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 Customer Service: Tel: 877-606-7323 (inside USA and Canada) Tel: 724-776-4970 (outside USA) Fax: 724-776-0790 Email: CustomerService@sae.org SAE Web Address: http://www.sae.org Printed in USA 2009-01-0649 Design and operation of a high pressure, high temperature cell for HD diesel spray diagnostics: guidelines and results Rik S.G. Baert, Peter J.M. Frijters, Bart Somers, Carlo Luijten, Wout de Boer Eindhoven University of Technology Copyright © 2009 SAE International ABSTRACT This paper first compares strengths and weaknesses of different options for performing optical diagnostics on HD diesel sprays. Then, practical experiences are described with the design and operation of a constant volume test cell over a period of more than five years. In this test rig, pre-combustion of a lean gas mixture is used to generate realistic gas mixture conditions prior to fuel injection. Spray growth, vaporization are studied using Schlieren and Mie scattering experiments. The Schlieren set-up is also used for registration of light emitted by the combustion process; this can also provide information on ignition delay and on soot lift-off length. The paper further describes difficulties encountered with image processing and suggests methods on how to deal with them. Results are presented that illustrate the wide range of capabilities of this test-rig when combined with high speed video registration, in particular its potential for studying issues related to vaporizing fuel spray dynamics. INTRODUCTION A major driver in the development of modern HD diesel engines is the need for increasingly cleaner but conventional CI combustion while retaining the high fuel efficiency of this concept. To realize this, a variety of technological pathways are being investigated: further increased injection pressure, complex multiple injection strategies, further fine-tuning of injector nozzle geometry and introduction of increasing amounts of re-circulated exhaust gas (EGR) [1]. Another promising path towards cleaner combustion is the introduction of different fuel formulations such as GTL, oxygenates and water-fuel emulsions. In the investigation of the potential of these different paths, the study with advanced laser-based diagnostics of the diesel spray combustion process, in dedicated optically accessible test rigs, takes up an increasingly important role both in academia and industry [2,3]. In fact, since 1997 [4] such research by different groups has lead to a new and better understanding of diesel combustion. The prime requirement of any optical test rig for the study of diesel spray combustion is that it should create ambient gas conditions that are representative of those in a diesel engine during the injection and combustion process. In conventional CI combustion, fuel is injected shortly before TDC. Figure 1 shows the corresponding p and T range for current premium single stage turbo- charged HD diesel engines. The test equipment that most closely resembles the actual engine is the optical research engine (ORE). Such engine typically applies a bow-ditch design with a large window in the piston. Additional access to the combustion chamber is through windows in the liner close to the cylinder head (alternatively also a sapphire ring can be applied) and/or through windows in the cylinder head (sacrificing one or more of the valves). Several of such HD-size research engines have been presented in the literature [5-9]. In these test rigs combustion has been examined at imep levels up to 1.8 MPa, be it with a reduced compression ratio (and therefore lower pressure levels).