With reference to cutting carbon emissions, as featured in your article ‘Cut carbon — and confusion’ (Viewpoint, 29 January) there are several issues missing from the current debate surrounding automotive solutions, or rather proposed solutions.
These include the comparatively low-energy transfer efficiency of present generation internal combustion engines that persist in using reciprocating pistons, and the choice of how the fuel is used.
This leads to energy transfer efficiencies of about 30 per cent when using petrol, and 40 per cent for diesel, meaning that the bulk of the stored fuel energy is wasted.
In moving over to biofuels — whether biodiesel or bioethanol — we should, as a minimum, aim to increase the energy transfer efficiency process within vehicles. One approach along these lines that does look promising is the Rotary Internal Combustion Turbine (RICT) which combines the best of gas turbines with internal combustion engines.
This should not be confused with the Wankel rotary engine, which is an internal combustion engine.
The RICT is similar to a jet engine insofar as it uses rotating turbines. but instead of fuel being forced into a single combustion chamber, there are multiple chambers around the perimeter of each turbine into which fuel is injected along with air and ignited. The expanding pressure moves the turbine blade in a rotary manner.
As there are multiple blades, any remaining unburned fuel is drawn across the next combustion chamber where another ignition source is presented; hence multiple ignition points in any one rotation of the turbine are presented.
By using this technique a near-complete combustion process takes place. This then leaves the exhaust, where after the last combustion point is passed, an exhaust outlet is reached. Having two such series of combustion chambers and exhaust outlets on each side of the turbine means that a very effective energy transfer process takes place, and the output from the turbine is already a rotary action.
And, unlike a conventional reciprocating internal combustion engine, there is no need to convert one directional, up-and-down movement into a rotary motion, and thus a restricted speed range.
The efficiency of a RICT is estimated to be about 70 per cent. So it presents, as a minimum, an effective way to improve the energy transfer efficiency for motor vehicle engines, and allows an easier introduction of biofuels, bearing in mind that biofuels take time to reach production volumes to match the present levels for petrol and diesel.
With reference to cutting carbon emissions, as featured in your article ‘Cut carbon — and confusion’ there are several issues missing from the current debate surrounding automotive solutions, or rather proposed solutions.