Modern Diesel Engines Research Articles

Numerical Simulation of the Flow Field and Chemical Reactions within a NSC Diesel Catalyst

In the present work three-dimensional steady and unsteady numerical simulations of the flow field and chemical reactions within aNOx Storage Converter (NSC) diesel catalyst have been made. In the first part of the paper, only the flow characteristics within a catalyst have been investigated by mean of a steady three-dimensional Reynolds-Averaged Navier-Stokes approach and a transport equation for each of the incoming chemical species. For flow simulations, the catalyst volume has been split in three zones: inlet, catalytic monolith, treated as porous media, and outlet, medium. The results have been reported in three different working points. Evidences on how the non-uniform flow distribution affects the catalyst efficiency have been described. In the second part, the fluid-dynamic solver has been coupled with a chemical reaction mechanism in order to catch the chemical surface reaction within a NSC catalyst. This coupled model has been validated according to the literature. Volumetric and superficial species concentration have been calculated imposing the site density and the kinetic of the reactions on a substrate Ba/Al2O3. NOx spatial distributions within the catalyst during a dsorption phase are reported. The model represent a reliable tool to investigate in detail the complex flow/chemistry interaction within the modern diesel engine catalysts.

Low Temperature Premixed Diesel Combustion with Blends of Ordinary Diesel Fuel and Normal Heptane

Premixed diesel combustion blending high volatility fuels into diesel fuel were investigated in a modern diesel engine. First, various fractions of normal heptane and diesel fuel were examined to determine the influence of the blending of a highly ignitable and volatile fuel into diesel fuel. The indicated thermal efficiency improves almost linearly with increasing normal heptane fraction, particularly at advanced injection timings when the fuel is not injected directly into the piston cavity. This improvement is mainly due to decreases in the other losses, ϕother which are calculated with the following equation based on the energy balance. No Caption Available ηu: The combustion efficiency calculated from the exhaust gas compositions ηi: The indicated thermal efficiency ϕex: The exhaust loss calculated from the enthalpy difference between intake and exhaust gas The decreases in the other losses with normal heptane blends are due to a reduction in the unburned fuel which does not reach the gas analyzer. Next, a blend of 50 vol% iso-octane and 50 vol% diesel fuel was examined to determine the influence of blending a low ignitability and high volatility fuel similar to gasoline into diesel fuel. With the iso-octane blend the range of premixed diesel combustion can be expanded to higher intake oxygen concentrations due to a longer premixing duration with increasing ignition delay, and smokeless combustion is possible at low intake oxygen concentrations. The unburned fuel arising from adhesion of fuel spray on the cylinder wall can be avoided with the high volatility fuel, resulting in higher efficiency.

A numerical study of the effects of pressure fluctuations inside injection nozzle on high-pressure and evaporating diesel spray characteristics

Effects of injection pressure fluctuations on high-pressure and evaporating spray behaviour, especially under the representative modern diesel engine injection conditions, were carefully evaluated by using a well validated two-stage modelling approach. The numerical results indicate that as the injection pressure fluctuates more drastically both liquid and gas phase motions in the spray field will be more intensively disturbed. Furthermore, the injection pressure fluctuations have strong potential to enhance fuel/gas mixing processes inside high-pressure and evaporating diesel spray field.

Visualization research on spray atomization, evaporation and combustion processes of ethanol–diesel blend under LTC conditions

Utilization of ethanol in diesel engines has been widely studied by means of engine experiments and emission detection. However, pertinent studies on the spray combustion process of ethanol–diesel blends are scarce. In order to verify the effect of ethanol in modern diesel engines, an experiment is conducted to visualize the spray combustion process of ethanol–diesel blend under LTC conditions. Stages including atomization, evaporation and combustion, are investigated individually to realize synergistic analysis. Meanwhile, considering the long time scale of combustion after fuel injection finishes, characteristics during and after injection period are both targeted in this paper. Moreover, measurement of macroscopic characteristics, such as spray tip penetration, spray spreading cone angle and flame lift off length, provides a quantitative profile of the spray structure. Results show that, evaporation, different from atomization, has little influence on spray penetration, but promotes the spray spreading angle and spray projected area. So does combustion, which enlarges the spray projected area further. Ignition takes place on the periphery behind the spray tip, then quickly extends to the whole head of the spray and forms a U-shape diffusion structure. After the injection period, the residual spray tail develops into wavelike structures due to absence of subsequent entrainment force. Also, the penetration speed falls greatly to an extent much slower than flame propagation, which frees the flame from the lift-off effect. Subsequently, the flame propagates upstream towards the nozzle orifice. After consumed all fuel in the spray tail, flame retreats downstream to the far end and combusts for a time much longer than the injection duration.

Deformation mechanisms of IN713C nickel based superalloy during Small Punch Testing

The role of local microstructure is critical in materials performance and integrity in a cast alloy. The grain size and grain boundary distributions as well as local texture can create various microstructure/microtexture clusters that cause deformation localisation in the alloy. Inconel 713C nickel base superalloys are used as turbocharger turbine wheels for modern diesel engines, produced via investment casting. In such an alloy localised deformation is highly expected during service, as the strain distribution is not uniform in the component due to casting geometrical factors in addition to non-homogenous microstructure and microtexture in the cast alloy. In the current investigation Small Punch (SP) tensile tests were carried out on IN713C at room temperature and 650°C in an air environment under stroke control at a rate of 0.02mm/s. The fracture surface examination and microstructure characterisation as well as detailed texture analyses were performed using Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD). Finite Element (FE) analysis of the SP test was also implemented to investigate the role of stress state on the local deformation. It was evident that microstructure parameters such as grain morphology and original texture existed in the disc were the most influential factors in governing the deformation texture in mixed columnar/equiaxed (transition) disc microstructure. Whereas, the temperature was the determining parameter in grain rotations and texture changes for wholly columnar disc microstructures.

In-cylinder soot radiation heat transfer in direct-injection diesel engines

The efficiency and CO2 are one of the main concerns of automotive manufacturers. There are several strategies under investigation to solve this problem. In the present work, the research effort has been focused on improving knowledge of in-cylinder heat transfer and its impact on engine efficiency. In particular, soot radiation was studied since it can be considered a significant source of the efficiency losses in modern diesel engines. Considering previous studies, the portion of total chemical energy released during combustion lost due to radiation heat transfer varies widely from 0.5% up to 10%, depending on engine parameters and combustion process. Thus, the main objective of this work was to evaluate the amount of energy lost to soot radiation relative to the input fuel chemical energy during the combustion event under different operating conditions in a completely controlled environment provided by an optical engine. Under these simplified conditions, two-color method was applied by using high speed imaging pyrometer with cameras (two dimensional results) and optoelectronic pyrometer (zero dimensional results). Once a detailed comparison between both diagnostics was performed, optoelectronic pyrometer was used to characterize radiant energy losses in a fully instrumented 4-cylinder direct-injection light-duty diesel engine. In particular swirl ratio, EGR and combustion phasing effects on radiation heat transfer were evaluated.

Transition of diesel spray to a supercritical state under engine conditions

Process operating conditions of modern internal combustion engines can exceed the thermodynamic critical point of an injected liquid fuel. This raises the question of whether the fuel, or at least some of its components, transition to a supercritical state, even in the presence of an ambient gas. Further investigation is required for a better understanding of heat and mass transfer during the process of fuel injection in diesel engines. This article investigates the phase behavior of fuels and their components under supercritical conditions or when injected into such. After a brief review of the current state of research on the topic, we present our study of the phase behavior of three single-component liquids (n-heptane, n-dodecane, n-hexadecane) and their binary mixtures under supercritical conditions in a nitrogen environment using equations of state. In first experiments, these liquids along with a diesel fuel were successfully transitioned to supercritical states by applying engine-relevant but steady state conditions inside a high-pressure, high-temperature constant volume chamber. No influence of the ambient nitrogen on the phase behavior of the examined fluids was found. For further investigation, multicomponent fuels were injected into the chamber in a transient injection process and at typical engine-relevant time scales using a production-type diesel injector. The fuel sprays were examined with Mie scattering, laser-induced fluorescence, and shadowgraphic imaging. The information obtained confirms the presence of a supercritical state and a transcritical phase change. Areas of high density with pronounced fluctuations were visible. The theoretical review in combination with the results obtained from the experiments indicate that fuel injected under the high-pressure and high-temperature conditions, that are present in modern diesel engines at higher loads, does not evaporate but rather shows transition to a supercritical state with a disappearing phase border, but without boiling or changing density.

Effect of shock waves on the evolution of high-pressure fuel jets

In the modern diesel engine, with increasingly higher injection pressures, shock waves will appear with high velocity fuel jets. To better understand the effect of shock waves on the atomization of fuel sprays, diesel fuel injected at a pressure of 60 to 120MPa was studied using a schlieren imaging visualisation system. The initiation and boundary conditions of the shock wave initiated by fuel jets were examined. A clear difference of spray penetration between the shock-wave state and the non-shock-wave state was recorded in a nitrogen (N2) and sulphur hexafluoride (SF6) gas atmosphere. By eliminating the other potential explanations, such as pressure drop differences and the enhancement of gas density, it is shown that the shock wave itself had a predominant effect on the evolution of high-pressure fuel jets. Additionally, a computational model considering the Mach number was developed to predict the spray penetration. The model was found to have excellent agreement with the presented experimental results.

Planar near-nozzle velocity measurements during a single high-pressure fuel injection

In order to reduce the fuel consumption and exhaust emissions of modern Diesel engines, the high-pressure fuel injections have to be optimized. This requires continuous, time-resolved measurements of the fuel velocity distribution during multiple complete injection cycles, which can provide a deeper understanding of the injection process. However, fuel velocity measurements at high-pressure injection nozzles are a challenging task due to the high velocities of up to 300 m/s, the short injection durations in the $$\upmu\text{s}$$ range and the high fuel droplet density especially near the nozzle exit. In order to solve these challenges, a fast imaging Doppler global velocimeter with laser frequency modulation (2D-FM-DGV) incorporating a high-speed camera is presented. As a result, continuous planar velocity field measurements are performed with a measurement rate of 200 kHz in the near-nozzle region of a high-pressure Diesel injection. The injection system is operated under atmospheric surrounding conditions with injection pressures up to 1400 bar thereby reaching fuel velocities up to 380 m/s. The measurements over multiple entire injection cycles resolved the spatio-temporal fluctuations of the fuel velocity, which occur especially for low injection pressures. Furthermore, a sudden setback of the velocity at the beginning of the injection is identified for various injection pressures. In conclusion, the fast measurement system enables the investigation of the complete temporal behavior of single injection cycles or a series of it. Since this eliminates the necessity of phase-locked measurements, the proposed measurement approach provides new insights for the analysis of high-pressure injections regarding unsteady phenomena.

Improved Efficiency in Engine Cooling System by Repositioning of Turbo Inter Cooler

Turbochargers are an integral part of today’s modern diesel engines and are a major reason that they are able to produce more power. Unlike a super charger that is driven via a belt from the engine, a turbo takes the exhaust that the engine is producing and puts it to good use. As Turbochargers are driven by exhaust, heat is an unwelcome by product and something that wasn’t really taken into account in automobiles. Then those intercoolers started to come into play in turbocharged automobiles. The forced air produced by the turbocharger is routed through the intercooler where its temperature is reduced before reaching the engine. The use of intercoolers has made turbocharged vehicles far more reliable and, in the case of today’s heavy duty diesel trucks, is a very important component. The inlet air of an IC engine from turbocharger temperature is very much high (due to compression) means oxygen content is very much less. And also air with high temperature causes pre-ignition and detonation. So fuel combustion does not take place properly. Inter Cooling of inlet air is very much essential according to performance point of view. Turbo intercoolers are used for cooling the inlet air of an IC engine from turbo chargers. Moreover cooling of air makes it denser and contributes for better combustion and more power they are mounted close to the radiators for achieving lower air temperature. This arrangement affects the performance of both. So in this project an attempt will be made to increase the efficiency of the turbo intercooler arrangement through design modification and repositioning of intercooler by taking the TATA MARCOPOLO-Star Bus 909 as a reference.

Effect of atmospheric aging on volatility and reactive oxygen species of biodiesel exhaust nano-particles

Abstract. In the prospect of limited energy resources and climate change, effects of alternative biofuels on primary emissions are being extensively studied. Our two recent studies have shown that biodiesel fuel composition has a significant impact on primary particulate matter emissions. It was also shown that particulate matter caused by biodiesels was substantially different from the emissions due to petroleum diesel. Emissions appeared to have higher oxidative potential with the increase in oxygen content and decrease of carbon chain length and unsaturation levels of fuel molecules. Overall, both studies concluded that chemical composition of biodiesel is more important than its physical properties in controlling exhaust particle emissions. This suggests that the atmospheric aging processes, including secondary organic aerosol formation, of emissions from different fuels will be different as well. In this study, measurements were conducted on a modern common-rail diesel engine. To get more information on realistic properties of tested biodiesel particulate matter once they are released into the atmosphere, particulate matter was exposed to atmospheric oxidants, ozone and ultra-violet light; and the change in their properties was monitored for different biodiesel blends. Upon the exposure to oxidative agents, the chemical composition of the exhaust changes. It triggers the cascade of photochemical reactions resulting in the partitioning of semi-volatile compounds between the gas and particulate phase. In most of the cases, aging lead to the increase in volatility and oxidative potential, and the increment of change was mainly dependent on the chemical composition of fuels as the leading cause for the amount and the type of semi-volatile compounds present in the exhaust.

Development of a Soot Load Sensor Using Electrical Capacitance Imaging

This paper presents an innovative approach for measuring particulate matter deposition (soot load) in a diesel particulate filter (DPF) using electrical capacitance imaging. Emission regulations on diesel engines for gaseous as well as particulate matter (soot) emissions are getting stringent every few years by the environment regulatory agencies. Modern diesel engines are equipped with DPFs, as well as on-board technologies to evaluate the status of DPF, because complete knowledge of DPF soot load is very critical for robust and efficient operation of the engine exhaust after treatment system. In course of time, soot will be deposited inside the DPF which will clog the filter and generate a back pressure in the exhaust system, negatively impacting the fuel efficiency. To remove the soot build-up, regeneration (active or passive) of the DPF must be done as an engine exhaust after treatment process periodically. Since the regeneration process consumes fuel, a robust and efficient operation based on accurate knowledge of the soot load becomes essential in order to keep the fuel consumption at a minimum. In this paper, we propose a novel sensing method for a DPF that can measure in situ soot load using electrical capacitance imaging. Experimental results show that the proposed method offers an effective way to measure the soot load in DPF. The proposed method is expected to have a profound impact in improving overall DPF filtering efficiency and durability of a DPF through appropriate closed-loop regeneration operation.

The Laser Doppler Vibrometry in mechatronics diagnostics

The article presents the possibility to diagnose a machine – physical object – in particular diesel engine. Studies were organized to demonstrate the possibility to use LDV (Laser Doppler Vibrometry) in the fundamental (diagnostic) studies. The object tested is a common model of modern diesel engine, frequently used in currently available vehicles. This paper describes the results of researches performed based on the displacement and the velocity, which indicates usefulness of each of these variables. In addition, the article presents older type of vibration detection system uses in vehicles (based on accelerometers) and conditioning path of the received vibroacoustic signal to become complete and fully useful diagnostic information.

Analysis of spray injection in a light duty CR diesel engine supported by non-conventional measurements

Abstract The injection process is one of the relevant phenomena occurring in modern diesel engine considering also that the fuel properties have been continuously changing. The interaction mechanisms between fuel quality, engine technologies, and emissions need to be understood to find the most effective approach towards innovative combustion strategies and low-emission diesel engines. In this work, the injection process occurring in a direct injection (DI) Common Rail (CR) diesel engine has been investigated from the start of injection up to the start of luminous combustion using different techniques. 2D visible and infrared imaging has been applied in single cylinder optical engine for several injection strategies typical of passenger car engine (homologation cycle NEDC). The spray penetration and cone angle obtained by 2D imaging are compared with the results of a 1D consolidated model for transient spray developed by the Sandia National Laboratory. Some modifications to the model boundary conditions have been made in order to assess the effect of fuel–wall interaction. This provided qualitative information of the impinged fuel inside the piston bowl. Finally, a good correlation between the fuel mass impinging on the chamber wall and the particulate matter (PM) emissions measured at the engine exhaust was found. The results of this study could be helpful for the determination of the best injection strategies in a diesel engine in order to reduce PM emissions.

Linking the Physical Manifestation and Performance Effects of Injector Nozzle Deposits in Modern Diesel Engines

Linking the Physical Manifestation and Performance Effects of Injector Nozzle Deposits in Modern Diesel Engines

Inter-cycle variability of ignition delay in an ethanol fumigated common rail diesel engine

An experimental study has been performed to investigate the ignition delay of a modern heavy-duty common-rail diesel engine run with fumigated ethanol substitutions up to 40% on an energy basis. The ignition delay was determined through the use of statistical modelling in a Bayesian framework—this framework allows for the accurate determination of the start of combustion from single consecutive cycles and does not require any differentiation of the in-cylinder pressure signal. At full load the ignition delay has been shown to decrease with increasing ethanol substitutions and evidence of combustion with high ethanol substitutions prior to diesel injection have also been shown experimentally and by modelling. Whereas, at half load increasing ethanol substitutions have increased the ignition delay. A threshold absolute air to fuel ratio (mole basis) of above ∼110 for consistent operation has been determined from the inter-cycle variability of the ignition delay, a result that agrees well with previous research of other in-cylinder parameters and further highlights the correlation between the air to fuel ratio and inter-cycle variability.Numerical modelling to investigate the sensitivity of ethanol combustion has also been performed. It has been shown that ethanol combustion is sensitive to the initial air temperature around the feasible operating conditions of the engine. Moreover, a negative temperature coefficient region of approximately 900–1050 K (the approximate temperature at fuel injection) has been shown with for n-heptane and n-heptane/ethanol blends in the numerical modelling. A consequence of this is that the dominate effect influencing the ignition delay under increasing ethanol substitutions may rather be from an increase in chemical reactions and not from in-cylinder temperature. Further investigation revealed that the chemical reactions at low ethanol substitutions are different compared to the high (>20%) ethanol substitutions.

Disturbance Rejection in Diesel Engines for Low Emissions and High Fuel Efficiency

This brief presents a novel and time-efficient control design for modern heavy-duty diesel engines using a variable geometry turbine and an exhaust gas recirculation valve. The goal is to simultaneously and robustly achieve low fuel consumption and low emissions of nitrogen oxides (NOx) and particulate matter (PM). A new combination of three controlled outputs is used: 1) specific engine-out NOx emissions; 2) air-fuel equivalence ratio; and 3) the pressure difference between intake and exhaust manifold, which reflect NOx and PM emissions and fuel efficiency, respectively. It is shown that this combination allows for effective disturbance rejection and results in a well-conditioned system. An underactuated input-output system is formed, for which a linear feedback controller is designed. In addition to this feedback controller, a feedforward controller is implemented, which improves the torque response and lowers the PM emissions during fast changes in torque demand. The combined control system is suitable for the full range of speed and load variations. This new controller is tested experimentally on a modern heavy-duty engine running a hot world harmonized transient cycle and compared with a baseline controller. The new controller reduces the NOx and PM emissions by 3.9% and 11.7%, respectively, without a fuel penalty.

Experimental investigations of the effect of pilot injection on performance, emissions and combustion characteristics of Karanja biodiesel fuelled CRDI engine

Pilot and post injections are being used in modern diesel engines for improving engine performance in addition to meeting stringent emission norms. Biodiesel produced from different feedstocks is gaining global recognition as partial replacement for mineral diesel in compression ignition (CI) engines. In this study, 10%, 20% and 50% Karanja biodiesel blends were used for investigation of pilot injections, injection pressures and injection timings on biodiesel blends. Experiments were carried out in a single cylinder CRDI research engine in multiple injection mode at 500 and 1000 bar fuel injection pressure (FIP) under varying start of pilot injection (SOPI) and start of main injection (SOMI) timings. Brake specific fuel consumption (BSFC) increased with increasing Karanja biodiesel concentration in test fuels however brake thermal efficiency (BTE) of biodiesel blends was slightly higher than mineral diesel. Lower biodiesel blends showed lower brake specific carbon monoxide (BSCO) and brake specific hydrocarbon (BSHC) emissions than mineral diesel. Brake specific nitrogen oxides (BSNOx) emissions from KOME20 and KOME10 were higher than mineral diesel. Combustion duration of KOME50 was also higher than mineral diesel.

The effects of emission control strategies on light-absorbing carbon emissions from a modern heavy-duty diesel engine

Control of atmospheric black carbon (BC) and brown carbon (BrC) has been proposed as an important pathway to climate change mitigation, but sources of BC and BrC are still not well understood. In order to better identify the role of modern heavy-duty diesel engines on the production of BC and BrC, emissions from a heavy-duty diesel engine operating with different emission control strategies were examined using a source dilution sampling system. The effect of a diesel oxidation catalyst (DOC) and diesel particulate filter (DPF) on light-absorbing carbon (LAC) was evaluated at three steady-state engine operation modes: idle, 50% speed and load, and 100% speed and load. LAC was measured with four different engine configurations: engine out, DOC out, DPF out, and engine out with an altered combustion calibration. BC and BrC emission rates were measured with the Aethalometer (AE-31). EC and BC emission rates normalized to the mass of CO2 emitted increased with increasing engine speed and load. Emission rates normalized to brake-specific work did not exhibit similar trends with speed and load, but rather the highest emission rate was measured at idle. EC and OC emissions were reduced by 99% when the DOC and DPF architecture was applied. The application of a DPF was equally effective at removing 99% of the BC fraction of PM, proving to be an important control strategy for both LAC and PM. BC emissions were unexpectedly increased across the DOC, seemingly due to a change aerosol optical properties. Removal of exhaust gas recirculation (EGR) flow due to simulated EGR cooler failure caused a large increase in OC and BrC emission rates at idle, but had limited influence during high load operation. LAC emissions proved to be sensitive to the same control strategies effective at controlling the total mass of diesel PM.Implications: In the context of black carbon emissions, very small emission rates of brown carbon were measured over a range of control technologies and engine operating conditions. During specific idle engine operation without EGR and adjusted fueling conditions, brown carbon can be formed in significant amounts, requiring careful management tactics. Control technologies for particulate matter are very effective for light-absorbing carbon, reducing black carbon emissions to near zero for modern engines equipped with a DPF. Efforts to control atmospheric brown carbon need to focus on other sources other than modern diesel engines, such as biomass burning.

A Study on the Performance Improvement in the Type VE Conventional Fuel Distributor System

The emission and the noise in the Diesel engines are the main factors causing the environment pollution. To overcome the disadvantage, the Electronic Diesel Control system (EDC) has been equipped with modern Diesel engines. This paper will analyze the installation and the conversion of the VE(*) conventional fuel system to the VE - EDC in Hyundai H100 1T25. The application of the VE - EDC in the traditional Diesel engine brings some advantages in the performance, the efficiency, the emission and the fuel consumption thanking to the exact control of the fuel flow and the injection timing which are respectively controlled with the spill control valves and the timing control valves. The results show that the engine performance is significantly increased (about 5 ÷10 % for the torque and 10 ÷15 % for the power); the fuel consumption is also reduced about 10 ÷30 % as the VE - EDC is used for the conventional Diesel engine. In additional, there is also the achievement in the improvement of the emission in engine: the reduction of CO is about 40 ÷50 %; of HC is about 5÷20 % and so on.