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Compression-Ignition Engine Combustion
Published in Kenneth M. Bryden, Kenneth W. Ragland, Song-Charng Kong, Combustion Engineering, 2022
Kenneth M. Bryden, Kenneth W. Ragland, Song-Charng Kong
Because engine load is controlled by the amount of fuel injected, the injector must handle a volume of fuel that ranges over an order of magnitude. For a fixed amount of fuel injected per cycle and a fixed injection duration, ideally, the injection pressure must increase in proportion to the square of the engine speed. Alternately, a positive displacement fuel injection system can be used to meter the fuel. Modern diesel engines have adopted electronically controlled fuel injection systems, including the common rail system and the unit injector system. The common rail system separates the injector body from the fuel pressurization unit (i.e., a common fuel pump with a high-pressure fuel rail). The unit injector system combines the individual injector with the fuel pressurization unit. Both systems can achieve high fuel injection pressure (e.g., 1000–3000 atm) to overcome the high in-cylinder gas pressure and produce fine droplets. Traditionally, diesel fuel is injected once per engine cycle. Modern injection systems allow multiple injections in the same engine cycle with a very precise control on the quantity and timing of the individual fuel pulse. Injection flexibility facilitates improved performance, lower emissions, and better fuel tolerance. For example, it is possible to have a pilot injection where a small amount of fuel is injected prior to the injection of the rest of the fuel. The combustion resulting from the pilot injection is expected to set up favorable in-cylinder gas conditions for cleaner and more efficient combustion of the main injection. More than two fuel pulses in one engine cycle can be easily achieved in modern diesel engines.
Diesel fuel injection systems
Published in M.J. Nunney, Light and Heavy Vehicle Technology, 2007
The Cummins PT system of fuel injection has been continuously refined since its inception, but essentially it comprises the following components: An engine-driven positive displacement fuel transfer pump of the external gear type with a pulsation damper to smooth the fuel flow. The pump draws fuel from the tank via a protective filter.A throttle control, which is combined with the fuel transfer pump for the driver manually to control the engine speed above idle, as required by varying operating conditions of speed and load. Rotation of the throttle shaft via the accelerator pedal varies the amount of flow and therefore the pressure of the fuel delivered to the unit injectors.A centrifugally operated governor, which is similarly combined with the fuel transfer pump. The governor maintains sufficient fuel for idling with the throttle control in the idle position, and it cuts off fuel to the injector units above maximum rated engine speed. During operation between idle and maximum speeds, the fuel flows through the governor to the injector units via the throttle control.A shut-down valve, which is also combined with the fuel transfer pump, so that fuel delivery to the unit injectors can be terminated to stop the engine.Unit injectors, which provide the means of introducing fuel into the engine combustion chambers and combine the functions of metering, timing and high-pressure injection (Figure 8.39). They receive fuel at a relatively low controlled pressure from the common supply system. Except during the metering stage, there is a through-flow of fuel to lubricate and cool the unit injectors, the unused fuel being returned to the tank.
Numerical analysis of modified crossbreed engine cycle under BS VI norms
Published in International Journal of Ambient Energy, 2022
P. V. Elumalai, M. Parathasarathy, S. Sathishkumar, M. Murugan, A. Saravanan, M. Sreenivasa Reddy, Keerty Venkata Sri Ramachandra Murthy
The fuel was directly injected into the cylinder by a EUI. The fuel injection was controlled by the actuation of the injector spindle and the amount of fuel injected was controlled by a solenoid coil by moving the plunger. This helps in controlling the fuel flow and metering the fuel injection into the cylinder based on the amount of fresh air passed in the cylinder to make the stoichiometric mixture. Figure 5 shows that Electronic unit injector.
Pressure Control of High Pressure Tubing Based on Fluid Mechanics
Published in IETE Journal of Research, 2023
Yuhong Tao, Zhixin Wang, Shengang Cai, Zhile Xia
At present, the research on pressure control in high pressure tubing mainly focuses on the modeling and improvement of the power system in high pressure tubing and how to prevent fuel leakage. For example, Lv [1] studied the variation law of the degree of pressure fluctuation when the high-pressure pipeline structure changes, and proposed the structural optimization scheme. Qian [2] explored the influence of the structural parameters of the common rail system, namely the length and diameter of the high pressure tubing on the frequency. Wang [3] discussed the influence of geometric structure parameters such as common rail diameter, plunger diameter, and high pressure tubing length on system injection characteristics and common rail pressure fluctuation, and optimized the structure of high pressure common rail fuel injection system. Dai and Zhang [4] constructed the simulation model of high pressure common rail fuel injection system. Liu [5] studied the influence of high pressure common rail parameters on the pressure field in orbit by numerical simulation. Prinz et al. [6] conducted mathematical modeling for hydraulic and mechanical components of the common rail system. Chung et al. [7] proposed a nonlinear mathematical model for solenoid actuators and piezoelectric actuators for control applications. Catania et al. [8] presented the pressure-time history and flow pattern in the orbit and at the injector inlet during a single and multiple injection, and also reported the amount of fuel injection measured at each injection pulse. Fisher et al. [9] measured the length of the liquid by using an electrically controlled unit injector driven by hydraulic fluid with an unsteady injection rate under the unsteady and non-reactive cylinder conditions. Xu et al. [10] studied the influence of injection pressure and injection time on injection rate and duration on a specially designed common orbit injection system experimental bench. The above papers mainly studied the pressure fluctuation characteristics of high pressure tubing and the structural parameters of common rail system. At the same time, some meaningful results are given.