F2010A073
An Novel Exhaust Heat Recovery System to Reduce Fuel Consumption
Internal combustion engines release about 1/3 of the energy wasted in the exhaust. On the other hand frictional losses are the third largest root cause for energy loss in internal combustion engines. During city driving frictional losses can be of the same size as the effective work, and during cold start these losses are even bigger. Therefore it is evident to utilise wasted exhaust energy to warm up the engine oil directly. The invention reduces the frictional losses of any engine. Measurements have confirmed fuel consumption reductions of over 7%. The Oil Viscosity Energy Recovery System (OVER 7(TM)) consists of 3 key features that add significant synergies if combined in a certain way. o Oil warm up circuit o Oil pressure control o Full Flow Exhaust Gas/Oil Heat Exchanger
The improvements have been confirmed at normal operating conditions. During cold start and warm up even bigger improvements will be possible.
Feature 1: Oil warm up circuit To warm up the oil faster an oil return bypass is connected directly to the oil pump (or oil pick up tube) so that a certain portion of the oil does not need to flow through the oil sump. For maximum warm-up result this by-pass connects to the oil gallery in the cylinder head, far away from the oil pump. The oil through the by-pass warms up much faster than compared to running it through the sump. The combined oil flow also warms up faster as a result. The underlying considerations and calculations will be explained.
Feature 2: Oil pressure control The by-pass flow rate - and therefore also the engine oil pressure - is electronically controlled by a valve located in the oil by-pass. The By-Pass flow is increased for low oil temperatures, low engine loads and high engine speeds. This firstly maximises the warm-up benefit of by-pass and secondly reduces the hydraulic oil pump power. Feature 3: Exhaust gas heat exchanger The oil flows through an exhaust gas heat exchanger (instead of coolant). This uses the exhaust energy in a much more efficient way to reduce the oil viscosity, compared to conventional exhaust heat recovery systems (EHRS). The efficiency of the heat transfer from exhaust gas to oil is around 20-times better compared to conventional EHRS. That is the main reason why these conventional EHRS systems only provide a marginal fuel economy improvement of around 1% at very high system costs of over $100 per percent fuel economy improvement.
Improved Engine Durability Most passenger cars are typically operated at oil temperatures of around 90°C or below. At these temperatures the water from the blow by gases condensate. Together with the oil this water builds emulsions with reduced lubrication capabilities and highly aggressive acids are attained in the lubrication system that increase engine wear. The OVER 7(TM) system can reduce wear rates by a large factor if the oil is warmed up faster.
This abstract is supplemented by a PDF, which can be viewed here.
Session: Consumption and Emission Reduction