INTERNAL COMBUSTION ENGINES
EFFECT OF TEMPERATURE ON CYLINDER LINER
FRICTIONAL LOSS
Table of Content
INTRODUCTION ..................................................................................................................... 3
Decrease thermal losses in internal combustion engine. ....................................................... 4
Effect the cylinder wall to gas emission. ............................................................................... 5
Cylinder liner temperature has a significant role in thermodynamic modelling ....................... 5
Effective sealing function of compression ring ..................................................................... 5
Effect increases of lubricant temperature on viscous friction ................................................ 6
DISCUSSIONS .......................................................................................................................... 7
Friction and power loss .......................................................................................................... 7
CONCLUSION ........................................................................................................................ 11
REFERENCES ........................................................................................................................ 12
INTRODUCTION
A cylinder liner, sometimes known as a sleeve, is a cylindrical component of a spark ignition
(SI) engine that is put into the engine block. The cylinder liner is the inner surface of the
cylinder that the piston goes up and down within. The cylinder liner is normally built of a
strong, heat-resistant material such as cast iron or aluminium, and it is designed to withstand
the high temperatures and pressures created during the combustion process. It also aids in the
maintenance of proper clearances between the piston and the cylinder wall, as well as the
reduction of wear on engine components. The cylinder lining might be dry or wet type.
Figure 1: Cylinder linear and piston in Diesel engine
According to (Rahmani, Rahnejat, Fitzsimons, & Dowson, 2017) when trying to improve the
energy efficiency of internal combustion engines, there are three main areas to focus on. The
first is reducing thermal losses, which make up about 50-60% of all losses. The second is
minimizing frictional and pumping losses in moving parts, such as the piston-cylinder system
and valves, which account for 15-20% of losses. The third is reducing emissions, which is
important for both environmental and regulatory reasons. Improving the management of energy
conversion and reducing sources of energy loss can help increase fuel efficiency, which is a
major goal in modern engine development.
Decrease thermal losses in internal combustion engine.
To decrease thermal losses in internal combustion engines, it is ideal to keep the temperature
of the cylinder walls close to that of the gases inside the cylinder. The temperature of the
lubricant in contact with the top compression ring is largely determined by the cylinder wall
temperature, rather than small increases caused by the lubricant's movement. This is supported
by a recent study using an analytical control volume and thermal mixing model. (Morris,
Rahmani, Rahnejat, King, & Fitzsimons, 2013). Limitations in material and cost affect the
maximum temperature that can be reached in cylinder liners. Cast iron and aluminum liners
can handle temperatures of 200-450 Celsius, while materials with lower thermal conductivity
can handle higher temperatures, but their high cost limits their usage, except for in specialized
race engines. Additionally, heat transfer from the hot cylinder wall to the incoming air-fuel
mixture prevents the use of certain materials for spark ignition engines. It's also hard to achieve
the desired temperature under cold start-up conditions or with intermittent stop-start and other
transient driving conditions which are becoming increasingly common.
Effect the cylinder wall to gas emission.
(Rahmani et al., 2017)The temperature of the cylinder walls plays a significant role in
determining the HC and NOx emissions from internal combustion engines. Studies have shown
that HC emissions decrease with higher liner temperatures, while the opposite is generally true
for NOx emissions. Therefore, it is important to find an optimal liner temperature that balances
these emissions. Additionally, technologies such as EGR can reduce NOx formation,
particularly at high loads, but it can also negatively impact the tribology of the engine and
increase other types of emissions.
Cylinder liner temperature has a significant role in thermodynamic modelling
The temperature of the cylinder liners is crucial for controlling the cycle-to-cycle temperature
of the exhaust gas in thermodynamic modelling. To improve these models, it is important to
determine the cylinder wall temperature based on engine load and coolant temperature. Optimal
control of internal combustion engines in both transient and steady-state conditions can be
achieved through an exergy-based analysis, which considers the main sources of energy loss,
including combustion inefficiency, heat loss, and friction losses. This approach has the
potential to save 6-7% in fuel consumption compared to more traditional control
methods.(Razmara, Bidarvatan, Shahbakhti, & Robinett, 2016)
Effective sealing function of compression ring
The compression ring is an important component in internal combustion (IC) engines. It
provides a sealing function to maintain engine performance and prevent the ingression of
combustion by-products into the bottom end of the engine, which can cause damage and reduce
performance. However, effective sealing also increases friction, which can decrease engine
efficiency and performance. Therefore, improving the tribological performance of the
compression ring is important, but poses a significant challenge because many factors affect
its performance, including temperature, pressure, surface roughness, and lubricant properties.
In order to improve the tribological performance of the compression ring, all these factors must
be considered simultaneously and optimized to achieve the desired balance between effective
sealing and low friction.(Rahmani et al., 2017).
Effect increases of lubricant temperature on viscous friction
(Rahmani et al., 2017)The temperature of the lubricant has an impact on the amount of friction
in the engine. An increase in lubricant temperature, which is largely determined by the
temperature of the cylinder liner, results in a decrease in viscous friction. However, at low
sliding velocities during piston reversals, boundary friction becomes the main contributor to
friction and the dependence on liner surface temperature is reduced. The power losses that
result from asperity interactions can become quite significant at high temperatures. The
fluctuations in oil temperature also affect the cooling fluid temperature because of its quicker
dynamics. Hence, there should be a specific "optimal" cylinder wall temperature for a particular
engine to minimize the overall cyclic fluctuations in frictional losses, which are caused by both
viscous friction and boundary friction. The cylinder wall temperature and its impact on engine
friction are closely related to the lubricating oil grade and its additives, which can impact
emissions from the engine.
DISCUSSIONS
A set of results were obtained by simulating the operating liner temperatures at 40, 80 and 120
Celsius. These temperature levels were selected to reflect the state of the lubricant during fast
movement within the contact area and align from (Morris, Rahmani, Rahnejat, King, &
Fitzsimons, 2012)
Friction and power loss
Figure 2: Variations of (a) total friction for an engine cycle and (b) boundary friction in
transition from compression to power strokes at three different working temperatures and at
1500 rpm.
Liner working
Crank angle for Crank angle for Total
start of boundary end of boundary angle(º)
temperature(ºC)
crank Peak total friction
(N)
friction (º)
friction (º)
120
-22
79
101
125.31
80
-10
46
56
93.15
40
1
16
15
41.02
Table 1: Crank angles with boundary friction at the TDC (from compression to expansion
strokes) and peak friction values.
(Rahmani et al., 2017) The figure 2 illustrates the change in the combined friction (viscous and
boundary) throughout the four-stroke engine cycle at a speed of 1500 rpm and for all three
studied liner temperatures. The total friction is seen to be highest during the power stroke at all
temperatures. The total friction reaches its highest point during the power stroke between the
moments of piston reversal and mid-span, with peak values near the Detonation Point (DP).
This is due to the high pressures applied in this region. The location of maximum friction
depends on the engine speed and liner temperature, which affects the thickness of the lubricant
film and its viscosity. This relationship is driven by both viscous shear (Poiseuille and Couette
contributions) and boundary friction, as shown in Fig. 2(b). The data in Table 1 shows the
extent of boundary friction and the overall friction for the engine running at 1500 rpm with
different liner temperatures. The results from Fig. 2 indicate that after reaching the maximum
combustion pressure, friction decreases significantly for higher liner temperatures. In fact, after
30 degrees of crank angle, the effect of viscous shear becomes the dominant factor. At around
mid-stroke in the power stroke, the lowest friction is found for the liner temperature of 120°C.
This is because in this area, viscous friction is the dominant factor and higher temperature leads
to lower viscous shear stress and hence lower viscous friction.
Figure 3:Variations of predicted total, viscous and boundary friction contributions with
temperature from (Rahmani et al., 2017) and those from (Ma, Henein, & Bryzik, 2006)
(Rahmani et al., 2017) Fig. 3 compares the average friction generated during the engine cycle
for three different liner temperatures and two engine speeds. The results show that at lower
temperatures (40°C), there is little contribution from boundary friction due to higher lubricant
viscosity and hence, higher load carrying capacity. On the other hand, at higher temperatures
(120°C), boundary friction is higher. The boundary friction is also found to have a linear
relation with temperature. The viscous friction is higher for the engine running at the higher
speed (2500 rpm) due to the higher shear rate, but the difference in viscous shear decreases as
the liner temperature increases. This highlights the significance of lubricant viscosity. The total
friction is a combination of these two friction-generating mechanisms (viscous shear and
boundary interactions). Fig. 3 identifies an optimum total friction condition for each engine
speed. This trend is consistent with the predictions made by previous study in a different engine
and operating conditions. The higher prevalence of boundary friction at lower temperatures
compared to the results in previous study may be due to the overestimation of contact load in
the(Rahmani et al., 2017).
Figure 3 .Cyclic average total power loss at different liner operating temperatures and at two
engine speeds.
(Rahmani et al., 2017) Figure 4 compares the average power loss at two engine speeds and
three liner temperatures. The minimum power loss occurs at 80°C for both engine speeds.
Despite high peak power loss at higher temperatures, overall average power loss is greater at
40°C, indicating the dominance of viscous friction. At 80°C and low engine speed, power loss
is 28.6% and 16.3% less than those at 40°C (higher HC) and 120°C (higher NOx) respectively,
leading to increased fuel consumption and emissions. The cold and hot parts of NEDC test are
at low vehicle speed and correspond to the conditions in the study.
CONCLUSION
In conclusion, temperature plays a significant role in frictional loss in cylinder liners. High
temperatures reduce the viscosity of lubricating oil and increase friction, while low
temperatures increase viscosity and reduce friction. Engine efficiency and performance can be
impacted by increased frictional loss, leading to decreased fuel economy, increased emissions,
and reduced engine life. To maintain efficient and reliable engine operation, engine designers
must consider the relationship between temperature and frictional loss in cylinder liners and
implement preventative measures, including using appropriate materials, cooling systems,
lubrication systems, and regular maintenance.
REFERENCES
Ma, Z., Henein, N. A., & Bryzik, W. (2006). A Model for Wear and Friction in Cylinder Liners and
Piston Rings. Tribology Transactions, 49(3), 315-327. doi:10.1080/05698190600678630
Retrieved from https://www.tandfonline.com/doi/abs/10.1080/05698190600678630
Morris, N., Rahmani, R., Rahnejat, H., King, P. D., & Fitzsimons, B. (2012). The influence of piston
ring geometry and topography on friction. Proceedings of the Institution of Mechanical
Engineers, Part J: Journal of Engineering Tribology, 227(2), 141-153.
doi:10.1177/1350650112463534 Retrieved from https://doi.org/10.1177/1350650112463534
Morris, N., Rahmani, R., Rahnejat, H., King, P. D., & Fitzsimons, B. (2013). Tribology of piston
compression ring conjunction under transient thermal mixed regime of lubrication. Tribology
International, 59, 248-258. doi:https://doi.org/10.1016/j.triboint.2012.09.002 Retrieved from
https://www.sciencedirect.com/science/article/pii/S0301679X12002988
Rahmani, R., Rahnejat, H., Fitzsimons, B., & Dowson, D. (2017). The effect of cylinder liner operating
temperature on frictional loss and engine emissions in piston ring conjunction. Applied Energy,
191,
568-581.
doi:https://doi.org/10.1016/j.apenergy.2017.01.098
Retrieved
from
https://www.sciencedirect.com/science/article/pii/S0306261917301022
Razmara, M., Bidarvatan, M., Shahbakhti, M., & Robinett, R. D. (2016). Optimal exergy-based control
of
internal
combustion
engines.
Applied
Energy,
183,
1389-1403.
doi:https://doi.org/10.1016/j.apenergy.2016.09.058
Retrieved
from
https://www.sciencedirect.com/science/article/pii/S0306261916313605