Investigations of the Friction Losses of Different Engine Concepts. Part 2: Sub-Assembly Resolved Friction Loss Comparison of Three Engines

Abstract

In this work, friction loss investigations and comparisons of three different four-cylinder engines for passenger car applications are presented, using a recently developed combined approach. By merging extensive experimental with reliable and predictive journal bearing simulation results, a sub-assembly-resolved friction loss analysis of the piston group, crankshaft journal bearings and valve train is conducted for all three engines. The engines have been chosen individually based on their specific power output and crank train geometry. The measurement program covers a wide range of corresponding engine operation points (identical speed, load and thermal boundary conditions). In addition, the investigations are carried out for different engine media supply temperatures ranging from 70 ∘ C to 110 ∘ C for a comprehensive consideration of the friction losses at reduced lubricant viscosity. For reasons of comparability, all investigations conducted in this work have been carried out using the same modern SAE 5W30 lubricant. This is done to exclude influences from different lubricant properties which may have significant effects on the tribological behaviour of the engines’ sub-assemblies. While the diesel engine showed a friction reduction potential over the entire engine operation range when increasing the engine media supply temperatures, the gasoline engines showed a different behaviour. For the gasoline engines, disadvantages arise especially at low engine speeds. By using the developed combined approach, it was possible to assign mixed lubrication regimes at the valve train systems and at the piston groups.

Investigations of the Friction Losses of Different Engine Concepts: Part 3: Friction Reduction Potentials and Risk Assessment at the Sub-Assembly Level

“…Subsequently, possible advantages using the presented combined approach are explained in detail. The resulting FMEP-maps at the base engine level of the investigated engine architectures are presented in Figure 7 (see also [4]). By increasing the lubricant supply temperature, a significant decrease of the lubricant viscosity is obtained (see Figure 2), and friction reduction potentials, as well as possible risks due to beginning mixed lubrication regimes are studied.…”

“…The results of the friction potential analysis and risk assessment at the base engine level represents a good example of the advantages when using the combined approach for friction analysis presented in the publicatiosn series [3,4]. At the base engine level, for example of gasoline engine 2, the arising risks are rather small between 0% and −2% at low engine speeds and high loads.…”

“…In the previous two parts of this series, a novel method to investigate friction in internal combustion engines was presented (see part 1 [3]), and applied to three engines from different engine architectures (see part 2 [4]). The friction losses were investigated by combining experimental testing with accurate simulation techniques.…”

Piston-Pin Rotation and Lubrication

“…The engine to be investigated is a turbocharged, 4-cylinder inline gasoline engine with 1.8 l volume displacement and a nominal power of 130 kW; its technical data are summarized in Table 1. This engine was already part of previous works of the authors on engine friction [14,15], where it was termed Gasoline 1 engine.…”

“…Within this work, the same engine oil of previous works of the authors [14,15] is also investigated; the basic lubricant data is listed in Table 2.…”