72 “Our only inertia to overcome is the mass of the gases themselves, which isn’t a lot, so throttle changes can execute really quickly, as needed,” he says, adding that changes from idle to maximum thrust can be achieved in under a second. More challenging is thermal management. The J-1 has been designed as an air-cooled engine (continuing the theme of simplicity), and the system will run extremely hot if forced to operate stationary in a braked UAV on a runway for too long. “For any UAV subsystems installed right next to the engine, we recommend using a little bit of reflective tape or similar heat shielding, which has been demonstrated to work well with most common airframe materials, including fibreglass and carbon fibre. If the engine is embedded inside the fuselage, the design must include prudent inlets and baffling for cooling airflow, as you would with many engine designs,” Maqbool says. “Granted, our demo videos show the J-1 mounted externally atop a model aircraft as a testbed, but that’s just because we wanted a really simple demonstrator. It could absolutely function completely normally in an embedded, internal integration or a rear-mounted configuration, so long as the design takes air cooling into account.” Additionally, as the J-1’s exhaust phase produces pulsations that radiate outwards, it is worthwhile to allow the pipe outlets to protrude from the craft (as one typically would with exhaust pipes) to ensure the pulses do not impact or affect any wing-, tail-, or fuselage-mounted subsystems, particularly for survey applications. ECU design The ECU can be mounted roughly anywhere except on the engine (to avoid overheating), with a common approach being to install it on the firewall. As mentioned, the ECU design is custom and entirely proprietary to Wave Engine (although manufacturing is provided by a third-party production house), with simplicity at the forefront of its development priorities. “The intent was for the ECU to handle all fuel supply, ignition and control functions over the engine as an integrated package handling all its inputs and outputs, with no significant ECU programming work left to the end-user, and a single wire harness linking it out to the flight controller,” Maqbool says. “On the fuel side, we supply the pump, filters and injectors – not just for ensuring a turnkey package with our ECU, but also because a lot of our technical IP revolves around specific selections of those items, with some pumps, for instance, working better than others.” Fuel is currently delivered using an electric pump powered by an integrated battery controlled by the ECU (for direct control and to prevent users having to power the pump themselves). Key selection criteria included the pump being able to hit the target fuel pressure and flow rates, and also that it could operate on minimal current draw to ensure the battery could be kept as small as possible. “We found most pumps on the market are actually overpowered for our application, so ours is on the smaller October/November 2024 | Uncrewed Systems Technology The ECU controls the fuel pumps and injectors via PWM, and it can be mounted anywhere except directly on the engine The intent was for the ECU to handle all fuel supply, ignition and control functions over the engine as an integrated package, all its inputs, outputs
RkJQdWJsaXNoZXIy MjI2Mzk4