Effects of Diesel-Butanol Blend Fuels on Emissions and Combustion in Diesel

Starting Point

It is generally accepted, that the fossil energy sources have to be gradually replaced by renewable and CO₂-neural energy carriers. The liquid biofuels, like ethanol, or biodiesel are most valuable and versatile alternatives in this context. In recent years; however, biobutanol has emerged as a potential biofuel, or blend-component to other fuels.

Butanol, a four-carbon alcohol, is a candidate alternative fuel, with properties closer to gasoline than Ethanol. Two of its isomers, n-Butanol (1-butanol) and iso-Butanol can be considered for use in spark ignition (SI) engines. Butanol can also be blended to the Diesel fuel.

The biorefineries producing cellulosic ethanol from wood or agricultural residues can be retrofitted to enable the production of butanol, which is actually practiced in US. There are several further developments and progressive activities of biorefineries, which according to the demand can produce biobutanol.

Generally, there are advantages of higher heat value (than Ethanol). The oxygen content of Butanol has similar advantages, like with other alcohols: tendency of less CO & HC, but possibility of increasing NO_x (depending on engine parameters setting).

The good miscibility (also with Diesel fuel), lower hygroscopicity and lower corrosivity make Butanol an interesting alternative.

Goals

Objectives of DiBut project

The project focuses on the application of butanol-blends in Diesel engines only. The project has three parts and its duration is 2.5 years. (October 2017 – February 2020).

Part 1: investigations of engine operation on engine dynamometer

This research is conducted on a Liebherr D 934 S engine with a cam-driven injection system. This engine is equipped with a programmable control unit, which allows variations of certain parameters. The test bench with eddy-current dynamometer is equipped with analysis of limited exhaust gas components and according to necessity with non-legislated compounds (like NP, or NH₃).

The most important objectives of the research with different Butanol content are:

• full load (FL) characteristics,
• influences on legislated gaseous emissions,
• influences on charging / regeneration of DPF.

Part 2: Investigations of combustion in real-world operation and of SCR on engine dynamometer

This research is conducted on an Iveco F1C engine with a common rail injection system. The test bench is equipped with 4-quadrant dynamic dynamometer, which allows performing any transient cycles. The exhaust system can be set up with DOC / DPF / SCR in modular way. There is also a possibility of analyzing the limited and non-legislated exhaust gas components.

The most important objectives of the research with different Butanol content are:

• full load characteristics (FL),
• adaptations of injection timing and EGR,
• performance of different transient cycles (ETC, WHTC),
• influences on SCR deNOx-efficiency.

On this engine, is installed a combustion chamber pressure indication with data acquisition and processing, which allows an accurate combustion diagnostic.

With this research on working packages, it is possible to investigate the influences of fuel quality on engine internal processes as well as on the actual exhaust aftertreatment systems.

The proposed research is with Bu0, B15, Bu30.

Part 3: Investigations of emissions in legal driving cycle on chassis dynamometer

This research is performed on two cars:

An older one (Euro 2), with traditional concept of injection (distributor pump) and exhaust aftertreatment (DOC) and a newer one (Euro 6), with common rail injection and exhaust aftertreatment (DPF + deNO_x).

The test vehicles are driven at WLTC cold & warm, as well as at a steady state cycle (SSC). The measurements of legislated and non-legislated emissions (NP & FTIR) are attached.

Special attempts of cold starts are conducted and compared with the equivalent results with Bu0. The tests are performed with Bu0, B15, Bu30.

This research enables a complete insight in the non-legislated emissions at cold start and in repetitive transient operation with quite different state of the art Diesel cars.

Approach

The testing procedures consist of two principal parts: 

• Testing of engines on engine dynamometers with different portions of Butanol in fuel and with consideration of combustion diagnostics and of the efficiency of exhaust aftertreatment systems.
• Testing of cars on chassis dynamometer with special attention to the non-legislated emissions, cold start and driving quality at transient operation.

Solutions

The project works are still in course (January 2019). It can be stated that the addition of Butanol changes the characteristics of the Diesel fuel blend, towards a fuel showing better evaporation, but worse self-ignition properties. Butanol lowers significantly the Cetane Number.

Another problem is the lower lubricity of Butanol, which can be addressed with special lubricating additives. Nevertheless, this problem needs further research and solutions.

Further statements at the present stage are:

• The highest investigated Butanol rate (Bu30) can be considered at present as a limit for a problem-free cold start and engine operation.
• A modern electronic control system of the engine, compensates very well the varying properties of the investigated fuels, so that in the combustion diagnostics no differences of heat release at part load operation can be noticed.
• It was confirmed that the addition of Butanol lowers the emitted particle mass PM.

Further results and information will be given at the end of the project 2019/2020.

• Single stage turbocharging system with VTG
• EGR valve (high pressure EGR)
• EGR cooler
• Throttle valve at exhaust
• Air mass flowmeter at intake
• Common rail injection system
• Exhaust aftertreatment system (ATS: DOC+DPF+SCR)

Publications

Publications of the research project GasBut (investigations with gasoline – Butanol blend fuels, 2016-2017).

1. Czerwinski, J.; Güdel, M.; Engelmann, D.; Pechout, M.: Influences of Butanol Blends on Combustion and Emissions of a Small SI Engine. SAE Technical Paper 2018-32-0058, SETC Düsseldorf, Nov. 2018, DOI:10.4271/2018-32-0058.    

2. Czerwinski, J.; Comte, P.; Engelmann, D.; Bonsack, P.: Non-legislated emissions and PN of two passenger cars with gasoline-butanol blends. PTNSS Journal Combustion Engines. 2018, 172(1), 64-72. DOI:10.19206/CE-2018-108.