High Engine Loads Research Articles

G0700303 軽油の高圧噴射による天然ガスデュアルフューエル圧縮着火エンジンの性能改善

The effect of injection pressure of diesel fuel on the engine performance in a dual fuel compression ignition engine with natural gas as a main fuel was investigated at low and high engine loads. With increasing in the injection pressure of diesel fuel, the unburned loss decreases and the thermal efficiency improves. In a low load operation, the NOx emissions decrease with increasing in the injection pressures. In a high load operation, lower intake oxygen concentrations with cooled EGR and higher intake pressures with supercharging are necessary to suppress the increases in the NOx emissions and in the maximum rate of pressure rise, maintaining small unburned losses and high thermal efficiencies.

COMPARISON OF INDICATOR AND HEAT RELEASE GRAPHS FOR VW 1.9 TDI ENGINE SUPPLIED DIESEL FUEL AND RAPESEED METHYL ESTERS (RME)

The results of investigation of 1,9 TDI engine (285 Nm, 85 kW, type AJM without any modification) equipped with injection units supplied conventional diesel fuel (ON) or B100 fuel (RME) have been presented in article. Investigations have been realized at the engine speed of 2000 rpm and variable load within the range of 0 to 275 Nm. The pressure, temperature and heat release velocity runs have been subjected to analysis. Particular attention has been paid to the release of the heat used for the effective work and internal energy increase of the working medium (enthalpy) during combustion inside the engine cylinder versus the crank angle for both investigated fuels. It was found among the others that mentioned fuels differ in the heat release, heat velocity and the maximal combustion temperature, which for the B100 fuel is bigger than for the conventional diesel fuel. Bigger combustion dynamics of tested biofuel (compared with standard diesel fuel) results higher concentrations of Nitrogen Oxides NOx in exhaust gases. The easiest way is of course the use of the later start of fuel injection biofuels and/or increase the exhaust gas recirculation EGR. These treatments, however, result in a worsening of the energy performance of the engine. It was concluded also that the combustion of RME works properly at higher engine loads. Then reduce the negative difference between the combustion of biofuel (RME) and standard Diesel fuel.

Alcohol (Ethanol and Diethyl Ethyl Ether)-Diesel Blended Fuels for Diesel Engine Applications-A Feasible Solution

The objective of improving the combustion, reducing the pollutants and to enhance the performance of diesel engines have intensified research in diesel engines. The goal of this study was to percept the combustion, performance and emission characteristics of diesel engine using oxygenated fuels (blending agents). In view of this, experimental investigations were carried out on a single cylinder four stroke direct injection water cooled diesel engine using ethanol and diethyl ether blended fuels in different volume ratios with diesel fuel. The experimental investigation was performed with four different blends of ethanol (E0 -neat diesel, E5, E10, E15 and E20)and diethyl ether (DEE0 - neat diesel, DEE5,DEE10, DEE15 and DEE20) to assess the impact of using ethanol and diethyl ether-diesel blends on diesel engine performance, combustion and emissions. In addition, 2% Ethyl acetate has been added to ethanol diesel blend to retain homogeneity and prevent the interfacial tension between two liquids. For the same rated speed and compression ratio, different blended fuels as well as pure diesel, various engine parameters such as brake thermal efficiency and fuel consumption, combustion parameters such as peak cylinder pressure and exhaust emissions such as smoke opacity, hydrocarbon, CO, and NOx, were measured. The results indicate that the brake thermal efficiency increased with an increase in ethanol and DEE contents in the blended fuels at overall operating conditions. At higher loads, reduced CO emission levels were observed for blends of ethanol and DEE at high load. HC emissions increased for all blends of ethanol and DEE compared with diesel fuel due to high fuel consumption and high latent heat of vaporization which lowers cylinder temperatures and causes the emission of unburned hydrocarbons at lower load. NOx emission slightly reduced with ethanol and DEE blends compared to diesel at lower loads. Further, due to lower calorific value and high latent heat of vaporization of ethanol and DEE results in reduced flame temperature and lower NOx emissions. The NOx emission is almost identical compared to diesel at higher engine loads. Ethanol and DEE showed lowest smoke emissions at high engine loads compared to diesel fuel operation.

The Effect of Ethanol Blending on Combustion and Soot Formation in an Optical DISI Engine Using High-speed Imaging

Biofuel components exhibit significantly different fuel properties as compared to gasoline leading to a very complex chain of effects in engine combustion. Therefore, the effects of varying composition on mixture formation, combustion and soot formation can hardly be predicted. In this study, the influence of blending 20vol% ethanol to isooctane is investigated by simultaneous OH*-chemiluminescence and soot radiation high-speed imaging. For both fuels engine load was varied for a typical catalyst heating operating point, which is characterized by increased soot formation probability. The study reveals an unexpected behavior for E20. Both the OH*-chemiluminescence and soot luminosity intensity are higher as compared to isooctane. Furthermore, for E20 the occurrence probability of droplet combustion is increased. High engine load increases the combustion intensities and probability of soot formation for both investigated fuels.

Impact of Diesel-butanol Blends on Performance and Emission of Diesel Engine

The aim of lowering the pollutants and to enhance the performance of diesel engines has intensified research in diesel engines. The goal of this study was to assess combustion, performance and emission characteristics of diesel engine using diesel-oxygenate blends. In this direction, experimental investigations were carried out on a single cylinder four stroke direct injection water cooled diesel engine using butanol blended fuels in different volume ratios with diesel fuel. The butanol had no solubility or stability problems when blended with diesel fuel. As there was not phase separation in the blends, no additive was added. The experimental investigation was done with four different blends of butanol on volume basis [B0 (0% Butanol and 100% Diesel), B5 (5% Butanol and 95% Diesel), B10 (10% Butanol and 90% Diesel), B15 (15% Butanol and 85% Diesel) and B20 (20% Butanol and 80% Diesel)] to study the impact of using butanol -diesel blends on diesel engine performance, combustion and emissions. The outcome indicates that the brake thermal efficiency increased with an increase in butanol contents in the blended fuels at overall operating conditions. At higher loads, reduced CO emission levels were observed for blends of butanol. HC emissions increased for all blends of butanol compared with diesel fuel due to high fuel consumption and high latent heat of vaporization which lowers cylinder temperatures and causes the emission of unburned hydrocarbons at lower load. NOx emissions with diesel–butanol blends were found to be comparable with neat diesel at low loads due to lower calorific value and high latent heat of vaporization of butanol results in reduced flame temperature and slightly higher NOx at high loads with increased butanol percentage in the blend compared to neat diesel. Butanol showed lowest smoke opacity at high engine loads compared to diesel fuel operation.

Experimental study on the heat transfer characteristics of subcooled flow boiling with cast iron heating surface

Subcooled boiling is an effective heat transfer form for modern engine cooling systems. The significantly higher heat transfer rate achievable with boiling can keep the temperature in key thermal areas within an acceptable level and optimize thermal management strategies even at high engine loads. In this study, an experimental setup was designed using cast iron as heating block to simulate the flow boiling in engine cooling passage. The heat transfer characteristics were obtained under comprehensive cooling conditions for an engine, where the inlet temperature ranges from 75 to 95 °C, the system pressure ranges from 100 to 300 kPa, and the flow velocity ranges from 0.2 to 2.0 m/s. The experimental results were used to verify the wall heat flux of subcooled flow boiling in the cooling system of diesel engine, which was predicted by three types of empirical boiling models with primitive parameters. The results indicate that the prediction models are not accurate. Based on the experimental results and Franz's correlation, a modified boiling model was developed to adapt to the cast iron heating surface status.

One-Dimensional Simulation of the Combustion Process in an Engine Cylinder with Ethanol

The diesel engine is one of the most important engines for road vehicles. The engine nowadays operates with different kinds of alternative fuels, such as natural gas and biofuel. The aim of this article is to study the combustion process that occurs in an engine cylinder of a diesel engine when using biofuel. The one-dimensional numerical analysis using GT-Power software is used to simulate the commercial four-cylinder diesel engine. The engine operated at high engine load and speed. The ethanol fuel used in the simulation is derived from the conventional ethanol fuel properties. The analysis of simulations includes the cylinder pressure, combustion temperature and rate of heat release. The simulation results show that in-cylinder pressure and temperature for ethanol is higher than for diesel at any engine speed. However, the mass fraction of ethanol burned is similar to that of diesel. MFB only affects the engine speed.

The prediction of fuel injection quality using a NOx sensor for the on-board diagnosis of heavy-duty diesel engines with SCR systems

The fuel injectors in a heavy-duty diesel engine with a selective catalytic reduction (SCR) system operate in harsh conditions that cause them to deteriorate, resulting in changes in the fuel injection quantity. In this study, a method for determining the injection quantity of fuel injected using the output of a NOx sensor in a heavy-duty diesel engine equipped with a SCR system is developed. A mathematical model was derived to calculate the fuel injection quantity based on the oxygen concentration in the exhaust gases. Bench tests were conducted at various engine operating conditions. The results indicate that at high engine loads, the absolute error between the oxygen concentration measured by the NOx sensor and that measured by a gas analyser was less than 2%, which is acceptable, and the reactions in the SCR reactor consumed no more than 1% of the oxygen in the exhaust gases, which is negligible. An analysis of the model demonstrates that the calculated value of the injection quantity based on the oxygen concentration in the exhaust is more accurate for lower oxygen concentrations (i.e., at greater engine loads). The test data reveal that the error in the fuel injection quantity obtained from the model was less than 2% at high engine loads. This research demonstrates that the on-board calculation of the fuel injection quantity based on the oxygen concentration signals from the NOx sensor is possible at high engine loads.

Effects of oxygenated fuel blends on carbonaceous particulate composition and particle size distributions from a stationary diesel engine

A systematic study was conducted to evaluate and compare the effects of blending five different oxygenated compounds, diglyme (DGM), palm oil methyl ester (PME), dimethyl carbonate (DMC), diethyl adipate (DEA) and butanol (Bu) with ultralow sulfur diesel (ULSD), on engine performance, particulate mass concentrations, organic (OC) and elemental (EC) carbon fractions of the particles and particle size distributions from a single cylinder, direct injection stationary diesel engine with the engine working at a constant engine speed and at three engine loads. A small increase in the brake specific fuel consumption (BSFC) and brake thermal efficiency (BTE) was observed with the use of oxygenates blended with ULSD. All five oxygenates were found to be effective at reducing particulate mass emissions at medium and high engine loads, with butanol being the most effective and DGM being the least effective. Analysis of the relative contribution of changes in the OC and EC emissions to the reduction of particulate matter indicated that under the same oxygen content, EC made a dominant contribution to the reduction of particulate mass. The results also indicated that reduction in both particle mass and number emissions was affected not only by the oxygen content, but also by the chemical structure and thermophysical properties of oxygenates as well as engine operating conditions.

Octane Appetite: The Relevance of a Lower Limit to the MON Specification in a Downsized, Highly Boosted DISI Engine

Market demand for high performance gasoline vehicles and increasingly strict government emissions regulations are driving the development of highly downsized, boosted direct injection engines. The in-cylinder temperatures and pressures of these emerging technologies tend to no longer adhere to the test conditions defining the RON and MON octane rating scales. This divergence between fuel knock rating methods and fuel performance in modern engines has previously led to the development of an engine and operating condition dependent scaling factor, K, which allows for extrapolation of RON and MON values. Downsized, boosted DISI engines have been generally shown to have negative K-values when knock limited, indicating a preference for fuels of higher sensitivity and challenging the relevance of a lower limit to the MON specification. The Ultraboost engine is an inline-4 downsized, highly boosted prototype DISI engine designed to achieve a 35% reduction in CO2 emissions whilst maintaining performance of a production V8. A series of 14 fuel formulations were tested to probe engine response to various fuel properties. This paper presents results from a 7 fuel RON and MON decorrelated matrix at four high-load engine conditions. The K-value was found to be negative at all engine conditions; fuels of higher sensitivity were found to yield improved engine performance. Furthermore, in-cylinder experimental data from high load knocking conditions with a single standard octane fuel were used to simulate the K-value; a similar trend between theory and experiment was observed.

Combustion and emission characteristics of a turbocharged diesel engine using high premixed ratio of methanol and diesel fuel

The combustion and emission characteristics of a dual fuel diesel engine with high premixed ratio of methanol (PRm) were investigated. Experiments were performed on a 6-cylinder turbocharged, inter-cooling diesel engine. Methanol was injected through the intake port and ignited by direct injected diesel in the cylinder, the maximum PRm was over 70%. The experimental results showed that with high PRm, the maximum in-cylinder pressure increased from medium to high engine load but varied little or even decreased at low engine speed and load. High PRm prolonged the ignition delay but shortened the combustion duration and decreased the in-cylinder gas temperature at ignition timing. Hydrocarbons (HC), carbon monoxide (CO), formaldehyde emissions and the proportion of nitrogen dioxide (NO2) in nitrogen oxides (NOX) increased significantly with the increase of PRm while NOX and dry soot emissions were significantly reduced, which meant the trade-off relationship between NOX and soot emissions disappeared. The increased HC, CO and formaldehyde emissions could be effectively reduced by diesel oxidation catalyst (DOC) when the exhaust gas temperature reached the light off temperature of the DOC. After DOC, the NO2 proportion in NOX was greatly reduced to less than that of baseline engine at methanol premixed mode but increased slightly at pure diesel mode. The maximum PRm was confined by in-cylinder pressure at high engine speed and load. But at low engine speed and load, it was confined by the high emissions of HC, CO and formaldehyde even after DOC.

Exhaust Emissions from a Light-Duty Diesel Engine with SME-Diesel Fuel

Researchers have recently attempted to discover alternative energy sources that are accessible, technically viable, economically feasible, and environmentally acceptable. The objective of this study is to investigate regulated and unregulated exhaust emissions with petroleum diesel fuel and Jatrophabased biodiesel blends at proportions of 20%, 40%, 60%, 80% and 100% (v/v). This study examines three regulated emissions: CO, NMHC and NOx, and two typical unregulated emissions: SO2 and formaldehyde. The CO and formaldehyde emissions increase at low engine loads, and decrease at high engine loads. The NMHC and NOx emissions of the five fuels continuously decrease as biodiesel blends increase. Besides, SME fuels can also reduce the SO2 emissions.

The Variable Outlet Turbine Concept for Turbochargers

A variable geometry concept for advanced turbocharger (TC) systems is presented. The variability of the device is based on outlet area changes as opposed to the more common systems that are based on inlet turbine geometry changes. In addition to the conventional variable turbine geometry (VTG), the new variable turbine type is termed variable outlet turbine (VOT). The flow variability is achieved by variation of the flow cross section at the turbine outlet using an axial displacement of a sliding sleeve over the exducer and provides a simple solution for flow variability. In order to predict the aerodynamic performance and to analyze the loss mechanisms of this new turbine, the flow field of the VOT is calculated by means of steady state 3D-CFD (computational fluid dynamics) simulations. The VOT design is optimized by finding a good balance between clearance and outlet losses. Furthermore, experimental results of the VOT are presented and compared to a turbine equipped with a waste gate (WG) that demonstrates an efficiency advantage of 5%. Additionally, engine performance measurements were carried out to investigate the influence of the VOT on fuel consumption and to asses the functionality of the new pneumatic actuating system. The VOT engine tests show also performance advantage in comparison to a WG turbine especially toward high engine loads. It is found that the use of the VOT at this condition shows a turbine efficiency advantage of 6% related to a reduction in engine fuel consumption of 1.4%. The behavior at part load is neutral and the peak turbine efficiency of the VOT is comparable with a fix turbine geometry.

Exhaust particles of modern gasoline vehicles: A laboratory and an on-road study

Vehicle technology development and upcoming particle emission limits have increased the need for detailed analyses of particle emissions of vehicles using gasoline direct injection (GDI) techniques. In this paper the particle emission characteristics of modern GDI passenger cars were studied in a laboratory and on the road, with the focus on exhaust particle number emissions, size distributions, volatility and morphology. Both during acceleration and steady conditions the number size distribution of nonvolatile exhaust particles consisted of two modes, one with mean particle size below 30 nm and the other with mean particle size approximately 70 nm. Results indicate that both of these particles modes consisted of soot but with different morphologies. Both in laboratory and on the road, significant emissions of exhaust particles were observed also during decelerations conducted by engine braking. These particles are most likely originating from lubricant oil ash components. The semivolatile nucleation particles were observed in the laboratory experiments at high engine load conditions. Thus, in general, the study indicates that a modern gasoline vehicle can emit four distinctive types of exhaust particles. The differences in particle characteristics and formation should be taken into account in the development of emission control strategies and technologies and, on the other hand, in the assessment of the impact of particle emissions on environment and human health.

Promoted Platinum Catalytic Activity and Thermal Stability with Nano-Scale Cobalt Oxide Coating via Atomic Layer Deposition

Platinum nanoparticles (NPs) play an important role in the catalytic conversion of automotive exhaust. The catalytic performance is closely related to the number of active sites. One drawback of platinum catalyst is its tendency towards sintering under high temperatures which may occur during high engine loads. Sintering of Pt NPs will cause larger particles formation and a decrease in the number of active sites. [1] Many methods have been tried to form core shell structures to encapsulate the metal nanoparticles with porous materials to minimize sintering.[2] The nanoparticles with a protective shell show good sintering resistance.[3] However in some cases the catalysis performance decreases because the thick protective shell blocks the access of the reactants. New methods are needed to improve the controllability of the coating layer thickness and structure to stabilize the metal nanoparticles and at the same time maintain the catalysis performance. Atomic layer deposition (ALD) shows it unique advantages in sub-nanometer thin film thickness control due to the self-limiting growth nature.[4] Recent works encapsulate the palladium nanoparticles with porous Al2O3 through ALD that effectively prevents sintering and coking in the ethane oxidation reactions.[5] Here we report the use of active oxide layer to coat the platinum NPs for CO oxidation. Our results indicate that with proper thickness control of the coating layer the catalysts have good thermal stability. At the same time the platinum and the active ingredients in the oxide layer may also form alloy particles, further promoting the total catalysis performance.Reference[1] M A Asoro, D Kovar, Y Shao-Horn, P J Ferreira, Nanotechnology 21 (2010)[2] Zhao M, Sun L, Crooks RM, J. Am. Chem. Soc. 120 (1998)[3] Z Ma, S. Brown, J.Y. Howe, S.H Overbury, S Dai, J. Phys. Chem. C 112 (2008)[4] Riikka L. Puurunen, J. Appl. Phys. 97, 121301 (2005)[5] Lu. J. L, Fu. B. S, Kung, M.C, J W Elam, P C Stair, Science 8, 2405 (2012)

Effect of Turbocharged Diesel Engine Operating Conditions on Intake Premixed Methanol Quantity and Performance

A multi-point low-pressure methanol injection system was installed on manifold of a four cylinder turbocharged diesel engine, and the experiments on the engine operated with intake premixed methanol were conducted under wide operating conditions. The influence of the engine operating conditions on premixed methanol quantity was analyzed. The results show that, compared with straight diesel model, premixed methanol prolongs the ignition delay time of pilot diesel at the engine high load with low speed, and more methanol quantity can be premixed. At more than medium load with high speed, diesel ignition delay time with premixed methanol is shorter than with straight diesel model, and substitution ratio of methanol for diesel is significantly lower than that of low speed. Compared with the straight diesel mode at high speed, the fuel economy of the dual fueling mode is better, and NOx and soot emissions also are decreased, but CO and HC emissions are increased.

Understanding the relationship between ignition delay and burn duration in a constant volume vessel at diesel engine conditions

Experiments were performed in a constant volume vessel, with fuel sprays injected into the vessel at various different pressure and temperature conditions chosen to represent diesel engine operation at various loads.A range of diesel primary reference fuels (i.e. mixtures of cetane and heptamethylnonane) of varying cetane number (CN) were tested, and as expected lower CN fuels have longer ignition delays. Burn period was plotted against ignition delay and two distinct trends can be seen: “mainly diffusion” diesel combustion in which burn period decreases with ignition delay and “mainly pre-mixed” diesel combustion in which burn period increases with ignition delay. There is typically a minimum in plots of burn period versus ignition delay which represents the transition between the two types of combustion mode. Higher CN, higher engine load and higher boost pressure would seem to favour “mainly diffusion” combustion whilst lower CN, lower loads and non boosted conditions favour “mainly pre-mixed” combustion.

Potentials for NOx and CO2 reduction of combined NSC + passive SCR system in Diesel passenger car application

The stringent pollutant and CO2 emission limitation in upcoming legislation norms for Diesel passenger car applications force the introduction of exhaust aftertreatment systems with maximum purification and energetic efficiency. The state-off-the-art technologies for NOx reduction, NOx storage and reduction catalyst (NSC) and selective catalytic reduction catalyst (SCR), show challenges for robust performance under strongly extended emission relevant operation conditions from cold start to high engine load and speed. One technical solution is the combination of NSC and passive SCR. This paper presents the experimental results obtained in the EU project “Powerful”. On engine test bench and demon-strator vehicle, an exhaust aftertreatment system combining NSC, passive SCR and fuel reformer technology was developed and experimentally investigated steady-state and on road. The engine independent NSC operation offers potentials for lowered fuel consumption penalty by avoiding engine rich operation. The intrinsic NH3 formation during the NSC regeneration is used for additional NOx conversion on the passive SCR and reduces NOx and CO2 emission.

Combustion characteristics and emissions of a compression ignition engine using emulsified jatropha biodiesel blend

An emulsified fuel containing 10% and 15% water by volume was prepared from a diesel blend with 10% Jatropha biodiesel (JB10) to evaluate the combustion characteristics of a 10.3 kW, single cylinder, 4-stroke, water cooled, direct injection (DI) diesel engine. Initially experiments were conducted to determine the required hydrophilic–lipophilic balance (HLB). The results showed that JB10 and its emulsified fuel exhibited similar combustion stages to that of diesel with no undesirable combustion features observed such as an unacceptable increase cylinder gas pressure. With increasing percentage of water, ignition delay was longer at higher engine loads. Reductions in emission of CO, CO2, HC and NOx were observed for the emulsified fuel compared to JB10. Emulsified biodiesel can be recommended for use in place of biodiesel.

Experimental investigation of DI diesel engine operating with eucalyptus biodiesel/natural gas under dual fuel mode

With the gradual depletion of petroleum and environmental degradation, intensive research activity has been addressed to the utilization of alternative fuels in internal combustion engines. In the present work, an experimental investigation is carried out to study the effect of eucalyptus biodiesel and natural gas under dual fuel combustion mode on the performance and the exhaust emissions of a single cylinder DI diesel engine. The natural gas (NG) is inducted with the intake air through the inlet manifold. The liquid pilot fuel (eucalyptus biodiesel or diesel fuel) is injected into the combustion chamber to cover approximately 10% of the maximum power output. Then, keeping constant the pilot fuel flow rate, the power output is further increased using only natural gas. The combustion characteristics (cylinder pressure, ignition delay and heat release rate), performance and exhaust emissions of the dual fuel mode (NG–diesel fuel and NG–biodiesel) are compared with those of conventional diesel engine mode at various load conditions. The combustion analysis has shown that biodiesel as pilot fuel exhibits similar pressure–time history, with highest peak, as diesel fuel in conventional and dual fuel modes. The performance and pollutant emission results show that, compared to diesel fuel in dual fuel mode, the use of eucalyptus biodiesel as pilot fuel reduces the high emission levels of unburned hydrocarbon (HC), carbon monoxide (CO) and carbon dioxide (CO2) particularly at high engine loads. However this is accompanied by an increase in the brake specific fuel consumption (BSFC) and the nitrogen oxide (NOx) emissions, which can be explained by the lower calorific value and the oxygen presence in the molecule of the eucalyptus biodiesel, respectively.