RCCI Engine Research Articles

Impacts of Using Egr and Different Di-Fuels on Rcci Engine Emissions, Performance, and Combustion Characteristics

Impacts of Using Egr and Different Di-Fuels on Rcci Engine Emissions, Performance, and Combustion Characteristics

Data-Based In-Cylinder Pressure Model including Cyclic Variations of an RCCI Engine

For advanced pre-mixed combustion concepts, Cylinder Pressure-Based Control is a key concept for robust operation. It also opens the possibility for on-line heat release shaping. For cost and time efficient development of these controllers, fast control-oriented combustion models that predict average in-cylinder pressure traces have been proposed. However, they are not able to capture cyclic variations. In this study, a data-based modelling procedure is proposed to predict the in-cylinder pressure trace and cyclic variation during the combustion cycle. The inputs to the model are the in-cylinder conditions at intake valve closing and the fuelling settings. The proposed model is based on experimental data, Principal Component Analysis and Gaussian Process Regression. This new data-driven approach is applied to model the combustion behaviour of a Reactivity Controlled Compression Ignition engine running on Diesel and E85. The resulting model has a root-square-mean-error of average behaviour and cyclic variance of 0.8° and 0.2°2 in CA50, 0.1bar and 0.03 bar2 in Gross Indicated Mean Effective Pressure, and 0.1% and 0.001 %2 in the Gross Indicated Efficiency, respectively.

Fuel flexibility study of various fuels with charge dilution and high compression ratio for medium-load operating RCCI engine

This study examines the dual-fuel (RCCI) combustion mode using gasoline, ethanol, methanol, and compressed natural gas (CNG) as low reactive fuels (LRF) and diesel, neem biodiesel as high reactive fuel (HRF). The fresh and diluted charge (with hot EGR) combustion is compared at a high compression ratio for medium load operation. For obtaining the near-zero NOx-soot emissions and improved performance, the feasibility of different reactivity and renewable fuels are studied. The use of methanol and gasoline as LRF and diesel as HRF with charge dilution shows improved fuel-air-mixing, reactivity stratification, and thermal efficiency. The use of ethanol and gasoline as LRF and biodiesel as HRF with charge dilution shows near-zero NOx emissions while soot emissions are above the minimum acceptable range. The use of CNG as LRF and diesel as HRF with charge dilution shows minimum thermal efficiency and high fuel consumption. The reduced combustion rate and increased premixed combustion with charge dilution result in lower combustion temperatures and pressure rise rates for G + D and M + D.

A simulation of ethanol substitution rate and EGR effect on combustion and emissions from a high-loaded diesel/ethanol dual-fuel engine

In this study, the combined effects of the ESR (ethanol substitution rate) and the EGR on combustion and exhaust emissions from high-loaded RCCI engine were investigated numerically to improve the engine with high ESR. RCCI experimental data were obtained from a study performed on a 2.771-liter diesel engine fueled with diesel/ethanol fuels. The simulation was performed via Converge Computational Fluid Dynamics (CFD) code, and numerical results were validated with the experimental data. The parameters such as in-cylinder pressure, in-cylinder gas temperature, heat release rate, CA10, CA50, indicated thermal efficiency, maximum pressure rise rate, NOx, soot, HC and CO emissions were investigated at 2000 rpm engine speed and high engine load (80% full load). The results show that the in-cylinder pressure, the in-cylinder gas temperature, and the maximum pressure rise rate significantly increases due to the increase of ESR. The maximum pressure rise rate was obtained for ESR40 as 1.24 MPa/CAD. Knocking tendency were determined for various ESR, but it increases rapidly with increasing of ESR. The highest soot and CO in cylinder decreases, and the highest NOx and HC in cylinder increases due to ethanol addition. EGR has a significant effect on combustion and emission from high-loaded RCCI engine when keeping ESR constant as ESR40. In-cylinder pressure, maximum pressure rise rate and in-cylinder gas temperature decreases due to EGR addition, while at the same time, indicated thermal efficiency also decreases. The maximum pressure rise rate was obtained for EGR25 as 0.59 MPa/CAD, and the maximum indicated thermal efficiency is 42%. The highest NOx in cylinder decreases, and the highest soot, HC, and CO in cylinder increases due to EGR addition.

Impacts of diesel injection timing and syngas fuel composition in a heavy-duty RCCI engine

This research aimed to assess the impacts of Diesel Direct Injection Timing (DDIT) [−6 to −16 Crank Angle (CA) After Top Dead Center (ATDC) with 2 CA steps], syngas to diesel energy ratio [0 (Pure Diesel Combustion (PDC)), 20% (DSC20), and 40% (DSC40) of total fuel energy per cycle], and syngas fuel composition [H2 to CO volumetric ratio of 75%-25% (R = 3), 50%-50% (R = 1), and 25%-75% (R = 0.33)] in a heavy-duty RCCI engine. The numerical findings revealed that increasing syngas energy ratio to 40% at DDIT of −10 CA ATDC and R of 1 is an effective strategy to reduce NOx, PM, HC, and CO2 emissions by about 12%, 88%. 82%, and 40.36% versus the baseline PDC case, respectively. Regarding engine performance, by advancing the DDIT from −6 to −16 CA ATDC under all engine operating conditions, Gross Indicated Efficiency (GIE) enhanced by about 2.76%, 1.93%, and 1.34%, respectively, in comparison to the baseline PDC, DSC20, and DSC40 cases. Besides, at DSC40 conditions, exhaust gas loss was improved by nearly 4.74% but combustion loss and heat transfer loss were increased by 2% and 3.4%, respectively, compared to the baseline PDC operating mode. Also, increasing syngas energy ratio to 40%, R to 3, and diesel injection at −16 CA ATDC led to about 15.9% and 41% reduction of HC and CO emissions, respectively, compared to the baseline DSC40 case. In addition, under diesel-syngas combustion conditions, regions near cylinder walls and the center of the piston bowl are the main sources of unburnt syngas emission.

Impact of the hybrid electric architecture on the performance and emissions of a delivery truck with a dual-fuel RCCI engine

Reactivity controlled compression ignition combustion showed great advantages in terms of NOx and soot emissions reduction, leading to virtually zero emissions. However, the average brake thermal efficiency of this concept is like that found with conventional diesel operation. The powertrain electrification using electric motors and battery packages appears as a potential solution to reduce the CO2 emissions. For this reason, several solutions for the powertrain electrification can be found currently in the market as the parallel, series and power split powertrain architectures. The aim of this work is to evaluate the hybrid architecture impact on the fuel consumption and emissions of a delivery truck (Volvo-FL) intended for urban and urban–rural applications. The truck equipped with a reactivity-controlled compression ignition diesel-gasoline engine is evaluated and compared against the conventional diesel case. In addition, to evaluate the impact of new e-fuels on the well-to-wheel CO2 emissions, a synthetic gasoline coming from carbon capture and green electricity is evaluated. The results show that hybridization allows reducing the tank-to-wheel CO2 emissions above 15% with the parallel hybrid set-up. The series and power split architectures show CO2 benefits of 12% with respect to the baseline diesel non-hybrid case. Using synthetic gasoline as low reactivity fuel allows to achieve a 50% well-to-wheel CO2 reduction in the P2 and 70% well-to-wheel CO2 reduction for the series and power split cases due to the higher average gasoline fraction used in the driving cycle.

Multi-Objective Optimization of a RCCI Engine Fueled with Diesel Fuel and Natural Gas Enriched with Hydrogen

The present study seeks to conduct the optimization of a heavy-duty diesel engine under RCCI combustion fueled with diesel fuel and natural gas enriched with hydrogen. Since NOx emission is one of the most important concerns of using hydrogen as a sole fuel or an additive to hydrocarbon fuels in an internal combustion engine like RCCI engine, thus, the main goals of this study are to overcome the NOx challenge, enhance the RCCI combustion characteristics, and reduce the fuel consumption when the conventional hydrocarbon fuels are substituted with hydrogen. In order to conduct the optimization process, an artificial neural network coupled with the design of the experiment concept was employed to identify the RCCI combustion mathematical model and provide the required population for two optimization algorithms, namely genetic algorithm, and particle swarm optimization algorithm. The results from the optimization process show that by advancing the diesel fuel injection along with the appropriate amount of exhaust gas recirculation and nitrogen as diluents, the level of EURO VI for NOx can be met. However, the losses in the RCCI engine output power is less than 5% meanwhile the gross indicated efficiency is over 50% and the reduction in hydrocarbon fuels consumption is about 40%.

Numerical Investigation of an RCCI Engine Fueled with Natural Gas/Dimethyl-Ether in Various Injection Strategies

Reactivity control compression ignition engines illustrated suitable abilities in emission reduction beside high thermal efficiency. In this research, nine various direct fuel injection strategies were studied numerically: three cases with single injection strategy and six cases with split injection and different start of injection (SOI). In all simulated cases, equivalence ratio kept constant (i.e., 0.3). Among various strategies, single injection showed higher IMEP as a factor of efficiency with about 5.39 bar that occurred at SOI = 60 before top dead center (bTDC), while lower efficiency was observed for split injection case with 50%-50% injections of fuel in each injection stage. Start of combustion (SOC), burn duration and CA50 as factors for combustion characteristics were affected with SOI changes. In single SOI strategies, more advanced injection caused more advanced SOC where there was about 1.3 CAD advancing from 40 to 80 bTDC injection. Spilt SOI showed more advanced SOC, which, also more advanced, was allocated to 50%-50% split injection strategy. There was also the same trend in CA50 changes during change in SOI. Burn duration variations were insignificant and all of them approximately close to 4.5 CAD. According to the emissions researched in this study (Nitrogen Oxides (NOx), monoxide carbon (CO) and unburned hydro carbons (UHC)), all of these pollutants are below euro six diesel standards. Contours of emissions show that there were appropriate SOI for each case study, which were 45 degree bTDC for single strategy, 48 degree bTDC for 80%-20% mass injection and 70 degree bTDC for 50%-50% cases.

Numerical Study on the Effect of Diesel Injection Parameters on Combustion and Emission Characteristics in RCCI Engine

Numerical Study on the Effect of Diesel Injection Parameters on Combustion and Emission Characteristics in RCCI Engine

Input-output Data-driven Modeling and MIMO Predictive Control of an RCCI Engine Combustion

This study presents a data-driven identification method based on Kernelized Canonical Correlation Analysis (KCCA) approach to generate a state-space Linear Parameter-Varying (LPV) dynamic representation for the RCCI engine combustion. An LPV model is used to estimate RCCI combustion phasing (CA50) and indicated mean effective pressure (IMEP) based on fuel injection timing and quantity. The proposed data-driven method does not require prior knowledge of the plant model states and adjusts number of states to increase the accuracy of the identified state-space model. The results demonstrate that the proposed data-driven KCCA-LPV approach provides a dependable technique to establish a fast and reasonably accurate RCCI combustion model. The established model is then incorporated in a design of a constrained MIMO Model Predictive Controller (MPC) to track desired crank angle for 50% fuel burnt and IMEP at various engine conditions. The controller performance results demonstrate that the established data-driven constrained MPC combustion controller can follow desired CA50 and IMEP with less than 1.5 CAD and 37 kPa error, respectively.

Application of Genetic Algorithm to Optimize the Variables Affecting Combustion Characteristics of RCCI Engine Over Wide Load Range

Application of Genetic Algorithm to Optimize the Variables Affecting Combustion Characteristics of RCCI Engine Over Wide Load Range

An experimental investigation on single cylinder RCCI engine fuelled with diesel/petrol

The objective of this research paper is to investigate the combustion and emission characteristics by developing a clean combustion phenomenon, with an improvement in efficiency in an internal combustion engine. Most of the commercial transportation is through the CI (Compressed Ignition) engine and these engines creates relatively high emission in the form of Oxides of Nitrogen (NOx) and Particulate Matter (PM). With an increase in fuel prices and emission norms globally, thus demands a clean combustion from IC engine. In order to overcome the above stated problems associated, a step ahead is taken by the use of Reactivity Controlled Combustion Ignition concept (RCCI). As per the experiment conducted RCCI is capable of achieving high thermal efficiency and low NOx and PM emissions. In this experiment a light-duty single-cylinder diesel engine is modified to run an RCCI mode using diesel and petrol as a fuel. The reduction and increase in efficiency and emissions has been obtained by carrying out a slight modification in the intake named as Port Fuel Injector (PFI) for using the Low Reactive Fuel (LRF). The engine speed is kept constant by varying the Start of Injection (SOI). The PFI injector is being run by using an Arduino setup, where the LRF injection will be monitored and controlled by the Arduino. Load is applied using an eddy current dynamometer. The experiment is run with two combinations fuels such diesel and diesel-petrol.

Heat release rate shaping for optimal gross indicated efficiency in a heavy-duty RCCI engine fueled with E85 and diesel

The understanding of reactivity controlled compression ignition has greatly improved throughout recent years. While its potential for extremely low NOx and soot emissions has been confirmed numerous times, there remain some ambiguities about the ability of this concept to attain very high efficiency. Now that increasingly stringent CO2 regulations come into effect worldwide, it is particularly the efficiency aspect that is of great interest. This work combines a heat release study with regression analysis to identify the influence of combustion parameters on the heat release rate shape and the relation it has with efficiency and associated loss channels. A metric called burn ratio is introduced as the ratio of burn durations after and before the centroid of combustion. The burn ratio is found to correlate well to fuel reactivity stratification, and generally characterizes the heat release rate shape. Further regression analysis revealed a synergy between fuel reactivity stratification and the intake manifold pressure. Heavily boosted conditions and relatively early diesel injections result in a notable suppression of heat transfer losses, although some stratification remains necessary to find a balance between heat loss and combustion efficiency. Specifically, this balance is essential to achieve high gross indicated efficiency, for which the burn ratio is finally used to optimize fuel injection.

Effect of reformed biogas as a low reactivity fuel on performance and emissions of a RCCI engine with reformed biogas/diesel dual-fuel combustion

Biogas can be used as a less expensive continuance renewable fuel in internal combustion engines. However, variety in raw materials and process of biogas production results in different components and percentages of various elements, including methane. These differences make it difficult to control the combustion, effectively, in internal combustion engines. In this research, under cleaning and reforming process, biogas components were fixed. Then the effect of reformed biogas (R.BG) was investigated, numerically, on the combustion behavior, performance and emissions characteristics of a RCCI engine. A 3D-computational modeling has been performed to validate a single-cylinder compression ignition engine in conventional diesel and dual-fuel operations at 9 bar IMEP, 1300 rpm. Then, the combustion model of the RCCI engine was simulated by replacing diesel fuel with 20%, 40% and 60% of R.BG as a low reactivity fuel while remaining constant input total fuel energy per cycle. The results demonstrated that when the R.BG substitution ratio increases with a constant equivalence ratio of 0.43, the mean combustion temperature decreases to 1354 K, 1312 K, 1292 K which are about 3.5%, 6.6%, 7.9% lower than the conventional diesel combustion, respectively. The maximum in-cylinder pressure increases up to 22.63%. Instead, it results in 2.3%, 7.9%, and 14.5% engine power output losses, respectively. Also, the NOx emission, against CO, is decreased by 50%. Soot and UHC emissions were found to be slightly decreased while was used R.BG more than 40%.

Influence of fuel injection pressure and injection timing on nanoparticle emission in light-duty gasoline/diesel RCCI engine

This work investigates the influence of fuel injection events on the nanoparticle emission characteristics of light-duty gasoline-diesel RCCI engine. The formation of nanoparticle emissions strongly depends on fuel injection events. The present study experimentally investigates the influence of diesel injection pressure, injection timing, and port-injected gasoline mass on the nanoparticles emitted from the gasoline-diesel RCCI engine. For this purpose, the engine is tested at different engine speeds and a fixed load of 1.5 bar BMEP without exhaust gas recirculation. The particle-size and number distribution (PSD) and total particle number (total PN) concentration are measured using a differential mobility spectrometer. The results depict that at higher diesel injection pressure (IP) operation, the peak of the NMP increases while the AMP peak decreases for neat diesel operation as well as RCCI engine. Nucleation, as well as accumulation mode particles, increases with advanced diesel injection timing in RCCI combustion. An increase in port fuel injected mass also leads to an increase in the total particle concentration and total unburned hydrocarbon (THC) emissions.

Influence of direct injection timing and mass of port injected gasoline on unregulated and nano-particle emissions from RCCI engine

The study aims to experimentally characterize the nano-particle emissions and un-regulated (i.e., saturated and unsaturated hydrocarbons and formaldehyde emissions) emissions. Present study experimentally investigates the effect of high reactivity fuel injection timings and port-injected-fuel mass on nano-particle and unregulated emissions in the gasoline-diesel RCCI engine. Additionally, empirical correlations are developed using experimental data for the estimation of particle emission characteristics. An automotive single cylinder diesel engine is modified for an in-cylinder blending of port-injection of gasoline during suction stroke and direct-injection of diesel fuel during the compression stroke. The experiments are performed on a modified engine for various diesel injection timings and port-injected gasoline mass using development electronic control unit (ECU). Nano-particle and unregulated emissions are measured using electrical mobility based particle-sizer and Fourier-transform infrared spectroscopy analyser respectively. Combustion analysis is performed by in-cylinder pressure measurement. The experimental data of nano-particle and combustion characteristics are used for the development of empirical correlation using a multivariable regression technique for determining the particle number characteristics. The parameters - premixing ratio, start of injection of diesel, and a novel parameter defined as premixed fraction of total heat release are used for the development of empirical correlations and found a good correlation for estimating the nano-particle emission characteristics. Results also indicate that advanced direct injection timing and increase in the port-injected gasoline mass leads to higher particle emissions as well as saturated, unsaturated hydrocarbon and formaldehyde emissions.

Hydrogen energy share enhancement in a heavy duty diesel engine under RCCI combustion fueled with natural gas and diesel oil

The aim of this study is to enhance hydrogen energy share in a RCCI engine. The engine under consideration is fueled with diesel oil and natural gas enriched with hydrogen or syngas and is set to operate at 9.4 bar gross indicated mean effective pressure (Mid- Load). The syngas used in this study consists of hydrogen and carbon monoxide which are mixed together on a volumetric ratio of 80:20. A fixed amount of diesel oil is injected per cycle into the combustion chamber of the RCCI engine. Based on two different strategies, hydrogen or syngas mixed with exhaust gas recirculation are admitted gradually along with natural gas while ensuring that always the low temperature combustion concept is fulfilled. The RCCI engine operation is simulated through commercial software coupled with chemical kinetics solver. The simulation results show that without any engine diesel knock occurrence, by adding hydrogen to natural gas, the share of hydrogen energy could be increased up to 40.43% while the engine power output is reduced only by about 1%. Also, syngas addition to natural gas causes that the share of hydrogen energy could be increased up to 27.05% while improves the engine power more than 4%. At the same time, by considering two mentioned strategies, the overall hydrocarbon fuel consumption per cycle can be reduced by up to 46.60% and 33.86%, respectively. Moreover, having the gross indicated efficiency of well over 50% and significant reduction in the engine emissions compared to RCCI combustion fueled solely with natural gas and diesel oil are achievable.

Energy and exergy analysis of the dual-fuel RCCI engine by ozone-assisted combustion of a lean mixture

An experimental investigation was carried out to explore the effects of ozone on the energy and exergy fractions in a single-cylinder light-duty Ricardo E/6 engine. This study undertook CNG that epitomizes the premixed low-reactivity fuel and diesel as the high-reactivity fuel. Measurements were taken for ozone additions of 0, 50, 100, 200, 250, 300, and 400 ppm, constant CNG-to-diesel energy ratio of 4, and the lambda number of 3.5. The results suggest that the increased seeded ozone augments energy and exergy efficiency. The growth rate at 0.26%, 1.85%, 3.00%, and 5.63% levels were derived in energy efficiencies through 100, 200, 300, and 400 ppm introduced ozone, respectively, compared to no ozone addition, while the corresponding exergy efficiency increments were found to be 0.09%, 0.78%, 2.82%, and 5.36%, respectively. The in-cylinder combustion improvement in the applied fuels with the ozone addition triggered the higher thermal efficiency of the engine, while denoting the higher rate of exhaust and cooling losses in all cases. The resultant experimental outcome also unveiled a significant load extension of RCCI engine operation using ozone-based additive. Furthermore, it was observed that the ozone usage holds promise for the emissions reduction of CO and HC although at the expense of the increased NOx emissions.

Experimental investigation on the effects of multiple injections and EGR on n-pentanol-biodiesel fuelled RCCI engine.

Stringent emissions and fuel economy regulations have necessitated the need to boost the research interest in oxygenated alternate fuels such as n-pentanol and biodiesel under low-temperature combustion strategies due to their renewability and cleaner combustion characteristics. Being higher alcohol, n-pentanol has desirable fuel properties that are comparable to mineral diesel, which enable easy blending of these fuels. In the present study, the Reactivity Controlled Compression Ignition (RCCI) operation in a modified single-cylinder diesel engine operating at the rated speed of 1500 rpm and 50% load was investigated with non-edible karanja oil-based biodiesel–diesel blend with B20 as high reactivity fuel (HRF) and n-pentanol as low reactivity fuel (LRF). The intake temperature was maintained constant at 40 °C, intake pressure was ambient and the LRF was varied from 20% to 50%. The engine's performance with split injection was investigated by sweeping starts of injection (SOI) crank angles and these were optimized at 47°, 27°, and 17° bTDC for SOI 1, SOI 2, and SOI 3 respectively at 400 bar injection pressure. The engine performance characteristics were investigated by introducing 10% to 30% cooled exhaust gas recirculation (EGR) and was optimized at 25%, based on the stable operation of the engine with acceptable ringing intensity and emission. The combined effect of EGR, multiple injections (three), and varying PFI mass fractions was investigated and compared with a single injection of HRF. A simultaneous reduction of 76% smoke and 91.5% NOX emission was obtained with a marginal increase in CO and HC emissions.

Research on Combustion and Emissions of RCCI Engine

Research on Combustion and Emissions of RCCI Engine