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Viewing 271 to 300 of 44063
2017-09-04
Technical Paper
2017-24-0150
Srinivas Padala, Minh Khoi Le, Atsushi Nishiyama, Yuji Ikeda
Abstract Recent trend in gasoline-powered automobiles focuses heavily on reducing the CO2 emissions and improving fuel efficiency. Part of the solutions involve changes in combustion chamber geometry to allow for higher turbulence, higher compression ratio which can greatly improve efficiencies. However, the changes are limited by the ignition-source and its location constraint, especially in the case of direct injection SI engines where mixture stratification is important. A new compact microwave plasma igniter based on the principle of microwave resonance was developed and tested for propane combustion inside a constant volume chamber. The igniter was constructed from a thin ceramic panel with metal inlay tuned to the corresponding resonance frequency. Microwaves generated by semiconductor based oscillator were utilized for initiation of discharge.
2017-09-04
Technical Paper
2017-24-0063
Sebastiano Breda, Alessandro D'Adamo, Stefano Fontanesi, Marco Del Pecchia, Simona Merola, Adrian Irimescu
Abstract The recent interest in alternative non-fossil fuels has led researchers to evaluate several alcohol-based formulations. However, one of the main requirements for innovative fuels is to be compatible with existing units’ hardware, so that full replacement or smart flexible-fuel strategies can be smoothly adopted. n-Butanol is considered as a promising candidate to replace commercial gasoline, given its ease of production from bio-mass and its main physical and chemical properties similar to those of Gasoline. The compared behavior of n-butanol and gasoline was analyzed in an optically-accessible DISI engine in a previous paper [1]. CFD simulations explained the main outcomes of the experimental campaign in terms of combustion behavior for two operating conditions. In particular, the first-order role of the slower evaporation rate of n-butanol compared to gasoline was highlighted when the two fuels were operated under the same injection phasing.
2017-09-04
Technical Paper
2017-24-0064
En-Zhe Song, Shi-Chao Chu, Li-Ping Yang, Zhen-Ting Liu
Abstract A CFD model of natural gas engine was established, and working process from intake stroke to combustion stroke was simulated in this paper. Based on the validation of CFD model through experimental method, the combustion characteristics of lean-burn natural gas engine are studied under different ignition timings and different ignition energies. Results indicate that, the in-cylinder indicated mean effective pressure increases with the ignition timing advancing from 22°CA BTDC to 32°CA BTDC at the same load level. Meanwhile, the heat release rate is increased by 23.18J/°CA and its peak phase is advanced by 9°CA. The peak pressure is also increased by 45.95% and its phase is advanced by 4.5°CA. On the other hand, when the ignition energy decreases from 91.97mJ to 33.1mJ at the same load level, the in-cylinder indicated mean effective pressure decreases.
2017-09-04
Technical Paper
2017-24-0081
Luigi De Simio, Michele Gambino, Sabato Iannaccone
Abstract In recent years the use of alternative fuels for internal combustion engines has had a strong push coming from both technical and economic-environmental aspects. Among these, gaseous fuels such as liquefied petroleum gas and natural gas have occupied a segment no longer negligible in the automotive industry, thanks to their adaptability, anti-knock capacity, lower toxicity of pollutants, reduced CO2 emissions and cost effectiveness. On the other hand, diesel engines still represent the reference category among the internal combustion engines in terms of fuel consumptions. The possibility offered by the dual fuel systems, to combine the efficiency and performance of a diesel engine with the environmental advantages of gaseous fuels, has been long investigated. However the simple replacement of diesel fuel with natural gas does not allow to optimize the performance of the engine due to the high THC emissions particularly at lower loads.
2017-09-04
Technical Paper
2017-24-0110
Lucio Postrioti, Giulio Caponeri, Giacomo Buitoni
Abstract In order to optimize gasoline direct injection combustion systems, a very accurate control of the fuel flow rate from the injector must be attained, along with appropriate spray characteristics in terms of drop sizing and jets global penetration/diffusion in the combustion chamber. Injection rate measurement is therefore one of the crucial tasks to be accomplished in order both to develop direct injection systems and to properly match them with a given combustion system. Noticeably, the hydraulic characteristics of GDI injectors should be determined according to a non-intrusive measuring approach. Unfortunately, the operation of all conventional injection analyzers requires the injection in a volume filled with liquid and the application of a significant counter-pressure downstream of the injector. This feature prevents any operation with low pressure injection systems such as PFIs.
2017-09-04
Technical Paper
2017-24-0154
Ruud Eichhorn, Michael Boot, David Smeulders, Michel Cuijpers
Abstract The Free Space Parameter (FSP) is evaluated as a predictor for the efficiency of a Variable Geometry Turbine (VGT). Experiments show an optimum value at 2 times the vane height. However, the optimum was found to be dependent on the pressure ratio, yielding an optimum closer to 2.5 at pressures of 2 and 2.5 bar. After this validation the FSP of a conventional VGT is evaluated and an attempt is made to improve the efficiency of this turbine using the FSP. A new geometry is proposed which yields more favorable FSP values. Experiments show that at the original design point the efficiency is unchanged. However, at both larger and smaller nozzle area’s the turbine efficiency improves as predicted by the FSP values. A relative efficiency improvement of 3 to 28 % is attained.
2017-09-04
Technical Paper
2017-24-0153
Sergey Shcherbanev, Alexandre De Martino, Andrey Khomenko, Svetlana Starikovskaia, Srinivas Padala, Yuji Ikeda
Abstract Requirements for reducing consumption of hydrocarbon fuels, as well as reducing emissions force the scientific community to develop new ignition systems. One of possible solutions is an extension of the lean ignition limit of stable combustion. With the decrease of the stoichiometry of combustible mixture the minimal size of the ignition kernel (necessary for development of combustion) increases. Therefore, it is necessary to use some special techniques to extend the ignition kernel region. Pulsed microwave discharge allows the formation of the ignition kernels of larger diameters. Although the microwave discharge igniter (MDI) was already tested for initiation of combustion and demonstrated quite promising results, the parameters of plasma was not yet studied before. Present work demonstrates the results of the dynamics of spatial structure of the MDI plasma with nanosecond time resolution.
2017-09-04
Technical Paper
2017-24-0158
Teresa Castiglione, Giuseppe Franzè, Angelo Algieri, Pietropaolo Morrone, Sergio Bova
Abstract In this paper, we propose a novel control architecture for dealing with the requirements arising in a cooling system of an ICE. The idea is to take advantage of the joint action of an electric pump and of an ad-hoc regulation module, which is used to determine adequate flow rates despite engine speeds. Specifically, a robust Model Predictive Control approach is exploited to take care formally of input/output constraints and disturbance effects of the resulting lumped parameter model of the engine cooling system, which incorporates the nucleate boiling heat transfer regime. Numerical simulations and test rig experimental data are presented. The results achieved show that the proposed control scheme is capable of providing effective and safe cooling while mitigating disturbance effects and minimizing coolant flow rates when compared with the action pertaining to standard crankshaft driven pumps.
2017-09-04
Technical Paper
2017-24-0156
Minh Khoi Le, Srinivas Padala, Atsushi Nishiyama, Yuji Ikeda
Abstract The Microwave Discharge Igniter (MDI) was developed to create microwave plasma for ignition improvement inside combustion engines. The MDI plasma discharge is generated using the principle of microwave resonance with microwave (MW) originating from a 2.45 GHz semiconductor oscillator; it is then further enhanced and sustained using MW from the same source. The flexibility in the control of semiconductors allows multiple variations of MW signal which in turn, affects the resonating plasma characteristics and subsequently the combustion performance. In this study, a wide range of different MW signal parameters that were used for the control of MDI were selected for a parametric study of the generated Microwave Plasma. Schlieren imaging of the MDI-ignited propane flame were carried out to assess the impact on combustion quality of different MW parameters combinations.
2017-09-04
Technical Paper
2017-24-0155
Marc Sens, Michael Guenther, Matthias Hunger, Jan Mueller, Sascha Nicklitzsch, Ulrich Walther, Steffen Zwahr
Abstract The combination of geometrically variable compression (VCR) and early intake valve closure (EIVC) proved to offer high potential for increasing efficiency of gasoline engines. While early intake valve closure reduces pumping losses, it is detrimental to combustion quality and residual gas tolerance due to a loss of temperature and turbulence. Large geometric compression ratio at part load compensates for the negative temperature effect of EIVC with further improving efficiency. By optimizing the stroke/bore ratio, the reduction in valve cross section at part load can result in greater charge motion and therefore in turbulence. Turbocharging means the basis to enable an increase in stroke/bore ratio, called β in the following, because the drawbacks at full load resulting from smaller valves can be only compensated by additional boosting pressure level.
2017-09-04
Technical Paper
2017-24-0162
Harald Stoffels, Jens Dunstheimer, Christian Hofmann
Abstract The application of a turbocharger, having an electric motor/generator on the rotor was studied focusing on the electric energy recuperation on a downsized gasoline internal combustion engine (turbocharged, direct injection) using 1D-calculation approaches. Using state-of-the art optimization techniques, the settings of the valve timing was optimized to cater for a targeted pre-turbine pressure and certain level of residual gases in the combustion chamber to avoid abnormal combustion events. Subsequently, a steady-state map of the potential of electric energy recuperation was performed while considering in parallel different efficiency maps of the potential generator and a certain waste-gate actuation strategy. Moreover, the results were taken as input to a WLTP cycle simulation in order to identify any synergies with regard to fuel economy.
2017-09-04
Technical Paper
2017-24-0167
Enrico Mattarelli, Carlo Rinaldini, Tommaso Savioli, Giuseppe Cantore, Alok Warey, Michael Potter, Venkatesh Gopalakrishnan, Sandro Balestrino
Abstract This work reports a CFD study on a 2-stroke (2-S) opposed piston high speed direct injection (HSDI) Diesel engine. The engine main features (bore, stroke, port timings, et cetera) are defined in a previous stage of the project, while the current analysis is focused on the assembly made up of scavenge ports, manifold and cylinder. The first step of the study consists in the construction of a parametric mesh on a simplified geometry. Two geometric parameters and three different operating conditions are considered. A CFD-3D simulation by using a customized version of the KIVA-4 code is performed on a set of 243 different cases, sweeping all the most interesting combinations of geometric parameters and operating conditions. The post-processing of this huge amount of data allow us to define the most effective geometric configuration, named baseline.
2017-09-04
Technical Paper
2017-24-0168
James W.G. Turner, James P. Lewis Monsma
Abstract Modern automotive engines almost exclusively operate on the 4-stroke Otto cycle and utilize poppet valves for gas exchange. This state of affairs has not always been the case, however, and one unusual and relatively successful technology that was once in mass production (albeit in piston aero engines) was the Burt-McCollum single sleeve valve. This paper investigates the timing and angle-area of a Bristol Centaurus engine cylinder, which utilized such a single sleeve valve for gas exchange, using some modern tools. A comparison with poppet valve angle-areas is made. Finally, the results are also used to study the potential of variable valve timing and the interaction with variable compression ratio of a single sleeve mechanism.
2017-09-04
Technical Paper
2017-24-0163
Apostolos Pesiridis, Angelo Saccomanno, Raffaele Tuccillo, Alfredo Capobianco
Abstract The modern automotive industry is under strict regulations to reduce emissions to comply with the Kyoto Protocol, a universally acknowledged treaty aiming at reducing exhaust gas emissions. In order to achieve the required future emission reduction targets, further developments on gasoline engines are required. One of the main methods to achieve this goal is the application of engine downsizing. Turbocharging is a cost-effective method of downsizing an engine whilst reducing exhaust gas emissions, reducing fuel consumption and maintaining prior performance outputs. For these reasons, the turbocharging is becoming the most widely adopted technology in the automotive markets. In 2012, 32% of passenger and commercial vehicles sold had a turbocharger installed, and is predicted to be 40% of 2017 [1]. Even if the engine turbocharging is a widespread technology, there are still drawbacks present in current turbocharging systems.
2017-09-04
Technical Paper
2017-24-0172
Haijun Chen, Lin Li, Mark Schudeleit, Andreas Lange, Ferit Küçükay, Christian Stamme, Peter Eilts
Abstract In view of the rapidly increasing complexity of conventional as well as hybrid powertrains, a systematic composition platform seeking for the global optimum powertrain is presented in this paper. The platform can be mainly divided into three parts: the synthesis of the transmission, the synthesis of the internal combustion engine (ICE) and the optimization and evaluation of the entire powertrain. In regard to the synthesis of transmission concepts, a systematical and computer-aided tool suitable both for conventional und hybrid transmissions is developed. With this tool, all the potential transmission concepts, which can realize the desired driving modes or ratios, can be synthesized based on the vehicle data and requirements.
2017-09-04
Technical Paper
2017-24-0173
Jean-Charles Dabadie, Antonio Sciarretta, Gregory Font, Fabrice Le Berr
Abstract Due to more and more complex powertrain architectures and the necessity to optimize them on the whole driving conditions, simulation tools are becoming indisputable for car manufacturers and suppliers. Indeed, simulation is at the basis of any algorithm aimed at finding the best compromise between fuel consumption, emissions, drivability, and performance during the conception phase. For hybrid vehicles, the energy management strategy is a key driver to ensure the best fuel consumption and thus has to be optimized carefully as well. In this regard, the coupling of an offline hybrid strategy optimizer (called HOT) based on Pontryagin’s minimum principle (PMP) and an online equivalent-consumption-minimization strategy (ECMS) generator is presented. Additionally, methods to estimate the efficiency maps and other overall characteristics of the main powertrain components (thermal engine, electric motor(s), and battery) from a few design parameters are shown.
2017-09-04
Technical Paper
2017-24-0170
Michael R. Buchman, Amos Winter
Abstract This paper evaluates the lag time in a turbocharged single cylinder engine in order to determine its viability in transient applications. The overall goal of this research is to increase the power output, reduce the fuel economy, and improve emissions of single cylinder engines through turbocharging. Due to the timing mismatch between the exhaust stroke, when the turbocharger is powered, and the intake stroke, when the engine intakes air, turbocharging is not conventionally used in commercial single cylinder engines. Our previous work has shown that it is possible to turbocharge a four stroke, single cylinder, internal combustion engine using an air capacitor, a large volume intake manifold in between the turbocharger compressor and engine intake. The air capacitor stores compressed air from the turbocharger during the exhaust stroke and delivers it during the intake stroke.
2017-09-04
Technical Paper
2017-24-0179
Marco Tonetti, Giorgio Rustici, Massimo Buscema, Luca Ferraris
Abstract Final Euro6d emission legislation with the new homologation cycle and Real Driving Emission requirements has set a strong challenge for the ICE Passenger Car applications. Thanks to their well-known low fuel consumption characteristics, Diesel Engines can play a key role for the fulfillment of the European 2020 CO2 fleet target but need to confirm their capability to fully control noxious emissions even in extreme operating conditions, while restraining the overall engine costs and complexity. CO2 and NOx emissions reduction are considered the main drivers for diesel engine evolution. In this perspective, Exhaust Gas After-treatment and Combustion System have been identified as the two main technology aspects to be developed. The purpose of this paper is to describe the evolution paths of these two technologies and the results achieved so far in terms of noxious emissions reduction.
2017-09-04
Technical Paper
2017-24-0116
Ekarong Sukjit, Pansa Liplap, Somkiat Maithomklang, Weerachai Arjharn
Abstract In this study, two oxygenated fuels consisting of butanol and diethyl ether (DEE), both possess same number of carbon, hydrogen and oxygen atom but difference functional group, were blended with the waste plastic pyrolysis oil to use in a 4-cylinder direct injection diesel engine without any engine modification. In addition, the effect of castor oil addition to such fuel blends was also investigated. Four tested fuels with same oxygen content were prepared for engine test, comprising DEE16 (84% waste plastic oil blended with 16% DEE), BU16 (84% waste plastic oil blended with 16% butanol), DEE11.5BIO5 (83.5% waste plastic oil blended with 11.5% DEE and 5% castor oil) and BU11.5BIO5 (83.5% waste plastic oil blended with 11.5% butanol and 5% castor oil). The results found that the DEE addition to waste plastic oil increased more HC and smoke emissions than the butanol addition at low engine operating condition.
2017-09-04
Technical Paper
2017-24-0009
Federico Millo, Giulio Boccardo, Andrea Piano, Luigi Arnone, Stefano Manelli, Giuseppe Tutore, Andrea Marinoni
Abstract To comply with Stage IV emission standard for off-road engines, 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, Ricardo, Denso and Politecnico di Torino was carried out to exploit the potential of new technologies to meet the Stage 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 Stage IV emission standard sets a 0.4 g/kWh NOx limit for the steady state test cycle (NRSC), that includes full load operating conditions, the engine must be operated with very high EGR rates (above 30%) at very high load.
2017-09-04
Technical Paper
2017-24-0011
Giulio Boccardo, Federico Millo, Andrea Piano, Luigi Arnone, Stefano Manelli, Cristian Capiluppi
Abstract Nowadays stringent emission regulations are pushing towards new air management strategies like LP-EGR and HP/LP mix both for passenger car and heavy duty applications, increasing the engine control complexity. Within a project in collaboration between Kohler Engines EMEA, Politecnico di Torino, Ricardo and Denso to exploit the potential of EGR-Only technologies, a 3.4 liters KDI 3404 was equipped with a two stage turbocharging system, an extremely high pressure FIS and a low pressure EGR system. The LP-EGR system works in a closed loop control with an intake oxygen sensor actuating two valves: an EGR valve placed downstream of the EGR cooler that regulates the flow area of the bypass between the exhaust line and the intake line, and an exhaust flap to generate enough backpressure to recirculate the needed EGR rate to cut the NOx emission without a specific aftertreatment device.
2017-09-04
Journal Article
2017-24-0001
Alexander Fandakov, Michael Grill, Michael Bargende, Andre Casal Kulzer
Abstract The most significant operation limit prohibiting the further reduction of the CO2 emissions of gasoline engines is the occurrence of knock. Thus, being able to predict the incidence of this phenomenon is of vital importance for the engine process simulation - a tool widely used in the engine development. Common knock models in the 0D/1D simulation are based on the calculation of a pre-reaction state of the unburnt mixture (also called knock integral), which is a simplified approach for modeling the progress of the chemical reactions in the end gas where knock occurs. Simulations of thousands of knocking single working cycles with a model representing the Entrainment model’s unburnt zone were performed using a detailed chemical reaction mechanism. The investigations showed that, at specific boundary conditions, the auto-ignition of the unburnt mixture resulting in knock happens in two stages.
2017-09-04
Journal Article
2017-24-0012
Andrea Piano, Giulio Boccardo, Federico Millo, Andrea Cavicchi, Lucio Postrioti, Francesco Concetto Pesce
Abstract 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
Journal Article
2017-24-0014
Fabio Bozza, Vincenzo De Bellis, Pietro Giannattasio, Luigi Teodosio, Luca Marchitto
Abstract The technique of liquid Water Injection (WI) at the intake port of downsized boosted SI engines is a promising solution to improve the knock resistance at high loads. In this work, an existing 1D engine model has been extended to improve its ability to simulate the effects of the water injection on the flame propagation speed and knock onset. The new features of the 1D model include an improved treatment of the heat subtracted by the water evaporation, a newly developed correlation for the laminar flame speed, explicitly considering the amount of water in the unburned mixture, and a more detailed kinetic mechanism to predict the auto-ignition characteristics of fuel/air/water mixture. The extended 1D model is validated against experimental data collected at different engine speeds and loads, including knock-limited operation, for a twin-cylinder turbocharged SI engine.
2017-09-04
Journal Article
2017-24-0021
Sabino Caputo, Federico Millo, Giancarlo Cifali, Francesco Concetto Pesce
Abstract One of the key technologies for the improvement of the diesel engine thermal efficiency is the reduction of the engine heat transfer through the thermal insulation of the combustion chamber. This paper presents a numerical investigation on the effects of the combustion chamber insulation on the heat transfer, thermal efficiency and exhaust temperatures of a 1.6 l passenger car, turbo-charged diesel engine. First, the complete insulation of the engine components, like pistons, liner, firedeck and valves, has been simulated. This analysis has showed that the piston is the component with the greatest potential for the in-cylinder heat transfer reduction and for Brake Specific Fuel Consumption (BSFC) reduction, followed by firedeck, liner and valves. Afterwards, the study has been focused on the impact of different piston Thermal Barrier Coatings (TBCs) on heat transfer, performance and wall temperatures.
2017-09-04
Journal Article
2017-24-0055
Enrico Corti, Claudio Forte, Gian Marco Bianchi, Lorenzo Zoffoli
Abstract The performance optimization of modern Spark Ignition engines is limited by knock occurrence: heavily downsized engines often are forced to work in the Knock-Limited Spark Advance (KLSA) range. Knock control systems monitor the combustion process, allowing to achieve a proper compromise between performance and reliability. Combustion monitoring is usually carried out by means of accelerometers or ion sensing systems, but recently the use of cylinder pressure sensors is also becoming frequent in motorsport applications. On the other hand, cylinder pressure signals are often available in the calibration stage, where SA feedback-control based on the pressure signal can be used to avoid damages to the engine during automatic calibration. A predictive real-time combustion model could help optimizing engine performance, without exceeding the allowed knock severity.
2017-09-04
Journal Article
2017-24-0052
Nicolo Cavina, Nahuel Rojo, Andrea Businaro, Alessandro Brusa, Enrico Corti, Matteo De Cesare
Abstract This paper presents simulation and experimental results of the effects of intake water injection on the main combustion parameters of a turbo-charged, direct injection spark ignition engine. Water injection is more and more considered as a viable technology to further increase specific output power of modern spark ignition engines, enabling extreme downsizing concepts and the associated efficiency increase benefits. The paper initially presents the main results of a one-dimensional simulation analysis carried out to highlight the key parameters (injection position, water-to-fuel ratio and water temperature) and their effects on combustion (in-cylinder and exhaust temperature reduction and knock tendency suppression). The main results of such study have then been used to design and conduct preliminary experimental tests on a prototype direct-injection, turbocharged spark ignition engine, modified to incorporate a new multi-point water injection system in the intake runners.
2017-09-04
Journal Article
2017-24-0061
James P. Szybist, Scott W. Wagnon, Derek Splitter, William J. Pitz, Marco Mehl
Abstract Numerous studies have demonstrated that exhaust gas recirculation (EGR) can attenuate knock propensity in spark ignition (SI) engines at naturally aspirated or lightly boosted conditions [1]. In this study, we investigate the role of cooled EGR under higher load conditions with multiple fuel compositions, where highly retarded combustion phasing typical of modern SI engines was used. It was found that under these conditions, EGR attenuation of knock is greatly reduced, where EGR doesn’t allow significant combustion phasing advance as it does under lighter load conditions. Detailed combustion analysis shows that when EGR is added, the polytropic coefficient increases causing the compressive pressure and temperature to increase. At sufficiently highly boosted conditions, the increase in polytropic coefficient and additional trapped mass from EGR can sufficiently reduce fuel ignition delay to overcome knock attenuation effects.
2017-09-04
Journal Article
2017-24-0057
Roberto Finesso, Omar Marello, Ezio Spessa, Yixin Yang, Gilles Hardy
Abstract A model-based approach to control BMEP (Brake Mean Effective Pressure) and NOx emissions has been developed and assessed on a FPT F1C 3.0L Euro VI diesel engine for heavy-duty applications. The controller is based on a zero-dimensional real-time combustion model, which is capable of simulating the HRR (heat release rate), in-cylinder pressure, BMEP and NOx engine-out levels. The real-time combustion model has been realized by integrating and improving previously developed simulation tools. A new discretization scheme has been developed for the model equations, in order to reduce the accuracy loss when the computational step is increased. This has allowed the required computational time to be reduced to a great extent.
2017-09-04
Journal Article
2017-24-0043
Thomas Kammermann, Jann Koch, Yuri M. Wright, Patrik Soltic, Konstantinos Boulouchos
Abstract The interaction of turbulent premixed methane combustion with the surrounding flow field can be studied using optically accessible test rigs such as a rapid compression expansion machine (RCEM). The high flexibility offered by such a test rig allows its operation at various thermochemical conditions at ignition. However, limitations inherent to such test rigs due to the absence of an intake stroke do not allow turbulence production as found in IC-engines. Hence, means to introduce turbulence need to be implemented and the relevant turbulence quantities have to be identified in order to enable comparability with engine relevant conditions. A dedicated high-pressure direct injection of air at the beginning of the compression phase is considered as a measure to generate adjustable turbulence intensities at spark timing and during the early flame propagation.
Viewing 271 to 300 of 44063