Improved liquid hydrogen-powered Corolla and GR86 (carbon-neutral fuel) to participate in Super Taikyu at Autopolis
Toyota Motor Corporation will enter the ENEOS Super Taikyu Series 2023 Supported by Bridgestone Round 4 Super Taikyu Race (5h x 1 race), to be held from 29-30 July at the Autopolis international racing course in Oita Prefecture, with the #32 ORC ROOKIE GR Corolla H2 Concept, which runs on liquid hydrogen (earlier post), and the #28 ORC ROOKIE GR86 CNF Concept running on carbon-neutral fuel (earlier post).
The hydrogen-powered Corolla, mobile liquid hydrogen stations, and carbon neutral fuel have evolved in the two months since the Round 2 NAPAC Fuji SUPER TEC 24 Hours Race from 26-28 May.
For the hydrogen-powered Corolla, the durability of the liquid hydrogen pump, which was an issue in the Fuji 24 Hours Race, has been improved, resulting in 30% enhanced durability under similar conditions. Lubricating oil is usually used in pumps to reduce stress through less friction in the pump; however, lubricating oil cannot be used in liquid hydrogen pumps as it contaminates the hydrogen. For this race, a buffer structure will be used to reduce stress on the pump gear drive unit, aiming to allow it to finish the race without needing to be replaced.
In addition, various liquid hydrogen systems, including safety valves and piping, have been optimized based on analyses of data collected in previous tests and races. In addition, pump stress has been reduced by optimizing fuel pressure, leading to a weight reduction for the pump drive motor battery. As a result, the vehicle now weighs 1,910 kg—40 kg lighter than the 1,950 kg it weighed during the Fuji 24 Hours Race in May.
Toyota has also succeeded in reducing the weight of joints and flexible hoses for the mobile liquid hydrogen station that was developed jointly by Iwatani Corporation and Toyota. Since the joint and flexible hose weight puts a burden on the workers who fill vehicles with hydrogen, reducing their size and weight is important in preparing for future commercialization.
Toyota reduced the weight of the filling joint from 8.4 kg to 6.0 kg and the return joint from 16.0 kg to 12.5 kg by eliminating the connection cover and changing the components that do not come into contact with hydrogen from iron to aluminum. The flexible hose on the return joint side has also been changed to a thinner hose, reducing the weight from approximately 4 kg to 1 kg, to reduce the burden on workers and improve workability during filling operations.
Joints used during the Fuji 24 Hours Race (top) and the improved joint (bottom). Filling joints are on the left; return joints (joints that returns vaporized hydrogen to the filling station) are on the right.
Until now, all hydrogen filling operations for the hydrogen-powered Corolla, such as opening and closing the filling valve and stopping filling when the hydrogen reaches full capacity, have been performed manually. For this race, Toyota automated these operations through electronic control. Automating hydrogen filling will enable it to be performed efficiently and error-free in a predictable time frame.
Return joint is at the back of the photo; the filling joint is at the front.
Further, a high-flow-rate filling-side stop valve developed by Fujikin Incorporated will be installed starting from this race. The filling-side stop valve is installed onto the filling port of the liquid hydrogen tank. Valve sizes increase as the flow rate increases to speed up the filling process, making sealing more difficult. However, Fujikin’s valve has succeeded in balancing both of these factors. As a result, hydrogen filling time has been reduced to approximately 1 minute, down from 1 minute 40 seconds at the Fuji 24 Hours Race.
High-flow-rate filling-side stop valves developed by Fujikin Incorporated (Left is pre-improvement, right is post-improvement)
A fuel cell generator has been installed in the pit to power the mobile liquid hydrogen station for the hydrogen-powered Corolla. Three types of Kyushu-produced gaseous hydrogen are being used: geothermal-derived hydrogen from Obayashi Corporation, solar-generated hydrogen from Toyota Motor Kyushu, and sewage biogas-derived hydrogen from Fukuoka City.
Carbon-neutral fuel. The CNF GR86 has been racing with the newly improved carbon-neutral fuel since the Round 3 SUGO Super Taikyu 3 Hours Race held from 8-9 July.
The problem with traditional carbon-neutral fuel is that it tends to dilute the engine oil, preventing the engine oil from performing as it should. Together with Subaru Corporation, which also uses carbon-neutral fuel in its races, and fuel manufacturers, Toyota adjusted the composition of the fuel to make it easier to vaporize and burn. This reduces engine oil dilution and improves reliability and exhaust performance by reducing the burden on the engine.