58655 - Assessment of Engine Operability and Overall Performance for Parallel Hybrid Electric Propulsion Systems for a Single-Aisle Aircraft 

Hybrid electric propulsion (HEP) is considered as one of the promising alternate for pollutant and noise emissions reduction, given the power source flexibility of the propulsion system. On the other hand the low power and energy density of the electric system may significantly affect the system performance at aircraft level. Additionally, the distinctly different behaviour of the electric system and of the gas turbine system, may give rise to operational challenges, while another important choice affecting both operability and performance for turbofans, is which spool is boosted by the electric power train.

This paper aims to assess the gas turbine operability and HEP system performance for a parallel hybrid electric configuration applied to a 150 passenger single-aisle aircraft for a 1,000 ~ 2,500nm range. Two cases are considered: one where the low pressure shaft is boosted and one where the high pressure shaft is boosted. For each case, different electrification strategies are employed. For identifying the most suitable solutions, steady state and transient operation are considered and the hybridization effect on operability is determined. The systems performance at aircraft level in terms of energy efficiency and emissions is quantified as well.

Despite the fact that pollutant emission and fuel consumption are marginally improved for hybrid propulsion, this comes at the cost of reduced payload and operability margins. The results indicate that boosting the low pressure shaft will give the highest performance benefits but low pressure compressor system operability is negatively affected.