Alternative method to evaluate discharge coefficients. Part 1: Feasibility study

Abstract

The purpose of the current paper is to demonstrate the feasibility of a new technique whereby mass flowrates, and hence discharge coefficients can be estimated for a range of pipe discontinuities such as poppet valves, throttles, cylinder ports, and orifices. The requirement to directly measure the mass flowrates using a standard conventional steady flow apparatus has been eliminated. As such, flow characteristics were examined during the transient charging or inflow of air, from atmosphere, through a sharp-edged orifice into a partially evacuated cylinder of known volume. In particular, the current study focused on measuring the transient mass flowrates, pressures, and temperatures of air during an inflow test. Comparison between measured gas pressures and temperatures were made with predicted values from an adiabatic and non-adiabatic zero-dimensional inflow model. Mass flowrates calculated from measured cylinder gas pressure data, without heat transfer correction, were shown to be approximately 20 per cent lower, across the full pressure ratio range, than those measured using the mass flow meter. Iterative trial and error techniques were employed to determine the constant and time varying convective heat transfer coefficients needed to correlate the cumulative mass during inflow with the total mass of air, from initial and final cylinder conditions. Heating the cylinder wall to ensure isothermal conditions resulted in an improved correlation between the measured and estimated mass flowrates.

Alternative method to evaluate discharge coefficients. Part 2: Case study

“…Flow pipes were manufactured and installed upstream and downstream of the cylinder head poppet valve. Prior to the cylinder head test, the same test orifice as that used in [10] was repeat tested on the QS-FR. Figures 2(a) and (b) show the orifice and cylinder head set-up on the QS-FR, respectively.…”

“…In addition to measuring the mass flowrate, the relationship between measured cylinder gas pressure, p 1 , ambient room temperature, T 0 , cylinder wall temperature, T wall , and cylinder gas temperature, T 1 , was derived [10], relating to the schematic diagram of Fig. 3.…”

“…Mass flowrates were also calculated using the measured cylinder gas pressures and corrected for heat transfer. The authors found that for the 11 mm diameter orifice tested, both a constant and time-varying heat transfer correction resulted in an acceptable correlation with steady flow data over most of the pressure ratio range [10]. This work was limited because of the fact that the test aperture used was not realistic of that typically found in an internal combustion engine.…”

“…As an extension to the initial conceptual work of Gault et al [10], this article presents the development of an operational type quasi-steady flow rig apparatus (QS-FR), where a cylinder head poppet valve was used as a case study. This was to ascertain if the technique could be used successfully for this type of aperture.…”

Dynamic interaction between the structure and the trolley of high performance gantry cranes

“…), ponekad se u motorskoj tehnici zaobilazi (Matareli (Mattareli) [85], Grau (Grau) [87,89] ili Golt (Gault) [90,91], npr.) i opravdava potrebom da se, inače složen proračun radnog procesa, pojednostavi.…”