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Power unit – engine
Published in Andrew Livesey, Motorcycle Engineering, 2021
Pistons – These move up and down in the cylinder bores. This up-and-down movement is called reciprocating motion. The piston forms a gastight seal between the combustion chamber and the crankcase. The burning of the fuel and air mixture in the combustion chamber forces the piston down the cylinder to do useful work. The pistons are usually made from aluminum alloy for its lightweight and excellent heat-conducting ability. The top of the piston is called the crown; the lower part is called the skirt. The pistons must be perfectly round to give a good seal in the bore when the engine is at its normal running temperature. However, aluminum expands a lot when it is heated up. The pistons have slits in their skirts to allow for their expansion in diameter from cold to their normal operating temperature. When cold, pistons may be a slightly oval shape, so that when at running temperature they are a perfect fit in the cylinder bore.
Reciprocating Engines
Published in Neil Petchers, Combined Heating, Cooling & Power Handbook: Technologies & Applications, 2020
The piston slides up and down within the cylinder and serves to seal the cylinder, compress the air charge or air-fuel mixture charge, resist the pressure of the gases while they are burning and expanding, and transmit the combustion-generated gas pressure to the crank pin via the connecting rod. Pistons may be made of cast iron, aluminum, steel, or a combination. Pistons are cooled by circulating lubricating oil (or, in some cases, cooling water) through the cavities or spaces in the piston — the method varying with different designs. Oil spray is also a common cooling method.
Fraudulent Insurance Claims
Published in Colin R. Gagg, Forensic Engineering, 2020
Although not possible to determine beyond doubt a failure mode for the piston rings, the most probable scenario would suggest rings that were worn past the maximum end gap specification. This would allow combustion pressure to seep past the rings and down the piston skirt (‘blow-by’). As erosion progressed, unsupported piston rings would fail by bending under loading from compression and ignition of the fuel. There was no physical evidence to suggest an issue with either the construction or quality of the piston itself. Clearly, the vehicle owner was not a lay-person in matters of engine operation, service and performance. On the balance of probability, he had been attempting to have the costs of his major engine repair covered by his insurer. Although ‘trying-it-on’ is not criminal fraud in the true sense, the insurer repudiated the claim and also issued a warning. Knowing that erosion failure can initiate from either incorrect fuel injection, injection timing or a damaged or incorrectly located injector, the advice given to the vehicle owner was to inspect and, if necessary, correct the fuel injection equipment and timing, or in simple terms, improve the quality and regularity of his engine maintenance.
Thermal efficiency enhancement using a ceramic coating on the cylinder liner and the piston head of the IC engine
Published in International Journal of Ambient Energy, 2021
P. Anand, D. Rajesh, M. Shunmugasundaram, I. Saranraj
Most of the internal combustion (IC) engine pistons are made of aluminium alloy which has a thermal expansion coefficient 80% higher than the cylinder bore material made of cast iron (Kamo et al. 1997). This leads to some differences between running and the design clearances. Therefore, analysis of the piston thermal behaviour is extremely crucial in designing more efficient engines. The thermal analysis of piston is important from a different point of views. First, the highest temperature of any point on piston should not exceed 66% of the melting point temperature of the alloy (Uzun, Cevik, and Akcil 1999). This limiting temperature for the current engine piston alloy is about 370°C. This temperature level can be increased in ceramic coating diesel engines. Thermal barrier coatings consist of three layers. They are the metal substrate, metallic bond coat and ceramic topcoat. The metal substrate and metallic bond coat are metal layers and the topcoat is the ceramic layer (Murthy et al. 2010).
W-Ti-N thin film tribological behaviour for piston skirt properties improvement
Published in Surface Engineering, 2021
Khaled Chemaa, Salim Hassani, Mohammed Gaceb, Noureddine Madaoui, Abdelhamide Guebli
The internal combustion engines industry today requires engines with better characteristics such as improved tribological properties i.e. reduced friction and wear. Richardson [1] reported that energy losses by friction represent about 4–15% of the total energy used in a diesel engine. Piston assembly contributes to about 40–50% of that energy loss. Within that amount, piston skirt contribution is about 25–47%. Furthermore, an estimation done by the US department of energy suggests that in heavy duty vehicles, the total energy losses because of friction consume about 160 million barrels of diesel fuel per year [2]. Concerning wear, it occurs generally on piston skirt surface when the contact between piston skirt and liner becomes dry or boundary. This occurs when the piston reaches the Top Dead Centre (TDC).
Variable selection for kriging in computer experiments
Published in Journal of Quality Technology, 2020
Hengzhen Huang, Dennis K. J. Lin, Min-Qian Liu, Qiaozhen Zhang
Piston slap is an unwanted engine noise caused by piston secondary motion. That is, the departure of a piston from the nominal motion prescribed by the slider crank mechanism. A computer experiment was performed by varying six factors to minimize the piston slap noise. The factors are set clearance between the piston and the cylinder liner (x1), location of peak pressure (x2), skirt length (x3), skirt profile (x4), skirt ovality (x5), and pin offset (x6). Because each computer experimental run requires intensive computational resources (because the power cylinder system is modeled using the multibody dynamics code ADAMS/Flex including a finite-element model and it takes 24 h for each run), a uniform design was employed to plan a computer experiment with 12 runs. The experimental design and the response data are displayed in Table 1. Note that this uniform design is a space-filling design where different factors may have different number of levels. For more details on the theory of uniform designs and their applications in computer experiments, refer to Fang et al. (2000, 2006).