Experimental and Theoretical Study of Instantaneous Engine Valve Train Friction

2003 ◽  
Vol 125 (3) ◽  
pp. 628-637 ◽  
Author(s):  
Riaz A. Mufti ◽  
Martin Priest
Keyword(s):  
Engine Speed ◽  
Gasoline Engine ◽  
Elastohydrodynamic Lubrication ◽  
Friction Model ◽  
Friction Torque ◽  
Operating Conditions ◽  
Valve Train ◽  
Friction Modifier ◽  
Timing Belt ◽  
Economy Benefit

A new method has been developed to directly measure valve train friction as a function of crank angle using specially designed timing belt pulley torque transducers fitted to the inlet and exhaust camshafts of a single-cylinder gasoline engine. Simultaneous and instantaneous friction torque of both the inlet and exhaust camshafts at any engine speed can be measured, with no apparent detrimental effect of timing belt loading on the output reading. Experiments are reported for valve train friction at a range of motored engine operating conditions with different lubricant formulations, with and without a friction modifier. These are compared with the predictions of an existing valve train friction model based upon elastohydrodynamic lubrication theory. Measured friction decreased with increasing engine speed but increased with increasing oil temperature and the fuel economy benefit of friction modifiers was observed. The model yielded similar magnitudes of friction at medium engine speeds and above but predicted much lower friction with high oil temperatures at low speed. Comparison of theory and experiments also suggests that some oil may leak from hydraulic lash adjusters during the cam event with a consequent reduction in geometric torque.

scholarly journals Study of the engine configuration effect on the maximum achievable load in CAI using water injection

2020 ◽  
pp. 146808742096085
Author(s):  
J Valero-Marco ◽  
B Lehrheuer ◽  
JJ López ◽  
S Pischinger
Keyword(s):  
Compression Ratio ◽  
Engine Speed ◽  
Gasoline Engine ◽  
Fuel Injection ◽  
Water Injection ◽  
Maximum Load ◽  
Operating Conditions ◽  
Work Related ◽  
Operating Strategies ◽  
Injection Strategies

The approach of this research is to enlarge the knowledge about the methodologies to increase the maximum achievable load degree in the context of gasoline CAI engines. This work is the continuation of a previous work related to the study of the water injection effect on combustion, where this strategy was approached. The operating strategies to introduce the water and the interconnected settings were deeply analyzed in order to optimize combustion and to evaluate its potential to increase the maximum load degree when operating in CAI. During these initial tests, the engine was configured to enhance the mixture autoignition. The compression ratio was high compared to a standard gasoline engine, and suitable fuel injection strategies were selected based on previous studies from the authors to maximize the reactivity of the mixture, and get a stable CAI operation. Once water injection proved to provide encouraging results, the next step dealt in this work, was to go deeper and explore its effects when the engine configuration is more similar to a conventional gasoline engine, trying to get CAI combustion closer to production engines. This means, mainly, lower compression ratios and different fuel injection strategies, which hinders CAI operation. Finally, since all the previous works were performed at constant engine speed, the engine speed was also modified in order to see the applicability of the defined strategies to operate under CAI conditions at other operating conditions. The results obtained show that all these modifications are compatible with CAI operation: the required compression ratio can be reduced, in some cases the injection strategies can be simplified, and the increase of the engine speed leads to better conditions for CAI combustion. Thanks to the analysis of all this data, the different key parameters to manage this combustion mode are identified and shown in the paper.

A Boundary Lubrication Friction Model Sensitive to Detailed Engine Oil Formulation in an Automotive Cam/Follower Interface

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Rupesh Roshan ◽  
Martin Priest ◽  
Anne Neville ◽  
Ardian Morina ◽  
Xin Xia ◽  
...  
Keyword(s):  
Boundary Lubrication ◽  
Fuel Efficiency ◽  
Lubricant Additive ◽  
Friction Model ◽  
Operating Conditions ◽  
Valve Train ◽  
Engine Oil ◽  
Contact Friction ◽  
Boundary Lubrication Friction ◽  
Base Oil

Theoretical studies have shown that in severe operating conditions, valve train friction losses are significant and have an adverse effect on fuel efficiency. However, recent studies have shown that existing valve train friction models do not reliably predict friction in boundary and mixed lubrication conditions and are not sensitive to lubricant chemistry. In these conditions, the friction losses depend on the tribological performance of tribofilms formed as a result of surface–lubricant additive interactions. In this study, key tribological parameters were extracted from a direct acting tappet type Ford Zetec SE (Sigma) valve train, and controlled experiments were performed in a block-on-ring tribometer under conditions representative of boundary lubrication in a cam and follower contact. Friction was recorded for the tribofilms formed by molybdenum dithiocarbamate (MoDTC), zinc dialkyldithiophosphate (ZDDP), detergent (calcium sulfonate), and dispersant (polyisobutylene succinimide) additives in an ester-containing synthetic polyalphaolefin (PAO) base oil on AISI E52100 steel components. A multiple linear regression technique was used to obtain a friction model in boundary lubrication from the friction data taken from the block-on-ring tribometer tests. The model was developed empirically as a function of the ZDDP, MoDTC, detergent, and dispersant concentration in the oil and the temperature and sliding speed. The resulting friction model is sensitive to lubricant chemistry in boundary lubrication. The tribofilm friction model showed sensitivity to the ZDDP–MoDTC, MoDTC–dispersant, MoDTC–speed, ZDDP–temperature, detergent–temperature, and detergent–speed interactions. Friction decreases with an increase in the temperature for all ZDDP/MoDTC ratios, and oils containing detergent and dispersant showed high friction due to antagonistic interactions between MoDTC–detergent and MoDTC–dispersant additive combinations.

Experimental Evaluation of Piston Assembly Friction Under Motored and Fired Conditions in a Gasoline Engine

2004 ◽  
Author(s):  
Riaz A. Mufti ◽  
Martin Priest
Keyword(s):  
Gasoline Engine ◽  
Operating Conditions ◽  
Cylinder Pressure ◽  
Connecting Rod ◽  
Friction Modifier ◽  
Indicated Mean Effective Pressure ◽  
Axial Forces ◽  
The Difference ◽  
Digital Channels ◽  
Piston Assembly

Piston assembly friction measurement has been carried out on a single cylinder gasoline engine using the IMEP (indicated mean effective pressure) method at realistic engine speeds and loads without any major engine modifications. Instantaneous and mean piston assembly friction were measured under motored and fired conditions at different lubricant temperatures. The forces acting on the piston assembly were carefully determinated by measuring the cylinder pressure, crankshaft angular velocity and strain in the connecting rod. The difference between the resulting gas pressure, inertia and connecting rod axial forces acting on the piston yields the piston assembly friction. To achieve this with confidence, an advanced instrumentation, telemetry and data acquisition system was designed and developed, giving special attention to the synchronisation and simultaneous sampling of analogue and digital channels. Experiments are reported for piston assembly friction at a range of engine operating conditions with different lubricant formulations, with and without a friction modifier.

Experimental Evaluation of Piston-Assembly Friction Under Motored and Fired Conditions in a Gasoline Engine

2004 ◽  
Vol 127 (4) ◽  
pp. 826-836 ◽  
Author(s):  
Riaz A Mufti ◽  
Martin Priest
Keyword(s):  
Gasoline Engine ◽  
Operating Conditions ◽  
Cylinder Pressure ◽  
Connecting Rod ◽  
Friction Modifier ◽  
Indicated Mean Effective Pressure ◽  
Axial Forces ◽  
The Difference ◽  
Digital Channels ◽  
Piston Assembly

Piston-assembly friction measurement has been carried out on a single-cylinder gasoline engine using the IMEP (indicated mean effective pressure) method at realistic engine speeds and loads without any major engine modifications. Instantaneous and mean piston-assembly friction were measured under motored and fired conditions at different lubricant temperatures. The forces acting on the piston assembly were carefully determined by measuring the cylinder pressure, crankshaft angular velocity, and strain in the connecting rod. The difference between the resulting gas pressure, inertia, and connecting rod axial forces acting on the piston yields the piston-assembly friction. To achieve this with confidence, an advanced instrumentation, telemetry, and data acquisition system was designed and developed, giving special attention to the synchronization and simultaneous sampling of analog and digital channels. Experiments are reported for piston-assembly friction at a range of engine operating conditions with different lubricant formulations, with and without a friction modifier.

Innovative technique of measuring follower rotation in real production engine using Gradiometer sensor and the effect of friction modifier

2015 ◽  
Vol 67 (4) ◽  
pp. 285-291 ◽  
Author(s):  
Riaz Ahmad Mufti ◽  
Rehan Zahid ◽  
Farrukh Qureshi ◽  
Jawad Aslam
Keyword(s):  
Rotation Speed ◽  
Research Work ◽  
Operating Conditions ◽  
Valve Train ◽  
Friction Modifiers ◽  
Friction Modifier ◽  
Content Type ◽  
Novel Technique ◽  
Novel Method ◽  
Direct Acting

Purpose – The purpose of this paper is to understand the effect of engine operating conditions and lubricant friction modifier on direct acting tappet rotation. In this research work, novel method of measuring engine tappet rotation speed has been developed. The technique is so novel. It allows the measurement on real production engine with no modification to the engine tappet bore. Also, In this paper, the effect of engine operating conditions and the effectiveness of friction modifier on tappet rotation is reported. Design/methodology/approach – For the very first time, for the purpose of measuring follower rotation in a real production engine, a 4 × 6 mm2 electronic chip called Gradiometer is mounted outside the tappet housing, allowing the monitoring of tappet rotation speed without the need to machine a hole in the tappet bore. This novel technique is adopted on Mercedes Benz OM464 engine to study the effect of engine conditions and lubricant chemistry on tappet performance. Findings – The main outcome of this research work is the development of novel method of measuring tappet rotation. Also, during the experiments, it was revealed that although friction modifiers help in reducing friction at the cam/tappet interface, they can also adversely affect the tappet rotation speed. Originality/value – The novel technique developed in the research work is one of the most cost effective and simple to use. Researches can adopt the technique to study the tribological performance of direct acting tappet on real production engine. Researches acknowledge the effectiveness of friction modifiers in valve train but its effect on rotation which plays a key role in the component durability has not been the focus of most of the researches mainly due to lack of effective techniques.

Engine friction: The influence of lubricant rheology

1997 ◽  
Vol 211 (3) ◽  
pp. 235-246 ◽  
Author(s):  
R. I. Taylor
Keyword(s):  
Shear Rate ◽  
Gasoline Engine ◽  
Hydrodynamic Lubrication ◽  
Valve Train ◽  
Boundary Friction ◽  
Friction Modifier ◽  
Cold Starting ◽  
Engine Friction ◽  
Viscosity Variation ◽  
Lubricant Viscosity

The sensitivity of engine friction to lubricant viscometry has been determined for a modern fuelefficient engine, the Mercedes Benz M111 2.0 litre gasoline engine, under both cold starting and fully warmed-up conditions. The study has taken into account realistic lubricant viscometric parameters such as the lubricant viscosity variation with shear rate and temperature. Results are reported for the variation of engine friction with different monograde and multigrade lubricants, including the distribution of friction losses between valve train, piston assembly and bearings with the different lubricant types. The work also enabled estimates to be made of the proportion of hydrodynamic and boundary friction in the engine, since the vast majority of boundary lubrication occurs in the valve train. Knowledge of the ratio of boundary to hydrodynamic lubrication was found to be important since the two key lubricant parameters that can be varied are (a) viscosity and (b) the introduction of a friction modifier additive. The viscosity of the lubricant will affect the hydrodynamically lubricated parts of the engine whereas the presence of a friction modifier will reduce boundary friction in the engine. Brief comparisons are made of the lubricant sensitivity of the Mercedes Benz M111 engine with other important fuel-efficient engines (such as the Ford Sequence VI and Ford Sequence VIA engines).

How much mixed/boundary friction is there in an engine — and where is it?

2019 ◽  
Vol 234 (10) ◽  
pp. 1563-1579 ◽  
Author(s):  
RI Taylor ◽  
N Morgan ◽  
R Mainwaring ◽  
T Davenport
Keyword(s):  
Boundary Lubrication ◽  
Mixed Boundary ◽  
Operating Conditions ◽  
Valve Train ◽  
Friction Modifier ◽  
Direct Measurements ◽  
Full Discussion ◽  
Engine Friction ◽  
The Individual ◽  
The Impact

Automotive engines are believed to operate predominantly in the hydrodynamic regime, as evidenced by the (1) the successful strategy of reducing lubricant viscosity to reduce engine friction and improve vehicle fuel consumption, and (2) for most engine operating conditions, direct measurements of engine friction (either motored or fired) find that engine friction increases with increasing engine speed. However, certain components in an engine are known to operate mainly in the mixed/boundary lubrication (e.g. the valve train) and other components (such as the piston rings) operate in the mixed/boundary regime for a portion of the time. In order to quantify the amount of mixed/boundary lubrication in an engine, and in the individual components of the engine, motored and fired friction tests have been carried out for a range of lubricants (of differing viscosity grade, and with/without friction modifier additives). A full discussion of the implications of this work, which includes the impact of fuel dilution and “running-in” is included with insights given into how the work reported here guides the development of future fuel-efficient engine lubricants.

Experimental and Theoretical Study of Instantaneous Piston Assembly Friction in a Gasoline Engine

2004 ◽  
Author(s):  
Riaz A. Mufti ◽  
Martin Priest ◽  
Richard J. Chittenden
Keyword(s):  
Gasoline Engine ◽  
Individual Performance ◽  
Friction Model ◽  
Concentric Cylinder ◽  
Friction Modifier ◽  
Piston Skirt ◽  
Indicated Mean Effective Pressure ◽  
Computationally Intensive ◽  
The Individual ◽  
Piston Assembly

A piston assembly friction model has been developed to predict the individual performance of compression rings, the oil control ring and the piston skirt. Validation of this model has been undertaken by comparing the predicted results with the experimental measurements of piston assembly friction in a gasoline engine under fired conditions using the IMEP (indicated mean effective pressure) method. The experimental results for an SAE 0W20 without friction modifier were compared with the predictions. The predicted results correlate very well with the measurements, especially at higher lubricant inlet temperatures. Piston skirt friction was predicted using both a simple concentric / cylinder model and a more realistic but computationally intensive method incorporating piston secondary motion. The results clearly indicate than the latter more realistic method is required to achieve satisfactory correlation with the measured data.

Experimental and Theoretical Evaluation of Simultaneous Piston Assembly, Valve Train and Engine Bearing Friction in a Fired Engine

2005 ◽  
Author(s):  
Riaz A. Mufti ◽  
Martin Priest
Keyword(s):  
Gasoline Engine ◽  
Fuel Efficiency ◽  
Research Work ◽  
Friction Model ◽  
Valve Train ◽  
Analysis Model ◽  
Theoretical Evaluation ◽  
Component Design ◽  
Analytical Tools ◽  
Piston Assembly

Engineers are constantly challenged to develop advanced products to meet more demanding emissions and fuel economy targets. In the past 20 years the automotive industry has greatly improved vehicle fuel efficiency by detailed engine component design improvement and formulating compatible lubricants, heavily relying on the computer based analytical tools. The sophistication and other complexity of these tools are growing rapidly. It is therefore important that the models, on which these techniques are based, are validated and continually improved by experimental techniques. For validating a predictive friction model, very accurate friction force data is required. Truly representative results can only be obtained if experiments are undertaken on a real fired engine and the friction loss in each component is recorded. The main aim of this research work is to validate an engine friction mathematical model called FLAME (Friction and Lubrication Analysis Model for Engines), over a range of load, engine speeds and lubricant temperatures, using 0W20 lubricant. The model was developed in a separate study and comprises of three parts, addressing each of the main tribological components (piston assembly, valve train and engine bearings). The validation was carried out by characterising the frictional losses generated from the major tribological components of a real fired engine. This was achieved by experimentally determining simultaneously the power loss in each component of a single cylinder, four valve, Ricardo Hydra gasoline engine under fired conditions.

Regulated and unregulated emissions from a spark-ignition engine fuelled with low-blend ethanol–gasoline mixtures

2011 ◽  
Vol 226 (4) ◽  
pp. 517-528 ◽  
Author(s):  
F-J Liu ◽  
P Liu ◽  
Z Zhu ◽  
Y-J Wei ◽  
S-H Liu
Keyword(s):  
Engine Speed ◽  
Gasoline Engine ◽  
Spark Ignition ◽  
Operating Conditions ◽  
Spark Ignition Engine ◽  
Exhaust Temperature ◽  
Fuel Blends ◽  
Before And After ◽  
Unregulated Emissions ◽  
Ethanol Fraction

The effects of ethanol addition to gasoline on the exhaust emissions (including regulated and unregulated emissions) and the conversion efficiencies of the three-way catalyst (TWC) were investigated in a three-cylinder spark-ignition (SI) gasoline engine. Three typical fuel blends – commercial 93# (Research Octane Number) gasoline (E0), E10, and E20 (with 0 per cent, 10 per cent, and 20 per cent ethanol in the blends by volume) – were used in the experiment. Unregulated emissions were measured by gas chromatography with a pulsed discharge helium ionization detector. Experimental results show that the regulated emissions of hydrocarbon, carbon monoxide, and nitrogen oxides decreased before and after the TWC with the increase of ethanol fraction in the fuel blends. However, the unregulated emissions of ethanol, acetaldehyde, and formaldehyde increased with the increase of ethanol fraction and decreased with increased engine speed and/or torque. Ethanol emission was not detected when fuelled with gasoline (E0). Ethanol emission was intensively influenced by the exhaust temperature and disappeared when the exhaust temperature was higher than 900 K for E10 and E20 operation. Acetaldehyde emission definitely comes from the oxidation of ethanol; the engine speed and load have opposite effects on acetaldehyde emission. Both ethanol and acetaldehyde can be converted effectively by the TWC. More formaldehyde was emitted at higher engine speed and lower load operating conditions.

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