A Fundamental Thermodynamic Investigation of Compression Ratio Effects in Relation to Diesel Engine Size

2021 ◽  
Author(s):  
Kevin Burnett ◽  
Ashwani Gupta ◽  
Dianne Luning Prak ◽  
Jim Cowart
Keyword(s):  
Heat Transfer ◽  
Compression Ratio ◽  
Internal Combustion Engines ◽  
Volume Ratio ◽  
Cylinder Wall ◽  
Transfer Coefficients ◽  
Cold Starting ◽  
Heat Transfer Coefficients ◽  
Starting Conditions ◽  
Engine Size

Abstract In this study, a fundamental generalized thermodynamic model of internal combustion engines was applied to evaluate engine compression ratio effects principally in relation to engine size. Performance and efficiency metrics were investigated systematically. Further, cylinder wall temperature was varied across a range of cold start to stabilized operating temperatures. A very broad range of engine bore sizes and bore-to-stroke ratios were evaluated, representing small to large diesel engines in service. In general, it was observed that engine efficiency increases moderately with increasing compression ratio and bore size. Additionally, surface area-to-volume ratio is a critical metric when evaluating various size engines. This leads to greater relative heat transfer in the smaller bore engines with higher compression ratios. The sensitivity to heat losses is also much greater in the smaller engines. Smaller engines with higher compression ratios are expected to be most affected by cold starting conditions. Exhaust enthalpy is highest for larger bore engines with lower compression ratios, an important consideration for engine boosting. Higher convective heat transfer coefficients are also expected in smaller bore engines with higher compression ratios due to the higher operating pressures.

Method for Estimating Compression Ratio and Heat Transfer Multiplier Using GT-Power and Experimental Pressure Traces

2020 ◽  
Author(s):  
Adam Klingbeil ◽  
Thomas Lavertu
Keyword(s):  
Heat Transfer ◽  
Compression Ratio ◽  
Engine Performance ◽  
Cylinder Pressure ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Power Simulation ◽  
Peak Cylinder Pressure ◽  
Crank Angle ◽  
Rate Of Heat Release

Abstract Crank-angle resolved cylinder pressure data is valuable for characterizing engine performance and various techniques have been developed for post-processing the pressure traces to understand the rate of heat release and its overall impact on engine performance. However, many of these techniques rely on accurate knowledge of the compression ratio, which may not be well-known because of uncertainties in component dimensions for new and rebuilt engines. Additionally, uncertainties in cylinder pressure referencing and top dead center (TDC) offset can lead to variation in the calculation of these parameters. A method was developed to estimate the compression ratio and heat transfer sensitivity for large bore diesel engines using GT-Power and experimental cylinder pressure traces. An injector cutout method was used on a 228.6mm bore 16-cylinder engine to record motoring cylinder pressure traces for an individual cylinder. The cylinder pressure traces were pegged thermodynamically by matching the slope of a 40-deg window of the compression trace with that of a GT-power simulation of a similar condition. Once the cylinder pressure was properly referenced, it was found that the compression ratio of the cylinder could be estimated by matching the slope of the compression trace over a larger crank angle window. Additionally, it is shown that the location of peak cylinder pressure is dependent on heat transfer and if the location of peak cylinder pressure relative to top dead center is accurately known, then the heat transfer coefficients in GT-Power can be estimated. For an engine where the exact compression ratio may not be known due to variations in hardware dimensions (for both new and rebuilt engines), this method provides a simple path to estimating compression ratio. Furthermore, by measuring the exact location of TDC and comparing that to the location of peak cylinder pressure, heat transfer can be estimated.

The Melting Process of Ice Inside a Horizontal Cylinder: Effects of Density Anomaly

1986 ◽  
Vol 108 (1) ◽  
pp. 166-173 ◽  
Author(s):  
H. Rieger ◽  
H. Beer
Keyword(s):  
Heat Transfer ◽  
Melting Process ◽  
Horizontal Cylinder ◽  
Convection Flow ◽  
Cylinder Wall ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Density Anomaly ◽  
Inner Diameter ◽  
Specific Temperature

In the present investigation heat transfer during melting of ice confined within a heated, horizontal cylinder is studied experimentally and by analysis. Because of the well-known density inversion effect of water in the proximity of the melting point of ice the first-order influence of convection flow for phase change processes becomes obvious. Depending on the inner diameter of the cylinder and on the specific temperature value Tw > 0° of the cylinder wall, quite different shapes of the melting ice body, the flow pattern, and the temperature field were predicted by numerical analysis. Also provided are local and overall heat transfer coefficients, revealing a reasonable agreement between experiments and predicted data. Computations were performed for wall temperatures in the range 4°C ≤ Tw ≤ 15°C and two inner diameters of the cylinder.

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

2007 ◽  
Vol 221 (12) ◽  
pp. 1653-1663 ◽  
Author(s):  
R I Gault ◽  
D J Thornhill ◽  
R Fleck
Keyword(s):  
Heat Transfer ◽  
Pressure Ratio ◽  
Flow Characteristics ◽  
Cylinder Wall ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Discharge Coefficients ◽  
Flow Apparatus ◽  
A New Technique ◽  
Predicted Values

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.

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