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Knock Onset Detection Methods Evaluation by In-Cylinder Direct Observation

Istituto Motori CNR-Francesco Catapano, Paolo Sementa, Bianca Maria Vaglieco
  • Technical Paper
  • 2019-24-0233
To be published on 2019-10-07 by SAE International in United States
Improvement of performance and emission of future internal combustion engine for passenger cars is mandatory during the transition period toward their substitution with electric propulsion systems. In middle time, direct injection spark ignition (DISI) engines could offer a good compromise between fuel economy and exhaust emissions. However, abnormal combustion and particularly knock and super-knock are some of the most important obstacles to the improvement of SI engines efficiency. Although knock has been studied for many years and its basic characteristics are clear, phenomena involved in its occurrence are very complex and are still worth of investigation. In particular, the definition of an absolute knock intensity and the precise determination of the knock onset are arduous and many index and methodologies has been proposed. In this work, most used methods for knock onset detection from in-cylinder pressure analyses have been considered. Moreover, same methodologies were applied also to the ionization signal collected through the spark plug, properly instrumented. High speed imaging has been carried out in the combustion chamber of a high performance DISI engine provided…
 

Efficiency Prediction for Optimal Load Point Determination of Internal Combustion Engines in Hybrid Drives

Vienna University of Technology-Bastian Beyfuss, Peter Hofmann, Bernhard Geringer
  • Technical Paper
  • 2019-24-0204
To be published on 2019-09-09 by SAE International in United States
The efficiency of a Hybrid Electric Vehicle (HEV) depends strongly on its implemented energy management strategy (EMS) that splits the drivers torque request onto the internal combustion engine (ICE) and electric motor (EM). For calibrating these EMS, usually, steady-state efficiency maps of the power converters are used. These charts are mainly derived from measurements under optimal conditions. However, while the EM’s efficiency can indeed be considered stable, the efficiency of a ICE fluctuates strongly under different conditions. Among others, these fluctuations can be induced by charge air temperature, engine oil temperature or the fuel’s knock resistance. This paper proposes a new approach for predicting the impact of any external influence onto the ICE efficiency. This is done by computing the actual deviation from the optimal reference ignition timing and adjusting the result by actual oil temperature and target air-to-fuel ratio. For calibrating, only a fuel consumption map, measured under random conditions, and some warm-up measurements are required. The efficiency prognosis is evaluated with measurements from the engine test bench. With this method being real time…
 

Knock and Pre-Ignition Limits on Utilization of Ethanol in Octane–on–Demand Concept

King Abdullah Univ. of Science & Tech.-Eshan Singh, Robert Dibble
Saudi Aramco-Kai Morganti
  • Technical Paper
  • 2019-24-0108
To be published on 2019-09-09 by SAE International in United States
Octane-on-Demand (OoD) is a viable technology for reducing global greenhouse emissions from automobiles. The concept utilizes a low-octane fuel for most operating conditions. Previous research has focused on the minimum ethanol content required for achieving a specific load at a given speed as the low-octane fuel becomes knock limited as the load increases. However, it is also widely known that ethanol has a high tendency to pre-ignite, attributed by few to its high laminar flame speed and surface ignition tendency. Moreover, ethanol has a lower calorific value, requiring a larger fuel mass to be injected to achieve similar power. A larger fuel mass increases the oil dilution by the liquid fuel, creating precursors for pre-ignition. Hence the limits on ethanol addition owing to pre-ignition also needs consideration before the technology can be implemented. In this regard, experiments were performed using light naphtha RON 68 gasoline and ethanol, in direct and port injection configuration respectively. Load was parametrically swept by increasing the intake air and fuel quantity, until pre-ignition limited IMEP was reached. Three different engine…
 

Knock Mitigation by Means of Coolant Control

Università della Calabria-Diego Perrone, Luigi Falbo, Teresa Castiglione, Sergio Bova
  • Technical Paper
  • 2019-24-0183
To be published on 2019-09-09 by SAE International in United States
The potentiality of knock mitigation by means of the control of the coolant flow rate is investigated. As a first step, the dynamic behavior of the wall temperature in response to a sudden variation of the coolant flow rate is analyzed experimentally in a small displacement, 4-valve per cylinder SI engine, which is equipped with an electrically driven pump. Subsequently, the influence of the wall temperature on knock onset is analyzed through a zero-dimensional model and the Livengood and Wu integral. Finally, an experimental activity on the engine test bed is carried-out in order to evaluate the influence of the coolant flow rate and of the engine inlet coolant temperature on the knock phenomenon. Results show that, even though a retarded spark advance and a mixture enrichment are not avoidable in the early stage of knock onset, a cooling control can help reducing the time of use of these fuel consuming strategies in the case of prolonged high-load conditions.
 

Sensitivity Analysis of the Combustion Parameters in a Stratified HCCI Engine with Regard to Performance and Emission

Mazandaran University of Science and Tech-Mohsen Pourfallah, Mahboud Armin
  • Technical Paper
  • 2019-24-0114
To be published on 2019-09-09 by SAE International in United States
Homogeneous charge compression ignition (HCCI) is a promised solution to environmental and fuel economy concerns for IC engines. Engine application for HCCI engine depends on an array of parameters such as fuel type, mixture composition, intake condition and engine specification, meaning that controlling an HCCI engine can only be done through the adjustment of these parameters. In this numerical study which is driven from an experimental work, thermal and charge stratification is used to control HCCI combustion. The effect of intake temperature, compression ratio, intake pressure, EGR, reformer gas (CO-H2 mixture) and glow plug temperature on engine performance and emission was investigated using a 3D model on AVL-FIRE parallel with 1D model on GT-Power software. Then AHP model as a multiple Attribute Decision making method has been used to analyze the sensitivity of these parameters on performance and emission. Results indicate that increasing intake temperature causes the operating condition approaches knock which results in a narrower operating region. Increasing EGR ratio makes possible the expanding of operating range rich limit since it causes delayed combustion…
 

CFD Analysis and Knock Prediction within the Crevices of Piston to Liner Fireland of a High Performance ICE

Ferrari Gestione Sportiva-Angelo Rosetti, Corrado Iotti, Andrea Bedogni
University of Modena e Reggio Emilia-Giuseppe Cantore, Stefano Fontanesi, Fabio Berni
  • Technical Paper
  • 2019-24-0006
To be published on 2019-09-09 by SAE International in United States
The paper aims at defining a methodology for the prediction and understanding of knock tendency in internal combustion engine piston crevices by means of CFD simulations. The motivation for the analysis comes from a real design requirement which appeared during the development of a new high performance SI unit: it is in fact widely known that, in high performance engines (especially the turbocharged ones), the high values of pressure and temperature inside the combustion chamber during the engine cycle may cause knocking phenomena. “Standard” knock can be easily recognized by direct observation of the in-cylinder measured pressure trace; it is then possible to undertake proper actions and implement design and control improvements to prevent it with relatively standard 3D-CFD analyses. Some unusual types of detonation may occur somewhere else in the combustion chamber: knocking inside piston/liner crevices belongs to the latter category and damages on the piston top land (very similar to pitting) are one of the evidence of knock onset in this region. The very localized regions of damage onset, the cycle to cycle…
 

Experimental Analysis of the Influence of Water Injection Strategies on DISI Engine Particle Emissions

IVK - University of Stuttgart-Antonino Vacca, Michael Bargende
Technische Universitat Berlin-Maike Sophie Gern
  • Technical Paper
  • 2019-24-0101
To be published on 2019-09-09 by SAE International in United States
Increasing the efficiency of modern gasoline engines (with direct injection and spark-ignition - DISI) requires innovative approaches. The reduction of the engine displacement, accompanied by an increase of the mean pressure, is limited by the tendency of increasing combustion anomalies. Conventional methods for knock mitigation, on the contrary, have a negative effect on consumption and efficiency. A promising technology to solve these conflicting objectives is the injection of water. Both the indirect and the direct water injection achieve a significant reduction in the load temperature. The fuel enrichment can be reduced, whereby the operating range of the exhaust aftertreatment can be extended. In addition, water injection paves the way for an increase in the geometric compression ratio, which leads to an efficiency advantage even at part load. The influence of water injection on combustion process and raw emissions was analyzed experimentally on a single-cylinder research engine with direct and indirect water injection. Even though water injection initially slows down the combustion process, both injection concepts allow a clear shift in the knock limit and a…
 

Fuel-Lubricant Interactions on the Propensity for Stochastic Pre-Ignition

Driven Racing Oil-Lake Speed
National Renewable Energy Laboratory-Bradley Zigler, Jon Luecke
  • Technical Paper
  • 2019-24-0103
To be published on 2019-09-09 by SAE International in United States
This work explores the interaction of lubricant and fuel properties on stochastic pre-ignition (SPI). Findings are based statistically significant measurements of cylinder pressure to SPI tendency and magnitude. Specifically, lubricant detergents, lubricant volatility, fuel volatility, fuel chemical composition, fuel-wall impingement, and engine load were varied to study the physical-chemistry effects of fuel-lubricant interactions on SPI tendency. The work illustrates that at low loads, with fuels susceptible to SPI events, lubricant detergent package effects on SPI were non-significant. However, with changes to fuel distillation, fuel-wall impingement or fuel chemistry, lubricant detergent effects could be observed even at reduced loads. Interestingly the effects of intentionally nitrogenation of the fuel, through 6.5% by volume addition of nitromethane, resulted in significant sensitivity to lubricant additive package effect on SPI, even at reduced loads, where no lubricant sensitivity was observed without the addition of nitromethane. The combined results highlight the interplay of fuel-lubricant interaction on SPI event, but more importantly suggest that there is the potential of a chemical interaction unique to high load engine operation that results in reactive…
 

Experimental Validation of a Model-Based Water Injection Combustion Control System for On-Board Application

Magneti Marelli SpA - Driveline Division-Matteo De Cesare
University of Bologna-Francesco Ranuzzi, Nicolo Cavina, Guido Scocozza, Alessandro Brusa
  • Technical Paper
  • 2019-24-0015
To be published on 2019-09-09 by SAE International in United States
Water Injection (WI) has become a key technology for increasing combustion efficiency in modern GDI turbocharged engines. In fact, the addition of water mitigates significantly the occurrence of knock, reduces exhaust gas temperatures, and opens the possibility to reach optimum heat release phasing even at high load.This work presents the latest development of a model-based WI controller, and its experimental validation on a GDI TC engine. The controller is based on a novel approach that involves an analytic combustion model to define the spark advance (SA) required to reach a combustion phase target, considering injected water mass effects. The calibration and experimental validation of the proposed controller is shown in detail in the paper. At first, the focus is on the open-loop branch, to evaluate the performance of the combustion model and its ability to manage Spark Advance (SA) taking in account the phasing implications of WI, maintaining a pre-defined combustion phase target. Then the closed-loop (CL) chain is introduced, defining a structure that allows reaching the target while keeping knock intensity (KI) levels under…
 

Evaluation of Water and EGR Effects on Combustion Characteristics of GDI Engines Using a Chemical Kinetics Approach

NAIS-Claudio Forte
University of Bologna-Giulio Cazzoli, Gian Marco Bianchi, Stefania Falfari, Matteo Ricci
  • Technical Paper
  • 2019-24-0019
To be published on 2019-09-09 by SAE International in United States
The modern spark ignition engines, due to the introduced strategies for limiting the consumption without reducing the power, are sensitive to both the detonation and the increase of the inlet turbine temperature. In order to reduce the risk of detonation, the use of dilution with the products of combustion (EGR) is an established practice that has recently improved with the use of water vapor obtained via direct or indirect injection.The application and optimization of these strategies cannot ignore the knowledge of physical quantities characterizing the combustion such as the laminar flame speed and the ignition delay, both are intrinsic property of the fuel and are function of the mixture composition (mixture fraction and dilution) and of its thermodynamic conditions.The experimental measurements of the laminar flame speed and the ignition delay available in literature, rarely report the effects of dilution by EGR or water vapor. To overcome the limitations of the experimentation is possible to predict the value of the ignition delay using numerical models based on chemical kinetics theory. The increased performance of computing systems…