Premixed Charge Compression Ignition Research Articles

PORT INJECTION OF DIESEL, BIODIESEL, AND PETROL IN A COMPRESSION IGNITION DIRECT INJECTION DIESEL ENGINE TO MITIGATE NITROGEN OXIDES AND SOOT EMISSIONS

The internal combustion engine is critical to modern society’s development. Spark ignition engine (SI) and compression ignition engine (CI) now use gasoline and diesel as their primary fuels. As a result of burning these fuels, significant amounts of pollutants are released into the atmosphere, resulting in environmental issues. Internal combustion (IC) engines are widely acknowledged as a significant source of environmental air pollution. The engine’s fuel oxidation process not only produces useful power, but also produces significant amounts of pollutant emissions such as carbon monoxide (CO), unburned hydrocarbons (HC), nitrogen oxide (NOx ), and particulate matter (PM). When developing a new combustion process, consideration must be given to: lean homogeneous air-fuel mixture, increased compression ratio, and total and instantaneous combustion, all of which result in Port Injection Compression Ignition (PICI), that is a highly efficient and clean method of combustion. The goal of this research is to conduct an experimental investigation of PICI process of compression in a Premixed Charge Compression Ignition (PCCI) mode with Pilot Injection (PI) as the combustion activator. It was found that when compared to the conventional mode, the PICI mode produces cooler exhaust gas temperatures. Temperatures were lower in the PICI mode with biodiesel and petrol as secondary and primary fuels than in the PICI mode with other fuel combinations. In the PICI mode, the HC emission decreases at higher load with all fuels. In the biodiesel conventional mode, HC emission is minimum than in other modes. For all modes of operation, the specific fuel consumption has reduced with load. Diesel and gasoline have the lowest specific fuel consumption as primary and secondary fuels, respectively. Fuel usage in the PICI mode is lower than in the normal mode.

A Simulation Study on a Premixed-charge Compression Ignition Mode-based Engine Using a Blend of Biodiesel/Diesel Fuel under a Split Injection Strategy

Environmental pollution from transportation means and natural resource degradation are the top concern globally. According to statistics, NOx and PM emissions from vehicles account for 70% of total emissions in urban areas. Therefore, finding solutions to reduce NOx and PM emissions is necessary. Changing the engine's internal combustion method is considered promising and influential among the known solutions. One of the research directions is a combustion engine using the Premixed Charge Compression Ignition (PCCI) method combined with biofuels to improve the mixture formation and combustion process, reducing NOx and PM emissions. Therefore, this study presents the mechanism of the formation of PM and NOx emissions in the traditional combustion and the low-temperature combustion process of internal combustion engines. Besides, the theoretical basis of flame spread during combustion is also introduced. The key feature of this research is that it has modeled the combustion process in diesel engines under the PCCI modes. This was accomplished using blends of waste cooking oil (WCO)-based biodiesel and diesel fuel, as well as the ANSYS Fluent software. The results showed that PCCI combustion using B20 fuel can significantly reduce NOx and PM emissions, although HC and CO emissions tend to increase, and thermal efficiency tends to decrease. In further studies, different modes of the PCCI combustion process should be thoroughly examined so that this process can be implemented in practice to reduce pollutant emissions.

RCCI combustion of ammonia in dual fuel engine with early injection of diesel fuel

Ammonia has gained considerable attention as a valuable, carbon-free alternative fuel for internal combustion engine (ICE) applications. The growing interest in ammonia's potential as an energy source stems primarily from its advantageous storage and transport properties. The reactivity-controlled compression ignition (RCCI) combustion mode presents a promising avenue for overcoming the challenges intrinsic to conventional diesel engines, such as elevated nitrogen oxides (NOx) and particulate matter (PM) emissions. Additionally, it addresses the limitations of both homogeneous charge compression ignition (HCCI) combustion (limited operational range) and premixed charge compression ignition (PCCI) combustion (diminished power output). The application of an ammonia-based RCCI combustion strategy emerges as a viable pathway for harnessing ammonia as a fuel. In this study, a numerical simulation on a single-cylinder heavy-duty engine operated in RCCI mode is conducted utilizing ammonia and diesel as fuels. The engine is operated at medium load and 910 RPM. The simulation results are validated against experimental data sourced from existing literature. The study investigates the impact of varying ammonia energy fractions, injection timing, and intake valve close temperature (TIVC) on key operational characteristics of the engine including in-cylinder pressure, heat release rate (HRR), combustion efficiency (CE), indicated mean effective pressure (IMEP), and emission levels. The results indicated that increasing the ammonia energy fraction within the RCCI combustion mode, transitioning from 30 % to 70 %, leads to a notable enhancement in IMEP, while maintaining low levels of carbon monoxide (CO), hydrocarbons (HC), unburned ammonia, and nitrous oxide (N2O) as greenhouse gases (GHG). Furthermore, increasing ammonia's energy fraction yielded a discernible reduction in NOx emissions and carbon dioxide (CO2). Conversely, the RCCI combustion mode attained superiority over the dual fuel combustion mode by simultaneously elevating CE and diminishing emissions of GHG, (CO2 and N2O) as well as unburned NH3.

A relative comparison of HCCI, PCCI, and RCCI combustion strategies: an alternative fuels perspective

Low temperature combustion (LTC) strategies have the potential for simultaneous reduction in oxides of nitrogen (NOx) and soot emissions while achieving higher thermal efficiency. Commercial widespread implementation of LTC strategies demands addressing several challenges, including narrow operating load range, lack of ignition timing control, and reducing high unburned hydrocarbon (HC) and carbon monoxide (CO) emissions. These challenges could be because the conventional engine design and fuels cannot adapt well to LTC modes. Thus, replacing conventional diesel fuel with suitable alternative fuels for LTC strategies is essential. In the present work, three LTC strategies, Homogenous Charge Compression Ignition (HCCI), Premixed Charge Compression Ignition (PCCI), and Reactivity Controlled Compression Ignition (RCCI), are compared with conventional diesel combustion in a production, light-duty diesel engine from an alternative fuel perspective to come up with a befitting strategy and fuel to achieve wider operating range and lower emissions. The fuel selection strategy based on the fundamental fuel property requirements of the three LTC strategies has been discussed in detail. The baseline reference data is fixed by comparing three LTC strategies with conventional diesel combustion using diesel and gasoline as reference fuel at 40% load, the maximum common achievable load among the three LTC strategies. This is followed by an investigation of the effect of alternative fuels across three LTC strategies to address the shortcomings of the LTC strategies. The results show that the engine operating load range could be extended, and HC and CO emissions are reduced significantly with alternative fuels in the three LTC strategies.

Combustion noise characterization and optimization of PCCI combustion using response surface methodology

The current work aims at characterizing the premixed charge compression ignition (PCCI) combustion with regression-based approach using response surface methodology. PCCI operating parameters such as load, pilot injection timing, main injection timing, pilot injection quantity, exhaust gas recirculation and injection pressure are considered as input variables. Engine performance indicators such as brake thermal efficiency, brake specific fuel consumption, carbon monoxide (CO), hydrocarbon (HC), oxide of nitrogen (NOx), smoke emissions, combustion phasing and combustion noise metric ringing intensity are considered as output responses. Experimental results validate the optimal solution from response surface methodology approach, and good agreement is found between mathematical models and experimental results. Comparative examination of optimized PCCI combustion versus conventional combustion showed a 66% and 44% decrement in NOx and smoke emissions. Except for CO and HC emissions, the percentage penalty of other responses with PCCI combustion is less than 10%. In addition to ringing intensity another combustion noise metric combustion noise level is computed from Fast Fourier Transform (FFT) analysis of cylinder pressure trace. A combustion noise level of 73.26 dB is obtained at optimized conditions.

Effects of using a novel fuel vaporizer on partially premixed charge compression ignition (PPCCI) engine emissions, performance, and combustion characteristics

Environmental concerns of toxic emissions and depleting of fossil fuel supplies due to their excessive usage as the main source of energy have raised interests in the creation of novel combustion modes that result in reduction of combustion temperatures and produce low emissions. In comparison to conventional diesel engines, the partially pre-mixed charged compression ignition (PPCCI) combustion strategy has demonstrated its ability to significantly reduce emissions carbon monoxide (CO), unburned hydrocarbon (HC), oxides of nitrogen (NOX), carbon dioxide (CO2) and smoke opacity. In order to compare the results with those of conventional engines, the current experimental work’s objective is to investigate the combustion, performance, and exhaust emissions characteristics of PPCCI engines. A single-cylinder, air-cooled, 4-stroke, direct-injection diesel engine that had been modified to run in PPCCI mode was used for the experiments. An external mixture formation technique with a fuel vaporizer is added to create the homogeneous mixture for PPCCI combustion. After being heated to the point of vaporization, liquid diesel fuel vapor was mixed with some fresh air and then the mixture directed to the intake manifold, where it was mixed with the remaining fresh air to create an external homogenous mixture that filled the combustion chamber. The tests were conducted at different premixed ratios of diesel fuel proportions of 15%, 20%, and 30% in the intake port. However, the fuel vaporizer chamber was kept at fixed temperature of 100 °C, 105 °C, 110 °C, 115 °C, and 120 °C. The PPCCI engine results were compared with the conventional engine data. Results from the PCCI technique at various premixed ratios indicate a certain decrement for HC, CO, NOX, and smoke emissions, rising in BTE “brake thermal efficiency”. At 30% premixed ratio of the fuel vapour inducted at 110 °C in PCCI mode give the best results as the brake thermal efficiency raised from 28.8% for CDC mode to 34.2% for PCCI mode at full load. Additionally, NOX emissions decreased from 615 PPM to 550 PPM, HC emission decreased to 30 PPM, CO emission decreased from 0.09% to 0.06% and a decrease in smoke opacity from 38% to 19.3%.

Experimental Study on Sustainability Involving the Pugh Matrix on Emission Values of High-Temperature Air in the Premixed Charged Compression Ignition Engine.

The main aim of the study was to reduce carbon emissions in the atmosphere using a novel Andropogon narudus (AN) biofuel using higher air temperatures and reducing the consumption of conventional fossil fuel (diesel). The use of a heat exchange chamber within the air intake manifold is a popular method to reduce hydrocarbon (HC) and carbon monoxide (CO) emissions during cold starts. A premixed charged compression ignition engine in the dual-fuel mode was used in this study with raw diesel, raw AN oil, AN70+D30, AN80+D20, AN80+D20 (35 °C), AN80+D20 (40 °C), and AN80+D20 (45 °C). A chamber was designed and analyzed to measure the exit temperature and density change and to determine the reduction in volumetric efficiency of the engine, using Ansys Fluent software. A sustainability assessment study was performed to understand the feasibility of the fuel and the design using the Pugh Matrix. The fuel AN80+D20 with an air temperature of 45 °C was found to be superior to all other fuels in terms of brake thermal efficiency, reaching at 32.1%. D100 used the least amount of energy, whereas AN80+D20 used the most. Engine HC emission was at the lowest (45.01 ppm) for AN80+D20 fuel at 45 °C air input and reached the highest (50 ppm) for AN100 fuel. With an air temperature of 45 °C, CO emission was at its lowest for AN80+D20 gasoline (0.018%) and was at its highest for AN100 (0.072%). Nitrogen oxide emissions were the highest for AN80+D20 fuel with an air temperature of 45 °C, with an air concentration of 1254 ppm, whereas they were the lowest for AN100 (900 ppm). CO2 values were reduced, with D100 showing the lowest levels and AN100 showing the highest. The smoke emission was minimum for AN80+D20 fuel at 45 °C, with a smoke number of 15 compared to 33 for D100 fuel. As per the Pugh Matrix assessment, AN80+D20 with 35 °C air temperature had higher scores compared to all of the other fuel mixtures.

Utilization of Ammonia Hydroxide /Diesel Fuel Blends in Partially Premixed Charge Compression Ignition (PPCCI) Engine: A Technical Review

Utilization of Ammonia Hydroxide /Diesel Fuel Blends in Partially Premixed Charge Compression Ignition (PPCCI) Engine: A Technical Review

Effect of Diesel Injection Strategy and Ammonia Energy Fraction on Ammonia-Diesel Premixed-Charge Compression Ignition Combustion and Emissions

The utilization of ammonia as a fuel is one of the effective measures to achieve decarbonization and carbon neutrality in internal combustion engines (ICEs). However, its slow laminar flame speed and high ignition energy limit the efficient application of ammonia-only in ICEs. In this study, based on a heavy-duty single-cylinder engine, the impact of ammonia energy fraction (AEF), start of diesel injection (SODI) timing, and diesel injection pressure (DIP) on combustion and emission characteristics of premixed-charge compression ignition mode under low load conditions was investigated. Combined with three-dimensional simulation, the mechanism of how AEF and diesel injection strategy regulation affected the in-cylinder equivalence ratio and reactivity distribution was analyzed. It was found that increasing the AEF and advancing the SODI timing can improve the homogeneity of mixture. However, the spatial distribution of the OH groups deteriorate continuously. Experimental results indicated that with the used of 50% AEF, 60 MPa DIP, and injecting diesel at −40°CA ATDC, a gross indicated thermal efficiency (ITEg) of 49.7% can be achieved. Compared to the diesel-only mode, the greenhouse gas (GHG) emissions reduced by 44%. To further improve the combustion of ammonia/diesel PCCI mode, the DIP was increased to 100 MPa, which optimized the in-cylinder fuel–air mixing process, improving the homogeneity of the mixture and enhancing the reactivity distribution before the ignition, and enabling faster combustion. As a result, an increase in ITEg to 51.4% with using 100 MPa DIP was achieved, and reduced the GHG emissions by 51% compared to the diesel-only mode.

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.

Effect of early intake valve closing, exhaust gas recirculation and split injection on combustion and emissions characteristics of a HDDI diesel engine operating in PCCI combustion mode

Premixed Charge Compression Ignition (PCCI) combustion is an alternative to conventional diffusion-controlled combustion for Mono-nitrogen oxides (NOx) and soot emissions reduction in DI diesel engines. However, bringing the center of combustion (CoC) near top dead center (TDC) to reduce brake specific fuel consumption is challenging. In this study, for two Early Intake Valve Closing (EIVC) profiles of split injection strategy, combustion characteristics and emissions of a heavy-duty direct injection (HDDI) diesel engine are evaluated by CFD simulations. Combustion efficiency, Indicated Specific Fuel Consumption (ISFC), NOx, soot, and carbon monoxide (CO) emissions are evaluated for 40 ˚CA and 80˚CA EIVC timings with respect to the base diesel combustion with 0, 30, 50, and 70% Exhaust Gas Recirculation (EGR) rates at 3 bar Brake Mean Effective Pressure (BMEP).CFD simulations reveal that EIVC strategy can displace the CoC towards TDC up to 5–10 ˚CA depending on the EGR rate. Moreover, up to 30% NOx reduction can be achieved in EIVC cases. In 70% EGR case, lower ISFC and near zero NOx emissions can be obtained compared to conventional diesel combustion due to CoC being closer to TDC. However, the EIVC strategy with EGR increases CO emissions due to incomplete combustion of a lower air/fuel ratio mixture.

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.

Effect of Plasto-Oil Blended with Diesel Fuel on the Performance and Emission Characteristics of Partly Premixed Charge Compression Ignition Engines with and without Exhaust Gas Recirculation (EGR)

Municipal mixed plastic waste (MMPW) recycling is an innovative way to turn environmental waste into energy fuels. In the present study, a thermochemical process was applied to depolymerize MMPW to produce hydrocarbon fuels known as plasto-oil. The obtained plasto-oil was blended with conventional diesel to test the performance of the PCCI-mode single-cylinder, four-stroke, direct-injection diesel engine. The PCCI combustion mixture was tested with 15% and 30% fuel vapor to ensure homogeneity with and without exhaust gas recirculation. The modified engine findings were compared to a standard conventional engine. At higher loads, PCCI combustion showed reduced emission of carbon monoxide and nitrogen oxides. While the thermal braking efficiency was marginally reduced at all engine loads while using the blends. The results showed that with and without 10% exhaust gas recirculation, an increase in air mix reduced NOx emissions; however, in the case of smoke emissions, an opposite trend was observed. A blend of plasto-oils also decreased CO and unburned hydrocarbon (HC) emissions at higher loads. In conclusion, it was shown that plasto-oils combined with conventional diesel fuel outperformed diesel fuel alone.

A new concept for high efficiency and clean diesel combustion by controlling mixture distribution with dual zone combustion chamber

While various measures are being promoted globally toward carbon-neutrality, internal combustion engines are required to achieve a further improvement in thermal efficiency in order to generate less CO2. For diesel engines, premixed charge compression ignition (PCI) combustion has been proposed as a combustion method that can achieve high thermal efficiency and clean emissions simultaneously. However, the application of PCI combustion remains limited to the light load range of certain mass-produced engines as it is difficult to control ignition timing and combustion noise. In this study, we developed a new combustion concept, Distribution Controlled partially Premixed Compression Ignition (DCPCI), which enables partially premixed combustion in medium load ranges by spatially controlling fuel mixture distribution. With this DCPCI combustion, we aim for highly efficient and clean combustion by suppressing the interference between the burned gas produced by the earlier stage injection and the subsequent spray with the use of a dual-zone combustion chamber and multi-stage injection. The effectiveness of the new combustion concept was validated by Computational Fluid Dynamics (CFD) analyses, and the improvement in thermal efficiency was confirmed by engine experiments.

A CFD Study on the Effects of Injection Timing and Spray Inclusion Angle on Performance and Emission Characteristics of a DI Diesel Engine Operating in Diffusion-Controlled and PCCI Modes of Combustion

In three-dimensional (3D) computational fluid dynamics (CFD) simulations, the effects of injection timing and spray inclusion angle (SIA) on performance and emissions of diffusion-controlled and Premixed Charge Compression Ignition (PCCI) combustion in part load for a heavy-duty direct injection (HDDI) diesel engine are studied. The start of injection (SOI) of a 146° SIA injector is varied between −70 and −10 °crank angle (°CA) after top dead center (ATDC). For −50 °CA ATDC SOI with various SIAs between 80° and 146°, PCCI combustion reduces mono-nitrogen oxide (NOx) emissions significantly compared to conventional diesel combustion (CDC). Due to incomplete combustion in rich zones formed by droplet–cylinder wall interaction, early wide SIA injection deteriorates combustion efficiency (CE) and Indicated Mean Effective Pressure (IMEP) and increases soot and carbon monoxide (CO) emissions. Narrow-angle sprays interacting with the piston bowl elevate CE and IMEP and decrease soot and CO emissions but increases NOx emissions. Optimal combustion is achieved by avoiding fuel droplet–cylinder wall interaction. By spray-targeting at the stepped lip of the piston bowl, 100° SIA and −50 °CA ATDC SOI yield, respectively, the highest CE and IMEP: 97.8% and 3.37 bar and the lowest soot and CO emissions: 33.5 and 2.2 ppm, with acceptable NOx emissions.

Experimental Investigation on the PCCI Engine Fueled by Algal Biodiesel Blend with CuO Nanocatalyst Additive and Optimization of Fuel Combination for Improved Performance and Reduced Emissions at Various Load Conditions by RSM Technique.

Fossil fuel depletion and environmental pollution are paramount problems the world faces. Despite several measures, the transportation industry is still battling to manage these issues. A combined approach of fuel modification for low-temperature combustion with combustion enhancers could offer a breakthrough. Due to their properties and chemical structure, biodiesels have piqued the interest of scientists. Studies have asserted that microalgal biodiesel might be a viable alternative. Premixed charge compression ignition (PCCI) is an easily adoptable promising low-temperature combustion strategy in compression ignition engines. The objective of this study is to identify the optimal blend and catalyst measure for improved performance and reduced emissions. Microalgae biodiesel at various proportions (B10, B20, B30, and B40) was amalgamated with CuO nanocatalyst and tested to arrive at the right concoction of biodiesel with nanoparticles in a 5.2 kW CI engine for different load conditions. The PCCI function warrants that about 20% of the fuel supplied is vaporized for premixing. Finally, the interplay factors of the independent variables of the PCCI engine were then explored by response surface methodology (RSM) to determine the optimal level of desired dependent and independent variables. The RSM experiment findings suggest that the best biodiesel and nanoparticle concoctions at 20%, 40%, 60%, and 80% loads were B20CuO76, B20Cu60, B18CuO61, and B18CuO65, respectively. These findings were experimentally validated.

Effect of premixed hydrogen on the performance and emission of a diesel engine fuelled with prunus amygdalus dulcis oil

There is a need to find alternative fuels to replace the fossil fuels and also to reduce the harmful emissions. Biomass based fuels are one such alternate fuel to diesel. The main aim of this study is to find the suitability of sweet almond oil (Prunus amygdalus dulcis oil) in compression ignition engine (CI), moreover to enchance the performance and emission parameters by premixed charge compression ignition (PCCI) combustion with hydrogen fuel. A decrease in diesel engine performance was observed with the blend. Further to reduce the fossil fuel consumption, hydrogen was introduced in the intake manifold. As hydrogen is inducted well before the combustion, it makes premixed charge with intake air for better combustion. The results reveal that 30LPM (litres per minute) hydrogen flow rate lead to maximum improvement in engine performance. Compared to the blend, the thermal efficiency increased by 8.38 % at full load, and a reduction of 70 %, 56 % and 27 %, for HC, CO and smoke emissions respectively was observed. However, an increase of 14 % in NO emission was observed. Hydrogen addition along with SAO20 (20 % blending of sweet almond oil biodiesel in diesel) operation increases the in-cylinder peak pressure from 79.8 bar to a maximum of 89.5 bar at full load. Hydrogen increases the rate of heat released in the premixed combustion but the peak heat release rate is delayed with different hydrogen flow rates due to lower centane number of the combustible mixture. The novelty of this paper is to run the engine with unexplored low carbon biofuel prunus amygdalus dulcis oil in diesel engine and also to improve the performance by premixed hydrogen fuel.

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.

Effect of injection strategy optimization on PCCI combustion and emissions under engine speed extension in a heavy-duty diesel engine

To mitigate the consequent emissions of greenhouse gases and to conform to increasingly strict vehicle emission requirements, experiments and numerical simulation were used to study effects of multiple injection strategy on premixed charge compression ignition (PCCI) combustion and emissions under speed extension in a heavy-duty diesel engine fueled with diesel. As the speed increases, the injection duration is prolonged, the injection rate is decreased, the fuel-oxygen mixing degree is decreased. In order to enhance fuel-oxygen mixing, the injection timing of single injection should firstly be optimized to fully utilize the shape of the chamber. Compared with single injection, the double injections can increase the mixing time, the optimized multiple injections can further increase the mixing time, making the premixing more sufficient and the combustion more complete. Compared with double injections, the optimized multiple injection strategy used in this paper adds a short pulse pilot injection before the main injection, which prolongs the duration of turbulent motion in the cylinder, and enhances the mixing rate of the main injection fuel and air. Results reveals that for single injection with injection timing of −15°CA ATDC, at low speed, through optimizing the injection strategy, the NOx and soot emissions are reduced by 38.5% and one order of magnitude, respectively, and the gross indicated thermal efficiency (ITEg) is increased by 8.66%; at medium speed, by optimizing the injection strategy, the NOx and soot emissions are reduced by 59.3% and 70.4%, respectively, and the ITEg is increased slightly by 0.33%; at high speed, by optimizing the injection strategy, the soot emission is decreased significantly, the NOx emissions and the ITEg are increased slightly. It was found that with the increase of speed, the effect of multiple injection strategy on the ITEg and emissions is gradually increased, and the optimization effect of multiple injection strategy is more obvious than that of low speed.