**Author details**

<sup>0</sup> <sup>10</sup> <sup>20</sup> <sup>30</sup> <sup>40</sup> <sup>50</sup> <sup>0</sup>

**Degree of hybridization for block energy Heblock [%]**

**Figure 12.** Relative change in MTOW versus block degree-of-hybridization for energy He*block* . Electric fan cruise

design ranges with increasing levels of Hp*use* is attributable to sizing cascade effects resulting from the higher electric energy requirement which leads to large increase in aircraft mass (see Figure 12). However, it must be noted that for a given He*block* the difference in delta block ESAR is small when comparing the different strategies. It is important to highlight at this point that in the current implemented electrical system model, the efficiency of the electrical components, with the exception of the battery, is assumed invariant with respect to the operational conditions and operating time. This assumption is made under the premise of an appropriate thermal management of the electric components and a thoughtful layout of the propulsion architecture. The efficiency of the electrical propulsion system chain in the model depends consequently only on the variation of the battery efficiency with respect to its discharge characteristic and upon the ducted-fan efficiency according to the flight state and the power setting. Moreover, in the current model the speciï ˇn ˛Ac weight of the electrical components wereconsidered independent of any scale effect. With the availability of more detailed electrical system models, the dependance of the electrical components efficiency with respect to the altitude-temperature envelope and power load conditions as well as

Hpuse [%]

<sup>15</sup> <sup>20</sup> <sup>25</sup> <sup>30</sup> <sup>35</sup> <sup>40</sup> <sup>45</sup> <sup>50</sup>

possible variations of the specific weight with scaling effects would be considered.

The impact of the hybrid-electric propulsion on aircraft size according to the EF cruise throttling strategy is illustrated by the change in MTOW versus the change in He*block* in Figure 12. Similar trends in MTOW change between the different strategies with respect to increase in design range and growing Hp*use* were identified. For an identical He*block*, similar

In summary, a similar level of reduction in block fuel can be achieved when selecting the throttling of the EFs during cruise. This second operational strategy results in similar change in block fuel and block ESAR as well as in MTOW for an identical He*block*. However, to reach the same potential in block fuel reduction, a higher level of Hp*use* (in other words a higher useful electric power relative to the total useful power) needs to be achieved. This translates into the installation of a larger electric motor power. This system implication is rooted in

Cargo volume/PAX = 0.14m³

900 1100 1300 <sup>1500</sup> <sup>1900</sup> <sup>1700</sup>

Design Range [nm]

55

2100

values in relative change in MTOW were observed.

throttling

**Relative change in MTOW [%]**

134 New Applications of Electric Drives

**Study settings:** ebattery = 1.5kWh/kg Electric fan cruise throttling

Clément Pornet∗

\*Address all coresspodence to: clement.pornet@bauhaus-luftfahrt.net

Bauhaus Luftfahrt, Munich, Germany
