Title: Particle and nanoparticle characterization at the exhaust of internal combustion engines

Author(s): C Tornatore, S S Merola, B M Vaglieco

Source: Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering

Volume: 222 Number 11 Pages: 2195-2217. Nov 2008

DOI: 10.1243/09544070JAUTO817

Publisher: Professional Engineering Publishing

Abstract:
The aim of this work is the characterization of the emissions of exhaust particles in terms of number size distribution and chemical–physical properties. Laser-induced incandescence and broadband ultraviolet–visible extinction and scattering spectroscopy were used at the exhaust of a common-rail diesel engine and of a port fuel injection (PFI) spark ignition (SI) engine. The optical results were compared with size distributions obtained with an electrical low-pressure impactor and a scanning mobility particle sizer. Moreover, the fundamental engine parameters and the particulate mass and gas concentrations were measured using conventional instrumentation.

With respect to the diesel engine, the effect of the exhaust after-treatment was investigated. The exhaust gas recirculation influenced the particle size distribution in terms of number concentration owing to the formation of accumulation mode particles. The catalysed diesel particulate filter strongly reduced the particle number concentration in the loading phase. Effects on the chemical nature of the particles were observed during the filter regeneration phase.

With respect to the PFI SI engine, high number concentrations of nanoparticles (D=<50nm) were measured for all the engine operating conditions. The chemical nature of the nanoparticles was investigated.

Title: The effect of diesel engine operating conditions on exhaust particle size distributions

Author(s): O Armas, R Ballesteros, A Gómez

Source: Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering

Volume: 222 Number 8 Pages: 1513-1525. August 2008

DOI: 10.1243/09544070JAUTO747

Publisher: Professional Engineering Publishing

Abstract: Owing to the negative effects that aerosols have on human health, the interest in knowing the size and the amount of particulate matter emitted by diesel engines is increasing. The measurement of this kind of aerosol is mainly influenced by three parameters: the ambient conditions, the sampling method used to characterize the emissions together with the system used to determine the particle size distributions, and, finally, the physical and chemical characteristics of the aerosol, which are a direct consequence of those processes occurring in the engine (composition, size, and concentration of particles in the aerosol, amount of volatile organic compounds, sulphur compounds, and different residues coming from the additives used in fuels and lubricants, etc.). An experimental study has been developed which combines the use of a partial dilution minitunnel and a scanning mobility particle sizer. The aim is to study the influence that the engine operating conditions which the driver can control by using the throttle while driving a vehicle, i.e. the torque and engine speed, have on the particle size distribution and its statistical parameters, namely the mean diameter and total concentration. This study was carried out on a light-duty direct-injection diesel engine which is used currently on European roads. Four steady operation modes were tested, from the most emissions-significant zones of the engine map. Likewise, a complementary study has been developed for a better understanding of the combined effect of both fuel-to-air and exhaust gas recirculation (EGR) ratios. In this latter study the EGR was completely eliminated from the engine modes previously studied.

Title: A regenerative flow compressor as a secondary air pump for engine emission control

Author(s): A Engeda, Y Elkacimi

Source: Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science

Volume: 222, Number 9 Pages: 1707-1715. September 2008

DOI: 10.1243/09544062JMES958

Publisher: Professional Engineering Publishing

Abstract: A secondary air pump (SAP) is an air compressor that supplies air to the exhaust system of an automotive engine for the emission control of the engine. The SAP system has been offered as an emission control device in later versions of cars, starting in the mid-1990s. Various types of rotary and positive displacement air pumps have been tested and used for SAP application. The regenerative flow compressor/pump (RFC or RFP) and the centrifugal compressor have been found to be best suited for SAP application. This paper discusses the performance of an RFC for SAP application and shows the RFC to be the best choice for satisfying the required specifications of the SAP.

Computational fluid dynamics analysis of the RFC for an SAP application was carried out to study its performance in detail.

Title: NOx and soot reduction in diesel engine premixed charge compression ignition combustion: a computational investigation

Author(s): R Diwakar, S Singh

Source: International Journal of Engine Research

Volume: 9 Number 3 Pages: 195-214. May 2008

DOI: 10.1243/14680874JER00308

Publisher: Professional Engineering Publishing

Abstract:
The objective of the present work is to study soot-EGR and soot-NOx tradeoff for premixed charge compression ignition (PCCI) combustion at a light-load (4?bar BMEP) operation of a medium-duty, large-bore, direct-injection diesel engine using multi-dimensional computational analysis. The simulations are performed using KIVA-3V computer code coupled with reduced chemical kinetics. Low (40 per cent) to heavy (70 per cent) EGR rates are applied to study the effects of reduced intake oxygen concentration on combustion and emissions. Model predictions of cylinder pressure and emissions are first validated against experimental data. Model-predicted temporal and spatial evolution of in-cylinder mixture in F–T coordinates is then used to explain the fundamentals of PCCI combustion and emissions. Using computational analysis, it is shown that lower exhaust soot emissions for the lower EGR dilution cases (45 per cent) are due to higher soot oxidation rates, and lower exhaust soot emissions for very high EGR rates (70 per cent) are due to lower soot formation rates. The trend seen in NOx emissions are primarily attributable to the inert effect of EGR dilution and varied ignition delay caused by varied percentages of oxygen in the intake mixture.

Title: Continuous regeneration of an electrically heated diesel particulate trap

Author(s): M. Arai, M. Saito, Y. Mitsuyama

Source: International Journal of Engine Research

Volume: 8 Number 5 Page: 477-486. November 2007

DOI: 10.1243/14680874JER01507

Publisher: Professional Engineering Publishing

Abstract: A wall-flow type diesel particulate trap using electrostatic field (E-DPT) was proposed to remove soot particles exhausted from diesel engines. This device was capable of trapping soot particles by electrostatic effect by applying a direct current electric field between two electro-plates separated by 1.5 mm. Soot trapped on the plates formed bridges of soot clusters in a narrow space between the electro-plates and it was burned by Joule heating owing to the direct electrification through the bridges. When the applied voltage to the E-DPT was lower than the critical value (Ep = 200 V), only the soot accumulation was observed. Its accumulation mechanism looked like a kind of electrostatic precipitator, and soot burning caused by the electrification through soot bridges was observed at higher applied voltages at 250-300 V. When soot accumulation and burning were balanced, a stable operation of E-DPT at 60-80 per cent removal efficiency was attained. An analysis of the experimental data on soot removal efficiency, power consumption, and heat balance during steady operation showed that the E-DPT developed is a potential system for practical application to actual diesel engines.

Title: Ion current combustion technology for controlled auto-ignition gasoline engines

Author(s): P. Attard, J. Micallef

Source: International Journal of Engine Research

Volume: 8 Number 5 Page: 429-437. September 2007

DOI: 10.1243/14680874JER03604

Publisher: Professional Engineering Publishing

Abstract: The use of ionization sensors, by means of a standard spark plug, in gasoline engines is well known. This paper focuses on the use of these sensors for controlled auto-ignition (CAI) gasoline engines, where the air-fuel mixture ignites without the need of a spark. The averaged ion current signals obtained are first observed and compared to the heat release rate and then a method to detect with accuracy the location of the 50 per cent mass fraction burned is described. The variation of emissions is studied and the effects of using a pressure sensor (to calculate the heat release rate) or an ion current sensor are portrayed. Thus it is proved possible to keep the emissions under strict control by using an ion current sensor.

Title: Artificial neural network as a predictive tool for emissions from heavy-duty diesel vehicles in Southern California

Author(s): N Hashemi, N N Clark

Source: International Journal of Engine Research

Volume: 8 No 4 Pages: 321-336. Aug 2007

DOI: 10.1243/14680874JER00807

Publisher: Professional Engineering Publishing

Abstract:
An artificial neural network (ANN) was trained on chassis dynamometer data and used to predict the oxides of nitrogen (NOx), carbon dioxide (CO2), hydrocarbons (HC), and carbon monoxide (CO) emitted from heavy-duty diesel vehicles. Axle speed, torque, their derivatives in different time steps, and two novel variables that defined speed variability over 150 seconds were defined as the inputs for the ANN. The novel variables were used to assist in predicting off-cycle emissions. Each species was considered individually as an output of the ANN. The ANN was trained on the Highway cycle and applied to the City/Suburban Heavy Vehicle Route (CSHVR) and Urban Dynamometer Driving Schedule (UDDS) with four different sets of inputs to predict the emissions for these vehicles. The research showed acceptable prediction results for the ANN, even for the one trained with only eight inputs of speed, torque, their first and second derivatives at one second, and two variables related to the speed pattern over the last 150 seconds. However, off-cycle operation (leading to high NOx emissions) was still difficult to model. The results showed an average accuracy of 0.97 for CO2, 0.89 for NOx, 0.70 for CO, and 0.48 for HC over the course of the CSHVR, Highway, and UDDS.

Title: Soot Wear in Diesel Engines

Author(s): E S Yamaguchi, M Untermann, S H Roby, P R Ryason, S W Yeh

Source: Proceedings of the I MECH E Part J Journal of Engineering Tribology

Volume: 220 No 5 Page: 463-469. Aug 2006

DOI: 10.1243/13506501J00505

Publisher: Professional Engineering Publishing

Abstract:
In response to regulatory requirements, lubricant manufacturers are seeking oils that minimize soot thickening and the accompanying soot wear. Formulation technology is being developed by additive manufacturers to satisfy these requirements. For example, such work is in progress at Chevron Oronite Company LLC, using the Cummins M-11 exhaust gas recirculation (EGR) engine test as a surrogate for the anticipated soot wear test for PC-10. Simultaneously, the authors developed bench tests to screen candidate formulations and reduce costs.

A ball-on-disc sliding wear test, using a PCS Instruments MTM® tribometer, has been investigated. Sliding conditions at high pressure are required for soot polishing wear. Conditions that correlate tribometer test results with M-11 engine results at high soot concentrations (~9 per cent) have been found. Both ball wear and Stribeck curves were determined in these tests. The high-wear oil progresses from mixed lubrication conditions to boundary lubrication at higher sliding speeds than the low-wear oil. X-ray photoelectron spectroscopy experiments were also conducted on the ball wear scars, revealing differences in the chemical constitution of the tribofilms from the two oils.

Title: Investigation of the impact of biodiesel fuelling on NOx emissions using an optical direct injection diesel engine

Author(s): A S Cheng, A Upatnieks, C J Mueller

Source: International Journal of Engine Research

Volume: 220 No 4 Pages: 297-318. Aug 2006

DOI: 10.1243/14680874JER05005

Publisher: Professional Engineering Publishing

Abstract:
The impact of biodiesel fuelling on NOx emissions was investigated using an optically accessible diesel engine. A soy-based biodiesel (B100) and three separate primary reference fuel (PRF) blends were evaluated over a range of loads at an engine speed of 800 r/min. Experimental operating conditions were carefully controlled to maintain a constant start of combustion (SOC), and a PRF blend was identified that would eliminate differences in premixed-burn fraction. A load-averaged NOx increase of ~10 per cent was observed for B100 relative to the PRF blend with matched premixed-burn fraction. The results indicate that factors other than SOC and premixed-burn fraction affect the tendency for biodiesel to increase NOx. Equilibrium calculations reveal no significant differences in stoichiometric adiabatic flame temperature between the test fuels; however, experimental data suggest that actual flame temperatures may be influenced by differences in soot radiative heat transfer. The effect of biodiesel on mixture stoichiometry at the lift-off length may also play an important role in increasing NOx emissions.

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