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.

Diesel Engine Research at High B.M.E.P.

1985 ◽  
Vol 199 (4) ◽  
pp. 285-292 ◽  
Author(s):  
A G Osborne
Keyword(s):  
High Pressure ◽  
Diesel Engine ◽  
Compression Ratio ◽  
Engine Performance ◽  
Research Programme ◽  
Boost Pressure ◽  
Effective Pressure ◽  
Cylinder Pressure ◽  
Experimental Part ◽  
Peak Cylinder Pressure

Demands for more power from the turbocharged diesel, without increase in bulk or weight, has led to an increase in levels of mean effective pressure by the application of high-pressure turbocharging. An investigation was conducted to determine engine performance under high b.m.e.p. conditions and this paper presents results of the experimental part of the research programme. Test work was carried out on a single-cylinder research engine equipped with an independent pressure-charging facility. Boost pressure ratios up to 6.2:1 were used with the geometric compression ratio reduced, in stages, to 8:1, to limit peak cylinder pressure. Power levels up to 35.4 bar b.m.e.p. were produced.

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.

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