Multi-cylinder Engine Research Articles

Exploring the synergies of dynamic fuel management and propulsion electrification

Active fuel management is a technology that allows a multi-cylinder internal combustion engine to shut off a bank of cylinders to reduce engine power output as needed to match driving conditions and driver power demand. This variation in engine power is taken a step further with a technology known as dynamic fuel management, wherein individual cylinders of a multi-cylinder engine may be turned off as needed. This approach allows a finer resolution in engine power variation. Dynamic fuel management allows an engine to operate with lower pumping losses, thereby maximising the potential for capturing regenerative braking energy. In this paper, the synergies of such an engine equipped with dynamic fuel management, coupled to an electrified driveline incorporating a 48V P1 architecture, are investigated. Detailed MATLAB models are developed to understand the influence of system parameters as well as to identify the optimal engine/motor torque arbitration required for maximum fuel economy. It is shown that the combination of dynamic fuel management and P1 hybridisation can provide a substantial fuel economy improvement.

Exploring the synergies of dynamic fuel management and propulsion electrification

Active fuel management is a technology that allows a multi-cylinder internal combustion engine to shut off a bank of cylinders to reduce engine power output as needed to match driving conditions and driver power demand. This variation in engine power is taken a step further with a technology known as dynamic fuel management, wherein individual cylinders of a multi-cylinder engine may be turned off as needed. This approach allows a finer resolution in engine power variation. Dynamic fuel management allows an engine to operate with lower pumping losses, thereby maximising the potential for capturing regenerative braking energy. In this paper, the synergies of such an engine equipped with dynamic fuel management, coupled to an electrified driveline incorporating a 48V P1 architecture, are investigated. Detailed MATLAB models are developed to understand the influence of system parameters as well as to identify the optimal engine/motor torque arbitration required for maximum fuel economy. It is shown that the combination of dynamic fuel management and P1 hybridisation can provide a substantial fuel economy improvement.

Research on the Characteristics of Operating Non-Uniformity of a High-Pressure Common-Rail Diesel Engine Based on Crankshaft Segment Signals

This paper studies the operating uniformity of a high-pressure common-rail diesel engine based on crankshaft segment signals. Engine nonuniformity or unevenness refers to the crankshaft torque fluctuation caused by cylinder-to-cylinder differences, which are caused by misfiring or difference in fuel supply or air supply. The experiments were conducted on a diesel engine of the YN30CR model. Based on the relationships among the cylinder pressure, the instantaneous crankshaft angular speed, and the crankshaft segment signal, it is found that the crankshaft segment signal can be used to characterize the operating nonuniformity of the diesel engine. Based on the Fast Fourier Transformation (FFT) from the angular domain to the frequency domain in analyzing the fluctuation patterns of the crankshaft segment signals at different operating conditions, the nonuniformity information was extracted. In order to further reveal the relationship between the fluctuation phenomena of the crankshaft segment signal and the cause of the fluctuation, the torque acting on the crankshaft of the multi-cylinder diesel engine was studied to quantify the operating nonuniformity of the diesel engine. The results show that the crankshaft segment signal can reflect the uniformity of the engine torque very well in both phase and amplitude, and the degree of nonuniformity of the engine torque can be reflected by the amplitudes of the low-order non-dominant harmonics of the crankshaft segment signal below the firing frequency. The crankshaft segment signal is very consistent with the variation pattern of the engine torque.

Multi-Type Diesel Engines Operating Condition Recognition Method Based on Stacked Auto-Encoder and Feature Transfer Learning

It is of great significance to diagnose the fault of diesel engine, which is widely used in many important fields as key power equipment. The accuracy of fault diagnosis can be effectively improved by obtaining the complex and changeable operating conditions, which can result in the change of monitoring signals. This study proposes a variable operating conditions recognition method based on stacked auto-encoder (SAE) and feature transfer learning. In this method, the vibration in the firing angle domain collected from multi-sensor signals is reconstructed. Then a feature set sensitive to working conditions is extracted from the recombinant signals by a well-constructed stack auto-encoder. According to the dataset test, the softmax classifier can effectively get a high recognition accuracy. Considering that the fault may affect the condition identification, the misfire fault that has a great influence on firing angle domain signals is used to test the robustness of the proposed method. Besides, to enable a well-trained test rig with a large amount of data to be effectively applied to another unit that lacks data, the BDA transfer learning method is used to map the operating conditions of two different engines to the same feature space. The results of experiments conducted on two large power marine multi-cylinder diesel engines show that BDA is capable of transferring the sensitive features of operating conditions.

Alcohol Fuels for Spark-Ignition Engines: Performance, Efficiency, and Emission Effects at Mid to High Blend Rates for Ternary Mixtures

This paper follows on from an earlier publication on high-blend-rate binary gasoline-alcohol mixtures and reports results for some equivalent ternary fuels from several investigation streams. In the present work, new findings are presented for high-load operation in a dedicated boosted multi-cylinder engine test facility, for operation in modified production engines, for knock performance in a single-cylinder test engine, and for exhaust particulate emissions at part load using both the prototype multi-cylinder engine and a separate single-cylinder engine. The wide variety of test engines employed have several differences, including their fuel delivery strategies. This range of engine specifications is considered beneficial with regard to the “drop-in fuel” conjecture, since the results presented here bear out the contention, already established in the literature, that when specified according to the known ternary blending rules, such fuels fundamentally perform identically to their binary equivalents in terms of engine performance, and outperform standard gasolines in terms of efficiency. However, in the present work, some differences in particulate emissions performance in direct-injection engines have been found at light load for the tested fuels, with a slight increase in particulate number observed with higher methanol contents than lower. A hypothesis is developed to explain this result but in general it was found that these fuels do not significantly affect PN emissions from such engines. As a result, this investigation supplies further evidence that renewable fuels can be introduced simply into the existing vehicle fleet, with the inherent backwards compatibility that this brings too.

Сравнительный анализ выбросов одно- и многоцилиндрового двигателя

In the research and test of diesel engine, because the performance test of multi cylinder engine with different configuration needs to be replaced, and there is a certain risk in the first test, while the single cylinder engine is more suitable for the research and test of different configurations because of its simple structure and convenient replacement of components. Therefore, by comparing the differences of combustion state between single cylinder engine and multi cylinder engine with the same configuration, the change law of performance characteristics of single cylinder engine and multi cylinder engine under different working conditions is confirmed. By analyzing the difference of emission performance of single cylinder engine with different configuration, the emission performance of multi cylinder engine under different configuration is predicted. The research in this paper has important significance for further research and test of diesel engine.

Methanol and OMEx as fuel candidates to fulfill the potential EURO VII emissions regulation under dual-mode dual-fuel combustion

Recent investigations show that there are different combustion strategies that promise to achieve higher efficiencies in internal combustion engines. Advanced combustion modes such as reactivity controlled compression ignition (RCCI) and dual-mode dual-fuel (DMDF) have proven to be able to achieve low NOx and soot engine-out emissions while being able to operate over the complete engine map. On another front, intensive research has been done in the fuels field. Oxygenated fuels, like oxymethylene dimethyl ethers (OMEx) and methanol, are of special interest because of their potential to reduce the soot emissions, while allowing to adjust parameters, such as EGR, to higher values to also reduce NOx emissions and avoid other problems like excessive in-cylinder peaks of pressure. In this research, the effects of diesel-methanol and OMEx-gasoline fuels were studied on a dual-mode dual-fuel (DFDM) multi-cylinder engine at 1800 rpm for various loads (25, 50, 80 and 100%). To do so, a dedicated calibration to optimize the brake thermal efficiency while trying to maintain NOx and soot emissions under EURO VI limitations was applied. Then, the combustion characteristics, performance and emissions results are compared to a base diesel-gasoline case. Boundary conditions (intake pressure, temperature and air mass) for each fuel combination where similar, with the exception of the premixed energy ratio, which was on average 20% lower for diesel-methanol. Each fuel combination was, weighted against each other by means of an merit function, where the fuel combination with the lowest value has the closest approximation to ideal BSFCeq, BSNOx, BSSoot, BSCO and BSHC targets. Results show that diesel-methanol presents no significant differences with respect to diesel-gasoline in terms of equivalent BSFCeq and NOx, while the substitution of diesel by OMEx in the dual-mode dual-fuel combustion has the potential of, although penalizing HC and CO emissions, not only achieving the EURO VI NOx (0.4 g/kWh) limits but also the future potential EURO VII (0.2 g/kWh) as well because of a negligible soot production that allows using EGR levels of up to 50%.

Experimental and Simulation Analysis of Natural Gas-Diesel Combustion in Dual-Fuel Engines

The recent strict emission regulations and the necessity to reduce the global CO2 levels have promoted research studies over alternative fuel combustion technologies. Dual fuel technology is a fascinating approach as it could combine the benefits of two fuels to achieve high thermal efficiency with lower harmful emissions. Natural gas burns cleaner than other fossil fuels and its recent low price makes it an attractive fuel as a near-term solution. The utilization of natural gas with diesel in a compression ignition engine can result in high engine performance with lower CO2 emissions. However, at low engine loads, natural gas-diesel operation suffers from low combustion efficiency with high unburned hydrocarbon and carbon monoxide emissions. The present paper collates the work of experimental and simulation studies on natural gas-diesel dual fuel operation over three different engine set-ups. Two single-cylinder, with and without optical access, and a multi-cylinder engine were used to analyze the effects of varying diesel injection and air-path strategies on the combustion performance, with a focus on the low load operation zone. The results showed that the injection timing, as well as intake charge dilution, can severely promote clean combustion at the low load zone. An early diesel injection can enhance the diesel-natural gas homogeneity within the cylinder and improve the combustion efficiency of the engine. On the other hand, high levels of exhaust gas recirculation (EGR) are mandatory to suppress NOx and further enhance the brake thermal efficiency of the engine.

Endoscopic high-speed particle image velocimetry (eHS-PIV) in a high tumble production engine

Major design features of high-tumble spark-ignition engines achieving over 40% brake thermal efficiency include a sub-square combustion chamber, less curved or more “straight” intake port shape and wider angle between the intake and exhaust valves, which are intended to enhance the turbulence at spark timing and thereby increasing the flame propagation speed. This new design requires a clear understanding of the in-cylinder flow field and its variation due to direct fuel injection into the cylinder. The present study reports a new endoscopic high-speed particle image velocimetry (eHS-PIV) technique implemented in a multi-cylinder high-tumble production engine, which can be used to acquire crucial flow field information in a timely manner with no significant resources required to develop a single-cylinder full optical engine. A laser beam at 35 kHz was inserted through a rigid endoscope (borescope) wherein a series of rod lenses producing a 60° diverging planar laser sheet to cover the pent-roof area. Hollow-glass spherical particles were supplied upstream of the throttle body. A camera borescope was installed to record particle movement at the same 35 kHz framing rate and the acquired movies of 100 cycles were post-processed using PIVLab. The feasibility tests performed in an available single-cylinder full optical engine indicated that the new eHS-PIV is applicable to direct-injection engines with both motoring flow fields and the injection-induced flow structure alteration is clearly visualised. The application of the eHS-PIV to a multi-cylinder production engine was also successful and achieved a finding of new flow structures unique to high-tumble engines and the significant enhancement effects of direct fuel injection on flow velocity and turbulence intensity. Graphic abstract

Resistance Heated Catalytic Converter (RHCC) with copper oxide catalyst for reducing HC/CO emission from automobile

Rigorous enforcement of emission norms requires a control over cold/cool start emissions on a present-day automobile with catalytic converter. After the car warms up, these converters are really capable in controlling HC and CO emissions. The catalyst isn’t efficient during warm-up or cool start period because of its low operating temperature. Emission reduction is actually possible by heating the catalyst and changing the substrate of the catalyst used in car. In this work, with the help of band type resistance heaters are used to heat the metal oxide catalyst placed in Resistance Heated Catalytic Converter (RHCC) which will help the conventional converter. It is attempted to study the emission from multi-cylinder SI automotive engine, by developing better catalysts. Form the experimental investigation, it’s observed that RHCC with copper oxide catalyst when utilized with the conventional catalytic converter (CCC), the CO and HC emissions are significantly reduced. It can be seen that in twelve seconds after cool start the value of CO% by volume is 4.3 and significant reduction of 0.7% of CO at 180 s is observed for RHCC-PC configuration with 90 lpm air supply for duration of forty seconds. It can be seen that in 120 s after cool start the value of HC in ppm is 315 in contrast with baseline readings. The maximum reduction is actually achieved when the RHCC with copper oxide catalyst and 90 lpm of air supply for forty seconds duration from the cool start of the engine.

Investigation of 2-butoxyethanol as biodiesel additive on fuel property and combustion characteristics of two neat biodiesels

Neat biodiesels are not preferred for use in the compression ignition (CI) engines due to their high viscosities and related operational difficulties. This study investigated the fuel properties and combustion characteristics when 2-butoxyethanol additive was mixed separately with waste cooking oil biodiesel (W100) and rapeseed oil biodiesel (R100). Compared to neat biodiesels, the viscosities (at 40 °C) of the W100 and R100 were reduced by 12.5% and 9.8% respectively, when they were blended separately with 15% 2-butoxyethanol. Four different samples such as W100, mixture of 85% W100 and 15% 2-Butoxyethanol (W85), R100, mixture of 85% R100 and 15% 2-Butoxyethanol (R85) were tested in a multi-cylinder CI engine. The thermal efficiency of the W85 fuel was higher than fossil diesel by approximately 3.7%. Total combustion duration of the biodiesel-additive blends were shorter than neat biodiesels and fossil diesel. Biodiesel-additive blends provided approximately 6% higher in-cylinder peak pressures. At full load, W85 fuel gave up to 5.4% reduced NOx emissions than neat biodiesel. The CO, HC and smoke emissions were decreased by up to 36%, 100% and 79% respectively. The study concluded that 2-butoxyethanol could effectively be used as biodiesel additive to improve fuel property; and to achieve better combustion and reduced pollution.

Emission Reduction Strategies for Small Single Cylinder Diesel Engine Using Valve Timing and Swirl Ratio

Small diesel engines are widely used for commercial vehicle and passenger car applications due to their higher torque requirements, fuel economy, and better thermal efficiency. These engines are exposed to different operating and environmental conditions and hence emissions from these engines are erratic. Strategies are required to enhance performance and reduce engine-out emissions considering environmental pollution and regulations. The main objective of this experimental study is to develop strategies for performance improvement and emission reduction for naturally aspirated engines, which can further be used for emission reduction of the multicylinder engine. Experimental work has been carried out on a single-cylinder naturally aspirated diesel engine to study the impact of engine operating parameters like valve timing, swirl ratio, and injection pressure on engine performance and emissions. Parameters considered for the study are: three intake valve opening timings, two fuel injection pump pressures, two-cylinder head swirls, and three start of injection timings. Results showed improvement in performance, lower exhaust gas temperature, and reduction of engine-out emission. Exhaust gas temperature was reduced by 5-18% with advanced valve opening and lower cylinder head swirl option. NOx emission was reduced by 5-50% at advanced intake valve opening (IVO) options with retarded start of injection (SOI) and lower swirl cylinder head. This has a penalty on CO and HC emissions since the availability of fresh air is less due to higher internal exhaust gas recirculation (EGR). Higher pressure fuel injection pump helps in improving engine torque with an adverse effect on engine-out NOx emission. As these engines are of low power capacity segment and are used in few countries, research on these engines is limited. All research work has been carried out in the field of intake valve closing timings, swirl ratio and injection timings; however, very limited research is available for the effect of intake valve opening timings due to practical limitations of the lower valve to piston clearance in diesel engines.

Journal Vol – 15 No -7, July 2020 Journal > Journal > Journal Vol – 15 No -7, July 2020 > Page 6 PERFORMANCE AND EMISSION CHARACTERISTICS OF GASOLINE-ETHANOL BLENDS ON PFI-SI ENGINE Authors: D.Vinay Kumar ,G.Samhita Priyadarsini,V.Jagadeesh Babu,Y.Sai Varun Teja, DOI NO: https://doi.org/10.26782/jmcms.2020.07.00051 admin July 26, 2020 Abstract: Alcohol based fuels can be produced from renewable energy sources and

Journal Vol – 15 No -7, July 2020 Journal > Journal > Journal Vol – 15 No -7, July 2020 > Page 6 PERFORMANCE AND EMISSION CHARACTERISTICS OF GASOLINE-ETHANOL BLENDS ON PFI-SI ENGINE Authors: D.Vinay Kumar ,G.Samhita Priyadarsini,V.Jagadeesh Babu,Y.Sai Varun Teja, DOI NO: https://doi.org/10.26782/jmcms.2020.07.00051 admin July 26, 2020 Abstract: Alcohol based fuels can be produced from renewable energy sources and

Experimental investigation on the characteristics and performance of homogeneous charge induced ignition(HCII) on a multi-cylinder heavy-duty engine

This paper is focused on the characteristics and performance of HCII in conditions close to practical engine operating. For this purpose, extensive experiments have been conducted on a modified six-cylinder heavy-duty diesel engine, with six-cylinder HCII, high pressure exhaust gas recirculation(EGR) loop and appropriate pressure rise rate. The experiments mainly include two aspects. Firstly, gasoline ratio(GR), EGR ratio and start of injection(SOI), are studied to summarize the combustion and emission characteristics of HCII. Secondly, European steady state cycle(ESC) test is conducted to evaluate HCII performance over the whole engine map.Results suggest that large GR is beneficial to effective thermal efficiency(ETE) or/and nitrogen oxide(NOx) and smoke emissions, however, it is limited by maximum pressure rise rate at low load and uncontrollable ignition time at high load. Similarly, the application of EGR can improve gasoline combustion and decrease NOx emission, while it cannot be too much because of decreased ETE at low load and uncontrollable ignition time at high load. Meanwhile, SOI can be advanced to 40 crank angle degree(CAD) before top dead center(BTDC) to achieve extremely low NOx and smoke emissions and relatively high ETE. However, this strategy can only be applied to B25 and C25 points. Finally, great success is achieved by HCII in ESC test. Just with diesel oxidation catalyst(DOC), the weighted specific emissions of NOx, particulate matter(PM), hydrocarbon(HC) and carbon monoxide(CO) can be 1.841 g/(kW·h), 0.024 g/(kW·h), 0.115 g/(kW·h) and 0.896 g/(kW·h) respectively.

Exploration of suitable injector configuration for dual-mode dual-fuel engine with diesel and OMEx as high reactivity fuels

Dual-mode dual-fuel (DMDF) combustion stands over other low temperature combustion strategies as it is able to operate over the entire engine map by transitioning between reactivity controlled compression ignition and diffusive combustion depending on the engine load. In combination with non-sooting e-fuels, it is able to achieve low NOx and soot levels even at high loads. Oxygenated fuels like poly-oxymethylene dimethyl ethers (OMEx) have been already proved to present an outstanding NOx-Soot trade-off improvement when used in combination with a DMDF combustion strategy. One drawback of OMEx is that, despite having a high reactivity, it has a low lower heating value, which requires considerably longer injection events compared to other traditional fuels in order to achieve the same engine power output. The long injections limit the flexibility of the injection strategy and result in extremely long combustion durations. A possible solution to this problem resides in moving towards injectors with higher flow rate capacities, but this may compromise the mixing and combustion processes. This work aims to shed some light on the implications of changing the engine hardware to overcome this limitation by testing a DMDF multi-cylinder engine using gasoline as the low-reactivity fuel and diesel or OMEx as the high reactivity fuels with injectors of different flow capacity. The results show that a concise analysis of the involved phenomenology of the combustion process allows to find out the trade-off between the engine-out emissions and the mixing capacity of the injection system while the engine performance is not significantly affected.

Experimental and computational study on the microwave energy based regeneration in diesel particulate filter for exhaust emission control

The uncontrolled combustion and early-life failure of the Diesel Particulate Filter substrate during fuel-based regeneration has raised the requirement for an alternate regeneration technique. The Latest emission norms have made it a mandatory requirement to retrofit the Diesel Particulate Filtration system in the exhaust line of CI engines to bring down the Particulate emissions. In this work, a novel technique through application of microwave energy has been developed for active regeneration of soot particles accumulated in the filter channel. Modelling of soot layer formation and microwave regeneration were carried out using CFD software (COMSOL MULTIPHYSICS). Performance and emission characteristics of multi-cylinder CI engine were evaluated after retrofitting the developed after-treatment system comprising of Diesel Oxidation Catalysis (DOC) and microwave regeneration based Diesel Particulate Filtration (DPF) systems. Soot accumulation rate and regeneration rate were experimentally investigated at different engine loads and magnetron (microwave radiation source) power levels. The experimental results showed that the developed after-treatment system has an average filtration efficiency of 90% for brake specific particle number emissions and 55% for hydrocarbon emissions. The regeneration rate was observed to be a maximum of 0.21 g/min at 50% power levels owing to the non-linear behaviour of magnetron. Energy consumption pattern of other regeneration techniques has been compared with the developed microwave regeneration system. The effect of soot accumulation and regeneration on the morphology, microstructure, chemical composition and particle size of DPF substrate were examined using characterization studies like Scanning Electron Microscopy – Energy Dispersive X-Ray Spectroscopy (SEM-EDS), Fourier Transform Infra-Red spectroscopy (FTIR), Particle Size Analysis (PSA) and microscopic imaging.

Experimental Analysis of Synergetic Effect of Part-Cooled Exhaust Gas Recirculation on Magnetic Field-Assisted Combustion of Liquefied Petroleum Gas

Magnetic field-assisted combustion has been under the focus of research for the last three decades around the globe. The effects of strong uniform and gradient magnetic fields on flame development, behaviour and propagation have been studied, and their applications have been experimented on Internal Combustion Engines. The present work investigates the synergetic effect of part-cooled EGR on the magnetic field-assisted combustion of liquefied petroleum gas in a multicylinder MPFI spark-ignited engine modified for neat LPG operation. Sintered neo-delta magnets with radial magnetization pattern of four different magnetic intensities (0G, 3200G, 4800G and 6400G) are fastened to the fuel line near to the gas injector with a non-magnetic stainless steel integument to prevent any loss of magnetic intensities during the operation. A portion of the exhaust gas is channelled to an intercooler and an optimum percentage of the partially cooled gases are inducted into the inlet manifold for combustion. The experimental study concludes that the optimum flow rate of part-cooled EGR acts synergistically with the applied magnetic fields to enhance the combustion characteristics of LPG emanating an improved fuel economy of 13.8% and brake thermal efficiency of 3.9%. The increased emission of oxides of Nitrogen which is the major setback of LPG combustion can be addressed through the combined effect of part-cooled EGR and magnetic field-assisted combustion. Moreover, the reduction in stability of combustion through the recirculation of exhaust can also be balanced by the applied magnetic field.

Performance of new and aged injectors with and without fuel additives in a light duty diesel engine

Two sets of diesel injectors are tested in combination with common fuel additives in a multi-cylinder light-duty diesel engine. One set consists of new injectors and the other is aged by over 100,000 km use in a vehicle. Four fuels are tested with these injector sets to investigate the impact of fuel additives on combustion and emission characteristics. The results show that the aged injectors consistently deliver larger quantities of fuel for a given injection strategy, leading to a higher power output and deviating emissions. This is hypothesized to be due to drift in the injector actuating characteristics. The fuels tested are a baseline diesel quality, and blends of this fuel with three additives: a cetane number improver (2-ethylhexyl nitrate), a soot reducer (tripropylene-glycol monomethyl ether), and a flow improver consisting of quaternary ammonium salts. At the selected low and medium load operating conditions, these additives had a smaller effect on the emissions than the injector ageing, the most notable effect being that TPGME reduces the soot emissions even at the oxygen-rich conditions studied here. These studies will be followed by optical investigations of the in-cylinder effects on spray and combustion characteristics.

Clean and efficient dual-fuel combustion using OMEx as high reactivity fuel: Comparison to diesel-gasoline calibration

From previous results in a single-cylinder engine platform, it can be concluded that the dual-mode dual-fuel (DMDF) concept can be a potential solution to overcome the major constraints found with other single-fuel low temperature combustion modes. To extend these findings to a real application, this work evaluates the potential of the diesel-gasoline DMDF concept on a multi-cylinder 8L engine in terms of performance and emissions. To do this, a full engine calibration map was obtained following a specific methodology. The emissions results show that diesel-gasoline DMDF allows to achieve EURO VI NOx and soot emissions in a great portion of the engine map. Nonetheless, the levels of these pollutant at high load conditions exceed the EURO VI limits by far due to the need of implementing a diffusive combustion strategy with high EGR levels to avoid excessive in-cylinder pressure gradients. To mitigate this issue, the use of Oxymethylene ether (OMEx) instead of diesel fuel is proposed. A dedicated engine calibration was developed for the OMEx-gasoline DMDF concept following the same methodology. The results show that the oxygen content in the OMEx molecule allows to achieve a fully EUVI compliant engine calibration in terms of NOx with engine-out soot levels lower than 0.01 g/kWh. Moreover, due to the lower stoichiometric air–fuel ratio with this fuel, the air management system requirements are lower, reducing the pumping losses and increasing the brake thermal efficiency in most of the calibration map.

Multi-objective optimization of the volumetric and thermal efficiencies applied to a multi-cylinder internal combustion engine

The engines produced with valve timing systems have been growing in recent years, given the growing demand to improve their operation and efficiency. Certain operating conditions of valve timing engine increasing volumetric efficiency have a reduction in thermal efficiency. This study aims to apply multi-objective optimization to find conditions for opening and closing valves of maximum volumetric and thermal efficiency, evaluating through performance metrics two optimization methods. The inlet and exhaust valves timing were chosen as design variables. The multi-objective optimization methods used are Non-dominated Sorting Genetic Algorithm – II and Multi-Objective Differential Evolution. Simulations are performed for four different engine speeds. The compressible duct flow is numerically solved by the two step Lax-Wendroff method with Total Variation Diminishing flow control. The performance metrics used in this study are maximum values, number of non-dominated solutions, spacing, hyper-volume and time simulation. The results showed a Pareto front maximizing the volumetric efficiency and decreasing thermal efficiency, and vice versa. The Multi-Objective Differential Evolution presented greater values than Non-dominated Sorting Genetic Algorithm – II, more non-dominated solutions, higher hyper-volume values, with the advantage of spent less computational time. Both approaches were able to optimize internal combustion engine efficiencies finding the optimal valve timing sets. Moreover, allows finding conditions for opening and closing valves that favor both efficiencies.