Presentation Title

Jet-A Combustion in an Indirect Injection Compression Engine versus a Direct Injection Compression Engine at Same Load and Speed

Location

Room 2903

Session Format

Paper Presentation

Research Area Topic:

Engineering and Material Sciences - Mechanical

Co-Presenters, Co- Authors, Co-Researchers, Mentors, or Faculty Advisors

Martin Muinos

Dr. Valentin Soloiu

Abstract

This study compares combustion of Jet-A fuel in an Indirect Injection (IDI) compression ignition engine and a Direct Injection (DI) compression ignition engine. At this time Jet-A is a fuel that is only used in the United States to fuel aircrafts. The Armed forces have over 300,000 High Mobility Multipurpose Vehicles, or Humvees. These Humvees run on and IDI engine. Although the Army and Navy have both set in policies to replace a majority of these Humvees, more than 100,000 of them will still be in service. Georgia Southern University is the only civilian university that researches diesel engines with similar combustion system with those used in the Humvees.

DI engines inject fuel directly into the piston combustion chamber while IDI injects it to a separate combustion chamber and the pressure is sent to the main chamber. The purpose of this study evaluates combustion property differences between the two injection strategies (IDI and DI) when Jet-A is used. The Jet-A has been blended: 75% Jet-A and 25% Ultra Low Sulfur Diesel #2 (ULSD#2) by mass. Both engines performed under identical loads and RPM’s. The IDI engine was instrumented with two pressure sensors: one in the pre-combustion chamber and the second one in the main chamber so that combustion properties and ignition delays could be investigated through each sensor. The combustion properties of Jet-A in a DI and an IDI engine was investigated because the recent legislation titled “The Single Fuel Forward Policy” mandates that all in-service vehicles must be operable with aviation fuel. A baseline test using ULSD#2 was taken on the DI and IDI engines.

The results show that in the DI engine, there is a low temperature heat release region at 8 Crank Angle Degree (CAD) Before Top Dead Center (BTDC) for both fuels with the Jet-A fuel causing an ignition delay of 0.5 CAD. On the other hand this phenomenon is present only for Jet-A in the IDI engine. This is currently being more thoroughly investigated to see what effects this low temperature heat release rate effects engines. The Jet-A heat release started at 4 CAD BTDC. The low temperature heat releases occurred for 6 CAD’s in both engines.

Mechanical efficiency in both engines maintained relatively the same when running on Jet-A and ULSD#2. In the DI engine, efficiency stayed within the range of 69-70%. In the IDI engine, efficiency was maintained between 66-67% and 55-56% for both fuels based on the main chamber and pre-chamber pressures respectively.

Thermal efficiency was maintained at 39.0% in the DI engine whether running on ULSD #2 or Jet-A. However, Jet-A caused a significant decrease in thermal efficiency in the IDI engine by reducing it from 39.2% when running on ULSD#2 to 31.3%.

Keywords

Compression ignition engine, Jet-A, Heat release

Presentation Type and Release Option

Presentation (Open Access)

Start Date

4-24-2015 9:30 AM

End Date

4-24-2015 10:30 AM

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Apr 24th, 9:30 AM Apr 24th, 10:30 AM

Jet-A Combustion in an Indirect Injection Compression Engine versus a Direct Injection Compression Engine at Same Load and Speed

Room 2903

This study compares combustion of Jet-A fuel in an Indirect Injection (IDI) compression ignition engine and a Direct Injection (DI) compression ignition engine. At this time Jet-A is a fuel that is only used in the United States to fuel aircrafts. The Armed forces have over 300,000 High Mobility Multipurpose Vehicles, or Humvees. These Humvees run on and IDI engine. Although the Army and Navy have both set in policies to replace a majority of these Humvees, more than 100,000 of them will still be in service. Georgia Southern University is the only civilian university that researches diesel engines with similar combustion system with those used in the Humvees.

DI engines inject fuel directly into the piston combustion chamber while IDI injects it to a separate combustion chamber and the pressure is sent to the main chamber. The purpose of this study evaluates combustion property differences between the two injection strategies (IDI and DI) when Jet-A is used. The Jet-A has been blended: 75% Jet-A and 25% Ultra Low Sulfur Diesel #2 (ULSD#2) by mass. Both engines performed under identical loads and RPM’s. The IDI engine was instrumented with two pressure sensors: one in the pre-combustion chamber and the second one in the main chamber so that combustion properties and ignition delays could be investigated through each sensor. The combustion properties of Jet-A in a DI and an IDI engine was investigated because the recent legislation titled “The Single Fuel Forward Policy” mandates that all in-service vehicles must be operable with aviation fuel. A baseline test using ULSD#2 was taken on the DI and IDI engines.

The results show that in the DI engine, there is a low temperature heat release region at 8 Crank Angle Degree (CAD) Before Top Dead Center (BTDC) for both fuels with the Jet-A fuel causing an ignition delay of 0.5 CAD. On the other hand this phenomenon is present only for Jet-A in the IDI engine. This is currently being more thoroughly investigated to see what effects this low temperature heat release rate effects engines. The Jet-A heat release started at 4 CAD BTDC. The low temperature heat releases occurred for 6 CAD’s in both engines.

Mechanical efficiency in both engines maintained relatively the same when running on Jet-A and ULSD#2. In the DI engine, efficiency stayed within the range of 69-70%. In the IDI engine, efficiency was maintained between 66-67% and 55-56% for both fuels based on the main chamber and pre-chamber pressures respectively.

Thermal efficiency was maintained at 39.0% in the DI engine whether running on ULSD #2 or Jet-A. However, Jet-A caused a significant decrease in thermal efficiency in the IDI engine by reducing it from 39.2% when running on ULSD#2 to 31.3%.