Designing Reliability and Maintainability Into the Racer System

Abstract

The current Naval Sea Systems Command (NAVSEA) program to design and develop an advanced, combined gas turbine and steam turbine (COGAS) power plant called RACER is discussed. RACER is an acronym for RAnkine Cycle Energy Recovery which describes the heat recovery steam cycle designed to recover energy from the exhaust of an LM2500 gas turbine and thus augment the main propulsion system of a surface combatant through a steam turbine. The main design objective of a COGAS power plant is to achieve fuel efficiency at both full power and part load conditions. However, even the most impressive fuel‐saving COGAS system is of little value unless system operability criteria are implemented in the design process as equal, if not more critical, design objectives. General design philosophy to improve COGAS plant reliability and maintainability (R&M) is discussed, and the primary RACER design approach of simplicity and modularity is described. Reliabilty and maintainability design criteria and techniques are presented as they relate to improved system operability. Components which require special R&M considerations are discussed and examples are presented of how R&M criteria have affected system design.

COGAS propulsion for LNG ships

“…However, the steam system in a COGAS system is also expected to require little maintenance. Mills (1977) points out, "… the combined-cycle steam generator experiences much more benevolent gas-side temperatures and none of the conventional boiler's problems associated with flame, oil, or ash impingement …" Mattson (1983) discussed design issues that would significantly influence the reliability and maintainability of the US Navy's proposed RACER system. He goes on to predict that the steam machinery will require "… less than 50 man-hours per week maintenance."…”

“…Halkola (1983) provides an estimate of the weight of the steam machinery. For a steam turbine power of 7500 hp (1 kW=1.341 hp), the estimated weight of the steam machinery is about 27 t. Writing about a steam system that would produce 8700 hp, Mattson (1983) states, "… although a single RACER system will weigh 40 to 60 t, there would be a reduction in mission fuel weight of several times this weight." In his thesis Combs (1979) estimates that a waste heat boiler for a gas turbine operating at 18 000 horsepower might have dimensions of 12 feet (1ft=0.3048m) by 12 feet perpendicular to the flow direction and 7 feet parallel to the flow direction.…”

Multifuel Gasturbine Propulsion for Naval Ships: Part I — Logistic and Operational Rationale

“…If one succeeds in optimizing the thermodynamic cycle by improving turbine inlet temperatures and/or by implementing bottoming rankine cycles or recuperative cycles, then the energy productivity can substantially be improved and the temperature of the outlet gases be reduced (11). So, we arrive at a following proposed solution: addition of fuel pre-treatment apparatus to the open gasturbine cycle and installment of equipment for internal or external recuperation.…”