Search Results

Statistical studies have shown that many electric vehicles existing in the market today can cater to most typical daily driving trips. However where such vehicles are sometimes found wanting are the occasional trips beyond the available electric vehicle range, or unexpected trips when the battery is already in a discharged state. These circumstances necessitate either maintaining a second internal combustion engine powered car or use of public transport. An alternative to this is the use of a range extended electric vehicle (REEV). A REEV can operate in two modes, either as an electric vehicle on short journeys or as a series hybrid with the aid of a small auxiliary power unit (APU) when the battery energy is low over longer distances. The addition of an APU eliminates the range anxiety experienced by electric vehicle owners by extending the range possible in a single charge.

The coupled EHL analysis of the small-end and the piston-pin boss are carried out using a technique of successive iteration. The pin is free to rotate in both the small-end and the pin-boss. The total frictional torque is used to calculate the angular velocity of the pin. After obtaining a converged solution of pin rotation, a wear simulation is performed by carrying out an additional set of EHL analysis. Results show that the pin rotational velocity is insignificant which suggests that the EHL performance of the small-end is satisfactory. Since it is the friction between small-end bush and the pin that drives the pin to move, less pin rotation is an indication of good lubrication in the small-end interface. Hence, the technique outlined is a useful tool for establishing that the small-end/pin-boss lubrication conditions are sufficient, or when more harsh conditions are encountered, helping to optimize the design.

This paper attempts to address the limitations of quasi-static elastohydrodynamic (EHD) bearing lubrication analysis where the structural inertia of the distributed rod mass is neglected. A procedure is outlined where the big-end bearing distortions due to the structural inertia are pre-calculated using the finite element (FE) method and then included in a subsequent EHD analysis via a dynamic deformation file. The effect on results in terms of oil film thickness and pressure are investigated for a 2.0L gasoline engine. A validation is presented showing good comparison of the EHD bore shape with an instrumented engine test and also a full dynamic FE model. The conclusion is made that distributed inertia effects become significant above 3000rpm and that the outlined method is valid for including such effects.

An elasto-hydrodynamic lubrication model is used to study the effects of multi-order journal lobing on the performance of a big-end bearing in a turbo-charged diesel engine. The journal has 5 lobes superimposed with 50 lobes of chatter. Results show that any form of lobing has adverse effects on bearing performance, reducing film thickness and increasing oil film pressure. The effects of low and high order lobing are additive, but the bearing system is more sensitive to high order lobing, i.e. chatter. To improve the reliability of big-end bearing systems lobing on the journal should be minimised especially chatter.

The effects of crank-pin surface circumferential waviness, also known as journal lobing or chatter in engineering terms, on bearing performance have been investigated by carrying out an elastohydrodynamic lubrication analysis. The big-end bearing in a 2.0 liter diesel engine has been used for the study. The operating condition is that of maximum torque with engine running at 1800rpm. The crank pin has been assumed to have 2, 3, 5, 9, 15, 30 and 50 lobes. Sufficiently fine meshes have been used to model the lobe profiles. Solutions cover a large range of lobe amplitude and lobe orientation angles. The results show that journal lobing has adverse effects on the bearing's lubrication performance because it severely reduces the oil film thickness and significantly increase the oil film pressure. The combination of large lobe numbers and big lobe amplitudes is particularly detrimental.

With the continuous demand to squeeze more performance from critical engine components such as crankshaft bearings, design analysis and calculations methods are also required to become more comprehensive. With the advent of Elasto Hydrodynamic Lubrication (EHL) methods, for example, designers could investigate theoretically the effects of housing geometry or stiffness on bearing performance; which was previously not possible with rigid bearing (mobility method) calculations. Traditional methods for EHL analyses of crankshaft bearings normally incorporate the elasticity of the connecting rod or housing but assume that the crankpin is rigid. This paper demonstrates the effects of including the flexibility of the crankshaft journal (up to the adjacent main bearing) for three examples of connecting rod bearings. The examples cover a typical Formula 1 (F1) racing engine at 16000rpm, an automotive gasoline engine at 5500rpm and a 120mm journal diameter diesel engine at 2000rpm.

This paper used an elasto-hydrodynamic model of a connecting rod large-end bearing to investigate the influence that the shape of the bearing bore had on the performance of the bearing system. Comparisons were made between cylindrical shapes, eccentrically bored shapes and complex shapes, i.e. the ‘Conecc’ profile. The effect of ‘cap-shift’ was also investigated together with effectiveness of joint face relief in overcoming some of its adverse effects.

This paper reports on attempts to correlate measured oil flow rates for a big-end connecting rod bearing with those predicted by theory. The oil flow measurements were made on a 2.0 litre naturally aspirated gasoline engine. The theoretical predictions were made using an elastohydrodynamic model of the bearing system. This model used a finite difference solution technique, which incorporated a lubricant mass conservation algorithm. The measured bearing bore shape was used to give precise clearance data. Measured bearing temperature was used to calculate the effective operating viscosity. Locally refined mesh densities were used in the region of the relief bearing to improve accuracy. The correlation between experimental measurements and theoretical predictions has proved excellent, except at very high speed when theory tends to over-estimate the measured oil flow.