Abnormal combustion in a spark ignition engine scribd. This provided us to find a threshold to make the classification. In a ci engine, irrespective of load, at any given speed, an approximately constant supply of air enters the cylinder. Abnormal combustion when the 2 conditions of normal combustion do not occur, the combustion process is abnormal, causing engine damages or simply performance worsening and noise. Laminar flame is too slow, however the mixture in the cylinder is turbulized and flame is turbulent, which makes the rate of combustion very high. There is a certain time interval between instant of s. Friends today we are going to discuss about the normal and abnormal combustion in s. The process of burning the fuel in the combustion chamber has always been the most misunderstood concept by people who modify engines and tune engines. The combustion process of the knocking case has two stages. Introduction classification of the combustion process normal combustion. Cycle world technical editor kevin cameron answers your engineering and mechanical questions. Les analysis for autoignition induced abnormal combustion. This paper presents a study of fuel performance in spark ignition engines in relation to abnormal combustion phenomena such as surface ignition and rumble.
This period tends to be very nearly constant in time. Abnormal combustion fuel composition, engine design and operating parameters, combustion chamber deposits may prevent occuring of the normal combustion process. Combustion starts from selfignition simultaneously at many locations in the slightly rich zone of the fuel jet, where the equivalence ratio is 1 to 1. The noise is generated by shock waves produced in the cylinder when unburned gas autoignites. Theoretical diagram of pressure crank theoretical diagram of pressure crank. Abnormal combustion detection in a compression ignition. This page should help to understand how the many factors determine the resulting engine performance. What is the difference between normal and abnormal. Knocking combustion in sparkignition engines sciencedirect.
Ignition lag or delay periodthis first phase is the duration between the occurrence of spark at spark plug and the deviation of combustion curve from motor curve ab in figure. This was accomplished by observation of the distribution of flame arrivals at ion gaps located within the engine. The propagation speed of the small flame kernel is low. Engine knock arises from autoignition of the end gas ahead of the propagating flame.
The small kernel is not highly wrinkled by turbulence. When the combustion gets deviated from the normal behavior resulting loss of performance or damage to the engine. Normal and abnormal knockabnormal knockknock free or knocking. The consequences of abnormal combustion are loss of engine power, recurring preignition and increased wear of the engine. Theoretical diagram of pressure crank angle diagram is shown in figure below. Knocking also knock, detonation, spark knock, pinging or pinking in spark ignition internal combustion engines occurs when combustion of some of the airfuel mixture in the cylinder does not result from propagation of the flame front ignited by the spark plug, but one or more pockets of airfuel mixture explode outside the envelope of the normal combustion front. It is therefore of great interest to develop capability to predict autoignition which leads to engine knock. Downsized spark ignition engines are highly efficient but promote abnormal combustion phenomena like preignition and knocking. Carburetor fuel injectioninternal combustion engines. Parameters controlling abnormal combustion in ci engines abnormal combustion means knocking. It results as from autoignition of the airfuel mixture at an undesirable period during engine operation. It is happened when the charge inside the cylinder may be ignite before the flame front reach it. Spark discharge creates a high temperature plasma kernel which expands rapidly 1mm, 100 s. Under normal operating conditions, the mixture is ignited by the spark plug in a optimized moment of the cycle usually 2040 before tdc.
Under normal operating conditions, combustion is initiated towards the end of compression stroke at the spark plug. In practice, the spark is often retarded to give a 1 or 2% reduction in. Bai tc in piston engines combustion stages ignition stage. What is the difference between normal and abnormal combustion in a motorcycle engine. Abnormal combustion fuel composition, engine design and operating parameters, combustion chamber deposits may prevent occurring of. When combustion starts, somewhere between 70% and 95% of the fuel in the combustion chamber is in the vapor state. Combustion normal combustion sparkignited flame moves steadily across the combustion chamber until the charge is fully consumed. To classify each combustion as normal or abnormal, we used support vector machines svm. With change in load, the quantity of fuel injected is changed, varying the airfuel ratio. Cycleresolved visualization of preignition and abnormal. The hot reactive gas at the outer edge of this kernel causes the. Pdf abnormal combustion diagnosis and combustion period.
Engine knock is generally considered as a result of endgas autoignition before the arrival of main. Greater the compression the temperature in the cylinder are higher and hence due to higher molecular activity the ignition delay will be less and the chances of abnormal combustion are less at higher compression ratios. Internal combustion engine quick revision pdf notes, book. How to make a high current 200a spot welding machine using 3000f capacitor duration. Abnormal combustion is the condition inside combustion chamber, when the flame is initiated by hot surface inside the chamber either prior or after the spark formation this is caused by the hot surface present in the cylinder or the autoignitio. Fuel must be injected into the cylinder at the desired time of combtibustion in. Traditionally, rather rudimentary skeletal chemical kinetics models have been used for au. Engines under normal operating condition, combustion is initiated towards the end of compression stroke at the spark plug by an electric discharge. Following conditions are necessary for combustion combustion to take place 1. During this time the mixture must be ignited, burnt and reburnt. Stabilization and propagation of flame in combustion chamber in s i engines, carburetor supplies a combustible mixture of petrol and air and spark plug initiates combustion combustion in s.