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Power unit – engine
Published in Andrew Livesey, Motorcycle Engineering, 2021
Cylinder head (head) – The head sits on top of the cylinder block. The head contains the combustion chambers and valves. Between the head and the block is a cylinder head gasket. The cylinder head gasket allows for the irregularities between the block and the head and keeps a gastight seal for the combustion chamber. The engine cylinder head locates the spark plugs.
Power unit – engine
Published in Andrew Livesey, Practical Motorsport Engineering, 2019
Cylinder head (head) – the head sits on top of the cylinder block. The head contains the combustion chambers and valves. Between the head and the block is a cylinder head gasket. The cylinder head gasket allows for the irregularities between the block and the head and keeps a gas-tight seal for the combustion chamber. A SI engine cylinder head locates the spark plugs; a CI engine cylinder head locates the injectors.
The reciprocating piston petrol engine
Published in M.J. Nunney, Light and Heavy Vehicle Technology, 2007
The sealing gasket is generally known as the cylinder head gasket or simply ‘head gasket’. In liquid-cooled engines the function of the cylinder head gasket is to seal the combustion chambers and coolant and oil passages at the joint faces of the cylinder block and head. The gasket is therefore specially shaped to conform to these openings, and is also provided with numerous holes through which pass either the studs or the set bolts for attaching the cylinder head to the block (Figure 1.16).
Experimental studies to evaluate the combustion, performance and emission characteristics of acetylene fuelled CI engine
Published in International Journal of Ambient Energy, 2022
The hydrocarbon (HC) emissions are formed when the unburnt fuel particles are trapped in the surrounding of the wall and engine cylinder. Unburnt HC emissions are primarily formed due to incomplete oxidation of petroleum fuel. The variation HC emission with varying BMEP is shown in Figure 8. The HC emissions for baseline diesel varied from 19.4 kg/kw-hr to 5.5 kg/kw-hr from nil loads to maximum loads; on the other hand, with the introduction of acetylene, HC emission gets reduced at all loading conditions except peak loads. The significant drop in HC emission during acetylene dual-fuel combustion is attributed to the rise in the flame velocity of the mixture, which further improves the combustion characteristics. The value of HC for dual fuel engine at full load for 2, 4, 6 and 8 LPM of gaseous flow rates was 5.1, 3.9, 4.2 and 4.5 kg/kw-hr, respectively. It was observed that at peak load, HC emissions were marginally escalated due to increase in a number of HC molecule at a higher flow rate; it means when the amount of acetylene is increased, the certain quantity of air is replaced consequently and further leads to incomplete combustion. Similar conclusions have been observed by many scientists (Lakshmanan and Nagarajan 2010a, 2010b; Behera, Murugan, and Nagarajan 2014; Srivastava et al. 2017). The lowest HC emission was 3.9 kg/kw-hr at 4 LPM acetylene induction, which is 27% lower than neat diesel. The reason might be proper burning of acetylene fuel, causing complete oxidation of the hydrocarbons during 4 LPM of inducted fuel. When gas is inducted at a higher flow rate, the air–fuel mixture tends to be heterogeneous, which may lead to an increased rate of HC emissions. The unburned hydrocarbons may be trapped in such areas like gaps close to piston top surface, the cylinder head gasket and piston ring, which may damage and deteriorate the life of the engine during long run.
Cylinder Head Bolt Tightening Strategies in Case of Multi-Cylinder Engines and Its Effect on Gasket Sealing Performance, Bore Deformation and Piston Ring Conformability
Published in Australian Journal of Mechanical Engineering, 2020
Abhijeet V. Marathe, G. Venkatachalam, Neelkanth V. Marathe
The cylinder head gasket is the most critical sealing element in the internal combustion engine. The area of the gasket, around the cylinder, must be robust enough to withstand the pressures that are exerted on the pistons while ensuring that there is no leakage of coolants or combustion gases. It must be able to accomplish this at all engine temperatures and pressures without malfunction, as the failure of the engine gasket usually results in a breakdown of the entire engine. Having adequate pressure distribution in the gasket at these critical sealing areas is of utmost importance. It also affects engine piston ring conformability in the cylinder bore, engine blow-by and lubricant oil consumption. During assembly of the cylinder head gasket joint, there is a loss of bolt preload and consequently, a reduction of compression force on the gasket when the bolts are tightened sequentially. This leads to the reduction of contact pressure in the gasket, which causes leakages. To obtain the required gasket sealing pressure at the critical sealing areas, it is necessary to combat this problem of bolt preload reduction. It is observed that the ‘bolt preloads applied for tightening the bolts’ and ‘the numbers of passes in which these preloads are applied’ are critical parameters affecting the bolt preload loss during tightening. Also, the sequence or pattern of tightening the bolts joining the mating surfaces plays a significant role in deciding the final bolt preload retention after complete tightening. In this regard, considerable number of investigations is reported in the literature in case of gasket pipe flange joints mostly found in pressure vessel applications. As per the same analogy, the methods of reducing bolt preload scatter in case of engine cylinder head gasket joints can be investigated. Cylinder head gasket joint is a slab in nature while Pipe flange joint of the pressure vessel is circular. The analogy is not directly applicable to the cylinder head gasket joint but can be explored. Experimental procedures are quite expensive and laborious for analysing the effect of various tightening strategies. Hence there is a need to find a numerical and analytical process through which the impact of such approaches can be examined. A primary tool used in this regard is Finite Element Analysis (FEA). But one must overcome the lack of an accurate and well-correlated methodology for modelling cylinder head gasket joint, which can capture the effects of the bolt tightening sequences while providing the gasket performance parameters like contact pressure distribution and gasket closure.