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PU thermal engine encapsulation for better fuel economy and lower emissions |
Polyurethane and other foams
PU thermal engine encapsulation for better fuel economy and lower emissions
Presented by Herrmann Völker, Head of Technical Market Development,
Automotive Specialties, Elastogran GmbH, Olching
Trade Press Conference K 2004, June 22, 2004, Ludwigshafen, Germany
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Polyurethane (PU) is the second biggest plastic in vehicle production after polypropylene. Most PU is currently found in the passenger compartment in the form of seats and backrest, headliners, gear knobs, steering wheels, and as a backing material for carpets and instrument panels. However, if thermal engine encapsulation (TEE) wrapping the engine in foam insulation – proves its worth, PU may soon break through into the engine compartment (figure 1).
The idea behind TEE is to reduce the number of cold starts by slowing the loss of heat from the engine after it has been switched off. The advantages of thermal encapsulation are:- reduced fuel consumption, especially for multiple short journeys
- less pollution through fewer cold-starts
- faster de-icing of windows
- less engine wear
- additional engine noise deadening.
The choice of polyurethane for engine encapsulation is based on the three properties density, thermal insulation capacity and thermal endurance (up to temperatures of 150°C) (figure 2).
The PU enclosure would typically consist of at least eight pieces to allow easier access to the engine during maintenance. Those areas subjected to extreme heat – from the exhaust manifold or catalytic converter for example – would be insulated by a refractory material and metal cladding. In the model shown in the figure, the insulation envelops both the alternator and gearbox; these would have to be included in the cooling circuit to prevent overheating. Engine encapsulation would only be feasible if incorporated into the design of new vehicles; retrofitting to existing models is not a realistic proposition (figure 3).
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Cooperation with Cologne University of Applied Sciences
TEE was developed in cooperation with researchers at the Cologne University of Applied Sciences, who carried out numerous trials and computer simulations. The first step was to determine the temperature profile inside the engine during a simulated MVEG (Motor Vehicle Emissions Group) driving cycle. It takes about 10 minutes for the cooling water to reach a steady operating temperature, while the engine oil takes twice as long and the transmission oil still longer (figure 4).
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Up to 9% fuel saving
Once a steady operating temperature had been reached, the engine was switched off and the temperature fall recorded at various locations. For an engine that was fully encapsulated, except for the exhaust manifold and engine mountings, it took 14 to 15 hours for the temperature to drop to 40°C, but only 2 to 3 hours for a non-insulated engine (figure 5).
It has been calculated that for an annual kilometrage of 12,300 km TEE can generate fuel savings of 5% percent during the summer months and 8 to 9% in winter. Practical trials on a 1.4-litre, four-cylinder gasoline engine confirmed the computational findings (figure 6).
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Commercial feasibility of TEE
Having presented the concept to selected car makers along with the research findings, an agreement was recently reached with a well-known manufacturer to study the commercial feasibility of TEE for a small diesel engine. The project will carry out a detailed cost/benefit analysis as well as investigate the potential of the system in different situations while taking into account the precise requirements of the automotive industry.
TEE has already cleared another hurdle on the road to commercialization. Elastogran commissioned an analysis by BASF's eco-efficiency laboratory to compare vehicles with and without TEE. The results, which were obtained by a certified method, prove that TEE stands a real chance of contributing to an improvement in the environmental record of future road vehicles (figure 7).
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