Conventional Ignition Research Articles

Comparison of performance and emission characteristics of homogeneous charge compression ignition with conventional compression ignition engine

The performance and emissions of homogeneous charge compression ignition (HCCI) diesel engines were analysed at varying intake air temperatures (Ti) and compared with conventional diesel engines. HCCI engines featured outside fuel–air mixing systems. Diesel was used as a fuel for the testing of port fuel injection pressure (two bars, four bars, and six bars), as well as intake temperature Ti (60 °C, 80 °C, 100 °C, 120 °C, and 140 °C). The outcomes of the experiments presented that both Ti and port fuel injection pressure had a substantial impact on the fuel–air mixture. Up to 120 °C, the blending of air and fuel had a proportionate effect on Ti. When heated above 120 °C, it caused significant knocking and emissions. The Brake thermal efficiency of HCCI is similar to that of diesel engine when HCCI engine operated at an intake air temperature of 120 °C and injection pressure of 4 bar where as in other modes it less than the efficiency of diesel engine. The nitrogen oxide emissions were significantly reduced in the all HCCI engine mode operations compared to diesel engine. The minimum emissions were engine when HCCI engine operated at an intake air temperature of 120 °C and injection pressure of 4 bar. The smoke opacity was significantly reduced in the all HCCI engine mode operations compared to diesel engine. The minimum emissions were engine when HCCI engine operated at an intake air temperature of 120 °C and injection pressure of 4 bar. The HC and CO emissions of HCCI engine at all conditions were slightly higher than the diesel engine. But, the minimum emissions were obtained when HCCI engine operated at an intake air temperature of 120 °C and injection pressure of 4 bar without knocking. Finally, it is concluded that HCCI engine operated at an intake air temperature of 120 °C and injection pressure of 4 bar will give the optimized perform ace and emission characteristics when compared to diesel engine.

An Experimental Study on the Emission Characteristics in CI Engine using Nano Particle Coated Catalytic Converter

A proven viable technology to reduce vehicular exhaust gas emission is the catalytic converter. Although catalyst converters are an effective and efficient method to react to certain pollutants, they are expensive due to the use of noble metals like palladium, platinum and rhodium. Various research has been carried out to find a viable alternative to the noble metal catalyst that can react over vehicular pollutants such as oxides of nitrogen (NOx), carbon monoxide (CO), unburnt hydrocarbon (UBHC) and particulate matter (PM) emitted by the combustion of hydrocarbon burnt internal combustion engine. This paper investigates the emission characteristics of a nano-particle-coated catalytic converter in a conventional fossil-fuelled compression ignition engine. The catalyst used in the research is a nano-particle of metal oxides such as aluminium oxide (nano-sized Al2O3) particle and titanium oxide nano-sized (TiO2) particle. This catalyst is less expensive compared to a noble catalyst. Experiments were made on a single cylinder four strokes water-cooled diesel-fuelled compression ignition engine with a catalytic converter coated with alternative nano-particles. The exhaust gas was allowed to pass through the nano-sized catalyst deposited over the honeycomb structure of the substrate of the catalytic converter and the emission was measured using a five-gas analyser. The result showed a decreased level of oxides of nitrogen.

Molecularly-controlled high swirl combustion system for ethanol/1-octanol dual fuel combustion

To achieve future targets for reducing greenhouse-gas and pollutant emissions from internal combustion engines, alternative fuels as well as alternative combustion modes offer great potential. The simultaneous use of two different fuels offers additional degrees of freedom to realize highly efficient and low-emission combustion, but also poses further challenges. To this end, this paper presents the Molecularly-Controlled high swirl Combustion system, MCC, which involves dual direct injection of a low- and a high-reactivity fuel in combination with lean relative air-fuel-ratios, high compression ratio, and compression ignition. The principle centers on the generation of a strong “molecular spark” – a spacially confined area in the combustion chamber where the reactivity of the fuel mixture is sufficient to form a robust, controllable ignition source. Subsequently, combustion spreads to the rest of the combustion chamber. Ethanol was used as the low-reactivity fuel and 1-octanol or conventional diesel fuel as the high-reactivity fuel to investigate the combustion characteristics, efficiency, and raw emission potential under various operating conditions with a light-duty single-cylinder research engine. The results are compared with compression ignition operation of conventional diesel fuel and neat 1-octanol. The MCC system achieves a large reduction in soot-emissions, even at very low NOx-levels below 0.1 g/kWh and a considerable increase in indicated efficiency over conventional compression ignition combustion.

VEHICLE STARTER SYSTEM FOR SAFETY BASED MICROCONTROLLER USING INTERNET OF THINGS

Technology is currently growing very fast which affects and has a significant purpose in human life. In the current era, the technology of the security system is something that is very necessary. The high crime rate has now reached an alarming stage. Motorcycles currently only use conventional ignition keys to turn them on to improve the vehicle's security system, so a vehicle security system with a microcontroller connected to an Internet of Things-based fingerprint sensor is needed to improve the vehicle's security system. Research shows that a motorcycle security system with a microcontroller is connected to a fingerprint sensor based on the Internet of Things, namely turning on and turning off the vehicle with fingerprints owned or via the internet of things using the telegram application for remote and realtime systems. The way the results of this study work is when the first finger taps on the fingerprint sensor on the registered finger, the motor will turn on, then the second finger taps on the fingerprint sensor, the motor will die, for remote systems, namely using telegram bots, the prefix is to enter chat instructions on the telegram bot if the telegram bot replies to the instruction then the motor will follow according to the instruction on or off and if the instruction is wrong then the telegram bot will tell that the instruction is wrong. The results of this study show that when adding fingerprints it has a delay of 1.74s, removing fingerprints is 0.24s and the IoT system itself is 90% successful.

Effects of 2-ethylhexyl nitrate (EHN) on combustion and emissions on a compression ignition engine fueling high-pressure direct-injection pure methanol fuel

Green methanol is a good carbon–neutral fuel, but the cetane number of methanol is so low that it is unsuitable for use in conventional compression ignition engines. Stable combustion of methanol is a great challenge at low load. Cetane improver such as 2-ethylhexyl nitrate (EHN), can improve the combustion stability of low cetane number fuel. In the current work, the effects of EHN on combustion and emissions were studied on a compression ignition engine at low load by using pure methanol fuel. Four methanol fuels with different EHN addition ratios were used, namely 0 % EHN (pure methanol), 0.1 % EHN, 1 % EHN and 3 % EHN, and diesel was used as the baseline. Results show that compared with diesel, the shortened combustion duration of pure methanol is mainly caused by the shortening of premixed combustion phase. The brake thermal efficiency (BTE) of pure methanol is relatively higher than that of diesel at 120 °C intake temperature. But the BTE of diesel at 50 °C intake temperature is slightly higher than that of pure methanol. As the ENH increases, the ignition delay decreases gradually, and the BTE decreases first and then increases. The NOx emissions of methanol are lower than those of diesel, but NOx emissions increase with the increase of EHN. NOx emissions of 3 % EHN are 31 % more than those of pure methanol and 77 % less than those of diesel. The soot emissions are close to zero for all test methanol fuels. The BTE of all fuels increases initially and decreases subsequently with the delay of start of injection. The higher EGR rate, lower intake temperature and injection pressure improve the BTE of all fuel. For 3 % EHN, the lowest intake temperature is not higher than 40 °C for stable operation, and the optimal operating strategy for the highest BTE (30.5 %) is single injection, 25 MPa injection pressure, 15 % EGR rate and 40 °C intake temperature. Methanol shows 0.6 % higher optimal BTE than diesel at the operating condition.

Performance Requirements on Laser Ignition System

Abstract: Combustion is one of the most prominent energy conversion processes used in all areas of human life, even though it is being used on a large scale in various fields it has vital drawbacks like emission of greenhouse gases from IC engines majorly affecting the environment on a global level. One of the reasons of this issue being improper or inefficient ignition of the air-fuel mixture. However, this can be reduced to an extent by employing methods like lean combustion and re-circulating the exhaust gases. This is when the need of an alternative ignition system is required, one such concept being LASER IGNITION SYSTEM for internal combustion engines. On comparison laser ignition system provides number of potential benefits over conventional ignition by electric spark plug. Use of laser ignition system comes with advantages like- Reduction of NOx emission by 20% also improved efficiencies are obtained. The thermodynamic requirements of high compression ratios and high power density are fulfilled well by this system. Therefore, laser ignitors could replace conventional spark plugs in automobile industry. This not only provides better performance and fuel economy, but would also create less harmful emissions

A Comprehensive Study of the Effects of Various Operating Parameters on a Biogas-Diesel Dual Fuel Engine

Alternative fuels are found to be the most promising solution to the problem of conventional IC engine pollution because their use curtails its huge emissions without exerting a negative impact on its performance. In this research, a conventional compression ignition engine is investigated by operating it with the combination of simulated biogas and neat diesel under a dual fuel mode of operations. The simulated biogas in the current work comprises different proportions of methane and carbon dioxide in the mixture. The full factorial approach in this work involved studying the effects of parameters such as biogas flow rate, composition, intake temperature, torque, and methane enrichment (complete removal of CO2 from biogas) on the engine performance, emissions, and combustion indices with an extensive number of experiments. It is witnessed from the research that biogas is capable of providing a maximum of 90% of the overall energy input, while the CI engine operates under dual fuel mode. Under the dual fuel mode of operation involving biogas, a significant amount of reductions are witnessed in secondary fuel consumption (67%), smoke (75%), and NOx (55%) emissions. At low flow rates, biogas is found to improve brake thermal efficiency (BTE), whereas it reduces hydrocarbon and carbon monoxide emissions. Methane enrichment resulted in more diesel substitution by 5.5% and diminishes CO and HC emissions by 5% and 16%, respectively. Increasing the intake temperature caused an increase in thermal efficiency (2%) and a reduction in diesel consumption (~35%), and it curtailed all emission elements except NOx.

Effect of passive pre-chamber orifice diameter on the methane combustion process in an optically accessible SI engine

Due to its potential to extend the lean limit or overcome knock-limited conditions on spark-ignited (SI) engines, the pre-chamber spark-ignition (PCSI) concept has gained attention as an efficient alternative to the conventional ignition architecture. Nevertheless, especially in engine-like conditions, the effect of the main geometrical parameters on combustion development is still not fully understood and might be a hindrance to the use of this technology. In this sense, the current study aims to evaluate the effect of the orifice diameter on the jet characteristics and main chamber combustion of a novel passive pre-chamber in an optically accessible single-cylinder SI engine, as well as to compare the PCSI with the typical SI ignition method. High-speed broadband chemiluminescence imaging was used to track the jet penetration and flame front propagation of three mixture compositions at various spark timings (ST). Additionally, based on the in-cylinder pressure, a heat-released analysis was performed to assess the overall combustion process. When compared with the typical SI, the pre-chamber concept presented a higher equivalent flame front velocity, which is also corroborated by the higher in-cylinder pressure rise rate and rate of heat released. For all mixtures tested, the 1.2 mm orifice diameter PC presented the shortest flame development angle (crank angle interval between ST and 10 % of mass fraction burned in the MC), followed by 1.5 and lastly 1.0 mm. When comparing different STs, the shortest flame development angle occurred at MBT condition. Despite the highest flame development angle, the PC 1.0 mm case presented the lowest main chamber combustion duration (CA10-90), which increases as the orifice diameter is increased.

RANCANGAN PERALATAN ALTERNATOR PADA SISTEM PENGAPIAN BUSI ELEKTRONIK CDI SEPEDA MOTOR

In automotive spark plug ignition, gasoline-fueled vehicles require spark ignition system equipment. One of the electronic cdi spark plug ignition systems uses electronic equipment and components that replace conventional spark plug ignition systems. In this study, the design of the electronic cdi spark plug ignition system using the main equipment of the alternator produces an ac output voltage source on the exiter coil winding. The results of the design of the equipment are generated by a timer signal from the pulser component related to the rpm speed of the alternator permanent magnet rotor shaft which is driven by the rotation of the ac electric motor shaft. The ignition timing process of the spark plug is controlled by the charge/discharge condition of the electronic capacitor charge in the cdi device to produce an ac power supply voltage, the output time function to the primary input of the coil is expressed as the Vprimer(t) parameter in volts. The result of the primary voltage Vprimer(t) at the primary input of the induced coil generates a high voltage at the secondary output of the ignition coil, which is expressed as the Vo(coil) parameter. The result of a high voltage Vo(coil) momentarily connected to the spark plug produces spark ignition which indicates that there is a spark in the spark plug gap.

Study of Flame Kernel Development at High EGR and High Flow Speed Using Conventional Spark Igniter and Non-Thermal Plasma Under Gasoline Engine Relevant Conditions

ABSTRACT As a novel ignition approach, nanosecond repetitively pulsed discharge (NRPD)-based non-thermal plasma offers significant benefits such as low energy consumption, and lean operating conditions. However, there is no investigation conducted on the early flame kernel formation and development induced by non-thermal plasma. Therefore, in this paper, experiments of conventional spark and non-thermal plasma ignition systems in constant volume combustion chamber (CVCC) are conducted under gasoline engine relevant conditions: wide initial ambient pressures (6.5, 8.3, 11.3 bar), a range of equivalence ratios (0.7–1.0), EGR rates (10−25%), and cross flow speeds (0–30 m/s). The discharge energy of non-thermal plasma is of around 210 mJ, while a single spark event can generate energy from 65 mJ to 83 mJ depending on ambient conditions. A consecutive spark strategy is adopted to guarantee comparable total input energy to non-thermal plasma. The ignition delay and combustion phase obtained from the chamber pressure history are calculated. In the meanwhile, flame kernel radius, flame propagation rate, and flame front length ratio via schlieren images are quantified and analyzed. Results showed that the flame initiated by non-thermal plasma can maintain a robust flame kernel and propagates fast. Under high-speed cross flow and high EGR rate conditions, non-thermal plasma can maintain a robust flame kernel at early stage supporting the initial flame kernel to survive and improve its ignition probability. Considering the effects of the EGR ratio and high-speed cross flow on flame kernel development, non-thermal plasma ignition can efficiently enhance the flame propagation and ignition probability. It is also concluded that non-thermal plasma can successfully ignite under lean (equivalence ratio between 0.7–1.0), high-diluted mixture (25% EGR), and high-speed cross flow of 30 m/s within the range of current study.

Ignition of an ionic liquid dual-mode monopropellant using a microwave plasma torch

The blend of hydroxylammonium nitrate (HAN) and imidazole-based ionic liquid has shown good feasibility in chemical and electric dual-mode green space propulsion. As conventional catalyst-driven ignition faces challenges arising from long preheat delay and catalyst failure, this work designs a novel ignition actuator using a microwave plasma torch. The precise tuning of the ¼-λ resonant cavity and improvement in the quality factor (QF) of the microwave igniter make the device efficient and thus allow the propellant to be ignited at a power of approximately 100 W. In the present reduced test rig, the maximum fuel flow rate corresponds to 0.1 N chemical thrusters, and the plasma-assisted ignition is mainly attributed to thermal and kinetic effects. The temperature of the actuator and the plasma torch is investigated by infrared thermometry and spectral fitting of excited molecule nitrogen, respectively. First, the hot electrode tube helps evaporate water molecules and accelerate the liquid jet through rapid gas expansion. Then, the ionic liquid quickly decomposes to small species when the flow reaches the torch with a nitrogen vibrational temperature above 4000 K and rotational temperature above 2000 K. Meanwhile, the nonequilibrium plasma-excited species enhance the combustion of gaseous intermediates by direct impact dissociation, where the OH radical profile is visualized using the planar laser-induced fluorescence technique. In addition, the copper atoms released by plasma erosion are expected to exhibit a significant catalytic effect on ionic liquid decomposition, which is a critical step in controlling the overall reaction rate. It is also noted that such mild erosion does not affect the multi-start operations during the firing test that lasts for at least 30 min.

Influence of Simarouba Glauca (Laxmi taru) biodiesel on engine performance and emissions of conventional compression ignition engine

The present paper reports the performance and emission studies for a four stroke single cylinder CI-DI unmodified engine using laxmi taru biodiesel as fuel. Laxmi taru biodiesel has 80% potential of extracting oil from the seeds as compared to other biofuels. The properties of laxmi taru biodiesel fuel nearly match the properties of diesel fuel. In this paper performance and emission tests are conducted for different blends such as S0 (0% laxmi taru + 100% diesel), S5, S10, S20, S40 by volume. At full load conditions (4.9 kW) brake thermal efficiency (BTE) decreased for S5, S10, S20 and S40 blends by 3.26%, 4.53%, 3.16% and 5.54% respectively as compared to diesel fuel operation because of poor heating value of laxmi taru biodiesel. Presence of oxygen content in the fuel and better combustion leads to decreased carbon monoxide (CO) emission for S5, S10, S20 and S40 blends by 4%, 8%, 12% and 28% as that of diesel. Similarly hydrocarbon (HC) emission reduced by 16.21%, 24.32% and 29.7% in S10, S20 and S40 blends respectively. Oxides of Nitrogen (NOx) emission increased by 27.19%, 30.57%, 15.2% and 19.3% for S5, S10, S20 and S40 blends respectively in comparison with diesel fuel, under full load conditions due to high incylinder temperature. Usage of laxmi taru biodiesel in CI engines resulting in drastic reduction in carbon based (CO, HC) emissions without altering the performance of the engine. Therefore laxmi taru biodiesel is better alternate fuel for CI engines.

Effect of shock wave formation on propellant ignition in capillary discharge

In order to study the effect of shock wave formation on propellant ignition in capillary discharge, the shock wave formation process was analyzed using experimental and theoretical methods; the plasma jet temperature was measured, and closed bomb and 30 mm gun experiments were carried out. The results show that the first shock wave has a smaller value and larger range of influence, while the second shock wave has a larger value and smaller range of influence. A plasma jet can generate a shock wave at the nozzle according to the calculated plasma pressure and velocity, which is well confirmed by experiments and calculations. The plasma jet temperature is high during the formation of a shock wave and then decreases sharply. Plasma ignition can increase the burning rate of a propellant by about 30% by increasing the burning surface area of the propellant. Compared to conventional ignition, the average maximum chamber pressure and average muzzle velocity of plasma ignition are increased by 9.1 MPa and 29.3 m·s−1 (∼3%), respectively, in a 30 mm gun. Plasma ignition has strong ignition ability and short ignition delay time due to the generation of a shock wave. By increasing the burning rate of the propellant, the muzzle velocity can be greatly improved when the maximum chamber pressure increases a little. The characteristics of the shock wave can be applied in the application of the capillary discharge plasma. For example, it can be applied in fusion, launching and combustion.

Assessment of CI Engine Performance and Exhaust Air Quality Outfitted with Real-Time Emulsion Fuel Injection System

The main target of the current research work is effectively eliminating fossil fuel dependency and improving the exhaust air quality of conventional Compression Ignition (CI) engines. This research paper demonstrates for the first time that a nanofluid (water without surfactant) stored in separate tanks can be quantified, collected, and immediately emulsified by a high shear mixer before transfer into the combustion chamber of a diesel engine. The experiment was carried out under different load states (25%, 50%, 75% and 100%) with a constant speed of 1500 rpm. Biofuel was extracted from citronella leaves using an energy-intensive process. The 5% water share was used for preparing the biofuel emulsion and nano-biofuel emulsion. A cobalt chromate nanoadditive was used to make the nanofluid. An experimental investigation was performed with prepared test fuels, namely, ultra-low sulphur diesel (ULSD), 100% Citronella (B100), surfactant-free Diesel emulsion (SDE), surfactant-free bioemulsion (SBE), and Surfactant free nano-bioemulsion (SNBE), in a test engine. The properties of the sample test fuels was ensured according to EN and ASTM standards. The observation performance results show that the SNBE blend exhibited lower BTE (by 0.5%) and higher SFC (by 3.4%) than ULSD at peak load. The emission results show that the SNBE blend exhibited lower HC, CO, NOx, and smoke emissions by 23.86%, 31.81%, 2.94%, and 24.63%, respectively, compared to USD at peak load. The CP and HRR results for SNBE were closer to ULSD fuel. Overall, the novel concept of an RTEFI (Real-time emulsion fuel injection) system was proved to be workable and to maintain its benefits of better fuel economy and greener emissions.

Influence of 1-pentanol as the renewable fuel blended with jatropha oil on the reactivity controlled compression ignition engine characteristics and trade-off study with variable fuel injection pressure

Compared to conventional compression ignition (CI) engines, the analysis on the advanced low-temperature combustion technologies like reactivity-controlled compression ignition (RCCI) engines produces better thermal efficiency with a simultaneous reduction in smoke and oxides of nitrogen (NOx) emissions. Instead of petroleum-based fuels, biofuels obtained from jatropha oil are anticipated to be employed in the current research. The purpose of this study is to examine the RCCI engine characteristics using Jatropha oil as the high reactivity and 1-pentanol as low reactivity fuel. To analyze the influence of operating parameters (i.e., fuel injection pressure (FIP) (400, 500, and 600 bar), an experiment was performed on a water-cooled single-cylinder engine (modified) for medium load and full load operations at a constant speed of 2000 rpm. The biodiesel (B20) obtained from jatropha oil is inducted into the chamber directly which is produced by transesterification. During the initial suction stroke, 1-pentanol (10%, 20%, and 30% energy share) is injected into the port. Tests were conducted at varying proportions to calculate the optimum proportion of biodiesel and 1-pentanol. The findings were analyzed and mapped under the same working conditions as diesel fuel, and a 2.5% gain (maximum) in thermal efficiency is observed while utilizing a 1-pentanol-biodiesel blend in contrast to diesel. Smoke opacity (7.82%) and NOx (3.42%) emissions were also lowered while employing the 1-pentanol-biodiesel blend. The ideal combination for minimizing emissions is the BD70P30 (70% biodiesel + 30% 1-pentanol) blend at maximum load with a FIP of 600 bar. According to this study, standard fossil fuel can be efficiently substituted with a 1-pentanol-biodiesel fuel combination in an RCCI engine.

Investigations into EGR dilution tolerance in a pre-chamber ignited GDI engine

EGR is a useful means to improve fuel economy in spark-ignited gasoline engines, especially under part-load conditions by means of reducing throttling losses. There is also a significant reduction in NOx emissions due to the reduced peak cylinder temperatures. However, the ability of conventional spark ignition systems to reliably ignite dilute mixtures limits the dilution tolerance due to the onset of combustion instability. In this study, an active pre-chamber system was evaluated at part load condition with various EGR rates using a regular grade full boiling range gasoline. A premixed air-fuel mixture was supplied to the pre-chamber, which assists in scavenging the residual mass fractions to enable reliable ignition of EGR dilute mixtures in the main combustion chamber. A range of pre-chamber injection, air-fuel mixture formulation, and ignition timing strategies were evaluated during the EGR sweeps. In addition, 0-D and 1-D simulations were conducted in GT-Power to assess the thermodynamic state and composition in the pre-chamber, as well as estimate the jet momentum at the various dilution rates. The active pre-chamber extended the EGR dilution limit from 20% for conventional SI to above 30%, with a higher pre-chamber flow rate (more scavenging) resulting in increased combustion stability. A tradeoff between the jet momentum and spark timing was observed when analyzing the GT-Power simulations and the pre-chamber jet momentum was found to decrease with increasing EGR rate. At unstable high EGR operation, no relation could be found between the pre-chamber indicated data and main chamber combustion stability.

A critical review: Application of methanol as a fuel for internal combustion engines and effects of blending methanol with diesel/biodiesel/ethanol on performance, emission, and combustion characteristics of engines

AbstractThis article presents a comprehensive overview of methanol as a potential oxygenated fuel for internal combustion engines. Here two approaches have been examined to evaluate the utilization of methanol, namely blending with diesel/biodiesel/methanol and premixing with intake air or fumigation. In conventional compression ignition engines, up to 95% and 25% diesel can be replaced by methanol through fumigation and blending, respectively. Higher latent heat of vaporization of alcohol led to lower peak in‐cylinder pressure and NOx; however, it negatively affects thermal efficiency and hydrocarbon and carbon monoxide emissions. Fumigation of alcohol requires modifications in the existing engine, whereas blending needed surfactants or additives to produce stable alcohol–diesel blends. High injection pressure and late direct injection, methanol–diesel blends have shown lower emissions and proved their potential as a suitable replacement for ethanol–diesel blends from the components durability perspective.

Effects of pilot injection strategy on in-cylinder combustion and emission characteristics of PODE/methanol blends

Polyoxymethylene dimethyl ethers (PODE) and methanol are both promising alternative fuels with high oxygen content, and the combustion and emission characteristics of PODE/methanol blends were investigated in a common-rail engine. The premixed charge compression ignition (PCCI) combustion was realized by appropriate match of main injection and pilot injection strategies. The effects of methanol ratio (0– 20%) on fuel economy and emissions formation were studied in conventional compression ignition (CI) and PCCI modes. The combustion and emission characteristics were improved by adjusting the pilot injection timing (−40 ~ −24 °CA ATDC) and pilot injection ratio (0– 20%). The results show that the increase of methanol ratio prolongs the ignition duration, increases the premixed combustion ratio and reduces NOx emissions. PCCI combustion increases the brake thermal efficiency (BTE) and improves the trade-off relationship between NOx and soot. The delay of pilot injection timing increases the BTE, decreases HC, CO and HCHO emissions, but increases NOx and soot emissions. The appropriate pilot injection ratio can significantly increase the BTE, and has little effect on the emission characteristics. Under the optimized pilot injection strategy and appropriate methanol ratio conditions, the maximum BTE of the blends can reach 46.58% and maintain low emission level.

Elastic breakdown via multi-core high frequency discharge for lean-burn ignition

An advanced ignition technique is developed to achieve multi-event breakdown and multi-site ignition using a single coil for ignition quality improvements. The igniter enables a unique elastic breakdown process embracing a series of high-frequency discharge events at the spark gap. The equivalent electric circuits and current/voltage equations are identified and verified for the first time to explain the working principle that governs such an elastic breakdown process. Benchmarking tests are first performed to compare the elastic breakdown ignition with the conventional and advanced multi-electrode ignition systems. The elastic breakdown and spark events are thereafter analyzed through current and voltage measurements and high-speed imaging techniques. Finally, ignition tests in combustion chambers are performed to examine the effects on the ignition process in comparison with conventional coil-based ignition systems. The experiments show that, the elastic breakdown ignition can distribute multiple high-frequency breakdown events at all electrode pairs of a multi-electrode sparkplug while using only one ignition coil, thereby offering significant cost saving advantage and packaging practicability.

Experimental study of the ignition of lean methane/air mixtures using inductive and NRPD ignition systems in the pre-chamber and turbulent jet ignition in the main chamber

The optimization of the combustion process in spark ignition engines has led to novel strategies to ignite lean and low reactivity mixtures, such as the application of turbulent jet ignition and Nanosecond Repetitively Pulsed Discharge (NRPD) ignition systems and Turbulent Jet Ignition (TJI). In the present experimental work, an optically accessible setup was used to investigate the ignition occurrence and early flame development in the pre-chamber and subsequent main chamber ignition of methane/air mixtures at density conditions relevant to engine application. Two schlieren setups coupled with fast recording cameras allow the visualization of both the pre-chamber and main chamber.NRPD ignition with different pulse patterns in terms of pulse number and repetition frequency is applied in the pre-chamber. Conventional inductive ignition and NRPD-assisted ignition are compared for the first time in terms of flame development in the pre-chamber and hot jet ignition in main chamber. The effect of different air to fuel ratios is assessed in both laminar and turbulent pre-chamber conditions.Results show that while NRPD is always advantageous when compared to standard inductive ignition, the higher amount of energy added by increasing the number of pulses only affects the ignition success in very lean conditions, thus showing that increased energy is not the main governing mechanism for successful ignition. Irrespectively of the initial conditions (laminar or turbulent) in the pre-chamber, it is shown that an optimum jet velocity exists that ensures increased ignition probability in the main chamber, thus suggesting that mixing plays a major role in main chamber ignition. The combination of both techniques, NRPD and TJI, allowed assessing the optimum conditions in terms of number and frequency of NRPD pulses for a reliable ignition in lean conditions.