Kawasaki Heavy Industries (KHI) has completed the development of a 30 MW gas turbine known as the Kawasaki L30A. This unit has achieved NOx emission levels of 15 ppm.

Within the KHI gas turbine line up (Figure 1), the L30A has the highest output power while retaining a similar thermal efficiency level to aeroderivative gas turbines of this class, despite having a heavy-duty design. At ISO conditions, the L30A supplies 30.9 MW of rated output, 41.3% thermal efficiency and an exhaust temperature of 470°C. These features are said to make it well suited to cogeneration and combined heat and power (CHP) applications.

The L30A borrows several design elements from earlier successful KHI machines. Its 14-stage axial flow compressor, eightcan combustors and horizontally split casing for the gas generator module, for example, is the same basic structure as the Kawasaki M7A and L20A series. In addition, its twin-shaft arrangement is the same configuration as the 1 MW class twin-shaft gas turbine named the KHI M1F and the 2.5 MW KHI Super Marine Gas Turbine (SMGT) research engine.

In addition, the L30A comes with ease-of-maintenance elements, such as multiple borescope inspection (BSI) ports on the engine casing. The specifications and general layout of the L30A are shown in Table 1 and Figure 2, respectively. The newly developed 14- stage compressor has a pressure ratio of 24.5 with a rated air flow of 86.5 kg/sec. Additionally, dry low emission (DLE) technologies have been adopted in its combustor design to attain NOx emission levels of below 15 ppm (15% = O2).

A newly designed two-stage gas generator turbine (GGT) employs a cooling design using conjugate heat transfer and flow (CHT) analysis. The three-stage power turbine (PT) has an interlocking tip shroud to reduce the vibration level for a wider operating range and lower pressure losses. The horizontally split casing enables rapid dismount of hot parts including combustors, GGT blades and vanes for inspection or replacement at site.

Component design and testing

The 14-stage axial compressor for the L30A was developed using 3D and CFD analysis. And a 63% scale model compressor test rig was used to initially test performance and durability in advance of actual engine testing.

In-house engine tests were then conducted on the L30A at KHI’s test cell beginning in July, 2010. KHI says that extensive testing has confirmed the achievement of all design targets.

During engine tests, turbine blade temperatures were measured with a pyrometer system by using the BSI ports. All stages of GGT blades and the 1st and 3rd stage blades of the PT were confirmed to meet the desired temperature criteria.

As mentioned earlier, the PT of the L30A has an inter-locking tip shroud. Instead of reducing the vibration level for a wider operating range, this structure has many vibration modes called diskmodes, because the blades can rub each other at the tip. PT vibrations were measured using a telemetry system, and confirmed to be below the High Cycle Fatigue limit.

The L30A DLE combustor consists of three burners — the pilot, main and supplemental burners. During DLE operation mode, fuel for the pilot burner is shut down except for a tiny amount to maintain the minimum (torch) flame. As the load increases, fuel distribution of the supplemental burner is raised to keep NOx levels down. A DLE combustor engine test was carried out, which confirmed NOx emissions to be less than the target value of 15ppm when the machine is running at 50% to 100% of its load range.

Field test

KHI performed an application study of the L30A for a CHP system under the foreseeable standard site conditions using typical inlet and outlet pressure losses. The L30A produced 28.4 MW of electric power and 46.2 tons/hour of saturated steam. Its thermal efficiency reached 83.1%.

The application of the L30A to CHP is said to be an effective way to achieve maximum energy utilization. Accordingly, the first commercial L30A CHP plant has been contracted with Daicel Corporation, a chemical company in Japan. Construction work started in July 2011. It will begin commercial operation in October 2012.