Passenger Car Diesel Engine Research Articles

Application of stochastic design optimization to a passenger car diesel engine to reduce emission spread in a vehicle fleet

Application of stochastic design optimization to a passenger car diesel engine to reduce emission spread in a vehicle fleet

Physicochemical and mutagenic analysis of particulate matter emissions from an automotive diesel engine fuelled with fossil and biofuel blends

In this paper, a complete characterization of diesel Particulate Matter (PM) in terms of mass, chemical composition, particles number, size distribution and mutagenic potential was carried out. As a test case, a Euro 5 1.3L passenger car diesel engine fueled with Ultra Low Sulphur Diesel (ULSD) and high-percentage blends (B30 − 30% vol.) of ULSD and biofuels (Rapeseed Methyl Ester, RME, and Hydrotreated Vegetables Oil, HVO) was considered. In addition, PM gravimetric analysis was compared with soot measurements carried out by means of standard laboratory equipment (e.g. smokemeters), showing a good correlation at medium and high load operating points. On the contrary, at low loads, as confirmed by thermo-gravimetric analysis, smokemeter measurements underestimated the Soluble Organic Fraction (SOF) fraction of PM, especially when for RME (B30). Then, a detailed investigation on Particles Number (PN) and size distribution was carried out, running the engine with the same fuel matrix. The results showed that adopting biofuel blends, both RME (B30) and HVO (B30), produces negligible differences in particles number distributions with respect to standard diesel. Finally, the analysis of the mutagenic potential of PM samples highlighted an increased genotoxicity for HVO (B30) and a decreased genotoxicity for RME (B30) with respect to ULSD.

Measurement of the crankshaft seals friction losses in a modern passenger car diesel engine

This paper presents results of experimental investigations on the friction losses of the crankshaft radial lip seals of a modern four-cylinder diesel engine for passenger car applications. A two stage strip-test has been conducted on a motored engine test bed to obtain the friction torque of the radial lip seals. For the experimental investigations with the crankshaft seals removed from the engine, a special sealing apparatus has been designed and built. A wide range of tests have been performed covering the full speed range of the engine at lubricant temperatures of 70 ℃, 90 ℃, and 110 ℃. The results show a dependency on crankshaft speed and engine media supply temperature but also revealed the presence of constant plateaus of friction torque over engine speed.

Dependence of combustion noise on engine calibration parameters by means of the response surface methodology in passenger car diesel engines

Combustion noise from a passenger car diesel engine has been expressed as a function of the heat release rate peaks of pilot and main combustions as well as of the crankshaft angles at which these peaks occur, using a statistical regression model. Furthermore, the values of these heat release rate peaks and of their angles have been correlated with the main engine calibration parameters by means of second-order polynomial regressions. The values of the coefficients of these polynoms have been found to depend on the engine working condition. As a result, it has been possible to calculate the combustion noise as a function of the main engine calibration parameters at different engine working points, which are representative of low, medium and high load and speed conditions within the NEDC working zone.The effects of the pilot injection quantity and timing, of the main combustion phasing and of the rail pressure level have been analyzed for both late PCCI and conventional combustion modes. The definition of the pilot injection quantity and timing has resulted to be relevant for a reduction in combustion noise at low and medium speeds and loads, while a pilot injection should be removed for an optimized combustion noise engine calibration at high speeds and loads.

Investigations of the Friction Losses of Different Engine Concepts. Part 1: A Combined Approach for Applying Subassembly-Resolved Friction Loss Analysis on a Modern Passenger-Car Diesel Engine

This work presents the application of a combined approach to investigate the friction losses in a modern four-cylinder passenger-car diesel engine. The approach connects the results from engine friction measurements using the indication method and the results from journal-bearing simulations. The utilization of the method enables a subassembly-resolved friction loss analysis that yields the losses of the piston group, crankshaft journal bearings, and valve train (including the timing drive and crankshaft seals). The engine and engine subassembly friction losses are investigated over the full speed and load range, covering more than 120 engine operation points at different engine media supply temperatures ranging from 70 to 110 ∘ C. The subsequently decreasing lubricant viscosity due to higher engine media supply temperatures allow for the identification of friction reduction potentials as well as possible risks due to an onset of mixed lubrication. Furthermore, additional strip-tests have been conducted to determine the friction losses of the crankshaft radial lip seals, the timing drive, and the crankshaft journal bearings, thus enabling a verification of the calculated journal-bearing friction losses with measurement results. For the investigated diesel engine, a friction reduction potential of up to 21% could be determined when increasing the engine media supply temperature from 70 to 110 ∘ C, at engine speeds higher than n = 1500 rpm and part load operating conditions. At low engine speeds and high load operations, the friction loss reduction potential is considerably decreased and below 8%, indicating mixed lubrication regimes at the piston group and valve train.

Modeling investigation of thermal insulation approaches for low heat rejection Diesel engines using a conjugate heat transfer model

Heat losses through combustion chamber walls are a well-known limiting factor for the overall efficiency of internal combustion engines. Thermal insulation of the walls has the potential to decrease substantially these heat losses. However, evaluating numerically the effect of coating and of its location in the combustion chamber and then design an optimized combustion system require the use of high-fidelity engine models. The objective of this article is to present the whole workflow implying the use of three-dimensional computational fluid dynamics techniques with conjugate heat transfer (CHT) models to investigate the potential benefits of a coating on a passenger car Diesel engine. First, the baseline combustion system is modeled, using CHT models to solve in a coupled simulation the heat transfers between the fluid in the intake and exhaust lines and in the combustion chamber, on one hand, and the solid piston, head and valves, on the other hand. Based on this setup, a second simulation is performed, modeling a thermo-swing insulation on all combustion chamber walls by a contact resistance, neglecting its thermal inertia to keep a manageable computational cost. Results show a decrease of 3.3% in fuel consumption with an increase in volumetric efficiency. However, decoupled one-dimensional/three-dimensional simulations highlight the inaccuracy of these results and the necessity to model the coating thermal inertia, as they show an overestimation of the heat insulation rate and, consequently, of the gain in fuel consumption (−2.1% instead of −1.6%), for a coating on the piston with no thermal inertia.

A model-based and experimental approach for the determination of suitable variable valve timings for cold start in partial load operation of a passenger car single-cylinder diesel engine

A manipulation of the charge exchange allows controlling the amount of residual gas during engine warm-up. The residual gas during the warm-up phase leads to an increase of the exhaust gas temperature and supports to reach the exhaust after-treatment system operating temperature faster. In addition, the warm residual gas increases the combustion chamber temperature, which reduces the HC and CO emissions. However, fuel consumption increases. For that reason, such heating measures should be the best compromise of both, exhaust gas temperature increase and engine efficiency, in order to provide efficient heating strategies for passenger car diesel engines. Therefore, simulative and experimental investigations are carried out at the Institute of Internal Combustion Engines of the Karlsruhe Institute of Technology to establish a reliable cam design methodology. For the experimental investigations, a modern research single-cylinder diesel engine was set up on a test bench. In addition, a one-dimensional simulation model of the experimental setup was created in order to simulate characteristics of valve lift curves and to investigate their effects on the exhaust gas temperature and the exhaust gas enthalpy flow. These simulations were based on design of experiments (DoE), so that all characteristics can be used sustainably for modeling and explaining their influences on the engine operation. This methodology allows numerically investigating promising configurations and deriving cam contours which are manufactured for testing. To assess the potential of these individual configurations, the results obtained were compared with each other as well as with the series configuration. Results show that the combination of DoE and one-dimensional simulation for the design of camshaft contours is well suited which was also validated with experimental results. Furthermore, the potential of residual gas retention by favorable configurations with a second event already revealed in various publications could be confirmed with respect to exhaust gas temperature increase and engine efficiency.

An experimental approach on fuelling a passenger car diesel engine with LPG

In the last years the interest on reducing harmful pollutant emissions of a passenger car engine has been greatly increased either because the number of cars increased or because the cities growth rate became very fast. The interest in improving driveability and the comfort of the passengers also increased. This can be achieved by reducing engine vibrations and improving smooth engine functioning. A viable solution for the diesel engine is fuelling with alternative fuels and in special with Liquefied Petroleum Gas. The advantage of LPG is that this fuel is an economical solution to protect the environment because its components are light hydrocarbons, without sulphur and with a number of carbon atoms less than the diesel fuel. The paper presents experimental investigations results of a car diesel engine fuelled with diesel fuel and liquefied petroleum gas. Also experimental investigations results on cyclic variability are presented. The engine used for investigations is a turbocharged 1.5 l diesel engine which and the investigated regimen was 2000 rpm and 70% engine load. The LPG fuelling led to a decrease in pollutant emissions level and to an increase in the smooth engine running, evaluated by the variability coefficient.

Reduction of particulate emissions in diesel hybrid electric vehicles with a PMP-based control strategy

Over the last decades the pollutant emissions of passenger-car diesel engines have been significantly reduced by the emission standards, but it is known that in real driving conditions these vehicles significantly exceed the regulation limits. For this reason, an increasing number of cities and municipalities already are or are thinking about banning diesel cars to cope with local air pollution. This aspect together with the upcoming EURO 7 air pollution regulations are expected to push diesel cars out of the market, because of a too-much demanding requirement on the reduction in particulate and carbon dioxide emissions. The only way to make these cars keep a share in the automotive market is probably their hybridization. The aim of these paper is to propose a control strategy for the power split in diesel-hybrid vehicles, aimed at minimizing particulate emissions and controlling the battery state of charge simultaneously. To this aim, a supervisory controller, based on Pontryagins Minimum Principle, is designed for on-line energy management optimization of a Diesel Plug-in Hybrid Electric Vehicle with a parallel architecture. The proposed strategy focuses on the reduction of particulate emissions that represents a major issue to meet emissions standards in such vehicles. In this study a methodology based on software in the loop simulations is applied in order to properly tune the proposed energy management strategy and to understand the overall powertrain performance. This work demonstrates the potential of using the hybrid architecture to limit particulate emissions even under real-world-like driving cycles.

Evaluation of a Hydrotreated Vegetable Oil (HVO) and Effects on Emissions of a Passenger Car Diesel Engine

In the coming years, the application of paraffinic biofuels, such as Hydrotreated Vegetable Oils (HVO), in the transportation sector is expected to increase. However, as the composition of HVO is different compared to conventional diesel, the engine optimized for conventional fuel cannot take full advantage of the HVO beneficial properties. Suitable adjustment of a number of engine parameters, if not complete engine re-calibration, will enable the full exploitation of such fuels’ potential for lower exhaust emissions and reduced fuel consumption. In the present work, the emission characteristics of HVO fuel in a light-duty Euro 5 diesel engine have been studied, under steady-state operation, as well as during the New European Driving Cycle (NEDC). The study was expanded to the investigation of exhaust emissions under modified Main Injection Timing (MIT) and EGR rate. The NEXBTL fuel, produced by Neste, was considered in the study and was compared with conventional market diesel. Emissions of nitric oxides (NOx), soot, carbon monoxide (CO), carbon dioxide (CO2) and hydrocarbons (HC) were studied. At default MIT and EGR settings the use of HVO resulted in a significant reduction of all regulated emissions. In addition, it was observed that the adjustment of MIT and EGR can enhance the exploitation of HVO potential for emissions reduction, highlighting the differences with the conventional diesel fuel.

Tribological characteristics comparison of formulated palm trimethylolpropane ester and polyalphaolefin for cam/tappet interface of direct acting valve train system

PurposeThere is a continuous drive in automotive sector to shift from conventional lubricants to environmental friendly ones without adversely affecting critical tribological performance parameters. Because of their favorable tribological properties, chemically modified vegetable oils such as palm trimethylolpropane ester (TMP) are one of the potential candidates for the said role. To prove the suitability of TMP for applications involving boundary-lubrication regime such as cam/tappet interface of direct acting valve train system, a logical step forward is to investigate their compatibility with conventional lubricant additives.Design/methodology/approachIn this study, extreme pressure and tribological characteristics of TMP, formulated with glycerol mono-oleate (GMO), molybdenum dithiocarbamate (MoDTC) and zinc dialkyldithiophosphate (ZDDP), has been investigated using four-ball wear tester and valve train test rig. For comparison, additive-free and formulated versions of polyalphaolefin (PAO) were used as reference. Moreover, various surface characterization techniques were deployed to investigate mechanisms responsible for a particular tribological behavior.FindingsIn additive-free form, TMP demonstrated better extreme pressure characteristics compared to PAO and lubricant additives which are actually optimized for conventional base-oils such as PAO, are also proved to be compatible with TMP to some extent, especially ZDDP. During cylinder head tests, additive-free TMP proved to be more effective compared to PAO in reducing friction of cam/tappet interface, but opposite behavior was seen when formulated lubricants were used. Therefore, there is a need to synthesize specialized friction modifiers, anti-wear and extreme pressure additives for TMP before using it as engine lubricant base-oil.Originality/valueIn this study, additive-free and formulated versions of bio-lubricant are tested for cam/tappet interface of direct acting valve train system of commercial passenger car diesel engine for the very test time. Another important aspect of this research was comparison of important tribological performance parameters (friction torque, wear, rotational speed of tappet) of TMP-based lubricants with conventional lubricant base oil, that is, PAO and its formulated version.

Steady-State Calibration of a Diesel Engine in Computational Fluid Dynamics Using a Graphical Processing Unit-Based Chemistry Solver

The prospect of analysis-driven precalibration of a modern diesel engine is extremely valuable in order to significantly reduce hardware investments and accelerate engine designs compliant with stricter fuel economy regulations. Advanced modeling tools, such as CFD, are often used with the goal of streamlining significant portions of the calibration process. The success of the methodology largely relies on the accuracy of analytical predictions, especially engine-out emissions. However, the effectiveness of CFD simulation tools for in-cylinder engine combustion is often compromised by the complexity, accuracy, and computational overhead of detailed chemical kinetics necessary for combustion calculations. The standard approach has been to use skeletal kinetic mechanisms (∼50 species), which consume acceptable computational time but with degraded accuracy. In this work, a comprehensive demonstration and validation of the analytical precalibration process is presented for a passenger car diesel engine using CFD simulations and a graphical processing unit (GPU)-based chemical kinetics solver (Zero-RK, developed at Lawrence Livermore National Laboratory, Livermore, CA) on high performance computing resources to enable the use of detailed kinetic mechanisms. Diesel engine combustion computations have been conducted over 600 operating points spanning in-vehicle speed-load map, using massively parallel ensemble simulation sets on the Titan supercomputer located at the Oak Ridge Leadership Computing Facility. The results with different mesh resolutions have been analyzed to compare differences in combustion and emissions (NOx, carbon monoxide CO, unburned hydrocarbons (UHC), and smoke) with actual engine measurements. The results show improved agreement in combustion and NOx predictions with a large n-heptane mechanism consisting of 144 species and 900 reactions with refined mesh resolution; however, agreement in CO, UHC, and smoke remains a challenge.

Filtration and coagulation efficiency of sub-10 nm combustion-generated particles

Particle size distributions are measured at the exhaust of a passenger-car diesel engine burning a Sulphur-free diesel oil. Different operating conditions of loads and engine speed, representative of low-loads are analyzed.Particles with sizes ranging from few nanometers up 1 µm are generated during diesel combustion. Operating conditions strongly affect the size distribution of the particles but overall they maintain a bimodality with a first mode, identified as nucleation mode, in the form of sub-10 nm particles, and a second mode in the form of soot particles and agglomerates. The lower is the engine load, the lower the emission of mass concentration of particulate matter but the higher the emission of particle numbers. Measurements performed in not-firing conditions confirmed that particles are generated during combustion more than by lube oil or mechanical friction.Filter efficiency with regard to the different particle sizes is evaluated by measuring particle size distributions before and after a diesel particulate filter. Results show that sub-10 nm particles are not sufficiently removed by the filter. Filter capture is almost complete for particles with sizes greater than 10 nm but the collection efficiency decreases to values of the order of 40–50% for sub-10 nm particles. This is of concern particularly when using fuels or operating conditions that produce a huge number of sub-10 nm particles not removed by the filter and hence emitted from the engine. The objective of the study is not to measure the filtration efficiency of a specific after-treatment system but to give a general warning on the capability of current particulate filters in removing sub-10 nm particles.

Oxymethylene Ethers as an Alternative for Passenger Car Diesel Engines

Oxymethylene Ethers as an Alternative for Passenger Car Diesel Engines

Dicarboxylic Acid Emissions from Aftertreatment Equipped Diesel Engines.

Dicarboxylic acids play a key role in atmospheric particle nucleation. Though long assumed to originate from primary sources, little experimental evidence exists directly linking combustion to their emissions. In this work, we sought definitive proof that dicarboxylic acids are produced in diesel engines and that they can slip through a modern aftertreatment system (ATS) at low exhaust temperatures. One difficulty in measuring dicarboxylic acid emissions is that they cannot be identified using conventional mass spectroscopy techniques. In this work, we refined a derivatization gas chromatography-mass spectroscopy technique to measure 11 mono- and dicarboxylic acids from plain and KOH impregnated quartz filters. Filters were loaded with exhaust from a modern passenger car diesel engine on a dynamometer sampled before and after an ATS consisting of an oxidation catalyst and diesel particulate filter. Our findings confirm that dicarboxylic acids are produced in diesel engine combustion, especially during low temperature combustion modes that emit significant concentrations of partially combusted hydrocarbons. Exhaust acids were largely removed by a fully warmed-up ATS, mitigating their environmental impact. Our results also suggest that dicarboxylic acids do not participate in primary particle formation in dilute engine exhaust as low quantities were collected on unimpregnated filters.

Dynamic Full Range Input Shaping of Injection Parameters for Reduction of Transient NOx Emissions

For modern passenger car Diesel engines strong limitations on emissions, due to legislation, require large efforts in combustion and aftertreatment control. This control problem is mainly approached by an intensive stationary calibration process and dynamic compensation techniques. However, large differences in combustion conditions between steady state, as used for calibration, and real transient maneuvers, such as tip-ins, can lead to undesired emission peaks. Against this background, the present work adapts a previously introduced input shaping strategy for injection parameters, such that it is applicable in the full engine operation range. Different to the former approach, the shape of the correction profile is determined directly from identified local models of the selected injection parameters to the NOx response. By using local linear models it is possible to consider variations in the system dynamics and parameterize the input shapers in an automated fashion. Additionally this approach can be applied together with a state of the art engine control, since it does not need a change in the base calibration. The improved strategy is evaluated on a passenger car Diesel engine and it is shown that a reduction of the undesired NOx overshoot can be achieved without impacting other performance indicators.

Potentialities of Boot Injection Combined with After Shot for the Optimization of Pollutant Emissions, Fuel Consumption and Combustion Noise in Passenger Car Diesel Engines

The present paper illustrates an investigation about the potentialities of injection rate shaping coupled with an after injection. A pilot shot can either be absent or present before the rate-shaped boot injection. The experimental tests have been performed on a partial PCCI Euro 5 diesel engine endowed with direct-acting piezoelectric injectors. Starting from optimized triple pilot-main-after injection strategies, boot injection was implemented by maintaining the direct-acting piezo injector needle open at part lift. The results of two steady state working conditions have been presented in terms of engine-out emissions, combustion noise and brake specific fuel consumption. In addition, in-cylinder analyses of the pressure, heat-release rate, temperature and emissions have been evaluated. Considering the in-cylinder pressure traces and the heat release rate curves, the injection rate shaping proved to influence combustion in the absence of a pilot injection to a great extent. A pilot shot, added before the boot injection, determined a mitigation of the influence of rate shaping. A simultaneous reduction in NOx and soot can be achieved for small quantities of fuel injected during boot injection, compared to the optimized triple injection strategies. However, a trade-off exists between emissions and combustion noise when boot injection is applied. On the other hand, the variations in bsfc were only minor. The advantages of the application of boot injection are greater for low to medium loads than for medium to high loads. However, it was not possible to find a working condition in which boot injection provided simultaneous advantages on emissions, noise and consumption, compared to the optimized triple injection.

Experimental investigation on a Common Rail Diesel engine partially fuelled by syngas

The high efficiency, reliability and flexibility of modern passenger car Diesel engines makes these power units quite attractive for steady power plants totally or partially running on fuels derived from biomass, in particular on syngas. The engine cost, which is obviously higher than that of current industrial engines, may not be a big obstacle, provided that the re-engineering work is limited and that performance and efficiency are enhanced. The goal of this work is to explore the potential of a current automotive turbocharged Diesel engine running on both Diesel fuel and syngas, by means of a comprehensive experimental investigation focused on the combustion process. The engine is operated at the most typical speed employed in steady power plants (3000rpm), considering three different loads (50–100–300Nm/16–31–94kW). For each operating condition, the syngas rate is progressively increased until it provides a maximum heating power of 85kW, while contemporarily reducing the amount of injected Diesel oil. Maximum care is applied to guarantee a constant quality of the syngas flow throughout the tests, as well as to maintain the same engine control parameters, in particular the boost pressure.It is found that in-cylinder pressure traces do not change very much, even when drastically reducing the amount of Diesel fuel: this is a very encouraging result, because it demonstrates that there is no need to radically modify the standard stock engine design. Another promising outcome is the slight but consistent enhancement of the engine brake efficiency: the use of syngas not only reduces the consumption of Diesel oil, but it also improves the combustion quality.The authors acknowledge that this study is only a starting basis: further investigation is required to cover all the aspects related to the industrial application of this syngas-Diesel combustion concept, in particular the impact on pollutant emission and on engine durability.

Effects of DME-Isobutane Blended Fuels on Combustion and Emissions Reduction in a Passenger Car Diesel Engine

AbstractThis paper investigates the effect of isobutane blended dimethyl ether (DME) fuels on the spray behaviors, combustion, and emission reduction characteristics in a diesel engine. To investig...

Comparative investigation of emissions and combustion characteristics between ethanol-biodiesel-diesel blends and diesel fuel in a passenger car diesel engine

This study investigated the comparison of emissions and performance characteristics between ethanol-biodiesel-diesel blends and diesel fuel in a passenger car diesel engine. In order to analyse the effect of ethanol-biodiesel blends, the combustion and emission reduction characteristics of a four-cylinder diesel engine with common-rail direct injection system were investigated under the various injection and blended ratios. The experimental results showed that the combustion pressure of ethanol-biodiesel-diesel blended fuels slightly increased than that of convention diesel fuel at higher load condition, while the coefficient of variance of the combustion pressure (COVimep) showed almost the similar values. Under low-load conditions, the effects of ethanol-biodiesel blending to conventional diesel fuel on exhaust emissions showed that brake specific CO emission (BS-CO) and BS-HC emissions remarkably increased while BS-NOx emissions decreased as ethanol blending ratio increased. Under high load conditions, BS-CO, BS-HC and BS-NOx emissions slightly increased as ethanol blending ratio increased. On the other hand, the BS-Soot emissions were reduced by more than 50% in all conditions. [Received: October 16, 2015; Accepted: June 8, 2016]