Statistical study on engine knock oscillation and heat release using multiple spark plugs and pressure sensors

Fuel ◽  
2021 ◽  
Vol 297 ◽  
pp. 120746
Author(s):  
Hao Shi ◽  
Kalim Uddeen ◽  
Yanzhao An ◽  
Yiqiang Pei ◽  
Bengt Johansson
Keyword(s):  
Heat Release ◽  
Statistical Study ◽  
Pressure Sensors ◽  
Engine Knock

scholarly journals Experimental Study on Dynamic Combustion Characteristics in Swirl-Stabilized Combustors

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1609
Author(s):  
Donghyun Hwang ◽  
Kyubok Ahn
Keyword(s):  
Experimental Study ◽  
Heat Release ◽  
Dynamic Pressure ◽  
Combustion Instability ◽  
Flame Structure ◽  
Pressure Sensors ◽  
Necessary Condition ◽  
Rayleigh Criterion ◽  
Pressure Oscillations ◽  
Geometric Conditions

An experimental study was performed to investigate the combustion instability characteristics of swirl-stabilized combustors. A premixed gas composed of ethylene and air was burned under various flow and geometric conditions. Experiments were conducted by changing the inlet mean velocity, equivalence ratio, swirler vane angle, and combustor length. Two dynamic pressure sensors, a hot-wire anemometer, and a photomultiplier tube were installed to detect the pressure oscillations, velocity perturbations, and heat release fluctuations in the inlet and combustion chambers, respectively. An ICCD camera was used to capture the time-averaged flame structure. The objective was to understand the relationship between combustion instability and the Rayleigh criterion/the flame structure. When combustion instability occurred, the pressure oscillations were in-phase with the heat release oscillations. Even if the Rayleigh criterion between the pressure and heat release oscillations was satisfied, stable combustion with low pressure fluctuations was possible. This was explained by analyzing the dynamic flow and combustion data. The root-mean-square value of the heat release fluctuations was observed to predict the combustion instability region better than that of the inlet velocity fluctuations. The bifurcation of the flame structure was a necessary condition for combustion instability in this combustor. The results shed new insight into combustion instability in swirl-stabilized combustors.

scholarly journals Effects of pre-spark heat release on engine knock limit

2019 ◽  
Vol 37 (4) ◽  
pp. 4893-4900 ◽  
Author(s):  
Derek A. Splitter ◽  
Arthur Gilliam ◽  
James Szybist ◽  
Jaal Ghandhi
Keyword(s):  
Heat Release ◽  
Engine Knock

Controlled ASSCI With Moderate Auto-Ignition for Engine Knock Suppression in a GDI Engine With High Compression Ratio

2014 ◽  
Author(s):  
Hui Liu ◽  
Zhi Wang ◽  
Jianxin Wang ◽  
Mengke Wang ◽  
Wanli Yang
Keyword(s):  
Heat Release ◽  
Compression Ratio ◽  
High Compression Ratio ◽  
Two Stage ◽  
Second Stage ◽  
High Compression ◽  
Auto Ignition ◽  
Crank Angle ◽  
Engine Knock ◽  
Gdi Engine

This paper presents an experimental study on controlled ASSCI (Assisted Spark Stratified Compression Ignition) for engine knock suppression in a GDI engine with high compression ratio. The direct injection is used for forming desired stoichiometric stratified mixture at WOT condition without turbo-charging. The engine is filled with 20% cooled external EGR and the ignition timing is maintained at MBT point. The combustion characteristics of the desired stoichiometric stratified mixture show two-stage heat release, where the first stage is caused by spark ignition and the second stage is due to moderate auto-ignition. Compared with engine knock, the second stage heat release of controlled ASSCI shows smooth pressure curve without pressure oscillation. This is due to the low energy density mixture around the cylinder wall caused by cooled external EGR. The stratified mixture could suppress knock. Fuel economy and combustion characteristics of the baseline and the controlled ASSCI combustion were compared. The baseline GDI engine reaches a maximum of 8.9 bar BMEP with BSFC of 291 g/(kWh), the controlled ASSCI combustion achieves a maximum of 8.3 bar BMEP with BSFC of 256 g/(kWh), improving the fuel economy over 12% while maintaining approximately the same power. CA50 (the crank angle of 50% heat release) of the controlled ASSCI is detected at 8.4° CA ATDC, which is 17.4° CA advanced than that of the baseline while the combustion duration of the controlled ASSCI is 52.84dG CA, 16.6° CA longer than that of the baseline caused by diluted mixture and two-stage heat release. The COV of the controlled ASSCI is 1.4%, 2.1% lower than that of the baseline. The peak pressure (Pmax) and the maximum pressure rise rate (PRRmax) of the controlled ASSCI are 59.7 bar and 2.2 bar/° CA, 22.9 bar and 1.5 bar/° CA higher than that of the baseline respectively. The crank angle of Pmax and PRRmax of the controlled ASSCI are 11° CA ATDC and −1° CA ATDC, 15.4° CA and 17.2° CA earlier than that of the baseline. The results show that controlled ASSCI with two-stage heat releases is a potential combustion strategy to suppress engine knock while achieving high efficiency of the high compression ratio gasoline engine.

scholarly journals Measuring the phase between fluctuating pressure and flame radiation intensity in a cylindrical combustion chamber

2019 ◽  
Author(s):  
S. Gröning ◽  
J.S. Hardi ◽  
D. Suslov ◽  
M. Oschwald
Keyword(s):  
Energy Transfer ◽  
Phase Shift ◽  
Heat Release ◽  
Acoustic Pressure ◽  
Dynamic Pressure ◽  
Rocket Engine ◽  
Pressure Sensors ◽  
Pressure Oscillations ◽  
Flame Radiation ◽  
Rate Oscillations

The energy transfer from the heat release of the combustion to the acoustic pressure oscillations is the driving element of combustion instabilities. This energy transfer is described by the Rayleigh criterion and depends on the phase shift between the pressure and heat release rate oscillations. A research rocket engine combustor, operated with the propellant combination hydrogen/oxygen, was equipped with dynamic pressure sensors and fibre optical probes to measure the flame radiation. This setup has been used for a phase shift analysis study which showed that unstable operation is characterized by a phase shift leading to an energy transfer from the heat release to the acoustic pressure oscillations.

scholarly journals Experimental Study of the Effect of Confining on the Development of Fire in a Closed Compartment

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Fidel Meskeoule Vondou ◽  
Claude Valery Ngayihi Abbe ◽  
Justin Tégawendé Zaida ◽  
Philippe Onguene Mvogo ◽  
Ruben Mouangue
Keyword(s):  
Heat Release ◽  
Thermal Stresses ◽  
Statistical Study ◽  
Reference Data ◽  
Fire Tests ◽  
Quantitative Investigation ◽  
Free Atmosphere ◽  
Experimental Campaign ◽  
Time Of Intervention

Backdraft is a complex phenomenon which occurs during cases of confined fires. It appears by a fast deflagration which occurs after the introduction of oxygen into a compartment filled with hot gases rich in unburned combustible vapor. Practically, this situation could occur at the time of intervention of firemen who break the door or when a window breaks under the action of thermal stresses. Based on a strong experimental campaign, the present paper aimed to make a quantitative investigation of the effect of confining on a totally closed fire. With this focus, fire tests were carried out in a completely closed room of dimensions 1.20 m × 1.20 m × 1.02 m, with five sources of fire of different heat release rates. The same fire sources were also tested in a free atmosphere in order to get reference data. After a statistical study of data, a comparative analysis between both results has been done. Its outcome is that confining has a major impact on the quality of combustion and on the fire duration. More precisely, it has been noticed comparatively to fire tests in free atmosphere that confining increases the fire duration by 14.85 percent while it decreases the heat release rate by 21.72 percent.

Suppressing Knock of the Dual-Fuel Engine by Injection Timing under Pressure Boundary Conditions

2013 ◽  
Vol 291-294 ◽  
pp. 1648-1652
Author(s):  
Cheng Wei Zhang ◽  
Bing Xiao
Keyword(s):  
Boundary Conditions ◽  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Dual Fuel ◽  
Injection Timing ◽  
Engine Knock ◽  
Intake Pressure ◽  
Pressure Boundary Conditions ◽  
Engine Reliability

The engine knock has direct relation with the energy release rate. The faster combustion speed is, the higher heat release rate is. If heat release rate is too high, it will deteriorate reliability of the engine. A dual-fuel engine combustion mechanism model is established and intake pressure boundary conditions influence on the dual-fuel engine reliability is studied. Injection timing can supress engine knock and inprove engine reliability. Studies have shown that the greater the intake pressure, the smaller injection timing should be selected and the smaller the intake pressure, the larger injection timing should be selected. Appropriate injection timing can ensure reliability and power of the engine.

Semi-empirical estimation model of in-cylinder pressure for compression ignition engines

2020 ◽  
Vol 234 (12) ◽  
pp. 2862-2877
Author(s):  
Youngbok Lee ◽  
Seungha Lee ◽  
Kyoungdoug Min
Keyword(s):  
Heat Release ◽  
Heat Release Rate ◽  
Release Rate ◽  
Dynamic Control ◽  
Pressure Sensors ◽  
Engine Control ◽  
Cylinder Pressure ◽  
Combustion Control ◽  
Compression Stroke ◽  
Engine Dynamic

There have been significant efforts in recent years to comply with automotive emission regulations. To resolve the issue, researchers have strived to reduce the emissions through combustion control. The heat release rate, or in-cylinder pressure information, is necessary to model engine-out emissions, and can also be used to optimize efficiency and emissions by controlling combustion and estimating torque for torque-based engine dynamic control. Piezoelectric pressure sensors are widely used. However, because of cost and durability issues, there have been studies which estimate the in-cylinder pressure using data available only from the engine control unit to reduce engine costs. Therefore, in this study, in-cylinder pressure was predicted, without additional pressure sensors, in light-duty diesel engines. A variable polytropic exponent model was first adopted during the compression stroke, assuming a polytropic process. A Wiebe function was then applied for describing cumulative heat release rate during the combustion phase. Using the in-cylinder pressure model, it was possible to calculate combustion-related parameters which are frequently used such as ignition delay, combustion duration, peaked pressure, and MFB50 (mass fraction burned: timing when 50% of the fuel is burned) without pressure sensors. Notwithstanding the simplification of the model which is targeting real-time applications, the model can predict the in-cylinder pressure at steady-state conditions. The pressure at the end of compression stroke, at start of main combustion timing, and when it has a peaked value by the main combustion were estimated with accuracy of R2 0.996, 0.993, and 0.956, respectively, in test engine. The model was also validated against a second engine. This study can contribute to emission models that need to calculate in-cylinder temperature using pressure data, and other studies to establish engine control strategies, including optimization through combustion control and torque prediction, which can be applied to engine dynamic control.

Controlled SSCI With Moderate End-Gas Auto-Ignition for Fuel Economy Improvement and Knock Suppression

2015 ◽  
Vol 137 (10) ◽  
Author(s):  
Hui Liu ◽  
Zhi Wang ◽  
Jianxin Wang ◽  
Mengke Wang ◽  
Wanli Yang
Keyword(s):  
Heat Release ◽  
Compression Ratio ◽  
Fuel Economy ◽  
Direct Injection ◽  
High Compression Ratio ◽  
Two Stage ◽  
Second Stage ◽  
Auto Ignition ◽  
Engine Knock ◽  
Gdi Engine

Hybrid combustion mode including flame propagation induced by spark ignition (SI) and auto-ignition could be an effective method to improve fuel economy and suppress engine knock simultaneously. An experimental research on controlled spark-assisted stratified compression ignition (SSCI) for this purpose was conducted in a gasoline direct injection (GDI) engine with high compression ratio. At wide open throttle (WOT) and minimum spark advance for best torque (MBT) condition without turbocharging, direct injection was used to form desired stoichiometric stratified mixture while 20% cooled external exhaust gas recirculation (e-EGR) was sucked into the cylinder. The combustion characteristics of controlled SSCI show two-stage heat release, where the first stage is caused by SI and the second stage is due to moderate auto-ignition. Compared with engine knock, the second stage heat release of controlled SSCI shows smooth pressure curve without pressure oscillation. This is due to the low energy density mixture around the cylinder wall caused by cooled e-EGR. The stratified mixture could suppress knock. Fuel economy and combustion characteristics of the baseline and the controlled SSCI combustion were compared. The baseline GDI engine reaches a maximum of 8.9 bar brake mean effective pressure (BMEP) with brake specific fuel consumption (BSFC) of 291 g/(kWh), and the controlled SSCI combustion achieves a maximum of 8.3 bar BMEP with BSFC of 256 g/(kWh), improving the fuel economy over 12% while maintaining approximately the same power. The results show that controlled SSCI with two-stage heat releases is a potential combustion strategy to suppress engine knock while achieving high efficiency of the high compression ratio gasoline engine.

Statistical Study of the Rotation Effect of Am Stars

1976 ◽  
Vol 32 ◽  
pp. 675-683
Author(s):  
Keiichi Kodaira
Keyword(s):  
Statistical Study ◽  
Rotation Velocity ◽  
General View ◽  
Slow Rotation ◽  
Rotation Effect

SummaryExcess of [m1] index of Am stars, relative to normal stars, is statistically found to be correlated with rotation velocity; the coefficient is estimated at ∆׀m1׀ /∆V(km/sec) ˜ - 0.0007 among Am stars. This result supports the general view that slow rotation is essential for Am phenomena.

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