(289c) Bench-Top Engine System for Fast Screening of Alternative Fuels and Fuel Additives

There is a renewed interest and use in diesel-powered vehicles because of better fuel economy and the emergence of alternative fuels such as biodiesel. At that same time, more stringent diesel emissions requirements are in place for both new and existing diesel vehicles and equipment.  This has motivated the development of emission after-treatment technologies as well as alternative diesel fuels and diesel fuel additives.  Fuel properties have an important effect on the generation of the two key diesel pollutants, which are NOx and particulate soot.  However, existing testing methods involve the use of cumbersome dynamometers. At the University of Houston, a high throughput fuel-testing system was developed to evaluate the combustion and emission characteristics of a variety of diesel fuels and additives.  The system enables rapid and accurate information, which has great utility in the evaluation of alternative diesel fuels, such as biodiesel and other oxygenated hydrocarbons and diesel fuel additives.

In this presentation, we will describe the system and the testing of several fuels and additives.  The main components of the apparatus are a 5kW engine generator, an additive/fuel injector, a load controller, a NOx analyzer, and a remote monitoring and controlling system as shown in Figure 1. This testing system has the capability to generate fuel/additive blends of different ratios and feed them into a single cylinder engine.  The blend ratio or additive concentration can be changed in situ. The engine can be operated at different loads using the programmable load control. NOx concentration, exhaust flow rate, and other parameters are monitored and recorded to evaluate the impact of the additive/alternative fuel being tested.

An injection testing protocol was developed for screening the effect of additive dose or fuel blend ratio on NOx emission. One example is shown in Figure 2. A commercial additive NOxtrol? emissions control additive (Baker Hughes Inc.) was tested in this experiment, and its concentration in the baseline fuel (Valero #2 diesel) is changed stepwise. Each step is carried out for 20 min. Figure 2 shows how the NOx changes with the additive concentration at a fixed engine load. In this experiment, the baseline fuel was used first and the engine was run at near full load. After 20 min of baseline testing (pre-injection baseline), the NOxtrol?  additive was continuously injected into the baseline fuel line using the ISCO pump. Initially, the additive was injected at a rate of 0.033ml/min for 20min, which gives a concentration of about 1000ppm.  The additive injection rate was then changed to 0.067ml/min (2000ppm) for an additional 20min. These steps were repeated for 3000ppm and 4000ppm. The final step was to stop the additive injection and run the baseline fuel for another 20 min (post-injection baseline). NOx concentration ([NOx]) for each step was calculated by averaging the measured NOx concentration in the last 10 min of each 20 min step. The NOx concentration for baseline fuel ([NOx]_base ) is calculated by averaging [NOx] in pre-injection and post-injection steps. The NOx reduction in each injection step is marked in Figure 2, which is calculated by the equation:

NOx reduction =([NOx]_base -[NOx])/ [NOx]_base*100%

The experiment results are repeatable and the experiment error for the NOx reduction is ±0.9%.

The results generated from this system are comparable with the data from a 500HP AC chassis dynamometer. Typical data will be presented for several diesel fuels and blends with selected results compared to vehicle emissions data from a heavy-duty chassis dynamometer.

Figure 1- schematic of bench-top engine generator testing system

Figure 2-NOx concentration in the diesel exhaust changes with the additive (NOxitrol^TM, Baker Hughes Inc.) concentration during the 2-hour testing at full engine load (5kW).

NOxitrol is a trademark of Baker Hughes Incorporated.