Bubble formation in high-pressure liquid–solid suspensions with plenum pressure fluctuation

This paper presents a computational study for a high-speed centrifugal compressor stage with a design pressure ratio equal to 4, the stage consisting of a splittered unshrouded impeller and a wedged vaned diffuser. The aim of this paper is to investigate numerically the modifications of the flow structure during a surge cycle. The investigations are based on the results of unsteady three-dimensional, compressible flow simulations, using large eddy simulation (LES) model. Instantaneous and mean flow field analyses are presented in the impeller inducer and in the vaned diffuser region through one surge cycle time intervals. The computational data compare favorably with the measured data, from the literature, for the same compressor and operational point. The surge event phases are well detected inside the impeller and diffuser. The time-averaged loading on the impeller main blade is maximum near the trialing edge and near the tip. The amplitude of the unsteady pressure fluctuation is maximum for the flow reversal condition and reaches values up to 70% of the dynamic pressure. The diffuser vane exhibits high-pressure fluctuation from the vane leading edge to 50% of the chord length. High-pressure fluctuation is detected during the forward flow recovery condition as a result of the shock wave that moves toward the diffuser outlet.

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Research on transmission and coupling characteristics of multi-frequency pressure fluctuation of high pressure common rail fuel system

Fuel ◽

10.1016/j.fuel.2021.122632 ◽

2021 ◽

pp. 122632

Author(s):

Yunpeng Wei ◽

Liyun Fan ◽

Yuelin Wu ◽

Yuanqi Gu ◽

Jing Xu ◽

...

Keyword(s):

High Pressure ◽

Pressure Fluctuation ◽

Common Rail ◽

Fuel System ◽

Coupling Characteristics ◽

High Pressure Common Rail

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Model-Based Optimization and Pressure Fluctuation Control of Pressure Reservoir in Electrically Controlled Fuel Injection System for Single Cylinder Diesel Engine

Volume 2: Emissions Control Systems; Instrumentation, Controls, and Hybrids; Numerical Simulation; Engine Design and Mechanical Development ◽

10.1115/icef2017-3513 ◽

2017 ◽

Cited By ~ 1

Author(s):

Ke Zhang ◽

Zhifeng Xie ◽

Ming Zhou

Keyword(s):

High Pressure ◽

Diesel Engine ◽

Diesel Engines ◽

Pressure Fluctuation ◽

Fuel Injection ◽

Common Rail ◽

Installation Space ◽

Injection System ◽

Fuel Injection System ◽

Single Cylinder

Single-cylinder diesel engines usually employ mechanically actuated or time-type electrically controlled fuel injection systems. But due to the lack of flexibility to provide high pressure and fully varying injection parameters, fuel efficiency and emissions are poor. Although modern multi-cylinder engines have employed high pressure common rail fuel injection system for a long time, this technology has not been demonstrated in single-cylinder diesel engines. Due to the small installation space and little fuel injection amount of single cylinder diesel engine, high pressure common rail fuel injection system cannot be employed directly. In this study an electrically controlled high pressure fuel injection system of time-pressure-type (PTFS) for single-cylinder diesel engine was demonstrated. PTFS integrated the fuel pump and pressure reservoir (PR) to reduce installation space, which enabled it to match various kinds of single-cylinder diesel engines. However, the volume of the PR of PTFS is still limited, leading to obvious pressure fluctuation induced by periodic fuel pumping and injection. Pressure fluctuation might affect the stability and consistency of fuel injection, deteriorating the combustion and emissions of the engine further. This work established a mathematical model for the system, and studied the effect of the main parameters of the PR to the pressure fluctuations in the PR. The structure and dimensions of the system were optimized and a damping mechanism was proposed to reduce the pressure fluctuation. The optimized pressure fluctuation of PTFS achieved an acceptable level which can support steady and effective fuel injection. As a result, the fuel consumption efficiency and emission level of single cylinder diesel engine were enhanced.

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Development of Robotic Spraying System in Narrow Space

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.442.221 ◽

2013 ◽

Vol 442 ◽

pp. 221-224

Author(s):

Yan Chen ◽

Wen Zhuo Chen ◽

Ken Chen ◽

Jun Yi Shao ◽

Wei Ming Zhang

Keyword(s):

High Pressure ◽

Pressure Fluctuation ◽

Feed System ◽

Fluid System ◽

Work Requirements ◽

High Solid ◽

Inner Surface ◽

Narrow Space ◽

And Control ◽

Spray Gun

The coating of the intermediate coating on the inner surface in narrow space is characterized by high solid, high density, sedimentation. LVMP process is qualified and adopted to spray this high solid coating. The designed pressure feed system is composed of a fluid system and a pneumatic system. The former is used to feed coatings into the spray gun, circulate coating and agitate coating, while the latter is used to actuate and control the fluid system and provide high pressure air as cylinder air, atomization air and pattern air. The experiments show that the robotic spraying system could satisfy the work requirements including good stabilization, no settling, ignorable pressure fluctuation and fine atomization in narrow space.

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Numerical and Experimental Investigation of Cavitation in a Pump

Volume 1: Symposia, Parts A and B ◽

10.1115/fedsm2005-77004 ◽

2005 ◽

Author(s):

Amit Gupta ◽

J. T. Kshirsagar

Keyword(s):

High Pressure ◽

Volume Fraction ◽

Bubble Formation ◽

Numerical Approach ◽

Working Fluid ◽

Suction Pressure ◽

Flowing Fluid ◽

Cavitation Phenomenon ◽

Research Activities ◽

Overall Performance

Cavitation in pumps is a well-known phenomenon that occurs when local static pressure approaches vapor pressure for the working fluid. The flowing fluid under this condition changes its phase from liquid to gas and form bubbles. These bubbles travel along with flowing fluid and reach a zone with relatively high pressure. As the pressure builds up, the size of the bubble reduces and at some stage bubbles collapse generating very high pressure locally that could damage the metallic blade surfaces. Extensive research activities are going to investigate cavitation phenomenon. At Kirloskar Bothers Ltd, a mixed flow pump was investigated thoroughly for its cavitation performance. The newly introduced Cavitation module in a CFD package, CFX, was used to predict the cavitation phenomenon for this pump. The performance of the pump was predicted first by using single-phase module. The overall performance prediction of the pump matched well with the measured results. The solver was switched over to account for cavitation study using multiphase flow phenomenon. The numerical approach brings out formation of vapor and growth of its volume fraction as the suction pressure is dropped. The paper describes both of these approaches and presents results in the form of impact of cavitation on overall performance of the pump. The vapor bubble formation and its volume fraction growth with reduction in suction pressure are brought out using numerical approach.

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