Start Of Injection Research Articles

Study on effects of molecule structure on exhaust emissions from RCCI engine fueled with low alcohol isomers

Due to the existence of reactivity stratification in mixture of Reactivity Controlled Compression Ignition (RCCI) engine, effects of molecule structure of low alcohols on exhaust emissions may be different. Three kinds of molecule structure, hydroxyl group position (OHP), methyl branches (MB) and straight carbon chain (SCC) are constructed through propanol and butanol isomers, and experimental data of exhaust emissions were drawn from RCCI engine under different oxygen mass contents (RO) and start of injections (SOI). Then, changes of exhaust emissions with OHP, MB, SCC, RO and SOI, and real influence factors and influence sequence of them on emissions are analyzed. The results show that: Although a certain emission changes with a certain impact factor, they may not be correlated with each other, which means the determination of real influencing factors and influence sequence is necessary. This determination is helpful to find out the strongest correlation influencing factors to optimize exhaust emissions. It is worth noting that, different emissions have different real influencing factors. NOX emission and particle mass concentration (PMC) are unrelated to molecule structure. On the contrary, they are only correlated to SOI. Moreover, all emissions are unrelated to OHP, and only HC emission is correlated to MB, while SCC is correlated to multiple emissions, and emission types correlated to Ro and SOI are the most.

Modeling of the entire processes of diesel spray tip penetration including the start- and end-of-injection transients

The start-of-injection (SOI) and end-of-injection (EOI) transients are important for sprays with multiple-injection strategy. Owing to the change of needle position and sac pressure, the spray behaviors in the transient processes are significantly different from those in the quasi-steady stage. In this study, considering the sac pressurization processes during the SOI transients and effects of ''entrainment wave'' after the EOI, a theoretical zero-dimensional model for the entire development processes of the spray tip penetration (Stip) is summarized. Then, a high-speed CMOS camera and constant-volume chamber are employed to study the spray characteristics and verify the model. The model and experimental results clarify four key time points in the entire development processes of Stip: the sac pressurization time (tp), breakup time (tb), injection duration (ti) and two injection durations (2ti). Five stages can be divided according to these four time points: the acceleration stage (Stip proportion to t1.5), transition stage 1 (t1 or t0.75), quasi-steady stage (t0.5), transition stage 2 (t0.5) and decelerating stage ((t-ti) 0.25). Moreover, the newly developed model is compared with the Wakuri model, the Hiroyasu & Arai model, and the Naber & Siebers model. The results show that all the models can well predict Stip during the quasi-steady stage and transition stage 2 with the optimized model constants. While the other models overpredict Stip in the acceleration and decelerating stages, the newly developed model still works very well.

Comparative assessment of n-butanol addition in CTL on performance and exhaust emissions of a CI engine

Coal to liquid (CTL) is a diesel alternative fuel based on Fischer-Tropsch (FT) process, which has shown promising application value. Besides, as an oxygenated biofuel with high oxygen content and volatility, n-butanol can be blended with hydrocarbon fuels to improve engine performance. This study aims to investigate the effects of CTL/n-butanol blends on the performance of the compression-ignition (CI) engine, and to reveal the influence of combustion boundary conditions such as n-butanol blending ratio, the start of injection (SOI), and exhaust gas recirculation (EGR) on the combustion and emissions characteristics. The results show that blending n-butanol with CTL is beneficial to improve the fuel-gas mixture distribution in the cylinder, and the premixed combustion ratio (PCR) increases by 13.66% as the energy ratio of n-butanol increases to 30% (B30) compared with the pure CTL. CTL/n-butanol blends make particulate emission tend to be shifted towards nucleation mode and the particulate mass emission significantly reduced, especially the particulate mass of B30 reduce by 68.6%; meanwhile, the NOx emission shows an upward trend. Compared with n-butanol blended, adjusting the SOI impacts NOx emissions significantly, while its influence on the indicated thermal efficiency (ITE) and particulate emissions is relatively slight. Moreover, through the synergistic control of n-butanol addition and EGR, the trade-off relationship between NOx and particles is mitigated.

Effect of injection timing on combustion and IMEP variation of a bi‐fuel compressed natural gas SI engine

AbstractCompressed natural gas (CNG) is a gaseous fuel stored under high pressure in a cylindrical tank. When the CNG is injected into the intake manifold, it expands in the manifold and displaces the air which reduces the volumetric efficiency of the engine. Thus, the corresponding overall energy inside the combustion chamber is also reduced, resulting in reduced power output. CNG injection timing with respect to intake valve opening and closing can be optimized to minimize the losses in volumetric efficiency loss and hence, the power output of the engine. In this study, the combustion instability of the CNG fueled engine has been studied under low throttle condition and compared with gasoline. A comparative investigation of the effects of the start of injection (SOI) timing on combustion stability was conducted on a single‐cylinder spark‐ignition (SI) engine fuelled with gasoline and CNG at 25% throttle opening condition. The ignition timing was kept fixed at 35°, and 40° CA bTDC for gasoline and CNG, respectively, and the SOI timing was varied from 240° CA bTDC to 100° CA aTDC of the intake stroke. The results indicated that SOI timing significantly affects in‐cylinder air‐fuel mixture formation and combustion stability for gasoline and CNG engine. SOI timing corresponds to the closed valve period, shows the higher fluctuation in combustion for gasoline compared to CNG. CNG shows lower fluctuation throughout SOI timing due to homogeneous air‐fuel mixture formation. Early SOI timing forms fuel stratification in the intake port and forms a rich air‐fuel mixture, which reduces the net power output of the CNG engine. CNG requires optimum SOI timing for improved combustion compared to gasoline. It reduced the combustion instability and fluctuation in indicated mean effective pressure. The results will benefit the development of a closed‐loop engine control system for a CNG system.

Optimization of Fuel Injection Parameters of Moringa oleifera Biodiesel-Diesel Blend for Engine-Out-Responses Improvements

Biodiesel has gained popularity in diesel engines as a result of the rapid decline of fossil fuels and population growth. The processing of biodiesel from non-edible Moringa Oleifera was investigated using a single-step transesterification technique. Both fuels had their key physicochemical properties measured and investigated. In a common-rail diesel engine, the effects of MB50 fuel blend on the symmetric characteristics of engine-out responses were evaluated under five load settings and at 1000 rpm. As compared to standard diesel, MB50 increased brake thermal efficiency (BTE), and nitrogen oxides (NOx) emissions while lowering brake specific fuel consumption (BSFC), and smoke emissions for all engine loads. A further study of injection pressure and start of injection (SOI) timing for MB50 fuel was optimized using response surface methodology (RSM). The RSM optimization resulted in improved combustion dynamics due to symmetry operating parameters, resulting in a simultaneous decrease in NOx and smoke emissions without sacrificing BTE. RSM is an efficient optimization method for achieving optimal fuel injection parameter settings, as can be deduced. As a result, a clearer understanding of the use of MB50 fuel in diesel engines can be given, allowing for the best possible engine efficiency.

Particulate characteristics of low-temperature combustion (PCCI and RCCI) strategies in single cylinder research engine for developing sustainable and cleaner transportation solution

In this experimental study, particulate matter (PM) characterizations of different low-temperature combustion (LTC) strategies have been compared with conventional compression ignition (CI) combustion for finding out a sustainable and cleaner transport solution. LTC strategies included premixed charge compression ignition (PCCI) and reactivity-controlled compression ignition (RCCI) combustion. Particulate sampling and characterization were carried out in a single-cylinder diesel engine. All engine tests were performed at 1, 2, 3, 4 bar brake mean effective pressure (BMEP) at 1500 rpm. CI and PCCI combustion experiments were performed using mineral diesel as the test fuel. However, mineral diesel and methanol were used as high reactivity fuel (HRF) and low reactivity fuel (LRF), respectively in the RCCI combustion strategy. For all combustion strategies, fuel injection pressure (FIP) was kept constant at 500 bar. However, the number of injections and start of injection (SoI) timings were varied to optimize the engine performance. Results showed that the RCCI combustion strategy emitted a relatively lower concentration of particles than the other two strategies (PCCI and CI). A relatively higher number concentration of accumulation mode particles (AMP) compared to nucleation mode particles (NMP) in the exhaust of the RCCI combustion strategy was an important finding of this study. Number-size and mass-size distributions of particles emitted from different strategies also exhibited the dominant concentration of particles in the CI combustion strategy. PM bound trace metal analysis was yet another critical aspect of this study, which showed that both RCCI and PCCI strategies emitted a relatively lower concentration of trace metals than the conventional CI combustion strategy. Parametric analysis of different PM characteristics and NOx-PM trade-off analysis also demonstrated the importance of LTC strategies over the conventional CI combustion strategy. Overall, this study demonstrated that all LTC strategies could be used for PM and NOx reduction; however, the RCCI combustion strategy was more dominant in NOx and PM reduction, in addition to having an excellent capability of using alternative fuel in the quest for developing sustainable transport solution.

Research of Parameters of a Compression Ignition Engine Using Various Fuel Mixtures of Hydrotreated Vegetable Oil (HVO) and Fatty Acid Esters (FAE)

The present study is aimed at studying the energy and environmental performance at various engine loads (BMEP) with identical start of injection (SOI) for all fuel types. The combustion parameters for the fuel mixtures were analyzed using the AVL BOOST software (BURN subroutine). Five different blends were tested, consisting completely of renewable raw materials based on hydrotreated vegetable oil (HVO) and fatty acid methyl ester (FE100), and the properties of diesel fuel (D) were compared with respect to these blends. The mixtures were mixed in the following proportions: FE25 (FE25HVO75), FE50 (FE50HVO50), FE75 (FE75HVO25). In this study, diesel exhaust was found to produce higher NOx values compared to FE blends, with HVO being the lowest. Hydrocarbon and smoke emissions were also significantly lower for blends than for diesel. Possible explanations are the physical properties and fatty acid composition of fuel mixtures, affecting injection and further combustion. The results showed that blends containing more unsaturated fatty acids release more nitrogen oxides, thus having a lower thermal efficiency compared to HVO. No essential differences in CO emissions between D and HVO were observed. An increase in this indicator was observed at low loads for mixtures with ester. CO2 was reduced in emissions for HVO compared to the aforementioned blends and diesel. The results of the combustion analysis show that with a high content of unsaturated fatty acids, mixtures have a longer combustion time than diesel fuel.

Numerical investigation on the combustion and emission characteristics of a heavy-duty natural gas-diesel dual-fuel engine

Natural gas (NG)-diesel dual-fuel combustion is an effective approach to reduce soot and greenhouse gas emissions and mitigate the liquid fossil fuel crisis. In this work, a comprehensive numerical study on the combustion and emission characteristics of a NG-diesel dual-fuel engine operating at the high load condition was performed. Six significant parameters such as the start of injection (SOI) timing, exhaust gas recirculation (EGR), injection and intake pressures, nozzle number, and NG substitution ratio were investigated. A pathway to achieve highly efficient and clean combustion was proposed. It was demonstrated that at least an EGR rate of 40% should be employed to meet the NOx Euro VI regulation limit. Although a higher injection pressure enhanced the diesel-air mixing process and promoted engine efficiency, the highest achievable engine efficiencies were similar using different injection pressures. An elevated intake pressure with an earlier SOI timing promoted the oxidation process. Therefore, it resulted in a lower combustion loss and thus higher engine efficiency. Furthermore, the increase of nozzle number effectively promoted the air utilization rate and expedited the combustion heat release, which resulted in a higher engine efficiency but lower soot emission. But the growing trend of engine efficiency was limited and a nozzle number of 11 was found to be the optimal option. Finally, a peak engine efficiency of about 47.6% was achieved with a NG substitution ratio of 95% and an optimized SOI timing, and meanwhile, both the NOx and soot emissions were below the Euro VI emission regulation limits.

Potential of reactivity-controlled compression ignition with reverse reactivity stratification (R-RCCI) fueled with gasoline and polyoxymethylene dimethyl ethers (PODEn)

To improve the trade-off between thermal efficiency and peak heat release rate (HRR) of partially premixed combustion (PPC) and the combustion efficiency of reactivity-controlled compression ignition (RCCI), the combustion mode with premixed high-reactivity fuel and direct-injection (DI) low-reactivity fuel, called RCCI with reverse reactivity stratification (R-RCCI), was explored at low loads in a light-duty diesel engine in this study. Compared with diesel, polyoxymethylene dimethyl ethers (PODEn) has better volatility, which is beneficial for the formation of premixed charge, so it was used as the premixed high-reactivity fuel for R-RCCI in this work. The gasoline and P20G80 (PODEn/gasoline blends with the volume fraction of 20%/80%) were respectively applied as the DI low-reactivity fuel. By investigating the combustion characteristics of R-RCCI, it is found that R-RCCI can break the trade-off between combustion efficiency and nitrogen oxides (NOx) emissions. This is because the combustion efficiency of R-RCCI is dominated by the spray location of the DI fuel rather than the 50% burn point (CA50). As the start of injection (SOI) timing is retarded, the fuel injected within the piston bowl increases, and combustion efficiency, as well as indicated thermal efficiency (ITE), is considerably promoted. Meanwhile, CA50 progressively retards with delayed SOI timing, which effectively reduces NOx emissions. The soot emissions of R-RCCI are also extremely low. The maximum ITE of PODEn/P20G80 R-RCCI is significantly higher than that of PODEn/gasoline R-RCCI. This occurs because the higher reactivity of P20G80 can reduce the sensitivity of CA50 to SOI timing and improve combustion stability, so a more delayed SOI timing is allowed to improve ITE. With the same engine configurations, R-RCCI can reduce peak pressure rise rate and improve combustion stability, while enhancing combustion efficiency and ITE compared with RCCI at the low-load conditions tested in this study.

Engine Malfunctioning Conditions Identification through Instantaneous Crankshaft Torque Measurement Analysis

In this study a coupled thermodynamics and crankshaft dynamics model of a large two-stroke diesel engine was utilised, to map the relationship of the engine Instantaneous Crankshaft Torque (ICT) with the following frequently occurring malfunctioning conditions: (a) change in Start of Injection (SOI), (b) change in Rate of Heat Release (RHR), (c) change in scavenge air pressure, and (d) blowby. This was performed using frequency analysis on the engine ICT, which was obtained through a series of parametric runs of the coupled engine model, under the various malfunctioning and healthy operating conditions. This process demonstrated that engine ICT can be successfully utilised to identify the distinct effects of malfunctions (c) or (d), as they occur individually in any cylinder. Furthermore by using the same process, malfunctions (a) and (b) can be identified as they occur individually for any cylinder, however there is no distinct effect on the engine ICT among these malfunctions, since their effect on the in-cylinder pressure is similar. As a result, this study demonstrates the usefulness of the engine ICT as a non-intrusive diagnostic measurement, as well as the benefits of malfunctioning conditions mapping, which allows for quick and less resource intensive identification of engine malfunctions.

Potential Analysis of a DMC/MeFo Mixture in a DISI Single and Multi-Cylinder Light Vehicle Gasoline Engine

<div class="section abstract"><div class="htmlview paragraph">In this study a mixture of dimethyl carbonate (DMC) and methyl formate (MeFo) was used as a synthetic gasoline replacement. These synthetic fuels offer CO<sub>2</sub>-neutral mobility if the fuels are produced in a closed CO<sub>2</sub>-cycle and they reduce harmful emissions like particulates and NO<sub>X</sub>. For base potential investigations, a single-cylinder research engine (SCE) was used. An in-depth analysis of real driving cycles in a series 4-cylinder engine (4CE) confirmed the high potential for emission reduction as well as efficiency benefits.</div><div class="htmlview paragraph">Beside the benefit of lower exhaust emissions, especially NO<sub>X</sub> and particle number (PN) emissions, some additional potential was observed in the SCE. During a start of injection (SOI) variation it could be detected that a late SOI of DMC/MeFo has less influence on combustion stability and ignitability. With this widened range for the SOI the engine application can be improved for example by catalyst heating or stratified mode. Furthermore, until λ = 0.8 no significant PN increase was noted in contrast to gasoline. This is also a positive capability for combustion modes with local rich areas in the mixture. From the experience of previous investigations, the synthetic fuels’ high knock-resistance potential enabled an increase in the compression ratio (CR) from epsilon ~ 11 to ~ 15 to enhance the indicated efficiency.</div><div class="htmlview paragraph">In general, in the 4CE the positive effects of DMC/MeFo on harmful emissions were confirmed. Even in the series configuration, the brake efficiency increased by 16 % at maximum low-end torque compared to gasoline. The increased in-cylinder cooling and the lower laminar flame temperature by the DMC/MeFo implies lower maximum exhaust temperatures. Therefore, a stoichiometric mixture could be used over the whole engine map. During the legislative driving cycles, for example WLTC, the PN, NO<sub>X</sub>, CO and CH<sub>4</sub> emissions decreased by 50 % or more.</div><div class="htmlview paragraph">In summary, oxygenated fuel opens great opportunities for replacing fossil fuel in gasoline engine applications.</div></div>

Numerical Investigation of an RCCI Engine Fueled with Natural Gas/Dimethyl-Ether in Various Injection Strategies

Reactivity control compression ignition engines illustrated suitable abilities in emission reduction beside high thermal efficiency. In this research, nine various direct fuel injection strategies were studied numerically: three cases with single injection strategy and six cases with split injection and different start of injection (SOI). In all simulated cases, equivalence ratio kept constant (i.e., 0.3). Among various strategies, single injection showed higher IMEP as a factor of efficiency with about 5.39 bar that occurred at SOI = 60 before top dead center (bTDC), while lower efficiency was observed for split injection case with 50%-50% injections of fuel in each injection stage. Start of combustion (SOC), burn duration and CA50 as factors for combustion characteristics were affected with SOI changes. In single SOI strategies, more advanced injection caused more advanced SOC where there was about 1.3 CAD advancing from 40 to 80 bTDC injection. Spilt SOI showed more advanced SOC, which, also more advanced, was allocated to 50%-50% split injection strategy. There was also the same trend in CA50 changes during change in SOI. Burn duration variations were insignificant and all of them approximately close to 4.5 CAD. According to the emissions researched in this study (Nitrogen Oxides (NOx), monoxide carbon (CO) and unburned hydro carbons (UHC)), all of these pollutants are below euro six diesel standards. Contours of emissions show that there were appropriate SOI for each case study, which were 45 degree bTDC for single strategy, 48 degree bTDC for 80%-20% mass injection and 70 degree bTDC for 50%-50% cases.

Effect of engine compression ratio, injection timing, and exhaust gas recirculation on gaseous and particle number emissions in a light-duty diesel engine

Along with other particulate and gaseous emissions, particle number (PN) from diesel engines has also been stringently regulated in the latest emission regulations. The present study focuses on combined effects of various parameters such as engine compression ratio (CR), start of injection (SOI) timing, and exhaust gas recirculation (EGR) rate on performance and emissions from a single-cylinder diesel engine with a special focus on PN. Three test cases with varying engine load were selected for this study. The engine was tested for these loading conditions with various compression ratios varying from 13.3 to 17. SOI sweep was carried out from −16 deg aTDC deg to −4 deg aTDC deg to identify the optimum injection timing with the best compression ratio. EGR sweep was also carried out with increasing EGR from 0% to 30% to see the effect of changing the EGR rate with increasing compression ratio on various emissions.For all the loading cases tested in this study, an increase in the compression ratio resulted in higher in-cylinder pressure, reduced ignition delay along with a slight improvement in fuel consumption. Higher NOx production with increasing compression ratio was observed because of higher combustion temperatures. Interesting trends were observed for PN and soot emissions during this study. Soot emissions and PN reduced with increasing compression ratio till CR16. A further increase in the compression ratio resulted in a further increase in PN and soot emissions.

Large-eddy simulation of spray assisted dual-fuel ignition under reactivity-controlled dynamic conditions

Here, a large-eddy simulation and a finite-rate chemistry solver (see Kahila et al. Combustion and Flame, 2019) is utilized to investigate diesel spray assisted ignition of a lean methane-air mixture. A compression heating model is utilized to emulate the ambient temperature and pressure increase in a compression ignition (CI) system. The key parameter is the start of injection (SOI) relative to a virtual top dead center (TDC), where the peak adiabatic compression pressure/temperature would be achieved. Altogether, five different cases are investigated by advancing the SOI further away from the TDC with constant injection duration. The main findings of the paper are as follows: 1) Advancing the SOI advances the ignition timing of the spray with respect to the TDC from 0.91 to 7.08 CAD. However, beyond a critical point, the ignition time starts retarding towards the TDC to 4.46 CAD due to the excessively diluted diesel spray. 2) Advancing the SOI increases the contribution of leaner mixtures to the heat release rate (HRR). Consequently, the low-temperature combustion HRR mode becomes more pronounced (from 33.9% to 76.7%) while the total HRR is reduced by a factor of 4. 3) Ignition is observed for all investigated SOI’s. However, the numerical findings indicate that advancing the SOI decreases the ignition kernel size, resulting in weaker ignition. 4) An ignition index analysis with frozen flow assumption indicates that for the SOI’s close to the TDC the HRR mode appears as spray mixing controlled, while for advanced SOI it becomes reactivity controlled, dominated by fuel stratification.

Creating a Virtual Test Bed Using a Dynamic Engine Model with Integrated Controls to Support in-the-Loop Hardware and Software Optimization and Calibration

In the current study, a 0D/1D engine model built in the commercial code GT-Suite was coupled with the Electronic Control Unit (ECU) model created in the Simulink environment, aiming to more accurately predict the interaction of the engine and aftertreatment system (ATS) operating parameters, both during steady-state and transient maneuvers. After a detailed validation based on extensive experimental data from a heavy-duty commercial diesel Internal Combustion Engine (ICE), the engine model was fine-tuned and the 0D predictive diesel combustion model, DIPulse, was calibrated to best predict the combustion process, including engine-out NOx emissions. For correct prediction of the engine’s behavior in transient operations, the complete control strategy of the air path, including boost, exhaust gas recirculation (EGR), main and pilot Start of Injection (SOI), injection pressure, and exhaust flap, was implemented in the Simulink environment. To demonstrate the predictive capability of the model, a hot World Harmonized Transient Cycle (WHTC) was simulated, obtaining good agreement with the experimental data both in terms of emissions and performance parameters, confirming the reliability of the proposed approach. Finally, a case study on possible fuel consumption improvement through thermal insulation of the exhaust manifold, exhaust ports, and turbocharger was carried out.

Performance analysis of a dual-loop bottoming organic Rankine cycle (ORC) for waste heat recovery of a heavy-duty diesel engine, Part I: Thermodynamic analysis

In this paper, which is the part 1 of this study, the energy and exergy characteristics of a dual-loop organic Rankine cycle (ORC) combining with a heavy-duty diesel engine were investigated. The proposed cycle is driven by the waste heat of the exhaust gases, intake air, and the coolant. Central composite design (CCD), which is a standard response surface methodology (RSM) technique, was applied to design of experiments (DoE) and to investigate the influence of both the engine and cyclic parameters such as the engine speed, the start of injection (SOI), the higher pressure of the high-temperature loop, and the higher pressure of the low-temperature loop. Adequacy of the developed RSM models has been evaluated by the ANOVA tables. The results revealed an increase in whether the engine or cycle parameters led to an enhance in the produced power of the system. As a comparison, the variation in engine variables has more impact on the produced power. On the opposite side, a change in the engine speed and SOI have a minor effect on the thermal efficiency of the system. The maximum produced power of the dual-loop ORC system was identified as 310 kW, which was resulted at the engine speed of 1800 RPM, and 0.0 degrees of CA bTDC for SOI; while the higher pressures of the HT and LT loops were in 2400 and 2100 kPa, respectively. This obtained power is 31% of the engine brake power. The maximum values for the thermal and exergy efficiencies were observed as 9.5% and 43%, respectively. Also, the exergy analysis demonstrated that the highest exergy destruction rate of the system is determined to be 500 kW.

Numerical Simulation of Marine Diesel Engine Combustion and Emissions Using Intake Air Humidification at the Different Injection Timing

ABSTRACT The computational fluid dynamics (CFD) model was established for the marine diesel engine. The effects of intake air humidification (IAH) and the start of injection (SOI) timing on cylinder pressure and temperature were studied; the influence rules and mechanisms of NOx and soot formation were analyzed. The results show that under the water-fuel mass ratio of 0.2 (WR0.2), the IAH contributed to the combustion reaction process, and the peak cylinder pressure increase slightly. As the IAH rate increases, the combustion reaction process was suppressed, and the cylinder pressure and temperature were both decreased. When the IAH rate was at WR2.0, the peak pressure dropped by 3.4% compared with it at the non-humidification (WR0). The concentration of OH groups, O, H and N radicals decreased with the IAH rate increase, especially that the concentration of N radical decline was most apparent. The NOx emissions decreased by 78% at WR2.0, but the soot emissions increased by the decrease of the oxygen concentration in the high-temperature zone. It was found that the cylinder pressure and average temperature increased with the increasing of the SOI, but the rising range of peak average temperature decreased. When the SOI was at 12°CA BTDC, the indicated mean effective pressure is the same as with the WR0. Affected by the cylinder temperature and oxygen concentration, both the rising range of NOx and the descent range of soot decreased. Due to the IAH, the oxygen concentration and temperature limited the rate of rapid oxidation of soot.

Numerical Investigation of Reactivity Controlled Compression Ignition Engine Performance under Fuel Aggregation Collision to Piston Bowl Rim Edge Situation

To better homogenize the mixture of fuel and air in the combustion chamber and to enhance the controllability of ignition timing in Reactivity Controlled Compression Ignition (RCCI) engines, controlling the start of injection (SOI) timing can be essential. By changing the SOI timing, at some specific crank angles (CAs), the fuel can impact the edge of the piston bowl and create some difficulties. In this research, initially, efforts are made to recognize the range of SOI timing in which this collision process takes place (in the range of 44-54° bTDC), then, performance and the emission levels of the engine were evaluated in the beginning and end of this interval. The findings suggest that the nitrogen oxides emissions and the maximum in-cylinder mean pressure are higher in SOI of 44° bTDC, as compared to those in the SOI timing of 54°bTDC, although the latter has higher ignition delay and unburnt hydrocarbon (UHC) emission. Moreover, some evaluations were carried out to examine how the temperature of the fuel-air mixture can affect the performance of the engine in this specific range. It was found that as the IVC temperature increases, it rises the indicated mean effective pressure (IMEP), in-cylinder pressure, and NOx emission.

Effect of initial turbulence on combustion with ECFM-3Z model in a CI engine

The effect of initial turbulence specifications at intake valve closure (IVC) on combustion in a compression ignition engine is studied through CFD simulations. The objective of this study is to understand the importance of the turbulence specifications for closed cycle simulations. Simulations are conducted using AVL – FIRE engine simulation program with DME as the fuel and ECFM-3Z as the combustion model. Results from simulations indicate that, for the conditions tested, the initial turbulence does not have any significant influence on the pressure trace. A higher initial turbulent kinetic energy and larger turbulent length scale leads to a higher temperature at the start of injection (SOI) and, consequently faster ignition and higher NO emissions. In contrast, the effect on turbulent time scales after injection is negligible.

The effect of low reactivity fuels on the dual fuel mode compression ignition engine with exergy and soot analyses

In this study, the effect of fuel injection timing of diesel on the dual fuelled compression ignition engine with gasoline, methanol and toluene has been investigated. Closed cycle combustion simulations have been conducted to complement the experiment results and for a better understanding of the in-cylinder dynamics. Second law of thermodynamics analysis has been done for the designing of energy recovery devices. Exhaust soot particles has been analysed by scanning electron microscopy to get soot particle structure. Distributions of soot particle number by size and particle mass by size have been investigated. Experiments have been conducted for respective premixed ratios of gasoline/methanol/toluene at different start of injection (SOI) timing of diesel. Outcomes revealed that the maximum gross indicated thermal efficiency (GITE) of 39% is obtained for gasoline/diesel mode. This mode shows 86% more oxides of nitrogen (NOx) in comparison with methanol/diesel mode at −25 crank angle degree (CAD) SOI case. About 54% more soot has been observed at −25 CAD SOI in toluene/diesel compared to that of gasoline/diesel mode. Maximum of 38.7% and minimum of 27.8% work exergies have been observed in gasoline/ and methanol/diesel modes respectively. Toluene/diesel mode shows the largest average primary particle diameter (Dp; 44 nm) among the dual fuel modes.