The distribution of fuel-air mixture inside the engine cylinder strongly influences the combustion process. Planar laser-induced fluorescence (PLIF) is commonly used for fuel distribution measurement, however, it is mostly reported on moderate- to large-sized engines. In the present work, PLIF is applied to measure the fuel distribution inside the cylinder of a small, four-stroke, port-fuel-injection (PFI), spark-ignition engine with displacement volume of 110 cm3. Iso-octane was used as the base fuel, and 3-pentanone (15% by volume) was added as a fluorescent tracer in the base fuel. The effect of equivalence ratio, considering ϕ = 1.2, 1.0, and 0.8, on in-cylinder fuel distribution was studied with low throttle opening of 25% at 1200 rpm. PLIF images were recorded at different crank angle degrees during both intake and compression strokes over a swirl measurement plane located at the TDC position. It was found that the fuel stratification was present from intake to even late

Garg, Shubham, Mittal, Mayank, Sahu, Srikrishna, Lakshminarasimhan, V

Improving Heavy Duty Natural Gas Engine Efficiency: A Systematic Approach to Application of Dedicated EGR

2020-01-081804/14/2020

The worldwide trend of tightening CO2 emissions standards and desire for near zero emissions is driving development of high efficiency natural gas engines for a low CO2 replacement of traditional diesel engines. A Cummins Westport ISX12 G was previously converted to a Dedicated EGR® (D-EGR®) configuration with two out of the six cylinders acting as the EGR producing cylinders. Using a systems approach, the combustion and turbocharging systems were optimized for improved efficiency while maintaining the potential for achieving 0.02 g/bhp-hr NOX standards. A prototype variable nozzle turbocharger was selected to maintain the stock torque curve. The EGR delivery method enabled a reduction in pre-turbine pressure as the turbine was not required to be undersized to drive EGR. A high energy Dual Coil Offset (DCO®) ignition system was utilized to maintain stable combustion with increased EGR rates. High compression ratio, reduced squish pistons were designed to maintain MBT combustion phasing

Kocsis, Michael C., Mitchell, Robert, Moiz, Ahmed Abdul, Kalaskar, Vickey, Williams, D. Ryan, Sjovall, Scott

Assessment of the Ignition System Requirement on Diluted Mixture Spark Engines

2020-01-111604/14/2020

In order to face the new challenges, spark ignition engines are evolving by following some strategies and technologies. Among them, alternative combustion processes based on the dilution of the homogeneous mixture, either with fresh air or with Exhaust Gas Recirculation (EGR), are being explored. In a higher or lower extent, these changes modify in-cylinder thermodynamic conditions during the engine operation (pressure, temperature and gas composition) thus conditioning the spark ignition system requirements that will have to evolve to become more reliable and powerful. In this framework, an experimental study on the effect of the key in-cylinder conditions on the ignition system performance has been carried out in a single-cylinder spark-ignition (SI) research engine. The study includes EGR, lambda and energizing time sweeps to assess the behavior of the engine in different operating conditions. Furthermore, various Insulated-Gate Bipolar Transistors (IGBT) and spark plugs have been

Molina, Santiago, Martin, Jaime, Novella, Ricardo, Gomez-Soriano, Josep, Padilla, Jose

Discharge Current Management for Diluted Combustion under Forced Flow Conditions

2020-01-111804/14/2020

Lean burn or EGR diluted combustion with enhanced charge motion is effective in improving the efficiency of spark ignition engines. However, the ignition process under these conditions is getting more challenging due to higher ignition energy required by the lean or diluted mixture, as well as the interactions of the gas flow on the flame kernel. Enhanced spark discharge energy is essential to initiate the combustion under these conditions. Moreover, the discharge process should be more carefully controlled to improve the effectiveness of the spark. In this study, spark ignition systems with boosted discharge energy are used to ignite diluted air-fuel mixture under forced flow conditions. The impacts of the discharge current level, the discharge duration and the discharge current profile on the ignition are investigated in detail using optical diagnosis. It is evident from the results that extended discharge duration helps promote the flame propagation, though the effectiveness is

Yang, Zhenyi, Wang, Linyan, Sandhu, Navjot S., Yu, Xiao, Zheng, Ming

Combustion Stability Improvement via Multiple Ignition Sites on a Production Engine

2020-01-111504/14/2020

For spark ignition (SI) engines, further improvement of engine efficiency has become the major development trend, and lean burn/EGR technologies, as well as intensified in-cylinder flow, need to be adapted to reach that target. Stronger ignition sources become more favorable under extreme lean/EGR conditions. Among the ignition technologies developed, multiple ignition sites technology has been proved to be an effective way to help with the initial flame kernel development. In this paper, a spark ignited 4-cylinder turbo-charged production engine is employed to investigate the impact of multiple ignition sites technology on engine performance under lean burn conditions. Four in-house designed 3-core sparkplugs are installed on the cylinders to replace traditional stock sparkplugs, in order to generate multiple ignition sites in the cylinders. Under partial load, the pumping loss can be reduced when engine is running under lean conditions, so the brake engine efficiency can be improved

Yu, Xiao, Zhang, Xiaoxi, Zhang, Tangliang, Chen, Guangyun, Tjong, Jimi, Zheng, Ming

Impact of Spark Plasma Length on Flame Kernel Development under Flow Condition

2020-01-111404/14/2020

Advanced ignition systems with enhanced discharge current have been extensively investigated in research, since they are highly regarded as having the potential to overcome challenges that arise when spark-ignition engines are running under lean or EGR diluted conditions. Local flow field is also of particular importance to improve the ignitability of the air-fuel mixture in SI engines as the spark plasma channel can be stretched by the flow across the spark gap, leading to longer plasma length, thus more thermal spark energy distributed to the air-fuel mixture in the vicinity of the spark plug. Research results have shown that a constantly high discharge current is effective to maintain a stable spark plasma channel with less restrikes and longer plasma holding period. However, with the further increase in discharge current, plasma channel becomes thicker, and the stretched plasma length becomes shorter under a constant flow speed, which may suppress the advantages of the enhanced

Zhu, Hua, Tan, Qingyuan, Yu, Xiao, Yang, Zhenyi, Liang, Li, Zheng, Ming, Reader, Graham, Qian, Jin

Two prototype engines with colliding and compression of pulsed supermulti-jets through a focusing process, leading to nearly complete air insulation and relatively silent high compression for automobiles, motorcycles, aircrafts, and rockets

2020-01-083704/14/2020

We have proposed a new compressive combustion principle based on pulsed supermulti-jets colliding through focusing process, by injection from chamber wall to chamber center. This principle has potential of relatively-silent high compression around chamber center because of auto-ignition far from chamber wall and nearly-complete air insulation due to encasing of burned high temperature gas. The present principle leading to higher thermal efficiency and higher power will be applicable for automobiles, aircrafts, rockets, and also flying cars to be realized in the future. Then, water cooling system made smaller or even eliminated will result in lower price, while auto-ignition in an area larger than that created by traditional spark-ignition will lead to less NOx emission at very lean burning. Thus, we here show four new evidences based on experimental data and computational and theoretical considerations. (1) Quantitative clarification of compression level at condition without combustion

Konagaya, Remi, Naitoh, Ken, Kobayashi, Tomotaka, Isshiki, Yuuki, Ito, Hajime, Makimoto, Hiroki, Kobayashi, Yoshiki, Tada, Yusuke, Kikuchi, Nozomu, Hosoi, Aya, Fujii, Yuto

Design and Simulation of a Multi Fuel Gas Mixture System of a Wankel Rotary Engine

2020-01-054804/14/2020

The paper first includes the main objective and boundary conditions for design and simulation of a multi fuel gas mixture system of a Wankel rotary engine. New regenerative fuels are more and more important for use in automotive propulsion and stationary applications of combustion engines. Due to the special design and operation of rotary engines there are opportunities for running these engines in future electric and hybrid applications with new designed liquids and gaseous fuels based on regenerative energy sources. Nevertheless, rotary engines have advantages in avoidance of preignition and detonation especially when using gaseous fuels with a higher percentage of hydrogen. The focus is on basic research and analyses of main physical and thermodynamic properties of separate lean burn gases (lower calorific value, mixed calorific value, AFR) and their effects on fuel mixing and engine performance. Furthermore, the scope of the investigation is on the development of simulation models

Dost, Tobias, Getzlaff, Joern

Combustion Enhancement in a Gas Engine Using Low Temperature Plasma

2020-01-082304/14/2020

Low temperature plasma ignition has been proposed as a new ignition technique as it has features of good wear resistance, low energy release and combustion enhancement. In the authors’ previous study, lean burn limit could be extended by low temperature plasma ignition while a voltage drop during discharge, leading to the transition to arc discharge, was found. In this study, the structure of plug and power supply’s performance with steep voltage rising with time, dV/dt, are examined to investigate the effects on combustion performance. As a result, the following conclusions were deduced. (1) The lean combustion limit was extended when a four-pole plug with IES power source was used due to volumetric ignition. (2) A modified one-pole plug to improve the electric insulation, leading to prevent the voltage drop, could not extend the lean limit due to less volumetric ignitability. The specifications of plug must be improved to expand the ignition volume. (3) Using a variable dV/dt power

Moriyoshi, Yasuo, Kuboyama, Tatsuya, Tanoue, Kimitoshi

A Numerical Study on the Ignition of Lean CH ₄ /Air Mixture by a Pre-Chamber-Initiated Turbulent Jet

2020-01-082004/14/2020

To provide insights into the fundamental characteristics of pre-chamber combustion engines, the ignition of lean premixed CH4/air due to hot gas jets initiated by a passive narrow throated pre-chamber in a heavy-duty engine was studied computationally. A twelve-hole pre-chamber geometry was investigated using CONVERGETM software. The numerical model was validated against the experimental results. To elucidate the main-chamber ignition mechanism, the spark plug location and spark timing were varied, resulting in different pressure gradient during turbulent jet formation. Different ignition mechanisms were observed for turbulent jet ignition of lean premixed CH4/air, based on the geometry effect. Ignition behavior was classified into the flame and jet ignition depending on the significant presence of hot active radicals. The jet ignition, mainly due to hot product gases was found to be advanced by the addition of a small concentration of radicals. In turbulent conditions, the ignition

Sanal, Sangeeth, Silva, Mickael, Hlaing, Ponnya, Cenker, Emre, Johansson, Bengt, Im, Hong G.

Analysis of a Prechamber Ignited HPDI Gas Combustion Concept

2020-01-082404/14/2020

High-pressure direct injection (HPDI) of natural gas into the combustion chamber enables a non-premixed combustion regime known from diesel engines. Since knocking combustion cannot occur with this combustion process, an increase in the compression ratio and thus efficiency is possible. Due to the high injection pressures required, this concept is ideally suited to 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 HPDI gas combustion concept presented in this paper is of a monovalent type, meaning that no fuel other than natural gas is used. The high-pressure gas jet is ignited with the aid of flame torches from

Zelenka, Jan, Kammel, Gernot, Wimmer, Andreas, Bärow, Enrico, Huschenbett, Matthias

Investigation of Homogeneous Lean SI Combustion in High Load Operating Conditions

2020-01-095904/14/2020

Homogeneous lean combustion (HLC) can be utilized to substantially improve spark ignited (SI) internal combustion engine efficiency. Higher efficiency is vital to enable clean, efficient and affordable propulsion for the next generation light duty vehicles. More research is needed to ensure robustness, fuel efficiency/NOx trade-off and utilization of HLC. Utilization can be improved by expanding the HLC operating window to higher engine torque domains which increases impact on real driving. The authors have earlier assessed boosted HLC operation in a downsized two-litre engine, but it was found that HLC operation could not be achieved above 15 bar NMEP due to instability and knocking combustion. The observation led to the conclusion that there exists a lean load limit. Therefore, further experiments have been conducted in a single cylinder research DISI engine to increase understanding of high load lean operation. HLC is known to suppress end-gas autoignition (knock) by decreasing

Clasen, Kristoffer H., Koopmans, Lucien

Quasi-Dimensional Multi-Zone Combustion Diagnostic Tool for SI Engines with Novel NOx and CO Emissions Models

2020-01-028904/14/2020

In this work an innovative quasi-dimensional multi-zone combustion diagnostic tool for homogeneous charge spark ignition (SI) engines is developed for the evaluation of heat release, flame propagation parameters, combustion velocities as well as engine-out NOx emissions based on in-cylinder pressure data analysis. The tool can be used to assess the effects of fuel, design and operating parameters on the SI engine combustion and NOx emissions formation processes. Certain novel features are included in the presently developed combustion diagnostic tool. Firstly, combustion chambers of any shape and spark plug position can be considered due to an advanced model for the calculation of the geometric interaction between a spherically expanding flame and a general combustion chamber geometry. Then, the temperature stratification in the burned gas developed during the combustion phase, which has to be captured for realistic calculations of emissions formation, is taken into account by a multi

Michos, Konstantinos N., Bikas, Georgios

Performance Investigation of a PFI Gasoline Engine by Applying Various Kinds of Fuel Injectors

2019-32-0546

01/24/2020

In this report, the effect of injection specification, such as droplet size, lengths of nozzle tip and spray angle, on the engine performance was investigated using a 1.2 L port fuel injection (PFI) four-cylinder gasoline engine. The experimental conditions were selected to cover the daily operating mode, including the cold start and catalyst heating process. The experiments were conducted by varying not only the injectors but also the injection timing which was shifted from the exhaust to intake stroke. The results were evaluated by the fuel consumption and exhaust gas emissions. When these tests were conducted on a production engine, a carefully designed tumble generator was installed at the intake port to enhance the intake air flow. As a result, the injection specifications showed a potential to obtain less fuel consumption and lower engine-out emissions was evaluated.

Shen, Fuchao, Moriyoshi, Yasuo, Kuboyama, Tatsuya, Iio, Toshiya, Miyatani, Yudai, Tsunoi, Akira

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