Turbocharged Gasoline Direct Injection Research Articles

Experimental Study of the Performance of Turbo-Charged Gasoline Direct-Injection Engine Based on Different Pre-Chamber Structures

In this paper, in order to improve the fuel economy of the actual application of the engine under multi-operating conditions, an experimental study is carried out on a turbo-charged direct-injection engine based on different pre-chamber structures. The engine used for the study is a four-cylinder turbo-charged direct-injection gasoline engine with different structures of pre-chamber spark plugs. The operating conditions in this study include load characteristics at 2000 r/min and characteristic loads at different speeds, including 3000 r/min, 3200 r/min, and 3600 r/min. With stable BMEP or fully open throttle and pedal, the experiment was conducted by the spark angle scanning method to collect data of engine power, economy, and emission under each condition. It was found that the pre-chamber structure has a direct effect on engine performance, with a clear load demarcation line for its effect. Under the WOT condition, the power of pre-chamber ignition is 1.6% higher than that of conventional spark plugs; at the low load of 2 bar, the economy of pre-chamber ignition is degraded by 6%; at the medium load of 8 bar, the economy of the two is comparable; at the large load of 16 bar, the fuel economy proves advantageous. Compared with conventional spark plugs, the pre-chamber spark angle can be advanced by 2~3 °CA, and the pre-chamber ignition with separate ground electrodes is highly reliable. The emission levels of the pre-chamber spark plugs and conventional spark plugs are comparable at all loads.

Estimation of Piston Surface Temperature During Engine Transient Operation for Emissions Reduction

Abstract Piston surface temperature is an important factor in the reduction of harmful emissions in modern gasoline direct injection (GDI) engines. In transient operation, the piston surface temperature can change rapidly, increasing the risk of fuel puddling. The prediction of the piston surface temperature can provide the means to significantly improve multiple-pulse fuel injection control strategies through the avoidance of fuel puddling. It could also be used to intelligently control the piston cooling jet (PCJ), which is common in modern engines. Considerable research has been undertaken to identify generalized engine heat transfer correlations and to predict piston and cylinder wall surface temperatures during operation. Most of these correlations require in-cylinder combustion pressure as an input, as well as the identification of numerous model parameters. These requirements render such an approach impractical. In this study, the authors have developed a thermodynamic model of piston surface temperature based on the global energy balance (GEB) methodology, which includes the effect of PCJ activation. The advantages are a simple structure and no requirement for in-cylinder pressure data, and only limited experimental tests are needed for model parameter identification. Moreover, the proposed model works well during engine transient operation, with maximum average error of 6.68% during rapid transients. A detailed identification procedure is given. This and the model performance have been demonstrated using experimental piston crown surface temperature data from a prototype 1-liter 3-cylinder turbocharged GDI engine, operated in both engine steady-state and transient conditions with an oil jet used for piston cooling turned both on and off.

An experimental investigation on the lean-burn characteristics of a novel hydrogen fueled spark ignition engine: Hydrogen injection via a micro-hole on the spark plug

Hydrogen addition in SI engines has been a subject of extensive research over the years, primarily owing to its environmentally friendly attributes and its potential to optimize combustion, especially in lean-burn conditions. However, the use of hydrogen as a gaseous fuel presents challenges due to its high mass-to-volume ratio, which can substantially reduce engine power density, whether in direct injection (DI) or port injection PI conditions. Thus, how to maximum hydrogen's benefits on combustion while minimizing its consumption has become a topic worthy to be studied. In this research, a novel concept where hydrogen direct injected through an aperture on edge of the spark plug (SHDI) was proposed and experimentally investigated on a 1.5 L turbocharged gasoline direct injection (GDI) engine under lean-burn condition. Experiments were conducted at 1600 rpm and medium load conditions with hydrogen injection ratios φH2 varying from 0 % to 5.5 % and excess air coefficients (λ) up to 1.5. Hydrogen port injection (HPI) strategy was also employed as a reference to gauge the performance enhancement achieved through SHDI. The experimental results reveal that, in comparison to HPI, SHDI exhibited more pronounced effects in enhancing initial flame propagation and assisting to formation of stable flame nucleus which, in turn, extended the lean-burn limit substantially. Moreover, SHDI strategy also resulted in a more substantial improvement in mean effective pressure (IMEP) and brake thermal efficiency (BTE) compared to the HPI. However, emissions of NOX, HC and CO were higher in the SHDI mode as opposed to the HPI mode This disparity may be attributed to the elevated local temperatures in the vicinity of the spark plug and the interference caused by the hydrogen jet flow, which disrupted the in-cylinder flow pattern, consequently leading to increased levels of unburnt mixture.

A parametric study to improve first firing cycle emissions of a gasoline direct injection engine during cold start

A parametric study was carried out for the first firing cycle of a 4-cylinder, 2.0-liter, turbocharged gasoline direct injection (GDI) engine. The primary goal was to see how changes in the fuel injection parameters would affect the GDI engine combustion and emissions for the first four combustion events that constitute the first firing cycle. Experimental studies were carried out with a custom-designed powertrain control system to measure the HC emissions and pressure development for the first firing cycle. The quantitative experimental results were accompanied by simulations of the detailed temporal and spatial fuel concentration profiles using Converge CFD engine simulation software. An alternative calculation method was used to calculate the average combustion equivalence ratio for each of the four cylinders. This method showed that the majority of the cold start HC emissions during the first firing cycle was unburned gasoline and its possible decomposition products, which did not contribute significantly to the combustion and heat release. For the same amount of fuel injected into a cylinder, increased fuel rail pressure resulted in better evaporation and combustion, while slightly increasing the HC emissions during the cold start process. A multiple injection strategy was studied that split the fuel delivery between the intake stroke and the compression stroke with either one or two injections in each of those strokes (two or four injections total). The quadruple injection strategy led to better first cycle combustion, with higher engine IMEP and lower HC emissions. This resulted from a richer fuel mixture in the region near the spark plug due to better fuel evaporation and a better spatial fuel distribution. While increasing fuel rail pressure with either injection strategy failed to significantly lower the HC emissions given the same amount of injected fuel mass, higher rail pressure with the quadruple injection strategy resulted in higher IMEP for the same amount of injected fuel; this may provide the possibility to reduce the total fuel injection mass which may have benefits for both fuel consumption and emissions.

An improved TRF mechanism for a new turbulent premixed combustion model with application to engine combustion CFD

In the present work, an existing TRF (toluene reference fuel) chemical kinetic mechanism has been improved. In the improvement, the existing TRF mechanism was found to have unphysically higher laminar flame speeds at temperatures greater than 750 K which are typical in engine compression-combustion operating conditions. Eight dominant reactions which mainly control the laminar flame speeds under higher temperatures ( T > 750 K) have been identified. Based on a recently published power-law laminar flame speed correlation which is able to provide good predictions under a wide range of engine conditions, correct reaction rate constants for the eight high-temperature dominant reactions have been determined for physical laminar flame speeds. The identification and improvement of the eight high-temperature dominant reactions are the first novelty of this work. In order to simulate ethanol and gasoline blends, a latest ethanol sub-mechanism has been implemented into the TRF mechanism. The improved TRF mechanism was validated using available experimental data in the literature. Based on the improved TRF mechanism, a new mechanism library has been generated, which can be used for an improved mechanism-dynamic-selection turbulent premixed combustion model in which turbulent diffusivity is constructed as a function of local turbulence/thermodynamics conditions. The dynamic turbulent diffusivity sub-model is the second novelty of this work. The improved TRF mechanism and its combination with the improved mechanism-dynamic-selection turbulent premixed combustion model were successfully applied to the prediction of combustion and emissions of GTDI (gasoline turbocharged direct injection) engines under both warm-up and transient cold start operating conditions, indicating that the improved models in this work are beneficial for predictive engine combustion CFD (computational fluid dynamics).

Consequence of Blowby Flow and Idling Time on Oil Consumption and Particulate Emissions in Gasoline Engine

Pollutant emission standards and, in particular, those concerning particles from an internal combustion engine (ICE) are becoming increasingly restrictive. Thus, it is important to determine the main factors related to the production of particulate matter. In this article, the phenomenon of oil sweeping by the blowby gases between the rings/piston/cylinder is investigated. First, a blowby gas simulation model based on experimental results from a Turbocharged Gasoline Direct Injection (TGDI) is developed. From this model, it is possible to characterise the amount of oil swept by the blowby gases. This depends on the endgap position of both the compression and sealing rings. It also depends on the intensity of the blowby flow rate, which is highest at low rpm and high load. At 1500 rpm and full load, this flowrate exceeds 25 mg.cycle−1. From this result, it is possible to quantify the amount of oil swept by these gases as a function of the endgap position. For θrings=180°, the quantity of oil swept rises to 20 µg.cycle−1 while for θrings=30°, this decreases to 6 µg.cycle−1. The oil concentration of the blowby gas has a direct impact on the particulate emissions because the oil concentration of the backflow gas is inversely proportional to the blowby gas flowrate. As the backflow gases return to the cylinder, the oil oxidises and produces particles. Therefore, it is essential to control the oil concentration of the backflow gases. In addition, the simulation model shows the blowby flowrate becomes negative and decreases to −3.4 mg. cycle−1 in idle conditions. The amount of oil swept by the blowby is no longer directed towards the oil pan, but towards the piston crown. This phenomenon of oil storage of the piston crown in idle condition is proportional to the duration of the idle time. In order to confirm these results, experimental tests are carried out on a TGDI engine. It appears that when the idling time changes from 0 s to 7 s between two strictly identical accelerations, the level of particulate emissions is multiplied by 1.3. When the idling time changes from 0 s to 22 s between two strictly identical accelerations, the level of particulate emissions is multiplied by 3. These results confirm the mechanism of oil storage at idle highlighted by the simulation model.

Post-oxidation phenomena enhancement with scavenging and secondary air injection in exhaust manifold of a turbocharged GDI engine

A detailed investigation of post-oxidation phenomena by individual and combined effects of scavenging (VVT tuning) and secondary air injection (SAI) was performed. The 1-D simulation including a post-oxidation model developed by Stuttgart University as an international collaboration was used for investigation which includes the main exhaust gas species as CO, H2, and O2-based chemical reactions. Then, experimental validation was conducted on a 4-cylinder turbocharged gasoline direct injection (GDI) engine. From the results, it was noted that the post-oxidation can be actuated at limited operating conditions as higher overlap in moderated speed and load only when scavenging phenomena are considered. However, at lower overlap, it is restricted due to lower O2 scavenging even though the exhaust temperature meets the post-oxidation requirement. Also, the in-homogeneity observed at higher overlap that restricts the significant post-oxidation before the turbocharger upstream. On the other hand, the SAI mechanism can actuate the post-oxidation even at lower overlap if enough O2 concentration, exhaust temperature, and adequate mixing are attained. Hence, the post-oxidation zone can be extended to lower speed-load and overlap if both parameters as scavenging and SAI introduced together. This can possibly lead to better turbo-performance along with lower emissions. However, thermal efficiency needs to be compromised to some extent. It was also found that the effective post-oxidation can be actuated by SAI compared to scavenging-based phenomena if the same concentration of the O2 and temperature are maintained by both mechanisms. This appeared due to the fresh air continuously injected at the exhaust port even at the time of exhaust valve opening duration in SAI mechanism that allows the better mixing of O2 and hot unburned gas species. However, in scavenging-based phenomena, firstly, hot unburned gas passed through the exhaust manifold and then scavenged air follows which restricts mixing between scavenged air and unburned gas species.

Effect of Miller cycle and exhaust gas recirculation on combustion characteristics of a gasoline direct-injection engine

ABSTRACT A numerical method is used to investigate the effect of variation Miller cycle and Exhaust gas recirculation (EGR) on fuel economy and combustion characteristics of a turbocharged gasoline direct-injection (GDI) engine, in which one-dimensional (1D) and three-dimensional (3D) model are established in GT-Power and CONVERGE software, respectively. The simulation values of the model are validated well with experimental results at part load and full load conditions. The results demonstrate that fuel economy is improved with Miller degree increasing at 50% loads because of the reduction of pumping loss. Further studies have shown that, especially at ±58°CA Miller degrees, early intake valve closure (EIVC) has a better performance than late intake valve closure (LIVC) on fuel economy. In addition, EGR can further decrease fuel consumption based on miller cycle because of further decline for pumping loss and combustion phase optimization. Meanwhile, LIVC can match wider EGR rates than EIVC in terms of good fuel economy. Compared to the baseline scheme, the brake specific fuel consumption is reduced by 4.3% with LIVC58 + 7% EGR. And combustion process of the LIVC58 + 7% EGR also gets optimized which result in lower maximum in-cylinder temperature due to the advance of CA50 and delay of combustion duration.

Simulation and experimental research on the influence of lubrication on the comprehensive friction of TGDI engine

PurposeThis paper aims to investigate the effects of low-viscosity and ultralow-viscosity engine oils on the comprehensive friction and fuel economy of turbocharged gasoline direct injection (TGDI) through simulation analysis and experiments.Design/methodology/approachNumerical analysis models of friction loss for reciprocating, crankshaft and valve train are established. Based on the FAST, the friction loss of 24 specific parts of a TGDI engine was analyzed. Finally, the engine test bench was built, which was used to test the mechanical loss, external characteristics and universal characteristics.FindingsCompared with the baseline oil, lower viscosity lubricating oil can reduce the friction loss of nine components to varying degrees. When the viscosity decreases, the friction distribution ratio of reciprocating, crankshaft and balance shaft will gradually decrease. The proportion of reciprocating when using 0W12 is reduced by 4%. Tests have shown that ultralow viscosity engine oil reduces torque loss by up to 15.74% (2,000 rpm, full throttle), but its fuel consumption rate becomes higher in low-speed and high-torque conditions.Originality/valueThis work helps to understand the effect of lubricating oil characteristics on the comprehensive friction performance of the engine.

Experimental investigation of water injection and spark timing effects on combustion and emissions of a hybrid hydrogen-gasoline engine

This paper aimed to study the effects of water injection and spark timing on performance of a hybrid hydrogen-gasoline engine. For this aim, a modified four-cylinder turbocharged gasoline direct injection (GDI) engine equipped with hydrogen port injection and port water injection system was developed. In this study, the engine speed was maintained at 1300 rpm and the throttle opening of 30% with an excess air/fuel ratio of 1. The hydrogen energy percentage of 15%, water fuel mass ratio of 0.2 and 0.4 was added into the intake port. When the hydrogen energy percentage was changed, the gasoline fraction was also adjusted to keep the mixture at the stoichiometric. For all tested conditions, the spark timing was varied from 1 to 42°CA before top dead center (BTDC) with a fixed interval of 2°CA. Experimental results showed that maximum brake torque (MBT) spark timing varied when water and/or hydrogen is added. With hydrogen addition, the worsened combustion caused by water injection can be improved. Also, the variation of IMEP and COVIMEP versus spark timing became more insensitive with hydrogen addition. With water injection, the high NO emission caused by hydrogen addition can be largely reduced, however with side effect of higher HC and CO emissions.

A Simulation Tool for Calculation of Engine Thermal Boundary Conditions

<div class="section abstract"><div class="htmlview paragraph">Reducing emissions and the carbon footprint of our society have become imperatives requiring the automotive industry to adapt and develop technologies to strive for a cleaner sustainable transport system and for sustainable economic prosperity. Electrified hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV) and range extender powertrains provide potential solutions for reducing emissions, but they present challenges in terms of thermal management. A key requirement for meeting these challenges is accurately to predict the thermal loading and temperatures of an internal combustion engine (ICE) quickly under multiple full-load and part-load conditions.</div><div class="htmlview paragraph">Computational Fluid Dynamics (CFD) and thermal survey database methods are used to derive thermal loading of the engine structure and are well understood but typically only used at full-load conditions. These methods are limited in terms of computational overhead with CFD and the validity of the database when wishing to look at part-load conditions to build up a thermal map of the engine for transient solutions.</div><div class="htmlview paragraph">This paper presents a new analytical Finite Element (FE) based tool for calculating thermal boundary conditions of all the components of the power cylinder using physical models and semi-empirical correlations, without the need for CFD analysis, and which overcomes the limitation of database methods which are not predictive. An iterative solution is used that captures all the heat paths in detail and where each solution runs quickly enough to allow different design variants to be assessed for multiple operating conditions. The calculated temperatures and the corresponding deformations can then be used to predict piston secondary motion and ring dynamics and to better predict friction, wear and oil consumption of the power cylinder and the structural durability of the components.</div><div class="htmlview paragraph">The toolset is applied to a 2.0 liter 4-cylinder Gasoline Turbocharged Direct Injection (GTDI) engine and validated with measurements on the piston, cylinder head and cylinder bore for different full and part-load conditions.</div></div>

Effect of late intake valve closing on the particle number emissions of a turbocharged gasoline direct injection engine

To achieve carbon-neutrality, efficient gasoline engines with minimal particle number emissions are being increasingly researched. In this study, the particle emission mechanism associated with late intake valve closing (LIVC) was investigated using borescopic method, and particle image velocimetry (PIV) in a 4-cylinder turbocharged gasoline direct injection engine, and a 2-cylinder optically accessible engine, respectively. The direct flame visualization of the borescope and flow visualization of the PIV measurement were used to analyze the blue flame propagation characteristics, mean in-cylinder flow velocity, and turbulent kinetic energy associated with the LIVC along with combustion analysis. The retardation of the LIVC timing reduced the particle number emissions, increased the in-cylinder flow velocity, and decreased the effective compression ratio. The improved flow velocity and reduced effective compression ratio mitigated the production of particle precursors at the expense of decelerated initial flame propagation. However, this decelerated flame propagation was compensated by the enhanced late-stage combustion generated from the increased turbulent kinetic energy of the retarded LIVC timings. The obtained results verify that the improved mixture formation and initial lower in-cylinder temperature conditions of the retarded LIVC timing reduced the particle production, which in turn enhanced the particle oxidation owing to the accelerated late-stage combustion.

Experimental investigation of particle number reduction in turbocharged GDI engines

Introduction (problem statement and relevance). Now it is difficult to imagine the automotive industry without constant improvement of the power plant. This is due to the constant tightening of environmental standards, so in environmental standards Euro 6 there is a limit of the countable concentration of particulate matters. To meet the Euro 6 environmental standard, vehicle manufacturers use catalytic converters, and gasoline particle filters (GPF). These methods of reducing the emissions of the exhaust gas are quite common, but they also have a limitation on the service life. The use of only catalytic converters and GPF may not be sufficient to meet the Euro 7 standards in the future. So, there is a need to reduce emissions with exhaust gases by improving the combustion process.The purpose of work is to investigate the combustion process of a turbocharged gasoline direct injection engine to reduce particulate matter by increasing the injection pressure and optimizing the injection timing. Methodology and research methods. The studies are of an experimental nature, the reliability of the data is confirmed by the use of modern measuring equipment and post processing of the measured data. Scientific novelty and results. The fuel injection parameters, which have a significant influence on the particulate matter formation and oxidation are defined.Practical significance. The recommendations to reduce particulate matter formation and to meet the requirements of the future Euro standards are given.

Quantitative Analysis of Gasoline Direct Injection Engine Emissions for the First 5 Firing Cycles of Cold Start

<div class="section abstract"><div class="htmlview paragraph">A series of cold start experiments using a 2.0 liter gasoline turbocharged direct injection (GTDI) engine with custom controls and calibration were carried out using gasoline and iso-pentane fuels, to obtain the cold start emissions profiles for the first 5 firing cycles at an ambient temperature of 22°C. The exhaust gases, both emitted during the cold start firing and emitted during the cranking process right after the firing, were captured, and unburned hydrocarbon emissions (HC), CO, and CO<sub>2</sub> on a cycle-by-cycle basis during an engine cold start were analyzed and quantified. The HCs emitted during gasoline-fueled cold starts was found to reduce significantly as the engine cycle increased, while CO and CO<sub>2</sub> emissions were found to stay consistent for each cycle. Crankcase ventilation into the intake manifold through the positive-crankcase ventilation (PCV) valve system was found to have little effect on the emissions results. Cold start experiments fueled by highly volatile iso-pentane saw an overwhelming majority of the injected carbon captured in the exhaust gases, while a significant portion of the injected carbon during the gasoline-fueled cold starts was not captured. The comparative results not only validated the experimental methods, but also demonstrated that a significant fraction of the injected gasoline failed to evaporate during cold starts. During the first 5 firing cycles, 22% to 34% of the injected fuel mass was estimated to remain in the liquid phase and escaped capture. Because fuel could be carried over from one cycle to the next, in some cases, the actual unevaporated gasoline portion in a given cold start cycle could be even higher than that measured.</div></div>

Performance of direct injected propane and gasoline in a high stroke-to-bore ratio SI engine: Pathways to diesel efficiency parity with ultra low soot

This work explores pathways to achieve diesel-like, high-efficiency combustion with stoichiometric 3-way catalyst compatible combustion in a single-cylinder spark ignition (SI) research engine. A unique high stroke-to-bore engine design (1.5:1) with cooled exhaust gas recirculation (EGR) and high compression ratio ( rc) was used to improve engine efficiency by up to 30% compared with a production turbocharged gasoline direct injection spark ignition engine. Engine experiments were conducted with both 91 RON E10 gasoline and liquified petroleum gas (LPG) (i.e. autogas) and were compared to legacy gasoline data on the production engine. Geometric compression ratio ( rc) of 13.3:1 was used for both fuels with additional experiments at 16.8:1 for LPG only. Measurements of exhaust soot particle size and number concentrations were made with both fuels. Significant reduction in soot particles across the whole particle size range were achieved with LPG due to the elimination of in-cylinder liquid films. The effects of EGR, late intake valve closing (IVC) and fuel characteristics were investigated through their effects on efficiency, combustion stability and soot production. Results of 47% gross thermal efficiency, and 45% net thermal efficiency at stoichiometric engine operation, at up to 17 bar IMEP and 2000 r/min with 16.8:1 rc were achieved with LPG. Estimated brake efficiency values were compared to a contemporary medium duty diesel engine illustrating the benefits of the chosen path for achieving diesel efficiency parity.

Research of Exhaust Gas Recirculation on Commercial Turbocharged Gasoline Direct Injection Engine With Intense Tumble Flow

Abstract The application of exhaust gas recirculation (EGR) technology on gasoline direct injection (GDI) engines can suppress knocking, reduce fuel consumption, and reduce NOx emissions. The effects of EGR with enhanced intake tumble flow, on the combustion phase, combustion duration, knock index and combustion cycle variation of the engine, were studied at two speeds of 1500 r/min and 2000 r/min from low to medium and to full load. The research shows that although the commercial engine has been well calibrated and optimized, the optimization of EGR and enhanced tumble flow together with the optimization of the ignition angle can improve the engine's economy and emission characteristics, while maintaining relatively fast burning speed and low combustion cycle variation. From medium to heavy load, the economy can be improved by 2.6–10%, and the minimum fuel consumption can be reduced to 213 g/kW. h. Under heavy load conditions (brake mean effective pressure (BMEP) more than 14 bars), power performance deteriorates due to insufficient boost performance. The 5–20% EGR rate brings 10% power loss. EGR combined with tumble intake has a significant effect on reducing the engine's NOx and CO, with average reductions of 60% and 22%, but HC increased by 32%.

Effects of turbocharger rotational inertia on engine and turbine performance in a turbocharged gasoline direct injection engine under transient and steady conditions

The effects of turbocharger (T/C) rotational inertia on engine and turbine performance under transient and steady engine conditions were analyzed in a 2.0 L 4-cylinder turbocharged-gasoline direct injection (T-GDI) engine. The test T/Cs consisted of heavy and light compressor wheels (C/W) and turbine wheels (T/W). The study was conducted in two research stages. First, transient engine load tests were conducted to evaluate the effect of T/C rotational inertia on transient response of the T/C, combustion performance, and fuel consumption. Seconds, steady engine load tests were conducted to find out if a light inertia T/C can run at higher efficiency under the same exhaust pulsating flow conditions within one engine cycle. In order to evaluate the engine on-board turbine instantaneous performances in the units of crank angle degree (CAD), T/C rotation speed and pressure data were measured in the experiment. The instantaneous exhaust gas mass flow rate and the temperature of upstream and downstream of the turbine were extracted by 1-D simulation. Turbine efficiency and mass flow rate parameters were calculated by combining these data. In the results, there existed positive effects of light inertia T/C on response and specific fuel consumption under transient conditions. It was also found that the light inertia T/C could show higher T/C speed fluctuation under the same exhaust pulsating flow conditions. Consequently, blade speed ratio (BSR) and turbine efficiency of light inertia T/C were partially higher than that of conventional one. However, it was not led to higher engine efficiency.

Effects of Turbocharger Rotation Inertia on Instantaneous Turbine Efficiency in a Turbocharged-Gasoline Direct Injection (T-GDI) Engine

Abstract The effects of turbocharger rotation inertia on instantaneous turbine efficiency were analyzed in a 2.0 L four-cylinder twin-scroll turbocharged gasoline direct injection (T-GDI) engine. Two turbochargers of different weights were prepared for comparison purposes: base T/C and light T/C. In order to evaluate the instantaneous efficiency of each turbocharger, a combination of engine tests and a 1D simulation was conducted. In the experiments, the instantaneous exhaust gas pressures, upstream and downstream of the turbine, were measured. The instantaneous turbocharger rotation speed was also measured. The instantaneous temperature and mass flow rate of the exhaust gas were taken from the 1D simulation results. Through a combination of measuring and simulating exhaust gas states for the turbines, the instantaneous turbine blade speed ratio (BSR), total-to-static turbine efficiency (ηts), reduced mass flow rate (φ), and reduced turbine speed (Nred) were calculated. The light T/C showed higher fluctuations in the instantaneous turbine rotation speed compared to the base T/C. This greater response from the light T/C is due to experiencing less inertia loss, this leads to higher fluctuations in the instantaneous Nred, BSR, ηts, and φ. As a result, the light T/C shows higher turbine efficiency at certain points after the start of the exhaust gas pulse cycle. This is because the greater response of the light T/C lead the operating conditions of the turbine to more efficient regions in the turbine map.

Combustion phenomena affecting particle emission under boosting conditions in a turbocharged gasoline direct injection engine

As emission regulations for vehicles have become stricter, the survival of direct injection technologies has been threatened due to increased particle emissions. By many researchers, there has been the effort to reduce the particle emissions. Nonetheless, the sources of particle emissions from turbocharged gasoline direct injection engines (T-GDI) were still not investigated enough. In this research, the particle emission from a modern turbocharged gasoline direct injection engine was investigated through combustion analysis accompanying simultaneous flame visualization. The experiments were conducted under three load conditions from naturally-aspirated to highly boosted conditions. The start of injection was swept to identify the effect of fuel mixing processes and differed combustion phenomena by the fuel injections and the boosting on engines. As results, the boosting changed the influence of heterogeneity and flow interaction by sprays, resulting differences in heat release from combustion and particle generation. The boosting on engines suppressed the agglomeration of particles into large aggregate in half, but promoted the nucleation of particles become double compared to natural aspiration. With optimized injection systems, the most impacting factors are the control of spray interaction with in-cylinder flow and oxidation processes of particles. In the boosted conditions, the uncertain particle sources could occur, such as spontaneous ignitions by mixture stratification and biased flame propagation by flow interaction. Through optimization of injection strategies, the combustion phenomena can be controlled to reduce the particle emissions in the moderate boosted conditions. The results of combustion analysis affecting the particle generation can provide the clues to reduce particle emission from T-GDI engines.

Effect of the Metal-Foam Gasoline Particulate Filter (GPF) on the Vehicle Performance in a Turbocharged Gasoline Direct Injection Vehicle over FTP-75

Worldwide regulations on particulate matter for passenger vehicles have become stricter in recent years, which makes it difficult to satisfy for gasoline direct injection (GDI) vehicles. In this study, the level of reduction efficiency of particle emissions with a metal-foam gasoline particulate filter (GPF) for the turbocharged GDI vehicle was evaluated in the federal test procedure (FTP)-75 mode operation. The particle number (PN) emissions were analyzed using the AVL particle counter (APC) and fast response differential mobility spectrometer (DMS500) for particle size distribution. The PN concentration from the base GDI vehicle with only TWC is 1.64 E+12 number/km (#/km), while the value of the GPF-equipped case is 5.02 E+11 #/km with 69 % filtration efficiency in the vehicle test mode. In particular, the reduction rate of small particles under 23 nm in size was strongly improved with the additional installation of the metal-foam GPF. The maximum pressure drop through the GPF reached approximately 39 mbar at the highest acceleration point of phase 1 of the FTP-75 mode. The upstream temperature of the GPF was distributed at approximately 380 ∼ 510 oC in the vehicle test. The results show that the GPF-equipped GDI vehicle can satisfy the stringent particle regulation by Euro 6 in a straightforward manner.