A New Method to Warm Up Lubricating Oil to Improve the Fuel Efficiency During Cold Start

Abstract

Cold start driving cycles exhibit an increase in friction losses due to the low temperatures of metal and media compared to normal operating engine conditions. These friction losses are responsible for up to 10% penalty in fuel economy over the official drive cycles like the New European Drive Cycle (NEDC), where the temperature of the oil even at the end of the 1180 s of the drive cycle is below the fully warmed up values of between 100°C and 120°C. At engine oil temperatures below 100°C the water from the blow by condensates and dilutes the engine oil in the oil pan which negatively affects engine wear. Therefore engine oil temperatures above 100°C are desirable to minimize engine wear through blow by condensate. The paper presents a new technique to warm up the engine oil that significantly reduces the friction losses and therefore also reduces the fuel economy penalty during a 22°C cold start NEDC. Chassis dynamometer experiments demonstrated fuel economy improvements of over 7% as well as significant emission reductions by rapidly increasing the oil temperature. Oil temperatures were increased by up to 60°C during certain parts of the NEDC. It is shown how a very simple sensitivity analysis can be used to assess the relative size or efficiency of different heat transfer passes and the resulting fuel economy improvement potential of different heat recovery systems system. Due to its simplicity the method is very fast to use and therefore also very cost effective. The method demonstrated a very good correlation for the fuel consumption within ±1% compared to measurements on a vehicle chassis roll.

Temperature Controlled Exhaust Heat Thermoelectric Generation

“…Some works have proposed the use of a heat exchanger at the exhaust pipe to recover the heat and redirect it to the system. It can then be used, for instance, to heat up the engine oil more quickly in order to improve energy efficiency during cold starts [6]. The gradual electrification of the vehicle is making the electric recovery of this thermal energy more attractive.…”

A numerical–experimental approach to assess emission performance of new generation engines during the cold transient

“…This entails higher friction between moving components and hence a lower efficiency of the engine [24]. Will and Boretti [25] estimated that frictional losses in the engine during the early stages of warm-up (when the engine is in the range of 20 °C) can be up to 2.5 times higher than those detected when the lubricant is fully warm. With these premises, therefore, it is clear that during the engine warm-up phase there are effectively three thermal masses interacting with each other, namely the main engine block, the lubricant and the coolant.…”

“…However, the cold-start performance of vehicle engines remains difficult because the thermal efficiency of the internal combustion engine is meaningfully lower at cold-start than in hot conditions owing to sub-optimal lubricant and component temperatures. During the cold-start phase, in fact, as little as 9% of the energy in the fuel is converted to effective work, as a result of components and fluids being below their optimal temperatures [24,25]. The energy thermal balance during the warm-up phase in the combustion chamber of a four-cylinder 1700 cm 3 spark ignition engine provided a breakdown of the 53% of energy that is transferred as heat to the cylinder walls.…”

Emission Treatment towards Cold Start and Back Pressure in Internal Combustion Engine against Performance of Catalytic Converter: A Review

“…Will and Boretti (2011) [24] had conducted an investigation on the heat exchanger that applied from the exhaust gas directly towards the lubricant device heat exchange. From their investigation, it showed an improvement for fuel consumption efficiency about 7% without installing heat exchanger system device from the exhaust combustion.…”