The Canadian Department of National Defense (DND) operates 36 Short Range Radar sites in Canada's far north. Each unmanned site is powered by three Lister-Petter HL-6 diesel engines coupled to Kato Engineering 30 kW brushless generators. Many of these engines have accumulated in excess of 30,000 hours of operation. DND required some means to remotely diagnose/assess the health of these engines in order to determine which gen-set should operate. In addition, there is a need to determine potential maintenance requirements and associated timing of maintenance site visits.

The power contribution of each cylinder of a diesel engine can be used to assess engine condition and assist in locating faults (i.e., fuel rack adjustment, injector fouling, valve seating, ring breakage, etc). In larger diesel engines, cylinder condition is usually assessed by measuring cylinder pressure during operation using permanently installed cylinder pressure access ports. Smaller high-speed diesel engines, such as the Lister-Petter HL-6, are not normally equipped with combustion pressure access ports and the cost of modifying cylinder heads made this approach unattractive to DND.

Advanced Engine Technology Ltd. (AET), has developed an engine condition monitoring system for this application under contract with the North Warning System Office of DND. AET is a research, development and manufacturing company with diesel engine/fuels laboratory facilities located in Nepean, a neighboring city to Ottawa, Ontario, Canada.

The AET Engine Condition Monitor (ECM) can detect any combination of cylinder faults in six-cylinder high-speed diesel generator sets under continually varying loads. The power balance of each cylinder can be predicted to within [+ or -]2 percent RMS and cylinder pressure measurements are not required. Operation of the ECM is fully automated, and engine data can be downloaded from the remote radar sites to a centrally located monitoring station.

The ECM is based on Instantaneous Crankshaft Angular Velocity technology (ICAV), initially developed and patented by the National Research Council of Canada. AET is the worldwide licensee of this technology. Following the initial development of the ICAV technology by NRC, AET has pursued the development and commercialization of this technology for diesel engine applications over the past several years. Current efforts are directed towards engine condition monitoring for generator set applications in both unmanned and manned settings. ICAV measures the periodic variations in crankshaft velocity during each engine cycle. Pattern recognition software compares the crankshaft velocity waveform to a knowledge base for the engine/generator family. AET creates this knowledge base by mapping a typical engine/generator over a range of loads. During mapping, cylinder power balance is perturbed by known amounts. The knowledge base created by mapping one engine/generator can be used on other diesel generator sets of the same family.

Flywheel speed is measured using two rugged, noncontacting Hall-effect sensors mounted on the engine bell housing. Variations in flywheel tooth spacing or tooth wear are taken into account in order to produce accurate results. The ECM can be quickly retrofitted in the field using common tools. Once installed, no further maintenance or periodic calibration is required, according to AET. Flywheel tooth spacing is measured by a custom timer board installed in a personal computer on each site. ICAV software processes this information and calculates the relative power from each cylinder. Data is automatically acquired and stored in a database on the computer at 30 minute intervals. When requested, stored engine data is transferred from each radar site to the central monitoring station via a satellite link.

Figure 2 shows a sample of data downloaded from one radar site. This display format is used to show the current cylinder power balance of all engines running at the radar site. Each bar represents the deviation from nominal power of an individual cylinder: cylinder No. 1 on the left and cylinder No. 6 on the right. An over-balance condition of +20 percent indicates that the cylinder was producing 20 percent more than 1/6th of the total power; no deviation (zero percent) means that the cylinder was producing exactly 1/6th of the total power. As a general rule, it can be assumed that the engine is performing well when the power balance for all cylinders is within [+ or -]10 percent. Both fuel consumption and exhaust emissions are minimized when cylinder balance is optimized.

Tests performed at AET on this engine/generator family showed that at a power setting of 20 kW, a power imbalance of -30 percent in just one cylinder caused an increase in fuel consumption of 2.5 percent, along with significant increases in N[O.sub.x], THC, and particulate emissions. By using the ECM, maintenance staff are now able to balance cylinder power levels during annual maintenance inspections, thereby minimizing fuel consumption and emissions.