K. Cupiał

Anomalies in combustion of hydrogen in a SI engine modified to work as a supercharged one

The paper describes combustion anomalies of various types randomly or permanently occurring while hydrogen is burnt in a supercharged spark ignited reciprocating engine. The anomalies were mainly identified as result of combustion pressure data analysis. Originally, the engine was a compression ignition one fuelled with diesel fuel. Modifications done on the engine dealt with decrease in its geometric compression ratio and equipping it with a spark plug located in diesel fuel injector position. The anomalies presented in the paper are typically associated with several abnormal phenomena as follows: flame propagation into intake manifold called back-fire, hydrogen spontaneous ignition by hot surface, flame propagation during valves overlap and extinguishing spark discharge flame kernel by high turbulence around a spark plug. These anomalies were observed in the supercharged engine, however, some of them were also detected while the engine was operated as a freely aspirated one. As investigated, some of these malfunctions would have been removed by change in engine operating parameters. Others need major changes in both exhaust pipeline geometry, hydrogen injection system, engine cylinder geometry and valve timing.

Accidental ignition in the engine intake system

Purpose – The purpose of this paper is to describe studies of accidental ignition of fuel‐air mixture. Studies were carried out in a laboratory that contains the naturally aspirated aircraft engine LYCOMNIG 320B1A IO type used in the EM‐11C Orka aircraft and the intake system to determine its resilience to the effects of accidental ignition and the occurrence of a backfire.Design/methodology/approach – Tests were performed on a model under extreme conditions (with the intake system closed) and under conditions similar to normal operation using fuels of different combustion rates.Findings – It was found that the positive pressure caused by such accidental ignition under normal operating conditions did not exceed 0.08 bar and did not pose any hazard of damaging the intake system of the IO‐320B1‐type LYCOMNIG naturally aspirated aircraft engine, as designed by the aircraft manufacturer.Practical implications – The positive results of the tests of the EM11C Orka aircraft intake systems resistance to flashbac...