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In the present research work an optimisation stuy of the Exhaust gas recirculation (EGR) rate for MIS adopted POME fueled CRDI Diesel Engine fitted with TRCC was carried out. The engine was operated with injection parameters such as 900 bar, 7 holes and 10° BTDC which have been optimized for better performance and lower emissions from our previous study. The experiments were carried out by employing an RSM-based D-optimal design, and the relationship between input and output was determined using an ANOVA. Using RSM-ANOVA, mathematical models were built for each result, and the predicted and actual outcomes were compared. With an R2 value greater than 99.34%, the prediction models were discovered to have a strong prediction efficiency. The desirability approach-based optimisation was used to determine the ideal engine operating parameters. EGR rate was varied from 0% to 20% and an MIS of 40 + 20+40 has been adopted for the engine. An EGR rate of 10% is optimized from the viewpoint of NOx reduction and penalty in power output which results in a decrease in brake thermal efficiency by 2.90%, peak pressure by 4.8%, heat release rate by 8.8% and oxides of nitrogen (NOx) by 1.35%. A drastic increase in emissions such as carbon monoxide by 5.8%, unburnt hydrocarbon by 13.3% and smoke by 20.6% was also observed. Both the ANN and RSM models correctly fit the experimental data, producing R2 values that ranged from 95.5% to 98.5%, respectively. The findings show that RSM and ANN are both highly accurate modelling approaches. Additionally, as compared to RSM, the ANN model's predictive accuracy was marginally better. This research could have a wide range of applications in CI engine-powered transportation systems.

• The fuel injection strategies of a 2021 HD diesel engine were investigated. • The SCR efficiency reported by ECU is consistent with NO x analyzer data. • The combustion phasing at high loads was optimized to increase thermal efficiency. • The combustion phasing at low loads was retarded to improve SCR efficiency. • The fuel injection strategy affects the dwell duration between injection pulses. Heavy-duty (HD) diesel vehicles exert significant environmental impact, especially in the case of nitrogen oxides (NOx) and soot, despite representing a relatively small portion of the overall vehicle population. Modern HD diesel engines employ multi-pulse fuel injection strategies to optimize the combustion process to achieve a better compromise between fuel economy and tail-pipe emissions, especially NOx. As such, improving our understanding of the combustion process and the characteristics of modern HD diesel engines operating under various fuel injection strategies is imperative. This research investigates the fuel injection strategy, combustion process and exhaust emissions of a Navistar 2021 MY HD E39 diesel engine. The impact of engine speed, load and injection strategy on engine performance, the combustion process, engine-out NOx and SCR efficiency is experimentally investigated. The relationships between these parameters provide a better understanding of the influence of the injection strategies on the combustion process, fuel economy and exhaust emissions. Fuel was injected into the cylinder with up to four injection pulses, including up to two pilot injections followed by one main injection pulse and one post injection pulse. The heat release process is featured with three peaks. The first and second peaks are associated with the combustion of fuel injected during the pilot and main fuel injection pulses, respectively. However, the third peak observed at medium to high load is associated with the combustion of fuel injected during post injection process. In comparison to its predecessors, the third peak observed at low load was associated with the diffusion combustion of fuel injected during the main injection pulse. The combustion process, which occurred at medium to high loads, was optimized to achieve high engine thermal efficiency, with the peak cylinder pressure held within the allowed limit while the exhaust temperature was high to achieve acceptable SCR efficiency. In comparison, the combustion phasing at low load was dramatically retarded to increase the exhaust temperature with the aim of maintaining SCR efficiency. The strategies for achieving the ideal compromise between fuel economy and tailpipe emissions are discussed and presented herein. [ABSTRACT FROM AUTHOR]

Peak combustion pressures (PCP) are increased in heavy-duty diesel engines to obtain higher thermal efficiency. Fuel injection strategy has been a major measure to improve the combustion and emissions of diesel engines. But most existing work of multi-injection strategies was not limited by PCP or was conducted under lower PCP (∼15 MPa). In this study, an experimental study is conducted to further improve the understanding of injection strategies on engine performance under a relative higher peak combustion pressure at 20 MPa. The four tested injection strategies are single main injection, pilot-main injection, main-post injection, and pilot-main-post injection. The effects of PCP on brake thermal efficiency (BTE) and other engine performances are also investigated under the same NOx emissions conditions. Results indicate that more advanced injection timing can obtain higher BTE, while the injection pressure has less effects on BTE as it is higher than 120 MPa. For double-injection, the smaller interval on pilot-main or main-post and the less pilot or post mass improves BTE and emissions. The PCPs are linearly correlated to the BTE, peak average temperature, and peak pressure rise rate (PRR), and the increment of BTE, peak average temperature, and peak PRR are about 0.3%, 30 K, and 0.1 MPa/CA for every 1 MPa increase in PCP, respectively. This also means that the improvement on BTE by the increase of PCP imparts greater thermal and mechanical loads on engine materials and components. At 20 MPa PCP, based on the optimized injection strategies, the BTE of all four strategies is about 42.8%, and the peak PRR of all four strategies is about 0.8 MPa/CA. At a given NOx emission of 17.4 g/kWh and approximate 20 MPa PCP, all four injection strategies have minor effects on distribution of fuel energy and emissions. Therefore, it can be concluded that the injection strategies have fewer effects on BTE and emissions at the higher peak combustion pressure of 20 MPa; the main purpose of injection strategies is to reduce the peak PRR or reach the potentially required temperature for aftertreatment devices.

As legislations set very stringent environmental and fuel economy standards, researchers have pushed into a continuous development in all areas of the diesel engine. The recent evolution of the injection technologies has permitted to modify the fuel-delivery strategies. From what was a single pulse per injection event, modern systems allow to inject up to eight different times precisely per combustion cycle. In such sense, experimental results of the rate of injection and momentum flux could be useful for validation and improvement of computational models. Moreover, accurately quantifying the injected mass per pulse in a fuel–gas interface can provide data with more realistic engine-like conditions. To this end, this research presents measurements of the rate of injection and momentum flux for two simple multiple injection strategies: a pilot-main and a main-post. Boundary conditions included two rail and discharge pressures, two different pilot/post quantities and four dwell times. A new approach was employed to estimate the mass allocation with the momentum flux data, and results were compared to the rate of injection traces to verify the distribution calculated. On the results, signals for each pulse were successfully decoupled using its rising and falling edge. The shot-to-shot variability of the pilot/post injection was highly dependent on its transitory characteristics, and on the dwell time for post injections due to internal pressure waves. The injected mass per pulse was successfully measured as well in the momentum flux test rig, and the energizing time changed slightly to account for the different operation interfaces. Signals from both measurement campaigns showed a remarkable agreement when compared, ascertain the possibility of measuring the injected mass, and its allocation for multiple injection strategies, in the momentum flux test rig. [ABSTRACT FROM AUTHOR]

An experimental study was performed to explore the influence of dwell time on the hydraulic interactions between injection events using pilot injection strategy, split injection strategy, post injection strategy and a solenoid diesel injector. To do so, a sweep of dwell time from 0.55 up to 2 ms using all multiple injection strategies and levels of rail pressure, of 80, 100 and 120 MPa, and single level of back pressure, of 5 MPa, was performed. The hydraulic interactions between injection events were characterized through the second injection hydraulic delay and second injection mass in an injection discharge curve indicator equipped with all the components required for its operation and control. In order to define the operating conditions of the multiple injection strategies, to ensure the same injected fuel mass in all cases, the characteristic curves of injection rate for the solenoid diesel injector studied were obtained. The second injection hydraulic delay increases with dwell time values in the range of 0.55–0.9 ms for all multiple injection strategies and levels of rail pressure tested. Conversely, the second injection hydraulic delay decreases with dwell time values higher than 0.9 ms. Moreover, the second hydraulic delay depends mainly on the dwell time and not on the injected fuel mass during the first injection event. The second injection mass increases with dwell values less than 0.6 ms. By contrast, the second injection mass is not significantly affected by that of the first injection at a dwell time higher than 0.6 ms.

• Additive manufacturing combustion techniques as a new frontier for high-efficiency and low emission ICE. • Optimized multiple injection strategies and radial lips piston bowl to achieve ultra-low soot combustion. • Improved mixture formation and reduced harmful and CO 2 emission. • Radial lips effective on particle number reduction. Internal combustion engines have been the most effective solution as the main mover for mobility. Despite the recent European regulations targeting zero tailpipe CO 2 emissions for new passenger cars and light vans from 2035 onwards, the upcoming emission regulations still require further technology and fuel developments in the transport sectors. In recent years, studies on internal combustion engines have been increasingly shifting from performance and refinement through advanced fuel injection and air charging technologies to ultra-low emissions and efficiency. Particular attention has also been paid to carbon–neutral fuels. The problem merits further investigation since all are key factors for the powertrain competitiveness in the electrified automotive future, as the pollutants and the CO 2 emissions will soon approach the Euro 7 regulation and the Fit to 55 standards, respectively. To this aim, the combustion system design is a crucial part of the internal combustion engine development in the view of exploiting renewable fuel characteristics. This study seeks to assess the effectiveness of a steel piston, realized through a specific design for additive manufacturing technologies, enabling an innovative bowl geometry. It features a highly re-entrant sharp-step and radial lips bowl profile enabling spray separation and radial mixing zone concept. A single-cylinder compression ignition engine has been employed to demonstrate the effectiveness of the innovative bowl shape to meet the challenging future ultra-low emission targets. The results confirm the additive manufacturing technology as a possible solution for innovative highly-stressed steel piston designs. The new bowl shape design, combined with optimised spray targeting and injection strategies, allows outstanding soot reductions, up to 80%, and ultra-low NOx emission levels compared to the conventional combustion system. Gains in fuel economy are also observed. Further emissions advantages are expected with renewable fuel applications. [ABSTRACT FROM AUTHOR]

In this paper, a combustion control algorithm is presented that, in combination with rate shaping, allows closed-loop control of a cylinder pressure trace. Given this system, it is possible to control the behaviour of the entire combustion process. The paper starts with an explanation of the control algorithm that was developed based on iterative learning control. Consequently, the so-called α-process, which comprises a constant pressure rise, is presented as an example of the additional degrees of freedom gained. Based on the exact analysis of experimental results and combustion simulations, the effects of a peak pressure limitation on the emission behaviour of a single-cylinder engine powered by an α-process are analysed in detail. The capability of the developed control system to isolate certain effects of ideal combustion processes gives a wide range of possible further investigations. However, for practical applications, the use of injection rate shaping is coupled with high hardware costs. Therefore, an additional concept study regarding the possible realisation of the developed control system with a conventional common-rail injector is presented. In this study, it is shown that injectors without rate-shaping capabilities are able to solve the feedback control problem through multiple injection strategies. [ABSTRACT FROM AUTHOR]

Abstract: The experimental analysis was conducted for a better understanding of the combustion stability and reduction of exhaust emission in low compression ratio (CR) engine. The combustion stability was analyzed in terms of combustion pressure, the rate of heat release (ROHR), the indicated mean effective pressure (IMEP), and coefficient of variation of indicated mean effective pressure (COVIMEP), and formation of exhaust emissions such as CO, HC, NO X , and soot was measured and compared in the low compression ratio single cylinder CI engine. It was revealed that maximum value of combustion pressure (P max) in two pilot injections was increased to almost the same level of single injection combustion although its maximum rate of heat release (ROHR) was decreased to 47.2% compared to single injection combustion. It was also observed that two pilot injections improves combustion efficiency, and these injection strategies operate engine more stably in low compression ratio engine, based on the results of increased IMEP (2.1%) and decreased COVIMEP (5.7%). Moreover, in multiple injection combustion, more CO formation and less HC emission were observed during combustion process, and remarkable simultaneous reduction of NO X up to 58.7% and soot up to 25% can be achieved in low compression ratio engine. [Copyright &y& Elsevier]

High-pressure common-rail injection systems nowadays allow a very high degree of flexibility in the timing and quantity control of multiple injections, which can be used to obtain significant reductions in engine noise and emissions. The aim of this study is to develop a better understanding of the relationship between injection strategies and the combustion and emission formation process. Some multiple injection strategies (pilot-pilot-main and pilot-main-after) have therefore been analysed to highlight their influence on the soot, NO[sub x], combustion noise and b.s.f.c. (brake specific fuel consumption) of a passenger car direct injection diesel engine prototype. Finally, the main combustion characteristics were determined, for each operating condition, on the basis of a heat release analysis and a correlation was attempted between the combustion parameters and emissions, noise and b.s.f.c. [ABSTRACT FROM AUTHOR]

An experimental study was performed to explore the influence of dwell time on the hydraulic interactions between injection events using pilot injection strategy, split injection strategy, post injection strategy and a solenoid diesel injector. To do so, a sweep of dwell time from 0.55 up to 2 ms using all multiple injection strategies and levels of rail pressure, of 80, 100 and 120 MPa, and single level of back pressure, of 5 MPa, was performed. The hydraulic interactions between injection events were characterized through the second injection hydraulic delay and second injection mass in an injection discharge curve indicator equipped with all the components required for its operation and control. In order to define the operating conditions of the multiple injection strategies, to ensure the same injected fuel mass in all cases, the characteristic curves of injection rate for the solenoid diesel injector studied were obtained. The second injection hydraulic delay increases with dwell time values in the range of 0.55–0.9 ms for all multiple injection strategies and levels of rail pressure tested. Conversely, the second injection hydraulic delay decreases with dwell time values higher than 0.9 ms. Moreover, the second hydraulic delay depends mainly on the dwell time and not on the injected fuel mass during the first injection event. The second injection mass increases with dwell values less than 0.6 ms. By contrast, the second injection mass is not significantly affected by that of the first injection at a dwell time higher than 0.6 ms. [ABSTRACT FROM AUTHOR]