Implementation of real-time combustion feedback for use in closed-loop combustion control is a technology that has potential to assist in the successful production implementation of advanced diesel combustion modes. Low-temperature, pre-mixed diesel combustion is presently of interest because it offers the ability to lower the engine-out emissions of oxides of nitrogen (NOx) and particulate matter (PM). The need for lowering these two emissions is driven by tighter regulations enacted worldwide, especially the NOx limits in the United States. Reducing engine-out emissions eases the need for additional exhaust aftertreatment devices and their associated cost and mass. In this paper we will describe an experimental cylinder pressure-based control system and present both steadystate and transient results from a diesel engine employing a pre-mixed type of combustion. Data are presented showing engine operation with the control system enabled and disabled, highlighting the control effectiveness of the real-time cylinder pressure feedback.

Citation: BARTLETT, L.M., 2009. Integrated system fault diagnostics utilising digraph and fault tree-based approaches. Reliability Engineering and System Safety, 94 (6), pp. [1107][1108][1109][1110][1111][1112][1113][1114][1115] Additional Information:• ABSTRACT:With the growing intolerance to failures within systems, the issue of fault diagnosis has become ever prevalent. Information concerning these possible failures can help to minimise the disruption to the functionality of the system by allowing quick rectification. Traditional approaches to fault diagnosis within engineering systems have focused on sequential testing procedures and real time mechanisms. Both methods have been predominantly limited to single fault causes. Latest approaches also consider the issue of multiple faults in reflection to the characteristics of modern day systems designed for high reliability. In addition, a diagnostic capability is required in real time and for changeable system functionality. This paper focuses on two approaches which have been developed to cater for the demands of diagnosis within current engineering systems, namely application of the fault tree analysis technique and the method of digraphs. Both use a comparative approach to consider differences between actual system behaviour and that expected. The procedural guidelines are discussed for each method, with an experimental aircraft fuel system used to test and demonstrate the features of the techniques. The effectiveness of the approaches are compared and their future potential highlighted.

No abstract

The manuscript was received on 3 May 2007 and was accepted after revision for publication on 25 July 2007. DOI: 10.1243/1748006XJRR88Abstract: The issue of fault diagnostics is a dominant factor concerning current engineering systems. Information regarding possible failures is required in order to minimize disruption caused to functionality. A method proposed in this paper utilizes digraphs to model the information flow within an application system. Digraphs are composed from a set of nodes representing system process variables or component failure modes. The nodes are connected by signed edges thus illustrating the influence, be it positive or negative, one node has on another. System fault diagnostics is conducted through a procedure of back-tracing in the digraph from a known deviating variable. A computational method has been developed to conduct this process. Comparisons are made between retrieved transmitter readings and those expected while the system is in a known operating mode. Any noted deviations are assumed to indicate the presence of a failure. The current paper looks in detail at the application of the digraph diagnostic method to an industrially based test stand of an aircraft fuel system. This research includes transient system effects; the rate of change of a parameter is taken into consideration as a means of monitoring the system dynamically. The validity of the results achieved, through performing fault diagnostics based on the use of a digraph model, is evaluated. Finally, the effectiveness and scalability issues associated with the application of the method are addressed.

This item was submitted to Loughborough's Institutional Repository (https://dspace.lboro.ac.uk/) by the author and is made available under the following Creative Commons Licence conditions.For the full text of this licence, please go to: http://creativecommons.org/licenses/by-nc-nd/2.5/ Enhanced diagnosis of faults using the digraph approach applied to a dynamic aircraft fuel system E M Kelly and L M Bartlett* Department of Aeronautical and Automotive Engineering, Loughborough University, Loughborough, Leicestershire, UKThe manuscript was received on 1 October 2007 and was accepted after revision for publication on 5 August 2008. DOI: 10.1243/1748006XJRR119Abstract: Malfunctions within commercial aircraft can considerably increase both the financial cost of downtime and the disruption caused to passenger travel. For this reason prompt detection, diagnosis, and rectification of faults is imperative to the successful operation of such a system. In this paper the fault diagnostic problem is tackled based on the application of the digraph procedure. Digraphs model the information flow, and hence fault propagation, through a system. A computational method has been successfully developed to conduct the fault diagnostics process and produce a list of the fault combinations determined. The scope of the method has been demonstrated by consideration of two modes of operation to the application of a commercial aircraft fuel system, namely that of a Boeing 777. In addition the paper highlights the contribution of the development of a reduction method to enhance the likelihood of identifying the possible failure causes in three ways from different viewpoints. The three methods provide the option of determining the component at fault, the most probable failure mode cause, and also evidence for a particular component fault.