WP6: Derive most suitable FT-BtL diesel-blend and naphtha composition in engine and vehicle tests
In work package 6 the most promising fuels which have been defined within the single cylinder tests (WP5) will be tested in full engines, in order to demonstrate the potential of reducing the HC, CO, NOx and PM emissions as well as the potential of increasing the engine efficiency. Therefore 3 different BtL-fuel blends as well as two reference fuels (CEC reference diesel and WWFC 4 diesel fuel) will be tested in a multiple cylinder engine. The fuel composition will be determined in WP5. The WWFC 4 diesel fuel is taken as an upper benchmark for comparison as well, in order to evaluate the additional benefit of BtL and naphthenes in comparison to the pure WWFC 4 fuel.
The objective was to verify the results from single cylinder tests with the 3 most promising fuel blends in full engines.
For all of these fuels, optimizations regarding the application towards reducing volumetric fuel consumption whilst complying with the legally binding exhaust gas emissions were performed. Afterwards, the fuel blend with the highest potential of volumetric fuel consumption savings was taken to a vehicle for testing.
As no BtL was available due to the insolvency of former beneficiary CHOREN, XtL was used instead of BtL. As the synthesis of BtL would have been done by the same FT principle the fuel properties of BtL and XtL are expected to have only marginal differences.
The following blends and the reference fuel were tested:
- CEC-RF-06-03 (EU4 registration fuel without FAME)
- 60% CEC-RF-06-03 + 40% XtL
- 80% CEC-RF-06-03 + 20% XtL
- 60% low cetane diesel + 40% XtL
CEC-RF-06-03 was selected as the reference fuel in this case. This fuel is the registration fuel for European exhaust emissions category EU4, and does not contain any renewable proportion of bio constituents such as FAMPE, for example
For all measurements, exhaust gas emissions were monitored and put into comparison to the reference fuel. This included the parameters HC, CO, NOx, soot, maximum cylinder pressure gradient and volumetric fuel consumption.
A current 2.0 l TDI engine with four cylinders was selected for the set measuring task. This engine is equipped with and engine management system regulated according to the cylinder pressure, and meets the US exhaust emissions legislation of Tier 2 Bin 5.
The variation of the engine parameters showed the highest effect on a variation of the position of 50% heat release for a reduction of volumetric fuel consumption
As a basis for the volumetric fuel consumption, the NEDC was chosen. It could be shown a compensation of the lower
energy density of the 80 % CEC-RF-06-03 20 % XtL blend could be compensated by an adaption of the engine control software. Outside the city cycle, the fuel could even perform better than the reference fuel resulting in an overall advantage in volumetric fuel consumption of 2 %.