Engine Speed Conditions Research Articles

Development of a reverse-loop scavenged poppet-valve 2-stroke diesel engine for down speed and performance comparisons with its 4-stroke baseline

In the present study, a reverse-loop scavenged poppet-valve 2-stroke (PV2S) diesel engine was developed and compared with its 4-stroke baseline experimentally. Firstly, the valve cam profiles and the valve timings for the PV2S engine was optimized using 1D simulations. Results show that, the present intake and exhaust cam profiles meet the design requirements under a series of designing allowances. The nonlinear relationship between the gas exchange performance and the power output for the PV2S engine is due to the fact that the expansion work loss increases more than the volume efficiency improvement with the exhaust valve closure timing changes from 95 °CA to 85 °CA. Then, the in-cylinder flow of the new designed upright-strait ports and masked head was simulated using 3D simulations in comparison with the original horizontal head. It is found that the upright-strait intake port can induce intense reverse tumble in-cylinder flow to make an effective gas exchange than the under 2-stroke mode. Finally, the performances of the new developed PV2S engine and the its 4-stroke baseline are compared on the single-cylinder engine test bench. Experimental results show that the brake specific fuel consumption of the PV2S engine is higher than that of the 4-stroke engine under same engine speed and same power output conditions because of the decreased thermal efficiency and the increased friction loss proportions. However, the PV2S engine shows a better economic performance than the 4-stroke engine at rated conditions due to the reduced friction losses from down-speeding.

Chemical kinetic investigation on NOx emission of SI engine fueled with gasoline-ethanol fuel blends

Understanding the nitrogen oxide (NOx) formation chemical kinetic mechanism and analyzing the effect of relevant influence parameters are the effective strategy for NOx emission control. Based on the essential role of ethanol-gasoline blends among oxygenate alternative fuel, the experiments in a GDI (gasoline direct injection) SI (spark ignition) engine and the chemical kinetic simulation were carried out. According to the validated model, seven NO contributing reactions and three reaction pathways were observed. Besides the thermal NO formation pathway, two other pathways with N2O and NNH through NH-HNO-NO have nonnegligible places in the high engine speed condition. As for the parameters, initial temperature aggravates NO emission, initial pressure and ethanol fraction inhibit NO, which influence it through thermal NO pathway and have slight impact on the other two pathways. While with the increase of equivalence ratio (ER) from 0.5 to 1.0, ER promotes first and then resists NO formation, getting highest emission when ER equals to 0.85. In a lean burn condition, the thermal pathway is highly inhibited and the N2O pathway is sharply accelerated. Through current work, NOx producing mechanism under high-speed condition is investigated comprehensively, which not only completes the total NO formation pathways from atmospheric N2 but also provides reference for the designing and modification of low harmful NOx emitting gasoline-ethanol engines.

Exhaust emissions from a prototype non-road natural gas engine

Since gas engines are considered a future solution to improve air quality and to mitigate climate impacts, there is an urgent need to understand their emissions. The aim for this study was to understand the phenomena affecting the formation of particulate emissions of a non-road natural gas engine. To achieve this, the engine’s exhaust emissions were characterized under different operating conditions. The regulated pollutants (gaseous CO, HC, and NOx; particulate matter (PM) and particle number (PN)) were determined experimentally and a detailed characterization of particulate pollutants over a wide particle size range (particles down to 1.2 nm) was conducted with state-of-the-art instrumentation considering both physical and chemical properties of the exhaust aerosol. The test engine was a prototype non-road spark-ignited natural gas engine, which was studied over the non-road steady test cycle (NRSC). The role of the three-way catalyst (TWC) was studied by sampling and characterizing the exhaust aerosol both with and without the TWC. The TWC was observed to efficiently remove the vast majority of the regulated gaseous (96% CO, 98% HC, 98% NOx) and particulate mass emissions (98%). In general, the measured particle number emission factors were highly dependent on the cut-off sizes of the condensation particle counters. Using CPCs with smaller cut-off sizes resulted in higher particle number emission factors. For black carbon (BC), the intermediate engine speed conditions (modes 5–7) led to lower BC emissions than the high speed conditions (modes 1–3). In contrast, highest BC emissions on a work basis were observed during idling. TWC did not influence BC levels. Without the TWC, PM was comprised mostly of organic compounds (70–100%). Downstream of the TWC, the majority of PM was, depending on the load, composed of organic compounds, sulfate, or black carbon. A statistical source apportionment based on mass spectra revealed that the PM1 was mostly related to unburned and burned lubricating oil, indicating a minor role of fuel in PM formation.

Analysis of ignition temperature range and surrogate fuel requirements for GCI engine

Gasoline compression ignition (GCI) technology aims to improve internal combustion engine (ICE) efficiency. However, much is still unknown about the detailed combustion behavior of fuels under this novel ICE technology, such as relevant ignition temperature regimes and surrogate requirements under various engine load and speed conditions as well as for different fuels. Engine and spray simulations require the use of carefully designed surrogate fuels that mimic the properties of real fuels. Generally, these surrogates range from simple primary reference fuels (PRFs) to complex multi-component mixtures. This study aims to identify the relevant temperature conditions and the surrogate requirements for GCI engines covering the entire engine speed-load map; engine loads between 1 and 22 bar indicated mean effective pressure (IMEP) and engine speeds between 800 and 2500 revolutions per minute (RPM). Simulations were performed using the constant volume zero-dimensional (0-D) and homogeneous charge compression ignition (HCCI) modules in Chemkin-Pro for two gasoline fuels with widely different sensitivities (11 and 0). Furthermore, homogeneous ignition delay times and Livengood-Wu integrals were used to analyze the fundamental characteristics of GCI combustion. It was found that, except at excessively high-load, the relevant ignition temperature in a GCI engine is in the 750–1000 K range. The low-temperature (less than700 K) reactivity exhibited negligible contribution to the ignition of the high-sensitivity fuel. Two stage ignition and cool flame formation were found to dominate mid-load kinetics of the low-sensitivity fuel. Simple PRF surrogate was found to be sufficient to mimic the ignition requirement of the low-sensitivity gasoline fuel at almost the entire GCI engine speed-load map. However, for the high-sensitivity gasoline fuel, TPRF and TPRFE surrogates were needed for a better representation of the auto-ignition behavior. The obtained knowledge of the surrogate requirement and the ignition temperature regimes inside GCI engine will aid in guiding GCI engine optimization and fuel design.

Investigation of Performance and Exhaust Emissions of Compressed Natural Gas-Diesel Dual-Fuel Engine under Different Engine Speed and Load Conditions

Investigation of Performance and Exhaust Emissions of Compressed Natural Gas-Diesel Dual-Fuel Engine under Different Engine Speed and Load Conditions

Impacts of gasoline fuel components on GDI engine performances: Part 1, influence on gaseous toxic pollutants

In this paper, effects of different components in gasoline fuel on GDI engine emission characteristics were investigated. To simplify this investigation, model fuel CDTRF (composed of n-heptane, iso-pentane, diisobutylene, cyclohexane and toluene) instead of real gasoline fuel were used. To see how components of gasoline fuel affect engine performances, iso-pentane, diisobutylene, cyclohexane or toluene in CDTRF was substituted by other iso-alkanes, olefins, naphthenes and aromatics for comparative researches. N-heptane fraction is varied to balance fuel octane number. It is found that variation of fuel components obviously affect engine regulated and unregulated emissions. While, such effects vary when engine operation condition varies and are more distinct under lower engine speed or load conditions. Fuel components affect engine emission not just simply via chemical manner, but also through accompanying thermal-power process (cylinder pressure and temperature history). Thus variation of fuel components remarkably affects engine NOx emission. Alkanes, olefins and alkynes, aromatics contribute most to VOC emission followed by aldehydes. While, proportion of alcohols in VOC is negligible. However, variation of fuel components does not remarkably affect the proportion of alkanes, olefins and alkynes, aromatics as well as aldehydes in VOC although it affects total VOC emission obviously. Olefins and alkynes contribute most to OFP followed by aromatics and aldehydes. The contribution of alkanes is relatively low although it takes significant proportion in VOC. While, variation of fuel components remarkably affects total OFP of VOC though it does not obviously affect OFP composition. According to the results, it is hinted that more short chain i-paraffins and less branch chained cyclohexane in gasoline fuel would potentially help to reduce OFP of VOC.

An assessment of soot chemical property from a modern diesel engine fueled with dimethyl carbonate-diesel blends

Dimethyl carbonate (DMC) is a promising alternative fuel for diesel engines. Comparing with the traditional diesel fuel, the DMC application can lead to a different combustion process where the soot is synthesized, yielding variation in chemistry of engine-out soot particles. Soot chemistry is highly related to the concentration and accessibility of radical sites for the reactions regarding to soot oxidation on the exhaust systems or during DPF regeneration. Therefore, the study on the chemical feature of soot emissions is of great necessity. Nevertheless, comprehensive determination on the soot chemical property for DMC-contained fuel and its instinctive explanation is not well understood in the previous studies. In this study, to reveal the effect of DMC addition on the chemical feature of soot emissions, the surface functional groups and their bonding states of soot particles from various DMC-diesel blends were characterized using FT-IR and XPS technologies. Results showed that the DMC addition exerts different influences on the surface oxygen content, oxygenated groups and their bonding states with various DMC content. Therein, DMC addition in large amount can significantly increase the C sp3/sp2 ratio and the concentration of C-O epoxies on soot surfaces. At relatively low engine speed and load conditions, the low-content addition of DMC leads to slight increase in the aromatic C–H/aromatic CC ratio in soot bulk structure. However, the large-content DMC addition distinctly reduces the aromatic C–H/aromatic CC and aliphatic C–H/aromatic CC ratios. The results are useful for the prediction of the subsequent soot oxidation behavior during DPF regeneration on diesel engines.

Model Predictive Control of Internal Combustion Engines: A Review and Future Directions

An internal combustion engine (ICE) is a highly nonlinear dynamic and complex engineering system whose operation is constrained by operational limits, including emissions, noise, peak in-cylinder pressure, combustion stability, and actuator constraints. To optimize today’s ICEs, seven to ten control actuators and 10–20 feedback sensors are often used, depending on the engine applications and target emission regulations. This requires extensive engine experimentation to calibrate the engine control module (ECM), which is both cumbersome and costly. Despite these efforts, optimal operation, particularly during engine transients and to meet real driving emission (RDE) targets for broad engine speed and load conditions, has still not been obtained. Methods of model predictive control (MPC) have shown promising results for real-time multi-objective optimal control of constrained multi-variable nonlinear systems, including ICEs. This paper reviews the application of MPC for ICEs and analyzes the recent developments in MPC that can be utilized in ECMs. ICE control and calibration can be enhanced by taking advantage of the recent developments in the field of Artificial Intelligence (AI) in applying Machine Learning (ML) to large-scale engine data. Recent developments in the field of ML-MPC are investigated, and promising methods for ICE control applications are identified in this paper.

Research on in-cylinder steam injection in a turbocompound diesel engine for fuel savings

Turbocompounding and in-cylinder steam injection (ICSI) are both effective methods for engine waste heat utilization. The fuel savings potential obtained by the combination of the two methods is not clear. In the paper, the effects of ICSI on the performance of a turbocompound engine are investigated. Firstly, the layout of the turbocompound engine with ICSI is described. Then, the simulation model of a turbocompound diesel engine is developed and calibrated. Finally, the influences of different ICSI parameters on the performance of the turbocompound engine are studied. The results show that the gross power and fuel economy of the turbocompound engine are remarkably improved by ICSI. With optimal steam injection mass, the brake specific fuel consumption of the turbocompound engine is reduced by 3.0%–5.4% under different engine speed conditions. The performances of turbocharged turbine and power turbine are both improved. In-cylinder combustion process is improved and overall in-cylinder pressure profile is enhanced. Steam injection mass and timing have great impacts on the performance of the turbocompound engine. As steam injection mass increases, the engine fuel economy is further improved. The earlier the steam is injected, the better the engine performance will be obtained.

Effects of short chain aromatics in gasoline on GDI engine combustion and emissions

Aromatics are parts of the main components in gasoline which play important roles in affecting engine performances. Short carbon chain aromatics (C8/C8-) takes more part of aromatics in gasoline. In this paper, the effects of toluene, ortho-xylene and ethylbenzene on engine combustion, emission and thermal efficiency are experimentally investigated. Gasoline and three quinary gasoline model fuels containing each of these three aromatics, with diisobutylene, cyclohexane, isooctane, n-heptane being the other four components, are used to support this research. Results show that all the aromatics favor engine combustion and particulate emission while aggravate THC and CO emissions. Toluene, ethylbenzene and ortho-xylene do not obviously affect NOx emission under lower engine speed. However, ethylbenzene and ortho-xylene elevate engine NOx emission much more than toluene does under higher engine speed conditions. Alkenes and alkanes take the vast majority of VOC emission, followed by aromatics and aldehydes. Yet, alkenes take the most responsibility on OFP followed by aldehyde, and then aromatics, alkanes. Ethylene is the major composition of alkenes while formaldehyde contributes the most to aldehydes emission. In compare, toluene would propel alkenes and aldehydes in VOC emissions more than ethylbenzene and ortho-xylene do, however, it greatly alleviates particulate emission. Toluene tends to improve thermal efficiency under low engine speed conditions while ortho-xylene and ethylbenzene improve it under higher engine speed conditions. Results from this paper indicates that short chain aromatics affect engine combustion and emission a lot. So, varying short chain aromatics in gasoline fuel is of great importance in adjusting fuel properties.

Modeling of post-injection strategies of ethanol and experimental analysis of the use of ethanol in the form of dual fuel and emulsion in diesel engine

In this research, as the first stage, the effects of the ethanol on engine performance and emissions under the fumigation and emulsion method were experimentally investigated under part load and various engine speed conditions. Diesel-ethanol blend containing 5% ethanol by volume was used as the mixture fuel. In the fumigation method, ethanol was used at the same rate and 99.9% purity as the emulsion method. As the second stage, the effects of ethanol post injection on engine performance and pollutant emissions were investigated in the experimental engine modeled in AVL Boost simulation program and compared with the experimental results. Simulation post injection tests were performed separately after the main injection at 3? CA (P1) and 7? CA (P2). In the experimental studies, NOx emission decreased with the emulsion method (E5) at low and high engine speeds. In post injection strategies, NOx emission in general increased due to improved combustion and increased in-cylinder temperature with P1 (first post injection) and P2 (second post injection) strategies. Soot emission decreased significantly with E5. This improvement in soot emissions was approximately 87% in post injection strategies.

Experimental investigation on four-stroke catalytic coated spark ignition engine to promote cleaner environment

In the present scenario, automobile manufacturing industries face challenges in marketing vehicles with internal combustion (IC) engine to customers due to strict government regulation on emission norms and customers expectation on better engine performance. Hence, it is very important to identify some technique to reduce the emission level and also to improve the engine performance. The catalytic coating is one of the most suitable techniques for reduction of pollution level and increasing the engine performance. In this paper, the outcomes of investigations carried out on the emission control and engine performance of catalytic coated single cylinder four-stroke spark ignition (SI) engine is discussed in detail. The engine combustion chamber and piston crown were coated with copper (catalyst). The performance parameters of catalytic coated engine such as torque, brake power at different engine speed and load conditions were measured using two-wheeler chassis dynamometer. In this investigation, a comparative study was also done in parallel with conventional (un-coated) SI engine. The results showed that copper coated engine has significantly reduced levels of carbon monoxide (CO), hydrocarbon (HC) and carbon dioxide (CO2) emission compared to conventional engine (un-coated).

Análisis de las prestaciones de un motor de combustión interna alternativo usando biocombustibles: (i) aceite de soya; (ii) aceite de canola

In the present study, two biofuels derived from cooking oil are evaluated. To carry out this work, an reciprocating internal combustion engine will be used, which is ready on a fully instrumented engine test bench. Firstly, the biodiesel production process is described, where soybean oil and canola oil have been used. Subsequently, the experimental section that has been used for the present investigation is described. The experimental tests are carried out: (i) modifying the degree of opening of the accelerator and (ii) using a constant load of the dynamometer. On the other hand, in the results section shows the performance of the two biofuels generated against diesel commercial. Also, in this section shows the percentage differences of: (i) engine power; (ii) mass fuel, (iii) thermal efficiency engine and, (iv) exhaust temperaturas. The tests have been carried out under different engine speed conditions of the reciprocating internal combustion engine. Where, the main average differences that have been registered in the engine test bench were: for engine power, 32 and 33%; for the mass fuel consumption of -4.5 and 5%, when using soybean biodiesel and canola biodiesel, respectively. These differences are due to the energy capacity of each biofuel and, the instantaneous evolution of combustion process inside the reciprocating internal combustion engine.

Experimental Investigation of the Effect of Fuel Injection Timing and Injector Opening Pressure on Performance and Emissions Characteristics of a Turbo-Charged Diesel Engine Under 8-mode Testing Cycle

For compression ignition (CI) engines, two of the fuel injection parameters affecting the engine’s performance and emissions formation, are fuel injection timing (FIT) and injector opening pressure (IOP). Other such parameters include the number of injections, rate of injection and injection pattern, etc. In the present study, a multi-cylinder, turbocharged, four-stroke, direct injection (DI) diesel engine was used to investigate the combined influence of FIT and IOP on performance and emissions characteristics. The experimentation was conducted for two IOPs (250 and 300 bar) with four FITs such as 20°, 23°, 26°, and 29° before top dead center (BTDC) at different engine speed and load conditions. To obtain the emissions characteristics, the engine was tested in accordance with the 8-mode steady-state cycle. Moreover, 250 bar and 23° BTDC were the original IOP and FIT, respectively. For all IOP conditions, in comparison to the results with the original FIT, the advancement or retardation in FIT provided the negative results in terms of brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC). Increasing the IOP from 250 to 300 bar, improved the performance parameters for retarded and original FITs (20° and 23° BTDC) and caused the deterioration in performance for advanced FITs. In terms of emissions characteristics, filter smoke number (FSN) and emissions of carbon monoxide (CO) and unburned hydrocarbon (UHC) decreased on advancing the FIT and increasing the IOP. On the other hand, oxides of nitrogen (NOx) and carbon dioxide (CO2) increased on advancing the FIT and increasing the IOP for all experimental conditions. The maximum improvement in the performance of the engine was observed at increased IOP with the original FIT. The original IOP with retarded FIT resulted in the minimum NOx and CO2 with a significant reduction in performance. Furthermore, improvement in performance and reduction in emissions were observed when the engine was operated at higher IOP and retarded FIT.

Lean-burn characteristics of a turbocharged opposed rotary piston engine fuelled with hydrogen at low engine speed conditions

Opposed rotary piston (ORP) engines have high power density and compact designs which meet the requirements of power sources of hybrid vehicles. Hydrogen applications to ORP engines can effectively decrease greenhouse gas emissions; however, hydrogen combustion in ORP engines around stoichiometric ratio generated large quantities of nitrogen oxides (NOx), especially for low engine speed conditions. Lean-burn as an effective method to decrease NOx emissions was adopted in this research. A 3D numerical simulation method was used to explore the effect of equivalence ratio (≤1) on combustion and NOx emission characteristics of this ORP engine fuelled with hydrogen. The results indicated that peak in-cylinder pressure increased with equivalence ratio for 1000 revolutions per minute (RPM); however, the value over the equivalence ratio of 0.9 was the maximum among 2000 RPM scenarios. The effect of equivalence ratio on heat release rates was greatly dependent on the engine speeds. Start of combustion over 1000 RPM engine speed was advanced with the increase of equivalence ratio; and it was the earliest over the equivalence ratio of 0.9 at 2000 RPM conditions. During the exhaust stroke, in-cylinder pressure of free discharge was much higher than atmosphere pressure, which significantly increased the pumping losses of exhaust stroke. Accumulated NOx emissions over the equivalence ratio of 0.9 reached the maximum value for given engine speeds; and the NOx emissions were almost zero for severe lean-burn (<0.7) conditions. Engine power output decreased with the drop of equivalence ratio for 1000 and 2000 RPM engine speeds; indicated thermal efficiency over the equivalence ratio of 0.9 was the maximum at 2000 RPM engine speed.

Comparative experimental investigation on the effects of heavy alcohols- safflower biodiesel blends on combustion, performance and emissions in a power generator diesel engine

The experimental works carried out in this article evaluates the potential of using heavy alcohol and safflower biodiesel as the blended fuel mixtures without making any modifications in the tests diesel engine. For this purpose, volumetrically 20% of Propanol, Pentanol, Butanol, and Octanol were blended with safflower biodiesel fuel and they were named as PR20, PE20, BU20, and OC20, respectively. The performance, combustion, and emission data were found out at the same conditions of constant engine speed and various loads and compared with pure biodiesel (B100) and diesel fuel(ULSD). In the experiments, a four-cylinder, water-cooled diesel engine that was loaded by an electrical power generator was used for the tests. The addition of alcohol causes an increase in fuel consumption due to a decrease in lower thermal performance. The use of heavy alcohols in diesel engine in specific quantities by mixing with biodiesel significantly increases engine brake thermal efficiency. Negative effects of low cetane number and high latent heat of vaporization that may decrease ignition delay and decrease cylinder pressure while increase peak heat release was considered to be compensated by the better mixing properties and atomization of alcohol blended biodiesel thus eventually improve the combustion. Alcohol addition to biodiesel fuel can be accepted as a useful application to increase brake thermal efficiency and reduce nitrogen oxide (NOx), carbon monoxide (CO), and hydrocarbon (HC) emissions by reducing the density and viscosity.

Numerical simulation on the combustion and NOx emission characteristics of a turbocharged opposed rotary piston engine fuelled with hydrogen under wide open throttle conditions

Under the stress of environmental pollutions and fossil fuel consumption caused by on-road transport, hybrid vehicles are attracting much attention. Opposed rotary piston (ORP) engines are a promising power source for hybrid vehicles, due to their compact designs and high power density. In this paper, combustion and emission characteristics of a turbocharged ORP engine fuelled with hydrogen were investigated to evaluate the overall performance of this engine. The results indicated that volumetric efficiency of this ORP engine was higher than 89.0% for all the given cases. Peak in-cylinder pressure was in the range of 51.0 ~ 69.0 bar; and 4000 RPM scenario had the maximum value, being benefitted from high intake temperature and pressure, and high volumetric efficiency. Combustion duration of this engine ranged 27 ~ 43° crank angle (CA), and combustion phase happened at 7.5 ~ 13°CA after top dead centre (TDC). Peak nitrogen monoxide (NO) formation rates were corresponding to 5 ~ 13°CA after TDC; accumulated NO decreased slightly after reaching the peak value for low engine speed conditions. Discharge pressure at the start of the exhaust stroke was higher than 6.0 bar, especially for 5000 RPM case whose value was approximately 11.0 bar. This ORP engine presented excellent torque characteristics, and the maximum indicated power density was approximately 104.0 kW·L−1 which was much higher than turbocharged four-stroke reciprocating engines fuelled with gasoline.

Aluminum Alloy Piston Fabrication Technology by Super Forging-KIRIU

This research aims to produce pistons a lighter and stronger piston, even in high compression and high engine speed conditions. The piston fabrication process is carried out by super forging using Aluminum as a raw material with a compound choice by Silicon or Magnesium. In addition, the outer layer of the piston is covered by molybdenum with the coating process as nanotechnology to prevent corrosion. Furthermore, the finishing is controlled by the programming system machine named CNC (Computerized Numerical Control). In addition to CNC, the automation system is carried out by the KIRIU machine which is also used in this study. The results of this study show that the use of Al-Si alloy base material has better piston quality and able to withstand high compression or high engine speed. Then, the Al-Si superforging piston compared to the two final automation processes of CNC and KIRIU. The evaluation results have proved that the KIRIU machine provides high accuracy and the actual production increases by 20% compared to CNC.

Experimental Study on the Performance of an SI Engine Fueled by Waste Plastic Pyrolysis Oil–Gasoline Blends

Pyrolyzed waste plastic-based green fuel has been reported to be used as an alternate fuel for diesel engines. Some of the main challenges for implementing this in current automotive technology include evaluating engine performance, emission, noise vibration harshness (NVH), and knock characteristics of this fuel. This study focuses on the engine performance of poly-ethylene terephthalate (PET)-based waste plastic oil (WPO) at varying engine speed conditions. The pyrolysis of mixed-waste plastic was carried out at 300 °C in a fixed-bed reactor. Physicochemical properties such as viscosity, density, calorific value, sulfur, and research octane number (RON) of the plastic fuel and its blends with gasoline were analyzed using ASTM standard test methods. The WPO was blended with two different types of gasoline (RON88 and RON90) at 10, 20, and 30%, and was tested in a spark-ignition (SI) engine. The experimental results showed that different WPO–gasoline blends can be used in an SI engine without any engine modifications, and the performance indicators for different blends were found to be close to that of pure gasoline. The brake power and brake specific fuel consumption (BSFC) were found to be 4.1 kW and 0.309 kg/kW h, respectively. The 10% WPO and 90% RON90 blend produced optimal engine performance at 3500 rpm.

Soot particles in piston-top pool fires and exhaust at 5 and 15 MPa injection pressure in a gasoline direct-injection engine

This study shows the structure of soot particles sampled directly from wall wetting-induced pool fires formed on the piston top in a spark-ignition direct-injection (SIDI) engine. Of particular interest is its variation with injection pressure considering the current trend of high-pressure DI system development to reduce engine-out particulate emissions. Thermophoretic particle sampling was performed for transmission electron microscope (TEM) imaging, which was post-processed for statistical analysis of key morphology and internal structure parameters. These include the size distribution of soot aggregates and primary particles as well as carbon-layer fringe-to-fringe gap and concentricity. With the fixed engine speed and load conditions, in-flame soot particles are compared to the exhaust particles sampled simultaneously at selected 5 and 15 MPa injection pressures corresponding to low-speed/low-load and high-speed/high-load in practical engine operation. From the TEM images and statistical analysis, it was found that more concentrated and taller pool fire developed for 5-MPa injection leads to smaller soot aggregates composed of smaller soot primary particles due to suppressed soot growth in fuel-rich flames. However, the soot particles formed in 15-MPa injection-induced pool fires are at a more reactive status evidenced by less defined core-shell boundaries and higher fringe separation. The higher soot reactivity results in enhanced soot oxidation, which explains smaller soot aggregates and primary particles found for the 15-MPa injection in the exhaust sample.