کتاب Selection and Matching Turbocharger to Large Propulsion Engine Performance

The diesel engine is a compression-ignition internal combustion heat engine which can be operated in both the four- and two-stroke cycle. This high efficiency translates to good fuel economy and low greenhouse gas emissions. Pressure charging is the process of force-feeding air into the combustion chamber of the diesel engine. All marine propulsion diesel engines have an air-charge system with an exhaust driven turbine. This is referred to as turbocharging. A modern turbocharger has simple, modular design, aimed at improving overall life cycle. Developments in turbocharger’s component design and manufacture all contribute to this goal. The key design criteria include: • High specific flow rates • High efficiencies and reliability • Low noise emissions • Ease of maintenance and mounting • Long-service life When comparing similar rated engines, in terms of environmental protection, one fitted with a modern turbocharger will consume some 10-15% less fuel while reducing gaseous emissions by equally significant amounts. However it is not just in fuel efficiency where environmental protection benefits lie, in noise and vibration for example, modern turbocharger has succeeded in lowering noise emissions to less than at one meter distance and has improved vibration characteristics, by having kept the natural frequencies well above any exciting frequencies from the diesel engine. In connection with turbocharger matching to marine propulsion diesel engine, years of experience have enabled makers of turbocharger to develop a simple, semi-empirical method for selecting the optimum turbocharger for any propulsion engine, turbocharging system, output data and ambient conditions, at low computation cost and with sufficient accuracy. The calculation of turbocharging system with pulsating admission of the turbine is based on an empirical ‘pulse factor’ and can thus be reduced to a simple computation of a system with ‘equivalent constant-pressure admission’ of the turbine. All the empirical characteristic variables are so defined that they can be determined from the usual, available numerical data from acceptance tests and turbocharger adaptation tests, and also by step-by-step computation of real working cycle.