An experimental study on the backfire occurrence and combustion stabilization of high-efficiency hydrogen-fueled free-piston linear power systems

A scavenging method suitable for high-efficiency hydrogen (H2)-fueled two-stroke freepiston linear power systems as a next-generation alternative engine is experimentally studied, investigating the driving and backfire suppression characteristics of various scavenging methods by using a rapid compression expansion machine. A simple structured loop-scavenging method which was expected to be unfavorable for suppressing backfire in H2-fueled power systems is more advantageous than the valve-driven scavenging methods when the system performance is evaluated together. For the loopscavenging method, no backfire is observed at the fuel-equivalence ratio 4 < 0.6 when the ignition timing IGT is set for the maximum pressure (MPT) and the backfire limit can be extended to 4 = 0.8 if IGT is advanced than MPT, showing the maximum indicated thermal efficiency of 48%. The performance test using a single-type H2-fueled free-piston linear power system adopting the loop-scavenging successfully demonstrates stable continuous operation with no backfire at 4 < 0.8. (c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.