Engine configuration and general structuring has proved to be a crucial factor in aviation related machinery. The paper takes vivid scrutiny of the opposed piston engine class type. The opposed piston engine has been in existence for a lengthy period of time and has established itself as a suitable selection, particularly for light aircrafts. In line with this, engines should be canopied under factors related to their proper breathing, less weight in regard to the reciprocating or sharing parts and the guarantee of optimal thermal efficiency. A solid configuration is also a considerable factor. All these factors should converge to ensure an engine devoid of vibrations and general smooth running. The opposed piston engine has its fair share of both pros and cons. However, it is first crucial to understand the basic operations and structuring of the opposed piston engine.
Opposed piston engines are characterized by the presence of pistons oppositely arranged but work in unison in a common cylinder. Cylinders can also be presented or structured in pairs and whereby each of the pair shares a mutual combustion chamber. Generally, the combustion chamber is structured in middle of the contrasting pistons immediate to the top center. It should also be noted that the opposed piston engines have the characteristic being devoid of classical poppet valves. As such there the rummaging process is controlled by the ported valves of the piston. The scavenging process is basically a way of forcing fumes from the cylinder in the engine and ensuring entry of fresh charge (Pulkrabek, 1997). A major advantage in the structuring of the cylinders in the opposed piston engine is that they do not have do not have a cylinder head. The pro to this is that thermodynamic efficacy is improved as there are no extreme heat losses incurred through the cylinder heads. Normally, the need to cool the mechanical parts of the engine normally leads to the heat loss via the cylinder heads.
Furthermore, it is good to note that operation of the engine involves each piston pair moving back and forth in unison and concurrently reach the TDC. The rationale behind this is that there are no unbalancing forces in the engine. Therefore, the opposed piston engine does not need a balance shift or other weights on the crankshaft, with the aim of balancing the reciprocating parts’ weight. In the opposed piston engine there are crankpins, with each controlling its own piston or cylinder. This is in contrast to the 180 degree engines which are succinctly known for their sharing of crankpins among the pistons. However, in this respect the opposed piston engine can be noisier as compared to other classes of engines. This type of engine is also written off as having a need for fuel that is of high- octane.
The combustion chamber in this specific class of engine is trailed by a major advantage. The advantage is that the heat that is produced in the combustion chamber is proportional to its volume. The same applies to the loss of heat, which is also proportional to the chamber’s surface area. Due to this, the thermal effectiveness is better in this engine class as compared to others where the surface area- volume aspect is relatively higher (Balmer, 2011). Another merit that should not be missed is the absence of the poppet valves. The absence of the poppet valves generally directs that the engine has lesser parts. The aspect of having fewer parts is an advantage since servicing is relatively easy and the mechanical-effectiveness is paramount. In addition, absence of the poppet valves ensures general reduction in the cost of the engine.
- Balmer, R. T. (2011). Modern engineering thermodynamics. Amsterdam ; Boston : Academic Press.
- Pirault, J.-P., & Flint, M. (2010). Opposed piston engines : evolution, use, and future applications. Warrendale, Pa.: SAE International.
- Pulkrabek, W. W. (1997). Engineering fundamentals of the internal combustion engine. Upper Saddle River, N.J: Prentice Hall.