Automotive Diesel Engine Research Articles

Study of the cycle variability at an automotive diesel engine fuelled with LPG

Liquid Petroleum Gas is a viable alternative fuel for diesel engines due to its ability of emissions and fuel consumption reduction. Combustion variability at LPG diesel engine is analysed for maximum pressure, maximum pressure angle and indicated mean effective pressure. Combustion variability is influenced by the increase of LPG cycle dose which lead to the increase of the cycle variability coefficients values, but without exceeding the admitted values that provide diesel engine reliability. Analysis of COV values establishes the maximum admitted values of LPG cycle.

An indirect method for the real-time evaluation of the fuel mass injected in small injections in Common Rail diesel engines

The pilot injected fuel masses generally are in the 1–4mg range for automotive diesel engines and are affected by significant dispersion, which represents an issue for injection control systems. A new methodology has been developed for real-time evaluation of the fuel injected in small injections in diesel engines.The measurement requires the installation of a single pressure transducer on a pipe connecting the injector to the rail. A simple algorithm, which is based on the mass conservation and momentum balance equations, written with respect to a reference frame that is integral with the pressure wave front, has been elaborated to convert the experimental pressure time history into an instantaneous flow rate. The results on the flow-rate through the pipe that connects the injector to the rail are compared with the corresponding numerical outcomes from a 1D model of the fuel injection system.The estimated fuel quantities that enter the injector have been verified to be well correlated with the measured volumes of the fuel injected in small injections. The relation that has been found could be implemented in the engine electronic control unit and employed together with the pressure transducer installed at the inlet of the injector for a more accurate real-time control of both the injected mass and the system high-pressure.

Regeneration of diesel particulate filters: Effect of renewable fuels

Current trends in diesel transport anticipate that in the upcoming future a range of renewable fuels will be necessary to comply with emission and sustainability legislations. Exhaust after-treatment devices such as diesel particulate filters –DPFs– will have to operate satisfactorily with this pool of biofuels. In particular, DPF regeneration is crucial to cut the fuel penalty and guarantee an acceptable lifetime for this device. In the present work, an automotive diesel engine was run with fossil fuel and three renewable fuels: a conventional biodiesel, a fuel manufactured through Fischer-Tropsch –FT– process and a HVO biofuel. The DPF was loaded and regenerated through an active process with fuel post-injections. Additionally, soot samples were investigated with thermo-gravimetry (TGA) and calorimetry (DSC) to confirm whether these techniques obtain relevant information for explaining DPF behavior. Both methods proved that biodiesel leads to a more economical regeneration being the biodiesel soot, more reactive than the other samples, the main reason. DPF regenerations with paraffinic fuels (FT-derived and HVO) did not reveal strong differences compared to diesel, though TGA and DSC results suggested that soot from paraffinic biofuels is more reactive than that from diesel. The exhaust gas temperature and composition are behind this apparent discrepancy.

Application of a global kinetic model on an SCR coated on Filter (SCR-F) catalyst for automotive applications

Selective Catalytic Reduction (SCR) catalysts coated on diesel particulate Filter, SCR-F, have been introduced for automotive applications in the last years due to the capability of reducing NOx and PM simultaneously below the limits imposed by emission regulations. In this context, the performance of a commercial silicon carbide Cu/zeolite SCR-F for controlling NOx emissions in an automotive diesel engine was analyzed both experimentally and numerically for different soot loading levels with the aim to investigate its catalytic properties and to build a simulation model of the aftertreament device capable of predicting NOx conversion efficiency, NH3 storage capacity and soot conversion due to passive regeneration.

Effect of Di-Tertiary Butyl Peroxide on the performance, combustion and emission characteristics of ethanol blended cotton seed methyl ester fuelled automotive diesel engine

An experimental study is carried out to examine and analyze the influence of Di-Tertiary Butyl Peroxide in bioethanol diesel blends on the performance, combustion and emission characteristics in a single cylinder, 4-stroke, naturally aspirated, automotive diesel engine for variable speed at full load conditions. Esterified cotton seed oil of 5% by volume is emulsified with 95% pure diesel to get the base fuel (BE0) for the experiments. Bioethanol diesel blends are produced from base fuel by adding 5% and 10% pure ethanol on a volumetric basis to obtain BE5 and BE10 respectively. The bioethanol fuels are low in Cetane number and hence Di-Tertiary Butyl Peroxide a Cetane enhancer is added by 0.4% by volume to produce BE5CN0.4% and BE10CN0.4% emulsions respectively. It is found from the experiments carried out, that an inverse trend exists between brake thermal efficiency and percentage of ethanol in base fuel. This is due to the lower calorific value of ethanol and an improvement in brake thermal efficiency is observed with ignition improver added blends. The presence of Cetane improver significantly reduced oxides of nitrogen and unburned hydro carbon emissions for overall engine speed and carbon monoxide emissions for low to medium speed range.

Review of Some Methods for Improving Transient Response in Automotive Diesel Engines through Various Turbocharging Configurations

Turbocharged diesel engines suffer from poor drivability, mostly at low loads and speeds, leading also to overshoot in exhaust emissions (primarily PM/soot and NOx) during the transient operation after a speed or load increase. The main cause for this problematic behavior is located in the turbocharger in the form of high moment of inertia and unfavorable aerodynamic-type compressor flow characteristics. In the present work, various alternative turbocharging configurations are reviewed that have proven successful in improving the dynamic diesel engine operation. The configurations studied are: combined supercharging, variable geometry turbine, electrically assisted turbocharging, two stage series and sequential turbocharging, as well as lower turbine moment of inertia. It is shown that significant improvement in the engine’s transient response can be realized through reduction in the turbocharger mass moment of inertia (using lighter materials and/or more than one units). Increasing the available turbine torque (e.g. through elevated turbine back pressure in a variable-geometry turbine) is another successful option, as well as enhancement of the compressor boost pressure (e.g. through the use of a positive displacement compressor upstream of the turbocharger). Finally, the use of external energy (e.g. in the form of electrical assistance on the turbocharger shaft during the critical turbocharger lag phase) is another recently developed and highly promising measure to mitigate the drawbacks of the poor transient performance of turbocharged diesel-engined vehicles and limit their exhaust emissions.

ДИЗЕЛЬНОЕ СМЕСЕВОЕ ТОПЛИВО: ПРОБЛЕМЫ И ИННОВАЦИОННЫЕ РАЗРАБОТКИ

The goal of the research is constructive adaptation of automotive diesel engines working by diesel mixed fuel. A perspective kind of an alternative motor fuel is biodiesel blend produced with mixing of vegetable oil and conventional diesel fuel in different percentages. The present diesel-powered machinery is not adapted to work on such kind of fuel because of the different properties of biodiesel and diesel fuels. Applying of the invented devices (such as dual-fuel supply system, the mixer-filter and ultrasonic fuel mixer) allows to adapt automotive diesel engines for work on biodiesel blend. The dual-fuel supply system performs engine start, warm-up and stop modes on mineral diesel fuel, and its work on biodiesel blend on other modes. The original design of the fuel mixer-filter provides effective mixing of components and filtration from contaminants. Due to the high frequency vibrations the ultrasonic mixer provides the obtaining of homogeneous fuel composition and molecular splitting of higher fatty acids contained in vegetable oil.

Optimal-Behavior-Based Dynamic Calibration of the Automotive Diesel Engine

This paper presents a novel automotive engine management system (EMS) calibration methodology for rapid dynamometer test-bed data collection and mapping I.C. engine controllers with significant dynamic and transient performance requirements. This paper applies the methodology to an industrial state of the art WAVE-RT 1 model of a 1.5 L Turbo EU6.1 Diesel engine acting as a virtual dynamometer based engine. The approach directly yields a feedforward controller in a nonlinear polynomial structure that can be either directly implemented in the EMS or converted into a dynamic or static lookup table format. The methodology is based on multistage black-box modeling and dynamic system optimization. The process can exploit the power of global constrained numerical optimization codes and use system identification techniques with dynamic design of experiments. The objective of the engine controller optimization is to improve the fuel economy while maintaining specified (legislated) limits on emissions and map smoothness for driveability. The key contribution is a novel approach to obtaining a feedforward dynamic calibration controller from the system identification of the computed optimal behavior. Model structure selection techniques are shown to be usefully employed to further improve the accuracy of the system identification and so enhance the control performance of the dynamic controllers. The results indicate that the dynamic calibration methodology leads to a considerably reduced requirement for testing time and an improvement of between 1.9% and 2.6% in fuel economy over extra urban driving cycle without violating the emission constraints compared with current steady-state model-based calibration methods. 1 Ricardo PLC.

Coordinated Performance Optimization of a Variable Geometry Compressor With Model Predictive Control for a Turbocharged Diesel Engine

The concept of variable geometry compressor (VGC) has been recently proposed as a future improvement for automotive turbochargers to further increase the efficiency and boosting at low engine speed, and to provide a more direct control over the stability margin at medium–high engine load. This paper presents a control design for the air path system of an automotive diesel engine equipped with exhaust gas recirculation (EGR), variable geometry turbine (VGT), and VGC systems. Starting from a validated model, a study of the steady-state and dynamic responses is conducted to understand the influence of the VGC combined with VGT–EGR actuators on the performance of the system. Then, a feedback control strategy that coordinates the VGC actuator with the existing VGT–EGR controller based on model predictive control is proposed to optimize the compressor performance. The new methodology shows how the VGC can be used to increase the stability range of the compressor while providing the opportunity to improve its efficiency, by means of shifting the surge limit and reshaping the peak efficiency region of the machine. Simulation results on a vehicle acceleration profile with gear shift transients are provided to verify the effectiveness of the proposed methodology.

Hybrid EGR and turbocharging systems control for low NOX and fuel consumption in an automotive diesel engine

An experimental investigation was made on a downsized Euro 5 turbocharged diesel engine managing high/low pressure EGR systems and the variable nozzle turbine, aiming at major reductions in NOX emissions while enhancing fuel consumption in comparison with reference configuration. Three part load engine operating conditions were chosen at low and medium speed levels, applying different strategies to a number of control variables (relative air–fuel ratio, VNT opening degree/intake pressure, valves position in low pressure EGR circuit), thus exploring the whole range of high/low pressure EGR proportion. In suitable operating modes of tested conditions, NOX emissions were reduced up to 58–66%. Brake specific fuel consumption decreased around 5–9.5% at low speed/load, 1.7–3.3% in the intermediate condition while no advantages were achieved in the third working point. The activation of low pressure loop confirmed to be beneficial for turbocharger performance, rising its rotational speed thus granting for a better transient response, while increase in soot emissions ranged in a wide interval. For each condition, optimal operating modes were identified, with the relevant EGR proportion. A prevailing contribution from the long route circuit was generally requested, up to the exclusion of short route loop at higher level of speed and load.

Enhanced combustion model with fuel-wall impingement oriented to injection pattern tuning in automotive Diesel engines

Nowadays the high competition reached by the automotive market forces original equipment manufacturers (OEMs) towards innovative solutions. Strict emission standards and fuel economy targets make the work hard to be accomplished. Therefore modern engines feature complex architecture and embed new devices for exhaust gas recirculation (EGR), turbocharging (e.g. multi-stage compressors), gas after-treatment (e.g. selective catalyst reduction (SCR)) and fuel injection (either high or low pressure). In this context the engine management system (EMS) plays a fundamental role to optimize engine operation. The paper deals with fuel spray and combustion simulation by a multi-zone phenomenological model aimed at the optimal tuning of the injection pattern. The fuel spray model simulates the injection process, the fuel-air mixture formation, the in-cylinder gas mixture evolution and accounts for the fuel-wall impingement that usually occurs in case of low-medium injection pressure or advanced injection timing. This feature is fundamental to investigate a wide range of injection pattern set-points, as those applied for advanced combustion concepts (i.e. Premixed Charge Compression Ignition (PCCI)). The impingement of the spray on cylinder walls is modeled by a zero-dimensional approach, simulating dynamics and evaporation of the fuel film with two different semi-empirical models. The numerical and experimental analyses have been performed with respect to an automotive Common-Rail Diesel engine, equipped with high pressure EGR and VGT turbocharger. The experimental measurements have been carried out at the engine test stand, investigating operating conditions with highly advanced injection timing and low rail pressure, in order to induce the fuel impingement process. Model validation against the experimental data exhibits satisfactory accuracy in predicting the impact of injection pattern control on impingement.

Evaluation of a Semiempirical, Zero-Dimensional, Multizone Model to Predict Nitric Oxide Emissions in DI Diesel Engines’ Combustion Chamber

In the present study, a semiempirical, zero-dimensional multizone model, developed by the authors, is implemented on two automotive diesel engines, a heavy-duty truck engine and a light-duty passenger car engine with pilot fuel injection, for various operating conditions including variation of power/speed, EGR rate, fuel injection timing, fuel injection pressure, and boost pressure, to verify its capability for Nitric Oxide (NO) emission prediction. The model utilizes cylinder’s basic geometry and engine operating data and measured cylinder pressure to estimate the apparent combustion rate which is then discretized into burning zones according to the calculation step used. The requisite unburnt charge for the combustion in the zones is calculated using the zone equivalence ratio provided from a new empirical formula involving parameters derived from the processing of the measured cylinder pressure and typical engine operating parameters. For the calculation of NO formation, the extended Zeldovich mechanism is used. From this approach, the model is able to provide the evolution of NO formation inside each burned zone and, cumulatively, the cylinder’s NO formation history. As proven from the investigation conducted herein, the proposed model adequately predicts NO emissions and NO trends when the engine settings vary, with low computational cost. These encourage its use for engine control optimization regarding NOxabatement and real-time/model-based NOxcontrol applications.

Reducing Cold Start Emissions from Automotive Diesel Engine at Cold Ambient Temperatures

ABSTRACTCold start performance of diesel engines is determined by engine design, fuel type, fuel injection strategies, lubricant and ambient temperature conditions. Prevailing emissions legislation regarding low temperature emission tests applicable for gasoline vehicles is likely to be implemented to diesel vehicles. The present research work investigates the effects of intake air heating on a Euro 5 diesel engine’s performance and exhaust emission (gaseous and particulate emissions) characteristics during the cold start followed by idling at cold ambient conditions. Heating of intake air entering the engine at cold ambient temperature conditions improved fuel combustion as well as reduced the cranking period and improved the fuel economy. More than 50% reduction in HC and 17% reduction in NOx emissions were achieved by intake air heating. Number count of accumulation mode particulates were higher during cold start compared to idle operation for all the temperature conditions. Intake air heating decreased the particulate number and size that led to reduction in total particulate mass by higher than 50% and 75% during cold start and idle respectively. The intake air heating strategy improved the cold start performance of the diesel engine at cold ambient temperature conditions and thereby would reduce the overall driving cycle emissions.

On Combustion of Diesel Fuel Drops at LPG Fuelling by Diesel Gas Method

The Liquid Petroleum Gas can be use at diesel engine with significant reductions in nitrous oxides and smoke emissions and affects the in-cylinder mixture forming and combustion process. The paper presents the results of a thermodynamic model developed for vaporization and combustion processes simulation for an automotive diesel engine fuelled with LPG by diesel gas method. The mass flow of vaporized substance at the particle area, drops combustion time and flame position are determinate, showing a significant influence of LPG cycle dose on their characteristic parameters. The drops combustion duration decreases for dual fuelling and the flame radius increases.

An Application of Reference Governor to a Diesel Engine Air Path System: Implementation of a Multi-Variable Reference Modification Algorithm

This paper considers an application of a reference governor (RG) to the air path system of an automotive diesel engine. The air path system can be represented as a multi-input-multi-output (MIMO) nonlinear system which has hardware interaction between fresh air and exhaust gas paths resulting from a turbocharger and an exhaust gas recirculation (EGR). The system has several constraints which should be considered in control design, such as maximal boost pressure, turbine speed and EGR min-max constraints. In order to explicitly deal with the constraints, we employ an online RG to modify boost pressure and the EGR rate references so that their predicted values ensure the constraints. Using a prediction model obtained via system identification the RG algorithm is established based on a planar search combined with the gradient descent method and a bisectional search. An experimental result using a real engine is shown to demonstrate the effectiveness of the present method.

Component Analysis of Deposits in Selective Catalytic Reduction System for Automotive Diesel Engine

In this paper, deposits in exhaust pipes for automotive diesel engines were studied by various chemical analysis methods and a kind of analysis process to determine the compositions of organic matter was proposed. Firstly, the elements of the deposits were determined through the element analysis method. Then using characteristic absorption properties of organic functional groups to the infrared spectrum, the functional groups in the deposits were determined. Finally, by GC-MS (gas chromatography - mass spectrometry) test, the content of each main component was determined quantitatively. Element analysis results indicated that the deposits adsorbed metal impurities from fuel oil, lubricating oil, mechanical wear and urea water solution. The result of GC-MS test showed that the area percentage of cyanuric acid was the biggest (about 85%), the second was urea (about 4%), and the content of biuret and biurea was scarce.

Aspects of in-Cylinder Mixture Formation Study for a Diesel Engine Fuelled with LPG by Diesel-Gas Method

The Liquid Petroleum Gas can be use for diesel engine fuelling with significant result in term of pollutant emissions improvement, with important reduction of nitrous oxides and smoke for a LPG dual fuelled diesel engine. Beside this the LPG fuelling affects the combustion process inside the cylinder and also the mixture forming. High degree of homogeneity of the air-LPG mixtures will accelerate the in-cylinder mixture forming between air-LPG and diesel fuel jets, since the LPG-air mixture combustion starts. The paper presents the results of a zero-dimensional, one-zone thermodynamic model developed by authors for diesel fuel jets vaporization and combustion at dual fuelling. The model shows the diesel fuel jet characteristic, the break-up period, the mass flow of vaporized substance on the particle surface, drops vaporization time, air-fuel mixture forming speed, drops combustion time and flame position, showing a significant influence of LPG cycle dose on their characteristic parameters. The drops vaporization and combustion duration decrease for dual fuelling and the flame radius increases. Thus, based on the experimental data, an evaluation model for mixture forming was developed for an automotive diesel engine fuelled with LPG and diesel fuel by diesel-gas method.

Multi-Technique Analysis of Soot Reactivity from Conventional and Paraffinic Diesel Fuels

A 2.0 L, 4-cylinder, turbocharged, common rail diesel engine was used for generating soot samples. Three fuels were tested: a “first fill” diesel fuel, a gas-to-liquid fuel (GTL) and a hydrotreated fuel derived from vegetable oils (HVO). A stationary low-load operating mode (1667 rpm and 78 Nm) was selected for testing, and some modifications in the injection process (strategy, timing and pressure) were evaluated experimentally to assess their influence in the soot reactivity. The collected soot samples were characterized using a thermogravimetric analyzer (TGA), a differential scanning calorimeter (DSC), a diffuse reflectance infrared Fourier transform spectrometer (DRIFTS) and a surface area analyzer. All techniques anticipated that HVO and GTL soot samples are more reactive (i.e. show higher potential to be oxidized at lower temperatures leading to more efficient regeneration processes in a Diesel Particle Filter – DPF) compared to diesel soot. Additionally, the four characterization techniques showed the same tendencies when analyzing the effect of the engine operating parameters. In view of the results, the paraffinic fuels – HVO and GTL – here tested confirm their promising perspective for future use in automotive diesel engines, while some guides are proposed to enhance the soot reactivity via calibration of engine operating parameters.

High-temperature and high-power-density nanostructured thermoelectric generator for automotive waste heat recovery

Given increasing energy use as well as decreasing fossil fuel sources worldwide, it is no surprise that interest in promoting energy efficiency through waste heat recovery is also increasing. Thermoelectric generators (TEGs) are one of the most promising pathways for waste heat recovery. Despite recent thermoelectric efficiency improvement in nanostructured materials, a variety of challenges have nevertheless resulted in few demonstrations of these materials for large-scale waste heat recovery. Here we demonstrate a high-performance TEG by combining high-efficiency nanostructured bulk materials with a novel direct metal brazing process to increase the device operating temperature. A unicouple device generates a high power density of 5.26Wcm−2 with a 500°C temperature difference between hot and cold sides. A 1kW TEG system is experimentally demonstrated by recovering the exhaust waste heat from an automotive diesel engine. The TEG system operated with a 2.1% heat-to-electricity efficiency under the average temperature difference of 339°C between the TEG hot- and cold-side surfaces at a 550°C exhaust temperature. The high-performance TEG reported here open up opportunities to use TEGs for energy harvesting and power generation applications.

Physico-chemical speciation of particulates emanating from Karanja biodiesel fuelled automotive engine

It is essential to reduce emissions from the existing vehicles, in order to preserve the environment. In this study, Karanja oil derived biodiesel generated particulates emanating from a medium-duty transportation diesel engine fitted with a diesel oxidation catalyst (DOC) were characterised. Regulated gaseous emissions, particle size–number distributions, elemental carbon (EC) and organic carbon (OC) of these particulates were determined under varying engine load conditions (no load, 25%, 50%, 75% and 100% load at rated torque speed of 2500rpm) in order to assess the effectiveness of biodiesel blend (B20) compared to mineral diesel in combination with the use of DOC. Particle size–number distribution showed significantly higher concentration of nuclei mode particles for both test fuels. Particle size–number distribution was observed to be bimodal in nature and in two size ranges: less than 10nm and 25–250nm, respectively. This study reports few important insights into possible use of biodiesel in effectively reducing overall particulate emissions as well as gaseous emissions from automotive diesel engines fitted with DOC.