Common-rail Turbocharged Diesel Engine Research Articles

Engine performance and emissions evaluation of surfactant-free B30 biodiesel–diesel/water emulsion as alternative fuel

Malaysia is one of the top exporters of palm oil, and although currently facing fierce resistance towards palm oil imports in some parts of the globe, one of the ways to utilize this commodity is by increasing palm biodiesel content in local commercial diesel. However, due to the oxygen-rich nature of biodiesel, its utilization suffers from increased nitrogen oxides (NOx) emission compared to conventional diesel. To mitigate this issue and improve diesel engine performance and emissions using biodiesel–diesel blends, this study attempted to investigate implementation of a real-time non-surfactant emulsion fuel supply system (RTES) which produces water-in-diesel emulsion as fuel without surfactants. NOx reducing capability of water-in-diesel produced by RTES has been well documented. Therefore, in this study, 30% biodiesel–diesel (B30) was used as the base fuel while B30-derived emulsions consisting of 10 wt%, 15 wt% and 20 wt% water content were supplied into a 100 kVA, 5.9-L common rail turbocharged diesel engine electric generator. Fuel consumption and exhaust emissions were measured and compared with commercially available Malaysian low grade diesel fuel (D2M). Evidence suggested that emulsified B30 biodiesel–diesel produced by RTES was able to increase brake thermal efficiency (BTE) up to a maximum of 36% and reduce brake specific fuel consumption (BSFC) up to 8.70%. Furthermore, B30 biodiesel–diesel emulsions produced significantly less NOx, carbon monoxide and smoke at high engine load. In conclusion, B30 biodiesel–diesel emulsions can be readily utilized in current diesel engines without compromising on performance and emissions.

Emulsifier Free Emulsion as Fuel in a Common Rail Turbocharged Diesel Electric Generator

In present study, performance and emissions of a 100 kVA common rail turbocharged diesel engine electric generator installed with an emulsifier free emulsion fuel supply system, known as Real-Time Non-Surfactant Emulsion Fuel Supply System (RTES) was investigated experimentally. This system uses a novel mixing system design upgraded from previous RTES design, with an omission of ultrasonic agitator component. In this system, water was injected into an emulsification device where water and diesel fuel were mixed and supplied to the engine as an emulsion fuel. It was found that water-in-diesel emulsions produced from this system increased the engine's Brake Thermal Efficiency (BTE) to a maximum point of 42.7%, a marked increase of 28.6% from the base diesel. Furthermore, Brake Specific Fuel Consumption (BSFC) was reduced as water percentage increases. Additionally, Nitrogen Oxides (NO x ) emissions and smoke opacity was also reduced. However, water-in-diesel emulsion emitted increased carbon monoxide (CO) in lower to middle loads before a reduction was observed in higher loads. Meanwhile, unburned hydrocarbons (UHC) emission was reduced as 14% to 22% water percentage was achieved. In short, emulsifier free emulsion fuel produced by RTES was able to improve thermal efficiency and reduce fuel consumption and harmful emissions.

Study on Diesel Engine Characteristics under Large Transient EGR

Modern diesel engines tend to employ up to 50-70% exhaust gas recirculation (EGR) together with high intake pressure and injection strategies to enable low temperature combustion (LTC) cycles for reducing NOx and soot emissions simultaneously. Obviously, the combustion conditions and exhaust emissions are sensitive at such high EGR rate. And any slight fluctuation in the EGR quantity will bring unintended deviations from the desired engine performance, thus LTC mode is only limited at partial engine operation points. So the engine has to switch combustion mode frequently between compression ignition (CI) and LTC region within a few engine cycles in real application, which may result in combustion cyclic variations and even misfire, especially during transient operation. In order to investigate effect of heavy EGR transient process on engine combustion cycles, the experimental work was carried out on a four-cylinder VM common-rail turbocharged diesel engine. The results show that the oxygen concentration in the intake charge almost maintains at steady level at EGR steady conditions, while the exhaust oxygen concentration is affected by exhaust values opening/exhaust values closing (EVO/EVC), and result in intra-cycle fluctuation, which will approximately bring 2% calculation error bandwidth for EGR ratio. From 37% to 55% EGR ratio, the EGR gas is mainly driven by the pressure ratio of intake and exhaust duct, and it will experience a long accumulating process to reach a new equilibrium. And the inordinate delayed injection timing will promote in-cylinder cycle-to-cycle variation and even misfire, especially during transition from CI to LTC region.

Analysis of the performance, emission and combustion characteristics of a turbocharged diesel engine fuelled with Jatropha curcas biodiesel-diesel blends using kernel-based extreme learning machine.

The purpose of this study is to investigate the performance, emission and combustion characteristics of a four-cylinder common-rail turbocharged diesel engine fuelled with Jatropha curcas biodiesel-diesel blends. A kernel-based extreme learning machine (KELM) model is developed in this study using MATLAB software in order to predict the performance, combustion and emission characteristics of the engine. To acquire the data for training and testing the KELM model, the engine speed was selected as the input parameter, whereas the performance, exhaust emissions and combustion characteristics were chosen as the output parameters of the KELM model. The performance, emissions and combustion characteristics predicted by the KELM model were validated by comparing the predicted data with the experimental data. The results show that the coefficient of determination of the parameters is within a range of 0.9805-0.9991 for both the KELM model and the experimental data. The mean absolute percentage error is within a range of 0.1259-2.3838. This study shows that KELM modelling is a useful technique in biodiesel production since it facilitates scientists and researchers to predict the performance, exhaust emissions and combustion characteristics of internal combustion engines with high accuracy.

Air-fuel Ratio Estimation Along Diesel Engine Transient Operation Using In-cylinder Pressure

The increasing competition among automotive OEMs together with the worsening of the environmental pollution has lead to the development of complex engine systems. Innovative control strategies are needed to simplify and improve the Engine Management System (EMS), moving towards energy saving and complying with the restrictions on emissions standards. In this scenario the application of methodologies based on the in-cylinder pressure measurement finds widespread applications. Indeed, the in-cylinder pressure signal provides direct in-cylinder information with a high dynamical potentiality that is fundamental for the control and diagnosis of the combustion process. Furthermore, the in-cylinder pressure measurement may also allow reducing the number of existing sensors on-board, thus lowering the equipment costs and the engine wiring complexity.The paper focuses on the estimation of the Air-Fuel ratio from the in-cylinder pressure signal. The methodology is based on the analysis of the statistical moments of the pressure cycle and was already presented by the authors and applied to a set of steady state engine operation conditions. In this paper the technique has been enhanced in order to be applied under the more critical engine transient operation. The results achieved show a satisfactory accuracy in predicting the Air-Fuel ratio during engine transients performed at the engine test bench on a Common-Rail turbocharged Diesel engine.

Influence of fuel-borne oxygen on European Stationary Cycle: Diesel engine performance and emissions with a special emphasis on particulate and NO emissions

Exploration of sustainable fuels and their influence on reductions in diesel emissions are nowadays a challenge for the engine and fuel researchers. This study investigates the role of fuel-borne oxygen on engine performance and exhaust emissions with a special emphasis on diesel particulate and nitric oxide (NO) emissions. A number of oxygenated-blends were prepared with waste cooking biodiesel as a base oxygenated fuel. Triacetin, a derivative from transesterified biodiesel was chosen for its high oxygen content and superior fuel properties. The experimental campaign was conducted with a 6-cylinder, common rail turbocharged diesel engine equipped with highly precise instruments for nano and other size particles and other emissions. All experiments were performed in accordance with European Stationary Cycle (ESC 13-mode). A commercial diesel was chosen as a reference fuel with 0% oxygen and five other oxygenated blends having a range of 6.02–14.2% oxygen were prepared. The experimental results revealed that the oxygenated blends having higher a percentage of fuel-borne oxygen reduced particulate matter (PM), particle number (PN), unburned hydrocarbon (UBHC) and carbon monoxide (CO) emissions to a significantly low level with a slight penalty of NO emissions. The main target of this study was to effectively utilise triacetin as an additive for waste cooking biodiesel and suppress emissions without deteriorating engine performance. The key finding of this investigation is the significant reductions in both particle mass and number emissions simultaneously without worsening engine performance with triacetin-biodiesel blends. Reductions in both particle mass and number emissions with a cost-effective additive would be a new dimension for the fuel and engine researchers to effectively use triacetin as an emission suppressor in the future.

Methodologies for Air-Fuel ratio and trapped mass estimation in Diesel engines using the in-cylinder pressure measurement

Nowadays the increasing automotive market competition together with the worsening of the environmental pollution leaded to the development of complex engine systems. Innovative control strategies are needed to simplify and improve the Engine Management System (EMS), moving towards energy saving engines and complying with the restrictions on emissions standards. In this scenario the application of methodologies based on the in-cylinder pressure measurement finds widespread applications. Indeed, the in-cylinder pressure signal provides direct in-cylinder information with an high dynamical potentiality, that is fundamental for the control and diagnosis of the combustion process. Furthermore, the in-cylinder pressure measurement may also allow reducing the number of existing sensors on-board, thus lowering the equipment costs and the engine wiring complexity.This paper focuses on the detection of the Air-Fuel ratio and the in-cylinder trapped mass after the intake valve closing from the in-cylinder pressure signal. The Air-fuel ratio estimation might allow replacing the lambda sensor, the estimation method is based on a statistical approach. The in-cylinder trapped mass estimation gives the opportunity to by-pass the CO2 measurement for the evaluation of the EGR rate, in this case the Δp method is proposed. The developed techniques were validated vs. experimental data measured at the engine test bench on a Common-Rail turbocharged Diesel engine. The results show a good accuracy in predicting Air-Fuel ratio and in-cylinder trapped mass in a wide engine operating range. Because of both the low computational burden and the good results, these methodologies are suitable to be implemented on-board.

Automotive Turbochargers Power Estimation Based on Speed Fluctuation Analysis

Turbocharging technology will play a crucial role in the near future as a way to meet the requirements for pollutant emissions and fuel consumption reduction.However, optimal turbocharger control is still an issue, especially for downsized engines fitted with a low number of cylinders. As a matter of fact, automotive turbochargers are characterized by wide operating range and unsteady gas flow through the turbine, while only steady flow maps are usually provided by the manufacturer. In addition, in passenger cars applications, real-time turbocharger optimal control is even more difficult because of the lack of information about pressure/temperature in turbine upstream/downstream circuits and turbocharger rotational speed.In order to overcome these unknowns, this work presents a methodology for instantaneous turbocharger rotational speed determination through a proper processing of the signal coming from one accelerometer mounted on the compressor diffuser, or one microphone facing the compressor. The presented approach can be used to evaluate both turbocharger speed mean value and the amplitude of turbocharger speed fluctuations caused by the pulsating gas flow in turbine upstream and downstream circuits. Once turbocharger speed has been determined, it can be used to estimate power delivered by the turbine.The whole estimation algorithm has been developed and validated for a light duty turbocharged Common-Rail Diesel engine mounted in a test cell. However, the developed methodology is general and can be applied to different turbochargers, both for Spark Ignited and Diesel applications.

Experimental Analysis of a Turbo-charged Common-rail Diesel Engine Fueled with Biodiesel

In an effort to evaluate the effect of biodiesel fuel on engine performance and emission, experiments are conducted based on a turbo-charged common-rail diesel engine. Results show that the injection timing can be slightly retarded when biodiesel fuel is applied for improved performance and reduced NOx emission. To explain this phenomenon, combustion analysis is conducted based on the cylinder pressure measurement. The shorter ignition delay of biodiesel combustion explains why the best torque timing should be retarded for biodiesel fuel.

Numerical Study of a Turbo-charged Common-rail Diesel Engine Fueled with Various Biodiesel Blends

The combustion processes of various biodiesel blends in a turbo-charged common-rail diesel engine with exhaust gas recirculation (EGR) is studied numerically. This computational fluid dynamics (CFD) model enables comprehensive investigation of the physical phenomena such as the effect of tumbling motions on the mixing and combustion, the spatial distributions of various species, temperature, pressure, and pollutant formation of NOx inside the combustion chamber. The mean cylinder pressures predicted by the CFD model at various injection timings and EGR rates are validated against the experimental data of cylinder pressure with pure diesel. Finally, numerical study of engine combusting various blends of biodiesel fuel is conducted. The effects of blend ratio on combustion process and NOx emission are discussed.

A Bayesian approach to the determination of ignition delay

A novel in-cylinder pressure method for determining ignition delay has been proposed and demonstrated. This method proposes a new Bayesian statistical model to resolve the start of combustion, defined as being the point at which the band-pass in-cylinder pressure deviates from background noise and the combustion resonance begins. Further, it is demonstrated that this method is still accurate in situations where there is noise present. The start of combustion can be resolved for each cycle without the need for ad hoc methods such as cycle averaging. Therefore, this method allows for analysis of consecutive cycles and inter-cycle variability studies. Ignition delay obtained by this method and by the net rate of heat release has been shown to give good agreement. However, the use of combustion resonance to determine the start of combustion is preferable over the net rate of heat release method because it does not rely on knowledge of heat losses and will still function accurately in the presence of noise. Results for a six-cylinder turbo-charged common-rail diesel engine run with neat diesel fuel at full, three quarters and half load have been presented. Under these conditions the ignition delay was shown to increase as the load was decreased with a significant increase in ignition delay at half load, when compared with three quarter and full loads.

Influence of Different Alternative Fuels on Particle Emission from a Turbocharged Common-Rail Diesel Engine

Influence of alternative fuels on diesel engine exhaust particle emission was investigated using an ultra-low sulfur diesel fuel as a baseline fuel where two biodiesels (canola & tallow), Fischer–Tropsch and bioethanol were used as alternative fuel. Both the biodiesels coming from canola and tallow feedstocks, as well as F-T were used as 100% to run the engine where up to 40% energy substitution by ethanol was achieved without any sacrifice of engine power output. It was found that up to 30% ethanol substitution reduced both particulate mass (PM) and particle number (PN) emission consistently for all load settings at 2000 rpm, highest 59% reduction in PM and 70% reduction in PN observed at 100% load. As previously suggested the possible mechanism for the observed reduction is the oxidation of particulate matter by OH radicals which are in excess with ethanol fumigation. For 40% ethanol substitution some inconsistency was observed for PM emission at different loads but consistent reduction was found for PN. Condensation of unburned/partially burned hydrocarbons that later condense on existing soot might be responsible for this, as the maximum increase of PM was observed at quarter load where low in cylinder temperature favour to nucleation of unburned hydrocarbons. PM emission was also reduced in case of using 100% FT, and 100% biodiesel and the highest 90% reduction in PM was observed for biodiesel at 100% load with almost no difference between the two biodiesels itself. On the other side a considerable difference was observed between canola and tallow biodiesel in case of PN emission. Canola biodiesel increased PN, due to the presence of the nucleation mode, for almost an order of magnitude for all load and speed settings where no such increase was observed for tallow biodiesel.

The effect of dynamic operating conditions on nano-particle emissions from a light-duty diesel engine applicable to prime and auxiliary machines on marine vessels

This study presents the nano-sized particle emission characteristics from a small turbocharged common rail diesel engine applicable to prime and auxiliary machines on marine vessels. The experiments were conducted under dynamic engine operating conditions, such as steady-state, cold start, and transient conditions. The particle number and size distributions were analyzed with a high resolution PM analyzer. The diesel oxidation catalyst (DOC) had an insignificant effect on the reduction in particle number, but particle number emissions were drastically reduced by 3 to 4 orders of magnitude downstream of the diesel particulate filter (DPF) at various steady conditions. Under high speed and load conditions, the particle filtering efficiency was decreased by the partial combustion of trapped particles inside the DPF because of the high exhaust temperature caused by the increased particle number concentration. Retarded fuel injection timing and higher EGR rates led to increased particle number emissions. As the temperature inside the DPF increased from <TEX>$25^{\circ}C$</TEX> to <TEX>$300^{\circ}C$</TEX>, the peak particle number level was reduced by 70% compared to cold start conditions. High levels of nucleation mode particle generation were found in the deceleration phases during the transient tests.

The effect of dynamic operating conditions on nano-particle emissions from a light-duty diesel engine applicable to prime and auxiliary machines on marine vessels

This study presents the nano-sized particle emission characteristics from a small turbocharged common rail diesel engine applicable to prime and auxiliary machines on marine vessels. The experiments were conducted under dynamic engine operating conditions, such as steady-state, cold start, and transient conditions. The particle number and size distributions were analyzed with a high resolution PM analyzer. The diesel oxidation catalyst (DOC) had an insignificant effect on the reduction in particle number, but particle number emissions were drastically reduced by 3 to 4 orders of magnitude downstream of the diesel particulate filter (DPF) at various steady conditions. Under high speed and load conditions, the particle filtering efficiency was decreased by the partial combustion of trapped particles inside the DPF because of the high exhaust temperature caused by the increased particle number concentration. Retarded fuel injection timing and higher EGR rates led to increased particle number emissions. As the temperature inside the DPF increased from 25 °C to 300 °C, the peak particle number level was reduced by 70% compared to cold start conditions. High levels of nucleation mode particle generation were found in the deceleration phases during the transient tests.

Impact of Intake Oxygen Enrichment on Oxidative Reactivity and Properties of Diesel Soot

Oxygen addition to a four-cylinder turbo-charged common rail diesel engine was carried out by intake oxygen enrichment and by fuel oxygenation in order to study the effect of additional oxygen on oxidative reactivity and properties of diesel soot at low and high loads. The analyses of heat release rates and cylinder temperatures indicate that the effect of oxygen enrichment is more appreciable at high load than at low load. Correspondingly, there are more noticeable changes in crystalline structure and oxidative reactivity of soot from high load than of soot from low load. However, the surface O content on the soot does not show a consistent trend at low and high loads with oxygen enrichment. In addition, soot generated from high load with intake oxygen enrichment is observed to contain some metallic species, whereas soot from low load has little or no metallic species, which is attributed to the oxidation of lubricating oil by a synergistic effect of high oxygen concentration and high temperature. There might be an effect of the soot crystalline structure on soot oxidative reactivity, but the major influence on the reactivity is shown to be closely related to the amounts of metallic species present in soot due to the catalytic role of metallic species in soot oxidation.

Combustion and emission characteristics of a turbo-charged common rail diesel engine fuelled with diesel-biodiesel-DEE blends

The combustion and emission characteristics of a turbo-charged, common rail diesel engine fuelled with diesel-biodiesel-DEE blends were investigated. The study reports that the brake-specific fuel consumption of dieselbiodiesel-DEE blends increases with increase of oxygenated fuel fractions in the blends. Brake thermal efficiency shows little variation when operating on different dieselbiodiesel-DEE blends. At a low load, the NOx emission of the diesel-biodiesel-DEE blends exhibits little variation in comparison with the biodiesel fraction. The NOx emission slightly increases with increase in the biodiesel fraction in diesel-biodiesel-DEE blends at medium load. However, the NOx emission increases remarkably with increase of the biodiesel fraction at high load. Particle mass concentration decreases significantly with increase of the oxygenated-fuels fraction at all engine speeds and loads; particle number concentration decreases remarkably with increase of the oxygenated-fuels fraction. HC and CO emissions decrease with increasing oxygenated-fuels fraction in these blends.

Comparative analysis of a DI diesel engine fuelled with biodiesel blends during the European MVEG-A cycle: Preliminary study (I)

The present work consists of introducing the tests and facilities used to perform a comparative analysis of a diesel engine working with different blends of biodiesel fuel during the New European Driving Cycle. Furthermore, as a preliminary study, it was interesting to know the effects of biodiesel fuel on a common-rail high pressure injection system, those more useful in modern light duty diesel engines, as a consequence of its different physicochemical properties compared with conventional diesel fuel. As the real goal of the study is to compare fairly performance and emissions from the engine, it was essential to know any injection effects owed to fuel's own characteristics that finally would affect those parameters that will be evaluated. A complete fuel characterization for diesel and biodiesel fuels, as the EN 590 and the EN 14214 standard specifications, was performed in order to quantify the differences between both fuels. A priori, it could be thought that viscosity and density values will be the most significant parameters capable of altering the injection rate. As positive results, it was obtained that the common-rail high pressure injection system was totally blind in the injection rate measurements, even the significant differences between both fuels, taking into account the counterbalancing effects generated by two parameters mentioned before. The second part of the study deals with engine performance and pollutant emissions on an unmodified common-rail turbocharged diesel engine running with biodiesel fuel blends during the New European Driving Cycle.

Combustion Study of a Common Rail Diesel Engine Optimized to be Fueled with Biodiesel

The automobile market is, nowadays, characterized by a growing demand for cars equipped with diesel engines. This is because these offer smaller fuel consumption and better engine performance. A modern common rail turbocharged diesel engine provides performance equal to a gasoline engine, with same displacement, not turbo-charged but with a higher torque at lower engine speeds and with smaller fuel consumption. The methyl esters of vegetable oils, known as biodiesel, are receiving increasing interest because of their low environmental impact and their potential as an alternative fuel for diesel engines as they would not require any significant modification of existing engines. The modern common rail (CR) diesel engines are normally optimized for commercial diesel fuel. Consequently, the Electronic Control Unit (ECU) calibrations are defined to offer the best compromise between performance and emissions. If the engine is fuelled with an alternative fuel with different characteristics (net heating value, stoichiometric air fuel ratio (a/f), density, viscosity, etc.), it is clear that the calibration must be modified. In past experiments the authors have demonstrated that it is possible to optimize emissions and performances of a light duty CR diesel engine fueled with a vegetable derived fuel (rapeseed methyl ester) pure or blended with commercial diesel fuel, changing ECU parameters. This paper will show a detailed analysis of combustion in a modern diesel engine fueled with biodiesel and in particular some of the influences on engine parameters will be analyzed in order to demonstrate how an optimization strategy of ECU parameters could be applied to a diesel engine, when it is fueled with different fuels, with different physical/chemical characteristics.

Characterization of Diesel Soot Aggregates by Scattering and Extinction Methods

Characteristics of diesel soot particles sampled from diesel exhaust of a common-rail turbo-charged diesel engine are quantified by scattering and extinction diagnostics using newly build two laser-based instruments. The radius of gyration representing the aggregates size is measured by the angular distribution of scattering intensity, while the soot mass concentration is measured by a two-wavelength extinction method. An approach to estimate the refractive index of diesel soot by an analysis of the extinction and scattering data using an aggregates scattering theory is proposed.

Investigation on exhaust emissions of a common rail high-speed direct injection diesel engine running with dimethyl ether

This research investigates engine performance and the potential to reduce exhaust emissions by using dimethyl ether (DME) as an alternative fuel to diesel for compression ignition engines. The main objective of this study it to evaluate on a test-bed the performance and emissions reduction potential of a four-cylinder passenger car HSDI common rail turbocharged diesel engine running with DME in the absence of specific modifications to the engine itself but some modifications to the fuel injection system. The results obtained from this engine running with DME using diesel fuel as reference are encouraging. In the next phase of this study the injection rate will be adapted to DME operation and to the geometric and thermodynamic conditions of the combustion process. A study of combustion reaction is also necessary in order to optimize the turbocharging system for exclusive DME operation.