The engines of the PW 100 series are leading in modern, ultra-modern regional and commuter turboprop engines. With its three-coil design, easy-to-maintain modular structure, and high power rating, the engine is a logical choice for medium to large turboprops, including the Bombardier Q400, DeHavilland Dash 8, and Embraer EMB 120. Some consider the PW 100 a replacement for the venerable PT6, but in reality the PW 100 picks up where the PT6 Large version left off in terms of performance, fuel consumption and reliability. The PW 100 series consists of a number of variations. There is no actual PW 100 motor. The motors start with the PW118 motor and end with the PW127J.
The engines are essentially the same, with mostly a steady increase in power output and minor fluctuations in engine power and the ratio of mechanical shaft power to generated thrust. In other words, each turboprop is rated in Equivalent Shaft Power (eshp), which is a combination of the actual mechanical power on the output shaft and the amount of power available that is available as the conversion of the thrust generated on the exhaust pipe. The proportion varies, but is typically in the range of 80% of the power produced by the propeller and 20% of the power produced by the exhaust pipe.
The powerful PW 100 motor is completely modular. That is, it consists of a number of interchangeable modules that can be easily removed and replaced if there is a problem with the engine. The modules consist of the turbomachine, the power turbine assembly, the inlet housing and the gearbox for power reduction. The compact turbo machine consists of the double-coil gas generator and the accessory gearbox. The power turbine is connected to the rear of the turbomachine and has a two-stage power turbine that drives a shaft that runs forward in the center of the turbomachine’s shafts. The inlet housing is attached to the front of the turbomachine and provides space for air to be drawn into the compressor and support for the gearbox to reduce power. The power reduction gearbox mounts to the front of the inlet housing and takes the high speed input from the turbine shaft and converts it to high torque, low speed power taken from the propeller flange on the front of the gearbox.
Atmospheric air is drawn through the engine nacelle behind the propeller into a passive particle separator that is part of the nacelle. Clean intake air is drawn up into the downward scrolling motor inlet. Air is sucked into the turbomachine by the single-stage radial compressor. The air is accelerated outwards by the compressor and fed into numerous curved diffuser channels, which distribute the air flow evenly over the surface of the single-stage centrifugal high-pressure compressor. The high pressure compressor increases the pressure on some later models to a design pressure ratio of nearly 15: 1. The high pressure compressor feeds the airflow to a diffuser which converts the dynamic pressure to static pressure as it enters the annular backflow combustion chamber. The compressed air enters the inner combustion liner where it is mixed with jet fuel and ignited. The resulting gas is expanded through the high pressure nozzle to meet the high pressure single stage axial turbine that powers the high pressure compressor and accessory gearbox. The gas is then further expanded through the low pressure nozzle to drive the low pressure turbine, which drives the low pressure compressor. Eventually, the gas is expanded through the two-stage power turbine to drive a concentric shaft to the front of the engine, which drives the gearbox to reduce power. The exhaust is then drawn out of the short, fixed section, axial flow exhaust outlet to provide nearly 2,000 lbs. Thrust on some popular models of the PW-100 engine. The gearbox for power reduction reduces the speed of the power turbine to a useful 1,200 or 1,300 rpm to drive a four-bladed propeller at a constant speed. Accessories include a generator, oil pumps, fuel pumps, hydraulic pumps, and a FADEC fuel controller.
The dual coil compressor offers many advantages over a similar single coil compressor. Since the two compressors can be operated at different speeds, the compressors can be optimized for a large number of air flows. This allows for a higher design pressure ratio, much better part performance efficiency, and very quick engine response. High pressure ratios and high turbine inlet temperatures allow very low specific fuel consumption, and advanced cooling techniques and state-of-the-art materials allow a long time between overhaul periods.
There are a few other variants of the PW 100 worth mentioning. The PW150 motor is a high-performance development of the PW 100; It is very similar in overall construction and dimensions to the PW 100, with the exception that the low pressure compressor is a single stage axial followed by a single stage centrifugal. The pressure ratio is greater than 18: 1, and the engine produces power in the 5000 horsepower class. This makes it a suitable replacement for the Allison T56 or an alternative to the Rolls Royce AE1107C. There are also turbo shaft versions of the PW 100 where the gearbox and inlet are removed to reduce power and replaced with a shielded inlet with bell mouth and a carrier bearing. The engine output is at turbine speed. The motor could be an alternative to the CT7 (T700) turbo shaft in medium-sized helicopters, although it has not previously been used in this application. However, there is a ship variant of this turbo wave for modern military surface effect ships. These models are called the ST18M. The power is around 3,200 hp.