Advanced HFO Common Rail Injector for Maximising the Performance of Medium Speed Engines
A new generation of common rail injector for marine, power and railway applications was developed by OMT as the result of a decade of research in high-performance fuel injection systems, and a series of thorough tests with HFO of a previous injector generation performed by the customer both on test rig and engine. In combination with other key components influencing the combustion performance of the engine as, for instance, the turbocharger and the valve actuation system, an advanced common rail injector enables the engine designer to optimise the engine for reducing the fuel consumption and complying with the forthcoming emission legislation standards. The paper presents the main design principles and features of the new injector, as well as the motivations that led to the choice of such design and the physical phenomena that play the major role in determining injector behaviour. The injector features a fuel reservoir integrated in its body to store the very high pressures required nowadays to further improve the combustion process, as well as a flow limiter valve for preventing engine overfuelling in case of injector failure. Multi shot capability is also mandatory for providing maximum flexibility in shaping the heat release curve. The paper presents how this was achieved by designing a control stage able to operate with high temperature HFO and placed very close to the injector needle for minimising injector response time and dwell time between injections. This concept required the custom design of a solenoid able to meet demanding specifications in terms of short switching time, high force with limited size and high working temperatures. A multidimensional numerical model of the injector was developed in-house, using a proprietary code that takes into account fuel compressibility and cavitation phenomena. The model couples the results of 3D-CFD analyses of the parts of the design that require threedimensional study of fluid flow to be properly characterised, with the lumped parameter model of the mechanical parts of the injector and the one-dimensional model of the fuel channels required to correctly predict pressure wave propagation. Rig tests were carried out to confirm the functional performance and durability of the new injector design, as well as to validate the numerical model predictions. This enabled the use of the model for studying the effect of design modifications on injector performance, thus speeding up the development process. The paper presents a comparison between experimental and numerical results of injector performance measured on the test rig at the beginning of its life as well as after one thousand hours of operation on an endurance test rig. The results obtained demonstrate the benefits of the technical solutions adopted and why they were needed to reach the good level of performance shown by the injector. In particular, the minimum controllable injected quantity was found to be very low and showing high repeatability, making this design ideal for operating in multi shot mode and also for dual fuel engines, where the customer requires to use the minimum possible amount of liquid fuel for performing gas ignition. The injector was undergoing prototype tests on a customer engine at the time of writing this abstract.
Marco Coppo Claudio Negri Klaus Heim Alessio Banno
OMT SpA,Italy
国际会议
上海
英文
1-11
2013-05-13（万方平台首次上网日期，不代表论文的发表时间）