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Experimental investigations on engine-out emissions sensitivity to fuel injection pressure of a high-performance DISI single cylinder engine

Ferrari S.p.A.-Vincenzo Rossi, Nicola Silvestri, Massimo Medda
  • Technical Paper
  • 2019-24-0169
To be published on 2019-08-15 by SAE International in United States
In recent times complying with increasingly stringent emission regulations has become ever more challenging. While an efficient after-treatment system that includes gasoline particulate filter enables compliance with legislation requirements, lowering engine-out emissions by improving combustion system has to be considered as a crucial advantage not only in regard to pollutants emission control, but also performance. In this respect, high-performance enabling contents such as relatively large displacement, flow-capacity oriented intake ports and a limited stroke-to-bore ratio have significant drawbacks on the charge motion quality and as direct consequence on mixture formation and homogeneity. As a countermeasure, fuel injection system components as well as control strategies need to be substantially improved; on the control side the increase of fuel injection pressure coupled with optimized injection timing and splitting, has proved to be effective in reducing emissions, with special regard to particulate matter. This paper provides results of an experimental study investigating the effect of different fuel injection strategies on engine-out emissions, with special emphasis on the influence of very high fuel injection pressures (up to 50 MPa)…
 

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.
 

PIV and DBI Experimental Characterization of Air flow-Spray Interaction and Soot Formation in a Single Cylinder Optical Diesel Engine using a Real Bowl Geometry Piston

GM Global Propulsion Systems-Alberto Vassallo
General Motors Italia S.r.l.-Francesco Concetto Pesce
  • Technical Paper
  • 2019-24-0100
To be published on 2019-08-15 by SAE International in United States
With demanding emissions legislations and the need for higher efficiency, new technologies for compression ignition engines are in development. One of them relies on reducing the heat losses of the engine during the combustion process as well as to devise injection strategies that reduce soot formation. Therefore, it is necessary a better comprehension about the turbulent kinetic energy (TKE) distribution inside the cylinder and how it is affected by the interaction between air flow motion and fuel spray. Furthermore, new diesel engines are characterized by massive decrease of NOx emissions. Therefore, considering the well-known NOx-soot trade-off, it is necessary a better comprehension and overall quantification of soot formation and how the different injection strategies can impact it. The present study aims to define a methodology to analyze the velocity field and consequently TKE distribution as well as to characterize soot formation inside of a real bowl geometry considering different operating conditions. For that purpose, two different optical techniques were simultaneously applied in this study. On the one hand, in-cylinder velocity fields were measured by using…
 

A Review of Spark-Assisted Compression Ignition (SACI) Research in the Context of Realizing a Production SACI Strategy

Clemson Univ-Robert Prucka
Clemson Univ.-Dennis Robertson
  • Technical Paper
  • 2019-24-0027
To be published on 2019-08-15 by SAE International in United States
Low temperature combustion (LTC) strategies have been a keen interest in the automotive industry for over four decades since they offer improved fuel efficiency compared to conventional spark-ignition (SI) engines. LTC strategies use high dilution to keep combustion temperatures below about 2000 K to reduce heat transfer losses while avoiding locally rich in-cylinder regions that produce high soot. High dilution also enables an efficiency improvement from reduced pumping work and improved thermodynamic properties, though it requires high ignition energy. Combustion can be achieved by triggering autoignition from compression energy. High compression ratios are typically required to produce this level of ignition energy, which further improves fuel efficiency. The timing of the autoignition event is influenced by fuel properties and mixture composition, and is exponentially sensitive to temperature. Control of autoignition timing is difficult without a direct actuator, and has been a significant obstacle for realizing LTC in production. Spark-assisted compression ignition (SACI) addresses this challenge by using a spark plug to initiate chemical reactions that trigger autoignition. The combustion chamber is slightly stratified to promote…
 

One-way Coupling Methodology of Nozzle Flow and Spray for a Multi-Hole GDi Injector

AKKA-Stefano Bergamini
Toyota Motor Corp-Jun Miyagawa, Kazuhiro Uehara, Yasushi Noguchi
  • Technical Paper
  • 2019-24-0031
To be published on 2019-08-15 by SAE International in United States
With future emission regulations, progressively tighter limitations on particulate number (PN) will be applied on GDi engines. The fuel spray plays an important role on PN formation as it directly affects the homogeneity of air fuel mixture. So detailed investigation of spray characteristics is required. To reduce high prototyping cost and time of making a new injector, a predictive spray model can be used to simulate nozzle flow and spray formation. However, those models are challenging due to the complex and multi-phase phenomena occurring in the combustion chamber, but also because of the different spatial and temporal scales in the different components of the injection systems. This work presents a methodology developed to accurately simulate the spray formation by Discrete Droplet Models (DDM) without experimentally measuring the injector mass flow rate and/or momentum flux. Transient nozzle flow simulations are used instead to define the injection conditions of the spray model. The methodology is applied for the first time to a multi-hole Gasoline Direct injection (GDi). Firstly, the DDM constant values are calibrated comparing simulation results…
 

A Study on Combustion Characteristics of a High Compression Ratio SI Engine with High Pressure Gasoline Injection

Mazda Motor Corp-Takashi Youso, Tatsuya Fujikawa, Masahisa Yamakawa
Waseda Univ-Takashi Kaminaga, Kyohei Yamaguchi, Sok Ratnak, Jin Kusaka
  • Technical Paper
  • 2019-24-0106
To be published on 2019-08-15 by SAE International in United States
In order to improve the thermal efficiency of spark ignition (SI) engines, an improved technology to avoid irregular combustion under high load conditions of high compression ratio SI engines is required. In this study, the authors focused on high-pressure gasoline direct injection in a high compression ratio SI engine, which its rapid air-fuel mixture formation, turbulence, and flame speed, are enhanced by high-speed fuel spray jet. Effects of fuel injection pressure, fuel mass ratio between direct injection and port fuel injection, and spark ignition timing on combustion characteristics were experimentally investigated. It was found that the heat release rate was drastically increased simultaneously by raising the fuel injection pressure. The increase of direct injected fuel mass ratio can also favorably improve the combustion speed. However, longer delay time between end-of-injection and spark timing worsens the combustion rate due to turbulence dissipation. A three-dimensional computational fluid dynamics simulation was also conducted to analyze and discuss the experimental results. The numerical results show that the high-pressure gasoline direct injection enhanced small-scale turbulent intensity and fuel evaporation, respectively.…
 

Compression Ratio and Intake Air Temperature Effect on the Fuel Flexibility of Compression Ignition Engine

King Abdullah Univ of Science & Tech.-Bassam S. E. Aljohani, Hassan Eid, Bengt Johansson
King Abdullah Univ. of Science & Tech.-Abdullah S. AlRamadan, Moez Ben Houidi
  • Technical Paper
  • 2019-24-0110
To be published on 2019-08-15 by SAE International in United States
The effect of compression ratio and intake air temperature on the combustion characteristics of fuels with different octane ratings were investigated on a single-cylinder heavy-duty engine. The study examined Primary Reference Fuels (PRFs) and commercial grade diesel with octane numbers that range from 0 to 100. The engine was configured at a lower compression ratio (CR) of 11.5:1 than typical heavy-duty CI engines to compare the fuels’ burning regime with recently reported measurements at CR17:1. Experiments were performed at different intake air temperature of 20 to 80 DegC, intake air pressure of 1.5 to 3 bar absolute, net indicated mean effective pressure (IMEPNet) of 5 to 20 bar, air/fuel equivalence ratio (lambda) of 1.7 to 3.5, and fuel injection pressure of 700 to 1400 bar. The injection rates have been characterized to determine the hydraulic delay of the injector and thus define the actual ignition delay time. At low loads, diesel-like fuels were found to burn in partially premixed combustion (PPC) mode whereas high octane fuels did not ignite. At high loads, fuels become diffusion…
 

Large eddy simulation of an ignition wave front in a heavy duty partially premixed combustion engine

Lund Univ.-Christian Ibron
Lund University-Hesameddin Fatehi, Mehdi Jangi, Xue-Song Bai
  • Technical Paper
  • 2019-24-0010
To be published on 2019-08-15 by SAE International in United States
In partially premixed combustion engines high octane number fuels are injected into the cylinder during the late part of the compression cycle, giving the fuel and oxidizer enough time to mix into a desirable stratified mixture. If ignited by auto-ignition such a gas composition can react in an ignition wave-front dominated combustion mode. 3D-CFD modeling of such a combustion mode is challenging as the reaction speed is dependent on both mixing history and turbulence acting on the reaction wave. This paper presents a large eddy simulation (LES) study of the effects of energetic turbulence scale on the fuel/air mixing and on the propagation of reaction wave. The results are compared with optical experiments to validate both pressure trace and ignition location. The studied case is a closed cycle simulation of a single cylinder of a Scania D13 engine running PRF81 (81% iso-octane and 19% n-heptane). One-equation-eddy transported SGS-turbulence closure is used in the LES; the fuel spray is modelled using an Lagrangian particle tracking (LPT) approach. The coupling of flow and chemical reactions is done…
 

Experimental tests on the feasibility of passive regeneration in a catalytic DPF at the exhaust of a light-duty Diesel engine

Univ. Of Salerno-Eugenio Meloni
Universita Degli Studi Di Salerno-Bruno Rossomando
  • Technical Paper
  • 2019-24-0045
To be published on 2019-08-15 by SAE International in United States
Diesel engines are attractive thanks to good performance in terms of fuel consumption, drivability, power output and efficiency. Nevertheless in the last years, increasing restrictions have been imposed to particulate emissions, concerning both mass (PM) and number (PN). Different technologies have been proposed to meet emissions standards and the wall-flow Diesel Particulate Filter (DPF) is currently the most common after-treatment system used to trap PM from the exhaust gases. This technology exhibits good features such that it can be regenerated to remove any accumulation of PM. However, this process involves oxidation of the filtered PM at a high temperature through after and post fuel injection strategies, which results in an increase of fuel consumption and may lead to physical damages of the filter in the long term. This work deals with the experimental testing of a catalytic silicon carbide (SiC) wall flow DPF, aiming at decreasing the soot oxidation temperature. The catalyst (CuFe2O4) was deposited on the filter by means of an optimized procedure based on a preliminary controlled chemical erosion of the SiC porous…
 

Influence of Injection Strategies on Engine Efficiency for a Methanol PPC Engine

Lund University-Erik Svensson, Martin Tuner, Sebastian Verhelst
  • Technical Paper
  • 2019-24-0116
To be published on 2019-08-15 by SAE International in United States
Partially premixed combustion (PPC) is one of several advanced combustion concepts for the conventional diesel engine. PPC uses a separation between end of fuel injection and start of combustion, also called ignition dwell, to increase the mixing of fuel and oxidizer. This has been shown to be beneficial for simultaneously reducing harmful emissions and fuel consumption. The ignition dwell can be increased by means of exhaust gas recirculation (EGR) or lower intake temperature. However, the most effective means is to use a fuel with high research octane number (RON). Methanol has a RON of 109 and a recent study found that methanol can be used effectively in PPC mode, with multiple injections, to yield high brake efficiency. However, the early start of injection (SOI) timings in this study were noted as a potential issue due to increased combustion sensitivity. Therefore, the present study attempts to quantify the changes in engine performance for different injection strategies. Simulations were performed on a heavy-duty multi-cylinder compression ignition engine fueled with methanol. Two operating conditions with different engine load…