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Forced induction
Published in M.J. Nunney, Light and Heavy Vehicle Technology, 2007
Clearly some form of control system is necessary for the automotive turbocharger, so that it can maintain constant the required degree of pressure charging over a suitable range of engine speeds. Otherwise, the output characteristics of its centrifugal compressor would place it at a similar disadvantage to that of a mechanical supercharger of the rotating impeller type. Of the various forms of control that can be applied to a turbo-charger, the conventional method is to incorporate a turbine bypass valve. This is now better known as an exhaust wastegate, and it is usually controlled by intake manifold pressure. It basically comprises a spring-loaded poppet valve, which seals against a seating in the entry passage to the exhaust turbine. However, the wastegate is not a simple exhaust blow-off valve that could be liable to flutter, because interposed between the valve spring and valve is a diaphragm that is acted upon by intake manifold pressure (Figure 9.6). The effect of this is such that when the intake manifold boost pressure builds up to about 35 kN/m2 (5 lbf/in2), the diaphragm exerts an opposing force that assists exhaust gas pressure to overcome the valve spring load, thereby allowing the opening of the wastegate. When this occurs the excess exhaust gases bypass the turbine rotor and are transferred directly to the silencer system (Figure 9.6).
Engine
Published in Andrew Livesey, Advanced Motorsport Engineering, 2012
Boost control on a turbocharger can be by: Dump valve – this allows excess inlet pressure to go straight to the atmosphere.Blow-off valve – this balances the pressure between each side of the turbine.Waste-gate – this allows the exhaust gas to by-pass the turbine and go straight to the exhaust, it is controlled by boost pressure.
Investigation on control strategy optimisation of harsh transient condition for a marine natural gas engine
Published in Ships and Offshore Structures, 2023
Chong Xia, Wei Zhang, Yongming Feng, Tong Wang, Yuanqing Zhu, Majed Shreka, Xuefei Wu, Weijian Zhou
The transient model of propulsion characteristics for a marine natural gas engine is shown in Figure 3(b). Different from the marine four-stroke diesel engine, it has a complex structure and contains a pre-chamber (with spark plug ignition), a throttle, a wastegate, and other components. Although some diesel engines have the wastegate function, it's mainly used to adjust the turbocharger to prevent surge. Whereas the wastegate function in natural gas engines is mainly used to adjust the AFR in the cylinder besides adjusting the operation of the turbocharger. Furthermore, the throttle is used to control the intake air flow to achieve the effect of adjusting the AFR. The natural gas fuel supply adopts a multi-point injection technology and is injected into the intake manifold. In the pre-chamber, the diesel is ignited with a spark plug, and then it is used to ignite the natural gas in the main combustion chamber, in which the diesel supply is about 0.7%∼1.5% of the total fuel.
Simulation-based investigation of a marine dual-fuel engine
Published in Journal of Marine Engineering & Technology, 2020
Gerasimos Theotokatos, Sokratis Stoumpos, Victor Bolbot, Evangelos Boulougouris
The main engine characteristics are illustrated in Table 1, whilst the engine layout and components are presented in Figure 1. The Engine Control System (ECS) is responsible for the smoothly load changing and operating modes switching. The engine cylinders air–fuel ratio is adjusted via an electronically controlled exhaust gas wastegate (WG), which bypasses a part of the exhaust gas along the turbocharger (TC) turbine (Christen and Brand 2013; Wärtsilä 2015). Each engine cylinder includes a combined diesel and a pilot fuels injector. The gas fuel is injected at each cylinder inlet port (upstream the intake valves) during the engine induction process by using solenoid valves. The gas fuel admission valves as well as the diesel fuel injectors are electronically controlled (in the gas and diesel operating modes, respectively) to regulate the engine power with a target of keeping the engine speed constant. The amount of the injected pilot fuel is also controlled depending on the engine operating mode and load.
The impact of Miller cycle in combination to exhaust gas recirculation and post-injection on controlling diesel engine NOx
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Table 2 presents the simulation scheme and key operating parameters utilized in this study. During the simulation, fuel injection quantity was maintained consistent across different Miller timings. Additionally, the wastegate valve was modified to achieve a similar air-fuel ratio to that of the base engine, guaranteeing matched intake air flow. The maximum EGR rate was set at 15%, as the engine’s exhaust pressure determines the maximum EGR rate.