High-speed Direct Injection Diesel Engine Research Articles

Simulation of the air/fuel mixing of an HSDI diesel engine. Part 1: A new dense spray vapour coupling submodel

A numerical study has been performed to investigate the soot emission from a high-speed single-cylinder direct injection diesel engine. The computational conditions were set to be the same as the test conditions in the experiments where measurements had been performed at two running speeds with two injector protrusions. It was shown that the KIVA CFD code can predict the experimental trend, where at a low-speed running condition a higher smoke reading is reached when increasing the injector protrusion into the piston chamber and, conversely, a lower smoke reading was recorded for the same change in injector protrusion at a high running speed condition. Although computational predictions yielded the same trend as the experimental results, the magnitudes of the smoke emissions were an order of magnitude over those predicted. Evidence of inappropriate air/fuel mixing of the model was seen via rates of heat release analyses, especially in the high-speed conditions. Therefore, efforts to reduce this discrepancy by way of improvements to the KIVA submodels were made. In particular, modifications to the breakup and evaporation models have been made in order better to represent the mixing of the high-speed liquid jets. A gaseous sphere per liquid droplet model was employed to improve the current KIVA model by improving the mass coupling effects, which effectively delays the addition of spray source terms to the gas phase equations. Results of the modified models showed improvements in the vapour dispersion of the atomizing liquid jet, thus affecting the mixing rates and predicted smoke emissions. Further improvements on the momentum coupling will be presented in Part 2 of this work.

The Use of Non-Parametric Regression to Investigate the Sensitivities of High-Speed Direct Injection Diesel Emissions and Fuel Consumption to Engine Parameters

A recently developed non-parametric regression (NPR) method, namely the component selection and smoothing operator (COSSO), was applied to a high-speed direct injection (HSDI) diesel engine optimization problem to analyse the complex correlations between NO x and soot emissions, and fuel consumption responses and control factors. Seven control factors were considered, including swirl ratio, fuel injection pressure, intake air boost pressure, exhaust gas recirculation (EGR), start-of-injection timings for each pulse of two-pulse injections, and the dwell between the injections. The responses are non-linearly and non-monotonically correlated to the control factors, which feature complex interactions. The models were constructed by extracting information from an undesigned and unevenly distributed data sample, whose size is small with regard to the high dimensionality of the inputs. The models perform well, as shown by cross-validations. This success reveals the potential of NPR methods as powerful analysis tools for problems of this type. Based on the current proposed well-constructed models, the importance of the control factors could be ranked according to their significance in the models, and interactions between control factors and their influence on responses could be quantitatively assessed. For example, a two-pulse injection featuring a very early first injection and a second injection well past top dead centre of compression provides excellent performance. The start-of-second-injection timing is shown to be most influential for fuel consumption and interactions between the boost pressure and the start-of-first-injection timing are important. Similarly, as expected, EGR is the most important main factor for NO x emissions, while the main and interaction effects of the second-injection timing and EGR are also very significant. All main and interaction effects were significant for soot emissions. With a complete and continuous description of response surfaces available using the method, response values at untried parameter points can also be estimated, and possibly optimal solutions can be derived without being restrained by specified search grid resolution. Moreover, the solutions can be diversified to meet various criteria. The potential of using the proposed NPR method for assisting optimal parameter search is also discussed.

Computational study of the effects of the throat diameter of the piston bowl for the performance and emissions of a high-speed direct-injection diesel engine

The purpose of this study is to investigate computationally the effect of the bowl shape with different throat diameters associated with different re-entrant lips using an experimentally validated KIVA3V-based computational fluid dynamics (CFD) program. In order to investigate individually the effects of the throat diameter and the re-entrant lip shape with the minimum interactive effects on other parameters, the bowl pip height and width were changed in order to maintain the same bowl height and volume. Three bowls, namely the baseline bowl, a bowl with increased throat diameter with limited pip height, and a bowl with increased throat diameter with the same pip height as the baseline, were investigated at the three speeds 4000 r/min maximum power, 2000 r/min maximum torque with three injector protrusions and three injection timings, and 1600 r/min part-load with two EGR fraction and injection timings respectively. It was found that the bowl with larger throat diameter and high pip has the best air-fuel mixing of all three bowls.

Computational fluid dynamics study of the effects of the re-entrant lip shape and toroidal radii of piston bowl on a high-speed direct-injection diesel engine's performance and emissions

The piston bowl design is one of the most important factors that affect the air-fuel mixing and the subsequent combustion and pollutant formation processes in a direct-injection diesel engine. The bowl geometry and dimensions, such as the pip region, bowl lip area, and toroidal radius, are all known to have an effect on the in-cylinder mixing and combustion process. In order to understand better the effect of re-entrant geometry, three piston bowls with different toroidal radii and lip shapes were investigated using computational fluid dynamics engine modelling. KIVA3V with improved submodels was used to model the in-cylinder flows and combustion process, and it was validated on a high-speed direct-injection engine with a second-generation common-rail fuel injection system. The engine's performance, in-cylinder flow, and combustion, and emission characteristics were analysed at maximum power and maximum torque conditions and at part-load operating conditions. Three injector protrusions and injection timings were investigated at full-load and part-load conditions.

Fuel design concept for improving the spray characteristics and emissions of diesel engines

This work investigated the improvement of spray characteristics and exhaust emissions of diesel engines by reformulating the fuel compounds and physicochemical parameters. Three oxygenated fuels, including ethanol, dimethyl carbonate (DMC), and dimethoxymethane (DMM), were mixed with diesel. Basic properties directly related to engine parameters and those characterizing fuel quality were investigated. A laser phase Doppler anemometry analyser was applied to obtain the spray characteristics, including the Sauter mean diameter and axial mean velocity distribution, of DMM-diesel hybrid fuels. Furthermore, engine tests of oxygenated hybrid fuels were performed on a four-cylinder water-cooled high-speed direct injection diesel engine. The results show that the evaporation properties and the fuel transportation parameters could be optimized using hybrid fuel, and the engine behaviour seemed to be improved in the presence of oxygenated additives with a reduction in pollutant emissions in exhaust gas.

Analysis of the effect of variations in fuel line pressure in high-speed direct injection diesel engines, with high-pressure common rail fuel injection systems on heat release, cylinder pressure, performance, and NOx emissions

This paper is a further development of work previously reported on a wholly analytical approach to heat release modelling and is applicable to high-speed direct injection (HSDI) diesel engines operating with high-pressure common rail fuel injection systems under conditions of predominantly mixing-controlled combustion. The key variable in this treatment is the fuel preparation or combustion rate factor WH which, in conjunction with the primary injection variables, i.e. rail pressure, injection velocity and duration, defines the shape and amplitude of the heat release curve. It was shown in a previous paper that by expressing the fuel preparation rate factor WH as a function of time rather than crank angle, i.e. WHt instead of WHθ, the former can be presented as a nearly linear function of the square of injection velocity, i.e. WHt is directly proportional to the kinetic energy of the injected fuel spray, the latter evidently being the primary influence on the rate of the fuel-air mixing process. The analytical treatment developed in the authors' previous paper then allows heat release rates in the engine, dQ/dθ, to be calculated over a wide range of engine speeds and loads, with the aid of the existing engine simulation code ODES (Otto diesel engine simulation) to predict the associated engine performance and emissions, without resorting to further engine testing.

An Integrated Approach for Creating Model Diesel Fuels

This paper describes a methodology that has been developed to facilitate a detailed study of molecular composition effects on particulate matter emissions in advanced diesel engines. This includes a sophisticated numerical optimization algorithm to formulate well-characterized diesel fuel blends and an analytical method to characterize diesel fuels more accurately than previously possible. These tools are described, together with application to the formulation of test fuels with identical boiling point distribution and cetane number, but differing molecular composition. Test results are discussed from an advanced high-speed direct injection diesel engine for several of these fuels, demonstrating the improved insight and understanding available from these combined techniques.

Computational study of the effects of the geometry of the piston bowl pip for a high-speed direct injection diesel engine

The piston bowl design is one of the most important factors that affect the air/fuel mixing and the subsequent combustion and pollutant formation processes in a direct injection diesel engine. The bowl geometry and dimensions, such as the pip region, the bowl lip area and the torus radius, are all known to have an effect on the in-cylinder mixing and combustion process. In order to understand better the effect of the pip region, three piston bowls with different pip designs but with the same lip area and torus radius were designed and investigated using computational fluid dynamics (CFD) engine modelling. A commercial CFD KIVA3V with improved submodels was used to model the in-cylinder flows and combustion process, and it was validated on a high-speed direct injection (HSDI) engine with a second-generation common rail fuel injection system. The engine performance, in-cylinder flow and combustion and emission characteristics were analysed at maximum power and maximum torque conditions and at part-load operating conditions. Three injector protrusions and injection timings were investigated at full load conditions. The effect of injection timing and exhaust gas recirculation (EGR) at the part-load condition was considered.

앞먹임 신경회로망을 이용한 HSDI Common-Rail 인젝터의 파라미터 추정 및 모델링

This study presents the process of the solenoid parameter estimation of an common-rail injector for HSDI(High Speed Direct Injection) diesel engines. The EMF(Electromotive Force) and solenoid inductance are the major parameters for presenting the injector dynamics, and also these parameters are estimated by using a multi-layer feedforward artificial neural networks(ANN) The performances of parameter estimators are verified by the simulation with Injector model. The feasibility of this methodology is closely examined through the simulation in the Various operating points of injector The simulation results have revealed that estimated parameters show favorable agreements with the common-rail injector model.br/

THE INFLUENCE OF FUEL ADDITIVES SO-2E ON DIESEL ENGINE EXHAUST EMISSION

One of the methods that allows substantially to reduce exhaust smoke of diesel engines and avoid possible damage of the environment by harmful emissions is the usage of multipurpose fuel additives. The efficiency of new Estonian made fuel additives SO-2E, that have been introduced recently for the experts attention, was investigated in small heating boilers and low-powered ships. The purpose of this research is to determine the influence of fuel additives SO-2E on the performance of a high-speed direct injection diesel engine in order to evaluate some of quantitative composition changes of the exhaust gases especially environmentally harmful nitrogen oxides, carbon monoxides and smoke emissions. Bench tests have been performed on the four-stroke, four-cylinder, water-cooled direct injection diesel engine D-243 with splash volume Vl = 4,75 dm3 and compression ratio ɛ = 16:1. Test results show that the application of diesel fuel additives SO-2E in proportion 1:500 (0,2 % by volume) at engine rated power reduces nitrogen monoxides NO and common NOx emission by 11,54 and 9,64 % respectively, however the amount of NO2 in totally diminished background of nitrogen oxides increases by 7,39 %. On the other hand, when running the engine at moderate (bmpe = 0,35 MPa) load, the fuel additives reduce emissions of all nitrogen components - NO by 16,1 %, NO2 by 11,8 % and NOx by 15,7 %. The influence of fuel additives on the amount of carbon monoxides in the exhausts seems to be more complicated. At engine rated speed/power fuel additives increase CO emission by 12,5 %, but as soon as engine load increases and revolution frequency drops down to the maximal torque area n = 1600-1800 min-1, they reduce the amount of CO in the exhaust gases on the average 20–28 %. It is important to notice that the changes in the smoke emission remain in close association with CO emissions. At certain revolution frequencies and moderate load the fuel additives SO-2E lead to noticeable reduction of the exhaust smoke, however at engine rated power and speed the smoke emission is obtained approximately 5 – 10 % higher. In spite of dissimilar influence of the fuel additives SO-2E on the quantities of CO produced and exhaust smoke it would be worth to apply them in high-speed DI diesel engines in order to reduce nitrogen oxides NOx emission.

The influence of fuel additives SO-2E on diesel engine exhaust emission

Abstract One of the methods that allows substantially to reduce exhaust smoke of diesel engines and avoid possible damage of the environment by harmful emissions is the usage of multipurpose fuel additives. The efficiency of new Estonian made fuel additives SO-2E, that have been introduced recently for the experts attention, was investigated in small heating boilers and low-powered ships. The purpose of this research is to determine the influence of fuel additives SO-2E on the performance of a high-speed direct injection diesel engine in order to evaluate some of quantitative composition changes of the exhaust gases especially environmentally harmful nitrogen oxides, carbon monoxides and smoke emissions. Bench tests have been performed on the four-stroke, four-cylinder, water-cooled direct injection diesel engine D-243 with splash volume Vl = 4,75 dm3 and compression ratio ɛ = 16:1. Test results show that the application of diesel fuel additives SO-2E in proportion 1:500 (0,2 % by volume) at engine rated ...

Response Surface Method Optimization of a High-Speed Direct-Injection Diesel Engine Equipped With a Common Rail Injection System

To overcome the tradeoff between NOx and particulate emissions for future diesel vehicles and engines it is necessary to seek methods to lower pollutant emissions. The desired simultaneous improvement in fuel efficiency for future DI diesels is also a difficult challenge due to the combustion modifications that will be required to meet the exhaust emission mandates. This study demonstrates the emission reduction capability of EGR and other parameters on a high-speed direct-injection (HSDI) diesel engine equipped with a common rail injection system using an RSM optimization method. Engine testing was done at 1757 rev/min, 45% load. The variables used in the optimization process included injection pressure, boost pressure, injection timing, and EGR rate. RSM optimization led engine operating parameters to reach a low-temperature and premixed combustion regime called the MK combustion region, and resulted in simultaneous reductions in NOx and particulate emissions without sacrificing fuel efficiency. It was shown that RSM optimization is an effective and powerful tool for realizing the full advantages of the combined effects of combustion control techniques by optimizing their parameters. It was also shown that through a close observation of optimization processes, a more thorough understanding of HSDI diesel combustion can be provided.

Combustion and Emission Characteristics of Direct-Injection Compression Ignition Engines by Means of Two-Stage Split and Early Fuel Injection

The objective of this study was to experimentally clarify the effect of two-stage split and early injection on the combustion and emission characteristics of a direct-injection (DI) diesel engine. Engine tests were carried out using a single-cylinder high-speed DI diesel engine and an injection system, combining an ordinary jerk pump and an electronically controlled high-pressure injection system, KD-3. In these experiments to compare the combustion and exhaust emission characteristics with two-stage split and early injection, a single-stage and early injection was tested. The FT-IR exhaust-gas analyzer simultaneously measured the exhaust emissions of 26 components. The results showed that HCHO, CH3CHO, and CH3COOH were emitted during the very early stage of both single injection and two-stage injection. These concentrations were higher than those from diesel combustion with ordinary fuel injection timings. These exhaust emissions are characteristic components of combustion by premixed compression ignition with extremely early injection. In particular, the HCHO concentration in exhaust was reduced with an increase in the maximum rate of heat release after cool flame due to pre-reaction of pre-mixture. At extremely early injection, the NOx concentration was extremely low; however, the indicated specific fuel consumption (ISFC) was higher than that of ordinary diesel combustion. In the case of two-stage injection, the degree of constant volume is increased, so that ISFC is improved. These results also demonstrated the possibility of reducing HCHO, NOx, and smoke emissions by means of two-stage split and early injection.

Study of nozzle characteristics on the performance of a small-bore high-speed direct injection diesel engine

As Co2 emissions from vehicles are gaining global attention, the low fuel consuming powertrain is in much greater demand than before. Some alternatives are suggested but the high-speed direct injection (HSDI) diesel engine would be the most realistic solution. Vehicle simulation shows that a car with low fuel consumption can be realized by applying a 1–1.2 L high-speed direct injection diesel engine in vehicles weighing about 750 kg. Although the direct injection diesel engine has been researched for a long time, enhancement of mixing between air and fuel in a limited space makes it a challenging area to develop a small swept volume HSDI diesel engine. The authors are investigating small HSDI diesel engine combustion technologies in an effort to realize a low fuel consumption vehicle. The main objective in this study is to obtain a better understanding of the combustion-related parameters from such a small size HSDI diesel engine in order to improve engine performance.

Calculation of fuel spray impingement and fuel film formation in an HSDI diesel engine

Spray impingement and fuel film formation models with cavitation have been developed and incorporated into the computational fluid dynamics code, STAR-CD. The spray/wall interaction process was modeled by considering the effects of surface temperature conditions and fuel film formation. The behavior of fuel droplets after impingement was divided into rebound, spread and splash using the Weber number and parameter\(K(\sqrt {We\sqrt {Re} } )\). The spray impingement model accounts for mass conservation, energy conservation, and heat transfer to the impinging droplets. The fuel film formation model was developed by integrating the continuity, momentum, and energy equations along the direction of fuel film thickness. Zero dimensional cavitation model was adopted in order to consider the cavitation phenomena and to give reasonable initial conditions for spray injection. Numerical simulations of spray tip penetration, spray impingement patterns, and the mass of film-state fuel matched well with the experimental data. The spray impingement and fuel film formation models have been applied to study spray/wall impingement in high-speed direct injection diesel engines.

Investigation on exhaust emissions of a common rail high-speed direct injection diesel engine running with dimethyl ether

This research investigates engine performance and the potential to reduce exhaust emissions by using dimethyl ether (DME) as an alternative fuel to diesel for compression ignition engines. The main objective of this study it to evaluate on a test-bed the performance and emissions reduction potential of a four-cylinder passenger car HSDI common rail turbocharged diesel engine running with DME in the absence of specific modifications to the engine itself but some modifications to the fuel injection system. The results obtained from this engine running with DME using diesel fuel as reference are encouraging. In the next phase of this study the injection rate will be adapted to DME operation and to the geometric and thermodynamic conditions of the combustion process. A study of combustion reaction is also necessary in order to optimize the turbocharging system for exclusive DME operation.

An Experimental Investigation of the Effects of Common-Rail Injection System Parameters on Emissions and Performance in a High-Speed Direct-Injection Diesel Engine

An investigation of the effect of injection parameters on emissions and performance in an automotive diesel engine was conducted. A high-pressure common-rail injection system was used with a dual-guided valve covered orifice nozzle tip. The engine was a four-valve single cylinder high-speed direct-injection diesel engine with a displacement of approximately 12 liter and simulated turbocharging. The engine experiments were conducted at full load and 1004 and 1757 rev/min, and the effects of injection pressure, multiple injections (single vs pilot with main), and pilot injection timing on emissions and performance were studied. Increasing the injection pressure from 600 to 800 bar reduced the smoke emissions by over 50 percent at retarded injection timings with no penalty in oxides of nitrogen NOx or brake specific fuel consumption (BSFC). Pilot injection cases exhibited slightly higher smoke levels than single injection cases but had similar NOx levels, while the single injection cases exhibited slightly better BSFC. The start-of-injection (SOI) of the pilot was varied while holding the main SOI constant and the effect on emissions was found to be small compared to changes resulting from varying the main injection timing. Interestingly, the point of autoignition of the pilot was found to occur at a nearly constant crank angle regardless of pilot injection timing (for early injection timings) indicating that the ignition delay of the pilot is a chemical delay and not a physical (mixing) one. As the pilot timing was advanced the mixture became overmixed, and an increase of over 50 percent in the unburned hydrocarbon emissions was observed at the most advanced pilot injection timing.

Reduction of NOx and Particulate of a High Speed Direct-Injection Diesel Engine with High Squish Combustion Chamber.

In order to realize simultaneous reduction of NOx and Particulate emissions, effects of combustion chamber geometry were investigated in a high speed direct-injection diesel engine. The reentrant combustion chambers with different throat diameter were compared in terms of engine performance, combustion characteristics and emissions such as NOx, particulate and THC. The phenomena of combustion process were also observed with endoscopic high speed photography. The results showed that when the throat diameter of a reentrant combustion chamber was reduced to an extent, NOx and particulate decreased simultaneously due to retarded injection timing and the intensified squish.

Effect of Rich and High Turbulence Combustion on Emissions and Flame Behavior in a Direct-Injection Diesel Engine.

This study tried to reduce NOx and particulate emissions simutaneously in a high speed direct-injection diesel engine. Fuel-rich combustion was used to reduce NOx emission at initial combustion stage and high turbulence combustion was used to reduce particulate emission at diffusion combustion stage. Experiments were carried out to investigate the effects of high squish combustion chambers with small throat on combustion process and exhaust emissions. Results showed that in the high squish combustion chamber, both NOx and particulate emissions reduced with retarded injection timing. Endoscopic high speed photography was employed to analyze experimental results. In the original combustion chamber at the early combustion stage, the high luminosity flame tended to spread out of the cavity. Fuel-rich mixture burned slowly over the piston crown. In the high squish combustion chamber, flame rotated violently around the bowl. Fuel-rich mixture was kept beneath the squish lip, and was mainly oxidized inside the bowl. This combustion phenomenon was considered to be one of the reasons for low particulate emission in high squish combustion chambers.

ディーゼル排気の低エミッション化技術に関する検討

Mechanisms of nitric oxide formation and emission for a conventional high-speed direct-injection diesel engine have been studied by a stochastic model that takes chemical kinetics into account. In calculations cetene was used as a fuel and its initiation processes were expressed by a one-step global mechanism. Detailed reduced chemical mechanisms were employed for the processes of heat release and NO formation. The calculated NO concentration coincides with a value measured in an exhaust gas within 10%. It is shown that most NO is formed locally at temperatures higher than 2000 K under a range of excess air ratios, 1< λ <3.The effects of EGR and water addition on reducing NO and soot emission were also discussed. Results show that EGR up to 10% shifts the local excess air ratio from those points where NO is formed intensively to fuel rich regions without almost any temperature drop. Thus, EGR reduces NO emission without sacrificing thermal efficiency. EGR, however, reduces the local oxygen concentration and this causes the increase in soot emission. On the other hand, water addition shifts the local mixing ratio from the NO forming region to lower temperature region without decreasing local oxygen concentration in a fuel rich region. For this reason, water addition for reducing NO emission basically results in a drop in fuel economy but it does not increase soot emission. Furthermore, the effects of CO2 addition on NO and soot emission were discussed and it is shown that CO2 addition shifts the local mixture to rich at λ >1 and to lean at λ <1. It suggests that CO2 addition is able to reduce NO and soot emission without the drop in thermal efficiency.