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2017-09-16
Journal Article
2017-01-9180
Johannes Wurm, Eetu Hurtig, Esa Väisänen, Joonas Mähönen, Christoph Hochenauer
Abstract The presented paper focuses on the computation of heat transfer related to continuously variable transmissions (CVTs). High temperatures are critical for the highly loaded rubber belts and reduce their lifetime significantly. Hence, a sufficient cooling system is inevitable. A numerical tool which is capable of predicting surface heat transfer and maximum temperatures is of high importance for concept design studies. Computational Fluid Dynamics (CFD) is a suitable method to carry out this task. In this work, a time efficient and accurate simulation strategy is developed to model the complexity of a CVT. The validity of the technique used is underlined by field measurements. Tests have been carried out on a snowmobile CVT, where component temperatures, air temperatures in the CVT vicinity and engine data have been monitored. A corresponding CAD model has been created and the boundary conditions were set according to the testing conditions.
2017-09-16
Journal Article
2017-01-9181
Zhongming Xu, Nengfa Tao, Minglei Du, Tao Liang, Xiaojun Xia
Abstract A coupled magnetic-thermal model is established to study the reason for the damage of the starter motor, which belongs to the idling start-stop system of a city bus. A finite element model of the real starter motor is built, and the internal magnetic flux density nephogram and magnetic line distribution chart of the motor are attained by simulation. Then a model in module Transient Thermal of ANSYS is established to calculate the stator and rotor loss, the winding loss and the mechanical loss. Three kinds of losses are coupled to the thermal field as heat sources in two different conditions. The thermal field and the components’ temperature distribution in the starting process are obtained, which are finally compared with the already-burned motor of the city bus in reality to predict the damage. The analysis method proposed is verified to be accurate and reliable through comparing the actual structure with the simulation results.
2017-09-04
Technical Paper
2017-24-0010
Federico Millo, Luciano Rolando, Alessandro Zanelli, Francesco Pulvirenti, Matteo Cucchi, Vincenzo Rossi
This paper presents the modelling of the transient phase of catalyst heating on a high performance turbocharged spark ignition engine with the aim to accurately predict the exhaust thermal energy available at the catalyst inlet and to provide a “virtual test rig” to assess different design and calibration options. The entire transient phase starting from the engine cranking until the catalyst warm-up is completed was taken into account in the simulation and the model was validated by means of a wide data-set of experimental tests. The first step of the modelling activity was the combustion analysis during the transient phase: the burn rate was evaluated on the basis of experimental in-cylinder pressure data, taking into account both cycle-to-cycle and cylinder-to-cylinder variations.
2017-09-04
Technical Paper
2017-24-0016
Morris Langwiesner, Christian Krueger, Sebastian Donath, Michael Bargende
Aiming on the evaluation of SI-engines with extended expansion cycle realized over the crank drive, engine process simulation is an important tool to predict the engine efficiency. One challenge is to consider concept specific effects as best as possible by using appropriate submodels. Particularly the choice of a suitable heat transfer model is crucial due to the significant change in cranktrain kinematics. The usage of the mean piston speed to calculate a heat-transfer-relevant velocity is not sufficient. The heat transfer model according to Bargende combines for its calculation the current piston speed with a simplified k-ε-model. In this paper the eligibility of this model for engines with extended expansion is assessed. Therefore a single-cylinder engine is equipped with fast-response surface-thermocouples in the cylinder head. The surface heat flux is calculated by solving the unsteady heat conduction equation.
2017-09-04
Technical Paper
2017-24-0018
Nikiforos Zacharof, Georgios Fontaras, Theodoros Grigoratos, Biagio Ciuffo, Dimitrios Savvidis, Oscar Delgado, J. Felipe Rodriguez
Heavy-duty vehicles (HDVs) account for some 5% of the EU’s total greenhouse gas emissions. They present a variety of possible configurations that are deployed depending on the intended use. This variety makes the quantification of their CO2 emissions and fuel consumption difficult. For this reason, the European Commission has adopted a simulation-based approach for the certification of CO2 emissions and fuel consumption of HDVs in Europe; the VECTO simulation software has been developed as the official tool for the purpose. The current study investigates the impact of various factors on the CO2 emissions of European trucks through vehicle simulations performed in VECTO. The chosen vehicles represent average 2015 vehicles and comprised of two rigid trucks (12 t and 18 t) and two tractor trailers (30 t and 40 t), which were simulated under their reference configurations and official driving cycles.
2017-09-04
Technical Paper
2017-24-0019
Alexander Mason, Aaron W. Costall, John R. McDonald
Mandated pollutant emission levels are shifting light-duty vehicles towards hybrid and electric powertrains. Heavy-duty applications, on the other hand, will rely on internal combustion engines for the foreseeable future. Hence there remain clear environmental and economic reasons to further decrease IC engine emissions. Turbocharged diesels are the mainstay prime mover for heavy-duty machines, and transient performance is integral to maximizing productivity, while minimizing work cycle fuel consumption and CO2 emissions. 1D engine simulation tools are commonplace for “virtual” performance development, saving time and cost, and enabling product and emissions legislation cycles to be met. A known limitation however, is the predictive capability of the turbocharger turbine sub-model.
2017-09-04
Technical Paper
2017-24-0022
Alessio Dulbecco, Gregory Font
Diesel engine pollutant emissions legislation is becoming more and more stringent. New driving cycles, including increasingly more severe transient engine operating conditions and low temperature ambient conditions, extend considerably the engine operating domain to be optimized to attain the expected engine performance. Technological innovations, such as high pressure injection systems, EGR loops and intake pressure boosting systems allow significant improvement of engine performance. Nevertheless, because of the high number of calibration parameters, combustion optimization becomes expensive in terms of resources. System simulation is a promising tool to perform virtual experiments and consequently to reduce costs, but for this models must be able to account for relevant in-cylinder physics to be sensitive to the impact of technology on combustion and pollutant formation.
2017-09-04
Technical Paper
2017-24-0023
Karim Gharaibeh, Aaron W. Costall
Internal combustion engines are routinely developed using 1D engine simulation tools. A well-known limitation is the accuracy of the turbocharger compressor and turbine sub-models, which generally rely on hot gas bench-measured maps to characterize their performance. Such discrete map data is inherently too sparse to be used directly in simulation, and so a pre-processing algorithm interpolates and extrapolates the data to generate a wider and more densely populated map. Methods used for compressor map interpolation vary. They may be mathematical or physical in nature, but there is no unified approach, except for the fact that they often operate on input map data in SAE standard format. Indeed, for decades it has been common practice for turbocharger suppliers to share performance data with their engine OEM customers in this form.
2017-09-04
Technical Paper
2017-24-0025
Francesco Sapio, Andrea Piano, Federico Millo, Francesco Concetto Pesce
Development trends in modern Common Rail Fuel Injection System (FIS) show dramatically increasing capabilities in terms of optimization of the fuel injection pattern through a constantly increasing number of injection events per engine cycle along with a modulation and shaping of the injection rate. In order to fully exploit the potential of the abovementioned fuel injection pattern optimization, numerical simulation can play a fundamental role by allowing the creation of a kind of a virtual injection rate generator for the assessment of the corresponding engine outputs in terms of combustion characteristics such as burn rate, emission formation and combustion noise (CN). This paper is focused on the analysis of the effects of digitalization of pilot events in the injection pattern on Brake Specific Fuel Consumption (BSFC), CN and emissions for a EURO 6 passenger car 4-cylinder diesel engine.
2017-09-04
Technical Paper
2017-24-0027
Nearchos Stylianidis, Ulugbek Azimov, Nobuyuki Kawahara, Eiji Tomita
A chemical kinetics and computational fluid-dynamics (CFD) analysis were performed to evaluate the combustion of syngas derived from biomass and coke-oven solid feedstock in a micro-pilot ignited supercharged dual-fuel engine under lean conditions. For this analysis, a new reduced syngas chemical kinetics mechanism was constructed and validated by comparing the ignition delay and laminar flame speed data with those obtained from experiments and other detail chemical kinetics analysis available in the literature. The reaction sensitivity analysis was conducted for ignition delay at elevated pressures in order to identify important chemical reactions that govern the combustion process. We found that HO2+OH=H2O+O2 and H2O2+H=H2+HO2 reactions showed very high sensitivity during high-pressure ignition delay times and had considerable uncertainty.
2017-09-04
Technical Paper
2017-24-0030
Vesselin Krassimirov Krastev, Luca Silvestri, Giacomo Falcucci, Gino Bella
A two-equation Zonal-DES (ZDES) approach has been recently proposed by the authors as a suitable hybrid URANS/LES turbulence modeling alternative for Internal Combustion Engine flows. This approach is conceptually simple, as it is all based on a single URANS-like framework and the user is only required to explicitly mark which parts of the domain will be simulated in URANS, DES or LES mode. The ZDES rationale was initially developed for external aerodynamics applications, where the flow is statistically steady and the transition between zones of different types usually happens in the URANS-to-DES or URANS-to-LES direction. The same “one-way” transition process has been found to be fairly efficient also in steady-state internal flows with engine-like characteristics, such as abrupt expansions or intake ports with fixed valve position.
2017-09-04
Technical Paper
2017-24-0034
Michele Battistoni, Carlo N. Grimaldi, Valentino Cruccolini, Gabriele Discepoli, Matteo De Cesare
Water injection in highly boosted GDI engines has become an attractive area over the last few years as a way of increasing efficiency, enhancing performance and reducing emissions. The technology and its effects are not new, but current gasoline engine trends for passenger vehicles have several motivations for adopting this technology today. Water injection enables higher compression ratios, optimal spark timing and elimination of fuel enrichment at high load, and possibly replacement of EGR. Physically, water reduces charge temperature by evaporation, dilutes combustion, and varies the specific heat ratio of the working fluid, with complex effects. Several of these mutually intertwined aspects are investigated in this paper through CFD simulations, focusing on a turbo-charged GDI engine with port water injection. Different strategies for water injection timing, pressure and spray targeting are investigated.
2017-09-04
Technical Paper
2017-24-0038
Golnoush Ghiasi, Irufan Ahmed, Yuri M. Wright, Jann Koch, Nedunchezhian Swaminathan
Engines with reduced emissions and improved efficiency are of high interest for road transport. However, achieving these two goals is challenging and various concepts such as PFI/DI/HCCI/PCCI are explored by engine manufacturers. Three dimensional computational fluid dynamics is becoming an integral part in analysing engine in cylinder processes, since it provides access to in-cylinder flow and thermo-chemical processes which gives a closer understanding to the tumble and swirling motions in order to construct clean engines. The combustion modelling, its accuracy and robustness play a vital role in this. Flamelet based methods are quite attractive for SI engine application. In this study, an unstrained flamelet model is used to simulate premixed combustion inside a GPFI single-cylinder, four-stroke SI engine.
2017-09-04
Technical Paper
2017-24-0036
S Krishna Addepalli, Om Prakash Saw, J M Mallikarjuna
Mixture distribution in the combustion chamber of gasoline direct injection (GDI) engines significantly affects the combustion, performance and emission characteristics. The mixture distribution in the engine cylinder in turn depends on many parameters viz., fuel injector hole diameter and orientation, fuel injection pressure, start of fuel injection, in-cylinder fluid dynamics etc. In these engines, the mixture distribution is broadly classified as homogeneous and stratified. However, with the currently available engine parameters it is difficult to objectively classify the type of mixture distribution. In this study, an attempt is made to objectively classify the mixture distribution in GDI engines using a parameter called the “stratification index”. The analysis is carried out on a four-stroke wall-guided GDI engine using computational fluid dynamics (CFD).
2017-09-04
Technical Paper
2017-24-0045
Blane Scott, Christopher Willman, Ben Williams, Paul Ewart, Richard Stone, David Richardson
In-cylinder temperature measurements are vital for the validation of gasoline engine modelling and useful in their own right for explaining differences in engine performance. The underlying chemical reactions in combustion are highly sensitive to temperature and affect emissions of both NOx and particulate matter. The two techniques described here are complementary, and can be used for insights into the quality of mixture preparation and comparing the in-cylinder temperatures of port fuel injection (PFI) compared with gasoline direct injection (GDI), so as to explain the differences in volumetric efficiency. The influence of fuel composition on in-cylinder mixture temperatures can also be resolved. Laser Induced Grating Spectroscopy (LIGS) provides point temperature measurements with a pressure dependent precision in the range 0.1 to 1.0%; as the pressure increases the precision improves. This allows resolution of temperature differences between PFI and GDI mixture preparation.
2017-09-04
Technical Paper
2017-24-0054
Francesco de Nola, Giovanni Giardiello, Alfredo Gimelli, Andrea Molteni, Massimiliano Muccillo, Roberto Picariello
In the last few years, the automotive industry had to face three main challenges: the compliance of more severe pollutant emission limits, better engine performance in terms of torque and drivability and the simultaneous demand for a significant reduction in fuel consumption as well. These conflicting goals have driven the evolution of automotive engines. In particular, the achievement of all these mandatory aims, together with the increasingly stringent requirements for carbon dioxide reduction, led to the development of highly complex engine architectures needed to perform advanced operating strategies. Thus, Variable Valve Actuation (VVA), Exhaust Gas Recirculation (EGR), Gasoline Direct Injection (GDI), turbocharging, powertrain hybridization and other solutions have gradually and widely equipped the modern internal combustion engines, enhancing the possibilities to achieve the required goals.
2017-09-04
Technical Paper
2017-24-0053
Silvio A. Pinamonti, Domenico Brancale, Gerhard Meister, Pablo Mendoza
The use of state of the art simulation tools to allow for effective front-loading of the calibration process is essential to off-set these additional efforts; therefore, the process needs a critical model validation where the correlation in dynamic conditions is used as a preliminary insight of representation domain of a mean value engine model. This paper focuses on the methodologies for correlating dynamic simulations with vehicle measured dynamic data (fundamental engine parameters and gaseous emissions) obtained using dedicated instrumentation on a diesel vehicle. This correlation is performed using simulated tests run within the AVL mean value model MoBEO (model based engine optimization).
2017-09-04
Technical Paper
2017-24-0009
Federico Millo, Giulio Boccardo, Andrea Piano, Luigi Arnone, Stefano Manelli, Giuseppe Tutore, Andrea Marinoni
To comply with TIER IV emission standard, Kohler Engines has developed the 100kW rated KDI 3.4 liters diesel engine, equipped with DOC and SCR. Based on this engine, a research project in collaboration between Kohler Engines and Politecnico di Torino has been carried out to exploit the potential of new technologies to meet the TIER IV and beyond emission standards. The prototype engine was equipped with a low pressure cooled EGR system, two stage turbocharger, high pressure fuel injection system capable of very high injection pressure and DOC+DPF aftertreatment system. Since the TIER IV emission standard sets a 0.4g/kWh NOx limit for the NRSC steady state test cycle, that includes full load operating conditions, the engine must be operated with very high EGR rates (above 30%) at very high load. As a consequence, the low air to fuel ratio and the risk of high soot emissions must be handled by means of high fuel injection pressure and proper injection patterns.
2017-09-04
Technical Paper
2017-24-0012
Andrea Piano, Giulio Boccardo, Federico Millo, Andrea Cavicchi, Lucio Postrioti, Francesco Concetto Pesce
Nowadays, injection rate shaping and multi-pilot events can help to improve fuel efficiency, combustion noise and pollutant emissions in diesel engine, providing high flexibility in the shape of the injection that allows combustion process control. Different strategies can be used in order to obtain the required flexibility in the rate, such as very close pilot injections with almost zero dwell time or boot shaped injections with optional pilot injections. Modern Common-Rail Fuel Injection Systems (FIS) should be able to provide these innovative patterns to control the combustion phases intensity for optimal tradeoff between fuel consumption and emission levels.
2017-09-04
Technical Paper
2017-24-0024
Andrea Piano, Federico Millo, Davide Di Nunno, Alessandro Gallone
The need for achieving a fast warm up of the exhaust system has raised in the recent years a growing interest in the adoption of Variable Valve Actuation (VVA) technology for automotive diesel engines. As a matter of fact, different measures can be adopted through VVA to accelerate the warm-up of the exhaust system, such as using hot internal Exhaust Gas Recirculation (iEGR) to heat the intake charge, especially at part load, or adopting early Exhaust Valve Opening (eEVO) timing during the expansion stroke, so to increase the exhaust gas temperature during blowdown. In this paper a simulation study is presented evaluating the impact of VVA on the exhaust temperature of a modern light duty 4-cylinder diesel engine, 1.6 liters, equipped with a Variable Geometry Turbine (VGT).
2017-09-04
Technical Paper
2017-24-0026
Davide Paredi, Tommaso Lucchini, Gianluca D'Errico, Angelo Onorati, Stefano Golini, Nicola Rapetto
The scope of the work presented in this paper was to apply the latest open source CFD achievements to design a state of art, direct-injection (DI), heavy-duty, natural gas-fueled engine. Within this context, an initial steady-state analysis of the in-cylinder flow was performed by simulating three different intake ducts geometries, each one with seven different valve lift values, chosen according to an estabilished methodology proposed by AVL. The discharge coefficient (Cd) and the Tumble Ratio (TR) were calculated in each case, and an optimal intake ports geometry configuration was assessed in terms of a compromise between the desired intensity of tumble in the chamber and the satisfaction of an adequate value of Cd. Subsequently, full-cycle, cold-flow simulations were performed for three different engine operating points, in order to evaluate the in-cylinder development of TR and turbulent kinetic energy (TKE) under transient conditions.
2017-09-04
Technical Paper
2017-24-0028
Adèle Poubeau, Stephane Jay, Anthony Robert, Edouard Nicoud, Christian Angelberger
A speed transient performed in a four-valve single cylinder optical gasoline engine under motored conditions is investigated by means of an experimental campaign and Large-Eddy Simulations. Thorough analysis of the flow phenomena is performed, including characterization of kinetic energy, tumble ratios and velocity fields. Comparison between experimental and numerical results shows that high-fidelity simulations are able to capture well the main features of the flow, validating the use of LES for this type of engine configuration.
2017-09-04
Technical Paper
2017-24-0029
Tommaso Lucchini, Gianluca D'Errico, Tarcisio Cerri, Angelo Onorati, Gilles Hardy
Heavy-duty engines have to be carefully designed and optimized in a wide portion of their operating map to satisfy the emissions and fuel consumptions requirements for the different applications they are used for. Within this context, computational fluid dynamics is a useful tool to support combustion system design, making possible to test effects of injection strategies and combustion chamber design. Within this context, the predictive capability of the combustion model play a big role since it has to ensure accurate predictions in terms of cylinder pressure trace and the main pollutant emissions in a reduced amount of time. For this reason, both detailed chemistry and turbulence chemistry interaction need to be included. In this work, the authors intend to apply combustion models based on tabulated kinetics for the prediction of Diesel combustion in Heavy Duty Engines. Three different approaches were considered: well-mixed model, presumed PDF and flamelet progress variable.
2017-09-04
Technical Paper
2017-24-0041
Daniele Piazzullo, Michela Costa, Luigi Allocca, Alessandro Montanaro, Vittorio ROCCO
In gasoline direct injection (GDI) engines, dynamics of the possible spray-wall interaction are key factors affecting the air-fuel mixture distribution and equivalence ratio at spark timing, hence influencing the development of combustion and the pollutants formation at the exhaust. Gasoline droplets impact may rebound with consequent secondary atomization or deposit in the liquid phase over walls as a wallfilm. This last slowly evaporate with respect to free droplets, leading to local enrichment of the mixture, hence to increased unburned hydrocarbons and particulate matter emissions. In this scenario, complex phenomena characterize the turbulent multi-phase system where heat transfer involves the gaseous mixture (made of air and gasoline vapour), the liquid phase (droplets not yet evaporated and wallfilm) and the solid wall, especially in the so-called wall-guided mixture formation mode.
2017-09-04
Technical Paper
2017-24-0057
Roberto Finesso, Omar Marello, Ezio Spessa, Yixin Yang, Gilles Hardy
A model-based control of BMEP (Brake Mean Effective Pressure) and NOx emissions has been developed and assessed for a Euro VI 3.0L diesel engine for heavy-duty applications. The control is based on a zero-dimensional real-time combustion model, which is capable of simulating the HRR (heat release rate), in-cylinder pressure, brake torque, exhaust gas temperatures, NOx and soot engine-out levels. The real-time combustion model has been realized by integrating and improving previously developed simulation tools. The chemical energy release has been simulated using the accumulated fuel mass approach. The in-cylinder pressure was estimated on the basis of a single-zone heat release model, using the net energy release as input. The latter quantity was obtained starting from the simulated chemical energy release, and evaluating the heat transfer of the charge with the walls.
2017-09-04
Technical Paper
2017-24-0072
Gabriele Di Blasio, Carlo Beatrice, Giacomo Belgiorno, Francesco Concetto Pesce, Alberto Vassallo
The paper describes the challenges and results achieved in developing a new high speed Diesel combustion system capable of exceeding the threshold of 100 kW/l. The high-quality state-of-art components of the automotive diesel technology was provided in order to set-up a single-cylinder research engine demonstrator. Key design parameters were identified in terms boost, speed, injection pressure and nozzle flow rates. In this regard, an advanced piezo injection system capable of 3000 bar maximum injection pressure was selected, coupled to a robust base engine featuring advanced combustion bowl and intake ports. The matching among the low compression ratio wide bowl, the high-density charge motion, engine speed and the highly efficient injector nozzles have been thoroughly examined and experimentally parametrized.
2017-09-04
Technical Paper
2017-24-0071
fadila maroteaux, Bianca Maria Vaglieco
Ignition delay time is key to any hydrocarbon combustion process. In that sense, this parameter has to be known accurately, and especially for internal combustion engine applications. Combustion timing is one of the most important factors influencing overall engine performances like power output, combustion efficiency, emissions, in-cylinder peak pressure, etc. In the case of low temperature combustion (LTC) mode (i.e. HCCI mode for example), this parameter is controlled by chemical kinetics and there is no direct control method as in spark ignition engine. For HCCI engine applications and especially Diesel engine, fuels with lower octane ratings such as n-heptane, diesel fuel, dimethyl ether (DME) are preferred. These fuels display a two stage ignition behavior, and therefore it is very difficult to build an accurate ignition delay time model over the wide range of engine operations.
2017-09-04
Technical Paper
2017-24-0084
Giacomo Belgiorno, Nikolaos Dimitrakopoulos, Gabriele Di Blasio, Carlo Beatrice, Martin Tuner, Per Tunestal
In this paper, a parametric analysis on the main engine calibration parameters applied on gasoline Partially Premixed Combustion (PPC) is performed. Theoretically, the PPC concept permits to improve both the engine efficiencies and the NOx–soot trade-off simultaneously compared to the conventional diesel combustion. This work is based on the design of experiments (DoE), statistical approach, and investigates on the engine calibration parameters that might affect the efficiencies and the emissions of a gasoline PPC. The full factorial DoE analysis based on three levels and three factors (33 factorial design) is performed at three engine operating conditions of the Worldwide harmonized Light vehicles Test Cycles (WLTC). The pilot quantity (Qpil), the crank angle position when 50% of the total heat is released (CA50), and the exhaust gas recirculation (EGR) factors are considered. The goal is to identify an engine calibration with high efficiency and low emissions.
2017-09-04
Technical Paper
2017-24-0090
Robert E. Morgan, Morgan Heikal, Emily Pike-Wilson
Urban air quality remains a major concern, in particular NOx and particle emission from diesel powered vehicles. Electrification offers a medium to long term solution, but there remains a need to significantly reduce internal combustion engine emissions in the short and medium term and potentially in the long term for long range inter city transportation. Late injection low temperature combustion (LTC) has the potential to achieve ultra-low emissions levels in a compression ignition engine by increasing the lean pre-mixed burn fraction. However, significant quantities of diluent are normally required to achieve the required delay in ignition and pre-mixing. This results in high boost requirements and increased pumping work negating the benefit of the LTC combustion strategy and increasing fuel consumption. Test results from a single cylinder light duty research engine are presented using a novel ramped combustion chamber.
2017-09-04
Technical Paper
2017-24-0093
Lorenzo Bartolucci, Stefano Cordiner, Vincenzo Mulone, Vittorio Rocco
The use of natural gas in internal combustion engines (ICEs) improves thermal efficiency and reduces exhaust emissions at lean mixture operating conditions. However, as the mixture is leaned out beyond the Lean Misfire Limit (LML), several technical problems are more likely to occur. The flame propagation speed gradually decreases, leading to a slower heat release, thus increasing the occurrence of misfiring and incomplete cycles. This gives in turn a steep increase of CO and UHC emissions, and of cycle-by-cycle variations. In order to limit the above-mentioned problems, several solutions have been proposed so far. Among them, the stratification or the partial stratification of the charge has been demonstrated to successfully extend the lean limit if compared with traditional lean burn engines. This result has been accomplished through the formation of a richer mixture in the vicinity of the spark plug location, improving the stability of the combustion and ignition processes.
Viewing 1 to 30 of 33250