI strategy could achieve UI of 0.95; however, majority of the fuel remained trapped in the port after valve closure. This indicated that except EDI, none of the above-mentioned strategies could help achieve the benefits of the PCCI mode. An optimized EDI (OptimEDI) strategy gave 20% NOx and soot reduction over the conventional CI mode. Although this strategy gave encouraging results, there was a need for more substantial reduction in emissions. Hence, a novel concept of utilizing Air-assisted Injection (AAI) into the air intake was employed. Experiments were carried out with AAI and combination of OptimEDI. Results with 48% Exhaust Gas Recirculation (EGR) and 5–10% of fuel injected using AAI gave substantial reduction in NOx and soot emissions at the part-load condition of the engine.

Investigations on premixed charge compression ignition engine with external mixture formation and exhaust gas recirculation technique

In present scenario it is need for automobile sector to develop clean technology which will result in less fuel consumption and green house gas. The Premixed charge compression ignition (PCCI) is one of the effective technologies that give efficiency close to conventional CI engine and eliminates generation of high NOx and PM simultaneously. In the present investigation twin cylinder four stroke water cooled CI engine is used for experimentation. One of the two cylinders of CI engine is modified to run on PCCI mode. An external mixture formation technique is used to achieve PCCI operation. For this purpose a device known as diesel vaporizer is designed and fabricated. The port fuel injector operates at 3 bar injection pressure is used to inject the fuel into the heated vaporizer where it vaporizes and mixes with air in the intake port to form a premixed charge. To control auto ignition of diesel vapor and air mixture, Exhaust gas recirculation (EGR) technique is used. In the present investigation 10 %, 20 % and 30 % EGR is used for PCCI mode of operation and the results were compared with CI mode of operation. The main objective of the present experimental study is to reduce exhaust emission percentage while maintaining thermal efficiency as close to CI engine. The brake thermal efficiency in PCCI mode little decreases comparing to CI mode but NOx and Smoke emissions decreases drastically in PCCI mode comparing to CI mode of operation.

A comprehensive study on the emission characteristics of E-diesel dual-fuel engine

Each year, the ultimate goal of emission legislation is to force technology to the point where a practically viable zero emission vehicle becomes a reality. Albeit the direction to reach this target is a formidable challenge, homogeneous charge compression ignition (HCCI) is a new combustion concept to produce ultra low nitrogen oxides (NOx) and smoke emissions. By the way, an endeavor has been made in this work to achieve a simultaneous reduction in both NOx and smoke levels in a direct injection compression ignition engine converted to operate on premixed charge compression ignition mode. Indeed, these promises were made possible in this work by preparing premixed fuel–air mixture outside the engine cylinder. For this purpose, ethanol was injected in the intake port at various premixed ratios (5%, 10%, 15%, 20%, 25% and 30%) and conventional diesel was injected as usual. It was extrapolated from the experimental results that e-diesel operation can significantly reduce NOx and smoke levels. In addition, NOx and smoke levels reduced in this experimental study with increase in premixed fraction. Nevertheless, unburned hydrocarbons (UBHC) and carbon monoxide (CO) emissions exhibited reverse trend with increase in premixed fraction and the maximum value of HC and CO emission levels was noted with 30% premixed fraction.