The Future of Advanced Air Mobility

Honeywell Reports Progress with One-MW Turbogenerator Tests

Honeywell Aerospace says it has completed the first round of testing of the one-MW turbogenerator it is developing to power hybrid-electric aircraft. The propulsion system, which the U.S. group announced in March 2021, combines a one-megawatt generator with the company’s existing HGT 1700 auxiliary power unit to provide two and a half times more power than a prototype unveiled in 2019.

During the latest ground tests, the turbogenerator operated at power levels of 1.02 MVA, which is around the one-MW level. Honeywell reported on June 1 that the demonstration ran continuously at 900 kW, which it says demonstrated a high power density of around eight kw/kg and an efficiency rate of about 97 percent. According to Honeywell, this compares with currently available generators that have an efficiency rating of between 88 and 90 percent and a power density of around two to three kW/kg.

The 280-pound unit, which Honeywell says weighs about the same as a motorscooter, will be able to work in conjunction with high-power electric motors and/or charge batteries. The company, which is making a concerted effort to expand its involvement in the advanced air mobility sector, says the generator's compact size and weight make it suitable for both on-aircraft propulsion and ground-based recharging units.

The turbogenerator will run on aviation biofuels, such as Honeywell’s own Green Jet Fuel, as well as conventional jet-A or diesel. In a bid to advance the use of sustainable aviation fuel, Honeywell has established its UOP Ecofining process, which produces cleaner-burning high-cetane fuel that is chemically identical to petroleum-based diesel. The resulting Honeywell Green Jet Fuel can be blended on a 50:50 basis with petroleum-based jet fuel that can be used in aircraft without modification.

“[The generator] represents an important step in providing scalable solutions that advance industry innovation and support more sustainable and efficient operations,” said Dave Marinick, president of Honeywell Aerospace Engines and Power Systems. “Essential high power through advanced and compact technology such as this impacts the future of flight and hybrid-electric aerospace propulsion.”

Honeywell’s engineering team is now expanding the capability of its test setup to support continuous operations with the new turbogenerator at higher power levels. Last month, Lilium selected Honeywell and Japanese automotive group Denso to provide electric motors for its eVTOL aircraft.

In December 2021, rival aircraft engine maker Rolls-Royce reported that the hybrid-electric propulsion system it is developing for possible use on future regional airliners has achieved a key milestone of generating more than one MW of power in ground tests. The UK-based group started testing the Power Generation System 1 (PGS1) with the goal of generating 2.5 MW, with further tests set to continue at the company’s renovated Testbed 108 facility in Bristol, UK.

The generator, which Rolls-Royce says is about the size of a beer keg, incorporates one of the group’s AE2100 turbofan engines, as well as special controls and a thermal management system. According to the company, the one MW generated in tests so far is sufficient to continuously power around 1,000 homes.