Chamber Shape Research Articles

Optical and Numerical Investigation of Flame Propagation in a Heavy Duty Spark Ignited Natural Gas Engine With a Bowl-in-Piston Chamber

Abstract Increasing the natural gas (NG) use in heavy-duty engines is beneficial for reducing greenhouse-gas emissions from power generation and transportation. However, converting compression ignition (CI) engines to NG spark ignition operation can increase methane emissions without expensive aftertreatment, thereby defeating the purpose of utilizing a low carbon fuel. The widely accepted explanation for the low combustion efficiency in such retrofitted engines is the lower laminar flame speed of natural gas. In addition, diesel engine's larger bowl size compared to the traditional gasoline engines increases the flame travel length inside the chamber and extends the combustion duration. Optical measurements in this study suggested a fast-propagating flame developed even at extremely lean operation. A three-dimensional numerical simulation showed that the squish region of the bowl-in-piston chamber generated a high turbulence intensity inside the bowl. However, the flame propagation speed reduced by 55% when transiting from the bowl to the squish region, due to the large decrease in turbulence intensity inside the squish region. Moreover, the squish volume trapped an important fuel fraction, which experienced a slow and inefficient burning process during the expansion stroke. This resulted in increased methane emissions and reduced combustion efficiency. Overall, it was the specifics of the combustion inside a bowl-in-piston chamber not the methane's slow laminar flame speed that contributed to the low methane combustion efficiency for the retrofitted engine. The results suggest that optimizing the chamber shape is paramount to boost engine efficiency and decrease its emissions.

Implementation of various bowl designs in an HPDI natural gas engine focused on performance and pollutant emissions.

The air-fuel mixture preparation in pilot spray-ignited natural gas engines is primarily dominated by piston bowl profiles and fuel injection strategy. Piston bowl geometry is regarded as the crucial point in controlling engine pollutant emissions. In the present work, the SAGE combustion model was applied coupled with a general reaction kinetic mechanism. The engine model was validated with experimental data achieved from a Cummins ISX 400 engine, and good agreement between predicted and measured in-cylinder pressure and heat release rate was obtained. The influence of various piston bowl designs, including Mexican-hat geometry, double-lip geometry, bow geometry, and toroidal geometry, on the combustion process, engine performance, and pollutant emissions of a high-pressure direct-injection natural gas engine have been studied and analyzed numerically. The present study confirms the benefit of the piston bowl design as a beneficial tool to enhance the performance and pollutant emissions of the pilot diesel-ignited natural gas engine. Results showed that different chamber shapes slightly influence the combustion initiation, and the difference in in-cylinder pressure presents noticeable as the combustion continues. A higher turbulent kinetic energy improves the flow movement and facilitates the mixture formation in the cylinder. However, the combustion behavior is unwished caused by the improper injection angle of natural gas. Increasing the recess depth of combustion chambers reduces NOx formations at the price of sacrificing fuel economy. For the bow combustion chamber design, the NOx emission declined by 31.1%, while the indicated specific fuel consumption increased by 5.5% compared with the original engine. Although the indicated mean effective pressure and specific fuel consumption of the optimal double-lip geometry almost remain the same, NOx emissions can be reduced by 16.7% compared with the base design.

Optimization of microfluidic functionalization of a plasmonic-based device for selective capture of anti-folic acid in solution

Recent advances in nanoscience and nanotechnology have led to the development of ultrasensitive plasmonic substrates with a theoretical limit of detection of a single molecule. However, the use of such devices in clinical practice and medicine is still hampered by their low selectivity and poor specificity. Even with the support of statistical data analysis methods, identifying specific biomarkers among hundreds of antagonists using an inherently label-free technology is still challenging. Here we develop a microfluidic device to optimize functionalization of the plasmonic substrate with a cysteine-folic acid complex for selective capture of anti-folic acid in solution. Since the latter is expressed by tumor cells, the device can potentially be used to detect and isolate circulating tumor cells from liquid biopsy samples. The plasmonic substrate is a 2D array of gold nanoparticle clusters fabricated by optical lithography and electrolytic deposition techniques. The system combines the sensitivity of a plasmonic substrate with the selectivity of a ligand recognition scheme to achieve identification of specific biomarkers in complex, low-abundance mixtures. The shape of the microfluidic chamber and the flow rate to be used were designed to functionalize the plasmonic substrate and to deliver biological solutions to the active sites of the device in an optimized and uniform manner. Fluorescence and SERS measurements were conducted on the functionalized samples. The results confirmed good and uniform immobilization and colocalization of receptors on plasmonic structures, enabling effective recognition of the target molecule.

Research on Anatomy of the Pulp Chamber Floor of the Maxillary Second Permanent Molar in CBCT

Objective: The objective of this study was to examine the pulp chamber floor anatomy of the maxillary second permanent molar in Chinese individuals by using Cone-Beam Computed Tomography (CBCT). These data may facilitate endodontic treatment success. Methodology: A total of 2505 CBCT images of maxillary second permanent molars were studied to evaluate the shape of the pulp chamber floor, the types of developmental root fusion lines (DRFLs), the number of canal orifices and their possible relationships. Results: Three pulp chamber floor shapes were identified: triangular (50.3%), rhomboid (34.3%) and oval (15.4%). The shape of the DRFLs and the number of canal orifices on the pulp chamber floor were variable. The frequency of non branching DRFLs was 63.8%, followed by branching DRFLs (33.6%). The I-shaped DRFL group had more variations in the number and location of canal orifices. Conclusion: The anatomy of the pulp chamber floor of the maxillary second permanent molar in Chinese individuals is diverse. Knowledge of variations in pulp chamber shape, types of DRFLs and canal orifice number of the maxillary second permanent molar can help reduce the risk of missing root canals in endodontic treatment.

An Exponential Solvent Chamber Geometry for Modeling the VAPEX Process

Accurate simulation of the VAPEX process relies heavily on precise modeling of the solvent chamber propagation. In the previously developed models, the solvent chamber possesses either a linear, circular, or parabolic shape. In this study, an exponential solvent chamber model was considered to represent the propagation of the chamber throughout the spreading and falling stages of the VAPEX process. The tuning parameters of the proposed model include the exponential function coefficient and the transition region thickness. These parameters are altered by employing a MATLAB-based Genetic Algorithm (GA) to minimize the error between determined and measured cumulative produced oil in four experimental case studies presented in the literature. According to the outcomes, the proposed method can accurately adjust the cumulative produced oil to the measured values in both spreading and falling stages. Additionally, the thickness of the transition region obtained by this model is in reasonable agreement with the laboratory measurements. Accordingly, the average relative errors of all four cases for cumulative produced oil and transition region thickness are 7.73% and 5.12%, respectively. Consequently, the model estimates the oil production rate with reasonable precision and the predicted solvent chamber shapes are well-aligned with the experimentally observed chambers.

Advanced efficiency improvement of a sloping wall oscillating water column via a novel streamlined chamber design

Despite the huge potential of ocean waves as an alternative renewable energy resource, very low wave to wire efficiency of wave energy converters (WECs) hampers its commercialization. In this study, a novel streamlined chamber design has been proposed for performance improvement of an oscillating water column (OWC) with a sloping wall. Physical experiments are carried out for the calculation of capture width ratio (CWR) as a measure of hydrodynamic performance for various levels of PTO damping and sea conditions. The results are compared with those of a classical OWC chamber design. It is found that streamlined chamber design has an important bearing on OWC efficiency. As opposed to classical chamber shape, proposed streamlined chamber geometry increases the OWC performance as much as 31% for the incident waves under which the OWC operates efficiently. Further, results show that optimal level of PTO damping that for utmost energy extraction depends on the chamber design. Streamlined chamber geometry even further improves the OWC efficiency even when dominant sloshing water column motion is present in the chamber with a maximum and average value of 54% and 44%, respectively, however, chamber design has no influence on the mechanism that generates sloshing phenomenon in the chamber.

Mixing performance of the induced charge electro-osmosis micromixer with conductive chamber edges for viscoelastic fluid

Enhancing the micro-channel flow mixing is always a difficult problem. In this study, a micromixer based on induced charge electro-osmosis is proposed. A T-shaped micromixer, which has a chamber with conductive surfaces in the channel, is chosen. Due to the electro-osmotic effect of the induced charge, the induced potential is generated on the conductive surface. The Oldroyd-B constitutive model is chosen to characterize the flow characteristics of polyacrylamide solution, and an open-source solver named rheoTool based on the finite-volume method is used. The effect of the chamber shape, the chamber size, the conductive edge numbers in the chamber, and the applied electric intensity on the mixing efficiency are investigated. The results show that the micromixer with conductive edges in the chamber has better mixing effect because of the vortices. At the same time, compared with other shapes, the micromixer with diamond chamber has the best mixing effect, and the mixing efficiency reaches 79.51%. In addition, the mixing efficiency of one conductive edge in the diamond chamber is 4.39% higher than that of the two conductive edges chamber. It is found that increasing the chamber size will improve the mixing efficiency, and the mixing efficiency increased by 12.76% with the increase in chamber size. On the other hand, when increasing the electric field intensity from 100 to 200 V/cm, the mixing efficiency will decrease.

Simulation of cooling in a magma chamber: Implications for geothermal fields of southern Peru

Numerical simulations of a geothermal reservoir often assume that the primary heat source is a magmatic system; however, heat from the host rock and the coupled complex transport phenomena between magma chamber and host rock also need to be considered. This research numerically simulated the cooling history of an enclosed magma chamber and the thermal effects on the host rock around it from which geothermal energy could be extracted. Modeling of the magma body included natural convection, the effect of latent heat of phase change when the crystals are being formed between the liquidus temperature and the solidus temperature, and heat conduction when the temperature is below the solidus temperature. This study takes as an example a geothermal reservoir in southern Peru (Western Cordillera) whose heat source is a rhyolitic magma chamber like those that gave rise to the intrusive rocks of the Peru coastal cordillera. This analysis varies the chamber shape and uses three solidification temperature ranges for convection and conduction models above the rock formation temperature (solidus) to study the implications for heating of the host rock. This is the first study of its kind in this area. The center of an average-sized magma chambers takes approximately 500 ka to cool from 800 °C to 300 °C. Simulated cooling times between intrusion and solidus temperatures decreased 3 ka when convection was modeled along with conduction cooling. Cooling times decreased by up to 6 ka when the solidification temperature range was increased. The host rock temperature pattern depends strongly on the stage at which the magma chamber is modeled to begin cooling. The temperatures results near the surface of the host rock obtained in this work match well with measurements at hot springs founded in several places in the Western Cordillera. Application of the methodology proposed in this study can reduce uncertainties in planning geothermal energy extraction wells. The accuracy of the numerical model described here could be improved by including more ground data from exploration wells, e.g., soil stratigraphy and temperatures variation with depth.

Reexamination of a Permian Tentaculites-Like Fossil Iwakiella ichiroi Hatai, Kotaka and Noda, 1972, as an Orthocerid Cephalopod

The holotype of Iwakiella ichiroi Hatai, Kotaka and Noda, 1972, from the Permian Kashiwadaira Member of Northeast Japan is reexamined. Although previously placed within the Tentaculitoidea or retained in the Problematica, the possession of the septum and the spherical shape of the initial chamber suggest that this specimen belongs to sphaerorthoceratid orthocerid of the Cephalopoda. The present result confirms that the Tentaculitoidea probably became extinct near the Carboniferous – Permian boundary with Hidagaienites arcuatus Niko, 2000, as the latest representative.

An analytical study of spatial resolution enhancement for a dual-frequency acoustic beamformer

In this paper, we address an acoustic directed-self-assembly (DSA) problem for aiming to pattern particles based on creating an appropriate acoustic field by the fine adjustment of transducer operating parameters. The proposed idea is to incorporate the DSA problem with multi-frequency beamforming techniques. First, the boundary element method (BEM) is implemented for the direct modeling of the proposed DSA problem. Then, it is integrated with the concept of dual-frequency beamforming. In this study, the influence of changing excitation frequency is investigated on the spatial resolution enhancement of the pressure field. Also, the optimal frequency difference is calculated theoretically to produce two adjacent pressure traps with maximum separability and, therefore, maximum spatial resolution in a two-frequency acoustic beamformer without any restriction on the chamber shape. The performance of the proposed Dual-Frequency Beamforming (DFB) method is evaluated by simulations based on the finite element method (FEM) and compared with conventional Delay-And-Sum (DAS), Eigen Vector-Based (EigVec-based), and Bessel Beam techniques. Several evaluation metrics such as Full Width at Half Maximum (FWHM), Peak Side-lobe Level (PSL), Contrast Ratio (CR), Positioning Accuracy (PA), and processing time are considered for comparisons. Simulation results indicate the superiority of the proposed DFB method over the mentioned methods in separability and focusing precision when the two pressure traps are close to each other.

Taxonomy and palaeoenvironmental distribution of palaeopascichnids

AbstractPalaeopascichnida is a problematic group of extinct organisms that is globally distributed in Ediacaran sequences of Avalonia, Baltica, Siberia, South China and Australia. The fossils related to Palaeopascichnida consist of serially or cluster-like arranged, millimetre- to centimetre-scale globular or allantoid chambers, which are characterized by substantial differences in preservation, leading to no consistent diagnosis for these organisms. Here we integrate morphometric variation, stratigraphic distribution and habitat settings of more than 1200 specimens from all known fossil localities. The results of the morphological analysis demonstrate variation in chamber shape and size, and allow us to recognize six valid species within the group. Statistical analysis of the specimen distribution with respect to sedimentary environments indicates a significant difference in palaeoecological settings between species, making a significant contribution to the evolution and systematic palaeontology of these problematic organisms and perspective on their use in Neoproterozoic biostratigraphy. Our revision and systematic study sheds new light on one of the least studied groups of the late Ediacaran biota.

RETRACTED: Effect of combined air cooling and nano enhanced phase change materials on thermal management of lithium-ion batteries

The thermal management of a lithium-ion battery (LINB) cell in three dimensions was described in this study. For the thermal control of the LINB, two strategies were used: active and passive. For the passive heat management approach, phase change material (PCM) was employed. The LINB was put in a PCM-filled chamber. Two circular and oval chambers were placed around the LINB. In order to actively manage the heat, the LINB was thermally managed by placing the chamber and the LINB in an air duct. By changing the inlet air flow rate 0.1 cm/s to 0.4 cm/s, the temperature of the LINB, the amount of heat transfer coefficient (CHTR) and the volume fraction (VLF) of the PCM were investigated at different times (0 to 5000 s) for the two chamber shapes. Finite element method and COMSOL software were used for simulation. The results of this study showed that increasing the inlet air flow rate increases the CHTR of the LINB. Also, increasing the air speed caused the VLF of PCM to decrease. Over time, the CHTR increases and also over time, the LINB temperature increases. The hexagonal chamber resulted in a higher quantity of molten PCM than the circular chamber, particularly at t = 1200 s. • 3D investigation of the thermal management of a lithium-ion battery • Utilizing active and passive strategies in the investigation • Putting the battery in a PCM-filled chamber with two different shapes in passive strategy • Obtaining temperature, CHTR and VLF of the PCM in different inlet air flow rate

Effect of injector nozzle parameters on fuel consumption and soot emission of two-cylinder diesel engine for vehicle

In this paper, a bench test of a two-cylinder diesel engine with high-pressure common rail direct injection (CRDI) system for the external characteristics was carried out. The shape of combustion chamber was determined by comparing the fuel economy and soot emission of diesel engines. Based on this result, the effects of different nozzle parameters attempted at reducing brake specific fuel consumption (BSFC) and smoke were investigated. The experimental results show that the improved combustion chamber with a high central convex platform can significantly reduce BSFC and it has little impact on smoke. The appropriate decrease of the nozzle tip penetration (NTP) as well as increase of nozzle-hole diameter contribute to reducing fuel consumption and soot emission. The BSFC at the spray angle of 156° is reduced by 16% at the engine speed of 4000 r/min compared with that at the spray angle of 150°. Comparative results on fuel consumption and smoke emission at all engine speeds reveal that the injector with 153° spray angle, 1.8 mm NTP, 6 injection holes and 0.12 mm nozzle-hole diameter is a better choice of the two-cylinder diesel engine.

Effects of Combustion Chamber Shapes on Combustion and Emission Characteristics for the N-Octanol Fueled Compression Ignition Engine

Effects of Combustion Chamber Shapes on Combustion and Emission Characteristics for the N-Octanol Fueled Compression Ignition Engine

Experimental investigation on the recovery performance and steam chamber expansion of multi-lateral well SAGD process

Multi-lateral well SAGD process is a newly proposed recovery process in recent years, in which a multi-lateral well is applied to replace the horizontal well in classic SAGD process. In this paper, a three-dimensional physical model is applied to simulate the recovery performance of multi-lateral well SAGD process in heavy oil reservoirs. First, on the basis of Pujol-Boberg similarity criterion, the Forchheimer's law is introduced to deal with the similarity of model permeability in 3D experiment. Thus, from the actual properties of Long Lake heavy oil reservoir, the lab scale experimental parameters are obtained. Then, by using a multi-lateral wellbore model, four scaled 3D SAGD experiments are performed, including one conventional dual horizontal well SAGD experiment (base case) and three multi-lateral well based SAGD experiments. From the experimental observation, the advantages of multi-lateral well are discussed from liquid production and steam chamber expansion. Finally, by the collected images, the distribution of residual oil saturation after SAGD process is also discussed. Results indicate that the introduction of Forchheimer's law can effectively handle with the problem of kinetic similarity damage caused by high permeability during a 3D experiment. Compared with the conventional dual horizontal well SAGD process, the application of multi-lateral well can increase the oil recovery factor by above 15%. To some extent, the application of multi-lateral well can increase the duration time of plateau stage or wind down stage. Simultaneously, compared with the single application of multi-lateral well in SAGD well pair, a dual multi-lateral well SAGD process has a higher expansion rate of steam chamber and a shorter recovery time. For steam chamber, under the dragging mechanism of branch wellbore, the shape of steam chamber is a “inverted trapezoid” shape instead of the “inverted triangle” shape for conventional dual horizontal well configuration. Under the effect of branch wellbore, steam chamber can effectively reach to the reservoir boundary and increase the volume of steam chamber. The residual oil saturation mainly distributed around the reservoir boundary, which is far from the main wellbore and branch wellbore. This paper further clarifies the EOR mechanisms and steam chamber expansion rules of multi-lateral well SAGD process.

Geometric Model and Numerical Study of Aqueous Humor Hydrodynamics in the Human Eye.

The flow of aqueous humor (AH) in the human eye plays a key role in the process of transporting nutrients to the intraocular tissues and maintaining normal intraocular pressure. The pathogenesis of many ophthalmic diseases is also closely related to the flow of AH. Therefore, it is of great significance to study the mechanism of AH dynamics in the human eye. In this paper, we used image processing technology to denoise and segment the anterior segment optical coherence tomography (AS-OCT) images and established a geometric model based on the human eye. At the same time, a model of AH dynamics in the human eye based on the lattice Boltzmann (LB) method was proposed. Then, we simulated the AH flow in the human eye with different morphological structures and different physical properties and analyzed the factors that affect the AH flow, including the shape of anterior chamber (AC), the crypts of iris, the indentation of cornea, the permeability of trabecular meshwork (TM), the secretion rate of AH, and the viscosity of AH. The results showed that the changes in eye tissue morphological structures and physical properties would affect the flow of AH. For example, the maximum velocity of AH flow decreases with the increases in cornea deformation. When the distance of cornea indentation changes from 0.3 mm to 0.5 mm, the maximum velocity of AH reduces by 17%. In the asymmetrical AC, the AH will form two different vortices. In the crypts of the iris, we found that the AH flow forms small vortices, a phenomenon that has not been reported in other papers. In addition, we found that the intraocular pressure (IOP) decreases with the increase of the TM permeability and increases with the increase of the AH secretion rate, and it is not sensitive to changes in the viscosity of AH.

Thermal Stress Simulation and Structure Failure Analyses of Nitrogen–Oxygen Sensors under a Gradual Temperature Field

Nitrogen–oxygen sensors are pivotal for NOX emission detection, and they have been designed as key components in vehicles’ exhaust systems. However, severe thermal stress concentrations during thermal cycling in the sensors create knotty structural damage issues, which are inevitable during the frequent start–stop events of the vehicles. Herein, to illustrate the effect of thermal concentration on a sensor’s structure, we simulated the temperature and stress field of a sensor through finite element analysis. The failure modes of the sensor based on the multilayer structure model were analyzed. Our simulation indicated that the thermal deformation and stress of the sensors increased significantly when the heating temperature in the sensors increased from 200 to 800 °C. High stress regions were located at the joint between the layers and the right angle of the air chamber. These results are consistent with the sensor failure locations that were observed by SEM, and the sensor’s failures mainly manifested in the form of cracks and delamination. The results suggest that both the multilayer interfaces and the shape of the air chamber could be optimized to reduce the thermal stress concentrations of the sensors. It is beneficial to improve the reliability of the sensor under thermal cycling operation.

Spark ignition timing effects on a converted diesel engine using natural gas: A numerical study

Since it is not expected to switch to fully electric and/or fuel cell vehicles in the near future, the search for alternative fuels for systems using internal combustion engines has accelerated. At the forefront of these studies is the use of natural gas instead of diesel fuel in on-road, off-road vehicles, or stationary power generation plants. Diesel engines with their special combustion chamber (i.e. bowl in-piston) can be converted to run entirely on natural gas by installing a natural gas fuel injector on the intake manifold and a spark plug instead of a diesel fuel injector. In this study, in-cylinder combustion characteristics, performance, and emission values for different Spark Ignition Time (SIT) of natural gas usage at 2300 rpm and full load in a tractor engine with a compression ratio of 17.5:1 were investigated numerically using ANSYS Forte three-dimensional analysis program. G-equation combustion model, RANS k-ε turbulence model, and methane chemical kinetic mechanism representing natural gas consisting of 29 species and 171 equations (a reduced mechanism) were used. First SIT was accepted as a 719.5 Crank Angle Degree (CAD) which is diesel injection start time. As a result, due to the special shape of the combustion chamber of diesel engines (re-entrant bowl in-piston), it was seen that the flame was faster and thicker in the bowl, while it was slower and thinner in the squish zone. With the advanced of SIT, the in-cylinder pressure ratio increased. By taking SIT too advanced (i.e. 690, 695, and 700 CAD SIT), more than one peak formation was observed in the heat release graph depending on the combustion characteristic. With the effect of both natural gas use and SIT, it was observed that HC and CO formations were almost not seen, while NOX formation remains above a certain level.

Analysis of the construction of nodes of a water pipeline network and modeling of planned overall dimensions of its working chambers

While designing water supply networks, an important task consists in establishing the place necessary for an installation of water supply wells along with water supply units located in them, in aim to determine the number of structural elements in the composition of individual pipelines of this water supply network. It has been proposed to apply a methodology for predictive calculation of a number of structural elements of the water supply pipeline system by indirect signs. An improvement of this technique was carried out by systematising the structural elements into simple and complex ones, with the determination of an indicator of the structural device for each of them. In order to analyse the role of each structural element of the same type, belonging to an assembly consisting of a linear part of a pipeline and nodes, a concept of coefficient of constructiveness was introduced. Analytical and graphical dependencies for predicting the value of the coefficient of constructiveness have been obtained. For typical (simple) nodes, the minimum value of the coefficient of constructiveness is 1.3 and maximum value is 2.54. The largest value of the coefficient of constructiveness for a conventional (complex) node is 1.45, the minimum value is 1.13. Recommendations have been given for assessment of the complexity of the installation of water supply units in practice in the design of new and reconstruction of existing water supply networks. For the above water supply units, working chambers of a round shape are recommended, which makes it possible in practice to reduce the overall planned dimensions of a water well in comparison with a rectangular shape of the same chamber.

Effect of double-layer hole nozzle with narrow spray angle on combustion and emissions in dual-fuel natural gas engine

Diesel injection plays a significant role in the mixing process of dual-fuel engine. The diesel nozzle is an important interaction between the injection system and the combustion chamber that deserves more investigation. To fully assess the effect of a diesel nozzle on combustion and emissions in a dual-fuel engine, and to avoid the diesel impingement on the wall and lubricant dilution with early injection strategy, a diesel nozzle with double-layer hole and a narrow spray angle was designed to enhance the air utilization of the central part of the pre-mixture natural gas, matching combustion with an open chamber shape. Comparison of the high dispersion nozzle with a narrow spray angle and a traditional nozzle on combustion was performed in a six-cylinder dual-fuel engine with a low compression ratio. The results showed that the narrow spray angle nozzle is beneficial at low load with earlier pilot injection, but the original nozzle achieves higher thermal efficiency than that of the narrow spray angle nozzle with the same injection strategy in high load conditions. The main cause remains that the narrow spray angle nozzle has a relatively small hole diameter and short spray penetration due to higher charge density at high load. The flame propagation ignited a natural gas mixture near the cylinder wall, resulting in a slower combustion process and a smoother heat release curve. With a relatively moderate combustion process and considerably earlier injection timing, a narrow spray angle nozzle will reduce rough combustion concerns at high load.