Piston Bowl Research Articles

Co-optimization of piston bowl and injector for light-duty GCI engine using CFD and ML

In this study, the piston bowl geometry and injector design of a light-duty GCI engine were co-optimized using computational fluid dynamics (CFD) and advanced machine learning (ML) techniques to maximize the capability of a GCI technology. This study was performed at low- (6 bar), mid- (11 bar) and high-load (22 bar) indicated mean effective pressure (IMEP) conditions. The 3-D CFD setup was first validated against experimental data. Then, the injector and the piston bowl were simultaneously co-optimized. In total, 13 (ten piston- and three injector-related) design parameters were considered. At each load condition, 128 DoE cases were generated, and the features and performance of the top three designs were analyzed. The best DoE solution was selected by defining weighted merit values to provide one best design across all load conditions. The simulated dataset was used for further optimization using advanced ML techniques. It was found that a flatter design with low center height, wide and shallow bowl, and the low lip was preferable in the low- and high-loads. At the low-load partially premixed compression ignition (PPCI) mode, spray targeting the upper lip and divided into the bowl and squish zones for enhanced mixing is preferred. At the high-load mixing-controlled diffusion combustion mode, where injection occurs near the top dead center (TDC) and diffusion burn is the dominant combustion mode, targeting the lower lip is favorable. At the mid-load with a high premixed ratio, the combustion was close to homogeneous charge compression ignition (HCCI), and the piston bowl design had limited effect. Regarding the optimum injector parameters, larger number nozzles with smaller diameters were favorable at low-load to control partially premixed charge. At high-load, larger and fewer number nozzles are recommended. Lastly, the optimum ML design provided similar performance at mid-load but a 3.8–4.5 % reduction in fuel consumption compared to the baseline cases at low- and high-load conditions.

Effects of Piston Bowl Geometries On Diesel and Gasoline Dual-Fuel Combustion under Low Load Conditions

Effects of Piston Bowl Geometries On Diesel and Gasoline Dual-Fuel Combustion under Low Load Conditions

Optical and computational investigations of the effect of Spray-Swirl interactions on autoignition and soot formation in a compression ignition engine fuelled by Diesel, dieseline and diesohol

Diesel engine injection strategy plays a crucial role in fuel–air mixing and consequent soot formation, requiring optimisation. Fuel properties affect the combustion characteristics of the engine significantly. In this study, the fundamental mechanisms of pilot-main injection interactions and the effects of fuel properties have been investigated using a combined approach of optical diagnostics in an optical engine and computational fluid dynamics (CFD) tools. A single-cylinder optical research engine (SCORE) with a cylindrical piston bowl was used for the optical engine investigations. Simulations were carried out using a re-entrant piston geometry model. Reynolds-Averaged Navier-Stokes (RANS) based Re-Normalization Group (RNG) k-ε model was adopted and solved using CONVERGE CFD solver. SAGE detailed chemistry solver was used for the calculations of combustion kinetics. The adaptive mesh refinement (AMR) strategy was used for improved grid resolution. The investigation results highlighted a striking difference between the combustion mechanisms of the pilot injection and the main injection. The pilot-main injection interactions became crucial for igniting the main fuel spray. The swirl intensity was dominant in the pilot-main injection interactions and the combustion initiation. The impinging spray jet and swirl interactions improved the radial mixing and reduced the soot in the up-swirl direction. Dieseline (a blend of diesel and gasoline) and diesohol (a blend of diesel and alcohol) resulted in lower soot formation than baseline diesel. This study demonstrated that in-cylinder swirl and oxygen concentration could be optimised to simultaneously reduce oxides of nitrogen (NOx) and soot emissions using oxygenated fuels.

Development of an Oxy-Fuel Combustion System in a Compression-Ignition Engine for Ultra-Low Emissions Powerplants Using CFD and Evolutionary Algorithms

This study uses an optimization approach for developing a combustion system in a compression–ignition engine that is able to operate under oxy-fuel conditions, and produces mainly CO2 and H2O as exhaust gases. This is achieved because the combustion concept uses pure oxygen as an oxidizer, instead of air, avoiding the presence of nitrogen. The O2 for the combustion system can be obtained by using a mixed ionic–electronic conducting membrane (MIEC), which separates the oxygen from the air onboard. The optimization method employed maximizes the energy conversion of the system, reducing pollutant emissions (CxHy, particulate matter, and carbon monoxides) to levels near zero. The methodology follows a novel approach that couples computational fluid dynamics (CFD) and particle swarm optimization (PSO) algorithms to optimize the complete combustion system in terms of engine performance and pollutant generation. The study involves the evaluation of several inputs that govern the combustion system design in order to fulfill the thermo-mechanical constraints. The parameters analyzed are the piston bowl geometry, fuel injector characteristics, air motion, and engine settings variables. Results evince the relevance of the optimization procedure, achieving very low levels of gaseous pollutants (CxHy and CO) in the optimum configuration. The emissions of CO were reduced by more than 10% while maintaining the maximum in-cylinder pressure within the limit imposed for the engine. However, indicated efficiency levels are compromised if they are compared with an equivalent condition operating under conventional diesel combustion.

Computational Investigation on the Performance Increase of a Small Industrial Diesel Engine Regarding the Effects of Compression Ratio, Piston Bowl Shape and Injection Strategy

This paper describes the simulative approach to calibrate an already extremely highly turbocharged industrial diesel engine for higher low-speed torque. The engine, which is already operating at its cylinder-pressure maximum, is to achieve close to 30 bar effective mean pressure through suitable calibration between the compression ratio, piston-bowl shape and injection strategy. The basic idea of the study is to lower the compression ratio for even higher injection masses and boost pressures, with the resulting disadvantages in the area of emissions and fuel consumption being partially compensated for by optimizations in the areas of piston shape and injection strategy. The simulations primarily involve the use of the 3D CFD software Converge CFD for in-cylinder calibration and a fully predictive 1D full-engine model in GT Suite. The simulations are based on a two-stage turbocharged 1950 cc four-cylinder industrial diesel engine, which is used for validation of the initial simulation. With the maximum increase in fuel mass and boost pressure, the effective mean pressure could be increased up to 28 bar, while specific consumption increased only slightly. Depending on the geometry, NOx or CO and UHC emissions could be reduced.

Implementation of various bowl designs in an HPDI natural gas engine focused on performance and pollutant emissions

The air-fuel mixture preparation in pilot spray-ignited natural gas engines is primarily dominated by piston bowl profiles and fuel injection strategy. Piston bowl geometry is regarded as the crucial point in controlling engine pollutant emissions. In the present work, the SAGE combustion model was applied coupled with a general reaction kinetic mechanism. The engine model was validated with experimental data achieved from a Cummins ISX 400 engine, and good agreement between predicted and measured in-cylinder pressure and heat release rate was obtained. The influence of various piston bowl designs, including Mexican-hat geometry, double-lip geometry, bow geometry, and toroidal geometry, on the combustion process, engine performance, and pollutant emissions of a high-pressure direct-injection natural gas engine have been studied and analyzed numerically. The present study confirms the benefit of the piston bowl design as a beneficial tool to enhance the performance and pollutant emissions of the pilot diesel-ignited natural gas engine. Results showed that different chamber shapes slightly influence the combustion initiation, and the difference in in-cylinder pressure presents noticeable as the combustion continues. A higher turbulent kinetic energy improves the flow movement and facilitates the mixture formation in the cylinder. However, the combustion behavior is unwished caused by the improper injection angle of natural gas. Increasing the recess depth of combustion chambers reduces NOx formations at the price of sacrificing fuel economy. For the bow combustion chamber design, the NOx emission declined by 31.1%, while the indicated specific fuel consumption increased by 5.5% compared with the original engine. Although the indicated mean effective pressure and specific fuel consumption of the optimal double-lip geometry almost remain the same, NOx emissions can be reduced by 16.7% compared with the base design.

Numerical study of different shape design of piston bowl for diesel engine combustion in a light duty single-cylinder engine

Diesel engine is the prime mover on land transportation industry and used in a variety of power generation applications due to their higher fuel efficiency. However, the engine research community faces a major hurdle rigorous restriction introduced in the Glob to reduce pollutant emissions from internal combustion engines. Different piston bowl shape designs allows more precise mixing before combustion to enhance in the optimization using computational calculations to reduce emissions. The investigation was to reduce the NOx and PM emissions using combustion simulation comparing with each piston of a single-cylinder engine at a CR of 24, 4-stroke, and water-cooled Engine. The four piston bowl shapes of DSEVL2 BMW M47T, Shallow Hesselman, Lombardini 15LD350, and DOOSANP158FE were analyzed by the Diesel-RK combustion simulation. After successful validating; the simulation model shows that the peak cylinder pressure of Piston-2 is 131bar and the peak cylinder pressure of Piston-4 is 113bar. The Maximum Cylinder Temperature of the Piston-2 is 2048.2k, and the lowest value of Cylinder Temperature of the Piston-4 is 1680.9k the cylinder temperature of Piston-2 is 18% higher than Cylinder Temperature of Piston-4. The simulation result indicates that the temperature is within the acceptable limit in between 1400-2000k except for the piston temperature of 2048.2k. The PHRR of the Piston-3 is 0.082 with great variation in between maximum and minimum due to the presence of pre-and post-injection, the HRR-P4 is 0.035 J/°CA with the single injections. The HRR of the Piston-3 is the highest while HRR of the Piston-4 lowest with 39%. The NOx in the exhaust gas is 25.62 in the NOx piston-1; 16 in NOx of Piston-2, 18.2 in NOx-P3, and NOx-P4 is 12.74 g/kWh respectively. The NOx of the NOx-P2 is lower than first and second piston due to the lower fuel fraction of NWF dilution outer the sleeve, low fuel fraction in core of the free spray, low fuel fraction in fronts of the free spray, low fuel fraction in the core of the fuel free spray. The Particulate Matter emission in PM-P1 is 0.35, and PM-P2 is 0.43 ​g/kWh which is higher than all the other. Although there is a substantial decrease in PM, a penalty in NOx is observed for PM-P1 but PM of the P2 is higher after the peak result of emission.

Investigation of piston bowl geometry, injection timing, and EGR mass fraction to improve the performance of ISM 370 diesel engine

In addition to the high price of clean fuels such as hydrogen and bio-propane, redesigning a diesel engine for clean fuels can be a costly task. It seems an affordable option is to improve the baseline engine specifications by slight changes in the injection strategy or piston bowl shape. In this paper, the emission and combustion characteristics of the ISM 370 heavy-duty diesel engine were numerically investigated by evaluating three distinct piston bowls (P1, P2, and P3), different injection timings, and an exhaust gas recirculation (EGR) system. After that, the outcomes were compared with previous works related to the use of clean fuels in the ISM 370 engine. The simulation was performed at 1200 rpm engine speed and full load state. The rate of heat released and the mean in-cylinder pressure results were compared with experimental data and an appropriate accord was obtained. The results showed that the best injection timing considering a balanced state between the emission and combustion characteristics was determined 2 deg before the top dead center (BTDC). The same carbon dioxide (CO2) mass fraction was predicted for all considered piston bowls at almost the exhaust valve opened. P2 had better thermal efficiency and internal power by around 12% and the same nitrogen monoxide (NO) emissions as well as lesser soot emission by 10.5% compared to P1. A more complete combustion reaction was detected for the engine equipped with P2 led to reducing the CO mass fraction by 20% compared to P1. In addition, a 10% EGR mass fraction reduced the NO by 37% and increased the CO2 by 6.4%. It was found that the use of P2 had better peak pressure compared to the use of methanol fuel by 20.9% and was competitive with dimethyl ether fuel at almost equal peak pressure and 30% lesser soot emission.

Numerical Assessment on the Influence of Engine Calibration Parameters on Innovative Piston Bowls Designed for Light-Duty Diesel Engines

The optimization of the piston bowl design has been shown to have a great potential for air–fuel mixing improvement, leading to significant fuel consumption and pollutant emissions reductions for diesel engines. With this aim, a conventional re-entrant bowl for a 1.6 L light-duty diesel engine was compared with two innovative piston designs: a stepped-lip bowl and a radial-bumps bowl. The potential benefits of these innovative bowls were assessed through 3D-CFD simulations, featuring a calibrated spray model and detailed chemistry. To analyse the impact of these innovative designs, two different engine operating conditions were scrutinized, corresponding to the rated power and a partial load, respectively. Under the rated power engine operating condition, a start of injection sensitivity was then carried out to assess the optimal spray–wall interaction. Results highlighted that, thanks to optimal injection phasing, faster mixing-controlled combustion could be reached with both the innovative designs. Moreover, the requirements in terms of swirl were also investigated, and a higher swirl ratio was found to be necessary to improve the mixing process, especially for the radial-bumps design. Finally, at part-load operating conditions, different exhaust gas recirculation (EGR) rates were analysed for two injection pressure levels. The stepped-lip and radial-bumps bowls highlighted reduced indicated specific fuel consumption (ISFC) and soot emissions values over different rail pressure levels, guaranteeing NOx control thanks to the higher EGR tolerance compared with the re-entrant bowl. The results suggested the great potential of the investigated innovative bowls for improving efficiency and reducing emissions, thus paving the way for further possible optimization through the combination of these designs.

RETRACTED: Exploration over combined impacts of modified piston bowl geometry and tert-butyl hydroquinone additive-included biodiesel/diesel blend on diesel engine behaviors

Nowadays, the use of biodiesel for diesel engines has been attracting researchers aiming to improve engine characteristics although the engine performance could be decreased while utilizing biodiesel. In this aspect, optimizing the piston bowl geometry is one of the useful approaches to enhance the efficiency of the biodiesel-powered diesel engine. In this study, the standard piston of an existing diesel engine was modified into two different combustion bowls, namely Symmetrical Stepped Curved-V (SSCV) and Symmetrical Spline-V (SSV), to evaluate the CI engine performance powered with mixtures of sesame-originated biodiesel, diesel fuel, and tert-butyl hydroquinone (TBHQ) additive through two-stage experiment. In the first phase, experiments were carried out on two modified piston bowls powered by diesel and S20 (20% sesame biodiesel + 80% diesel fuel). Resultantly, SSV piston revealed superior engine characteristics to SSCV piston and standard piston due to enhanced air–fuel mixing and more complete combustion of SSV piston-based engine. Indeed, SSV piston operation exhibited an 8.68% of increased brake thermal efficiency (BTE), 6.54% of curtailed brake-specific fuel consumption (BSFC), 4.76% of lowered carbon monoxide (CO), 4.84% of decreased unburnt hydrocarbon (HC), and 2.22% of lowered smoke opacity but with increased nitrogen oxide (NOx) by 14.14% in comparison to diesel. In the 2nd phase, to control the NOx emission effectively, a TBHQ additive was added to the S20 sample at different proportions (500 mg and 1000 mg) to analyze the test engine behaviors with modified piston shapes. As a result, S20 + 500 mg TBHQ at 100% load improved BTE by 5.79% and reduced BSFC by 4.36% in the case of SSV piston. Moreover, it curtailed emissions of CO, HC, NOx, and smoke opacity by 13.33%, 15.49%, 12.09%, and 9.44%, respectively, when equated with diesel. Overall, S20 + 500 mg TBHQ could be thought of as a possible alternative fuel on SSV piston as it resulted in superior performance and emission characteristics in the existing standard engine. The current study's findings could pave the way for the development of diesel engines with modified piston geometry that is more efficiently compatible with biodiesel blends and additives.

Analyzing the Combustion Behavior of different Ceramic Porous Media in the Piston Bowl of a Diesel Engine

Analyzing the Combustion Behavior of different Ceramic Porous Media in the Piston Bowl of a Diesel Engine

The effect of fuel injection pressure and combustion chamber configuration on fuel spray, combustion and emissions of a direct injection diesel engine: a CFD approach

In the present study, the combined impacts of injection pressure and piston bowl configuration on fuel–air mixing, combustion and emissions of a diesel engine have been analysed numerically. An investigation has been conducted at four different fuel injection pressures and three different combustion chamber configurations for the same bowl volume to have a constant compression ratio. The in-cylinder transient flow and subsequent turbulent combustion process have been modelled using computational fluid dynamics code AVL FIRE. The predicted results indicate that the brake-specific fuel consumption (BSFC) is decreased by 4.19%, 8.96% and 11.92% for HCC, 5.77%, 9.92% and 13.68% for CCC, and 5.13%, 9.19% and 12.92% for TRCC when engine operates with an injection pressure of 215, 230 and 250 bar, respectively compared to 200 bar at full load operation. Soot emissions for CCC and TRCC engines are decreased by 23.4% and 33.43%, respectively, compared to baseline HCC engines.

A Simulation Study on the Transient Behavior of a Gasoline Direct Injection Engine under Cold Start Conditions

<div class="section abstract"><div class="htmlview paragraph">The cold start process is critical to control the emissions in a gasoline direct injection (GDI) engine. However, the optimization is very challenging due to the transient behavior of the engine cold start. A series of engine simulations using CONVERGE CFD™ were carried out to show the detailed process in the very first firing event of a cold start. The engine operating parameters used in the simulations, such as the transient engine speed and the fuel rail pressure (FRP), came from companion experiments. The cylinder pressure traces from the simulations were compared with experiments to help validate the simulation model. The effects of variation of the transient parameters on in-cylinder mixture distribution and combustion are presented, including the effects of the rapidly changing engine speed, the slowly vaporized fuel due to the cold walls, and the low FRP during the first firing cycle of a 4-cylinder engine. Comparison was also made with non-transient steady state operation. It was shown that the injection-induced tumble ratio in the cylinder varied for different engine speed cases, resulting in a better fuel distribution in the low engine speed case. A relatively high turbulence level during the combustion process was seen in the transient engine speed case that led to strengthened combustion. The fuel tracking from the simulation indicated that about 30% of the fuel remained unreacted at a very late crank angle, in which 8% was in the gas phase and 22% in the liquid phase as wall films. As the FRP increased, the fuel droplets became smaller, and more fuel vaporized before hitting the piston. But the splash and rebound fuel fraction off the piston bowl was even less, resulting in a lower overall gas-phase equivalence ratio in the first firing event for the high FRP case. On the other hand, the fuel distribution was more homogeneous under the high FRP condition due to the high injection velocities. There should be an optimal FRP value, but it was difficult to discern since the peak pressures in different FRP cases were similar and turbulence levels varied in a non-monotonic way, as well, which would lead to cycle-to-cycle variations in the real engine.</div></div>

Prediction of Suitable Piston Bowl Chamber for 2,5-Dimethyl Furan (Dmf) Direct Injection on Ci Engine

Prediction of Suitable Piston Bowl Chamber for 2,5-Dimethyl Furan (Dmf) Direct Injection on Ci Engine

Enhancing the NOx and soot emissions reduction benefits of a low compression ratio light duty diesel engine by optimization of piston bowl design

In the present work, the benefits of the low compression ratio (LCR) concept on simultaneous reduction of oxides of nitrogen (NOx) and soot emissions could be further enhanced by optimizing the piston bowl design using a 3-dimensional computational fluid dynamics (CFD) tool. A single-cylinder, direct-injection diesel engine was used for the present investigations. In its mass-production version, the engine had a compression ratio (CR) of 18:1 that was considered as the stock CR from which the LCR variants were derived. The initial and unoptimized piston design of the LCR variant with CR of 14:1 was arrived at using an offset bowl geometry from the stock compression ratio variant, and the corresponding benefits were quantified. The NO (nitric oxide) and soot reduction potential of the LCR variant could be further enhanced by adopting a step-by-step optimization procedure focused on the principal parameters of the bowl viz., piston bowl diameter, centre pip depth, reentrancy and bottom profile. Based on numerical investigations, an optimal piston bowl design could be arrived at that can significantly enhance the benefits of the LCR approach on NO and soot emissions. At a reference operating point of 2000 rpm and 40 N-m, by adopting the optimized profile, the NO reduction potential of the LCR variant could be improved from 10.3% to 40.2%. Moreover, the soot reduction potential could also be improved from 79.1% to 84.2%. The benefits of the optimized bowl design were also confirmed by engine dynamometer measurements across the engine’s operating speed range. Thus, it can be concluded that optimization of the piston bowl design specific to the LCR variant could enhance the NOx and soot emission benefits that can help diesel engines comply with the stringent emission regulations.

Spark ignition timing effects on a converted diesel engine using natural gas: A numerical study

Since it is not expected to switch to fully electric and/or fuel cell vehicles in the near future, the search for alternative fuels for systems using internal combustion engines has accelerated. At the forefront of these studies is the use of natural gas instead of diesel fuel in on-road, off-road vehicles, or stationary power generation plants. Diesel engines with their special combustion chamber (i.e. bowl in-piston) can be converted to run entirely on natural gas by installing a natural gas fuel injector on the intake manifold and a spark plug instead of a diesel fuel injector. In this study, in-cylinder combustion characteristics, performance, and emission values for different Spark Ignition Time (SIT) of natural gas usage at 2300 rpm and full load in a tractor engine with a compression ratio of 17.5:1 were investigated numerically using ANSYS Forte three-dimensional analysis program. G-equation combustion model, RANS k-ε turbulence model, and methane chemical kinetic mechanism representing natural gas consisting of 29 species and 171 equations (a reduced mechanism) were used. First SIT was accepted as a 719.5 Crank Angle Degree (CAD) which is diesel injection start time. As a result, due to the special shape of the combustion chamber of diesel engines (re-entrant bowl in-piston), it was seen that the flame was faster and thicker in the bowl, while it was slower and thinner in the squish zone. With the advanced of SIT, the in-cylinder pressure ratio increased. By taking SIT too advanced (i.e. 690, 695, and 700 CAD SIT), more than one peak formation was observed in the heat release graph depending on the combustion characteristic. With the effect of both natural gas use and SIT, it was observed that HC and CO formations were almost not seen, while NOX formation remains above a certain level.

An Experimental and Computational Investigation of Tailor-Developed Combustion and Air-Handling System Concepts in a Heavy-Duty Gasoline Compression Ignition Engine

This study investigates using tailor-developed combustion and air-handling system concepts to achieve high-efficiency, clean gasoline compression ignition (GCI) combustion, aimed at addressing a future heavy-duty ultralow NOx standard of 0.027 g/kWh at the vehicle tailpipe and the tightening CO2 limits around the world by combining GCI with a cost-effective engine aftertreatment system. The development activities were conducted based on a 15 L heavy-duty diesel engine. By taking an analysis-led design approach, a first-generation (Gen1) GCI engine concept was developed and tested, encompassing tailor-designed piston bowl geometry, fuel spray pattern, and swirl motion paired with a customized, fixed-geometry, two-stage turbocharging system and a high-pressure EGR loop with two-stage cooling. Across four key steady-state operating points, the Gen1 GCI concept demonstrated 85–95% lower smoke and 2–3% better diesel-equivalent gross indicated fuel consumption compared to the diesel baseline at 1 g/kWh engine-out NOx. By upgrading to a Gen2 air-handling concept that was composed of a prototype, single-stage, variable-geometry turbocharger and a less restrictive EGR loop, 1D system-level analysis predicted that the pumping mean effective pressure was reduced by 43–54% and the diesel-equivalent brake-specific fuel consumption was improved by 2–4%, thereby demonstrating the performance enhancement potential of refining the air-handling system.

CFD-guided optimization of the injector and injection parameters for light-duty GCI engine

In this study, computational fluid dynamics (CFD) and machine learning (ML) were used to investigate the effects of and optimize the injector design parameters for light-duty gasoline compression ignition (GCI) engine. This study was performed at part- (6 bar) and high-load (22 bar) indicated mean effective pressure (IMEP) conditions. The effects of number of nozzles (nNoz), spray angle (SA) and plume angle (PA) while maintaining total nozzle area (TNA) and start of injection (SOI) were first investigated. The increased nNoz and PA enhanced fuel/air mixing, especially in the bowl region, by even spray distribution at part-load condition, but the effects are negligible at high-load mixing-driven combustion due to high in-cylinder temperature and pressure at the time of main injection. On the other hand, SA had significant effect on the air utilization and hence engine performance and emissions at both part- and high-load conditions. The best design from this manual parametric study produced a balanced air utilization between piston bowl and squish region resulting from the fuel spray targeting the upper lip of the bowl. The second phase of this study focused on the optimization of the injector and injection parameters including nNoz, SA, nozzle hole diameters (dNoz) and SOI using design of experiment (DoE) approach. 32 DoE cases were generated and best design was selected at each load point. It was found that the SA and SOI are the most influential injection parameters. Specifically, two optimum SOI regimes at part-load conditions have been identified. These are a) early injection resulting in retarded combustion and low pressure rise rate and b) late injection yielding high combustion efficiency and low hydrocarbon emission. At high-load condition, SOI right before top dead center (TDC) is most preferable and early injection should be avoided to minimize pressure rise rate. The narrow SA (90 degrees (deg) in this study) as well as wide SA were found to produce optimum performance. Subsequently, ML algorithm was used to further optimize the injector and injection parameters. As a result of this optimization study, 10.7% reduction of fuel consumption at part-load and 7.5% reduction at high-load were achieved.

An experimental investigation on performance of converted CNG engine by varying piston bowl geometry: A case study

ABSTRACT Using natural gas as an alternative fuel will be reduced exhaust emissions and dependence on petroleum. The practical solution for Vietnam’s conditions is to convert diesel engines into natural gas engines. Understanding the effect of piston geometry on the performance of converted CNG engines helps domestic manufacturers come up to spark ignition natural gas engines with high performance and low emission. In this work, three different types of combustion chamber were made from milling piston head and varying thickness of cylinder head gasket. The experiment results showed that torque and power of ε = 11.5 were more significant than ε = 12.5. During experiment processes, the stable operation state of the converted engine with ε = 12.5 was challenging to control, and the noise levels were intense. The results of mass fraction burned were presented the effect of squish gap on performance was more substantial than that of the squish area. It can be concluded that for modifying the original diesel engines to run on CNG fuel, the maximum compression ratio should be set to 12.5 and must be redesigned accordingly to use the natural results. Implications: This manuscript shows the new technology to convert traditional engines into engines fueled by renewable energy. It contributes to reducing the fossil fuel crisis and environmental emissions.

Effect of novel fuel vaporiser technology on engine characteristics of partially premixed charge compression ignition (PCCI) engine with toroidal combustion chamber

Partially pre-mixed charge compression ignition (PCCI) and combustion chamber geometry are significant factors that improve the potential of compression ignition engines and the sustainable effect on the environment. The considerable decline in brake thermal efficiency in PCCI has always been a point of halt in the progress of this technology. The toroidal combustion chamber (TCC) has proved its effectiveness in enhancing the performance characteristics of a conventional engine. The primary aim of this experiment is to improve the engine characteristics for PCCI mode when it operates with a TCC piston bowl geometry and compare the behavior with the conventional direct injection (DI) technology. A novel fuel vaporiser technology is developed and retrofitted in a single-cylinder DI diesel engine in this work. A comparative study on the effect of combustion chamber geometry (hemispherical and toroidal) on engine characteristics was performed and the engine setup was operated in conventional and PCCI mode. The PCCI mode was tested by using fuel vapour induction in intake manifold via the fuel vaporizer unit. Liquid diesel fuel was heated up to its vaporization temperature and sent to the intake manifold, wherein fresh air was mixed with vaporized fuel, forming an external mixture that enters the combustion chamber. The different vapour induction rates (2 ml/min and 4 ml/min) were used to understand the changes in combustion behavior. Compared to conventional, the PCCI mode proved its worth in limiting NOx emission with 7 g/kW-h reduction at 4 ml/min vapour induction rate with HCC at moderate engine load. Diesel vapour induction rate of 2 ml/min along with TCC piston resulted in improved engine characteristics with a marginal decrement in BTE by 1.2%, significant decrease of NOx by 5 g/kW-h at moderate engine load. Moreover, at full engine load, the PCCI anomaly is observed as the rate of pressure rise (ROPR) surpasses the conventional by 2 bar/deg for 2 ml/min induction rate with HCC, thereby favouring conditions for engine knock. Overall, the brake thermal efficiency limitations in PCCI can be countered by TCC piston bowl geometry; however, the PCCI usage is limited to a specific vapour flow rate and engine load range.