 |
| Perhaps one of the UKs most powerful turbojets in its class the Noel Penny Turbines 301 engine was the last design to be produced before the company folded in 1990. This unit bares a number of similarities to its predecessor the similar but much less powerful NPT109. This unit was developed to power recoverable drone type un-manned aircraft and UAVs. Two units were also fitted to the a remarkable prototype four seat bizjet in the late 1980s. A simple but thirsty engine now replaced by much more elaborate units such as the Williams FJX33 turbofan.
NPT Wrote- The NPT301 turbojet has an annular axial flow intake with three struts supporting the nose bullet which houses a direct driven, self-exciting homopolar alternator. The alternator supplies electrical power of 2.8kw at 28V dc for vehicle use. The single stage two piece radial compressor discharges via radial diffusers and axial straighteners. The combustion chamber is a single reverse flow type with fuel supplied through twelve vaporizers by an electrically driven fuel pump. Fuel metering is electronically controlled by varying pump speed in accordance with power demand, engine speed and exhaust gas temperature. The engine can be either air impingement or windmill started with ignition achieved by high energy ignitor and pilot atomizer. The single stage axial turbine with integrally cast disc and blading is directly coupled to the compressor. Similarly, the turbine nozzle has integrally cast nozzle guide vanes and stator diaphram. The exhaust system consists of an annular diffuser jet pipe with six struts supporting the propelling nozzle. Two rolling element bearings support he rotor assembly. Each bearing incorporates a squeeze film damper to ensure smooth running of the rotor assembly over the entire operating rnage. A total loss, pulsed injection oil system is used to supply the squeeze film dampers and to lubricate the engine bearings. The NPT301 is sea water immersion tolerant and requires only a simple decontamination procedure after immersion. The engine adopts an almost classic mechanical layout for a small turbojet engine. The NPT301 can be likened to a very large model aircraft powerplant, it is similar mechanically (Although slightly bigger) to the Mircroturbo TRS18 engine. To keep mechanical complexity down to a minimum, fuel and oil are delivered to the engine by means of electric pumps. The fuel supply is metered to vaporizing burners by varying the pump speed as is the case with later model NPT109s. A slightly awkward engine to run due to the need for high volume high pressure air for impingement starting. An otherwise straight forward and unsophisticated engine to control provided the necessary electronics can be mastered. The NPT301 would make for a very quick BD5J! Noel Penny Turbines planned to produce a whole family of small turbojet engines and also a turboshaft unit. Prototype NPT151 and NPT171 units were produced, a very small NPT051, a larger NPT401 and an even an axial flow NPT901 where on the drawing board. Had the company not gone bust, the UK today could have had a very innovative supplier of small gas turbines. Competition from Willaims and Microturbo was probably to blame for the down-fall of NPT. |
 |
 |
 |
| NPT301 Brushless high speed homopolar alternator normaly mounted in the intake bullet |
 |
| Six Pole Rotor |
