Marine Power & Propulsion: October 2017
As a generic platform developed for use on Wärtsilä four-stroke engines, the proprietary UNIC automation technology has been taken to a new level of sophistication in a second-generation system. In its initial application, the embedded control and management system is pivotal to the performance of the latest addition to the company’s medium-speed portfolio, the Wärtsilä 31 vee-type.
In 2015, Guinness World Records rated the W31 as the “most efficient four-stroke diesel engine”, adding credibility to the manufacturer’s claims for the product. The upgraded UNIC solution encapsulates Wärtsilä’s cornerstone objectives in automation development, namely flexibility, modular architecture and more advanced control technology, directly reflecting key characteristics of the engine itself. The overarching goal is to meet both tightening regulatory requirements and rising customer demands and expectations.
Through the ‘building block’ approach, UNIC offers a wide range of options and permutations, from a single-module installation to a multi-module configuration, exploited to the full in the W31, distinguished in providing a concurrent design basis for distinct diesel, dual-fuel and
gas-only variants.
The hardware of the second-generation UNIC, as embraced by the W31 engine, is comprised of cylinder control modules (CCM), input/output modules (IOM) and a safety module (ESM), plus a system interface consisting of communication modules (COM) and local display units (LDU). In addition to facilitating the delivery of a product-specific package, whereby the make-up and layout of the various modules can be tailored to an engine’s and a user’s precise requirements, modularisation allows step-by-step pre-testing, ensuring a solid validation chain. The critical parts are either redundant or highly fault-tolerant in the interests of safety and availability.
Improved diagnostics and prognostics are embodied in the new iteration of UNIC, in keeping with the drive for higher engine availability factors. For example, the electrical actuators used in the W31 installation can provide prognostics data to detect possible service needs before failure, enabling condition-based service to be planned according to the vessel’s operating schedule.
Wärtsilä’s long experience in automation electromechanical design provided a solid base for this aspect of the W31. “Feedback from field experience has been consolidated into updated design guides and applied to the Wärtsilä 31 automation design to ensure high reliability as well as easy serviceability of the engine controls,” says Tomi Vuollet, the company’s director in charge of four-stroke R&D engine performance and controls.
The cable layout and routing of the engine automation components were considered in the engine mechanical design, and special attention was paid to temperature and vibration endurance. Potential vibration issues arising with the engine control and automation modules were addressed by using proven wire rope dampers.
The W31 development project gave rise to a new electronic module enclosure, the WTB-20. Besides affording the requisite ingress protection (IP) for the modules, the WTB-20 ensured a lean mechanical fit and ease of access for service and maintenance purposes.
A new local display unit (LDU) has been introduced as part of the second-generation UNIC system. The LDU-30 has been devised in keeping with the design strategy of reducing complexity for the user, and has drawn on feedback from customers. It provides an intuitive interface with touch controls to browse through engine and measurement statuses, and to enable “a deep dive” into engine measurement details and visualised engine diagnostics information when needed.
In its further refined form, UNIC has addressed the issue of the greater challenges to troubleshooting that have arisen with the increasing sophistication and compass of vessel automation technology. For example, it is not uncommon for several individual alarms to be triggered by a single failure in one of the ship’s automation systems, such as a communications line break. “The improved capacity of the second-generation UNIC system can now combine different alarms so that operators or service personnel are able to pinpoint the actual root cause for the failure,” says Vuollet.
Interfacing and integration possibilities have been taken a stage further in the new UNIC solution. Several design aspects have been considered in the second-generation UNIC to facilitate the integration of the W31 with other machinery or systems, such as emission after-treatment equipment, and with the company’s digital service offerings.
The UNIC engine control, in conjunction with the advanced injection system and variable valve timing, makes it possible to achieve optimal running performance with the new engine across the load range, even at very low loads. Vuollet continues: “Although robust steady-state control is still very important, the ability to react rapidly to changing conditions must also be part of the normal control routines, making transient control algorithms necessary.” Fast transient response is an increasingly important factor in engine performance and monitoring.
The second-generation UNIC control system supports the calculation of combustion parameters, extracted from cylinder pressure measurements, which are seen as essential for future combustion control concepts. In-cylinder pressure contains information that characterises the combustion behaviour.
In its diesel version, the W31 promises a fuel consumption rate down to 165g/kWh, thought to be lower than any other four-stroke engine currently available. With an output of 610kW per cylinder, the series will cover the 4,200-9,800kW band at maximum power. The opening orders for the engine to date include a Russian icebreaker, Danish ro-pax ferries and a Norwegian fishing vessel.
