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Study of fuel octane sensitivity effects on gasoline partially premixed combustion using optical diagnostics

Kaust-Hao Shi
King Abdullah Univ of Science & Tech-Yanzhao An, Bengt Johansson
  • Technical Paper
  • 2019-24-0025
To be published on 2019-08-15 by SAE International in United States
Partially premixed combustion (PPC) is a low-temperature combustion (LTC) concept that could deliver higher engine efficiency, as well as lower NOx and soot emissions. Gasoline-like fuels are beneficial for air/fuel mixing process under PPC mode because they have superior auto-ignition resistance to prolong ignition delay time. In current experiments, the high octane number gasoline fuel E10 (US market used gasoline, RON=91) and low octane number GCI blend fuel (RON=77) were tested respectively in a full-transparent AVL single cylinder optical compression ignition (CI) engine. Aiming at investigating the fuel sensitivity on engine performances under different combustion modes as well as soot particle emissions, the engine operating parameters and emission data were analyzed from CI to HCCI (homogeneous charge compression ignition) via PPC (partially premixed combustion) by changing fuel injection timing. In addition, in order to get a deep insight of in-cylinder auto-ignition and combustion evolution process, planar laser-induced fluorescence (PLIF) imaging and high-speed natural flame luminosity (NFL) imaging techniques are used for visualizing fuel distribution, auto-ignition kernel development and combustion processes.

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 2019-08-15 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…

Quantification and Analyses of Knock in Gasoline Engines

Ford Research and Advanced Engineering-Maziar Khosravi
Ford-Werke GmbH-Albert Breuer
  • Technical Paper
  • 2019-24-0089
To be published on 2019-08-15 by SAE International in United States
The continuously increasing demand for improved fuel efficiency, low-emissions and high performance in gasoline engines has led to down-sizing and down-speeding. This promising and broadly applied concept, which necessitates ever higher Break Mean Effective Pressure (BMEP), is impeded at high loads by knock, stochastic Low Speed Pre-ignition (LSPI), and mega-knock. Significant research has been conducted in recent years in the field of abnormal combustion phenomena in gasoline engines and the impacts of potential mitigation concepts by using various simulation tools. In the present study, a knock analysis methodology has been developed to investigate knock in Gasoline Engines. The strategy employs multiple techniques to quantify knock tendency and severity as well as identify outlier cycles for frequency analysis. By incorporating a Continuous Wavelet Transform in addition to conventional Fast Fourier Transform the amplitude, frequency, and temporal location of the oscillations can be analyzed simultaneously. The analysis led to the detection of numerous peculiar cycles with high peak oscillation amplitudes but negligible resonance. A low amplitude oscillation with a frequency of 24 kHz likely caused by the…

Exploration of Cavitation-suppressing Orifice Designs for a Heavy-duty Diesel Injector Operating with Straight-Run Gasoline

Aramco Research Center - Detroit-Yuanjiang Pei, Michael L. Traver
Argonne National Laboratory-Roberto Torelli, Gina M. Magnotti, Sibendu Som
  • Technical Paper
  • 2019-24-0126
To be published on 2019-08-15 by SAE International in United States
The occurrence of cavitation inside injectors is generally undesirable since it can cause material erosion and result in deviations from the expected operating conditions and performance. Previous numerical work employing an injector geometry measured with x-ray diagnostics and operating with a high-volatility straight-run gasoline has shown that: (1) most of the cavitation is generally observed at low needle lifts, (2) needle motion is responsible for asymmetric structures in the internal flow as well as large pressure and velocity gradients that trigger phase transition at the orifice inlets, and (3) cavitation affects the injector discharge coefficient and distribution of injected fuel. To explore the potential for material damage within the injector orifices due to cavitation cloud collapse, the cavitation-induced erosion risk assessment (CIERA) tool has been applied for the first time to the realistic geometry of a heavy-duty injector using the CONVERGE software. Critical locations with high erosive potential matched qualitatively well with x-ray scans of an eroded injector sample that underwent a durability test with straight-run gasoline. This motivated a CFD exploration of a series…

Validation of Using a Steady-State Friction Model for Determining CO2 Emissions in Transient Driving Cycles

Mahle International GmbH-Tobias Funk, Holger Ehnis, Reiner Kuenzel
Universität Stuttgart-Michael Bargende
  • Technical Paper
  • 2019-24-0054
To be published on 2019-08-15 by SAE International in United States
MAHLE is conducting extensive parameter studies regarding friction savings on the piston group of fired gasoline and diesel engines to further increase the efficiency of the internal combustion engine. For each tested piston variant, steady-state fired friction measurements are taken across the entire operating range of the engine using the indication method. Based on these measurements, an empirical model is created which describes the Friction Mean Effective Pressure (FMEP) depending on engine speed, engine load and coolant and oil temperature. The friction map is then used in a drive cycle simulation in order to determine fuel consumption and CO2 emissions. A drive cycle corresponds to transient conditions both as a result of the changes in operating point and the engine warm-up. The current legislative drive cycles aim to better reflect real-world driving conditions and thus contain frequent and steep transient events. This article therefore assesses if the confidence interval of the steady-state friction model is also valid in transient engine operation with warm-up. For this purpose, fired friction measurements are taken both with defined speed…

Imaging and vibro-acoustic diagnostic techniques comparison for a GDI fuel injector

Istituto Motori CNR-Luigi Allocca, Daniela Siano, Alessandro Montanaro, Maria Antonietta Panza
  • Technical Paper
  • 2019-24-0058
To be published on 2019-08-15 by SAE International in United States
This work presents the results of an experimental investigation on a GDI injector, in order to analyze fuel injection process and atomization phenomenon, correlating imaging and vibro-acoustic diagnostic techniques. A single-hole, axially-disposed, 0.200 mm diameter GDI injector was used to spray commercial gasoline in a test chamber at room temperature and atmospheric backpressure. The explored injection pressures were ranged from 5.0 to 20.0 MPa. Cycle-resolved acquisitions of the spray evolution were acquired by a high-speed camera. Contemporarily, the vibro-acoustic response of the injector was evaluated. More in detail, noise data acquired by a microphone sensor were analyzed for characterizing the acoustic emission of the injection, while a spherical loudspeaker was used to excite the spray injection at a proper distance detecting possible fuel spray resonance phenomena. In order to monitor vibration throughout the injection event, the injector was also equipped with an accelerometer sensor, adhesively mounted on the holder. Tests in both dry and fuel injection conditions allowed to distinct the pure mechanical operation of the injector related to the needle opening and closing, and…

On the HCCI octane boosting effects of γ-Valerolactone

King Abdullah Univ. of Science & Tech.-Jean-Baptiste Masurier, Binod Giri, Gani Issayev, Bengt Johansson, Aamir Farooq PhD
  • Technical Paper
  • 2019-24-0026
To be published on 2019-08-15 by SAE International in United States
Transportation sector is almost entirely powered by internal combustion engines (ICEs) burning petroleum-based liquid fuels. This makes the transportation sector the main culprit of global warming due to the large quantity of CO2 emission from burning these petroleum-based fuels. Over the last few decades, there are growing concerns over global warming and diminishing petroleum reserves. Such concerns have led to concentrated efforts directed at a paradigm shift from conventional fuels to renewable alternatives which can promote cleaner combustion. Therefore, future research directions should orient towards exploring new fuels suitable for future ICEs to achieve better engine efficiency and significantly less harmful emissions. One way to achieve these objectives is to focus on improving the combustion technology by developing new fuel-engine systems. Consequently, scientists and engineers are showing growing interest towards non-petroleum-based fuels coming from renewable resources. Among bio-derived fuels, γ-Valerolactone (GVL), a fuel derived from lignocellulosic biomass, has recently attracted considerable attention due to its potential for increasing the octane number and reducing harmful emissions. This study aims to examine GVL as an octane booster…

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

IVK - University of Stuttgart-Antonino Vacca
Technische Universitat Berlin-Maike Sophie Gern
  • Technical Paper
  • 2019-24-0101
To be published on 2019-08-15 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…

Gasoline Spray_Models_Calibration_Under_Diesel_Engine_Like_Conditions

  • Technical Paper
  • 2019-24-0032
To be published on 2019-08-15 by SAE International in United States
Atomization of liquid fuel jets is critical to the performance of Internal Combustion (IC) engine, as it plays a key role in affecting mixture formation, combustion efficiency and soot emissions. In the Gasoline Compression Ignition (GCI) engine investigation, the experimental measurements on the gasoline injection into diesel engine like condition, shows the difficulty in matching the liquid penetration length when the diesel spray model is used. Additional tests performed at lower ambient densities, seen in early injection, revealed a lot of information on liquid jet dynamics behavior. It requires a lot of model calibration effort in matching the measured liquid and vapor penetration length under different ambient pressure conditions. It is found that using droplet Sauter Mean Diameter distribution model shows better match with experiment at low density condition, whereas the KH-ACT breakup model correlates well with measurement at high density condition.

Biogenous Ethanol: CO2 Savings and Operation in a Dual-Fuel Designed Diesel Engine

Vienna University of Technology-Aleksandar Aleksandrov Damyanov, Peter Hofmann
  • Technical Paper
  • 2019-24-0040
To be published on 2019-08-15 by SAE International in United States
The usage of ethanol and two different mixtures of ethanol and gasoline (E85 and E65) was investigated on a modified diesel engine designed to work in a dual-fuel combustion mode with intake manifold alcohol injection. The maximum ratio of alcohol to diesel fuel was limited by irregular combustion phenomena like degrading combustion quality and poor process controllability at low load and knock as well as auto-ignition at high load. With rising alcohol amount, a significant reduction of soot mass and particle number was observed. At some testing points, substituting diesel with ethanol, E65 or E85 led to a reduction of NOx emissions; however, the real benefit concerning the nitrogen oxides was introduced by the mitigation of the soot-NOx trade-off. With regard to the engine efficiency aspect, the results show bidirectional behaviour: at low load points engine efficiency degrades, whereas the process becomes by up to 6 % (rel.) more effective at higher engine loads. Substituting diesel via manifold injected alcohol at higher mean effective pressures also enhances the EGR tolerance, making it possible to apply…