This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Monitoring the Spark-Plug Gap of Natural-Gas-Fuelled Stationary Engines
Annotation ability available
Sector:
Language:
English
Abstract
The demands on the performance of spark plugs are increasing because of developments in lean-burn engines leading to adverse conditions for ignition and because of the desire for a longer life of the plugs. For improving spark plugs and ignition systems, more insight into the relationship between gap wear and spark-plug design, ignition-system characteristics and in-cylinder conditions is required. For that purpose, an instrument has been developed to measure on-line the gap size of spark plugs. This monitor can also be used for on-condition maintenance indicating that a necessary replacement of the spark plugs will be near. The monitor, called SPECTOR, receives a signal from an inductive coil around the high-voltage cable which, under given conditions, is representative for the gap size.
SPARK PLUGS are commonly used to initiate the combustion process in natural-gas-fuelled engines. Natural gas is a suitable fuel for spark- ignition engines because of its high knock resistance and wide ignition range. Its low cetane number and low density hamper its use as a single diesel fuel, although dual-fuel and pilot-injection engines running on natural gas, where injected diesel oil is the ignition source, are common practice. The natural-gas-fuelled engines in the expanding market of combined-heat-and-power units are of the spark-ignition type, for emission reasons.
Units for the combined generation of electric power and heat are attractive because of their total energy efficiency of close to 90%. However, the units driven by reciprocating engines have to compete economically and ecologically with conventional power plants and with new developments such as fuel cells. The desire for higher shaft efficiencies and higher power densities shift developments towards a higher cylinder load (bmep) by turbocharging and towards a higher compression ratio. These developments are necessarily accompanied by further leaning of the fuel-air mixture, because otherwise the peak temperatures in the cylinder process would increase and result in higher NOx emissions. The current generation of open- chamber lean-burn gas engines operates on an air-to-fuel ratio, lambda, between 1.55 and 1.65 (1)*. Stoichiometrically operating engines of industrial quality cannot attain the current performance of lean-burn engines, as yet.
A leaner mixture requires more energy for ignition than a mixture closer to stoichiometric. Moreover, it is more difficult to establish an electric current in the gap of a spark plug if the density of the medium between the electrodes is higher. Thus, all new developments in engine performance are putting an increased demand on the performance of ignition systems. This tends to shorten the life of spark plugs. However, the necessities of low maintenance costs and a high reliability require the life of spark plugs to be extended to beyond a few thousand operating hours at an engine speed between 1000/min and 1800/min. Currently, the spark plugs determine the maintenance interval.
To be able to find ways to improve spark-plug life, it is necessary to establish a relationship between the lifetime, the design of the plug, the operating conditions in the engine and the properties of the ignition system. This is a difficult task, considering the many different engines, operating conditions and spark-plug types. The literature and our practical experience thus far give insufficient answers to these problems. This paper first gives an introduction into the nature of spark-plug wear, followed by a discussion of a literature study on the ignition process. The major part of this paper is used to describe a special on-line monitor developed to measure indirectly the gap width of a spark plug. This work was part of a program of Gasunie Research to improve engines fuelled by natural gas. The monitor can be used as a tool for on-condition maintenance, indicating spark-plug wear. Next to that, it can be used to study the wear rate of spark plugs in relationship with operating conditions and engine design.
Recommended Content
| Technical Paper | Erosion Mechanisms of Automotive Spark Plug Electrodes |
| Technical Paper | A Lean Burn Turbocharged, Natural Gas Engine for the US Medium Duty Automotive Market |
Authors
Topic
Citation
Klimstra, J. and Overmars, F., "Monitoring the Spark-Plug Gap of Natural-Gas-Fuelled Stationary Engines," SAE Technical Paper 912361, 1991, https://doi.org/10.4271/912361.Also In
References
- Klimstra, J. ‘Performance of Lean-Burn Natural-Gas-Fueled Engines - On Specific Fuel Consumption, Power Capacity and Emissions’ SAE paper 901495
- Quader, A.A. ‘What Limits Lean Operation in Spark Ignition Engines - Flame Initiation or Propagation?’ SAE paper 760760
- Schwarz, H. ‘Ignition Systems for Lean Burn Engines’ paper C95/79 in ‘Proceedings of the Conference on Fuel Economy and Emission of Lean Burn Engines’ The Institution of Mechanical Engineers 1979
- Pischinger, S. Heywood J.B. 1991 2 82 92
- Ballal, D.R Levebvre A.H ‘The Influence of Flow Parameters on Minimum Ignition Energy and Quenching Distance’ Fifteenth Symposium (Int.) on Combustion The Combustion Institute 1975 1473 1481
- Bradley, D Lung F. K-K. ‘Spark Ignition and Early Stages of Turbulent Flame Propagation’ Combustion and Flame 69 1987 71 93
- Ronney, P.D. ‘Research on Combustion Processes Associated with Natural Gas Used as an Internal Combustion Engine Fuel’ Final Report, Gas Research Institute Acession no. 90/0242 July 1990
- ‘ Straight Talk about Spark Plugs ’ Technical and Engineering Guide Champion Spark Plug Company Toledo, Ohio 1987
- ‘Visual Analysis’ Stitt Spark Plug Company Conroe, Texas
- Maly, R. ‘Spark Ignition: Its Physics and Effect on the Internal Combustion Engine ’ ‘Fuel Economy in Road Vehicles Powered by Spark Ignition Engines’ Hilliard J.C. Springer G.S. Plenum Press New York 1984
- Albrecht, H. Bloss W.H. Herden W. Maly R. Saggau B. Wagner E. ‘New Aspects on Spark Ignition’ SAE paper 770853
- Ziegler, G.F.W. Maly R.R. Wagner E.P. ‘Effect of Ignition System Design on Flammability in Ultra Lean Turbulent Mixtures ’ Paper C47/83, International Conference on Combustion in Engineering I April 11-14 1983
- ‘ Ignition System Measurements Procedure ’ SAE Recommended Practice J973a 1973
- Wesner, F. 91 1970 521 524
- Modien, R.M. Checkel M.D. Dale J.D. ‘ The Effect of Enhanced Ignition Systems on Early Flame Development in Quiescent and Turbulent Conditions’ SAE paper 910564
- Dale, J.D. Oppenheim A.K. ‘Enhanced Ignition for I.C. Engines with Premixed Gases’ SAE paper 810146
- Mueller, H. Haahtela O. 1972 10 408 414
- Klimstra, J. ‘The Optimum Combustion Phasing Angle - A Convenient Engine Tuning Criterion’ SAE paper 852090
- Anderson, R.W. ‘The Effect of Ignition System Power on Fast Burn Engine Combustion ’ SAE paper 870549
- Heijman, H. Huijzers A. Graduation thesis, Apeldoorn Polytechnic July 1988
- Oerlemans, F. Overmars F. Graduation thesis, Apeldoorn Polytechnic June 1989
- Dijkstra, P.J. Hofman S. May 1990