Aircraft Piston Engine Design and Performance Analysis Report, RMIT

This report provides a comprehensive overview of aircraft piston engine design and performance. It begins with an introduction to aircraft piston engines, also known as reciprocating engines, and their operational principles, highlighting the conversion of pressure into rotational motion. The report then delves into the different types of engines, emphasizing the evolution of engine design. Key components of the aircraft piston engine are described, including the cylinder, pistons, connecting rod, crankshaft, valves, and spark plugs, with accompanying figures for visual clarity. The operational principles of the aircraft piston engine are explained, focusing on the relationship between temperature, pressure, and volume of gases within the engine and the four-stroke cycle. The four-stroke cycle is elaborated upon, detailing intake, compression, power, and exhaust strokes. References to relevant literature support the information provided, offering additional resources for further study. The report is designed to fulfill the requirements of the AERO5960C course, applying scientific principles and techniques in aeronautical engineering.

AIRCRAFT PISTON ENGINE DESIGN AND PERFORMANCE
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Introduction
An aircraft piston engine also often known as reciprocating engine or otherwise a recip
refers to a combustion engine which makes use of a single or multiple reciprocating piston in the
conversion of pressure into rotational motion. The aircraft piston engine works using the same
principles as those of the engines which are common in most of the automobiles. Nonetheless,
modifications including dual ignition systems used in the enhancement of redundancy as well as
safety and the air cooling used in the reduction of weight have been included into the engines
that are designed for the purposes of aviation use (El-Sayed, 2017). In some cases, turbocharges
and in very rare cases superchargers may be added to the piston engines so as to enhance
performance. In most case, aircraft piston engines are fuels using AVGAS even though diesel
engines are gaining popularity mostly in light aircraft.
Figure 1: Aircraft piston engine (El-Sayed, 2017)
Types of Engines

There have been tremendous changes in the engine design over the last century since the
invention of the first powered flight. Most of the engines that are installed in the current
generation aircraft are majorly of horizontally opposed configuration. Nonetheless, there are
illustrations of all these engine kinds which are still flying in vintage, production as well
experimental aircraft. Among the engine types include in-line engines, v-type engines, rotary
engines, radial engines as well as horizontally opposed engines (Carlucci, Ficarella & Trullo,
2016).
Components/Design of an aircraft piston engine
Cylinder: This defines the enclosed space where combustion occurs. There are several
ways of arrangement of cylinders including single row arrangement, W-shape arrangement, a V-
shape arrangement as well as flat or horizontal arrangement
Pistons: These are often attached to every cylinder. Pistons slide up and down, a motion
that leads to rotary motion. The wall of a piston is often grooved to aid in holding the rings
which tightly fit against each wall thereby preventing the escape of gases from the combustion
chamber (Ostapski, Wierzchoń, Rudnicki & Dowkontt, 2017).

Figure 2: Components of engine and brief description: Extracted from (Sadraey, 2017)
Connecting Rod is used in the linkage of the crankcase which is held by crankshaft and
the piston. The connecting rod is used in the turning of a propeller when connected to a rotary
motion piston. The overall result is a rotary motion being experienced by the crankshaft.
Crankshaft is used in the transformation of the up and down movement of the piston into
a rotary motion. The crankshaft generates rotary motion when connected to the piston using a
connecting rod even as the piston experiences an up and down movement (Sadraey, 2017). The
piston is pulled downward an intake stroke in the piston engine lead to the creation of a vacuum
in the chamber of the cylinder. Such a back and forward motion generates rotary movement in
crankshaft even as the pressure levels in the cylinder are varied.

Figure 3: The crankcase (El-Sayed, 2017)
Valves: An aircraft piston engine has both exhaust and intake valves which are placed
close to the mixture inlet of fuel and air as well as the exhaust outlet which is at the highest point
of the cylinder in that order. The intake valve is used in the regulation of the fuel and air
mixtures entry while the exhaust valve is used in the elimination of burned and exhausts gases
from combustion chamber.
Spark Plugs are often located at the top of the cylinder just above the valves. They are
used in the ignition of compressed fuel and air mixture when compression and ignition strokes
take place in the engine. Ignition occurs just prior to a piston getting to its top position leading to
the rapid expansion of hot gases which in turn drive down the piston even as the crankshaft is
turned to result in rotary motion.

Figure 4: components of aircraft piston engine (El-Sayed, 2017)
Operation Principles of Aircraft Piston Engine
The basis principles of operation of the engine revolve around the relationship between
temperature, pressure and volume of gases. An internal combustion engine is used in the
conversion of heat energy into mechanical energy. In the engine, gasoline is turned to vapour and
the mixed with air, directed into a cylinder, compressed using a piston and finally ignited using
an electric spark. Conversion of the resulting heating energy into mechanical energy and
thereafter into work is achieved in the cylinder. The different components of engine needed in
the attainment of the conversion as well as the key terms used in operation of indicate engine is
as shown in the figure below

Figure 5: Components of engine required for conversion (Iwaniuk, Wiśniowski & Żółtak, 2016)
The functioning cycle of an internal combustion aircraft piston engine encompasses a
number of activities need for induction, compression, ignition as well as burning which result in
the fuel-air charge expansion in cylinder as well as elimination of the byproducts of the process
of combustion. Upon ignition of the compressed air, the resulting gases undergo rapid expansion
forcing the piston to move off the head of the cylinder. The downward motion of piston which
acts upon the crankshaft via the connecting rod in transformed into a rotary or circular motion
with the aid of the crankshaft (Iwaniuk, Wiśniowski & Żółtak, 2016).

Figure 6: Operation of reciprocating engine (Iwaniuk, Wiśniowski & Żółtak, 2016)
The burned gases are allowed to escape through the opening of the exhaust valve which
is located at the head of the cylinder and the piston is forced back up in cylinder by the propeller
forces and crankshaft money in which it prepares for the subsequent event in cycle. The intake
valve thereafter opens permitting entry of fresh charge of fuel-air mixture (Nickl, Kaiser, Seitz &
Hornung, 2016). The mechanical opening and closing of the valves occur at appropriates times
with the aid of valve-opening mechanism.

Figure 7: Four stroke operation of aircraft piston engine (Iwaniuk, Wiśniowski & Żółtak, 2016)
Four Stroke Cycle
Most of the aircraft engines are four stroke cycle type: intake, compression, power as
well as exhaust, a process that occur in the four strokes with the crankshaft making two rotation
to achieve the full cycle. This reduces to two power strokes for every revolution for the sake of a
cylinder having four engines. For the case of a cylinder with four engines, there would be three
power strokes for every revolution and four power strikes for each revolution for the case of an
eight cylinder engine (Zhang, Huang, Zhifeng & Ming, 2018). Therefore the higher the number

of cylinders, the greater the even distribution of the power pulses and hence the smoother the
running of the engine
Figure 8: Four stroke internal combustion engine (El-Sayed, 2017)

References
Carlucci, A. P., Ficarella, A., & Trullo, G. (2016). Performance optimization of a Two-Stroke
supercharged diesel engine for aircraft propulsion. Energy conversion and
management, 122, 279-289
El-Sayed, A. F. (2017). Aircraft propulsion and gas turbine engines. CRC press
Iwaniuk, A., Wiśniowski, W., & Żółtak, J. (2016). Multi-disciplinary optimisation approach for a
light turboprop aircraft-engine integration and improvement. Aircraft Engineering and
Aerospace Technology: An International Journal, 88(2), 348-355
Nickl, M., Kaiser, S., Seitz, A., & Hornung, M. (2016). Performance modeling of a composite
cycle engine with rotary engine. In German Aerospace Congress, Braunschweig,
Germany, Paper No. DLRK2016_420144
Ostapski, W., Wierzchoń, T., Rudnicki, J., & Dowkontt, S. (2017). Simulation and bench studies
of the constructively and technologically modernized high performance piston aircraft
engine. Stage I. Bulletin of the Polish Academy of Sciences Technical Sciences, 65(1), 93-
105
Sadraey, M. H. (2017). Aircraft Performance: An Engineering Approach. CRC Press
Zhang, K., Huang, X., Zhifeng, X. I. E., & Ming, Z. H. O. U. (2018). Design and optimization of
a novel electrically controlled high pressure fuel injection system for heavy fuel aircraft
piston engine. Chinese Journal of Aeronautics, 31(9), 1920-1928