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Influence of port water injection on the combustion characteristics and exhaust emissions in a spark-ignition direct-injection engine

Shanghai Jiao Tong University-Yadong Fan, Tianbao Wu, Xuesong Li, Min Xu, David Hung
  • Technical Paper
  • 2020-01-0294
To be published on 2020-04-14 by SAE International in United States
It is well known that spark-ignition direct-injection (SIDI) gasoline engines have a huge advantage in fuel economy due to their good anti-knock performance compared to port fuel injection engines. However, higher particle number (PN) emissions associated with fuel impingement make the SIDI engines have additional difficulties to meet the upcoming China VI emission standards. In this study, the port water injection (PWI) techniques on a 1.0-L turbocharged, three cylinder, SIDI engine were investigated. PWI strategies were optimized to quantify port water injection as a means of mitigating the knock and improving the combustion performance by sweeping water-fuel mass ratios and PWI timing at different operating conditions. Measurements indicate that regardless of engine load, PWI induced a worsening of the maximum in-cylinder pressure (P-Max) and cycle-to-cycle variations (IMEPN-COV ) , which mainly due to the effects of water dilution and slower burning velocities. But by the advance of spark timing with knock mitigation, we find that the improvement of combustion phasing finally makes it possible to eliminate fuel enrichment, which bring the potential advantages on the…
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On Maximizing Argon Engines' Performance via Subzero Intake Temperatures in HCCI Mode at High Compression Ratios

King Abdullah University of Science & Technology-Ali Elkhazraji, Abdulrahman Mohammed, Sufyan Jan, Jean-Baptiste Masurier, Robert Dibble, Bengt Johansson
  • Technical Paper
  • 2020-01-1133
To be published on 2020-04-14 by SAE International in United States
Maximizing the indicated thermal efficiency with minimal amount of emissions is one of the main challenges to overcome in the field of internal combustion engines. The main obstacle that hinders achieving this goal is the typically low thermodynamic efficiency which is the ratio of the positive produced work on the piston to the amount of heat released inside the cylinder. Many concepts and technologies were innovated to maximize the thermodynamic efficiency. One of the main guidelines that have been followed to achieve so, is the ideal Otto’s cycle that predicts that increasing the compression ratio and/or the specific heat ratio of the combustion reactants, will maximize the thermodynamic efficiency. This study combines both high compression ratios and a high specific heat ratio via two of the main approaches used to maximize the thermodynamic efficiency. First, is the HCCI combustion mode. HCCI is typically operated at fuel-lean conditions, allowing to operate at higher compression ratios without having intense knock (pressure waves, generated by undesired autoignition, that can damage the engine). Second, air was replaced by an…
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Is the “K Value” of an Engine Truly Fuel Independent?

Nissan Motor Co., Ltd.-Masaharu Kassai, Taisuke Shiraishi
Shell Global Solutions (Deutschland) GmbH-Sandro Gail
  • Technical Paper
  • 2020-01-0615
To be published on 2020-04-14 by SAE International in United States
The octane appetite of an engine is frequently characterised by the so-called K value. It is usually assumed that K is dependent only on the thermodynamic conditions in the engine when knock occurs, and not dependent on the fuel. In this work we test this hypothesis: further analysis was conducted on experimental results from SAE 2019-01-0035 in which a matrix of fuels was tested in a single cylinder engine. The fuels consisted of a relatively small number of components and the RON and MON were decorrelated. This simplifies the analysis of the chemical kinetic proprieties. It was shown previously that K increases with engine speed because a higher temperature and pressure is reached along the compression isentrope before knock onset. Through dividing the original fuels matrix into subsets, it was possible to explore the variation of K value with fuel properties. It was found that K value tends to increase slightly with RON. The explanation for this finding is that higher RON leads to advanced ignition timing (i.e. closer to MBT conditions) and advanced ignition…
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A path towards high efficiency SI combustion in a CFR engine: Cooling the intake to sub-zero temperatures

King Abdullah University of Science & Technology-Sufyan M. Jan, Abdulrahman Mohammed, Ali Elkhazraji, Jean-Baptiste Masurier
University of California-Robert Dibble
  • Technical Paper
  • 2020-01-0550
To be published on 2020-04-14 by SAE International in United States
Textbook engine thermodynamics predicts that SI (Spark Ignition) engine efficiency η is a function of both the compression ratio CR of the engine and the specific heat ratio γ of the working fluid. In practice the compression ratio of the SI engine is often limited due to “knock”. When this knock limit is reached, increase in heat transfer losses result in reduction in efficiency. One way to lower the end-gas temperature is to cool the intake gas before inducting it into the combustion chamber. With colder intake gases, higher CR can be deployed, resulting in higher efficiencies. In this regard, we investigated the indicated efficiency of the standard Waukesha CFR engine. The engine is operated in the SI engine mode. The engine was operated with three different mediums using the same fuel Methane (Gas). First is Air + Methane at room temperature, second was O2 + Argon + Methane gas mixture at room temperature, and lastly O2 + Argon +Methane at sub-zero conditions. We replace the Air by an Oxygen-Argon mixture to increase the specific…
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Impact of Engine Oil Detergent on Low Speed Pre-Ignition (LSPI) and Fuel Economy Performance

Afton Chemical Corp.-Ashutosh Gupta, Mark Devlin
  • Technical Paper
  • 2020-01-1424
To be published on 2020-04-14 by SAE International in United States
Low Speed Pre-Ignition (LSPI), also referred to as Stochastic Pre-Ignition (SPI), Superknock or Megaknock is an undesirable combustion phenomenon that limits the fuel economy, drivability, emissions and durability performance of modern turbocharged gasoline engines. Numerous studies have previously reported that the frequency of LSPI is sensitive to engine oil composition. One of these drivers is the concentration of Calcium, which is usually delivered in the form of a detergent in the additive package. Switching to completely all-Magnesium detergent and/or severely limiting the concentration of Ca in the engine oil have recently been proposed as potential means to reduce LSPI. In this work, we evaluate the impact of detergent type on LSPI performance as well as on other performance that the modern engine oil needs to deliver. Particularly the impact of detergent type on Fuel Economy performance is evaluated. To ensure a rigorous and high precision measurement of the impact of engine oil on fuel economy, representative of real-world conditions, under well-controlled conditions, the ASTM D8114 test (Sequence VIE) was used to quantify fuel economy performance…
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Numerical investigations on strong knocking combustion under compression ignition conditions

State Key Lab of Engines-Jiaying Pan
Tianjin University-Lin Chen, Jianfu Zhao
  • Technical Paper
  • 2020-01-1137
To be published on 2020-04-14 by SAE International in United States
Homogeneous charge compression ignition (HCCI) combined with high compression ratio is an effective way to improve engines’ thermal efficiency. However, the severe thermodynamic conditions at high load may induce knocking combustion thus damage engine body. In this study, compression ignition knocking characteristics were parametrically investigated through RCM experiments and simulation analysis. First, the knocking characteristics were optically investigated. The experimental results show that there even exists detonation when the knock occurs thus the combustion chamber is damaged. Considering both safety and costs, the effects of different initial conditions were numerically investigated and the results show that knocking characteristics is more related to initial pressure other than initial temperature. The initial pressure have a great influence on peak pressure and knock intensity while initial temperature on knock onset. Further analysis shows that knock intensity is mainly related to the energy density of the in-cylinder mixture and energy density is higher under higher pressure conditions. Then the effects of different cylinder wall temperature on the local auto-ignition thus knocking characteristics were further discussed. The results show that…
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Analytical approach to characterize the effect of engine control parameters and fuel properties on ACI operation in a GDI engine

Argonne National Laboratory-Johannes Rohwer, Ashish Shah, Toby Rockstroh
  • Technical Paper
  • 2020-01-1141
To be published on 2020-04-14 by SAE International in United States
Advanced compression ignition (ACI) operation in gasoline direct injection (GDI) engines is a promising concept to reduce fuel consumption and emissions at part load conditions. However, combustion phasing control and the limited operating range in ACI mode are a perennial challenge. In this study the combined impact of fuel properties and engine control strategies are investigated. A design of experiments method was implemented using a three level orthogonal array to determine the sensitivity of five engine control parameters on four engine response variables under low load ACI operation for three 98 RON gasoline fuels, exhibiting disparate chemical composition. Furthermore, the thermodynamic state of the compression histories was studied with the aid of the pressure-temperature framework and correlations were drawn to analogous HCCI experiments conducted in an instrumented CFR engine. Due to the compression ratio constraints imposed by knock limited SI operation, considerable intake temperature heating was required resulting in advanced compression ignition mode resulting in the intermediate to high temperature autoignition regime. The olefin containing fuel was found to require the least amount of intake…
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Determination of Octane Index and K in a 2L, 4-cylinder turbocharged SI engine using the PRF method

Michigan Technological University-Siddharth Gopujkar, Jeremy Worm, Joel Duncan, William Hansley
  • Technical Paper
  • 2020-01-0552
To be published on 2020-04-14 by SAE International in United States
Research Octane Number (RON) and Motor Octane Number (MON) have traditionally been used to describe fuel anti-knock quality. The test conditions for MON are harsher than those for RON, causing the RON for a particular fuel to be higher than the MON. Researchers have proposed the anti-knock performance can be described using the Octane Index (OI), defined as OI=RON-K(RON-MON), where ‘K’ is a weighing factor between RON and MON. The K-factor indicates that at a particular operating condition, knock tolerance is better described by RON as K approaches a value of 1, and MON as K approaches a value of 0. Previous studies claim that K-factor is dependent only on the engine combustion system and the speed-load point, and that it is independent of fuel chemistry. In these studies, K was determined experimentally using linear regression. In this particular study, K was determined using the PRF method for two test fuels; EPA certification tier 2 and tier 3 fuel. K was calculated for these fuels at multiple test points and the results showed that the…
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Knock detection with series cylinder pressure sensors - Function principles – Realization in the engine control unit – vehicle measurement results from the chassis dyno -

Technical University of Munich-Matthias Gaderer
Vitesco Technologies GmbH-Harry Schuele, Johannes Beer
  • Technical Paper
  • 2020-01-1143
To be published on 2020-04-14 by SAE International in United States
Current legal requirements based on new driving cycles like WLTP or RDE focus on elevated power and torque from the engine. The gear ratios are chosen so as to permit low engine speeds to reduce fuel consumption and consequently CO2 emissions by shifting the operating point to higher loads with reduced throttling and friction losses at low engine speeds. To achieve the required acceleration values the engine tends to be operated more frequently close to its power and torque limits. Thus, the knock occurring at the load limits will increase in significance. Today, in series production, knock is detected via structure-borne sound sensors and eliminated via retarded ignition. New low-cost in cylinder-pressure sensors (ICPS) suitable for series-production now permit evaluation of every single combustion, thus detecting knock in the engine control unit at all speed and load ratios independent of parasitic noise. This paper presents the potential for knock detection and knock control using series-production capable cylinder-pressure sensors. First, the basic differences of the algorithm of a structure-borne sensor and a cylinder-pressure sensor and the…
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Characteristics of Auto-ignition for Lubricants and Lubricant/Gasoline based on An Innovative Single Droplet Combustion System

Tongji University-Yang Yu, Kaifeng Pan, Jun Deng, Zongjie Hu, Wei Xie, Zhijun Wu, Liguang Li
  • Technical Paper
  • 2020-01-1428
To be published on 2020-04-14 by SAE International in United States
Due to the advantages of low weight, low emission and good fuel economy, downsized turbocharged gasoline direct injection (GDI) engines are widely-applied nowadays. However, Low-Speed Pre-Ignition (LSPI) phenomenon observed in these engines restricts their improvement of performance. Some researchers have shown that auto-ignition of lubricant in the combustion chamber has a great effect on the LSPI frequency. To study the auto-ignition characteristics of lubricant, an innovative single droplet auto-ignition measurement system for lubricant and its mixture is designed and developed, with better accuracy and effectiveness. The experiments are carried out by hanging lubricant droplets on the thermocouple node under active thermo-atmosphere provided by a small Dibble burner. The auto-ignition process of lubricant droplets is recorded by a high-speed camera. Influences of different base oil types, viscosities, calcium contents, initial droplet diameters, co-flow speeds, new oil, used oil and blending ratios of lubricant and gasoline on the ignition delay time of droplets are investigated at different droplet temperatures. The co-flow field temperature varies from 823K to 1323K. Equivalent diameters of droplets, 0.99mm, 1.24mm and 1.63mm, generated…