Two-Stage ‘Ecocharge’ Turbocharging Pushes Gas Engine to World’s Highest Class Efficiency

August 19, 2020
PBST has announced that Kawasaki Heavy Industries’ (KHI) new type KG-18-T gas engine, equipped withits two-stage-turbocharging ‘Ecocharge’ system, has recorded the world's highest class power generationefficiency of 51% with Japanese standard city gas.
Designed for power applications, the KG-18-T’s Ecocharge solution consists of 1 × PBST TCX23 and 1 ×PBST TCA66 turbochargers that have improved its power-generation efficiency by 1.5% compared to theprevious generation of the engine, delivering a world-best class 51.0% in its output class.
KHI notes that engine and turbochargers have passed a durability test and are now ready for serialproduction. The turbochargers themselves were inspected after the durability test with KHI reporting theircondition as very good.
KHI’s Mr. Sakai – Senior Manager Four-stroke Engine Department and Head of Design Department – said:“Our new KG-18-T gas engine raises high expectations. This engine is the latest and most-efficient additionto our "Kawasaki Green Gas Engine” series. The design is based on its previous models KG-18-V and KG-18, which count more than 180 sold units since their introduction ten years ago. The newly developed two?stage turbocharging system improves power generation efficiency significantly resulting in the world'shighest class efficiency in this output range. Consequently, we are keen awaiting to continue this engine’ssuccess story.”
PBST’s Ralph Klaunig – Vice President of Sales & License Turbochargers & Exhaust-Gas Treatment – said:“Naturally we are very happy with this announcement since KHI is the very first Original EquipmentManufacturer in the medium speed segment to launch an engine with our two-stage turbocharging solution.
PBST is a market leader within two-stage turbocharging, with more than 35 million operating hours recordedfrom over 2,000 units, and it is very pleasing that we can now add the world’s most efficient gas engine toour reference list.”
The ECOCHARGE principle

The ECOCHARGE principle optimally combines a low-pressure turbocharger – usually a TCT, TCA or TCR– with a high-pressure stage for which the newly developed TCX series was designed.
PBST ECOCHARGE offers major benefits for engine builders. The increase in turbocharging efficiencies, incomparison to single-stage turbochargers, is mainly related to the intercooler – positioned between the low?pressure-stage and high-pressure-stage turbochargers – that significantly reduces the energy required tocompress the intake air to high pressure. The resulting, higher efficiencies have an instantaneous impact onthe engine by advantageously increasing the air pressure over the cylinder during the scavenging process.
Additionally, greater charged pressure by two-stage turbochargers foster the reduction of NOx emissionsthrough the Miller cycle, while the improved scavenging efficiencies provided by the ECOCHARGE systemmake the engine more fuel efficient.
The higher power-density generated by the ECOCHARGE technology presents the opportunity to choosebetween significantly boosting an engine’s power output or reducing engine size, all the while maintaining anexcellent engine performance. The ECOCHARGE system’s increased efficiencies and higher cylinder ratingfacilitate the use of a smaller engine with the same power output of a larger unit that employs traditional,single-stage turbocharging.

Ecocharging KHI’s new KG-18-T engine
PBST TCX23 and TCA66 turbocharger