Paper 3: An Experimental Study of Flow through Poppet Valves

1965 ◽  
Vol 180 (14) ◽  
pp. 32-41 ◽  
Author(s):  
W. A. Woods ◽  
S. R. Khan
Keyword(s):  
Boundary Conditions ◽  
Constant Pressure ◽  
Reverse Flow ◽  
Pressure Ratio ◽  
Effective Area ◽  
Valve Lift ◽  
Exhaust Pipe ◽  
Poppet Valve ◽  
Flow Through ◽  
Poppet Valves

This report gives an account of steady flow tests carried out on poppet valves. The object of the investigation was to determine the boundary conditions for exhaust and inlet valves for subsequent use in the general programme of unsteady flow research. The exhaust valve was tested with and without pipes over a much wider range of pressure ratio and valve lift than has been carried out before and the boundary conditions have been found to be independent of the pipe and also almost independent of the position of the pressure tapping in the exhaust pipe. This result is very important and it will simplify subsequent boundary curve tests. Comprehensive tests have also been performed on the inlet valve and for reverse flow through each valve. The two usual mathematical flow models, namely, the constant pressure and the sudden enlargement, are discussed in detail and the concept of an effective area for a poppet valve is clearly explained. The effective areas for the exhaust and inlet valves for normal and reverse flow have been computed on the basis of the constant pressure flow model. The pressure ratio has been found to have little effect on the effective areas at low valve lifts but has considerable effects at high valve lifts. The results are presented graphically on a complete set of charts. It is illustrated in Appendix 3.II that the effective area of an exhaust poppet valve may be predicted for low valve lifts.

Paper 3: Steady Flow Tests on Twin Poppet Valves

1967 ◽  
Vol 182 (4) ◽  
pp. 126-133 ◽  
Author(s):  
W. A. Woods
Keyword(s):  
Steady Flow ◽  
Pressure Loss ◽  
Pressure Ratio ◽  
Effective Area ◽  
Valve Lift ◽  
Cylinder Wall ◽  
Large Area ◽  
Pressure Losses ◽  
Flow Through ◽  
Poppet Valves

This paper presents the results of an experimental investigation of steady flow through a pair of exhaust poppet valves. An account is given of the gas exchange process on engines which use poppet valves and the reason why pressure losses should be kept to a minimum is explained. Tests carried out on the cylinder head of a uniflow two-stroke cycle engine are described following a brief description of the apparatus used. The results of a simple analysis of incompressible flow are also given. It is shown that the two previous models of flow through a valve, namely the sudden enlargement and constant static pressure, both give unrealistic pressure losses for large area ratios, i.e. at high valve lifts. A new model is introduced which leads to realistic pressure losses at small and large area ratios, i.e. at low and high valve lifts. Effective areas for the present tests are calculated on the basis of the constant pressure model, and details of calculation of pressure losses are outlined. The blockage effect caused by placing the exhaust valves near the cylinder wall is given in the discussion of the test results. This is zero for 0 < l/d < 0·08, but reaches a maximum blockage of 10 per cent at l/d = 0·28. With unrestricted twin valves the effective area is about twice that of a single valve up to l/d = 0·18 with a progressively larger effective area at lifts up to 13 per cent higher at l/d = 0·4. A comparison is also made with other data readily available. The pressure losses determined from the tests were analysed using a parameter derived in the simple theory. The parameter used is found to be almost independent of pressure ratio and the results are presented by means of this pressure loss parameter as a function of valve lift. The representation provides a quantitative method of comparing the performance of a given configuration of valve and port. On this basis the twin poppet valves are shown to give a slightly higher pressure loss than a single valve.

Paper 14: Discharge from a Cylinder through a Poppet Valve to an Exhaust Pipe

1967 ◽  
Vol 182 (8) ◽  
pp. 137-144 ◽  
Author(s):  
W. A. Woods ◽  
S. R. Khan
Keyword(s):  
Gas Exchange ◽  
Unsteady Flow ◽  
Pulse Generator ◽  
Pressure Ratio ◽  
Effective Area ◽  
Exhaust Pipe ◽  
Pipe System ◽  
Method Of Calculation ◽  
Poppet Valve ◽  
Exchange Processes

This paper is concerned with the gas exchange processes which occur in an engine. Previous work has been concerned with unsteady flow within the exhaust pipework; the present investigation provides a link between the cylinder and the pipe. The modifications to the pulse generator machine which was used to simulate an engine are described, and an account is given of the tests carried out with the machine. The previous steady flow tests are briefly summarized and the unsteady flow tests which were carried out are summarized with the aid of a table. The paper also presents a discussion of the test results and of calculations carried out to compare with the experiments. The main conclusion from the results is that a very satisfactory method has been devised for calculating the gas exchange processes occurring in an engine model. The main detailed conclusions are: (1) The dependence upon pressure ratio of the effective area of a poppet valve need not be taken into account for the analysis of unsteady flow tests. (2) Calculations on unsteady flow and gas exchange should be made on a theoretical model which has an exhaust pipe equal in length to the actual external exhaust pipe plus the length of the ‘exhaust bend’. (3) The method of calculation using the cylinder boundary conditions is an improvement on the previous type of calculations, which used a ‘pressure input’ as a boundary condition. Finally, the present work on a pulse generator with fixed piston using cold air, has provided a means of calculating the gas exchange processes from a knowledge of the release and supercharge pressures and the engine geometry. It has, therefore, provided an important link between the engine cylinder and the exhaust pipe system.

Aerodynamic instabilities modeling under asymmetric boundary in a centrifugal compressor for turbocharger

2022 ◽  
pp. 095440702110726
Author(s):  
Chenxing Hu ◽  
Xue Li ◽  
Siyu Zheng
Keyword(s):  
Boundary Conditions ◽  
Centrifugal Compressor ◽  
Reverse Flow ◽  
Pressure Ratio ◽  
Safety Margin ◽  
Wake Flow ◽  
Wave Number ◽  
Vaneless Diffuser ◽  
The Impact ◽  
Continuous Adjoint

The increasing demand for compression systems with high pressure ratio and wide safety margin has set new prerequisites for designers to meet the industrial needs without increasing the manufacturing costs excessively. In this work, the turbulent stability of the vaneless diffuser of the centrifugal compressor was analyzed. Unsteady Reynolds-averaged numerical simulations of the isolated diffuser and full annular diffuser with or without circumferential asymmetric boundary conditions downstream were performed. And a continuous adjoint approach was adopted, which is rarely applied in the stability analysis of compressor flow. Then, the origin of instability under different inflow and outflow conditions was sought with a sensitivity analysis. The prediction of the growth rate reveals that the flow near the shroud dominates the global stability of the diffuser. When connected with an impeller in the upstream direction, the most unstable region is localized at the backflow regions near the outlet. The wave number, however, is altered under the impact of the jet-wake flow. When connected to a circumferential asymmetric condition, the structural sensitivity of the vaneless diffuser with a radius ratio of 1.53 indicates that the interaction between the inlet reverse flow and outlet backflow is responsible for the occurrence of stall. The most unstable regions are localized at the region 90°–135° away from the volute tongue. The present work mainly contributes to the instabilities identification with novel sensitivity methods under asymmetric boundary conditions.

Improvement of Poppet Valve Injection Performance in Large-Bore Natural Gas Engines

2004 ◽  
Author(s):  
Gi-Heon Kim ◽  
Allan Kirkpatrick ◽  
Charles Mitchell
Keyword(s):  
Natural Gas ◽  
Pressure Loss ◽  
Internal Combustion Engines ◽  
Gas Flow ◽  
Flow Characteristics ◽  
Stagnation Pressure ◽  
Natural Gas Engines ◽  
Poppet Valve ◽  
Flow Through ◽  
Poppet Valves

Poppet valves have been used as fuel delivery mechanisms in internal combustion engines due to their excellent sealing characteristics. For example, in large-bore stationary natural gas engines, gas is directly injected by a poppet valve into the engine cylinder. The objectives of this paper are to show that a significant amount of stagnation pressure is lost during the gas flow through a conventional poppet valve and to suggest design improvements to obtain more efficient poppet valves with reduced stagnation pressure loss. In this paper, simple converging-diverging nozzles are incorporated into the poppet valve configuration to reduce the stagnation pressure loss originating from compressible flow structures. Numerical simulations of the gas flow through various poppet valve geometries were performed. Both push and pull poppet valve geometries with nozzle were studied. The stagnation pressure losses, momentum delivery downstream and downstream flow characteristics of the jets from conventional poppet valves and the modified valves were compared. A pressure-based valve injection efficiency was defined and used to compare the valve injection performance. A mixing fraction parameter was also defined to compare valve performance in a moving piston simulation. The results indicate that a conventional poppet valve is an inefficient mechanism to deliver momentum to the fuel-air mixture. Comparison of the results indicates that it is possible to make significant improvements of injection performance in momentum delivery by incorporating well-designed nozzles into the poppet valve geometry.

Paper 21: A Quasi-Steady Flow Representation of Centrifugal Compressor Performance Characteristics in Non-Steady Flow Systems

1967 ◽  
Vol 182 (8) ◽  
pp. 197-208 ◽  
Author(s):  
R. S. Benson ◽  
A. Whitfield
Keyword(s):  
Steady Flow ◽  
Centrifugal Compressor ◽  
Pulse Generator ◽  
Reverse Flow ◽  
Pressure Ratio ◽  
Pulse Frequency ◽  
Rotary Valve ◽  
Pipe Length ◽  
Flow Through ◽  
Compressor Performance

This paper describes a theoretical and experimental study of the non-steady flow performance of a centrifugal compressor. The experimental work was designed to study the effect of pulse frequency on the compressor performance, for a given delivery configuration, using a rotary valve pulse generator. The experimental rig was designed so that it was possible to study the reverse flow and the pressure pulsations in the suction side of the compressor. The objective of the investigation was to discover how the compressor performance deteriorated with pulse frequency, and also to determine the frequency at which reverse flow through the compressor first occurred. The objective of the theoretical work was to predict the onset of reverse flow through the compressor and the mean and transient delivery pressure ratio using the conventional stationary pipe non-steady solutions by the method of characteristics. The compressor unit was replaced by a boundary condition within the pipe system equal to the experimentally known steady flow characteristics of the compressor. The physical size of the compressor was replaced by an equivalent pipe length; this technique is described. The theoretical results are compared with an extensive series of experimental results. This work is a direct extension of that given in reference (3).

Study of fluid flow through a channel deformed by piezoelement

2018 ◽  
Vol 13 (3) ◽  
pp. 1-10 ◽  
Author(s):  
I.Sh. Nasibullayev ◽  
E.Sh Nasibullaeva ◽  
O.V. Darintsev
Keyword(s):  
Fluid Flow ◽  
Pressure Drop ◽  
Boundary Conditions ◽  
Flow Rate ◽  
Contact Surface ◽  
Piezoelectric Element ◽  
Neumann Boundary ◽  
Differential Pressure ◽  
Physical Parameters ◽  
Flow Through

The flow of a liquid through a tube deformed by a piezoelectric cell under a harmonic law is studied in this paper. Linear deformations are compared for the Dirichlet and Neumann boundary conditions on the contact surface of the tube and piezoelectric element. The flow of fluid through a deformed channel for two flow regimes is investigated: in a tube with one closed end due to deformation of the tube; for a tube with two open ends due to deformation of the tube and the differential pressure applied to the channel. The flow rate of the liquid is calculated as a function of the frequency of the deformations, the pressure drop and the physical parameters of the liquid.

scholarly journals A Simple Transient Poiseuille-Based Approach to Mimic the Womersley Function and to Model Pulsatile Blood Flow

Dynamics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 9-17
Author(s):  
Andrea Natale Impiombato ◽  
Giorgio La Civita ◽  
Francesco Orlandi ◽  
Flavia Schwarz Franceschini Zinani ◽  
Luiz Alberto Oliveira Rocha ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Boundary Conditions ◽  
Quadratic Function ◽  
Pulsatile Blood Flow ◽  
Flow Through ◽  
Simplified Analysis ◽  
Function Models ◽  
Flow Reversals

As it is known, the Womersley function models velocity as a function of radius and time. It has been widely used to simulate the pulsatile blood flow through circular ducts. In this context, the present study is focused on the introduction of a simple function as an approximation of the Womersley function in order to evaluate its accuracy. This approximation consists of a simple quadratic function, suitable to be implemented in most commercial and non-commercial computational fluid dynamics codes, without the aid of external mathematical libraries. The Womersley function and the new function have been implemented here as boundary conditions in OpenFOAM ESI software (v.1906). The discrepancy between the obtained results proved to be within 0.7%, which fully validates the calculation approach implemented here. This approach is valid when a simplified analysis of the system is pointed out, in which flow reversals are not contemplated.

Modeling of a Steam Turbine Including Partial Arc Admission for Use in a Process Simulation Software Environment

2011 ◽  
Author(s):  
Eric Liese
Keyword(s):  
Steam Turbine ◽  
Process Simulation ◽  
Process Model ◽  
Constant Pressure ◽  
Pressure Ratio ◽  
Simulation Software ◽  
State Variables ◽  
Steam Turbines ◽  
Software Environment ◽  
Last Stage

A dynamic process model of a steam turbine, including partial arc admission operation, is presented. Models were made for the first stage and last stage, with the middle stages presently assumed to have a constant pressure ratio and efficiency. A condenser model is also presented. The paper discusses the function and importance of the steam turbines entrance design and the first stage. The results for steam turbines with a partial arc entrance are shown, and compare well with experimental data available in the literature, in particular, the “valve loop” behavior as the steam flow rate is reduced. This is important to model correctly since it significantly influences the downstream state variables of the steam, and thus the characteristic of the entire steam turbine, e.g., state conditions at extractions, overall turbine flow, and condenser behavior. The importance of the last stage (the stage just upstream of the condenser) in determining the overall flowrate and exhaust conditions to the condenser is described and shown via results.

Sign in / Sign up

Export Citation Format

Share Document