Showing papers in "International Journal of Engine Research in 2013"
TL;DR: This study illustrates how it is thus possible to unambiguously quantify the cyclic variability of Reynolds-averaged Navier–Stokes ensemble average and turbulence and proposes practical procedures for application to internal combustion engine flows.
Abstract: Proper orthogonal decomposition has been utilized for well over a decade to study turbulence and cyclic variation of flow and combustion properties in internal combustion engines. In addition, proper orthogonal decomposition is useful to quantitatively compare multi-cycle in-cylinder measurements with numerical simulations (large-eddy simulations). However, the application can be daunting, and physical interpretation of proper orthogonal decomposition can be ambiguous. In this paper, the mathematical procedure of proper orthogonal decomposition is described conceptually, and a compact MATLAB® code is provided. However, the major purpose is to empirically illustrate the properties of the proper orthogonal decomposition analysis and to propose practical procedures for application to internal combustion engine flows. Two measured velocity data sets from a motored internal combustion engine are employed, one a highly directed flow (each cycle resembles the ensemble average), and the other an undirected flow (...
133 citations
TL;DR: In this article, the authors compared conventional diesel combustion and reactivity controlled compression ignition combustion in a light-duty engine at NOx levels equivalent to US Tier 2 Bin 5 and proposed a simple...
Abstract: This study compares conventional diesel combustion and reactivity controlled compression ignition combustion in a light-duty engine at NOx levels equivalent to US Tier 2 Bin 5 and proposes a simple...
80 citations
TL;DR: The authors analytically explores the fundamental thermodynamics of operation in these regimes under realistic burn duration, heat loss, boosting, and friction constraints, identifying the benefits of this approach and the path to achieving optimum engine and vehicle-level fuel economy.
Abstract: Recent developments in ignition, boosting, and control systems have opened up new opportunities for highly dilute, high-pressure combustion regimes for gasoline engines. This study analytically explores the fundamental thermodynamics of operation in these regimes under realistic burn duration, heat loss, boosting, and friction constraints. The intent is to identify the benefits of this approach and the path to achieving optimum engine and vehicle-level fuel economy. A simple engine/turbocharger model in GT-Power is used to perform a parametric study exploring the conditions for best engine efficiency. These conditions are found in the mid-dilution range, a result of the tradeoff between fluid property benefits of lean mixtures and friction benefits of higher loads. Dilution with exhaust gas is nearly as effective as air dilution when compared using a ‘fuel-to-charge’ equivalence ratio defined as Φ′≡Φ (1-RGF) where RGF is the total residual gas fraction. Optimal brake efficiencies are obtained over a range...
70 citations
TL;DR: In this paper, mass and energy exchange processes near the in-cylinder walls have become increasingly important for internal combustion engine research and development, and heat transfer and fuel-deposition processes have been investigated.
Abstract: Mass and energy exchange processes near the in-cylinder walls have become increasingly important for internal combustion engine research and development. Heat-transfer and fuel-deposition processes...
67 citations
TL;DR: In this article, the effect of biodiesel on injection processes, combustion and emission formation under diesel engine conditions remains somewhat unclear, although it has begun to penetrate the fuel market, its effect on injection process, combustion process, and emissions formation under Diesel engine conditions is discussed.
Abstract: Although biodiesel has begun to penetrate the fuel market, its effect on injection processes, combustion and emission formation under diesel engine conditions remains somewhat unclear. Typical exha...
66 citations
TL;DR: A chemical reaction mechanism has been developed for modeling the combustion process and polyaromatic hydrocarbon formation of diesel and n-heptane/toluene fuels.
Abstract: A chemical reaction mechanism has been developed for modeling the combustion process and polyaromatic hydrocarbon formation of diesel and n-heptane/toluene fuels A reduced n-heptane/polyaromatic h
58 citations
TL;DR: A common rail injection system for diesel engines has a potential to realize low emission and low fuel consumption diesel combustion The core technology of this system is accumulated on spray char as mentioned in this paper. But it is not suitable for the use of diesel fuel.
Abstract: A common rail injection system for diesel engines has a potential to realize low emission and low fuel consumption diesel combustion The core technology of this system is accumulated on spray char
54 citations
TL;DR: In this article, a generalized renormalization group closure model based on the dimensionality of the flow strain rate is proposed and applied to engine flows in a diesel engine under motoring conditions.
Abstract: A generalized renormalization group closure model based on the “dimensionality” of the flow strain rate is proposed and applied to engine flows in this study. In the model, the model coefficients C1, C2, and C3 are constructed as functions of the flow strain rate. Computations were made for compressing/expanding flows in a diesel engine under motoring conditions. It was found that the generalized renormalization group model performs better than the standard renormalization group k−e model in terms of its predictions of turbulent kinetic energy and model length scales. Computations in a diesel engine operating under low-temperature combustion conditions were also investigated to further assess the performance of the present model. Predictions of the spatial distributions of unburned hydrocarbons were significantly improved and agreed well with available experimental images. Engine-out unburned hydrocarbon emission was predicted to be smaller with the generalized renormalization group model than with the st...
50 citations
TL;DR: A large-bore, four-stroke, medium-speed, compression-ignition railway traction locomotive engine was fueled with cottonseed methyl ester (Biodiesel) as discussed by the authors.
Abstract: A large-bore, four-stroke, medium-speed, compression-ignition railway traction locomotive engine was fueled with cottonseed methyl ester (Biodiesel). The cottonseed methyl ester was stored for 6 mo...
42 citations
TL;DR: In this article, a real-size quartz optical nozzles for direct-injection spark-ignition engines were designed and developed for high-temperature applications and also compatible with new fuels such as alcohols.
Abstract: High-pressure multi-hole injectors for direct-injection spark-ignition engines have shown enhanced fuel atomisation and flexibility in fuel targeting by selection of the number and angle of the nozzle holes. The nozzle internal flow is known to influence the characteristics of spray formation; hence, understanding its mechanisms is essential for improving mixture preparation. However, currently, no data exist for fuel temperatures representative of real engine operation, especially at low-load high-temperature conditions with early injection strategies that can lead to phase change due to fuel flash-boiling upon injection. This challenge is further complicated by the predicted fuel stocks, which may include new (e.g. bio-derived) components. The physical/chemical properties of such components can differ markedly from gasoline, and it is important to have the capability to study their effects on in-nozzle flow and spray formation, taking under consideration their different chemical compatibilities with optical materials as well. The current article presents the design and development of a real-size quartz optical nozzle, 200 µm in diameter, suitable for high-temperature applications and also compatible with new fuels such as alcohols. First, the internal geometry of a typical real multi-hole injector was analysed by electron microscopy. Mass flow was measured, and relevant fluid mechanics dimensionless parameters were derived. Laser and mechanical drilling of the quartz nozzle holes were compared. Abrasive flow machining of the optical nozzles was also performed and analysed by microscopy in comparison to the real injector. Initial validation results with a high-speed camera showed successful imaging of microscopic in-nozzle flow and cavitation phenomena, coupled to downstream spray formation, under a variety of conditions including high fuel temperature flash-boiling effects. The current work used gasoline and iso-octane to provide proof-of-concept images of the optical nozzle, and future work will include testing of a range of fuels, some of which will also be bio-derived.
40 citations
TL;DR: In this article, an accelerated multi-zone model for engine cycle simulation (AMECS) of homogeneous charge compression ignition (HCCI) combustion is proposed. But the model is not suitable for use in system-level simulation software.
Abstract: We have developed an accelerated multi-zone model for engine cycle simulation (AMECS) of homogeneous charge compression ignition (HCCI) combustion. This model incorporates chemical kinetics and is intended for use in system-level simulation software. A novel methodology to capture thermal stratification in the multi-zone model is proposed. The methodology calculates thermal stratification inside the cylinder based on a single computational fluid dynamics (CFD) calculation for motored conditions. CFD results are used for tuning zone heat loss multipliers that characterize wall heat loss from each individual engine zone based on the assumption that these heat loss multipliers can then be used at operating conditions different from those used in the single CFD run because the functional form of thermal stratification is more dependent on engine geometry than on operating conditions. The model is benchmarked against detailed CFD calculations and fully coupled HCCI CFD chemical kinetics calculations. The resul...
TL;DR: In this paper, the authors discuss the advantages of engine downsizing by gasoline direct injection in combination with turbocharging to reduce fuel consumption and presents the results of experimental and numerical investigations of stratified exhaust gas recirculation in a single-cylinder gasoline engine to reduce nitrogen oxide emissions.
Abstract: The combination of gasoline direct injection and turbocharging is a promising method to reduce the fuel consumption of internal combustion engines through engine downsizing, which leads to increased engine efficiencies and a reduction of CO2 emissions at a comparable power output. Spray-guided direct injection allows overall lean and unthrottled operation, which is realized with a highly stratified mixture at part load. However, exhaust gas aftertreatment with conventional three-way catalysts is currently not possible. Furthermore, insufficient mixture preparation, especially at the upper load limit of stratified charge operation, causes increased particulate matter emissions. This paper discusses the advantages of engine downsizing, by gasoline direct injection in combination with turbocharging, to reduce fuel consumption and presents the results of experimental and numerical investigations of stratified exhaust gas recirculation in a single-cylinder gasoline engine to reduce nitrogen oxide emissions. Th...
TL;DR: In this article, the characteristics of ambient gas motion induced by a single diesel spray were measured quantitatively by using a laser-induced fluorescence-particle image velocimetry technique under non-evaporating quiescent conditions.
Abstract: The characteristics of ambient gas motion induced by a single diesel spray were measured quantitatively by using a laser-induced fluorescence-particle image velocimetry technique under non-evaporating quiescent conditions. The effects of fuel injection pressure, ambient gas density and nozzle hole diameter on the ambient gas mass flow rate into the spray through the whole spray periphery (spray side periphery and tip periphery) were investigated quantitatively according to the gas flow velocity measurements. The results show that the captured gas mass flow rate through the spray tip periphery is prominent in the whole periphery and the proportion of the gas entrainment through the spray side periphery increases with spray development. The higher injection pressure significantly enhances the total gas mass flow rate through the whole periphery; however, the increase in the ratio of ambient gas and fuel mass flow rate becomes moderate gradually with the increase in the injection pressure. The higher ambient gas density results in a slight increase in ambient gas flow velocity along the spray side periphery and the tip periphery and a reduction of the spray volume; however, the ambient gas mass flow rate was apparently enhanced. The smaller nozzle hole diameter results in a significant decrease in the ambient gas mass flow rate and an increase in the ratio of the gas and fuel mass flow rate. Numerical simulation results provide more understanding of the spray-induced gas flow field and validate the measurement accuracy of the laser-induced fluorescence-particle image velocimetry results. © IMechE 2012.
TL;DR: In this article, a control structure for combined feedback control of the air-path variables boost pressure and exhaust gas recirculation rate and of the NOx emissions is presented for improved control of diesel engines.
Abstract: Variations of engine-out emissions due to ageing, component drift or production tolerances pose serious problems to meet legislative restrictions on exhaust tailpipe pollutant emissions. This paper addresses feedback of the raw emissions for improved control of diesel engines. A discussion of issues regarding the inclusion of raw-emission feedback into the engine control structure is provided, and a novel control structure for combined feedback control of the air-path variables boost pressure and exhaust gas recirculation rate and of the NOx emissions is presented. The proposed control structure basically consists of an optimal linear output feedback controller and a setpoint-adaption loop on the exhaust gas recirculation rate. With this approach, a simple control structure is available requiring a marginal calibration effort to meet desired NOx-emission values. Unfavourable injection timing in connection with NOx control is minimized by adapting the exhaust gas recirculation rate setpoint. The performanc...
TL;DR: In this paper, high-resolution numerical simulations of cavitating flow in a 500-µm-diameter submerged nozzle using the in-house HRMFoam homogeneous relaxation model constructed from the OpenFOAM toolkit were conducted at 1 MPa inlet pressure and atmospheric outlet pressure, corresponding to a cavitation number.
Abstract: Cavitation plays an important role in the formation of sprays in fuel injection systems. With the increasing use of gasoline–ethanol blends, there is a need to understand how changes in fluid properties due to the use of these fuels can alter cavitation behavior. Gasoline–ethanol blends are azeotropic mixtures whose properties are difficult to model. We have tabulated the thermodynamic properties of gasoline–ethanol blends using a method developed for flash-boiling simulations. The properties of neat gasoline and ethanol were obtained from National Institute of Standards and Technology REFPROP data, and blends from 0% to 85% ethanol by mass have been tabulated. We have undertaken high-resolution three-dimensional numerical simulations of cavitating flow in a 500-µm-diameter submerged nozzle using the in-house HRMFoam homogeneous relaxation model constructed from the OpenFOAM toolkit. The simulations are conducted at 1 MPa inlet pressure and atmospheric outlet pressure, corresponding to a cavitation number...
TL;DR: In this article, the effect of fuel properties and fuel temperature on the behaviour of the internal nozzle flow, atomization and cyclic spray fluctuations was examined for a three-hole direct injection spark igniti...
Abstract: The effect of fuel properties and fuel temperature on the behaviour of the internal nozzle flow, atomization and cyclic spray fluctuations is examined for a three-hole direct injection spark igniti...
TL;DR: In this paper, an experimental study of the combination of low-pressure and high-pressure exhaust gas recirculation architectures has been carried out, and the results show that the low pressure configuration improves high-pressurization and results in brake-specific fuel consumption, nitrogen oxides and exhaust gas opacity; nevertheless, hydrocarbon emissions are increased, especially during the engine warm up.
Abstract: In this paper, an experimental study of the combination of low-pressure and high-pressure exhaust gas recirculation architectures has been carried out. In the first part of the paper, the effects of both high-pressure and low-pressure exhaust gas recirculation architectures on engine behaviour and performance are analysed by means of a series of steady tests. In the second part, the effects of the combination of both architectures are addressed. The results show that the low-pressure configuration improves high-pressure exhaust gas recirculation results in brake-specific fuel consumption, nitrogen oxides and exhaust gas opacity; nevertheless, hydrocarbon emissions are increased, especially during the engine warm up. In addition, the exhaust gas recirculation rate achieved with low-pressure systems is limited by the pressure difference between diesel particulate matter outlet and compressor inlet; therefore, the high-pressure system can be used to achieve the required exhaust gas recirculation levels witho...
TL;DR: In this paper, the authors simulated the flow with soot deposition using the lattice Boltzmann method and discussed the flow in a real cordierite filter, and the inner structure of the filter was scanned using a three-dimensional X-ray computed tomography technique.
Abstract: To reduce particulate matter, including soot in diesel exhaust gas, a diesel particulate filter has been developed. In the after-treatment of exhaust gas, the filter traps particulate matter when the exhaust gas passes its porous wall. An increase of particulate matter accumulation could cause technological problems due to the higher filter back-pressure. This can result in a subsequent worsening of fuel efficiency and a decrease in engine output. However, it is difficult to experimentally observe the phenomena in diesel particulate filters. In this study, we simulated the flow with soot deposition using the lattice Boltzmann method. To discuss the flow in a real cordierite filter, a tomography-assisted simulation was conducted, and the inner structure of the filter was scanned using a three-dimensional X-ray computed tomography technique. The local velocity and pressure distributions in the filter were clearly visualized. To model the soot deposition, a parameter of soot deposition probability was used. ...
TL;DR: In this paper, the authors investigated the potential of a split (50/50) main fuel-injection strategy to reduce smoke, total unburned hydrocarbons and carbon monoxide emissions at exhaust gas recirculation levels lower than those required to achieve singleinjection diesel low-temperature combustion at a medium-load, medium-speed operating condition.
Abstract: Diesel engine emissions of oxides of nitrogen and smoke can be reduced simultaneously through the use of high levels of exhaust gas recirculation to achieve low-temperature combustion. However, single fuel injection per cycle diesel low-temperature combustion is also characterized by high fuel consumption and high total unburned hydrocarbons and carbon monoxide emissions. This work focuses on investigating the potential of a split (50/50) main fuel-injection strategy to reduce smoke, total unburned hydrocarbons and carbon monoxide emissions at exhaust gas recirculation levels lower than those required to achieve single-injection diesel low-temperature combustion at a medium-load, medium-speed operating condition. Experiments were performed on a 0.51 l single-cylinder high-speed direct-injection diesel engine running at 1500 r/min at an operating condition corresponding to a gross indicated mean effective pressure of 500 kPa. At this load, exhaust gas recirculation levels of 62% are needed to realize near-...
TL;DR: In this paper, the authors present different aspects of air inlet behavior near the inducer of a radial compressor and show how the geometry can contribute to its stability and performance, in order to study the effects that elbows and abrupt changes in flow directions originate on the compressor performance.
Abstract: This paper presents different aspects of air inlet behaviour near the inducer of a radial compressor and shows how the geometry can contribute to its stability and performance. Unfortunately, the space reserved for installation of an automotive turbocharger in a vehicle is constantly being reduced, so it is necessary to study the effects that elbows and abrupt changes in flow directions originate on the compressor performance. The work presented in this paper studies the effect that different 90° elbows have on the compressor with respect to its ideal, straight, no-elbow configuration, in order to obtain the best possible elbow configuration.The methodology followed has been to, initially, study different geometries in computational fluid dynamics code in order to obtain the best possible configuration. Then, several 90° elbows were constructed and characterized on a continuous flow test bench in order to validate the computational fluid dynamics results and to obtain optimum results. The elbows were then...
TL;DR: In this paper, the effect of reduction in the sac volume of diesel fuel injectors utilised in medium/heavy-duty applications on the internal nozzle flow was demonstrated by comparison of two heavy-duty diesel engine injector nozzles that feature a large difference in sac volume size.
Abstract: Reducing the sac volume size of medium-/heavy-duty diesel engine injector nozzles can minimise the fuel dripping into the combustion chamber at the end of injection events, which has been linked to reduced engine-out emissions. This study demonstrates the effect of reduction in the sac volume of diesel fuel injectors utilised in medium-/heavy-duty applications on the internal nozzle flow. This is realised by comparison of two heavy-duty diesel nozzles that feature a large difference in sac volume size of almost three times. For visualisation purposes, the nozzles have been enlarged by six times, and replicas were manufactured from a transparent material. High-speed digital imaging was used to capture the instantaneous spatial and temporal characteristics of geometric as well as dynamic vortex cavitation structures. The investigation was conducted in a steady-state flow test rig for three different needle valve lifts. For all tested conditions, the flow behaviour was analysed at three distinct areas of the nozzle, these being the needle seat, the sac volume and the injection hole. Interpretation of experimental observations was supported by parallel computational fluid dynamics simulations of the exact conditions measured during the experiments. Post-processing of the captured images has revealed the ensemble – average cavitation location, its standard deviation and the cavitation structures life – time inside the sac volume. Results showed a significant dependency of the internal nozzle flow on the sac volume size and identified clear differences in the structure of the cavitation pockets inside the sac volume under certain operating conditions.
TL;DR: In this article, the combustion and emission characteristics of dual-fuel compound homogeneous charge compression ignition combustion were investigated and n-heptane and oxygen-containing alcohols were chosen as catalysts.
Abstract: This paper investigates the combustion and emission characteristics of dual-fuel compound homogeneous charge compression ignition combustion. n-heptane and oxygen-containing alcohols were chosen as...
TL;DR: In this article, Su and Yu showed that the interaction of mixing and chemical combustion control parameters, including fuel injection timing, injection details (such as multi-pulse injections), boost pressure, EGR and in-cylinder temperature, as regulated by the timing of intake valve closing, play a decisive role in the determination of thermal efficiency and exhaust emissions.
Abstract: The world relies heavily on internal combustion (IC) engines for transportation, commerce and power generation, and this consumes vast quantities of fuel. Thus, there is much interest in increased fuel efficiency, which has stimulated research in advanced engine combustion concepts due to their higher operating efficiencies when compared with conventional engines. In particular, low-temperature combustion (LTC) strategies, including homogeneous charge compression ignition (HCCI) and its variants, have attracted much interest, as seen, for example, in recent International Journal of Engine Research (IJER) Special Issues. In these engines, the combustion and ignition chemistry of the fuel play a crucial role. This introduces significant challenges for engine control, since the thermodynamic and chemical state of the fuel–air mixture determines the combustion phasing, rather than the fuel injection or spark timing, as in diesel and spark-ignition gasoline engines, respectively. Thus, real-world variations in intake temperature, pressure and gas composition (e.g. exhaust gas recirculation (EGR)), as seen during cold-start or engine transients, can lead to lack of engine control, and complex control systems are required. This introduces additional cost and the need for reliable sensors, such as in-cylinder pressure transducers, for feedback control. In a study of partially premixed LTC engines, Su and Yu showed that the interaction of mixing and chemical combustion control parameters, including fuel injection timing, injection details (such as multi-pulse injections), boost pressure, EGR and in-cylinder temperature, as regulated by the timing of intake valve closing, play a decisive role in the determination of thermal efficiency and exhaust emissions. The superior fuel efficiency of LTC engines is partly due to reduced heat losses. The low peak gas temperatures and locally lean mixtures in the combustion chamber also lead to low NOx and particulate emissions, but higher exhaust CO and unburned hydrocarbons. Since LTC also features low exhaust gas temperatures, this can lead to issues with emissions control, for example, when exhaust temperatures are below the light-off temperature of aftertreatment catalysts. This is an important consideration, which demands additional research in view of the evertightening emissions standards being faced by the engine industry. A further significant challenge is expanding the operating window of LTC engines, which can be limited by misfire at light load and by pressure rise rate and engine noise constraints at high load. Many approaches have been proposed, including exploiting fuel effects, as highlighted by Manente et al., who explored using low-reactivity gasoline in LTC compression ignition engines, and Xu et al., who considered using onboard fuel-reforming technologies and the application of supercharging combined with trapping of residual gases for improved fuel–air preparation. As pointed out by Nakata et al., lean boosted spark-ignition engines, fueled with high-research-octane-number (RON) fuels, are also of considerable interest, and they can exhibit thermal efficiencies comparable to those of diesel engines. In automotive applications, diesel and gasoline fuels are dominant, while in power generation applications, natural gas and, recently, biomass-derived fuels are also of interest. IC engine fuels are complex mixtures of hundreds of paraffins, aromatics, naphthenes and olefins, and even oxygenates (especially in the case of bioderived fuels). Thus, the development of chemical kinetic models that represent all these components is difficult, and such models would be too large for practical application, even if all the chemistry mechanisms and reaction rates were known. Accordingly, simplified surrogate models are often used to represent real fuels. In addition, reduced chemistry models are of interest since they can be used in engine computational fluid dynamics (CFD) computations and applied to engine design (e.g. Shi et al.). Reduced chemistry mechanisms for the primary reference fuels (PRF) n-heptane and iso-octane are commonly used to represent the ignition and combustion characteristics of diesel and gasoline fuels, respectively,
TL;DR: The challenge of continuously improving engine fuel economy and emissions has pushed the automotive industry to adopt more efficient procedures for modeling, system simulation and model-based contr... as discussed by the authors, which has led to more efficient procedure for modeling and simulation.
Abstract: The challenge of continuously improving engine fuel economy and emissions has pushed the automotive industry to adopt more efficient procedures for modeling, system simulation and model-based contr...
TL;DR: In this paper, a homogeneous charge compression ignition engine operating on multi-component reference diesel fuels is simulated using two surrogate representation methods, i.e., charge compression and charge compression simulation.
Abstract: Numerical simulations of combustion have been performed for a homogeneous charge compression ignition engine operating on multi-component reference diesel fuels. Two surrogate representation method...
TL;DR: The most useful technology to reduce particulate matter from the exhaust gas of internal combustion engines is the diesel particulate filter as discussed by the authors, which has been developed for the last few decades.
Abstract: Diesel particulate filters are the most useful technology to reduce particulate matter from the exhaust gas of internal combustion engines. Although these devices have suffered an intense developme...
TL;DR: In this paper, an experimental study on the mode transition between low-temperature combustion and conventional combustion was carried out in a light-duty diesel engine, and the characteristics of combustion mode transition with various operating meters, including rate of exhaust gas recirculation change, residual gas, exhaust gas path length, fuel infusion pressure and engine speed, were analyzed based on the in-cylinder pressure and hydrocarbon emission of each cycle.
Abstract: An experimental study on the mode transition between low-temperature combustion and conventional combustion was carried out in a light-duty diesel engine. The characteristics of combustion mode transition with various operating para- meters, including rate of exhaust gas recirculation change, residual gas, exhaust gas recirculation path length, fuel injec- tion pressure and engine speed, were analysed based on the in-cylinder pressure and hydrocarbon emission of each cycle. In the case of mode transition from low-temperature combustion to conventional combustion, rapid decreases in indicated mean effective pressure and hydrocarbon emission occurred due to the improper injection timing and the decrease of the exhaust gas recirculation rate. On the other hand, indicated mean effective pressure and hydrocarbon emission changed slowly during mode transition from conventional combustion to low-temperature combustion owing to the thermal effect of hot residual gas from conventional combustion. Faster mode transition could be achieved by the use of a shorter exhaust gas recirculation path. Although the trends of mode transition in terms of indicated mean effec- tive pressure were similar, the noise levels, as represented by the maximum pressure rise rate, and hydrocarbon emis- sions were significantly affected by residual gas, fuel injection pressure and engine speed. In addition, smooth combustion mode transition could be achieved by cycle-by-cycle injection modulation without rapid changes of indicated mean effec- tive pressure and maximum pressure rise rate.
TL;DR: In this article, the impact of post-injection strategy on emissions, combustion and lubricant dilution was investigated with a common-rail turbocharged directinjection (DI) engine.
Abstract: A 100 hour (h) engine experiment was conducted to investigate the impact of post-injection strategy on emissions, combustion and lubricant dilution with a common-rail turbocharged direct-injection ...
TL;DR: In this paper, double injection strategies with single-stage heat release and two stage heat release process of straight-run naphtha were investigated on a single-cylinder diesel engine from low to high load.
Abstract: Double injection strategies with single-stage heat release and two-stage heat release process of straight-run naphtha were investigated on a single-cylinder diesel engine from low to high load. The two-stage combustion strategy is realized by split spray and combustion events around the compression top dead center with a dominant feature of “Combust After Injection End, Inject After Combustion End” to ensure the premixed compression ignition. The single-stage combustion is realized by the “spray–spray–combustion” process with the start of combustion separated from the end of injection. The straight-run naphtha has a research octane number of 58.8, and the compression ratio and displacement of the test engine are 16.7 and 0.5 L. Double injection strategy is used to generate the single- and two-stage combustion modes with different injection timing. NOx and total hydrocarbon emissions of the two-stage combustion mode are lower than that of single heat release mode in this study, and it is much easier to pro...
TL;DR: In this article, the spectral extinction coefficients of commercial diesel were measured by means of a simple optical arrangement and the contribution of cavitation flow and temperature to the variation in spectral extinction coefficient was identified.
Abstract: Samples of commercial diesel were subjected to forty hours of intense cavitation flow across a diesel injector in a specially designed high-pressure recirculation flow rig. Changes to the optical absorption and scattering properties of the diesel over time were identified by the continuous measurement of spectral extinction coefficients at 405 nm by means of a simple optical arrangement. Identical diesel samples were maintained at 70 oC for forty hours in a heated water bath, in order to distinguish the effects of hydrodynamic cavitation and temperature on the cavitated diesel samples. The commercial diesel samples subjected to high pressure cavitation flow and water bath heating revealed a response to the flow and temperature history that was identified by an increase in the optical extinction coefficients of the cavitated and heated samples. The contribution of cavitation flow and temperature to the variation in spectral extinction coefficient was identified. It was concluded that the increases observed in the spectral extinction coefficients of the cavitated commercial diesels were caused by the cavitation affecting the aromatics in the commercial diesel samples.