Engine Load Conditions Research Articles

Applicability of high-pressure direct-injected methane jet for a pure compression-ignition engine operation

Natural gas has been suggested as an alternative fuel for compression ignition (CI) engines because it generates significantly less pollutants and has a smaller carbon footprint, while maintaining the cycle efficiency. However, the high auto-ignition temperature of natural gas typically requires the use of a quasi-compression ignition method such as homogenous charge compression ignition (HCCI) or a dual-fuel mode. Yet, methods such as these are unable to realize the full potential of high efficiency and low emissions. This motivated us to evaluate the applicability of a high-pressure direct-injected natural gas jet for a pure CI engine under various engine load, injection timing, and injection pressure conditions using a single cylinder CI engine with a compression ratio of 15.5. The intake temperature was raised to 400 °C to achieve the auto-ignition temperature of methane after compression and a multi-hole GDI injector capable of operating at a pressure of 400 bar was used for fuel injection.As a result, CI operation was possible, but ignition occurred after the end of the injection in the form of a partially premixed flame rather than a diffusion flame for all conditions under which the engine was operated. A sufficient equivalence ratio of 0.8 was achieved at an injection pressure of 300 bar and injection duration of 1.6 ms with the multi-hole GDI injector, and the GMEP value varied from 2 bar to 5.5 bar according to the equivalence ratio. However, at an equivalence ratio of 0.7 or higher, the combustion efficiency decreased drastically because of the limit of the volume fraction of the piston bowl at TDC and the narrow nozzle distribution of the GDI injector. Measurement of the pollutants indicated that the total number of particles from methane CI operation exceeded that of diesel at an equivalence ratio of 0.74 in the same engine setup because of incomplete combustion; however, the total mass of the particulate matter (PM) was approximately 15% of the diesel because the average particle size from methane CI was approximately one third smaller than that of diesel. However, the high post-compression temperature for the auto-ignition of methane gas resulted in a high peak temperature, which resulted in the production of approximately 2000 ppm NOx under all test conditions. The results of the parametric study showed that, as the injection timing retarded, the ignition timing was almost equally retarded, thus the combustion was still observed in the form of a diffusion flame. As the injection pressure increased, the ignition delay became shorter and the emission of PM could be further reduced, but the NOx emission increased.

Numerical study on combustion characteristics of six-stroke-cycle gasoline compression ignition engine with continuously variable valve duration valve technology

Engine performance and emissions of a six-stroke gasoline compression ignition engine with a wide range of continuously variable valve duration control were numerically investigated at low engine load conditions. For the simulations, an in-house three-dimensional computational fluid dynamics code with high-fidelity physical sub-models was used, and the combustion and emission kinetics were computed using a reduced kinetics mechanism for a 14-component gasoline surrogate fuel. Variation of valve timing and duration was considered under both positive valve overlap and negative valve overlap including the rebreathing of intake valves via continuously variable valve duration control. Close attention was paid to understand the effects of two additional strokes of the engine cycle on the thermal and chemical conditions of charge mixtures that alter ignition, combustion and energy recovery processes. Double injections were found to be necessary to effectively utilize the additional two strokes for the combustion of overly mixed lean charge mixtures during the second power stroke. It was found that combustion phasing in both power strokes is effectively controlled by the intake valve closure timing. Engine operation under negative valve overlap condition tends to advance the ignition timing of the first power stroke but has minimal effect on the ignition timing of second power stroke. Re-breathing was found to be an effective way to control the ignition timing in second power stroke at a slight expense of the combustion efficiency. The operation of a six-stroke gasoline compression ignition engine could be successfully simulated. In addition, the operability range of the six-stroke gasoline compression ignition engine could be substantially extended by employing the continuously variable valve duration technique.

On greenhouse gas emissions and thermal efficiency of natural gas/diesel dual-fuel engine at low load conditions: Coupled effect of injector rail pressure and split injection

Replacing diesel by natural gas in diesel engine is of great interest for transportation and power station industry due to larger availability and lower environmental impact of natural gas compared to diesel fuel. However, natural gas/diesel dual-fuel (NDDF) engine has lower thermal efficiency and produces higher greenhouse gas (GHG) emissions than its counterpart diesel engine at low load conditions when conventional diesel combustion strategy is used. In order to overcome this drawback, the present paper experimentally and numerically investigates the coupling of two strategies; namely increasing diesel injection rail pressure and splitting diesel injection of a heavy-duty NDDF engine at low engine load conditions. The results revealed that increasing the injection rail pressure decreases thermal efficiency of the NDDF engine with split injection as a result of overly advanced combustion phasing. However, a higher thermal efficiency (37.2%), than that of the diesel-only and the NDDF engine with a single injection, can be achieved under optimized combustion phasing. Increasing the injection rail pressure significantly reduces the unburned methane emissions of the NDDF engine with split injection, especially at lower split ratios (mass of the injected diesel in the first pulse divided by that of the total injected diesel). However, increasing the injection rail pressure does not affect the unburned methane emissions under a split ratio of 65%. This is due to the fact that a larger portion of diesel fuel impinges onto the cylinder wall surface as revealed by the simulation results. The optimum methane emissions of the NDDF engine with split injection is reduced by 50% compared to the best condition of the NDDF engine with a single injection. Moreover, the indicated specific carbon dioxide equivalent (ISCO2-equivalent) emissions of the NDDF engine with split injection are reduced by 11% compared to those of the NDDF engine with a single injection and diesel-only engine. All in all, the present study demonstrated that thermal efficiency and GHG emissions of the NDDF engine can be further improved when simultaneously varying diesel fuel injection split ratio and rail pressure increase. This strategy is also found to help reducing pressure rise rate (PRR) and NOx and soot emissions.

Experimental investigation of doped mwcnts on biodiesel for enhancement of the performance and exhaust emissions in a diesel engine

This article deals with an experimental work that aims to examine the effects of MWCNTs dispersed into diesel fuels. Nano diesel fuels were prepared by dispersing multi-walled carbon nanotubes into base liquid. The MWCNT nanomaterial was mixed in the fuel blend along with a surfactant by means of an ultrasonicator, to attain stable dispersion. Physicochemical properties of nano-additive based diesel were measured and compared with pure diesel fuel. Physicochemical properties of nano-additive based diesel were measured and compared with pure diesel fuel. An experimental investigation was performed at a constant speed of 1500 revolution per minutes at different engine load conditions. The engine performance and exhaust emissions of a diesel engine burning MWCNTs were compared with pure diesel fuel. MWCNTs to diesel oil is effectively enhancing the performance and decreasing exhaust emissions in a diesel engine. The properties of N80 + JB20 with MWCNT fuel blend are changed owing to the mixing of biodiesel and the combination of the MWCNT nanomaterials.

Effects of Operating Temperature of SI Engine on Performance and Emissions of SI Engine Using Ethanol Gasoline Blends as Fuel

The main objective of this research is to reveal the operating temperature range of the engine that provides the best emission and performance. In this experimental work, the operational parameters of a four-stroke three-cylinder gasoline engine, such as brake power, and specific fuel consumption, were investigated experimentally with different ethanol gasoline blends. Brake power and specific fuel consumption are measured at various engine speeds, loads and operating temperature, i.e. coolant temperature. Ethanol mixtures with gasoline in varying proportions (E5, E10 and E15) are prepared and studied in three cylinders, four-stroke SI computer test-rig. The experiments were carried out at 2000 rpm with 3 kg load and 40, 50, 60, 70, 80℃ coolant temperature. The research has focused on determining the best operational conditioning by using different mixtures of ethanol gasoline instead of pure gasoline. The results obtained on performance and emissions of engine parameters at 2000 rpm with constant engine loading conditions, i.e., brake power (bp), brake specific fuel consumption (bsfc) and NOx, HC have presented graphically with respect to the coolant temperature of the engine. The present study showed that it is suitable to operate the engine at temperature 65˚C-75˚C for obtaining better performance indications for gasoline and ethanol gasoline blends.

Enhancement in combustion, performance, and emission characteristics of a diesel engine fueled with diesel, biodiesel, and its blends by using nanoadditive.

This article presents the results of investigations carried out to evaluate the improvement in combustion, performance, and emission characteristics of a diesel engine fueled with neat petro-diesel (PD), soybean biodiesel (SB), and 50% SB blended PD (PD50SB) by using carbon nanotube (CNT) as an additive. The acid-alkaline-based transesterification process with sodium hydroxide (NaOH) as a catalyst was applied to derive the methyl ester of SB. A mass fraction of 100ppm CNT nanoparticle was blended with base fuels by using an ultrasonicator and the physiochemical properties were measured based on EN standards. The measured physiochemical properties are in good agreement with standard limits. The experimental evaluations were carried out under varying brake mean effective pressure (BMEP) conditions in a single-cylinder, four-stroke, and natural aspirated research diesel engine at a constant speed of 1500rpm. The results reveal that the SB and its blend promote shorter ignition delay period (IDP) that is resulting in lower in-cylinder pressure (ICP) and net heat release rate (NHR) compared to PD. The SB and its blend increase the brake specific fuel consumption (BSFC), and reduce the brake specific energy consumption (BSEC) and exhaust gas temperature (EGT), due to lower heating value, and efficient combustion, respectively. As far as the emission characteristics are concerned, the SB and its blend promote lower magnitude of hydrocarbon (HC), carbon monoxide (CO), carbon dioxide (CO2), and smoke emissions compared to PD except for oxides of nitrogen (NOx) emission. The CNT nanoparticle inclusion with base fuels significantly improves the combustion, performance, and emissions level irrespective of engine load conditions.

Combustion and emissions behaviour assessment of a partially premixed charge compression ignition (PCCI) engine with diesel and fumigated ethanol

The study is aimed to evaluate the combustion and emission characteristics of a partially premixed charge compression ignition (PCCI) engine with diesel and ethanol fuels. Ethanol was fumigated with preheated intake air at 40°C and inducted into the intake manifold of the test engine. Experimental tests were carried out with varying proportions of premixed ethanol at different engine loading conditions of 1, 2, 3, and 4 bar brake mean effective pressures (BMEP). It was explored that at lower BMEP, oxides of nitrogen (NOx) were decreased with an increment of premixed ethanol, however, at higher BMEP, the emissions increased. At all loads, smoke opacity decreased exceedingly with increasing premixed ethanol share. At part loads, hydrocarbon (HC) and carbon monoxide (CO) emissions were increased because of the high latent heat of vaporization of ethanol. Net heat release rate and in-cylinder pressure rise were found to be increased with an increasing engine load. Overall, it could be determined that the performance of the PCCI engine with ethanol fumigation is comparable with the conventional diesel fuel operation.

Effects of EGR and combustion phasing on the combustion and emission characteristic of direct-injection CI engine fueled with n-butanol/diesel blends

Shortage of fossil fuel and stringent emission regulations require less pollutant emissions and better fuel conversion efficiency from modern internal combustion (IC) engines. Butanol is of particular interest as a renewable biofuel for advanced compression ignition (CI) engines, which has been receiving widely researches consequently. In order to more comprehensively evaluate the application of butanol on modern CI engine, exploration strategy was focused on the combining of EGR and combustion phasing control to achieve ultra-low NOx and smoke emission without penalty on fuel economy. Experiment was conducted under constant engine speed and both the high and low engine load conditions with three volume fractions of butanol up to 30%. Results indicate that butanol blending causes extended ignition delay, increased premixed combustion ratio (PCR) and retarded combustion phasing, which is more significant at low load condition. Butanol/diesel blends can dramatically reduce exhaust smoke and particle emissions without increasing NOx emissions at, however, the expense of lower thermal efficiency than that of pure diesel. Reduced thermal efficiency can be recovered by properly matching EGR and combustion phasing under a low level of overall emission.

Experimental assessment and multi-response optimization of diesel engine performance and emission characteristics fuelled with Aegle marmelos seed cake pyrolysis oil-diesel blends using Grey relational analysis coupled principal component analysis.

This research focuses on the detailed experimental assessment of compression ignition (CI) engine behavior fuelled with Aegle marmelos (AM) seed cake pyrolysis oil blends. The study on effects of engine performance and emission a characteristic was designed using L25 orthogonal array (OA). These multi-objectives were normalized through gray relational analysis (GRA). Likewise, the principal component analysis (PCA) was performed to assess the weighting values respective to every performance and emission characteristics. The variability induced by using the input process parameters was allocated using analysis of variance (ANOVA). Hence, GRA-coupled PCA were employed to determine the optimal combination of CI engine control factors. The greater combination of engine characteristics levels were selected with F5 and W5. The higher brake thermal efficiency (BTE) have been obtained for F20 fuel as 22.01% at peak engine load, which is 11.43% for diesel. At peak load condition, F20 fuel emits 14.99% lower HC and 18.52% lower CO as compared to diesel fuel. The improved engine performance and emission characters can be attained by setting the optimal engine parameter combination as F20 blend at full engine load condition. The validation experiments show an improved average engine performance of 67.36% and average lower emission of 64.99% with the composite desirability of 0.8458.

Determination of a Spark Ignition Engine’s Performance Parameters Using Response Surface Methodology

The combustion process in engines is highly influenced by the combined effect of various parameters. As far as the internal combustion engines are concerned, emission is the important parameters for which the other design and operating parameters have to be optimized. This paper studies the use of RSM (Response Surface Methodology) to optimize the performance parameters of a 4-stroke spark ignition engine. In this work, a description of the facilities developed for conducting experimental work on the test engine experiment was conducted. Theoretical evaluation, experimental evaluation, prediction of performance parameters using RSM and statistical evaluation of SI engine were performed. The study also explained how to build an analytical model for the complicated problem. The development of the incombustible gases concentration (part per million-ppm) as a function of engine speed (rpm), loading condition (%) and operating time (seconds) was done via 23 factorial designs of the experiment (DoE )and RSM. The results obtained from HC, CO and NOx emission models showed that the engine speed, loading condition and time were found to have significant influence on the emission. The HC, CO and NOx emission models have also proved positive response from the regression analysis of actual and predicted responses. In the error estimation with 95% confidence interval the equations are within the ranges. Thus, the response surface methodology provides useful information required for the experiment and also useful in predicting the response of engine parameters to engine emissions.

Simulation of ammonia combustion in dual-fuel compression-ignition engine

Ammonia is regarded as an attractive alternative fuel for combustion engines with a great potential to replace currently used petroleum-based energy carriers. Its direct combustion does not result in emission of carbon dioxide and it can be produced from renewable sources. The energy density of ammonia is reasonable, it is relatively easy to store and has well established infrastructure for production, storage, handling and distribution. However, ammonia is corrosive to some materials, difficult to ignite due to high octane number and high autoignition temperature, and has low heating value. Therefore theoretical and experimental studies are needed to enhance the performance and expand the operating range of ammonia-fuelled engines. This study investigates the feasibility of introducing ammonia to dual-fuel compression-ignition engine, where a pilot dose of diesel oil initiates the ignition of ammonia-air mixture. Numerical simulations of the combustion process were carried out using a one-dimensional model, parametrized according to the specifications of a four-cylinder, turbocharged compression-ignition engine with conventional direct injection supply system, modified slightly for ammonia induction. The model was validated by comparison with empirically determined data. The simulations were performed for different combinations of ammonia-diesel oil ratios at various engine load. Ammonia was treated as an energy replacement for diesel oil. Engine performance and emissions of selected pollutants in dual-fuel operation mode were compared to that with diesel oil only. The results showed that different ammonia–diesel oil ratios can be used to achieve the same engine torque. A higher than rated power, depending on engine load conditions, can be obtained with the addition of an extra dose of ammonia. The influence of ammonia on the emissions of particular pollutants varied and was discussed in detail. Acquired combustion characteristics and engine performance parameters allow for a positive verification of the proposed model. The drawn conclusions may be useful for the development of dual-fuel engine control algorithms.

Adaptation of Air-Gas Regulator for Small Capacity Producer gas Engine

Producer gas (PG) is a biomass derived multi component gaseous fuel, which is popularly used for power generation application via internal combustion (IC) engine. Due to the fluctuating tendency of a PG composition across the upstream end of a down draft gasifier (DDG), the combustion properties of a PG fuel vary. Thus, the variation in PG composition influences the combustion process and eventually the engine performance. This paper reports, an attempt made in adapting an air-gas regulator (AGR) for an effective operation of a small capacity (2.2 kW & 359 cm3) engine close to stoichiometry condition. These regulators are known to support gas engines under variable engine load conditions and fuel composition. The technical challenges faced while adapting the available AGR for the given engine is brought out in detail. Since the existing port diameter of an AGR was not in match for the present engine, an optimization approach was followed to achieve a stable and full load (14 Nm) engine operation. The experimental results were obtained considering a bottled PG under naturally aspirated mode with constant speed (1500 rpm) at compression ratio (CR) of 11:1. The analysis revealed an optimum gas port diameter of 33.3% of 30 mm on an existing commercial AGR model 7218-2. The measured PG engine performance parameters like brake power and work output were in agreement with available literature.

Experimental investigation on performance and combustion characteristics of spark-ignition dual-fuel engine fueled with methanol/natural gas

This study aims to evaluate the performance, emissions, and combustion characteristics of a methanol/natural gas dual-fuel spark-ignition engine by conducting several experiments. A heavy-duty natural gas engine is modified by adding a methanol port-injection system to accelerate the burning rate, increase the thermal efficiency, and reduce the hydrocarbon emission. The effects of the methanol energy substitution ratio (MSR) on the brake thermal efficiency, heat release rate, peak cylinder temperature, flame development period, flame propagation period, and emissions are investigated under light, medium, and heavy loads (brake mean effective pressures of 0.387, 0.775, and 1.163 MPa, respectively) at an engine speed of 1600 rpm and a relative air/fuel ratio of 1.3. The results show that the peak cylinder pressure, peak cylinder temperature, and heat release rate increase with an increase in the MSR. A larger MSR leads to a shorter flame development period and flame propagation period as well as earlier combustion phasing. In addition, the brake thermal efficiency increases and the equivalent brake specific fuel consumption decreases significantly with methanol enrichment under the three engine load conditions. For exhaust emissions, the brake specific total hydrocarbon emission decreases while the brake specific nitrogen oxide emission increases slightly with an increase in the MSR. For cycle-by-cycle variation, the coefficient of variation in the indicated mean effective pressure increases slightly with an increase in the MSR. In addition, the peak ringing/knocking intensity is found to be 2.05 MW/m2 that is much less than the critical knocking point (5 MW/m2). Therefore, there was no knocking throughout the entire experiment.

Combustion stability study of partially premixed combustion with low-octane fuel at low engine load conditions

The study aims to investigate the sensitivity of combustion stability to the intake air temperature for partially premixed combustion (PPC). The experiments were carried out in a full view optical engine at low load condition. The ω shape optical piston crown as same as the actual product piston, rather than the flat crown piston used in the previous study, was employed for the present experimental test. The continuous-fire mode rather than the skip-fire mode was used to run the optical engine ensuring the similarity to the actual engine operating conditions. The interaction among fuel spray jets, piston and cylinder wall was visualized by fuel-tracer planar laser-induced fluorescence. The high-speed combustion images were processed to determine the combustion stratification based on the natural flame luminosity. The combustion phasing, maximum in-cylinder pressure, and indicated mean effective pressure (IMEP) were compared at various intake temperatures. The results showed that the lower intake temperature could be used for achieving better combustion stability at low load condition along with the retarded CA50, the lower maximum in-cylinder pressure, and the higher IMEP. 70 °C was the lower limit of intake temperature to achieve stable PPC operation with the single-injection strategy. The same trend of the combustion characteristics with respect to the start of injection timing was confirmed at various intake temperatures. The combustion stratification analysis indicated more inhomogeneous low-temperature combustion with decreased natural flame luminosity and increased soot emission when the intake temperature reduced from 120 °C to 70 °C. Nitrogen oxides emission decreased when compared to the higher intake temperature cases at the expense of increased unburned hydrocarbon and carbon monoxide emissions at PPC mode. The fuel tracer measurements showed that most of the injected fuel hit on the piston top and only less amount of fuel was injected into the piston crown bowl at PPC mode due to the wider spray umbrella angle. The fuel trapped in crevice zone was verified as an important source for the unburned hydrocarbon and carbon monoxide emissions at PPC mode. The injector dribbling during the late stage of combustion attributed to soot formation. The injector with a relatively narrow spray umbrella angle was suggested for optimized interaction among the fuel spray jets, piston and the cylinder wall at PPC mode.

Assessment of diesel engine performance using spirulina microalgae biodiesel

The present work encompasses combustion, performance, and emission parameters of experimental investigations of a single cylinder, four stroke, water cooled, direct injection (DI), naturally aspirated compression ignition (CI) engine with a rated power output of 3.7 kW at constant engine speed (1500 rpm) using diesel and different blends of microalgae spirulina. The microalgae spirulina blend of ratio with diesel (BYY) where YY indicates blending percentage (0%, 20%, 40%, 60%, 80%, and 100% volume basis with diesel respectively) with different engine loading condition (25%, 50%, 75% and 100%) were compared with diesel at CR17.5:1. The output illustrates that the most optimum value is B20% when compared with diesel. The result depicts firstly that there is a reduction in brake thermal efficiency by 0.98%, exhaust gas temperature by 1.7%, hydrocarbon (HC) by 16.3%, carbon monoxide (CO) by 3.6%, NOX emission by of 6.8%, and smoke emission by 12.35% respectively. Secondly, there is an increase in specific fuel consumption by up to 5.2% and CO2 emission by 2.8% for spirulina blend ratio (B20%) as compared to diesel (B0%) at full load condition engine with constant engine speed.

Study on Soot Mass Fraction and Size Distribution in a Direct Injection Diesel Engine Using Particulate Size Mimic Soot Model

Abstract With today's computing technology, research on soot particles using simulation works has become more preferable as a supplementary to the existing experimental methods. The objective of this study is to investigate the effect of different engine load conditions to in-cylinder soot particles formation. This is to clarify the relationship between soot mass fraction (SMF) and size distribution. The first section of the study is conducted by computational analysis using a detailed kinetics soot model, particulate size mimic (PSM), which is based on the concept of the discrete sectional method. The analysis is carried out within closed-cycle combustion environment which is from the inlet valve closing (IVC) to the exhaust valve opening (EVO). The next section is conducted by experimental work deliberately for validation purpose. The total soot mass obtained from the computational work during EVO is comparable to the calculated value by less than 13% error for all of the experimental cases. The soot size distribution measurement indicates that exhaust out particles are dominantly in the dual-mode size range, <10 nm and 11–30 nm. The relationship between the soot mass and size distribution demonstrates that soot mass fraction does not completely rely on soot size distribution as well as particle size range. In most of the cases, particles with the moderate size range (11–60 nm) hold the highest mass fraction during EVO. On the whole, this paper provides significant information that contributes key knowledge to indicate that soot mass fraction is not entirely dependent on soot size distribution as well as particle size range.

Twd-10 b/pzl-10s engine emissions evaluation for PZL M28b Bryza airplane

The specificity of measurements of the concentration of harmful exhaust components of turbine engines used for propulsion of aircraft is connected with tests carried out in stationary conditions during engine tests. The conditions of engine load during the test and the concentration of harmful exhaust compounds determined during the measurements may be used to estimate the emissions of these compounds during the flight of the aircraft. A prerequisite is to obtain a correlation of the engine load conditions during a stationary test to the engine load conditions during the flight of the aircraft. This correlation was carried out on the basis of records of the operating parameter values recorded by the on-board aircraft flight recorder. The article presents the results of measurements of concentration of harmful compounds carried out during the pre-start test of the TWD-10B/PZL-10S engine being the source of propulsion of the PZL M28B “Bryza” airplane, implemented on the airport board. The article presents the results of tests and their analysis, allowing us to assess the emission of harmful exhaust gases from turbine propeller engines.

Experimental and modeling study of liquid fuel injection and combustion in diesel engines with a common rail injection system

Fuel injection is one of the most important processes in compression-ignition internal combustion engines owing to its significant impact on the exhaust emissions and thermal efficiency. In this study, experiments were carried out to investigate the influence of injection pressure and injection timing on the temporal evolution of the injection rate and injection duration in a specially designed experiment rig equipped with a common rail injection system. It is well known that the injection signal from the electronic control unit (ECU) of the injection system, which is often the only injection information available in engine operation and experiments, gives little information about the actual injection rate profile. It is shown in the present experiments that the actual injection duration is usually longer than the energizing time (ET). The time delay between the actual injection of the fuel and the ECU signal is about 0.3–0.4 ms, and the time delay appears to be insensitive to the injector geometry and injection pressure condition. The injection process can be characterized as five stages, a fast injector valve opening stage, a slow valve opening stage, a valve fully open stage, followed by a slow valve closing stage, and finally a rapid valve closing stage. It is found that the first stage, the fast valve opening stage, is insensitive to the injection pressure and injector nozzle diameter; however, the peak injection rate is a strong function of these parameters. The second and the third stage may not appear with a short injection duration. A new injection model was developed for the common rail injection system, which was capable of simulating the instantaneous fuel injection rate and injection duration for a range of injection pressure and injection duration. The model was shown to be able to replicate the experimental injection rate profile of the present experiments and experiments found in the literature for common rail injection system. The new injection model was applied to predict the effect of injection pressure and injection duration on the performance of a diesel engine under various engine speed and load conditions. The new injection model was shown to be able to describe the injection mass flow rate, which eventually leads to a reasonably good prediction of the variations of the spray development, in-cylinder pressure, heat release rate, and emissions.

Effects of dual-direct injection parameters on performance of fuel Jet Controlled Compression Ignition mode on a high-speed light duty engine

Fuel Jet Controlled Compression Ignition (JCCI) was proposed to control the combustion phasing of premixed charge. In this mode, a small quantity of jet-injection diesel fuel was used to ignite the premixed charge, which was prepared by the main pre-injection blended fuels of diesel and ethanol-gasoline. Experiments of JCCI mode combined with dual-direct injection strategy were conducted on a modified single-cylinder naturally aspirated diesel engine. Effects of jet-injection and pre-injection parameters on the combustion and emission characteristics were investigated in detail under four engine load conditions at the rated speed of 3000 r/min. Experimental results showed that the diesel fuel jet-injection could control the ignition timing and combustion phasing robustly at all the four engine load conditions. The combustion process was composed of two stages, the jet fuel spontaneous combustion stage and the pre-mixture combustion stage. Besides, sensitive analysis of the jet-injection and pre-injection parameters on the JCCI mode performance were also accomplished. Advancing the jet-injection timing could shorten the combustion duration and improve the indicated thermal efficiency (ITE), but along with an increase in the nitrogen oxides (NOx) emissions, especially at higher engine loads. As the pre-injection energy ratio was upgraded, the local equivalence ratio and the diffusion-controlled combustion could be reduced, resulting in the reduction of soot emissions. Sensitivity interval was introduced to access the effects of pre-injection timing. Beyond this interval, the pre-injection timing showed insignificant effects on the combustion characteristics and emissions. With the increase of pre-injection pressure, more pre-injection fuels penetrated into the crevice and near liner regions, and the total hydrocarbon (THC) emissions were increased. Finally, the enhanced reactivity of pre-injection fuels was demonstrated to effectively reduce THC emissions at lower engine loads.

Effect of sulphur and vanadium spiked fuels on particle characteristics and engine performance of auxiliary diesel engines

Particle emission characteristics and engine performance were investigated from an auxiliary, heavy duty, six-cylinder, turbocharged and after-cooled diesel engine with a common rail injection system using spiked fuels with different combinations of sulphur (S) and vanadium (V) spiking. The effect of fuel S content on both particle number (PN) and mass (PM) was clearly observed in this study. Higher PN and PM were observed for fuels with higher S contents at all engine load conditions. This study also found a correlation between fuel S content and nucleation mode particle number concentration which have more harmful impact on human health than larger particles. The highest PN and PM were observed at partial load conditions. In addition, S in fuel resulted in higher viscosity of spiked fuels, which led to lower engine blow-by. Fuel V content was observed in this study, evidencing that it had no clear effect on engine performance and emissions. Increased engine load also resulted in higher engine blow-by. The lower peak of in-cylinder pressure observed at both pre-mixed and diffusion combustion phases with the spiked fuels may be associated with the lower energy content in the fuel blends compared to diesel fuel.