Benefits of Supercharger Boosting on H2 ICE for Heavy Duty Applications

Abstract

The fast acceleration of GHG (CO2 in particular) emitted by human activities into the atmosphere is accelerating the average temperature increase of our globe causing heavy climate change. This phenomenon has triggered a strong pressure on GHG emission reduction in all the human activities including the transportation sector which contributes for the 29% to the total emissions in EU [1]. A mitigation to this tendency can come from synthetic fuels: when produced by using clean energy, they can be considered CO2 neutral. H2 is the building block of synthetic fuels and can be used in spark ignited engines where releases the energy accumulated during its production. This solution is particularly attractive for HD applications thanks to the high energy density. H2 can be burned in a quite wide range of λ, but staying on 2,2 the amount of engine out NOx will be low enough for the use on a 13L engine with a relatively simple aftertreatment system. This λ value is difficult to maintain in the full speed range for the turbocharger system as the exhaust gases energy may not be enough to spin compressor meeting the boost demand. This is particularly true at low speed and during acceleration. The Eaton Supercharger system driven by the engine crankshaft through a belt can compensate this gap and guarantee required λ also in critical conditions. The benefit of the additional boosting at full load is large enough for measuring in the mid/low speed range an increase in torque matching the Diesel values, and a 3% BTE rise. Going higher with the speed the Supercharger will not provide any more an advantage as turbocharger system is good enough for the λ 2,2. A clutch will disconnect the supercharger in that speed range and will prevent a drop in performance due to the power absorbed by the Supercharger itself. The use of Supercharger will also bring almost 30% improvement in transient response of the engine with no impact on air fuel ratio. With this strategy it is possible to convert a 13L Diesel engine for HD into an H2 maintaining same full load torque and power curves, while maximizing transient performance and efficiency.