bluuebunny/crossref_metadata_2025_split huggingface dataset:
In-Cylinder Flow Correlations Between Steady Flow Bench and Motored Engine Using Computational Fluid Dynamics
Authors: Yang Xiaofeng , Kuo Tang-Wei , Guralp Orgun , Grover Ronald O. , Najt Paul 
Published: December 2016

Intake port flow performance plays a substantial role in determining the volumetric efficiency and in-cylinder charge motion of a spark-ignited engine. Steady-state flow bench and motored engine flow CFD simulations were carried out to bridge these two approaches for the evaluation of port flow and charge motion (such as discharge coefficient, swirl/tumble ratios). A one dimensional block analytical model was used to mimic the downstream honeycomb in a flow bench experiment, which forced the flow motion in one direction. The intake port polar velocity profile and polar physical clearance profile were generated to evaluate the port performance based on local flow velocity and physical clearance in the valve-seat region. The measured data were taken from standard steady-state flow bench tests of an intake port.
When using an appropriate mesh resolution near the walls, the steady-state flow bench simulation predicted that discharge coefficient and swirl/tumble index are in agreement with the measured data. It was reconfirmed that the predicted discharge coefficients and swirl/tumble index of steady flow bench simulations have a good correlation with those of motored engine flow simulations. The polar velocity inhomogeneity factor correlates well with the port discharge coefficient, swirl/tumble index. A port performance evaluation guideline was generated by taking advantage of steady flow bench and motored engine flow simulations and port polar velocity inhomogeneity factor.
Impact of Intake Induced Swirl on Combustion and Emissions on a Single Cylinder Diesel Engine
Authors: Barrientos Eduardo , Bortel Ivan , Takats Michal , Vavra Jiri 
Published: December 2016

Engine induced swirl improves mixing of fuel and air and at optimal values accelerates burn, improves the combustion stability and can decrease particulate matter (PM). However, swirl increases convective heat loss and cylinder charge loss and could increase nitrogen oxides (NOx) emissions. High intensity of swirl could impede flame development and increases emissions of total hydrocarbons (THC) and carbon monoxide (CO). Therefore, careful and smart selection of optimal swirl values is paramount in order to obtain beneficial impact on combustion and emissions performance.
This study is conducted on a 0.5L single cylinder research engine with common rail (CR) diesel injection system, with parameters corresponding to modern engines of passenger cars. The engine has three separate ports in the cylinder head. The change of swirl ratio is defined by closing appropriate ports. There are three levels of swirl ratio under study — 1.7, 2.9 and 4.5, corresponding to low, medium and high swirl levels respectively.
This study highlights the influence of intake induced swirl on combustion parameters and emissions. Assessed combustion parameters are, among others, heat release rate, cylinder pressure rise and indicated mean effective pressure. Assessed emissions are standard gaseous emissions and smoke, with emphasis on PM emissions. An engine speed of 1500 rpm was selected, which well represents common driving conditions of this engine size. Various common rail pressures are used at ambient inlet manifold pressure (without boost pressure) and at 1 bar boosted pressure mode. It is found that when the swirl level is increased, the faster heat release during the premixed combustion and during early diffusion-controlled combustion causes a quick increase in both in-cylinder pressure and temperature, thus promoting the formation of NOx. However, since swirl enhances mixing and potentially produces a leaning effect, PM formation is reduced in general. However, maximum peak temperature is lower for high swirl ratio and boosted modes due to the increase of heat transfer into cylinder walls. Furthermore, it is necessary to find optimal values of common rail pressures and swirl ratio. Too much mixing allows increase on PM, THC and CO emissions without decrease on NOx emissions in general. Common rail injection system provides enough energy to achieve good mixing during all the injection time in the cases of supercharged modes and high common rail pressure modes. Positive influence of swirl ratio is found at lower boost pressures, lower revolution levels and at lower engine loads. The results obtained here help providing a better understanding on the swirl effects on diesel engine combustion and exhaust emissions over a range of engine operating conditions, with the ultimate goal of finding optimal values of swirl operation.
Lubricant Flow Optimization of Large Two Stroke Marine Diesel Engine Piston Ring Packs
Authors: Stark Matthias , Mittler Richard 
Published: December 2016

Approaching a characterization of different contributors to the lube oil balance of an engine becomes important when aiming at enhancing lubrication performance and reducing its contribution to exhaust gas emissions. It is essential to quantify relevant data helping to determine lubrication losses related to particular tribosystem components. Recent activities focused on rating distinct tribosystem component effects on their contribution to total lube oil consumption and the possibility to most effectively modify those.
This paper thus describes the most effective tribosystem component modifications, consisting of the application of a substantially modified piston ring pack and the introduction of lube oil accumulating grooves in order to considerably enhance lubrication performance.
A proper prediction of piston ring pack dynamics and tribodynamic effects on the lube oil film is essential to design a superior piston ring pack in terms of an optimized piston running behaviour and lube oil transportation. One major step designing such a ring pack is based on the consequent application of a novel 3D piston ring pack simulation tool to enhance lube oil transportation characteristics and distribution.
Lube oil accumulating grooves are introduced to reduce lubrication losses due to so called ring pack spray. The ring pack spray is a result of accumulated lubricant in the pressurized piston ring pack expanding into the scavenge air receiver during the scavenging phase. Mentioned effect was analysed in detail in order to determine the amount of related lubricant losses. Investigations in this context lead to the application of lube oil accumulating grooves and hence can be considered an important design aspect to reduce total lube oil consumption.
Tribosystem performance validation was performed on the basis of the application of an SO2 tracing technology on a full scale engine test in order to determine relevant tribosystem component modifications in real time. The sulphur content of fuel and lube oil considerably influences the formation of particulate matter in the exhaust gas, following chemical reactions of sulphur oxidation. Hence detecting SO2 in the exhaust gas is a direct measure to determine the amount of lubricant in the exhaust gas composition.
Finally this report demonstrates measurement results describing the superior performance of the modified tribosystem.
Effect of Fuel Reactivity on Ignitability and Combustion Phasing in a Heavy-Duty Engine Simulation for Mixing-Controlled and Partially-Premixed Combustion
Authors: Voice Alexander K. , Kumar Praveen , Zhang Yu 
Published: December 2016

Light-end fuels have recently garnered interest as potential fuel for advanced compression ignition engines. This next generation of engines, which aim to combine the high efficiency of diesel engines with the relative simplicity of gasoline engines, may allow engine manufacturers to continue improving efficiency and reducing emissions without a large increase in engine and aftertreatment system complexity.
In this work, a 1-D heavy-duty engine model was validated with measured data and then used to generate boundary conditions for the detailed chemical kinetic simulation corresponding to various combustion modes and operating points. Using these boundary conditions, homogeneous simulations were conducted for 242 fuels with research octane number (RON) from 40 to 100 and sensitivity (S) from 0 to 12.
Combustion phasing (CA50) was most dependent on RON and less dependent on S under all conditions. Both RON and S had a greater effect on combustion phasing under partially-premixed compression ignition (PPCI) conditions (19.3°) than under mixing-controlled combustion (MCC) conditions (5.8°). The effect of RON and S were also greatest for the lowest reactivity (RON&gt;90) fuels and under low-load conditions. The results for CA50 reflect the relative ignition delay for the various fuels at the start-of-injection (SOI) temperature. At higher SOI temperatures (&gt;950K), CA50 was found to be less dependent on fuel sensitivity due to the convergence of ignition delay behavior of different fuels in the high-temperature region.
Combustion of light-end fuels in CI engines can be an important opportunity for regulators, consumers and engine-makers alike. However, selection of the right fuel specifications will be critical in development of the combustion strategy. This work therefore provides a first look at quantifying the effect of light-end fuel chemistry on advanced CI engine combustion across the entire light-end fuel reactivity space, and provides a comparison of the trends for different combustion modes.
Impact of a Yttria-Stabilized Zirconia Thermal Barrier Coating on HCCI Engine Combustion, Emissions, and Efficiency
Authors: Powell Tommy , O’Donnell Ryan , Hoffman Mark , Filipi Zoran 
Published: December 2016

In-cylinder surface temperature has significant impacts on the thermo-kinetics governing the Homogeneous Charge Compression Ignition (HCCI) process. Thermal Barrier Coatings (TBCs) enable selective manipulation of combustion chamber surface temperature profiles throughout a fired cycle. In this way, TBCs enable a dynamic surface temperature swing, which prevents charge heating during intake while minimizing heat rejection during combustion. This preserves volumetric efficiency while fostering more complete combustion and reducing emissions.
This study investigates the effect of a Yttria-Stabilized Zirconia (YSZ) coating on Low Temperature Combustion (LTC) engine combustion, efficiency, and emissions. This is an initial step in a systematic effort to engineer coatings best suited for LTC concepts. A YSZ coating was applied to the top of the aluminum piston using a powder Air Plasma Spray process, Final thickness of the coatings was approximately 150 microns. The coated piston was subsequently evaluated in the single-cylinder HCCI engine with exhaust re-induction.
Engine tests indicated significant advancement of the autoignition point and reduced combustion durations with the YSZ coating. Hydrocarbon and carbon monoxide emissions were reduced, thereby increasing combustion efficiency. The combination of higher combustion efficiency and decreased heat loss during combustion produced tangible improvements in thermal efficiency. When the effects of combustion advance were removed, the overall improvements in emissions and efficiency were lower, but still significant. Overall, the results encourage continued efforts to devise novel coatings for LTC.
Investigation of RCCI Characteristics of Combustion and Emissions With PFI of N-Butanol and Direct Injection of High Linoleic Content Biodiesel
Authors: Soloiu Valentin , Naes Tyler , Muiños Martin , Rivero-Castillo Alejandro , Harp Spencer 
Published: December 2016

This study investigated the RCCI (Reactivity Controlled Compression Ignition) of PFI (Port Fuel Injection) of n-butanol with direct injection (DI) of a high linoleic acid content biodiesel, cottonseed (CS100). The experimental omnivorous-fuel engine was operated at 1400 rpm and 6 bar indicated mean effective pressure (IMEP) with 20% cooled EGR. The mass ratio of n-butanol injected comprised of 50% of the total fuel mass.
The dual fueling strategy of RCCI changed the conventional diesel combustion (CDC) apparent heat release profile. With the new fueling strategy the heat release was split into two regions of high temperature heat release when using CS100. The first occurred before top dead center (BTDC) from the high reactivity fuel and the second peak occurred due to the combustion of the low reactivity fuel (n-butanol) after top dead center (ATDC). ULSD did not produce this same split in heat release due to the longer ignition delay.
The ignition delay for CS100 was shortened by 0.15 ms when compared to ULSD because of the high palmitic acid content in the biodiesel. The RCCI process itself extended the ignition delay about 0.17 ms (about 1.4 CAD) suggesting the possibility of controlling combustion phasing for both RCCI fueling strategies of ULSD and CS100. The CA50 occurred similarly at 10° ATDC for ULSD and CS100 however, RCCI shifted the CA50’s (7° and 8° ATDC for CS100 and ULSD respectively). Soot emissions exhibited a decrease with the PFI of n-butanol because of the highly oxygenated nature of the fuel by 80%. In summary, RCCI stratification using n-Butanol as the low reactivity fuel significantly reduced soot emissions when using either a high linoleic acid content biofuel or ULSD while also suggesting control over combustion phasing.
Effect of Fuelling Control Parameters on Combustion Characteristics of Diesel-Ignited Natural Gas Dual-Fuel Combustion in an Optical Engine
Authors: Khosravi Mahdiar , Rochussen Jeremy , Yeo Jeff , Kirchen Patrick , McTaggart-Cowan Gordon , Wu Ning 
Published: December 2016

Its inherent economic and environmental advantages as an internal combustion engine fuel make natural gas (NG) an attractive alternative to diesel fuel as the primary energy source for some compression ignition (CI) engine applications. Diesel pilot-ignition of NG is an attractive fueling strategy as it typically requires minimal modification of existing CI engines. Furthermore, this strategy makes use of the highly developed direct injection (DI) diesel fuel systems already employed on modern CI engines for to control dual-fuel (DF) combustion. Despite the increasing popularity of the dual-fuel NG engine concept, the fundamental understanding of the fuel conversion mechanisms and the impact of the fueling parameters is still incomplete. A conceptual understanding of the relevant physics is necessary for further development of fueling and pilot-ignition strategies to address the shortcomings of dual-fuel combustion, such as low-load emissions and combustion stability.
An experimental facility supporting optical diagnostics via a Bowditch piston arrangement in a 2-litre, single-cylinder research engine (Ricardo Proteus) was used in this study to consider the effect of fueling parameters on the fuel conversion process in a dual fuel engine. Fueling was achieved with port injected CH4 and diesel direct injection using a common rail system. Simultaneous, high-speed natural luminosity (NL) and OH* chemiluminescence imaging was used to characterize dual-fuel combustion and the influence of pilot injection pressure (300 bar vs. 1300 bar) and relative diesel-CH4 ratios (pilot ratio, PR), as these have been noted as key operating dual-fuel control metrics.
The pilot injection pressure was observed to have a significant impact on the fuel conversion process. At higher pilot injection pressures, the auto-ignition sites were concentrated around the piston bowl periphery and the reaction zone propagated towards the center of the bowl. At lower pilot injection pressures, ignition initiated in the vicinity of the pilot fuel jet structures and resulted in a more heterogeneous fuel conversion process with regions of intense natural luminosity, attributed to particulate matter. An increase in the pilot ratio (i.e., increased diesel fraction) resulted in a more aggressive combustion event, due to a larger fraction of energy released in a premixed auto-ignition event. This was coupled with a decrease in the fraction of the combustion chamber with significant OH* or NL light emission, indicating incomplete fuel conversion in these regions. The insight to the dual-fuel conversion processes presented in this work will be ultimately used to develop dual-fuel injection strategies, as well as provide much needed validation data for modeling efforts.
The Estimation of Nitrogen Oxides Reduction Potential Through Enhanced Heat Release Analysis
Authors: Gao Tongyang , Yu Shui , Xie Kelvin , Jeftic Marko , Wang Meiping , Zheng Ming 
Published: December 2016

An enhanced heat release analysis method is proposed to investigate the NOx emission reduction potential in diesel low temperature combustion and the combustion of premixed ethanol ignited by diesel injections. The heat release analysis from the in-cylinder pressure is a commonly applied diagnostic tool to gain insights in various aspects of combustion, such as start of combustion, ignition delay, combustion phasing, and combustion duration. However, these parameters are more qualitative than quantitative when they are correlated to engine efficiency and emissions. The results are often inconsistent at different engine operating conditions, such as different intake pressure levels, EGR rates and engine loads.
In this work, the authors proposed a new parameter named as peak of combustion acceleration, which is the maximum of the first derivative of the heat release rate over an engine cycle. It was observed that the peak of combustion acceleration had a close correlation with the emissions of smoke and NOx at different engine loads and in the combustion of both diesel LTC and premixed ethanol ignited by diesel injections. With the test engine platform, the NOx emission reduced to lower than 50 ppm when the peak of combustion acceleration was less than 25 for diesel LTC and 35 for premixed ethanol ignited by diesel injections. The detailed cylinder pressure sampling and treatment processes were described in this paper. The impact of cycle to cycle variation in the cylinder pressure on the calculation of the peak of combustion acceleration was discussed. The peak of combustion acceleration and the corresponding engine crank angle from each individual engine cycle were calculated and the statistic performance of these parameters was evaluated. The comparison indicated an acceptable consistency between the results from individual engine cycle and from the averaged engine cycles. The proposed peak of combustion acceleration can be potentially integrated in the engine control as an indication of the NOx reduction potential.
Prediction of Flame Burning Velocity at Early Flame Development Time With High Exhaust Gas Recirculation (EGR) and Spark Advance
Authors: Lian H. , Martz J. B. , Maldonado B. P. , Stefanopoulou A. G. , Zaseck K. , Wilkie J. , Nitulescu O. , Ehara M. 
Published: December 2016

Diluting Spark-Ignited (SI) stoichiometric combustion engines with excess residual gas improves thermal efficiency, and allows spark to be advanced towards Maximum Brake Torque (MBT) timing. However, flame propagation rates decrease and misfires can occur at high Exhaust Gas Recirculation (EGR) conditions and advanced spark, limiting the maximum level of charge dilution and its benefits.
The misfire limits are often determined for a specific engine from extensive experiments covering a large range of speed, torque and actuator settings. To extend the benefits of dilute combustion while at the misfire limit, it is essential to define a parameterizable, physics-based model capable of predicting the misfire limits, with cycle to cycle varied flame burning velocity as operating conditions change based on driver demand. A cycle averaged model is the first step in this process.
The current work describes a model of cycle averaged laminar flame burning velocity within the early flame development period of 0 to 3 percent mass fraction burned. A flame curvature correction method is used to account for both the effect of flame stretch and ignition characteristics, in a variable volume engine system. Comparison of the predicted and the measured flame velocity was performed using a spark plug with fiber optical access. The comparison at a small set of spark and EGR settings at fixed load and speed, shows an agreement within 30% of uncertainty, while 20% uncertainty equals ± one standard deviation over 2,000 cycles.
Mechanistic Studies on Type 300 Stainless Steels Manufactured by Hot Isostatic Pressing: The Impact of Oxygen Involvement on Fracture Behaviour
Authors: Cooper Adam J. , Dhers Jean , Sherry Andrew H. 
Published: December 2016

With near-net shape technology becoming an increasingly desirable route toward component manufacture due to its ability to create components with increasingly complex geometries, minimizing the number of potential welded joints, as well as reducing machining time and associated costs, it is important to demonstrate that components fabricated via Hot Isostatic Pressing (HIP) are able to perform to similar standards as those set by equivalent forged materials. Hot Isostatically Pressed (HIP’d) materials are typically accredited with displaying enhanced yield strengths, ultimate tensile strengths, and ductility over their forged counterparts.
In this paper we explore the effects of oxygen, which resides in the austenite matrix during the HIP manufacture process, on a material’s fracture toughness properties. We quantify the influence of different concentrations of oxygen on both the microstructural and mechanical properties of HIP’d 304L and 316L stainless steel, highlighting the benefit of reducing the oxygen as much as possible. Various mechanical tests have been performed on materials containing a range of oxygen contents (between 100 ppm and 200 ppm) and over a large temperature range, including J1C fracture toughness testing, instrumented Charpy, and tensile, and the mechanistic involvement of residual oxygen on the results is discussed. The effects of oxygen become more apparent at cryogenic temperatures, whereas the fracture behavior of HIP’d and forged variants of 304L and 316L at elevated temperatures appears to be comparable.