Refine Your Search

Topic

Search Results

Technical Paper

Preliminary Testing of n-Butanol HCCI on High Compression Ratio Diesel Engines

2019-04-02
2019-01-0577
The control of combustion phasing in homogeneous charge compression ignition (HCCI) combustion is investigated with neat n-butanol in this work. HCCI is a commonly researched combustion mode, owing to its improved thermal efficiency over conventional gasoline combustion, as well as its lower nitrogen oxide (NOx) and particulate matter emissions compared to those of diesel combustion. Despite these advantages, HCCI lacks successful widespread implementation with conventional fuels, primarily due to the lack of effective combustion phasing control. In this preliminary study, chemical kinetic simulations are conducted to study the auto-ignition characteristics of n-butanol under varied background pressures, temperatures, and dilution levels using established mechanisms in CHEMKIN software. Increasing the pressure or temperature lead to a shorter ignition delay, whereas increasing the dilution by the application of exhaust gas recirculation (EGR) leads to a longer ignition delay.
Technical Paper

A Study of Energy Enhanced Multi-Spark Discharge Ignition in a Constant-Volume Combustion Chamber

2019-04-02
2019-01-0728
Multi-spark discharge (MSD) ignition is widely used in high-speed internal combustion engines such as racing cars, motorcycles and outboard motors in attempts to achieve multiple sparks during each ignition. In contrast to transistor coil ignition (TCI) system, MSD system can be greatly shortened the charging time in a very short time. However, when the engine speed becomes higher, the ignition will be faster, electrical energy stored in the ignition system will certainly become less, especially for MSD system. Once the energy released into the spark plug gap can’t be guaranteed sufficiently, ignition will become more difficult, and it will get worse in some harsh environment such as strong turbulence or lean fuel conditions. With these circumstances, the risks of misfire and partial combustion will increase, which can deteriorate the power outputs and exhaust emissions of internal combustion engine.
Technical Paper

An Investigation on the Regeneration of Lean NOx Trap Using Ethanol and n-Butanol

2019-04-02
2019-01-0737
Reduction of nitrogen oxides (NOx) in lean burn and diesel fueled Compression Ignition (CI) engines is one of the major challenges faced by automotive manufacturers. Lean NOx Trap (LNT) and urea-based Selective Catalytic Reduction (SCR) exhaust after-treatment systems are well established technologies to reduce NOx emissions. However, each of these technologies has associated advantages and disadvantages for use over a wide range of engine operating conditions. In order to meet future ultra-low NOx emission norms, the use of both alternative fuels and advanced after-treatment technology may be required. The use of an alcohol fuel such as n-butanol or ethanol in a CI engine can reduce the engine-out NOx and soot emissions. In CI engines using LNTs for NOx reduction, the fuel such as diesel is utilized as a reductant for LNT regeneration.
Technical Paper

Boosted Current Spark Strategy for Lean Burn Spark Ignition Engines

2018-04-03
2018-01-1133
Spark ignition systems with the capability of providing spark event with either higher current level or longer discharge duration has been developed in recent years to help IC engines towards clean combustion with higher efficiency under lean/diluted intake charge. In this research, a boosted current spark strategy was proposed to investigate the effect of spark discharge current level and discharge duration on the combustion process. Firstly, the discharge characteristics of a boosted current spark system were tested with a traditional spark plug under crossflow conditions, and results showed that the spark channel was more stable, and was stretched much longer when the discharge current was boosted. Then the boosted current strategy was used in a spark ignition engine operating under lean conditions. Boosted current was added to the spark channel with different timing, duration, and current levels.
Technical Paper

Ion Current Measurement of Diluted Combustion Using a Multi-Electrode Spark Plug

2018-04-03
2018-01-1134
Close-loop feedback combustion control is essential for improving the internal combustion engines to meet the rigorous fuel efficiency demands and emission legislations. A vital part is the combustion sensing technology that diagnoses in-cylinder combustion information promptly, such as using cylinder pressure sensor and ion current measurement. The promptness and fidelity of the diagnostic are particularly important to the potential success of using intra-cycle control for abnormal cycles such as super knocking and misfiring. Many research studies have demonstrated the use of ion-current sensing as feedback signal to control the spark ignition gasoline engines, with the spark gap shared for both ignition and ion-current detection. During the spark glow phase, the sparking current may affect the combustion ion current signal. Moreover, the electrode gap size is optimized for sparking rather than measurement of ion current.
Technical Paper

A Simplified Circuit Model for the Emulation of Glow Phase during Spark Discharge

2018-04-03
2018-01-0092
The ever-growing demand to meet the stringent exhaust emission regulations have driven the development of modern gasoline engines towards lean combustion strategies and downsizing to achieve the reduction of exhaust emission and fuel consumption. Currently, the inductive ignition system is still the dominant ignition system applied in Spark Ignited (SI) engines. It is popular due to its simple design, low cost and robust performance. The new development in spark ignition engines demands higher spark energy to be delivered by the inductive ignition system to overcome the unfavorable ignition conditions caused by the increased and diluted in-cylinder charge. To meet this challenge, better understanding of the inductive ignition system is required. The development of a first principle model for simulation can help in understanding the working mechanism of the system in a better way.
Technical Paper

A Fuel Sensitive Ignition Delay Model for Direct Injection Diesel Engine Operating under EGR Diluted Conditions

2018-04-03
2018-01-0231
This empirical work investigates the impacts of thermodynamic parameters, such as pressure and temperature, and fuel properties, such as fuel Cetane number and aromatic contents on ignition delay in diesel engines. Systematic tests are conducted on a single-cylinder research engine to evaluate the ignition delay changes due to the fuel property differences at low, medium and high engine loads under different EGR dilution ratios. The test fuels offer a range of Cetane numbers from 28 to 54.2 and aromatic contents volume ratios from 19.4% to 46.6%. The experimental results of ignition delays are used to derive an ignition delay model modified from Arrhenius’ expression. Following the same format of Arrhenius’ equation, the model incorporates the pressure and temperature effects, and further includes the impacts of intake oxygen concentration, fuel Cetane number and aromatic contents volume ratio on the ignition delay.
Technical Paper

Early Pilot Injection Strategies for Reactivity Control in Diesel-ethanol Dual Fuel Combustion

2018-04-03
2018-01-0265
This paper examines the diesel-ethanol dual fuel combustion at medium engine loads on a single-cylinder research diesel engine with a compression ratio of 16.5:1. The effect of exhaust gas recirculation (EGR) and ethanol energy ratio was investigated for the dual fuel combustion to achieve simultaneously ultra-low NOx and soot emissions. A medium ethanol ratio of about 0.6 was found suitable to meet the requirements for mixing enhancement and ignition control, which resulted in the lowest NOx and soot emissions among the tested ethanol ratios. A double-pilot injection strategy was found competent to lower the pressure rise rate owing to the reduced fuel quantity in the close-to-TDC injection. The advancement of pilot injection timing tended to reduce the CO and THC emissions, which is deemed beneficial for high EGR operations. The reactivity mutual-modulation between the diesel pilot and the background ethanol mixture was identified.
Technical Paper

Ignition Improvement for Ultra-Lean Dilute Gasoline Combustion

2017-10-08
2017-01-2244
In this work, a spatially distributed spark ignition strategy was employed to improve the ignition process of well-mixed ultra-lean dilute gasoline combustion in a high compression ratio (13.1:1) single cylinder engine at partial loads. The ignition energy was distributed in the perimeter of a 3-pole igniter. It was identified that on the basis of similar total spark energy, the 3-pole ignition mode can significantly shorten the early flame kernel development period and reduce the cyclic variation of combustion phasing, for the spark timing sweep tests at λ 1.5. The effect of ignition energy level on lean-burn operation was investigated at λ 1.6. Within a relatively low ignition energy range, i.e. below 46 mJ per pole, the increase in ignition energy via ether 1 pole or 3 pole can improve the controllability over combustion phasing and reduce the variability of lean burn combustion. Higher ignition energy was required in order to enable ultra-lean engine operation with λ above 1.6.
Technical Paper

Investigation of Multi-Pole Spark Ignition Under Lean Conditions and with EGR

2017-03-28
2017-01-0679
In order to meet the future carbon dioxide legislation, advanced clean combustion engines are tending to employ low temperature diluted combustion strategies along with intensified cylinder charge motion. The diluted mixtures are made by means of excess air admission or exhaust gas recirculation. A slower combustion speed during the early flame kernel development because of the suppressed mixture reactivity will reduce the reliability of the ignition process and the overall combustion stability. In an effort to address this issue, an ignition strategy using a multi-pole spark igniter is tested in this work. The igniter uses three electrically independent spark gaps to allow three spatially distributed spark discharges. The multi-pole spark strategy displayed more advanced combustion phasing and lower phasing variability compared to single spark discharges.
Technical Paper

Improvement on Energy Efficiency of the Spark Ignition System

2017-03-28
2017-01-0678
Future clean combustion engines tend to increase the cylinder charge to achieve better fuel economy and lower exhaust emissions. The increase of the cylinder charge is often associated with either excessive air admission or exhaust gas recirculation, which leads to unfavorable ignition conditions at the ignition point. Advanced ignition methods and systems have progressed rapidly in recent years in order to suffice the current and future engine development, and a simple increase of energy of the inductive ignition system does not often provide the desired results from a cost-benefit point of view. Proper design of the ignition system circuit is required to achieve certain spark performances.
Journal Article

Preliminary Investigation of Exhaust Pressure Waves in a Single Cylinder Diesel Engine and the Impacts on Aftertreatment Sprays

2017-03-28
2017-01-0616
The pressure wave actions were investigated in the exhaust system of a single cylinder diesel engine through both experimental and simulation methods. The characteristics of the exhaust pressure waves under different engine operating conditions, such as engine load and exhaust backpressure, were examined. The results showed that the strength of the exhaust pressure wave was affected by both the in-cylinder pressure and the exhaust backpressure in the exhaust system during the period when the exhaust valves were open. The exhaust gas flow velocity was also estimated by the one dimensional simulation tool AVL BOOST™. The results suggested that the velocity of the exhaust gas fluctuated during the engine cycle, and followed trends similar to the exhaust pressure wave. The transient gas flow velocity was high when there was a strong compression wave, and it was reduced when the pressure fluctuations in the exhaust manifold were small.
Technical Paper

A Feasibility Study of Using DI Butanol as an Ignition Source for Dual-Fuel Combustion

2017-03-28
2017-01-0770
The combustion of dual-fuel engines usually uses a pilot flame to burn out a background fuel inside a cylinder under high compression. The background fuel can be either a gaseous fuel or a volatile liquid fuel, commonly with low reactivity to prevent premature combustion and engine knocking; whereas the pilot flame is normally set off with the direct injection of a liquid fuel with adequate reactivity that is suitable for deterministic auto-ignition with a high compression ratio. In this work, directly injected butanol is used to generate the pilot flame, while intake port injected ethanol or butanol is employed as the background fuel. Compared with the conventional diesel-only combustion, dual-fuel operations not only broaden the fuel applicability, but also enhance the potential for clean combustion, in high efficiency engines. The amount of background fuel and the scheduling of pilot flame are investigated through extensive laboratory experiments.
Technical Paper

Mode Switching to Improve Low Load Efficiency of an Ethanol-Diesel Dual-Fuel Engine

2017-03-28
2017-01-0771
The dual-fuel application using ethanol and diesel fuels can substantially improve the classical trade-off between oxides of nitrogen (NOx) and smoke, especially at moderate-to-high load conditions. However, at low engine load levels, the use of a low reactivity fuel in the dual-fuel application usually leads to increased incomplete combustion products that in turn result in a significant reduction of the engine thermal efficiency. In this work, engine tests are conducted on a high compression ratio, single cylinder dual-fuel engine that incorporates the diesel direct-injection and ethanol port-injection. Engine load levels are identified, at which, diesel combustion offers better efficiency than the dual-fuel combustion while attaining low NOx and smoke emissions. Thereafter, a cycle-to-cycle based closed-loop controller is implemented for the combustion phasing and engine load control in both the diesel and dual-fuel combustion regimes.
Technical Paper

Fuel Burn Rate Control to Improve Load Capability of Neat n-Butanol Combustion in a Modern Diesel Engine

2016-10-17
2016-01-2301
This research work investigates the control strategies of fuel burn rate of neat n-butanol combustion to improve the engine load capability. Engine tests of homogeneous charge compression ignition (HCCI) and partially premixed combustion (PPC) with neat n-butanol show promising NOx and smoke emissions; however, the rapid burn rate of n-butanol results in excessive pressure rise rates and limits the engine load capability. A multi-event combustion strategy is developed to modulate the fuel burn rate of the combustion cycle and thus to reduce the otherwise high pressure rise rates at higher engine load levels. In the multi-event combustion strategy, the first combustion event is produced near TDC by the compression ignition of the port injected butanol that resembles the HCCI combustion; the second combustion event occurs near 7~12 degrees after TDC, which is produced by butanol direct injection (DI) after the first HCCI-like combustion event.
Technical Paper

High Energy Ignition Strategies for Diluted Mixtures via a Three-Pole Igniter

2016-10-17
2016-01-2175
A three-pole spark igniter, with the concept to broaden the ignition area, is employed in this paper to investigate the effect of spark discharge strategies on the early ignition burning process. The prototyped three-pole igniter has three independent spark gaps arranged in a triangular pattern with a circumradius of 2.3 mm. Direct-capacitor discharge techniques, utilizing close-coupled capacitors parallel to the spark gap, are applied on the three-pole igniter to enhance either the transient spark power or the overall energy. In particular, the simultaneous discharge of high energy plasma on three spark gaps can produce a surface-like ignition process which intensifies the plasma-flame interaction, thereby producing a rapid flame kernel development. The ignition strategies are evaluated in both constant volume combustion vessels and a modified single-cylinder metal engine.
Technical Paper

Measurement of Temperature and Soot (KL) Distributions in Spray Flames of Diesel-Butanol Blends by Two-Color Method Using High-Speed RGB Video Camera

2016-10-17
2016-01-2190
Taking advantages of high speed RGB video cameras, the two-color method can be implemented with a relatively simple setup to obtain the temporal development of the two dimensional temperature and soot (KL) distributions in a reacting diesel jet. However, several issues such as the selection of the two wavelengths, the role of bandpass filters, and the proper optical settings, etc. should be known to obtain a reliable measurement. This paper, at first, discusses about the uncertainties in the measurement of temperature and KL distributions in the diesel flame by the two-color method using the high speed RGB video camera. Since n-butanol, as an alternative renewable fuel, has the potential application in diesel engines, the characteristic of spray combustion of diesel-butanol blends under the diesel-like ambient conditions in a pre-burning constant-volume combustion chamber is studied.
Technical Paper

Heat Release Analysis of Clean Combustion with Ethanol Ignited by Diesel in a High Compression Ratio Engine

2016-04-05
2016-01-0766
The control of nitrogen oxide and smoke emissions in diesel engines has been one of the key researches in both the academia and industry. Nitrogen oxides can be effectively suppressed by the use of exhaust gas recirculation (EGR). However, the introduction of inert exhaust gas into the engine intake is often associated with high smoke emissions. To overcome these issues there have been a number of proposed strategies, one of the more promising being the use of low temperature combustion enabled with heavy EGR. This has the potential to achieve simultaneously low emissions of nitrogen oxide and smoke. However, a quantitative way to identify the transition zone between high temperature combustion and low temperature combustion has still not been fully explored. The combustion becomes even more complicated when ethanol fuel is used as a partial substitution for diesel fuel.
Journal Article

Experimental Investigation of Diesel-Ethanol Premixed Pilot-Assisted Combustion (PPAC) in a High Compression Ratio Engine

2016-04-05
2016-01-0781
In this work, empirical investigations of the diesel-ethanol Premixed Pilot-Assisted Combustion (PPAC) are carried out on a high compression ratio (18.2:1) single-cylinder diesel engine. The tests focus on determining the minimum ethanol fraction for ultra-low NOx & soot emissions, effect of single-pilot vs. twin-pilot strategies on emissions and ignition controllability, reducing the EGR requirements, enabling clean combustion across the load range and achieving high efficiency full-load operation. The results show that both low NOx and almost zero soot emissions can be achieved but at the expense of higher unburned hydrocarbons. Compared to a single-pilot injection, a twin-pilot strategy reduces the soot emissions significantly and also lowers the NOx emissions, thereby reducing the requirements for EGR. The near-TDC pilot provides excellent control over the combustion phasing, further reducing the need of a higher EGR quantity for phasing control.
Journal Article

Investigation of Fuel Injection Strategies for Direct Injection of Neat n-Butanol in a Compression Ignition Engine

2016-04-05
2016-01-0724
In this study, impacts of neat n-butanol fuel injection parameters on direct injection (DI) compression ignition (CI) engine performance were investigated to gain knowledge for understanding the fuel injection strategies for n-butanol. The engine tests were conducted on a four-stroke single-cylinder DI CI engine with a compression ratio of 18.2:1. The effects of fuel injection pressure (40, 60 and 90 MPa) and injection timing in a single injection strategy were investigated. The results showed that an increase in injection pressure significantly reduced nitrogen oxides (NOx) emissions which is the opposite trend seen in conventional diesel combustion. The parallel use of a higher injection pressure and retarded injection timing was a proposed method to reduce NOx and cylinder pressure rise rate simultaneously. NOx was further reduced by using exhaust gas recirculation (EGR) while keeping near zero soot emissions.
X