Determination of thermal efficiency of the spark ignition systems

The paper presents results of measurements performed to determine thermal efficiency of spark ignition systems. Because of small pressure change after sparking process smali volume chamber has been proposed for measurements. A direct measurement method of pressure increment determination has been chosen. In this method one pressure chamber is used. The caloric chamber isfilledwith nitrogen, which is a neutral gas. It is preferable medium than air because it is one-component gas and it has a precisely-known value of a specific gas constant. The value of speciflc gas constant is reąuested to calculate a value of discharge energy given to the gas. In the chosen method pressure increment in the chamber during spark discharge is measured. The pressure increment in the chamber during ignition is strictly related to the energy of spark discharge. The energy balance calculations determined values of heat los s es for two types of electrodes (normal and "thin") anddifferent initial pressure (p=0 bar and p=25 bar). The maximal value of the thermal efficiency was observedfor the higher value of pressure in chamber and thin electrodes of spark ping. It was also stated, that the higher thermal efficiency for" thin " spark ping electrodes is a result of reduced heat transfer. The paper presents results of the tests carried out in the caloric chamber of 4. l cm3 filled with nitrogen at ambient temperature using PCB transducer direct measurement method. Results of the measurements done using differential pressure transducer for the same parameters like in thefirst measurement method were similar.