Measurement and Prediction of Discharge Coefficients in Highly Compressible Pulsating Flows to Improve EGR Flow Estimation and Modeling of Engine Flows

Abstract

An assumption of constant discharge coefficient (C d) is often made when modeling highly compressible pulsating engine flows through valves or other restrictions. Similarly, orifices and flow-nozzles used for real-time EGR flow estimation are often calibrated at a few steady-state points with one single constant C d that minimizes the error over the selected points. This quasi-steady assumption is based on asymptotically constant C d observed at high Reynolds number for steady (non-pulsating) flow. It has been shown in this work that this assumption is not accurate for pulsating flow, particularly at large amplitudes and low flow rates. The discharge coefficient of a square-edged orifice placed in the exhaust stream of a diesel engine produced C d 's varying between 0.60 and 0.90 for critical/near-critical flows. A novel pulsating flow measurement apparatus that allowed independent variation of pressure, flow rate and frequency and allowed reproducible measurements independent of transducer characteristics, produced C d 's in the range of 0.25-0.60 with a similar square-edge orifice. The variation in C d was found to be correlated to two dimensionless variables, η and ξ , defined as the standard deviation of the pulsating pressure signal, σ p , normalized by ρV 2 and p across the orifice, respectively. The results suggest that many aspects of compressible pulsating flow through flow restrictions are yet to be understood.

Implementation of a Multi-Zone Numerical Blow-by Model and Its Integration with CFD Simulations for Estimating Collateral Mass and Heat Fluxes in Optical Engines

“…As a result, the Reynolds number at firing conditions will be lower, thus, the discharge coefficient will be higher. It is also underlined that the tuned values reported in Table 3 are consistent with respect to the typical range (0.6-0.85) reported in similar works [8,25]. As a further proof of the proposed discussion, one can observe that in the orifices from volumes 3 to 4, and from volumes 4 to 5, the discharge coefficients decrease towards lower values comparable with those of the motored case because of the lower temperatures in these volumes.…”

Dynamic characteristics of orifice flowmeter impulse response based on CFD simulation

“…The results show that the differential pressure and the instantaneous flow rate of the throttle orifice are in the same frequency and different phases, and the differential pressure amplitude increases linearly with the increase of the amplitude of the inlet flow rate. Brahma et al [9] . built a pulsating flow device to study the pulsating flow measurement of an orifice flowmeter.…”

Flowing Liquid-Based Triboelectric Nanogenerator Performance Enhancement with Functionalized Polyvinylidene Fluoride Membrane for Self-Powered Pulsating Flow Sensing Application

“…This concept holds significant relevance in various industries and medical fields, with applications spanning heat transfer augmentation, improved cleaning processes, fluid mixing, mass transport in porous media, and biofluid engineering [ 29 , 30 , 31 ]. Pulsating flow in pipes has been observed in diverse technical areas such as physiology, roller and finger pumps, transportation of blood flow, oxygen, and sanitary fluids, among others [ 32 , 33 , 34 , 35 , 36 , 37 ]. Scientists have shown considerable interest in studying pulsating flow, especially focusing on accurate flow rate measurement, which is crucial for evaluating system performance [ 38 , 39 , 40 ].…”