Influence of Miller cycle on thermal load of high-boosted diesel engine

With the increase of the engine intensified degree, mechanical load and thermal load become to the two main factors limiting the engine to intensify. Application of Miller cycle, which can be realized by late intake valve closing (LIVC) and deeper late intake valve closing (DLIVC), has the potential to reduce the effective CR, mechanical load, and thermal load. In this paper, the effects of LIVC and DLIVC on the mechanical load and thermal load of a boosted DI diesel are experimentally compared. Compared to the original base case, the average cylinder temperature of LIVC and DLIVC is reduced by 90 and 52 K. The exhaust temperature of LIVC and DLIVC decreased by 26 and 14 K, and the maximum combustion pressure of LIVC and DLIVC decreased by 1.6 and 9.7 bar. The pumping losses of LIVC and DLIVC are reduced by more than 25%, while the actual cycle power does not decrease due to the late closing of the inlet valve. The fuel consumption rate decreased from 250.1 g/kWh of base case to 240 g/kWh of LIVC, reduced by 4.0%. The indicated thermal efficiency increased from 41.9% of base case to 43.7% and 42.5% of LIVC and DLIVC. Miller loss is only 2.55% with Miller inlet phase.

Estimates of the air-fuel ratio at the time of ignition in a pre-chamber using a narrow throat geometry

The benefits of pre-chamber combustion (PCC), such as improved engine efficiency and reduced NOx emissions, are primarily observed when operating at lean conditions with an active pre-chamber, where auxiliary fuel is supplied directly to the pre-chamber. Estimating the pre-chamber excess air ratio (λ) is important in the active pre-chamber concept to gain insights into the pre-chamber combustion phenomenon. Experimental investigations were performed using a narrow-throat pre-chamber at global-λ 1.6, 1.8, and 2.0. The fraction of fuel energy injected in the pre-chamber over the total fuel energy was fixed at 3%, 7%, and 13% for each global-λ. The mixture formation process inside the pre-chamber is first simulated using the 1-D simulation software GT-Power to analyze the pre-chamber λ at the ignition timing. However, the 1-D results were unable to reproduce the experimental observations on the pre-chamber pressure buildup accurately. Upon simulating the same conditions using the 3-D CFD software CONVERGE, the pre-chamber λ estimated from the CFD model is well-correlated to the experimental data. The CFD results indicate that the amount of fuel trapped in the pre-chamber at the inlet valve closing timing is over-predicted by the 1-D simulations. A correlation between the injected and the trapped fuel in the pre-chamber is proposed by theoretical scavenging models and applied to the 1-D simulation results to improve pre-chamber λ prediction accuracy.

Optimization of Piston Grooves, Bridges on Cylinder Head, and Inlet Valve Masking of Home-Fueled Diesel Engine by Response Surface Methodology

Naturally replenished biodiesel fuels are more precise in place of diesel engine applications as they have complying thermal properties, which are extensively used by various researchers. However, there is necessity to optimize their utility to meet stringent emission norms as per Bharat Stage VI (BS VI) and Euro 6. From the exhaustive survey on the studies, number of piston grooves (NG), number of grooves-n-bridges on cylinder head (Gr-Br), and inlet valve masking (IVM) using the response surface methodologies (RSM) technique have not been reported on the competence, emissions, and combustion attributes of diesel engines running on Honge oil methyl ester (HOME), hence this is an identified gap in literature. The present simulation work is for optimizing the performance and lessoning exhaust emitted from the diesel prime mover tested on non-conventional and petro fuels. Experimentation was carried out to inquest the competence, combustion, and emittance of a vertical cylinder, overhead valve, water cooling, open or induction swirl diesel engine running on HOME as the injecting fuel. The object of the present effort is to optimize competence of diesel engines via a statistics inquest called designs of experiments (DoE). To curtail the diverse variations to be experimented on, full factorial designs (FFDs) array was employed. The response surface methodologies (RSM)-based nonlinear or quadratic predictors establish the relation between the input parameters and proposed attributes. The RSM-based mathematical predictors are established to prognosticate the distinguished engine output attributes at 95% confidence interval. The response surface assay discovered that a combination of 2B 3G, ‘IVM’ of 900, and ‘NG’ of six grooves yields highest brake thermal efficiency (BTE), lessoning smoke, carbon monoxide (CO), and hydrocarbon (HC), but nitrogenous oxides (NOx) emissions increased slightly. Additionally, combustion attributes, such as Ignition delay (ID) and combustion duration (CD), were lessoned, but peak pressure (PP) and heat release rate (HRR) had a higher contrast to performance of HOME biodiesel in a conventional CI engine.

Design, simulation, and experiment research on fast control system of steam turbine inlet valve

In this paper, a new fast control system of steam turbine inlet valve is designed, which is composed of the fast closing system and the fast opening system. For the first time, this paper proposes that the fast closing system is designed by means of the special structure of the slide valve in an oil servo motor on the basis of the transformation of the hydraulic control system of steam turbine inlet valve. For the first time, a differential oil discharge fast opening system is designed by use of two cartridge valves. The mathematical model of electro-hydraulic fast control system is presented. With the use of simulation software Advanced Modeling Environment for Simulation of engineering systems , the curves of parameters such as piston displacement, piston velocity, oil pressure of upper and nether cavities of oil servo motor, and flow flux of upper and nether cavities of oil servo motor are obtained. The fast closing time of the piston for whole journey from the simulation results is 0.36 s. The fast opening time of the piston for whole journey from the simulation results is 1.55 s. According to the designed structure of the fast control system, the fast control experiment system is built. The fast closing time of the piston for whole journey from the experiment results is 0.22 s. The fast opening time of the piston for the whole journey from the experiment results is 1.97 s. The simulation and experimental results show that the designed fast control system can realize the fast closing and fast opening of the inlet valve. The fast closing time of the fast control system is <0.5 s, and the fast opening time of the fast control system is <3 s, which meets the fast control time requirement of the steam turbine inlet valve. Compared with the existing fast control system products, the fast control system and the inlet valve servo regulation system share a set of oil sources. And the fast control system has the advantages of low cost, simple structure, easy implementation, etc.

Research on the performance of a novel electro-hydraulic proportional directional valve with position-feedback groove

Accurate posture control of hydraulic roof supports, which use pressurized water as their fluid power source, is an important part and research direction of intelligent fully mechanized mining face. At present, the large flow on/off directional valve used on the hydraulic roof support cannot meet the requirement of precise posture control of the roof support. To overcome the conundrum, a novel two-position three-way electro-hydraulic proportional directional flow valve for hydraulic roof support is proposed. The new valve contains two pilot stages and two main spools. The two pilot stages cooperate with each other to control the movement of the two main valve spools, which are the inlet valve spool and the outlet valve spool. The inlet valve spool adopts the Valvistor principle. The valve can realize manual pilot control and electro-hydraulic proportional flow control of the passage P-A, which has been verified by a simulation model. In this paper, the static and dynamic mathematical models of the new proportional valve are established, and the key parameters affecting the valve performances are analyzed and verified by the simulation model. An optimization control scheme is proposed to overcome the influence of supply pressure, P-A pressure difference, and nonlinear interference force on steady-state displacement and response speed of the valve. The results show that this optimization method can significantly improve the response speed of the spool and promote the linearity of spool displacement under a slope signal. In addition, the fluctuation of chamber pressure and spool displacement caused by the discontinuous flow of a fast switching valve is systematically analyzed. The analysis shows that increasing pulse-width modulation carrier frequency is an effective way to reduce fluctuation amplitude. The research provides a new design idea and control method for an electro-hydraulic proportional directional valve of hydraulic roof support.

Resonant Type Piezoelectric Pump Driven at the Power Frequency Using a Tuning Fork Vibrator

A resonant type piezoelectric pump driven by a tuning fork vibrator (TFV) is developed in this study. The resonant frequency of the TFV is designed to be the power frequency, thus the pump can directly work in a resonant state under a power frequency power supply. Three factors affecting the performance of the piezoelectric pump are investigated in this paper, including the thickness of the TFV, the material of the pump chamber diaphragm and the quantity of inlet valve. The Taguchi method is adopted to obtain the best combination among the three factors. In accordance with the optimized results of the Taguchi method, a final prototype piezoelectric pump is fabricated via 3D printing technology. When driven by the power frequency power supply, the maximum flow rate of the prototype piezoelectric pump can reach 441.77 ml/min.