Kwonse KimMechanical Engineering Department,

Mississippi State University,

Starkville, MS 39762

Omid Askari1Mechanical Engineering Department,

Mississippi State University,

Starkville, MS 39762

e-mail: askari@me.msstate.edu

Understanding the Effect ofCapacitive Discharge Ignition onPlasma Formation and FlamePropagation of Air–PropaneMixtureThis work is an experimental and computational study to investigate the effect of capaci-tive discharge ignition (CDI) on plasma kernel formation and flame propagation ofair–propane mixture. This paper is mainly focused on the plasma formation and flamepropagation characteristics, pressure rise, propagation time, velocity field, and speciesconcentrations. A conventional ignition system is used for comparison purpose. A con-stant volume combustion chamber with volume of 400 cm3 is designed for experimentalstudy. This chamber is utilized to visualize the plasma formation as well as the flamepropagation induced from two ignition sources. The experiments are performed in a widerange of operating conditions, i.e., initial pressure of 2–4 bar, temperature of 300 K,chamber wall temperature of 350 K, spark plug gaps of 1.0–1.5 mm, discharge durationof 1 ms, discharge energy of 500 mJ, and equivalence ratio of 0.5–1.0. The computationalstudy is performed by ANSYS FLUENT using the partially premixed combustion (PPC)model having the same conditions as experimental study. It is shown that the averagepeak pressure in CDI increased by 5.79%, 4.84% and 4.36% at initial pressures of 2, 3,and 4 bar, respectively, comparing with conventional ignition. It could be determinedthat the impact of combustion pressure in CDI system is more significant than conven-tional ignition particularly in lean mixtures. Consequently, the flame propagation rate inCDI system, due to the large ionized kernel around the spark plug, can be significantlyenhanced. [DOI: 10.1115/1.4042480]

Keywords: capacitive discharge ignition, plasma kernel, flame propagation, partiallypremixed combustion model, constant volume combustion chamber, propane, ANSYSFLUENT, lean mixture

1 Introduction

Nowadays, more than 85% of the energy is converted by com-bustion devices [1,2]. Several advanced combustion technologieshave been developed in internal combustion engines includingpartially premixed combustion ignition [3], homogeneous chargecompression ignition [4], reactivity-controlled compression igni-tion [5], gasoline direction injection [6–8], and turbo gasolinedirection injection [9]. These engines are utilized to operate athigher compression ratio, lower combustion temperature, andfaster response control to increase engine efficiency. In theseadvanced engines, it is desired to lower the energy loss includingheat transfer from the chamber wall, exhaust gases, pump, andblowdown. Over the past several decades, different ignition tech-nologies have been investigated to study the kernel formationcharacteristics on spark ignition engine performance [10]. Thecombustion is highly influenced by spark ignition and flamekernel formation [11], which is also associated with physical char-acteristics including temperature [12], latent heat [13], turbulentflow [14], compressed pressure [15], and residual gases [16].Other important considerations to improve the combustion effi-ciency, from the mechanical and material standpoints, are sparkplug design, combustion chamber design, durable material, andnonresistance plugs. Moreover, ignition systems [17] are directly

responsible on engine efficiency and pollutant emissions in inter-nal combustion engines. Therefore, it is essential to have a properair/fuel mixture composition around the spark plug gap in order tocreate a plasma kernel, which leads to a flame propagation. Thespark plug electrode geometry can be designed in such a way thatto reduce heat loss accumulated from the plasma kernel and speedup the kernel growth. The electrode material of spark plug isimportant to improve pre-ignition protection, service life, foulingresistance, and ignitability.

Different types of plasma discharge are plasma torch [18], fila-mentary discharge [19], dielectric barrier discharge [20], fre-quency or radio capacitive plasma source [21], surface discharge[22], nanosecond pulsed discharge [23], and high frequency dis-charge [24]. As far as the fundamental of plasma is concerned, itis obviously necessary to classify the plasma types. One type isthe high-temperature (equilibrium or thermal) plasma at which thetemperature of electrons, ions, and neutral particles are almostequal Te ffi Ti ffi Tnð Þ due to a continuous discharge. The applica-tions of high-temperature plasma are cutting, spraying, wastetreatment, welding, surface processing, arc furnaces, lighting, re-entry of space vehicles, propulsion, fusion, water purification, andmagnetohydrodynamic convertors [25,26]. The other type is low-temperature (nonequilibrium or nonthermal) plasma at whichelectron temperature is greater than ions and neutral temperatures(Te � Ti;TnÞ. Therefore, the gliding arc, glow discharge, micro-wave, streamer discharge, nanosecond pulsed discharge, DC arcdischarge, capacitor discharge, and DC jet discharge can belongto low-temperature plasma area owing to a noncontinuous dis-charge. In internal combustion engines, which utilize gasoline,

1Corresponding author.Contributed by the Advanced Energy Systems Division of ASME for publication

in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received December24, 2018; final manuscript received January 4, 2019; published online January 30,2019. Editor: Hameed Metghalchi.

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liquefied petroleum gas, and natural gas are obviously necessaryto improve the combustion performances using different plasmasources listed in Table 1.

In the past five decades, different transistors have been devel-oped to control the discharge duration, flame kernel formation,and combustion propagation. The bipolar transistor ignition [34]was utilized to support the energy of electromagnetic field to cre-ate low temperature plasma [35] in 1970. Thereafter, in 1980, abipolar transistor located inside an engine control unit wasimproved in order to increase the speed of plasma kernel forma-tion in the combustion system [36]. In 1990, voltage strength wasupgraded from field coil to closed-magnetic circuit [37] with aninsulated gate bipolar transistor. In 2000, the stick type ignitioncoil [38] was utilized to reduce the system volume and weight,which was developed to be used in the direct ignition systems[39] inside constant volume chamber. In particular, an insulatedgate bipolar transistor was studied to adjust the high-speed igni-tion and to reduce inverse voltage characteristics. Ever since2000, these ignition technologies have been studied to improvethe engine combustion performance. Current studies have beencarried out to investigate the coupled plasma discharge [40],plasma-assisted combustion [41], and matching effect of highvoltage [42].

Capacitive discharge ignition (CDI) is one of the promisingtechnologies that can be used in the internal combustion engines[43]. CDI system includes a charging circuit, a main capacitor, atriggering circuit, and a small transformer. The system voltage israised up to 250–600 V by a transformer inside the CDI module.An ignition coil acts as a pulse transformer rather than an energystorage as it does in an inductive system. Moreover, the voltagedischarge between spark plug electrodes is highly dependent onthe CDI design. However, the voltage exceeding the insulationcapabilities of existing ignition components can lead to early fail-ure of those components. Therefore, most CDI systems are madeout of materials, which can tolerate very high discharge voltages.

The main goal of this research work is to show the advantagesof CDI system comparing with a conventional ignition system.This paper represents the experimental and numerical resultsincluding plasma formation characteristics, flame propagationcharacteristics, pressure rise, propagation time, velocity field, andspecies concentrations for both conventional ignition and CDIsystems. The structure of this paper is explained in subsequentsections. Section 2 explains the research method including designconcept of CDI system comparing with the conventional ignitionand describes the experimental setup as well as computationalmodeling using the partially premixed combustion (PPC) modelthrough ANSYS FLUENT software. Section 3 discusses the plasmacombustion characteristics analyzed by experimental methodincluding discharge voltage, kernel formation, propagation time,and pressure rise. Sections 3.5 and 3.6 show the computationalresults of velocity field and species concentration. The summaryand conclusion are given in Sec. 4 followed by references.

2 Research Methods

2.1 Ignition Systems’ Design. Figure 1 shows two schematicdiagrams of conventional spark ignition and capacitor dischargeignition at which the plasma kernel is generated through a trans-former controlled by pulsed source. The electrode gap is adjusted

by a moving screw in three steps as 1, 1.25, and 1.5 mm using apassive dial gage. A transformer located in ignition systems uti-lizes a closed-loop type in order to create the magnetic field. Thehigh-voltage cable is connected to transformer outlet and sparkplug inlet. The cable material is RG58-AU, including five cores,to minimize the internal resistance. Also, the insulated gate bipo-lar transistor switching the transformer is transiently controlled by1 ms pulse signal via LabVIEW software and NI hardware(cDAQ-9172). The CDI switch is significantly analogous to theconventional ignition system, because the secondary ignition out-put and ground wire are directly connected to the CDI modulearound the spark plug unit. Table 2 lists the specifications of con-ventional ignition and CDI systems.

2.2 Ignition Systems’ Circuit. Figure 2 shows the circuitdiagrams of the conventional ignition and CDI systems, whichcan generate ignition at spark plug location using an external sup-ply unit. The circuit diagram of conventional ignition system, asshown in Fig. 2(a), is divided into the primary and secondary cir-cuits. In the primary circuit, electronic components consisted of abattery power, a signal source, a transistor, a resistor, and an inputignition transformer connected to a low voltage supply. The sec-ondary circuit includes a high-voltage cable, a transformer forvoltage amplification, a resistor for overvoltage protection, and acapacitor for voltage stabilization. A spark plug with nonresis-tance characteristics is used to investigate the plasma formationand flame kernel growth. The circuit diagram of CDI system issimilar to the conventional one except that in CDI system there isa tertiary circuit to create the ionized plasma kernel using a high-voltage capacitor, which includes a piezoelectric ceramic materialas shown in Fig. 2(b).

The total energy Uc stored in capacitor is electrostatic potentialenergy and is thus related to the charge Q and voltage V betweenthe capacitor plates. A charged capacitor stores energy of the elec-trical field between plates as much as the given capacity capableof storing energy. As the capacitor is being charged, the electricalfield builds up. When a charged capacitor is disconnected from aswitch, stored energy remains in the space between plates in thecapacitor. The space between plates has a volume of Ad and it isuniformly filled with an electrostatic field E. The energy densityuE in a region of free space occupied by an electric field Edepends only on the magnitude of an electric field, which can bedefined as the following equation:

uE ¼1

2�0E2 (1)

where �0 is the permittivity. If the energy density is multiplied byvolume between capacitor plates, the amount of capacitor storedenergy Uc is obtained as

UC ¼ uE Adð Þ ¼ 1

2�0E2Ad (2)

Considering E ¼ V=d and C ¼ �0A=d, the above equation can berewritten as:

UC ¼1

2CV2 (3)

Table 1 Characteristics of different of plasma classifications

Type Pressure (bar) Current (A) Voltage (kV) E/N (Td) Tg (K) Te (eV) Ne (m3) Ref.

Arc/spark Up to 20 1–105 10–100 10–100 500–20,000 1–5 1015–1022 [27,28]Corona 0.1–10 0.01–50 0.1–50 20–200 500–1000 1–5 1012–1015 [29]DC/microwave 0.1–1 0.1–1 0.1–100 10–50 300–6000 1–5 1015–1023 [30]Nano-second discharge Up to 2 50–200 1–100 100–1000 300–600 5–30 1017–1019 [31]RF 10�3–1 10�4–2 0.5–2 10–100 300–1000 1–5 1017–1019 [32,33]

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or in other equivalent forms [44,45] as

UC ¼1

2

Q2

C¼ 1

2QV (4)

where V is the potential difference between plates in a capacitorq=Cð Þ and Q is the electric charge on the plates. This expression

for the energy stored in capacitor UCð Þ is generally valid for alltypes of capacitors. Initially, the electrical charge is q ¼ 0. As thecapacitor is being charged, the electric charge gradually builds upon its plates and it reaches to the value Q. To move an infinitesi-mal charge dq from the negative plate to the positive pate (from alower to a higher potential), the amount of work dW that must bedone on dq is obtained [46] as

dW ¼ Vdq ¼ q

Cdq (5)

This work becomes the energy stored in the electrical field of thecapacitor. In order to charge the capacitor to a charge Q, the totalwork required is [47]

W ¼ðWðQÞ

0

dW ¼ðQ

0

q

Cdq ¼ 1

2

Q2

C(6)

Because the geometry of the capacitor has not been specified, thisequation can be utilized for any type of capacitor. The total work

W needed to charge a capacitor is equal to the electrical potentialenergy stored UCð Þ. If the charge is expressed in Coulombs,potential difference in volts and the capacitance in Farads, thisrelation gives the energy in Joules. Therefore, the total energy UC

of CDI can be defined as the following equation:

UC ¼1

2CV2 (7)

where C is a capacitance in a capacitor and V2 can be calculatedby the potential difference of the secondary voltage induced fromCDI transformer.

2.3 Experimental Setup. Figure 3 represents the schematicview of experimental setup including constant volume combustionchamber, filling/supply system, electronic control unit, mass flowcontrollers, gas cylinders/regulators, two different ignition sys-tems, nonresistance spark plugs, lambda sensor, data acquisitionsystem, and a high-speed camera. A constant volume combustionchamber (CVCC) with volume of 400 cm3 is designed to study thecombustion characteristics. This chamber is utilized to visualizethe plasma formation and flame propagation induced by both con-ventional ignition and CDI systems. In this work, it is intensivelyattempted to investigate the plasma kernel formation, flame propa-gation, secondary coil signal characteristics, and pressure trace fortwo available ignition systems.

Mass flow controllers are used to measure and control the massflow rate of fuel and air using the LabVIEW program. Gas regula-tors are employed to properly regulate the high pressure inside thegas cylinders. To collect the experimental data, a high-speed cam-era with a T lens (F4.0 ZEISS Tesser*24 mm) and a capture rateof 1000 frames per second is utilized. A lambda sensor (LSU-4.9)is integrated with the CVCC to accurately control the air/fuelequivalence ratio (k). A nonresistance spark plug, developed byresearch cooperation Yura Tech. Co., Ltd. (Sejong-si, Korea), isemployed to induce the plasma discharge. An oscilloscope is uti-lized to record signal characteristics of combustion event includ-ing the plasma kernel, pressure trace, and flame propagation.Additionally, an electronic control unit is used to control theamount of injection to adjust the air/fuel equivalence ratio.

Figure 4 shows an input pulse signal algorithm to control theignition switch for both conventional ignition and CDI systems.This pulse algorithm includes various properties, which can ana-lyze the voltage and current for turn-on delay, turn-off delay, col-lector, emitter, and gate. Table 3 shows more details abouttransistor specifications. Moreover, Table 4 shows the

Fig. 1 Schematic diagrams of (a) conventional ignition and (b) CDI systems

Table 2 Specifications of conventional ignition and CDIsystems

Classifications Specifications

Ignition coil Input 12.5 V, primary 300 V,secondary (plug gap) 25 kV and current 3 A

Oscilloscope 1 Gsaps, 70 MHzHigh voltage cable RG58-AU, NonresistanceSpark plug IridiumCDI plug Iridium and partially platinumDial-gage Resolution 0.02 mm, Frist round 0.5 mmCDI device Voltage 25 kVPlug gaps 0.0–10 mmCapacitor type 100 PF, 101 high ceramic capacitorPulse generator Duration 1–2 msSignal probe 500:1 and 1000:1Spark resistance Inside resistancePlasma resistance Inside nonresistance

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Fig. 2 Circuit diagrams of (a) conventional ignition and (b) CDI systems

Fig. 3 Schematic of experimental setup

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experimental system specifications and Table 5 represents the sig-nal scale specifications for controlling the experimental system.

2.4 Computational Combustion Model. Figure 5 shows the3D model of the constant volume combustion chamber designedusing Catia V5 program. This design is composed of an actualcombustion chamber with the same volume (size), materials, andlocation of components. The numerical simulation using ANSYSFLUENT is performed to calculate the combustion characteristicsvia a PPC model. This simulation is performed to obtain the infor-mation, which could not be collected through experiment such asvelocity field and species concentrations. The species model inPPC is utilized to compute the unburned properties including den-sity, temperature, specific heat, thermal diffusivity, and laminarburning speed. The model constants are calculated as standardconstant values where length scale is 0.37, flame speed is 0.52,stretch factor is 0.26, and turbulent Schmidt number is 0.7. Inaddition, the standard setup of initial values in PPC model is set tocompute swirl velocity, turbulent kinetic energy, turbulent dissi-pation rate, temperature, progress variable, and flame area density.Table 6 shows the three-step chemical reactions used for air/C3H8

mixture in the computational modeling.Because combustion occurs in a closed system without inlet or

outlet, a chamber wall is used as the internal boundary. Withregard to stoichiometric conditions, the combustion propagation ismodeled using a transport equation to solve the density-weightedmean reaction progress variable [48]

@

@tqcð Þ þ r�qv

*c ¼ r� lt

Sct

� �þ qSc (8)

where c is the mean reaction progress variable, Sct is the Schmidtnumber of turbulent, and Sc is the reaction progress source term.The combustion progression could be defined as the followingequation of a normalized sum with respects to the product species[49]:

c ¼

Pni¼1

Yi

Pni¼1

Yi;eq

(9)

where n is mole numbers, Yi is mass fraction, and Yi;eq is equilib-rium mass fraction of ith species. As mentioned above, the pro-gressive condition could be mathematically calculated based onthe boundary condition, which was defined as c ¼ 1 for burnedand c ¼ 0 for unburned. As to the mean reaction rate presented inEq. (8), a premixed combustion model could be defined as the

Fig. 4 Input pulse signal algorithm

Table 3 Specification of input pulse signal algorithm

Classifications Specifications

Collector-emitter voltage 5 VCollector-gate voltage 5 VGate-emitter voltage 5 VDC working current 1 mADC collector current 24 ATotal power dissipation 125 WTemperature �55 to 150 �CTurn-on delay time (Td (on)) 25 nsTurn-on rise time (Tr) 45 nsTurn-on energy loss 0.6 mJTurn-off delay time (Td (off)) 230 nsTurn-off full time (Tf) 400 nsTurn-off energy loss 1 mJInput capacitance 1250 pFOutput capacitance 120 pFFeedback capacitance 50 pF

Table 4 Experimental system specifications

Items Specifications

Pressure sensors 0–160 barMass flow controllers 0–1.5 L/mHigh pressure safety valves 150 barCVCC volume 400 ccOscilloscope bandwidth 70 MHzTransformer 15–25 kVHV probe scale factor 1000:1cDAQ-Chassis resolution time 1000 msGaseous substances C3H8, N2 and O2

High speed camera 1000 fpsAmplification probe Electronic ceramicCombustor material Duralumin

Table 5 Signal scale specifications of the experimental system

Items Scales

Mass flow and analog output of C3H8 meter 3 L/min and 5 VMass flow and analog output of N2 meter 10 L/min and 5 VMass flow and analog output of O2 meter 10 L/min and 5 VMinimum ignition duration and voltage 0.00001 s and 5 VMaximum ignition duration and voltage 0.1 s and 12 VOxygen sensor warmup time and voltage 10 s and 12 VMinimum k 0.5Maximum k 2.0Combustion pressure and output scale 160 bar and 10 V

Fig. 5 Computational model design

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following equation that was calculated by Zimont and Trushin[50] based on high Reynolds numbers:

qSc ¼ quUt rcj j (10)

where qu is unburned mixture density and Ut is defined as turbu-lent flame speed (TFS). The key of premixed combustion model isto accurately predict the normal TFS on the mean surface of thecombustion flame. Moreover, TFS is influenced by laminar burn-ing speed [51–60], which is determined by fuel concentration,temperature, pressure, and molecular diffusion properties. There-fore, the authors also take into account the methods for flame frontwrinkling and thickness in TFS calculations [61]

Ut ¼ Aðu0Þ3=4ðUlÞ1=2a�1=4‘1=4t (11)

where A is the model constant, u0 indicates velocity of root meansquare, Ul is the laminar burning speed, a ¼ k=qcp is the thermaldiffusivity of unburned mixture, and ‘t is the turbulence lengthscale. Eq. (11) can be also written as

Ut ¼ Au0st

sc

� �1=4

(12)

where st ¼ ‘t=u0 is the turbulence time scale and sc ¼ a=U2l is the

chemical time scale. The turbulence length scale ‘tð Þ can be com-puted as the following equation [62]:

‘t ¼ CDðu0Þ3

�(13)

where � is the turbulence dissipation rate and CD is a default con-stant value (0.37), which is suitable for most premixed flames.Figure 6 shows the simulation model, which is set as the wallboundary condition in the chemical reaction area of internal flowlayer using Eqs. (8)–(13).

2.5 Spark Modeling. In the spark discharge modeling, allphysical characteristics including volume (size), electrodes gap,electrical energy, kernel formation, ambient temperature, andpressure conditions are included. This model has been imple-mented by Lipatnikov et al. [63,64] who conducted a study on tur-bulent flame speed and thickness. The premixed flame model,which includes the mean reaction progress variable (c), can bemathematically shown as the following transport equation by Kar-pov et al. [64] and Zimont et al. [65]:

@qc

@tþr� qv

*c

� �¼ r� Dtrcð Þ þ quUt rcj j (14)

where Dt is the turbulent diffusivity, qu is the unburned mixturedensity, and is the Ut turbulent flame speed. Notably, Karpovet al. [64] found that the meshing size of a spark formation couldbe remarkably decreased in laminar condition. Therefore, the pre-mixed flame model could be redefined as the following equation:

@qc

@tþr� qv

*c

� �¼ r� aþ DttÞrcð Þ þ quUt rcj j (15)

where a is the thermal diffusivity ðk=qcpÞ wherein k is the thermalconductivity and cp is a specific heat at constant pressure. Dtt is

the effective diffusivity, which can be defined as the followingequation [66]:

Dtt ¼ Dt 1� exp�ttd

s0

� �� �if ttd � 0

Dt ttd < 0

8<: (16)

where ttd is the time of spark initiation, which is defined by sparkgrowth as t� tig and s0 is the effective diffusion time. However,the spark model can be also created as a high temperature sourcein combustion simulation. Therefore, the initial temperature ofspark used in PPC model has been verified through the actualexperiment in the constant volume combustion chamber.

2.6 Experimental and Computational Conditions. Table 7shows the experimental and computational conditions of conven-tional ignition and CDI systems. Experimental conditions are setas initial pressure of 2, 3, and 4 bar, temperature of 300 K, cham-ber wall temperature of 350 K, electrodes gap of 1.0, 1.25, and1.5 mm, discharge duration of 1 ms, discharge energy of 500 mJ,and air/fuel equivalence ratio of 1.0–1.7. The computational studyis performed by ANSYS FLUENT program using the PPC modelhaving the same conditions as experimental study. To validate thecollected data and verify the repeatability of experimental study,the experiments are repeated 10 times.

The air/fuel equivalence ratio is changed in eight different stepsfrom k¼ 1.0 to k¼ 1.7 in the ANSYS FLUENT setup tool. In fact,the fuel/air equivalence ratio (/) can be reversely calculated usingair/fuel equivalence ratio (k) as the following equation [67]:

/ ¼ 1

k(17)

Mathematically, / can be defined as [68,69]

/ ¼ mfuel=mox

ðmfuel=moxÞst

(18)

where m is mass and suffix st stands for stoichiometric condition.Therefore, Table 8 shows the associated mass fractions for speciesavailable in the initial mixture in terms of air/fuel equivalenceratio.

3 Results and Discussions

3.1 Plasma Ignition in Atmospheric Air. In this experiment,the voltage signals are analyzed to study the ignition characteris-tics of both conventional ignition and CDI systems. Figure 7shows the voltage signals of plasma ignition induced by trans-former for three different electrode gaps of 1, 1.25, and 1.5 mm.The x-axis of the graph represents time in milliseconds and the y-axis represents the voltage signal in kV. The experiment is per-formed using the setup shown in Fig. 1 in atmospheric air. Theignition frequency is changed from 13 to 87 Hz. Voltage signalsbetween two ignition systems show completely different behaviorin terms of signal amplitude and duration. In conventional igni-tion, the discharge voltage is remained constant within dischargeduration except for the peak voltage in the breakdown process. Inthe CDI system, the high voltage is first stored inside the capacitorbefore discharging. The stored time is changing by electrode gap,i.e., 0.27, 0.29, and 0.31 ms for 1, 1.25, and 1.5 mm gaps,

Table 6 Chemical reaction species of an air/C3H8 mixture

Chemical reactions Exponential factor Ai [kmol/(m3s)] Activation energy Ei [J/kmol]

C3H8þ 5(O2þ 3.76N2)¼ 3CO2þ 4H2Oþ 18.8N2 5.62� 109 1.25� 108

COþ 0.5O2¼CO2 2.23� 1012 1.71� 108

CO2¼COþ 0.5O2 5.02� 108 1.71� 108

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respectively. The stored time is shown to have an inverse relationwith the stored voltage and direct relation with the discharge volt-age in CDI system. As shown in Fig. 7, the average maximumstored voltage is remarkably higher than the average maximumdischarge voltage for CDI system. Notably, plasma duration canbe seen to delay the discharge signals at downstream as much as0.49 ms. This delayed characteristic is shown to include the timeconverting from electrical charges to discharge voltage because ofhaving a self-resistance inside the capacitor.

In order to clearly analyze the peak signal of stored, break-down, and discharge voltages, the effect of input pulse frequencyas well as electrode gap is investigated in Figs. 8 and 9. As seen inFig. 8, the stored voltage in CDI and breakdown voltage in con-ventional ignition show inverse trend with electrode gap. As elec-trode gap increases, the stored voltage decreases and breakdownvoltage increases. The breakdown voltage seems to remain

constant for the entire range of frequency from 13 to 87 Hz but thestored voltage in CDI system exhibits a slight increase byfrequency.

Figure 9 shows that the discharge voltage in conventional igni-tion is independent than electrode gap while the discharge voltagein CDI has a direct relation with gap distance. As gap increases,the discharge voltage increases in CDI system, which is associatedwith having sufficient time for flowing the electrons. The dis-charge voltage at 1 mm electrode gap for CDI system shows a sta-bilized trend as changing the frequency, because the kernel isgenerated easier in a narrower gap between anode and cathode. Inthe case of 1.25 mm gap in CDI system, due to sufficient time forstoring the electrical charges, the discharge voltage shows morestable behavior compared with the case of 1 mm gap. However, inthe case of 1.5 mm gap, the discharge voltage is shown to gradu-ally decrease by increasing the frequency, which is associatedwith the insufficient time for storing the electrical charges.

Consequently, the discharge characteristics of CDI areimproved by larger kernel size compared with conventional igni-tion. Also, the improved discharge voltage is shown to promotethe electron impact dissociation and dielectric breakdown strengthwhen adjusting the plug electrode gap.

Fig. 6 Simulation model and boundary conditions

Table 7 Experimental and computational conditions

Items Experimental conditions Analytical conditions

Initial pressure 2, 3 and, 4 barInitial temperature Air and fuel 300 KWall temperature 350 KInitial plasma kernel radius 0.5 mm (60.5%) 0.5 mmElectrode gap 1.0 mm, 1.25 mm, and 1.5 mm (60.02%)Input pulse duration 1 msPlasma energy Secondary (spark plug) 500 mJAir/fuel equivalence ratio k ¼ 1:0–1:7Combustion model Partially premixed combustion

Table 8 Species mass fraction of initial mixture

Mass fraction

Air/fuel equivalence ratio (k) C3H8 O2 N2

1.0 0.0603 0.2189 0.72071.1 0.0552 0.2202 0.72471.2 0.0508 0.2212 0.72801.3 0.0471 0.2220 0.73091.4 0.0439 0.2228 0.73341.5 0.0411 0.2234 0.73551.6 0.0386 0.2240 0.73741.7 0.0364 0.2245 0.7391 Fig. 7 Voltage signal characteristics for conventional ignition

and CDI systems

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3.2 Flame Propagation. In this work, the flame propagation,through both experiment and computation, is shown in Fig. 10 ina wide range of air/fuel equivalence ratio of 1.0–1.7, at combus-tion time of 14 ms and initial pressure of 4 bar. In order to analyzethe combustion characteristics of CDI comparing with conven-tional ignition, the fuel is diluted by nitrogen in different percen-tages of 0, 10, 20, and 30% inside the CVCC. This dilution is tointentionally change the flame propagation rate. The PPC modelis used to simulate the flame propagation and the results are com-pared with the corresponding experimental data. The flame propa-gation in conventional ignition system shows spherical structurefor the whole range of k while in CDI system, the flame propa-gates in ellipsoidal structure. In conventional ignition system, themisfire occurs at air/fuel equivalence ratios of 1.6, 1.3, 1.2, and1.1 in dilution percentages of 0%, 10%, 20%, and 30%,respectively.

As it can be seen, the flame resulted by CDI system has a higherflame radius compared with conventional ignition system. In theCDI system, the air/fuel equivalence ratio, at which the misfireoccurs, has been extended by k¼ 0.1 toward the lean mixturescompared with conventional ignition system. Computationalresults show similar trend and flame front growth with experimen-tal data. However, one can see that the flame radius, for the entirerange of k, is slightly higher in computational results than theexperimental data collected through high-speed photography. Thisis mainly associated with the lack of energy loss including naturalconvection, flame resistance, and electron impact dissociation in

the PPC model for combustion simulation. Consequently, the CDIsystem shows to significantly improve the flame propagation pro-cess by dielectric breakdown strength offered from capacitor dis-charge. Moreover, the combustion growth is significantly affecteddue to the large initial kernel size generated between electrodegaps in CDI system.

3.3 Combustion Pressure. Figure 11 shows the average peakpressure at different initial pressures of 2, 3, and 4 bar and variousnitrogen dilution of 0%, 10%, 20%, and 30%. The x-axis repre-sents the air/fuel equivalence ratio (k) and the y-axis is the experi-mental combustion pressure measured inside a CVCC using apiezoelectric pressure transducer. The average peak pressure inconventional ignition system decreases by air/fuel equivalenceratio. It can be also seen that the peak pressure decreases as nitro-gen dilution increases. At initial pressure of 2 bar and k¼ 1.0, theaverage peak pressures are 16.2, 15.9, 15.5, and 15.1 bar for 0%,10%, 20%, and 30% dilution, respectively. As shown in Fig. 11,for the entire range of k and dilution, the average peak pressureinside the CVCC is higher in CDI comparing with the conven-tional ignition. At initial pressure of 2 bar and k¼ 1.0, the averagepeak pressures using CDI system are 17.3, 16.8, 16.5, and15.8 barfor 0%, 10%, 20%, and 30% dilution, respectively. It can be alsoseen that the average peak pressure in CDI system improves by5.79%, 4.84%, and 4.36% at initial pressures of 2, 3, and 4 bar,respectively.

It can be concluded that similar combustion peak pressure ofconventional ignition can be achieved by the CDI under less fuelconcentration. This conclusion demonstrates the CDI capability ofincreasing the combustion performance through fuel economyenhancement and emissions reduction. The peak pressureimprovement percentages of CDI compared with the conventionalignition are listed in Tables 9–12 for different dilution percen-tages. As seen in Figs. 11(a) and 11(b), the pressure improvementrate in CDI system is more significant in smaller air/fuel equiva-lence ratios. It is shown in Figs. 11(b) and 11(d) that the computa-tional peak pressures are slightly higher than the experimentalones. It can be also seen that in simulation, the rate of peak pres-sure reduction with respect to k is smaller than experiment.

Consequently, the combustion reaction rate and flame propaga-tion of air/C3H8 mixture are greatly promoted due to the large ion-ized plasma kernel around the electrode gap. Also, one can seethat the electrical energy in CDI system is converted to the ther-mal energy faster than conventional ignition.

3.4 Combustion Propagation Time. Figure 12 shows thecombustion propagation time at initial pressure of 4 bar, widerange of air/fuel equivalence ratios from 1.0 to 1.7, and four dif-ferent nitrogen dilutions. The propagation time is defined as thetime between the start of ignition and the time when flame reachthe chamber wall on the opposite side of spark plug. The x-axis ofthis graph is air/fuel equivalence ratio (k) and the y-axis representsthe flame propagation time in milliseconds. The propagation timeis calculated for both experimental and computational studies andcompared together. The results represent the effectiveness of CDIin reducing the propagation time and in turn increasing the propa-gation speed comparing with the conventional ignition. As shownin Fig. 12(a), the flame propagation time using conventional igni-tion system is increased from 34 ms at k¼ 1.0–96 ms at k¼ 1.6for 0% dilution. The propagation time increases by nitrogen dilu-tion, i.e., from 34 to 68 ms for 0% and 30% dilution, respectively,at k¼ 1.0. On the other hand, the flame in CDI hits the chamberwall sooner than conventional ignition. In CDI system, the propa-gation time is reduced by 6 and 8 ms at k¼ 1.0 for dilution of 0%and 30%, respectively, comparing with conventional ignition.

3.5 Velocity Field. Figure 13 shows the velocity field at dif-ferent flame propagation times obtained through the computa-tional study for the case with no nitrogen dilution at initial

Fig. 8 Average maximum stored and breakdown voltages interms of input frequency for different electrode gaps of 1, 1.25,and 1.5 mm

Fig. 9 Average maximum discharge voltage in terms of inputfrequency for different electrode gaps of 1, 1.25, and 1.5 mm

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pressure of 4 bar and four different air/fuel equivalence ratios of1, 1.2, 1.4, and 1.6. It is shown in Fig. 13(a) that the velocity fieldin k¼ 1.0 and 5 ms is intensively affected by CDI more than theconventional ignition around the spark plug. The velocity field ink¼ 1.0 and 10 ms shows that the flame in CDI is propagated withmarginal turbulence faster than conventional ignition. It is shown,in k¼ 1.0 and propagation time of 15 ms, that the velocitystrength is remarkably promoted in the burned zone comparingwith conventional ignition in the air/C3H8 mixture. It is also indi-cated that the velocity field is significantly enhanced for all air/fuel equivalence ratios in CDI system. Consequently, thisincreased combustion velocity helps to improve the combustionpressure as shown in Sec. 3.3.

3.6 Species Mass Fraction. In this section, the mass fractionsof five species of C3H8, O2, N2, CO2, and H2O are shown inFig. 14 at initial pressure of 4 bar, flame propagation time of10 ms, and four different air/fuel equivalence ratios. The x-axis ofthe graph is the distance from the ignition point in cm and the y-axis represents the species mass fraction. As shown in Fig. 14(a),

for k¼ 1.0, the distance at which the C3H8, O2, N2, CO2, and H2Oconcentrations are greatly affected by chemical reactions isbetween 2.93 and 3.6 cm from ignition source. The thickness ofthis affected region is around 0.67 cm. This thickness is decreasedby air/fuel equivalence ratios as 0.67, 0.6, 0.58, and 0.42 cm fork¼ 1.0, 1.2, 1.4, and 1.6, respectively. As shown in Fig. 14, thechemically reacting region in CDI system occurs after conven-tional ignition. The distance difference between these chemicallyreacting regions in two ignition systems is 0.36, 0.33, 0.25, and0.21 cm for k¼ 1.0, 1.2, 1.4, and 1.6, respectively. As can be seenin Fig. 14, the O2 concentration in combustion products increasesby increasing the air/fuel equivalence ratio, which is due to theincomplete combustion in nonstoichiometric mixture of k¼ 1.2,1.4, and 1.6. At the same time, the mass fractions of CO2 and H2Oare decreased. The mass fractions of O2, CO2, and H2O in bothCDI and conventional ignition systems are listed in Table 13. Ascan be seen in Table 13, the mass fraction of O2 in CDI is slightlylower than conventional ignition, which proves that the combus-tion resulted by CDI is closed to complete more than conventionalignition.tp

Fig. 10 Flame propagation snapshots in air/C3H8 mixture with different N2 dilution atinitial pressure of 4 bar and a wide range of air/fuel equivalence ratios: (a) 0% N2, (b)10% N2, (c) 20% N2, and (d) 30% N2

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4 Conclusion

As conducting the investigation of the plasma kernel formationand flame propagation based on the capacitive discharge ignition,the following conclusions have been obtained:

Fig. 11 Combustion pressure characteristics for a wide range of air/fuel equivalence ratios and dilutions: (a) conventionalignition system (experiment) and (b) CDI system (experiment), (c) conventional ignition system (simulation), and (d) CDI sys-tem (simulation)

Table 9 Peak pressure improvement percentage by CDI at 0%N2 dilution

Method Experiment PPC model

Initial pressure 2 bar 3 bar 4 bar 2 bar 3 bar 4 bar

k¼ 1.0 6.39 5.4 4.9 6.88 6.00 5.63k¼ 1.1 6.10 5.2 4.7 6.62 5.77 5.43k¼ 1.2 5.85 5.0 4.5 6.56 5.66 5.31k¼ 1.3 5.66 4.9 4.4 6.75 5.68 5.25k¼ 1.4 5.53 4.7 4.2 7.25 5.85 5.28k¼ 1.5 5.47 4.5 4.0 8.15 6.20 5.41k¼ 1.6 5.51 4.2 3.9 9.62 6.80 5.65Average 5.79 4.84 4.36 7.40 6.00 5.42

Table 10 Peak pressure improvement percentage by CDI at10% N2 dilution

Method Experiment PPC model

Initial pressure 2 bar 3 bar 4 bar 2 bar 3 bar 4 bar

k¼ 1.0 5.18 4.11 3.31 6.64 5.01 4.21k¼ 1.1 5.58 4.04 3.09 6.52 4.44 3.51k¼ 1.2 5.51 3.95 3.00 6.48 4.16 3.15k¼ 1.3 4.81 3.83 3.04 6.56 4.24 3.20Average 5.27 3.98 3.11 6.55 4.46 3.52

Table 11 Peak pressure improvement percentage by CDI at20% N2 dilution

Method Experiment PPC model

Initial pressure 2 bar 3 bar 4 bar 2 bar 3 bar 4 bar

k¼ 1.0 5.94 4.34 3.05 7.01 4.55 3.67k¼ 1.1 5.63 4.16 3.49 5.15 3.09 2.44k¼ 1.2 6.35 4.25 3.46 3.17 1.65 1.35Average 5.97 4.25 3.33 5.11 3.09 2.49

Table 12 Peak pressure improvement percentage by CDI at30% N2 dilution

Method Experiment PPC model

Initial pressure 2 bar 3 bar 4 bar 2 bar 3 bar 4 bar

k¼ 1.0 4.551 3.71 2.71 7.02 4.06 3.46k¼ 1.1 4.918 3.71 2.78 4.70 2.15 1.94Average 4.735 3.71 2.74 5.86 3.11 2.70

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(1) The discharge characteristics of CDI are improved by ker-nel growth expanded between electrode gaps comparedwith conventional spark.

(2) The discharge voltage is more promoted by the electronimpact dissociation and dielectric breakdown strengthwhen adjusting the plug electrode gap.

Fig. 12 Flame propagation time at initial pressure of 4 bar, wide range of air/fuel equivalence ratios and fourdifferent nitrogen dilutions: (a) 0% N2 dilution, (b) 10% N2 dilution, (c) 20% N2 dilution, and (d) 30% N2 dilution

Fig. 13 Velocity field at three different propagation times of 5, 10 and 15 ms: (a) k 5 1.0, (b) k 5 1.2, (c) k 5 1.4,and (d) k 5 1.6

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(3) The combustion reaction of CDI improves the flame propa-gation process by dielectric breakdown strength offeredfrom capacitor discharge.

(4) The combustion reaction by CDI efficiently leads toincreasing the flame promotion in an air/propane mixture.

(5) Large ionized flame kernel around spark plug is influen-tially enhanced discharge from stored voltage in CDIsystem.

(6) The discharge effect for CDI is more efficiently shown toreact a chemical reaction of O2, CO2 and H2O comparingwith conventional ignition.

References[1] Verhelst, S., Turner, J. W., Sileghem, L., and Vancoillie, J., 2018, “Methanol as

a Fuel for Internal Combustion Engines,” Prog. Energy Combust. Sci., 70, pp.43–88.

[2] Yue, Z., and Reitz, R. D., 2018, “Numerical Investigation of Radiative HeatTransfer in Internal Combustion Engines,” Appl. Energy, 235, pp. 147–163.

[3] Tang, Q., Liu, H., Li, M., Yao, M., and Li, Z., 2017, “Study on Ignition andFlame Development in Gasoline Partially Premixed Combustion Using Multi-ple Optical Diagnostics,” Combust. Flame, 177, pp. 98–108.

[4] An, Y., Jaasim, M., Raman, V., Hern Andez, P., Erez, F. E., Sim, J., Chang, J.,Im, H. G., and Johansson, B., 2018, “Homogeneous Charge Compression Igni-tion (HCCI) and Partially Premixed Combustion (PPC) in Compression IgnitionEngine With Low Octane Gasoline,” Energy, 158, pp. 181–191.

[5] Wang, Y., Yao, M., Li, T., Zhang, W., and Zheng, Z., 2016, “A ParametricStudy for Enabling Reactivity Controlled Compression Ignition (RCCI) Opera-tion in Diesel Engines at Various Engine Loads,” Appl. Energy, 175, pp.389–402.

[6] Liu, Q., Fu, J., Zhu, G., Li, Q., Liu, J., Duan, X., and Guo, Q., 2018,“Comparative Study on Thermodynamics, Combustion and Emissions of Tur-bocharged Gasoline Direct Injection (GDI) Engine Under NEDC and Steady-State Conditions,” Energy Convers. Manag., 169, pp. 111–123.

[7] Askari, O., Metghalchi, H., Kazemzadeh Hannani, S., Moghaddas, A.,Ebrahimi, R., and Hemmati, H., 2012, “Fundamental Study of Spray and

Fig. 14 Species mass fraction at initial pressure of 4 bar, propagation time of 10 ms, and different air/fuel equivalence ratios:(a) k 5 1.0, (b) k 5 1.2, (c) k 5 1.4, and (d) k 5 1.6

Table 13 Mass fractions of O2, CO2, and H2O in CDI and conventional ignition systems

Type Conventional ignition CDI

Species O2 CO2 H2O O2 CO2 H2O

A1, B1, and C1 in k¼ 1.0 0.00831 0.16000 0.09500 0.00795 0.16100 0.09510A2, B2, and C2 in k¼ 1.2 0.02227 0.15717 0.08808 0.02206 0.15780 0.08821A3, B3, and C3 in k¼ 1.4 0.03734 0.14886 0.08169 0.03726 0.14919 0.08179A4, B4, and C4 in k¼ 1.6 0.05101 0.13966 0.07612 0.05100 0.13982 0.07619

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Partially Premixed Combustion of Methane/Air Mixture,” ASME J. EnergyResour. Technol., 135(2), p. 021001.

[8] Askari, O., Metghalchi, H., Kazemzadeh Hannani, S., Hemmati, H., and Ebra-himi, R., 2014, “Lean Partially Premixed Combustion Investigation of MethaneDirect-Injection Under Different Characteristic Parameters,” ASME J. EnergyResour. Technol., 136(2), p. 022202.

[9] Kim, J., Chun, M., Song, S., Baek, H.-K., and Lee, S. W., 2017, “The Effects ofHydrogen on the Combustion, Performance and Emissions of a Turbo GasolineDirect-Injection Engine With Exhaust Gas Recirculation,” Int. J. HydrogenEnergy, 42(39), pp. 25074–25087.

[10] Cho, H. M., and He, B.-Q., 2006, “Spark Ignition Natural Gas Engines—AReview,” Energy Convers. Manag., 48(2), pp. 608–618.

[11] Eisazadeh-Far, K., Parsinejad, F., Metghalchi, H., and Keck, J. C., 2010, “OnFlame Kernel Formation and Propagation in Premixed Gases,” Combust.Flame, 157(12), pp. 2211–2221.

[12] Wan, H., Gao, Z., Ji, J., Zhang, Y., and Li, K., 2018, “Experimental and Theo-retical Study on Flame Front Temperatures Within Ceiling Jets From TurbulentDiffusion Flames of n-Heptane Fuel,” Energy, 164, pp. 79–86.

[13] Vasiliev, L. L., Burak, V. S., Kulakov, A. G., Mishkinis, D. A., and Bohan, P.V., 2000, “Latent Heat Storage Modules for Preheating Internal CombustionEngines: Application to a Bus Petrol Engine,” Appl. Therm. Eng., 20(10), pp.913–923.

[14] Gritti, F., 2018, “High-Resolution Turbulent Flow Chromatography,” J. Chro-matogr. A, 1570, pp. 135–147.

[15] Badica, P., Batalu, D., Burdusel, M., Grigoroscuta, M. A., Aldica, G. V., Encu-lescu, M., Gabor, R. A., Wang, Z., Huang, R., and Li, P., 2018, “CompressiveProperties of Pristine and SiC-Te-Added MgB2 Powders, Green Compacts andSpark-Plasma-Sintered Bulks,” Ceram. Int., 44(9), pp. 10181–10191.

[16] Szwaja, S., Ansari, E., Rao, S., Szwaja, M., Grab-Rogalinski, K., Naber, J. D.,and Pyrc, M., 2018, “Influence of Exhaust Residuals on Combustion Phases,Exhaust Toxic Emission and Fuel Consumption From a Natural Gas FueledSpark-Ignition Engine,” Energy Convers. Manag., 165, pp. 440–446.

[17] Rinc�on, R., Mu~noz, J., and S�aez, M., 2013, “Spectroscopic Characterization ofAtmospheric Pressure Argon Plasmas Sustained With the Torche �a InjectionAxiale Sur Guide D’Ondes,” Spectrochim. Acta Part B, 81, pp. 26–35.

[18] Caliari, F. R., Miranda, F. S., Reis, D. A. P., Filho, G. P., Charakhovski, L. I.,and Essiptchouk, A., 2016, “Plasma Torch for Supersonic Plasma Spray atAtmospheric Pressure,” J. Mater. Process. Technol., 237, pp. 351–360.

[19] Dalvand, E. S., Ebrahimi, M., and Pouryoussefi, S. G., 2018, “ExperimentalInvestigation, Modeling and Prediction of Transition From Uniform Dischargeto Filamentary Discharge in DBD Plasma Actuators Using Artificial NeuralNetwork,” Appl. Therm. Eng., 129, pp. 50–61.

[20] Duchmann, A., Simon, B., Tropea, C., and Grundmann, S., 2014, “DielectricBarrier Discharge Plasma Actuators for in-Flight Transition Delay,” AIAA J.,52(2), pp. 358–367.

[21] Park, J., Henins, I., Herrmann, H. W., Selwyn, G. S., and Hicks, R. F., 2001,“Discharge Phenomena of an Atmospheric Pressure Radio-Frequency Capaci-tive Plasma Source,” J. Appl. Phys., 89(1), pp. 20–28.

[22] Nanto, T., Nakahara, H., Awaji, N., Wakitani, M., Shinoda, T., Konno, K.,Yanagibashi, Y., and Sakamoto, N., 1999, “Surface Discharge Plasma DisplayIncluding Light Shielding Film Between Adjacent Electrode Pairs,” IEEETrans. Ind. Appl., 24(2), pp. 223–231.

[23] Starikovskii, A. Y., Anikin, N. B., Kosarev, I. N., Mintoussov, E. I., Nudnova,M. M., Rakitin, A. E., Roupassov, D. V., Starikovskaia, S. M., and Zhukov, V.P., 2008, “Nanosecond-Pulsed Discharges for Plasma-Assisted Combustion andAerodynamics,” J. Propul. Power, 24(6), pp. 1182–1197.

[24] Masuda, S., Akutsu, K., Kuroda, M., Awatsu, Y., and Shibuya, Y., 1988, “ACeramic-Based Ozonizer Using High-Frequency Discharge,” IEEE Trans. Ind.Appl., 24(2), pp. 223–231.

[25] Askari, O., Beretta, G. P., Eisazadeh-Far, K., and Metghalchi, H., 2016, “Onthe Thermodynamic Properties of Thermal Plasma in the Flame Kernel ofHydrocarbon/Air Premixed Gases,” Eur. Phys. J. D, 70, p. 159.

[26] Askari, O., 2017, “Thermodynamic Properties of Pure and Mixed Thermal Plas-mas Over a Wide Range of Temperature and Pressure,” ASME J. EnergyResour. Technol., 140(3), p. 032202.

[27] Salunkhe, A. B., Khot, V. M., Phadatare, M. R., and Pawar, S. H., 2012,“Combustion Synthesis of Cobalt Ferrite Nanoparticles—Influence of Fuel toOxidizer Ratio,” J. Alloys Compd., 514, pp. 91–96.

[28] Cerny, P., Bartos, P., Olsan, P., and Spatenka, P., 2019, “Hydrophobization ofCotton Fabric by Gliding Arc Plasma Discharge,” Curr. Appl. Phys., 19(2),pp. 128–136.

[29] Lee, T., Puligundla, P., and Mok, C., 2018, “Intermittent Corona DischargePlasma Jet for Improving Tomato Quality,” J. Food Eng., 223, pp. 168–174.

[30] Murugapandiyan, P., Ravimaran, S., and William, J., 2017, “DC and Micro-wave Characteristics of Lg 50 nm T-gate In AlN/AlN/GaN HEMT for FutureHigh Power RF Applications,” AEU–Int. J. Electron. Commun., 77,pp. 163–168.

[31] Chen, Q., Sun, J., and Zhang, X., 2018, “Kinetic Contribution of CO2/O2 Addi-tive in Methane Conversion Activated by Non-Equilibrium Plasmas,” Chin. J.Chem. Eng., 26(5), pp. 1041–1050.

[32] Du, H., Wang, H., Yao, P., Wang, J., and Sun, Y., 2018, “In2O3 NanofibersSurface Modified by Low-Temperature RF Plasma and Their Gas Sensing Prop-erties,” Mater. Chem. Phys., 215, pp. 316–326.

[33] Attrash, M., Kuntumalla, M. K., and Hoffman, A., 2019, “Bonding, StructuralProperties and Thermal Stability of Low Damage RF (N2) Plasma TreatedDiamond (100) Surfaces Studied by XPS, LEED, and TPD,” Surf. Sci., 681, pp.95–103.

[34] Yang, J., Yang, F., Hua, H., Cao, Y., Li, C., and Fang, B., 2018, “ABipolar Pulse Power Generator for Micro-EDM,” Procedia CIRP, 68, pp.620–624.

[35] Filimonova, E., Bocharov, A., and Bityurin, V., 2018, “Influence of a Non-Equilibrium Discharge Impact on the Low Temperature Combustion Stage inthe HCCI Engine,” Fuel, 228, pp. 309–322.

[36] Nakaya, S., Iseki, S., Gu, X., Kobayashi, Y., and Tsue, M., 2016, “Flame Ker-nel Formation Behaviors in Close Dual-Point Laser Breakdown SparkIgnition for Lean Methane/Air Mixtures,” Proc. Combust. Inst., 36(3), pp.3441–3449.

[37] Zhang, Z., and Tan, X., 2012, “Review of High Power Pulse TransformerDesign,” Phys. Procedia, 32, pp. 566–574.

[38] Hwang, J., Bae, C., Park, J., Choe, W., Cha, J., and Woo, S., 2016,“Microwave-Assisted Plasma Ignition in a Constant Volume CombustionChamber,” Combust. Flame, 167, pp. 86–96.

[39] Poggiani, C., Battistoni, M., Grimaldi, C. N., and Magherini, A., 2015,“Experimental Characterization of a Multiple Spark Ignition System,” EnergyProcedia, 82, pp. 89–95.

[40] Zhao, S.-X., 2016, “Mode Transition and Hysteresis in Inductively CoupledPlasma Sources,” Plasma Science and Technology, InTech Open, Rijeka,Croatia.

[41] Starikovskiy, A., and Aleksandrov, N., 2013, “Plasma-Assisted Ignition andCombustion,” Prog. Energy Combust. Sci., 39(1), pp. 61–110.

[42] Kim, K., and Choi, D., 2018, “Thermodynamic Kernel, IMEP, and ResponseBased on Three Plasma Energies,” J. Mech. Sci. Technol., 32(8), pp.3983–3994.

[43] Bane, S. P. M., Shepherd, J. E., Kwon, E., and Day, A. C., 2011, “StatisticalAnalysis of Electrostatic Spark Ignition of Lean H2/O2/Ar Mixtures 5,” Int. J.Hydrogen Energy, 36(3), pp. 2344–2350.

[44] Kinjo, T., Senjyu, T., Urasaki, N., and Fujita, H., 2006, “Output Levelling ofRenewable Energy by Electric Double-Layer Capacitor Applied for EnergyStorage System,” IEEE Trans. Energy Convers., 21(1), pp. 221–227.

[45] Malesani, L., Rossetto, L., Tenti, P., and Tomasin, P., 1995, “AC/DC/AC PWMConverter With Reduced Energy Storage in the DC Link,” IEEE Trans. Ind.Appl., 31(2), pp. 287–292.

[46] Miller, J. R., and Simon, P., 2008, “Electrochemical Capacitors for EnergyManagement,” Science, 321(5889), pp. 651–652.

[47] Teymourfar, R., Asaei, B., Iman-Eini, H., and Nejati fard, R., 2012, “StationarySuper-Capacitor Energy Storage System to Save Regenerative Braking Energyin a Metro Line,” Energy Convers. Manag., 56, pp. 206–214.

[48] Zimont, V. L., 2000, “Gas Premixed Combustion at High Turbulence. Turbu-lent Flame Closure Combustion Model,” Exp. Therm. Fluid Sci., 21(1–3), pp.179–186.

[49] Zimont, V., Polifke, W., Bettelini, M., and Weisenstein, W., 1998, “An Effi-cient Computational Model for Premixed Turbulent Combustion at High Reyn-olds Numbers Based on a Turbulent Flame Speed Closure,” ASME J. Eng. GasTurbines Power, 120(3), p. 526.

[50] Zimont, V. L., and Trushin, Y. M., 1969, “Total Combustion Kinetics of Hydro-carbon Fuels,” Combust. Explos. Shock Waves, 5(4), pp. 391–394.

[51] Askari, O., Vien, K., Wang, Z., Sirio, M., and Metghalchi, H., 2016, “ExhaustGas Recirculation Effects on Flame Structure and Laminar Burning Speeds ofH2/CO/air Flames at High Pressures and Temperatures,” Appl. Energy, 179, pp.451–462.

[52] Askari, O., Moghaddas, A., Alholm, A., Vein, K., Alhazmi, B., and Metghalchi,H., 2016, “Laminar Burning Speed Measurement and Flame Instability Studyof H2/CO/air Mixtures at High Temperatures and Pressures Using a NovelMulti-Shell Model,” Combust. Flames, 168, pp. 20–31.

[53] Roy, S., Zare, S., and Askari, O., 2018, “Understanding the Effect of Oxygen-ated Additives on Combustion Characteristics of Gasoline,” ASME J. EnergyResour. Technol., 141(2), p. 022205.

[54] Yu, G., Askari, O., Hadi, F., Wang, Z., Metghalchi, H., Kannaiyan, K., andSadr, R., 2017, “Theoretical Prediction of Laminar Burning Speed and IgnitionDelay Time of Gas-to-Liquid Fuel,” ASME J. Energy Resour. Technol., 139(2),p. 022202.

[55] Rokni, E., Moghaddas, A., Askari, O., and Metghalchi, H., 2015, “Measurement ofLaminar Burning Speeds and Investigation of Flame Stability of Acetylene (C2H2) /Air Mixtures,” ASME J. Energy Resour. Technol., 137(1), p. 012204.

[56] Askari, O., Wang, Z., Vien, K., Sirio, M., and Metghalchi, H., 2017, “On theFlame Stability and Laminar Burning Speeds of Syngas/O2/He PremixedFlame,” J. Fuel, 190, pp. 90–103.

[57] Yu, G., Askari, O., and Metghalchi, H., 2017, “Theoretical Prediction ofthe Effect of Blending JP-8 With Syngas on the Ignition Delay Time andLaminar Burning Speed,” ASME J. Energy Resour. Technol., 140(1), p.012204.

[58] Yu, G., Metghalchi, H., Askari, O., and Wang, Z., 2018, “Combustion Simula-tion of Propane/Oxygen (With Nitrogen/Argon) Mixtures Using Rate-Controlled Constrained-Equilibrium,” ASME J. Energy Resour. Technol.,141(2), p. 022204.

[59] Askari, O., Elia, M., Ferrari, M., and Metghalchi, H., 2017, “Cell FormationEffects on the Burning Speeds and Flame Front Area of Synthetic Gas at HighPressures and Temperatures,” Appl. Energy, 189, pp. 568–577.

[60] Askari, O., Elia, M., Ferrari, M., and Metghalchi, H., 2017, “Auto-IgnitionCharacteristics Study of Gas-to-Liquid Fuel at High Pressures and Low Tem-peratures,” ASME J. Energy Resour. Technol., 139(1), p. 012204.

[61] Zimont, V. L., 1979, “Theory of Turbulent Combustion of a HomogeneousFuel Mixture at High Reynolds Numbers,” Combust. Explos. Shock Waves,15(3), pp. 305–311.

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[62] Zimont, V. L., and Biagioli, F., 2002, “Gradient, Counter-Gradient Transportand Their Transition in Turbulent Premixed Flames,” Combust. Theory Model.,6(1), pp. 79–101.

[63] Lipatnikov, A. N., and Chomiak, J., 2002, “Turbulent Flame Speed and Thick-ness: Phenomenology, Evaluation, and Application in Multi-Dimensional Sim-ulations,” Prog. Energy Combust. Sci., 28(1), pp. 1–74.

[64] Karpov, V., Lipatnikov, A., and Imont, V., 1996, “A Test of an EngineeringModel of Premixed Turbulent Combustion,” Symp. Combust., 26(1), pp.249–257.

[65] Zimont, V. L., Biagioli, F., and Syed, K., 2001, “Modelling Turbulent PremixedCombustion in the Intermediate Steady Propagation Regime,” Prog. Comput.Fluid Dyn., 1(1/2/3), p. 14.

[66] Zimont, V. L., 2015, “Theoretical Study of Self-Ignition and Quenching Limitsin a Catalytic Micro-Structured Burner and Their Sensitivity Analysis,” Chem.Eng. Sci., 134, pp. 800–812.

[67] Jaojaruek, K., 2014, “Mathematical Model to Predict Temperature Profile andAir–Fuel Equivalence Ratio of a Downdraft Gasification Process,” EnergyConvers. Manag., 83, pp. 223–231.

[68] Nakamura, N., Baika, T., and Shibata, Y., 1985, “Multipoint Spark Ignition forLean Combustion,” SAE Trans., 94, pp. 611–620.

[69] Zervas, E., Montagne, X., Lahaye, J., 2002, “Emission of Alcohols andCarbonyl Compounds From a Spark Ignition Engine. Influence of Fuel andAir/Fuel Equivalence Ratio,” Environ. Sci. Technol., 36(11), pp.2414–2421.

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