Design Considerations of an Airborne Free Piston Compressor

1987 ◽  
Vol 201 (3) ◽  
pp. 177-184 ◽  
Author(s):  
E Sher
Keyword(s):  
Ambient Pressure ◽  
Pressure Ratio ◽  
Combustion Process ◽  
Piston Compressor ◽  
Computer Code ◽  
Thermodynamic Efficiency ◽  
Atmospheric Conditions ◽  
Ambient Conditions ◽  
Free Piston ◽  
Detailed Computer

The effect of the atmospheric conditions on the performance of a spark ignition free piston engine has been investigated. A detailed computer code has been developed to simulate the unit cycle and was used to evaluate the effect of its geometrical proportions and the ambient conditions on the cycle performances. The model includes a semi-empirical model for the scavenging process, calculations of the flows into and out of the cylinders, empirical expressions for the combustion process and a practical approach for the heat transfer. The model has been calibrated by using experimental results of a conventional two-stroke engine having identical cylinder and port assemblies. It was concluded that the thermodynamic efficiency of the unit is strongly dependent on the receiver to the atmospheric pressure ratio, the compression ratio of the compressor, the compressor aspect ratio and the ambient pressure. It was shown that the thermodynamic efficiency varies insignificantly with the ambient temperature.

scholarly journals Superhydrophobic surfaces for extreme environmental conditions

2020 ◽  
Vol 117 (44) ◽  
pp. 27188-27194
Author(s):  
Henry Lambley ◽  
Thomas M. Schutzius ◽  
Dimos Poulikakos
Keyword(s):  
Surface Texture ◽  
Ambient Pressure ◽  
Water Repellency ◽  
Dynamic Imaging ◽  
Superhydrophobic Surfaces ◽  
Atmospheric Conditions ◽  
Ambient Conditions ◽  
Gas Layer ◽  
Penetration Behavior ◽  
Air Compression

Superhydrophobic surfaces for repelling impacting water droplets are typically created by designing structures with capillary (antiwetting) pressures greater than those of the incoming droplet (dynamic, water hammer). Recent work has focused on the evolution of the intervening air layer between droplet and substrate during impact, a balance of air compression and drainage within the surface texture, and its role in affecting impalement under ambient conditions through local changes in the droplet curvature. However, little consideration has been given to the influence of the intervening air-layer thermodynamic state and composition, in particular when departing from standard atmospheric conditions, on the antiwetting behavior of superhydrophobic surfaces. Here, we explore the related physics and determine the working envelope for maintaining robust superhydrophobicity, in terms of the ambient pressure and water vapor content. With single-tier and multitier superhydrophobic surfaces and high-resolution dynamic imaging of the droplet meniscus and its penetration behavior into the surface texture, we expose a trend of increasing impalement severity with decreasing ambient pressure and elucidate a previously unexplored condensation-based impalement mechanism within the texture resulting from the compression, and subsequent supersaturation, of the intervening gas layer in low-pressure, humid conditions. Using fluid dynamical considerations and nucleation thermodynamics, we provide mechanistic understanding of impalement and further employ this knowledge to rationally construct multitier surfaces with robust superhydrophobicity, extending water repellency behavior well beyond typical atmospheric conditions. Such a property is expected to find multifaceted use exemplified by transportation and infrastructure applications where exceptional repellency to water and ice is desired.

scholarly journals Ambient Temperature and Pressure Corrections for Aircraft Gas Turbine Idle Pollutant Emissions

1976 ◽  
Author(s):  
J. W. Marzeski ◽  
W. S. Blazowski
Keyword(s):  
Ambient Temperature ◽  
Ambient Pressure ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Pollutant Emissions ◽  
Pollutant Emission ◽  
Emission Model ◽  
Correction Factors ◽  
Ambient Conditions ◽  
Temperature And Pressure

Recent investigations have indicated that aircraft engine exhaust emissions are sensitive to ambient conditions. This paper reports on combustor rig testing intended to evaluate variations due to ambient temperature and pressure with special emphasis on idle engine operating conditions. Empirically determined CO, CxHy, and NOx correction factors — the ratio of the pollutant emission index value obtained during standard day operation to that resulting during actual ambient conditions — are presented. The effects of engine idle cycle pressure ratio, primary zone fuel-air ratio, and fuel type were investigated. Ambient temperature variations were seen to cause substantial emission changes; correction factors in excess of 2.0 were determined in some cases. Ambient pressure variations were found to be less substantial. A previously published NOx emission model and a simplified hydrocarbon combustion analysis are shown to be in general agreement with the empirical results.

The Influence of Atmospheric Conditions on the Performance of Combined Cycle Gas Turbine Power Plants

2006 ◽  
Author(s):  
Manuel Valde´s ◽  
Antonio Rovira ◽  
Jose´ A. Ferna´ndez
Keyword(s):  
Gas Turbine ◽  
Heat Recovery ◽  
Power Plants ◽  
Ambient Pressure ◽  
Combined Cycle ◽  
Atmospheric Conditions ◽  
Heat Recovery Steam Generator ◽  
Ambient Conditions ◽  
Air Density ◽  
Waste Energy

This paper deals with the calculation of the ambient conditions influence on combined cycle gas turbine (CCGT) power and efficiency. The main parameters influencing the CCGT performances when ambient conditions change are the air density and the steam condenser pressure. An 800 MW CCGT is studied in order to obtain numerical results in a particular case. This power plant is analyzed working with different condenser cooling techniques (direct or indirect cooling with open or closed circuits) at both 100% and 50% load. The results show that power output drops by 0.60% to 0.65% are to be expected for every 1 °C rise in ambient temperature and by 0.13% to 0.14% for every 1 mbar decrease in ambient pressure. The efficiencies are affected to a lesser extent since some of the gas turbine waste energy is recovered in the heat recovery steam generator and the steam turbine power is almost constant.

Design of an External Combustion Engine and its Application in a Free Piston Compressor

2007 ◽  
Vol 3 ◽  
Author(s):  
Jonathan Hogan Webb
Keyword(s):  
Combustion Engine ◽  
Piston Compressor ◽  
Dead Volume ◽  
Transfer Energy ◽  
Free Piston ◽  
Combustion Gases ◽  
Intermediate Chamber ◽  
Fuel Mixtures ◽  
External Combustion ◽  
External Combustion Engine

The design of a free piston compressor and an analysis on integrating an external combustion engine into the compressor design are presented in this article. A free piston compressor is a device which converts chemical energy to work on a volume of air through the kinetic energy of an inertia driven piston, which is not rigidly attached to a ground. An external combustion engine serves as in intermediate chamber which transfers combustion gases to a device to perform some work. The following discusses the design and experiments on an external combustion engine, with a focus on eliminating an injection holding force on a free piston compressor’s elastomeric membranes. The efficiency of the external combustion engine to transfer energy without significant losses due to heat, dead volume, air/fuel mixtures, and actuated valve speed are also presented.

scholarly journals Research on the Operating Characteristics of Hydraulic Free-Piston Engines: A Systematic Review and Meta-Analysis

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3530
Author(s):  
Fukang Ma ◽  
Shuanlu Zhang ◽  
Zhenfeng Zhao ◽  
Yifang Wang
Keyword(s):  
Systematic Review ◽  
High Efficiency ◽  
Meta Analysis ◽  
Combustion Process ◽  
Research Progress ◽  
Future Research ◽  
Operating Characteristics ◽  
Piston Engine ◽  
Free Piston ◽  
Free Piston Engine

The hydraulic free-piston engine (HFPE) is a kind of hybrid-powered machine which combines the reciprocating piston-type internal combustion engine and the plunger pump as a whole. In recent years, the HFPE has been investigated by a number of research groups worldwide due to its potential advantages of high efficiency, energy savings, reduced emissions and multi-fuel operation. Therefore, our study aimed to assess the operating characteristics, core questions and research progress of HFPEs via a systematic review and meta-analysis. We included operational control, starting characteristics, misfire characteristics, in-cylinder working processes and operating stability. We conducted the literature search using electronic databases. The research on HFPEs has mainly concentrated on four kinds of free-piston engine, according to piston arrangement form: single piston, dual pistons, opposed pistons and four-cylinder complex configuration. HFPE research in China is mainly conducted in Zhejiang University, Tianjin University, Jilin University and the Beijing Institute of Technology. In addition, in China, research has mainly focused on the in-cylinder combustion process while a piston is free by considering in-cylinder combustion machinery and piston dynamics. Regarding future research, it is very important that we solve the instabilities brought about by chance fluctuations in the combustion process, which will involve the hydraulic system’s efficiency, the cyclical variation, the method of predicting instability and the recovery after instability.

Piston-retardation insert in a free-piston compressor

AIAA Journal ◽  
1970 ◽  
Vol 8 (1) ◽  
pp. 169-171
Author(s):  
STELLAN KNOOS
Keyword(s):  
Piston Compressor ◽  
Free Piston

The Effects of Ambient Conditions on Gas Turbine Emissions—Generalized Correction Factors

1978 ◽  
Vol 100 (4) ◽  
pp. 640-646 ◽  
Author(s):  
P. Donovan ◽  
T. Cackette
Keyword(s):  
Gas Turbine ◽  
Pressure Ratio ◽  
Turbine Engines ◽  
Inlet Temperature ◽  
Gas Turbine Engines ◽  
Correction Factors ◽  
Oxides Of Nitrogen ◽  
Ambient Conditions ◽  
Nitrogen Emission ◽  
Wide Range

A set of factors which reduces the variability due to ambient conditions of the hydrocarbon, carbon monoxide, and oxides of nitrogen emission indices has been developed. These factors can be used to correct an emission index to reference day ambient conditions. The correction factors, which vary with engine rated pressure ratio for NOx and idle pressure ratio for HC and CO, can be applied to a wide range of current technology gas turbine engines. The factors are a function of only the combustor inlet temperature and ambient humidity.

Detailed Performance Analysis of a 10kW Dish∕Stirling System

2007 ◽  
Vol 130 (1) ◽  
Author(s):  
W. Reinalter ◽  
S. Ulmer ◽  
P. Heller ◽  
T. Rauch ◽  
J.-M. Gineste ◽  
...  
Keyword(s):  
Electric Energy ◽  
Optical Quality ◽  
Stirling Engine ◽  
Thermodynamic Efficiency ◽  
Ambient Conditions ◽  
Camera System ◽  
Charge Coupled Device ◽  
Mapping System ◽  
Conversion Unit ◽  
A Charge

The CNRS-Promes dish∕Stirling system was erected in Jun. 2004 as the last of three country reference units built in the “Envirodish” project. It represents the latest development step of the EuroDish system with many improved components. With a measured peak of 11kW electrical output power, it is also the best performing system so far. The measurement campaign to determine the optical and thermodynamic efficiency of the system is presented. The optical quality of the concentrator and the energy input to the power conversion unit was measured with a classical flux-mapping system using a Lambertian target and a charge coupled device camera system. An efficiency of the concentrator including the intercept losses of 74.4% could be defined for this particular system. For the thermodynamic analysis all the data necessary for a complete energy balance around the Stirling engine were measured or approximated by calculations. For the given ambient conditions during the tests, a Stirling engine efficiency of 39.4% could be measured. The overall efficiency for the conversion of solar to electric energy was 22.5%.

Free-Piston Compressor-Engines

1947 ◽  
Vol 156 (1) ◽  
pp. 253-271 ◽  
Author(s):  
H. O. Farmer
Keyword(s):  
Fuel Injection ◽  
Piston Compressor ◽  
Gas Generator ◽  
Compression Pressure ◽  
Compression Ignition Engine ◽  
Free Piston ◽  
Alternative Scheme ◽  
Free Piston Engine ◽  
New Type ◽  
Commercial Work

The Pescara free-piston engine has been developed in France during the last twenty years, and the paper gives a description of a portable air compressor which has been proved in commercial work, and is now in production. An explanation is given of those characteristics in which this engine differs from the orthodox engine-driven crankshaft compressor. The power unit is an opposed-piston two-stroke compression-ignition engine, the compressor piston being directly attached to one of the engine pistons, while the cushion piston is directly attached to the other. The cushion piston gives stability, ensures that the energy available for the return stroke is constant for any conditions of operation, and thus gives a constant compression pressure in the combustion cylinder. The velocity characteristics of the pistons during the inward and outward strokes are described with their effect on the compressor and other sections. The fuel injection gear and also an alternative scheme is described; and indicator diagrams show the results obtained. The output of the compressor is controlled by the governor; the governor controls the fuel injected and thus determines the stroke of the pistons and thereby the quantity of air delivered. The efficiency of the combustion section is given, with the specific fuel consumption loop of the compressor as a whole. Methods of starting, by use of a spring or compressed air, are given to illustrate the characteristics dealt with. The development of the free-piston compressor has led to the development of the power gas-generator, in which the combination of free-piston compressor and turbine forms a new type of prime mover.

WETTING BEHAVIOR IN ULTRASONIC VIBRATION-ASSISTED BRAZING OF ALUMINUM TO GRAPHITE USING Sn-Ag-Ti ACTIVE SOLDER

2015 ◽  
Vol 22 (03) ◽  
pp. 1550035 ◽  
Author(s):  
WEI-YUAN YU ◽  
SEN-HUI LIU ◽  
XIN-YA LIU ◽  
JIA-LIN SHAO ◽  
MIN-PEN LIU
Keyword(s):  
Oxide Layer ◽  
Ultrasonic Vibration ◽  
Pure Aluminum ◽  
Decomposition Temperature ◽  
Ultrasonic Waves ◽  
Atmospheric Conditions ◽  
Liquid Solder ◽  
Ambient Conditions ◽  
Composite Oxides ◽  
Surface Oxides

In this study, Sn - Ag - Ti ternary alloy has been used as the active solder to braze pure aluminum and graphite in atmospheric conditions using ultrasonic vibration as an aid. The authors studied the formation, composition and decomposition temperature of the surface oxides of the active solder under atmospheric conditions. In addition, the wettability of Sn -5 Ag -8 Ti active solder on the surface of pure aluminum and graphite has also been studied. The results showed that the major components presented in the surface oxides formed on the Sn -5 Ag -8 Ti active solder under ambient conditions are TiO , TiO 2, Ti 2 O 3, Ti 3 O 5 and SnO 2. Apart from AgO and Ag 2 O 2, which can be decomposed at the brazing temperature (773 K), other oxides will not be decomposed. The oxide layer comprises composite oxides and it forms a compact layer with a certain thickness to enclose the melted solder, which will prevent the liquid solder from wetting the base metals at the brazing temperature. After ultrasonic vibration, the oxide layer was destroyed and the liquid solder was able to wet and spread out around the base materials. Furthermore, better wettability of the active solder was observed on the surface of graphite and pure aluminum at the brazing temperature of 773–823 K using ultrasonic waves. The ultrasonic wave acts as the dominant driving factor which promotes the wetting and spreading of the liquid solder on the surface of graphite and aluminum to achieve a stable and reliable brazed joint.

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