This paper presented the evaluation of the effect of different thermal systems on the vehicle powertrain performance, mainly the fuel consumption. The different systems evaluated are: TEG, Rankine system and storage tanks (with and without PCM (phase change material)). These systems have different fuel consumption improvement potentials. TEG and Rankine systems provide electric power generated from the exhaust gases particularly after the warm up phase. TEGs show the particular feature to accelerate the coolant warm up, due to the cooling of the TEG cold legs with engine coolant. This particularity may be very interesting for operation at low ambient temperature. Rankine system is therefore more efficient on long and high load cycles such as the Motorway cycle. They are also more suited for gasoline engines than to Diesel engines due to the higher exhaust gases temperature. It has to be noted that Rankine systems, depending on Rankin fluid and architecture system, can use the cooling fluid as cold source, and therefore can get the same advantage for the engine cooling warm-up as the TEG. Storage tanks provide hot water at the beginning of the cycle to warm up the thermal engine. They are more efficient for short and low loaded cycles, as well as at low ambient temperatures. Storage with PCM is more efficient and more suited for low ambient temperature and low load cycles such as the NEDC, notably because the energy stored in the PCM is greater than in a storage tank alone. Better results are obtained with gasoline engine due to the lower thermal inertia than that of the Diesel engine. A first reflection of possible synergies or complementarities has been done based on simulations. Thermal systems are generally adapted to particular operating conditions. Outside these optimal operating conditions, they are generally less efficient. The use of several systems could thus be an interesting way to improve vehicle fuel consumption in the whole operating conditions: cold and hot temperatures, short and long driving cycles. The gasoline engine is clearly the best candidate to be optimised by means of thermal systems. As its efficiency is generally lower than that of a Diesel engine, more waste energy is thus available in the cooling circuit and in the exhaust gases (which can be recovered by heat recovery systems). The lower thermal inertia of the gasoline engine (compared to Diesel one) is also an advantage regarding its warm-up by energy stored in the storage tank. Specific thermal systems can thus be an interesting way to decrease gasoline engine fuel consumption and reduce the gap with Diesel engines.
Thermal systems evaluation in hybrid electric vehicle by simulation
2013
13 Seiten, 9 Bilder, 1 Tabelle, 4 Quellen
Aufsatz (Konferenz)
Englisch
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