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Fuel Combustion Lab

NREL's Fuel Combustion Laboratory focuses on characterizing fuels at the molecular level. This information can then be used to understand and predict the fuel's effect on engine performance and emissions. By understanding the effects of fuel chemistry on ignition we can develop fuels that enable more efficient engine designs, using both today's technology and future advanced combustion concepts.

This lab supports the distributed Renewable Fuels and Lubricants (ReFUEL) Laboratory, and the Biofuels activity.

Photo of assembled IQT.

Ignition Quality Tester

The central piece of equipment in the Fuel Combustion Laboratory is the Ignition Quality Tester (IQT™). The IQT™ is a constant volume combustion vessel that is used to study ignition properties of liquid fuels.

The IQT™ consists of three components: 1) a cabinet that houses temperature controllers and other electronics, 2) a base tool cabinet that houses a closed-loop cooling system, and 3) the main combustion vessel unit. The heart of the main unit is the constant volume combustion chamber designed so that fuel contact with the walls is minimal. Nine cartridge heaters controlled to maintain a constant chamber temperature surround the combustion chamber. A high-speed pressure transducer measures chamber pressure to detect fuel ignition. Air-actuated intake and exhaust valves are used to feed fresh charge air and to vent combustion product gases. Fuel samples are injected into the combustion chamber through a pintle-type injector nozzle.

The IQT™ unit is interfaced with a computer that allows the user to set temperature and pressure conditions as well as to process the experimental data. A typical experiment consists of 47 separate injections — 15 preinjections to reach steady state temperatures and 32 measurements of the actual ignition delay. The ignition delay is determined as the time difference between when the injector opens and where the pressure begins to increase.

Unregulated Emissions Measurement

Sample output of ignition delay measurement using the IQT™.

The Fuels Chemistry Laboratory also houses equipment for measuring toxic unregulated exhaust emissions. This is important to better understand the impacts and compliance of advanced engines and fuels being proposed for high fuel-efficiency transportation. A gas chromatograph (GC) will allow for the speciation and quantification of C1-C12 hydrocarbon emission including 1,3-butadiene and benzene — both carcinogens being considered by CARB for future regulations. Gaseous exhaust samples are collected in passivated Summa canisters that are cleaned and evacuated prior to use. A preconcentrator will soon be acquired that will allow for detection at sub-ppbv levels. A high performance liquid chromatograph (HPLC) will quantify emissions of aldehyde and ketone, which are known to be pulmonary irritants. These carbony emissions are collected on DNPH adsorbent cartridges and eluted with acetonitrile for analysis via HPLC. Both of these capabilities allow NREL researchers to better understand potential impacts (positive or negative) that alternative fuels may have.