Project 04 Biofuel Conversion of an Internal Combustion Engine
The aim of the project was to convert a naturally aspirated, spark ignition, internal combustion engine for use of 100% ethanol. The overall engine had to comply with strict formula student regulations such as spatial and acoustic constraints. To achieve this three sub groups were established: intake, exhaust and control.
It was decided that a key objective would be to incorporate a turbocharger into the design.
Constant communication between the intake and exhaust was required to ensure the turbocharger was positioned and orientated such that it benefited both groups; with the priority being short runners in order to minimise turbo lag.
To prevent corrosion of the fuel injectors, due to the use of ethanol fuel, they were replaced. This directly impacted the control group as the electronics and fuel timing are dependent on the coil resistance and the fuel flow rate of the injector. The control group and intake group, therefore, had to liaise throughout the project to ensure all design criteria were met.
The control group also had to provide sensor data to the exhaust team for testing the air-to-fuel ratio, pressure and temperature. Pressure measurements at the collector are required to verify that back pressure was minimised. Temperature sensors are required before and after the catalytic converter to ensure light off time is adequate and lambda sensors are required to measure the air to fuel ratio to ensure emissions requirements are met.
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DMT04A Fuel and Inlet
To participate in the IMechE Formula Student competition, Imperial Racing Green groups design, manufacture and test race cars that commonly run on gasoline. However, due to the increasing importance of environmental sustainability, and with it the increasing popularity of biofuels, a proof-of-concept project was undertaken to convert an existing gasoline race car to one that runs on pure ethanol.
Our DMT sub-group, the Fuel and Inlet Group, is tasked to ensure that parts which come into contact with fuel are compatible with ethanol and to improve and redesign important parts of the inlet subsystem to achieve smooth and even air supply to the engine.
An improved intake manifold design was produced after extensive CFD analysis using Star CCM+ software, to be manufactured with a suitable polymeric material. The design is updated to include a turbocharger which improves the performance of the car. The new design also features an intercooler to cool charged air from the turbocharger and a heated fuel rail to address cold start issues of using pure ethanol fuel.
The task of this sub-project was to design, make and test the exhaust system of the 100% pure ethanol engine, for a Formula Student (FS) compliant race car. The use of ethanol, which is highly knock resistant, facilitated the inclusion of a turbocharger to increase the low-speed torque and efficiency of the engine. This decision had a significant impact on the entire design process, requiring multiple adjustments in several areas.
The project is of a large, sprawling nature, and had to fit on the engine compactly with enough space for the intake subproject. We moved the catalytic converter (chosen to meet Euro 6 emission guidelines) completely to one side, allowing at the same time easy access from the outside for the purpose of pre-ignition heating, and permitting the muffler to be easily placed with its outlet right at the back of the vehicle.
A turbocharger was fitted to increase of 50% in peak torque while maintaining a power band of 3500 RPM can be achieved. GT Power, an industry standard engine simulation software, has been used to identify which turbocharger would best suit the engine characteristics and provide the desired increase in torque.
Fitting the turbocharger in front of the engine maximised the turbo boost available, though it complicated the geometry of the primaries leading to it, requiring as they do equal lengths to provide as even a pulsating flow as possible. Fortunately, an experienced workshop was found with the capacity to fabricate complex pipe geometries using mandrel bending. The manufacturing however is subject to various geometric uncertainties, so slip joints were added to give higher tolerance. All other pipe joints were a mixture of custom cut and standard bolt flanges.
The system will be ready for use on an alternative-fuel competition entry and could prompt Imperial Racing Green to pursue this as a long term venture.
The Engine Control Unit (ECU) is the core of any engine which controls and monitors the operation of the engine and most importantly, determine the correct injection and ignition timings. The ECU is programmed to calculate the timings based on many parameters, such as engine speed, engine temperature, and manifold pressure. For the engine to run effectively on ethanol, the ECU needs to be modified/reprogrammed to ensure the engine operates using the optimal spark and fuel injection timings.
The aim of this project is to design a new control system that will allow the engine to run on ethanol. Optimal ignition and injection timings were determined using simulations on GT power and implemented using an Arduino Micro, based on the signals from the engine crankshaft and camshaft. The signals created from the Arduino are modified appropriately through high-powered transistors that have been built into a custom Printed Circuit board (PCB).
A suitable housing for this PCB was designed considering protection against water and vibration, easy access to the microcontroller for reprogramming, and sufficient heat dissipation from the high-powered components.
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