Your Selections

Ignition timing
Show Only

Collections

File Formats

Content Types

Dates

Sectors

Topics

Authors

Publishers

Affiliations

Committees

Events

Magazine

   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

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…
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

Effects of direct injection timing and air dilution on the combustion and emission characteristics of stratified flame ignited (SFI) hybrid combustion in a 4-stroke PFI/DI gasoline engine

Brunel University London-Hua Zhao
CATARC-Jian-Jun Yang, Shuang-Xi Liu, Haiyang Gao
  • Technical Paper
  • 2020-01-1139
To be published on 2020-04-14 by SAE International in United States
Controlled Auto-Ignition (CAI) combustion can effectively improve the thermal efficiency of traditional spark ignition (SI) flame propagation combustion, due to the obviously shortened combustion process resulted by the occurrence of auto-ignition. However, its commercial application is limited by the difficult control in the occurrence of combustion process and violent heat release process at high loads. Stratified flame ignited (SFI) hybrid combustion has been proposed to overcome these challenges, in which rich mixture around spark plug is consumed by flame propagation after spark ignition and the unburned lean mixture closing to cylinder wall auto-ignites due to the increased in-cylinder temperature during the flame propagation. The combustion and emission characteristics in the SFI hybrid combustion were experimentally investigated in a single-cylinder 4-stroke gasoline engine at medium-high loads when direct injection (DI) timing was retarded from -100 °CA after top dead center (ATDC) to -40 °CA ATDC and excess air coefficient was increased from 1.0 to 1.2 at the DI ratio of 0.3. The results show that DI timing and excess air coefficient control the ignition timing and…
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

Combined experimental/numerical study of the soot formation process in a gasoline direct-injection spray in the presence of laser-induced plasma ignition

Sandia National Laboratories-Fabien Tagliante, Hyung S. Sim, Lyle M. Pickett, Tuan Nguyen, Scott Skeen
  • Technical Paper
  • 2020-01-0291
To be published on 2020-04-14 by SAE International in United States
Gasoline engines with direct-injection systems operated in a stratified mode provide improved engine efficiency. However, in such mode the particulate emissions are increased compared to conventional spark engine due to the limited mixing between air and fuel, which results in locally rich burn zones where soot is formed. Eliminating these rich combustion events requires detailed understanding of the complex physical phenomena occurring in an engine, including a very high Reynolds number two-phase flow with a complex chemistry. This study proposed a combined experimental/numerical work to better understand the soot formation process when varying the local fuel-air mixture at the spark-ignition location. Combustion issued from an eight-hole, direct-injection spray was experimentally studied in a constant-volume pre-burn combustion vessel using simultaneous high-speed diffused backlit imaging (DBI) and OH* chemiluminescence. DBI has been employed to observe the liquid-phase of the spray and to investigate the soot formation and oxidation taking place during the combustion, while OH* chemiluminescence was used to track the high-temperature ignition and flame. In the current study, the fuel-air mixture was ignited with a plasma…
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

The Isochoric Engine

University of Stuttgart-Benjamin Burger, Michael Bargende
  • Technical Paper
  • 2020-01-0796
To be published on 2020-04-14 by SAE International in United States
At the Institute for Internal Combustion Engines and Automotive Engineering at the University of Stuttgart, a single-cylinder gasoline engine with an actually isochoric combustion was developed and experimentally investigated regarding its thermodynamic behaviour. The constant-volume cycle is the most efficient in terms of thermodynamics. In this case, heat is supplied isochorously, which means at a constant volume. Due to the kinematics of the crank drive of a conventional reciprocating piston engine, combustion would have to take place infinitely fast. However, the conversion of the air-fuel mixture into heat actually requires a certain amount of time. Therefore, the approach taken in the research project was to eliminate the volumetric change during the combustion period. By superimposing the displacement functions of two counter-rotating crankshafts with different speeds and strokes, a variable stagnation of the piston movement around the top dead center is realized. For this purpose, a crankcase with appropriate mechanics was developed, designed and manufactured. By using different kinematic configurations, the dwell time of the piston can be up to 70 degrees crank angle. In the…
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

Water Injection System Application in a Mild Hybrid Powertrain

Chalmers University of Technology-Jayesh Khatri, Lucien Koopmans
  • Technical Paper
  • 2020-01-0798
To be published on 2020-04-14 by SAE International in United States
The potential of 48V Mild Hybrid is promising in meeting the present and future CO2 legislations. There are various system layouts for 48V hybrid system including P0, P1, P2. In this paper, P2 architecture is used to investigate the effects downsized SI engine equipped with water injection system, in a mild hybrid system. Electrification of the conventional powertrain uses the benefits of an electric drive in the low load-low speed region where the conventional SI engine is least efficient and as the load demand increases the IC Engine is used in its more efficient operating region. Engine downsizing and forced induction trend has gained popularity in a hybrid system architecture. However, the engine efficiency is limited by combustion knocking at higher loads, and fuel enrichment becomes must to operate the engine at MBT (Maximum Brake Torque) timing otherwise ignition retard is used to avoid knocking; in turn neutralize the benefits of fuel savings by electrification. Water injection suppresses engine knocking while operating at stoichiometric air-fuel ratio. Additionally, the injection of water reduces flame temperature, giving…
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

Control of Ignition Timing and Combustion Phase by means of Injection Strategy for Jet-Controlled Compression Ignition Mode in a Light Duty Diesel Engine

CATARC-Li Bo
Dalian University of Technology-Jingyu Zhu, Wuqiang Long
  • Technical Paper
  • 2020-01-0555
To be published on 2020-04-14 by SAE International in United States
Premixed charge low temperature combustion such as PCCI (Premixed charge compression ignition) and HCCI (Homogeneous charge compression ignition) has been considered as a promising way to simultaneously improve the fuel economy and reduce the NOx/soot emissions compared to the traditional combustion mode. However, how to realize the stable combustion phasing is still one of the main challenges since reaction of the premixed charge is sensitive to the intake air properties (temperature, oxygen concentration) and chemical kinetics. In this work, effects of multi-injection strategy on the controllability of premixed charge compression ignition were investigated in a light duty prototype diesel engine. Cylinder head was modified to ensure the configuration of two common rail direct injectors. One is for delivering the blended fuel of diesel and ethanol-gasoline to form the premixed charge, another is for injecting the jet-injection diesel fuel in order to trigger the ignition. Piston cavity shape was also optimized to reduce the THC and CO emission resulted from wall-wetting and incomplete combustion in the crevice. Several important factors including pre-injection timing, jet-injection timing, stratified…
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

Analysis of a Prechamber Ignited HPDI Gas Combustion Concept

Graz University of Technology-Andreas Wimmer
Hoerbiger Wien GmbH-Matthias Huschenbett
  • Technical Paper
  • 2020-01-0824
To be published on 2020-04-14 by SAE International in United States
Direct gas injection of natural gas under high pressure (HPDI) into the combustion chamber enables a non-premixed combustion regime known from diesel engines. With this combustion process, knocking combustion cannot occur, enabling an increase in the compression ratio and thus, a possible increase in efficiency. Due to the high injection pressures required, this concept is ideally suited for applications where liquefied natural gas (LNG) is available. In marine applications, the bunkering of and operation with LNG is state of the art. Existing HPDI gas combustion concepts typically use a small amount of diesel fuel for ignition, which is injected late in the compression stroke. The diesel fuel ignites due to the high temperature of the cylinder charge. The subsequently injected gas ignites at the diesel flame. The presented HPDI gas combustion concept is of a monovalent type, meaning that no other fuel than natural gas is used. The high-pressure gas jet is ignited with the aid of flame torches from a gas-scavenged prechamber. Design and layout of the combustion process and the prechamber shape was…
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

Effects on cycle-to-cycle variations and knocking combustion of turbulent jet ignition (TJI) with a small volume pre-chamber

Tianjin University-Jianxiong Hua, Lei Zhou, Qiang Gao, Zhonghui Feng
  • Technical Paper
  • 2020-01-1119
To be published on 2020-04-14 by SAE International in United States
Turbulent jet ignition (TJI) has the advantages of improving burning rates and expanding lean burn limitations of gasoline engines. Based on a single cylinder engine, combustion process with different ignition methods, including single spark ignition, twin spark ignition, one-hole TJI and seven-hole TJI, are studied in this work. Experiments are carried out under conditions with different air/fuel equivalence ratios and different engine loads. Results show that the cycle-to-cycle variations of TJI combustion, which is evaluated by coefficient of variations (CoV) of IMEP and CoV of peak pressure, are obviously reduced due to the fast burning rate induced by the jet flame, and one-hole TJI combustion has the best combustion stability, especially for reducing the CoV of peak pressure. Furthermore, under full-load conditions, pressure oscillations are observed in TJI combustion, and the intensity distribution is different from that in SI combustion, which means that the roots causing the pressure oscillations of TJI and SI are different. Pressure oscillations in TJI combustion are caused by the local fast burning rate of the hot jets, while the pressure…
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

An Optimization Study of Occupant Restraint System for Different BMI Senior Women in Vehicle Frontal Impact

Chongqing University-Guan Lin, Zhenfei Zhan, Huijie Xu, Yue Fu, Ling Jiang, Yunlei Yin
State Key Lab of Vehicle NVH & Safety Technology-Ruyi Chen
  • Technical Paper
  • 2020-01-0981
To be published on 2020-04-14 by SAE International in United States
Accident statistics have shown that older and obese occupants are less adaptable to existing vehicle occupant restraint systems than ordinary middle-aged male occupants, and tend to have higher risk of death and injury in vehicle crashes.However, the current research on the mechanism of injury in vehicle frontal impact for aging and obese occupants is scarce. This paper mainly focuses on the optimization design method of occupant constraint system parameters for specific body type characteristics. The damage attributes of vehicle crash on elderly female with different BMI (body mass index) was analyzed. The design variables in the constraint system were screened for DOE analysis. We selected five parameters for optimization, namely the force limiter force limit value of the seat belt, the pretensioner preload of the seat belt, the preload time of the seat belt, the ignition time of the airbag, the proportionality coefficient of the mass flow rate of the airbag. The objective of this study is to minimize the risk of comprehensive injuries, and the constraints are that indicator values for head injury, neck…
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.
new

High Efficiency by Miller Valve Timing and Stoichiometric Combustion for a Naturally Aspirated Single Cylinder Gas Engine

Karlsruhe University of Applied Sciences-Jörn Judith, Denis Neher, Maurice Kettner
SenerTec Kraft-Wärme-Energiesysteme GmbH-Danny Schwarz, Markus Klaissle
  • Technical Paper
  • 2019-32-0588
Published 2020-01-24 by Society of Automotive Engineers of Japan in Japan
Small-scale cogeneration units (Pel < 50 kW) frequently use lean mixture and late ignition timing to comply with current NOx emission limits. Future tightened NOx limits might still be met by means of increased dilution, though both indicated and brake efficiency drop due to further retarded combustion phasing and reduced brake power. As an alternative, when changing the combustion process from lean burn to stoichiometric, a three-way-catalyst allows for a significant reduction of NOx emissions. Combustion timing can be advanced, resulting in enhanced heat release and thus increased engine efficiency.Based on this approach, this work presents the development of a stoichiometric combustion process for a small naturally aspirated single cylinder gas engine (Pel = 5.5 kW) originally operated with lean mixture. To ensure low NOx emissions, a three-way-catalyst is used. In order to achieve high engine efficiency, measures implemented include Miller valve timing, optimized intake system, reduced engine speed and increased compression ratio. In the first step, a detailed 1D engine cycle simulation model was used to investigate the efficiency benefit of Miller valve timing…
This content contains downloadable datasets
Annotation ability available