Simultaneous OH- and Formaldehyde-LIF Measurements in an HCCI Engine

Collin, Robert; Nygren, Jenny; Richter, Mattias; Aldén, Marcus; Hildingsson, L.; Johansson, Bengt

doi:10.4271/2003-01-3218

Cited by 73 publications

(28 citation statements)

References 9 publications

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“…Hultqvist et al [82] showed cool-flame emission spectra from iso-octane/nheptane HCCI combustion and discussed that these spectra originated from the presence of formaldehyde (HCHO). LIF studies have shown how HCHO and OH species are present within the 'cool' flame period and subsequent 'hot' combustion [84][85][86]. The absence of carbon atoms, and thus HCHO, from the in-cylinder mixture of a hydrogen HCCI engine means that a totally different mechanism of autoignition is in operation and that OH generation would be very different from that of hydrocarbon fuels.…”

Section: Introductionmentioning

confidence: 99%

Hydrogen SI and HCCI Combustion in a Direct-Injection Optical Engine

Rosati¹,

Aleiferis²

2009

SAE Int. J. Engines

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The Engineering Meetings Board has approved this paper for publication. It has successfully completed SAE's peer review process under the supervision of the session organizer. This process requires a minimum of three (3) reviews by industry experts. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. ISSN 0148-7191 Positions and opinions advanced in this paper are those of the author(s) and not necessarily those of SAE. The author is solely responsible for the content of the paper. SAE ABSTRACTHydrogen has been largely proposed as a possible alternative fuel for internal combustion engines. Its wide flammability range allows higher engine efficiency with leaner operation than conventional fuels, for both reduced toxic emissions and no CO 2 gases. Independently, Homogenous Charge Compression Ignition (HCCI) also allows higher thermal efficiency and lower fuel consumption with reduced NO X emissions when compared to Spark-Ignition (SI) engine operation. For HCCI combustion, a mixture of air and fuel is supplied to the cylinder and autoignition occurs from compression; engine is operated throttle-less and load is controlled by the quality of the mixture, avoiding the large fluid-dynamic losses in the intake manifold of SI engines. HCCI can be induced and controlled by varying the mixture temperature, either by Exhaust Gas Recirculation (EGR) or intake air pre-heating. A combination of HCCI combustion with hydrogen fuelling has great potential for virtually zero CO 2 and NO X emissions. Nevertheless, combustion on such a fast burning fuel with wide flammability limits and high octane number implies many disadvantages, such as control of backfiring and speed of autoignition and there is almost no literature on the subject, particularly in optical engines. Experiments were conducted in a singlecylinder research engine equipped with both Port Fuel Injection (PFI) and Direct Injection (DI) systems running at 1000 RPM. Optical access to in-cylinder phenomena was enabled through an extended piston and optical crown. Combustion images were acquired by a highspeed camera at 1° or 2° crank angle resolution for a series of engine cycles. Spark-ignition tests were initially carried out to benchmark the operation of the engine with hydrogen against gasoline. DI of hydrogen after intake valve closure was found to be preferable in order to overcome problems related to backfiring and air displacement from hydrogen's low density. HCCI combustion of hydrogen was initially enabled by means of a pilot port injection of n-heptane preceding the main direct injection of hydrogen, along with intake air preheating. Sole hydrogen fuelling HCCI was finally achieved and made sustainable, even at the low compression ratio of the optical engine by means of closed-valve DI, in synergy with air-pre-heating and negative valve overlap to promote intern...

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Section: Introductionmentioning

confidence: 99%

Hydrogen SI and HCCI Combustion in a Direct-Injection Optical Engine

Rosati¹,

Aleiferis²

2009

SAE Int. J. Engines

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“…With varying levels of complexity of both equipment and technique, they have been applied extensively by many researchers in SI and CI engines for a long period of time [11,12]. For CAI, many researchers have successfully applied PLIF techniques to capture fluorescence of OH and formaldehyde to analyse the autoignition and combustion process [13][14][15]. Application of simpler techniques which do not rely on laser illumination and doped fuels for imaging combustion can allow for more realistic engine conditions.…”

Section: Introductionmentioning

confidence: 99%

Combustion Characteristics of CAI Combustion with Alcohol Fuels

Tongroon

Zhao

2010

SAE Technical Paper Series

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Due to its potential for simultaneous improvement in fuel consumption and exhaust emissions, controlled autoignition (CAI) combustion has been subject to continuous research in the last several years. At the same time, there has been a lot of interest in the use of alternative fuels in order to reduce reliance on conventional fossil fuels. Therefore, this experimental study has been carried out to investigate the effect of alcohol fuels on the CAI combustion process and on the resulting engine performance.The experimental work was conducted on an optical single cylinder engine with an air-assisted injector. To achieve controlled autoignition, residual gas was trapped in the cylinder by using negative valve overlap and an intake air heater was used to ensure stable CAI combustion in the optical engine. Methanol, ethanol and blended fuels were tested and compared with the results of gasoline. The combustion processes were analysed through total chemiluminescence images captured with a high speed camera equipped with an intensifier. In addition, the effect of spark discharge was investigated.The images show that CAI combustion of alcohol fuels was characterized with fast and early autoignition combustion compared with pure gasoline. Chemiluminescence of the gasoline fuel was most visible and it decreased with increasing percentage of oxygenated fuels. During the re-compression stroke, chemiluminescence images of the gasoline engine indicated the presence of oxidation reactions. In the presence of spark discharge, the location of charge ignition was dominated by spark discharge at the center of cylinder while simultaneous autoignition sites were found around the periphery of the combustion chamber for nonspark-assisted ignition.

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“…Hence, the low-temperature reactions (cool flames) and the early phase of the main heat release in an HCCI engine can be investigated by probing the formation and consumption of formaldehyde. Conventional planar laser induced fluorescence from formaldehyde, i.e., with one image captured per engine cycle, has been used earlier in investigations of the Controlled Auto Ignition (CAI) combustion concept [11] and for characterization of HCCI combustion [12,13,14]. In the latter publication it was reported how the concentration of formaldehyde increased as the Low Temperature Reactions (LTR) progressed.…”

Section: K Lombaertmentioning

confidence: 99%