P. G. Hill

A Fundamental Equation of State for Heavy Water

A fundamental equation of state has been formulated for heavy water in the form Ψ = Ψ(p,T) in which Ψ = Helmholtz free energyp = density T = thermodynamic temperature. The complete range of single phase states in the range up to 100 MPa and 600 °C is covered by a single equation which is fitted both to P v T values, for saturated and unsaturated states, and to enthalpy values for saturation states only. The equation is constrained to fit the critical point conditions determined by Blank. It represents all thermodynamic properties of D2O, in the above range of states, within what is believed to be the accuracy of the experimental data.

A Unified Fundamental Equation for the Thermodynamic Properties of H2O

A new unified equation of state for H2O is presented, which includes the revised and extended scaling equation of Levelt Sengers, Kamgar–Parsi, Balfour and Sengers, is continuous over all single phase states of H2O from triple point pressure and temperature to 1000 MPa (or the melting line) and 1000 °C and provides accurate representation of existing thermodynamic data in that range. In addition it provides a smooth transition from singular critical region functions to the nonsingular far‐field functions. This is demonstrated by the variations of isochoric specific heat, isothermal compressibility, speed of sound, specific heat ratio and coexistence line properties in the critical region.

Turbulent Transient Gas Injections

Compressible transient turbulent gaseous jets are formed when natural gas is injected directly into a diesel engine. Multi-dimensional simulations are used to analyze the penetration, mixing, and combustion of such gaseous fuel jets. The capability of multi-dimensional numerical simulations, based on the k-e turbulence model, to reproduce the experimentally verified penetration rate of free transient jets is evaluated. The model is found to reproduce the penetration rate dependencies on momentum, time, and density, but is more accurate when one of the k-e coefficients is modified. The paper discusses other factors affecting the accuracy of the calculations, in particular, the mesh density and underexpanded injection conditions. Simulations are then used to determine the impact of chamber turbulence, injection duration, and wall contact on transient jet penetration. The model also shows that gaseous jets and evaporating diesel sprays with small droplet size mix at much the same rate when injected with equivalent momentum injection rate.

Transient Turbulent Gaseous Fuel Jets for Diesel Engines

Existing data on transient turbulent jet injection in to large chambers demonstrates self-similar behavior under a wide range of conditions including compressibility, thermal and species diffusion, and nozzle under expansion. The Jet penetration distance well downstream of the virtual origin is proportional to the square root of the time and the fourth root of the ratio of nozzle exit momentum flow rate to chamber density. The constant of proportionality has been evaluated by invoking the concept of Turner that the flow can be modeled as a steady jet headed by a spherical vortex. Using incompressible transient jet observations to determine the asymptotically constant ratio of maximum jet width to penetration distance, and the steady jet entrainment results of Ricou and Spalding, it is shown that the penetration constant is 3 ± 0.1. This value is shown to hold for compressible flows also, with substantial thermal and species diffusion, and even with transient jets from highly under-expanded in which, as in diesel engine chambers with gaseous fuel injection, the jet is directed at a small angle to one wall of the chamber. In these tests, with under expanded nozzles. Observations of transient jet injection have been made in a chamber in which, as in diesel engine chambers with gaseous fuel injection, the jet is directed at a small angle to one wall of the chamber. In these tests, with under-expanded nozzles it was found that at high nozzle pressure ratios, depending on the jet injection angle, the jet penetration can be consistent with a penetration constant of 3. At low pressure ratios the presence of the wall noticeably retards the penetration of the jet.

Assessment of critical parameter values for H2O and D2O

Recommendations for the most likely values of the critical parameters of light and heavy water as accepted by the International Association for the Properties of Steam are presented, together with an assessment of their reliability. The results are, for H2O: Tc=(647.14+δ1)K, δ1=0.00±0.10; Pc=(22.064+0.27δ1±0.005) MPa; ρc=(322±3) kg/m3; and for D2O: Tc=(643.89+δ2) K, δ2=0.00±0.20; Pc=(21.671+0.27 δ2±0.010) MPa; ρc=(356±5) kg/m3. Supporting material for these choices of values and the assessment of their reliability is provided. Temperature values are on the International Practical Temperature Scale of 1968 (IPTS 1968) unless otherwise indicated.

The Effects of High-Pressure Injection on a Compression–Ignition, Direct Injection of Natural Gas Engine

This study investigated the effects of injection pressure on the performance and emissions of a pilot-ignited, late-cycle direct-injected natural gas fueled heavy-duty engine. The experiments, conducted on a single-cylinder engine, covered a wide range of engine speeds, loads, and exhaust gas recirculation fractions. The injection pressure was varied at each operating condition while all other parameters were held constant. At high loads, increasing the injection pressure substantially reduced particulate matter and CO emissions, with small increases in NOx and no significant effect on hydrocarbon emissions or fuel consumption. At low loads, injection pressure had no significant impact on either emissions or performance. At high loads, higher injection pressures consistently reduced both the number density and the size of particles in the exhaust stream. Injection pressure had reduced effects at increased engine speeds.

Cyclic variations and turbulence structure in spark-ignition engines

Abstract Cyclic variations in pressure and burning time in a single cylinder spark-ignition engine have been determined as a function of equivalence ratio and engine speed. For the same operating conditions, measurements of turbulence intensity are available and these have been used with an estimate of the integral scale to estimate the magnitude of the Taylor microscale. It has been shown that the standard deviation in the burning time associated with the early stages of burning is predictable from knowledge of the Taylor microscale and the laminar burning velocity. This result is an implication of the Tennekes model of small scale turbulence and the Chomiak explanation of high flame propagation rate in regions of concentrated vorticity.

Sixteen Thousand Evaluated Experimental Thermodynamic Property Data for Water and Steam

As part of the activities of the International Association for the Properties of Water and Steam, all reliable sources of experimental data on the thermodynamic properties of ordinary (light) water and steam have been collected and converted to common temperature, pressure, volume, mass and heat scales. The data are grouped by state or phase: ideal‐gas properties; sublimation and melting curves; saturation properties; properties of liquid water at ambient pressure; thermodynamic properties of the single‐phase state; and those of metastable states. In each category, a subdivision is made by property. Properties include the volume, enthalpy, heat capacities, sound velocity, internal energy and Joule‐Thomson and related coefficients. The total data collection contains approximately 16 000 data points and covers a century of experimental work at temperatures from 253 to 1273 K and pressures up to 1 GPa. This report characterizes the data and gives the literature references. The actual data collection is avail...

A supercharged heavy-duty diesel single-cylinder research engine for high-pressure direct injection of natural gas

Abstract A single cylinder of a heavy-duty diesel engine has been commissioned for research on the use of pilot diesel ignited natural gas which is directly injected into the cylinder. The cylinder is supercharged and equipped for exhaust gas recirculation. Performance and emissions measurements have been made over a range of loads, speeds, timings and equivalence ratios to indicate the potential for emissions reduction of high-pressure direct injection of natural gas. With independent control of boost pressure and engine backpressure, an examination has been made of the similarities and differences in performance of the single-cylinder engine and its multi-cylinder counterpart.

The relationship between cyclic variations in spark-ignition engines and the small structure of turbulence

Abstract The hypothesis that cyclic variations in combustion in spark-ignition engines originate in the small-scale structure of turbulence has been further examined in the light of experimental data from a single-cylinder research engine. The data cover a wide range of engine speed and equivalence ratio. The effects of spark electrode geometry, spark gap, chamber geometry, and throttling have also been examined. The general conclusion is that the standard deviation in burning time, deduced for the smallest size flame kernels, is estimated within experimental uncertainty by a parameter λ 4u l , in which λ is the Taylor microscale and ul is the laminar burning velocity of the unburned mixture. The experimental results are thus consistent with the interaction of an effectively point-source ignition with the turbulence structure model of Tennekes, and with the idea that rapid burning takes place in the “vortex tube” regions of high dissipation.