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Abstract

This thesis describes an investigation into the operation and performance of internal combustion engines boosted by an electric supercharger (eSC) in combination with a turbocharger.

Engine downsizing offers one of the most effective ways to meet increasingly demanding CO2 reduction targets set for the automotive vehicles. The addition of a turbocharger has enabled significant downsizing but the loss of torque at low engine speeds remains a key barrier to further downsizing. A known solution to this problem is to additionally boost the engine using a supercharger. However, until recently, this was very difficult to implement economically on engines with modest engine power suitable for small to medium sized vehicles due to the low air mass flow rates for such engines. Now, a new turbo-machinery innovation, the high forward swept TurboClaw compressor, allows significant boosting to be done at low flow rates yet with moderate compressor shaft speeds.

Since this compressor can be driven at a moderate speeds, the electric motor which drives for the electric supercharger (eSC) is more affordable. The research objective was to assess this new eSC system be means of a theoretical and experimental investigation.

There are two possible combinations in terms of whether the (eSC) goes before the turbocharger (ETC), or after (TEC). Employing the eSC after turbocharger generally has the advantage of broadening the eSC map, towards higher-mass flows since a denser air exits the turbo-compressor as the turbocharger provides boosted air to the system. This augments the overlap of the two operating maps for the two devices. However the real benefit of eSC in each layout depends on the engine (baseline). In this research ETC and TEC produce basically the same torque increase; the real eSC benefit is at low speed where the nominal maximum torque is recovered for all the range. However since the current drawn from the battery is a key factor for this application, the investigation shows that the thermodynamic power requested by eSC is less than 1.5kW for ETC layout while this value is 2.5kW for TEC layout. Therefore ETC layout was chosen as the final configure to be implemented on the selected vehicle for the dyno test purposes since it requires less power.

Theoretical models for the engine, turbocharger and TurboClaw eSC including electric motor were created and validated. The system of all components was designed including control system and strategy. A key result showed that the eSC was found to boost the torque of a 1.0 litre turbocharged engine by 125% and 58% for 1000 rpm and 1200 rpm respectively.

Publication Type:	Thesis (Doctoral)
Subjects:	T Technology > TJ Mechanical engineering and machinery
Departments:	Doctoral Theses School of Science & Technology > School of Science & Technology Doctoral Theses School of Science & Technology > Engineering

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