R6-H2 Engine

The R6-H2 engine has been developed by a small, dedicated team over a period of about 10 years, with c.£1.5m cash spent, including grants from the European Commission and Innovate UK. The main technical challenges concerning the design of the R6-H2 engine have been overcome: mechanical, thermal, balancing, sealing, materials and manufacturing. The R6-H2 engine is currently at TRL 3 – concept proven.

The R6-H2 engine is ideally suited as a high-efficiency, high-power, low-cost, zero-carbon electricity generator due to: rapid pressure increase converted into torque directly from top-dead-centre (TDC) (impossible for pistons) and a power phase in every revolution; separate dynamic chambers for intake, compression and expansion avoiding pre-ignition and backfire; internal EGR assisting HCCI and prohibiting NOx formation (90% below Euro 7 standard); exceptionally high/ asymmetric compression and expansion ratios for >50% brake thermal efficiency; and non-contact labyrinth sealing with abradable ceramic coatings for reduced thermal and friction losses. The beyond state-of-the-art aspects are:

A). Major expansion of the HCCI high load operating range due to early direct injection and 50% higher torque leverage immediately from TDC (impossible for pistons), to eliminate the problem of knock.

B). Major expansion of the HCCI low load operating range due to H2’s wide flammability range, autoignition assisted by the heat of internal EGR and a glow plug, to overcome the problem of poor ignition.

C). Near zero NOx emissions due to low combustion temperature <1,800k, c.38% EGR and stoichiometric fuel-air ratio (lambda 1.0), reducing NOx emissions to <200mg/kWh without aftertreatment and <20mg/kWh with a low-cost catalytic converter (compared to Euro 7 standard of 230 mg/kWh).

D). Does not require 99.999% pure H2, making it highly suitable for use with lower cost blue-H2 during the transition to green-H2.

HCCI combustion range

The following points provide more detailed estimates for the performance validation targets at TRL 4.

• 6 phase cycle (3 pairs): (1) intake/ 2nd compression, (2) 1st compression/ power, (3) scavenge-EGR/ exhaust

• Power phase in every shaft rotation, MEP c.23 bar, torque c.190Nm, eliminates pumping losses

• Rapid heat release of H2 converted into torque directly from TDC by rotors (impossible for pistons)

• Separate dynamic chambers for intake, compression and expansion avoids pre-ignition and backfire

• Exceptionally high asymmetric compression (18:1) and expansion (23:1) ratios, for efficiency >50% BTE

• Efficient combustion geometry and ceramic/ abradable 0.5mm coatings reduce radiation losses to c.4%

• Internal EGR assists HCCI autoignition and prohibits NOx formation <1,800K, <0.02g/kWh (with aftertreatment)

• Non-contact labyrinth sealing losses c.5%, friction losses reduced to c.0.5%

• Finely balanced – max distance of centre of mass from origin < 0.25mm

• 40kg unit weight, >200kW @ 12,500 rpm = power to weight ratio 5:1, max power c.240kW @ 15,000 rpm

• Factor of safety c.4 at 15,000 rpm, no oil lubrication, minimal mechanical wear, service life >50,000 hrs

• Prototype production costs c.€20,000 (estimated c.€4,000 at high volume) = €20/kW