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Hydrogen Assisted Jet Ignition (HAJI) is a novel method of maintaining combustion stability during ultra-lean operation of conventional, homogeneously charged, SI engines. When operating with HAJI above λ=2, CO and NOx emissions fall to low levels while HC emissions rise to approximately double their stoichiometric value. HC emissions were investigated by operating a HAJI equipped, optically accessible, four-valve single cylinder engine at 600 r/min, wide open throttle (WOT), and from λ=1 to λ=2.4. A fast flame ionisation detector was used to collect real time hydrocarbon concentration data from behind one of the exhaust valves, inside the HAJI pre-chamber, and from near the combustion chamber wall. Flame images were also obtained. Exhaust port sampling shows that the HC concentration during blowdown and early exhaust is increased, but the concentration at the end of exhaust is decreased.

A fast flame ionisation detector (FID) is able to measure the hydrocarbon (HC) concentration at a single point in the exhaust port. However, when sampling is conducted near the plane of the exhaust valve, these measurements are not representative of the entire port cross-section. This paper describes a multi-point extension to a standard fast FID probe, enabling the instantaneous measurement of a more representative HC concentration near the plane of the exhaust valve. Construction and use of the multi-point probe is discussed, and results are compared with standard single-point measurements.