Uncrewed Systems Technology 048 | Kodiak Driver | 5G focus | Tiburon USV | Skypersonic Skycopter and Skyrover | CES 2023 | Limbach L 2400 DX and L 550 EFG | NXInnovation NX 100 Enviro | Solar power focus | Protegimus Protection

84 Dossier | Limbach L 2400 DX and L 550 EFG part, based on a series turbocharger from a third-party manufacturer. Intake air from the compressor is first piped through to the charge-air cooler, which is optional as its optimal form factor and mounting spot depends largely on the end-user’s platform (particularly to ensure sufficient access to cooling air for the unit), before going to the intake manifold. The company notes that the turbo is not a variable-geometry system. Instead, as Simmerkuss explains, “It uses an internal wastegate flap which is driven by a rod and is controlled by a pressure cell. “The pressure cell on the other hand is controlled by an electric valve. This is done by the valve passing on the charge pressure generated by the turbine side of the turbocharger to the pressure cell.” As soon as the boost pressure exceeds a limit value, it is released to the atmosphere by the ECU activating the valve. That limits the charge pressure generated by the turbocharger, and thus protects the engine from excessive power overboost and the engine knocking that comes with it. “Also, just above the intake ports, where each pipe runs into each cylinder, the manifold has plugs where we install our fuel injectors, so fuel enters the air stream at the very end, right before each cylinder inlet, so the mixing largely takes place within the tumble of the compression phase,” says Simmerkuss. “Each pair of IWP 43 injectors – for each pair of cylinders – is connected through a bridge, which also mounts the fuel intake from our fluid line, with a single circuit of fuel going from the tank, through the engine and back to the tank with any unused fuel.” The fuel piping thus runs across the injection nozzles for (in order) cylinders 4, 2, 1 and 3, ensuring a constant feed, before then running to a pressure sensor and then a pressure regulator, with unused fuel subsequently returning to the tank. Electric pumps powered by a generator feed the gasoline at up to 100 litres/hour through fuel lines optimised for a design pressure of 2.5 bar and to a limit of at least 6 bar. In addition to the fuel pressure sensor, piping for an air pressure sensor is connected to a composite arched pipe running between the throttle and the air filter enclosure. Meanwhile, the throttle integrates a two-channel Hall effect sensor for position sensing, the second channel serving as an emergency back- up in case the first fails. Power for the throttle position and other sensors and injectors can be provided using an optional starter/ generator for the L 2400 DX – again, assuming the end-user chooses not to supply their own. This system has a 28 V DC output and is capable of up to 7 kW output, supplying the 9 A consumed by the engine during regular operations. A 14 V, 55 A alternator is also available. “We’ve chosen torque over high speed with how we’ve designed and programmed this engine to function at its core,” Simmerkuss says. “Theoretically, we could have chosen to leave the torque increases to a reduction gearbox, as we’ve done now with our two-stroke 550 EFG, and as many companies do with their larger, more powerful February/March 2023 | Uncrewed Systems Technology The fuel injectors are installed at the ends of the air streams, with fuel-air mixing occurring mostly within the cylinders The L 2400 DX’s starter/generator produces up to 7 kW of electric power over a 28 V DC output