Experimental analysis on a spark ignition petrol engine fuelled with LPG (liquefied petroleum gas)

The use of LPG (liquefied petroleum gas) as alternative fuel to petrol is common practise in spark ignition engines. While the main driving force to the use of LPG still remains the low cost for the end user, its favourable pollutant emissions, in particular carbon dioxide, will in the middle term probably increase interest in LPG as an IC engine fuel. In addition, there are both theoretical and technical reasons to consider LPG as an attractive fuel also in terms of engine performance. Despite the continuously increasing stock production of dual-fuel (petrol–LPG) passenger car models, doubts still exist about both real engine performance in LPG operation and the reliability of the dual-fuel feeding system. This paper deals with the theoretical advantages of using LPG as fuel for SI engines. Brake performance tests of a passenger car engine fed with petrol and LPG are analysed and compared. The stock engine has been equipped with a “third-generation” standard kit for dual-fuel operation. The performance reductions in LPG operation are discussed in both steady state and transient condition. The results of some modifications to the set-up of both the petrol and LPG metering devices, designed for a better justification of the measured performance, are also presented.

► Experimental research on the actual performances of an SI engine fed with petrol and gaseous LPG. ► Theoretical advantages and drawbacks of fuelling SI ICE’s with LPG. ► Brake performance analysis shows a noticeable gap between LPG and petrol operation. ► Local measurements confirm that the thermodynamic operation of the evaporator-pressure reducer device is crucial for the engine performance. ► The performance of the up-to-date kit for petrol–LPG dual-fuel operation is greatly affected by the settings of the mechanical components of the LPG evaporator device.