Direct Injection Diesel Research Articles

Experimental investigation on the influence of engine operating conditions on combustion and nanoparticle emission characteristics of a small DI diesel engine

The influence of variations in engine speed, injection pressure, injection timing, and multiple injection strategies on the combustion and nanoparticle characteristics of a small Direct injection (DI) diesel engine was experimentally investigated. To measure the size distribution and number concentration of particle emissions, a rotating disk thermo-diluter (dilution system), a Condensation particle counter (CPC), and a Scanning mobility particle sizer (SMPS) were used. The injection pressure was changed from 60 MPa to 120 MPa, at an engine speed of 1200 rpm. Injection timing was varied from Before top dead center (BTDC) 40˚ to Top dead center (TDC). To investigate the effect of multiple-injection strategies, the injection strategies consisted of two pulse signals with different dwell time. The experimental results show that the peak combustion pressure and Rate of heat release (ROHR) profile are increased and ignition delay is shortened with the increase of injection pressure from 60 MPa to 120 MPa. The concentration of soot emission for 120 MPa is lower than that of 60 MPa at advanced injection timing from TDC up to BTDC 25°. As the injection timing advances to over BTDC 30°, soot emissions rapidly increase and the high injection pressure case (120 MPa) creates more emissions than the 60 MPa case. The overall trends of total particle number are relatively increased with high injection pressure for single injection conditions. In the advanced injection timings of over BTDC 30°, the trend of total particle number is high for all injection pressures. For multiple injections, the peak combustion pressures and ROHR of multiple-injection strategies are slightly lower compared with those of single-combustion results. Comparing the multiple injection strategies, soot emission is reduced with the retard of second injection timing (-30°+5°). The overall trends of particle size and total number for the 7 mg+3 mg case revealed the lowest level compared with other cases, which is 50% lower than that for the 5 mg+5 mg case. When compared with single injection results, the total particle number and Dp of multiple injection cases were eventually lower.

Use of Adaptive Injection Strategies to Increase the Full Load Limit of RCCI Operation

Dual-fuel combustion using port-injection of low reactivity fuel combined with direct injection (DI) of a higher reactivity fuel, otherwise known as reactivity controlled compression ignition (RCCI), has been shown as a method to achieve low-temperature combustion with moderate peak pressure rise rates, low engine-out soot and NOx emissions, and high indicated thermal efficiency. A key requirement for extending to high-load operation is moderating the reactivity of the premixed charge prior to the diesel injection. One way to accomplish this is to use a very low reactivity fuel such as natural gas. In this work, experimental testing was conducted on a 13 l multicylinder heavy-duty diesel engine modified to operate using RCCI combustion with port injection of natural gas and DI of diesel fuel. Engine testing was conducted at an engine speed of 1200 rpm over a wide variety of loads and injection conditions. The impact on dual-fuel engine performance and emissions with respect to varying the fuel injection parameters is quantified within this study. The injection strategies used in the work were found to affect the combustion process in similar ways to both conventional diesel combustion (CDC) and RCCI combustion for phasing control and emissions performance. As the load is increased, the port fuel injection (PFI) quantity was reduced to keep peak cylinder pressure (PCP) and maximum pressure rise rate (MPRR) under the imposed limits. Overall, the peak load using the new injection strategy was shown to reach 22 bar brake mean effective pressure (BMEP) with a peak brake thermal efficiency (BTE) of 47.6%.

Cold start particle number, size and mass emissions from a CRDI diesel engine running on biodiesel blends in a cold environment

ABSTRACTBiodiesel is a renewable alternative fuel, used as a blending component for diesel, which reduces hydrocarbon and particulate matter emissions with marginal increases in nitrogen oxide emissions. Engine performance varies with ambient temperature conditions, engine design, fuel, lubricant and operating conditions. This research investigated the impact of biodiesel blends on a common rail direct injection (CRDI) diesel engine performance and exhaust emission characteristics during cold start at different ambient temperature conditions. Biodiesel blends improved the combustion and thereby reduced the sudden rise in peak speed and the gaseous emissions at normal ambient temperature. At cold ambient conditions biodiesel severely affected the cold start performance and increased the gaseous emissions. During cold start, the biodiesel blends emitted a larger number of particles of diameter 100–1000 nm at cold ambient temperature compared to normal ambient temperature. The particulate surface area and mass was increased by 2–3 times and 3–6 times, respectively, for the biodiesel blends with the drop in ambient temperature. The higher number of larger diameter particles increased the particulate mass significantly at cold ambient temperature conditions.

Impact of edible and non-edible biodiesel fuel properties and engine operation condition on the performance and emission characteristics of unmodified DI diesel engine

ABSTRACTThe purpose of this work is to test the feasibility of biodiesel as a substitute for diesel used in a direct injection (DI) diesel engine. The biodiesel was produced by an esterification and transesterification process. Experiments were conducted with diesel–biodiesel blends containing 10 and 20% biodiesel with the diesel fuel. The results of the biodiesel blends are compared with baseline diesel which was assessed at constant speed in a single cylinder diesel engine at various loading conditions. The physicochemical properties of palm and Calophyllum inophyllum biodiesel and their blends meet the standard specification ASTM D6751 and EN 14214 standards. The maximum brake thermal efficiency was attained with diesel fuel, 10% palm biodiesel (PB10) and 10% C. inophyllum biodiesel (CI10) at all load condition except low load condition. Engine emission results showed that the 20% C. inophyllum with 80% diesel blend exhibited 6.35% lower amount of brake specific carbon monoxide, and the PB20 blend and CI20 blend reduced brake specific hydrocarbon emission by 7.93 and 9.5%, respectively. NOx emission from palm and C. inophyllum biodiesel blends are found to be 0.29–4.84% higher than diesel fuel. The lowest smoke intensity is found at 27.5% for PB10 and CI10 biodiesel blends compared with diesel fuel.

Linking instantaneous rate of injection to X-ray needle lift measurements for a direct-acting piezoelectric injector

Internal combustion engines have been and still are key players in today’s world. Ever increasing fuel consumption standards and the ongoing concerns about exhaust emissions have pushed the industry to research new concepts and develop new technologies that address these challenges. To this end, the diesel direct injection system has recently seen the introduction of direct-acting piezoelectric injectors, which provide engineers with direct control over the needle lift, and thus instantaneous rate of injection (ROI). Even though this type of injector has been studied previously, no direct link between the instantaneous needle lift and the resulting rate of injection has been quantified. This study presents an experimental analysis of the relationship between instantaneous partial needle lifts and the corresponding ROI. A prototype direct-acting injector was utilized to produce steady injections of different magnitude by partially lifting the needle. The ROI measurements were carried out at CMT-Motores Térmicos utilizing a standard injection rate discharge curve indicator based on the Bosch method (anechoic tube). The needle lift measurements were performed at the Advanced Photon Source at Argonne National Laboratory. The analysis seeks both to contribute to the current understanding of the influence that partial needle lifts have over the instantaneous ROI and to provide experimental data with parametric variations useful for numerical model validations. Results show a strong relationship between the steady partial needle lift and the ROI. The effect is non-linear, and also strongly dependent on the injection pressure. The steady lift value at which the needle ceases to influence the ROI increases with the injection pressure. Finally, a transient analysis is presented, showing that the needle velocity may considerably affect the instantaneous ROI, because of the volume displaced inside the nozzle. Results presented in this study show that at constant injection pressure and energizing time, this injector has the potential to control many aspects of the ROI and thus, the heat release rate. Also, data presented are useful for numerical model validations, which would provide detailed insight into the physical processes that drive these observations, and potentially, to the effects of these features on combustion performance.

Investigation of the DI Diesel Engine Performance using Ethanol-Diesel Fuel Blends

Ethanol-diesel blend is a promising candidate as a fuel for direct injection (DI) diesel engine. In this research, solubility of different compositions of ethanol-diesel blends from 2 to 15% (v/v) ethanol were tested for 20 days. Significant increases in solubility of the blends were observed after addition of 1% (v/v) n -butanol. The Kubota’s RT140 diesel engine was operated using E7B1D92 blend at several engine speeds (1,000 to 1,600 rpm). The obtained results demonstrated that, when using E7B1D92 blend at an engine speed of 1,500 rpm, the engine power and torque of the RT140 engine were increased from 8.6 PS to 10.1 PS and 4.1 kg f -m to 5.1 kg f -m compared to pure diesel fuel. However, specific consumption fuel increased when E7B1D92 blend was used during the engine test. Additionally, analysis of exhaust gas revealed a decrease in smoke density when E7B1D92 was used instead of pure diesel.

Experimental analysis of ethanol dual-fuel combustion in a heavy-duty diesel engine: An optimisation at low load

Conventional diesel combustion produces harmful exhaust emissions which adversely affect the air quality if not controlled by in-cylinder measures and exhaust aftertreatment systems. Dual-fuel combustion can potentially reduce the formation of nitrogen oxides (NOx) and soot which are characteristic of diesel diffusion flame. The in-cylinder blending of different fuels to control the charge reactivity allows for lower local equivalence ratios and temperatures. The use of ethanol, an oxygenated biofuel with high knock resistance and high latent heat of vaporisation, increases the reactivity gradient. In addition, renewable biofuels can provide a sustainable alternative to petroleum-based fuels as well as reduce greenhouse gas emissions. However, ethanol–diesel dual-fuel combustion suffers from poor engine efficiency at low load due to incomplete combustion. Therefore, experimental studies were carried out at 1200rpm and 0.615MPa indicated mean effective pressure on a heavy-duty diesel engine. Fuel delivery was in the form of port fuel injection of ethanol and common rail direct injection of diesel. The objective was to improve combustion efficiency, maximise ethanol substitution, and minimise NOx and soot emissions. Ethanol energy fractions up to 69% were explored in conjunction with the effect of different diesel injection strategies on combustion, emissions, and efficiency. Optimisation tests were performed for the optimum fuelling and diesel injection strategy. The resulting effects of exhaust gas recirculation, intake air pressure, and rail pressure were investigated. The optimised combustion of ethanol ignited by split diesel injections resulted in higher net indicated efficiency when compared to diesel-only operation. For the best emissions case, NOx and soot emissions were reduced by 65% and 29%, respectively. Aftertreatment requirements that are generally associated with cost and fuel economy penalties can be minimised. Combustion efficiency of 98% was achieved at the expense of higher NOx emissions.

Effects of rapid burning characteristics on the vibration of a common-rail diesel engine fueled with diesel–methanol dual-fuel

The diesel–methanol dual-fuel (DMDF) combustion mode is conducted on a six-cylinder, turbo-charged, inter-cooled diesel engine. In DMDF mode, methanol is injected into the intake pipe to premix methanol and air, and then ignited by the direct-injected diesel in cylinder. This study is aimed to investigate the effects of rapid burning characteristics on the vibration performance of the DMDF engine. The experimental results show that the combustion process of the DMDF engine can be divided into two phases. The rapid burning characteristics, the centroid angle of rapid burning (α) and the rapid burning fraction (β) have important influence on the vibration characteristics of the DMDF engine. The co-combustion rate (CCR) and engine load affect β greatly, and diesel injection timing also affects α and β greatly. However, the diesel injection pressure has little effect on rapid burning characteristics. By means of optimized diesel injection timing and pressure, the vibration can be reduced and the peak value of CCR can be increased.

Effect of the diesel injection strategy on the combustion and emissions of propane/diesel dual fuel premixed charge compression ignition engines

In this research, the effects of the propane ratio and diesel direct injection strategy on the emissions and combustion characteristics of a propane-diesel dual fuel PCCI (premixed charge compression ignition) engine were evaluated. Under low speed and low engine load, the propane ratio was varied from 30 to 70% to investigate the effect of the LHV (low heating value) fuel content in the supplied fuel (propane and diesel mixture). The EGR rate was adjusted to suit each propane ratio to ensure combustibility and restricted emissions. Early diesel injection strategies have an excellent effect on the dual fuel combustion in terms of simultaneously reducing NOx (nitrogen oxides) and PM (particulate matter) emissions. This concept is based on PCCI combustion, in which the ignition delay is longer than the diesel injection. Meanwhile, although early single diesel injection has been an effective strategy for reducing NOx and PM emissions simultaneously, it was possible to further reduce NOx emissions using an early split injection strategy with a 30% propane ratio. Additionally, when the propane ratio was 70%, the ignitibility deteriorated due to early single diesel injection, which led to a much leaner air–fuel mixture condition locally prior to auto-ignition, causing unstable combustion. As a result, a multiple injection strategy with earlier main injection and a small diesel post-injection as a triggering source was adopted to stabilize dual fuel PCCI combustion with a high propane ratio. The results emphasized that the diesel injection strategy could be adjusted to suit various propane ratios under dual fuel PCCI combustion to reduce NOx and PM emissions while maintaining thermal efficiency.

Performance and emission characteristics of a low heat rejection engine using Nerium biodiesel and its blends

In the present study, the surface of cylinder head, piston, exhaust and inlet valves of a four stroke direct injection and single cylinder diesel engine has been coated with partially stabilised zirconia (PSZ) by the plasma spray method. The coated engine was tested with the neat diesel and methyl ester of neat Nerium oil. The performance and emission results were compared with the uncoated engine fuelled with diesel and methyl ester of Nerium oil (MEON). Specific fuel consumption of the PSZ-coated engine was lower at all loads, because of the insulation effect of coating and changes in combustion process due to coating. The brake thermal efficiency of PSZ-coated engine fuelled with MEON is 3.8% higher than uncoated engine fuelled with MEON. The emission for the PSZ-coated engine with diesel was improved compared with uncoated engine except NOx.

An experimental study on premixed charge compression ignition-direct ignition engine fueled with ethanol and gasohol

This paper investigates the combustion, performance and emission characteristics of a partial Premixed Charge Compression Ignition-Direct Injection (PCCI-DI) Engine with premixed fuels ethanol and gasohol (90% gasoline and 10% ethanol by volume) along with direct injection of diesel fuel into the combustion chamber. The experiments were conducted in a four stroke, naturally aspirated, air cooled, constant speed diesel engine with 20% premixed fuels from no load to full load condition. The addition of premixed fuel enhances the air fuel mixture strength and for that the combustion duration is decreased in dual fuel operation. From this experiment it was observed the 70% and 67% reduction in smoke emission from premixed gasohol and ethanol fuel when compared to neat diesel operation. In addition to that, the oxides of nitrogen emissions were reduced to 30% and 24% for premixed gasohol and ethanol fuel. In particular, premixed gasohol reduces the smoke and oxides of nitrogen emissions more than the ethanol and also, significant increase in brake thermal efficiency was noted in 20% premixed gasohol and ethanol in dual fuel mode, when compared to neat diesel operation.

Combustion characteristics of a DI diesel engine fuelled with blends of methyl ester of cotton seed oil

The combustion characteristics of a single-cylinder, four-stroke, air-cooled and direct injection (DI) diesel engine fuelled with methyl ester of cotton seed oil (MECSO) and its blends with neat diesel fuel were examined. The experiments were conducted at a constant speed under steady-state condition with a Kirloskar TAF 1 engine. Combustion characteristics such as cylinder pressure, heat release rate (HRR), cumulative heat release rate (CHRR), maximum cylinder pressure, rate of pressure rise, ignition delay, duration of injection and combustion duration of MECSO and its blends with diesel were evaluated and compared with those of diesel fuel. From the analysis, it was found that the peak cylinder pressure and HRR of diesel were higher when compared with those of MECSO blends. The ignition delay, duration of injection and combustion duration decreased for MECSO blends compared to those of diesel. However, the CHRR of MECSO and its blends were higher than that of diesel. Finally, the study showed that B25 (25% of MECSO and 75% of diesel) gave optimum combustion characteristics for all loads and could be used as a viable alternative fuel in a DI diesel engine without any engine modifications.

Effects of hydrocarbon fuel extracted from waste transformer oil on a DI diesel engine

In this study, hydrocarbon fuel (HCF) was derived from waste transformer oil through a traditional base-catalysed trans-esterification process. The experimental investigations using its blends of 25%, 50%, 75%, 100% and diesel fuel were carried out separately. The HCF obtained from waste transformer oil is used in a direct injection (DI) diesel engine without any engine modification to evaluate its performance, emission and combustion characteristics. The results indicate that the engine operating on test fuel blends shows a marginal increase in brake thermal efficiency (BTE) with a significant reduction in smoke. Nitrous oxides (NOx) emission was slightly higher for test fuel blends than for diesel. The results show that at maximum load conditions, 25% HCF reduces carbon monoxide, smoke and hydrocarbon emission by 50%, 31% and 10%, respectively, whereas 50% HCF shows a greater BTE than other blends and is 12% higher than that of the diesel fuel. The combustion characteristics of fuel blends closely followed those of standard diesel.

Emission analysis of a Diesel Engine Operating in Diesel–Ethanol Dual-Fuel mode

Among the motivating factors for studies involving thermal machines is the need to increase the range of options. Thus, various systems combinations can co-exist, causing the reduced reliance on a single source. This is the context of studies involving Dual-Fuel systems. Additional to this factor is the requirement to reduce emissions. Thus, the combination of fuel, one being an alternative fuel becomes a very convenient opportunity. In this work, emissions results of a Diesel–Ethanol Dual-Fuel system are presented. A single cylinder research engine with diesel direct injection and port ethanol injection that aim to form a homogeneous air–fuel mixture in the intake port was used. The initial idea was to achieve the highest possible diesel substitution rate by ethanol. After investigation, described in a previous study with different compression ratios, different flow structures, different diesel injectors’ flows and injection pressures it was found that the highest substitution rate occurred with higher injector flow, compression ratio of 17:1, high swirl flow structure. The present work will discuss the emissions results obtained in that engine configuration which was considered optimal balance between diesel substitution rate and efficiency. Diesel Engine Operating in Diesel–Ethanol Dual-Fuel mode reduced the NOx emission in up to 60%. On the other hand, there was increase of the THC, the CO and the aldehydes, showing a trade-off that must be further investigated with a final design engine, in the beginning of product development process.

A Reduced Chemical Kinetic Mechanism for Low Temperature Diesel Combustion and Soot Emissions

A reduced diesel surrogate fuel chemical kinetic mechanism of n-heptane/toluene/1-hexene including poly-aromatic hydrocarbons (PAHs) formation was developed for prediction of the diesel combustion process and soot emissions. The proposed mechanism, which includes 60 species and 123 reactions, agrees well with experimental ignition delays in shock tubes. The proposed mechanism was coupled with the KIVA-3V Release 2 computational fluid dynamics (CFD) code to predict the combustion process and soot emissions in constant volume spray chamber and diesel direct injection combustion cases. The simulation results predict the combustion processes for diesel fuel under various conditions well. However, the predicted soot emissions have notable deviations compared to the experimental data when C2H2 or phenanthrene (A3) were chosen as precursors in the soot model at lower oxygen concentration conditions. The predicted soot emissions at different oxygen concentrations have better agreement with the experimental data when pyrene (A4) was chosen as the soot precursor. Compared to C2H2 or A3, A4 is a more suitable precursor for soot predictions in the LTC simulations. The overall results show that the present mechanism can be used to predict the combustion process and soot emissions of low temperature diesel combustion.

Study of the control strategies on soot reduction under early-injection conditions on a diesel engine

To explore the more effective method to fulfill soot reduction challenges of early-injection conditions, different engine operating parameters such as intake pressure, exhaust gas recirculation (EGR), equivalence ratio, intake temperature, coolant temperature, injection pressure and fuel properties such as using the blends of diesel/gasoline, diesel/n-butanol and dual-fuel were investigated on a diesel engine. A wide range of injection timing from 5°CA to −70°CA ATDC were tested, which covered both conventional diesel injection and early-injection conditions. Results showed that the soot emission increased as the injection timing was advanced from −35°CA to −55°CA ATDC, which was attributed to that more spray liquid was out of the piston bowl and impinged on the piston top and cylinder liner. The soot emission decreased as the injection timing further advanced from −55° to −70°CA ATDC, which was attributed to the suppressed soot formation. Although more advanced injection (−55° to −70°CA ATDC) decreased soot emissions, the combustion efficiency was deteriorated. EGR combined with higher intake pressure resulted in lower soot emissions than that of sole EGR control under the same equivalence ratio. Increasing intake temperature and coolant temperature reduced soot emissions at the injection timing later than −55°CA ATDC but barely affected the soot peak-value. Increasing injection pressure had little impact on soot emissions at early-injection conditions. Regarding to fuel properties, employing the diesel/gasoline and diesel/n-butanol blends dramatically reduced soot emissions and the smokeless combustion was achieved by using pure gasoline or n-heptane. Soot peak-value of diesel/gasoline combustion was higher than that of diesel/n-butanol at low diesel replacement ratio (30%), while for high replacement ratio (70%) the opposite trend was presented. The dual-fuel injection composed by port-injection of gasoline and direct-injection of diesel was more effective in reducing soot emissions than that of single direct-injection under the same gasoline/diesel ratio.

Study of Cylinder Charge Control for Enabling Low Temperature Combustion in Diesel Engines

Suitable cylinder charge preparation is deemed critical for the attainment of a highly homogeneous, diluted, and lean cylinder charge, which is shown to lower the flame temperature. The resultant low temperature combustion (LTC) can simultaneously reduce the NOx and soot emissions from diesel engines. This requires sophisticated coordination of multiple control systems for controlling the intake boost, exhaust gas recirculation (EGR), and fueling events. Additionally, the cylinder charge modulation becomes more complicated in the novel combustion concepts that apply port injection of low reactivity alcohol fuels to replace the diesel fuel partially or entirely. In this work, experiments have been conducted on a single cylinder research engine with diesel and ethanol fuels. The test platform is capable of independently controlling the intake boost, EGR rates, and fueling events. Effects of these control variables are evaluated with diesel direct injection and a combination of diesel direct injection and ethanol port injection. Data analyses are performed to establish the control requirements for stable operation at different engine load levels with the use of one or two fuels. The sensitivity of the combustion modes is thereby analyzed with regard to the boost, EGR, fuel types, and fueling strategies. Zero-dimensional cycle simulations have been conducted in parallel with the experiments to evaluate the operating requirements and operation zones of the LTC combustion modes. Correlations are generated between air–fuel ratio (λ), EGR rate, boost level, in-cylinder oxygen concentration, and load level using the experimental data and simulation results. Development of a real-time boost-EGR set-point determination to sustain the LTC mode at the varying engine load levels and fueling strategies is proposed.

Dual-Fuel Diesel Engine Combustion With Hydrogen, Gasoline, and Ethanol as Fumigants: Effect of Diesel Injection Timing

Premixed compression ignition (CI) combustion has attracted increasing research effort recently due to its potential to achieve both high thermal efficiency and low emissions. Dual-fuel strategies for enabling premixed CI have been a focus using a low-reactivity fumigant and direct diesel injection to control ignition. Alternative fuels like hydrogen and ethanol have been used as fumigants in the past but typically with diesel injection systems that did not allow the same degree of control or mixing enabled by modern common rail systems. In this work, we experimentally investigated hydrogen, ethanol, and gasoline as fumigants and examined three levels of fumigant energy fraction (FEF) using gasoline over a large, direct diesel injection timing range with a single-cylinder diesel engine. It was found that the operable diesel injection timing range at constant FEF was dependent on the fumigant's propensity for autoignition. Peak indicated gross cycle efficiency occurred with advanced diesel injection timing and aligned well with combustion phasing near top dead center (TDC), as we found in an earlier work. The use of hydrogen as a fumigant resulted in very low hydrocarbon (HC) emissions compared with ethanol and gasoline, establishing that they mainly result from incomplete combustion of the fumigated fuel. Hydrogen emissions were independent of diesel injection timing, and HC emissions were strongly linked to combustion phasing, giving further indication that squish and crevice flows are responsible for partially burned species from fumigation combustion.

Effects of Intake Port Optimization on Soot Emission from Diesel Engine

All future engine developments must consider the primary task of achieving the required emission levels. An important step towards the development of combustion engines is the optimization of the flow in the intake ports. The charging movement in the combustion chamber, which is generated by the intake flow, considerably influences the quality of the combustion engine. In this paper, steady CFD analysis were applied to different structures of double-tangent-port. The swirl ratio can be improved while flow coefficient remains unchanged if port eccentricity is 34.4 mm. By defining three characteristic parameters, the speed non-uniformity index, standard deviation and mixture concentration standard deviation and equivalent ratio range, quantitatively describing the combustion process in cylinder, and then compared with transient CFD three-dimensional contours, we can see that characteristic parameters can be more accurate and comprehensive in analyzing the influence of inlet structure of soot formation. Effects of different intake ports on fuel-air mixing in a turbocharged diesel direct injection engine during intake and compression strokes are analyzed. It turns out that the optimized double-tangent-port has the highest uniformity of velocity, in the meanwhile, air/fuel mixing is relatively uniform. On the other hand, mixed-port and double-helix-port can cause uneven flow field which is bad for combustion, even though the swirl ratio can increase largely. Finally, the simulation results show that soot emissions of the optimized double-tangent-port have significantly lower levels, at 2200 r/min under full load.

Experimental and numerical characterization of a direct solenoid actuation injector for Diesel engine applications

In the present paper, a non-conventional Diesel injection system is analyzed by means of a detailed numerical and experimental investigation.The analyzed system, the Magneti Marelli DDI Diesel direct injection, is based on a direct-actuation solenoid injector. The DDI system operates up to 60.0MPa injection pressure, with a multi-hole nozzle resulting in a conventional fuel spray plumes distribution inside the combustion chamber, which suites the requirements of small industrial and automotive Diesel applications.In the present research activity, the hydraulic behavior of the DDI system was analyzed in terms of injected volumes and injection rate time-histories varying the injection pressure from 30.0MPa to 60.0MPa with a back pressure of 2.0MPa. The resulting injection process was also analyzed in terms of spray global shape evolution along with droplet sizing and velocity in a pressurized (1.0MPa) test vessel in quiescent and room temperature conditions.In order to investigate and to validate the capability of adopted CFD models to reproduce the spray behavior at such non-conventional injection pressure levels for Diesel applications, an experimental and numerical comparison was performed, in terms of liquid spray morphology, tip penetration and droplet sizing.A numerical methodology, based on a preliminary Eulerian Steady Simulation of the nozzle, has been developed in order to gain correct flow rates and turbulence data at each of the nozzle holes exit. Then the Lagrangian spray simulations have been carried out by means of a new atomization approach able to take into account the cavitation phenomena and the turbulence effects. A tuning campaign has been performed in order to validate the secondary KH–RT breakup model, and a grid sensitivity analysis has been carried out.